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HELIOS 


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CORRECTIONS 
Page  51,  line  13  and  14  from  bottom. 

For  "H.  C.  Meinholdt"  read  "H.  C.  Meinholtz" 
Page  57,  line  10  from  bottom. 

For  "10  lb."  read  "21/2  lb." 
Page  83,  line  6  from  bottom. 

Cross  out  sentence  beginning  "Its  specific  heat" 
Page  118,  caption. 

For  "Sixteen"  read  "Twenty" 
Page  401,  Fig  193  caption. 

For  "or"  read  "and" 
Page  607,  line  6  from  bottom. 

For  "Fig.  263"  read  "Fig.  264" 
Page  608,  line  16  from  top. 

For  "Fig.  258"  read  "Fig.  259" 


ib.  Google 


STEAM  BOILER  ENGINEERING 

A  Treatise  on  Steam  Boilers  and 

the  Design  and  Operation 

of  Boiler  Plants 


HEINE  SAFETY  BOILER  CO. 


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255362 

HAY  -  J  i'J22 
THN 

•H3b 

Heine  Safety  Boiler  Co. 

Qeneral  O0uxs 
ST.  LOUIS,  MO. 


t^tC)/r 


Plants 

St.  Louis,  Mo.  Phoenixville,  Pa. 

Branch  Offices 

NEW  YORK  BOSTON  PHILADELPHIA  PITTSBUROH 

II  Broadifir         SO  CongreM  Street       PenDiylvanJi  BIdg.  Park  Bldg. 


CHICAGO 
Firat  National  Bank  BlAg. 


CINCINNATI 
UnioD  Traat  Bldg. 


NEW  ORLEANS 
Godchaux  Bldg. 


DETROIT 
Dime  Bank  Bid)!' 


CLEVELAND 
Scbofield  BIdg. 


DENVER 
Steama- Roger  Mfg.  Co. 
1718  California  Slraet 


Representatives 

DALLAS 

Smith  AWbitoey 

Sonthweatem  Life  BIdg. 


SAN  FRANCISCO 

IDomard  Engineering  Co. 

Cunard  Bldg. 


TORONTO 
Henry  Engineering  Co. 


ib.  Google 


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Preface  to 
Twenty-seventh  Edition 

THE  present  edition  of  Helios  is  entirely  new. 
Since  the  book  was  first  published,  almost 
twenty-seven  years  ago.  steam  engineering 
practice  has  been  completely  revolutionized. 
Our  knowledge  of  fuels,  of  their  proper  combus- 
tion, and  of  steam-power  applications  has  been 
developied  to  a  remarkable  extent. 

This  new  Helios  is  intended  to  summarize  the 
latest  commercial  developments  in  boiler-plant 
practice.  It  was  written,  compiled  and  edited 
by  the  Research  Department  of  the  Heine  Safety 
Boiler  Co.  for  the  large  number  of  engineers  and 
men  with  engineering  interests  who  have  to  deal 
with  prdDlems  of  boiler  plant  design  and  instal- 
lation. 

The  preface  to  the  first  edition  of  Helios,  which 
appeared  in  July,  1893.  was  written  by  Col. 
E.  D.  Meier,  founder  and  first  president  of  the 
Heine  Safety  Boiler  Co.  This  preface,  which  is 
reprinted  on  the  next  two  pages,  carries  a 
message  that  is  as  true  today  as  when  it  was 
written  by  Colonel  Meier. 

Helios — a  Text  Book  on  Steam  Boiler  Engi- 
neering— is  respectfully  dedicated  to  all  those 
interested  in  increasing  the  efficiency,  economy 
and  capacity  of  steam  power-plants. 

HEINE   Safety  Boiler  Co. 

St.  LouU.  December  11,  192a 


ly  Google 


HELIOS 

Source  of  AH  Power  I  Fouruotn  of  Light  and  Wormtfi  / 

Adored  by  the  ancient  husbandman  as  the  God  who  blessed  his  labors 
with  a  harvest  of  golden  grain ;  revered  by  the  early  sage  as  the  great  visible 
means  of  the  divine  creative  force;  pictured  by  the  inspired  artist  as  the  tire- 
less charioteer  who  drives  his  four  fiery  steeds  daily  across  the  heavens,  his 
head  circled  by  a  crowd  of  rays,  his  chariot  wheel  the  disk  of  the  sun  itself. 

When  primeval  man  began  to  think,  the  sun  seemed  to  him  the  cause  of 
all  those  wonders  in  nature  which  ministered  to  his  simple  wants,  or  taught 
his  soul  to  hope.  His  crude  feelings  of  awe  and  gratitude  blossomed  into 
worship,  and  we  find  the  sun  as  central  figure  in  all  early  religions.  He  was 
the  Suraya  of  the  Hindoos,  the  Baal  of  the  Phoenicians,  the  Odin  of  the 
Norsemen,  and  his  temples  arose  alike  in  ancient  Mexico  and  Peru.  As  Mithras 
of  the  Parsees,  he  was  adored  as  the  symbol  of  the  Supreme  Deity,  his  mes- 
senger and  agent  for  all  good.  As  Osiris  he  received  the  worship  and 
offerings  of  the  Egyptians,  whose  priests,  early  adepts  in  the  rudiments  of 
science,  saw  in  him  the  cause  of  the  annual  fructifying  overflow  of  the  Nile. 

Modem  knowledge,  with  its  vast  array  of  facts  and  figures,  can  but  verify 
and  seal  the  faith  of  these  ancient  observers.  What  they  dimly  discerned  as 
probable  is  now  the  central  fact  of  physical  science.  From  him  are  derived 
all  the  forces  of  nature  which  have  been  yoked  into  the  service  of  man.  All 
animal  and  plant  life  draws  its  daily  sustenance  from  the  warmth  and  light  of 
the  sun,  and  it  is  but  his  transmuted  energy  we  expend,  when,  with  muscle 
of  man  or  horse,  we  load  our  truck  or  roll  it  along  the  highway. 

Do  we  irrigate  the  soil  from  the  pumps  of  a  myriad  of  windmills?  His 
rays,  on  plains  far  inland,  supply  the  energy  for  the  breeze  which  turns  their 
vanes.  Does  a  lumbering  wheel  drive  a  dozen  stamps  and  a  primitive  arastra 
in  some  Mexican  canyon?  Do  mighty  turbines  whirl  a  million  flying  spindles 
and  shake  thousands  of  clattering  looms  on  the  banks  of  some  New  England 
stream?  From  the  bosom  of  the  ocean  and  the  swamps  of  the  tropics,  Helios 
lifted  those  vapory  Titans  whose  lifeblood  courses  in  the  mountain  torrent  and 
the  river  of  the  plain.  Do  a  hundred  cars  rattle  up  the  steep  streets  of  the 
smiling  city  by  the  Golden  Gate?  Are  massive  ingots  of  steel  forged  lo  shape 
and  size  by  the  giant  hammers  of  Bethlehem  ?  The  fuel  which  gives  them  mo- 
tion was  stored  for  us,  ages  before  man  was  evolved,  by  the  rays  which  flash 
from  his  chariot  wheels !  "The  heat  now  radiating  from  our  fire  places  has  at 
some  time  previously  been  transmitted  to  the  earth  from  the  sun.  If  it  be 
wood  that  we  are  burning,  then  we  are  using  the  sunbeams  that  have  shone  on 
the  earth  within  a  few  decades.  If  it  he  coal,  then  we  are  transforming  to 
heat  the  solar  energy  which  arrived  at  the  earth  millions  of  years  ago." 

Professor  Langley  remarks  that  "the  great  coal  fields  of  Pennsylvania 
contain  enough  of  the  precious  mineral  to  supply  the  wants  of  the  United 
States  for  a  thousand  years.  If  all  that  tremendous  accumulation  of  fuel 
were  to  be  extracted  and  burned  in  one  vast  conflagration,  the  total  quantity 


ib.  Google 


of  heat  that  would  be  produced  would,  no  doubt,  be  stupendous,  and  yet,"  says 
this  authority,  who  has  taught  us  so  much  about  the  snn.  "all  the  heat  de- 
veloped by  that  terrific  coal  fire  would  not  be  equal  to  that  which  the  sun 
pours  forth  in  the  thousandth  part  of  each  single  second." 

The  almost  limitless  stores  of  petroleum  which  are  found  in  America  and 
in  Asia,  and  the  smaller,  though  still  vast  supplies  of  natural  gas  which  some 
favored  localities  are  now  exploiting,  represent  but  so  much  sun-energy  trans- 
muted through   forests  of  prehistoric  vegetation. 

Another  authority  tells  us  that  the  total  amount  of  living  force  "which 
the  sun  pours  out  yearly  upon  every  acre  of  the  earth's  surface,  chiefly  in  the 
form  of  heat,  is  800,000  horse-power,"  And  he  estimates  that  a  flourishing  crop 
utilizes  only  four-tenths  of  one  per  cent  of  this  power. 

Remembering,  then,  that  this  sun-energy  reaches  us  only  one-half  of  each 
day.  we  may,  whetifrer  we  learn  hou;  pick  up  on  every  acre  an  average  of  175 
horse-power  during  each  hour  of  daylight,  as  a  surplus  which  nature  does  not 
require  for  her  work  of  food  production. 


Attempts  to  utilize  this  daily  waste  have  been  made,  and  future  ii 
may  fire  their  boilers  directly  with  the  radiant  heat  of  the  sun.  But  whether 
we  depend  on  what  he  garnered  for  us  ages  ago,  or  quite  recently,  or  on  the 
stores  he  will  lavish  on  us  in  ihe  future,  it  is  clear  that  man's  continued 
existence  on  earth  is  directly  dependent  on  HELIOS. 

In  olden  times  the  various  trades  or  guilds  chose  as  their  patron  saint 
^ome  prominent  person  who  was  thought  to  have  embodied  in  his  life-work 
the  special  means  and  methods  of  their  craft.  By  that  token  we  claim  Helios 
as  our  own.  He  has  always  carried  the  record  for  evaporative  efficiency.  He 
provides  both  the  fuel  and  the  water  for  our  boilers.  He  teaches  us  perfect 
circulation,  upward  as  mingled  vapor  and  water  by  the  action  of  heat,  and 
down  again  by  gravity  as  rain  and  river  in  solid  water.  It  is  therefore  (it 
that  the  boiler  in  which  this  perfect  and  unobstructed  circulation  is  made  the 
leading  feature  of  construction  should  have  HELIOS  as  its  emblem. 

In  the  following  pages  we  have  some  account  of  the  fuels  used  in  the 
practical  arts,  of  the  water  which  becomes  the  vehicle  for  transmitting  their 
energy  into  mechanical  power,  and  of  the  limitations  imposed  by  their  varying 
conditions.  These  must  all  be  taken  into  account  in  estimating  how  much  we 
may  expect  of  certain  combinations  of  machinery. 

We  trust  that  the  tables  and  data  may  be  found  convenient  for  ready  ref- 
erence alike  by  professional  men,  by  manufacturers,  and  by  that  growing  class 
of  practical  steam  engineers  who  realize  that  true  theory,  consonant  with 
collective  experience,  is  within  the  reach  of  every  thoughtful  man  who  pulls 
the  throttle. 

E.  D.  MEIER. 

This  explanation  of  the  choice  of  the  word  HELIOS,  as  the  name  of  this 
book,  appeared  as  the  preface  of  the  first  edition  in  July,  1893,  and  the  word 
has  ever  since  been  a  prominent  feature  of  our  trade  mark. 


ib.  Google 


CONTENTS 

Preface 9 

Helios,  by  E.  D.  Meier  ___ 10 

Chap.  1,  Heine  Practice 15 

Manufacturing  Facilities       Operation  of  Heine  Boilers  Superheaters 
Heine  Boiler  Characteristics  Adaptabili^  Cross  Drum  Boilers 

Heine  Service  Installation  Marine  Boilers 

Longitudinal  Drum  Boilers  Facilities  for  Oeaning  Standard  Specification!. 

Chap.  2,  Boiler  Rating  and  Design. __55 

Boiler  Horsepower  Heating  Surface  Ratios         Capacity  and  Economy 

Heating  Surface  Gas  Passages  Water  Circulation 

Grate  Surface  Baffling  Steadiness  of  Water  Level 

Chap.  3,  Superheaters _ .69 

Advantages  Limit  of  Superheat  Superheating  Surface 

Reciprocating  Engines  Control  of  Superheat  Superheater  Materials 

Steam  Turbines  Types  of  Superheaters  Industrial  Uses 

Chap.  4,  Fiunaces  and  Settings „ _.85 

Furnace  Design  Powdered  Coal  Waste  Heat 

Class ilication  of  Settings      Oil  Burning  Marine  Settings 

Hand  Firing  Tar  Burning  Refractory  Materials 

Mechanical  Stokers  Gas  Burning  Firebrick 

Ashpits  Refuse  Burning  Radiation  and  Leakage 

Chap.  5,  Mechanical  Stokers 159 

Overfeed  Underfeed  Chain  Grate 

Chap.  6,  Chimneys  and  Flues 173 

Sizes  by  Horsepower  Evas4  Chimneys  Radial  Brick 

Draft  and  Capacity  Chimneys  at  Altitudes  Reinforced  Concrete 

Draft  Required  for  Coal      Chimney  Construction  Remodeling 

Sizes  by  Gas  Self- Supporting  Steel  Breechings 

Oil,  Gas  and  Wood  Guyed  Steel  Dampers 

Chap.  7,  Mechanical  Draft 223 

Forced  Draft  Fan  Characteristics  Ducts  and  Dampers 

Fan  Drives  Testing  Fans  Induced  Draft 

Operating  Difficulties  Pitot  Tube  Stack  Connections 

Chap.  8,  Hping  and  Accessories 243 

Water  Hammer  Weight  of  Pipe  Steam  Pipe  Sizes 

Piping  Systems  Bursting  Pressure  Water  Pipe  Sizes 

Identification  by  Color  Pipe  Fittings  Expansion  and  Contraction 

Materials  Flanges  Pipe  Anchors 

Temperature  and  Strength  Valves  Expansion  Joints 

Standard  Pipe  Sizes  Blow-off  Piping  Steam  Separators 

Chap.  9,  Auxiliaries 297 

Steam  Pumps  Feed  Water  Regulators         Closed  Feed  Heaters 

Centrifugal  Feed  Pumps        Injectors  Economizers 

Power  Pumps  Feed  Water  Heating  Air  Heaters 

Automatic  Regulation  Open  Feed  Heaters  Engines  and  Turbines 


ib.  Google 


CONTENTS 


Cbap.  10,  Heat  Insulation _ 347 


Surface  Resistance  "85  per  cent  Magnes 

Bare  Surface  Heat  Lois  Diatomaeeoua  Earth 
Conductivities  of  Materials  Heat  Transmission 
Insulation  Uaterials  Thickness  of  Insulation 

Asbestos  Economy  of  Insulation 


Boiler  Drums 
Boiler  Walls 
Outdoor  Pipe  Lines 
Underground  Lines 
Cold  Water  Lines 


Chap.  11,  Heat  and  Combustion ___ ; 

Theory  of  Heat  Pyrometers                                Combustion 

Thermometry  Heat  Units                             Ignition  Temperatures 

Absolute  Temperature  Specific  Heat  of  Solids          Air  for  Combustion 

Thermodynamic  Scalz  Heat  Transfer                          Properties  of  Gases 

Thermometers  Temperature  Drop,  Boilers  Specific  Heat  of  Gases 


Chap.  12,  Steam.. 

Entropjr 
Expansion 
Saturated  Vapors 

Chap.  13,  Fuel 

Qassiftcation  of  Coals 
Location  of  Coal  Deposits 
Composition  of  U.S. Coats 
Commercial  Sizes 
Sampling  Coal 
Analyzing  Coal 
Heat  Value  of  Coal 
Mahler  Coal  Calorimeter 


Superheated  Vapors 
Pcabody  Diagram 
M  oilier  Diagram 


407 

Steam  Flow.  Nozzles 
Saturated  Steam  Tables 
Superheated  Steam  Tables 

_„. 435 


Ash 

Clinker 

Storage  of  Coat 

Deterioration  in  Storage 

Spontaneous  Combustion 

Briquets 

Tan  Bark 


Chap.  14,  Feed  Water 

Impurities  in  Water  Concentration  Test 

Analysis  of  Water  Mechanical  Treatment 

Hardness  Test  Thermal  Treatment 

Alkalinity  Test  Chemical  Treatment 

Causticity  Test  Zeolite  Process 

ChcQ).  15,  Boiler  Testing.. 

Personnel 

Duration 

Sim;)le  Test  Data 

Weighing  Feed  Water 

Weighing  Coal 

Quality  of  Steam 


Bagasse 

Liquid  Fuels 

Tar 

Colloidal  Fuel 

Gaseous  Fuels 

Junker  Gas  Calorimeter 

High  and  Low  Heat  Values 

Specifications 

499 


Starting  and  Stopping 
Simple  Test  Report 
Simple  Test  Calculations 
Complete  Test  Data 
Flue  Gas  Analysis 
Complete  Test  Report 

Chap.  16,  Operation 

Boiler  Fittings  Carbon  Monoxide 

Hand  Firing  CO>  Recorders 

Cleaning  Fires  Draft  Regulation 

Firing  Tools  Economical  Operation 

Banked  Fires  Control  Boards 

Quick  Steaming  from  Bank  Measuring  Water 
Load  Signals  Metering  Steam 

Smoke  and  Cinders  Weighing  Coal 

Carbon  Dioxide  Handling  Coal 


Boiler  Compounds 

Priming 

Foaming 


513 

Complete  Test  Calculations 


Heat  Balance 

Efficiency 

.Accuracy 

Steam  Used  by  Auxiliaries 

Liquid  and  Gaseous  Fuels 

551 


Storing  Coal 
Submerged  Stor^e 
Conveyors 
Handling  Oil  Fuel 
Cleaning  Boilers 
Renewing  Tubes 
Care  of  Idle  Boilers 
Boiler  Inspection 
Steam  Cost  Accounts 


ib.  Google 


Heine  Standard  Two  Pau  Boiler  with  Setting  for  Hand  Firing. 


ib.  Google 


CHAPTER  1 


HEINE  PRACTICE 

THE  first  Heine  Boiler  was  designed  by  Colonel  E.  D.  Meier  and 
built  in  St.  Louis  in  1882.  It  is  still  in  first-class  working  order, 
and  is  open  to  public  inspection  at  the  St.  Louis  Plant  of  the 
Heine  Safety  Boiler  Company. 

Colonel  Meier  founded  the  Heine  Safety  Boiler  Company  in 
1884  and  was  president  of  the  company  until  his  death  in  1914. 
Heine  Boilers  have  been  built  without  interruption  since  the  com- 
pany was  founded ;  the  fact  that  many  of  those  sold  in  the  'eighties 
are  still  in  operation,  testifies  to  the  superiority  that  has  always 
characterized  them. 

This  long  period  of  operation,  in  conjunction  with  up-to-date 
factory  methods  and  equipment,  has  enabled  the  Heine  Company 
to  build  up  an  organization  of  experts  in  boiler  design,  manufacture, 
and  operation. 

There  are  two  plants — St,  Louis,  Mo.,  and  Phoenixville,  Pa. 
Each  plant  has  complete  manufacturing  facilities,  and  consequently 
is  an  entirely  independent  source  of  supply.  The  general  offices  of 
the  company  are  at  St.  Louis. 

Heine  Boilers  are  of  two  general  classes,  longitudinal  and  cross 
drum.  While  the  longitudinal  drum  type  is  the  standard  for  land 
service,  many  Heine  users  prefer  the  cross  drum  on  account  of  the 
low  head  room  required.  They  are  built  in  both  types  for  marine 
service,  though  the  cross  drum  is  general  practice  for  this  work  and 
the  rect^nized  standard. 

All  Heine  Boilers  for  land  service  are  built  to  conform  to 
the  requirements  of  the  Boiler  Code  formulated  by  the  American 
Society  of  Mechanical  Engineers,  notwithstanding  that  weaker  (and 
cheaper)  construction  is  permitted  in  many  states.  In  this  code 
are  incorporated  the  most  rigid  requirements  for  boiler  construction 
and  materials. 

Heine  Boilers  for  marine  service  are  built  in  accordance  with 
the  rules  and  regulations  of  the  United  States  Board  of  Supervising 
Inspectors.  They  are  approved  by  Lloyds'  Register  of  Shipping  and 
by  the  American  Bureau  of  Shipping. 


ib.  Google 


ibiGoogle 


HEINK    PRACTICE  17 

Heine  Manufacturing  Facilities 

THE  two  large  plants  owned  and  operated  by  the  Heine  Safety 
Boiler  Company  are  shown  on  pages  6  and  7.  Both  are  fully 
equipped  with  electric,  hydraulic  and  pneumatic  machinery,  as  well 
as  with  powerful  cranes  and  hoists  for  handling  the  heavy  weights 
involved  in  the  manufacture  of  boilers. 

Steam  is  generated  at  each  plant  by  a  battery  of  Heine  Boilers. 
At  each  plant  the  power  equipment — steam  turbines,  generators, 
condenser  and  cooling  tower,  engines,  hydraulic  pumps  and 
accumulators,  air-compressors — is  installed  almost  entirely  in  dupli- 
cate, every  precaution  being  taken  to  avoid  a  shutdown.  Parts  of 
the  turbine-room  and  of  the  engine  and  pump  rooms  of  the  St.  Louis 
plant  are  shown  on  pages  16  and  18.  The  power  plant  at  Phoenix- 
ville  is  similar  to  that  at  St.  Louis. 

The  boiler-making  tools  found  in  the  Heine  plants  include 
rolling  and  bending  machines,  flanging  and  forging  presses, 
hydraulic  riveters,  punches,  shears,  steam  hammers  and  forges, 
heating  and  annealing  furnaces,  for  various  purposes.  Lathes,  drill 
presses,  boring  mills,  and  other  machine  tools  are  used.  Special 
machines  and  equipment,  designed  and  built  by  the  Heine  Ojmpany, 
are  employed  for  various  purposes  such  as  for  accurately  reaming 
rivet  and  tube  holes.  The  larger  electrically  driven  machines  have 
individual  motors,  while  the  smaller  machine-tools  are  belted  to 
motor-driven  line-shafts. 

Page  20  shows  a  heavy  flanging  press  and  one  of  the  large  steam 
hammers  in  the  St.  Louis  plant.  Portable  hydraulic  riveters  are  useil 
for  some  operations,  such  a.s  riveting  waterlegs  to  the  drums, 
shown  on  page  24.  Hydraulic  "bull'  riveters,  page  26,  are  installed 
in  lowers  equipped  with  high  overhead  cranes  for  handling  boiler 
drums  and  other  long  parts.  Page  22  shows  part  of  the  machine 
shop  at  Phoenixville.  Page  30  shows  the  testing  floor  at  St.  Louis. 
In  the  sheet  iron  department,  parts  not  subjected  to  pressure  are 
fabricated,  such  as  infernal  mud  drums,  deflection  plates,  boiler 
fronts  and  breechings. 

Ten  Characteristics  of  Heine  Boilers 

CERTAIN  features  of  design  and  construction  insure  continuous, 
satisfactory  service  from  all  types  of  Heine  Boilers.   They  can 
be  summarized  as  follows: 

1.  IVorkmoKship.  Heine  Boilers  are  built  by  expert  workmen, 
in  modern  shops  equipped  particularly  for  the  production  of  high- 
class  water-tube  boilers.  The  materials  and  the  construction  of 
every  Heine  Boiler  conforms  with  the  rules  and  regulations  issued 
by  the  highest  authorities.  This  means  that  Heine  Boilers  comply 
with  the  best  standards  as  regards  safety,  economy  and  durability. 


ib.  Google 


D,B,i,.ab,GoOglc 


HEINEPRACTICE  19 

2.  Strength.  The  construction  of  the  waterlegs  or  headers, 
flanged  plates  with  ample  staybolts,  is  approved  and  widely  accepted 
practice.  It  has  given  the  greatest  satisfaction  under  such  severe 
service  as  in  the  locomotive  boiler  and  the  Scotch  marine  boiler, 
and  is  highly  commended  by  the  foremost  boiler  authorities  of  all 
countries.  It  avoids  welding,  and  permits  better  general  design  and 
accessibility,  closer  tube  spacing,  easier,  freer  circulation  and  less 
punishment  of  material  during  construction  than  do  any  of  its  sub- 
stitutes. The  unusual  strength  of  structure  obtained  by  the  direct 
connection  of  the  drum  and  headers,  virtually  makes  the  Heine  a 
"one-piece"  boiler,  well  qualified  for  prolonged  hard  service.  The 
first  Heine  boiler  built  was  used  continuously  for  35  years,  after 
which  period  an  inspection  by  The  Fidelity  and  Casualty  Company 
showed  that  it  was  still  in  proper  working  condition. 

3.  Overload  Capacity.  Heine  Boilers  are  adapted  for  operation 
at  high  overloads,  because  of  the  unusual  provision  for  rapid 
circulation,  the  large  combustion  space  and  the  method  of  baffling. 

4.  Water  Purification.  In  the  Heine  Boilers  a  large  proportion 
of  the  scale-forming  impurities  in  the  feed-water  are  deposited  in 
the  internal  mud  drum,  and  are  thus  prevented  from  accumulating 
on  the  heating  surfaces.  The  ordinary  mud  drum  is  simply  a  recep- 
tacle for  the  collection  by  gravity  (even  this  is  hindered  by  the 
water  circulation)  of  impurities  precipitated  within  the  boiler. 
With  the  Heine  internal  mud  drum  the  new  feed-water  must  be  at 
least  partly  purified  before  it  enters  the  water  circulating  in 
the  boiler.  The  solids  deposited  are  not  hardened  by  heat,  but 
remain  in  the  form  of  a  sludge,  which  can  be  easily  blown  off. 

5.  Free  Circulation  and  Dry  Steam.  These  are  attained  in  the 
standard  Heine  Boiler  by  the  use  of  spacious  headers  at  each  end 
of  the  tube  nest,  which  are  connected  to  the  drum  by  large  throat 
passages.  The  generated  steam  ba.s  ample  room  to  escape  without 
pulling  water  along.  In  the  cross  drum  boiler,  free  steaming  ability 
is  promoted  by  a  device  in  the  upper  part  of  the  rear  box  header, 
which  effects  a  primary  separation  of  the  steam  and  water.  The 
return  water  circulation  is  along  the  upper  tubes  of  the  main  bank 
The  steam  passes  along  the  horizontal  tubes  and  the  final  separation 
takes  place  in  the  cross  drum. 

6.  Tube  Design.  Straight  tubes,  as  used  in  the  Heine  Boiler, 
are  the  easiest  to  clean,  install,  examine,  and  renew ;  they  give  max- 
imum efficiency  and  the  best  circulation. 

7.  Healing  Surface.  The  gases  flow  parallel  with  the  tubes  in 
the  Heine  Boiler.  After  entering  the  nest  of  tubes,  they  do  not 
leave  it  until  they  are  discharged  to  the  breeching.  This  method  of 
pfas  passage  has  been  proved  to  give  the  highest  rate  of  heat  trans- 
mission with  the  least  draft  loss. 


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HEINE    PRACTICE  21 

8.  Combustion  Chamber.  This  is  of  ample  size  so  that  the 
gases  are  thoroughly  mixed  and  burned  before  they  strike  the  cool 
heating  surface.  The  lower  baffling  forms  the  roof  of  a  reverbera- 
tory  chamber,  providing  ideal  conditions  for  perfect  combustion, 

9.  Floor  Space.  The  compact  arrangement  of  heating  surface 
due  to  the  close  tube  spacing,  lessens  the  floor  space  and  head  room 
re<iuired.  Any  number  of  Heine  Boilers  can  be  set  in  a  single 
battery ;  alleyways  are  unnecessary,  so  that  the  saving  of  space  is 
large.  Boilers  set  in  a  solid  battery  are  immune  from  most  of  the 
losses  by  air  infiltration  and  radiation. 

10,  Cleaning  Facilities  The  outsides  of  the  tubes  are  cleaned 
quickly  and  thoroughly  by  a  soot  blowing  system  operated  from  the 
front  and  back,  and  provided  with  every  boiler.  Side-wall  dusting 
doors  are  unnecessary,  and  their  absence  greatly  reduces  the  air  in- 
Icakage,  insuring  a  high  percentage  of  CO^  with  consequent  fuel 
economy.  Since  straight  tubes  only  are  used,  the  inside  surfaces 
are  easily  inspected  and  cleaned  through  the  handholes  in  the  water- 
legs.  In  the  cross  drum  boiler,  the  tubes  and  nipples  connecting 
the  drum  with  the  box  headers  are  quickly  cleaned  through  the 
manholes  provided. 


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T 


HEINrt    PRACTTCE  23 

Heine  Service 

HE  Heine  Safety  Boiler  Company  maintains  an  Engineering  De- 
partment for  the  assistance  of  its  clients  in  the  arrangement  and 
improvement  of  new  and  existing  boiler  plants.  Experience  in  the 
installation  of  boilers  in  plants  of  widely  diversified  size  and  type, 
qualifies  us  to  recommend  the  best  method  of  procedure  to  meet  the 
conditions  prevalent  in  any  particular  plant.  This  service  covers 
not  only  boiler  and  furnace  design  for  the  various  types  of  fuel  and 
operating  conditions,  but  includes  recommendations  as  to  building 
design,  coal  and  ash  handling  equipment,  piping,  stacks,  breech- 
ings,  etc. 

The  Research  Department,  besides  being  engaged  upon  new  de- 
velopments in  boiler  engineering,  is  constantly  rendering  assistance 
in  such  problems  as  the  efficient  handling  and  combustion  of  all 
kinds  of  staple  and  reftise  fuels,  special  furnace  and  boiler  settings, 
baffling  to  meet  unusual  conditions,  recovery  of  heat  from  waste 
gases,  chimneys,  draft,  etc. 

The  Library  contains  a  copy  of  almost  every  domestic  and 
foreign  work  on  power  plant  engineering,  besides  a  large  collsction 
of  references  on  every  conceivable  phase  of  boiler  practice.  This 
information  is  at  the  disposal  of  our  clients. 

The  continuous  satisfactory  performance  of  every  Heine  boiler 
is  our  vital  concern  as  well  as  that  of  the  customer.  Our  interest  in 
the  boiler  does  not  cease  when  it  has  left  our  shop.  A  Trouble  De- 
partment is  maintained,  composed  of  technically  and  practically 
trained  engineers  whose  principal  duties  are  to  assist  our  clients  in 
overcoming  any  difficulties  which  may  occur  in  boiler  operation. 
This  service  includes  snch  investigations  as  the  study  of  firing 
methods,  scale  formation  or  priming  due  to  poor  water  conditions, 
boiler  inspection,  boiler  testing,  etc.,  etc. 

There  are  sixteen  branch  offices  and  three  distributing  ware- 
houses for  repair  parts.  The  production  of  parts  in  large  quantities 
by  modern  manufacturing  methods,  the  storage  of  patterns,  etc, 
results  in  the  supply  of  renewals  at  small  cost ;  and  an  efficient  system 
of  records  of  every  I-Teine  boiler  since  the  first,  insures  prompt 
shipment. 

Standard  Longitudinal  Drum  Boilers 

THE  standard  Heine  Boiler,  shown  on  pages  8  and  14,  consists  of 
a  cylindrical  shell  or  drum  to  which  box-shaped  headers  (water- 
legs)  are  riveted  at  each  end.  These  waterlegs  are  connected  by  the 
main  nest  of  tubes. 


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HEINE    PRACTICE  25 

The  drum  consists  of  three  sheets,  riveted  in  accordance  with 
the  approved  rules.  It  varies  in  diameter  from  30  to  48  in.  and 
in  length  from  about  17  to  22  ft.,  according  to  the  horsepower 
required.  The  longitudinal  seams  are  of  the  double-strap  butt-joint 
type,  while  girth  or  circumferential  seams  are  of  the  lap-joint  type, 
.single  or  double  riveted.  The  design  of  the  riveting  depends  upon 
the  pressure  to  be  carried. 

The  heads  are  dished  to  a  radius  equal  to  the  diameter  of  the 
shell,  and  thus  require  no  internal  staying.  A  flanged  manhole,  pro- 
vided with  a  pressed  steel  cover,  forms  part  of  the  rear  head.  The 
main  ."^team  outlet  and  the  safety  valve  are  attached  to  pressed  steel 
saddles,  riveted  to  the  top  of  the  drum  near  its  front  end. 

The  material  for  both  wateriegs  and  drums  is  the  be-st  firebox 
steel  plate,  made  especially  to  Heine  specifications  and  tested  before 
shipment 


Hollow  Staybolti  of  Heavy  GauKC  Steel  Tubing. 

The  waterless  are  connected  to  the  bottom  of  the  drum  near  each 
end  by  a  throat  opening,  page  21,  braced  by  forged  steel  throat  stays. 
page  46,  which  are  riveted  across  when  the  wateriegs  are  attached. 
The  wateriegs  consist  of  two  plates — the  tube  sheet  and  the  hand- 
hole  sheet.  These  plates  are  machine-flanged  and  are  joined  by  a 
narrow  plate  similar  to  a  butt-strap.  The  wateriegs  are  stayed  by 
hollow  staybolts  made  of  carefully  tested  mild  steel  tubing;  these 
are  screwed  into  tapped  holes  in  the  two  plates,  and  the  projecting 
ends  upset  from  the  outside.  The  tube  holes  and  handholes  are 
located  accurately  and  bored  to  exact  diameters.  The  wateriegs 
are  bnilt  complete  and  then  hydraulically  riveted  over  the  throat 
openings. 

The  handholes  are  round,  except  a  few  at  the  top  and  bottom. 
which  are  oval  and  are  used  for  the  introduction  of  the  round  plates 
into  the  wateriegs.  The  handholes  are  closed  in  three  different 
ways;  by  strong  cast  iron  plates;  by  drop-forged  steel  plates;  or 
by  the  Key  pressed  steel  handhole  caps.  All  of  these  are  inserted 
from  the  inside  so  that  the  steam  pressure  tends  to  tighten  them, 
and  does  not  loosen  them  as  in  the  case  of  plates  applied   from 


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HEINE    PRACTICE  27 

the  outside.  The  plates  are  held  in  position  by  bolts  and  yokes,  the 
latter  bearing  against  the  outside  of  the  handhole  sheet.  Gaskets  are 
required  with  the  plates,  but  not  with  the  Key  caps  which  are  rolle<I 
in  slightly  tapered  holes  so  that  the  pressure  within  the  boiler  tends 
to  hold  them  more  tightly. 

Lap-welded  steel  tubes  are  supphed  with  the  Heine  Boiler,  but 
charcoal  iron  or  seamless  steel  tubes  can  be  supplied  as  optional 
etiuipment.    The  tubes  extend  between  the  two  waterlegs,  and  are 


(b) 


Hflndhole  Closurea.     (n)  Cast  Iron;    (b)  Drop  Forged  Steel; 
(c)  Key  Premed  Steel  Handhole  Caps. 


expanded  into  the  tube  sheet  by  roller  expanders.    The  tube  ends 
are  slightly  flared  to  increase  the  holding  power. 

The  baffling  on  Heine  boilers  is  varied  somewhat  according  to 
the  conditions  of  operation.  Page  8  shows  the  single-pass,  and 
page  12  the  two-pass  system.  The  simple.st  arrangement  is  to  place 
the  baffle  tile  on  the  lowest  row  of  tubes,  and  a  second  baffle  on 
the  second  row  of  tnbes  from  the  top,  giving  a  single  pass  of  the 
pases  through  the  tube  nest.  The  lower  baffle  may  be  placed  on  the 
third  row  of  tubes  from  the  bottom,  thus  giving  a  partial  pass 
through  the  three  lower  rows,  and  a  complete  pass  through  the 
remainder  of  the  nest  of  tubes.  In  still  another  arrangement  one 
baffle  is  placed  on  either  the  first  or  third  row  of  tubes  from  the 


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HEINE    PRACTICE  29 

bottom,  and  another  baffle  introduced  a  little  more  than  half-way 
up  the  height  of  the  tube  nest,  thus  giving  the  products  of  combus- 
tion two  full  passes  through  tlie  nest  of  tubes. 

The  baffle  tiles  are  designed  to  rest  on  or  between  the  tube 
rows.  The  bottom  row  is  formed  of  specially  shaped  fire-clay  tile, 
while  the  upper  and  middle  rows  are  either  fire-clay  or  cast  iron 
shapes,  according  to  conditions, 

Heine  Superheaters 

THE  standard  Heine  Superheater,  page  34,  is  placed  at  the  side 
of  the  drum  toward  the  front.  It  may  be  single — on  one  side, 
or  in  two  parts — one  on  each  side  of  the  boiler.  One  or  two  units 
are  used,  according  to  the  capacity  and  degree  of  superheat  required. 

The  superheater  consists  of  a  header  box  divided  horizontally 
into  three  compartments,  and  with  U-tubes  inserted  into  one  side 
and  bridging  the  partitions.  Steam  from  the  boiler  enters  the  lower 
compartment,  passes  through  the  lower  nest  of  tubes  into  the  middle 
compartment,  then  through  the  upper  nest  of  tubes  into  the  upper 
compartment,  from  which  it  issues.  These  passages  effect  a  thor- 
ough mixture  of  the  steam  and  ensure  a  uniform  temperature. 

A  small  flue  built  in  the  side-wall  carries  part  of  the  hot  gases 
direct  from  the  furnace  into  the  rear  of  the  superheater  chamber. 
After  making  a  first  upward  pass  over  the  outermost  ends  of  the 
tubes,  the  gases  make  a  second  downward  pass  over  the  rest  of  the 
tube  surface;  and  after  leaving  the  superheater  chamber  pass  along 
the  boiler  drum,  thus  giving  up  the  remainder  of  their  available  heat. 

The  header  box  is  built  with  one  seam  and  one  row  of  rivets, 
the  caulking  edge  being  to  the  front.  The  two  sheets  of  the  box  are 
braced  by  hollow  staybolts.  Access  to  the  interior  is  gained  by 
handholes  closed  by  inside  plates,  which  are  placed  opposite  the 
tubes.     The  U  tubes  are  Ij^-in.  diameter,  of  seamless  steel. 

The  superheater  chamber  is  of  brickwork,  with  a  firebrick  roof 
carried  by  T-bars.  The  front  of  the  superheater  is  closed  in  by 
doors,  which  prevent  radiation  and  give  access  to  the  header  box. 

A  damper  in  the  outlet  of  the  superheater  chamber  controls  the 
flow  of  gases;  there  is  no  danger  of  its  becoming  overheated,  since 
the  gases  do  not  come  in  contact  with  it  until  they  have  been  cooled 
by  passing  through  the  superheater.  The  damper  is  regulated  by 
hand  from  the  front  of  the  boiler,  or  an  automatic  thermostatic 
control  regulates  the  superheat  to  within  5  deg.  above  and  below 
the  temperature  desired.  A  full  and  illustrated  explanation  of  the 
temperature  control,  as  well  as  a  discussion  of  the  dangers  result- 
ing from  uncontrolled  and  excessive  superheats,  is  given  in  "Super- 
heater Logic,"  which  also  contains  a  complete  description  of  the 
construction  of  the  superheater.  This  Heine  publication  is  mailed 
on  rec|uest. 


ib.  Google 


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HEINE    PRACTICE  31 

No  scale  is  deposited  in  the  tubes  because  flooding  of  Heine 
superheaters  is  unnecessary,  Qosing  the  damper  isolates  the  tubes 
from  the  hot  gases,  and  then  only  saturated  steam  is  dehvered. 

The  superheater  is  built  complete  and  tested  before  shipment,  so 
that  it  is  ready  for  erection  upon  arrival. 

The  arrangement  is  such  that  it  can  be  cleaned  easily  and  thor- 
oughly while  in  operation,  insuring  eflFiciency,  close  temperature 
regulation,  and  economy.  The  tubes  are  smooth  and  therefore  acai- 
mulate  very  little  soot ;  this  is  easily  removed  by  a  steam  lance 
passed  through  the  hollow  staybolts,  or  by  a  permanent  soot  blower 
similar  to  that  on  the  boiler. 

Adaptability  of  Heine  Boilers 

HEINE  Boilers  suit  the  conditions  and  plans  of  any  power  plant. 
There  are  no  doors  in  the  sidewalls  and  no  aisles  are  required 
between  boilers,  because  all  cleaning,  inspection  and  tube  renewals 
are  done  from  the  front  and  back.  Consequently,  any  number  of 
boilers  may  be  set  in  single  battery  and  this  materially  reduces  the 
cost  of  brickwork.  With  center-retort  and  side-feed  stokers, 
hand  firing,  oil  or  gas  firing,  the  space  required  is  greatly  reduced 
as  is  seen  by  comparing  with  layouts  of  other  standard  boilers ;  and 
this  lowers  the  cost  of  the  boiler  house.  Such  plants  are  generally 
simplified  as  there  are  no  aisles  to  bridge,  and  this  also  applies  to 
piping  arrangements  Operating  efficiency  is  noticeably  increased 
owing  to  the  shorter  flues,  elimination  of  sidewall  radiation  and 
infiltration  of  air,  and  avoidance  of  air-leakage  through  sidewall 
cleaning  and  dusting  doors  and  the  numerous  cracks  inevitably 
starting  from  them. 

Heine  boilers  are  running  satisfactorily  with  stokers  and  mechan- 
ical furnaces  of  every  standard  type.  All  kinds  of  fuel  are  being 
successfully  burned  under  them — fuel  oil,  gas,  pulverized  coal,  tan 
bark,  bagasse  and  sawdust.  They  are  giving  excellent  service  under 
the  most  varied  conditions  of  power  production,  manufacture  and 
process,  where  steam  is  required  either  steadily  or  in  heavy  and 
irregular  drafts. 

The  unusual  adaptability  of  Heine  Boilers  for  the  utilization  of 
waste  heat  from  kilns,  stills,  metallurgical  furnaces  and  other  pro- 
cesses is  discus.sed  in  Chapter  4. 

Installation  of  Heine  Boilers 

HEINE  Boilers  of  500  H.P.  or  less  are  shipped  completely  assem- 
bled, page  36,  while  the  larger  sizes  are  knocked  down  for 
shipment,  page  38.  For  export,  they  are  shipped  in  separate  parcels, 
containing  the  tubes,  the  central  part  of  the  drum,  and  the  waterlegs 
with  short  section  of  drum  attached.  The  cross  drum  boilers  can 
be  shipped  entirely  knocked  down,  page  40,  the  headers  and  drum 


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HEINE   PRACTICE  33 

being  complete  in  all  respects  so  that  assembling  consists  only  of 
expanding  the  tubes. 

When  set  up  ready  for  service,  the  Heine  Boiler  inclines  upward 
from  rear  to  front  at  a  slope  of  one  in  twelve.  The  front  end  of  the 
boiler  is  carried  by  heavy  cast  iron  columns.  For  hand-firing,  the 
waterleg  rests  directly  on  the  columns ;  while  for  stoker  firing, 
brackets  riveted  to  the  waterlegs  are  supported  on  the  columns,  or 
the  front  of  the  boiler  is  carried  on  an  overhead  support.  The  rear 
end  rests  on  rollers  bearing  on  iron  plates  which  are  set  in  the  top 
of  the  low  brick  wall  forming  part  of  the  setting.  These  rollers 
permit  expansion  and  contraction  and  avoid  injurious  strains. 

On  each  side  of  the  boiler  is  a  solid  brick  wall  lined  with  fire- 
brick and  carried  to  the  height  of  the  ornamental  front.  Returns 
are  made  at  both  front  and  rear,  following  the  curvature  of  the 
drum  and  waterlegs,  the  weight  of  the  brickwork  being  carried 
by  metal  supports.  The  space  tetween  these  supports  and  the  boiler 
is  filled  with  asbestos  fiber,  which  prevents  the  ingress  of  air.  The 
space  prevents  any  displacement  of  brickwork  due  to  expansion  and 
contraction  of  the  boiler,  since  the  walls  are  supported  independently 
and  slightly  away  from  the  boiler.  The  brickwork  is  tied  together 
by  longitudinal  and  transverse  anchor  bolts  secured  at  each  end  of 
the  setting  and  at  several  places  on  the  sides  to  substantial  rolled 
steel  buckstays.  The  top  of  the  setting  is  closed  on  each  side  of  the 
drum  by  cast  iron  plates,  which  rest  on  the  sidewalk  and  on  a  tile- 
bar  carried  by  brackets  attached  to  the  drum.  Openings  are  left 
at  the  rear  for  the  exit  of  the  gases.  A  brick  arch  is  built  over 
•he  drum  to  prevent  radiation,  and  is  of  firebrick  in  the  uptake. 

Over  the  uptake  openings,  and  supported  by  the  boiler  walls,  is 
placed  a  breeching  hood  of  suitable  shape  to  connect  with  the 
breeching. 

The  cast  iron  fire  fronts  carrying  the  fire  and  ash  door  frames 
are  bolted  to  the  supporting  columns,  and  a  substantial  firebrick  wall 
is  built  inside  to  prevent  overheating.  The  fire  fronts  support  the 
upper  ornamental  front,  page  42.  Large  doors  are  provided  at  both 
front  and  back  for  access  to  the  waterlegs. 

Stationary  grates  are  ordinarily  furnished,  but  shaking  grates  or 
any  other  form  of  furnace  or  stoker  can  be  substituted.  Stokers  are 
frequently  set  directly  under  Heine  Boilers  owing  to  the  large  com- 
bustion space,  and  no  more  floor  space  is  then  occupied  than  with 
hand-firing;  but  it  is  often  advantageous  to  use  an  extension  furnace 
or  Dutch  oven.  The  Dutch  oven  is  generally  the  best  arrangement 
for  burning  sawdust,  shavings,  tan  bark,  bagasse  and  similar  fuels, 
owing  to  the  large  furnace  chamber  desirable  and  the  convenience 
of  the  top-feed.  Methods  of  applying  stokers  and  furnaces  are 
shown  in  Chapters  4  and  5. 


ib.  Google 


Heine  Standard  Superheater. 


ib.  Google 


HEINE    PRACTICE  35 

Operation  of  Heine  Boilers 

THE  water  circulation  and  steam  separation  in  the  Heine  Boiler 
are  absolutely  definite.  The  capacious  headers  and  large  throat 
openings  allow  a  freedom  of  flow  unattainable  with  sectional 
headers.  The  throat  openings  are  from  two  to  four  times  the  area 
of  the  tubes  which  connect  sectional  headers  to  their  drums.  The 
resistance  at  the  entrance  of  these  tubes  and  of  the  zig-zag  path 
along  sectional  headers  is  a  further  obstruction  to  circulation,  Heine 
box-headers  are  common  to  all  the  tubes,  and  water  enters  the  tubes 
round  their  whole  circumference,  whereas  side-entry  is  cut  off  in 
sectional  headers.  The  slope  of  the  Heine  drum  provides  deep  water 
at  the  rear  for  the  effective  supply  of  the  back  header. 

The  water  rises  through  the  large  throat  into  the  Heine  drum  at 
a  sufficiently  low  velocity  to  allow  of  efficient  separation  of  the 
steam  by  the  deflector  plate ;  while  the  steam  and  water  is  shot 
with  considerable  violence  from  the  single  tubes  of  sectional  headers, 
making  the  drying  of  steam  uncertain. 

The  water  surface  in  the  drum  is  more  than  ample,  for  steam 
is  not  disengaged  from  it  as  in  tank  and  fire-tube  bailers.  What 
little  circulation  there  is  in  fire-tube  boilers,  is  entirely  haphazard, 
and  the  water  surface  must  be  large  because  the  steam  is  disengaged 
at  any  point.  In  the  Heine  Boiler  the  circulation  is  vigorous  and 
orderly,  and  the  steam  is  separated  from  the  water  by  a  properly 
arranged  deflector  at  a  definitely  established  point  over  the  front 
throat  passages,  page  46.  The  deflector  plate  throws  down  the  water 
and  allows  the  steam  to  pass  quietly  into  the  steam  space  above ;  it 
then  enters  the  dry  pipe  connected  to  the  steam  outlet. 

A  salient  feature  of  the  Heine  Boiler  is  the  internal  mud  drum, 
in  which  the  feed-water  is  partly  purified  and  heated  to  the  boiling 
point  before  it  enters  the  water  in  circulation.  The  feed-water 
pipe  enters  through  the  top  of  the  drum  and  passes  down  to  the 
front  end  of  the  mud  drum.  The  mud  drum  is  entirely  submerged ; 
and  as  the  entering  water  is  colder  and  therefore  heavier  than 
the  water  already  inside,  it  travels  along  the  bottom  and  becomes 
heated  gradually.  The  mud  drum  is  large  enough  to  permit  of  such 
slow  motion  of  the  water  that  the  dissolved  impurities  thrown  down 
at  steam  temperatures  have  time  to  be  deposited,  together  with  mat- 
ter carried  in  suspension.  As  the  water  becomes  heated,  it  rises  and 
finally  flows  in  a  thin  sheet,  thrgugh  the  opening  in  the  top  of  the 
front  end  of  the  drum,  into  the  circulation  system.  It  is  therefore 
possible  to  drive  the  Heine  Boiler  at  heavy  loads  with  very  cold  feed- 
water.  As  the  matter  deposited  is  not  subjected  to  fire  tempera- 
tures, it  does  not  tend  to  become  baked  and  hard,  but  remains  as  a 
sludge  easily  blown  out  through  the  pipe  at  the  rear  of  the  drum. 


ib.  Google 


ibiGoogle 


HEINE  PRACTICE  37 

Because  of  the  internal  mud  drum,  the  Heine  Boiler  works  much 
more  satisfactorily  than  any  other  boiler  when  only  cold  and  dirty 
water  are  available.  But  it  is  always  more  economical  to  treat 
impure  water  before  feeding  it  into  the  boiler,  and  to  pre-heat  it 
with  waste  steam  or  waste  hot  gases. 

The  boiler  is  drained  through  a  valve  at  the  bottom  of  the  rear 
waterleg.  The  steam  connection  of  the  water  column  is  made  at 
the  top  of  the  front  head,  and  the  water  connection  at  the  top  of  the 
waterleg.  The  pressure  gage  is  attached  to  the  middle  of  the  orna- 
mental front  and  piped  from  the  water  column  connection. 

The  gases  of  combustion — whatever  type  of  furnace  or  stoker 
is  used — pass  over  the  bridge  wall  into  a  large  combustion  chamber. 
The  bridge  wall  is  low  enough  to  provide  ample  area  between  its 
top  and  the  tubes.  The  large  combined  capacity  of  the  furnace 
and  combustion  chambers  is  one  of  the  outstanding  merits  of  the 
Heine  Boiler.  Plenty  of  time  and  space  is  provided  for  the  thorough 
mixture  and  complete  combustion  of  the  gases  before  they  come 
in  contact  with  the  comparatively  cool  heating  surfaces.  This  pro- 
vision for  complete  combustion,  and  the  consequently  improved 
efficiency  and  reduction  of  smoke  has  been  proved  so  valuable  that 
the  Heine  method  has  replaced  the  vertical  baffling  of  many  hori- 
zontal water-tube  boilers  and  has  even  replaced  the  method  of 
baffling  of  some  types  of  vertical  water-tube  boilers. 

In  Heine  Boilers,  the  gases  travel  parallel  to  the  tubes,  except 
when  entering  and  leaving  the  tube  bank.  This  parallel  flow  is  used 
whether  the  gases  make  one  or  more  passes.  With  parallel  flow,  the 
gases  completely  encircle  the  tubes.  When  the  gases  flow  across  the 
tubes,  as  in  cross-  or  vertically-baffled  boilers,  a  dead  pocket  occurs 
on  the  "down-stream"  side  of  each  tube.  This  effect  can  be  seen 
by  watching  the  almost  stagnant  water  at  the  down-stream  side  of 
the  piers  of  any  bridge  crossing  a  swiftly  flowing  river.  Owing 
to  the  close  tube  spacing  possible  by  the  rational  design  of  Heine 
header,  the  gases  are  broken  up  into  smaller  streams  than  is  usual, 
so  that  the  whole  volume  of  gas  is  brought  into  intimate  contact 
with  the  tube  surface.  That  more  efficient  heat  transmission  is 
attained  with  parallel  flow  than  with  cross  flow,  has  been  frequently 
demonstrated  in  tests  of  cross-flow  boilers  that  have  been  changed 
to  parallel-flow. 

It  is  important  that  the  gases  should  be  kept  in  contact  with  the 
heating  surface  until  all  the  available  heat  is  absorbed.  In  all  cross- 
or  vertically-baffled  boilers,  however,  the  gases  are  twice  taken 
entirely  away  from  the  tubes,  where  they  waste  heat  by  radiation.  In 
addition  to  the  evident  waste  of  heat,  the  hot  gases  from  the  first 
pass  flow  along  the  bottom  of  the  drum  causing  ebullition  in  the 
wrong  place,  the  avoidance  of  which  should  be  one  of  the  main 
advantages  of  the  water-tube  boiler.     Another  advantage  of  the 


ib.  Google 


ibiGoogle 


HEINE   PRACTICE  39 

water  tube  boiler — that  of  keeping  hot  gases  away  from  the  drum 
and  from  riveted  joints — is  absent  in  cross  baffled  boilers.  In  the 
Heine  Boiler,  the  gases  are  confined  to  the  tube  bank  until  they 
have  parted  with  nearly  all  of  their  available  heat.  Not  until  then 
do  they  come  in  contact  with  the  drum ;  consequently  the  last  of  their 
useful  heat  is  given  up  without  disturbing  the  quiet  flow  of  solid 
water  to  the  rear. 

The  construction  of  the  Heine  Boiler  combines  sturdiness  and 
resiliency.  Water  is  boiled  and  steam  generated  in  the  bank  of  tubes 
and  not  in  the  drum  or  shell.  The  gases  are  kept  where  they  belong 
— among  the  tubes — until  discarded  to  the  uptake.  The  circulation 
path  is  large  and  unrestricted,  making  the  flow  of  water  and  steam 
slow  enough  for  efficient  separation — or  for  dry  steam  and  a  solid 
water  stream. 


Soot  BlovvinB  System,  Side  Blevation. 


ib.  Google 


ibiGoogle 


HEINE    PRACTICE  41 

Cleaning  of  Heine  Boilers 

ALL  cleaning — both  inside  and  out — is  performed  from  the  front 
and  rear.  There  are  no  openings  in  the  sidewalls,  or  aisles 
between  boilers. 

Soot  and  dust  are  blown  from  the  tubes  by  a  soot  blower, 
which  is  provided  with  every  Heine  Boiler.  It  consists  of  a 
series  of  small  nozzles  which  pass  through  the  hollow  stay-bolts,  and 
which  are  supplied  from  permanent  headers,  so  that  the  only  manual 
labor  required  is  to  open  and  close  the  valves.  The  jets  of  steam 
issuing  from  the  main  nozzles  create  an  intense  momentary  draft 


Soot  Blowini;  Syitem. 

D,g,tze:Jbi  Google 


Standard  Fire  Front  of  Heine  Crosa  Drum  Biriler. 


i,  Google 


HEINE    PRACTICE  43 

which  effectively  dislodges  the  soot  and  dust  and  carries  it  to  the 
uptake.  The  auxiliary  jets  are  so  located  as  to  stir  up  accumula- 
tions on  the  baffling  and  in  all  corners.  This  work  is  done  in  a  few 
minutes,  generally  during  the  noon  rest,  or  just  before  or  after 
closing  down  at  night.  It  is  so  easy  as  to  be  entirely  out  of  com- 
l>arison  with  the  old-fashioned  "steam-lance,"  whose  use  is  naturally 
neglected  whenever  possible.  Thorough  cleaning  is  immediately 
profitable  as  may  be  seen  by  the  quick  drop  in  temperature  of  the 
exit  gases. 

Cleaning  doors  are  provided  on  each  side  of  the  drum  so  that 
accumulations  of  dust  and  soot  can  be  easily  and  quickly  removed 
from  the  space  over  the  upper  baffle  beneath  the  drum.   The  com- 
bustion chamber  is  cleaned  through  a  door  in  the  wall  under  the 
.  rear  waterleg. 

The  interior  of  the  drum  is  thoroughly  inspected  through  the 
manhole  in  the  rear  head,  which  also  permits  of  attention  to  the 
mud-drum,  deflection  plale,  etc. 

The  inside  of  the  tubes  is  washed  by  a  stream  of  water  directed 
through  some  of  the  handholes.  Only  a  few  of  the  handholes  need 
be  opened  for  this  purpose,  since  each  gives  sufficient  access 
to  four  or  five  of  the  surrounding  tubes.  In  scraping  the  tubes, 
however,  each  handhole  must  be  opened  to  admit  the  scraper, 
although  in  both  this  and  the  washing  process  the  handholes  at  one 
end  only  are  opened. 

As  only  straight  tubes  are  used,  every  part  of  the  boiler  can  be 
reached,  properly  and  quickly  cleaned,  and  visually  inspected,  so 
that  there  is  absolutely  no  uncertainty  as  to  its  condition. 

Renewing  tubes  is  done  from  the  outside  as  in  cleaning  tubes, 
the  men  standing  erect  and  working  comfortably  and  quickly.  The 
inside  of  the  box-waterleg  is  easily  cleaned  and  inspected,  because 
alt  the  hand  holes  give  light  and  access  to  one  space. 

Heine  Cross  Drum  Boiler— Land  Service 

THE  Heine  Cross  Drum  Boiler  for  land  service,  page  44,  consists 
of  two  box  headers  carrying  a  nest  of  inclined  tubes  and  of  a 
drum  placed  above  and  across,  slightly  to  the  rear  of  the  front  or 
lower  header.  The  drum  is  connected  to  the  top  of  each  header  by  a 
row  of  tubes — short,  nearly  vertical,  to  the  front  header — and  long, 
nearly  horizontal,  to  the  rear  header. 

The  main  nest  of  tubes,  with  the  headers,  form  a  virtually 
closed  or  complete  circulation  system  of  remarkably  low  resistance 
owing  to  the  capacious  headers.  The  steam  rises  in  the  rear  header, 
where  its  primary  separation  from  the  water  is  promoted  by  a 
device  at  the  upper  part.  It  then  flows  along  the  almost  horizontal 
tubes,  parting  with  most  of  the  entrained  water  by  gravity,  to 
the  final  separator  in  the  steam  drum,  where  it  is  dried  by  centri- 
fugal action  set  up  by  a  deflector.   The  water  carried  into  the  drum 


ib.  Google 


ibiGoogle 


HEINE   PRACTICE  4S 

is  returned,  together  with  the  new  feed  water,  to  the  circulation 
system  through  the  short  tubes  leading  into  the  top  of  the  front 
header.  Steam  is  drawn  from  the  ample  storage  space  through  a 
dry  pipe  extending  nearly  the  whole  length  of  the  drum  and  pro- 
vided with  small  holes  on  the  upper  side. 

This  closed  circulating  system  and  the  means  used  in  collecting 
and  drying  the  steam  while  maintaining  quiet  water  in  the  drum,  is 
the  outcome  of  exhaustive  and  prolonged  research  into  the  direction 
and  velocity  of  flow  in  the  different  rows  of  tubes.  As  a  result  the 
tubes  and  baffling  have  been  so  proportioned  and  arranged  that  the 
overload  performance  of  Heine  Boilers  of  this  type  is  acknowledged 
by  users  as  a  notable  achievement. 

The  mud-drum  is  constructed  and  operated  on  the  same  prin- 
ciple as  that  employed  in  the  longitudinal  drum  boiler,  described  on 
pages  19  and  35.  The  movement  of  the  feed-water  therein  is  very 
slow,  so  that  dissolved  impurities  which  are  thrown  down  at  steam 
temperatures  are  deposited,  as  is  matter  carried  in  suspension.  As 
the  deposit  is  not  hardened  by  exposure  to  fire  temperatures,  it 
remains  as  an  easily  blown-ofF  sludge.  Owing,  also,  to  the  slow 
movement  of  the  feed  water  in  the  mud  drum,  it  is  heated  to  the 
boiling  point  before  passing  into  the  circulation  system,  so  that 
Heine  Boilers  can  be  heavily  driven  with  cold  feed  water.  As  the 
water  issues  from  below  the  surface  in  the  mud-drum,  any  oil  accu- 
mulated does  not  enter  the  boiler  proper,  but  is  discharged  through 
the  blow-off. 

Except  in  large  boilers,  the  drum  is  made  of  a  single  sheet,  with 
longitudinal  double-strapped  butt-joints.  The  heads  are  dished  to  a 
radius  equal  to  their  diameter,  so  that  internal  staying  is  not  re- 
quired. One  head  is  generally  provided  with  a  flanged  manhole 
with  pressed  steel  cover  and  yoke;  but  when  more  than  two  boilers 
are  set  in  battery,  the  manholes  of  all  but  the  end  boilers  are  placed 
in  the  drum  proper  instead  of  in  the  head. 

A  reinforcing  plate  is  riveted  to  the  drum,  where  each  row  of 
tubes  enters.  Forged  steel  pads  are  provided  for  the  feed,  blow-off, 
and  water  column  connections,  and  pressed  steel  saddles,  page  44, 
for  safety  valve  and  main  steam  outlet — alt  shaped  to  a  snug  fit  on 
the  drum,  and  either  threaded  or  with  stud-bolts  to  fasten  the 
connections. 

The  box  headers  consist  of  two  heavy  steel  plates  with  long 
radius  flanging  at  top  and  bottom  and  with  flat  parts  formed  at  the 
proper  angle  to  allow  the  drum  tubes  to  enter  squarely ;  these  plates 
are  fully  annealed  before  assembling.  They  are  connected  by  a 
single-riveted  lap  joint,  no  butt  straps  being  required.  The  resulting 
boxes  are  closed  by  trough-shaped  end-plates,  flanged  by  hydraulic 
machinery  at  a  single  heat  to  a  close  fit,  and  riveted  to  the  side 
plates.  The  holes  in  the  tube  and  handhole  sheets  are  accurately 
located  and  bored  to  exact  diameters  to  secure  proper  angular 
relation   between  the   drum   tubes   and   those   of  the   main   bank. 


ib.  Google 


ibiGoogle 


HEINE   PRACTICE  47 

These  headers  are  stayed  by  hollow  staybolts,  page  25,  of  tested 
seamless  tubing,  which  are  screwed  into  tapped  holes  in  both  plates 
and  the  projecting  ends  neatly  upset. 

The  handholes  are  opposite  the  tube  ends  and  are  closed  by  one 
of  several  methods — cast  iron  or  drop  forged  steel  plates  and  gaskets 
making  joints  on  the  insi<le,  or  the  Key  handhole  caps  which  are 
expanded  in  and  require  no  gaskets,  page  27 . 

The  tubes  are  the  best  quality  lap-welded  mild  steel,  made  espe- 
cially to  Heine  specifications.  They  are  %Yz-va..  diameter,  secured 
by  roller  expanders  and  the  ends  flared  for  additional  strength. 

The  steam  drum  and  the  lower  header  are  usually  at  the  front  end 
of  the  boiler,  but  to  save  head  room  this  arrangement  can  be  reversed. 

The  front  of  the  boiler  is  carried  by  columns  which  are  secured 
to  heavy  lugs  riveted  to  the  header  end  plates.  These  columns  are 
made  of  any  length  to  give  the  desired  height  of  furnace.  Similar 
heavy  lugs  are  riveted  to  the  rear  header,  and  these  are  connected 
to  the  rear  columns  by  massive  suspender  bars.  This  provides  a 
flexible  support  which  allows  for  expansion  and  contraction  due  to 
temperature  changes. 

The  whole  boiler  is  enclosed  by  brick  side-walls,  the  rear  wall 
being  underneath  the  rear  header.  The  top  is  closed  by  fire-brick 
and  insulating  covering,  carried  by  T-bars  resting  on  the  side-walls. 

Casing  doors  at  front  and  back  give  access  to  the  headers  for 
cleaning  and  inspection. 

Safety  valves  of  proper  size,  a  large  high  and  low  water  alarm 
column  with  quick  acting  shut-off  device  operated  from  the  floor  by 
chains,  and  three  try  cocks,  are  provided.  A  steam  gage  is  attached 
to  the  boiler  front,  and  feed,  check  and  blow-off  valves  are  supplied 
and  located  so  as  to  be  easily  accessible  and  conveniently  manipu- 
lated. The  required  buck-stays,  cleaning  doors  and  anchor  rods  are 
supplied. 

The  soot  blower  system  applied  to  the  cross-drum  boiler  consists 
of  the  nozzles  inserted  through  the  hollow  staybolts  of  the  rear 
header.  The  main  jets  create  an  intense  momentary  draft,  which 
dislodges  the  accumulations  from  the  tube  surfaces  and  carries  them 
to  the  uptake.  Auxiliary  nozzles  are  so  located  as  to  stir  up  and 
dispose  of  any  accumulations  on  the  baffle  tiling. 


Heine  Marine  Boilers 
E  Heine  Cross  Drum  Marine  Boiler,  page  50,  is  similar  to  the 
cross  drum  boiler  for  land  service,  the  main  difference  being  that 
it  is  shorter  due  to  the  lack  of  space.  The  standard  marine  boiler 
has  V/i-vn.  tubes  throughout ;  but  for  oil-fuel,  space  is  saved  and  sat- 
isfactory results  obtained  by  the  use  of  2-in.  tubes  in  the  main  bank. 


cr 


ib.  Google 


ibiGoogle 


HEINE   PRACTICE  49 

For  low  or  medium  superheat  temperatures,  superheaters  of  the 
type  used  for  land  installations  are  fitted.  They  are  of  the  "waste- 
heat"  kind,  placed  in  the  base  of  the  uptake,  as  close  as  possible  to 
the  exit  of  the  gases  from  the  boiler.  For  higher  superheat,  the 
elements  are  passed  through  the  middle  of  the  main  tube  bank,  where 
they  are  in  contact  with  gases  of  high  temperature. 

In  ocean  service  the  feed  water  cannot  be  kept  entirely  free  from 
sea  water,  which  sets  up  electrolytic  action.  Zinc  plates  are  there- 
fore placed  in  the  drum  to  act  as  the  electro-negative  agent  and 
prevent  corrosion.  In  the  Heine  Marine  Boiler  the  United  States 
Navy  standard  is  used— ^  sq.  ft,  of  exposed  zinc  for  each  100  sq.  ft. 
of  heating  surface — and  the  zinc  plates  are  so  secured  as  to  ensure 
perfect  electrical  contact  with  the  metal  of  the  boiler.  At  the  same 
time  they  are  easily  removable.  A  pressed  steel  basket  is  provided 
to  catch  the  disintegrated  zinc. 

The  setting  consists  of  a  framework  of  rolled  steel  shapes  so 
constructed  that  the  four  main  columns — one  on  each  side  of  eacli 
box  header — are  tied  and  securely  braced  against  any  motion.  This 
framework  carries  a  steel  plate  casing  lined  with  firebrick,  non- 
conducting material,  or  a  combination  of  the  two. 

The  construction  and  operation  of  Heine  Marine  Boilers  is 
explained  more  completely  in  another  Heine  publication — Marine 
Boiler  Logic — which  is  sent  upon  request  to  those  interested. 


Standard  Boiler  Specifications 

A  NATIONAL  and  even  an  international  standard  of  steam- 
boiler  design  is  represented  by  the  Boiler  Code  formulated  in 
1914  by  the  American  Society  of  Mechanical  Engineers,  and  since 
that  time  kept  up  to  date  by  frequent  revisions.  The  value  of  the 
Code  is  indicated  by  the  fact  that  it  has  been  adopted  by  more 
than  twelve  states  in  this  country,  by  foreign  countries,  and  by 
branches  of  the  L'nited  States  Government. 

For  many  years  the  necessity  of  uniform  boiler  specifications 
has  been  recognized  both  by  makers  and  users  of  boilers.  In  1889, 
the  American  Boiler  Manufacturers'  Association  adopted  what  were 
known  as  the  Uniform  American  Boiler  Specifications.  These  speci- 
fications, which  were  revised  in  later  years,  gave  information 
relating  to  material,  construction  and  calculation  for  all  kinds  of 
boilers.  In  this  fundamental  work  Col.  E.  D.  Meier,  founder  and 
president  of  the  Heine  Safety  Boiler  Co.,  until  his  death  in  Decem- 
ber, 1914,  took  an  important  part.  Colonel  Meier  was  chairman  of  the 
committee  which  prepared  the  first  specifications  in  1898,  was  presi- 
dent of  the  American  Boiler  Manufacturers'  Association  from  1908 
to  1914,  and  was  its  secretary  for  several  years  previous  to  1908. 


ib.  Google 


Longitudinal  Section  of  Heine  Crou  Drum  Marine  Btiler. 


D,g,tze:Jbi  Google 


HEINE    PRACTICE  51 

In  1907  a  board  .was  appointed  by  the  state  of  Massachusetts  to 
prepare  a  set  of  boiler  rules.  The  members  of  this  board  repre- 
sented different  boiler  interests,  such  as  the  users,  makers,  insur- 
ance companies,  and  operating  engineers.  The  chairman  of  the 
board  was  the  chief  inspector  of  the  Massachusetts  Boiler  Inspec- 
tion Department.  The  Massachusetts  boiler  rules  were  issued  in 
1909  and  engineers  considered  that  they  represented  a  real  advance 
in  the  art.  From  a  national  standpoint,  however,  the  Massachusetts 
rules  simply  made  one  more  set  of  conditions  with  which  the  boiler 
manufacturers  and  users  had  to  comply.  A  boiler  that  is  safe  in 
Massachusetts  certainly  should  be  safe  in  any  other  state  of  the 
Union,  but  practically  every  state  (at  least  in  1911)  had  special  re- 
quirements for  boiler  construction,  and  these  were  ri^dly  enforced. 

The  remedy  for  this  condition  was  found  by  Colonel  Meier ;  he 
had  already  noticed  the  beneficial  working  of  the  Steamboat  and 
Locomotive  Inspection  Laws  under  Federal  control.  The  best  an- 
swer to  the  problem  was  to  have  the  different  states  adopt  uniform 
specifications  for  boilers,  since  a  constitutional  amendment  would 
be  required  to  put  stationary  boilers  under  Federal  supervision.  The 
ilifferent  state  legislatures  and  other  authorities  were  willing  to 
use  such  specifications,  provided  they  could  be  assured  of  their  value. 

In  1911  Colonel  Meier,  then  president  of  the  American  Society 
of  Mechanical  Engineers,  suggested  that  a  committee  of  the  Society 
"formulate  standard  specifications  for  the  construction  of  steam 
boilers  and  other  pressure  vessels  and  for  the  care  of  same  in 
service."  This  committee  came  into  existence  on  Sept.  15,  1911,  and 
was  instructed  to  formulate  a  model  engineers'  and  firemen's  license 
law,  a  model  boiler  inspection  law,  and  a  standard  code  of  boiler 
rules.  Its  first  chairman  was  John  A.  Stevens,  who  had  been  a 
member  of  the  Massachusetts  Board  of  Boiler  Rules.  The  boiler 
makers  were  represented  by  H,  C.  Meinholdt,  vice-president  of  the 
Heine  Safety  Boiler  Co.  Upon  Mr.  Meinholdt's  death  in  1913, 
Colonel  Meier  was  appointed  a  member  of  the  committee.  The 
other  members  represented  different  interests  connected  with  boiler 
operation  and  construction. 

Three  years  were  devoted  to  hearings  and  consultations.  The 
Code  was  finally  presented  at  the  Annual  Meeting  of  the  American 
Society  of  Mechanical  Engineers,  in  December,  1914,  and  on  Febru- 
ary 13,  191S,  it  was  approved  by  the  Council  of  the  Society.  In 
preparing  the  Code  every  source  of  information  was  utilized,  in 
order  that  the  boiler  situation  should  be  thoroughly  covered.  Colonel 
Meier's  original  committee  of  seven  members  was  assisted  in  the 
final  preparation  of  the  Code  by  eighteen  notable  boiler  specialists  in 
the  design,  installation  and  operation  of  boilers. 


ib.  Google 


ibiGoogle 


HEINE    PRACTICE  53 

Although  in  ill  health,  Colonel  Meier  was  interested  in  the  Code 
until  his  death.  According  to  John  A.  Stevens,  Chairman  of  the 
Code  Committee: 

"Colonel  Meier  took  a  most  active  part  in  the  formation  of 
the  A,  S.  M.  E.  Boiler  Code,  and  up  to  within  a  few  days  of 
his  death,  had  it  constantly  before  him.  It  is  one  of  the 
regrets  of  the  Committee  that  he  could  not  have  lived  to  see 
the  fruition  of  the  work  he  so  wisely  started." 

The  Boiler  Code  is  too  long  to  give  in  full  here,  but  can  be 
obtained  from  the  American  Society  of  Mechanical  Engineers, 
29  West  39th  Street,  New  York,  by  the  payment  of  fifty  cents.  The 
Code  is  divided  into  two  parts,  the  first  applying  to  new  installa- 
tions, and  the  second  to  existing  installations. 

The  Code  as  completed  is  much  more  far-reaching  than  the 
Massachusetts  Rules,  Quoting  Mr.  Stevens  again,  "It  specifies  in 
detail  the  chemical  and  physical  properties  of  all  materials  entering 
into  the  construction  of  boilers,  and  gives  rules,  formulas  and  tables 
that  have  been  checked  and  rechecked  by  men  of  national  reputa- 
tion, and  in  many  cases  verified  by  testing  laboratories;  that  is  to 
say,  in  many  cases,  rules  or  formulas  were  withheld  until  actual 
tests  in  laboratories  were  made  in  order  to  prove  the  mathematics." 
The  Committee  formulating  the  Code  has  been  made  permanent, 
and  holds  regular  meetings  for  the  purpose  of  interpreting  any 
points  on  which  questions  are  raised.  From  time  to  time  the  Code 
is  revised  to  include  the  latest  knowledge  of  steam-boiler  con- 
struction. 

The  work  of  bringing  the  A.  S.  M.  E,  Boiler  Code  into  use  is 
being  done  by  the  American  Uniform  Boiler  Law  Society,  which  is 
carrying  on  an  educational  campaign  in  the  states  that  have  not  yet 
adopted  the  Code.  The  Society  is  made  up  of  representatives  of 
the  organizations  interested  in  the  construction  or  operation  of  steam 
boilers.  In  many  states  laws  have  been  passed  creating  a  board  of 
boiler  rules.  Such  boards  are  authorized  to  adopt  the  standard 
A.  S.  M.  E.  Code,  and  to  amend  it  in  accordance  with  the  amend- 
ments made  by  the  Society. 

State  legislatures  and  authorities  move  slowly  along  engineering 
lines,  but  the  use  of  the  Code  is  increasing,  and  in  time  it  undoubt- 
edly will  be  adopted  in  every  state  of  the  Union.  At  present  "Code" 
boilers  are  required  in  certain  states,  but  in  others  boilers  built  to 
l<;ss  rigid  rules  can  be  installed. 

All  Heine  Boilers,  no  matter  in  what  state  they  are  used,  comply 
with  the  requirements  of  the  Code.  The  Heine  Company  is  also 
assisting  in  its  adoption  through  the  work  of  its  executives  on 
the  Code  Committees  of  the  American  Society  of  Mechanical  Engi- 
neers, the  American  Boiler  Manufacturers  Association  and  tfie 
American  Uniform  Boiler  Law  Society.  The  Company  believes 
that  the  Code  should  be  adopted  not  only  in  every  state  in  this 
country,  but  should  also  be  made  international  in  scope. 


ib.  Google 


ibiGoogle 


CHAPTER  2 


BOILER  RATING  AND  DESIGN 

rIE  rating  of  a  machine  should  naturally  be  expressed  in  terms  of  the 
jseful  work  done  by  the  machine.    The  useful  work  done  by  a  boiler  is 
representerl  by  the  heat  transferred  to  the  water  in  the  boiler ;  thereby 
causing  evaporation. 

In  actual  practice  boiler  pressures,  initial  steam  conditions  and  feed 
water  temperatures  vary  widely.  If  performances  are  to  be  compared, 
they  must  be  reduced  to  an  equal  basis.  The  actual  evaporation  is  therefore 
referred  to  an  equivalent  evaporation  from  a  feed  water  temperature  of 
212  deg.  into  dry-saturated  steam  at  the  same  temperature,  or  as  it  is  com- 
monly expressed,  "from  and  at  212  deg.  Fahr," 

The  heat  added  to  each  pound  of  water  under  these  conditions  will  then 
be  L  at  212  deg.  The  1915  A.  S.  M.  E.  Boiler  Code  stipulates  that  this 
quantity  is  970.4  B.  t.  u.  per  pound,  Goodenough  gives  a  slightly  higher  value 
(9?17)  which  is  probably  more  accurate. 

The  heat  actually  absorbed  by  one  pound  of  water  while  in  the  boiler  will 
be  //  —  g,  where  H  is  the  heat  content  of  the  steam  as  it  leaves  the  boiler 
— it  may  be  wet-saturated,  dry-saturated  or  superheated— and  g  is  the  heat 
of  the  liquid  at  the  lempeiature  of  the  teed  water  entering  the  boiler. 
IT      Jf  —  q 

^  =  -mj-  ti) 

gives,  therefore,  the  pounds  of  water  evaporated  from  and  at  212  deg.  and 
equivalent  to  the  actual  evaporation  of  one  pound. 

This  quantity  F  is  called  tlie  "factor  of  evaporation."  When  multiplied 
by  the  pounds  of  water  fed  to  the  boiler  for  any  given  time,  Uie  product  is 
the  equivaleilt  evaporation  from  and  at  212  deg,  expressed  in  pounds  for 
thnt  time.  This  equivalent  evaporation  is  usually  exprested,  however,  in 
pounds  per  pound  of  coal. 

Bcnler  Horse  Power 

A  boiler  horsepower  was  originally  defined  as  the  actual  evaporation 
of  30  lb.  of  water  per  hour  from  feed  water  at  100  deg.  into  dry-saturated 
steam  at  70  lb.  gage  pressure.  When  the  term  "equivalent  evaporation" 
came  into  use,  however,  it  was  applied  to  the  boiler  horsepower,  which  is 
now  defined  as  the  equivalent  evaporation  of  34.S  lb.  per  hour  from  and  at 
212  deg. 

A  formula  for  finding  this  term  would  be  expressed  thus : 


B.H.P. 


{H  —  tj)  (lb.  H,0  fed  per  hr.)  _    F  X  lb.  H.O  fed  per  hr.  (2) 
971.7  X  34.5  ~  34.5 


The  boiler  horsepower  and  the  engine  horsepower  are  in  no  way  related. 
When  the  original  boiler  horsepower  unit  was  selected  a  one  horsepower 
boiler  would  supply  a  one  horsepower  engine.  Increase  in  the  economy  of 
engines,  however,  has  changed  that  ratio  until  now  a  lOO  horsepower  boiler 
will  supply  250  engine  horsepower,  at  least. 

The  term  boiler  horsepower  Has  thus  lost  much  of  its  significance. 
Almost  any  modern  boiler  will  run  continuously  at  from  ISO  to  200  per 
cent  over  its  rating  and  for  short  periods  400  and  even  500  per  cent  have 
been  reached. 


ib.  Google 


LowerinB  Heine  Standard  Boiler  into  Hull  of  Dredge  Boat  "Texaa"  of 
The  Atlantic,  Gulf  fc  Pacific  Company.       ,  -  i 

,C-ooglc 


BOILERS  57 

Heating  Surface 

The  better  measure  of  boiler  capaci^  is  the  heating  surface.  Heating 
surface  is  that  surface  which  has  hot  gases  on  one  aide  of  it  and  water  or 
steam  on  the  other  side.  By  the  A.  S.  M.  K  code,  it  is  the  surface  "in  con- 
tact with  £re  or  hot  gases."  In  all  water-tube  boilers  and  in  most  fire-tube 
boilers  (the  common  vertical  and  Manning  types  are  exceptions)  the  whole 
surface  of  the  tubes  is  heating  surface.  Tube  heating  surface  constitutes  by 
far  the  greater  part  of  the  total,  in  any  type  of  boiler.  As  boilers  are  built,  it 
is  usually  the  most  effective  part  except  in  intemally-Sred  boilers.  Additional 
heating  surface  is  provided  in  horizontal  tubular  boilers,  by  the  shell  up  to 
the  line  where  the  setting  racks  in,  and  by  the  heads  up  to  the  same  level. 
The  inner  faces  of  the  waterlegs,  and  part  of  the  drum  shell,  in  a  Heine 
boiler  are  heating  surface. 

Formerly  10  or  12  sq.  ft.  of  heating  surface  was  allowed  per  boiler 
horsepower.  The  corresponding  rale  of  evaporation  was  usually  around  3  lbs. 
of  water  per  sq.  ft.  of  heating  surface  per  hour,  for  it  was  observed 
that  if  the  rate  of  evaporation  greatly  exceeded  3  Ibl.  per  sq.  ft.,  the 
increase  of  coat  consumption  outran  the  gain  in  water  evaporation,  and  the 
flue  gas  temperature  became  high.  In  good  modem  design,  rates  of  evapora- 
tion much  higher  can  be  secured  without  serious  sacrifice  of  efficiency. 
As  high  as  10  lb.  is  frequent  in  marine  practice.  From  A%  to  6  lb.  is 
justified  in  power  stations  carrying  highly  variable  loads,  the  slight  loss  in 
economy  being  more  than  offset  by  the  reduced  investment  for  boilers  and 
power  house  space.  The  obtaining  of  these  higher  rates  of  evaporation 
is  chiefly  a  matter  of  draft  Their  attainment  without  a  serious  sacrifice  of 
efficiency  ts  a  matter  of  boiler  design.  The  proportions,  tube  sizes  and 
spacing,  baffling  and  general  arrangement  must  all  be  properly  worked  out 
The  higher  rates  cannot  le  obtained  at  all  with  certain  types,  the  common 
vertical  boiler  being  an  example. 

The  cost  of  a  given  boiler,  and  also  its  size,  varies  almost  directly  wiUi 
the  amount  of  heating  surface.  Hence  the  desirability  of  high  rates  from 
an  investment  standpoint. 

Grate  Surface 

The  grate  surface  is  important  in  determining  the  capacity  of  a  boiler, 
although  related  only  indirectly  to  its  efficiency.  The  rate  of  combustion 
depends  upon  the  kind  of  fuel  andthe  draft.  The  latter  may  be  determined 
hy  reference  to  the  chart  given  m  Chapter  5  oa  CHIMNEYS. 

For  oil,  there  is  no  grate,  and  capacity  is  based  upon  furnace  volume. 
In  marine  work  a  maximum  oil  consumption  ofUOjlb.  per  cu.  ft  of  furnace 
volume  per  hour  is  permissible,  but  in  land  praetiWNmuch  less  than  this  is 
allowed.  \ 

The  grate  surface  required  for  hand-fired  boilers  Vender  normal  opera- 


1  can  be  found  by: 


>* 


_  33.480  H.  P.  -fC^       (3) 

-   IT     f     C  ^ 


G  =  Total  grate  surface,  sq.  ft 
UP,=  Horsepower  rating  of  boiler. 
B  =  Heat  value  of  coal,  B.  t.  u.  per  lb. 
AT  =  Rate  of  combustion  per  sq.  ft  of  grate  per  hr.,  lb. 
£  1=  Combined  efficiency  of  boiler  and  furnace,  per  cent 


ib.  Google 


Heatdsg  Surface  Ratios 

A  ratio  of  1  sq.  fL  of  grate  area  to  35  or  40  sq.  ft.  of  heating  surface  ii 
rommon  for  boilers  that  operate  at  rated  capacity,  when  burning  commercial 
sizes  of  anthracite.  For  overload  capacity  the  ratio  is  taken  at  about  1  to  25, 
and  for  burning  low  grade  coals  a  forced  draft  system  is  necessary.  For 
bituminous  coals,  the  ratio  of  grate  area  to  the  boiler  heating  surface  runs 
as  low  as  1  to  30,  and  as  high  as  t  to  70  in  dilTerent  instances.  L.  S.  Markt 
recommends  the  ratios,  of  grate  proportions  to  operating  economy  and  boiler 
capacity,  given  in  Table  1. 


Ratio,  of  Gnte  Snrlu  to  B«tinc  Soilue 

NuHotCaul 

Tut  EeoBomy         1         F«  CBpuctty 

^^ 

Bliek 

^^\     ^ 

^IZ' 

siMk 

Va.,  W.  Va..  Neb.,  Pa. 
Ohio,  Ky.,Tenn..  Ala. 
III.,  Ind..  Kan.,Okla.. 
Colo..  Wyoming 

llo60 
lto55 
ItoM 
1  to50 

lto55 
Ho  50 
1  to45 
1  to45 

1  to65 
lto50 
lto45 
1  to45 

Ho  60 
Ho  46 
1  to40 
1  to40 

»=« 

i 

Heat  Transfer 

The  rate  of  transmission  of  heat  through  the  boiler  surface  depends 
chiefly  upon  the  difference  in  temperature  between  the  hot  gases  and  water 
on  the  two  sides  of  the  beating  surface,  and  upon  the  rate  of  movement  of 
the  two  fluids  across  the  surface.  For  those  surfaces  directly  exposed  to  the 
fire,  the  transmission  is  due  chiefly  to  radiation,  which  varies  as  some  power 
of  the  temperature  difference.  A  sustained  high  temperature  in  this  region  is 
therefore  important.  Other  surfaces  act  more  by  convective  iransmission. 
The  fluid  flow  then  is  of  chief  importance,  the  transmission  varying  about 
as  the  first  power  only  of  the  temperature  differences.  As  forced  water 
circulation  is  not  employed  in  large  boilers,  the  water  flow  cannot  be  con- 
trolled at  will.  In  general,  the  harder  the  boiler  is  driven,  the  better  will 
be  the  water  circulation,  which  is  the  condition  desired. 

The  heating  surface  directly  exposed  to  the  fire  does  most  of  the  work. 
CebkardI  states  that  this  would  be  true  even  if  the  furnace  transmission 
varied  as  the  first  power  only  of  the  temperature.  Here  the  last  20  per 
cent  of  the  surface  reduces  the  flue  gas  temperatures  only  65  deg.  This 
is  of  course  an  understatement.  Allowing  for  the  much  greater  effective- 
ness of  that  portion  of  the  surface  immediately  adjacent  to  thi:  furnace,  the 
last  20  per  cent  must  necessarily  reduce  the  flue  temperature  considerably  less 
than  65  deg.  Even  at  65  deg.,  however,  with  ordinary  operation,  the  omission 
of  the  last  20  per  cent  of  the  surface  would  cause  a  loss  of  only  about  300 
B.  t.  u.  per  pound  of  coal,  or  about  2  per  cent.  Hence  where  first  costs  arc 
high  or  loads  variable  the  ratio  of  heating  surface  to  grate  surface  should 
be  low.  Hence  also  the  slight  loss  of  elTiciency  due  to  increasing  rates  of 
evaporation.  In  European  practice,  the  healing  surface  has  been  strictly 
limited  and  economizer  surface  employed  to  obtain  low  final  stack  tempera- 
tures. The  fluid  temperature  difference  is  greater  at  the  economizer,  so 
that  one  square  foot  of  economizer  surface  more  than  replaces  a  square  foot 
of  boiler  surface. 

See  Chapter  11  on  HEAT. 


D,g,tze:Jbi  Google 


Oaa  Passages 

Gas  circalation  is  subject  to  control  both  in  desMHi  and  operation.  Since 
tfae  effort  is  made  to  have  all  of  the  teas  strike  all  of  the  beating  surface 
(thus  keeping  down  the  flue  temperature  and  stack  loss),  the  gas  velocity 
at  a  given  rate  of  driving  is  determined  solely  by  the  nature  and  dimensions 
of  the  gas  passages.  Formerly  certain  proportions  of  the  grate  surface  were 
allowed  for  the  cross-sectional  area  through  or  around  tubes,  but  the  results 
were  only  accidentally  correct.  With  proper  operation,  the  kind  and  weight 
of  coal  to  be  burned  per  hour  determines  within  reasonable  limits  the  weight 
of  gas  produced  per  hour.  The  volume  of  this  gas  depends  upon  its  tempera- 
ture, and  the  rate  of  decrease  of  temperature  from  furnace  to  stack  has 
l>een  determined  by  experiments  for  certain  boilers.  The  velocity  of  this 
gas  depends  upon  the  draft  (which  is  related  to  the  rate  of  combustion)  and 
upon  frictional  resistance,  all  of  which  can  be  valuated  with  fair  accuracy. 
The  volume  and  the  velocity  being  known,  the  cross-sectional  area  necessary 
for  i^s  passage  can  be  calculated.  With  high  draft,  small  area  and  high 
velocity,  gases  yield  their  heat  at  a  rapid  rate,  but  they  are  also  moving  to 
the  stack  at  a  rapid  rate.  The  best  rate  of  yield  as  compared  with 
rate  of  movement  determines  the  cross- sectional  areas.  For  anthracite  coal 
at  low  rates  of  combustion,  the  old  rule  was  to  use  1/7  of  the  grate  surface 
for  the  area  over  the  bridge  wall,  1/8  for  the  flue  area  and  1/9  for  the 
chimney  area.  Areas  naturally  decrease  from  passages  near  the  furnace 
lo  those  near  the  stack. 

Areas  for  gas  passage  can  be  correct,  and  operation  nevertheless  unsatis' 
factory,  if  the  details  of  the  bafHing  are  wrong.  The  gas  should  as  far  as 
possible  be  compelled  to  strike  the  surfaces  without  indulging  in  short  cuts  or 
leaving  dead  spaces  where  the  circulation  is  sluggish.  A  boiler  is  a  machine, 
the  moving  parts  being  gas  and  water,  and  these  motions  must  be  correct 
if  efficiency  is  lo  be  good. 

Baffling 

PARTITIONS  are  placed  among  the  tubes  to  direct  the  flow  of  the  hot 
gases.  These  baffles  can  be  vertical,  causing  the  gases  to  flow  across 
the  tubes ;  or  horizontal,  so  that  the  gases  travel  the  length  of  the  tubes.  In 
selecting  the  design  of  baffling  for  a  given  installation,  its  flexibility,  ease  and 
cost  of  upkeep,  and  influence  on  heating  surface  must  all  be  considered.  In- 
vestigations by  the  Bitreait  of  Minet  show: 

(1)  A  boiler  whose  heating  surface  is  arranged  to  ^ve  long  gas  passages 
of  small  cross-section  will  be  more  efficient  than  a  boiler  in  which  ihe  gas 
passages  &re  short  and  of  larger  ctoss-sectioa 

(2)  The  efliciency  of  a  water-tube  boiler  increases  as  the  free  area 
between    individual    tubes    decreases    and    as    the    length    of    the    gas    pass 


(3)  By  inserting  baffles  so  that  the  heating  surface  is  arranged  in 
series  with  respect  lo  the  gas  flow,  the  boiler  efficiency  will  be  increased. 

These  results  point  to  the  desirability  of  horizontal  baffles  and  the 
importance  of  the  long,  unchilled  flame  and  the  large  furnace  volume  ob- 
tained by  their  use. 

The  entire  heating  surface  in  a  boiler  is  not  active,  because  of  the 
eddies  peculiar  to  gas  flow.  With  practical  baffling,  the  inactive  surface 
caused  by  dead  gas  pockets  can  be  minimized. 

During  tests  by  W.  N.  Polakov  on  the  vertically  baffled  boiler,  shown 
in  Fig.  I,  pyrometer  measurements  showed  that  only  about  60  per  cent 
of  the  surface  was  an  active  heal  absorber,  the  remaining  40  per  cent  repre- 
senting the  dead  pockets.  Horizontal  baffles  may  not  eliminate  the  dead 
regions,  but  tiiey  can  reduce  the  inactive  surface  considerably  by  decreasing 


ib.  Google 


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ib.  Google 


the  size  of  the  dead  corners.  In  Heine  boilers.  Fig.  5,  a  large  percentage 
of  the  tube  surface  absorbs  heat  because  of  the  baffle  construction. 

Horizontal  baffles  are  recognized  as  standard  for  srnokeless  settings. 
Smokctess  combustion  usually  cannot  be  obtained  with  vertically  baffled 
boilers  unless  the  setting  is  very  high.  With  hand-firing  and  bituminous 
coal,  vertically  balTled  boilers  are  not  allowed  where  smoke  ordinances  are 
siringent.  For  this  reason  horizontal  baffling  has  been  applied  to  many 
boilers  designed  originally  with  vertical  baffling.  By  substituting  the  hori- 
zontal for  the  vertical  pass,  a  longer  flame  travel  between  the  furnace  and 
the  tube  region  is  obtained,  without   increasing   the   floor  space. 

In  tests  by  Henry  Kreiiinger  and  M.  T.  Ray,  the  draft  through  the 
vertically  baffled'  boiler  was  0.5  in.  for  an  average  load  of  128  per  cent. 
When  the  same  boiler  was  baffled  horizontally,  ihe  draft  was  only  0J75  in. 


Fia.  3.     Original  Vertical  BafHing  of  Test  Baiter. 


Fig.  4.     Two-Paw  Horiiontal  BafHing  of  Teat  Boiler. 


ib.  Google 


at  127  per  cent  load,  with  the  same  CO,  percentage.  These  tests  were  con- 
ducted to  determine  whether  horizontal  passes  gave  good  results  when 
burning   Pocahontas   and   Clinchheld    (high- volatile)    coals. 

Nineteen  tests  were  run  under  actual  plant  operating  conditions  with  the 
same  boiler,  baffled  as  shown  in  Figs.  3,  4,  and  5-  Table  2  summarizes  these 
tests.  The  flue-gas  temperatures  at  the  different  boiler  loads  are  shown  in 
Fig.  2.  At  "120  per  cent  capacity,  the  average  temperature  with  the  vertical 
bafHes  was  590  deg.,  and  with  the  horizontal  baffling  only  500  deg. 


Kg.  5.     Thrce-PaM  Horizontal  Baffling  of  Test  Btriler. 


Table  2.     Results  of  Boiler  Teats  with  EHfTerent  Baffling. 


"■^ar"" 

P*mm 

^P^l™"' 

N>imolC«l 

& 

CUneb- 
fleld 

& 

"SS? 

b^Mt 

Number  of  ttmU  Bvanced.   ,    . 

Water    evaporated    under 
actual  conditions  per  lb. 
of  coal  as  6red,  lb 

per  lb.  of  coal  aa  fired, 

7..a 

9.42 
320 
341 
14.828 

4.9 

61.3 

7.49 

8.90 
285 

297 
14,122 

7.9 

60.9 

8.54 

9.92 
335 
355 
15,050 

4.72 

63.fi 

8.18 

9.61 
357 
365 
13,801 
10.26 

67.2 

8.83 

10.33 
303* 
317 
14.731 
5.5 

67.7 

8.52 

Maximum  hp.  developed. 
B.  t.  u.  per  lb  of  dry  coal 

311 

13.750 

9.85 

A[^oximate   efficiency  of 

boiler  and  furnace,  per 

69.9 

ritb  tbnc  horixoDtm] 


lad  mtar  wu  too  hot  and  Out  lnjcelor  would 


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BOILERS  65 

When  the  boiler  is  bafFlcd  horiiontally  mudi  better  results  can  be 
obtained  with  high^vojatile  coal.  There  is  also  a  marked  improvement,  when 
the  horizontal  baffling  is  used,  for  Pocahontas  coal.  The  horizontal  three- 
pass  baffling  gave  the  highest  evaporation  and  the  horizontal  two-pass 
developed  the  highest  horsepower.  With  the  two-pass  horizontal  baffling 
higher  evaporation  and  horsepower  can  be  obtained  with  Chnchfield  coal, 
than  with  vertical  l)afning  and  the  higher  grade  Pocahontas.  The  draft 
loss  through  the  boiler  is  less  for  the  horizontal  two-pass  than  for  the 
original  vertical  baffling.  The  numlKr  of  turns  taken  by  the  gages  ii  the 
>an:e,  but  the  resistance  at  the  points  of  reversal  is  less  with  the  horizontal 
two-pass  baffling. 

Smoke  records  from  a  boiler  baffle<l  vertically  and  later  changed  over 
to  horizontal  baffling  are  shown  in  I'ig.  6.  The  vertical  baffles  were  re- 
sponsible for  a  high  percentage  of  smoke,  while  with  the  horizontal  baffles 
the  boiler  had  a  clean  record. 


Horizontal      Baffle- 
Fig.  6.     Smoke  Charts. 

Vertical  baffles  i.';m  be  kept  fight  only  with  ditficully.  Kalfles  that  arc 
nut  gas-tight  allow  the  hoi  gases  of  combustion  to  short-circuit,  resulting 
in  high  stack  temperatures  and  a  reduction  in  boiler  efficiency.  Because 
of  the  difficulty  in  installing  the  tiles,  vertical  baffles  are  often  repaired 
with  ordinary  fire  clay.  With  vertical  baffling  soot  cleaning  is  difficult 
and  the  installation  expensive.  Frequently  the  cleaner  is  built  in  as  a  part 
of  the  baffles  I  when  the  tile  crumble  away  both  the  soot  cleaner  and  the 
tiaffic  must  be  renewed. 

According  to  the  requirements,  the  horizontal  baffles  can  be  arranged 
for  single,  double,  or  triple  gas-passes.  Typical  arrangements  are  shown 
in  Chapter  4.  The  horizontal  passes  allow  the  gas  to  travel  in  scries, 
in  parallel,  or  for  the  two  combined.  The  gases  flow  par.illel  to  the  tubes, 
as  well  as  at  right  angles,  when  the  pass  is  divided.  The  first  balTlei  Fig. 
8,  is  then  placed  on  the  lowest  row  of  tubes  and  extends  to  within  S  ft. 
of  the  rear  waterleg.  This  baffle  serves  as  a  roof  for  the  furnace  and 
combustion  chamber  and  permits  of  a  simple  stoker  arrangement,  with 
ample  room  for  the  gases  to  burn.  The  gases  entering  the  boiler  divide 
into  two  streams,  one  flowing  beneath  and  the  other  above  the  middle  baffle. 


ib.  Google 


This  rests  upon  the  ninth  row  of  tubes,  with  an  opening  at  both  front  and 
rear.  The  top  baSle  extends  from  the  rear  waterleg  to  within  several  feet 
of  the  front  waterleg,  leaving  an  opening  for  the  discharge  of  the  gases 
from  the  boiler  tubes.  Before  passing  to  Hie  smoke  outlet,  all  the  gases 
flow  under  the  boiler  drums. 

The  baffle  tile  used  in  Heine  boilers  are  of  high  grade  refractory  mate- 
rials, designed  for  easy  installation  and  to  withstand  the  high  temperatures. 
The  shapes  used  in  different  settings  are  shown  in  Fig.  7.  Cast-iron  plates 
are  sometimes  used  for  the  center  set  of  two-pass  horizontal  baffles. 

Capacity  and  Economy 

Every  mechanical  device  has  its  own  type  of  characteristic  curve  in 
which  efficiency  is  plotted  as  ordinates  against  output  as  abscissas.  This 
characteristic  curve  for  a  steam  boiler  resembles  the  curve  for  a  steam 
engine  or  turbine,  or  an  electric  motor  or  generator,  in  being  convex  upward 
and  having  a  well  defined  though  broad  peak.  With  all  these  devices,  the 
efficiency  falls  to  zero  at  light  loads  (losses  absorbing  the  output).  Their 
characteristic  curves  differ  chiefly  at  maximum  loads  and  at  heavy  overloads. 
Electrical  machinery  has  clearly  defined  maximum  loads  depending  upon 
temperature.  A  given  overload  can  be  carried  only  for  a  short  time.  Over- 
loads do  not  reduce  the  efficiency  much.  The  boiler  is  similar  in  maintaining 
efficiency,  but  is  greatly  superior  in  its  ability  to  carry  overloads.  It  has 
no  definite  time  limit,  but  can  be  driven  indefinitely  by  increasin([  the  draft- 
Except  under  extreme  conditions  the  boiler  can  carry  maximum  load 
indefinitely- 

With  economical  operation  steam  engines  and  turbines  of  the  constant 
speed  type  have  only  moderate  maximum  overload  capacity.  The  efficiency 
under  overload  drops  off  more  rapidly  than  that  of  a  boiler.  To  obtain 
high  overload  capacity  by  admitting  live  steam  to  low  pressure  cylinders 
or  stages  leads  to  an  abrupt  drop  of  the  efficiency,  and  even  then  there 
is  a  definite  limit  of  capacity.  The  steam  boiler,  therefore,  is  almost  unique 
in   its   advantageous   performance. 

Water  Circulation 

In  many  heat-transfer  appliances  the  rate  of  transmission  Increases' 
as  the  fluid  velocities  increase.  On  the  reception  side  high  fluid  velocity 
leads  to  rapid  replacement  of  warmed  fluid  by  new  and  colder  fluid ;  (on 
Ihe  emission  side,  cooled  fluid  is  replaced  by  warmer  fluid,  if  the  heat- 
emitting  fluid  is  other  than  a  vapor)  and  hence  to  augmented  temperature 
difference.  In  a  steam  boiler,  however,  the  water  temperatures  at  various 
points  usually  differ  imperceptibly.  The  quantity  of  heat  transferred  can 
scarcely  vary  much  with  the  water  velocity,  and  the  efficiency  does  not  in 
any  marked  degree  depend  upon  water  circulation.  The  heat  transfer  which 
occurs  by  radiation,  at  surfaces  directljr  exposed  to  the  fire,  does  not  in  any 
marked  degree  depend  upon  water  arculation,  assuming  that  the  circula- 
tion is  sufficient  to  keep  the  surface  wet.  The  hzat  transfer  which  occurs 
by  radiation,  at  surfaces  directly  exposed  to  the  fire,  does  not  depend  upon 
gas  circulation. 

Good  circulation  is  important,  however.  It  reduces  stresses  arising 
from  differences  of  temperature,  cUscourages  the  accumulation  of  scale  or 
mud  in  pockets  and  (still  more  important)  tends  to  prevent  the  formation 
o[  adhesive  bubbles  against  the  sheets.  Such  unwetted  spots  may  cause 
local  overheating.  They  are  most  apt  to  exist  when  boilers  with  insufficient 
liberating  surface  and  poor  circulation  are  driven  hard. 


D,g,tze:Jbi  Google 


Steadiness  of  Water  I-evel 
This  implies  a  large  water  surface  "disengaging"  or  "litterating"  surface, 
in  proportion  to  the  volume  of  water;  or  perhaps  more  strictly,  in  proportion 

to  the  expected  total  evaporation.  Priming  may  result  from  inadequate 
liberaling  surface  and  occurs,  consequently,  in  many  vertical  boilers  having 
the  water  level  below  the  tops  of  the  tubes.  Drums  should  not  be  loo  small, 
else  slight  variations  of  water  level  may  carry  it  rapidly  below  the  danger 


B-Tlle.  T-Tile.  L-Tilc. 

Pig.  7.    Forms  of  Tile  Uied  with  Heine  Bt^era. 


Fig.  8.     Divided  Pan  Baffle  in  Heine  Bmler. 


ib.  Google 


ibiGoogle 


CHAPTER  3 


SUPERHEATERS 

SUPERHEATED  steam  is  steam  whose  temperature  is  higher  than  tliat 
corresponding  to  saturated  steam  at  the  same  pressure ;  steam  which,  when 

heat  is  removed,  will  not  immediately  begin  the  process  of  condensation. 
The  properties  of  superheated  steam  approximate  those  of  a  perfect  gas. 
Tables  of  these  properties  are  given  in  Chapter  12  on  STEAM. 

Adfanlages  of  SttperhcatUig,  These  are  important  because  superheating 
reduces  pipe  and  cylinder  con<knsatian.  In  a  well-designed  attached  super- 
heater, the  efficiency  of  the  heating  surface  is  at  least  as  high  as  that  of. 
the  boiler;  and  as  the  total  healing  surface  is  increased  by  that  of  the 
superheater  the  exit  temperature  of  the  gases  will  be  decreased.  This  in- 
creases Ihe  overall  efficiency  of  the  boiler  and  superheater  t<\a  point  which 
will,  in  general,  make  up  for  the  increased  heat  required  hy  the  steam.  With 
an  independently  fired  superheater,  more  fuel  will,  of  course,  have  to  be 
iiurned. 

The  measure  of  the  extra  fuel  for  superheating  is  the  difference  in 
the  total  heat  of  the  steam  when  saturated,  and  when  superheated ;  this  will 
depend  upon  the  pressure  and  the  superheat  temperature,  and  also  upon  the 
lemperatnre  of  the  feed  water.  The  following  figures  are  based  on  a  gage 
pressure  of  165  pounds : 


auMrtwl. 


2.73 
n.  13 

5.38 

7.40            ! 

7.74 

H.Ol 

\tt.m 

I 


The  superheater  does  some  of  the  work  which  the  heating  surface  of 
the  boiler  would  have  to  do  if  the  same  number  of  heat  units  were  to  he 
supplied  in  saturated  steam,  so  that  the  boilers  can  be  run  at  lower  rating. 
The  superheater  may  not  increase  the  first  cost  of  the  boiler  plant,  for 
with  the  increased  economy  the  number  of  units  used  may  be  decreased.  The 
increased  economy  of  the  engines  due  to  the  use  of  superheated  steam  may 
naturally  enable  smaller  condensers  to  be  used,  and  may  lessen  the  cost  of 
pumping  owing  to  less  water  being  used.  Superheated  sleam  is  used,  almost 
without  exception,  in  the  largest  and  most  economical  plants. 

The  pipe  radiating  surface  can  be  reduced  by  the  use  of  smaller  pipes. 
owing  to  the  fact  that  higher  velocities  (as  high  as  13,000  ft.  per  min.)  are 
permitted  with  superheated  steam. 

The  theoretical  gain  is  indicated  in  the  temperature-entropy  diagram. 
Fig.  9,  in  which  areas  represent  heat  quantities.  The  line  (oa)  starting  at 
a  temperature  of  32  deg.  is  the  liquid  line  and  the  area  under  (oa)  represents 
the  heat  of  the  liquid,  q,  that  is,  the  heat  necessary  to  raise  the  temperature 
of  one  pound  of  water  from  32  deg.   to   the   temperature   corrcspondinR  to 


ib.  Google 


I 

ft 

r- 

6? 


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Si 


ibiGoogle 


SUPERHEATERS 


the  pressure  in  the  boiler  where  the  vaporization  takes  place.  The  line  (ab) 
rwresents  this  process  of  vaporisation  and  the  area  under  it  is  the  heat,  L, 
added  during  the  process.  At  (b)  the  steam  is  in  a  dry-saturated  condi- 
tion :  (be)  shows  the  superheating  of  the  steam  at  constant  pressure  and  the 
area  below  is  the  heat  added  during  the  process.  The  steep  slope  of  the 
line  (be)  shows  that  the  point  (c),  which  is  the  final  condition  of  super- 
beat,  must  be  carried  to  a  high  temperature  in  order  to  have  the  area  below 


Pig.  9.     Temperature — Entropy  Di«grem. 


of  any  size.  A  high  degree  of  superheat,  which  means  a  high  temperature, 
will  add  only  a  small  number  of  heat  units  to  the  dry-saturated  steam. 

For  example,  dry  steam  at  150  lb.  abs.  pressure  has  a  heat  content  of 
1195  B.  t.  u.  per  pound.  If  this  steam  is  superheated  141.5  deg.  to  a  tem- 
perature of  500  deg.,  the  heat  content  will  be  1274  B.  t  u.  or  a  gain  of  only 
79  B.  t  u.  per  pound  for  an  increase  in  temperature  of  141.5  deg.;  or  6a 
per  cent  increase  in  heat  for  39Ji  per  cent  gain  in  temperature. 

Effect  OH  Reciprocating  Enginet.  Steam,  admitted  to  the  cylinder  of 
an  engine,  comes  in  contact  with  walls  that  have  been  cooled  by  contact 
with  the  low  pressure  steam  exhausted  during  the  previous  stroke.  Heat 
flows,  therefore,  from  the  steam  to  the  cylinder  walls,  and  if  the  steam  is 
saturated  part  of  it  will  be  condensed;  sometimes  this  will  be  as  much  as 
20  or  30  per  cent.  The  loss  due  to  surface  condensation  is  one  of  the  most 
serious  occurring  in  the  reciprocating  steam  engine.  If  the  steam  entering 
the  cyFmder  is  superheated,  then  the  flow  of  heat  caused  by  contact  with  the 
colder  cylinder  walls  will  cause  a  decrease  in  the  amount  of  superheat,  but  no 
condensation  until  the  temperature  has  been  reduced  to  that  of  saturated 
steam. 

The  many  tests  made  on  reciprocating  engines  using  saturated  and 
superheated  steam  have  shown  a  smaller  steam  consumption  for  superheated 
steam.  With  moderate  amounts  of  superheat,  that  is,  up  to  200  de^.,  the 
gains  have  been  greater  than  for  the  higher  temperatures.    The  extra  mvest' 


ib.  Google 


S  UPERHEATEKS 


and  c 


t     of     II 


tictitralizc  the  t;aiii  from  the  hight-r  teni|>(rr- 
economy  due  to  superheat  is  most  striking  with 
whtcli   the  cylinder   condensation   losses  are  the 


Tlie  gain  in  st« 

small,    simple   engines,   i 

Tests  on  Buckeye  engines  (simple  12  by  16  in.,  and  compound  10  and  I7f4 
by  16  in.)  with  steam  at  100  to  110  lb,  pressure,  show  abotit  what  can  be 
expected  in  this  way.  Table  3  gives  results  of  tests  wilh  superheats  up  to 
200  dee. 

Tabic  3,     Pounds  ot  Steam  Per  H.  P.  Per  Hour  for  Different  Superheats. 
Superheat  tempcrAtUTQ.  docrflvA 


Simple,  noii-condenHiiig  . , . 
Simple,  non-condensing.. .  . . 

Simple,  non-condenu:^ 

Compound,  non-condcnidng 
Compound,  condensing, , .   . 


_1_ 

35.0 
31. S 
28.5 

so 

38.0 
25..'; 
24.0 

i» 

21.5 
1».0 
18.0 

15,5 
12.5 

200 

34.0 

20.0 
17.5 
14.0 

lit. 5 
17.5 
17.5 

18.0 

16.5 

11.5 

icbhardt  stales  lliat  a  fair  estiiii^ 
am  consumption  per  horsepowei 
3m   100  to   125  deg.,  based  on 


If  of  the  iivcragc  [icrccnlage  rcduc- 
hour  with  moderate  supi-rbeating. 
continuous   operation    of   existing 


1.  Slow  running,  full  stroke  or  tbrottling  engiiies,  including 

direct- acting  pumps „ _ 40 

2.  Simple  engines,  non -condensing,  with  medium  piston  spcetl, 


including  compound,  direct-acting  pumps 

.   Compound  condensing  Corliss  engines 

.   Triple  expansion  engines 


..-10 


European  builders  guarantee  slcam  consumption  (in  Ui.  per  I.ll.P.  i>er 
lir.)  wilh  highly  superiieated  steam  (total  temperatures  750  to  850  deg.) 
as  follows: 

Single  cylinder  condensing  engines  (unillow) 8.S 

Single  cylinder   non-condensing  engines    (uniHow) 12.0 

Compound  condensing  engines   (locomobile) 8J) 

Clompound  non -condensing  engines   (locomobile) _ _10.5 

W.  E.  Daihy  gives  results  on  a  small  engine  using  superheated  steam, 
taking  the  data  from  tests  by  Professor  Ripper.  Table  4  shows  the  differ- 
ence in  the  increase  of  the  efficiency  of  theoretical  and  actual  engines,  both 
working  under  the  same  conditions ; 

The  steam  is  dry-saturated  in  the  first  case.  The  theoretical  cfficiencj- 
increases  from  14.2  to  1S.9  per  cent,  or  11.6  per  cent,  while  the  actual 
efficiency  gains  6S.0  per  cent,  the  increase  being  from  6.3  to  10.4  per  cent. 
This  shows,  of  course,  that  the  superheat  acts  lo  decrease  the  losses  in  the 
actual  engine. 

In  comparing  the  performances  of  diilerenl  engines,  the  heat  consuinp- 
lion,  rather  than  the  steam  consumption,  should  be  used,  Tlic  number  of 
heat  units  required  to  develop  one  indicated  horsepower  in  the  actual  engine 
lakes  into  consideration  the  pressure,  superheat  and  the  steam  consumption 
The  avoidance  of  cylinder  condensation  by  the  use  of  superheat  will  affect 
both  heat  and  steam  consumption.  So  whatever  the  basis  of  comparison,  the 
employment  of  superheated  steam  is  an  advantage. 


D,g,tze:Jbi  Google 


SUPERHEATERS 
Table  4.     KfTect  of  Superheat  on  Actual  and  Theoretical  Enginet. 


lCSTR. 

XT 

UN^^./hr. 

TlMcmaltA 

siwy.mant 

I.  H.P. 

AM.«n|. 

^.„ 

13.33 
13.33 
13.47 
13. 4B 

101. T 
»8.5 

0.0 
»8.3 
254.2 
319.6 

39.02 
33.80 
23.36 
20.08 

tf.3 

7.1 
9.5 
10.4 

1 

14.2 

u.a 

16.2 
15.0 

Effect  on  Steam  Tmbines.  The  theoretical  gain'  from  ihc  use  of  super- 
heated steam  is  the  same  in  steam  turbines  and  in  reciprocating  engines; 
in  either  the  available  number  of  heat  units  are  increased  by  the  use  of  the 
superheating  process.  The  actual  gain,  however,  is  less  in  the  turbine  than 
in  the  engine,  for  the  action  of  the  steam  in  the  former  is  continuous  while 
in  the  latter  it  is  intermittent.  Superheated  steam  is  of  little  value  in  cor- 
recting surface  ctmdensation,  beoiuse  practically  none  occurs  in  the  turbine. 

The  water  rate  of  the  turbine  is  decreased  by  the  superheating  of  the 
steam  but  to  a  less  extent  than  in  the  reciprocating  engine.  Superheating  is 
of  importance  in  that  erosion  of  the  turbine  blades  caused  by  the  presence 
of  water  in  the  saturated  steam  is  almost  entirely  done  away  with. 

The  effect  of  expansion  on  saturated  steam  is  to  increase  its  moisture 
content,  so  that  even  if  the  steam  were  dry  at  entrance,  moisture  would  be 
present  in  Ihe  low  pressure  stages.  If  the  eteam  is  sufficiently  superheated 
ihe  heat  reduction  due  to  the  expansion  will  not  lower  the  temperature  to 
that  of  saturated  steam,  which  must  be  reached  before  condensation  begins. 
Any  moisture  present  in  saturated  steam  has  the  effect  of  reducing  the 
economy. 

The  steam  consumption  of  certain  large  turbines  using  superheated  steam 
is  decreased  about  1  ^er  cent  for  every  8  to  12  deg.  of  superheat  up  to  200 
deg. ;  the  variation  being  from  about  1%  for  12  deg.  at  50  deg.  superheat  to 
8  d^.  at  200  deg.  superheat.  In  the  same  boiler  plant  the  minimum  saving  in 
coal  due  to  superheating  is  4  to  5  per  cent.  This  coal  saving  depends  upon 
(1)  the  saving  of  steam  resulting  from  the  economy  of  the  prime  mover; 
and  (2)  the  amount  of  coal  necessary  to  obtain  the  superheaL 

Limit  of  Superheat.  As  far  as  material  goes  power  plant  apparatus 
might  be  designed  to  withstand  temperatures  of  800  or  even  1000  deg. 
Other  considerations,  however,  limit  the  amount  of  superheat,  so  that  the 
most  economical  degree  is  determined  by  the  operating  conditions. 

In  this  country  steam  temperatures  in  power  plants  are  seldom  more  than 
600  deg.;  the  superheat  is  from  200  to  250  deg.,  depending  upon  the  boiler 
pressure.  In  Europe,  however,  where  superheaters  are  almost  invariably 
employed,  600  deg.  is  a  common  temperature  and  400  deg.  superheat,  which 
would  b«  a  temperature  oi  about  850  deg.,  is  sometimes  used. 

With  these  very  high  temperatures  the  first  cost  and  maintenance  are 
high,  and  the  thermal  gain  is  considerable.  This  would  be  advantageous 
when  materials  and  labor  costs  are  reasonable  and  fuel  costs  high.  Such 
conditions  were  formerly  found  in  Europe.  In  this  country,  however,  labor 
and  materials  are  expensive  while  fuel  has  been  cheap.  It  is  more  economical, 
therefore,  to  use  moderate  degrees  of  superheat,  even  at  the  sacrifice  of 
some  gain  in  heat ;  but  as  the  cost  of  fuel  increases,  the  tendency  will  be 
towards  increased  superheat. 

The  engine  design  also  determines  to  some  extent  the  temperature  to  be 
used.    The  Corliss  and  slide-valve  types  of  engines  seem  to  reach  their  limit 


ib.  Google 


"1 

it 
I: 


.So- 
il 

IS 


D,B,i,.ab,GoOglc 


SUPERHEATERS  75 

at  about  500  deg.     Higher  temperatures  cause  warping  of  the  valves  and 
interfere  with  lubrication. 

Very  highly  superheated  steam,  at  temperatures  of  600  deg.  or  more, 
is  used  in  poppet-valve  engines,  since  sUch  valves  do  not  warp  and  require 
no  lubrication.  Balanced  piston  a/id  specially  designed  Corliss  valves  are 
also  successful  with  high  superheats. 

Steam-turbine  construction  and  operation  permit  the  use  of  steam  tem- 
peratures as  high  as  800  deg.  Nevertheless  for  reasons  of  economy  of  main- 
tenance, even  the  latest  designed  turbine  plants  are  working  with  steam  at 
temperatures  not  over  650  deg. 

Control  of  Suferheal.  Superheat  temperatures  may  vary  widely  with 
the  temperature  oi  furnace,  volume  of  air  used,  and  rate  of  firing  coal. 
Extreme  variations  should  be  avoided,  as  they  may  cause  serious  difficulties 
with  the  piping,  valves  and  gaskets.  Stoker  firing  and  automatic  feed  and 
damper  regulation  will  do  much  toward  eliminating  superheat  fluctuations. 

Any  variation  in  the  boiler  load  will  affect  to  a  marked  degree  the  tem- 
perature in  superheaters  placed  inside  the  boiler  setting,  in  the  path  of  the 
not  gases.  The  truth  of  this  last  statement  is  shown  by  Fig.  10,  and  by  the 
following  quotation  from  "Superheater  Logic,"  by  the  Heine  Safety  Boiler 
Company : 

"If  the  increase  in  load  is  sudden  and  there  is  a  large  momentary  draft 
of  steam  with  accompanying  fall  in  boiler  pressure,  the  superheat  tempera- 
ture will  fall  because  the  rate  of  combustion  is  not  increased.  Conversely 
if  a  boiler  is  steaming  at  a  heavy  load  and  the  load  decreases  suddenly,  then 
the  superheat,  which  is  already  very  high  due  to  the  heavy  load,  will  be 
further  increased  because  of  the  smaller  ^ow  of  steam  through  the  tubes.  In 
this  way  very  excessive  superheats  are  obtaiited  from  an  equipment  designed 
for  only  a  moderate  superheat  at  normal  load, 

"Evidently  the  greatest  economy  is  secured  when  a  plant  is  designed 
and  built  for  a  certain  lixed  superheat  and  this  temperature  is  maintained 
constant." 

:  are  (1)  the  separately-fired, 
superheater.  The  former  is  placed  in  its  own 
setting  and  has  a  furnace  of  its  own  to  supply  heat;  the  latter  is  located 
within  the  setting  of  the  boiler  and  receives  heat  from  the  hot  gases  as  th^ 
pass  on  toward  the  stack.  Both  types  receive  steam  containing  perhaps  2 
|>er  cent  moisture  from  the  boiler  and  increase  its  temperature  by  the  auldi- 
tion  of  heat  without  changing  the  pressure.  The  steam  elements  arc  prac- 
tically the  same  in  both  types — a  number  of  tubes  or  pipes  arranged  to  contain 
a  relatively  small  volume  but  to  expose  a  large  surface  to  the  heat. 

The  final  temperature  of  steam  in  a  superheater  depends  upon  the  tem- 
perature, volume  and  quality  of  the  steam  entering  it,  and  upon  the  volume 
and  temperature  of  the  hot  gases  coming  in  contact  with  the  tubes.  The 
temperature  and  quality  of  the  steam  can  be  considered  as  constant  while 
the  load  on  the  boiler  determines  the  quantity  of  steam.  Therefore  die 
amount  of  superheat  will  be  principally  affected  by  the  temperature  and 
volume  of  the  hot  gases.  If  it  is  desired  to  maintain  a  constant  degree  of 
superheat,  the  How  of  hot  gases  over  the  tubes  must  be  controlled. 

Separately-fired  superheaters  are  intended  to  give  higher  temperatures 
to  the  steam  than  can  be  obtained  from  attached  superheaters.  The  super- 
heating coil  is  suspended  over  the  furnace,  protected  from  the  direct  heat 
of  the  furnace.  BafHes  are  provided  so  that  tiie  hot  gases  make  two  or  more 
passes  around  the  tubes.  Steam  enters  at  the  top  and  leaves  at  the  bottom. 
The  tube  surface  is  increased  by  putting  on  cast  iron  rings  outside  the  tubes. 

A  flow  of  steam  through  the  superheater  must  be  provided  to  prevent 
burning,  should  the  load  be  suddenly  thrown  o6f  the  boiler.  All  super- 
heaters should  be  equipped  therefore  with  independent  safety  valves  of  the 


ib.  Google 


SUPERHEATERS 


:  for  getting  rid  of  any  collected  water 
before  atartii^.  The  superheater  should  be  so  proportioned  that  the  same 
quantity  of  steam  will  pass  through  all  of  the  tubes  in  order  that  none  of 
these  can  be  by-passed,  and  consequently  in  danger  of  burning. 

Superheaters  musi  be  protected  from  exposure  to  hot  gases  with  no 
steam  flowing,  as  when  firing  up,  cooling  down  or  standing  idle.  With 
apparately-fired  superheaters  the  hot  gases  can  be  deflected  so  as  to  by-pass 
the  superheating  coil  and  flow  directly  from  the  furnace  to  the  stack; 
or  an  outer  cast  iron  covering  with  flanges  may  be  provided  to  protect 
the  steel  tubes  and  store  the  heat.  Also  the  superheater  should  be  fllled  with 
water,  or  flooded  whenever  the  flow  of  steam  ceases.  Flooding  is  objectionable 
in  that  scale-forming  material  can  be  deposited  in  the  tubes,  which  cannot 
be  cleaned. 

Any  of  the  above  methods  may  be  applied  to  attached  superheaters. 
When  these  are  flooded  they  generally  are  connected  in  parallel  with  the  boiler 
beating  or  evaporating  surface,  so  that  they  can  be  drained  and  connected 
in  series  with  the  boiler  when  superheat  is  desired. 

The  attached  or  indirectly-tired  superheater  may  be  placed  (1)  at  the 
rear  of  the  furnace;  (2)  at  the  end  of  the  heating  surface  just  before  the 
gases  leave  the  boiler  setting;  and  (3)  at  some  intermediate  point 

The  steam  passing  through  the  superheater  will  absorb  heat,  depending 
upon  the  temperature  difference  between  the  gases  and  the  steam,  and  upon 
the  amount  of  superheating  surface.  Therefore  to  obtain  the  same  degree  of 
superheat  the  amount  of  surface  required  in  the  furnace  where  the  gases 
are  hottest  may  be  small  as  compared  with  the  amount  required  when  the 
superheater  is  placed  at  the  end  of  the  heating  surface,  where  the  gases  are 
cooler.  The  usual  location  of  the  superheater  in  the  boiler  setting  is  such  that 
the  temperature  of  the  hot  gases  reaching  it  seldom  exceeds  1500  deg-  In 
this  position  the  attached  superheater  is  subjected  to  the  fluctuating  tempera- 
tures of  the  hot  gases.  The  amount  of  superheat  will  vary,  therefore,  with 
the  load  on  the  boiler  and  will  increase  as  the  boiler  is  forced. 


w 

^ 

^ 

^ 

-^ 

^ 

^ 

^ 

■  m 

^ 

y 

c    ^ 

/ 

/• 

S 

s.  « 

/ 

'' 

/ 

Percent ,  Looi<4 
Fig.  10.    Effect  of  Load  on  Superlieat  with  tbe  Superheater  in  the 
Path  of  All  the  Boiler  Oaaee. 


D,B,i,.ab,GoOglc 


SUPERHEATERS 


The  more  positive  method  of  maintaining  a  constant  superheat  is  by 
locating  elements  in  a  separate  chamber,  where  a  daimier  can  be  used  to 
regulate  the  flow  of  gases,  automatically  if  desired.  The  superheater  can 
then  be  by-passed  altogether  in  an  emergency. 

Figs.  11  and  12  illustrate  the  details  and  location  of  the  Heine  super- 
heater. This  consists  of  two  parts,  the  superheater  box  and  the  tubes.  Into 
this  box  are  expanded  the  steel  tubes  arranged  in  four  passes  as  shown. 
Two  interior  partitions  separate  the  superheater  box  into  three  chambers. 
The  steam  enters  at  the  botloni.  passes  through  the  lower  tubes,  returns  lo 
the  central  chamber  through  the  second  pass  tnhes  and  then  flows  through 
the  third  and  fourth  passes,  returning  to  the  upper  chamber. 


Fig.  1 1.  Details  of  Hdne  Superheater 
The  location  of  the  superheater  is  shown  in  Fig.  12,  Tt  can  be  installed 
on  one  or  l>oth  sides  of  the  boiler,  according  to  the  boiler  size,  and  the 
superheat  desired.  The  entire  superheater  is  encased  in  brick  work  with 
a  firebrick  roof  supported  by  special  T-bars.  This  superheater  chamber 
communicates  with  the  furnace  by  a  flue  formed  in  the  side  wall,  through 
which  a  small  part  of  the  furnace  gas  rises.  This  gas  enters  the  rear  of 
the  chamber,  makes  two  passes  over  the  tubes  and  leaves  at  the  front  of  the 
setting,  passing  over  the  surface  of  the  boiler  drum.  A  damper  in  the 
cliamber  outlet  controls  the  flow  of  hot  gas  and  is  regulated  from  the  front 
of  the  boiler,  either  by  hand  or  by  an  automatic  temperature  i-mitrol. 


ib.  Google 


7»  SUPERHEATERS 

Obviously,  the  temperature  of  the  superheated  steam  can  be  changed 
as  desired  by  simply  manipulating  the  damper  io  the  outlet  of  the  super- 
heater chamber,  and  the  superheat  can  be  maintained  constant,  regardless  of 
the  boiler  load,  the  rate  of  combustion,  the  amount  of  air  used  for  combus- 
tion, the  furnace  temperature,  the  opening  of  furnace  doors  or  any  other 
variable,  such  as  the  amount  of  soot  on  boiler  and  superheater  surface. 


Fig.  12.     The  Heiae  Superheater. 

c  regulation  of  the  superheat  temperature,  a  complete  regu- 
lator is  installed  as  shown  in  Fig.  13.  This  regulator  is  quick  acting  and 
responds  to  small  variations  in  steam  temperature,  as  will  be  evident  from 
its  consiruciion. 

The  entire  device  consists  of  two  main  parts,  the  controller  and  the 
diaphragm-motOT.  The  controller  comprises  a  thermostat  which  con- 
trols a  small  supply  of  compressed  air  in  accordance  with  the  temperature  of 
the  superheated  steam.  The  air  is  admitted  to  or  released  from  the 
diaphragm-motor,  connected  by  a  link  to  the  superheater  damper  handle. 

Provision  for  soot  blowing  is  described  on  pages  31  and  41. 


D,g,tze:JbiGOOt^lC 


SUPERHEATERS 


!  Reculatoc 

The  requirements  of  a  successful  superheater,  as  given  by  Gcbhardt,  are: 

1.  Security  of  operation  or  minimum  danger  of  overheating. 

2.  Economical  use  of  heat  applied. 

3.  Provision   tor  free  expansion, 

4.  Disposition  so  that  it  may  be' cut  out  without  interfering  with  the 
operation  of  the  plant.  ' 

5.  Provision  for  keeping  the  tubes  free  from  soot  and  scale. 
Superheating   Surface.     The   surface   required   is   dependent  upon   the 

amount  of  heat  to  be  transferred  lo  the  sleam,  and  upon  the  rate  of  heat 
iransfer  per  unit  of  surface.  The  operation  is  conveniently  divided  into  three 
stages: 


ib.  Google 


D,B,i,.ab,GoOglc 


SUPERUEATIiRS  81 

1.  Heat  yiveii  up  by  tlio  gases. 

2.  Eicat  transniided  through  the  niclal  wulls  of  the  eleiiietns. 

3.  Heat  absorbed  by  the  steam. 

The  amount  of  heat  involved  in  each  of  these  stages  is  the  same  cxeeiil 
for  loss  by  radiation. 

The  heat  given  up  by  the  gases  is: 

the  licat  transferred  is : 

:)Rd  (5) 

anil  the  heat  ;tbs<irbcd  hv  the   ^reani  i^:: 

IKr,   (/,-/.)  (.6) 

S^^SuperheatinK  surface,  sq.  ft.  per  H.II.P. 

R^=B.tM.  traiisferred  per  hour  per  sii.  ft.  of  superheating  surface 
per  deg.  F  difference  between  the  mean  temperainres  of  the 
gases  and  of  the  steani,  and  approximates; 

1  to  3  for    superheaters    located    at   the    end   oi   the    boiler 

heating  surface. 

3  lo  5  when    located   between   the   first    and   second   parses, 

8  to  12  for  separately  fired  superheaters  and  for  superheaters 

located  immediately  over  the  furnace  in  stSittonary 

boilers  or  in  the  smoke  box  of  locomotive  boilers. 

d=difrererice  lietween  tlie  mean  temperatures  of  the  gases  and  steam. 

If^:weiKht  of  gases  passing  through  the  superheater,  lbs.  per  B.U.P. 

per  hour. 
If—weight  of  steam  passing  through  the  supcrlicattr,  lbs.  per  D.II.P. 

per  hour. 
(S^nean  specific  heat  of  the  gases. 
(-,=inean  specific  heat  of  superheated  steam. 
/,i=Temperature  of  gases  entering   superheater,  dcg.   F. 
(.^Temperature  of  gases  leaving  superheater,  deg.   F. 
f]=Temperature  of  superheated  steam,  deg.  F. 
t^=Temperature  of  saturated  steam,  deg.  F. 
Neglecting  radiation,  (1)   is  equal  to  (2);  and  neglecting  the  moisture 
in  the  incoming  steam,  (2)  is  equal  to  (3),  therefore  r 


-— Alrf    "  (8) 

(9) 

/■/,=Tolal  heat  of  superheated  steam  above  32  deg.  F. 

//,=Total  heat  of  saturated  steam  above  32  deg.  e„  which  may  he 
easily  corrected  to  allow  for  evaporating  the  moisture  preseut, 
Tnstead  of  basing  R  on  the  difference  in  the  temperatures  of  the  gases 
and  of  the  steam,  it  is  more  correct  to  divide  the  heat  transfer  into  two 
stages— gas  to  metal  and  metal  to  steam.  As  this  necessitates  a  knowledge 
of  the  metal  temperatures  it  is  generally  confined  to  laborator>'  research. 
The  precise  value  of  R  is  dependent  upon  so  many  variable  conditions,  such 
as  the  velocity  of  the  gases  and  of  the  steam,  the  condition  of  the  surfaces 
as  to  soot  and  scale,  the  arrangement  of  the  superheater  tubes  and  the 
temperature  dilTerenccs  involved,  that   refinements  are  out  of  place.     The 


ib.  Google 


,Google 


SUPERHEATERS  83 

amonnt  of  surface  is  usually  determined  empirically  on  formulae  derived 
from  the  results  obtained  in  a  Urge  number  of  cases  of  the  same  general 
design,  operating  under  similar  conditions.  This  leaves  the  result  in  con- 
siderable doubt  where  the  whole  of  the  gases  flow  over  the  superheater 
with  no  possible  control.  With  only  a  part  of  the  gases  flowing  over  the 
superheater  under  perfect  control,  the  amount  of  surface  can  be  simply 
related  to  the  boiler  heating  surface,  according  to  the  degree  of  superheat 
required,  and  the  resulting  steam  temperature  will  be  kept  constant  within 
±   5  deg,  F.,  as  shown  in  Fig.  14. 

SufierhcaUr  Materials.  Heine  superheaters  are  built  of  wrought  steel, 
insuring  ease  of  construction  and  durability. 

Superheater  Piping  and  Fittings.  Cast  iron  has  been  used  for  valves  and 
fittings.  Up  to  GOO  deg.,  it  is  safe  if  the  temperature  is  maintained  constant. 
Under  higher  or  fluctuating  temperatures  permanent  increase  in  dimensions 
and  numerous  failures  have  resulted.  Cast  iron  failures  are  undoubtedly  due 
more  to  fluctuations  in  temperature  than  to  constant  high  temperatures  when  it 
develops  cracks  and  distortions. 

The  advantage  of  cast  steel  for  superheater  material  is  that  it  is  not 
damaged  at  high  temperatures.  This  decreases  the  importance  of  protection 
and  simplifies  the  installation.  The  construction,  however,  must  be  heavy 
and  thick-walled. 

The  strength  of  superheater  materials  drops  off  rapidly  for  temperatures 
above  600  deg.,  as  shown  by  Gebhardt  and  others.  Because  of  this  rapid 
decrease  in  tensile  strength,  steam  is  seldom  superheated  to  temperatures 
above  850  deg. 

Piping  for  superheated  steam  is  usually  made  of  mild  steel.  With  the 
greater  number  of  heat  units  in  superheated  steam,  the  pipe  capacity  is 
increased  and  relative  conduction  losses  and  leakage  are  reduced.  Under 
superheated  conditions  much  higher  steam  velocities  can  be  used,  12,000  ft. 
per  min.  not  being  uncommon  and  16,000  ft.  per  min.  having  been  used. 
This,  of  course,  increases  the  pipe  line  capacity.  With  the  high  tempera- 
tures resulting  from  superheat  the  problem  of  expansion  must  be  carefully 
considered,  especially  when  temperatures  are  likely  to  fluctuate  widely.  See 
chapter  on  piping. 

Industrial  Uses.  Superheated  steam  is  used  elsewhere  than  in  engines 
and  turbines.  A  Chicago  gas  company  blows  its  water  gas  generators  with 
superheated  exhaust  steam  at  about  2.5  lb.  pressure,  instead  of  using  live 
steam.  This  results  in  a  20  per  cent  saving  of  boiler  fuel  The  capacity  of 
the  generators  is  increased  because  of  the  lengthening  of  the  making  period. 
The  superheated  steam  relieves  the  generator  of  the  work  of  re-evaporating 
the  water,  which  is  always  present  when  saturated  steam  is  used. 

Superheated  steam  is  successfully  used  for  process  work,  where  both 
the  latent  heat  and  the  heat  of  the  superheat  of  the  steam  can  be  used,  as  for 
example,  when  the  steam  can  be  blown  directly  into  the  substance  to  be 
heated.  When,  however,  only  the  heat  of  the  superheat  can  be  employed, 
the  use  of  superheated  steam  does  not  pay.  it^4p«w&fe^iMk4fc^at)hrfbaut 
w  half  that  of  oaturotod  Dtoom  and  thcreforo)  about  twiec  as  mueh  auper- 
■heated  steam  weald  be  reqaifetk  Superheated  steam  may  be  justified  when 
the  heat  of  the  superheat  can  be  used  in  one  operation  and  the  latent  heat 
or  part  of  it  in  a  connecting  operation.  The  saturated  steam  left  after  the 
first  operation  must  then  contain  enough  heat  for  the  second  operation. 


ib.  Google 


5« 
a-S-s 


||5 

.s   ^ 

'•2 


ib.  Google 


Chapter  4 
furnaces  and  settings 

PROPER   furnace   JesiRii   and   adequate   proportiuns   are   the   essentials   in 
securing   high   boiler   elTiciency.     A   single   design   of   setting  cannot   be 
stanitardiied  to  meet  the  various  fuel,  operation  and  space  requirements. 
To  ohtain  complete  combustion,  special  designs  are  required  for  low  and  hiRh 
vnlatile  coals,  gas,  fuel  oil,  waste  heat,  and  for  hand  or  sinker  firing. 

Furnace  Design 

THE  main  problem  in  furnace  design  is  to  determine  the  volume  of  the 
furnace  and  the  length  of  the  flame  travel.  Furnaces  with  a  small  com- 
bustion space,  in  which  the  Ilame  travel  must  be  short,  are  not  suited  for  the 
burning  of  high  volatile  coals  at  high  rates  of  combustion.  For  reasonably 
complete  combustion,  the  combustion  chamber  must  tie  large  enough  to  permit 
thorough  mUriHg  of  the  air  and  gases;  sufficient  fi'nii*  for  comliustion ;  and  to 
maintain  temperature  sufficiently  high  to  secure  combustion. 

Mixing.  To  secure  efficient  combustion,  the  volatile  distilled  from  coal. 
which  in  part  is  composed  of  tar  vapor,  gases  and  small  solid  particles  of 
floating  carbon,  must  be  intimately  mixed  wilh  an  adequate  supply  of  air.  Fuel 
oil  and  gas  must  also  be  mixed  uioroughly  with  air.  If  the  right  mixture  is 
not  maintained,  the  result  is  stratification,  such  as  is  common  in  hand-fired 
furnaces  not  operated  properly.  In  stoker-fired  installations  the  fuel  is  more 
evenly  distributed  over  the  grate.  This  prevents  the  inrush  of  large  quantities 
of  air  in  spots  and  the  choking  of  air  in  other  parts;  the  products  of  com- 
liustion are,  therefore,  mixed  more  uniformly  with  oxygen -bearing  air. 

Additional  air  is  sometimes  supplied  above  the  fuel  bed  to  obtain  thor- 
ough burning.  Arches,  piers,  wing  walls  and  steam  jets  are  sometimes  added 
in  hand-fired  furnaces  to  give  a  thorough  mixture  of  air  and  gas  so  that  the 
higher  volatile  coals  can  be  burned  without  smoke.  The  locations  of  these 
parts  depend  upon  the  kind  of  coal  and  the  manner  in  which  the  boiler 
is  to  be  operated.  Such  structures  increase  the  draft  loss  through  the  boiler, 
so  that  the  steaming  capacity  for  a  given  draft  is  reduced.  Generally,  how- 
ever, they  improve  combustion. 

Time.  This  is  next  in  importance  to  the  mixing  requirement.  The  time 
available  for  combustion  (before  the  gases  are  cooled  by  the  boiler  heating 
surface)  depends  upon  the  length  of  gas  travel,  or  for  the  same  grate  area, 
upon  the  cubical  contents  of  the  furnace.  The  combustion  space  must  be 
correctly  related  to  the  rale  of  combustion  for  a  given  fuel,  otherwise  economy 
ivill  be  sacrificed. 

Experiments  by  the  Bureau  of  Mines  with  a  Heine  Boiler  indicate  the 
relation  between  boiler  economy  and  furnace  volume,  as  in  Fig.  15.  In 
these,  semi -hi  luminous  coal  was  burned  on  a  Murphy  stoker  having  a  pro- 
jected grate  area  of  25  square  feet.  Pocahontas  steaming  coal  was  con- 
sumed at  the  rate  of  6S.4  lb.  per  sq.  ft.  of  grate  per  hour.  When  the 
products  of  combustion  had  passed  through  80  cu.  ft.  of  combustion  space, 
the  gases  contained  fully  3.7  per  cent  of  unconsumed  combustible,  but  as 
the  space  traversed  increased  to  160  cu.  ft.  the  combustible  decreased  to 
1  per  cent  When  a  point  corresponding  to  260  cu.  ft.  of  the  furnace  volume 
had  been  passed  less  than  0.5  per  cent  of  combustible  remained  in  the 
srases.  This  indicates  that  the  larger  the  combii-ition  space,  the  more  nearly 
complete  is  combustion. 


ib.  Google 


FURNACES    AND    SETTINGS 


Tftttperature.  The  combustible  gases  in  a  boiler  furnace  must  be 
kept  at  a  temperature  sufficiently  high  to  permit  complete  combustion. 
economically  and  without  smoke.  The  ignition  temperature  of  hydrocarbon 
gases  is  between  1000  and  1500  degrees.  However,  this  temperature  varies 
with  the  amount  of  air,  kind  of  fuel,  and  the  quantity  of  neutral  gases  present. 

A  high  furnace  temperature  generally  means  rapid  combustion  and  good 
efficiency.  It  is  the  result  of  higher  CO,  and  the  absence  of  CO.  so  that 
the  gases  are  more  nearly  burnt  while  traversing  the  furnace.  The  varia- 
tion of  furnace  temperature  and  boiler  load  is  shown  in  Fig.  16,  which 
represents  tests  by  the  U.  S.  Geological  Survey  on  a  Heine  boiler  and 
underfeed  stoker. 


MM 

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D,B,i,.ab,GoOglc 


FURNACES    AND    SETTINGS  87 

The  effect  of  temperature  is  also  shown  by  tests  of  the  Universily  of 
Hlittoit  on  a  Heine  boiler  equipped  with  a  Green  chain  grate,  Fig.  17.  An 
economizer  and  a  large  induced  draft  fan  were  used,  so  that  the  rates  of 
combustion  were  high.  Coals  having  a  combustible  volatile  content  of 
from  30  to  40  per  cent  were  successfully  burned.  Fire  clay  tiles  are 
placed  on  the  boiler  lubes  directly  over  the  fire,  forming  the  roof  of  the 
furnace  and  pre\-enting  the  hot  gases,  which  are  still  not  fully  mixed,  from 
coming  in  contact  with  the  cooler  tubes. 


Fig.  17.     Heine  Boiler  Teited  for  SmokeleMnem. 

Tests  were  conducted  on  this  boiler  with  C-tile  on  the  bottom  row  of 
tubes,  and  then  with  7'-tile.  The  C-tile  encircle  the  tubes  completely  and 
present  to  the  furnace  a  roof  of  solid  firebrick.  The  T-tile  rest  upon  the 
top  of  the  tubes  only,  and  therefore  present  to  the  furnace  a  roof  of  part  brick 
and  part  water  tubes. 

With  T-titc,  the  smoke  record  varied  from  9  to  17  per  cent,  which 
corresponds  to  Nos.  Yi  and  1  on  the  Ringelmarin  scale,  respectively.  The 
C-tile  record  showed  zero  smoke.  The  temperature  oi  the  gases  entering 
the  nest  of  tubes  from  the  combustion  chamber  averaged  1384  deg.  in  the  first 
test,  and  1678  deg,  in  the  second  test.  The  corresponding  temperatures 
over  the  bridge  wall  were  about  1850  and  2150  degrees. 

Over  100  trials  were  rtiade  at  loads  varying  from  60  to  ISO  per  cent  of 
rated  boiler  capacity,  and  from  these  L,  P.  Breckenridge  concluded  that  it 
is  almost  impossible  to  make  smoke  with  this  setting  under  any  condition 
and  that  it  operates  with  economy. 

Furnace  Volume.  The  Bureau  of  Mines  shows  that  the  furnace  size  is 
influenced  mainly  by  the  percentage  of  excess  air,  the  rate  of  combustion  and 
the  kind  of  coat 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS 


A  Heine  boiler  and  a  special  Murpliy  side-feed  stoker  furnace  were 
used  in  the  tests.  Table  5  gives  the  composition  of  the  three  grades  of  coal 
— Pocahontas,  Pittsburgh  and  Illinois — burnt  in  these  tests.  The  results, 
Fig.  18,  represent  a  supply  of  50  per  cent  excess  air  for  two  rates  of  com- 
bustion of  the  different  coals,  and  K'^e  the  combustion  space  necessary  per 
square  foot  of  Rrate  area  for  various  combustion  conditions,  which  arc 
expressed  in  terms  of  the  ratio  of  undeveloped  heat  to  the  total  heat  in 
the  coal.  These  figures  can  be  used  as  a  guide  in  proportioning  almost  any 
style  of  furnace. 


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5 

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5 — i 

Unconaumcd  Cotnburttble.  ^rctn-t. 


ib.  Google 


FURNACES    AND    SETTINGS 


Table  S.     Analyais  of  Coala  Uied  in  the  Testa. 
PROXIMATE  ANALYSIS  OF  COAL  AS  RBCEIVBD 

Coal 

Co.1 

lUDofa 

Co.! 

VolatUe  matter percent 

2.21 
15.78 
71.66 
10.36 

2.S1 
30.28 
S6.82 
10.39 

16.16 
34.09 
39.19 

Ash percent 

10.66 

100.00 

100.00 

100.00 

ANALYSIS  OF  DRY  COAL 


Hydn^en 

Carbon 

percent 
percent 

3.82 
80.90 
1.00 
2.97 
.56 
10.59 

4.82 
76.57 
1.55 
4.99 
1.41 
10.66 

4.66 
69.63 

^EE:E= 

percent 
percent 
percent 

ved B.  t.  u. 

9.56 
2.08 
12.59 

100.00 

100.00 

100.00 

Calorific  value  per  pound,  as  recei 

13,762 

1335 

10,433 

A  long  narrow  combustion  space  is  to  be  favored  rather  than  a  short 
wide  one  of  the  same  cubical  contents.  For  conditions  other  than  Mnrphy 
type  farnaces  the  secondary  air  supply  should  be  tborouRhly  mixed  with 
the  gases  arising  from  the  fuel-bed.  The  secondary  air  should  always  be 
admitted  near  and  over  the  fuel-bed,  at  hi[th  velocity,  and  in  a  large  number 
of  streams. 

A  variation  of  50  to  100  per  cent  in  the  excess  of  air  makes  no  appre- 
ciable difference  in  the  efficiency  of  the  small  furnace.  In  a  furnace  of 
large  size,  however,  a  small  variation  in  the  excess  air  will  affect  the  oper- 
ating efficiency,  so  that  close  control  o£  the  air  supply  becomes  necessary 

The  minimum  percentage  of  unconsumed  combustible  in  the  products  of 
combustion  is  much  larger  in  a  furnace  having  a  small  combustion  space  than 
in  a  furnace  having  a  large  combustion  space.  The  efficiency  obtained  with 
the  large  combustion  space  is  therefore  much  higher.  For  boilers  operated  at 
heavy  overloads,  a  large  furnace  volume  is  particularly  essential. 

Efficient  combustion  is  secured  when  the  furnace  volume  permits  ample 
time,  adequate  mixing  and  sufficient  temperature  for  thorough  burning  of 
the  gases.  The  boiler  settings  should  be  high  and  the  baffles  placed  horizon- 
tally on  the  tubes.  The  horizontal  baffling  promotes  the  mixing  of  strat- 
ified layers  of  the  gases,  and  gives  the  gases  time  to  burn  completely  before 
the  tubes  cool  them  below  the  temperature  of  ignition. 

Head  Room  for  Coal  Burning  Boilers.  A  definite  height  of  boiler  setting 
is  required  for  complete  fuel  combustion.  Investigations  by  0.  MonHell  on 
settings  for  the  smokeless  combustion  of  soft  coal  are  summarised  in  Table 
6,  applying  to  water-tube  boilers  under  average  operation. 


ib.  Google 


FURNACES    AND    SETTINGS 


Table  6.     Headfoom  Requlremmt»  for  SmolceleM   8«ttingi 


Hot.   T«rt.  Rot.    V«rt. 


^Fltdi 


(All  Dimer 


No.  6 

■BNo-T 

.SNo.8 

J  Down  draft 
McMillan 
Twin  fire 

Semi.  eirt.  refuse 
burning 

■f-g  Burke 

&[»  McMillan 

Chain  grate 

e -a  Moore 

S  SRoney 

f*-"*- 20th  tint 

^Detroit 

.g-P  Model 

iJt[£McKenae 

*Mur|Ay 

jl  -a  American 

|l">°- 

Taykw 

WeMiogbouK 


Shell  to  dead  plate  Front  header  tc 

33  I  34  I  34  I  3a  I  72  I  *  I  78  I 
36404042  t  t  t 
32l34|34|80|72l  *|78| 
SieUu 


«0 

BO 

BO 

60 

72 

• 

78 

• 

m 

M 

60 

60 

72 

7« 

58 

tw 

m 

64 

T2 

• 

78 

• 

tt 

tt 

tt 

tt 

84 

• 

90 

• 

48 

48 

fiO 

M 

flO 

• 

6« 

• 

48 

48 

60 

64 

60 

• 

66 

• 

72 

72 

78 

78 

W 

114 

96 

120 

4ft 

M 

AO 

BO 

72 

102 

78 

108 

m 

60 

m 

7?. 

84 

1(V 

90 

120 

« 

60 

66 

Ti 

84 

108 

9U 

120 

fW 

7?. 

78 

84 

00 

■ 

96 

• 

m 

72 

7K 

84 

HO 

96 

m 

70 

70 

70 

flO 

96 

60 

72 

78 

84 

90 

96 

• 

FuUe 
FuUe: 
Full^Ttension 
Fidle; 


Shell  to  Dead  Hate 


42 
36 

42 
38 

42 
40 

42 
42 

78 
78 

84 
84 

96 
96 

102 
102 

84 
84 

90 
00 

102 
102 

108 
108 

W 

ir  H.  R.  T.  bolUn. 


ib.  Google 


t'URNACES    AND    SRtTlMr.S 


Classification  of  Settings 

IN'  die  burning  of  fuels  economy  is  repreaented  by  completeness  of  com- 
bustion and  sraokelessncss.  As  this  depends  upon  the  style  of  setting,  air 
■upply  and  method  of  feeding  coal,  it  is  used  by  //.  Kreisinger  as  a  basis 
for  classifying  furnaces,  as  shown  in  Fig.  19,  At  (A)  is  a  hand-^red  furnace 
into   which   the   cnal   is   fed   interniittemlv   on  the  top  of  the  fire.     The  air 


Coa/ 


Jna»rfe»d    Stok»r 


comes  in  a  continuous  stream  through  the  grate,  from  the  bottom.  Some 
air  should  also  be  supplied  over  the  fuel-bed. 

In  the  side-feed  stoker  (B)  the  coal  is  ted  continuously  from  the 
side  and  the  air  from  the  bottom  at  right  angles  to  the  path  of  the  coal. 
The  coal  moves  down  the  srate  by  gravity  and  by  the  agitation  of  the 
grate  bars.  Air  can  also  be  admitted  through  special  tuyeres  placed  imme- 
diately above  the  fuel-bed,  at  the  entrance  of  the  coal  into  the  furnace. 
Some  air  enters  through  the  coal  in  the  -magazine. 

The  diagram  (C)  shows  a  furnace  equipped  with  traveling  or  chain 
grate.  The  feeding  of  the  coal  is  accomplished  by  the  motion  of  the  grate. 
The  air  and  coal  are  both  fed  coniiruously,  the  air  l>«ing  fed  at  right  angles 
to  the  coal  path.  Additional  air  is  supplied  through  the  coal  in  the  maga- 
zine, through  the  thin  fucl-beil  near  the  bridge  wall,  and  through  leaks  along 
the  side  walls. 

In  the  underfeed  stoker  (D)  the  air  and  coal  are  fed  uniformly  and 
in  the  same  direction.  Air  ts  also  admitted  through  the  damper  in  the  front 
door  of  the  furnace. 

These  styles  of  furnaces  are  shown  in  the  following  illustrations  with 
settings  of  Heine  boilers  as  installed  in  modern  plants  under  standard  as  well 
as  special  conditions,  and  for  a  variety  of   fuels.     In  practice  each  problem 


ib.  Google 


FURNACKS    AND    SKTTINGS  9.! 

has  to  be  studied  to  decide  upon  the  proper  furnace  design  and  proportions. 
Generally  a  change  in  the  location  and  in  the  type  of  tile  used  in  the  baffles 
will  give  furnaces  for  particular  combustion  requirements. 

In  vertically-baffled  boilers  the  extinguishing  action  of  the  tubes,  wKh 
the  short  flame  travel,  produces  an  undesirable  amount  of  smoke.  If  the 
tombustion  in  these  boilers  is  to  be  smokeless  the  furnace  volume  anil  there- 
fore the  settinR  heiKht  must  be  increased  considerably.  Even  then  the  mixing 
effect  of  the  bridge  wall  and  combustion  chamber  arc  absent 

The  horizontally-baffled  boiler  has  the  necessary  furnace  volume  with 
the  ordinary  height  of  seltinK.  Horizontal  baffles,  in  hand  or  stoker  fired 
Ijoilers,  permit  a  long  travel  of  unciiilled  flame  and  maximum  lime  for  com- 
pletion of  combustion.  The  turn  of  the  gases  at  the  bridge-wall  disrupts 
any  tendency  to  stratify,  and  this  mixing  effect  also  promotes  comliuslion. 


Settii^s  for  Hand  Firing 

1\'  burning  bituminous  coal,  it  is  not  practicable,  according  to  O.  MonncU, 
to  combine  a  hand-fired  furnace  with  a  vertically  baffled  water-lube  boiler. 
To  prevent  smoke  the  furnace  must  be  arranged  with  a  horizontal  baffle. 
as  in  Fig.  20.  In  this  design  the  lower  part  of  the  tubes  over  the  fire  is 
left  bare  by  using  T-tiles  for  the  bafFle.  For  the  high  temperature  zone 
over  the  bridge  wall  and  for  some  distance  back  of  it,  the  tubes  are  entirely 
encased  in  C-tiles,  This  pnrt  of  the  baffle  is  extended  from  the  T-tiles 
to  the  deflection  arch  provided  to  mix  [he  air  and  gases  thoroughly. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  95 

Th«  proportions  of  the  furnace  for  this  setting  are  determined  on  a 
basis  of  grate  area.  The  parts  are  placed  so  that  there  will  be  from  20  to 
25  per  cent  of  the  grate  surface  in  the  free  opening  above  the  bridge-wall, 
40  per  cent  between  the  bridge-wall  and  arch,  and  50  per  cent  free  area 
under  the  arch.  The  installation  of  four  siphon  steam  jets,  placed  across 
Ihe  furnace  above  the  fire  doors,  is  recommended  to  give  a  secondary  air 
supply.  This  type  of  setting  has  been  successful  where  soft  coal  is  used 
and  where  municipal  smoke  ordinances  are  enforced. 

Another  form  of  setting  for  hand-firing  of  bituminous  coal  is  the  down- 
draft  furnace,  shown  in  Fig.  25.  Boilers  so  arranged  have  given  excellent 
results  both  in  smoke  prevention  and  in  fuel  economy. 

As  anthracite  coal  runs  much  lower  tn  volatile  matter  than  bituminous 
coal,  the  flame  is  much  shorter  and  practically  all  of  the  combustion  occurs  in 
the  fuel-bed.  The  style  of  setting  shown  in  Fig,  21,  can  be  used  for  such 
service.  The  T-tilea  are  placed  on  top  of  the  first  row  of  tubes.  This 
leaves  the  bottom  of  the  tubes  exposed  to  the  heat  of  the  fire  but  still  forms 
the  roof  af  a  combustion  chamber  in  which  the  gases  are  retained  and 
thoroughly  mixed  until  combustion  is  complete. 


Pig.  31.     Setting  for  Hand-Gring  of  Anthracite  Coal. 

D,g,tze:Jbi  Google 


Fl'RNACES    AND    SETTINGS 


When  the  distance  between  the  grate  and  first  tube  bank  is  greater  than 
that  shown  in  Fig.  21,  the  lower  baffle  can  be  placed  on  the  second  or  third 
row  of  tubes.  In  another  modification,  Fig.  22,  the  baffle  on  the  lowest 
row  of  tube?  is  not  used,  and  the  bridge  wall  is  built  up  to  the  bottom  tow 
of  tubes. 


FiK.  32.     Alternative  Setting  for  Hand-firing  of  Anthracite  Coal. 


Grates  for  Hand-Firing 

THE  Krate  in  a  boiler  furnace  not  only  supports  ihe  fuel-bed.  but  also 
admits  the  air  for  combustion.  It  is  almost  invariably  made  of  cast  iron, 
which  melts  at  about  2100  deg.,  while  the  lower  layer  of  the  fuel-bed  on  it  is 
at  about  4000  deg.  temperature.  A  grate  does  not  become  very  hot  when  the 
air  is  passing  throutth  it,  and  it  is  further  protected  against  high  temperatures 
by  the  insulating  effect  of  the  l.iycr  of  ash  lictwcen  the  gr.ite  bars  and  the 
fuel.  The  surfaces  and  air  spaces  siiould  lie  so  proportioned  that  they  will  lie 
kept  uniformly  cool  by  the  flowing  air.  However,  with  a  burning  fire  on  the 
grate  and  the  draft  obstructed  or  shut  off.  heat  will  accumulate,  and  the 


D,g,tze:Jbi  Google 


FURNACES    AND    SETTINGS 


grate  will  become  red  hot.  If  the  grate  does  tiol  burn  out  or  melt  and  fall 
into  the  ash-pit  at  this  high  lemperature,  it  will  be  twisted,  warped,  and  will 
sag.  The  same  harmful  effects  are  caused  by  accumulations  of  ash  and  burn- 
ing coal  in  the  ash-piL 

Cast  iron  is  weak  at  a  dull-red  heat  and  Ihc  high  temperature  causes  it 
to  grow.  Repeated  heating  will  cause  a  grate  bar  15  in.  long  to  grow  Yi  in., 
accordingto  W.  J.  Keep,  and  the  pressure  it  will  exert  on  the  dead  plate  and 
bridge  wall  will  force  it  into  a  curved  shape,  unless  proper  provision  for 
expansion  is  made.  The  strength  of  cast  iron  decreases  rapidly  above  680 
deg..  which  is  about  the  ordinary  temperature  of  the  front  grate  bar.  At 
this  temperature  the  tensile  breaking  load  is  23,750  lb.  per  sq.  in.,  while  at  a 
temperature  of  1250  deg.  the  breaking  load  is  only  8,023  lb.  per  sq.  in.  After 
being  reheated  cast  iron  never  contracts  to  its  original  length.  The  cast  iron 
for  grates  should  be  composed  of  the  highest  grade  materials  having  great 
heat-resisting  qualities,  so  that  the  grate  will  expand  and  contract  evenly. 

Hand-fired  Rrates  are  of  the  stationary,  shaking,  dumping,  and  the  com- 
bined rocking  or  shaking  and  dumping  types.  Grate  bars  are  manufactured 
in  numerous  patterns  and  designs  with  curved  or  flat  tops.  The  styles  used 
for  the  burning  of  the  regular  sires  of  coal  are  illustrated  in  Fig.  23. 


Sloftcil 
Fig.  23.     Typical  Styles  of  Stationary  Grate  Bara. 

The  sljle  of  Krate  bar  and  the  number,  size  and  shape  of  air  spaces 
are  determined  by  the  coal  for  which  the  grate  is  to  be  used.  The  free 
area  through  the  grate  should  not  allow  the  coal  to  drop  through  into  the 
ashpit,  but  should  be  large  enough  to  prevent  clogging  with  ashes  and 
cinders.  Air  space  areas  of  30  to  50  per  cent  of  the  total  grate  area  have 
lieen  found  satisfactory  with  natural  draft.  It  is  common  practice  to  allow 
%  in.  air  space  for  No.  3  buckwheat,  '/i  in.  for  No.  2  buckwheat,  5/16  in.  for 
No.  1  buckwheat,  Hi  in.  air  sp.nce  for  pea  coal  and  Vi   in.  openings  for  bitu- 

In  small  plants,  where  larger  sizes  of  anthracite  are  burnt,  the  plain 
grate  is  probably  as  satisfactory  as  any ;  when  coals  of  high  ash  content  and 
wliich  clinker  are  used,  the  shaking  or  rocking  grate  is  to  be  preferred.  The 
grate  must  be  so  constructed  that  the  moving  parts  will  not  clog  and  so 
that  their  action  will  break  up  the  clinker. 

Anthracite  dust,  silt,  culm  and  screenings  are  burnt  on  grates  with  small 
openings  and  require  mechanical  draft. 


ly  Google 


ib.Google 


Fl'RNACES    AND    SETTINGS 


Hollow  grate  bars,  with  a  blower  system,  are  sometimes  used  for  burn- 
ing sawdust,  chips,  shavings,  tanbatk  and  bagasse.  Such  grates  should 
have  large  air  spaces  so  tliat  partial  <illing-up  of  the  openings  will  not  inter- 
fere with  the  air  supply  for  proper  combustion.  In  making  up  the  required 
grate  surface,  the  hollow  bars  are  sometimes  alternated  with  ordinary  bars 
to  suit  the  fuel. 


Fig.  24.     Water  Orate. 


Grate  bars  are  generally  made  in  sections  not  more  than  3  ft.  long,  so 
that  the  total  grate  extension  is  a  multiple  of  this  length.  Grate  bars  are 
3  to  6  in,  deep  at  the  middle,  taperinR  down  to  about  1  in,  at  the  ends.  To 
allow  for  expansion,  the  bars  are  usually  made  about  2  per  cent  shorter 
than  the  space  for  which  they  are  intended,  so  that  they  will  fit  when  the 
boiler  is  operating.  Most  grate  bars  arc  in  one  piece,  although  some  have 
a  body  portion  and  a  removable  sectional  top,  which  contains  the  air  spaces. 

The  total  grate  length  is  limited  by  the  physical  ability  of  the  fireman  to 
throw  the  coal  to  the  farthest  end.  Grates  10  to  12  ft.  in  length  are  some- 
times used  for  anthracite.     The  limits  for  bituminous  coal  are  6  to  8  ft. 


Fig,  35.     Water  Grate  ai  Used  in  Down-draft  Boiler  Setting. 


ib.  Google 


100  rrRXAci'.s   Axn   sfttinhs 

becaiis;  it  is  moro  <1ifFLciilt  i 
itidiiied  from  •>  i  in.  to  t '  j  in 
aid  in  liriiig. 

Doivn-ilrafi  settings  for  tlie  smokeless  combustion  of  soft  coal  utilize  n 
so-called  wler-gralc,  l''ig.  24,  which  is  placed  above  the  ordinary  grale  in  the 
boiler,  as  shown  tn  Fig.  25.  The  water-grale  consists  of  a  series  of  pipes 
fastened  to  steel  headers,  so  connected  to  the  boiler  that  water  will  circulate 
through  it  Fresh  coal  is  fed  onto  the  water  grate,  and  the  air  admitted 
above  it  travels  downward  llirough  the  fuel-bed.  As  the  coal  becomes  partly 
consumed,  It  falls  through  to  the  grate  below,  where  the  combustion  is  com- 
jileted.  The  space  between  these  two  grates  is  the  combustion  chamber,  in 
which  the  gases  are  consumed  before  passing  through  to  the  chimney. 

Settings  for  Mechanical  Stokers 

WITH  cliain  grale  stokers.  Heine  boiler  settings  are  as  shown  in  Fig.  26. 
The  tiles  of  the  lower  l>alfle  are  placed  on  the  first  row  of  tubes,  either 
encircling  the  tubes  entirely  or  exposing  the  bottom  half.  A  head  room 
of  7'/t  feet  from  the  floor  line  to  the  underside  of  the  waterleg  gives  the 
desired  furnace  proportions.  This  dimension  may  vary  considerably  without 
alTectiiiR  the  boiler  performance,  but  should  not  be  less  than  6'A  feet.  This 
setting  has  been  found  to  Rive  good  economy  and  smokeless  operation  for 
loads  uo  to  200  per  cent  of  ratimj. 


Fig.  26.     Chain  Grate  Setting. 

With  side-feed  or  double  inclined  stokers,  the  boiler  can  be  set  with  an 
extended  furnace  or  with  a  flush  front.  In  the  typical  setting.  Fig.  27, 
the  bottom  row  of  tubes  is  enclosed  in  baffle  tiles  to  give  a  solid  roof,  and  an 
auxiliary  bridge  wall  breaks  up  the  currents  of  gases  and  insures  a  thorough 
mixture.  The  side-feed  stoker  combined  with  a  vertically  baffled  boiler  will 
not  give  smokeless  combustion.  With  horizontal  baffles  a  I'A-iX.  clearance 
is  sufficient  between  the  bottom  of  the  front  header  and  the  floor  line. 


ib.  Google 


!■■  [J  K  \'  A  r  !■:  S     AND     S  I',  T  T  I  X  C  S  101 

The  o^(i-fe,-d  type  of  stoker  fits  in  nt  the  front  of  the  boiler  and  tia^i 
a  shaking  or  dumping  grate  al  the  foot  of  th^'  hridge-wall.  For  boilers  with 
horizontal  baffles,  a  6-fi.  setting  is  required,  while  for  vertical  baffles  the 
clearance  should  be  abnnt  9  feet.     Fig.  28  shows  a  Heine  boiler  and  a  front- 


Fig.  37.     Side  Peed  Stoker  and  Extension  Furnace  Setting. 


feed  stoker.  The  typical  baffle  arrangement  is  nsed,  hut  deflection  arches 
or  piers  sometimes  aid  in  mixing  the  gases.  When  the  clear  opening  between 
the  lop  of  the  bridge-wall  and  the  bottom  of  the  lirst  row  of  lubes  is  not 
less  than  40  per  cent  of  the  grate  area,  piers  are  not  required. 


ib.  Google 


sS 


1^ 


ib.Google 


FURNACES    AND    SETTINGS 


Pig.  28.     Setting  for  Overfeed  Stoker. 

With  the  underfeed  stoker,  the  rates  of  comhuslion  are  usually^  high. 
so  that  a  great  volume  of  combustible  gas  has  to  be  burned  in  the 
furnace  before  being  chilled  by  the  boiler  surface.  For  this  reason,  the 
standard  Heine  furnace  design.  Fig.  29,  is  generally  retained.  The  settings 
can  be  lower  for  the  horizontal  types  of  underfeed  stokers  than  tor  the  in- 
cV      ' 


Fig.  29.     Setting  for  Horiiontal  Underfeed  Stoker. 

D,g,tze:Jbi  Google 


I-  U  K  N  A  C  H  S    AND    SETTINGS 


Via.  -'0  shows  a  Heine  boiler  and  superhealer  set  for  niechanic-al  draft, 
ml  an  underfeed  stoker  of  the  inclined  type.  The  headroom  between  the 
raterleg  and   the  floor  line  is  about   7   feet.     The  lower  balTle  is  made   to 


enclose  the  tubes.  By  changitig  the  tile  to  the  third  rnw  of  tubes,  the  setting  ii 
Fig.  31  is  obtained.  In  this,  more  heal  is  absorbed  by  direct  radiation,  an< 
excessive   furnace  temperatures  are  avoided. 


ib.  Google 


FURNACliS    AN'D    SliTTIKGS  105 

By  installing  doable  ilokcrs,  boiler  capacity  and  efficiency  can  be  in- 
creased for  almost  the  same  space.  One  stoker  is  placed  at  the  front  and 
nnc  at  the  rear  of  the  settinK-  as  in  Kig-  32.  By  forcing  a  greater  weight  of 
^ses   through    the    boiler,    the    capacity    is    increased.      The   larger    furnace 


Fig.  31.      Modified  Stoker  Setting. 


volume  gives  belter  combustion ;  also,  a  larger  proportion  of  heal  is  radiated 
to  the  boiler.  At  heavy  loads  the  overall  efficiency  is  higher  than  when 
one  stoker  is  used.  Any  variation  in  the  etficieiicy  is  due  to  changes  in  the 
furnace  operation,  because  the  elTiciency  of  the  boiler,  proper,  as  a  heat 
absorber,  is  practically  c 


ib.Google 


FURNACES    AND    SETTINGS 


Fig.  32.     Double  Stoker  Setting  for  Hrine  Boiler  with  Superheater. 


D,g,tze:Jbi  Google 


FURNACES    AND    SFTTINHS  107 

Ashpits 

P[K  ashpit  is  made  of  concrete  or  brick.  The  design  depends  upon  the 
boiler  load,  kind  of  coal,  type  of  furnace,  whether  hand  or  stoker  fired. 
and  of  setting.  Ashpits  satisfactory  with  a  mechanical  or  pneumatic  system 
may  give  trouble  for  hand  removal,  while  pits  for  hand  operation  may  also 
prove  satisfactory  with  a  conveyor. 

The  ashpit  should  be  large  enough  to  accommodate  the  ashes  from  an 
18  to  20-hr.  run.  Such  pits  eliminate  the  handling  of  ashes  by  the  night  shift. 
They  al.so  protect  the  grates  or  stokers  against  destruction  by  the  action  of 
accumulated  ash  and  clinker.  In  practice,  however,  ashpits  for  hand-fired 
furnaces  are  seldom  of  more  than  an  8  or  10-hr,  capacity.  Pits  having  capac- 
ities of  12  to  14  hr.  are  generally  provided  for  stoker  installations. 

To  proportion  the  pit  for  a  given  period,  the  maximum  amount  ot 
fuel  that  can  be  burned  on  the  grates  must  tirst  be  determined.  The  maximum 
perceniage  of  ash  or  refuse  should  be  figured  on  the  basis  of  the  lowest 
grade  of  fuel  to  be  burned.  The  pounds  of  ash  and  refuse  to  be  handled 
per  hour  is  the  product  obtained  by  multiplying  the  percentage  refuse  and 
the  hourly  fuel  consumption.  The  volume  is  determined  by  allowing  40  lb. 
of  ash  to  the  cubic  foot.  The  total  capacity  required  then  depends  upon  thu 
periods  of  ash  removal. 

Ashpits  should  be  so  accessible  that  they  can  be  easily  cleaned ;  otherwise 
the  work  may  not  be  attended  to  regularly,  and  the  grates  or  stoker  mech- 
anism will  be  damaged.  Fairly  small  pits  are  easily  cleaned  and  give  better 
results  than  large  pits,  which  involve  heavy  labor,  .\mple  room  must  be 
provided  for  the  use  of  a  hoe  or  shovel.  The  pit  should  be  not  longer  than 
8  feet.  Doors,  gates  or  valves,  as  used  on  hoppers,  should  be  arranged  to 
open  anil  close  easily  and  should  he  accessible  from  the  floor.  Means  of 
inspection  should  be  provided  to  make  sure  that  all  the  ash  has  been  dis- 
charged. With  reasonable  care,  the  cost  of  ashpit  repairs  or  relining  can 
l>e  kept   low. 

Some  typical  designs  of  ashpits  are  given  for  different  operating  con- 
ditions. The  simplest  form  is  the  usual  pit  for  hand-fired  furnaces,  as  shown 
in   Fi^.  3,1. 


Pig.  33.     Coromoc  AahiMt  for  Hand  Firing. 

A  modification  to  obtain  greater  ash  capacity  without  sacrificing  ease  of 
ash  removal  is  shown  in  Fig.  34. 


ib.  Google 


Grand  Central  Terminal  of  the  New  York  Central  Railroad,  New  York  City, 

in  course  of  construction.     Thii  building  contains  8550  H.  P. 

of  Heine  Standard  Boilen. 


F  r  R  M  A  C  E  S    AND    S  K  T  T  I  N  f;  S 


Fit.  34.    Large  Capacity  AihiHt  for  Hand  Firing. 


_ I  form,  particularly  for  si<lc-feeil  stokers,  is  shown  in  Fig.  35, 

t  of  construction  and  maintenance  is  low;  liiit  it  is  very  difficult  lo 
emove  ash   frotn  pits  of  this   form   unless  a   pneitmalic  or  steam  conveyor 


Pig.  3S.     Rectangular  Ashpit  of  Large  Capacity. 


In  modem  stoker-fired  plants  it  is  the  general  practice  to  use  hoppsr 
ashpits.  The  labor  of  handling  the  ash  is  greatly  reduced  and  the  installa- 
tion of  ash  conveyors  is  more  convenient.  The  tunnel  under  the  firing  floor 
enables  the  at<h  to  be  easily  hoed  from  the  hopper  ashpit  into  conveyors 
or  ash  cars  without  interfering  with  the  work  on  the  firing  floor.  Fig.  36 
shows  an  example  of  such  an  arrangement. 


ib.  Google 


FURNACES    AND    SETTINGS 


This  system  is  also  frequenlly 
Inw  grade  fuels  having  a  high  ash  c 
plates  are  Ihcn  generally  used. 


F"ig,  36,     Hopper  Ashpit 


A  still  more  convenient  method  which  is  adopted  in  most  modem  power 
plants  is  to  provide  a  basement  as  larse  as  the  boiler  room.  Ample  space 
is  then  available  for  ash-handling  apparalus,  forced-draft  air  ducts  and  other 
auxiliaries;  and  the  removal  of  ash  is  done  under  more  comfortable  condi- 
tions.   A  typical  arrangement  of  this  kind  is  shown  in  Fig.  37, 


D,g,tze:Jbi  Google 


I-"  I-  R  N  A  C  K  S    AND    S  E  T  T  I  .\  G  S 


Fig.  37.     Hopper  Aihpiti  mth  Basement  under  Bmler  Room. 

In  many  cases  separate  lioppers  are  provMcd  to  receive  ash  and  clinker, 
and  to  recover  coal  dropping  from  the  front  part  of  the  grate.  The  com- 
bustion chamber  is  often  provided  with  a  hopper  bottom  to  facilitate  the 
removal  of  dust. 

Some  suggestion  on  the  design  of  ashpits  may  also  be  obtained  from 
chapter  on  mechanical  stokers,  and  from  the  part  of  the  chapter  on  economi- 
cal boiler  operation,  referring  to  ash  handling. 

Hopper  ashpits  should  be  lined  with  firebrick.  There  is  always  the 
possibility  of  combustible  matter  burning  in  the  ashpit  owing'  to  careless 
operation  of  mechanical  stokers  or  dumping  grates,  and  fairly  high  tempera- 
lures  are  often  encountered  in  such  rases. 

Ash  doors  and  valves  at  the  bottom  of  hopper  a.sh-pits  should  be  air- 
tight or  nearly  so.  With  natural  draft  sufficient  air  will  be  drawn  in  through 
leaky  doors  lo  cause  brisk  combustion  under  conditions  described  above, 
and  the  ash  may  be  melted  into  large  clinkers,  which  are  difficult  t 
and  which  sometimes  must  bs  broken  up  before  they  t 
the  doors  or  valves.  With  forced  draft  under  pressure 
pit,  leaky  doors  may  increase  the  load  on  the  fans  and  cs 
consumption. 

Settings  for  Powdered  Coal 
pOWDERED    coal    has    been    used    extensively    for    the    past    twenty-five 
''-    years  in  certain  metallurgical  processes,  particularly  in  the  cement  indus- 
try, and  its  success  in  this  and  similar  industries  is  amply  testilied  by  its 
extensive  use.     Certain  characteristics  in  the  coQibustion  of  pulverized  coal 


1  be  got  through 
1  the  hopper  ash- 
ae  wasteful  power 


ib.  Google 


112  FL'RN'ACES    AND    SETTINGS 

have  brought  out  the  fact  that  under  some  conditions  it  is  feasible  to 
utilize  this  fuel  for  use  in  generating  steain.  In  the  past  live  years  a  number 
of  boiler  plants  have  been  equipped  to  burn  this  type  of  fuel. 

Boiler  furnace  setting  design  for  the  successful  combustion  of  pulverized 
coal  was  a  subject  which  was  not  thoroughly  understood  when  the  first 
installations  of  this  sort  were  made,  and  hence  the  early  results  obtained 
were  not  satisfactory.  However,  the  subject  is  now  past  an  experimental 
stage  and  it  can  be  said  that  the  following  remarks  on  furnace  design  are 
in  general  indicative  of  good  practice.  The  furnace  volume  should  be  so 
proportioned  that  combustion  is  completed  before  the  tube  bank  is  reached. 

About  2  to  2^4  cu.  ft.  of  furnace  volume  should  be  provided  for  each 
boiler  horsepower  developed,  assuming  that  the  combustion  chamber  is  nearly 
in  the  form  of  a  cube.  Boiler  furnaces  are  not  always  of  cubical  form,  so 
that  the  velocity  of  the  gases  should  be  limited  to  7  ft.  per  second,  through 
the  smallest  cross  sectional  area  and  where  the  temperatures  are  highest. 
This  rule  for  contents  holds  good  for  coals  in  which  at  least  25  per  cent  of 
the  total  combustible  is  volatile  matter.  It  does  not  apply  to  anthracite, 
coke  bree«,  or  other  low  volatile  fuels. 

An  extension  furnace  is  usually  employed  to  obtain  the  required  com- 
bustion space.  Inasmuch  as  the  ash  will  tend  to  adhere  in  the  form  of  slag 
on  furnace  sides  and  bottoms,  it  is  desirable  to  have  these  surfaces  slope 
downward  to  a  slag  hole,  through  which  the  molten  slag  can  be  tapped  off. 
runiace  temperatures  arc  high  in  this  class  of  tiring,  and  it  is  essential  that 
the  walls  be  heavy  and  constructed  of  hrst  quality  refractories. 

Fig.  38  shows  a  Heine  cross  drum  boiler  with  a  typical  setting  for  burn- 
ing pulverized  coal  with  the  Bonnot  system. 


Pig.  38.     Typical  Powdered  Coal  SetUng. 


ib.  Google 


FURNACES    AND    SETTINGS  113 

The  use  of  powdered  coal  necessitates  the  iiistalbtimi  of  a  [ire  pa  ration 
plant,  which  generally  consists  of  a  cnisher.  a  dryer,  a  pulverizer  and  suit- 
ahLe  elevators,  conveyors,  dust  collectors,  hoppers,  etc.  Fig.  39  shows  the 
layout  of  a  typical  preparation  plant. 


ib.  Google 


ni 


ll 


K 


D,B,i,.ab,GoOglc 


FURNACES    AND    SETTINGS  115 

Powdered  coal  requires  care  in  handling.  In  a  well-designed  and  prup- 
erly  operated  plant  there  is  but  little  danger  from  explosions.  However. 
where  hoppers,  conveyors,  elevators  and  dust  collectors  are  not  tight,  and 
the  powdered  coal  is  allowed  to  escape  into  the  room,  tliere  is  great  liability 
of  explosion  due  to  the  possibility  of  the  ignition  of  the  cloud  of  coal  dusi 
by  an  open  flame. 

Pulverized  coal  when  newly  ground  is  practically  a  fluid,  because  of  the 
entrained  air,  hence  it  is  readily  handled  by  conveyors  and  flows  easily  from 
hoppers.  But,  after  standing  from  36  to  43  hours,  the  entrained  air  escapes 
and  the  coal  settles  down  and  packs  in  the  hoppers.  The  correct  way  to 
overcome  the  ditliculty  of  packed  hoppers  is  to  provide  compressed  air  lines 
in  the  hopper  sides  and  thus  agitate  the  packed  coal  with  air,  supplemented 
bj  hand  poking.  Hammering  the  hopper  sides  to  make  the  coal  flow  only 
causes  it  to  pack  the  tighter  in  the  bin.  The  sides  of  powdered  coal  hoppers 
should  have  a  slope  of  not  less  ihan  sixty  degrees. 

In  order  to  handle  the   crushed   coal  in   the  pulverizers   it   is   generally 

The  pulverizer  is  generally  adjusted  for  grinding  the  coal  down  to  a  fineness 
of  8S  per  cent  through  the  200-mesh  sieve,  and  95  per  cent  through  the  tOO- 
raesh  sieve.  The  better  combustion  conditions  obtained  with  coal  of  greater 
fineness  than  given  above  docs  not  warrant  the  cost  of  the  extra  pulveriza- 


Powdered  Coal  Burners 

D  UR\ER  installations  usually  include  a  feeder  of  the  screw  conveyor 
*-'  type,  such  as  Fig.  40.  The  capacity  of  the  feeder  depends  upon  the  pitch 
and  depth  of  the  screw,  while  the  amount  of  feed  Is  controlled  by  its  speed. 
which  is  adjusted  by  a  variable  speed  motor  drive.  Air  for  feeding  and 
mixing  is  supplied  "by  a.  blower  at  6  oz.  pressure.  The  fuel,  as  it  drops  into 
this  blast  of  air,  is  agitated  by  a  paddle  wheel  so  that  the  mixture  of  air 


T\z.  40.     Lopulco  Type  Variable-apeed  Fuel  Feeder. 

D,g,tze:Jbi  Google 


FURNACES    AND    SETTINGS 


and  coal  remains  practically  of  constant  density  until  injected  into  the  fur- 
nace. The  tvpe  of  hnrner  recommended  with  this  eiitiipment  is  shown  in 
FiR.  41. 


Fig.  41.     Lopuico  Type  PulverUed  Fuel  Burner. 


In  ihe  humer  shown  in  Fig.  42.  a  variable  speed  screw  feeder  at  the 
bottom  of  the  pulverijed  fuel  bin  delivers  the  coal,  the  amount  being  regu- 
lated by  a  hand  wheel.  A  feeder  of  this  type  having  a  capacity  of  500  lb. 
of  fuel  an  hour  can  he  regulated  to  deliver  as  little  as  26  lb.  an  hour.  There 
lire  two  air  supplies,  both  controlled  by  blast  Ka'es.  The  air  for  combustion 
is  at  l^-oi.  pressure,  while  the  air  conveying  the  fuel  is  at  6-oz.  pressure, 
expanding  down  to  Ij^-oz.  in  the  burner.  The  burner  used  is  of  cast  iron 
pipe  with  II  specially  shapeil  elbow  in  which  the  fuel  pipe  is  placed. 


In  another  lutrncr  arrangement  no  mechanism  whatever  is  used.  The 
air  in  motion  through  a  mass  oS  powdered  fuel  picks  up  sufficient  fuel  to 
make  a  combustible  mixture. 

According  to  W.  A.  Evans,  the  control  of  the  fuel  supply  to  the  burners 
by  air  regulation  rather  than  by  varying  the  speed  of  a  screw  feed  gives  best 
results.  The  speed  of  the  screw  conveyor  cannot  be  adjusted  closely,  but  the 
air  blast  is  subject  to  exact  control.  For  any  given  feed  adjustment,  a 
burner  arrangement  should  deliver  the  required  fuel  with  not  more  than  a 
3  per  cent  variation  in  iiuaniity  for  any  number  of  S-min.  intervals. 


ib.  Google 


FURNACKS     ANn    SFTTrNGS  il7 

Settings  for  Oil  Burning 

THE  1156  o!  petruleuni  as  fuel  for  ste.ini  generation  has  increased  remark- 
ably within  the  last  decade.  Tliis  has  been  brought  about  by  the  abun- 
dant supply  resulting  from  the  development  of  new  oil  fields,  and  by  certain 
ndvanlages  of  oil  Hring  over  coal  firing.  But  as  the  supply  of  petroleum 
suitable  for  fuel  has  not  kept  pace  with  the  unusual  demand,  uncertain 
deliveries  and  increasing  cost  are  now  working  to  the  disadvantage  of  those 
plants  using  oil.  There  is  no  doubt  but  that  oil  ranks  second  in  imporiance 
to  coal  as  fuel  for  steam  generation,  but  with  the  present  rapid  depletion  of 
oil  resources  it  is  evident  that  oil  firing  will  never  supercede  the  use  of  coal. 

In  general  ihe  petroleum  used  for  steam  generation  is  of  two  types,  the 
one  commonly  called  fuel  oil  is  the  heavy  oil  resulting  from  a  partial  relin- 
ina  of  paralTin  crude,  and  the  other  is  the  unrefined,  a  sph  a  hum -base,  crude 
oil  The  oiU  found  in  the  mid-continent  and  Kastern  fields  contain  a  paraf- 
fin base,  while  thn^e  produced  in  the  Gulf  and  Western  fields  contain  an 
aTiphallum  base.  A  discussion  of  petroleum  with  t}^ical  analysis  is  given  in 
Chapter  13  on  FUEL. 

The  success  of  oil  firiiig  depends  largely  upon  proper  furnace  design, 
and  there  are  a  number  of  important  points  which  must  be  considered. 
First,  a  large  amount  of  refractory  radiating  surface  must  be  provided  to 
assist  in  combustion.  Good  practice  in  this  regard  is  to  allow  from  0,9  to  1.2 
square  feet  of  radiating  surface  per  i>oiler  horsepower  developed.  Second, 
the  furnace  volume  must  be  so  proportioned  that  the  gases  are  given  time 
for  complete  combustion  before  reaching  the  comparatively  cool  heating 
surface.  A  combustion  space  of  about  2.0  cubic  feet  per  developed  boiler 
horsepower    will    satiiifactority    meet    the    averapfe    volumetric    requirements. 


Pig.  43.    Typical  Oil  Burning  Setting. 


ib.  Google 


si 


1} 


^1 


D,B,i,.ab,GoOglc 


FURNACES    AND    SETTINGS  119 

In  proportioning  both  radiating  surface  and  combustion  space,  the  proposed 
ratings  at  which  the  boilers  are  to  be  operated  should  be  used  in  the  calcu- 
lations rather  than  the  manufacturers'  nominal  rated  horsepower. 

The  setting  of  the  Heine  boiler,  with  its  large  combustion  space  and 
ample  refractory  radiating  surface,  satisfactorily  meets  the  requirements  of 
oil  firing,    A  typical  setting  is  illustrated  in  Fig.  43. 

The  location  of  the  burners  in  oti-fired  setting  design,  should  be  such 
that  the  flame  action  will  not  be  localized  on  portions  of  the  heating  surface, 
so  that  trouble  from  blow-torch  action  with  the  resultant  blistering  of  tubes 
will  be  obviated.  The  oil  or  flame  should  not  impinge  direclly  on  any  por- 
tion of  the  furnace  brickwork,  because  when  starting  up  a  furnace  the  oil 
dripping  down  after  impingement  on  such  cold  surfaces  may  collect  on  the 
floor  of  the  combustion  chamber  in  such  quantities  that  a  serious  explosion 
may  occur  when  this  pool  of  oil  becomes  heated  up  to  the  ignition  point. 

Certain  features  in  chimney  design  for  oil  firing  are  discussed  in 
Chapter  6  on  CHIMNEYS. 

Oil  Burners 

ONK  advantage  in  the  use  of  oil  for  fuel  lies  largely  in  the  fact  that  it 
can  be  broken  up  into  minute  drops  so  that  the  air  for  combustion  comes 
into  intimate  contact  with  every  particle  of  the  liquid  with  the  combustible 
gases  evolved.  The  requirements  for  efficient  combustion  are  a  chamber  of 
the  proper  proportions  with  the  correct  air  supply  properly  distributed,  and 
the  thorough  atomization  of  the  entering  fuel,  the  term  "burner"  being  applied 
to  the  atomizing  device.  The  desired  effect  is  secured  either  by  the  action 
of  steam  or  compressed  air,  which  atomizes  the  oil  and  carries  it  into  the 
furnace,  or  by  purely  mechanical  means. 

There  are  many  types  of  oil  burners  and  these  are  arranged  differently 
because  of  the  method  of  operation  and  the  shape  of  the  flame.  Sometimes 
the  oil  is  sprayed  out  in  a  fan-lilce  flame  between  firebrick  blacks,  which  form 
the  approximate  boundaries  for  the  flame. 

The  burner  can  be  inserted  through  the  firing  door,  with  the  grates  cov- 
ered with  checkerwork  with  J^-in.  space  between  the  bricks,  but  the  "low 
setting"  is  preferred,  in  which  the  grates  are  removed,  and  the  checkerwork 
laid  on  supporting  brick  in  the  ashpit  and  the  bridge  wall  cut  level  with  the 
top  of  the  checkerwork. 

Steam  atomizers  include  outside  mixers,  in  which  the  steam  impinges  on 
the  oil  current  just  beyond  the  tip  of  the  burner,  and  inside  mixers  in  which 
the  two  come  into  contact  within  the  burner,  A  combustible  mixture  of  atom- 
ized liquid  and  volatile  gases  issues  from  the  nozzle.  In  air  atomizers,  a  jet 
of  air  under  high  or  low  pressure  is  used  to  break  up  the  oil,  part  of  the 
air  for  combustion  entering  in  this  manner.  With  mechanical  atomizers  the 
oil,  preferably  heated,  is  forced  out  under  pressure  through  a  distributing 
tip,  or  by  the  whirling  action  of  a  revolving  carrier. 

Burners  utilizing  steam  for  atomi^ation  are  installed  in  many  stationary 
oil-burning  power  plants.  They  produce  thorough  atomization,  with  a  long 
flame,  but  cannot  be  used  where  the  steam  would  be  liable  to  condensation, 
and  great  care  must  always  be  taken  to  keep  the  steam  consumption  down 
to  a  minimum.  Air  atomizers  are  desirable  in  marine  worlc  or  in  stationary 
plants  where  it  is  necessary  to  conserve  the  water  supply,  and  they  have  the 
further  advantage  that  the  latent  heat  in  the  exhaust  from  the  blowers  or 
compressors  is  returned  to  the  boiler,  and  no  heat  is  carried  away  by  the 
steam  in  the  flue  gases.  They  give  a  short,  intense  flame  and  the  furnace  brick- 
work must  be  proportioned  accordingly.  Under  proper  conditions,  either 
steam  or  air  atomizers  can  be  operated  with  a  steam  consumption  of  2  or 
3  per  cent  of  that  produced  by  the   boilers.     Mechanical   atomizers   require 


ib.  Google 


tNACtiS    AND    SETTINGS 


little  steam,  and  their  exhaust  can  all  be  returned  to  the  boilers.  Tlii'y  arc. 
in  general,  susceptible  of  very  fine  adjustment  to  meet  varying  load  con- 
ditions. 

Illustrated  below  are  several  types  of  burners  now  on  the  market. 

In  the  Ilammel  Burner,  Fig.  44,  the  oil,  either  heated  or  cold,  is  fed  into 
the  upper  pipe,  b  forced  through  the  sloping  passage  in  the  burner  to  the  mix- 
ing chamber  C.  Here  it  encounters  the  entering  steam  jet  at  an  angle,  the 
heavy  hydrocarbons  are  atomized,  and  the  lighter  ones  vaporized,  and  the 
mixture  issues  from  the  burner  to  the  combustion  chamber.  Thin  renewable 
plates  forming  the  lop  and  botiom  of  combustion  chamber  C  receive  any 
wrar  due  to  grit  in  the  oil,  while  moisture  carried  in  with  the  Steam  flows 
along  the  lower  passage  ind  is  blown  out  under  the  steel  plate.  The  Ham- 
mcl  Oil  Burning  Syitem  is  ordinarily  installed  without  arches,  bridge  walls 
or  target  walls. 


Fig.  44.     The  Hammel  Oil  Burner. 


H*aa 

^n — 13—' 


The  Starlet  fr  Pfeifcr  Burner.  Fig.  45,  operates  with  steam  or  air, 
which  flows  through  the  large  pipe  encasing  the  oil  pipe,  until  it  enters  the 
mixer,  which  is  set  with  the  apex  P  slightly  below  the  center  of  the  lip. 
The  flow  of  oil  is  regulated  by  the  valve  rod  inside  the  steam  pipe,  operated 
i>y  the  wheel  shown. 


Fig.  45.     The  Staplea  and  Ffeifer  Oil  Burner. 


D,g,tze:Jbi  Google 


F  U  R  X  A  C  E  S    A  X  U    S  J£  T  T  1  X  U  S  121 

In  llic  I'ocrsI  Fuel  Oil  Burner,  Fig.  46,  the  oil  under  gravity  or  pres- 
sure feed  flows  in  through  the  lower  pipe,  and  ihe  atomizing  steam  or  ;iir 
thrmigli  the  upper  pipe.  The  lllnstraiion  shows  a  fan-tail  burner,  although 
liurncrs  giving  a  cone-shaped  flame  are  also  furnished. 


Fig.  46.     The  Poerst  Fan-tail  Type  Oil  But 


The  /('.  .\'.  Bal  Calorcx  lltimfr.   Kig,  47 

ins  a  jet  of  the  atomizing  fluid  Issuing  at  right ,...» —  — 

lip  is  hehl  tighlly,  but  can  be  raised  for  blowing  out  incrustations  -■... 
nid  of  l)ie  hj--pa's.  Burners  are  made  for  throwing  a  long,  narrow  flame, 
a  fan-shaped  one  up  lo  9  feet  wide. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS 


Fig.  47.     The  W,  N.  Bert  "Calorex"  Oil  Burner. 

The  Kofriing  Cyclone  OH  Burner,  Fig.  48,  is  designed  for  use  where 
forced  draft  is  required,  or  where  it  is  desired  to  make  use  of  a  low  pressure 
oil  pump  already  installed-  The  oil  issues  from  an  atomizing  nozzle,  while 
the  pipe  through  which  it  flows  is  surrounded  by  a  passage  carrying  com- 
pressed air,  which  receives  a  gyratory  motion,  so  thai  the  mixture  coming  out 
of  the  cylinder  forms  a  spreading  cone,  in  which  the  flame  remains  close  to 
the  burner.  Air  atomizing  burners  are  also  supplied,  and  burners  for  use 
where  the  oil  is  under  gravity,  as  in  small  plants. 


Kegister  c/linier 

Hg.  48.     The  Koerting  Cyclone  Oil  Burner. 

Of  more  general  application  i;   .   _  .   .. 
ie»,  in  which  the  fuel  is  pumped  at  high  pre 

at  a  temperature  of  about  260  deg.  F.    The  burner  is  surrounded  by  a 
justable  cylindrical  air  register,  admitting  air  through   rectangular  openings, 
giving  an  intimate  mixture  of  combustible  material. 

"Hie  Coen  System,  Fig.  49,  utilizes  a  mechanical  burner  into  which  the 
oil  is  pumped  under  pressure  and  receives  a  whirling  motion.  The  adjusting 
wheel  shown  in  the  sketch  is  used  to  regulate  the  flow ;  by  turning  it  the  small 
ball  at  the  cone  end  can  be  lowered,  reducing  the  flow  to  a  minimum  without 
shutting  it  off. 


ib.  Google 


F  I'  R  X  A  C  E  S    A  N  n    S  F.  T  T  I  \'  G  S 


Fig.  49.     The  Coen  OH  Burner. 


The  tfay  Rotary  Burner,  Fig.  50,  atomizes  the  oil  in  an  open  cup.  re- 
volving at  high  speed,  while  air  under  ^  lb.  pressure  issues  from  a  cylindrical 
slot  surrounding  the  atomiier  and  directs  the  mixture  into  the  furnace.  The 
pump,  blower  and  ntomizer  are  driven  by  a  ^i  H.  P.  motor,  and  can  be  swimg 
from  the  furnace  front.    . 


Fig.  so.     The  Ray  Rotary  Crude  Oil  Burner, 

Oil  as  fuel  requires  the  use  of  certain  auxiliary  apparatus,  most  important 
of  which  is  the  oil  pump  and  oil  heater. 

Fig.  51  illustrates  a  combination  oil  pump  and  condensing  lype  heater 
set  manufactured  by  the  G.  E.  Witt  Co.  The  oil,  afier  passing  through  the 
pump,  is  delivered  to  the  heater,  after  which  it  passes  through  a  strainer  tn 
the  oil  burner  line.  The  beater  consists  of  copper  tubes,  through  which 
the  exhaust  steam  from  the  pump  circulates,  healing  the  oil  in  the  cast  iron 
chamber  surrounding  the  copper  coils. 


ib.Google 


FURNACES    AND    SETTINGS 


Oil.  Inn 
To  Puf 


Oil 
ToH 


f"ig.  51.     Witt  Oil  PumpinE  Set  with  Condennng  Type  Heater. 


W' 


Tar  Burning 
ATER  gas  tar,  which  is  a  by-product  from  gas  works  using  the  v 


gas  system,  maitcs  excellent  fuel  for  n^e  under  sieam  boiler 
age  tar  will  have  a  calorific  value  of  about  15,000  to  17.000  B.  t.  u.  per  lb. 
and  will  weigh  about  9.5  lbs.  per  gallon. 

In  general  it  may  be  said  that  a  furnace  suitable  for  burning  crude  oil 
will  give  satisfactory  re5ults  when  using  water  gas  lar  as  fusl.  Refer  lo 
remarks  given  elsewhere  on  oil  burning  furnace  design. 

Grade  oil  burners  can  be  safisfacloHly  used  for  burning  tar,  though 
provision  should  be  made  for  straining  the  tar  before  it  reaches  the  burner, 
and  clean-out  connections  for  blowing  out  tar  lines  and  burners  with  steam 
or  compressed  air  should  be  provided.  Inasmuch  as  a  low  flash  point  is  a 
characteristic  of  water  gas  tar,  it  should  not  be  preheated  beyond  the  tempera- 
ture at  which  it  is  sufl'iciently  fluid  to  be  handled. 

Coal  gas  tar  may  be  used  tor  boiler  firing,  but  the  present  high  value 
nf  coal  tar  derivatives,  which  arc  used  as  bases  for  dyes,  explosives,  etc., 
precludes  its  use  as  a  fuel. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  127 

Gas  Burning 

NATURAL  gas.  blast  furnace  gas,  coke  oven  gas  and  producer  gas  are 
the  four  principal  types  of  gaseous  fuels  which  are  available  for  use 
under  steam  boilers. 

NATURAL  GAS:  Natural  gas  is  probably  the  most  widely  used  of  the 
four  principle  gases,  although  the  depletion  of  the  natural  gas  fields  is  now  so 
rapid,  that  its  utilisation  is  being  rapidly  curtailed. 

Representative  analvses  of  natural  gas  from  various  locations  are  given 
in  Chapter  13  on   FUEL. 

The  defign  of  a  boiler  furnace  for  biirning  natural  gas  involves  several 
important  points.  First,  the  furnace  volume  or  combustion  space  must  be 
proportioned  so  that  the  gases  will  not  come  into  contact  with  the  cool 
heat  absorbing  surface  until  combustion  is  completed.  A  furnace  volume  of 
about  2  cu.  ft.  per  rated  horsepower  will  give  sufficient  combustion  space 
to  meet  the  above  conditions.  The  standard  Heine  boiler,  with  its  arrange- 
ment of  horiionial  baffling  on  the  lower  row  of  tubes,  gives  a  furnace 
volume  particularly  well  adapted  for  the  burning  of  natural  gas.  Dulch 
oven  furnace  construction  is  not  necessary  with  Heine  boilers  burning  natural 
gas.  Second,  in  order  to  prevent  laning  action  of  the  gases  in  their  passage 
through  ihe  boiler  it  is  more  desirable  to  use  a  large  number  of  small 
burners  than  a  few  large  ones.  One  burner  for  25  to  30  rated  boiler 
horsepower  will  give  satisfactory  results.  Third,  where  furnace  widths  are 
over  5'Cr  it  is  desirable  to  install  checkerwork  to  act  as  an  igniter  for  the 
gases.  In  some  cases  one  checkerwall  placed  about  three  or  four  feet  from 
the  burner  outlets  is  used  as  an  igniter  and  a  second  checkerwall,  some 
three  or  four  feet  behind  (he  first,  acts  to  break  up  the  flame  and  mix  the 
gases  thoroughly  after  passing  through  the  first. 

Fig.  52  shows  a  typical  natural  gas  burning  setting  for  a  Heine  boiler. 


Fig.  SI.     Typical  Natural  Qaa  Burning  Setting. 


ib.  Google 


12g  !■■  U  R  X  A  C  K  S    AND    S  li  T  T  [  N  G  S 

The  "Kirkwood"  natural  gas  burner,  Fig.  53,  consists  of  an  outer  and 
inner  casing,  and  a  nozzle.  Into  the  inner  casing  is  driven  a  large  number 
of  small  brass  spuds  which  are  drilled  half  way  through  in  two  directions. 
These  two  holes  meeting  make  a  passage  for  (he  gas  from  the  annular 
space  between  the  oilier  and  inner  casing  into  the  inner  cylindrical  space. 
Here  the  gas  is  introduced  in  a  great  number  of  fine  jets  into  the  air  which 
is  drawn  through  the  burner.  Air  regulation  is  obtained  by  adjusting  the 
front  slide. 


Fig.  53.     End  View  of  Kirkwood  Natural  Gas  Burner. 


Due  to  tiie  fact  ihat  the  supply  uf  natural  gas  in  certain  localities  is 
erratic  and  uncertain,  it  is  generally  the  custom  to  install  the  burners  above 
coal  fired  grates  or  even  stokers.  The  grates  or  stokers  are  normally  com- 
pletely covered  with  firebrick,  but  in  case  of  the  gas  supply  failing,  the 
bricks  can  lie  easily  removed,  the  burner  swung  out  of  position  and  a  coal 
fire  quickly  started. 

BLAST  FURNACE  GAS  or  the  gas  resulting  from  the  chemical  reaction 
in  the  iron  blast  furnace,  is  extensively  nsed  for  steam  generation  in  the 
iron   industry. 

A  typical  analysis  of  blast  furnace  gas  is  given  in  the  table  in  Chapter 
13  on  FUEL. 

It  is  to  be  noted  that  this  gas  is  "lean"  or  low  in  calorific  power,  and 
that  the  chief  combustible  constituent  is  carbon  monoxide.  These  two  facts 
establish  the  necessity  of  special  furnace  design  tor  burning  it.  The  furnace 
volume  required  will  vary  with  the  quality  of  gas  available  and  also  with 
the  type  of  burner  used.  With  an  inside  mixing  burner,  where  the  air 
necessary  for  combustion  is  partially  mixed  with  the  combustible  within  the 
burner  shell,  the  furnace  volume  need  not  be  as  large  as  when  the  air  neces- 
sary for  combustion  is  induced  around  tlie  burner  nozzle.  For  average  condi- 
tions the  furnace  volume  should  be  between  2  and  ZYi  cubic  feet  per  rated 
boiler  horsepower.  With  this  type  of  fuel  as  well  as  with  oil  or  natural  gas, 
the  Heine  boiler  with  its  large  combustion  space  is  particularly  well  adapted 
for  efficient  and  high  capacity  operation. 


ib.  Google 


FURNACKS    AND    SETTINGS  129 

Inasmuch  as  blast  furnace  gas  contains  such  a  high  percentage  of  carbon 
monoxide,  it  is  necessary  to  mainiain  an  auxiliary  fuel  bed  to  act  as  an 
igniter.  Coal  fired  grates  are  most  commonly  used,  but  stokers  or  even  oil 
burners  are  entirely  practicable  for  this  purpose. 

It  is  preferable  to  use  washed  blast  furnace  gas  for  firing  boilers,  but 
not  absolutely  necessary.  Where  coal  fired  auxiliary  grates  are  used,  the 
dust  precipitated  in  the  furnace  from  the  unwashed  gas  may  be  removed 
when  the  fires  arc  cleaned.  However,  this  dust  when  allowed  to  accumulate 
becomes  fused  and  is  difficult  to  remove. 


FIs.  54.     Kirtcwood  Natural  Oaa  Burner*  under  Heine  Birilera  at 
Chartier*  Water  Company's  Plant,  IMttsburgh,  Pa. 


Due  to  the  fact  that  pulsations  and  mild  explosions  are  liable  to  occur 
when  burning  this  type  of  fuel,  it  is  necessary  that  the  settings  be  particularly 
well  buckstayed.  Quick  opening,  unlatched  explosion  doors  should  also  be 
provided  in  the  setting. 


ib.  Google 


FURNACES    AND    SETTINGS 


FtK.  55  illustrates  a  Birkholz-Terbeck  burner,  which  is  often  applied  lo 
blast  furnace  gas-lired  boilers.  In  this  burner  the  primary  air  supply  is 
admitted  through  openings  in  the  back  of  the  air  nozzle,  being  aspirated  by 
the  force  of  the  gas  blowing  through  the  burner.  The  primary  air  suppl; 
is  not  sufficient  for  proper  combustion  and  a  secondary  supply  is  drawn  in 
by  the  furnace  draft  through  the  secondary  openings  around  the  nose  of  the 


Sneitdarjf  Air  • 
Fig.  55>     The  Biikholi-Terbeck  Burner  for  Blaat  Furnace  Oa*. 


Fig.  56  shows  a  Kling-Weidlein  Burner  in  which  the  gas  leaves  the 
primary  nozzle  at  high  speed  and  in  two  streams,  drawing  primary  air  in 
between  the  gas  streams.  The  air  mixes  with  the  inside  layers  of  the  gas 
streams  on  their  way  to  the  ignition  chamber,  but  before  the  latter  is 
reached,  ihe  secondary  air  in  two  streams  is  brought  in  and  mixes  with 
the  outside  layers  of  Uie  gas. 


ib.  Google 


FURNACES    AND    SETTINGS 


Pig.  56.     The  KUiiB-W«idlein  Blaat  Furnace  0«a  Burner. 


In  the  Bradshaw-Fraser  Burner.  Fig,  57,  the  aspirating  action  o£  the 
blast  furnace  gas  which  has  attained  high  velocity  as  a  result  of  the  con- 
stricted passage  is  used  to  draw  in  air  through  an  internal  c 


Fig.  57.     The  Brsdabaw-FrMer  Qu  Burner. 

PRODUCER  GAS  has  but  a  limited  use  under  boilers,  and  for  the 
sake  of  economy  it  should  be  used  only  in  an  emergency,  A  representative 
producer  gas  analysis  is  given  in  Chapter  13  on  FUEL,  and  it  will  be  noted 
that  in  calorific  power  and  in  percentage  of  combustible  it  resembles  blast 
furnace  gas. 

COKE  OVEN  GAS  is  a  product  of  the  destructive  distillation  of  coal 
as  carried  out  in  the  bjr-product  coke  oven.  This  gas  has  a  relatively  high 
calorific  value,  as  is  indicated  by  the  analysis  given  in  Chapter  13  on  FUEL. 
In  general,  the  proper  methods  of  burning  this  fuel  are  the  same  as  for 
natural  gas.  However,  as  this  gas  may  contain  tar,  which  has  not  been 
entirely  removed  in  the  scrubbing  process,  it  is  necessary  to  have  the  gas 
lines  and  burner  pipes  arranged  for  easy  cleaning. 


ib.  Google 


h 


^ 
1 


ib.Google 


FURNACES    AND    SETTINGS  133 

Settings  for  Burning  Refuse 

WOOD   chips,   shavings,   sawdust,  and   other    refuse    from    sawmills    or 
industrial  processes  require  a  boiler  furnace  in  which  a  large  mass  of  fire- 
brick is  continuously  radiating  heat  to  the  fuel  and  evaporating  the  moisture 

In  the  Heine  boiler,  a  semi -extension  or  Dutch  oven,  Fig.  58,  meets 
the  requirements  of  wood  refuse  or  tan  bark.  The  thickness  of  the  fuel-bed 
carried  on  the  grate  depends  upon  the  size  and  nature  of  the  fuel,  as  well  as 
upon  the  quantity  of  air  that  the  available  draft  can  draw  through  the  bed, 
A  long  flame  is  produced  by  the  burning  fuel,  but  it  is  prevented  from  coming 
in  contact  with  the  tubes  of  the  boiler  by  the  baffle  tiles  lying  horizontally 
on  the  bottom  row.  As  wood  refuse  generally  contains  a  large  amount  of 
moisture,  a  considerable  percentage  of  the  total  heat  is  consumed  in  evapo- 
rating the  water  from  the  fuel 


Pig.  58.     Setting  with  Semi-Bxtention  Purnnce  for 
Burning  Wood  Refute  or  Tan  Bark. 


Fig.  59  shows  a  method  of  firing  when  the  wood-refuse  is  brought  to 
the  boilers  by  pneumatic  conveyors,  the  fuel  being  deposited  in  the  cyclone 
separator  and  fed  to  the  boilers  through  10  or  12  inch  galvanized  sheet  iron 
piping  to  burners  discharging  over  the  fuel  bed.  These  burners  are  usually 
attached  to  a  length  of  pipe,  the  upper  end  of  which  is  carried  by  a  ball  joint, 
and  the  lower  end  latched  to  the  burner.  Y-branches  or  switches  allow  of 
one  cyclone  separator  feeding  several  boilers.  The  piping  from  the  separator 
should  not  slope  more  than  30°  from  the  vertical. 


ib.  Google 


134  FURNACES    AND    SETTINGS 

If  dry  chips  and  shavings  are  to  be  fed  to  ihe  furnace,  or  if  a  mixture 
of  wood  and  coal  is  to  be  burned,  the  resulting  high  temperatures  may  bum 
the  firebrick.  But  if  the  amount  of  heat  absorbed  directly  from  the  fire  is 
increased  by  the  use  of  the  standard  setting.  Fig.  60,  the  furnace  temperature 
will  remain  normal.  The  necessary  cooling  effect  is  obtained  by  the  arrange- 
ment of  the  baffles.     Near  the  front  header  the  underside  of  the  tubes  is 


Fig.  59.     Burning  Wood  Refuse  Carried  by  Pneumatic  Conveyor*. 


D,g,tze:Jbi  Google 


FURNACES    AND    SETTINGS  13S 

exposed  for  a  short  distance,  while  the  rest  of  the  firsi  row  of  tubes  is 
encased  in  baffle  tile.  The  gases  are  directed  upward  against  the  tile  roof. 
then  over  the  top  of  the  wall  and  under  the  deflection  arch.  The  air  and 
gases  are  thoroughly  mixed  and  smoke  formation  prevented. 


Pig.  60.     Setting  for  Burning  Coal  and  Wood  Mixture. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  137 

For  burning  bagasse  a  s|>ecial  extension  furnace  is  required  for 
combustion.  These  wet  fuels  should  be  burnt  on  hearths  at  the  bottom 
of  high  reverberatory  chambers  as  shown  in  Figs.  61  and  62.  The  raw 
material  is  fed  in  from  the  top,  and  is  dumped  directly  onto  the  fire,  so  that 
the  fuel  bed  is  generally  in  a  thick  pile.  The  necessary  air  is  brought  in 
through  the  tuyeres  under  light  pressure.  Combustion  is  completed  in  return 
Bues,  which  carry  the  gases  to  the  boiler. 


F'lg.  61.     Preferred  Setting  for  Burning  Bagaaie. 


Oppositely  inclined  grates  converging  downwards  may  be  installed  near 
the  bottom  of  the  furnace.  These  can  be  automatic  or  hand-operated. 
One  furnace  can  be  used  for  two  bailers,  by  setting  it  between  them. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  139 


^ 


Flf.  63.     Alternative   SettinK*  for  Bumint 


Waste  Heat  Settinga 

CERTAIN  manufacturing  processes  depending  on  the  direct  combustion 
of  fuel  are  inherently  inefficient  when  considered  from  a  thermal  stand- 
point. The  term  efficiency,  as  applied  to  these  various  procesaes.  has  the 
same  significance  as  it  has  when  applied  to  the  operation  of  a  direct  fired 
steam  boiler.  In  boiler  practice  the  object  is  to  utilize  every  available  B.  t.  ti. 
for  the  generation  of  steam ;  but  there  are  certain  unavoidable  heat  losses  of 
which  the  greatest  is  the  heat  carried  away  by  the  stack  gases. 

In  some  industrial  burning  operations  the  thermal  efficiency  is  not  above 
40  per  cent  That  is  to  say,  the  number  of  B.  t.  u.  actually  utilized  in  the 
melting,  smelting  or  treatment  of  the  material  involved,  is  only  40  per  cent 
of  the  number  of  B.  t.  u.  actually  supplied  to  the  furnace  as  fuel.  In  these 
operations,  as  in  steam  boiler  practice,  the  largest  thermal  loss  is  the  heat 
carried  away  by  the  waste  or  stack  gases. 

In  order  to  increase  the  efficiency  of  the  primary  furnace,  waste  heat 
boilers  are  installed,  which  generate  steam  for  plant  use.  This  steam  is  a 
direct  saving.  With  the  ever  increasing  price  of  fuel,  the  installation  of 
waste  heat  boilers  is  decidedly  advisable  wherever  conditions  permit. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  141 

The  operation  of  the  following  types  of  furnaces  with  their  relatively 
low  thermal  efficiencies,  is  in  general  such  that  waste  heat  boilers  can  be 
profitably  installed. 

Open  Hearth  Steel  Furnaces. 

Rotary  Cement  Kilns. 

PuddlinK  Furnaces. 

Malleable  Iron  Melting  Furnaces, 

Forge  Heating  Furnaces. 

Bee  Hive  Coke  Ovens. 

Coal  Gas  Benches. 

Oil  Stills. 

Zinc,  Copper,  Nickel,  etc.,  Refining  Furnaces. 

Soda  Ash  Furnaces. 

Glass  Melting  Furnaces. 

Waste  heat  boilers  cannot  be  conveniently  installed  with  every  such 
furnace,  because  raw  materials,  fuels  and  operating  conditions  differ  so 
widely  that  each  proposed  installation  requires  individual  study  to  determine 
the  feasibility  of  a  waste  heat  boiler  installation,  and  the  best  method  of  its 
application. 

Inasmuch  as  the  temperatures  of  waste  gases  available  for  waste  heat 
boilers  van-  from  below  KWO"  F.  for  long  cement  kilns  up  to  2200  for  melting 
furnaces,  it  is  obvious  that  there  can  be  no  set  or  standard  proportion  of 
boiler  heating  surface.  With  gases  around  1000°  F.  the  heat  transferred 
to  the  boilers  by  radiation  is  almost  negligible  and  the  steam  is  generated 
principally  by  convected  heat.  Where  the  gases  are  at  temperatures  above 
2000°  F.  the  radiation  is  appreciable,  approaching  that  of  a  direct-fired  boiler. 
Hence  a  boiler  for  high  temperature  waste  heat  work  varies  but  little  in 
design  from  a  standard  direct-fired  unit. 

The  majority  of  waste  beat  boilers  in  service  are  utiliiing  gases  at 
temperatures  ranging  from  1100°  to  1600°  F.  In  this  class  steam  is  generated 
by  convected  heat  and  therefore  the  arrangement  of  heating  surface  and 
baffling  departs  materially  from  the  standard  for  direct-fired  work. 

The  transfer  of  heat  by  convection  follows  certain  laws,  of  which  c(^- 
nizance  is  taken  in  the  design  of  Heine  waste  heat  boilers  for  relatively  low 
temperature  work.  As  early  as  1874  Professor  Osbom  Reynolds  developed  a 
law  of  convection,  which  has  been  later  substantiated  by  such  investigators 
as  Nicholson,  Jordan,  Stanton  and  Fessenden.  This  law  states  that  the  rate 
of  heat  transfer  bears  a  certain  definite  relation  to  the  velocity  with  which 
the  gases  sweep  over  the  heat  absorbing  surface.  Or  stated  in  different 
words — -the  B.  t.  u.  transferred  per  square  foot  of  heating  surface  per 
hour  per  degree  difference  in  temperature  between  gas  and  water  increase 
with  increasing  gas  velocities.  Therefore,  in  a  waste  heat  boiler  of  the 
convected  heat  type,  in  order  to  obtain  a  satisfactory  rate  of  heat  transfer 
and  to  keep  the  heating  surface  within  reasonable  limits,  the  gas  velocities 
employed  are  considerably  higher  than  in  direct-fired  practice. 

The  first  modern  high  gas  velocity  waste  heat  boiler  was  a  standard 
Heine  boiler  installed  in  1910  by  C.  J.  Bacon  at  the  South  Chicago  Works  of 
the  Illinois  Steel  Co.  The  gas  velocity  in  this  boiler  was  equal  to  5300  lbs. 
of  gas  per  square  foot  of  gas  passage  area  per  hour,  and  established  the 
high  limit  up  to  the  present  time. 

High  gas  velocities,  which  generally  run  from  2500  to  4500  lbs.  of  gas 
per  hour  per  square  foot  of  average  gas  passage  area,  are  obtained  in  the 
Heine  waste  heat  boiler  by  various  methods  of  baffling.  In  instances  where 
the  gases  are  comparatively  free  from  dust,  horizontal  baffling  is  employed. 
This  is  easily  installed  and  replaced,  and  readily  rearranged,  should  it  be 
desired  to  increase  or  decrease  the  gas  velocity  in  order  to  alter  the  rate  of 
heat  transfer. 


ib.  Google 


FURNACES    AND    SETTINGS 

where  the  gases  arc  burdened  with  dust,  which  would 
accumulate  on  horizontal  bafiFIes,  there  are  employed  other  methods  of 
baffling  which  maintain  a  high  gas  velocity  and  allow  the  dust  to  fall  clear 
of  the  tube  bank.  Several  different  types  of  baffling  are  used  in  Heine 
waste  heat  boilers,  and  these  make  such  a  variety  of  possible  arrangements 
that  no  typical  illustration  can  be  given.  The  dust  falls  into  hoppers  built 
integral  with  the  setting  and  equipped  with  air  light  cleanout  doors. 

Due  to  the  high  gas  velocity  employed,  there  is  an  unusually  high  draft 
loss  through  the  boiler,  which  is  taken  care  of  by  induced  draft  tans.  Fans 
have  a  steadying  effect  on  the  draft  at  the  primary  furnace,  and  when  so 
desired  the  draft  at  the  furnace  may  be  increased  with  increased  furnace 
output  It  is  desirable  that  the  fans  be  driven  by  a  variable  speed  motor 
or  steam  turbine,  so  that  any  variation  in  the  quantity  of  gas  may  be  satis- 
factorily handled. 

In  plants  where  the  temperature  of  the  waste  gases  approaches  that  of 
direct-fired  practice,  or  where  the  conditions  do  not  warrant  the  expense  of 
an  induced  draft  fan  installation,  it  is  customary  to  use  a  single  pass  waste 
heat  boiler  and  to  employ  natural  draft.  The  boiler  is  then  very  similar 
in  design  to  a  standard  direct-fired  unit. 

It  is  generally  preferable  to  install  waste  heat  boilers  in  connection  with 
continuously  operated  furnaces.  If  the  furnace  is  operated  only  part  of 
the  time,  it  is  customary  to  install  auxiliary  grates  under  the  boiler  and  to 
fire  coal  directly,  when  the  boiler  is  not  being  supplied  with  waste  heat  from 
the  furnace. 

The  necessity  of  having  tight  settings  is  continuously  brought  to  the  at- 
tention of  direct-fired  boiler  operators ;  but  in  waste  heat  utilization  Ihis 
requirement  is  even  more  important,  for  there  is  a  greater  vacuum  in  waste 
heat  settings,  and  hence  a  greater  tendency  for  air  leakage  through  crevices 
in  the  brickwork,  around  loose  doors,  etc.  The  waterleg  construction  of  the 
Heine  waste  heat  boiler  is  such  that  one  continuous  surface  is  presented  at 
both  the  front  and  rear  of  the  setting.  There  arc  no  separate  headers  and 
therefore  no  crevices  to  caulk  with  asbestos  rope,  which  quickly  becomes 
brittle,  often  drops  out,  and  thus  increases  the  air  leakage.  The  soot  blower 
elements  project  through  the  hollow  stayholis  of  the  front  and  rear  waterlegs, 
so  that  it  is  not  necessary  to  place  dusting  doors  in  the  side  walls.  The 
fewer  the  openings  in  the  setting  brickwork  the  more  durable  it  is  and  the 
less  the  tendency  for  air  leakage.  All  cleanout  or  access  doors  should  be 
provided  with  gaskets  to  insure  tight  closure.  Steel  casings  for  waste  heat 
boiler  settings  are  not  altogether  satisfactory,  because  cracks  are  likely  to 
develop  in  the  brickwork,  and  being  inaccessible  behind  the  casiig  are  hard 
to  detect  and  repair.  Asphaltic  compounds  suitable  for  painting  the  exterior 
of  the  brickwork  are  satisfactory  for  reducing  air  leakage. 

One  fact  in  the  design  of  a  complete  waste  heat  boiler  installation  should 
be  constantly  borne  in  mind. — the  operation  of  the  boiler  must  in  no  way 
interfere  with  the  operation  of  the  primary  furnace  to  which  it  is  connected. 
By-pass  flues  and  dampers  must  be  arranged  so  that  in  case  something  un- 
foreseen happens  the  gases  of  combustion  can  either  be-  passed  up  the 
stack  or  to  another  waste  heat  lioiler.  Where  there  are  two  or  more  trailers 
utilizing  the  waste  gases  from  two  or  more  furnaces,  it  is  desirable,  where 
space  or  operating  conditions  permit,  to  arrange  one  common  flue  into  which 
the  waste  gases  from  all  furnaces  discharge,  and  from  which  branch  flues 
lead  to  as  many  boilers  as  are  necessary  to  handle  the  gases  satisfactorily. 
With  this  arrangement  the  dampers  can  be  placed  so  that  any  desired  flexi- 
bility of  operation  is  obtained. 


ib.  Google 


FURNACES    AND    SETTINGS  143 

Marine  Settings 

IN  shipping  practice  boilers  of  eompacl  design"  and  light  weight  are  re- 
quired so  that  the  cargo  capacity  will  be  a  maximnnl.     Only  water-tube 
boilers  fulfill  these  requirenients.  ';. 

For  cargo  carriers  and  other  steamships,  boilers,  Fig.  63.  are  supported 
by  a  steel  siructure  secured  to  the  framing  in  the  vessel.  On  this  slruCTure 
is  a  steel-plate  casing,  which  encloses  the  entire  settii^.  Inside  of  the  casing 
is  insulating  material,  faced  with  firebrick.  This  construction  insures  pro- 
tection against  high  temperatures  and  minimizes  the  radiation  and  infiltration 


Pig.  63.     Heine  Marine  Cra*a  Drum  Boiler. 


For  dreagc  boat  service,  the  setting  is  built  t:ii  of  lUebrick,  JioUow  tile, 
asbestos  and  sheet  iron.  Alt  parts  of  the  furnace  interior  exposed  to  high 
temperatures   are   lined   with   firebrick.      Back  of   this   is   the   tile,   which   is 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS  145 

covered  with  asbestos  on  the  outside.  The  sheet  iron  encases  the  entire 
setting,  as  shown  in  Fig.  64.  The  boiler  itself  is  carried  on  steel  supports  at 
Ihe  front  and  rear,  while  the  breeching  and  suck  are  carried  by  structural 
framing. 

Separate  Heine  publications  dealing  with  marine  boiler  practice  are  sent 


Fig.  64.     Heine  Dredge  Boat  Boiler  Scttine. 

Boiler  Setting  Requirements 

THE  essentials  of  a  boiler  selling  are  a  lirm  foundation,  proper  distribu- 
lion  of  brickwork  and  steel  supports,  adequate  furnace  and  ashpit  space, 
and  insulation  against  heat  losses.  The  furnace  proper  and  masonry  parts 
included  in  the  furnace  should  be  made  of  materials  that  will  stand  severe 
service  and  high-  temperature  with  the  least  maintenance.  The  refractory 
material  should  be  combinations  of  fire-clay,  or  else  special  firebrick. 

The  boiler  must  be  supported  on  a  solid  base  to  prevent  settling  and 
cracking  of  the  walls.  A  weak  base  may  impose  severe  strains  upon  the 
boiler  piping,  resulting  in  sprung  and  leaky  joints  and  ruptured  connections. 

The  soil  is  the  determming  factor  in  proportioning  the  foundation.  In 
soft  ground  under  a  large  boiler,  it  may  be  necessary  to  drive  piles  or  to  lay 
a  concrete  base  at  least  2  ft.  diick  over  the  entire  space  occupied  by  the 
setting.  The  walls  are  started  on  this  base  or  a  concrete  foundation  with 
footings  is  laid  to  receive  the  brick  and  sieel  structure.  The  depth  of 
foundations  and  width  of  footings  then  depend  upon   the  size  of  boiler. 

The  side  and  end  walls  of  a  boiler  setting  should  not  be  less  than  12  in. 
thick.  In  older  designs,  a  2-in,  air  space  was  generally  provided.  It  was 
thought  that  the  double  wall  prevented  heat  losses  and  also  cracking  due  to 
e:tpansion.  Tests  by  the  U.  S.  Geological  Survey  indicate  that  an  air  space 
is  of  little  value  in  setting  walls.  The  radiation  losses  appear  to  be  greater 
for  a  wall  with  an  air  space  than  for  a  solid  wall,  especially  if  the  air  space 
is  near  the  furnace  side. 


ib.  Google 


ib.Google 


FURNACES    AND    SETTINGS 


While  concrete  has  been  used  in  several  installations,  the  walls  of  the 
setting,  as  a  rulci  are  made  of  well-burned  red  brick.  These  should  be  laid 
tme  and  in  high  grade  irorrar,  consisting  of  a  thorough  mixture  of  one  part 
Portland  cement,  three  parls  unslaked  lime  and  sixteen  parts  of  clean  sharp 
sand.    Each  brick  should  be  solidly  imbedded  and  the  joint  fully  filled. 

Ordinarily,  the  furnace,  ashpit,  bridge  wall,  arches  and  floor  of  the 
combustion  chamber  are  built  of  red  brick.  All  parts  of  the  brickwork  in 
contact  with  the  hot  gases  or  exposed  to  the  flame,  should  be  faced  with 
or  else  built  entirely  of  firebrick  capable  of  withstanding  the  high  tem- 
peratures. 

The  firebrick  should  be  highly  refractory  and  should  be  mechanically 
strong  and  sound  so  that  it  will  not  spall,  flake  or  crumble.  Firebrick 
linings,  walls  and  arches  must  be  given  reasonable  care.  They  should  be 
laid  in  fire-clay  mortar  having  the  same  properties  as  the  brick  itself.  Flux- 
ing material,  such  as  lime,  should  not  be  used  in  making  the  joints.  Fig.  65 
can  be  used  in  estimating  the  number  of  brick  required  for  standard  water- 
tube  boiler  settings. 


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Boilar  Rating   In   Horsepower 

Fi{  OS.     Approziinate  Number  of  Brick  Required  for 
Standard  Heine  Etoiler  Settings. 


ib.  Google 


H8  FURNACES    AND    SETTINGS 

The  furnace  construction  can  be  made  stronger  or  more  durabla  by 
using  special  blocks  in  place  of  the  standard  firebricks.  These  blocks  are 
larger  and  therefore  reduce  the  number  of  joints  required.  By  the  use 
of  a  plastic  refractory,  a  one-piece,  continuous,  monoJithic  structure  can 
be  built  up,  thus  eliminating  all  joints. 

The  walls  should  be  strengthened  by  steel  channel  buck-stays  placed 
at  each  end  of  the  setting  and  at  several  points  along  the  sides.  These 
should  be  secured  to  the  walls  by  longitudinal  and  transverse  anchor  rods 
built  into  the  brickwork.  Other  structural  members  are  required  for  the 
support  of  the  boiler,  their  number  and  distribution  depending  upon  the 
type  of  setting  and  the  style  of  furnace. 

Refractory  Materials 
'T'  HE  refractories  used  for  linings,  arches  and  bridge  walls  of  boiler 
■*■  furnaces  must  withstand,  without  serious  physical  or  chemical  change, 
high  and  changing  temperatures,  action  of  flame  and  gases,  and  mechanical 
stresses  due  to  the  cleaning  and  adding  of  fuel  to  the  lire.  The  refractories 
for  boiler  furnaces  consist  of  bricks,  blocks  or  special  forms,  and  paste. 
Fire  clay  (a  mixture  of  silica  and  alumina)  forms  the  basis  of  most  refrac- 
tory materials.  According  to  F.  T.  Havard,  fire  clay  is  used  either  alone 
on  account  of  its  admirable  qualities  of  burning  to  a  firm  clinker  and  resisting  . 
high  temperatures  and  mechanical  abrasion,  or  it  is  added  to  other  refractory 
matter,  such  as  bauxite  and  magnesia,  to  lend  plasticity. 

Fire  clays  are  divided  into  two  classes ;  flint  clay  and  plastic  clay,  the 
former  being  the  harder  and  more  nearly  chemically  pure.  Flint  clays  are 
white,  gray  or  mottled  black  in  color.  Plastic  fire  clays  vary  in  color  from 
white  to  black,  including  gray,  brown  and  olive.  The  plastic  is  added  to 
the  flint  clay  to  increase  the  deform  ability,  generally  at  the  cost  of  its 
refractoriness.  Commercial  fire  clay  contains  many  impurities,  and  the  color 
is  not  a  safe  guide  to  its  quality. 

Materials  such  as  silica,  bauxite,  chrome,  magnetite  and  dolomite  have 
melting  points  higher  than  Rre  clay,  but  have  tiot  proved  satisfactory  in 
boiler  practice.  These  materials  do  not  withstand  sudden  heating,  cooling. 
pressure,  and  action  of  the  gases  and  ash. 

The  conditions  that  obtain  in  a  coal  furnace,  according  to  Wm.  A.  Heuel, 
are  not  favorable  to  the  long  life  and  general  use  of  silica  brick.  With  an  oil 
or  gas  flame  they  give  good  service,  as  far  as  chemical  action  goes,  but  the 
extreme  temperature  variations  due  to  sudden  starting  or  stopping  cause 
rapid  physical   destruction   through   spalling  or  the  breaking  off  of  lai^e 

Bauxite  brick,  according  to  A.  D.  Williams,  cost  two  to  three  times  as 
much  as  lire  clay  or  silica  brick.  They  are  hard  and  tough,  cinder  does 
not  stick  to  them ;  and  they  last  longer  than  silica  brick  when  exposed  to 
slag  action.  However,  bauxite  tends  to  spall  and  break  off  when  suddenly 
chilled. 

At  high  pressures  and  temperatures  chrome  and  magnesite  brick  cannot 
withstand  the  strains  of  sudden  heating  and  cooling,  so  that  they  have  not 
found  favor  except  in  some  metallurgical  operations. 

Fire  Brick 

PLASTICITY,  according  to  L.  S.  Marks,  is  considered  the  main  factor  in 
selection  of  fire  brick.  It  indicates  the  tendency  of  a  brich  to  become 
plastic  at  a  temperature  lower  than  its  melting  point  and  to  become  deformed 
under  a  given  load.  Under  a  unit  stress  of  100  lb.  per  sq.  in.,  the  plastic  point 
should  be  more  than  2400  deg-,  otherwise  the  brick  is  not  suitable  for 
boiler   furnaces. 


ib.Google 


FURNACES    AND    SETTINGS 


Fusing  point  is  the  temperature  at  which  fire  brick  will  fuse.  A  hiffh 
value  ordinarily  indicates  that  the  critical  temperature,  or  that  of  plasticity, 
is  correspond  ing'ly  high. 

ExfiattsioH  represents  the  tendency  of  the  brick  to  change  in  siie  with 
change  in  temperature.  Lineal  expansion  of  from  O.Ol  to  0.08  in.  in  a  Q-Jn. 
brick  is  the  permissible  limit   for   furnace  construction. 

Compression  is  measured  by  the  strength  or  load  necessary  to  cause 
crushing  at  the  center  of  a  45j-in.  face,  by  a  steel  block  1-in.  square. 

Hardntss  indicates  the  brittleness  of  brick  and  its  tendency  to  crumble; 
it  is  ordinarily  estimated  on  an  arbitrary  scale  of  10. 

Ratio  of  nodules  expresses  the  percentage  occupied  by  flint  grains  in  a 
given  volume-  The  scale  is:  high,  90  to  100  per  cent;  medium,  SO  to  90 
per  cent ;  low,  10  to  50  per  cent. 

These  nodules  are  the  average  size  flint  grains  found  in  a  carefully 
crushed  brick.  Small  nodules  are  the  size  of  anthracite  rice;  large  nodules 
are  the  size  of  anthracite  pea. 

These  characteristics  are  summarized  in  Table  6,  for  the  three  classes 
of  firsl-grade  or  No.  I  brick.  Oass  A  brick  are  suitable  for  stoker  settings 
operated  at  high  overload  or  for  other  extremes  of  operation.  Class  B  brick 
are  used  for  furnaces  of  stoker-tired  boilers  operating  at  normal  load,  and 
for  hand-fired  boilers  under  overloads.  Gass  C  brick  are  recommended  for 
standard  boiler  settings,  for  occasional  short  overloads. 


Table  6.     Propertiea  of  Commercial  Fire  Brick 


nitST  GRADE  (No.  1) 


Safe  Fusion  Point,  deg.. 
Com{H'essioD,  lb.  per  sq, 

Rdative  Hardness 

See  of  Nodules 

Ratio  (rf  Nodules 


1,200-3,300 
),500-7,600 


2,900-3,200 
7,600-11,000 


8,500-16.000 14,200-32.000 


medium  to 

large 
medium  low 
to  medium 


6-10 
small  to  very 

f  to  very 


The  fisurea  in  Table  6  indicate  that  the  better  the  brick  the  softer 
it  is.  It  should  not  be  any  harder,  therefore,  than  is  required  for  the 
necessary  strength.  The  unequal  expansion  and  localized  stresses  due  to 
sudden  temperature  changes  often  cause  failure  when  the  fire  brick  is 
hard  and  brittle. 

The  melting  temperatures  of  refractory  brick,  as  determined  by  C.  W. 
Kanolt,  are  given  in  Table  7.  The  temperatures  do  not  indicate  the  lit- 
ness  of  the  material  for  use  in  boilers,  because  the  erosion,  crushing  strength, 
ability  to  withstand  sudden  load  changes  and  to  resist  fluxion,  must  all  be 
considered.  In  stoker-fired  boilers  temperatures  of  nearly  3200°  F,  have  been 
obtained,  although  the  melting  point  of  chemically  pure  fire  clay  is  only 
3326  degrees. 


ib.  Google 


FURNACES    AND    SETTINGS 


Table  7.     Melting  Pmntt  of  Fire  Brick 


Bri* 

T«,p^  Dx- 

brick  the  fracture  will  be  fine  and  uniform,  like  bread.     In  a  better  q 
brick  the  surface  is  open,  clean,  white  and  flinty. 

Fire  brick  9-in.  long  are  considered  standard.  Manufacturers  carry  a 
stock  of  the  shapes  and  sizes  shown  in  Fig.  66.  Special  sizes  can  sometimes 
be  purchased  from  stock,  but  usually  have  to  be  made  to  order. 


Feather  Edge. 


Fig.  66.     Some  Standard  Rre  Brick  Sbapea. 


ib.  Google 


FURNACES    AND    SETTINGS  ISl 

Table  8  gives  the  weight  of  different  refractories,  as  brick  and  as  mortar. 
Table  8.     Appforimatc  Weight!  of  Reff «ctoriea 


Common  Clay. . 

Fire  Clay 

Silka 

M^nesia 

PlaBtic 


If  ortar  er  Canmt, 


Influence  of  Aih.  Refractory  materials  may  deteriorate  because  of  tiic 
chemical  action  of  the  fused  ash  and  of  the  gases.  Certain  constituents  of 
ash,  according  to  E.  G.  Bailey,  influence  the  fusibility  of  the  fire  brick. 
In  one  installation,  where  the  furnace  lining  gave  trouble,  the  fusing  tempera- 
ture of  the  fire  brick  was  3100  deg.,  and  that  of  the  ash  was  2600  deg.; 
the  chemical  action  of  the  combination  caused  fusion  at  2400  degrees.  Ash 
from  other  coals  would  not  have  melted  the  lire  brick  used ;  other  brick 
and  the  same  ash  might  not  have  so  materially  affected  the  melting  point. 
Many  arches  and  walls  seem  to  have  failed 
1  making  the  joints  melts  and  allows  the  brick 
or  blocks  to  fall.  The  mortar  used  should  be  of  practically  the  same 
composition  as  the  brick  itself.  For  lire  clay  brick,  finely  ground  iire  clay 
mortar  should  be  used;  silica  cement  for  silica  brick;  and  magnesia  cement 
lor  magnesia  brick. 

The  fire  clay  mortar  should  be  of  the  iirst  quality,  otherwise  it  will 
melt  and  run  long  before  the  brick.  Common  sand,  salt,  or  lime,  hasten 
fusion,  and  cement  the  brick  thoroughly,  but  at  high  temperatures  this 
fusion  destroys  the  brick  prematurely.  Tests  by  Raymond  M.  Howe 
show  that  the  addition  of  only  5  per  cent  of  Portland  cement,  asbestos  or 
salt  lowered  the  fusion  point  of  fire  clay  almost  400  degrees.  On  the  other 
hand,  Hre  tand,  which  is  calcined  clay  or  fire  brick  in  powder  form,  can  be 
added  to  the  mortar  and  prevents  shrinkage  of  the  raw  clay  and  crumbling 
of  the  joints.  This  shrinkage  can  be  prevented,  and  a  firmer  joint  estab- 
lished, not  by  adding  foreign  materials  to  the  tire  clay,  but  by  using  the 
same  material,  taking  the  precaution,  however,  that  a  certain  amount  of 
clay  has  previously  been  shrunk. 

Several  commercial  cements  withstand  temperatures  as  high  as  3100 
deg.,  and  are  recommended  for  use  with  high  grade  fire  brick. 

The  trend  of  opinion  favors  furnace  wails  of  as  few  different  materials 
as  possible;  the^e  must  be  selected  carefully,  even  though  solid  fire  brick 
are  to  be  used.  The  use  of  two  grades  of  brick,  rather  than  one,  may  be 
preferable  and  economical,  especially  as  the  burden  on  side  walls  and 
on  an  arch  is  different.  Side  walls  for  coal  fuel,  states  Heisel,  generally 
require  a  refractory  less  porous  and  soft  than  would  be  used  in  an  arch,  to 
withstand  the  abrasion  caused  by  the  fire  tools,  and  the  cutting  caused  by 
breaking  or   removing  the   clinkers. 

Furnace  walls  are  safeguarded  and  the  lining  preserved  by  devices 
which  supply  air  to  the  walls  and  thus  prevent  clinker  from  adhering 
to  them.  This  reduces  the  temperatures  without  reducing  the  furnace 
efficiency.  Perforated  refractory  blocks,  Fig.  6?,  are  used  for  the  lining 
in  the  lower  parts  of  the  side  walls,  bridge  walls,  and  wherever  the  action 
is  most  severe.  Air  is  admitted,  through  holes  in  the  wall  blocks.  The 
holes  are  connected  by  ducts  to  the  fan  draft  system.  With  underfeed 
ilokers,  these  blocks  may  materially  increase  the  life  of  the  linings. 


ib.  Google 


FURNACES    AND    SETTINGS 


Longitudinal     Section. 
Pig.  67.     Refractory  Block*  for  Venttlating  Furnace  Walli 


With  standard  brick  the  joints  and  parts  to  lay  are  so  numerons  that 
blocks  are  made  for  door  arches,  furnace  walls,  and  bridge  walls.  The 
blocks  are  keyed  or  have  a  tongue  and  groove,  and  sometimes  are  machined 
to  insure  a  good  lit.  It  is  said  that  one  24-in.  block  takes  the  place  of  40 
standard  brick,  and  reduces  by  more  than  two-lhirds  the  running  inches  in 
the  joints  in  the  face  of  the  wall. 

In  place  of  the  blocks,  so-called  plastic  fire  brick  is  used  for  boiler 
settings.  This  is  a  moist  plastic  mass,  compounded  of  fire  clays  mechan- 
ically treated  so  that  expansion  is  practically  eliminated.  The  piastic 
refractory  is  placed  by  hand  and  pounded  so  that  the  front  arch,  side  and 
front  walls,  bridge  wall,  or  combustion  chamber  lining  is  one  continuous 
structure.  This  material,  it  is  said,  does  not  break  or  spall  under  varying 
furnace  temperatures. 


ib.  Google 


FURNACES    AND    SETTINGS  1S3 

Arch  Conslniction.  All  brick  in  the  same  row  should  be  of  even  shape 
and  thickness,  this  applying,  states  Heisel,  to  arches  particularly.  The  vari- 
ation in  size  should  not  exceed  %-'m.  in  a  maximum  length  of  9  inches.  The 
dry  brick  selected  should  be  tried  over  the  arch  form,  and  those  of  uneven 
thickness  should  be  cut  and  rubbed  to  avoid  large  mortar  joints.  Wedges 
should  be  used  to  keep  the  brick  bottom  in  even  contact  with  the  arch  form. 
The  key  course  should  be  a  true  fit  from  top  to  bottom  and  should  be  driven 
from  1  to  IVS  in.,  depending  upon  ihe  hardness  of  the  brick  and  the  width 
of  the  arch. 

Suspended  flat  arches  are  sometimes  used  instead  of  the  ordinary  sprung 
arch.  Fig.  68  shows  a  double  suspension  arch,  about  3  in.  deeper  than  the 
ordinary  single  arch.  A  so-called  reserve  arch  is  placed  above,  and  supports 
the  lower  arch.  An  air  space  is  provided  between  the  two  arches.  If  a 
bum-out  occurs,  the  upper  arch  protects  the  supporting  beams  until  the 
boiler  can  be  shut  down  and  the  damaged  blocks  repl&ced.  The  new  parts 
are  slid  into  the  grooves  of  the  reserve  arch. 


Pig.  68.     Liptak  Typ«  of  Suspended  Flat  Arch. 


Radiation  and  Leakage 

COMMON  brick  is  somewhat  unsatisfactory  for  boiler  settings.  As  it  is 
not  a  refractory  material,  it  is  always  protected  from  high  temperatures 
by  a  lining  of  firebrick.  It  is  a  poor  heat  insulator ;  it  is  porous  and  permits 
considerable  infiltration  oE  air,  and  it  cracks  easily,  especially  around  openings 
such  as  dusting  doors,  and  allows  further  air  inleakage. 


ib.  Google 


-Google 


FURNACES    AND    SETTINGS  IS5 

Insulating  material  will  decrease  heat  loss  to  a  considerable  extent. 
Siliceous  insulating  material  may  be  cut  into  blocks  of  standard  Brebrick 
size  which  have  sufficient  strength  to  be  laid  as  a  core  wall  between  the 
fireback  furnace  lining  and  the  outer  red  brick  course.  Such  a  wall  is  shown 
in  FifT.  69. 


Plain  Wall  ln«ul«+«d  W«ll 

Fig.  69.     He«t  Flow  Temperature  arsdienta  in  Brick  Wall. 


The  insulating  brick  should  be  at  least  4}^  in.  thick.  It  should  be  laid 
with  broken  joints  and  in  a  mortar  made  of  material  having  the  same 
characteristics.  The  temperature  drops  through  a  standard  boiler  wall  and 
an  insulated  wall  are  compared  in  Fig.  69,  by  A.  L.  Gosiman. 

Metal  wall  ties  are  used  in  bonding  or  else  firebrick,  insulating  brick 
and  red  brick  are  tied  into  a  solid  wall  by  brick  headers  staggered  in  at 

Fig.  70  shows  the  thermal  conductivities  o^  refractories  and  insulation, 
9  being  made  on  slabs  one  inch  thick  and  one  square  foot 


ib.  Google 


FURNACES    AND    SETTINGS 


The  insulation  reduces  the  radiation  loss,  but  on  account  of  the  joints 
in  the  brick  setting  the  air  leakage  is  not  eliminated.  To  offset  the  infiltra- 
tion only,  state*  /.  Harrington,  a  glazed  or  vitrified  brick,  laid  in  cement 
mortar,  gives  a  hard  and  durable  wall,  but  the  heat  transmission  is  high. 
A  boiler  setting  encased  in  sheet  steel  is  practically  air  tight,  but  the  steel 
has  no  insulation  value. 


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Temperature  Dif ferenc« ,  D«gre«« 
Rg.  70.    Heat  Conductivity  of  Brick,  One  Inch  Thick. 


ib.  Google 


FURNACES    AND    SETTINGS 


Radiation  and  infiltration  losses  are  both  eliminated  by  applying  asbestos 
or  magnesia  on  the  outside  of  the  setting  walls,  and  then  encasing  the  whole 
witb  sheet  steel.  This  construction  is  expensive  and  carries  the  objection  that 
cracks  in  the  brickwork  are  difficult  to  detect  or  repair. 

A  less  costly  construction,  which  also  reduces  both  losses,  is  described 
by  E.  S.  Might.  The  details  are  shown  in  Fig.  71.  The  saving  effected  by 
this  insulation  is  said  to  be  sufficient  to  repay  the  first  cost  in  less  than  six 
months,  providing  the  boilers  are  operated  at  full  load  50  per  cent  of  the 
time.  Wire  loops  are  inserted  into  the  red  brick  of  the  setting  wall,  so 
that  they  overhang  at  every  fifth  or  sixth  course.  After  the  wall  has  been  laid 
upi  a  Vi*  in.  finish  (two  or  three  coals)  of  coal  tar  is  applied.  This  should 
be  boiled  to  a  thin  consistency  and  have  asbestos  wool  stirred  into  it.  After 
the  mixture  has  dried  a  plastic  asbestos  paste  or  cement  is  applied  to  a 
thickness  of  about  I^  inches.  Over  this  a  wire  mesh  is  stretched  and 
fastened  to  the  protruding  loops  by  small  wire  clips.  Then  another  J:i-in. 
layer  of  asbestos  cement  is  applied.  When  the  plastic  mass  is  dry,  the 
surface  is  covered  with  10-oz.  duck  or  canvas.  This  is  pasted  down  tightly 
and  the  edges  are  fastened  by  wires  or  metal  strips  to  the  steel  work  of 
the  setting.    The  duck  is  finished  with  two  coats  of  asphalt  paint  or  vami^. 


SttttinqWira 
loop  jnTlaea 


For  the  covering  of  boiler  tops  and  drums,  insulating  brick  have  been 
found  most  desirable.    This  can  be  strengthened  by  a  course 
brick  and  then  a  2-in.  topping  of  concrete. 


ib.  Google 


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ib.Google 


Chapter  5 


MECHANICAL  STOKERS 

THE  advantage  of  automatic  stokers  as  compared  with  hand  firing  lies 
mainly  in  the  more  efficient  combustion  of  the  fuel,  the  elimination  of 
smoke  and  dirt  in  the  boiler  room,  and  in  the  ability  to  drive  boilers  at 
high  rating.  In  large  plants  where  automatic  coal  and  ash  handling  equip- 
ment can  also  be  installed  advantageously,  the  use  of  stokers  reduces  the 
labor  cost  and  the  labor  difficulties.  The  emission  of  smoke,  except  for 
brief  periods,  is  forbidden  in  many  cities ;  and  when  smoke  is  eliminated,  the 
general  efficiency  of  the  boiler  plant  is  usually  increased.  With  stokers  the 
fuel  is  fed  and  the  air  supplied  uniformly;  no  lire  doors  need  be  opened 
to  chill  the  boiler  and  dilute  the  stack  gases ;  thus  combustion  is  most 
thorough  even  with  poor  fuel,  at  combustion  rates  that  produce  the  highest 
steaming  values.  The  grade  of  fuel  influences  the  choice  and  design  of 
a  stoker,  but  when  it  is  difficult  to  secure  coal  from  the  same  source  con- 
tinually, the  load  conditions  are  even  more  important.  A  plant  that  must  be 
operated  frequently  at  300  or  400  per  cent  of  rating  must  necessarily  be 
equipped  with  stokers  that  can  be  driven  at  corresponding  rates,  with  forced 
draft,  regardless  of  the  fuel  available.  When  the  load  conditions  are  more 
nearly  uniform,  the  stokers  can  be  of  lower  forcing  ability,  and  those  best 
suited  to  the  coal  available  can  be  chosen. 

The  following  illustrntions  are  given  as  examples  of  the  types  classified. 


Overfeed  Stokers 
TN  overfeed  stokers  the  coal  is  generally  burnt  on  sloping  grates.  The  general 
*■  position  of  these  is  fixed,  but  reciprocating  grate  sections  gradually  work 
the  burning  fuel  down  to  the  ash  receiver.  The  coal  is  fed  from  hoppers 
adjoining  the  upper  part  of  the  grates  and  passes  first  over  a  coking  section, 
where  the  volatile  gases  formed  are  burned  by  the  aid  of  secondary  air. 
Overfeed  stokers  are  used  with  a  wide  variety  of  fuels,  and  boilers  are 
operated  up  to  200  per  cent  of  rating  without  overheating  the  grates. 

Cleveland  Stoker,  Fig.  72.  The  coal  from  the  hopper  is  pushed  in  by 
feed  plates  and  pokers,  so  arranged  that  by  increasing  the  speed  of  the 
rectangular  feed  plates  the  depth  of  the  fuel  bed  can  be  increased.  The 
draft  is  adjustable  for  the  particular  coal  used;  the  three  dampers  in  the 
wind  box  below  the  grates  distributing  the  required  air.  The  entire  unit 
is  shipped  assembled,  and  runs  on  tracks  so  that  it  can  be  removed  to  gain 
access  to  the  setting. 

Detroit  Automatic  Furttace,  Fig.  73.  Coal  is  fed  to  the  magazines  by  hand 
or  from  chutes,  and  is  driven  to  the  coking  plate  by  pusher  boxes,  from 
which  it  slides  down  the  grates  to  the  clinker  grinder,  where  a  supply 
of  exhaust  steam  softens  the  clinker.    Air  for  combustion  is  supplied  at  a 


ib.  Google 


STOKERS 


Fig.  72.    CkveUuid  Overfeed  Stoker. 

number  of  points — that  entering  through  the  upper  dampers  being  heated 
between  the  furnace  arches  and  entering  the  furnace  at  the  arch  boxes, 
in  addition  to  that  which  passes  through  Uie  grates. 


Pig.  73.     Detr<Ht  Automatic  Furnace. 


ib.  Google 


Model  Stoker  is  also  of  the  self-cleaning,  side-feed  type.  The  srates 
slope  to  the  center  and  are  in  pairs,  set  on  e<tee,  with  a  small  surface  exposed 
to  the  fire  and  a  large  surface  to  the  cooling  action  of  the  entering 
air.  Every  alternate  grate  is  movable,  the  upper  end  being  hinged  to  the 
stationary  grate,  while  the  lower  end  is  rocked  by  a  moving  bar;  the  burn- 
ing fuel  is  moved  down  by  this  bar,  and  the  fine  ashes  are  dropped.  Both 
the  feed  and  the  speed  of  the  crusher  bar  at  the  bottom  can  be  varied  to 
suit  operating  conditions.  The  stoker  has  been  used  with  mine  refuse  con- 
taining 30  per  cent  of  ash.  Natural  draft  can  be  used,  or  an  induced  suc- 
tion of  0.2  in.  at  the  fire  chamber;  with  0.4  in.  it  is  claimed  that  the  boiler 
can  be  driven  at  300  per  cent  rating. 

WesttHghouse-Roney  Stoker.  The  grates  are  horizontal,  arranged  in 
steps,  and  rock  backward  and  forward,  gradually  passing  the  coal  to 
the  lower  part  of  the  slope.  The  coal  is  fed  to  the  coking  plate  at  the 
top  by  the  hopper  plate  outside,  and  ignition  is  helped  by  the  arch  above. 
The  guard  between  the  combustion  grate  and  the  dumping  grate  is  lifted 
when  the  ashes  and  clinker  are  dumped.  This  stoker  operates  on  natural 
draft,  0.25  to  0.6  in.  at  maximum  load,  and  has  a  reserve  capacity  of  200 
per  cent  of  rating.  It  is  used  for  both  high  fixed  carbon  and  high  volatile 
coals,  at  maximum  combustion  rates  of  35  to  50  lb.  per  sq.  ft  per  hour. 

Wetzel  Stoker.  Moving  coking  grates  are  placed  immediately  behind 
the  hopper.  Main  grates  extend  down  to  the  dumping  grates.  The  bars 
of  the  main  grates  are  alternately  stationary  and  moving.  The  openings 
in  the  coking  grates  are  Urge,  supplying  air  for  the  combustion  of  the  volatile 
in  the  space  above;  the  holes  further  down  are  smaller,  while  those  in  the 
lower  part  of  the  main  grates  and  in  the  dumping  grate  are  still  smaller, 
supplying  just  enough  air  to  bum  the  remaining  solid  combustible.  For 
loads  less  than  200  per  cent  of  rating  natural  draft  is  sufficient 


Underfeed  Stokers 

IN  THE  underfeed  type  fresh  coal  is  fed  from  below  the  fuel  bed  by 
some  form  of  pusher,  is  gradually  forced  to  the  upper  zone,  and  toward 
the  ash  dump.  The  fuel  bed  consists  of  three  layers,  a  lower  one  of  green 
coal,  next  a  layer  of  coal  being  coked,  and  an  upper  or  incandescent  lone, 
in  which  the  fixed  carbon  is  consumed  and  the  volatile  gases  from  the  coking 
coal  underneath  are  mixed  with  air  and  ignited.  The  action  is  similar  to 
that  of  a  gas  producer,  except  that  in  the  stoker  the  combustible  gases  pro- 
duced are  consumed  within  the  furnace.  Underfeed  stokers  have  been  suc- 
cessful in  large  plants  for  as  high  as  400  per  cent  of  boiler  rating. 


slope  slightly  toward  the  outside  dump-trays.  The  coal  is  pushed  into 
the  bottom  of  the  retort,  raised  to  the  grate  bars  by  pushers,  and  worked 
toward  the  outside  by  reciprocating  rocker  bars  in  the  grate.  Each  unit  is 
Operated,  and  can  be  banked  or  forced,  independently.  Air  is  fed  in  through 
a  central  wind  box  under  the  retort,  and  through  the  ventilated  grate  bars; 
the  fan  speed  is  controlled  by  a  damper  regulator  responsive  to  the  steam 
pressure,  while  the  supply  of  coal  is  controlled  by  adjusting  the  number  of 
Strokes  of  the  pusher.  The  stoker  is  recommended  for  semi-anthracite,  semi- 
and  sub-bituminous  coals.  The  wind  box  pressure  should  be  from  1  to  5-5 
in,  say  1  in.  per  10  lb.  combustion  rate,  and  the  suction  at  the  fuel  bed  is 
OSK  in.  Boilers  can  be  driven  at  225  per  cent  continuously,  and  at  300  per 
cent  or  more  of  rating,  for  several  hours. 


ib.  Google 


162  STOKERS 

Jones  Stoker,  Fig.  74.  A  series  of  retorts  arc  inclined  slightly  to  the 
back  of  the  hoppers.  A  steam  cylinder  operates  a  pusher  rod,  which  feeds 
a  charge  of  coal  and  forces  the  preceding  charge  of  green  coal  backward 
and  up.  The  coke  on  top  and  the  volatile  gases  formed  below  are  burned  in 
the  upper  incandescent  zone.  The  balanced  dump  plate  is  dropped  to  remove 
accumulated  ashes.  Air  under  pressure  is  supplied  to  tuyeres  at  (he  dead 
plale,  and  other  points  in  the  furnace.  The  rates  of  supply  of  air  and  coal 
can  be  varied  by  hand,  or  are  automatically  controlled  by  the  sleam  pressure. 


Fig.  74.     Jonea  Automatic  Self-Cleaning  Underfeed  Stoker. 

Moloch  Stoker,  Fig.  75.  The  horizontal  retorts  are  fed  by  a  steam  ram. 
Air  is  admitted  through  the  tuyeres  in  the  upper  part  of  the  retorts.  In  the 
larger  units  clinker  grinders  are  placed  between  the  retorts  and  remove  the 
refuse  automatically.  The  stoker  is  used  for  bituminous  and  semi-bitumin- 
ous coals.  Fair  ratings  can  be  developed  with  0.30  to  0.45  in.  natural  draft; 
with  forced  draft  of  3.5  to  4  in.,  practically  any  desired  rating  can  be  main- 


Fig.  75.     Moloch  Self-Cleaned  Underfeed  Stoker. 

Roach  Stoker,  Fig.  76,  has  a  ram-fed  central  retort,  live  and  dead  grate 
bars  sloping  away  from  it  on  each  side.  Part  of  the  air  is  supplied  through 
the  bottom  of  the  retort,  while  that  to  the  grates  is  regulated  by  several 
gates.    Refuse  is  removed  by  dump  plates  at  the  side  of  the  grates. 


ib.  Google 


STOKERS 


Fii.  76.     Roach  Underfeed  Stoker. 

Stevens  Stoker.  Screw  conveyors  force  the  coal  through  horizonlal 
troughs.  The  space  between  the  troughs  is  filled  by  rocking  grates,  set  flush 
with  the  tops  of  the  troughs.  Full  boiler  rating  is  developed  with 
025-in.  natural  draft  over  the  fire,  and  200  per  cent  is  secured  with  a  1-in. 
ashpit  pressure. 

Unh-ersal  Stoker,  Fig.  77.  Coal  is  forced  into  the  retort  by  a  steam  ram 
bearing  a  breaker  bar.  Air  is  admitted  under  pressure  through  tuyeres  ar- 
ranged in  steps  at  the  sides  of  the  retort.  At  the  rear  is  placed  a  supple- 
mental combustion  chamber,  where  the  fuel  is  reduced  to  ash  and  dumped 
into  the  water-sealed  ashpit. 


Fig.  77.     Univeraal  Automatic  Underfeed  Stoker. 


ib.  Google 


164  STOKERS 

Wesiinghouse  Underfeed  Stoker,  Fig.  78,  is  of  the  gravity  underfeed 
type;  the  coal  is  fed  to  the  lower  zone,  but  its  movement  toward  the  dump 
plate  is  aided  by  the  slope  of  the  retorts.  Between  the  retorts  are  semi' 
circular  corrugated  tuyeres  D,  which  supply  air  under  pressure.  The  coal  is 
moved  by  the  upper  ram  K,  by  the  lower  ram  O  in  the  bed  of  the  retort,  and 
by  the  moving  "overfeed  section"  G  at  the  rear  and  bottom.  The  ash  dumps 
are  in  pairs,  pivoted  front  and  rear-  Air  enters  through  the  tuyeres  separat- 
ing the  retorts,  through  the  overfeed  section,  and  through  box  J  at  the 
front.  This  stoker  is  recommended  for  plants  where  the  load  is  subject 
to  wide  and  sudden  variations.  Natural  draft  can  be  used  at  light  loads, 
and  400  per  cent  of  rating  can  be  secured  for  peaks,  at  6  to  7-iD.  pressure 
in  the  wind  box. 


Ftg.  78.     Weatinghouse  Underfeed  Stoker. 


Taylor  Slokrr,  Fig.  79.  The  retorts  are  sloping,  with  perforated  tuyeres 
in  between ;  each  step  is  V-shaped,  the  opening  being  toward  the  front.  The 
coal  is  pushed  into  the  retorts  1  by  feeding  rams  5,  and  is  either  crowded 
upward  or  pushed  into  the  fire  by  short-stroke  rams  6,  6,  the  final  combus- 
tion taking  place  on  the  extension  grates  7.  The  combustible  gases  arc 
ignited  in  the  incandescent  ^one  at  the  front  and  top  of  the  coal  bed.  The 
power  dump  plate  8  is  rapidly  oscillated  to  dislodge  and  dump  the  refuse 
and  clinkers.  In  an  alternative  design  the  refuse  is  ground  between  crush- 
ers, at  a  speed  which  keeps  the  discharge  ash-sealed.  Bituminous,  semi- 
bttuminous,  and  semi-anthracite,  and  even  lignite  coals  can  be  burned. 
At  normal  ratings  a  forced  draft  of  1.5  to  2  in.  is  used,  with  0.03-in.  suction. 
A  wind  box  pressure  of  3  to  4  in.  with  0.03-in.  suction,  will  permit  continuous 
operation  at  20O  to  300  per  cent  rating.  During  peaks,  from  60  to  80  lb.  of 
coal  per  sq.  ft.  per  hr.  can  be  burned. 


ib.  Google 


PtE-  79.     Taylor  Underfeed  Stoker. 

Riley  Stoker,  Fig.  80.  The  retort  walls  move  and  also  agitate  the 
"overfeed  grate  bars,"  which  supply  air  for  combustion.  Farther  down  the 
slope,  at  the  moving  overfeed  bars,  the  unconsumed  coke  is  burned  wilh  the 
aid  of  smaller  quantities  of  air.  The  refuse  finally  passes  to  the  rocker 
dump  plates,  which  are  in  continuous  operation;  here  the  refuse  is  crushed 
and  ejected  at  a  rate  depending  on  the  size  of  the  opening.  The  stoker  can 
bum  lignite  and  all  grades  of  bituminous  coals.  Forced  draft  is  used,  up 
to  S  in.,  with  a  slight  suction.  At  peak  loads  200  to  300  per  cent  rating 
&nd  over  is  obtained. 


Fig.  80.     Riley  Underfeed  Stoker. 


ib.  Google 


1500  H.  P.  Inatallation  of  Heine  Standard  Boilera  «et  over  Weitinghouae 

Underfeed  Stokert  in  the  Plant  of  Harrisona,  Inc., 

Philadelphia,  Pa. 


ib.  Google 


STOKERS  167 

Chain  or  Traveling  Grate  Stokers 

IN  THE  chain  grale  stoker  the  coal  is  deposited  on  the  grate  in  front,  and 
is  ignited  by  the  aid  of  arches.  It  is  then  coked,  gradually  burned  to  ash 
without  agitation  or  cleaning,  and  is  automatically  dumped  at  the  rear.  The 
gear-trains  driving  the  pulley-shafts  are  actuated  by  a  ratchet  and  pawl,  an 
adjustable  arm  being  reciprocated  by  an  eccentric  on  a  line  shaft.  Chain 
grates  handle  normal  loads  efficiently,  and  with  a  minimum  of  smoke,  al- 
though the  maximum  rate  of  driving  is  only  about  250  per  cent.  They  work 
particularly  well  with  low-grade,  free-burning  bituminous  coals,  such  al 
those  from  Illinois  and  Iowa,  containing  30  to  40  per  cent  volatile  and  10 
to  20  per  cent  ash.  With  coals  of  a  lower  ash-content,  the  stoker  may  over- 
heat. 

Coittinenlal  Chain  Crate  Stoker  consists  of  small  units,  with  dove-tail 
and  semi-circular  recesses  for  locking  each  grate,  and  of  rollers  traveling 
on  upper  and  lower  tracks-  The  ignition  arch  over  the  front  is  made  of 
ventilated  tile.  The  depth  of  fuel  bed  is  regulated  by  a  tile-lined  gate. 
A  water-cooled  chamber  in  front  of  the  bridge  wall  prevents  adhesion  of 
clinker.  The  stoker  is  built  for  all  grades  of  free-burning  coal  and  lignite 
with  ash  content  over  7  per  cent,  and  for  all  sizes  from  slack  to  2-in.  nut  A 
suction  of  02  in.  over  the  lire  is  sufficient  when  burning  Illinois  and  Indiana 
coal  at  a  30-lb.  rate,  or  O.S  in.  at  a  50-lb.  rate. 


Fig.  81.    Green  Chain  Orate  Stoker — Type  K. 


ib.  Google 


168  STOKERS 

Coxe  Traveling  Grate.  The  pressure  in  the  air  compartments  below 
the  lire  is  varied  according  to  the  thicknesses  of  fuel  bed.  A  combustion 
arch  covers  the  greater  part  of  the  grate.  This  stoker  is  designed  for  small 
anthracite  and  coke  breeze,  but  also  operates  with  free-burniog,  high-ash 
coals.  The  former  have  been  burnt  at  rates  up  to  50  lb.  per  sq.  ft.  per  hour. 
Forced  draft  of  I  to  2  in.  is  used. 

Type  K  Green  Chain  Crate,  Fig.  81,  employs  a  large,  flat,  ventilated 
ignition  arch.  In  some  installations  a  stationary  waterback  is  placed  in  the 
bridge  wall.  Natural  draft  is  used;  about  0.1  in.  is  required  for  each  10 
lb.  of  coal  burned  per  square  foot  per  hour,  the  usual  rate  being  30  to  40 
lb.    The  Type  K  stoker  is  designed  for  free-burning  coals. 

Type  L  Green  Chain  Grate  is  built  for  coking  coals.  The  coal  passes 
from  the  hopper  to  a  stationary  inclined  plate,  where  it  is  coked  before 
dropping  onto  the  grate.  Either  natural  or  forced  draft  is  used  with  this 
type,  or  induced  draft  when  economizers  are  installed.  Installations  are 
operated  up  to  250  per  cent  of  rating. 


Fig.  83.     Harringtoa  Chain  Orate  Stoker. 


Brady  (Harrinston)  Crate,  Fig.  82,  is  designed  for  forced  draft,  at 
combustion  rates  up  to  75  lb.,  although  natural  draft  can  be  used  at  normal 
rating.  The  grate  is  built  of  small  interlocking  bars,  giving  a  continuous 
surface,  no  parts  of  which  are  exposed  to  excess  heat  in  turning  at  the 
rear.    The  air  supply  at  different  points  is  controlled  by  adjustable  dampers 


ib.  Google 


STOKERS  169 

Illinou  Chain  Grate  has  a  slight  dip  to  the  rear,  and  a  long,  flat  com- 
bustion arch.  Middle  Western  coals  with  over  20  per  cent  ash  are  burnt. 
At    a   40-lb.    rate   the   draft    is   0,63   in.    over   the   fire   and    1    in.    at  the 


Pig.  83.     IlUnCHB  Chain  Qrate  Stoker. 


damiper.  With  coals  containing  from  10  to  20  per  cent  asli,  0.4  in.  over  the 
fire  is  sufficient.  Under  forced  draft,  the  draft  over  the  fire  can  be  less 
than  0.15  in.,  with  1  to  4-in.  wind-box  pressure. 


ib.  Google 


170  STOKERS 

LacUde-Chruty  Chain  Grate,  Fig.  84,  has  a  slightly  inclined  grate, 
in  an  air-tight  setting,  with  long  overhead  arch.  Air  enters  through  small 
openings  in  the  links,  a  swinging  damper  being  used  to  reduce  the  suppljr 
at  the  rear.  This  stoker  is  designed  for  high 'Volatile,  high-ash  coals,  espe- 
cially those  from  the  West,  and  operates  under  natural  draft.  A  chimney 
height  of  200  ft  is  sufficient  for  operation  at  more  than  200  per  cent  rating. 


Fig  84.    Lacledc-Cbricty  Chain  Qrate  Stoker. 


Playford  Chain  Grate.  The  flat  ignition  arch  is  air-cooled,  a  water- 
cooled  fuel-gate  preventing  back-firing  of  coal  in  the  hopper.  The  bridge 
wall  is  protected  from  clinker,  and  air  inleakage  prevented,  by  a  fixed  water- 
back.  In  some  installations  a  movable  back  is  cooled  by  either  water  or  air; 
the  material  at  the  back  of  the  grate  can  then  be  held  back  or  dumped  at  will. 
The  stoker  is  adapted  for  bituminous  coals  with  25  to  40  per  cent  volatUe 
matter.    Natural  draft,  0.15  to  0.4  in.,  is  used. 


ib.  Google 


STOKERS  171 

National  Stoker,  Fig.  85.  Rows  of  pushers  in  recesses  in  the  middle  and 
lower  parts  of  the  inclined  grate  are  hand  operated  by  levers  in  the  boiler 
front.  The  fuel  is  fed,  coked  and  burned  as  in  mechanically  operated 
stokers.    This  stoker  is  applied  to  small  or  medium-sized  furnaces- 


Fig.  S5.     NatiODal  Hand  Operated  Overfeed  Stoker. 


ib.  Google 


ib.Google 


CHAPTER  6 


CHIMNEYS  AND  FLUES 

THE  prcaiure  of  the  draft  is  the  difference  in  the  weight  of  die  column  of 
hot  fcasea  within  the  chimney  and  of  the  corresponding  column  of  air 
outside.    It  is  measured  by  the  difference  in  level  of  water  in  the  legs 
of  a  "U"  tube,  of  which  one  leg  is  connected  to  the  base  of  the  stack  and  the 
other  is  open  to  the  atmosphere.     The  hotter  the  gases,   the  higher  the 
chimney,  or  the  cooler  the  atmosphere,  the  greater  is  the  draft 

The  performance  of  chimneys  is  disturbed  by  many  circumstances, 
particnlarly  by  the  weather.  Variations  in  the  barometer  affect  the  draft 
nearly  10  per  cent.  The  draft  may  be  nearly  SO  per  cent  greater  when  the 
air  temperature  is  lero  than  when  it  is  100  degrees.  As  the  quantity  of  gas 
flowing  up  the  chimney  is  increased,  the  pressure  necessary  to  overcome  the 
friction  of  the  gas  flow  is  increased,  leaving  a  lower  draft  reading  on  the 
"U"  gage. 

While  there  is  a  minimum  height  for  any  draft  requirement,  the  height 
is  generally  influenced  by  local  considerations.  For  satisfactory  results, 
chimneys  should  be  higher  than  surrounding  buildings,  hilts,  trees  or  other 
nearby  obstructions,  so  that  wind  eddies  will  not  interfere  with  the  draft. 

The  minimum  chimney  height  necessary  in  any  case  depends  upon  the 
fuel  tiled.  Wood  requires  the  least  height,  good  bituminous  coal  requires 
a  medium  height,  while  fine  sizes  of  anthracite  need  the  greatest  chimney 
height  The  rate  of  combustion,  boiler  gas  passages,  flue  design,  and  the 
number  of  boilers,  also  influence  the  stack  height 

Small  plants  burning  bituminous  coal  or  large  anthracite  may  have  stacks 
from  70  to  100  ft.  high.  If  burning  anthracite  pea  or  buckwheat,  they 
should  be  125  to  150  ft  high.  Plants  of  800  H.P.  or  more  should  have  stacks 
not  less  than  150  ft.,  whatever  kind  of  coal  is  burned.  To  burn  No.  3  buck- 
wheat at  any  practical  rate,  the  chimney  will  have  to  be  more  than  twice  as 
high  as  would  be  required  to  burn  pea  coal.  This  height  is  generally 
prohibitive,  and  small  anthracites  are  almost  invariably  burned  with  artificial  - 
draft. 


Chimneys  over  200  ft.  high  are  usually  unnecessary.  Unless  conditions 
call  for  a  taller  stack,  two  or  more  shorter  stacks  should  be  erected,  as  the 
two  will  usually  cost  less  than  the  taller  stack.  There  is  a  diameter  corres- 
ponding to  the  most  economical  construction  for  any  stack  height  Accord- 
ing to  W.  Deinlein,  the  smallest  product  of  diameter  and  height  represents 
the  chimney  of  minimum  cost  For  any  given  conditions,  this  relation  can 
be  established  graphically  as  shown  in  Fig.  86:  Assuming  a  masonry  chim- 
ney, we  find  from  the  "H  ^  height"  curve  that  this  particular  chimney  could 
be  175  ft  high  by  20  in.  diameter,  or  125  ft.  by  23  in.,  or  JOO  ft.  by  31  in.,  and 
so  forth.  These  products  are  then  plotted  to  form  the  curve  "dH  ^  Relative 
Cost"  and  we  see  that  the  lowest  point  of  this  curve  occurs  at  25  in.,  for 
which  diameter  the  appropriate  height  is  115  feet  This  is  the  lowest  priced 
chimney  that  can  be  built  to  meet  the  conditions. 


ib.  Google 


CHIMNEYS 


-Mi 

^ 

k 

1 

i 

^\ 

1 

.'^^i 

I, 

\ 

,^ 

r- 

^ 

! 

r 

\ 

4S= 

r 

s 

=^ 

^ 

V 

^ 

!^^ 

H^ 

w- 

~ 

0 













, 

The  gas  temperature  in  the  stack  falls  as  the  distance  above  the  entering 
flue  increases.  This  is  shown  in  Fig.  87,  based  upon  tests  by  Kilbom  and 
Alexander,  on  a  tall  masonry  chirruiey. 

An  analysis  of  numerous  tests,  by  E.  J.  Miller,  shows  that  the  observed 
draft  intensity  usually  does  not  vary  more  than  3  per  cent  from  that  calcu- 
lated when  the  temperature  drop  in  the  chimney  is  allowed  for.  Still,  in 
general  chimney  calculations,  uniform  temperature  is  assumed,  and  the 
temperature  of  the  entering  f;ases  is  the  temperature  used.  Hence,  the 
great  difference  between  the  draft  calculated  and  that  actually  observed. 
This  difference  is  stated  by  different  authorities  as  10,  IS,  and  20  per  cent. 
and  they  recommend  that  appropriate  allowance  be  made. 

In  the  following  treatment,  the  fall  in  temperature  of  the  gases  as  they 
ascend  the  stack  has  been  taken  into  consideration.  The  average  temperature 
of  the  gases  in  stacks  of  different  diameters  and  heights  has  been  deduced 
from  observation,  and  curves  convenient  for  general  use  have  been  drawn. 

The  logical  method  of  treating  the  subject  is  to  compute  the  character- 
istics of  chimneys,  as  is  done  with  fans.  The  minimum  draft  necessary  at 
the  base  of  the  chimney  should  first  be  found,  and  then  chimney  sizes  to 
produce  that  draft  at  the  required  capacity  can  easily  be  chosen.  In  the 
following  discussion,  reasonable  values  of  air  and  gas  temperatures,  and 
operating  efficiency,  will  be  assumed  and  the  effect  of  departures  therefrom 
.indicated.  These  assumed  conditions  must  be  lived  up  to  in  operation,  or 
the  calculated  results  will  not  be  attained. 


ib.  Google 


CHIMNEYS 


Chimney  Sizes  by  Horsepower 

>  include  the 
n  Table  9. 

The  draft  to  be  observed  at  the  base  of  the  stack  as  given  in  the  table, 
computed  on  the  following  assumptions: 

The  horsepower  given  is  the  rated  horsepower  of  the  boilers. 

The  boilers  are  run  at  130  per  cent  of  their  rating. 

Five  pounds  of  coal  are  burned  per  boiler  horsepower  hour. 

Each  pound  of  coal  produces  20  lb.  of  flue  gases. 

Atmospheric  temperature,  60  deg.     Barometer,  30  inches. 

Humidity  ignored  as  negligible. 

Temperature  of  gases  entering  stack,  500  deg. 

Allowance  has  been  made  for  the  drop  of  temperature  of  the  gases 

as  they  ascend  the  stack. 
n  example,  take  five  boilers,  each  rated  at  160  H.P.,  making  800  H.P. 

t  by  the  following  propor- 


all. 
From  the  table,  it  is  seen  that  this  load  ii 


72  inches  dia.  100  feet  high  0.50  inch  draft 
66  inches  dia.  ISO  feet  high  0.65  inch  draft 
60  inches  dia.  200  feet  high  0.74  inch  draft 


ib.  Google 


CHIMNEYS 


To  decide  which  of  these  is  apprc^riate,  local  conditions  must  be  first 
considered.  Then  the  necessary  draft  at  the  stack  base  must  be  determined 
from  the  draft  resistances  of  the  fuel  bed,  boiler  setting  and  so  forth,  as 
expbined  later;  and  the  sum  of  these  will  determine  the  draft  necessary  at 
the  stack  base  and  consequently  the  minimum  height  of  chimney.  Then  the 
most  economical  proportion  of  height  to  diameter  should  be  found  by  apply- 
ing the  principle  illustrated  in  Fig.  86,  so  that  the  chimney  of  least  cost, 
wbkh  will  meet  the  various  conditions,  may  be  adopted. 


Table  9 

Si 

BBm- 

HKIOHT  or  CHIHNSY,  Ft. 

Sid*  at 

vi+4 

t 

«.8 

K. 

80  1  TO  1  SO  1  »     IDol  110     I2E  1  lEO     178  1  200  j  225  1  SEO 

vr 

JSHia^S?r52'5'SBSS5-W„ 

„ 

„ 

■i 

im 

i 

1 

1 

21 
24 

87 

»i 

78 
58 

so 

111 

1 

M 
39 

so 

' 

iS 

'i 

i 

0.41 
0.41 

.1! 

Om\  0.6B 

diSffl::::: ;::::::::::::::     » 

IE 

so 

18 

Bl 

OSS 

ail 

0.89 

0.48 
SSI 

0.41 

0.48 
44S 

0.4S 

D.Bl    0.G5    0.G9    0.S1 

ri 

0«    0.68   0.60    0.B4    O.SB 

O.SSI  0.6T    0.K     O.fl'      O.TI     0.T4 

2S 

« 

20 

88 
06 

BM 

0.41 
«M 

(I.BO 
8SS 

O.EO 

O.ES    0.E7    0.84    0.70    0.74    0.77    0.7 
7n     TTf     S4t     S18     Ml  l,MO  l.S>7 
0,6»    0.68    0.S6    0.72    0.78    0.80    0.82 

o.Bd    o.6s|  b.E'    b.7s|  0.78    o.aa   b.e 

48 

40 

'ffl'ffl'b'iS'q'ffi'b'S'ffl 

SO 
se 

27 

40 
GE 
KB 

2S 
88 

78 
9B 

M 
OS 

7S 
SS 

2£ 

lis 

ISE 

7S 

121 

78 
S2 

128 

1(0 

ib.Google 


CHIUNEYS 


Tbe  asstunptions  on  which  the  table  is  based  meet  all  OTdinaTj  condi- 
tions.   The  effect  of  otiier  conditiaas  will  now  be  discussed  and  compared. 

As  slated  above,  the  draft  at  the  chimney  base,  as  given  in  the  table, 
was  cmnpated  at  130  per  cent  of  boiler  rating.  In  the  example  jusi  taken 
the  drafts  read  from  die  table  are  those  to  be  expected  when  Uie  bailers  are 
running  at  IX  per  cent  of  rating  or  developing  800x130  per  cent=1040  B.H.P. 
In  the  following  discussion,  the  draft  read  from  the  table  is  considered  as  one 
hundred  per  cent. 

Tbe  first  change  considered  will  be  that  caused  by  adding  or  taking  off 
boilers,  the  load  on  individual  boilers  remaining  ihe  same.  Under  these 
circnmstances,  the  temperature  of  the  gases  entering  the  chimney  remains  the 
same,  and  the  draft  falls  off  as  the  addition  of  more  boilers  increases  the 
load  on  the  chinmey.  The  rate  at  which  tbe  draft  falls  off  depends  upon 
tbe  ratio  of  diameter  to  height  (H/D)  and  curves  have  been  drawn  for 
different  ratios  in  Fig.  88.  These  show  very  clearly  that  tbe  draft  diminishet 
mtich  wore  rapidly  in  slender  than  in  squat  chimneys. 


^ 

b: 

■— 

^ 

;§ 

^ 

"s 

!:''■ 

^ 

fe. 

0 

S' 

Si 

■vT 

« 

■% 

^^ 

5^ 

I  ' 

\i 

^f 

M 

« 

\N 

V 

^ 

- 

Taking  the  first  chimney  of  the  above  example  H''D^100/6=16.?.  Using 
the  nearest  curve  given  in  Fig,  88.  where  H/D=16,  and  talcing  off  one  boiler 
so  that  the  chimney  load  is  reduced  to  80  per  cent  of  chimney  rating,  the 
draft  is  now  shown  (as  at  C)  to  be  107  per  cent  The  draft  at  100  per  cent 
of  chimney  rating  was  0.50  inch,  therefore  the  draft  with  only  four  boilers 
in  operation  will  be  107  per  cent  of  0.50,  or  0:54  inch. 

Continuing  with  the  first  chimney  of  the  example,  and  adding  one  boiler, 
tbe  load  will  now  be  120  per  cent  of  chimney  rating.  The  draft  (as  at  D)  is 
now  92  per  cent,  so  that  the  draft  at  the  base  of  the  stack  with  six  boilers 
in  operation  will  be  92  per  cent  of  0.5O  or  0.46  inch. 

The  change  in  the  draft  cansed  by  varying  the  load  on  a  fixed  number  of 
boilers  will  now  be  considered.  The  temperature  of  the  gases  leaving  the 
boilers  increases  as  their  rale  of  driving  is  increased,  as  shown  by  Fig.  90.  As 
the  temperature  rises,  the  gases  become  lighter.  This  increases  the  static 
draft  and  lowers  the  increase  of  friction  loss,  as  explained  later.    The  rate 


ib.  Google 


178  CHIMNEYS 

at  which  the  draft  falls  off  is  less  than  in  the  previous  case,  and  may  even 
rise.  The  curve  is  now  dependent  upon  the  ratio  of  square  root  of  diameter 
to  height  (H/yD)  and  curves  have  been  drawn  for  several  different  ratios  in 
Fig.  ^.  It  will  be  seen  that  this  chart  is  marked  for  both  chimney  rating 
and  boiler  rating,  and  that  130  per  cent  of  boiler  rating  is  equal  to  100  per 
cent  of  chimney  rating. 

Again  taking  the  first  chimney  of  the  example,  H/V^^^'>  U^iog  the 
nearest  curve  in  Fig.  89,  where  H/\/D=;40,  and  decreasing  the  chimney  load 
to  80  per  cent,  which  reduces  the  boiler  load  to  104  per  cent  ot  rating,  the 
draft  (as  at  C)  is  now  96.5  per  cent  of  that  at  chimney  rating.  The  draft 
at  the  base  of  the  stack  is  now  96.5  per  cent  of  0.50  or  0.48  inches.  At  120 
per  cent  of  chimney  rating  equal  to  boilers  running  at  156  per  cent,  the  draft 
(as  at  D)  is  108  per  cent  or  0.54  inches. 


^/ 

/ 

/ 

£ 

ffp 

,' 

"t 

t  ! 

■^ 

SI 

pn 

•7 

u 

^ 

fcz= 

i= 

=r 

4 

% 

- 

fiE; 

zz 

=: 

=5 

— 

V 

t 

/ 

f 

/ 

to 

"1 

A, 

!« 

^,1* 

i. 

fh 

vR.. 

U    L 

10 

jO  1 

•0    IN 

On  each  of  the  charts  the  dotted  line  A-B  represents  the  proportionate 
amount  of  draft  TeqM\rtd.  This  curve  is  drawn  on  the  assumption  that  the 
draft  required  varies  as  the  square  of  the  horsepower  developed  in  a  given 
boiler,  which  is  not  true,  but  is  as  close  as  is  necessary,  in  Fig.  88,  it  is  a 
horizontal  line.  The  draft  required  is  constant,  since  the  load  is  varied 
by  adding  or  shutting  down  boilers.  The  amount  of  draft  must  he  increased 
somewhat  as  more  boilers  are  added,  owing  to  greater  length  of  tines  and 
more  turns  and  enlargements.  This  increase  is  not  large  and  is  different  in 
every  case,  so  that  it  has  been  ignored  in  the  chart.  In  Fig.  89,  the  curve 
rises  quickly.  In  both  figures  the  unnecessary  draft  at  C  is  extinguished  by 
partly  closing  the  damper,  while  the  defect  of  draft  at  D  must  be  made  up 
by  artificial  or  mechanical  draft. 

The  curves  drawn  in  Figs.  88  and  89  are  based  on  the  temperatures  of 
the  gases  leaving  the  boiler  in  excess  of  the  temperature  due  to  the  steam 
pressure.    The  curve  in  Fig.  90,  due  to  Gio,  H,  Gibson,  is  based  upon  the 


ib.  Google 


CHIMNEYS 


of  500 
89  the 


developed,  taken 

boilers  runnini;  s 

deg.  is  assumed  «^  ...».  ^ 

temperatures  appropriate 


,s  3  percentage  of  the  commercial  rating,  and  assum- 
of  350  deg.,  or  120  lb.  pressure.  As  Fig.  88  is  based 
130  per  cent  of  their  rating,  the  constant  temperature 
c  that  of  the  gases  entering  the  stack,  while  in  Fig. 
"''"*-  *"  the  power  as  given  in  Fig,  90  have  been 


, 

1 

y\     1 

^ 

X 

- 

«j!^ 

l"° 

'1 

plJ 

£, 

.< 

^ 

L, 

' 

" 

.J 

Percent  of  Rated   Hariepowtr  Divtiopcd. 


So  far,  we  have  used  the  same  basis  as  Kent  in  assuming  5  pounds  of 
coal  per  B.H.P.  and  20  pounds  of  flue  gases  per  pound  of  coal.  These  fig- 
ures are  sufficiently  liberal  for  reasonably  careful  operation.  But  where  an 
excess  of  air  is  allowed  to  leak  in  through  defective  settings,  firedoors,  holes 
in  the  fire,  and  so  forth,  the  quantity  of  gases  to  be  dealt  with  may  be  greatly 
increased.    This  increases  the  load  on  the  chimney.    The  amount  of  excess  air 


tt 

aR 

^\ 

\  N 

^^^ 

^fS 

Si^ 

s,     \ 

\    "^^ 

N^      ^^ 

■^-..., 

•^ 

I--*—'"  '—*—'-'    1    '    1    [  ^    [  [   '    [  I  }■  ^  i'-'it 

ib.Google 


15 

1| 
II 

Ss 

Co; 


ib.Google 


*■  CHIMNEYS  181 

■9  found  from  analysis  of  the  flue  gases  as  explained  in  Chapter  15  on 

BOILER  TESTING,  and  is  shown  by  the  percentage  of  CO,.  Fig.  91  is  a 
representative  example  of  the  weight  of  gases  per  pound  of  fuel  with  different 
percentages  of  COi.  With  the  coal  of  analysis  used  in  drawing  the  curve,  20 
pounds  of  gas  per  pound  of  fuel  is  due  to  11  per  cent  of  Cd.  If  the  CO,  is 
reduced  to  7  per  cent,  then  the  weight  of  gas  is  increased  to  30  pounds,  or 
50  per  cent  more.  Under  these  conditions  a  given  chimney  could  only  care 
for  two-thirds  the  load  expressed  in  boiler  horsepower.  In  many  instances 
overloaded  chimneys  have  been  relieved  by  the  addition  of  forced  draft 
and  otherwise  improved  operation  so  that  the  weight  of  gas  per  boiler  horse- 
power has  been  sufficiently  reduced  to  enable  more  power  to  be  developed 
without  alteration  to  the  chimney. 

Draft  and  Capacity  of  Chimneys 
"T^E  curves,  Fig.  92,  are  deduced  from  observations  by  Peabody  and  MHUr 
■^    and  by  /.  C.  Smalhoood,     All  are  for  temperatures  above  that  of  the 
fttmosphere.      Thus,     taking    gases     entering    at    500    deg.,    and    atmos- 
pheric temperature  of  60  deg.,  the  difference  is  440  deg.    In  a  masonry  stack 


1 

f 


7  ft.  diameter.  200  ft.  high,  the  average  temperature  will  be  80  per  cent  of 
the  entering  temperature,  440  X  OH),  or  350  +  60  =  410  deg.  as  actual 
average  temperature.  At  heavy  loads  the  average  temperature  will  probably 
be  a  larger  proportion  of  the  entering  temperature,  and  at  light  loads  a 
smaller  proportion  than  those  shown  by  the  curves.  Any  such  differences 
from  the  curves  given  are  likely  to  be  negligibly  small. 

Fig.  93  gives  the  weight  per  cubic  foot  of  the  chimney  gases  under  aver- 
age conditions,  at  different  temperatures,  and  Fig.  94,  that  of  air. 

The  static  draft  appropriate  to  anjf  chimney  can  be  calculated  by  means 
of  these  three  charts.  Continuing  with  the  last  example  and  taking  the 
temperature  of  the  air  at  60  deg.  (the  common  assumption  in  designing  chim- 
neyai,  the  weight  of  air  per  cubic  foot  is  seen  to  be  0.0?64  pounds.  A  column 
of  air  of  one  square  foot  cross-section,  20O  ft.  high,  will  weigh  200  X  0.0764 
^  1523  pounds.  The  column  of  gas  (at  410  deg.)  of  the  same  height  will 
weigh  200  X  0.48+  =  9.68  pounds.  The  difference,  1528  —  9.68,  or  5.6  lb.. 
is  the  pressure  per  square  foot  of  the  resulting  draft.  Then  the  static  draft 
■s  5jS  X  0.192  =  1.08  in.  of  water. 


ib.  Google 


CHIMNEYS 


Ttmptrature,   Deg,  F»hr. 

Fig.  93.     Weight  of  Flue  Oaset. 




1 

1 

1 

1 

1 ' 

1 

1 

1 1 

1 — 1 

1 — t 

s 

i 

0M5 

1 1 

1 1 

1 J 

A 

tl 

f. 

— r 

51 

1 — J 

Ttmptroture,  OagrcM 
Pig.  04.     Wright  of  Air. 

ti  practice,  the  entering  temperature  of  SOO  deg.  would  be  taken, 
giving  a  static  draft  of  \26  in.,  which  is  wrong.  This  static  draft  of  1.08  in. 
cannot  be  read  on  a  U-gage,  because  part  of  it  is  lost  in  overcoming  the 
friction  of  the  gases  in  the  chimney. 

The  draft  loss  by  chimney  and  flue  friction  can  be  read  from  Fig.  95. 
The  curves  are  drawn  for  a  temperature  of  440  degrees.  The  draft  loss  for 
any  other  temperature  can  be  obtained  by  multiplying  that  read  from  the 
curves  by  the  multipliers  given  by  the  upper  curve..  For  instance,  take  the 
dotted  lines  as  an  example ;  if  the  temperature  is  S?5  degrees,  enter  the  upper 
scale  with  this  temperature  and  proceed  vertically  downwards  to  intersection 
with  the  curve,  then  horizontally  to  the  right  hand  scale  and  read  the  multi- 
plier as  0.87.     If  the  upper  scale  be  entered  with  440  degrees,  the  multipliei 


ib.  Google 


CHIMNEYS 


i 

Ttfflper»li 

3§  % 

rt 

H 

5 

1 

it 

\ 

\ 

L6tt 

^ 

\ 

l.!^g 

3 

\ 

\ 

.4.^™^^ 

^Hs 

^m 

\ 

-^ 

"tri"*" 

'■^1 

■s 

\ 

\ 

\ 

LlOf 

S,„ 

\ 

\ 

\ 

l" 

> 

^^ 

-^ 

: 

J» 

\ 

\ 

■^ 

^ 

«E; 

* 

- 

^ 

(ito| 

2.  I 

j4 

-^ 

i. 

^ 

^^ 

■^ 

h 

— 

^ 

ttTO 

^Si^ 

-^-S 

^ 

"~ 

— 



ato 

■^J 

>^?^^ 

7~- 

= 

— 1 

__ 

= 

— 

— 

^.^Si-p-;:: 

^ 

— L_j 

— ' — 

[ 

= 

= 

=1 

=£ 

=j 

=; 

— ' — — \ — \ — 

The  draft  loss  can  be  calculated  from  this  formula,  due  to  A.  L.  Mentin, 
on  which  Fig.  95  is  based: 

h  —  tAH  (10) 

DT 
A  =  Draft  loss,  inches  of  water. 
Z,=Hetght  of  chimney,  or  length  of  flue,  feet. 
D^  Diameter  of  fiue  or  chimney,  feet. 
!■':=  Velocity  of  gases,  feet  per  second. 
r=AbsoIute  temperature,  degrees. 
/^O.OOS  for  circular  masonry  stacks  or  flues. 
^0.007S  for  unlined  circular  steel  stacks  or  flues. 
Fig.  95  was  drawn  with  /  =  0.008. 
For  square  stacks  or  flues  having  the  same  area  as   round  ones  of 
diameter  D.  multiply  h  as  found  above  by  1.06.    For  other  shapes,  the  follow- 
ing  multipliers  can  be  used : 

Ratio  of  Sides  Multiplier 


ol 
lto2 


1,06 
1.09 


Taking  the  last  chimney  example,  7  ft  diameter  by  200  ft.  high  with  an 
average  temperature  of  the  gases  of  410  deg.  and  a  velocity  of  30  ft.  per 
second,  we  enter  Fig,  95  and  find  the  draft  loss  for  38.5  sq.  ft.  to  be  0.114 
inch.    As    the   curves   are   drawn    for   440   deg.    we   enter    the    correction 


ib.  Google 


CHIMNEYS 


Sortion  with  410  de^.  and  find  a  multiplier  of  1.035;  applyins  this  to  the 
.114  we  get  0.118.  This  is  the  draft  loss  per  100  ft.,  so  doubling  it  we  get 
0.24.    This  result  can  be  checked  by  the  Mensin  formula  (10). 

Under  the  assumed  conditions  the  static  draft  for  this  chimney  is  1.08 
inches.  Deducting  the  friction  draft  loss  of  054  in.,  we  find  that  the  avail- 
able draft  at  the  base  of  the  stack  is  0.84  inch.  This  is  the  "draft"  which  is 
read  on  the  U-gage. 

To  convert  this  to  horsepower,  30  ft.  per  second  multiplied  by  the  chim- 
ney area  of  38.S  sq.  ft.,  gives  IISS  cu.  ft.  per  second.  From  Fig.  93  we 
find  the  weight  per  cu.  ft.  of  the  gases  to  be  0.484,  so  that  we  have  56  lb,  of 
gas  per  second  or  201,600  lb.  per  hour.  As  we  have  been  assuming  100  lb, 
of  gas  per  hour  per  horsepower,  the  rate  becomes  2016  horsepower. 

With  Western  coals,  the  sizes  given  in  Kent's  table  should  be  increased 
25  to  60  per  cent.  It  is  wiser,  however,  to  determine  the  amount  of  coal 
to  be  burned  per  horsepower,  either  by  Fig,  96  or  independently  of  it,  bearing 
in  mind  that  the  efficiency  generally  attained  with  poor  coal  is  low,  while 
a  higher  draft  loss  through  the  fuel-bed  will  be  read  from  Fig.  97. 

Chimney  proportions  of  existing  stoker-fired  plants  in  different  parts  of 
the  country  are  given  in  Table  10.  A  comparison  with  the  Kent  table  is 
included. 


Table  10 

COAL-BURNING 

STOKEa-FIRBD 

^"^^ 

CU»Hy 

H/D 

AnK 

"s- 

^s:^ 

H*<iht 

D.™. 

1,630 
2,600 
2,800 

3 
4 
4 

125 
160 
230 

8 
9 
10 

15.6 
16.7 
23.0 

30 
39 
36 

1,708 
2,400 
3,690 

90 
104 
76 

Taylor 
Roney 
Chain  Grate 

3,600 
3,600 
4,000 

6 
6 
8 

225 
226 
210 

13 
U 
12 

17.3 
20.5 
17.6 

27 
37 
36 

6,290 
4,450 
5,140 

57 
81 

78 

Murphy 

Roney 

Murphy 

4.800 
4300 
5,800 

8 
8 
10 

180 
210 

250 

14 
13 
17 

12.9 
16.2 
14.7 

31       1     6,530 
36            6,080 
26       1    11,480 

73 

79 
51 

Taylor 
Chain  Grate 

9,600 
9,760 
10,400 

16 
8 
20 

275 
260 
300 

18 
19 
18 

17.2 
13.2 

16.7 

48 
34 
41 

11,640 
14,400 

14,100 

83 
68 

74 

Taylor 
Chain  Grate 
Roney 

12,000 
16,600 

12 
24 

250 
250 

20 
21 

12,5 
11.9 

38 
45 

18,000 
17,600 

75 
89 

Taylor 
Taylo. 

Five  Siscs.  Formula  (,10)  is  appropriate  for  flues  as  well  as  for  chimneys. 
As  an  example,  find  the  draft  loss  in  a  straight  brick  flue  8  ft.  high,  4  ft. 
wide,  200  ft.  long,  with  gases  at  550  deg,,  traveling  at  30  ft.  per  second? 
Entering  the  lower  scale  of  Fig.  9S  with  32  square  feet  and  proceeding 
vertically  upwards  to  the  curve  of  velocity  of  30  feet  per  second,  and  then 
horizontally  to  the  left-hand  scale,  the  draft  loss  of  0.125  is  read.  Entering 
the  upper  scale  with  a  temperature  of  5S0  degrees,  and  proceeding  as  directed 
on  the  previous  page,  a  multiplier  of  0,89  is  obtained,  and  apply- 
ing this  to  0.125.  a  draft  loss  of  0.111  is  found.  This  is  for  100  feet, 
so  that  for  200  feet  the  loss  is  0222.  But  this  loss  is  for  a  circular  tlue. 
The  ratio  of  sides  is  4  :  8  or  1  : 2  for  which  the  multiplier  is  1.09,  and  applying 
this  to  0.222,  the  draft  loss  for  the  conditions  laid  down  is  found  to  be 
0.24  inch. 


ib.  Google 


CHIMNEYS 


Draft  Required  for  Coal 
"T^E  draft  required  at  the  base  of  the  chimney  is  the  sum  of  the  draft  losses 
'■    caused  by  the  resistance  of  the  fuel-bed,  boiler  setting,  economizer  (if 
there  is  one),  flues   and   dampers,  and  the  draft  absorbed  in  setting  the 
gases  in  motion. 

Fig.  96  will  give  the  number  of  pounds  of  coal  which  will  be  burned  per 
boiler-horsepower-hour.  This  should  be  confirmed  by  the  expected  evapora- 
tion per  pound  of  fuel,  by  talcing  the  appropriate  point  on  the  evaporation 
curve  and  then  moving  vertically  to  the  coal  curve,  where,  for  example,  an 
evaporation  of  10  lb.  of  water  is  seen  to  necessitate  burning  3.45  lb.  of 
coal  per  boiler-horsepower  per  hour. 


1 

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.* 

A_ 

/ 

\ 

/' 

' 

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ih 

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5.m 

m 

mir. 

n.n 

C 

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nri 

J 

Buckwheat 

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i 

H^B 

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iti. 

^ 

Knowing  the  weight  of  coal  to  be  burned  per  hour  and  dividii^  it  by 
the  total  grate  area,  the  number  of  pounds  to  be  burned  per  square  foot  per 
hour  is  obtained.  Fig.  97  shows  the  draft  required  through  the  fuel-bed.  The 
curves  have  been  plotted  from  a  large  number  of  boiler  tests  and  represent 
good  general  practice.  Reference  should  also  be  made  to  Chapter  2  on 
BOILERS. 

The  draft  loss  through  a  regular  Heine  Boiler  setting  is  given  by  Fig.  98, 
for  both  one  and  two  passes.  With  poor  management,  allowing  excess 
air,  the  draft  required  will  be  greater.  Fig.  98  is  based  on  the  use  of  12 
cu.  ft.  of  air  per  horsepower  per  minute.  It  can  also  be  used  to  show 
the  increase  of  draft  necessitated  by  an  increase  of  air  due  to  poor  firing 
or  leaks.  Suppose  that  15  cu.  ft.  of  air  per  horsepower  per  minute  is  used 
instead  of  12.  Then  the  air  used  is  15/12  or  125  per  cent  of  that  forming 
the  basis  of  the  chart.  The  actual  proportion  of  rated  horsepower  developed 
is  multiplied  by  125  per  cent  to  find  the  draft  necessary.  If  the  boilers  arc 
running  at  120  per  cent  of  rating,  120  X  125  =  150  per  cent,  and  the  draft 
required  is  read  for  a  single  pass  boiler  as  0.28  inch. 

For  cross  or  vertically  baffled  boilers,  a  sufficiently  close  approximation 
is  obtained  by  adding  10  to  20  per  cent  to  the  draft  loss  read  from  Fig.  98. 


ib.  Google 


CHIMNEYS 


Z     ^?     Z_Hy 

^      Z^,^      ^" 

ac 

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iix 

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5«< 

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L 

y/ifyt/     ^  ,/^^ 

-^uM.^'  -.^ ^.^'^' » 

3CM^.  7^^^^^z: 

, '           ^.m<^x  1  !rkii5a!5TJ#B%Jn 

i«         ^4 

^G     ^'^^M<*s^!S*     ^^ 

^»       ^^? 

/I    -^  / 'i^^ls'^^S&J' s*  ^ 

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J-^  ^  ^  :^^<jip*' 

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T  '  ^  ''  "H  T 

H 

■■  j.    '    il    Jb  K  M  w  ta  Jd  K  M  Jt  »  ■ 

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<^6«>p<r 

B5,rw..-^s. 

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0      00 

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r- 

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s 

The  draft  loss  through  economizers  5  to  8  ft.  wide  can  vary  between 
.02  and  0.5  in,  for  each  10  ft.  of  length.  They  are  generally  built  long 
nd  narrow  with  tubes  9  to  12  ft.  high,  because  their  efficiency  is  greater 
s  the  speed  of  the  gases  is  increased,  as  is  shown  in  discussing  heat  transfer 
1  Chapter  11.   The  draft  loss  can  be  computed  from 


ib.  Google 


CHIMNEYS  187 

A=i^^»''Wr  (11) 

A  =  Draft  loss,  inches  of  water 
If  ^Weight  of  gases,  pounds  per  hour,  divided  by  the  number 

of  lineal  feet  of  pipe  in  each  economizer  section, 
ATs^number  of  economizer  sections. 
7"^  mean  absolute  temperature  of  gases,  degrees. 
The  draft  loss  through  breechings  and  flues  can  be  taken  as  0.1  in.  of 
water  per  lOO  ft.  length  and  0.05  in.  for  each  right  angle  turn,  if  the  area 
is  about  20  per  cent  greater  than  that  of  the  stack. 

The  loss  due  to  altering  the  speed  of  the  gases  at  each  abrupt  enlargement 
and  change  of  shape  is : 

1  =  0.125  <il=5i>l  <■» 

A  =  Draft  loss,  inches  of  water. 
y,  and  Fi^Different  velocities,  feet  per  second. 

7=^  Absolute   temperature   of  gases,   degrees 
In  long  flues  having  several  sudden  enlargements,  changes  in  form  of  cross- 
section  and  sharp  turns,  the  loss  may  be  considerable. 
The  draft  lost  in  accelerating  the  gases  is: 

fc  =  0.I2s£l 
T 

For  a  gas  temperature  of  500  deg.,  this  becomes 

h-     ^ 

'■"7686 

The  following  are  values  of  draft  lost  in  producing  velocity  for  practical 

Velocity,  feet  per  second 20  30  40  50  60 

Draft  loss,  inches  of  water— 0.05       0.12       0.21        0.33       0.47 

The   foregoing  draft  losses   should  be  tabulated   for   any  given   case, 
showing  the  assumptions  on   which   they  are  based,   as  in   the    following 
example: 
Fuet'Bed  Resistance 
Boilers,  200  H.P,    Grate  area,  40  sq.  ft.  Good  bituminous  run  of  mine 
coal.    Say  3.75  lb.  of  coal  per  hour  per  horsepower,  as  in  Fig,  96, 
Boilers  to  operate  at  rated  capacity  200  X  3.75  =  750  lb.  of  coal  per 
hour  per  boiler.     Divide  by  40  sq.  ft.  of  grate  =  19  lb.  per  sq.  ft 

per  hour.    Read  from  Fig.  97 0.21 

BoSer  Resistance 
If  single-pass  Heine  boilers,  read  from  Fig,  98  as  0.12.    It  desired, 
allow  20  per  cent   for   more  air,   reading  draft  at   120   instead  of 

100  per  cent - .0.18 

Breeckings  and  Flues 
Flue  80  ft.  long  at  0.10  per  100  ft.  gives  0.08  and  two  bends  at  0.05 

each,  0.10.    Tapers  where  required,  no  abrupt  enlat^ements .0.18 

Vehcily  of  Gases 

Say  25  ft.  per  second  so  that  -^  gives  ..._ 0.06 

Minimum  draft  at  chimney  base  necessary  to  operate  the  plant 0.6S 


D,g,tze:Jbi  Google 


ib.Google 


I 


CHIMNEYS  189 

Chimney  Sizes  as  Determined  by  Oas 
N  _  departing  from  ordinary  condilions,  for  which  Kent's  table  was  de- 
signed, it  IS  well  to  make  calculations  on  the  basis  of  the  quantity  of  gas 
<  be  dealt  with,  rather  than  on  weight  of  fuel  or  horsepower.  The 
quantity  of  gas  can  be  based  on  the  heat  value  of  the  coal,  as  recom- 
mended by  y.  J.  Atbe.  It  has  been  shown  that  the  weight  of  air  required 
per  10,000  6.  t.  u.  generated,  varies  with  the  available  hydrogen  in  the  fuel 
from  7.65  lb.  for  anthracite  to  7.04  for  oil.  In  solid  fuel  the  maximum  varia- 
tion from  7.6  is  less  than  ±  1  per  cent  Therefore,  while  the  weight  of  air 
per  pound  of  coal  will  vary  greatly  with  its  heat  value  the  weight  of  air 
per  horsepower  for  100  per  cent  boiler  and  furnace  efficiency  will  remain 
constant  at  25.4  !b.,  and  the  weight  of  flue  gases  at  about  31  pounds.  Dividing 
this  by  the  efficiency,  we  have  the  weight  of  gas  per  hour  per  horsepower 
developed.    Following  are  the  weights  of  gases  for  different  fuels : 

Efficiency,         Weight  of  Gases, 
per  cent  lb.  per  hr.  per  H.P. 

Anthracite 65  48 

Semi-Bituminous .. 60 


.50 


56 


Oil 70  42 

The  volume  of  the  gases  at  any  temperature  is  obtained  by  dividing  the 
total  weight  by  the  weight  per  cubic  foot  as  read  from  Fig.  93.  Dividing  this 
volume  by  3600  times  the  chimney  or  flue  area,  will  give  the  veloci^  in 
feet  per  second. 

The  following  have  been  recommended  as  economical  velocities,  consid- 
ering the  total  quantity  of  gases: 

Velocity, 
Gases,  lb.  per  hr.  feet  per  second 

1,™ 10 

WOO _- . 15 

25.000. -20 


These  velodliei  should  be  considered  only  as  at^nvximate.  The  draft 
losses  should  be  determined  for  several  velocities  with  different  sizes  of 
chimney  so  that  the  most  economical  can  l>e  chosen. 

Chimneys  for  Oil,  Gas  and  Wood 

GENERALLY  the  sizes  of  chimneys  calculated  on  a  gas  basis  are  much 
smaller  than  those  found  from  Kent's  table.  Ample  allowance  should 
be  made  for  driving  boilers  above  their  rated  power,  poor  coal,  poor  firing, 
leakage  of  air  through  brickwork  and  from  idle  boilers. 

With  oil  burning  excessive  draft  is  more  wasteful  and  more  likely  to 
occur  than  with  coal.  Undue  chimney  height  and  capacity  must  therefore 
be  avoided.  The  loss  of  draft  through  the  burners,  boiler  setting  and  flues 
is  considerably  lower  than  for  coal,  because  the  weight  of  gases  per  horse- 
power is  less;  the  weight  per  pound  of  fuel  is  greater,  however,  as 
shown  in  Fig.  91.  The  temperature  of  the  gases  is  lower,  so  that  oil- 
stacks  produce  less  draft  than  coal  stacks.  The  burners,  however,  give  some- 
what of  a  forced  draft  effect.  Defective  draft  is  also  to  be  avoided,  since 
pressure  within  the  boiler  setting  generally  causes  rapid  deterioration  of 
brickwork.  Owing  to  the  imaller  quanti^  of  gases,  the  chimney  diameter 
ahould  be  smaller. 


ib.  Google 


CHIMNEYS 


C.  R.  Weymouth  observes  that  the  necessary  height  for  oil  chimneys  i* 
much  less  than  ordinarily  supposed  when  boilers  are  operated  at  rating,  and 
considerably  greater  at  heavy  overloads. 

The  sizes  of  oil  chimneys  should  be  based  on  the  maximum  load  and 
the  draft  resistance  due  thereto,  rather  than  on  the  rated  horsepower  of  the 
connected  boilers.  Table  11  is  based  on  the  horsepower  developed  (not  on 
rated  horsepower  of  boilers,  as  was  Table  9  for  coal)  when  the  boilers  are 
being  operated  at  ISOper  cent  of  rating.  It  is  a  modification  of  C.  R.  Wey- 
mouth's table  for  plants  at  sea-level,  assuming  temperature  of  air  as  80 
deg.  and  of  gases  as  500  deg.  With  properly  designed  connections  and  short 
flues,  the  sizes  given  will  be  found  satisfactory. 


Table  11.     Chimney  S 

les  for  Oit-BuminK  Planti. 

HEIGHT  ABOVE  FLOOR  LtNS,  FEET 

% 

BO 

90 

lOO 

no 

IM 

ISO 

... 

160 

too 

30 
33 

as 

206 
366 
312 

249 
310 
379 

280 

349 
427 

304 

381 
466 

324 
405 

497 

340 
428 
523 

354 
444 
546 

366 
459 

664 

377 

472 
581 

39 
42 

4fi 

376 
443 

518 

455 
539 
630 

614 
609 
713 

561 
665 
779 

599 
711 
834 

631 
749 
879 

657 
782 
918 

681 
810 
962 

701 
835 
981 

48 

64 
60 

699 
779 
985 

729 

951 

1.200 

827 
1,080 
1,370 

904 
1,180 
1,500 

967 
1.270 
1,610 

1,020 
1,340 
1.710 

1,070 
1,400 
1,790 

1.110 
1,460 
1,860 

1,140 
1,500 
1.920 

66 

72 
78 

1220 

1,470 
1,750 

1.490 
1.810 
2,150 

1,700 
2,060 
2,460 

1.860 
2.260 

2.710 

2.000 
2.430 

2.910 

2,120 
2,580 
3,090 

2,220 
2,710 
3.250 

2.310 

2,820 
3,380 

2,390 
2,910 
3,500 

84 
90 

96 

2,060 
2,390 
2,750 

2,630 

2,950 
3,390 

2,900 
3,370 
3,880 

3,190 
3,720 
4,290 

3,440 
4,010 
4,630 

3,660 
4.260 
4,920 

3,840 
4,480 
5.180 

4.000 
4,670 
6,400 

4,150 
4.860 
5.610 

102 
108 

3,140 
3,550 

3,870 
4,380 

4,440 
5,020 

4,900 
6.550 

5,290 
6.000 

6,630 
6,390 

6,930 
6.730 

6,190 
7,030 

6.430 

7.300 

114 
120 

3,990 
4,440 

4,920 
5,490 

5.650 
6,310 

6,250 
6.990 

6,760 

7.660 

7,200 
8,060 

7,590 
8.490 

7.930 
8.890 

8.250 
9,240 

Analysis  of  figures  on  several  oil  chimneys  shows  the  height  to  be  be- 
tween 100  and  180  ft.;  Ihe  diameter  l/IO  to  1/15  of  the  height,  depending 
upon  local  conditions ;  one  square  foot  of  chimney  area  serves  40  to  50  rated 
horsepower  of  boilers. 

The  general  practice  of  engineers  on  the  Pacific  Coast,  states  Georgt 
Dorward,  is  to  use  50  per  cent  of  the  area  as  stated  in  Kent's  table  for  stacks 
for  coal.  For  Heine  boilers  up  to  200  H.P.,  stacks  not  in  excess  of  60  ft  in 
height  from  the  boiler  room  floor  line  to  the  top  of  stack,  are  the  general 
practice.  Over  200  H.P.  the  same  rule  is  used.  i.  e^  50  per  cent  of  the  area 
as  stated  by  Kent,  and  not  in  excess  of  80  ft.  in  height  This  practice,  it 
has  been  found,  works  very  successfully. 

With  blast  furnace  gas,  the  volume  of  chimney  ^ases  is  greater  and  at 
a  higher  temperature  than  with  coal,  so  that  stack  diameters  are  about  the 
same.  The  draft  loss  through  horizontally  balTled  boilers  nirs  from  0.6  to  0,9 
in.  when  operating  at  capaaties  up  to  about  175  per  cent  of  rating,  which  arc 
attained  in  practice  with  chimneys  from  US  to  140  ft.  high. 

As  in  oil-burning  chimneys  the  height  and  capacity  should  be  deter- 
mined by  the  draft  requirement  at  maximum  capacity.  Excessive  and  defec- 
tive draft  should  be  avoided  as  causing  waste  and  setting  deterioration 
respectively. 


ib.  Google 


CHIMNEYS 


:   and   high   f 


:   temperatures   : 


Owing  to  the  greater  volume  of  gases,  the  diameter  should  be  10  per  cent 
greater  than  for  coal. 

Because  of  the  variations  in  the  properties  of  different  kinds  of  wood, 
variations  in  size  and  wetness,  and  different  methods  of  tiring,  draft  losses 
through  the   fuel-bed  and  boiler  setting  can   be  approximated  only. 

Wood  burning  chimneys  are  best  located  directly  on  top  of  the  boiler,  to 
avoid  accumulations  of  unburned  particles  that  might  otherwise  be  deposited 
in  the  base  of  the  stack.  Such  deposits  have  been  ignited,  thus  destroying 
the  stacks.  If  such  accumulations  cannot  be  avoided,  the  lower  part  of  the 
stack  should  be  lined  with  tirebrick. 

Municipal  rrfuie  destructors  and  garbage  incinerators  should  have  chim- 
neys at  least  200  ft.  high  to  meet  popular  demand  that  the  effects  of  odors 
be  eliminated.  High -temperature  destructors  operated  under  forced  draft  do 
not  require  such  heights  to  take  care  of  the  draft;  and  with  proper  handling, 
no  objectionable  odors  are  emitted. 

Owing  to  variation  in  the  proportion  of  combustible  matter  and  water  in 
the  refuse  of  different  cities,  and  the  frequent  use  of  coal  or  oil  when  only 
the  garbage  is  burned,  no  general  figures  on  draft  requirements  are  possible. 
For  any  particular  city,  these  proportions  are  usually  known  or  ascertained 
sufFiciently  closely  so  that  bailer  and  chimney  sizes  can  be  determined.  Un- 
sorted  municipal  refuse  as  collected  averages  one-third  carbon,  one-third  ash, 
and  one-third  water.  Boilers  and  chimneys  based  on  this  proportion  will  give 
satisfactory  results. 

F.vasi  or  Venturi  Chimneys  are  used  to  a  limited  extent  in  Europe  and 
a  few  have  been  installed  in  this  country.  Fig.  99  is  diagrammatic  and 
explains  the  system,  which  is  identical  with  that  of  jet-blowers  and  ex- 
hausters. 


ib.  Google 


CHIMNEYS 


A  fan  suppliea  air  for  the  motor  jet,  which  creates  a  greater 
the  chimney  base  than  the  vacuum  due  to  the  natural  draft  of  the  chimney. 
Roughly  speaking,  the  ratio  between  the  vacuum  at  the  chimney  base  and 
the  air  pressure  at  the  motor  jet  equals  the  ratio  between  the  area  of  the 
air  nozzle  and  the  area  of  the  throat  of  the  chimney.  This  ratio  may  be 
conveniently  made  from  1    :  6  to  1   :  10. 

Usually  each  stack  is  connected  to  one  or  two  boilers.  Therefore,  since 
the  throat  diameter  is  kept  small,  such  stacks  may  be  made  only  50  to  75 
feet  high  without  disturbing  the  proper  proportions. 

With  the  low  stack  height  and  small  throat  diameter,  only  light  loads 
are  carried  on  natural  draft,  and  the  motor  jet  is  used  for  the  higher  ratings. 
The  ■draft  may  be  controlled  either  by  varying  the  area  of  the  motor  nozzle, 
or  by  varying  the  air  pressure  with  a  damper  in  the  air  pipe,  or  by  using  a 
variable  ipeed  motor  to  drive  the  fan. 

Chimneys  at  Altitudes 

AT  high  altitudes  the  specific  gravity  of  the  gases  is  B/30  of  the  specific 
gravity  at  sea  level,  where  B  is  height  of  barometer  in  inches  due  to 
altitude,  which  may  be  read  from  Fig.  100;  therefore  their  velocity  through 
the  fuet-bed,  bailer  setting  and  economizer  must  be  increased  by  30/S  in 
order  to  deal  with  the  same  weight  of  gases.  Since  the  draft  loss  varies  as  the 
square  of  the  velocity  and  as  the  specific  gravity  of  the  gases,  it  will  be  30/6 
or  R  times  the  draft  loss  at  sea-level.  This  ratio  is  given  in  one  of  the 
curves  of  Fig.   100  or  can  be  calculated. 


^ 

p; 

i 

~ 

r 

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--i" 

■' 

\ 

pa 

h* 

/ 

^ 

*., 

' 

~~- 

^ 

/ 

f^ 

r~ 

^-^ 

y 

" 

~-J 

Lf^ 

/ 

'1 

"^ 

■^ 

-r  ? 

y 

^ 

- 

,.n 

•*i 

^ 

■ 

i"- 

^ 

T 

."i 

f 

f] 

a- 

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et^ 

^ 

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u 

g. 

^ 

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A 

^ 

e 

J 

U 

J 

L 

V 

^ 

fii 

y 

7f 

w 

4 

=fH 

^ 

in 

-in? 

a 

The  draft  lost  in  giving  velocity  to  the  gases  and  at  sudden  enlarge- 
;nts  is  5/30  of  that  lost  in  giving  the  same  velocity  at  sea-level. 

For  the  same  draft  loss  with  the  same  length  of  flues,  their  diameter 
r  equivalent  diameter)  must  be  increased  if*.    But  it  will  simplify  mat* 


ib.  Google 


CHIMNEYS  193 

ters  to  make  this  increase  the  same  as  the  increase  of  chininey  diameter, 
the  flue  area  continuing  to  be  20  per  cent  greater  than  that  of  the  diimney. 
The  draft  loss  through  the  flues  will  then  be  a  little  less  than  at  sea-level. 

The  draft  power  of  the  chimney  is  primarily  S/30  of  that  at  sea-level. 
But  the  normal  temperature,  being  less  than  at  sea-level,  reduces  this  ratio. 
The  height  necessary  to  give  the  same  draft  at  the  base  would  have  to  be 
increased  as  30/S,  nearly.  But  the  increased  height  is  accompanied  by  a 
lower  average  temperature  within  the  chimney  and  by  an  increased  friction 
loss  due  to  the  increased  height.  Also,  the  draft  required  at  the  chimney  base 
is  increased  as  30/fl  less  the  advantage  derived  from  the  larger  flues  men- 
tioned above.  If  the  diameter  of  the  chimney  is  not  changed,  the  velocity  is 
greater   with   still   more   friction  loss. 

From  a  careful  analysis  of  these  changes,  compared  with  results  in  actual 
practice,  it  is  recommended  that  the  height  be  increased  as  (R'-i),  and  the 
diameter  as  iff  ').    Curves  are  drawn  in  Fig.  100,  giving  both  of  these  ratios. 

Take  the  example  set  forth  in  tabular  form  on  page  187,  resulting  in  a 
chimney  say  150  ft.  by  66  in.  diameter  at  sea-level,  and  assume  that  the  plant 
is  to  be  at  an  altitude  of  SOOO  feet  From  Fig.  100,  read  R'-'  as  128  and 
ISO  X  128  equals  192  feet.  Read  «»-6  as  1.12  and  66  X  1 12  =  74  in. 
diameter. 

The  figures  for  any  given  design  should  be  checked  as  follows :  A  table 
like  that  on  page  187  should  be  prepared,  showing  the  draft  necessary  at  the 
stack  base,  the  barometer  ratio  R  being  considered.  The  static  draft  of  the 
stack  of  the  sizes  derived  as  in  the  last  paragraph  should  be  calculated, 
taking  the  gas  temperature  average  from  Fig.  92,  The  weight  of  air  and  gas 
taken  from  Figs.  93  and  94  are  divided  by  R  from  Fig.  100  and  their  differ- 
ence, multiplied  by  the  height  of  the  stack  and  by  0.192,  is  the  static  draft  in 
inches  of  water.  The  friction  loss  is  row  read  from  Fig.  95  or  calculated 
from  the  formula  (10)  and  corrected  by  dividing  by  R.  It  is  then  deducted 
from  the  static  draft,  giving  the  available  draft  at  the  base  of  the  stack, 
which  can  be  compared  with  that  required. 

As  the  altitude  is  increased,  the  height  of  the  chimney  increases  fast«r 
than  its  diameter ;  consequently  the  proportion  of  diameter  lo  height  will 
sometimes  become  unmanageable.  This  can  be  overcome  by  increasing  the 
grate  area  or  by  the  use  of  induced  or  forced  draft. 


Chimney  Construction 

CHIMNEYS  for  modern  power  houses  and  industrial  plants  are  made  of 
steel  plate,  radial  brick  or  reinforced  concrete,  either  lined  or  unlined. 

and  are  usually  of  circular  cross  section.  For  the  same  area  a  round  chimney 
has  a  greater  capacity ;  its  shape  requires  the  least  weight  for  stability,  and 
presents  the  least  resistance  to  the  wind.  A  maximum  wind  velocity  of  100 
m.  p.  h.  is  used  in  the  design  of  such  stacks,  the  equivalent  pressure  being 
taken  at  50  lb.  per  sq.  ft.  for  flat  surfaces,  and  30  lb.  per  sq.  ft.  of  projected 
area  of  circular  stacks, 

The  following  notes  deal  only  with  the  practical  features  that  must  be 
considered  in  selecting  the  type  of  stacks.  The  structural  design  of  a  chim- 
ney, including  calculations  for  foundation,  stability  and  strength,  is  an  intri- 
cate subject,  which  is  a  study  for  the  chimney  specialist. 

Chimney  foundations  are  usually  made  of  concrete  in  a  mixture  of  1  part 
cement,  2^  parts  sand,  and  S  parts  broken  stone  or  gravel,  and  poured  in  a 
'"wet"  condition  in  layers  6  to  8  in.  thick,  which  are  thoroughly  rammed  into 
place.  The  safe  bearing  load  for  ordinary  soil  is  2  tons  per  square  foot, 
because  the  chimney  represents  a  concentrated  weight  on  a  small  area.  This 
is  considerably  lower  Uian  the  loads  permissible  in  building  construction. 


ib.  Google 


CH IMNEYS 


Foundations  for  brick  chimneys  are  not  as  massive  as  the  foundations 
used  for  steel  and  reinforced  concrete  stacks,  because  they  function  only  as 
supports  of  the  chimney  column.  In  sleel  and  concrete  construction  the 
foundation  acts  both  as  a  support  and  anchor  for  the  stack,  the  two  forming 
practically  one  mass,  giving  the  desired  stabili^.  Reinforcing  bars  are 
frequently  used. 

Table  12  indicates  the  proportions  of  foundations  necessary  for  self-sup- 
porting sleet  and  ra.dial  block  stacks.  The  least  depth  and  width  of  square 
or  block  foundations  are  considered.  In  steet  stacks  with  a  foundation  hav- 
ing tapering  sides,  the  widths  at  the  top  should  not  be  reduced  more  than  3 
or  4  ft.  over  those  given  in  the  table.  For  normal  soil,  the  foundations  sup- 
porting brick  stacks  can  be  battered  or  stepped  off,  using  the  widths  given 
as  the  size  of  the  bottom  slab.  The  top  slab  should  be  at  least  a  foot  wider 
than  the  stack,  all  around,  and  the  offsets  made  so  that  a  line  drawn  along 
the  edge  of-  foundation  will  make  an  angle  of  60  deg.  with  its  base. 

Table  12.     Dimenaion*  of  Concrete  Foundatiana  For  Brick  and  Steel  Stacki 


** 

Rrital  Brick 

8«lf.8>I|>p<>rtli«SC»t 

DIUMtar.Fnt 

-— 

WWth,F.i« 

DiVttwFM 

Width,  rw( 

D.pth.F«. 

4 

100 

12 

4H 

16 

6 

5 

125 

18"^ 

20 

7 

ft 

ISO 

20 

6 

23 

8 

175 

24>4 

7 

26 

SH 

8 

200 

8 

29 

9 

200 

30 

8 

31 

10 

200 

31 

9 

32 

lOM 

2  to  iiTTt 
bed  of 


il,  it  may  be  necessary  to  sink  piles.    These  are  usually  spaced 
renters,  and  the  tops  cut  off  below  the  surface  water  line.  A 
r  3  f t.  thick,  into  which  the  piles  extend,  is  dien  formed 
the  regular  chimney  foundation. 


Self-Supporting  Steel  Stacks 

SELF-SUSTAINING  stacks  as  a  rule  are  practically  straight;  that  is,  the 
walls  above  the  flue  openings  are  parallel.  The  base  section  can  also  be  cyl- 
indrical. However,  it  is  usually  flared  and  includes  the  flue  connection.  The 
height  of  the  bell-mouth  base  depends,  therefore,  upon  the  run  of  breeching 
and  the  location  of  the  flue  opening.  When  the  flared  part  is  one-quarter  of 
the  stack  height,  the  sides  take  the  slope  of  a  cone  having  its  apex  on  the 
center  line  along  the  top  of  the  stack.  This  flared  base  has  a  diameter  about 
one-third  greater  than  the  stack  proper,  permitting  the  connection  of  a  larger 
flue,  and  the  entry  of  the  flue  gases  with  the  least  interference. 

The  flue  opening  in  the  plate  of  the  chimney  base  weakens  the  structure, 
and  requires  reinforcing.  Stiffening  members  across  the  top  and  bottom  of 
tiie  opening  are  sometimes  used.  More  often  the  cut-away  section  is  strength- 
ened by  angle  or  T-shapes  riveted  to  the  sides  and  extended  beyond  the  top 
and  bottom  of  the  opening,  or  a  combination  of  these  methods  can  be  used 
to  reinforce  the  flue  opening  all  around. 

The  flanged  base  plate  riveted  to  the  bottom  of  the  liase  section  is  gen- 
erally made  of  two  or  more  cast  iron  segments.  More  modern  practice  calls 
for  a  built-up  steel  base  ring.  Equally  spaced  around  this  are  lugs  drilled  for 
the  anchoi*  bolts  that  hold  the  stack  down  to  its  foundation. 


ib.  Google 


CHIMNEYS  195 

Above  the  base  the  stack  is  divided  into  several  sections,  each  consist- 
ing of  front  five  to  twelve  courses.  4  to  7  ft.  high.  Each  course  is  made  up 
of  one  or  more  sheets,  depending  upon  the  stack  diameter.  Lap  joints  are 
invariably  used  for  vertical  seams  and  often  for  girth  seams ;  the  latter  are 
also  made  with  butt  joints  either  inside  or  outside  of  the  shell.  Fre- 
quently intermediate  courses  have  lap  joints,  but  the  sections  are  assembled 
with  butt  joints  that  reinforce  the  stack.  In  unlined  stacks,  an  outside  butt 
joint  is  preferred  as  it  leaves  the  stack  smooth  on  the  inside.  In  lined  stacks. 
the  inside  connections  can  be  utilized  to  support  the  brickwork.  Butt  joints 
can  be  made  either  with  the  ordinary  straps,  or  else  flanged  with  angles 
riveted  to  the  shell  and  bolted  ti^ether.  The  riveting  is  generally  figured  on 
a  factor  of  safety  of  four  as  a  minimum. 

It  is  a  moot  question  whether  self -supporting  steel  stacks  should  be 
lined.  The  brick  linmg  does  not  add  to  the  sirenKth  of  the  chimney,  although 
often  the  stack  must  carry  it.  Sometimes  the  lining  is  isolated  and  made 
self-supporting,  acting  as  an  inner  core.  Moisture  may  collect  in  the  air 
space  formed  between  the  lining  and  the  shell,  thus  promoting  corrosion. 
The  lining  reduces  radiation  and  protects  the  steel  from  the  corrosive  action 
of  the  chimney  gases. 

When  a  lining  is  used  in  a  sleel  stack  it  should  be  carried  up  the  full 
height.  Radial  firebrick,  common  brick,  concrete  and  sometimes  a  filler  of 
sand  for  the  air  space  provided  by  independent  linings  are  used  for  lining 
construction.  Generally  a  4-in.  wall  supported  by  an  angle  iron  ring  fastened 
to  the  stack  every  15  to  20  ft.  will  serve.  The  lower  section  of  slack  can  be 
lined  with  firebrick,  and  the  upper  section  with  common  brick,  using  fire  clay 
and  cement  mortar  joints  respectively.  For  an  independent  lining  6-tn.  brick 
will  be  required  for  the  lower  half  of  the  stack  and  4-in.  brick  for  the  upper 
half.  The  brick  can  be  set  close  to  the  shell,  or  an  air  space  of  1  to  2  in.  left 
between  the  steel  and  the  brickwork. 

To  preserve  the  stack,  the  steel  is  usually  given  one  coat  of  paint  on 
bath  surfaces  before  erection.  After  the  stack  is  in  place,  it  is  usually  treated 
with  two  or  three  coats  of  hea ('resisting  paint.  This  is  intended  to  protect 
the  stack  from  the  corrosive  action  of  the  atmosphere  as  well  as  to  prevent 
air  inleakagc. 

To  maintain  the  stack  a  painter's  ring  should  be  fitted  near  the  top.  This 
consists  of  a  circular  metal  track  with  trolley  and  block  to  facilitate  painting, 
in  the  base  of  the  stack  a  cleanout  door  should  be  provided  for  access  to 
the  interior  and  for  the  removal  of  soot  and  cinder  accumulation.  Standard 
size  cleanouts  measure  24  by  36  in.  and  are  made  of  cither  heavy  cast  iron 
or  steel  plate  fitted  with  frames,  hinges  and  clamps.  The  contact  surfaces 
should  be  planed  so  that  the  door  will  .be  air-tight  when  closed.  It  is  also 
advisable  to  install  a  steel  ladder  extending  from  the  base  to  the  top  of 
the  stack.  This  can  be  on  the  inside,  although  it  is  generally  placed  on  the 
outside  about  8  in,  from  the  stack  and  fastened  to  the  shell  through  riveted 
bracket  connections.  Ladders  are  frequently  built  with  3-in.  side  bars,  )ii  in. 
thick,  with  rungs  or  steps  of  >i-in.  round  iron,  IS  to  18  in.  long,  and  spaced 
12  to  15  in.  on  centers.  In  fastening  the  ladder  to  the  stack,  care  must  be 
taken  to  prevent  strains  due  to  the  unequal  expansion  and  contraction  of  the 
Steel  shell  and  the  ladder. 

Table  13  illustrates  the  size  and  sections  and  thickness  of  plate  used  in 
the  construction  of  self-supporting  stacks.  Other  instances  of  good  practice 
are  afforded  by  the  stacks  serving  some  of  the  large  central  stations. 

Four  steel  stacks  in  an  electric  light  plant,  each  297  fl.  above  the  boiler 
grates  and  21  fL  in  diameter,  are  made  of  W-in.  and  J^-in.  steel  plate  in 
courses  7  ft.  high.  Ten  vertical  stiffening  posts  of  6  by  4  in.  angle  iron  arc 
riveted  to  thwinside  of  each  shell.  At  each  20  ft.  of  height  two  angle  irons 
support  a  stack  lining,  which  consists  of  1-in.  concrete  and  4-iD.  red  brick 
for  the  entire  height.    An  18-in.  sleel  ladder  on  the  outside  gives  access  to 


ib.  Google 


if 

8? 


ii 


If 
if 

si 

«.s 
II 


ib.Google 


CHIMN  EYS 
Table  13.    Plate  Dimenuona  For  Self-SupportluB  Steel  Stack* 


■Sir- 

«a'- 

End 

Seetkrn 

3rd 

sTk. 

Sth 

SKtlon 

w 

iDdM 

■KS' 

PUta 
Inehn 

^ 

PUU 

■SS' 

PlaU 

W 

FiBte 

100 

166 
185 

40 
30 
65 

i 

JO 

50 
60 

t 

30 
45 
60 

t 

40 

A 

200 
225 
250 

50 
85 
80 

t 

ao 

20 
30 

i 

»0 
25 
30 

1 

95 
30 

S^ 

144 

80 

H 

each  stack,  and  a  gallery  or  grated  walkway  with  hand  railing  is  placed 
around  the  top.  The  stacks  rest  on  plate  girders  that  are  part  of  the  build- 
ing construction,  and  are  also  braced  against  swaying  and  wind  action. 

In  a  street  railway  plant  the  two  steel  stacks,  each  serving  16  boilers, 
are  supported  and  braced  by  the  framing  of  the  building.  The  stacks  are  132 
ft.  in  height  above  the  foundation  and  are  made  in  three  sections  of  ^-in., 
Vi-in.  and  ^-in,  steel  plate,  each  44  ft.  high.  An  8-in.  red  brick  lining,  backed 
by  1-in.  cement,  is  supported  every  2S  ft.  on  rings  that  stiffen  the  stacks. 

Another  central  station  has  three  stacks,  each  260  ft.  high  and  22  ft. 
diameter.  The  support  and  wind  bracing  is  furnished  by  the  building  con- 
struction. Five  sections  varying  in  thickness  from  '/n  to  ^-in:  plate  make 
up  the  height.  At  each  section  an  angle  iron  stitTener  and  Z~bar  ring  support 
the  lining,  which  is  of  4-in.  red  brick  backed  with  1  in.  of  concrete. 

The  details  of  a  self- supporting  steel  stack  for  moderate  size  plants  are 
shown  in  Fig.  101.  This  stack,  which  was  designed  and  fabricated  by  the 
Chicago  Bridge  &  Iron  IVorks,  is  13  ft.  diameter  and  185  ft.  high.  It  is  made 
up  0(32  courses  in  iive  sections,  including  the  base  with  the  flue  opening. 
Bach  course  consists  of  three  sheets  and  is  about  5  ft.  9  in.  high.  The  thick- 
ness of  plate  varies  from  !4-in.  at  the  top  to  W-in.  at  the  bottom.  The  stack 
is  anchored  to  a  concrete  foundation  on  top  of  which  is  a  sectional  cast  iron 
base  2  in.  thick,  in  12  segments.  Immediately  above  the  base  ring  and 
riveted  to  the  base  of  the  stack  are  24  built-up  steel  plate  lugs  that  hold 
the  anchor  bolts. 

The  base  section  is  conical  or  tapered,  18  ft.  high  and  19  ft.  diameter. 
The  first  parallel  or  cylindrical  plate  course  above  this  is  13  ft.  I'/i  in.  while 
the  last  course  at  the  top  is  only  1  in.  less  inside  diameter.  The  individual 
courses  7  ft.  high.  Ten  vertical  stiffening  posts  of  6  by  4  in.  angle  iron  are 
the  different  girth  seams.  In  the  base  section  a  flue  opening  7  by  20  ft  is  rein- 
forced by  plates  and  angles  to  strengthen  the  cut-away  part  of  the  stack.  A 
steel  ladder  on  the  outside  extends  the  full  height.  It  is  14  in.  wide  with  side 
bars  2  by  fi  in.,  and  rungs  of  H  in.  square  iron.  The  ladder  is  strapped 
to  the  shell  at  the  top  of  every  second  course,  8  in.  from  the  stack. 

Guyed  Steel  Stacks 
'X'HE  guyed  or  supported  steel  stack  is  designed  to  simply  carry  its  own 
-^  weight.  Stability  or  resistance  against  wind  pressure  is  cared  for  by  fas- 
tenings to  adjoining  walls  or  by  guy  wires.  Guyed  or  supported  stacks  do  not 
require  heavy  foundations,  because  they  are  much  lighter  than  self-supporting 
stacks.  Usually  they  are  riveted  to  the  smoke  breeching  or  else  are  con- 
nected with  the  smoke  up-take  and  with  the  boiler  setting. 


ly  Google 


CHIMNEYS 


I 
-f 

i 

-* 


PART  OF  TOP  SECTOH 


WRT  or  tUE  SECTHM 


™»fcw«i™' 


-&:" 


«-af«- 

h 

1 

1     i 

, 

^ 

I 

f 

, 

, 

1 

1          ^ 

1 

f  i 

, 

: 

h 

^ 

■ 

. 

- 

ir>w- 

d 

X?V4*'- 

'■■     L 

J, 

i 

1 

W 

Pig.  101.     Conatniction  Detail*  of  a  Setf-SupportinE  Ste«l  SUck. 


ib.  Google 


CHIMNEYS 


The  thickness  of  plate  used  varies  considerably  and  is  largely  governed 
by  the  degree  of  permanence  required.  Corrosive  action  by  the  elements  and 
stack  gases  gradually  reduce  the  thickness  of  the  sheets  until  the  stack  is  no 
longer  safe. 

The  thickness  of  plate  is  ordinarily  kept  within  the  limits  given  in 
Table  14. 


Table  14. 

Dinien*ion«  of  Guyed  Steel  Stacks. 

TbieVtu 

M  of    Plate 

Inch™ 

Maximum 

30 
36 
42 

No.  8  gage 
14  in.' 

No.  10  gage 
No.  10  gage 
No.  10  gage 

48 
54 
60 

■tt. 

V»  in. 

No.    8  gage 
V*  in! 

The  size  of  rivets  used  should  be : 

^  in,  diameter   for   No.   10  and   No.  8  gage  plate. 
V»  in.  diameter  for  '/m  in.  plate, 
V"  or  J4  in.  diameter  for  yi  in.  plate. 
Yi  or  s|  in.  diameter  for  '/■•  ■"■  plate- 
The  circumferential  pitch  is  generally  niade  equivalent  to  one  rivet  for 
each   inch   of   diameter  of   the   stack   or  3Vt   in.   pitch,  and   the   longitudinal 
pitch  is  made  3  to  4  inches. 


"-S 


Fig.  101.     Styles  of  Jcnnt*  for  Ouyed  or  Supported  Steel  Stack*. 


ib.  Google 


CHIMNEYS 


1  to  make  the  plates  thinner  in  the  upper  portion  of  the 
stack.  As  the  corrosive  action  is  more  energetic  at  the  top,  many  prefer 
to  make  the  upper  part  thicker  than  the  lower,  or  at  least  to  keep  the 
thickness  the  same  for  the  full  height. 

The  plate  courses  may  be  assembled  as  shown  in  Fig.  102,  in  which 
the  "shingle"  lap  (a)  is  composed  of  tapered  sections  and  is  designed 
to  shed  water.  In  joints  like  (b)  the  larger  sections  slip  over  the  ends  of  the 
smaller  sections  and  all  the  sections  are  parallel  or  cylindrical..  With  another 
method  (c)  the  lower  end  of  the  upper  course  slips  into  the  lower  course. 
Sometimes  a  strap-joint  (d)  is  used,  in  which  the  ends  of  sections  are  butted 
logelher  and  a  steel  band  placed  around  the  joint  and  riveted  to  each  plate, 
making  a  very  strong  but  much  more  expensive  chimney. 


^A"<iyP9an^.  itipatt^ot/n/ifg 


Fig.  103.     Construction  of  a  Ouycd  Steel  Stack. 


ib.  Google 


CHIMNEYS  201 

White  each  of  these  methods  have  their  advocates,  the  best  practice  ap- 
pears to  be  indicated  by  (c).  With  (a)  the  seams  cannot  be  made  tight,  and 
water  from  the  inside  of  the  stack  leaks  through,  and  corrodes  and  discolors 
(he  outside.  With  (c)  the  joints  are  easily  filled  with  paint  and  made 
perfectly  tight,  so  that  corrosion  is  reduced  to  a  minimum. 

Guys  should  be  of  not  less  than  'A  in.  wire  rope.  Each  guy  .ihould  have 
a  tuTubuckle  to  take  up  slack  and  equali/e  tautness.  The  anchorage,  whether 
'dead  men"  or  buildings,  must  be  ^uch  that  there  is  no  possibility  of  failure 
in  the  highest  wind.  The  guys  are  attached  to  the  stack  either  by  eyebolts, 
with  reinforcing  plates  inside,  or  by  a  guy-ring,  carried  around  the  stack  in 
sections  whose  ends  are  bent  out  to  form  lugs.  While  the  guy  ring  is  the 
strongest  construction  when  new,  corrosion  appears  to  concentrate  about  it, 
and  so  weakens  the  stack  that  the  eyebolt  method  is  perhaps  the  strongest 
permanently. 

The  number  of  guys  and  their  arrangement  depends  upon  the  height  of 
the  stack.  Low  stacks  up  to  50  or  60  feet  may  have  one  set  of  three  or  four 
guys.  Over  60  feet,  there  should  be  two  sets  of  four  guys  each,  and  stacks 
over  125  feet  usually  have  three  sets  of  four  guys  each.  The  upper  or  single 
set  is  generally  attached  to  the  stack  about  12  feet  below  the  top.  When 
there  are  two  sets  of  guys,  the  lower  set  is  attached  about  2/3  of  the  height 
from  the  ground  to  the  upper  set.  When  there  are  three  sets  of  guys,  the 
upper  set  is  attached  about  12  feet  from  the  top,  the  lower  set  at  about  half 
the  height  of  the  upper  set,  and  the  middle  set  a"bout  half  way  between  the 
upper  and  lower  sets, 

Guys  arc  commonly  anchored  at  a  distance  from  the  base  equal  to  the 
height  of  the  guy  band,  so  that  they  are  stretched  at  an  angle  of  45°.  When 
two  or  three  sets  of  guys  are  used,  the  upper  set  may  be  arranged  to  form 
an  angle  of  only  60°  with  the  vertical. 

In  congested  city  sections,  stacks  are  often  fastened  to  building  walls  by 
brackets  or  strap-iron  anchors.  StilT  guys  may  be  made  of  2  in.  pipe  (or 
stacks  up  to  75  feet  high,  and  of  3  in.  pipe  for  higher  stacks.  Ail  stiff  guys 
should  be  well  braced  against  bending  unless  they  are  very  short. 

A  guyed  stack  of  Yi-in,  steel  plate,  built  by  the  New  York  Central  Iron 
IVorki.  is  shown  in  Fig.  103.  It  is  intended  for  direct  connection  to  the  smoke 
flue.  This  stack  has  an  inside  diameter  of  72  in.  and  is  104  ft.  high  overall. 
Each  course  is  5  ft.  high  and  is  made  with  lap-joints  single  riveted.  At  about 
40  ft.  from  the  top  a  heavy  ring  is  fastened  to  the  stack,  reinforcing  it  to 
receive  the  lugs  for  the  guy  wires.  The  top  is  finished  with  a  steel  band 
on  the  outside  and  reinforced  with  another  band  on  the  inside. 

Radial  Brick  Chimneys 

COMMON  brick  is  seldom  used  for  chimney  walls  except  for  small  house- 
heating  plants.  Larger  stacks  have  walls  of  vitrified  hollow  or  perforated 
brick  formed  to  occupy  a  certain  position  in  the  circular  and  radial  lines  of 
Ihe  chimney.  It  is  said  that  the  perforations  in  the  brick  form,  a  dead  air 
space,  which  reduces  the  loss  from  radiation  and  prevents  sudden  temperature 
changes  within  the  stack.  These  radial  blocks  are  larger  than  common  brick 
and  are  made  in  sizes  and  shapes  for  all  diameters.  The  method  of  laying 
and  bonding  as  used  in  Heinicke  chimneys,  and  some  of  the  shapes  used  in 
Custodis  construction,  are  illustrated  in  Fig.  104. 

The  brick  are  laid  in  cement  lime  mortar,  with  V^  in.  joints,  to  give 
a  straight  batter  or  taper  from  top  to  bottom.  The  outside  surface  is 
invariably  smooth  while  the  inside  surface  sometimes  has  a  series  of  steps, 
owing  to  the  change  in  wall  thickness  of  the  different  sections"  of  the 
chimney  wall.  Starting  with  a  thickness  of  one  brick,  or  about  7  in.,  at 
the  toji,  the  wall  thickness  is  increased  about  2  in.  for  each  section, 
which  is  generally  20  ft.  high.  A  circular  chimney  200  ft.  high  would 
have  an  actual  thickness  of  24  in.  at  the  base.    The  wall  thicknesses,  in 


ib.  Google 


CHIMNEYS 


Table  15.     Outiide  Diameter  (Feet)  of  Base  of  Brick  Chimneys 


ib.  Google 


CHIMNEYS 


IBnrm 

Opining. 
merry 


'xSVJ.fir, 
tofco/un 
iveemtit 


Qiimn^  on  Octagonal  Bos*  Chimn^  Round  fer  Full  HeiflM 

Fig.  105.     Example  of  KeU<^s  Radial  Brick  Chimneys. 


ib.  Google 


,  Google 


CH IMNEYS 


two  styles  of  Kellogg  radial  block  chimneys,  are  shown  in  Fig.  lOS.  The 
batter  indicated  is  based  upon  the  figures  in  Table  15,  from  which  layouts 
can  be  made  tor  stacks  3  to  10  ft.  diameter  and  75  to  225  ft.  high.  The 
design  should  be  checked  to  see  that  tension  does  not  occjr  on  the  windward 
side,  with  the  maximum  wind  pressure  allowed,  as  the  chimney  would  then 
be  unsafe. 

It  is  common  practice  to  use  regular  hard  building  brick  for  the  base 
of  the  chimney,  when  it  is  of  a  square  or  octagonal  form.  If  the  base  forms 
part  of  the  building  wall,  the  two  sliould  be  bonded  by  a  slip  joint,  shown 
ill  the  lower  left-hand  view  of  Fig.  IU6.    The  radial  brick  above  the  breeching 


I'U/ut  ofiinij.  ftafkmfS' 
fieM  flm  xtnkvFsr  fin  *- 


Fig.  106.     Typical  Details  of  Radial  Brick  Chimney  Construction. 

entrance,  shown  in  the  upper  right-hand  view  of  Fig.  106.  is  supported  by 
heavy  beams  on  bearing  plates  with  air  spaces  at  each  end  to  permit  ex- 
pansion. The  steel  is  protected  against  the  effects  of  the  gases  of  combustion 
by  a  flat  arch. 

To  prevent  cracking,  radial  brick  chimneys  arc  provided  with  rein- 
forcing bauds  that  take  up  the  stresses  due  to  expansion.  One  company 
conceals  three  or  four  3  by  S/16  in.  bar  steel  bands  in  the  brick  work.  These 
rings  are  placed  below  and  above  the  flue  opening,  at  or  near  the  top  of  the 
lining  and  in  the  chimney  cap  or  cornice.  Another  method  is  to  place  these 
bands  at  every  change  in  wall  thickness,  omitting  some  of  them  when  the 
bricks  have  corrugated  sides.  When  gas  temperatures  are  high,  additional 
expansion  rings  are  placed  on  the  outside,  spaced  about  6  ft.  on  centers. 

A  lining  inside  the  chimney  is  also  necessary  as  a  further  safeguard 
against  expansion  strains.  This  lining  is  independent  of  the  stack  and 
is  separated  from  it  by  an  air  space  of  at  least  2  in.,  which  prevents  the 
gases   from   coming  in   contact   with    ihe   chimney  brickwork.     For  steam 


ib.  Google 


CHIMNEYS 


boiler  plants  the  lining  is  made  30  to  50  ft.  high,  or  about  one-fifth  the 
stack  height  For  very  high  gas  temperatures  the  lining  should  be  carried 
up  at  least  half  way,  preferably  to  the  full  height. 

Expansion  linings  are  made  of  ordinary  lire  brick  or  of  perforated 
blocks  about  4  in.  thick.  They  are  started  2  ft.  below  the  flue  opening  in 
the  stack.  Sometimes  the  space  between  the  lining  and  stack  is  covered 
at  the  top.  One  method  is  to  corbel  or  rack  out  the  shell  of  the  chimney. 
This  protecting  ledge  prevents  soot  or  dirt  from  filling  the  air  space. 

Ladders  are  also  a  necessary  adjunct  to  chimneys.  These  are  located 
either  inside  or  outside  for  the  full  height  of  the  stack.  The  rungs  should 
be  of  ^  in.  round  iron,  preferably  galvanized,  of  "U"  shape,  spaced  on  15-in. 
centers  and  securely  anchored  to  the  masonry. 

Lightning  rods  should  be  provided  to  protect  brick  chimneys.  A  number 
of  pointed  rods,  above  the  top  of  the  stack,  are  connected  to  one  or  more  con- 
ductors extending  down  to  a  ground  connection  beneath  the  grade  tine.  Points 
extending  6  to  8  ft.  above  the  top  are  subject  to  rapid  deterioration  owing  to 
the  action  of  the  outflowing  gases.  It  is  advisable,  therefore,  to  locate  a 
greater  number  of  points  around  the  stack  so  they  will  not  project  more 
than  6  ft.  above  the  top.  Less  than  two  points  should  not  be  used  on  any 
stack.  On  large  chimneys  the  lightning  rods  can  be  spaced  from  6  ft.  to  3  ft. 
1  the  outside  circumference  of  the  stack. 


ZS^Hf- 

CruM  Sactton 

PlC.  107.     Soot  C<rilector  Syatem  In  a  Large  Chimnejr. 


ib.  Google 


CHIMNEYS  20? 

The  lightning  rods  are  usually  made  of  J^-in.  copper,  tipped  with  yi-in. 
platinum  thimble  points.  They  are  fastened  to  the  masonry  and  are  inter- 
connected by  a  copper  cable  placed  completely  around  the  top  of  the  stack. 
To  complete  the  circuit  one  or  two  bare  copper  cables,  of  Vi  or  7/16-in. 
diameter,  are  connected  to  this  ring.  These  conductors  extend  down  the 
side  of  the  chimney,  where  they  are  fastened  at  intervals,  and  terminate 
in  a  copper  ground  plate  located  in  permanently  moistened  earth,  in  a 
charcoal  bed,  or  in  a  pocket  filled  with  crushed  coke,  and  placed  away  from 
the  chimney  foundation.  The  grounding  terminal  can  be  of  the  coil,  plate 
or  cylinder   type. 

For  access  to  the  interior  of  the  stack  and  to  facilitate  cleaning,  a 
cleanout  door  should  be  located  in  the  base.  Standard  cast  iron  cleanouts 
measure  24  by  36  in.  and  are  fitted  with  frames,  hinges  and  latches,  A 
tight  tit  is  essential,  so  the  contact  surfaces  should  be  planed. 

An  effective  method  for  the  removal  of  soot  and  cinders  from  large 
chimneys  is  represented,  according  to  Tkos.  S.  Clark,  by  a  collector  system 
installed  in  a  radial  brick  chimney  300  ft.  high,  19  ft.  diameter  at  the  top, 
and  about  23'/i  ft.  at  the  base.  Super-imposed  hoppers,  Fig.  107,  are  lo- 
cated below  the  flue  opening  in  the  base  of  the  stack.  These  hoppers  are  de- 
signed to  collect  the  soot  and  cinders  dropped  by  the  gases  in  passing  up 
the  chimney. 

The  hopper  floors  are  concrete  lined  with  brick.  Two  are  used  so  that 
the  door  in  one  is  closed  when  the  door  in  the  other  is  open,  to  prevent  the 
possibility  of  an  open  draft  up  the  chimney  through  both  hoppers.  Access 
to  each  hopper  is  provided  through  a  manhole,  which  is  reached  by  a  ladder 
on  the  outside  of  the  chimney.  Each  hopper  can  be  cleaned  from  a  gallery 
built  around  the  rim.  In  the  chimney  base  are  doors  targe  enough  to  allow 
a  cart  to  be  backed  in  under  the  lower  hopper  to  remove  the  soot  and  cinders. 

Reinf<nt»d  Concrete  Stacks 
'  I  "HE  advantages  claimed  for  reinforced  concrete  chimneys  are  light  weight, 
X  minimum  apace,  strength,  and  rapidity  of  construction.  All  joints  are 
eliminated,  the  stack  and  foundation  being  one  monolithic  structure.  Patented 
steel  forms  are  used  rather  than  wood  forms.  The  structural  design  is 
ordinarily  based  upon  a  maximum  compression  in  the  concrete  of  350  lb. 
per  sq.  in.  and  a  maximum  tension  in  the  steel  of  16,000  lb.  per  sq.  in. 

The  details  of  a  reinforced  concrete  stack  180  ft.  high  and  8  ft.  in 
diameter,  are  shown  in  Fig.  109.  The  walls  are  considerably  lighter  than  brick 
construction  and  are  concentric  with  an  even  taper  from  top  to  bottom.  The 
'  ■  ■■     '  The  c '-  -=- 


wall  thickness  is  5  in.  at  the  top  and  11  in.  at  the  base, 
turc  is  1  part  cement.  2  parts  sand  and  3  parts  crushed  stone  or  gravel.  This 
is  poured  "wet"  and  then  tamped  in  the  steel  forms  and  around  the  reinforc- 
ing bars  to  secure  a  thorough  bond,  as  well  as  smooth  inside  and  outside 

Vertical  reinforcing  bars  are  placed  about  3  in.  from  the  outer  surface 
and  are  distributed  proportionately  to  the  load.  Around  the  circumference 
the  stack  is  reinforced  horizontally  by  heavy  wire  mesh,  woven  in  triangular 
form.  This  is  set  close  to  the  outside  surface  of  the  wall,  as  indicated  in 
Fig.  108.  The  flue  opening  in  the  stack  is  also  reinforced  and  the  walls  there 
are  about  50  per  cent  thicker. 

Figs.  110  and  111  show  the  process  of  constructing  a  concrete  stack.  One 
view  shows  the  steel  forms  and  reinforcing  rods  in  place,  ready  to  receive 
the  concrete  mixture  and  the  other  the  completed  base  section  of  the  stack 
with  the  forms  removed.  The  entire  chimney  is  usually  finished  with  a 
cement  wash. 


ib.  Google 


C  H  I  M  N  K  Y  S 


Pic-  108.     Base  and  Foundadon  of  Heine  Reinforced  Concrete  Stack. 

To  protect  the  chimney  column  from  the  stresses  due  to  expansion  an 
isolated  inner  core  or  lining  must  be  installed.  This  is  built  of  firebrick  or 
perforated  blocks  in  the  same  manner  as  described  for  brick  chimneys. 

Instead  of  the  ladder  steps  used  in  brick  construction,  concrete  stacks 
are  equipped  with  tackle,  consisting  of  a  bronie  pulley  anchored  to  the  top 
of  the  stack,  and  a  S/ld-in.  wire  cable. 

A  soot  separator  is  an  integral  part  of  the  reinforced  concrete  stack 
shown  in  Fig.  112.  This  stack  serves  a  plant  in  which  patent-leather  is  manu- 
factured. Soot  and  cinders  issuing  from  the  old  chimney  lodged  upon  and 
damaged  the  leather,  which  is  dried  in  the  open.  The  stack  has  an  outside 
diameter  of  8  ft.  8  in.  at  the  top  and  23  ft.  8  in.  at  the  base.  The  unusual 
taper  is  due  to  the  soot  separator,  which  is  built  in  at  the  base  as  part  of 
the  chimney.  The  soot  separator,  which  consists  of  two  concentric  stacks  29 
ft.  high,  is  made  of  radial  brick.  The  separating  chamber  is  in  the  outside 
circular  passage  while  the  inside  section  is  the  chimney  proper,  the  two  being 
connected  by  three  openings  in  the  wall.  These  openmgs  are  of  sufficient 
area  to  handle  the  volume  of  gases  through  the  8  ft,  area,  which  corresponds 
to  the  inside  diameter  of  the  chimney  at  the  top. 

The  t!ue  gas  entering  the  chimney  through  the  5  by  11  ft.  breeching 
connection  has  its  velocity  reduced  and  owing  to  the  shape  of  the  passage, 
it  flows  spirally.  This  combined  action  separates  the  soot  and  cinders  from 
the  gas,  which  then  passes  up  and  out  of  the  chimney  free  from  ash. 

The  outside  wall  of  the  soot  separator  also  serves  as  the  expansion 
lining  for  the  chimney.  The  top  of  the  separating  chamber  is  closed  with 
a  cast  Iron  cap.  In  the  base  of  the  chimney  proper  are  two  cast  iron 
cleanout  doors  for  removal  of  soot,  A  2~in.  perforated  steam  pipe  has 
been  provided.  Tile  drains,  as  indicated  in  Fig.  112,  have  been  installed,  to 
keep  the  chimney  free  from  water. 


ib.  Google 


CHIMNEYS 


einfor^ing  irt  Smoka  Optning 


Pig.  109.     Heine  Reinforced  Concrete  Chimney. 


ib.  Google 


Pig.   110.      Steel  Forms  and  ReinforcUii  Rods  in  Place  to  Receive  Concrete. 


Fig.  111.     Completed  BaM  Section  of  a  Concrete  Stack. 


ib.  Google 


CHIMNEYS 


Stctianal  Eltvatlan 

Fig,  113.     Soot  Separator  in  a  Rust  Concrete  Chimney. 


Reinforced  concrete  is  sometimes  considered  in  the  experimental  stage, 
but  some  concrete  stacks  have  weathered  the  elements  for  15  and  20  years 
without  appreciable  deterioration.  One  of  the  tallest  chimneys  is  a  reinforced 
concrete  stack  550  ft.  high  with  a  wall  thickness  of  7  in.  at  the  top  and 
29j/i  in.  at  the  hase ;  the  average  diameter  is  32  feet.  This  stack  is  located 
in  an  earthquake  country,  Saganoaeki,  Japan,  at  about  450  ft,  above  sea-level. 

The  Wiederholt  chimney  construction  is  "reinforced  tile  concrete." 
Hollow  tile  blocks  made  of  hard  burned  clay  are  used  as  the  forms  to  receive 
the  concrete  during  construction.  The  tile  remains  permanently  as  the  inner 
and  outer  surfaces  of  the  stack,  surrounding  the  concrete  at  every  point. 

Foundations  for  this  type  of  chimney  are  made  of  concrete  reinforced 
with  horizontal  steel  bars  running  in  two  directions.  Vertical  bars  are  em- 
bedded to  act  as  anchors  for  the  chimney  column.  Around  these  vertical 
reinforcing  bars  the  tile  are  set,  each  course  being  separately  filled  with  con- 
crete. The  horiiontal  rings  arc  set  in  the  concrete  core.  It  is  said  that  these 
chimneys  are  well  adapted  to  chemical  plants  where  acid  gases  occur  and 
for  other  special  service  where  gas  temperatures  are  high. 


ib.  Google 


ib.Google 


CHIMNEYS 


Original  Brick  Stock 


--3   <S'  S6^ 


-i, 


^^■j 


[ 


«'!  «!f5 


.-*^-| 


tsr 


.'I 


U 2SiS' J 

Stack  Af ie  r  Concreting 


Fis.  113.     Reinforcing  an  Old  Brick  Stack. 


ib.  Google 


214  CHIMNEYS 

Remodeling  of  Chimneya 

BRICK  chimneys  are  increased  in  height  by  adding  a  guyed  length  of  steel 
stack.     In  some  instances  the  added  portion  is  built  of  radial  brick. 
Where  the  old  part  is  of  square  cross  section,  an  octagonal  adapting  portion 
is  worked  in.     Sometimes  this  work  is  done  while  the  boilers  are  tmder  fire. 
Bent  brick  chimneys  can  be  straightened  by  sawing  out  mortar  from  the 
convex  side. 

Chimneys  that  are  dangerously  defective  may  be  made  safe  by  applying 
a  casing  of  reinforced  concrete.  Fig.  113  illustrates  an  example.  Steel 
chimneys  that   have  become   badly  corroded  may  be   renovated  with   a   con- 

Breechinga 

THE  breechings  or  fines  should  be  so  arranged  as  to  offer  a  minimum 
of  resistance  to  the  fiow  of  gases.  The  a.rea  should  be  large  enough  so  that 
a  reasonable  accumulation  of  flue  dust  will  not  cause  any  noticeable  choking. 
The  run  should  be  as  short  and  direct  as  possible.  Connecting  flues  should 
be  so  designed  that  the  entering  gases  tend  to  flow  parallel  with  the  gases 
already  in  the  main  flue.  Access  doors  should  be  placed  conveniently  to 
facilitate  cleaning. 

Flues  are  frequently  made  15  to  25  per  cent  larger  in  area  than  the 
slack,  depending  upon  the  amount  of  flue  dust  expected.  Where  fine  fuel 
is  burned  with  forced  draft,  the  deposit  of  flue  dust  is  relatively  large  and 
therefore  liberal  areas  should  be  allowed.  Builders  of  chimneys  prefer  to 
limit  the  area  of  flue  openings  to  7  to  10  per  cent  greater  than  that  of  the 
stack.  For  structural  reasons,  the  width  of  opening  in  the  chimney  should 
not  be  more  than  one-third  the  outside  diameter  of  the  chimney,  the  neces- 
sary area  being  obtained  by  increasing  the  height  of  flue  opening. 

Sometimes  the  breeching  area  is  proportioned  to  the  total  grate  area 
served  by  allowing  22  per  cent  of  the  grate  surface  as  the  minimum  cross- 
sectional  area  of  the  flue.  But  this  is  not  good  practice,  for  the  size  of  flue 
is  entirely  dependent  upon  the  volume  of  gases  to  be  dealt  with,  while  the 
volume  of  gases  due  lo  any  given  grate  surface  varies  with  the  intensity  of 
the  draft  A  breeching  suitable  for  a  given  grate  area  under  natural  draft 
may  be  far  too  small  for  the  same  size  of  grate  under  forced  draft 

The  breeching  area  should  be  determined  by  gas  velocity.  The  draft 
loss  depends  upon  the  gas  velocity  in  relation  to  the  length,  area  and  shape 
of  the  flue.  The  velocity  may  vary  from  15  feet  per  second  for  long 
rectangular  flues  of  small  area,  to  35  or  40  feet  per  second  for  large  short 
circular  flues.  The  draft  loss  may  be  found  by  formula  (10)  on  page  183. 
Whatever  velocity  is  chosen,  the  resulting  area  should  be  increased  sufficiently 
to  allow  for  the  deposit  of  Rue  dust. 

A  breeching  of  circular  cross -sect  ion  causes  less  draft  loss  than  a 
rectangular  or  square  section,  and  the  flatter  the  rectangle,  the  greater  is  the 
draft  loss.  This  is  clearly  shown  by  the  cnefTicienls  of  formula  (10).  Square 
or  rectangular  breechings  with  a   semi-circular  top  are  good  designs. 

In  practice,  sharp  bends  and  right  angle  turns  are  the  most  common 
faults  found  in  breechings  and  smoke  connections.  While  it  is  not  difficult 
to  make  or  connect  long-sweep  turns  and  to  install  necessary  deflectors, 
these  details  may  be  neglected  unless  the  work  is  carefully  supervised. 
Space  conditions  often  make  the  installation  of  some  bends  necessary.  The 
designer  must  then  use  the  least  number  of  bends  and  make  them  as  long 
and  gradual  as  possible.  The  bends  necessary  for  a  change  in  direction 
should  have  an  inside  radius  at  least  equal  to  1>4  times  the  diameter  or 
width  of  the  breeching. 


ib.  Google 


CHIMNEYS 


Fig.  114  will  emphasize  the  bad  effect  of  sharp  gas  turns.  The  entering 
gases  tend  to  strike  the  opposite  wall  and  leave  eddies  as  at  A,  A,  which 
are  the  equivalents  of  reduction  in  flue  area.  Rounded  corners  at  X  and 
near  A  would  reduce  the  draft  loss,  but  the  gases  from  Boiler  No.  1  would 
still  interfere  with  the  flow  from  Boiler  No.  2.  This  figure  also  shows  poor 
design  in  making  the  breeching  parallel.  The  gases  from  Boiler  No.  2  lose 
velocity  in  filling  the  larger  area  of  the  main  flue,  and  as  this  velocity  has 
been  given  to  the  gases  by  the  effect  of  the  chimney,  velocity  so  lost  is  wasted 
chimney  effort.  As  the. gases  from  Boiler  No.  I  crowd  into  the  main  flue, 
the  gases  from  Boiler  No.  2  have  less  space  and  their  velocity  is  again 
increased,  putting  more  work  on  the  chimney. 


-¥ 


Pig.  114.     Effect*  of  Sight-angle  Tuma  in  a  Smoke  Flue. 

Fig.  115  illustrates  excellent  practice  in  designing  a  breeching  to  serve 
several  boilers.  The  bottom  of  the  sides  is  made  horizontal  to  agree  with 
the  boiler  settings,  and  the  increase  in  area  as  each  boiler  is  connected  is 
taken  care  of  by  the  sloping  lop.  The  deflection  plates  forming  the  bottom 
are  made  parallel  with  the  top,  keeping  the  gas  velocity  uniform,  and  the 
steps  between  them  provide  ideal  locations  for  the  dampers. 


Fig.  115.     Breeching  and  Damper  Arrangement  for  a  Battery  of  Boilers. 

A  good  example  of  breeching  design  for  several  boilers  is  shown  on 
page  218. 

The  connection  to  the  stack  should  be  through  an  easy  upward  bend, 
so  as  to  enter  the  chimney  at  about  45  degrees. 

Where  breechings  from  boilers  on  both  sides  of  a  chimney  meet  before 
entering  it,  care  should  be  taken  to  guide  the  two  currents  into  fairly 
parallel  streams  before  they  meet.  Fig.  116  is  given  to  emphasize  the  bad 
effect  of  two  opposing  gas  currents  in  a  hull-headed  or  T-connection.  To- 
gether with  the  area-reducing  eddies  at  A,  A,  as  in  Fig.  116,  this  head-on 
collision  of  the  two  streams  may  cause  sufficient  draft  loss  to  reduce  the 
boiler  capacity  seriously. 


ib.  Google 


BqiutBble  Building,  New  York  City. 

3500  H.  P.  of  Heine  Standu-d  Boilen. 

Tallest  Chimney  in  the  World.  ' 


i,  Google 


CHIMNEYS 


£C*7tV" 


J-^ 


L4J 


Pig.  116.     Bifects  of  Bull-head«d  Connection  o 


Gas  Flow  in  Breechine. 


In  such  instances  curved  defecting  plates  as  at  X,  particularly  when  a 
dividing  plate  is  carried  from  X  to  the  entrance  of  the  flue  leading  to  the 
stack,  have  made  a  notable  improvement.  Rounding  the  comers  as  at  A,  A, 
is  a  still  further  advantage. 

Fig.  117  shows  two  flues  connected  to  a  central  stack.  To  reduce  the 
draft  loss  from  the  head-on  collision  of  the  gases,  a  baffle  is  placed  in  the 
base  of  the  chimney,  so  that  the  gases  are  deflected  into  parallel  directions. 


Pig.     117.     Baffle  WaU  in  Chimney 


■Slack 
Prevent  ColliMon  of  Gaies. 


Examples  of  good  practice  in  breeching  design  where  the  chimney  is 
carried  by  a  symmetrical  hood  are  illustrated  by  Figs.  118  and  119,  which 
show  breeching  hoods  for  one  and  two  boilers  respectively. 

As  most  engineering  problems  are  solved  by  compromise,  so  the  power 
plant  designer  must  frequently  compromise  between  ideal  flue  design  and 
increased  height  of  stack.  Flat  rectangular  breechings  and  sharp  curves  may 
become  necessary  to  meet  space  restrictions,  and  the  increased  chimney 
height  resulting  therefrom  must  be  accepted  as  unavoidable. 

Steel  or  iron  plate  is  used  in  constructing  breechings  and  smoke  connec- 
tions. For  main  breechings  of  square  section,  metal  S/ie  in.  thick  is  required. 
The  sides,  bottom  and  top  are  braced  or  reinforced  on  the  outside  with 
Zyi-'m.  angle  iron.  Individual  smoke  connections  between  boilers  and 
breeching  are  usually  made  of  No.  10  gage  metal,  although  for  longer  runs 
and  large  size  boilers  No.  8  gage  plate  is  sometimes  used.  When  of  square 
section,  these  are  held  at  the  comers  by  1-^-in.  angle  iron,  and  are  also 
reinforced  or  further  stiffened  with  angle  iron  on  the  outside. 

For  the  removal  of  soot  accumulation  and  for  access  to  the  breeching, 
deanout  doors  should  be  provided  at  convenient  points.  It  is  good  practice  to 
install  one  cleanout  at  the  far  end  of  the  breeching  and  at  least  one  other 
deanout  along  the  run  of  flue,  either  in  one  side  or  at  the  bottom.  Clean- 
out  doors  are  made  of  heavy  cast  iron  or  steel  plate,  lilted  u '  ' 


ib.  Google 


ib.Google 


CHIMNEYS 


Fig.  118.    Ideal  BreecbinK  Arrangement  for  Single  Boiler. 


3ail»r  Nt.  S 
Vii.  119.     Ideal  BreechiaK  ArranKement  for  Two  Boiler*. 


ib.  Google 


2»  CHIMNEYS 

hinges  and  one  or  two  cUnip^  to  facilitate  opening  and  closing  of  the  door. 
Door  frames  are  riveted  to  the  breeching;  both  the  frames  and  doors 
should  be  planed  so  as  to  be  air-tight.  Sliding  doors  are  sometimes  used 
for  cleanouls. 

Breechings  and  smoke  Hues  should  be  covered  with  non-conducting 
material,  such  as  asbestos  or  magnesia  heat  insulation,  or  else  be  protected 
with  refractory  brick  or  other  vitrified  material.  The  coverings  or  linings 
are  frequently  placed  inside  the  breeching  to  protect  the  metal  against 
the  possible  corrosive  action  of  the  gases,  although  it  is  advisable  to  have 
the  insulation  or  lining  on  the  outside.  The  breeching,  smooth  on  the 
inside,  will  then  permit  a  straight  uninterrupted  ilow  of  the  gases  into  the 
smoke  stack ;  there  will  be  no  loose  pieces  to  fall  into  the  breeching  and 
obstruct  the  gas  passage,  and  repairs  can  be  made  without  interfering  with 
plant  operation.  The  insulation  on  smoke  flues  is  important  because  it  pre- 
vents lowering  the  gas  temperature,  by  reducing  heat  losses.  If  this  temper- 
ature is  lowered  while  the  gases  are  passing  through  the  flue,  the  effective 
draft  will  be  reduced. 

Overhead  steel  breechings  are  usually  hung  from  the  building  construc- 
tion, although  special   supports  are   frequently   required. 

Underground  flues  involve  a  high  friction  loss  because  of  the  large  num- 
lier  of  turns  in  the  gas  path  from  the  boilers  to  the  stack.  The  brick 
or  concrete  used  for  these  fines  is  porous,  so  that  the  flue  is  subject  to  leak- 
age. Being  located  below  the  boiler  room  floor  the  flues  are  diflicult  to  keep 
clean   and    the   soot   gradually   accumulates   and    obstructs   the   gas   passage. 


Dampers 

DAMPEHS  are  used  both  to  vary  the  gas  flow  in  controlling  the  rate  of 
combustion,  and  to  close  the  flue  entirely  in  isolating  idle  boilers.  Dampers 
should  move  easily  and  when  wide  open  oner  the  least  possible  resistance  to 
gas  flow. 

Dampers  used  for  isolating  idle  boilers  or  flues  should  be  reasonably 
gas-tight.  levers  or  handles  to  operate  dampers  should  be  located  in  par- 
ticularly convenient  and  easily  accessible  positions,  and  be  so  arranged  that 
they  definitely  indicate  how  wide  the  dampers  are  open. 

Dampers  should  be  made  the  full  area  of  the  breeching  or  uptake.  If  a 
rectangular  damper  is  used,  it  will  cause  the  least  disturbance  to  orderly  gas 
flow  if  swung  about  its  longer  axis.  Fig.  120,  for  a  rectangular  damper 
turning  about  its  shorter  axis,  illustrates  faulty  design,  by  showing  the  area 
wasted  in  the  formation  of  eddies.  Fig.  121  illustrates  good  practice  in 
damper  arrangement.  The  dampers  swing  in  unison  about  their  longer  axes; 
and  when  wide  open,  the  gas  flow  is  virtually  undisturbed. 

Each  boiler  must  be  provided  with  an  independent  damper.  It  should 
fit  well,  so  that  when  the  boiler  is  idle  there  will  be  very  little  leakage. 
Inleakage  of  cold  air  into  the  main  flue  through  defective  dampers  of  Idle 
boilers  reduces  the  draft  very  seriously. 

Individual  boiler  dampers  are  set  by  band  so  as  to  divide  the  load 
equally  between  the  boilers  by  correcting  the  unavoidable  differences  between 
the  drafts  at  boilers  near  the  stack  and  those  at  boilers  rnore  remote.  Varia- 
tions in  the  general  or  total  load  are  cared  for  by  a  main  damper  near  the 
chimney,  controlled  either  by  hand  or  by  an  automatic  regulator.  Damper 
regulators  are  discussed  in  Chapter  16  on  OPERATION.  The  main  damper 
need  not  be  tight  unless  there  are  more  than  one,  such  as  when  two  or  more 
Hues  enter  the  same  chimney.  Sometimes  the  main  damper  is  prevented  from 
forming  a  tight  closure,  either  by  providing  a  hole  in  it,  by  stops  to  limit 
its  travel,  or  by  adjustment  of  the  operating  mechanism. 


ib.  Google 


CHIMNEYS 


Fig'  110.     Faulty  Damper  Installation. 


Pit  131.     Proper  Location  of  Dampen. 


ib.  Google 


CHIMNEYS 


Dampers  should  be  balanced  and  should  move  easily.  Swivel  or  "butter- 
fly" dampers  are  generally  used,  since  they  swing  freely  and  are  not  apt  to 
get  out  of  order.  Sluice  or  slide  dampers  are  sometimes  necessary  to  meet 
space  requirements,  but  are  avoided  wherever  possible,  as  they  are  difficult 
to  move,  especially  when  there  is  dust  in  the  slides  or  the  dampers  are 
slightly  warped. 

Dampers  are  operated  by  chain,  v 
because  they  give  positive  action,  whi 
must  be  placed  on  the  overbalance  for  r 
F  the  bearings  stick,  the  damper  may  i 


defect  becoming 
once.  For  this  re 
much  heavier  th: 
difficult. 


:  rope  or  rods.  Rods  are  preferable, 
if  chain  or  rope  is  used,  reliance 
ivement  in  one  direction.  If  any 
main  in  one  position  without  the 
nmediately  known ;  whereas  rods  show  such  a  trouble  at 
in,  where  rope  or  chain  is  used,  the  overbalance  is  made 
is    generally    necessary,    thus    making    movement    more 


Unless  the  handles  for  operating  the  dampers  are  brought  to  a  con- 
venient position,  so  that  the  attendant  can  work  them  easily,  they  will  not 
be  adjusted  as  frequently  as  they  should  be,  and  waste  of  fuel  will  result 
from  failure  1o  relate  the  draft  to  the  load  and  the  fuel.  The  bad  effects 
of  controlling  the  draft  by  means  of  the  ashdoors  and  tiredoors  are  fairly 
well  known,  but  blame  for  this  condition  should  usually  be  placed  on  those 
responsible  for  making  damper  operation  difficult  and  awkward. 

The  handles  should  be  arranged  so  as  to  definitely  indicate  how  much 
the  damper  is  open.  This  indication  is  sufficiently  important  to  warrant 
checking  from  time  to  time.  Lost  motion  prevents  correct  indication  and 
should  be  eliminated,  either  by  overbalance  or  refitting.  The  Jamper  shaft 
should  be  squared  where  the  operating  lever  is  attached  to  prevent  any 
possibility  of  shpping.  The  same  requirement  applies  also  to  any  oth;r  shaft 
and  lever  of  the  operating  mechanism. 

Fig.  122  shows  the  construction  details  and  general  proportions  of  a  good 
damper  design. 


Fig.  133.     Conitruction  Details  of  a  Damper. 


Steel  plate  Ji-in,  thick  down  to  No,  8  gauge  is  used  for  dampers.  Angle 
iron  shapes  are  employed  as  ribs  for  large  surfaces,  set  about  2  ft.  apart.  Bar 
iron  or  extra  heavy  pipe  is  used  for  the  spindle  which  is  supported  on  roUeri 
or  even  ball  bearings  on  the  outside  of  the  steel  flue. 


ib.  Google 


CHAPTER  7 


MECHANICAL  DRAFT 

MECHANICAL  draft  is  adopted  for  obtaining  economy  of  operation,  in- 
creased capacity,  or  both.     It  is  called  either  forced  or  induced  draft, 
according  to  whelher  the  draft  is  intensified  by  increasing  the  pressure 
at   the   inlet  or  decreasing   the  pressure  al   the   outlet   of   the   boiler.     Both 
tnethoda,  and  the  combination  of  the  two,  are  in  general  use. 

Forced  draft  may  be  of  the  closed  ashpit  or  closed  slc^ehold  system; 
but  as  the  latter  is  confined  to  marine  practice,  it  will  not  be  discussed  here. 
The  economic  advantages  resulting  from  the  use  of  mechanical  draft  are 
best  explained  by  diagrams.  In  the  following  diagrams  the  pressures  and 
vacua  are  not  drawn  to  scale,  but  they  clearly  indicate  the  effect  of  the 
different  ways   of  applying   mechanical   draft. 

Fig.  123  represents  graphically  the  circumstances  present  in  natural  draft 


Pig.  123.     Diagram  of  Natural  Draft  Plant. 

The  vacuum  in  ihe  boiler  setting  and  fiues  draws  in  cold  air  through  the 
porous  brickwork,  cracks,  leaky  cleaning  and  dusting  doors,  and  through 
firedoors  opened  for  hand  firing.  The  heavily  shaded  area  indicates  where 
the  greatest  heat  loss  occurs,  due  lo  the  large  quantity  of  cold  air  reducing 
the  temperature  of  the  gases  and  rate  of  heat  transfer  to  the  water  in  the 
boiler.  The  tighter  shaded  area  shows  the  draft  loss  through  leaky  flues. 
which  reduces  the  static  chimney  draft  by  lowering  the  gas  temperature,  and 
reduces  the  available  draft  by  increasing  the  volume  of  gas  to  be  handled  by 
the  chimney. 

Pig.  124  shows  the  conditions  when  forced  draft  is  applied  to  lake  care 
of  the  draft  resistance  of  the  fuel  bed. 

The  vacuum  in  the  boiler  setting  and  flues  is  much  less,  so  that  the 
inleakage  of  cold  air  and  consequent  waste  of  fuel  is  greatly  reduced.  Verr 
little  cold  air  is  drawn  in  through  open  firedoors,  as  the  vacuum  above  the 
fire  is  extremely  small. 


ib.  Google 


Ml^CII  AN  ICAL    DRAFT 


t 

r^/S^ 

Boi/er   Safting 

Flutt 

c^,^ 

^ 

^\, 

I 

//// 

^ — ' 

ll 

' 

i 

i 

PiE.  124.     E>iBBrBr 


of  Forced  Draft  Plant. 


A  further  economy  may  be  gained  by  the  use  of  cheaper  fuels  which 
generally  offer  much  greater  draft  resistance,  since  there  is  no  reasonable 
limit  to  the  air  pressure  which  may  be  maintained  in  the  closed  ashpit. 

When  forced  draft  is  used  for  increasing  boiler  capacity,  an  operating 
limit  is  set  by  the  capacity  of  the  chimney,  and  to  pass  this  limit,  induced 
draft  must  be  used  as  -well.  Fig,  125  shows  how  the  condition  illustrated  by 
Fig.  124  is  modified  by  the  addition  of  the  induced  draft  fan. 


1  K- 

Bo'ltr  S*ff'i<y 

Fl«ts 

Ftr, 

ChirT<nt 

^'  \~ 

"77-?--^ 

. 

M 

~A 

■^ 

1  1 

1 

Pig.  125.     Diagram  of  Combined  Forced  and  Induced  Draft  Plant. 

Even  under  these  intensified  conditions,  the  loss  as  shown  by  the  heavily 
shaded  area  is  less  thau  under  those  for  the  natural  draft  of  Fig.  123,  because 
the  vacuum  over  the  hre  is  so  small. 

The  dotted  lines  in  Fig.  125  show  wh^t  happens  when  the  operating 
limit  of  forced  draft  alone  is  passed.  As  the  chimney  is  overloaded,  it  cannot 
cause  sufficient  draft  to  overcome  the  resistance  of  the  setting  and  flues  at 
this  higher  capacity,  and  the  forced  draft  builds  up  pressure  above  the  fire. 
This  pressure  continues  through-  a  part  of  the  boiler  setting  as  shown  by 
the  dot-shaded  area.  Where  this  pressure  occurs,  the  gases  escape  through 
leaks  into  the  boiler  room,  causing  great  discomfort;  brickwork,  furnace 
fronts,  fircdoors,  and  so  forth,  deteriorate  rapidly.  While  the  draft  n 
of  the  fuel  bed  is  unchanged,  the  ashpit  pressure,  which  is  n 


ib.  Google 


JECHANICAL    DRAFT 


atmospheric  pressure,  is  higher  than  when  the  induced  draft  is  added.  There- 
fore, the  cost  of  operating  die  induced  draft  is  somewhat  offset  by  the 
reduction  in  cost  of  operation  of  the  forced  draft,  due  to  the  lowered  ashpit 
pressure. 

Induced  draft  alone  is  not  generally  applicable  for  increasing  boiler 
capacity.  Fig.  126  illustrates  how  it  increases  the  leakage  loss  in  compari- 
son with  Fig.  123,  which  is  represented  by  the  dotted  curve. 


Fig.  116.     Diagram  of  Induced  Draft  Plant. 


When  economizers  are  installed,  the  temperature  of  the  chimney  gases 
is  reduced,  and  the  resistance  of  the  economizer  is  added  to  those  of  the  fuel 
bed,  boiler  setting,  and  so  forth,  and  the  natural  draft  of  the  chimney  is 
often  rendered  insufficient  to  carry  the  desired  load.  This  defect  of  draft 
may  be  made  up  by  induced  draft  fans.  Fig.  127  is  a  diagram  illustrating  the 
addition  of  an  economizer  and  induced  draft  fan  to  the  plant  as  shown  in 
Fig.  123. 


Fig.  137.     Diagram  of  Economizer  and  Induced  Draft  Plant. 

As  shown  by  the  dotted  line  from  Fig.  123,  the  induced  draft  fan  just 
makes  up  the  draft  losses  due  to  the  resistance  of  the  economizer  and  the 
reduced  static  chimney  draft  occasioned  by  the  lowered  gas  temperature. 


ib.  Google 


ib.Google 


MECHANrCAL    DRAFT  227 

There  are  two  ways  of  producing  mechanical  draft  in  common  practice. — 
by  fans  and  by  jets.  Each  method  hag  its  advantages  and  is  better  suited  to 
some  conditions  than  the  other  is.  Fans  usually  take  much  less  power  to 
operate  than  jet-blowers,  because  the  simplicity  of  jet-blowers  has  resulted 
in  their  haphazard  manufacture.  However,  A.  Cotton  states  that  steam  jet- 
blowers  whose  power  consumption  compares  favorably  with  that  of  fans  are 
made;  although  ill-proportioned  and  wasteful  blowers  arc  widely  offered. 
Jet-blowers  have  nothing  which  can  break  down  or  wear  out,  so  that  in 
reliability  they  are  not  approached  by  fans.  Furthermore,  they  cost  less  and 
need  no  foundations.  Chi  the  other  hand,  the  steam  used  by  jet-blowers  is 
lost,  while  that  used  by  fan  engines  or  turbines  may  be  recovered  in  feed- 
water  heaters  or  condensers.  The  steam  of  jet-blowers,  by  raising  the  posi- 
tion of  highest  temperature,  keeps  the  grate  bars  cooler  than  usual  and  tends 
to  reduce  the  formation  of  clinker. 

Disk  fans  mounted  on  the  same  shaft  with  steam  turbines  are  used  for 
low  pressure  forced  draft  work,  generally  a  separate  fan  to  each  boiler. 
Owing  to  their  extremely  high  speed,  sufficient  pressure  is  generated  to  give 
fairly  high  combustion  rates.  In  some  types,  the  turbine  exhaust  is  discharged 
intp  the  ashpit ;  in  others  the  turbine  is  fully  enclosed,  and  the  exhaust  may 
be  recovered  by  condensation. 

The  best  examples  of  jet-exhausters  for  induced  draft  are  offered  by 
locomotives  and  by  the  evasi  chimneys  mentioned  in  Chapter  6. 

Forced  Draft 

'  I  'HE  first  considerations  in  designing  a  forced  draft  installation  are  the 
'■  quantity  of  air  required  and  the  pressure.  It  is  common  to  allow  either 
12  cubic  feet  per  minute  per  B.H.F.,  or  18  lbs.  of  air  per  pound  of  coal. 
These  figures  should  not  be  used  indiscriminately,  as  the  air  required  will 
depend  upon  the  kind  of  coal  and  the  method  of  burning  it.  For  stoker 
work,  fans  should  be  capable  of  furnishing  50  per  cent  excess  air  above  the 
theoretical  amount.  The  pressure  required  will  depend  upon  the  kind  of 
coal  to  be  burned  and  upon  the  rate  of  combustion.  Reference  should  be 
made  to  Fig.  97.  In  stoker  firing,  the  stoker  manufacturer  should  be  con- 
sulted, since  the  pressure  necessary  to  generate  a  given  boiler  capacity  differs 
greatly  with  different  types  of  stokers.  With  fans,  great  care  should  be 
taken  to  get  these  quantities  as  accurate  as  possible,  for  if  the  fan  proves  to 
be  improperly  proportioned  for  its  work,  it  cannot  be  changed  without  con- 
siderable expense.  With  jet-blowers,  more  latitude  is  offered,  since  changes 
in  the  size  of  nozzles  are  readily  made.  But  the  characteristics  of  any  jet- 
blower  under  advisement  should  be  carefully  considered,  as  it  is  the  lack  of 
such  consideration  that  is  responsible  for  frequent  waste  of  power. 

Forced  draft  pressures  have  increased  rapidly  in  recent  years,  A  few 
years  ago,  pressures  above  2  in.  of  water  were  not  called  for.  Such 
pressures  as  were  used  were  met  by  fans  driven  at  slow  speed  by  engines. 
At  present,  underfeed  stokers  developing  high  boiler  ratings  need  pressures 
up  to  8  in.  o£  water,  and  the  higher  fan  speeds  necessary  have  caused  the 
engine  to  give  way  to  the  more  dependable  steam  turbine  or  electric  motor. 

The  principal  resistance  against  which  the  forced  draft  fan  must  operate 
is  offered  by  the  fuel  bed.  This  is  changing  constantly,  varying  the  pres- 
sure and  the  volume  of  the  air  delivered  by  the  fan.  The  fan  speeds 
are  usually  controlled  by  an  automatic  device  and  are  continually  changing. 
The  pressures  required  from  the  fan  vary  with  the  boiler  load,  from  1  to  8 
in.  of  water.  The  speeds  of  the  fans  are  high  and  they  require  con- 
siderable strength.  Because  of  the  changing  speed,  the  fan  impeller  must  be 
strong  enough  to  resist  not  only  centrifugal  forces,  but  also  stresses  caused 
by  the  changes  in  torque. 


ib.  Google 


MECHANICAL    DRAFT 


(  ^V.  ^ 

X 

^ 

f^ 

n 

' 

i 

c 

u 

.     '.1 

Table  le.     Sise>  and  Weight  of  Forced  DiaR:  Pens 

'"Wi.—- 

INCHES 

■^ 

A 

B           ]           C 

500 
1,000 

1.500 

4.3 
8.6 
13 

55 

77 
95 

50 
68 
80 

43 

61 
74 

1.700 
3.300 
4,800 

2.000 
3.000 
4.000 

17 
20 
24 

110 
135 
155 

94 
115 
129 

86 
105 
122 

6.500 
9.000 
12.000 

5,000 
10,000 
16,000 

43 
86 

.    130 

174 
246 
300 

145 
195 

233 

136 
192 
236 

15.000 
30,000 
46.000 

Fan  Drives.  Forced  draft  fans,  whether  automatic  regulator  is  used 
or  not.  should  be  driven  at  variable  speed.  The  most  satisfactory  method 
is  by  steam  turbine.  For  the  smaller  fans  (capacity  about  25,000  cu.  ft.  per 
min.)  good  steam  economies  can  be  secured  with  a  direct  connected  turbine. 
For  volumes  in  excess  of  this  helical  gears  should  be  installed  between  tur- 
bine and  fan. 

The  direct-current  motor  with  a  speed  reduction  of  SO  per  cent,  is  well 
adapted  to  driving  fans.  The  reduction  should  be  first  accomplished  by 
field  control,  then  at  th;  lower  speeds  by  armature  control.  The  speed  con- 
trol is  important  as  the  horsepower  of  a  fan  operating  against  a  given  re- 
sistance changes  as  the  cube  of  the  speed. 

In  large  power  plants  power  for  auxiliaries  is  often  furnished  by  a. 
turbine-driven  alternator ;  this  is  not  an  advantage,  as  far  as  the  fans  are 
concerned,  because  alternating  current  motors  are  not  efhcient  a:  reduced 
speeds.  This  motor  is  preferable,  however,  when  the  fans  are  to  be  placed 
in  a  boiler  bouse  or  other  part  of  the  plant  where  the  commutator  of  the 
direct  current  motor  would  be  exposed  to  dust  and  dirt. 


ib.  Google 


MECHANICAL    DRAFT 


Operatine  Difficulties.  A  properly  designed  forced  draft  fan  should  be, 
and  usually  is,  one  of  the  most  reliable  piecea  of  apparatus  in  the  power 

plant  However,  certain  troubles  and  difficulties  are  encountered  more  fre- 
quently than  necessary.  Oil  escapes  from  the  fan  bearings,  being  picked  up  by 
the  entering  air  and  carried  into  the  fan  impeller.  As  fan  bearings  are  ring 
oiling  the  oil  reservoir  may  become  empty  and  cause  the  loss  of  a  bearing 
lining  or  shaft 

The  fans  may  fail  to  deliver  the  required  volume  at  the  neces&ary 
pressure.  This  reduction  in  pressure  may  easily  occur  even  with  fans 
that  will  meet  their  guarantees  when  tested  on  the  manufacturer's  test 
plate.  This  discrepancy  is  due  to  the  difference  between  the  test  and  installa- 
tion conditions.  On  the  test  plate  the  fan  is  connected  to  a  long  straight 
duct  Very  seldom  is  any  such  arrangement  found  in  an  actual  plant 
Whenever  possible  a  layout  of  the  duct  work  leading  to  the  fan  should  be 
given  the  fan  manufacturer,  and  he  should  be  asked  for  approval  and  recom- 
mendations. 

The  lack  of  proper  balance  is  the  most  serious  difficulty  encountered 
in  fans.  If  this  is  allowed  to  continue,  the  metal  in  some  part  of  the  fan 
impeller  will  be  fatigued  to  the  point  of  rupture.  Out-of -balance  is  largely 
in  the  control  of  the  manufacturer,  but  is  occasionally  caused  by  negligence 
on  the  part  of  the  operating  force.  All  fan  wheels  will  accumulate  dust  and 
should  be  cleaned  regularly.  Ordinarily  a  forced  draft  fan  that  is  cleaned 
every  two  months  will  not  accumulate  sufficient  dirt  to  impair  its  running 
balance. 

Types  of  Fans.  Fans  may  be  classified  according  to  the  style  of  blading, 
whether  backwardly  curved,  radial,  or  forwardly  curved.  Characteristics  of 
each  type  are  given  in  l-'igs.  128,  129  and  130.  The  behavior  of  these  different 


20D    100     10 


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Fig.  138.     Presiure  CharacteriBtica  of  Backwardly  Curved  Blade  Pana. 

types  determines  their  applicability  to  meet  the  particular  problem  under 
consideration.  The  conditions  imposed  by  hand  tiring  and  by  each  of  the 
various  types  of  stokers  are  different,  and  the  demands  of  each  at  different 


ly  Google 


McCormlck  Buil<UnK>  Cbicngo,  HI.,  equipped  with  Hdne  Standard  BaU«n. 

.Google 


MECHANICAL    DRAFT 


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fCuFtp«-Mirt. 

Fir.  H9.     Premure  Cbaracteriatics  of  Radial  Type  of  Fans. 


loads  are  different.  The  pressures  required  at  different  loads  must  therefore 
be  compared  with  the  fan  characteristics  to  determine  which  type  of  fan 
will  be  appropriate. 


zm 

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iWiThousorids  of  Cu.F  t.  ptr  Hin. 
Pressure  Characteristics  of  Porwardly  Curved  Blade  Fans. 


ib.  Google 


232  M  ECU  AN  ICAL    DRAFT 

For  use  with  stokers,  there  is  a.  teniptaiion  to  pick  a  small  fan  and  accept 
a  poorer  efliciency  for  the  peak  loads,  especially  when  they  occur  for  only 
a  short  time  each  day.  Whether  this  is  good  economics  will  depend  upon 
the  frequency  and  duration  •<{  the  peak  loads.  There  is  always  danger  that 
the  tip  speed  of  the  fan  so  selected  will  be  too  high  at  the  peak  load.  Fans 
are  designed  for  a  safe  tip  speed  of  16,000  to  IS.OOO  ft.  per  min.  An  excellent 
specificatioti  requirement  is  that  the  fans  shall  be  run  without  showing  any 
signs  of  permanent  distortion  for  two  hours  at  a  speed  25  per  cent  above 
the  highest  operating  speed.  As  stresses  due  to  centrifugal  force  increase 
as  the  square  of  the  speed,  the  stress  during  the  two-hour  run  will  be  about 
50  per  cent  greater  than  under  the  most  severe  specified  condition.  This  test 
can  be  met  by  any  properly  designed  fan  without  causing  harm  to  show  up 
then  or  later.  Tests  at  higher  than  25  per  cent  overspeed  should  not  be 
called  for,  as  the  stresses  put  upon  the  fan  might  be  great  enough  to  start 
ruptures,  which  might  escape  inspection  after  the  test  run. 

Performance  of  Fan.  A  test  on  a  manufacturer's  test  plate  with  the 
fan  blowing  into  a  long  straight  duct  is  simple  enough,  although  it  requires 
extreme  care,  but  to  test  a  fan  after  installation  is  extremely  difficult  The 
only  readily  available  instrument  for  measuring  the  volume  of  air  Jn  a  duct 
is  the  double  pitot  tube.  Fig.  131  shows  this  tube  and  its  connections  to  the 
indicating  gages.  When  the  pitot  tube  is  carefully  used,  volumes  can  be 
determined  within  2  per  cent  accuracy.  To  secure  this  accuracy,  measure- 
ments must  be  made  in  a  straight  run  of  pipe  far  enough  away  from  the 
fan  so  that  the  turbulence  it  sets  up  in  the  air  is  dissipated,  and  a  smooth 
steady  parallel  flow  is  insured.  Usually  the  distance  from  the  fan  outlet  to 
the  pitot  tube  should  equal  10  or  15  pipe  diameters.  In  most  forced  draft 
installations  there  is  no  straight  pipe  of  this  length,  so  that  the  results  must 
be  regarded  as  indeterminate.  The  readings  with  a  pilot  tube  are  sometimes 
surprisingly  accurate,  even  when  it  is  placed  close  to  the  fan  outlet,  but  never- 
theless one  should  always  select  as  a  place  of  measurement  the  longest  run 
of  straight  pipe  available. 

The  volume  delivered  by  the  fan  can  be  determined  from  the  manufac- 
turer's pressure,  volume  and  horsepower-volume  curves,  drawn  for  the 
Speed  al  which  the  fan  is  tested.  The  pressure  can  be  determined  by  taking 
^ve  or  six  readings  at  different  places  in  the  main  duct,  allowing  about  '/» 
in.  for  the  loss  from  the  tan  outlet  to  the  main  duct.  The  volume  corre- 
sponding to  this  pressure  can  be  determined  from  the  pressure- volume  curve. 
If  the  fan  is  driven  by  a  motor  so  that  the  horsepower  can  be  determined 
for  the  same  conditions  an  additional  check  can  be  secured  from  the  horse- 
power-volume curve.  The  volumes  determined  by  pressure  and  by  horse- 
power should  check  within  5  per  cent. 

When  the  air  velocities  are  measured  by  a  pitot  tube,  the  duct  must  be 
divided  into  at  least  16  equal  areas  and  a  reading  taken  at  the  center  of  each. 
In  obtaining  the  average  of  the  16  readings  of  velocity  pressure,  the  veloci- 
ties can  be  calculated  for  each  reading  and  the  averag:  then  determined ; 
or  the  average  velocity  pressure  can  be  calculated  by  squaring  the  mean  of 
the  square  roots  of  the  16  readings. 

The  pitot  tube  shown  in  Fig.  131  is  double.  The  small  inside  tube  is 
open  only  at  the  end,  which  must  point  directly  and  truly  into  the  air  stream. 
The  pressure  indicated  on  a  U  tube  with  one  leg  connected  to  this  inner 
tube  and  the  other  leg  open  to  the  atmosphere,  is  the  static  pressure  in  the 
pipe  plus  the  velocity  pressure.  The  larger  outside  lube  is  plugged  at  the 
end  and  has  four  0.02  in.  holes  drilled  perpendicularly  through  the  sides.  The 
pressure  indicated  on  a  U  tube  with  one  leg  connected  to  this  outer  tube 
and  the  other  leg  open  to  the  atmosphere  is  the  static  pressure  in  the  pipe 
only,  since  because  of  the  small  perpendicular  holes,  the  pressure  is  entirely 
independent  of  the  air  velocity.  The  difference  between  these  readings  is  the 
velocity  pressure.     If,  instead  of  connecting  U  gages  as  just  described,  the 


ib.  Google 


MECHANICAL    DRAPT 


PJK-  131.      A  Oouble  Pilot  Tube  for  MeaBuring  the  Volume  of  Air  in  a  Duct. 

inner  tube  of  the  double  pilot  tube  is  connected  to  one  leg  of  the  U  gage,  and 
the  outer  tube  to  the  other  leg,  the  reading  of  the  U  gage  will  now  be  the 
velocity  pressure,  since  the  static  pressure  is  applied  to  both  legs  of  the 
U  gage  and  is  thus  canceled. 

The  velocity  can  be  calculated  from  the  velocity  pressure  by  the  follow- 
ing formula : 

i-^\im,lj_  (13) 


■>i^ 


y  =  velocity,  feet  per  minute. 
p  =  velocity  pressure,  inches  of  water. 
w^  density  of  air  in  pipe,  pounds  per  cubic  foot. 
At   65  deg.   and   standard   barometric   conditions,   the   density   of   air    h 
0.0?S  !b,  per  cubic   foot.     The  above   formula  is   readily  derived  from 

Vl=2sh  (14) 

J',^  velocity,  feet  per  second, 
g  =32.2=:  acceleration  due  to  gravity. 
A  ^ head,  feet  of  air  (equivalent  to  f  in  inches  of  water). 


ib.  Google 


.S'6- 

II 


2|S 
1^ 


ib.Google 


MECHANICAL    DRAFT 


The  horsepower  represenled'  hy  the  air  leaving  the  fan,  usually  called  air 
horsepower,  is  the  fan  output  and  can  be  calculated  from 

H.P.  =  0.000.158  0?  (15) 

Q  =  volume,  cubic  feet  per  minute. 
f  =  pressure,  inches  of  water. 

If  this  fan  output  is  used  to  determine  the  mechanical  efficiency  of  the 
fan,  p  should  be  the  total  or  impact  pressure ;  that  is,  the  sum  of  the  static 
and  velocity  pressures,  which  sum  is  given  by  the  reading  at  the  small  open 
end  tube.  If  the  static  efficiency  is  to  be  found,  the  fan  is  not  credited  with 
the  energy  due  to  the  velocity  of  discharge,  and  p  should  be  the  static 
pressure,  or  the  reading  given  by  the  large  outside  tube.  The  quantity  of  air 
handled  per  minute  by  forced  draft  fans  is  frequently  a  large  percentage  of 
the  cubical  contents  of  the  room  in  which  the  fans  are  placed,  so  that  not 
infrequently  the  static  pressure  in  the  room  is  02  in.  below  atmosphere.  This 
condition  will  automatically  be  taken  care  of  by  the  readings  of  the  U 
tubes  themselves,  provided  they  are  always  placed  in  the  same  room  from 
which  the  fans  are  exhausting  their  air. 

Duels  and  Dampert,  The  shape  and  arrangement  of  ducts  and  the  plac- 
ing of  dampers  has  an  important  effect  upon  the  pressure  of  the  fan  as  car- 
ried through  to  the  stoker  windbox.  Bends  should  have  an  inner  radius  of 
from  l|/i  to  3  diameters.  Y's  should  be  used  in  preference  to  T's,  and  if  T's 
are  necessary  the  "Poor  Type"  of  Fig.  132  should  be  avoided,  if  possible,  or 
the  sharp  comers  changed  to  be  like  the  dotted  lines.  The  one  marked 
"Good  Type"  with  rounded  comers  and  deflecting  plates  is  preferred;  and  if 
the  ducts  are  of  rectangular  cross-section,  the  deflecting  plates  are  easily 
applied. 


t   f 

t  H' 

t  t 


horTyp*  Good  Type 

Fig.  133.     Oood  and  Poor  Forms  of  Tee*. 

Dampers.  When  two  or  more  fans  blow  into  a  comtnon  duct,  outlet 
dampers  for  each  fan  must  be  provided;  these  can  be  closed  when  any  fan 
is  not  in  operation.  These  dampers  frequently  cause  Urge  reductions  in 
fan  pressure.  An  ordinary  butterfly  damper  should  have  a  small  indi- 
cator placed  parallel  to  the  damper  and  fastened  to  the  damper  shaft  outside 
the  duct,  whenever  the  damper  handle  itself  will  not  serve  as  an  indicator. 
When  the  handle  can  be  placed  in  a  position  other  than  parallel  to  the 
damper  itself  no  one  can  be  sure  when  the  damper  is  open.  The  butterfly 
damper  should  be  placed  as  far  from  the  fan  as  is  convenient.  Its  shaft 
should  lie  in  a  plane  perpendicular  to  the  fan  shaft ;  that  is,  the  damper 
shaft  should  always  be  vertical  rather  than  horizontaL 

Louver  dampers  are  frequently  placed  in  or  close  to  the  fan  outlet 
The  shafts  of  these  should  also  be  provided  with  an  indicating  mechanism. 
They  should  be  vertical,  particularly  with  the  small  housing  types  of 
fans.    The  air  in  the  fan  outlet  is  in  a  highly  turbulent  condition  due  to  the 


ib.  Google 


236  MTCH  AN' 1  CAl.    DRAFT 

action  of  the  wheel  and  docs  not  come  from  tlic  oiillet  in  parallel  lines 
and  with  even  velocity  distribution.  When  louver  dampers  are  used  in 
the  fan  outlet  with  horizontal  shafts  arranged  parallel  to  Ihe  fan  shaft. 
the  pressure  readings  taken  beyond  the  damper  will  invariably  show  that 
the  best  position  of  Ihe  damper  is  partly  closed  and  not  wide  open.  If  the 
shafts  are  vertical,  the  damper  in  its  wide  open  position  wi!l  always  ofFer 
the  least  restriction,  and  the  resistance  will  be  less  than  in  any  position  with 
the  horizontal  shafts. 

Screens  for  forced  draft  fan  inlets  should  always  be  provided.  Serious 
accidents  have  occurred  in  instances  where  the  arms  and  legs  of  attendants 
have  been  drawn  into  contact  with  the  impeller.  These  screens  sometimes 
present  a  serious  obstruction;  but  they  need  not  be  heavier  than  !^-in.  wire. 
nor  closer  than  2-in.  mesh.  There  have  been  occasions  when  inlet  screens 
made  of  ordinary  expanded  metal  have  offered  a  resistance  sufficient  to  cause 
a  1-in.  drop  in  pressure  in  the  tan  inlet. 

Air  Leakage  in  Ducts.  All  ducts  carrying  air  under  pressure  must  be 
tight  The  leakage  that  can  occur  in  ordinary  ducts  is  seldom  appre- 
ciated because  the  air  cannot  be  seen.  Air  will  leak  through  joints  much 
more  easily  than  water  will.  The  pressure  on  a  forced  draft  duct  may  be 
6-in.  of  water,  representing  a  head  of  air  of  416  feet.  In  carrying  water 
at  a  head  of  this  magnitude  ihe  utmost  precautions  would  be  taken  to  keep 
the  ducts  tight,  but  with  air  the  importance  of  this  point  is  apt  to  be  over- 

The  leakage  loss  in  the  average  installation  is  always  rearer  20  per 
cent  than  10  per  cent.  Even  concrete  ducts  do  not  prevent  the  leakage. 
In  some  large  concrete  ducts  it  is  so  great  that  pressure  cannot  be  created 
in  them.  The  inner  surfaces  of  all  air  ducts,  whether  concrete  or  metal, 
should  be  liberally  coated  with  a  good  paint.  The  larger  ducts  of  the  sys- 
tem will  have  the  most  leakage,  and  should  be  painted  while  under  pressure. 

Induced  Draft 

TO  decide  upon  satisfactory  induced  draft  installation  necessitates  a  great 
deal  of  experience  and  common  sense.  It  is  simple  enough  to  Rgure  the 
weight  of  the  gases  from  the  amount  of  air  supplied  to  burn  the  fuel,  and  if 
the  temperature  is  known,  to  figure  the  volume  of  those  gases.  The  tem- 
perature, however,  and  consequently  the  volume,  cannot  be  predetermined 
accurately.  The  intiitration  through  boiler  settings,  flue  connections  and 
economizer  ts  an  uncertain  quantity;  it  does  not  remain  constant,  but  in 
time  increases ;  the  fan,  however,  must  always  be  capable  of  overcoming 
any  pressure  set  up  in  the  fire-box.  The  infillering  air  is  cold  and  not 
only  adds  to  the  weight  of  the  gases  but  reduces  their  temperature.  An 
induced  draft  fan  should  be  selected  therefore  with  plenty  of  reserve 
capacity.  The  driver  for  the  fan  should  also  be  large,  with  at  least'20 
per  cent  excess  power. 

Table  17  may  be  used  as  an  example  of  induced  draft  fan  sizes;  but  the 
dimensions  differ  considerably  with  different  manufacturers. 

The  chief  troubles  with  induced  draft  fans  are  mechanical;  high  speed 
fans,  particularly,  becoming  unbalanced.  The  cinders  passing  through 
the  fan  cause  a  certain  amount  of  erosion.  The  scroll  sheet  or  round- 
about of  the  fan  housing  suffers  most,  and  the  inlet  edges  of  the  fan 
blades  sometimes  show  signs  of  wear.  In  all  induced  draft  fans  the  scroll 
sheet  should  be  at  least  V«-in.  thick.  When  oil  leakage  occurs,  dust 
and  cinders  are  deposited  on  the  blades.  They  pack  down  tight  and  form 
with  the  oil  a  heavy  hard  cake.  The  leakage  oil  runs  along  the  shaft 
through  the  shaft  opening  in  the  housing,  and  from  there  is  carried  into 
the  fan  wheel,  covering  the  blades. 


ib.  Google 


MECHANICAL    DRAFT 


Table  1 7.     Kzes  and  Weighta  of  Indticed  Draft  Pant. 


*«.<,«,-. 

Fu  OtttM  Aiw. 

A 

INCHES 

C 
60 

'^ 

100 
200 
400 

1.6 
3.2 
6.4 

52 
70 
95 

48 
04 

87 

1.000 
2,000 
3.700 

GOO 
800 
1.000 

9.6 
13.00 
15.00 

120 
140 

156 

110 
128 

143 

109 
120 
138 

5,500 
7,000 
9,000 

2.000 
3,000 

32.00 
48.00 

220 
270 

202 
248 

146 
170 

17,000 
25,000 

Most  induced  draft  installations  are  of  single  inlet  fans  with  overhung 
wheels.  The  two  bearings  are  then  outside  of  the  flow  of  hot  gases.  Tbi; 
wheel  is  satisfactory,  provided  the  shaft  is  large  enough. 

The  heat  of  the  gases  handled  by  the  fan  is  conducted  along  the  shaft 
to  the  bearings,  and  these  bearings  must  be  water-cooled,  A  short  cast  iron 
pedestal  set  in  concrete  is  a  satisfactory  support.  The  concrete  can  often  be 
brought  up  almost  to  the  bearing  bases ;  the  bearings  are  then  mounted  on 
I-beams  securely  embedded  in  the  concrete.  Built-up  structural  steel  pedes- 
tals should  be  used  only  for  very  slow  speeds  and  low  powers. 

In  the  larger  cities  the  nuisance  caused  by  the  discharge  of  solid 
matter  from  the  stacks  of  power  houses  must  be  overcome.  The  under- 
feed stoker  has  to  some  degree  eliminated  the  discharge  of  black  clouds 
of  smoke.  But  owing  to  the  high  draft  pressures  used  at  large  boiler 
loads,  the  discharge  of  heavy  cinders  has  been  aggravated.  In  one  type  of 
draft  fan,  the  dust  and  soot  are  separated  from  the  gases,  and  are  delivered 
into  dust  chambers,  from  which  they  fall  by  gravity  into  collecting  hoppers. 
The  cinder-separating  induced  draft  fan  has  an  c^ictency  of  dust  removal 
of  75  per  cent  It  is  substantially  a  paddle  wheel  fan  of  good  propor- 
tions and  takes  about  10  per  cent  more  power  than  the  plain  fan. 

The  allowable  speed  on  induced  draft  fans  u  considerably  less  than 
ihat  on  forced  draft  fans,  even  when  the  construction  is  identical.  The 
temperatures  of  the  gases   handled  by  the  induced  draft   fan  range  from 


ib.  Google 


ib.Google 


MECHANICAL    DRAFT 


300  to  750  deg.  At  lower  boiler  ratings  with  the  gases  passing  through 
the  economizer,  temperatures  may  be  as  low  as  300  deg.  The  flues  are 
usually  arranged  so  that  the  gases  can  be  by-passed  and  do  not  pass  through 
the  economizer.  With  high  boiler  ratings  and  the  economizer  by-passed, 
temperatures  n-ill  sometimes  be  as  high  as  750  deg.  A  high  fan  speed  is 
then  required,  as  the  draft  loss  at  these  high  ratings,  even  without  thu 
economizer,  is  considerable.  In  addition,  owing  la  the  high  temperature, 
the  fan  must  handle  a  large  volume  of  gases. 

Somewhere  between  500  and  700  deg.,  the  elastic  limit  of  iron  and 
mild  steel  is  only  SO  per  cent  of  the  elastic  limit  at  ordinary  temperatures. 
say  of  70  deg.  The  designers  of  rotating  machinery  have  found  that  jl 
is  not  safe  to  stress  material  above  one-third  the  elastic  limit.  These  con- 
siderations are  borne  out  specifically  by  the  behaviour  of  induced  draft  fans. 
The  desire  for  high-speed  direct-connected  units  resulted  in  many  installa- 
tions of  the  backwardly  curved  blade  fan  for  induced  draft.  This  practice 
has  been  almost  entirely  discontinued,  as  the  fans  were  installed  for  speeds 

4^000 


S'JO.OOO 

ft  20,000 
E 

I  IftOOO 


1 

1  1  1  I  1 

~ 

/- 

.- 

1  Im/itcfil'D^'ft  Ti,«ptnjfimtf  "■> 

^ 

s 

1 

~v. 

j.^; 

L. 

__ 

~' 

'- 

- 

u 

_^ 

Pig.  133.     Variation  of  Yield  Point  with  Temperature. 

that  produce  stresses  of  10,000  lb.  per  sq.  in.,  and  ihey  failed  when  the 
clastic  limit  of  the  materials  was  reduced  because  of  the  high  temperatures. 
Fig.  133  shows  how  the  elastic  limit,  or  more  properly  the  yield  point,  varies 
with   the   temperature. 

The  peripheral  speed  of  induced  draft  fans  should  be  limited  to  11,000 
ft.  per  min.  It  is  true  that  most  of  the  time  when  the  gases  are  passing 
through  the  economizer  a  fan  so  limited  will  be  unnecessarily  strong.  But 
even  though  the  high  temperatures  and  large  volumes  occur  only  seldom  the 
fan  must  always  handle  the  necessary  load. 

Load  on  Indnced  and  forced  Draft  Fans.  The  induced  draft  fan  must 
take  care  of  all  the  resistances,  from  the  lire-box  through  the  boiler  and 
economizer.  The  resistance  cannot  be  overcome  by  the  forced  draft  fan, 
because  positive  pressures  would  be  produced,  blowing  the  gases  of  com- 
bustion out  through  the  leaks.  The  forced  draft  fan  has  the  advantage 
of  working  with  gas  of  greater  density,  and  should  supply  the  pressure  nec- 
essary to  overcome  the  resistances  as  far  as  the  top  of  the  fuel  bed. 

Suppose  the  density  of  the  gases  handled  by  the  induced  draft  fan  is 
htlt  that  of  the  air  handled  by  the  forced  draft  fan,  a  not  unusual  condi- 
tion; then  to  overcome  a  given  resistance  the  induced  draft  fan  will  require 
twice  the  power.  Consider  an  installation  in  which  4  in.  of  water  is 
required  for  the  forced  draft  and  a  static  sucticti  of  2  in.  of  water  is  required 


ib.  Google 


240  MECHANICAL    DRAFT 

at  the  stack  end  of  the  economizer.  The  difference  between  these  two 
pressures  (one  positive  and  the  other  negative)  is  6  in.  of  water.  If  the 
forced  draft  fan  supplied  the  whole  pressure  drop  of  6  in.  the  horsepower 
required  would  be 

0.000158   X   Volume   X  6 
Fan  Efficiency 
If,  however,  (he  whole  pressure  drop  was  taken  ( 
draft    fan   the    volume    handled    would    be    twice    t 
same  fan  efficiency  the  horsepower  will  be 

0.000158  y    (2  X   Forced  Draft  Volume')    X  6 

Fan  Efficiency 
^  2  X   Forced  Draft  Horsepower, 
The   fundamental   formula   for   the   work  done   by  a   fan   shows   this  differ- 
ence more  clearly.    The  work  done  by  a  fan  can  be  expressed  by 

J  =  wXQXh  (16) 

where  /  is  the  work,  w  the  density,  Q  the  volume,  and  h  the  head  in  feet 
of  gas  of  density  w.  For  both  forced  and  induced  draft  fans  the  product 
(ui  X  Q),  which  equals  the  weight  of  gases,  is  the  same,  ignoring  very  slight 
change  in  specific  gravity  due  to  the  different  chemical  composition  of  the 
two  gases.  But  h  for  the  forced  draft  is  only  half  the  h  required  to  produce 
the  same  difference  in  the  water  column  when  the  work  is  don:  by  the  in- 
duced draft  fan.  The  6-in.  water  pressure  represents  415  ft  of  the  cold  air 
and  830  ft,  of  the  hot  air.  In  view  of  this  peculiarity  the  induced  draft  fan 
should  do  only  that  work  which  on  account  of  the  nature  of  the  service 
cannot  be  done  by  the  forced  draft  fan. 

Tetling  of  Induced  Draft  Fans.  The  greatest  difficulty  in  testing  these 
fans  as  installed  is  to  locate  a  straight  run  of  pipe  where  a  steady,  uniform 
and  straight  gas  flow  can  be  obtained.  The  pitot  tube.  Fig.  131,  gives  some 
indication  of  the  fan  performance.  The  volume  of  gases  is  sometimes 
determined  from  the  weight  of  coal  burned  and  the  CO,  readings.  Theo- 
retically the  results  should  be  fairly  accurate,  but  practically  they  are  uncer- 
tain, owing  partly  to  the  fact  that  a  small  difference  in  the  percentage  of 
CO,  corresponds  to  a  great  difference  in  volume  of  the  air.  Ths  densities 
of  the  hot  gases  of  combustion  and  of  the  cold  infiltering  air  differ  greatly, 
so  that  the  mixture  stratifies,  and  it  is  extremely  difficult  to  secure  a  fair 
sample.  The  leakage  is  through  the  walls  of  the  passages ;  consequently  the 
air  almost  entirely  surrounds  the  moving  mass  of  gas  and  the  percentage 
of  CO,  will  be  greatest  near  the  center.  Even  after  passing  through  the 
fan  this  stratification  is  still  evident. 

The  most  satisfactory  method  of  testing  an  induced  draft  fan  is  to 
divide  the  fan  inlet  duct  into  say  16  equal  areas  and  take  a  reading  of 
velocity  with  the  pitot  tube  at  the  center  of  each  of  these  areas.  Knowing 
the  temperature  and  consequently  the  gas  density,  the  volume  of  the  gases 
can  be  calculated  from  these  readings.  The  formulas  for  the  testing  of 
forced  draft  fans  are  applicable.  The  velocity  should  be  measured  on  the 
inlet,  rather  than  the  outlet  side.  The  flow  to  the  inlet  is  almost  invariably 
accompanied  by  an  increase  in  velocity,  and  is  a  maximum  at  the  fan  inlet 
The  movement  of  the  gases  tends  then  to  become  steady  and  uniform,  and 
the  velocity  can  be  measured  accurately  in  a  short  run  of  straight  flue 

On  the  outlet  side  the  fan  wheel  causes  local  eddies  in  the  air,  so  that 
any  velocity  determination  is  extremely  difficult  The  test  must  be  made 
with  the  pitot  tube  or  its  close  equivalent. 

In  the  smaller  plants  the  induced  draft  fan  may  furnish  all  tlic  neces- 
sary draft,  the  stack  being  only  a  short  connection  to  discharge  the  hot  gases 
above  the  roof.  This  is  good  practice  from  the  standpoint  of  cost  but  a 
plant  of  any  size  may  create  a  nuisance,  as  the  discharged  soot  and  cinders 
settle  thickly  on  nearby  structures.    Most  of  the  latter  plants  use  fair  sized 


ib.  Google 


JECHANICAL    DRAFT 


by-pass;  the  second  damper  separates  the  suctioi 
fan.  The  fan  damper  should  be  on  the  inlet  rather 
because  the^  dead  pockets  formed  by  a  fan  with  i 
be  avoided  in  induced  draft  flues.  When  the  fan  is 
datnper  closed,  there  is  no  movement  of  gas  in 
Such  an  arrangement  has  been  known  to  result 
damper  in  the  by-pass  should  be  as  tight  a 
between  fan  outlet  and  inlet  is  equal  to 


1  and  discharge  of  the 
than  on  the  outlet  side, 
n  outlet  damper  should 
by-passed  and  the  outlet 
the   whale    fan    housing. 


Pig.  134.     Ideal  Connection  of  Pen  to  Stack. 


by  the  fan  and  any  leakage  space  around  the  by-pass  damper  will  permit  a 
recirculation  of  gas,  which  will  reduce  the  capacity  of  the  fan  for  handling 
fresh  products  of  combustion  from  the  boiler. 

In  laying  out  the  connection  from  the  fan  outlet  to  the  stack  port  all 
bends  (sharp  ones  especially)  should  be  avoided.  The  static  pressure  in 
this  connecting  duct  is  below  atmosphere  only  by  the  amount  of  suction 
produced  by  the  stack.  When  air  flows  around  bends  the  pressure  is 
greater  on  the  outside  of  the  curve.  If  a  pressure  around  a  bend  becomes 
greater  than  the  stack  suction,  some  of  the  products  of  combustion  leak 
into  the  boiler  room.  Even  a  very  small  amount  of  this  leakage  is  objec- 
tionable, as  it  makes  the  boiler  house  unpleasant  to  work  in.  Fig.  134  shows 
an  ideal  connection  between  fan  and  stack. 


ib.  Google 


I! 

12 

P 
Si 

P 


II 


ib.Google 


CHAPTER  8 


PIPING  AND  ACCESSORBES 

THE  same  care  given  to  the  design  and  inslallation  of  boilers  and  engines 
should  be  given  to  the  piping  system.  The  object  of  any  system  of  bolter 
room  piping  is  to  conduct  el  fluid  safely  from  one  point  to  another.  This 
must  be  done  with  economy,  but  no  commercial  consideration  should  be 
allowed  to  interfere  with  the  fundamental  requirement  of  safety.  More 
accidents  originate  in  defective  piping  than  in  defective  boilers.  The  failure 
of  pipe,  fittings  and  valves  is  due  not  as  a  rule  to  excessive  fluid  pressure, 
but  to  the  presence  of  water  in  steam  lines,  excessive  and  continued  vibra- 
tion, changes  of  temperature,  and  faulty  methods  of  support. 

Water  in  sUam  lines  is  a  source  of  danger,  and  every  precaution  should 
be  taken  to  avoid  its  presence. 

The  chief  danger  from  water  in  steam  lines  is  water-hammer,  which 
generally  results  from  admitting  high  pressure  steam  into  a  cold  pipe  con- 
taining condensed  water.  In  pipes  nearly  horizontal,  Stromeyer  has  shown 
that  under  these  conditions  a  slug  of  water  may  attain  sufficient  velocity 
to  burst  massive  fittings.  He  cites  an  instance  where  a  large  boiler  stop 
valve  disk  was  turned  inside  out  and  driven  into  the  boiler  against  the  steam 
pressure.  Piping  systems  should  be  designed  either  to  avoid  the  possibility 
of  water  accumulating  on  top  of  closed  valves  or  to  provide  ample  and 
accessible  drainage  facilities.  This  requirement  is  of  especial  importance  in 
connecting  boilers  into  a  main  steam  line.  Where  pipes  are  connected  to 
safety  valves  to  enable  them  to  discharge  above  the  roof,  the  connection  to 
the  safety  valve  casing  should  be  fay  means  of  a  Tee,  A  pipe — at  least  I'/i 
in. — should  be  taken  from  a  blank  flange  on  the  lower  leg  of  the  Tee  to 
insure  permanent  drainage;  and  this  pipe  should  be  without  a  valve  or  other 
obstruction,  but  should  discharge  into  the  atmosphere  or  blow-off  tank. 

Piping  should  be  erected  so  that  water-collecting  traps  or  packets  will 
not  be  formed.  Large  drain  pipes  should  be  provided  wherever  pockets 
cannot  be  avoided.  Drains  should  be  placed  at  the  bases  of  risers  and  wher- 
ever water  can  accumulate  because  of  the  closing  of  a  stop  valve.  If  drain 
valves  are  not  likely  to  be  attended  properly,  drains  should  be  trapped,  so 
that  the  water  will  be  removed  automatically.  Steam  supply  branches  should  be 
connected  to  the  upper  side  of  mains.  Drains  should  be  connected  to  the  low- 
est point  of  reducing  flanges,  reducing. tees,  and  taper  reducers.  Steam  lines 
should  be  installed  with  a  uniform  grade  of  about  1  in.  to  40  ft.,  so  that 
they  will  drain  to  some  predetermined  point.  Drainage  is  more  complete  it 
the  water  and  steam  flow  in  the  same  direction. 

yibralion  in  piping  is  a  source  of  trouble  and  danger  to  the  pipe  itself, 
and  to  joints,  valves,  fittings,  supports  and  anchors.  It  is  often  set  up  by 
water  slugs  delivered  by  ill-designed  or  carelessly  operated  boilers,  or  from 
accumulations  of  condensed  water.  Modern  power  plant  practice  favors 
high  steam  velocities,  which  tend  to  diminish  condensation.  But  slugs  of 
water  are  then  driven  along  at  higher  velocities,  and  as  their  kinetic  energy 
increases  as  the  square  of  their  velocity,  the  vibration  trouble  is  aggravated. 
Consequently,  drainage  facilities  cannot  be  neglected  because  of  high  velocity 
alone.  As  a  matter  of  fact,  condensate  is  more  apt  to  be  carried  past  drip- 
pockets  and  separators  by  high,  than  by  tow  velocity.  Vibration  is  also 
caused  by  the  intermittent  flow  of  steam  to  reciprocating  engines,  unless 
separators  or  receivers  are  installed  in  the  steam  lines  close  to  the  engmes. 


ib.  Google 


Erfiansion  and  Contraction.  Pipes  are  bound  to  expand  when  heated 
by  the  entering  steam  and  hot  water  and  to  contract  as  the  temperature  falls 
with  the  shutting  off  of  the  steam  or  water.  The  increase  in  the  circum- 
ference of  a  pipe  becaQse  of  an  increase  in  its  temperature  is  of  little  practical 
consequence.  The  lengthwise  (linear)  expansion  of  a  pipe  is  great,  how- 
ever, for  pipes  used  in  power  planl  practice.  The  force  exerted  by  expand- 
ing and  contracting  pipe  is  practically  irresistible.  Therefore,  piping  must  be 
anchored,  and  then  the  direction  in  which  it  will  expand  and  contract  can  be 
predetermined  and  the  expansion  and  contraction  absorbed,  so  that  it  will  not 
damage  the  pipe  itself,  the  iitlings  forming  a  part  of  the  line,  or  the  appara- 
tus to  which  the  pipe  is  connected. 

Selection  of  Syslcm.  The  selection  of  the  piping  system  shotild  be  based 
upon  the  factors  of  uninterrupted  service,  low  cost  of  operation,  and  low 
cost  of  instaUation.  The  piping  system,  boiler  and  prime  movers  should 
be  selected  at  the  same  time,  and  to  form  a  single  uniL  If  uninterrupted 
plant  operation  is  of  value,  piping  must  be  so  designed  that  its  failure  tn 
part  will  not  shut  down  the  whole  plant.  The  point  to  which  it  is  justifiable 
to  carry  refinements  insuring  continuous  plant  operation  depends  upon  the 
commercial  value  of  uninterrupted  service. 

The  layout  of  essential  power  plant  piping  should  be  consistent.  If 
steam  mains  are  well  protected,  feed  mains,  exhaust  mains,  oil  lines,  and 
other  essential  portions  of  the  piping  equipment  should  be  protected  in  the 
same  way.  Heater,  economizer  or  condenser  connections  need  not  be  thus 
refined,  because  operation  without  them  is  possible,  although  it  may  be 
decidedly  undesirable.  This  is  especially  true  of  plants  containing  more 
than  one  of  each  economic  auxiliary.  These  should  be  connected  so  that 
they  can  be  operated  temporarily  at  an  overload  with  reduced  economy, 
should  one  unit  or  its  connections  fail.  The  feed-water  temperature  may 
be  ISO  deg.  when  two  healers  are  used  instead  of  three,  but  even  that  is 
preferable  to  cold  water.  Overloaded  condensers  may  mean  a  vacuum  much 
less  than  normal,  but  this  is  preferable  to  exhausting  to  atmosphere. 


_^^ 


I       ■<on<ttrtt*r 

-fMJ 


-5 


Fig.  135.     IKacrain  of  End  to  End  Kngle  Header  Syatem. 


The  single  header  syslem.  Figs.  135  and  136.  is  simple  and  the  first  cost  is 
low.  For  the  end-to-end  arrangement  of  boiler  room  and  engine  room. 
Fig.  135,  this  system  is  not  reliable,  as  a  break  in  one  of  the  mains  shuts  down 
the  entire  plant.  For  the  back-to-back  arrangement  of  boiler  room  and 
engine  room,  Fig.  136,  the  feed-water  header  and  exhaust  header  are  still 
undesirable,  although  the  steam  header  can  be  divided  by  valves  and  part  of 
the  plant  operated  if  some  one  section  fails. 


ib.  Google 


Fig.  136.     Diagrt 


o  Beck  SiitEle  Header  System. 


With  the  duplicate  header  system.  Figs.  137  and  138,  the  plant  is  much 
more  reliable,  but  the  first  cost  of  the  system  is  high,  aud  each  piece  of 
apparatus  must  be  connected  to  two  independent  headers.  Unless  both 
headers  are  in  continuous  operation,  or  are  located  at  a  considerable  distance 
from  the  apparatus,  joints  and  connections  are  subjected  to  severe  strains 
due  to  expansion  and  contraction. 


^B.  137.    Diagram  of  Duplicate  Header  System. 


D,g,tze:Jbi  Google 


,Google 


I>^K.  138.     Diagrani  of  Duplicate  Header  Syitem. 


The  hop  or  ring  header  system.  Figs.  139  and  140,  is  more  reliable  than 
the  single  header  system,  but  its  tirst  cost  is  high.  It  has  advantages  when 
the  physical  limitations  of  property  or  buildings  prevent  the  installatinn  of 


fe. 


Wtz^^H 


fita  Mrttr  ioije-'- 

Fig.  139.     Diagram  of  Loop  Header  System. 

The  ii'iiV  lyslem,  P'ig.  141,  represesits  llie  l>est  standard  practice  for  large 
plants,  but  it  can  well  be  used  in  plants  of  moderate  size.  The  complete 
plant  is  virtually  composed  of  small  independent  units,  any  one  of  which 
can  be  shut  down  without  aifectin^  the  others.  The  lirst  cost  of  this  sys- 
tem is  high,  but  is  more  than  justified  when  uninterrupted  service  must  be 
had.  The  high  first  cost  is  due  not  alone  to  the  piping  system  but  also  to  the 
fact  that  each  engine  or  turbine  has  its  own  separate  boilers,  condensers,  feed 
pumps,  circulating  pumps,  vacuum  pumps,  and  feed-water  heaters.  Separate 
coal-and-ash  handling  equipment  is  also  supplied  for  large  units. 


ib.  Google 


I  f  ntd  WattrLoofi-^--' 


J 


Cnglnt  [ngint  £n^n* 


^ 


Fig.  140.     Diagram  of  Loop  Header  System, 

Balm 


g^^^ggggg 


'Sftenn  >fitd  Uifer 


go 


trttco 


1 


^>Sfvam ^Fttl  W 


Sailm 
Fig.  141.     J^agrtun  of  Unit  System. 


ib.  Google 


In  a  modiSed  unit  sytlem.  Fig.  142,  the  complete  plant  is  divided  into 
distinct  sections,  each  entirely  independent  of  the  others  and  operated  as  a 
complete  plant.  This  system  is  not  so  reliable  as  the  unit  system  because 
sections  of  the  same  mains  must  be  used;  fewer  auxiliaries  however  are 
required.  It  is  not  desirable  for  plants  which  operate  at  a  high  toad  factor, 
but  is  adapted  to  those  whose  daily  light  load  period  is  long  enough  so  that 
the  mains  can  be  repaired.  The  number  of  the  sections  into  which  the  plant 
is  divided  depends  upon  the  load  characteristic.  If  a  plant  requires  two- 
thirds  of  its  capacity  for  its  lightest  load,  three  sections  would  be  necessary. 
A  plant  operated  at  half  load  for  the  greater  part  of  each  day  could  be 
divided  into  (wo  "■' 


ft  •a'  Wir^tn' 


Diagram  of  Divided  or  Sectional  System. 


The  modified  unit  system,  Fig.  142,  actually  requires  but  two  auxiliaries 
of  each  Kind ;  each  set  of  auxiliaries  however  should  be  able  to  handle  the 
light  load  for  the  entire  plant.  If  the  capacity  of  each  set  is  sufficient  for 
full  load,  even  though  it  is  overloaded,  the  danger  of  shutdown  due  to  failure 
of  mains  or  connections  is  greatly  reduced.  A  complete  set  of  auxiliaries 
for  each  section  of  the  plant  adds  materially  to  its  flexibility,  economy,  and 
reliability.  In  deciding  upon  the  number  of  sections,  the  size  and  accessi- 
bility of  the  mains  and  the  time  required  for  their  repairs  should  be  con- 
Piping  should  always  be  accfssible,  for  safety  and  economy.  The  ac- 
cessibility possible  for  any  given  set  of  physical  conditions  should  be  a  factor 
in  the  selection  of  a  piping  system,  because  it  affects  the  time  required  for 
repairs  and  therefore  the  reliability  of  plant  operation. 


ib.  Google 


A  part  of  the  8S50  H.  P.  instaUatioa  of  Heine  Standard  BoUeri  and  Heine 

Superheater*  in  the  New  York  Central  Railroad  Terminal,  New  York  City. 

Thii  company  operate*  18,000  H.  P.  of  Heine  Boiler*. 


ib.  Google 


The  durability  of  boiler  room  piping  has  an  important  effect  on  the 
continuity  of  service.  Irrespective  of  its  first  cost,  the  best  pipe  and  pipe- 
^tting  material,  will  be  the  cheapest  in  the  long  run,  for  any  but  the  most 
temporary  installations. 

A  diagramalic  layout  of  boiler  room  and  engine  room  piping  should  be 
made  for  every  plant,  and  a  copy  of  this  diagram  posted  m  a  conspicuous 
and  accessible  place  in  both  boiler  and  engine  room.  The  diagram  should 
be  large  enough  so  that  all  the  lines  and  captions  can  b«  quickly  distin- 
guished. All  valves  should  be  numbered  and  the  diagram  accompanied  by  a 
tabulation  of  the  lines  or  equipment  controlled  by  each  valve.  The  diagram 
can  well  be  made  as  a  tracing.  Any  requisite  number  of  copies  can  then  be 
made,  and  it  can  be  easily  corrected  and  kept  up  to  flate  in  the  event  of 
changes  in,  or  additions  to,  the  piping  system. 


Identification  of  Piping 
A  STANDARDIZED  color  scheme  is  a  practical  aid  to 
■**■  piping.  The  report  of  the  A.  S.  M.  E.  Committte 
Power  House  Piping,  suggests  that  color  shall  be  used  on 
fittings  only,  the  piping  Itself  being  painted  to  conform  t 
of  the  room.  The  colors  recommended  are  as  follows : 
Division 

High  pre 


the  identification  of 

on  IdentiUcation  of 
flanges,  valves  and 
o  the  color  scheme 


Fresh  water,  low  pressure  ., 


Flanges  and  Rttings.... 


...White  and  Green  Stripes 


Pipe  and  Piping  Materials 

PRACTICALLY  all  boiler  room  piping  is  made  of  either  mild  steel  or 
wrought  iron.  Because  of  its  lower  price,  steel  pipe  is  more  common 
than  wrought  iron,  and  for  most  purposes  fulfills  all  requirements. 

Wrought  Iron  pipe  is  more  durable  than  steel  pipe,  especially  when  buried 
under  ground  or  subjected  to  extreme  exposure.  It  is  said  not  to  corrode  a 
easily  as  steel  and  therefore  is  to  be  preferred  for  blow-off  pipes,  drips  and 
drains,  and  wherever  corrosion  may  be  severe.  The  term  "wrought  iron 
pipe"  is  often  used  loosely,  for  bo!h  steel  and  wrought  iron  pipe.  In  the  trade 
steel  pipe  is   furnished,  unless  genuine  wrought  iron  pipe  is   specified. 

Cast  iron  pipe  is  used  for  low  pressure  work.  Because  of  its  low  tensile 
strength  and  consequent  great  weight,  it  is  seldom  used  for  high  pressure 
pipe.  Cast  iron  is  used  however  in  the  construction  of  headers,  although 
it  is  not  recommended  for  high  temperatures.  For  complicated  headers  with 
a,  number  of  branch  lines,  a  casting  is  cheaper  than  Rtttngs,  and  the  number 
of  joints  is  considerably  less. 


ib.  Google 


CasI  steel  is  used  for  headers,  especially  for  highly  auperheated  steam, 
and  resists  high  temperatures  much  l>et(er  than  cast  iron.  The  cost  of  cast 
steel  is  high,  and  it  is  difficult  to  secure  uniform  castings,  free  from  hidden 
defects. 

Bran  withstands  the  corrosive  action  of  hot  water  better  than  iron  or 
steel,  and  i$  sometimes  used  for  feed-water  lines  and  headers.  Its  high  cost 
limits  its  use  even  for  this  service  and  practically  prohibits  its  use  in  other 
parts  of  a  piping  system.    It  is  weak  and  brittle  at  high  temperatures. 

Copfier  is  expensive,  deteriorates  rapidly  under  high  temperatures,  and 
weakens  under  recurrent  stress  variations.  It  was  formerly  popular  in  marine 
service  because  of  its  flexibility,  although  this  is  offset  by  its  low  tensile 
strength. 

The  use  of  high  pressures  and  high  degrees  of  superheat  is  increasing, 
so  that  the  total  tcmperatvre  of  water  and  steam  must  be  considered  in  se- 
lecting materials.  Table  18  gives  the  average  tensile  strength  of  metals 
at  different  temperatures,  as  determined  by  the  Crane  Company.  The  table 
amiies  to  the  initial  effect  of  high  temperatures,  but  does  not  indicate  the 
effect  of  continued  high  temperature,  as  the  time  each  specimen  was  heated 
had  to  be  limited.  The  results  show  however  that  cast  iron  undergoes  a 
slow  but  constant  loss  of  strength  when  subjected  to  temperatures  over  400 
deg..  and  that  steel  does  not  undergo  any  material  decrease,  other  than  its 
initial  loss   of  strength,   because   of   continued   temperatures   as   high   as  800 


Commercial  wrought  iron  and  steel  pipe  is  divided  into  four  weight 
classifications ;  standard,  extra  heavy,  double  extra  heavy  and  large  O.D. 
A  fifth  classification,  lighter  than  standard  pipe  and  known  as  "merchants 
pipe,"  was  formerly  made  but  its  use  has  generally  been  discontinued. 

Standard,  extra  heavy  and  double  extra  heavy  commercial  iron  pipe  is 
designated  by  its  nominal  internal  diameter,  in  si^es  from  Jg  to  12  inches. 
The  external  diameter  of  extra  heavy  and  double  extra  heavy  pipe  is  the 
same  as  that  of  standard  pipe,  and  the  internal  diameter  therefore  is  smaller. 
Above  the  12-in.  size,  pipe  is  usually  classed  as  "large  O.D."  and  is  desig- 
nated by  its  actual  outside  diameter,  although  some  manufacturers  list  sizes 
with  nominal  internal  diameters  of  13,  14  and  15  inches. 

Commercial  wrought  iron  and  steel  pipe  is  butt-welded  in  sizes  114  in. 
or  less  for  wrought  iron,  and  3  in,  or  smaller  for  steel.  The  larger  siies  are 
lap -welded. 

The  principal  dimensions  and  the  weight  of  standard  wrought  iron  and 
steel  pipe  are  given  in  Table  19. 

The  same  data  for  extra  heavy  and  double  extra  heavy  pipe  are  given 
in  Table  20  and  21,  respectively. 


ib.  Google 


I 


ib.Google 


ib.Google 


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TaUe  22. 

Ouflds 

THICKNESS,  INCHES 

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16 

Pounds 
36.71 
39.38 
42-05 

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45.68 
49.02 

52.35 

Pounds 
54.56 
58.57 
62.57 

Pounds 
63.37 
68,04 
72.71 

Pounds 
72.09 
77.43 

82.77 

Pounds 
80.72 
86.73 
92.74 

Pounds 
89.27 
95.95 

102 . 62 

Pounds 
106.00 
114,00 
122.00 

17 
18 
20 

44.72 
47.39 
57.00 

55.69 
59.03 
65.70 

66.58 
70.58 
78,59 

77.38 
82.06 
91.40 

93^45 
104.13 

98.74 
104.75 
116,77 

109.30 

115.97 
129.33 

130.00 
138.00 
154,00 

21 
22 
24 

59.20 
62.60 

6S.00 

69.04 

72.38 
85.00 

82.60 
86.60 
94.61 

96.07 

100,75 
110.09 

109,47 
114  81 

125.49 

122.78 
128.78 
140.80 

136.00 
142,68 
156.03 

162.00 
170.00 
186.00 

2a 

28 
30 

74.00 
80.00 
85.00 

93.00 
100.00 
107.00 

102,62 
120,00 
128.00 

119.44 
128.78 
138.13 

136.17 
146.85 

157.53 

152.81 
164.83 
176.84 

169.38 
182.73 
196,07 

202.00 
218.00 
234.00 

which  pipe 

(17) 


Large  O.D.  pipe  is  generally  made  in  outside  diameters  of  from  14  to  30 
in.,  and  in  thicknesses  ranging  from  J4  to  J^  inches.  Table  22  gives  the 
weight  of  large  O.D.  pipe  of  standard  thicknesses. 

Cold  drawn  steel  tubing  can  be  obtained  in  regular  pipe  sizes  from 
Ji  to  4  in. ;  and  in  the  standard,  extra  heavy  and  double  extra  heavy  weights, 
as  well  as  in  special  tubing  dimensions  and  weights. 

The  pipe  weight  should  be  selected  to  give  durability  and  to  maintain 
safety,  rather  than  for  initial  safety.  The  standard  bydrosUitic  test  pres- 
sures, to  which  pipes  are  subjected  at:  the  mills,  exceed  even  modern  power 
plant  pressures ;  ihe  initial  ultimate  strength  of  pipe  is  greater  than  any 
pressure  stress  likely  to  occur  in  ordinary  practice. 

The   following  lormula   gives   the   approximate  pressure   a 
will  burst : 

D 

P  ^  Bursting  pressure,  lb.  per  sq.  in. 
T  =:  Thickness  of  pipe  wall,  inches 

D  =  Outside  diameter  of  pipe,  inches 

S  —  Tensile  strength  of  material,  lb.  per  sq.  in. 

Machinery's  Handbook  gives  the  value  of  S,  determined  by  actual  bursting 
tests,  as  40,000  for  butt-welded  steel  pipe  and  50,000  for  lap-welded  steel 
pipe.    Table  23  of  bursting  pressures,  is  based  on  the  above  formula. 

Butt-welded  pipe  in  sizes  3  in.  and  smaller  and  lap-welded  pipes  in  sizes 
3J^  in.  and  larger,  are  used  in  calculating  the  table.  It  is  stated  that  the 
accuracy  of  the  figures  has  been  checked  by  exhaustive  tests  conducted  by 
the  National  Tube  Company. 

The  pressures  given  in  Table  23  are  the  approximate  pressures  at 
which  new  pipe  will  burst  In  designing  or  selecting  piping,  a  factor  of 
safety  is  used  ranging  from  six  to  fifteen,  depending  upon  the  severity  of 
the  service,  the  degree  of  exposure  or  corrosive  action  encountered,  the  dura- 
bility desired,  and  the  probability  of  future  operation  at  increased  pressure. 

The  second  edition  of  the  specifications  issued  by  the  Power  Plant  Piping 
Society  recommends  that  all  pipe  (except  boiler  feed  lines)  be  wrought  sted 
with  welded  seams,  butt-welded  for  the  2-in.  and  smaller  sizes  and  lap- 
welded  for  the  2^-in.  and  larger  sizes.  (General  commercial  steel  pipe  is 
butt-welded  in  the  3-in.  and  smaller  sizes.) 


ib.  Google 


ib.Google 


Table  23.     Appro»linate  Bunting  PrcMuret  for  Steel  Pipe. 


BtJKSTDIG  PRESSURE,  POUNDS  PER  SQUARE  INCH 
Standud  Extra  Hiary  Doubia  Eitn  HsTy 


s 

10.784 
10.384 

14,928 
14,000 

28.666 

8,608 

8.088 

6.744 

1             8.104 

I             5,184 

!             5,648 

11,728 
10,888 
9.200 

23,464 

21,776 
18.408 

2H 

8,416 
7.336 

7,680 

16,840 
15,360 
14,680 

3 

4 

1             4.936 

5.610 

1             5.266 

6,866 
7,950 
7,480 

13,714 
15.900 
14.970 

4M 
5 

e 

i               4,940 
4,630 
4.220 

6,740 
6,660 

14,200 
13,480 
13,040 

7 
8 
B 

3,940 

3,730 

1             3,560 

6,620 
5,780 
5,190 

11,470 
10.140 

BURSTINQ  PRESSURE.  POITNDS  PER  SQUARE  INCn 
I      IdTca  O.  D^  yi-iu.  Tfal:k       |       Lug*  O.  D,  H-tn.  TUek 


14 
15 
16 

2,680 
2.500 
2340 

3.670 
3333 
3,120 

18 
20 
22 
24 

2,080 
1.870 
1.700 

1.560 

2,770 
2,500 
2,270 
3.080 

For  pipe  sizes  up   Co  and   including   7   in.,   standard   wrought  steel  pipe 
should  be  used  for  saturated  or  superheated  steam  lines  with  a  working  pres- 
sure not  exceeding  250  lb.  per  sq,  in.  and  a  total  temperature  not  « 
700  degrees. 

For  saturated  steam  lines  with  a  working'  pressure  of  not  ove 
per  sq.  in.  the  weight  of  pipe  in  pounds  per  foot  should  be 

3.69  for    8  in., 

3424  for  10  in., 

4377  for  12  in., 
and  O.D,  sizes  should  be  from  '/«  to  '/«  in.  thick.     For  saturated  c 
heated  steam  lines  with  a  working  pressure  from   150  to  250  lb.  per  sq. 
in.  and  a  total  temperature  of  not  over  700  d^.  the  weight  of  pipe  in  pounds 
per  fool  should  be, 

28.55  for    8  in., 
40.48  for  10  in., 

49.56  for  12  in., 
and  O.D.  sizes  should  be  from  '/■  to  '/n  in.  thick. 


ceding 
■  ISO  lb. 


ib.  Google 


For  saturated  or  superheated  steam  lines  with  a  working  pressure  of 
not  over  350  lb.  per  sq.  in.  and  a  total  temperature  of  not  over  700  deg.,  all 
pipe,  up  to  and  including  12  in.,  should  be  extra  heavy,  and  O.D.  sizes  should 
be  ^-in.  thick.  For  boiler  feed  tines  with  a  working  pressure  of  from 
200  to  400  lb.  per  sq.  in.,  extra  heavy  wrought  steel  pipe  should  be  used  up 
to  and  including  12  in.,  and  O.D.  sizes  should  be  'A  in.  thick.  If  the  water 
is  extremely  bad,  the  use  of  extra  heavy  drawn  brass  pipe  or  extra  heavy 
galvanized   wrought   steel  pipe  is    recommended. 

For  boiler  feed  lines  with  a  workinfj  pressure  of  not  over  200  lb.  ^r 
sq.  in.  and  with  favorable  water  conditions,  standard  wrought  steel  pipe 
should  l>e  used  for  siies  to  and  including  7  in. ;  the  weight  of  pipe  in  pounds 
per  foot  should  be 

2a3S  for    8  in.. 

40.48  for  10  in., 

49.56  for  12  in. 


Table  24.     Standard  Iron  Pipe  Sic*. 


-.a." 


ACTUAI,  DIAMETERS.  INCHES 


APPROXtUATE  WEIGHT, 


0.405 
0.540 
0.675 


0.281 
0.375 
0.484 


.^ 

1.050 
1.315 

0.822 
1.062 

KM 
1,70 
2.50  " 
3.00 
4.00 

1.31 
1.79 

f 

1.660 
1.900 
2.375 

1.368 
1.600 
2.062 

2.63 
3.15 
4.20 

2H 

3 

3H 

2.875 
3.500 
4.000 

2.600 
3.062 
3.500 

5,75 
8.30 
10.90 

6.04 
8.72 
U.45 

4 
6 

4.500 
5.000 
5.563 
6.625 

4.000 
4.500 
5.062 
0.126 

12.70 
13.90 
15.75 
18.31 

13.33 
14.60 

16.54 
19.23 

For  blow-off  lines  for  boilers  operating  with  either  superheated  or  sat- 
urated steam,  extra  heavy  wrought  steel  pipe  should  be  used.  (Galvanized 
extra  heavy  steel  pipe  is  preferable  to  black  for  this  service.) 


I  and  including  7  in.;  the  weight  of  pipe 


23.55  for    8  in., 
40.48  for  10  in., 

49.56  for  12  in., 

s  should  be  from  */■  to  Vii  in.  thick. 


When  the  corrosion  due 


ib.  Google 


s  laid  i 
Hanged  pipe,  built  to  American  Water 
exclusively. 

Seamless  drawn  brass  and  copper  pipe  can  likewise  be  obtained  in  pipe 
sizes  from  ^^  to  6  in.,  and  in  the  standard  and  extra  heavy  weights.  The 
actual  inside  diameter  and  the  weights  per  foot  of  brass  and  copper  pipe, 
Tables  24  and  25,  dilTer  from  those  of  wrought  iron. 


T«ble  25. 

Bxtra  H««vy  Iron  Pipe  Sixes. 

■-,SL'~ 

ACTUAL   DIAMETER,  INCHES 

^'?0^zS1.^B?§^=^ 

OuM<l> 

lodd* 

B« 

c„ 

SI 

0.406 
0.540 
0.675 

0.205 
0.2S4 
0.421 

0.370 
0.625 
0.830 

0.389 
0.661 
0.872 

g 

0.840 
l.OGO 
1.315 

0.542 
0.736 
0.951 

1.200 
1.660 
2.360 

1.260 
1.743 

2.478 

¥ 

1.660 
1.900 
2.375 

1,272 
1.494 
1.933 

3.300 
4.250 
5.460 

3.465 
4.462 
5.733 

2^ 

2.876 
3.500 
4.000 

2.316 
3:358 

8.300 
11.200 
13.700 

8.715 
11.760 
14.385 

fi    ■ 

4.500 
6.000 
5.663 
6.626 

3.818 
4.250 
4.813 
5.750 

16.600 
19.470 
22.800 
32.000 

17.326 
20.440 
23.940 
33.600 

t  steel,  brass,   c 


Pipe  Fittingi 

PIPE  fittings   are  made  of  cast   iron,   malleable   i 
Other  alloys. 

Cast  iron  fittings  are  the  most  common,  as  they  fulfill  the  usual  service 
requirements.  They  are  made  in  standard  weight,  for  125  lb.  working  steam 
pressure,  and  in  extra  heavy  weight,  for  250  lb.  working  steam  pressure. 

Malleable  iron  fittings  are  generally  restricted  to  2-in.  or  smaller  sites. 
In  these  they  are  used  extensively  on  saturated  steam  lines  and  on  boiler 
feed  lines  with  working  pressures  of  not  over  250  lb.  per  sq.  in.  Malleable 
fittings  are  made  in  standard  weight,  for  125  lb.  working  steam  pressure, 
and  in  extra  heavy  weight  for  250  (b.  working  steam  pressure. 

Cast  steel  fittings  are  now  generally  used  on  superheated  steam  lines, 
especially  when  the  working  pressure  is  over  200  lb.  and  the  total  tempera- 
ture is  more  than  500  degrees.  They  are  made  for  superheated  steam  pres- 
sures as  high  as  350  lb.  per  sq.  in.  and  for  a  total  temperature  of  800  degrees. 

Iron  pipe-size  brass  fittings  are  made  in  two  weights, — a  standard  weight 
for  working  steam  pressures  up  to  125  lb.  per  sq.  in.  and  an  extra  heavy 
we^ht  for  working  steam  pressures  up  to  250  lb.  per  sq,  in.  They  are  used 
only  when  brass  piping  is  installed,  which  is  rarely. 


ib.  Google 


§1 
-I 


it 


,Google 


Pipe  fittinga  are  divided  into  two  classes,  screwed  and  flanged.  Screwed 
fittings  are  used  generally  in  the  smaller  sizes.  The  making,  and  more  par- 
ticularly the  breaking,  of  joints  is  much  easier  with  flanged  than  with 
screwed  fittings.  No  hard  and  fast  rule  governs  the  limits  within  which 
each  type  of  Jitting  should  be  used.  Some  authorities  specify  flanged  flttingg 
on  all  lines  2j4  in.  or  larger,  while  others  state  that  all  Jittings  4  in.  or 
larger  should  be  flanged.  The  present  tendency  seems  to  be  to  use  flanged 
Rttings  on  all  lines  larger  than  3  inches. 

Standard  weight  and  extra  heavy  cast  iron  flanged  fittings  are  listed  in 
sizes  from  ^  to  24  inches.  Screwed  fittings  in  the  aame  material  are  listed 
in  sizes  from  J.^  to  12  in.,  in  standard  weight ;  and  from  Yi  to  12  in.,  in  the 
extra   heavy. 

Extra  heavy  cast  steel  flanged  fittings,  for  3S0  lb.  pressure,  and  600  deg. 
total  temperature,  are  listed  in  sizes  from  )!4  to  24  inches.  Similar  screwed 
fittings  are  listed  in  a  more  limited  range,  from  about  3  to  6  inches. 

Iron  pipe-size  brass  flanged  fittings  are  made  in  a  limited  range  in 
standard  weight  (from  about  2  to  6  in.),  but  extra  heavy  brass  flanged  fit- 
tings can  be  obtained  in  any  of  the  extra  heavy  cast  iron  patterns.  Iron 
pipe-size  brass  screwed  fittings  are  listed  for  125  lb.  pressure  in  sizes  varying 
from  about  >£  to  4  in.,  and  in  cast  iron  patterns,  for  steam  pressures  up  to 
250  lbs.,  in  sizes  varying  from   'A   to  6  inches. 

Malleable  iron  screwed  fittings  for  125  lb.  pressure  are  listed  in  sizes 
from  H  to  about  7  inches.  Extra  heavy  malleable  screwed  fittings,  for  250 
lb.  pressure,  are  listed  in  sizes  from  Ifi  to  about  6  inches. 

Only  the  thread  dimensions  of  screwed  fittings  are  standardized.  Un- 
fortunately the  other  principal  dimensions  have  not  been  standardized,  as 
have  those  for  flanges  and  flanged  fittings.  Consequently  the  ditnensions  of 
screwed  fittings  vary  widely  with  the  different  manufacturers. 

The  American  Standard  dimensions  of  flanges  and  flanged  fittings  are 
accepted  and  used  by  nearly  all  manufacturers.  The  complete  standard  in- 
cludes sizes  up  to  100  in.  diameter.  The  standards  most  used,  from  1  to  48 
in.,  are  given  m  Tables  26  to  29,  the  first  two  being  for  125  lb.  and  the  other 
two  for  250  lb.  working  pres.siire.  The  letters  in  the  tables  of  fittings  refer 
to  the  lettered  dimensions  in  Fig.  143. 

The  following  explanatory  notes  apply  to  the  tables  of  flanges  and  flange 
fittings : 

a — Standard  and  extra  heavy  reducing  elbows  carry  same  dimen- 
sions center  to   face  as    regular  elbows  of  largest  straight 


c — All  extra  heav^  fittings  and  flanges  to  have  a  raised  surface 
Vh  in.  high  inside  of  bolt  holes  for  gaskets. 

d — Standard  weight  fittings  and  flanges  to  be  plain  faced. 

e — Bolt  holes  to  be  '/i  in.  larger  In  diameter  than  bolts. 

f— Bolt  holes  to  straddle  center  line. 

g — Face  to  face  dimension  of  reducers,  either  straight  or  eccen- 
tric, for  all  pressures,  shall  be  the  same  face  to  face  as  given 
in  table  of  dimensions. 

h — Square  head  bolts  with  hexagonal  nuts  are  recommended. 

i— For  bolts,  Ij^-in.  diameter  and  larger,  studs  with  a  nut  on 
each  end  are  satisfactory. 

j — Specifications  of  long  radius  fittings  refer  only  to  elbows 
made  in  two  center  to  face  dimensions.  These  are  to  be  known 
as  elbows  and  long  radiua  elbows,  the  latter  being  used  only 
when  so  specified. 


ib.  Google 


The  general  methods  of  conneclittx  pipe  are  by  couplings,  nut  unioni, 
or  flange  unions.    The  first  two  are  screwed  connections,  and  the  last  can 

be  made  with  a  gasket  or  with  metal -to- metal  seats. 

Couplings  are  made  of  cast  iron,  standard  or  extra  heavy,  from  about 
!^  to  3  in.;  of  malleable  iron,  in  standard  weight  from  14  to  6  in.;  of  brass, 
in  standard  weight,  from  ^  to  4  in. ;  and  in  extra  heavy  weight,  from  ^  to  6 
inches.  They  can  be  obtained  in  all  three  materials;  threaded  right-hand, 
or  right  and  left.  Couplings  should  be  used  only  for  the  smaller  sizes  of 
pipe. 


Mi     ^ 


DoubkBronchEtl 


l-M 


LDnsRodiiMCII 


OouUeSrwcpTcc 


SitkOirtmtTtt. 


EacanhicRiductr 


ib.  Google 


T*U«2 

SIZE 

J 
1 

J 

3 

1 

11 

il 

il 

Il 

1 

1 

■B 

1 

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■5 

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II 

A-A 

A 

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c 

D 

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F 

a 

1 

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^\(, 

5 

1H 

7M 

«M 

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4 

i 

3 

^ 

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7H 

■AH 

5H 

2 

8 

ew 

IH 

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3*^ 

4 

m 

aw 

7 

2 

ft 

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4 

2 

4W 

2H 

lOH 

X 

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A*4 

4 

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10 

5 

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«H 

2H 

7 

fiw 

4 

6^ 

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a 

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714 

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4 

3H 

12 

rt 

KH 

3H 

14^^ 

iiH 

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liH 

HH 

4 

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13 

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tt 

4h 

14 

4 

16H 

L2H 

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7h 

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8 

5 

15 

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25 

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iV«if  Bnionr  are  made  with  malleable  iron,  steel  or  brass  bodies,  with 
gaskets  or  with  brass  or  bronze  seats.  The  commercial  size  range  is  from 
J<  to  4  in.,  but  they  are  not  used  in  sizes  larger  than  2  inches.  Nut  unions 
are  not  intended  primarily  for  high  pressure  work;  for  low  or  medium  pres- 
sures however  the  connection  is  satisfactoty  and  easily  broken.  Their  use 
permits  desirable  piping  layouts  and  connections  that  would  otherwise  be  im- 
practicable. Unions  with  brass  or  bronze  seats  arc  usually  preferable  to  the 
all-iron   gasket  type. 


ib.  Google 


ib.Google 


"Ssr-  ".Ssr  '^    9^ 


isS"    "^"^ 


-1H_ 


7!i    I     8 


JM_ 


27  >i 


<3H    I 
46 
48)i    I 


2K    I      « 

2X  I    m 


50H 
S3 

-55M_ 


2H    I      SH 
2K  5M 

2M  5>j 


47K 


SSH 


Ftangt  nttiotti  are  of  two  general  types,  those  with  cast  or  malleable 
bodies  and  brasa-to-brass  or  brass-to-iron  seats,  similar  to  those  of  nut 
unions;  and  those  in  which  a  gasket  is  used. 

The  first  type  is  expensive  and,  although  made  in  sizes  from  yi  to  12  io^ 
its  use  in  practice  is  limited  to  the  smaller  sizes.  It  has  an  advantage  for 
connections  that  must  be  often  broken  and  remade. 

The  second  and  more  common  type  of  flange  union  is  that  in  which  the 
pipe  ends  to  be  connected  are  secured  in  or  by  two  meial  flanges ;  a  gasket 
is  inserted  between  the  flanges  and  the  flanges  are  drawn  together  by  bolts. 
The  most  satisfactory  forms  of  this  type  of  union  are  the  screwed  joint, 
the  peened  joint,  the  lapped  or  Van  Stone  joint,  and  the  welded  joint.  Fig. 
144  gives  examples  of  these  four  joints. 


ib.  Google 


Z88  PIPING 

Table  18.     American   Standard   Dimenrions   for    Flanged    I^ttdnK*    for 


In  the  screwed  joint,  the  flange  is  screwed  on  the  pipe  until  the  pipe 
projects  about  '/>■  in.  beyond  the  face  of  the  flange.  A  facing  cut  is  then 
taken  across  the  face  of  the  flange  and  the  end  of  the  pipe.  The  face  of  the 
flange  should  then  be  square  with  the  axis  of  the  pipe  and  the  gasket  should 
bear  on  the  end  of  the  pipe.  This  joint  is  accepted  for  all  sizes  of  pipe  in 
saturated  steam  lines  with  working  pressures  not  greater  than  125  lb.,  on 
boiler  feed  lines  with  working  pressures  up  to  ISO  lb.,  for  blow-off  lines, 
and  (or  low  pressure  water  lines.  It  Is  also  used  on  medium  and  high  pres- 
sure saturated  and  superheated  steam  lines  and  boiler  feed  lines  in  sizes  up 
to  about  8  inches. 


ib.  Google 


Fig.  144.     Tyi»c«l  PknBe  'Jointa. 


1*  for  Pipe  FlaoflcB  for 

DUlMtM 

IMsusCw 

ThkkiAc 

WMth  o< 

w™^ 

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20 

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ib.Google 


I 

II 


If 

n 


11 


ib.Google 


The  peened  joint  is  formed  by  shrinking  a  flange  onto  the  end  of  the 
pipe,  which  is  peened  or  expanded  into  a  recess  in  the  face  of  the  flange. 
A  light  facing  cut  is  then  taken  across  the  face  of  the  flange  and  the  end 
of  the  pipe.  This  joint  is  belter  than  the  simple  screwed  flange,  especially 
for  sizes  larger  than  6  in.,  but  cannot  be  made  up  well  at  the  place  of  erection. 

The  iapped  or  Van  Stone  joint,  one  of  the  most  flexible  in  use,  is  made 
by  upsetting  and  flattening  the  heated  end  of  the  pipe  so  as  to  form  a  flare 
oi  lap.  The  flared  end  is  faced  to  insure  uniform  thickness  and  a  tjght 
joint.  The  lapped  portion  of  the  pipe  is  also  finished  on  the  edge.  The 
flanges  are  loose  on  the  pq>e,  their  hubs  being  bored  stishtly  larger  than  the 
outside  diameter  of  the  pipe,  and  simply  serve  to  draw  the  lapped  ends  of 
the  pipe  against  a  gasket.  In  some  forms,  the  lapped  part  of  the  pipe  is 
not  of  uniform  thickness  but  tapers  toward  the  edge ;  the  face  of  the  flange 
inside  the  bolt  holes  are  then  faced  to  the  angle  of  inclination  of  the  back 
side  of  the  lapped  part  of  the  pipe.  The  lapped  joint  is  recommended  for 
practically  all  kinds  of  service.  It  is  especially  valuable  on  high  pressure 
fluperfaeated  steam  lines  and  high  pressure  boiler-feed  lines. 

The  welded  joint  is  made  by  welding  a  flange  on  the  end  of  the  pipe. 
Theoretically  thia  is  the  nearest  perfect  of  all  jointa,  because  a  welded  ilange 
becomes  a  part  of  the  pipe  itself.  Its  success  depends  upon  the  care  with 
which  the  weld  is  made.  In  practice  the  welded  joint  is  reliable  and  satis- 
factory and  is  considered  to  be  the  best  for  high  pressures  and  high  de- 
grees of  superheat. 

TTiere  is  little  choice  between  a  well-made  lapped  joint  and  a  well-made 
welded  joint.  Both  are  more  expensive  than  the  simpler  types,  but  in  high 
pressure  work  their  cost  is  more  than  justified. 

Flange  materials.  Cast  iron,  malleable  iron,  cast  steel,  wrought  steel  and 
brass  are  used  for  flanges.  Cast  iron  flanges  are  extensively  used  on  sat' 
urated  steam  lines,  boiler  feed  lines,  and  low  pressure  water  lines. 

Malleable  iron  flanges  are  not  as  common  as  cast  iron  flanges,  but  are 
applicable  to  the  same  service. 

Cast  steel  and  wrought  steel  flanges  are  recommended  for  high  pres- 
sure saturated  and  superheated  steam  lines,  high  pressure  boiler  feed  lines, 
and  blow-ofE  lines. 

Brass  flanges  are  used  only  with  brass  pipe  and  almost  exclusively  in 
the  screwed  type  of  joint. 

The  following  figures,  due  to  the  Crane  Company,  show  the  ultimate 
strength  of  pipe  flange  metals: 

Ultimate  strength. 
Material  Ib.per  sq.  in. 

Cast  iron,  ordinary  grade  ..- 14flOO 

Gray  east  iron,  high  grade .221500 

Malleable  iron  „ _ „37,000 


Valves 

VALVES  control  to  a  great  extent  the  safely  of  a  plant.    Their  location 
determines  the  flexibility  of  the  piping  system,  either  in  normal  opera- 
lion  or  in  times  of  emergency. 

Safety  valves  tor  boilers  generally  must  comply  with  the  specifications 
of  local  or  national  codes.  The  A.  S-  M,  R  Boiler  Code  requires  that  they 
shall  be  of  the  direct  spring-loaded  pop  type,  with  seat  and  bearing  surface 
of  the  disk  either  inclined  at  an  angle  of  about  45  deg.,  or  flat  at  an  angle 
of  about  90  deg.  to  the  center  of  the  spindle. 


ib.  Google 


The  safety  valve  charts.  Figs.  145  and  146,  may  be  used  for  determining 
the  proper  number  and  sizes  of  safety  valves  required.  The  charts  are  made 
up  so  that  it  is  necessary  to  take  only  the  rated  horsepower  of  the  boiler  and 
run  up  the  vertical  line  to  the  slanting  line  corresponding  to  the  relieving 
pressure  desired,  and  the  proper  size  and  number  of  safely  valves  are  indi- 
cated at  tlie  left  of  the  zone  in  which  the  vertical  horsepower  rating  line 
crosses  the  relieving  pressure  line.  If  the  intersection  comes  on  a  zone  divi- 
sion line,  the  smaller  valves  are  to  be  used. 

Example.  One  806  H.P.  boiler  to  operate  at  190  pounds  gage  pressure. 
The  two-valve  chart  stops  below  806  H.P.  Therefore,  wc  must  go  to  the 
three-valve  chart  We  find  that  the  806  H.P.  vertical  line  does  not  inter- 
sect the  190  lb.  pressure  line.  This  indicates  that  more  than  three  valves 
are  necessary.  We  then  take  one-half  the  rated  horsepower,  and  find  that 
two  4  in.  safety  valves  will  relieve  403  H.P,  The  proper  valve  speciiica- 
tion  in  this  case  is  therefore  four  4  in.  safety  valves. 


BOILER   HOR&E   POWER. 

ng.  145,    Rellevinc  Capacitiea  of  Two  A*htoa  Safety  Valvet. 


Fig.  146.    Relieving  Capacitiet  of  Thre«  Achtoa  Safety  Vaivea. 

D,3,tze:Jb.GOOg[e 


Safety  valves  are  also  discussed  in  Chapter  16  on  OPERATION. 

Globe  vahiet,  probabl;  the  most  common  type  of  stop  valve,  can  be  used 
simply  as  a  stop  valve,  or  also  to  partly  throttle  the  flow  of  a  fluid.  These 
valves  should  be  installed  so  as  to  close  against  the  pressure,  because  if 
the  pressure  acts  above  ihe  disk  and  the  latter  becomes  detached  from  the 
stem,  they  cannot  be  opened.  A  further  advantage  in  closing  globe  valves 
against  the  pressure  is  the  ease  of  packing  the  spindle  stuffing  box  when  the 
valve  is  closed.  These  valves  should  not  be  placed  in  a  horizontal  return 
line,  especially  with  the  stem  vertical,  because  the  condensate  must  fill  the 
pipe  about  half  full  before  it  can  flow  through.  The  globe  valve  should 
be  designed  so  that  it  can  be  packed  under  full  line  pressure  and  so  that 
the  disk  or  the  seat  can  be  qtiickly  repaired. 

Valves  with  outside  screws  are  prcfErable  to  those  with  inside  screws, 
unless  the  screw  must  be  protected  because  of  the  valve  location.  The  out- 
side screw  type  indicates  more  quickly  whether  it  is  open  or  closed.  This 
is  especially  true  of  the  type  having  a  rising  stem  or  spindle  and  a  stationary 

Globe  valves  are  made  in  both  screwed  and  flanged  types,  with  brass, 
iron  or  steel  bodies  and  with  composition,  babbitt,  bronxe,  nickel  and  nickel 
alloy  disks  and  seat  rings. 

Standard  pattern  screwed  brass  globe  valves,  rated  for  about  ISO  lb. 
working  steam  pressure  or  250  lb.  working  water  pressure,  are  made  in 
sizes  from  }ii  to  3  inches.  Extra  heavy  screwed  brass  valves,  rated  for  about 
300  lb.  working  steam  pressure,  or  about  500  lb.  working  water  pressure,  are 
made  in  sizes  from  ^  to  3  inches.  Flanged  standard  brass  valve  sii^es  range 
from  14  to  3  inches.  Extra  heavy  flanged  brass  valves  are  made  in  sizes  from 
Si  to  3  inches.  Brass  globe  valves  are  not  commonly  more  than  2  in. 
diameter.  Their  use  is  limited  to  saturated  steam  lines,  boilsr  feed  Imes 
and  water  lines  of  medium  or  low  pressure. 

Standard  pattern  iron-body  screwed  globe  valves,  rated  for  about  150  lb. 
steam  or  250  lb.  water  pressure,  are  made  in  sizes  from  2  to  12  in.,  and  the 
same  type  Hange  is  made  in  sizes  from  2  to  24  inches.  Extra  heavy  iron-body 
globe  valves,  rated  for  about  250  lb.  steam  or  4O0  lb.  water  pressure,  are 
made  in  either  screwed  or  flanged  types,  and  in  sizes  from  2  to  12  inches. 
Iron-body  valves  with  disks,  seat  rings  and  spindles  of  other  materials,  are 
satisfactory  for  saturated  steam  lines,  boiler  feed  lines  and  water  lines  with 
pressures  up  to  their  ratings,  but  are  not  so  good  as  steel  valves  for  pres- 
sures over  150  pounds.  Valves  5  in.  and  larger  should  be  equipped  with 
by-passes,  especially  for   the   higher  pressures. 

Steel  valves  should  be  used  in  superheated  steam  lines  and  high  pres- 
sure feed  lines.  These  are  made  in  sizes  from  2  to  12  in.,  in  the  extra 
heavy  weight,  and  are  rated  for  350  lb.  working  steam  pressure. 

Disks  for  globe  valves  arc  made  of  a  wide  variety  of  materials.  Com- 
position disks  are  made  in  several  grades ;  .wf t  for  low  pressure  water, 
rubber  for  cold  water  up  to  250  lb.  pressure,  semi-hard  for  hot  water  and 
boiler  feed  lines,  hard  for  steam  lines  up  to  150  lb.  pressure.  Babbitt  metal 
disks  arc  often  used  in  low  pressure  hot  water  and  steam  lines.  Brass  or 
bronze  disks  are  used  in  high  pressure  saturated  steam  lines  and  feed  lines, 
.Ihe  harder  grades  for  the  higher  pressures.  Nickel  and  alloys  high  in  nickel 
are  recommended  for  the  highest  pressures  and  for  superheated  steam.  Valve 
seats,  or  at  least  seat  rings,  should  be  made  of  non-corrosive  metal  of 
characteristics   similar  to  those   required   of  metallic   disks. 

Gate  valves  offer  a  minimum  resistance  to  the  flow  of  a  fluid,  but  when 
throttled  are  hard  to  regulate  and  are  likely  to  chatter.  They  are  made  of 
the  same  materials  as  globe  valves  and  are  applicable  to  the  same  types  of 
i^ervice,  except  for  throttling.  For  high  class  installations,  particularly  in 
the  larger  sizes,  gate  valves  represent  the  best  standard  practice.  By-passes 
should  be  used  with  high  pressure  gale  valves  of  6-in.  or  larger  diameter. 


ib.  Google 


A  stop  valve  should  not  be  placed  in  a  vertical  iteam  line,  unless  it  is 
possible  to  drain  the  condensate  that  collects  above  the  valve  seat  when  the 
valve  is  closed.  , 

Aulomalic  nott-reiuni  valves  should  be  installed  on  each  boiler  when  the 
plant  contains  more  than  one.  These  valves  automatically  equalize  the  pres- 
sures of  the  different  boilers,  thereby  lending  to  equalize  the  loads.  They 
can  be  used  to  cut  in  or  cut  out  boilers  automatically,  will  automatically  cut 
a  boiler  oR  the  line  in  case  of  an  internal  rupture,  and  will  prevent  steam 
being  accidentally  turned  into  a  cold  boiler. 

These  automatic  valves  are  made  in  many  forms,  all  essentially  check 
valves,  although  they  may  be  slop  valves  as  well.  The  control  can  be  re- 
mote non-automatic,  as  well  as  hand  and  automatic,  so  that  their  automatic 
action  can  be  tested  at  any  time. 

The  non-return  valve  should  be  carefully  made  and  should  be  extreme^ 
rugged,  because  it  is  subjected  to  ereat  stresses.  It  is  usually  attached  di- 
rectly to  the  boiler  nozzle,  so  that  tne  boiler  must  be  shut  down  if  the  valve 
has  to  be  repaired.  Besides  the  non-return  valve,  a  gate  valve  should  be 
placed  between  each  boiler  and  the  header  or  main,  b^ond  the  non-return 
valve. 

Check  vah-i's.  Aniong  these,  the  ball  check  is  uncommon.  The  weighted 
check  is  more  popular,  as  it  can  be  used  as  a  combination  relief  valve  and 
check.  The  disk  check  has  much  the  same  body  as  a  globe  valve  and  offers 
about  the  sanie  resistance  to  flow.  The  swing  check,  by  far  the  most  com- 
mon, is  simple,  effective  and  offers  the  least  resistance  to  flow. 

A  check  valve  is  subject  lo  severe  service  and  must  be  so  designed  that 
its  disk  and  seat  can  be  repaired.  In  essential  lines,  such  as  boiler  feed 
lines,  a  check  valve  should  be  protected  by  a  stop  valve  on  each  side,  so 
that  a  defective  disk  can  be  repaired  without  taking  the  pressure  off  the 
line.  For  feed  lines  to  boilers  in  continuous  operation,  or  when  regulating 
valves  are  subjected  to  severe  usage,  both  the  check  valve  and  the  regulating 
valve  should  be  protected  by  a  slop  valve  on  each  side  of  the  tv^o ;  the  stop 
valves  are  normally  wide  open  and  are  closed  only  when  either  the  check 
or  the  regulating  valve  must  be  repaired. 

Combination  stop  and  check  valves  are  used  frequently  in  boiler  teed 
lines  and  can  be  combined  with  regulating  valves  to  reduce  the  number  of 
valves   required   to   obtain   a   fair   protection. 

In  blovi-off  connections,  three  types  of  valve  are  commonly  used ;  a 
specially  designed  blow-ofi  valve,  a  blow-off  cock,  and  a  gate  valve.  In  the 
best  practice  a  special  blow-off  valve  and  either  a  cock  or  a  gate  valve  are 
installed  in  each  blow-off  connection  between  the  boiler  and  the  blow-off 
main,  the  cock  or  gate  valve  being  located  next  to  the  boiler.  The  cock  or 
gate  valves  should  be  opened  first  and  closed  last,  when  blowing  down,  so 
as  to  reduce  the  wear  on  them,  and  so  that  they  can  be  depended  upon  to 
hold  pressure  when  the  regular  blow-off  valve  is  being  repaired.  Plug  cocks 
are  satisfactory  for  this  service,  especially  on  boilers  operated  at  low  or 
medium  pressures,  but  a  gate  valve  is  better  and  can  more  easily  be  used 
as  a  wash-out  valve.  Plug  cocks  should  be  equipped  with  a  spring  or  other 
compensating  device,  to  automatically  take  up  wear.  Steel  or  iron  blow-off 
valves,  gate  valves  and  cocks  should  be  extra  heavy,  steel  being  preferable 
for  the  higher  pressures  and  temperatures.  Valve  disks  and  seats  should 
be  so  arranged  that  they  can  be  repaired.  Blow-off  service  is  severe  and  is 
particularly  harsh  when  scale  and  sediment  is  present  in  quantity. 

The  manufacturers  have  proposed  that  blow-off  valves  for  power  boilers 
operating  with  pressures  up  to  250  lb.  be  made  only  in  the  extra  heavy  pat- 
tern and  in  the  1,  V/i,  2  and  2'/i-in.  sizes;  the  1-in.  size  to  be  screwed,  the 
lyi  and  2-in.  sizes  screwed  or  flanged,  and  the  2'/i-'m.  size  flanged. 


ib.  Google 


Blow-Off  Piping.  Each  boiler  should  have  its  own  blow-off  pipe.  This 
should  end  in  the  boiler  room,  or  where  discharge  on  account  of  a  leaky 
valve  will  be  sure  to  attract  attention.  In  most  cities  hot  water  is  not  per- 
mitted to  be  discharged  into  the  sewer.  A  blow-off  tank  is  then  placed  at  a 
sufficient  height  that  it  will  drain  by  gravity  into  the  sewer.  This  tank 
should  be  provided  with  a  man-hole,  an  open  vent  pipe,  and  with  inlet  and 
outlet  pipes  connected  with  the  blow-off  pipe  and  the  sewer  respectively.  A 
valve  should  be  placed  in  the  outlet  pipe. 

In  horizontal  return  tubular  boilers,  the  blow-off  pipe  should  be  covered 
with  magnesia,  asbestos  or  fire  brick  where  it  passes  through  the  back  con- 
nection. It  can  be  protected  by  a  connection  from  it  to  the  boiler  just 
below  the  water  line.  In  this  way,  water  is  continually  circulated,  and  the 
blow-off  pipe  will  not  bum.  A  valve  should  be  placed  in  this  connection,  and 
closed  before  the  blow-off  cock  is  opened. 

Reference  should  also  be  made  to  Chapter  16  on  OPERATION. 

Size  of  Steam  Pipes 

ASIDE  from  the  attraction  of  gravity,  a  fluid  flows  through  a  pipe  only 
because  the  pressure  at  one  end  is  greater  than  that  at  the  other.  The 
higher  the  velocity  desired,  the  greater  must  be  the  difference  between  initial 
■nd  final  pressures. 

The  problem  of  selecting  a  pipe  to  conduct  a  given  quantity  of  steam  or 
water  in  a  given  time  therefore  resolves  itself  into  striking  a  balance  between 
high  velocity,  which  requires  a  high  pressure  drop  but  permits  the  use  of 
a  small  pipe ;  and  low  velocity,  which  requires  a  large  pipe  but  can  be 
obtained  with  a  small  drop  in  pressure. 

The  drop  in  pressure  caused  by  friction  does  not  represent  an  equivalent 
loss  of  energy,  because  the  energy  reappears  .?s  heat.  If  the  steam  enter- 
ing the  pipe  line  is  wet,  this  heat  tends  to  evaporate  the  moisture  in  the 
steam.  If  steam  is  dry  when  it  enters  the  line,  the  heat  tends  to  superheat 
it,  or  if  it  entered  as  superheated  steam,  to  add  to  its  superheat.  The  equip- 
ment to  which  the  steam  is  delivered  and  in  which  it  is  used  determines 
whether  this  heat,  gained  at  the  expense  of  a  drop  in  pressure,  is  utilized  or 
wasted.  If  it  is  utilized,  the  net  loss  due  to  friction  is  negligible;  if  not.  the 
pressure  consumed  in  overcoming  friction  becomes  a  loss. 

The  use  of  a  high  veloci^  reduces  the  size  of  steam  mains  and  thereby 
directly  reduces  the  Toss  by  radiation  and  the  cost  of  the  equipment.  Steam 
velocities  of  from  3SO0  to  fiOOO  tL  per  min.  have  been  common  in  the  past, 
but  in  present  practice  velocities  are  from  12,000  to  20,000  ft.  per  min.  This 
increase  has  occurred  partly  because  superheated  stenm  is  being  more  com- 
monly used  and  also  because  prime  movers  utilize  the  superheat  from  pipe 
friction  to  reduce  their  steam  consumption.  Pipe  friction  represents  an 
absolute  toss  if  the  steam  consumption  of  an  engine,  pump  or  other  apparatus, 
instead  of  being  reduced  because  of  the  superheat,  is  increased  because  of 
the  lower  pressure. 

It  has  been  determined  analytically  and  experimentally  that  the  pressure 
loss  due  to  the  steady  flow  of  a  fluid  through  a  pipe  of  uniform  diameter 
varies  with  the  density  of  the  fluid,  is  proportional  to  the  length  of  the  pipe, 
decreases  as  the  diameter  of  the  pipe  increases,  increases  with  the  roughness 
of  the  interior  surface,  and  increases  nearly  as  the  square  of  the  velocity. 

The  old  method  of  basing  steam  pipe  sizes  on  the  velocity  of  the 
steam,  has  given  place  to  the  more  correct  method  of  determining  the  pipe 
diameter  in  accordance  with  the  drop  of  pressure  allowable.  It  is  almost 
immaterial  what  the  veloci^  may  be  so  long  as  this  pressure  drop  condition 
is  met. 


ib.  Google 


The  formula  generally  used  i: 


'■(■.-f) 


P:=I>rop  in  pressure,  lb.  per  aq.  in. 
JV  =  Weight  of  steam  flowing,  lb.  per  min. 
h  =  Length  of  pipe,  feet 
d^  Internal  diameter  of  pipe,  inches 
w^Mean  density  of  steam,  lb.  per  cu.  fi. 

This  formula,  as  simplified  hy  Sfitsglas  (Armour  Engineer.  1917),  is: 


W  ^  Weight  of  steam  in  pounds  per  second 
P  =■  Pressure  drop  in  pounds 
it>=:  Mean  density  of  steam 
h  =  Length  of  pipe  in  feet 


100     for  16 

in.  pipe 

TOO     for  14 

in.  pipe 

SSO     for  12 

m.  pipe 

J50     for  10 

■n.  pipe 

195     for    8 

in.  pipe 

97     tor    6 

in.  pipe 

60     for    5 

in.  pipe 

32.S  for    4 

in.  pipe 

1S.S  for    3 

in.  pipe 

8.S  for    2V, 

in.  pipe 

5.1  for    2 

in.  pipe 

2.5  for    VA 

in,  pipe 

tl.7Sfor     I 

in.  pipe 

GebhardI  says  that  this  formula  (19)  gives  results  which  accord  closely 
with  observation,  and  as  it  is  more  convenient  to  use  than  (18)  it  is  lo  be 
preferred.  To  facilitate  the  determination  of  steam  pipe  sizes,  the  following 
charts;  Figs.  147,  148,  149.  150  and  151,  have  been  prepared  in  accordance 
with  the  above  values  of  k  as  determined  by  Spitsgias.  Particular  care 
has  been  taken  to  make  them  very  easy  lo  use.  The  following  inalnictions 
will  make  this  quite  clear : 

Saturated  Steam. 

1.  Enter  the  lower  left-hand  scale  with  the  weight  of  steam  to  be  carried 
in  pounds  per  hour. 

2.  Proceed  vertically  to  the  proper  curve  of  pressure,  which  is  the 
initial  pressure  at  the  entrance  of  the  pipe. 

3.  From  this  intersection,  proceed  horizontally  to  the  right  to  the  curve 
of  pressure  drop  per  100  feet. 

4.  Proceed  vertically  downwards  from  this  intersection  to  the  lower 
right-hand  scale  and  read  the  size  of  pipe  required. 


ib.  Google 


1^ 


ib.Google 


ib.Google 


ib.Google 


*l 


ib.Google 


Superkeoted  Steam. 

Enter  the  lower  scale  of  Fig.  151  with  the  pressure  at  the  pipe  e 
and  proceed  vertically  upwards  to  the  proper  curve  of  the  temperature  of 
the  saturated  steam  (not  degrees  of  superheat).  Proceed  from  this  inter- 
section horiiontally  to  the  right,  and  read  the  pressure  found  on  the  right- 
hand  scale.  Now  proceed  as  directed  above  Cor  saturated  steam,  using  as 
initial  pressure  the  pressure  just  found  from  Fig.  151. 

The  reason  of  this  procedure  is  that  the  steam  flow  depends  upon  the 
average  density  of  the  steam,  and  Fig.  151  simply  finds  a  pressure  at  which 
saturated   steam   has  the  ;ame   density  as  that  of   the  superheated   steam   in 

To  find  the  weight  of  steam  per  hour,  divide  the  equivalent  evaporation 
per  hour  hy  the  factor  of  evaporation.  Or  multiply  the  B.H.P.  by  34.5  and 
divide  by  the  factor  of  evaporation. 

The  pressure  drop  is  for  100  feet  of  pipe,  and  (he  drop  for  any  other 
length  is  in  direct  proportion. 

The  drop  of  pressure  per  hundred  feet  varies  in  old  installations  from 
half  a  pound  to  five  pounds.  Modem  practice  allows  two  to  four  pounds 
pressure  drop  per  hundred  feet.  The  final  result  is  governed  in  each  instance 
by  the  smallness  of  pressure  drop  desired,  modified  by  the  cost  of  the  pipe 
required  to  attain  it. 

Formulas  for  ihe  length  of  pipe  with  resistance  equivalent  to  that  offered 
by  valves  and  fittings,  give  results  that  vary  widely  and  are  of  little  practical 
assistance.  It  is  therefore  customary  to  assume  the  following  values  for 
resistance : 

Obstruction  Pipe  Diameters 

Entrance  of  pipe  60 

90  deg.  elbow  40 

Globe  valve  60 

The  resistance  of  long  radius  bends  is  assumed  to  be  equal  to  the  same 
length  of  straight  pipe.  The  resistance  of  gate  valves  is  considered  negligible. 

In  the  steam  flow  formulas,  the  figure  for  density  should  represent  the 
mean  density  of  the  steam  in  the  pipe.  The  point  of  mean  density  may  or 
may  not  coincide  with  the  middle  section  of  a  given  pipe,  for  if  the  fittings 
are  numerous  at  or  near  one  end  and  few  at  the  other,  the  pressure  drop 
and  consequently  the  density  will  vary  accordingly.  For  exact  calculations, 
and  for  well  insulated  pipes,  the  change  in  density  due  to  superheat  by  fric- 
tion should  be  considered. 

Size  of  Water  Pipes 

FORKfULAS  for.  the  flow  of -mater  in  pipes  are  based  upon  the  fundamental 
hydraulic  equation  used  in  deriving  the  steam  flow  formulas,  although  the 
coefficient  of  friction  is  different.  (Sebhardt  gives  the  following  formula, 
credited  to  Cos.  for  the  loss  of  head  due  to  friction  in  water  pipes : 

/^..-'i_^-+-_S'-:^I*  (20) 

1200rf 
H  =  Friction  head,  feet 
V  =  Velocity,  ft.  per  sec. 
ft  =  Length  of  pip^  feet 
J  =  Diameter  of  pipe,  inches 

This  formula  applies  only  to  the  flow  of  water  through  clean  straight 
cylindrical  pipes  of  uniform  diameter.  The  friction  head  caused  by  bends. 
valves,  fittings  or  obstructions  must  be  added  to  the  friction  head  of  the 
pipe,  in  order  to  determine  the  total  head  required  to  overcome  friction. 


ib.  Google 


ib.Google 


The  losses  due  to  obstructions  can  be  determined  by: 

2g  (21) 

H  =  Friction  head,  feet 
k  ^  Constant 
r  =  Velocity,  fL  per  sec. 
{■  =  Acceleration  due  to  gravity 
For  the  constant  k,  Gebhardt  gives  the  following  values; 

45  deg.  ell - 0.182 

90  deg.  ell  0.98 

Gate  valve  „.-.0.182 

Globe  valve  „ 1.91 

Angle  valve  -2.94 

The  friction  caused  by  valves  and  fittings  can  be  expressed  in  terms  of 
equivalent  length  of  straight  pipe;  the  following  values  are  used: 
Obstruction  Pipe  Diameters 

45  deg.  ell  „ 6 

90  deg.  cH 30 

90  deg.  tec 60 

Gate  valve 6 

Globe  valve  „.  60 

Angle  valve  _ - 90 

Bend,  with  radius  equal  pipe  diaineeer-..  20 

Bend,  with  radius  equal  2  to  8  diameters  10 

Water  velocities  in  power  plant  practice  range  from  SO  to  400  ft  per 

minute.    The   velocities   in   suction  lines,  especially   in  those   carrying  hot 

water,  should  be  from  7S  to  ISO  ft.  per  minute.    A  velocity  of  from  SM  to 

400  ft.  per  min.  is  common  in  boiler  feed  lines. 

Expansion  and  Contraction 
■  I  HE  expansion  and  contraction  of  piping  because  of  temperature  changes 
*■  is  large  enough  to  demand  careful  consideration.  Higher  pressures  and 
higher  degrees  of  superheat  emphasize  the  importance  of  the  subject,  as  does 
also  the  increasing  use  of  efficient  insulating  materials.  Formerly  it  was 
assumed  that  radiation  from  the  surface  of  a  pipe  reduces  its  expansion  to 
about  half  the  theoretical  amount,  but  actual  tests  have  shown  that  the 
expansion  of  well -insulated  pipe  closely  approaches  the  theoretical  value. 

The  amount  a  pipe  will  expand  depends  upon  its  initial  length,  the  rise 
in  temperature  to  which  it  is  subjected,  and  the  coefficient  of  linear  expansion 
of  the  material.    This  statement  is  expressed  by  the  following  formula : 

i  =  C  A  ((,  —  0  (22) 

1-=  Expansion,  inches 

C  =  GDefficient  of  linear  expansion,  per  deg.  F. 
k  :=  Initial   length,   inches 
t  =  Initial  temperature,  deg.  F. 
ti  ^  Final  temperature,  deg.  F, 
The  coefficient  of  linear  expansion  is  not  constant  at  all  temperatures. 
In  calculating  the  expansion  of  piping,  the  mean  coefficient  must  be  used. 
The  coefficients  of  expansion  of  cast  iron  at  different  temperatures  have  the 
following  values : 

Deg.  Coefficient 

100 „ oxwoooeoo 

ISO  , 0.00000612 


ib.  Google 


Si 


,Google 


The  coefficient  of  linear  expansion  of  other  materials  can  be  obtained 
by  multiplying  these  values  by  1.1  for  wrought  mild  steel,  1.5  for  wrought 
copper,  and  1.6  for  wrought  brass.  Table  3C^  due  to  Gebhardt,  gives  the 
mean  coefficient  of  Ibear  expansion  of  materials  for  different  temperature 
ranges. 

Table  30.     CoefBciente  of  Linear  E»panrion  of  H|mi>k  Materlala. 


Wrought  iron  and  mild  steel 

Wrought  iron 

Cast  iron 

Cast  steel 

Hardened  steel 

Nickel-steel,  30  per  cent  nickel. 

Copper,  cast 

Copper,  wrought 

Brass  wire  and  sheets 


0.000009S5 
0.00001092 
0.00001043 
0.00001075 


Table  31.     Increase  of  Length.  In  Inches  per  100  Feet,  of  Steam  Pipes. 


-^r 

CMtlron 

Wrsucht  Iron 

suti 

60 
100 
126 

0.38 

0.72 
0.88 

0.40 
0.79 

0.97 

0.38 
0.76 
0.92 

0.67 
1.14 
1.40 

160 
176 
200 

1.10 
1.2S 
1.50 

1.21 
1.41 
1.65 

1.15 
1.34 
1.67 

1.76 
2.04 
2.38 

225 
250 

276 

1.70 
1.90 
2.15 

1.87 
2.09 
2.36 

1.78 
1.99 
2.26 

2.70 
3.02 
3.42 

300 
325 
360 

2,35 
2.60 
2.80 

2.68 
2.86 
3.08 

2.47 
2.73 
2.94 

3.74 
4.13 
4.46 

375 
400 
425 

3.15 
3.30 
3.68 

3.46 
3.63 
4.05 

3.31 
3.46 
3.86 

5.01 
6.24 
6.86 

6.18 
6.68 
7.06 


4.76 
6.05 
6.36 


5.22 
5.56 
6.00 


625 
650 

6.05 
6.40 

6,65 
7.06 

6.35 
6.71 

9.62 
10.18 

675 
700 
726 

6.78 
7.16 
7.68 

7.46 
7.86 
8.33 

7.12 
7.50 

7.96 

10.78 
11.37 
12.06 

760 
776 
800 

8!42 
8.87 

■     8:75 
9.26 
9.76 

8!84 
9.31 

12.66 
13.38 
14.10 

ib.Google 


^proximate  values  for  the  linear  expansion  of  steam  pipes  of  cast  iron, 
wrought  iron,  steel,  brass  and  copper  as  given  in  Mackmer^t  Handbook, 
will  be  found  in  Table  31. 

If  the  ends  of  a  pipe  were  fixed  and  the  pipe  were  heated,  the  tendency 
to  expand  would  create  a  compressive  stress.  For  the  temperature  changes 
common  in  power  plants  this  stress  would  far  exceed  the  compressive  strength 
of  the  material.  The  axial  force  exerted  by  expanding  or  contracting  pipe 
can  be  calculated  as  follows : 

P  =  C  E  A  ((.  —  ()  (23) 

P  :=  Axial  force,  pounds 
Cr^  Cocffident  linear  expansion 
B  ^=  Modulus  of  elasticity 
A  ^  Sectional  area  of  pipe  wall,  tq.  in. 
t  ~  Initial  temperature,  deg. 
t,  =  Final  temperature,  deg. 
The  moduli  of  elasticity  of  materials  are  as  follows: 


Steel 

300000CO 

Copper 

__ „ lofloosm 

According  to  this  formuliL,  a  6-in.  extra  heavy  wrought  iron  pipe  200 
ft.  long,  if  heated  or  coined  through  a  temperature  range  of  300  deg.,  exerts 
an  axial  force  of  573,750  pounds.  The  sectional  area  of  the  metal  of  the  pipe 
is  8.5  sq.  in.  so  that  the  unit  stress  produced  is  much  larger  than  the  ultimate 
strength  of  the  material.  A  temperature  range  of  300  deg.  is  by  no  means 
uncommon,  so  that  for  runs  much  shorter  than  the  one  assumed,  piping  must 
be  free  to  expand  or  contract,  and  its  expansion  must  be  so  controlled  and 
directed  that  it  will  not  strain  connections,  valves  or  fittings. 

Pipe  Anchors 

THE  expansion  of  piping  cannot  be  limited,  but  its  direction  can  be  pre- 
determined by  anchoring  one  end,  both  ends  or  the  middle  of  a  run.  If 
one  end  is  anchored,  the  expansion  must  be  absorbed  at  the  free  end  of  the 
line.  If  both  ends  are  anchored,  the  expansion  will  be  from  them  toward  the 
middle  of  the  run  and  must  be  absorbed,  preferably  at  some  one  place.  With 
center  anchorage  the  expansion  is  forced  toward  the  free  ends  of  the  line, 
where  it  must  be  absorbed. 

Anchors  must  be  firmly  fastened  to  a  rigid  and  heavy  part  of  the  power- 
plant  structure,  and  must  also  be  securely  fastened  to  the  pipe.  If  the  pipe 
IS  not  prevented  from  moving  at  the  point  at  which  the  anchor  is  applied, 
the  entire  equipment  for  absorbing  expansion  is  useless,  and  severe  stresses 
will  be  thrown  on  all  parts  of  the  piping  system.  When  both  ends  of  a 
straight  run  are  anchored  with  an  expansion  joint  between,  the  end  thrust 
is  the  steam  pressure  multiplied  by  the  cross -sectional  area  of  the  pipe  at  its 
largest  diameter.  With  slip  joints  like  Fig.  153,  the  area  is  that  of  the  out- 
side diameter  of  the  sleeve ;  and  with  corrugated  joints  as  Fig.  154,  or  their 
equivalent,  the  largest  inside  diameter  of  the  corrugations  is  to  be  taken. 
Thus,  a  IZ-inch  pipe  with  a  slip-joint  carrying  steam  at  250  lbs.,  will  develop 
an  end  thrust  of  nearly  17  tons,  and  it  may  be  greater  than  this  with  a 
corrugated  joint. 

Expansion  Joints 
iPE  bends  offer  a  satisfactory  means  of  providing  for  expansion.  The 
radius  of  a  bend  should  not  be  less  than  five  pipe  diameters.  The  pipe 
should  be  straight  on  each  end  for  a  distance  equal  to  twice  its  diameter. 
Pipe  bends  should  be  fitted  with  extra-heavy  lapped  or  welded  flanges,  be- 
cause the  joints  are  subjected  to  severe  stresses.  Expansion  is  absorbed  by 
a  bend  only  because  it  is  sprung  out  of  normal  shape,  thus  permitting  the 
line  to  expand. 


P- 


ib.Google 


Pic-  153.    TyjAcal  IHpe  Anchors. 

Table  32,  due  to  the  Crane  Company,  shows  the  linear  expansion  pos- 
sible with  quarter  bends.  The  expansion  values  can  be  multiplied  by  2 
tor  "U"  bends,  by  4  tor  Eingle  offset  bends  or  "Expansion  U"  bends, 
and  by  5  for  double  offset  bends  or  circle  bends.  The  values  given  do 
not  take  into  consideration  the  springing  of  the  bends  when  installing  them. 
When  a  bend  is  sprung  a  distance  equal  to  that  in  the  table,  twice  the  linear 
expansion  given  can  be  absorbed. 

Springing  pipes  when  cold,  so  that  they  are  then  under  tension,  in- 
creases the  linear  expansion  that  can  be  cared  for,  and  affords  relief  to  lines 
used  almost  continuously  at  or  near  their  maximum  temperature. 


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the  table  show  different  designs. 

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ib.  Google 


ib.Google 


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anchor  bases,  and  with  traverses  up  to  about  10  inches.  In  the  second  type, 
expansion  is  cared  £or  by  the  axial  spring  of  a  corrugated  copper  pipe. 
For  high  pressures,  the  copper  is  re-enforced  by  inner  and  outer  iron  equaliz- 
ing rings.    Both  types  are  useful  when  lack  of  space  prevents  the  use  of  pipe 

Fig.    153   illustrates   the   Ross   expansion   joint,   showing   the   guide   for 
maintaining  the  pipes  in  alignment. 


Fig.  153.     Row  Croishead  Ouided  Expanaioo  Joint. 

The  piping  between  the  anchors  should  be  carefully  lined  up  so  that 
there  will  be  no  tendency  for  it  to  spring  or  buckle  it  the  slip  joint  is  loo 
tightly  packed.  Bolts  are  necessary  to  prevent  the  sleeve  being  drawn  out 
by  such  circumstances  as  the  failure  of  an  anchor. 

Fig.  154  is  the  Badger  corrugated  copper  expansion  joint,  showing  the 
reinforcing  rings  which  he  in  the  corrugations  and  relieve  the  copper  pipe 
of  carrying  the  pressure. 


Pig.  154.     Badger  Self-BqualUing  Bipansion  Jmnt. 


ib.  Google 


The  number  of  corruKations  is  dependent  upon  the  amount  of  expansion 
to  be  absorbed. 

2  corrugations  take  care  of  1       in.  expansion. 

3  corrugations  tahc  care  of  V/i  in.  expansion. 

4  corrugations  take  care  of  2      in.  expansion. 

The  advantage  of  this  type  of  joint  is  that  no  packing  is  required. 

Donbte-s^iring  Uttingi  are  satisfactory  for  small  piping  in  short  runs,  but 
not  for  heavy  pipes  or  long  runs.  For  a  really  good  expansion  joint,  the 
threads  of  the  screwed  connections  should  be  carefully  cut  and  then  ground 
in.  It  is  hardly  to  be  expected  that  a  screwed  connection  can  bo  steam- 
tight,  and  at  the  same  time  permit  easily  any  movement  in  fitting  the  pipe. 

Stvivel  Joints  are  similar  to  the  double-swing  screwed  fittings,  without 
the  disadvantage  of  the  latter.  They  can  be  used  for  lines  containing  flanged 
fittings,  or  when  pipe  bends  cannot  be  installed. 


Pig.  155.   Three  CIbstci  of  Pipe  Supports — Hangeti,  StandardB,  andBrackets. 


ib.  Google 


gCQ 


SI 


ib.Google 


FltxMe  mclollii:  lubing  is  excdlcTit  for  absorbing  expansion  in  small 
pipes.  Care  must  be  taken  that  it  is  not  subjected  to  thrust  or  tension.  It 
nniBt  be  arranged  in  the  same  manner  as  Pifie  bends  jnst  described. 


Supports  and  Hangers 
^IPE  supports  and  hangers  vary  of  necessity  with  the  plant  layouts,  but 
^  their  construction  is  fairly  well  standardized.  Pipe  supports,  Fig.  155, 
can  be  divided  roughly  into  three  classes, — hangers,  standards  and  brackets. 
Hangers  are  used  for  supporting  piping  from  ceilings  and  overhead  structural 
members ;  standards  for  supporting  piping  on  and  from  engine  and  boiler 
room  floors ;  and  brackets  for  supporting  piping  on  and  from  walls  and 
vertical  structural  members. 

The  plainer  and  lighter  types  of  pipe  hanger  can  be  used  for  short  runs, 
with  steam  or  water  lines  up  to  about  6  in.  diameter.  On  long  runs  they 
can  be  used  if  the  connection  between  the  hanger  ring  and  the  ceiling  is  long, 
and  if  its  upper  end  is  not  rigidly  attached  to  the  ceiling. 

For  large  pipe,  long  runs  or  when  the  supporting  strap  must  be  short  or 
rigid,  the  hanger  should  be  equipped  with  one  or  more  rollers,  The  support 
for  high  temperature  lines  should  be  equipped  with  a  lower  roller  and  also 
with  a  roller  resting  on  the  top  of  the  pipe.  The  upper  roller  should  be 
bolted  liy  tie-rods  to  the  support.  Springs  should  be  placed  between  the  sup- 
port and  the  rods,  so  that  the  latter  can  move  slightly.  Supports  for  large 
■  or  heavy  mains  should  be  adjustable  to  maintain  alignment. 


Steam  Separators 

TO  protect  plant  equipment  and  obtain  economical  operation,  all  piping 
systems  should  be  provided  with  separators  to  eliminate  entrained  mois- 
ture, condensate  oil,  grease  or  other  foreign  matter.  Moisture  carried  into  the 
steam  cylinder  lessens  the  economy  in  steam  and  lubricants,  and  may  also 
rause  damage.  Oil  in  exhaust  sieam  fouls  the  condensate,  lodges  in  condensers, 
accumulates  on  turbine  blades,  and  on  the  inner  surfaces  of  radiators,  and 
renders  the  condensate  unsuitable  for  boiler  feed. 

The  function  of  a  steam  separator  is  to  deliver  clean,  dry  steam.  Steam 
separators  are  used  on  live  and  superheated  steam  lines.  The  oil  separator 
extracts  the  grease,  leaving  a  condensate  that  is  pure  distilled  water  and 
therefore  suitable  for  boiler  feeding  or  for  industrial  processes.  Oil 
separators  are  used  on  exhaust  and  vacuum  steam  lines,  for  low  pressure 
turbines,  feed  water  heaters,  condensers  and  heating  systems. 

Steam  and  oil  separators  operate  either  by  intercepting  the  steam  cur- 
rent, or  by  changing  its  direction.  Cast  iron  bodies  having  various  shaped 
grids  in  tile  f'lrm  of  single  or  multiple  baffles  are  ordinarily  used  for 
separators.  The  accumulated  matter  is  drawn  off  intermittently  or  is  taken 
care  of  continuously  by  a  trap. 

The  separators.  Figs.  156,  157  and  158,  are  practical  designs  intended  for 
vertical,  horizontal  or  angle  pipe  connection.  A  single,  ribbed  baffle  has  a 
steam  port  at  each  side ;  below  it  is  the  collecting  well  with  its  water  gage 
column.  Steam  entering  from  one  end  of  the  pipe  line  impinges  on  the 
baffle,  where  it  leaves  the  water  or  oil,  and  continues  on  around  cither  side 
of  it,  through  the  sleam  ports.  The  intercepted  water  or  oil  is  directed, 
by  the  ribs  on  the  baffle,  down  to  the  well.  A  drain,  to  catch  any  con- 
densation, is  also  provided  on  the  "dry"  or  steam  outlet  side. 


ib.  Google 


Fis.     1S6.     Horizontal  and  Vertical  Steam  Separators. 


L 


Fig.  157.     Horiioatal  and  Vertical  Oil  Separatort. 


ib.  Google 


The 

may  have 
of  piping 


-  lyfie  separators.  Fig.  1S8,  are  usually  made  of  plate  and 
riveted  or  welded  joints.  This  construction  is  used  when  long  lines 
might  be  subject  to  violent  vibration.  The  large  receiver  serves 
k'oir  for  steam  and  is  useful  to  supply  the  intermittent  demand  of 
a  slow  speed  engine,  and  receives  any  inrush  of  water  from  the  main.  The 
water  in  the  receiver  is  stored  until  a  trap  drains  it  away.  The  steady  flow 
of  Steam  resulting  from  the  installation  of  a  receiver  separator  often  makes 
possible  the  use  of  smaller  mains,  which  decrease  the  first  cost,  and  reduce 
the  loss  of  heat  by  radiation. 


Fig.  I5B.     Horizontal  and  Vertical  Rccriver  Separator 


ib.  Google 


h 


Sj5 
II 


HI 

II 


If 


■i! 

SI 


ib.Google 


CHAPTER  9 


AUXILIARIES 

Quantity  of  Peed  Water 

THE  qiuntity  of  feed  water  required  per  hour  is  the  B.H.P.  to  be  devel- 
oped, multiplied  by  34,5,  and  divided  by  the  factor  of  evaporation.  To 
allow  some  margin,  the  division  by  the  factor  of  evaporation  is  omitted. 
As  there  are  8,3  lb.  of  water  to  (he  gallon,  the  rate  becomes  4.15  gallons  per 
hour  or  0,C7  gal,  per  minute.  This  tigure,  expressed  as  7  g.p.m,  per  100 
B.H.P.,  is  frequently  used  in  determining  pump  sizes;  but  it  is  too  small. 

Boilers  are  often  run  at  considerable  overloads  for  long  periods.  There- 
fore, the  quantity  of  feed  water  required  must  be  based  on  the  probable 
B.H.P.  to  be  developed,  and  not  on  the  boiler  rating.  As  the  demand  for 
feed  water  fluctuates  with  the  load,  the  supply  must  be  large  enough  to  take 
care  of  peak  loads.  Pump  makers  allow  from  lYi  to  10  g,p.m.  per  100  B.H.P. 
developed  to  take  care  of  contingencies. 

The  feed  pump  must  not  only  overcome  the  steam  pressure  in  the  boiler, 
but  must  also  develop  a  head  sufficient  to  overcome  pipe  friction  in  the 
system,  the  resistance  of  the  feed  check  valves,  and  some  excess  pressure 
besides.  Therefore  the  feed  pump  must  usually  discharge  at  a  pressure 
of  25  to  30  lb.  in  excess  of  the  boiler  pressure. 

Direct -Acting  Steam  Pumps 
pUMPS  are  divided  into  three  general  types:  direct-acting  steam  pumps, 
^    centrifugal  pumps,  and  positive  displacement  power-driven  pumps. 

The  popularity  of  the  direct-acting  steam  pump  as  a  boiler  feeder  is 
due  in  great  part  to  the  fact  that  it  is  the  oldest  and  best  known  type.  Often 
it  is  the  only  type  of  pump  well  understood  by  the  operating  engineer,  and  so 
represents  the  only  good  solution  to  the  feed  problem. 

For  feed  purposes  the  simple  steam  end  is  generally  used.  Tt  is  not  so 
economical  of  steam  as  the  compound  or  triple  expansion  steam  end,  but  the 
latter  cost  so  much  more  that  only  rarely  are  they  selected.  The  greater 
number  of  parts  with  the  complication  and  extra  space  are  also  against  the 
compound  and  triple  pumps. 

Tables  36  and  37  show  the  economies  of  steam-turbine-driven  centrifugal 
pumps  and  ihe  direct-acting  steam  pump.  If  the  plant  layout  does  not  provide 
an  excess  of  exhaust  steam  for  feed  heating,  or  other  useful  work,  the 
exhaust  steam  from  the  pump  can  be  thus  used  to  increase  the  thermal 
efficiency  of  the  plant.  On  the  other  hand,  if  the  exhaust  steam  has  to  be 
wasted  to  the  atmosphere,  the  economy  of  auxiliaries  becomes  important  and 
the  direct-acting  feed  pump  is  often  displaced  by  a  more  efficient  type.  The 
pump  that  gives  the  average  water  horsepower  for  the  least  expenditure  for 
coal  is  the  one  to  be  desired,  therefore  the  great  difference  in  the  steam 
consumption  of  direct-acting  pumps  and  centrifugals,  in  the  larger  sizes, 
eliminates  the  former  from  consideration. 

The  centrifugal  pump  is  not  suited  to  the  smaller  capacities,  so  that  the 
direct-acting  steam  pump  finds  one  of  its  most  useful  helds  in  installations  up 
to  2.000  boiler  horsepower,  in  which  a  compact  steam  pump  is  desired.    Its 


ib.  Google 


AUXILIARIES 


chief  competitor  in  this  capacity  range  is  the  motor-driven  triplex  pump,  but 
owing  to  the  lower  cost  and  greater  ease  with  which  steam  can  be  supplied, 
the  steam  pump  is  often  preferred.  Above  2000  boiler  horsepower  the  cen- 
trifugal pump  IS  usually  favored. 

Direct-acting  steam  pumps  can  be  classified  as  to  the  number  of  steam 
and  water  cylinders,  that  is,  simplex  or  duplex,  one  steam  and  one  water 
cylinder,  or  two  of  each  side  by  side. 

Simplex  pumps  are  often  preferred  for  boiler  feed  service  because  the 
design  always  insures  a  full,  complete  stroke.  When  the  pump  cannot  "short 
stroke,"  the  piston  rods,  cylinder  liners  and  plungers  cannot  wear  down  in 
the  center,  leaving  a  shoulder  at  each  end.  These  shoulders  may  cause 
sticking  of  the  pump  or  breakage  of  the  cylinder  or  stuffing  boxes  due  to 
the  wedging  effect  of  the  "shouldered"  portions,  when  the  stroke  is  unex- 
pectedly long  or  full. 

Another  advantage  of  the  simplex  pump  is  that  it  has  only  about  half 
as  many  working  parts  as  has  a  duplex  pump.  Consequently  fewer  parts 
wear  out  and  fewer  spare  parts  need  to  be  carried.  This  applies  particularly 
to  the  water  valves. 

The  simplex  pump  has  but  one  water  piston.  Even  if  this  is  double  act- 
ing, 3  Steady  and  uniform  flow  of  water  from  the  pump  is  precluded.  The 
steam  valve-gear  always  reverses  quickly  at  the  end  of  the  stroke,  but  there 
will  still  be  some  pause  at  this  point.  A  break  in  the  Row  of  the  water 
results,  sometimes  developing  a  water  hammer  in  the  discharge  lines.  Sim- 
plex pumps  should  be  equipped  with  a  generous  sized  air  chamber  on  the 
discharge  line.  The  chamber  must  always  be  kept  well  filled  with  air  to 
act  as  a  cushion  and  to  compensate  for  that  absorbed  by  the  water. 


Table  34. 

RatingB  of  Kmplex  Direct-Acting  Steam  Pumpi. 

SIZE 

S. 

„lr„. 

.^•s. 

WaUriwrHT.) 

PfatM 

57 
50 
49 

28.5 

25 

24.5 

3 

7.5 
12.2 

imi::::::::: 

110           25 

175     1      25 

48.6 

48 

42 

24.3 

24 
21 

21 
40 

61 

5SI'°::::.::::: 

680     '      40 
870           42 

10x7x12 

14x8x12 

42 

42 

21 
21 

84 
109 

1.220          42 
1,670           42 

Table  34  gives  the  usual  commercial  sizes  of  simplex  pumps  and  their 
normal  ratings  for  boiler  feed  service.  Under  the  heading  "size"  the  three 
figures  indicate  the  diameter  of  the  steam  and  water  cylinders  and  the  length 
of  the  stroke.  The  sizes  and  ratings  are  the  average  prevsiling;  among  sev- 
eral of  the  prominent  pump  manufacturers.  Some  pumps,  by  virtue  of^ large 
valve  areas  and  water  passages,  are  rated  for  greater  boiler  horsepowers 
than  others  of  the  same  dimensions.  The  factor  of  safety  may  dilTer,  thus 
affecting  the  rating.  The  sizes  given  indicate  the  usual  range  for  this  type 
of  pump.  The  simplex  pump  is  most  popular  in  the  smaller  sizes,  as  the  pul- 
sating discharge  effect  is  magnified  in  the  larger  sizes. 

The  rated  capacities,  in  Tables  34  and  3S.  are  based  upon  a  volumetric 
efficiency  of  from  85  to  90  per  cent.  The  efficiency  attained  in  the  boiler 
room  depends  upon  the  care  taken  of  the  pumps,  and  probably  will  not  ex- 
ceed 60  to  65  per  cent    This  is  equivalent  to  realizing  a  capacity  of  about 


ib.  Google 


AUXILIARIES 


70  per  cent  of  the  boiler  horsepower  given  in  Tables  34  and  35.  The  pump 
should  then  be  of  a  size  so  that  it  can  gain  on  the  largest  load  likely  to  be 
carried,  or  so  that  the  water  level  can  be  raised  during  a  peak  load  if  it 
has  fallen  too  low.  without  racing  the  pump. 

When  hot  water  is  handled  the  piston  speed  is  from  one-half  to  one- 
third  of  what  would  be  good  practice  for  pumping  cold  water.  This  is  to 
K event  vaporization  of  the  water  and  keep  the  pump  from  becoming  "steam 
und."  If  the  piston  speed  is  too  high,  the  water  will  not  follow  the 
piston  or  plunger  during  the  suction  stroke,  and  a  partial  vacuum  is  formed 
in  the  plunger  chamber.  When  the  plunger  is  reversed  it  travels  quickly 
through  the  vacuous  space  created  and  meets  the  water  with  an  impact  suffi- 
cient to  cause  a  serious  knock.  The  pump  then  vibrates  badly  and  the  knock 
may  even  damage  the  water  valves  or  other  parts,  as  well  as  the  pipe  lines. 
The  duplex  pump  (two  water  cylinders)  discharges  the  water  at  a  much 
more  uniform  rate  of  flow  than  the  simplex  type,  as  the  steam  valve  gear 
of  one  side  is  actuated  hv  the  piston  on  the  other  side  of  the  pump,  and 
the  steam  valves  are  so  designed  that  the  two  pistons  are  90  deg.  apart  in 
the  working  cycle.  Generally  both  water  pistons  are  moving.  At  the  end 
of  the  stroke  of  one  piston,  during  the  slight  pause,  the  other  side  is  working, 
thus  maintaining  a.  more  even  water  flow  than  is  present  in  a  simplex  pump. 
In  operating  these  pumps  both  sides  should  have  a  "full"  stroke,  or  the  cylin- 
ders or  slufTing  boxes  may  be  broken  through  the  shculders  formed  wboi 
"short  stroking." 

Table  35  gives  the  prevailing  sizes  and  ratings  of  duplex  pumps. 


T«ble  35. 

Radngs  of  Duplex  Direct-Acting  Steam  Pump*. 

EACH  SIDE 

-5?- 

Boner  H.F. 
Hr.) 

SIZE 

SSl  „&. 

.». 

72         !       36 
57              28.5 
53        !      26.5 

6,7                  95 
11.4                  190 
21-5       1           360 

\y^^.:.\'.v:.. 

19 
22 

6x4x6 

60              25 
50              25 
4g        ;      24 

32           1           535 
50                   840 
95          1       1,080 

26 
25 
40 

9x6MxlO 

10x6x10 

10x7x10 

48              24 
48              24 

87          1       1,450 
116          1       1,940 
156          1       2,600 

40 
40 
40 

12.7x12 

12x8Wxl2 

16x10^x12 

42 

21 
21 
21 

164 
243 
370 

2,750 
4,050 
6.200 

42 
42 
42 

Piston  pumps,  or  those  having  water  pistons  operating  inside  the  water 

a  Under,  and  packed  to  a  good  nt,  are  necessarily  more  subject  to  water 
ppage  or  leakage  past  the  pistons  than  is  the  plunger  type,  in  which  the 
leakage  is  through  a  stufiing  box  to  outside  the  pump.  In  the  plunger  type 
the  packing  in  the  stuffing  box  can  easily  be  adjusted  to  care  for  any  leakage 
that  develops  due  to  wear.  In  the  piston  type  the  adjustment  of  the  pack- 
ing in  the  piston,  if  there  is  any,  necessitates  partly  dismantling  the  pump. 
This  is  so  troublesome  as  to  be  often  neglected.  The  fact  that  the  leakage 
cannot  be  easily  detected  renders  this  ^pe  unsuited  to  high  pressure  work, 
since  the  leakage  increases  with  the  pressure. 


ly  Google 


fl 


h 


I' 
I 


ib.Google 


AUXILIARIES  301 

Although  wear  of  the  plunger  can  be  easily  detected,  the  plunger  is 
easily  scored  from  dust  and  grit.  Also  plunder  pumps  cost  more  than  the 
piston  type  so  that  they  are  used  principally  for  the  higher  pressures.  Piston 
pumps  are  not  used  for  water  pressures  over  ISO  to  200  pounds.  The  plunger 
type  is  preferred  where  the  pressures  are  in  excess  of  ISO  pounds. 

Hoe  water  has  a  corrosive  effect  upon  iron,  especially  when  it  travels 
over  the  iron  surface  at  velocities  such  as  are  present  in  a  pump.  It  is  well 
therefore  to  preserve  the  pump  by  making  certain  parts  of  brass  or  bronie. 
The  water  cylinder  should  have  a  brass  liner,  and  the  piston  should  be  bronze 
or  brass.  The  water  valves  can  be  of  bronze  or  hard  rubber,  with  bronze 
seats.  The  water  piston,  rod,  or  plunger,  can  be  of  iron  or  steel.  Iron 
plungers  are  usually  preferred,  especially  in  the  larger  siz«s.  but  unusual 
water  conditions  often  dictate  llie  use  of  bronze,  even  at  a  considerable  in- 
crease in  cost. 

^  pumps  can  be  calculated 


M£.P.^F  <_P~BP)^(iyo  (P~HP) 


M£.P.  -^  ^"' 

H  =  Discharge  head,  feel 
H'  =  Head,  feet 
W  ^z  Head,  pounds 
C  =  Ca(»acity,    gal.   per    min..    double    acting   pumps   only,    either 

simplex  or  duplex 
S=  Piston   speed   of   pump,    ft.   per   min.    (for   one   side   only   of 

duplex  pump) 
d  ^=  Diameter  of  plunger  or  water  piston,  inches 
D  ^=  Diameter  steam  cylinder,  inches 
H.P.  ^^  Delivered  or  water  horsepower 

k  ^=  Constant  =  5  in.  for  simplex  pumps 
^d.SS  for  duplex  pumps 
MJE.J'.  =^  Mean  e6tective  pressure  in  steam  cylinder 
P  ■=z  Steam  pressure  at  throttle,  absolute 
Sr^Back  or  exhaust  pressure,  absolute 
F  =  Diagram  factor  =  OJD. 

Direct-acting  pumps  must  be  large  enough  to  feed  the  boilers  when 
operated  at  normal  or  slow  speeds.  A  high  speed  direct-acting  putnp  hand- 
ling hot  water  aixy  "knock"  badly  and  cause  damage  to  the  discharge  pipe 
lines. 


ib.  Google 


AUXILIARIES 


Table  36.      Steam  Consumption — Kmple  Direct-Acting  Steam  Pumps. 
In  pounds  pei  water  horaepower  per  hour. 


»~. 

p™. 

mtPiin|>.Fa<»idi 

Gmv> 

so 

«c 

w 

100 

no 

I« 

1.0 

... 

,«. 

4 

8 

8 

230 
200 
160 

210 
170 
145 

2W 
165 

142 

200 
162 

139 

195 
158 
137 

190 
156 
135 

188 
154 
134 

187 
153 
133 

1S6 
Iffi 
132 

10 

12 

16 

140 
130 
120 
100 

130 
120 
110 
104 

m 

116 
106 
100 

122 
112 
104 
97 

120 
110 
102 
96 

119 
109 
100 
94 

117 
108 
90 
94 

118 
lOT 

98 

115 

106 
97 

Table  36  give*  the  steam  consumption  of  the  simple  pumps  used  for 
boiler  service.  Some  designs  will  be  more  efficient  than  others,  so  that 
the  table  will  not  apply  to  every  simple  direct-acting  boiler  feed  pump.  The 
values  are  for  pumps  in  good  condition,  with  a  well  la^ed  steam  cylinder, 
receiving  dry  saturated  steam  at  the  throttle,  and  exhausting  to  the  atmos- 
phere. 

Centrifugal  Pumps 
^ENTRIFUGAL  pumps  are  compact,  practically  noiseless,  require  small 
^•^  foundations,  and  pump  at  practically  a  uniform  rate.    They  require  little 
lubrication  or  adjnstmcnt  of  packing.     Once  started,  they  can  be  left  without 
attention   for  a  considerable  time. 

These  pumps  arc  most  in  favor  for  the  larger  installations,  in  which  the 
boiler  capacity  is  2000  horsepower  or  more.  The  running  clearance  inside  the 
pump  is  small,  at  points  where  the  water  under  discharge  pressure  is  sep- 
arated from  the  suction  side,  so  that  slippage  must  be  considered.  Many 
ingenious  devices  are  used  to  reduce  this  leakage  and  to  serve  as  a  correc- 
tion when  it  does  occur.  The  clearances  cannot  be  reduced  enough  to  elimi- 
nate slippage,  so  that  the  capacity  and  hence  the  loss  in  small  pumps  is 
proportionately  greater  than  in  the  larger  ones.  The  larger  siies  therefore 
give  the  best  results. 

Centrifugal  feed  pumps  are  usually  of  the  multi-stage  type,  each  stage 
doing  its  proportionate  part  of  the  work  of  increasing  the  water  pressure. 
The  maximum  pressures  are  from  60  to  100  lb.  per  stage.  Thus  a  250-lb. 
discharge  pressure  would  mean  a  three-stage  pump.  The  water  is  received 
by  the  first-stage  impeller,  which  picks  it  up  and  imparts  to  it  a  velocity  head. 
This  velocity  is  reduced,  either  in  a  channel  of  gradually  increasing  area. 
or  in  a  diffusion  ring  having  vanes  and  passages,  while  the  water  is  conducted 
to  the  impeller  of  the  next  stage. 

The  head  developed  depends  upon  the  velocity  imparted  to  the  water, 
and  will  therefore  be  governed  by  the  peripheral  velocity  of  the  impelier. 
Thus  for  a  given  head  there  can  be  used  either  a  large  diameter  impeller 
with  a  slow  rotative  speed  or  a  smaller  diameter  and  proportionately  in- 
creased  R.P.M,  lo  give  the  same  rim   speed.     As  the  diameter  of  the  im- 


ib.  Google 


A  I'  X  r  L  t  A  R  I  i;  S  303 

peller  governs  the  diameter  of  tlie  [lump  it  is  desirable  to  have  high  speeds, 
with  smaller  impellers,  to  reduce  the  cost  and  the  space  required. 

For  ordinary,  or  small  changes,  the  capacity  of  a  centrifugal  pump 
varies  directly  as  the  speed,  and  the  head  as  the  square  of  the  speed.  This 
applies  particularly   for  maximum  efficiency  at  the  different   heads. 

The  operating  characteristics  of  a  well  designed  feed  pump  are  shown 
in  Fig.  159.  The  curves  are  laid  out  so  that  heads,  capacities  and  speeds  are 
expressed  in  percentages.  Thus  if  SOO  g.p.m.  is  the  normal  capacity  it  will 
be  shown  as  100  per  cent  on  the  capacity  scale:  2S0  g.p.m.  will  be  given 
as  50  per  cent;  and  625  g.p.m.  as  125  per  cent  of  normal. 


FtrcvrY  of  Capacity  trt  Ma;iimomEffici«ncy  Point 

Pig.  1S9.     Opcratins  Cbaractcrirtic*  of  Centrifugal  Pumpa. 

The  heavy  lines  show  the  head,  capacity  and  characteristics  for  normal 
speed  operation  and  the  lighter  lines  the  [wrformancc  at  fractional  speeds. 

As  boiler  feeding  takes  place  practically  at  constant  pressure  a  change 
in  capacity  must  be  met  by  a  change  in  speed  or  by  throttling.  Hence  the 
head  can  be  considered  as  fixed,  and  can  be  indicated  as  100  per  cent  or  the 

The  head-capacity  lines  for  different  speeds  cut  the  line  "A"  at  points 
indicating  the  percentage  or  normal  speed  for  the  capacities  at  this  head. 
The  brake  horsepower  capacity  lines  will  then  show  the  percentage  of  normal 
horsepower  for  different  speeds.  Maximum  efficiency  lines  give  the  actual 
pump  efficiency  for  any  he^d  and  capacity.  These  also  are  based  upon 
percentages. 

As  an  example,  lake  a  pump  designed  for  400  g.p.m.,  200  !b.  pressure.  2600 
r.p.m.,  62  per  cent  efficiency,  and  75  brake  horsepower  required   for  driving. 
AH  these  are  represented  by  100  per  cent  on  the  curve.     Suppose  it  is  desired 
to  find  the  other  conditions  for  a  capacity  of  300  g.p.m.     Then  say — 
Capacity  =^  300  g.p.m,  'given)  —  75  per  cent  of  normal 
Head  =  200  lb,   ~   lOO  per  cent  of  normal   (no  change) 
Speed   =   96  per  cent  of  normal   ffrom   curve)    =  2500  r,p.m. 
Efficiency  =  96  per  cent  of  normal  (from  curve)  =  58.5  per  cent 
Brake  horsepower  =  80  per  cent  of  normal  (from  curve)  ^  60  brake 
horsepower. 


ib.  Google 


Kimball  ButldinK.  Chicago,  111.,  equipped  with  Heine  Staadard  Boilen, 

I;.  Google 


AUXILIARIES  305 

Fig.  159  shows  the  relations  upp"  which  depend  the  regulation  of  the 
pnmp  to  meet  varying  demands.  The  head-capacity  curves  give  the  best 
information  as  to  the  operation  of  centrifugal  pumps.  The  efficiency  curve 
should  be  fiat,  so  that  the  efficiency  is  high  over  a  wide  capacity,  thus  main- 
taining good  economy  under  speed  regulation. 

The  horsepower  curve  should  rise  to  a  maximum  at  the  normal  operating 
capacity  and  then  fall  off  so  that  no  overload  will  be  thrown  on  the  dnver 
should  the  pressure  he  reduced.  This  is  particularly  important  in  motor 
driven  pumps,  since  overload;  can  be  serious- 
Table  37  gives  capacities  and  steatn  consumption  for  different  sizes  of 
centrifugal  feed  pumps. '  The  calculation  of  capacity  is  explained  elsewhere. 

Table  37.     Performance  of  Three  Stuge  Centrifugal  Feed  Pumps. 
(150  Lb.  Steam  Pressure — 175  Lb.  Water  FreMure — 135  Ft.  Per  Stage) 


& 

,., 

„. 

G.P.M 

BHP. 

Pn«Bt 

H.P. 

2,500 1 
2,600 1 
2,200 1 
1,500  t 
1.500  t 

o  3.000        300 
o3,000        500 

4,000 
6,700 
10,000 
13,200 
20,000 

56 
04 

G7 
70 
71 

58 

78 

no 

140 
210 

42      ;       75 

42             66 

6 

8 

o  2,000 

o  2,000 

1,000 
1,500 

1      3V     .       56 
38             54 
1                1 

•  0.075  gal,  pLT  B.H.P.  used  to  provide  a  factor  of  safety. 

The  turbine  water  rates  represent  commercial  averages.  The  column  at 
the  right  (steam  per  water  H.P.  per  hour)  is  given  so  that  the  performance 
can  be  compared   directly  with  that  of  direct-acting  steam   pumps. 

Performance  data,  due  to  /.  Brestav,  are  given  in  Table  33  (or  a  boiler 
feed  pump  and  for  a  compounc  duplex  direct -act  in([  steam  pump.  Both  pumps 
were  designed  for  250  g.p.m.  and  were  operated  nine  hours  a  day  at  160  lb. 
steam  pressure  and  2  Iti.  tiark  pressure. 

Table  38.     Operating  Coat  Compariaoti  of  Boiler  Feed  Pumpt. 

Turbo       Com  p. 
Centrifugal  Duplex 

First  cost  _ $1,008  $980 

Valves  to  be  watched 0  14-18 

Packing  boxes  ..„ _ _ 4  18 

Oil  used  in  15  days,  pints  _ _ About  4  30 

Grease,  pounds - „ _ 4  0 

Maintenance,  packing,  etc..  per  year  $30  S120 

Steam  consumption,  pounds  per  boiler  horsepower  per  hour     38-40         40-55 

.\  simple  duplex  steam  pun^p  mouIiI  have  cost  here  about  $600  but  the 
steam  consumption  would  then  be  about  100  lb.  per  B.H.P.  per  hour.  The 
comparison  shows  that  the  compound  steam  end  type  of  a  direct-acting 
pump  is  required,  if  the  economy  of  the  turbine  driven  centrifugal  pump  is 
10  be  obtained.  The  direct-acting  pump  is  more  complicated  however,  and 
the  maintenance  and  lubrication  charges  are  much  greater. 

The  leading  advantages  of  centrifugal  pumps  are  compactness,  silent 
running,  durability  and  superior  economy  in  cost  of  power,  attendance  and 
repairs,  and  the  facility  with  which  they  may  be  adapted  to  any  location 


ib.  Google 


306  AUXILIARIES 

where  they  may  be  supplied  with  power  by  direct  connection  to  an  electric 
motor  or  steam  turbine.  As  boiler  feeders,  they  have  the  advantage  over 
reciprocating  pumps  of  continuous  delivery  without  shock  or  hammering,  and 
of  producing  no  excessive  pressure  on  feed  mains  for  any  adjustment  of 
feed  stop  valves  or  other  stoppage  of  pipe  connections. 

The  commercial  forms  of  centrifugal  ptimps  are  usually  of  the  muhi- 
siage   type,   either    with   or   without    diffusion   rings. 


r 


Pig.  160.      De  Laval  Turbine  Driven  Centrifugal  Boiler  Feeder. 

Fig.  160  shows  a  pump  without  diffusers.  The  water  after  being  picked  up 
y  the  impeller  of  one  stage  is  discharged  to  the  next  stage  through  a  return 
'  nnel  cast  as  a  part  of  the  pump  casmg.  This  channel  is  designed  so  as 
to  reduce  gradually  the  velocity  of  the  water  leaving  the  impeller  and  trans- 
form this  velocity  to  pressure  head.  The  advantages  of  this  type  of  pump 
are  said  to  be  simplicity  nf  construction  and  ihe  absence  of  small  water  pas- 
sages that  might  become  blocked  by  foreign  matter. 

A  single  stage  direct  turbine-driven  centrifugal  feed  pump  has  aiiained 
some  favor  In  Europe  and  is  also  beginning  to  be  recognized  in  this  country. 
This  has  a  pump  impeller  and  turbine  wheel  mounted  on  one  short  shaft. 
The  pump  and  turbine  housings  are  close  to  each  other  and  as  the  machine 
runs  at  a  high  speed,  5000  to  8000  r.p.m.,  it  is  a  compact  unit.  These  pumps 
are  designed  to  produce  sufficient  pressure  to  feed  any  usual  boiler,  and  can 
operate  against  a  pressure  of  250  lb.  or  greater.  Owing  to  the  high  speed, 
this  pump  is  not  accepted  for  general  boiler  feed  use  in  this  country,  in 
spite  of  its  low  cost  and  the  small  space  required. 

When  the  water  is  fed  through  an  economizer  to  the  boiler  a  four-stage 
pump  can  be  arranged  so  that  one  stage  pumps  to  Ihe  economizer  and 
through  it  to  the  main  feed  pump,  which  has  three  stages  und  discharges 
into  the  boiler.  Sometimes  the  pumping  unit  is  made  up  of  iwo  separate 
pumps,  each  with  its  own  driver;  but  two  pumps  on  one  base,  and  driven 
by  one  prime  mover,  are  to  be  preferred.  Thus  each  pump  always  works  in 
harmony  with  the  other.  The  iwo  pumps  can  be  arranged,  wiih  the  econo- 
miier  stage  uncoupled  or  by-passed,  to  feed  directly  to  the  boilers.  These 
economizer  sets  are  particularly  well  adapted  to  plants  in  which  it  is  de- 
sired to  decrease  the  water  pressure  in  the  economizer  tubes,  because  the 
pressure  in  the  economizer  is  usually  one  quarter  of  that  with  the  ordinary 
feed  pump. 


ib.  Google 


AUXILIARTF.  S  307 

Fig.  160a  shows  a  multi-stage  high-pressure  centrifugal  pump  used  for 
boiler  feeding.  It  is  really  a  volute  pump  so  arranged  that  the  volute  of 
one  stage  is  led  into  the  suction  of  the  next  stage,  and  the  high  pressure  is 
attained  by  putting  in  series  as  many  stages  as  necessary.  It  is  claimed  that 
the  advantage  of  the  volute,  besides  the  simplici^,  is  that  the  efficiency  is 
maintained  for  a  greater  range  than  with  the  dllTusion  vane  type  of  pump ; 
also  the  cost  of  the  diffusion  vanes,  which  are  subject  to  wear,  is  eliminated. 
The  force  on  the  horizontal  split  of  the  case,  due  to  the  high  pressure  of 
the  water,  is  taken  care  of  by  the  bolts  on  the  outside  flange,  and  by  through 
bolts  nearer  the  center  line.  The  hydraulic  balancing  mechanism,  which  per- 
forms the  functions  of  a  thrust  bearing,  is  so  arranged  that  both  stuffing 
boxes  are  under  a  low  pressure  and  sealed  with  water.  Every  part  of  the 
pump,  except  the  case  and  shaft,  is  made  of  bronze.  The  two  ring-oiled 
bearings  are  equipped  with  large  oil  reservoirs. 

Turbine -driven  centrifugal  boiler  feed  pumps  have  many  advantages  in 
addition  to  their  compactness  and  reliability. 


They  give  reliable  and  uninterrupted  service  with  little,  and  often  un- 
skilled, attention. 

There  is  an  entire  absence  of  pulsation,  shock,  vibration  or  over-pressure 
in  pipe  lines,  thus  making  relief  valves  unnecessary  and  rendering  the 
pump  suitable  for  use  with  automatic  boiler  feed  regulators  acting  inde- 
pendently at  each  boiler,  or  with  feed-water  meters. 

The  cost  of  maintaining  the  piping  system  is  reduced,  because  less  strain 
is  thrown  upon  it. 

Close  governing  is  obtained,  either  at  constant  speed  or  at  constant 
excess  pressure. 

There  is  entire  freedom  from  liability  to  injury  by  overloading. 

Troublesome  parts,  such  as  valves,  packings,  sliding  surfaces,  air  chamber, 
etc.,  are  eliminated. 

There  is  little  expense  for  attendance  and  upkeep,  due  to  the  simplici^ 
and  few  wearing  parts.    All  parts  are  easily  accessible. 

Cylinder  lubricants  are  not  required  and  little  oil  of  any  kind. 

The  steam  consumption  is  lower  than  that  of  direct-acting  pumps,  and 
superheated  steam  or  low  pressure  steam  can  be  used. 

The  exhaust  is  entirely  free  of  oil  and  can  be  used  in  open  feed  heaters, 
or  introduced  into  an  intermediate  stage  of  the  main  turbine  without  danger 
of  introducing  oil  into  the  boilers. 


ib.  Google 


ib.Google 


AUXILIARIES 


Direct-Acting  Power  Pumps 

DIRECT-ACTING  power  pumps  are  rarely  used  for  boiler  feeding.  These 
positive  displacement  pumps  are  selected  usually  where  the  available 
sources  of  motive  power  prevent  the  use  of  the  direct-acting  steam  pump. 

These  pumps  are  reliable,  their  maintenance  cost  is  low  and  in  small 
capacities  their  efficiency  usually  higher  (lower  brake  horsepower  required) 
than  centrifugal  pumps. 

In  the  larger  sizes,  3000  boiler  horsepower  and  over,  tliey  become  ex- 
pensive and  the  centrifugal  pump  is  more  generally  used. 

The  triplex  plunger  pump  gives  3  steady  flow  of  water,  the  cost  of  power 
is  less  than  the  centrifugal  pump  when  applied  to  boiler  feeding,  it  can  be 
automatically  regulated,  it  is  reliable  and  if  given  intelligent  attention  it  will 
maintain  its  high  efficiency  for  IS  to  20  years  with  no  cost  for  repairs  ex- 
cept for  packin|c  and  valves. 

The  hi^h  efficiency  of  the  triplex  pump  U  attained  not  merely  at  its 
rated  capacity,  but  is  nearly  constant  throughout  the  full  range  of  operation 
provided  its  capacity  is  regulated  by  changing  the  speed.  The  average  efli- 
ciency  is  therefore  greater  than  a  mere  comparison  of  catalog  percentages 
would  indicate. 

The  triplex  pump  has  a  practically  constant  efficiency  at  different  speeds. 
The  capacity  is  proportional  to  the  speed.  The  discharge  head  does  not 
have  to  be  throttled  to  regulate  its  capacity.  The  efficiency  of  the  variable- 
speed  direct-current  motors  used  to  drive  triplex  pumps  is  more  nearly 
constant  at  variable  load  and  speed  than  the  efficiency  of  constant- speed 
motors  is  at  the  variable  load  used  to  drive  centrifugal  pumps.  Small  re- 
ciprocating engines  have  much  better  efficiencies  at  variable  speeds  than  small 
turbines  at  variable  loads. 

Comparing  two  types  of  boiler-feeding  units,  one  a  motor-driven  cen- 
trifugal pump  and  the  other  a  motor-driven  triplex  pump,  taking  into  con- 
sideration the  daily  load  curve  of  the  plant  and  the  efficiency  curves  of  the 
two  pumps,  together  with  the  efficiency  curves  of  the  two  motors,  it  was 
found  that  the  actual  coal  required  by  the  triplex  pump  would  be  less  than 
one-half  that  re<^uired  by  the  centrifugal.  A  similar  comparison  covering 
steam  driven  units  would  show  even  greater  difference  in  favor  of  the 
triplex  pump.  Against  these  advantages  are,  more  space  required,  higher 
first  cost,  more  complicated  apparatus  and  more  attendance. 

Wilh  stokers  of  the  forced-draft  type,  states  /.  C.  Hawkins,  the  engine 
that  drives  the  fan  can  be  used  to  drive  the  triplex  pump  also.  The  feed 
pump  is  then  operated  at  a  speed  in  proportion  to  the  amount  of  steam  used 
and  needs  little  other  regulation.  If  automatic  feed-water  regulators  are 
used  a  relief  valve  set  at  about  30  lb.  in  excess  of  the  boiler  pressure  must 
he  placed  in  the  discharge  line  (probably  by-passed  back  to  the  suction)  to 
prevent   overpressure. 

The  triplex  pump  is  simple,  ^ves  a  nearly  constant  flow  of  water,  and 
at  all  speeds  has  about  equal  efficiency,  ranging  from  70  to  S5  per  cent.  The 
first  cost  of  a  pump  and  motor,  however,  is  higher  than  that  of  a  duplex 

Methods  of  Driving  Pumps 

MOTORS  are  selected  primarily  because  of  plant  conditions  limiting  the 
use  of  steam  from  auxiliaries.  Because  of  the  difficulty  of  regulating 
its  speed  to  meet  the  varying^  capacity  demands  the  electric  motor  is  not 
selected  when  steam  power  is  permissible.  If  any  of  the  power  plant 
auxiliaries  are  steam -actuated,  the  boiler  feed  pump  should  be  one.  The 
alternating  current  motor  must  be  run  at  constant  speed,  and  the  direct  cur- 
rent machines  equipped  with  complicated  control  devices  if  the  speed  is  to 
be  varied  consideraoly.    This  speed  variation  is  essential  in  feed  pumps. 


ib.  Google 


310  AUXILIARIES 

For  alternating  current,  the  squirrel -cage  induction  motor  is  used. 
The  starting  current  is  high,  but  a  feed  pump  continues  in  operation 
for  a  considerable  time,  hence  the  great  starting  current  does  not  justify  the 
use  of  a  slip-ring  motor. 

On  direct -current  service  a  compound-wound  motor  is  used.  The  series- 
wound  is  unsatisfactory  because  it  runs  away  if  the  load  is  suddenly  taken 
off,  as  when  the  pump  becomes  vapor  bound  or  loses  its  suction.  The  shunt 
wound  motor  is  valuable  for  some  services  on  account  of  its  constant-speed 
characteristic.  The  com  pound -wound  motor  speeds  up  under  lessened  load, 
but  not  to  a  dangerous  extent;  it  will  slow  down  if  overloaded  and  thus 
furnish  relief. 

Steam  turbines  are  used  principally  with  centrifugal  pumps,  as  the  high 
speeds  possible  with  this  pump  are  met  with  a  reduction  of  cost  and  floor 
space.  Turbines  are  uneconomical  at  low  speeds  (400-tiOO  r.p.m.).  The 
water  rates  of  the  steam  turbine  and  the  direct-acting  pump  are  compared 
in  Table  37. 

The  turbin'e  can  be  regulated  closely  to  meet  varying  power  demands. 
Its  speed  can  be  changed  either  manually  or  automatically,  by  throttling  the 
steam  supply. 

Turbines  should  be  direct-connected  to  a  centrifugal  pump.  The  turbine 
wheel  and  pump  motor  should  be  on  one  shaft,  or  a  flexible  coupling  should 

Steam  engines  run  at  a  maximum  rotative  speed  of  SOO  to  600  r.p.m.; 
this  is  too  low  for  direct  drive  to  centrifugal  pumps,  which  are  too  lar^e 
and  costly  when  driven  at  slow  speeds.  Belt-drive  for  centrifugal  pumps  is 
not  desired,  as  the  belt  is  always  a  source  of  trouble  and  renewal  expense. 
Steam  engines  are  susceptible  to  the  same  speed  regulation  as  turbines,  and 
give   good   economy. 

Automatic  Regulation  of  Pumps 

THE  regulating  eQuipment  tor  a  feed  pump  consists  of  the  pressure  regu- 
lator at  the  pump,  and  of  a  feed-water  control  device  at  the  boilers. 

The  pressure  regulator  maintains  an  even  pump  discharge  pressure  by 
throttling  the  steam,  the  speed  of  the  pump  being  reduced  so  that  with  a 
throttling  of  the  feed  at  the  boilers,  pressure  in  the  feed-water  lines  is  not 
increased. 

The  feed-control  device  is  essentially  a  throttle  valve  in  the  feed  line, 
which  is  opened  or  closed  to  vary  the  amount  of  feed  water  supplied  to  the 
boilers. 

In  steam -actuated  pumps,  the  pressure  regulator  consists  of  a  balanced 
valve,  placed  in  the  steam  line  to  the  pump,  near  the  pump  valve  chest.  The 
balanced  valve  construction  is  used  to  render  operation  easier  and  prevent 
sticking.  The  cylinder  of  a  piston  on  the  throttle-valve  stem  communicates 
with  the  feed-water  line  so  that  its  pressure  acts  against  the  piston.  When 
this  pressure  is  increased,  the  stem  is  depressed,  closing  the  valve  and  throt- 
tling the  sleam  to  the  prime  mover  so  that  the  speed  is  reduced.  A  spring 
or  loaded  lever  on  the  valve  stem  opposes  the  action  of  the  piston,  thus 
balancing  the  water  force.  The  Spring  can  be  adjusted  to  maintain  any 
desired  pressure  in  the  water  lines.  A  diaphragm  can  be  used  instead  of 
the  piston  and  water  cylinder  for  simplicity  and  to  reduce  the  cost 

The  so-called  constant  excess~pressMre  regulator  has  the  same  elements 
as  a  constant  pressure  regulating  valve.  The  discharge  water  pressure, 
however,  acts  on  one  side  of  the  piston  or  diaphragm  and  the  boiler  steam 
pressure  on  the  other.  The  spring  or  loaded  lever  is  adjusted  so  that  the 
difference  between  boiler  and  water  pressure  is  maintained  constant,  and  the 
excess  pressure  is  just  sufficient  to  force  the  feed  water  into  the  boiler. 


ib.  Google 


AUXILIARIES  311 

This  regulator  is  used  with  widely  varying  sieam  pressures  to  prevent 
the  pump  from  discharging  against  too  great  a  head  when  the  steam  pres- 
sure in  the  boilers  is  low.  With  a  constant  pressure  governor,  the  water 
pressure  must  be  sufficiently  high  to  feed  the  boiler  under  maximum  steam 
pressure.  When  the  boiler  pressure  drops,  the  water  pressure  will  be  much 
greater  than  actually  requir^,  and  the  pump  will  be  consuming  more  steam 
dian  necessary. 

Positive  displacement  power  pumps  are  regulated  either  by  varying  the 
speed  of  the  prime  mover,  or  by  a  by-pass  control,  which  opens  the  discharge 
from  the  pump  to  the  suction,  allowmg  the  water  to  circulate  through  ihe 
pump.  A  check  valve  prevent*  the  water  in  the  discharge  line  from  flowing 
back  into  the  pump. 


Fig.  161,     Detaila  of  a  Motor-Driven  Pump  ReBulator. 

These  machines  are  usually  belted  to  a  constant  speed  source  of  power, 
or  are  motor-driven ;  the  speed  of  the  driver  can  be  varied  only  when  it  is 
a  direct-current  or  wound-rotor  motor,  and  even  then  the  control  apparatus 
is  likely  to  be  unduly  complicated. 

The  essential  elements  of  a  constant  excess- pressure  governor  for  a 
wound  rotor  motor-driven  feed  pump  are  described  by  C.  H.  Sonnlag  as 
follows:  The  regulator,  Fig.  161,  works  on  the  follow-up  motion  principle, 
such  as  is  used  on  steam  steering  engines.    The  base  casting  is  made  from 


ib.  Google 


I 


Ii 

II 


Ii 


ib.Google 


AUXILIARIES  313 

■n  old  motor  rail.  The  diaphragm  chamber  and  parts  below  it  are  from  a 
154-in.  constant  excess-pressure  steam-pump  governor.  The  motor  used  is 
of  the  wound-rotor  type,  and  the  three  brush  holders  of  the  regulators, 
being  in  metallic  contact  with  their  supporting  arm,  short-circuit  tnore  or  less 
of  the  resistance  in  the  rotor  circuit,  according  to  their  position  on  the  face 
of  the  contact  panel.  The  subdivisions  of  the  rotor  resistance  are  equal  in 
the  three  phases,  but  corresponding  sections  of  this  resistance  in  the  three 
phases  are  shunted  successively  instead  of  at  the  same  time.  This  gives 
three  times  as  many  subdivisions  of  speed  as  there  are  contacts  on  the  panel, 
and  the  result  is  smooth  acceleration,  with  a  speed  for  almost  any  rate  of 
feed. 

The  regulator  does  not  open  the  primary  circuit  of  the  motor,  nor  stop 
it,  but  it  will  bring  the  motor  down  to  a  low  speed.  The  pump  is  fitted  with 
a  spring-loaded  relief  valve  set  above  the  working  pressure,  which  acts  as  a 
safety  device  when  the  discharge  line  is  absolutely  stopped.  The  panel  is  so 
connected  to  the  resistance  that  the  lowest  position  of  the  brushes  shunts  all 
the  r.    ■ 


To  start  the  pump  and  regulator,  the  valves  leading  to  the  upper  and 
lower  diaphragm  surfaces  are  opened,  also  the  one  supplying  service-water 
pressure  to  the  follow-up.  The  drip  valve  should  be  open  enough  to  let  the 
plunger  and  the  brush  rigging  down  slowly  when  the  follow-up  valve  is 
closed.  The  follow-up  valve  is  then  held  open  by  raising  the  upper  lever 
until  the  brushes  arc  at  the  top  of  the  panel  and  the  primary  switch  is 
closed,  when  the  motor  will  start  slowly.  The  follow-up  valve  is  released 
and  the  motor  will  accelerate  up  to  the  desired  excess  pressure.  This  is 
determined  by  the  position  of  the  7-lb.  weight  on  the  lever  arm,  15  lb.  being 
about  right   for  boiler   feeding. 

When  the  plant  is  small  and  steaming  Is  steady,  the  pumps  are  started 
and  run  until  there  is  a  good  level  of  water  in  the  gage  glass.  The  pump  is 
stopped  when  the  level  begins  to  rise  too  high,  and  started  again  when  the 
glass  begins  to  show  that  the  water  level  is  below  normal. 

Centrifugal  motor -driven  pumps  can  be  operated  either  with  the  by-pass 
or  with  the  control  described  for  the  power  pump.  The  capacity  of  centrifugal 
pumps  drops  off  with  an  increase  in  head  pressure ;  consequently  the  pump 
Speed  tends  to  be  regulated  automatically,  and  pressures  cannot  become  dan- 
gerous. This  characteristic  is  not  so  pronounced  that  a  centrifugal  pump  is 
independent  of  regulating  devices.  The  control  is  usually  of  the  by-pass  type, 
consisting  of  a  safety  valve  which  under  a  predetermined  pressure  opens  up 
and  allows  the  discharge  to  flow  hack  to  the  suction.  This  pressure  is  above 
normal,  but  is  lower  than  the  shut-olT  or  zero  capacity  head  of  the  pump. 

In  si  earn -actuated  pumps  the  control  is  simpler,  since  the  speed  can  easily 

be  changed  by  throttling  the  steam  supply.    With  this  method,  power  Is  not 

wasted  by  circulating  water  through  the  pump,  and  the  pump  is  not  constantly 

being  stopped  and  started  again.     The  supply  is  throttled  by  utilizing  the  rise 

■    and  fall  of  water  in  the  boilers,  hot  well,  or  open  heater. 

Feed  Water  Regulators 

c  in  the  feed  lines  is  controlled  by  the 
rum  or  in  the  hot  well.  The  hot  well  level 
ice.   and   calls   for   operation   on   a   closed 

.    .    .  1  the  form  of  liquid  or  steam)   must  be 

correct,  therefore,  in  the  entire  system,— water  lines,  steam  lines,  and  boiler. 


ib.  Google 


AUX  [LIARIES 


of  flow  is  regulated  in  accordance  with  the  water  level  in  the  drum;  pr  they 
are  o(  the  intcTrntttent-feed  type,  and  the  water  is  fed  or  not  fed,  as  the 
level  falb  below  or  exceeds  a  predetermined  point  in  the  steam  drum. 

The  continuous- feed  regulator  is  designed  to  give  even  steaming  and 
close  regulation  with  slight  danger  of  the  water  level  dropping  to  a  dan- 
gerous point.  The  water  in  the  drum  is  not  cooled  off  suddenly  by  the 
addition  of  large  quantities  of  water,  but  feeding  is  continuous  so  that  Steam 
can  be  generated   uniformly  and  most   economically. 

One  intermittent-feed  regulator  contains  3  vertiiial  expansion  pipe,  the 
top  of  which  is  connected  with  the  steam  drum  at  the  normal  water  level: 
the  bottom  of  this  pipe  is  connected  with  the  steam  drum  below  the  normal 
water  level.  As  the  water  level  in  the  drum  falls,  it  also  falls  in  the  expansion 
pipe.  Steam  is  then  admitted  to  the  pipe,  thus  increasing  its  temperature, 
since  the  water  in  the  pipe  is  cooler  than  the  steam.  This  increase  in  tem- 
perature expands  the  pipe  and  causes  a  motion  that  is  transmitted  to  the  feed- 
water  valve-stem.  The  valve  is  thus  opened  and  more  water  admitted.  When 
water  rises  in  the  steam  drum,  the  level  also  rises  in  the  expansion  pipe. 
The  temperature  of  the  expansion  pipe  is  reduced,  and  the  pipe  contracts, 
closing  the  feed  valve.  Fig.  162  shows  the  design  of  this  intermittent  regu- 
lator. 


P^g.  162.     Cope*'  Feed  Water  Regulator. 


In  another  type  of  intermittent  regulator,  a  rise  of  water  in  the  steam 
drum  or  water  column  above  the  normal  is  followed  by  the  overflow  of  the 
water  into  a  trap,  thus  opening  it.  Steam  is  then  admitted  to  the  pressure 
chamber  of  the  feed  valve,  which  is  promptly  closed.  When  the  water 
level  falls  below  the  normal,  the  trap  automatically  closes.  The  pressure' 
chamber  of  tlie  feed  valve  exhausts  into  the  hot  well. 

Feed  regulators  of  the  continuous  type  talce  into  account  the  rise  and 
fall  of  water  in  the  gage  glass,  due  not  only  to  the  quantity  in  the  drum, 
but  also  to  the  change  in  density  of  the  water  in  the  steam  drum.  When 
the  boiler  load  is  increased  suddenly,  steam  is  generated  more  rapidly  and 
the  steam  pressure  drops.  More  steam  bubbles  will  rise  through  the  water 
in  the  drum,  thus  decreasing  the  density  of  this  water.  The  density  in  the 
gage  glass  remains  unchanged.  Hence  the  level  in  the  gage  glass  rises  more 
slowly  than  does  the  water  level  in  the  drum,  until  the  increased  rate  of 


ib.  Google 


AUXILIARIES  3IS 

steam  generalion  causes  it  to  tall.  The  water  level  in  the  gage  glass  then 
fails,  and  the  rate  of  feeding  is  increased  in  response,  to  maintain  an  even 
level  In  the  glass. 

When  the  load  falls  off  suddenly,  the  steam  pressure  is  increased;  this 
is  followed  by  a  less  rapid  generation  of  steam  and  a  reduction  in  the  amount 
of  steam  bubbles  rising  through  the  water  space.  The  density  of  the 
water  in  the  drum  is  increased,  while  as  before,  the  water  level  in  the  g^e 
glass  falls  more  slowly  than  does  that  of  the  level  in  the  drum.  When  the 
evaporation  is  less  rapid,  the  water  level  in  both  the  steam  drum  and  gage 
glass  is  ultimately  raised;  and  the  rate  of  feeding  is  reduced.  Consequently 
rise  and  fall  due  to  density  changes  and  changes  in  level  due  to  variation  in 
the  rate  of  evaporation,  do  not  occur  simultaneously. 

This  lagging  action  is  used  in  some  continuous-feed  regulators,  which 
provide  a  strong  feed  during  the  decreasing  load  and  lessen  the  feed  rate 
in  proportion  to  the  evaporation  rate  when  the  load  is  increasing  rapidly. 
Under  decreasing  load  the  furnace  heat  is  thus  stored,  and  is  not  wasted  or 
discharged  to  the  flues.  When  the  load  is  increasing,  the  rate  of  feed  is  not 
increased  greatly  but  is  kept  as  low  as  is  consistent  with  safety.  The  furnace 
can  then  be  used  to  generate  steam  instead  of  to  beat  targe  quantities  of  feed 
water. 


Fig.  163.     Continuous  Regulator  of  Float  Type. 

In  still  another  type.  Fig.  163.  a  float  normally  rests  upon  the  water  in  a 
chamber  installed  at  the  level  of  the  water  in  the  boiler  drums.    The  rising 

and  falling  of  the  float  is  communicated  to  the  throttle  valve  and  thus  regu- 
lates the  feed  continuously.  The  float  can  be  partly  filled  with  a  volatile 
liquid,  which  expands  because  of  the  temperature  changes  in  the  float  cham- 
ber. This  expansion  tends  to  equalize  the  external  pressure  on  the  float,  due 
to  the  steam.  The  feed  control  valves  used  with  the  float  are  placed  inside 
the  regulating  chamber,  so  that  there  are  no  outside  stuffing  boxes  to  be 
packed. 


ib.  Google 


ib.Google 


A  U  X  1 1- 1  A  R  I  F  S 


Location  of  Feed  Pumps 
POR  cold  waler  service,  that  is,  water  at  60  to  70  deg.,  feed  pumps  )iive 
■^  satisfaction  with  a  suction  lift  as  high  as  15  feet.  Generally,  however,  the 
suction  lift  of  the  feed  pump  is  decreased  by  the  temperature  of  the  water. 
The  atmospheric  pressure  which  is  equivalent  to  a  head  of  34  feet 
of  water,  forces  the  water  into  the  pump.  In  practice,  deductions  must  be 
made  for  the  loss  of  head  at  the  pipe  entrance,  pipe  friction,  valve  friction. 
acceleration  of  water  to  its  highest  velocity,  and  pressure  necessary  to  pre- 
vent vaporiration  of  hot   water.     For  example: 

Entrance    toss,   say...- „ 2.0  feet 

Suction  pipe   friction 2  S  feet 

.Acceleration,  or  velocity  head 2.0  feet 

Pressure  to  prevent  vaporiiration  at  120°....  3.9  feet 
Assumed  lift 15.0  feet 

25.4  feet 
Available    head    for   lifting   suction   valves 
and   as   a    factor   of    safety    for   contin- 
gencies    8.6  feel 

Total   34.0  feet 

The  velocity  head  of  2  ft  is  a  typical  figure  for  a  centrifugal  pump,  in 
which  the  water  velocity  through  the  eye  of  the  impeller  wdl  be  about 
12  ft.  per  second. 

Fig.  164  shows  curves  of  suction  lift  or  suction  head  for  different  water 
temperatures.  The  right-hand  curve  represents  theoretical  conditions  as  in 
the  steam  tables,  or  the  pressure  to  prevent  vaporization  of  the  waler.  The 
curve  in  the  middle  represents  the  maximum  suction  lift  or  maximum  suction 
head.    For  ordinary  pipinc;.  the  left-hand  curve  should  be  used. 


Pig.  164.     Suction  Lift  or  Suction  Head  at  Different  Temperatures. 

If  the  capacity  is  too  high  for  a  pump  or  suction  pipe  handling  hot 
water  the  velocity  head  will  be  increased  and  the  water  handled  will  be 
vaporized.  If  the  suction  pressure  is  too  low,  or  the  lift  is  loo  high,  the 
hot  water  will  be  vaporized.  Vaporization  causes  knocking  in  the  dis- 
charge lines  and  greatly  reduces  the  capacity  and  efficiency  of  a  direct-acting 
pump.  The  capacity  will  also  be  decreased  with  centrifugal  pumps,  since 
the  water  passages  will  be  filled  partly  with  vapor  and  partly  with  water. 

The  effect  of  temperature  on  capacity  is  shown  by  a  test  of  a  centrifugal 
boiler  feed  pump,  due  to  John  Howard,  This  was  a  3-in.  three-stage  pump, 
designed  for  150  gal.  per  min.  against  195  lb.  pressure,  and  was  driven  al 
3O0O  r.p.m.  by  a  steam  turbine.  The  water  was  measured  by  a  flow  meter, 
which  was  afterward  calibrated  and  found  correct. 


ib.  Google 


AUXILIARIES 


The  capacity  test  (see  Fig,  165)  gave  the  results  for  3  constant  head  and 
far  constant  speed.  The  lirst  curve  was  obtained  by  the  use  of  a  pump 
governor,  and  the  second  when  the  governor  was  cut  out,  the  capacity  being 
varied  by  throttling  the  discharge. 


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3 

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^ 

^ 

4 

STOOi. 

leio 

\A 

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1 

'"" 

\ 

.UUU| 

i_ 

A 

0 

6 

0 

M 

0 

160 

Flow,SaJlons  per  Minute 


In  making  the  temperature-capacity  test  (Fig.  165)  the  temperature  of 
Ihe  water  in  the  open  heater  from  which  the  pump  took  its  suction  was 
varied  by  controlling  the  amount  of  steam  passing  into  it  The  great  varia- 
tion was  undoubtedly  due  to  the  extremely  small  head  (only  about  30  in. 
above  the  center-line)  on  the  suction  side  of  the  pump.  Because  of  this 
small  head,  the  guarantee  was  only  for  180  deg.,  but  by.  speeding  up  the 
pump  water  at  190  deg.  could  be  safely  handled. 

The  suction  lift  should  be  kept  low  or  the  suction  pressure  high  in  ac- 
cordance with  Fig.  164.  The  suction  pipe  should  be  as  direct  as  possible 
with  no  unnecessary  elbows  or  valves.  The  suction  piping  should  be  o( 
generous  siie;  a  velocity  of  2  ft,  per  second  should  not  be  exceeded  for  hot 

Suction  pipes  should  be  accessible  for  inspection  and  arranged  so  that 
valve  spindles  can  be  repacked  easily.  Particular  care  should  be  taken  to 
avoid  leaks  in  the  suction  pipe.  These  do  not  show  directly  on  the  dis- 
charge side,  although  they  are  sometimes  indicated  by  a  "jump"  of  the  pump 
at  the  start  of  every  stroke. 

With  long  lines  or  deep  lifts,  the  line  and  pump  can  be  kept  "primed" 
by  a  check  or  foot  valve  at  the  bottom.  With  long  suction  lines,  more  par- 
ticularly with  single  cylinder  pumps,  an  air  vessel  should  be  fitted  on  the 
line,  to  prevent  knocking. 


ib.  Google 


AUXILIARIES 


Injectors  as  Boiler  Feeders 
T  NJECTORS  are  made  in  many  forms,  but  Fig.  166  shows  the  typical  ar- 
*■  rangemetit  and  illustrates  the  method  of  operation.  Steam  is  admitted 
through  the  valve  M,  by  turning  the  handle  K,  and  enters  the  expanding 
nozzles  where  the  pressure  is  reduced  and  the  velocity  greatly  increased.  The 
steam  jet  is  then  guided  to  the  contracting  nozzle  or  lifting  tube  V.  In 
passing  from  the  first  to  the  second  nozzle  it  carries  along  the  air  in  the 
chamber  and  creates  a  vacuum.  The  water  to  be  pumped  rises  in  the  suc- 
tion pipe  and  fills  the  chamber.  The  steam  and  water  thus  enter  the  lifting 
tube,  passing  to  the  mixing  nozzle  C,  and  the  steam  is  condensed.  When 
the  water  and  steam  have  reached  the  delivery  nozzle  D  the  steam  has  been 
condensed  and  the  water  is  traveling  at  a  high  velocity  imparted  to  it  by 
the  steam.  The  delivery  nozzle  is  increased  in  cross- sectional  area,  reduc- 
ing the  velocity  and  hence  increasing  the  pressure  of  the  water.  Conse- 
quently its  head  is  sufficient  to  overcome  the  resistance  of  the  feed  valve, 
and  the  water  enters  the  boiler.  The  steam  has  thus  imparled  kinetic  energy 
to  the  water ;  this  energy  is  converted  from  velocity  to  pressure  in  the  de- 
livery nozzle.    The  water  is  heated  through  the  condensation  of  the  steam. 

The  action  of  the  injector  depends  not  only  upon  the  impact  of  the  jet 
of  steam,  but  also  upon  its  efficient  and  complete  condensation,  which  must 
occur  during  its  passage  through  the  combining  tube.  At  180  lb.  boiler  pres- 
sure the  water  must  attain  a  terminal  velocity  of  163  ft.  per  sec.  to  balance  the 
fressure,  and  something  more  to  lift  the  check  valve  and  enter  the  boiler, 
f  the  total  length  of  the  converging  combining  tube  is  7j4  in.,  the  interval 
of  time  during  which  the  steam  can  he  condensed  is  only  0.008  of  a  second 
and  the  acceleration  is  4  miles  per  second  per  second. 

Anything  that  tends  to  diminish  rapid  condensation  operates  against 
mechanical  efficiency.  An  increase  in  the  temperature  of  the  water  supply, 
moisture  or  superheat  in  the  steam;  all  tend  to  reduce  the  proper  ratio  be- 
tween the  weight  of  the  water  delivered  into  the  boiler  and  that  of  the 
motive  steam.  The  steam  must  undergo  instant  and  complete  condensation, 
and  its  velocity  must  reach  a  maximum  at  the  instant  of  impact  with  the 


Fis.  166.     A  Boiler  Peed  Injector. 


ib.  Google 


Lytton  Building,  Chicaio,  111.,  containine  1500  H.  P.  of  Hunc  Standard  Boiler*. 

D,slz.:hyCOOglC 


A  U  X  I  L I  A  R  1  K  S 


Experiments  with  saturated  steam  prove  that  the  flon  is  in  accord  with 
the  well-known  formula  based  upon  adiabatic  expansion.  The  velocity  of 
superheated  steam  is  slightly  higher  as  it  follows  the  law  of  a  perfect  gas 
until  condensation  due  to  expansion  begins ;  the  velocity  of  the  combined 
jet  would  consequently  be  increased,  but  this  advantage  is  overbalanced  by 
the  shorter  interval  of  contact  and  condensation,  during  which  the  additional 
heat  in  the  steam  must  be  abstracted.  Consequently  the  mechanical  efficiency 
is  lowered.  To  obtain  good  results  with  superheated  steam,  the  injector  tubes 
and  nozzles  must  be  specially  designed. 

The  practical  effect  of  superheated  steam  upon  the  action  of  an  injector 
is  to  reduce  the  maximum  capacity,  increase  the  mininjum  capaci^,  and  to 
lower  the  limiting  temperature  of  the  water  supply  with  which  the  injector 
can  operate.  Further,  with  high  pressure  and  superheat,  an  inefficiently  de- 
signed  instrument  is  inoperative.  It  is  therefore  advantageous  and  usually 
practicable  to  supply  tbe  injector  with  saturated  steam  through  a  special  pipe. 

The  steam  pressure  range  over  which  an  injector  will  work  depends  upon 
the  distance  between  the  steam  nozzle  and  the  lifting  tube.  With  a  fixed  dis- 
tance between  these  two  points  the  injector  will  operate  only  with  a  pressure 
range  of  about  7S  pounds.     If  the  injector  is  designed  for  175  lb.  maximum 

Sressure  the  minimum  steam  pressure  under  which  it  will  operate  will  be 
DO  pounds.  After  the  maximum  and  minimum  pressures  are  passed  the 
ratio  of  steam  velocity  to  quantity  of  water  for  complete  condensation  of 
the  steam  is  not  correct.  The  injector  can  be  operated  only  by  throttling 
or  opening  its  suction  line,  or  by  varying  the  distance  between  the  steam 
and  lifting  nozzles. 

Commercial  devices  are  supplied  to  render  the  injector  operative  over 
a  wider  steam  pressure  range.  In  one  tyf>e  a  half  turn  of  the  valve  handle 
allows  the  nozzle  to  remain  in  one  position  so  that  the  pressure  range  is 
90  or  100  lb.  maximum.  A  full  turn  of  the  handle  changes  the  position  of 
the  nozzle,  giving  a  higher  range  of  steam  pressures,  100  or  175  pounds. 
The  action  of  this  type  is  indicated  in  Table  39. 


Table  39.     Steam  Prewurcs  at  Lifting  Nonl«i  of  Injectors. 


FMd  WaUr  >t  100  Da(. 


Another  injector  has  a  double  set  of  nojtries;  the  first  lifts  the  water  and 
delivers  it  to  the  second,  which  acts  as  a  forcing  nozzle  to  deliver  the  water 
to  the  boiler.  The  capacity  of  this  type  can  be  changed  by  varying  lie 
amount  of  steam  admitted  to  the  lifting  nozzje.  The  quantity  of  water  varies 
directly  with  the  steam  pressure  at  the  lifting  nozzle ;  this  reduction  in 
water  is  desired  for  the  proper  functioning  of  the  forcing  nozzle.  Any 
change  in  steam  pressure  or  in  quantity  of  water  to  condense  the  steam  thus 
affects  both  nozzles,  so  that  pressure  changes  require  no  hand  adjustment 
-  This  type  has  operating  characteristics  as  indicated  in  Table  40. 


ib.  Google 


AUXILIARIES 


Table  40.     Steam  PreMurei  at  Lifting  Nonlet  of  Injector. 


Pnd  W>Ur 

Lift. 

7SD-,. 

100  Doc- 

ISO  Dx. 

140  D<«. 

suit  |uptfl 

sun 

Up  to 

Stut      Upta' 

stut    1   Upto 

25 

25 

350 
300 

25 
30 
40 

205 
205 
235 

35 
35 
45 

230 
230 
205 

35 

45 

45 
66 

240 
I8S 

50 
70 

210 
166 

55 
66 

140 
120 

20 

:!::  ■; 

Another  type,  commonly  called  an  inspirator,  Fig.  \S7,  has  two  nozzles, 
but  the  steam  pressure  cannot  be  adjusted  at  the  lifting  nozzle.  The  lifting 
and  forcing  nozzles  receive  steam  from  separate  openings,  so  that  the  steam 
pressures  can  be  adjusted  separately  through  vnlves  in  the  steam  lines. 


Fig.  167.     An  Impirator  Type  Injector. 

In  all  injectors  a  checic  valve  is  placed  in  the  mixing  chamber,  with 
openings  into  the  mixing  nozzle,  so  that  in  starting,  before  vrater  is  drawn 
into  the  mixing  tube  to  condense  the  steam,  the  mixture  of  steam  and  air 
can  esc.ipe  to  the  atmosphere.  When  the  steam  is  condensed  a  partial  vactmtn 
is  formed  in  this  chamber  and  the  check  valve  automaticall](  closet,  opening 
only  when  condensation  fails. 


ib.  Google 


AUXILIARIES  323 

The  thermal  efficiency  of  an  injector,  considered  as  a  pump  only,  is  about 
2  per  cent.  As  a  combined  pump  and  feed-water  heater  the  thermal  efficiency 
is  nearly  100  per  cent,  the  only  heat  of  the  steam  not  returned  to  the  boiler 
being  a  small  percentage  lost  by  radiation.  If  the  exhaust  steam  available  for 
feed-water  heating  is  not  sufficient  to  heat  the  water  above  its  limit  possible 
with  the  injector,  the  latter  is  a  good  feedbg  apparatus.  On  the  other  hand 
the  injector  is  not  so  economical  if  it  interferes  with  the  economic  use  of 
exhaust  steam  in  the  plant  It  is  rarely  installed  as  the  main  feed  unit, 
unless  in  small  plants  where  a  feed  pump  might  not  receive  attention.  The 
injector,  however,  is  so  reliable,  compact  and  inexpensive  that  it  almost  always 
is  placed  in  the  boiler  room  as  an  auxiliary  feed  device,  to  be  used  should 
die  main  feed  pumps  become  inoperative. 

Many  plants  operate  at  high  over-all  economy  during  the  heating  season 
when  all  the  exhaust  steam  is  utilized,  but  decrease  their  economy  when 
the  exhaust  is  wasted  to  the  atmosphere.  Extra  exhaust,  winter  or  summer, 
can  be  used  to  feed  the  boilers  by  means  of  an  exhaust  steam  injector.  The 
heat  taken  from  the  boiler  in  the  form  of  steam  is  nearly  all  returned  at 
once  by  the  live-steam  injector,  but  the  exhaust-steam  injector  returns  heat 
to  the  boiler  that  is  about  to  escape  through  the  engine  exhaust  pipe.  The 
water  so  condensed  is  tree  from  scale-forming  matter,  but  all  oil  should  be 
removed  from  the  exhaust  steam.  Restarting  an  exhaust-steam  injector  is 
not  difficult  when  the  water  flows  to  it  under  pressure  or  live  steam  is 
available. 

Air  entering  the  injector  will  always  cause  a  "break,"  so  l^at  unusual 
care  should  be  taken  to  avoid  leaks  in  the  suction  pipe.  With  some  waters 
trouble  is  caused  by  scale  in  the  lifting,  mixing  and  discharge  nozzles;  this 
is  probably  due  to  evaporation  to  dryness  of  water  remaining  after  a  stop. 

Economy  of  Feed  Water  Heating 
T^E  principal  function  of  a  feed  water  heater  is  to  utilize  the  heat  from 
J-  exhauBt  steam  or  flue  gases,  which  would  otherwise  be  wasted.    The  per 
cent  of  saving  effected  by  heating  the  feed  water  may  be  expressed  by  the 
following  formula: 

Per  cent  saving  =  lOO  —Jr^±-^  (28) 

where  d  =  the  temperature  of  water  entering  the  heater,  t,  =  the  tempera- 
ture of  water  leaving  the  heater  and  H  =  the  total  heat  above  32  degrees 
per  pound  of  steam  at  the  boiler  pressure. 

Feed  water  heating  results  in  the  further  advantages:  first,  of  increasing 
the  steaming  capacity  of  the  boiler  by  eliminating  the  heat  required  for 
heating  the  feed  water;  second,  by  its  action  as  a  purifier  certain  scale- 
forming  ingredients  in  the  feed  water  are  removed;  and  third,  by  feed- 
ing water  into  the  boiler  drum  at  or  near  the  steam  temperature  the  tendency 
of  setting  up  temperature  strains  in  the  boiler  metal  is  eliminated. 

Classification  of  Feed  Water  Heaters 
l-lEATERS  may  be  classified  into  three  main  groups,  viz:  closed  heaters, 
■^  *•  open  heaters  and  economizers.  Open  or  closed  heaters  may  utilize  ex- 
haust or  live  steam,  while  economizers  utilize  the  waste  heat  in  the  exit  flue 
gases.  The  selection  of  one  or  more  of  these  types  of  beaters  will  depend 
largely  upon  conditions  at  the  particular  plant  in  question. 

Open  heaUrt  may  be  of  three  different  types.  In  the  one  type,  generally 
known  as  the  live  steam  purifier,  live  steam  is  used  to  heat  the  feed  water 
up  to  a  temperature  of  approximately  300  degrees  in  order  to  precipitate  out 


ib.  Google 


ib.Google 


AUXILIARIES  325 

such  scale-forming  elements  as  the  sulphates  of  lime  and  magnesia.  The  use 
of  the  live  steam  purifier  should  be  confined  to  those  plants  where  the  feed 
water  contains  sulphates. 

A  second  type  of  open  healer  is  designed  for  the  use  of  exhaust  steam 
at  atmospheric  pressure  or  less,  while  the  third  type  is  designed  for  the  use 
of  exhaust  steam  at  back  pressure  up  to  10  or  20  lbs.,  depending  upon  the 
back  pressures  on  the  auxiliary  engines  and  pumps. 

In  the  open  heater.  Fig.  168,  steam  enters  the  opening  of  the  shell  on 
one  side,  pear  the  top,  and  passes  through  an  oil  separator  into  the  mixing 
chamber.  The  cold  feed  water  enters  at  the  top  of  the  shell,  and  passes 
over  and  through  a  set  of  perforated  trays,  where  it  is  broken  into  fine 


Fig.  168.     Cochrane  Metering  Open  Feed  Water  Heater. 

particles,  to  insure  thorough  and  intimate  contact  with  the  steam.  The  mix- 
ing of  steam  and  water  condenses  the  steam  and  the  mixture,  or  hot  water, 
falls  to  the  bottom  of  the  shell  through  a  bed  of  filtering  material.  A  float 
controls  the  amount  of  water  entering  the  heater  so  that  a  constant  water 
level  is  maintained  at  the  bottom.  An  overflow  provides  against  the  water 
level  rising  too  high  in  the  shell  and  backing  up  into  the  exhaust  steam  lines, 
should  the  float  control  become  inoperative. 

Since  the  heat  given  up  by  the  steam,  plus  the  losses  due  to  radiation,  must 

Tial  that  gained  by  the  water,  the  amount  of  steam  to  raise  a  given  amount 
water  to  a  desired  temperature,  is  easily  calculated,  as  is  also  the  resulting 


ib.  Google 


326  AUXILIARIES 

feed-water  temperature,  when  the  amounts  of  ateam  and  water  are  given.  The 
radiation  losses  can  be  made  negligible  with  proper  insulation,  so  this  factor 
is  eliminated  in  the  formula: 


(29) 


W  ~  H  +  32- 


^  =  Temperature  of  water  to  boilers  (hot) 
ti  =  Temperature  of  water  to  beater  (cold) 
//  =  Total  heat  of  steam  at  back  pressure  conditions,  B.tn. 
,S  =  Weight  of  steam,  pounds 
JT  =  Weight  of  water,  pounds. 

The  heat  of  the  liquid  at  the  two  temperatures  should  be  used  for  exact 
calculations,  but  the  foregoing  is  sufficiently  accurate  for  commercial  pnr< 
poses. 

In  selecting  an  open  heater,  the  following  features  should  be  considered: 

1.  Site.    The  heater  must  have  sufficient  steam  space  and  tray  area. 

2.  OH  Separator.  This  is  necessary  if  exhaust  steam  contains  oil,  as 
when  reciprocating-engines  or  pumps  exhaust  into  the  heater.  Oil 
must  be  efficiently  separated  and  drained  off. 

3.  FUter  Bed.    This  is  frequently  omitted. 

A,  Hoi  Well,  or  space  at  bottom  must  be  ample  so  as  to  act  as  a  settling 
basin  and  reservoir  for  the  feed  pump.  Vapor  vent  should  be  pro- 
vided  for  escape  of  air  and  vapor.  (Hot  well  can  also  be  used  as  a 
purifier  space.) 

>  maintain  proper  water  level  in  the 

The  design  should  also  be  considered  in  the  light  of  its  applicability 
to  plant  requirements. 

That  part  of  the  heat  so  used  which  is  not  converted  into  work  is  re- 
turned to  the  boiler  instead  of  being  rejected  to  the  condenser  circulating 
water,  giving  the  maximum  thermal  efficiency. 

In  one  heater  an  indicating  and  recording  mechanism  is  supplied  to 
measure  the  feed  water,  so  that  the  quantity  can  t>e  checked  closely  and  the 
heat  balance  and  performance  easily  calculated.  These  devices  are  valua- 
ble in  order  to  maintain  a  running  check  on  performance. 

When  the  exhaust  steam  pressure  is  above  atmosphere,  exhaust  valves  are 
used  on  the  heater  or  exhaust  steam  lines.  These  allow  the  steam  to  be  ex- 
hausted to  the  atmosphere  or  to  the  low  pressure  end  of  the  main  turbine. 
In  one  valve  a  nest  of  spring-loaded  relief  valves  performs  this  function.  These 
valves  have  individual  dash  pots.  The  action  with  them  is  smoother  and  less 
likely  to  stick  than  with  one  large  valve.  The  tension  of  the  valve  springs 
out  be  regulated  by  a  handwheel  from  outside  the  valve.  The  high  back 
pressure  that  may  be  required  in  the  morning  to  run  the  heating  system  can 
be  decreased  in  the  afternoon  when  the  buildings  have  been  warmed. 

A  thermostat  can  be  attached  to  a  heater  to  control  the  drives  of  auxili- 
aries. These  can  be  arranged  for  double  drive,  with  motor  on  one  side  and 
turbine  on  the  other.  When  too  much  steam  is  exhausted  to  the  heater  the 
pressure  in  the  exhaust  lines  is  raised,  and  the  temperature  is  increased.  The 
thermostat  then  operates  to  throttle  the  turbine,  and  more  of  the  load  is 
taken  by  the  motor.  Thus  less  exhaust  steam  is  supplied,  and  the  excess  of 
steam  is  reduced  in  proportion.  When  the  supply  of  steam  in  the  heater  is 
insufficient,  the  pressure  in  the  exhaust  line  drops,  the  temperature  is  re- 
duced and  the  thermostat  permits  more  steam  to  flow  to  the  turbine.  The 
turbine  then  picks  up  the  load  and  furnishes  more  steam  to  the  heater. 


ib.  Google 


AUXILIARIES  327 

Relief  valves  can  be  used  to  bleed  steam  from  one  of  the  low  pres- 
sure stages  of  the  main  turbine  and  lead  it  to  the  heater  during  periods 
of  low  pressure  in  the  exhaust  line.  A  high  feed-water  temperature  is  thus 
maintained. 

Closed  feed  water  heaters  may  be  grouped  into  two  classes,  steam  tube 
and  water  tube.  Those  in  which  the  steam  passes  through  tubes  and  the 
water  is  contained  in  the  heater  shell  are  known  as  steam  tube  types,  while 
those  in  which  the  water  flows  through  the  tubes  and  the  steam  is  con- 
tained in  the  heater  shell  are  classified  as  water  tube  types.  Steam  tube  and 
water  tube  heaters  may  operate  on  the  parallel  current  or  counterflow 
principle,  and  they  may  be  designed  so  that  the  steam  or  water  makes  one 
pass  through  the  heater  (single  flow),  or  so  that  the  steam  and  water  may 
make  several  passes  (multi-flow). 


F^ig.  169.     CloMd  Feed-Water  Heater. 

F^.  1^  illustrates  a  typical  closed  water  lube  feed-water  heater  of  the 
multi-now  type.  Water  is  circulated  in  six  passes  to  insure  maximum  heat 
transfer  from  steam  to  water.  The  number  of  passes  varies,  but  two  is  die 
usual  practice.  Tubes  are  secured  to  tube  sheets  by  screwing,  welding  or  ex- 
panding. In  some  designs  each  tube  is  packed  with  ferrule  glands,  to  simplify 
replacements. 

The  floating  head  construction  provides  for  expansion  and  contraction  of 
the  tubes  under  varying  temperatures.  This  feature  is  important  when 
straight  tubes  are  secured  rigidly  at  each  end  to  the  tube  sheet. 

Most  closed  heaters  are  arranged  so  that  they  can  be  installed  either 
vertically  or  horizontally,  as  best  suits  the  space  and  piping. 

The  Patterson-Berry  man  closed  feed-water  heater,  illustrated  in  Fig. 
17C^  is  of  the  water  tube  type.  The  water  makes  a  double  pass  through 
inverted  U-tubes,  while  the  steam  passes  through  the  body  of  the  heater.  A 
chamber  at  the  bottom,  provided  with  a  blow-off  connection,  serves  as  a 
receptacle  for  the  collection  of  scale,  sediment,  etc. 

In  one  heater,  Fig.  171,  coiled  water  tubes  are  connected  to  the  top  and 
bottom  water  headers  with  special  leakproof  unions.  The  coils  allow  for  ex- 
pansion and  contraction  of  the  lubes  and  present  maximum  heating  surface 
This  type  is  of  the  one-pass  design,  water  entering  at  the  bottom  header  and 
leaving  from  the  top.  Tubes  are  examined  or  repaired  through  a  door  id 
the  front  of  the  shell 


ib.  Google 


ib.Google 


AUXILIARIES 


Pig.  170.     U-Tube  Feedwater  Heater. 

Open  or  Closed  Heaters 
'T^HE  general  construction  of  the  power  plant  usually  determines  the  type  of 
■*■  healer.  In  marine  service,  for  instance,  because  of  space  htnitations  and 
the  rolling  of  the  ship,  closed  heaters  are  usually  installed.  Open  heaters 
adapted  to  this  service  are  in  general  use,  however,  by  the  English  mercantile 
marine.  In  ice  plants  the  closed  heater  might  be  preferable,  since  the  con- 
densed steam  would  be  available  for  ice-making ;  on  the  other  hand,  much 
better  ice  is  made  with  the  open  heater,  because  it  acts  as  a  reboiler,  driving 
off  the  air  and  other  gases,  which  purge  off  through  the  vent.  With  closed 
heaters  this  air  passes  through  the  heater  into  the  bailer  and  engine.  A 
greater  amount  of  boiling  is  then  required  in  the  reboiler,  with  greater  waste 
of  steam.  Vacuum  reboilers  are  sometimes  found  inadequate,  and  the 
capacity  must  be  increased  by  the  use  of  atmospheric  reboilers. 


ib.  Google 


AUXILIARIES 


Fig.  171.     Hulti-tubular  Feedwatcr  Heater. 


nipared  in  the  following  tabulation: 


Open  Heater 

Eff^ 
With  sufficient  exhaust  steam  for 
heating,  the  feed  water  can  reach 
the  same  temperature  as  the  enter- 
ing steam. 
Scale  and  oil  do  not  affect  the 


Closed  Heater 

The  maximum  temperature  of  the 
feed  water  will  always  be  several 
degrees  lower  than  the  temperature 
of  the  steam. 

If  the  scale  or  oil  are  deposited 
upon  the  tubes,  heat  transmission 
is  lowered. 

Prtssurrs 

It  is  not  ordinarily  subjected  to  The    water    pressure    is    slightly 

much   more   than    the  atmospheric  greater  than  that  in  the  boiler,  when 

pressure.  ihe  heater  is  placed  on  the  pressure 

Can  be  made,  however,  for  back  side  of  the  feed  pump,  as  is  cus- 

pressures  of  15  lb.  or  more.  tomary. 


ib.  Google 


AUXILIARIES 


If  the  heater  is  to  be  used  with  It  will  safely  withstand  any  ordi- 

a  back  pressure,  a  good  valve,  pre-  nary  pressure.    However,  any  shul- 

ferably  with   more  than  one  disk,  off  valve  in  the  feed  line  should  be 

should     be     fitted.    Otherwise,  the  placed  between  ihe  feed  pump  and 

teck  pressure  valve  might  stick  and  the  heater,  with  a  check  valve  be- 

blow  up  the  heater.  Iween  the  heater  and  the  boiler. 

PurifiealioH 

Since  the  exhaust  steam  and  feed  The  oil  does  not  come  in  con- 

water    mingle,    provision    must    be  tact  with  the  feed  water, 

made  to  remove  the  oil  from  the  Scale  is  removed  only  with  diffi- 

Eteam.  cnlty. 

Scale  and  other  impurities  pre- 
cipitated in  Ihe  heater  are  easily 
removed  and  do  no  harm. 

CorrotioH 

The  open    heater     prevents  cor-  With  the  closed  heater  the  oxy- 

rosion  by  driving  out  oxygen  orig-  gen  is  not  discharged  and  corrosion 

inally  dissolved  m  the  water.  of  piping  and  boilers  occurs. 

Location 

Must  always    be  placed     higher  May  be  placed  anywhere  on  the 

than  the  pump  on  the  suction  side.  pressure  side  of  the  pump. 

The  greater  the  vertical  distance 
between  the  pump  and  heater,  the 
better. 

Feed  Pumps 

With  supply  under   suction  two  Only  one  cold-water  feed  pump 

pumps  are  necessary  and  one  roust  is  necessary, 

handle  hot  water. 

AdaptabUity 

Particularly   adaptable   for  beat-  Adapted  to  use  in  small  space, 

ing  systems  and  wherever  the  re-  and  when     condensate  of  exhaust 

turns  are     piped     directly     to  the  steam  can  be  used  in  process  work, 

heater, 

Bconomizera 

PIE  economizer  is  a  closed  feed-water  heater  utilizing  the  hot  waste  gases 
of  combustion.  As  a  piece  of  apparatus  for  the  promotion  of  boiler 
room  economy,  the  economizer  is  rapidly  gaining  favor,  due  to  increasing 
prices  of  fuel,  and  to  the  large  stack  losses  inherent  with  the  present  prac- 
tice of  forcing  boilers  to  high  ratings. 

Two  types  of  economizer  may  be  met  in  practice,  one  in  which  the 
economizer  is  an  integral  part  of  the  boiler  and  the  other  in  whidi  it  is  an 
independent  unit.  When  an  economiier  forms  an  integral  of  a  boiler  its 
design  is  generally  such  that  steel  tubes,  headers  and  drums  have  to  be 
used.  Inasmuch  as  there  is  extreme  liability  for  corrosion  due  to  the  con- 
densation of  moisture  or  sweating  of  the  outside  of  economizer  tubes,  cast 
iron  should  be  used  rather  than  steel,  due  to  its  lesser  tendency  to  fail 
by  corrosion,  unless  there  is  some  special  method  taken  to  prevent  the  cor- 
rosion of  the  steel. 

Fig.  172  illustrates  one  widely  used  type  of  independent  economizer.  It 
consists  of  vertical  cast  iron  tubes,  which  are  arranged  in  sections  in  the  f!ue 
leading  from  boiler  uptake  to  stack.  When  in  position  the  sections  are  com- 
posed of  bottom  and  top  headers  into  which  the  tubes  are  pressed,  a  metal-to- 
melal  joint  being  formed.  The  top  and  bottom  headers  of  the  sections  are 
connected  to  branch  pipes,  one  extending  lengthwise  at  the  top  of  the 
economizer  and  the  other  extending  lengthwise  at  the  bottom.    Both  top  and 


ly  Google 


,Google 


AUXILIARIES 


Pig.  173.     Oreen  Fuel  Bconomiser. 

bottom  branch  pipes  are  located  accessibly  outside  of  the  economizer  setting 
or  casing.  The  feed  water  enters  the  economizer  through  the  lower  branch 
pipe  nearest  the  gas  outlet  of  the  economizer  and  leaves  through  the  upper 
branch  pipe  nearest  the  point  where  the  Rue  gases  enter  the  economizer  from 
the  boiler. 

Either  mechanical  soot  blowers  or  mechanically  operated  scrapers  may 
be  used  for  cleaning  the  external  tube  surfaces.  If  scrapers  are  used,  their 
operating  mechanism  is  generally  placed  on  the  top  at  the  economizer.  The 
motive  power  for  scraper  operation  may  be  supplied  from  some  convenient 
line  shaft  or  by  individual  motor  or  engine. 

Blow  off  valves  and  safety  valves  must  be  provided  with  economizers. 
For  flexibility  and  continuity  of  boiler  operation  it  is  desirable  to  have 
a  by-pass  flue  from  boiler  uptake  directly  to  the  stack.  Inasmuch  as  gas 
explosions  sometimes  occur  within  economizer  settings,  it  is  desirable  to 
provide  quick  opening  explosion  doors  therein. 

Economizer  Performance 
T^E  stack  gases  in  a  boiler  indicate  the  amount  of  heat  available  for  feed- 
*■   water  heating.    Table  41  gives  roughly  the  heat  content  of  the  gases  of 
combustion  in  the  flues  and  uptakes. 

If  the  fuel  has  a  heat  value  of  10,000  B.t.u.  per  pound,  the  stack  gases 
are  at  500  deg.,  and  the  stoker  is  of  the  overfeed  type,  then  Table  41  shows 
that  the  heat  in  the  stack  gases  will  be  about  182  per  cent,  or  1820  B.t.u., 
for  every  pound  of  fuel  consumed  in  the  furnace.  The  difference  between 
the  heat  in  the  gases  entering  and  leaving  the  economizer  represents  the 
saving.  In  the  example  just  mentioned,  if  the  gases  leave  at  350  deg..  they 
contain  12  per  cent  of  the  heat  in  the  fuel;  the  economizer  then  saves  62 
per  cent. 

The  economizer  is  most  useful,  therefore,  when  the  heat  of  the  stack 
gases  is  greatest  in  proportion  to  the  heat  of  the  fuel  or  when  the  losses 
would  ordinarily  be  die  greatest ;  as  with  an  overloaded  boiler,  hand-fired  or 
having  an  overfeed  stoker  and  draft,  The  overload  on  the  boiler  will  be 
indicated  by  high  stack  temperature.  As  is  shown  by  Table  41  with  normal 
load  and  efficient  tiring,  the  stack  losses  may  not  be  sufficient  to  warrant 
the  expense  of  an  economizer.  The  slack  gases  will  not  heat  the  feed  water 
appreciably,  unless  the  economizer  is  large  and  costly. 


ib.  Google 


AUXILIARIES 


Table  41.     Heat  of  Fuel  (in  Percent)  Pretent  in  Flue  Oaae*. 


T_.5=?t^ 

"■ssas- 

OnrfMd  or  Natainl  ' 
DnftBtokw          I 

N^S^JTSS. 

^bE'.i'' 

ol  combust- 

18 

M                  1 

30 

:::: 

n.b 

14.0           ! 

400 

17.4 

12.2 
13.8 
15.4 

16.1  I 

18.2  r 
20.3 

650 

26.2 

17.0 
18.6 
20.1 

22.4 
24.4 
26.6 

700 

750 

21.7 
23.2 

::::      1 

The  method  of  calculating  economizer  performance  is  given  by  A.  B. 
Clark  as  follows:  Assume  that  the  economizer  is  to  be  so  proportioned 
that  the  combined  efficiency  of  both  boiler  and  economizer  will  be  80  per 
cent,  the  coat  containing  10;000  B.t.u.  per  pound.  The  steam  has  a  pressure 
of  250  lb.  g^e,  and  250  deg.  of  superheat,  the  feed  water  entering  the 
economizer  at  100  deg.  The  heat  contained  will  then  be  1340  B.Ln.  per 
pound  of  steam.  The  feed  water  contains  68  B.t.u.,  so  that  the  heat 
given  up  by  boiler  and  economizer  is  1272  B.t.u.  per  pound  of  steam.  As 
the  efficiency  is  80  per  cent.  8000  B.t.u.  of  the  10.000  B.t.u.  in  each 
pound  of  coal  is  used,  and  the  evaporation  is  8000  ~  1272,  or  6.3  lb.  of  water 
per  po'md  of  coal. 

Allowing  for  excess  air  and  infiltration  of  air,  about  12.25  lb.  of  flue 
gases  will  be  produced  per  pound  of  coal  burned.  If  the  radiation  joss  is 
neglected,  the  heat  given  up  by  the  flue  gases  must  equal  the  heat  absorbed 
by  the  water;  that  is,  the  product  of  the  specific  heat,  weight  and  drop  of 
temperature  of  the  flue  gases  must  equal  the  product  of  the  specific  heat, 
weight  and  rise  of  temperature  of  the  water. 

Let  tg  represent  the  drop  of  temperature  of  the  flue  gases  and  fur  repre- 
sent the  rise  of  temperature  of  the  water.    Then 

0.24  X  12.25  X  <g  =  1   X  6J    X  iw 

Ig  _        1x6-3        „214 
'tw  ~     0.24  X  1225" 

This  means  that  for  every  degree  of  temperature  increase  of  the  6J  lb. 
of  water,  the  12.25  lb.  of  flue  gases  will  drop  2.14  deg.  in  temperature. 

The  water  passing  through  the  economizer  is  taken  as  lOOjiOO  lb.  per 
iKHir,  which  the  boiler,  it  is  assumed,  can  evaporate.  The  temperature  of 
the  ^ses  leaving  the  boiler  is  taken  as  tiOO  degrees. 

The  average  temperature  difference  between  the  water  and  gases  in  the 
case  assumed  above  is  484 J  degrees.  Tests  on  economizers  show  that 
the  rate  of  heat  transfer  from  gas  to  water  is  about  5.5  B.t.u.  per  square 
foot  of  surface  per  hour  per  degree  temperature  difference  between  the 
gases  and  the  water,  when  the  economizer  is  proportioned  for  a  gas  flow  of 
3.O0O  lb.  per  hour  per  square  foot  of  area.  It  will  be  4  B.t.u.  per  square 
foot  if  the  flow  is  reduced  to  3,000  lb.  per  hour  and  in  proportion  between 
these  two  points. 

The  water  usually  flows  through  all  of  the  sections  in  parallel.  With  long. 
narrow  economizers  and  where  the  gases  have  a  large  drop  in  temperature 
the  economizer  is  sometimes  subdivided  into  groups,  through  which  the 
water  is  passed  in  series,  progressing  in  a  direction  counter  to   that  of  the 


ib.Google 


AUXILIARIES 


gases,  thus  obtaining  a  greater  total  transmission  of  heat  according  to  the 
coutiter-flow  principle.  The  individual  sections  can  also  be  connected  in 
series,  but  this  complicates  cleaning  and  blowing  down. 

The  transmission  coefficient  varies  with  the  mean  gas  temperature  as 
shown  in  Fig.  173,  due  to  Geo.  II.  Gibson.    The  rate  of  heat  recovery  by  the 


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en 

in  Hr.  p<r  Ft.of  npa 'm  Sccttcn 


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/ 

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• 

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/ 

/*/ 

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w 

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IS '  re  I    le  n  n  II 

Water.  hl«KLbip«r5q.Ft.  per  hiour. 

174.    Variation  of  Rate  of  Heat  Recovery  by  the  Bconomiier. 


ib.  Google 


,Google 


AUXILIARIES 


...  iirectly  as  the  load  on  the  boiler  to  which  it  is  con- 
nected. This  is  shown  by  Fig.  174,  also  due  to  Geo.  H.  Gibson.  The  heal 
recovery  while  the  load  is  increasing  appears  to  be  somewhat  less  than  while 
it  is  decreasing,  owing  to  the  fact  that  the  rate  of  heat  recovery  can  be 
determined  only  by  measuring  the  temperature  of  the  water  as  it  leaves  the 


Using  the  higher  value  for  calculation,  the  heat  transfer  per  square 
toot  per  hour  is  5.5  X  484J.  or  2663  B.t.u.  Therefore  the  surface  required 
to  raise  100,000  lb.  of  water  through  10  deg.  is  100,000  X  10  ^  2663  =  376 
sq.  ft.  The  next  step  is  to  assume  new  values  for  gas  and  water  temper- 
atures and  calculate  the  surface  required. 

Table  43.     General  Dimcnsioiu  of  Economlsers. 


^^ 

9 
10 

n 

Wetchtof 

Eitacnal 

Ktuntoot 

^jgiOw 

Ft— In. 

4 
4 

4 

1,636 
1,756 

1877 

51.0 
55.8 
60.7 

4 
8 

12 

2—  5 
4^10 
7—3 

4 
6 
6 

12 

9 
10 
11 

12 
9 

2,006 
2,388 
2,570 

65.4 
76.5 
83.8 

16 
20 
24 

7—  8 
12—  1 

14—  6 

6 
6 
8 

2,751 

2,942 
3.096 

Sl.O 
98.3 
1(E.0 

28 
32 
36 

16—11 
19—  4 
22-llH 

8 
8 

8 

10 
11 
12 
9 
10 
11 

iiiiil 

1U.7 
121.4 
131.0 

40 

44 
48 

25—  4H 

27-9^ 
31—  5 

10 
10 
10 

127,5 
139.6 
161.7 

52 
56 
60 

33-10 
36—  3 
38—  8 

10 
12 
12 

12 
9 
10 

4,684 
4,380 
4.742 

163.8 
153.9 
107.6 

64 
68 
72 

42-3^ 
44—  8J4 
47—  IH 

12 
12 

11 
12 

5.104 
5.488 

182.0 
196.6 

76 
80 

49— 6M 
63-2 

As  the  temperatures  of  the  water  and  gas  approach,  the  surface  must 
be  increased  for  a  given  rise  of  the  water  temperature.  The  ashpit  loss  will 
be  about  3  per  cent  and  the  unaccounted-for  losses  and  radiation  are  about 
3.S  per  cent.  As  the  efficiency  of  boiler  and  economizer  is  80  per  cent,  the 
flue-gas  loss  will  be  13.5  per  cent,  or  1350  B.t.u.  per  pound  of  coal. 

Flue  gases  from  the  coal  will  contain  about  0.5  lb.  of  water  in  the  form 
of  superheated  steam ;  therefore,  as  the  total  weight  of  the  gases  is  12.25  lb. 
per  pound  of  coal,  the  gases  will  weigh  11J5  lb.  and  the  water  vapor 
0.50  pound. 

Assuming  that  the  air  entering  the  boiler  is  at  a  temperature  of  70  deg. 
the  temperature  of  the  escaping  gases  can  be  found  from  the  equation, 
11.75X054   ('  —  70)    -f-  O.SX0.48((— 212) -1-0.5x970.4 
+  0.S  (212  —  70)  =  1350 


:  340  c 


8,000 


ib.  Google 


ib.Google 


AUXILIARIES 


deg.  from  the  assumed  initial  temperature.  The  return  in  heat  units  per 
pound  of  coal  is  fired  is  6J  X  120  =  756  B.tu.,  or  a  return  of  7.56  per  cent 
on  a  heat  value  of  10,000  B.t.u. 

Having  determined  the  surface  area  of  the  economizer,  the  space  require- 
ments can  be  checked  with  fair  accuracy  from  Table  42,  which  gives  the 
dimensions  of  the  economizer  made  by  a  prominent  manufacturer.  This 
table  will  apply  as  a  general  guide  in  delermming  Ihe  room  required. 

Air  Heaters 

HEATING  the  air  supply  to  furnaces  by  abstracting  beat  from  the  exit 
gases  is  just  as  logical  a  method  of  saving  fuel  as  is  heating  the  feed 
water  in  the  same  way.  The  saving  effected  can  be  directly  measured  by 
the  drop  in  temperature  of  the  flue  gases  in  passing  through  the  air  healer, 
or  by  the  rise  in  temperature  of  the  air,  when  the  weights  of  air  and  gas  per 
pound  of  fuel  are  known. 

Usually  the  gases  are  passed  through  vertical  pipes  of  about  3-tn.  bore. 
around  which  the  air  flows  horizontally.  In  a  system  recently  described 
by  /.  I'an  Brunt,  the  heater  consists  of  a  nest  of  serai-circular  plates  ar- 
ranged in  pairs  so  that  the  air  flows  in  a  path  curved  circumferentially  from 
inlet  to  outlet,  while  the  gases  flow  between  the  plates  in  straight  chordal 
paths.     This  design  makes  a  very  compact  and  convenient  arrangement. 

The  rate  of  heat  transmission  varies  with  the  cleanliness  of  the  surface. 
with  the  gas  and  air  velocities,  and  with  the  diflference  in  temperature  be- 
tween the  gas  and  the  air.  Consequently,  the  areas  of  the  passages  and  of 
the  heating  surface  are  directly  related. 

In  Table  43  the  symbols  have  the  following  meanings : 
W  ^  Weight  of  air  or  gas,  pounds  per  hour. 
A  =  Area  of  passages,  square  feet. 

R  =  B.t.u.  transmitted  from  flue  gas  to  air  per  square  foot  of 

surface   per    boar   per    degree    difference   between    average 

temperatures  of  gas  and  air. 

Table  43  can  be  entered  with  W/A,  and  the  value  of  R  found.     The 

heat  (in  B.t.u.)  to  be  transmitted  per  hour  divided  by  R  times  the  average 

temperature  difference  between  the  gas  and  air  is  the  heating  surface  required. 

Table  43.     Heat  Transmitted  Between  Flue  Oases  and  Air. 


Vdw 

•  at  R 

100 

1.6 
1.9 
2.2 
2.S 

1 
1 

200 

1.7 
2.S 
2.9 
3.S 

soo 

2,000 

2.7 

Jooo::::: 

This  table  has  been  prepared  on  the  assumption  that  the  values  of  IV/A 
for  gas  and  air  will  not  vary  more  than  10  to  15  per  cent.  The  area  through 
the  tubes  is  commonly  from  30  to  50  per  cent  greater  than  that  of  the  equiva- 
lent breeching.  The  air  passages  can  be  proportioned  in  the  same  manner 
as  directed  in  Chapter  6  on  CHIMNEYS,  allowing  for  the  temperature  of  air 
desired,  and  making  the  area  between  the  tubes  the  mean  of  the  hot  and  cold 
air  ducts.  The  toss  of  draft  through  a  well-designed  heater  will  be  about  0.1 
in,  of  water  column.  The  loss  of  air  pressure  will  be  from  0.1  to  02  in.; 
and  to  this  must  be  added  the  resistance  of  the  air  ducts,  making  allowance 
for  bends  that  cannot  be  avoided. 


ib.  Google 


ib.Google 


AUXILIARIES  341 

Heating  the  air  for  combustion  is  practiced  to  a  considerable  extent  in 
marine  work,  witli  mechanical  draft.  In  the  Howden  system  the  air  is  forced 
through  the  heater,  while  in  the  Elhs  and  Eaves  system  it  is  drawn  through 
t^  the  induced  draft  fan. 

Most  of  the  applications  in  land  service  have  been  confined  to  municipal 
refuse  destructors  wherein  forced  draft  fans  or  steam-jet  blowers  draw  the 
air  through  the  heater  and  dischat^e  it  into  a  closed  ashpit,  the  tempera- 
ture rise  being  from  300  to  500  deg. 

When  the  air  for  combustion  is  heated  300  deg.  or  more,  trouble  mi^ht 
be  expected  from  grate  bars  burning  out  more  rapidly,  and  from  excessive 
clinkering;  btit  this  does  not  appear  to  be  the  case. 

When  heat  that  wotild  otherwise  be  wasted  in  industrial  processes  can 
be  used  to  heat  the  air  for  combustion,  the  thermal  efficiency  of  the  whole 
plant  is  increased.  In  electric  power  plants  it  is  becoming  general  so  to 
utilize  the  heated  air  resulting  from  ventilating  the  generators,  the  air  ducts 
being  piped  from  the  generators  to  the  forced  draft  fan  inlets.  The  forced 
draft  air  can  be  drawn  from  parts  of  the  boiler  room  or  from  the  space 
near  industrial  processes,  space  that  otherwise  might  become  unpleasantly 
hot,  making  for  more  comfortable  operation  and  increased  thermal  efficiency. 

Auxiliary  Engines  and  Turbines 

IN  certain  definite  fields,  according  to  /.  S.  Barttow,  the  small  turbine  is  of 
conceded  superiority,  and  in  other  fields  the  engine  must  hold  sway.  The 
following  factors  determine  the  adaptability,  cost  and  economy  of  the  equip- 
ment to  be  installed  for  any  given  service ; 

Ar^Maximum  or  minimum  permissible  speed,  and  whether  the  Kp- 

paratus  is  driven  at  constant  or  variable  speed. 
6.— Steam  pressure   (initial  and  final)    and  superheat  temperature, 

C. — Power  capacity  of  apparatus. 

D. — Space  requirements  of  turbine  and  engine  units,  available  room, 
power  house  construction,  and  cost  of  foundation  or  other  sup- 
porting structure. 
E. — Use  or  application,  if  any,  of  exhaust  for  feed  water  heating, 

steam  heating  or  process. 
F. — Available  cooling  water  supply;  if  the  turbine  or  engine  is  to 
be  run  condensing,  the  temperature  of  the  water  and  whether  it 
must  be  artificially  cooled  and  re-circulated. 
G. — Operating  conditions,  attendance,  oiling,  starting  and  stopping, 

vibration  and  noise. 
H.— Cost  of  complete  installations,  including  foundations,  piping  and 
condenser  equipment,  if  any. 
Not  until  about  20  years  ago  was  a  practicable  small  turbine  developed, 
and  even  up  to  ten  years  ago  the  turbine  was  looked  upon  mainly  as  an 
experiment    In  the  last  few  years,  however,  this  type  of  prime  mover  has 
been  buitt  not  only  in  small  sizes,  but  also  in  50,000  H.P.  umts  for  large  cen- 
tral stations.    The  turbine  therefore  is  as  well  developed  as  a  the  steam 
engine  after  more  than  one  hundred  years  of  improvement. 

Speed  Limitation  is  of  first  importance  in  selecting  the  type  of  prime 
mover.  Peripheral  velocities  must  be  high  to  utilize  efficiently  the  energy 
of  a  steam  jet  in  the  turbine.  Its  water  rate  is  lowest,  therefore,  when  run- 
ning at  a  constant  high  speed.  When  speed  variation  or  reversal  is  required, 
or  when  the  speed  is  necessarily  low,  the  engine  is  much  better  adapted  to 
the  service. 


ib.  Google 


ib.Google 


AUXILIARIES  343 

1  engine  is  run  at  very  high  speeds,  operating  troubles  are  sure  to 
__  ._.  _rous,  the  upkeep  is  excessive,  and  the  service  unsatisfactory.  The 
lack  of  driven  apparatus  designed  to  run  efficiently  at  speeds  consistent  with 
high  turbine  economy  has,  in  the  past,  frequently  dictated  the  use  of  engines 
as  prime  movers. 

Speed  reduction  gears  have  been  used  with  the  turbine  almost  from 
the  beginning  of  its  commercial  development  Recent  improvements  in  high 
speed  gearing,  as  well  as  in  the  manufacture  of  high  speed  direct-connected 
generators,  blowers  and  pumps,  running  at  3000  r.p.m.  and  above,  have 
greatly  increased  the  possibilities  for  turbine  installations.  Direct-current 
generators  as  small  as  10  K.W.  capacity,  and  60  cycle  alternators  of  capacities 
as  low  as  ISO  K.W^  designed  for  gear  drive,  are  now  obtainable.  It  is  said 
tiiat  the  increased  efficiency  of  the  higher  speed  turbine,  and  the  saving 
effected  in  the  generator  construction  by  reason  of  the  slower  speed  per- 
missible in  the  driven  end,  justify  the  expense  and  complication  that  the  gears 
introduce. 

For  power  station  work,  where  some  of  the  auxiliaries  are  usually  motor 
driven,  the  exhaust  steam  can  be  entirely  condensed  in  the  fe^-water  heater, 
and  the  water  rate  of  the  steam  driven  auxiliaries  is  not  a  limiting  factor. 
Reliability,  accessibility,  low  maintenance  and  labor  costs  are  of  more  vital 
importance.  Power  station  designers  have  always  preferred,  therefore,  the 
turbo-auxiliary  units,  and  there  is  now  a  decided  tendency  toward  geared 
installations. 

Small  engine  units  are  run  at  high  speeds,  so  that  it  is  exceedingly 
difficult  to  keep  them  in  continuous  service,  and  almost  impossible  to  secure 
smooth,  quiet  operation.  The  reciprocating  units  require  close  attention,  and 
must  be  shut  down,  overhauled,  and  adjusted  at  frequent  intervals;  the  cost 
of  maintenance  is  high  and  breakdowns  are  by  no  means  rare.  An  accident 
to  a  circulating  or  hot-well  pump,  for  example,  usually  necessitates  a  shut- 
down of  the  main  generator,  with  consequent  loss  of  production,  and  in  a 
public  utilities  plant,  loss  of  prestige  and  the  incurrence  of  public  ill-will. 
In  central  stations,  therefore,  where  the  main  units  are  few  in  number  and 
of  large  size,  the  circulating,  hot-well  and  boiler  feed  pumps  are  usually 
turbine-driven. 

For  driving  fans  of  large  capacity  at  low  pressures,  say  less  than  l^i  in. 
of  water,  for  induced  draft,  hot  air  heating  and  ventilating  systems,  engines 
seem  well  suited.  Fans  built  for  this  service  run  at  less  than  200  r.p.m.,  and 
are  of  the  paddle-wheel  type.  In  induced  draft  work,  load  fluctuation  may 
require  frequent  changes  in  speed;  the  engine  is  under  the  control  of  a 
throttling  regulator,  which  is  automatically  actuated  by  a  change  of  steam 
pressure.     Thei^e  conditions  are  unfavorable  to  turbine  economy. 

The  furnaces  of  underfeed  stokers  often  carry  air-duct  pressures  as  high 
as  6  or  8  in.  of  water ;  the  high  speed  multi-blade  fan  then  makes  the  better  in- 
stallation, particularly  when  one  fan  serves  several  boilers.  The  size  of  the 
blower  units  would  be  excessive  at  speeds  below  400  r.p.m..  and  the  engine 
drive  is  uncertain  and  expensive  at  this  speed.  Underfeed  stokers  at  best 
can  develop  only  from  one-quarter  to  one-third  their  maximum  capacity  with 
natural  draft,  so  that  a  blower  breakdown  under  peak  load  is  a  serious  matter. 
The  ability  of  the  turbin-;  to  stand  up  under  the  conditions  justly  entitles  it 
to  preference. 

Owing  to  the  freedom  from  reciprocating  motion,  the  foundations  re- 
quired for  turbines  are  small  and  light,  there  being  little  vibration  to  be 
absorbed  when  the  machines  are  well  aligned  and  balanced.  The  small  sizes 
can  be  safely  operated  on  floors  designed  for  the  ordinary  loads.  No  diffi- 
culty is  experienced  with  the  transmission  of  vibration  to  the  structural  mem- 
bers of  the  building  or  to  the  piping  system. 


ib.  Google 


11 


Is 
183 


k 

I 
I 


ib.Google 


AUXILIARIES  345 

The  turbine  is  often  tued  for  boiler  feed-pumps  (centrifugal  type}  of 
more  than  250  gal.  per  niin.  capacity,  or  about  3,000  boiler  horsepower 
developed,  and  on  account  of  its  small  size  the  layout  is  usually  neater  and 
more  compact.  When  regulation  by  throttling  is  unnecessary,  and  the  pumps 
run  at  or  near  capacity,  the  economy  is  better  than  that  of  the  direct  acting 
type.  Valve  renewal  and  packing  troubles  are  avoided-  The  overload  capa- 
ci^  of  the  centrifugal  type  is  small,  so  that  the  pump  must  be  proportioned 
to  meet  the  niaximum  demand,  not  the  average  boiler  horsepower  require- 
ments. In  the  smaller  sizes,  the  cost  of  turbine  units  is  high;  when  the 
load  fluctuates  widely  and  the  speed  must  vary,  the  economy  is  poor  and 
it  is  better  to  install  reciprocating  pumps. 

The  turbine  possesses  a  gnat  advant^e  in  the  simplicity  of  its  con- 
struction, which  tends  toward  increased  reliability  and  lower  cost  of  main- 
tenance. It  can  be  started  and  loaded  more  quickly.  In  operation,  it  re- 
quires much  less  attention  than  an  engine  of  corresponding  capacity.  The 
lubrication  devices  are  few  in  number  and  of  simple  design. 

Applicability  af  Turbines.     Summarizing  the  foregoing,  the  field  of  use- 
fulness of  the  turbine  can  be  stated  to  be : 
1. — Direct-connected   units,  operating  condensing.  60  cycle  generators   In  all 

to  1000  K.W.  capacity,  including  exciter  units 

Centrifugal  pumps  operating  under  substantially  constant  head  and  quan- 
tity conditions,  and  at  heads  say  from  100  ft.  up,  depending  upon  the  siie 
of  the  unit  (This  includes  boiler  feed  pumps  of  more  than  250  g.p.m. 
capacity,  or  3.000  boiler  horsepower  developed.) 

Fans  and  blowers  for  delivering  air  at  pressure  from  V/i  in.  water  col- 
umn to  30  lb.  per  sq.  in. 

Z. — Direct  connected  units,  operating  non-condensing  for  all  the  above  pur- 
poses, when  steam  economy  is  not  the  prime  factor,  or  when  the  ex- 
haust steam  can  be  completely  utilized,  particularly  if  exhaust  steam 
must  be  oil-free. 

3L— Oeared  units,  operating  either  condensing  or  non-condensing,  for  all  the 
above  applications;  and  for  others  where  a  steam  engine  is  required  on 
account  of  the  slow  speed  of  the  driven  apparatus. 

Applicability  of  Engines.    The  fields  of  usefulness  of  the  engine  are 
given  as  follows: 
1. — Non-condensing  units,  direct-connected,  or  belted  and  used  for  driving 

electric  generators  of  all  classes  except  exciter  sets  of  small  capacity, 

unless  b«lted   from  the  main  engine. 

Centrifugal  pumps,  operating  under  variable  head  and  quantity  conditions 

and  at  low  heads,  say  up  to  100  ft,  depending  on  the  capacity  of  the 

unit. 

Pumps  and  compressors  tor  delivering  water  or  gases  in  small  quantities 

and  at  high  pressures;  pumps  at  pressures  above  100  lb.  per  sq.  in.  and 

compressors  at  pressures  from  1  lb.  per  sq.  in.  and  above. 

Fans  and  blowers   (including  induced  draft  fans)   for  handling  air  in 

variable  quantities  and  at  low  pressures,  say  not  over  5-in.  water  column. 

All  apparatus  requiring  reversal  in  direction  or  rotation,  as  in  hoisting 

and  traction  engines. 

2^— Condensing  units  directly  connected  or  belted,  tor  all  the  above  purposes, 
particularly  when  the  condensing  water  supply  is  limited,  and  the  water 
must  be  re-cooled  and  recirculated. 


ib.  Google 


ib.Google 


Chapter  lO 


HEAT  INSULATION 

THE  function  of  a  heaE  insulating  material  is  to  retard  heat  flow.  It  is 
heal  insulation  whether  used  to  keep  heat  where  it  u  wanted,  as  in  a 

steam  pipe;  or  to  keep  heat  away  from  where  it  u  not  wanted,  as  from 
the  cold  water  in  a  drinking  water  line. 

Surface  Resistance.  The  heat  lost  per  degree  temperature  difference 
between  steam  and  air  from  metal  1-in.  thick,  heated  by  steam  on  one  side, 
and  exposed  to  air  on  the  other,  is  much  less  than  the  value  of  k  shown  for 
the  metal  because  the  temperature  difference  between  surfaces,  d — (t,  is  much 
less  than  the  temperature  difference  between  steam  and  air,  tg-Ha,  (See 
Fig.  175.)  The  air  cannot  take  up  the  heat  as  rapidly  as  it  can  be  trans- 
mitted by  the  metal;  therefore,  the  temperature  drop  from  the  outside  surface 
of  the  metal  to  the  surrounding  air  is  almost  alt  of  the  total  temperature 
difference  between  the  steam  and  air.  The  drop  through  the  metal,  t, — h,  is 
only  a  small  part  of  the  total.  The  amount  of  heat  transmitted  per  hour 
through  unit  thickness  of  material  on  flat  surface  is  k  (I,  —  tj.  This  hold- 
ing back  of  the  heat  due  to  the  inability  of  air  to  take  it  up  as  quickly  as  it 
can  be  transmitted  is  called  "surface  resistance." 


ib.  Google 


INSULATION 


resistance  is  in  the  insulation,  and  the  surface  resistance  has  less  effect  on 
the  amount  of  heat  transmitted. 

The  surface  resistance  of  a  surface  submerged  in  water  ia  small  as  com- 
pared with  that  of  one  exposed  to  air.  A  pipe  submerged  in  water  will  there- 
fore transmit  a  vastly  greater  amount  of  heat  than  the  same  pipe  sur- 
rounded by  air,  even  though  the  internal  conductivity  of  the  metal  is  the 
same  for  each  pipe. 

Losses  from  Bare  Healed  Surfaces.  Curve  1,  Fig.  176,  shows  the  rate 
of  heat  loss  at  various  temperature  differences  between  hot  surface  and  sur- 
rounding air.  Curve  2  shows  the  total  beat  loss  at  any  particular  tempera- 
ture difference.  Ordinates  for  curve  1  are  on  the  left,  and  for  curve  2  on 
the  right  of  the  chart 


MOT 

/ 

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ot  Surface  ana  Surrounding  Air,D«gro«« 


ib.  Google 


INSULATION 


Table  44,  for  dtflerent  steam  pressures  and  temperatures,  shows  the  heat 
lost  per  year  from  a  square  foot  of  heated  surface,  the  amount  of  coat  re- 
quired to  replace  these  losses  and  the  square  feet  required  to  waste  a  ton 
of  cr^  per  year. 

Table  44.     Heat  Loaaea  from  Uainaulated  Hot  Surfaces. 


colSoTS.. 

'•Sr- 

Rto. 

PooDdsolCaal 

WuUdHT 

IToDofCDul 
[wYw 

0 
10 
26 

212 
240 

142 
170 
197 

334 
425 
^2.5 

293 
372 

468 

6.82 

4;37 

60 
75 
100 

298 
320 

228 
250 
26S 

644 

737.6 

820 

564 
046 
718 

3.66 
3.10 
2.79 

160 
200 
250 

306 
406 

296 
318 
336 

960 
1,079 
1,184 

840 
945 
1.036 

2^12 
1.93 

Temperatuiea  Bdow  311  Desreea. 


^^r 

"^^ 

HMtlMpM-Sq. 
n.  p«  Hr..  B-tu. 

So.  Ft.  d  Surlus 

100 
120 
140 

30 
60 
70 

66.6 
97.5 
142.0 

40.6 
85.4 
124.3 

40.3 
23.4 
Ifl.l 

160 
180 
200 

90 
110 
130 

190.0 
242.0 
298.5 

166.3 
212.0 
261.6 

12.03 
9.44 
7.66 

Abov*  Bfiina  baHd  upoD 
~  ra  of  tb* 


10,000  B.bD.mnIl>blapH  pound  of  eo^  which  kaqulnlnt  b 

.,._.._• •-'-asalMnsuwiaadu  U,000  B.t.11.  par  pou 

■  TO  Ottma  in  both  pHt>  ol  tba  tabU. 


At  100  lb.  pressure,  less  than  3  sq,  ft.  of  bare  surface  are  required  to  waste 
a  ton  of  coal  in  a  year.  An  area  greater  than  this  is  exposed  when  a  pair 
of  10-in.  flanges  is  left  uninsulated.  Also,  many  surfaces  at  low  temperatures 
are  left  uninsulated  on  the  ground  that  the  temperature  is  not  high  enough  to 
justify  insulation.  Table  44  shows,  however,  that  only  12  sq.  ft.  of  surface 
at  160  deg.  are  required  to  waste  a  ton  of  coal  per  year.  Surfaces  too  hot  to 
be  touched  with  comfort  represent  a  loss  of  heat.  Fig.  177  shows  the  saving 
by  the  use  of  a  good  insulation. 

Valve  of  Heat  Insulation.  Heat  insulation  saves  fuel  directly  or  in- 
directly ;  in  addition,  insulated  equipment  renders  better  service,  workti^  con- 
ditions near  heated  surfaces  are  more  comfortable,  and  the  safety  from  Are 
and  accident  is  greater. 

Insulation  cannot  prevent  the  flow  of  heat  completely,  as  it  does  the 
flow  of  electricity,     All  substances  conduct  heat  to  some  extent.    Table  45 


ib.  Google 


■SS 

II 
u 

It 


9; 


ib.Google 


INSULATION 


Dif fitnnec  between  Pipe  and  Room  Tcmpcrcrtms,  Dcgrccj 
Fig.  177.     Heat  Lom  from  Bare  Steam  Pipe  and  Saving  Effected  by  Good 


Conductivities  of  Materials.  Table  4S  shows  the  conductivities  of  com- 
mon materials.  The  cooductivily.  k,  is  expressed  in  B.t.u.  per  square  foot 
per  degree  temperature  difference  between  surfaces  per  inch  thickness  per 

Requirements  of  Good  Insulation.  In  order  to  be  satisfactory,  an  insula- 
tion must  withstand  the  temperature  and  the  wear  and  tear  imposed  upon 
it.  The  mechanical  form  mast  permit  its  application  in  workmanlike  manner 
to  the  surface!  to  be  insulated.  The  insulation  must  be  durable  and  must 
be  efficient  in  preventing  heat  flow.  Insulating  materials  of  laminated  fibrous 
structure  are  considered  more  durable  than  molded  forms  of  insulation. 


ib.  Google 


II 


"J 


ib.Google 


1  N  S  U  L  A  TI  O  N 


Table  45.     ConductiTitiea  of  Materiala. 


aiwr 

Aluminuni 

Aluminum 

Pure  Iron 

Wrought  Iron 

SteelfScrft) 

Cast  Iron 

Coai; 

Ice \^^[\[V^'  /..\'.'.'.['.'.'.'.V.'.'.\'.'.'.\'.y.'.'.\'.'. 

Maible 

Umestone 

Sandstone 

SmlfWM) 

Soil  (Dry) 

Firebrick 

Concrete  (Stone) 

Concrete  (Stone) 

Concrete  (Cinder) 

Glass 

Brickwork 

Water 

Sand  (White.  Dry) 

Wood— Maple 

Wood— Oak 

Wood— Yeltow  Pine 

Wood— White  Pine 

Diatomaceous  Earth  Blocks 

Air  Cell  Asbestos . 

85  percent  Magneua 

Aabesto-Sponfle,   Felted 

Cork 

Hair  Felt 

Air  (True  Conductivity,  Radiation  and  Convection 
eliminated)" 


IuUmis 


n  Dl>Iommeea»  Eutli  to  Hair  Fait,  Induiln,  tba  tai 


to  ba  M  or  naar  that  of  Uh  OTdlnaiy 

■CarboBi  In  Ita  Tarisiu  f  onni,  Imi  m 
SonH  fonni  et  cnphlta  luiva  coeductlwlM : 
OMl  «U)a  poiAnd  (ftucoal  has  a  St    ' 


In,  tbfl  tamparatu] 
.aatablOtli  u 


It  aa  that  ^nn  aboT*  lor 
1   of    beat  throu^ 


Practically  all  commercial  insulations  depend  upon  entrapped  air  for 
their  insulating  value.  Air  has  a  low  heat  conducting  power  (see  Table  45) 
and  if  confined  in  small  spaces  to  minimize  ihe  effect  of  cotiveclion  within 
the  spaces,  and  of  radiation  of  heat  across  them,  the  resistance  to  heat  flow 
is  high.  Even  perfect  vacuum  would  be  ineffective  in  preventing  heat  flow 
unless  the  bounding  surfaces  were  mirrored  to  prevent  radiation. 


ib.  Google 


INSULA  TI  ON 


In  Fig.  ITS  the  tieat  losses  through  different  commerckl  insulating  mate- 
rials are  compared.  Tabic  46  shows  the  thicknesses  and  weights  per  lineal 
foot  of  the  materials  referred  to  in  Fig.  !?8.  The  uses  for  which  materials 
are  recommended  by  manufacturers  are  also  given. 


Materials  for  Iniulalioits.  Asbestos,  Fig.  179,  is  the  most  important  of  all 
materials  use<l  as  insulations  at  steam  temperatures.  Many  insulations  con- 
sist almost  entirely  of  asbestos,  and  on  account  of  its  fibrous  form  asbestos 
is  used  as  a  binding  material  in  almost  every  insulation  manufactured  for 
high  temperatures. 


ib.  Google 


INSULATION 


Table  46.     Thickness  and  Weight  of  IniulatinK  Materials. 


ReeoninHnded  (a 


L  i-M  as  par  nnt  Ii 

L  J-MIiutentad.... 

[  J■M\^tribt^Um... 

'  J-MEuraka. 

r  J  M  Molded  Aibe 


i    Cvey  Cuiieel. 

:    CanySamtad 

:    Cu«y  Dupln 

[    CBnySGper  Mnt  Miinol* 

I    S^mo  Wool  Felt 

~'i>iipveU  UiibPrcamra 


ia  diiUnca  (ram  pipe  hi 


» to  outer  HufaM  ol 


e  of  magnesia.    A  typical  analysis 


Ferric  oxide   (Fe,6j)    . 


Asbestos,  although  highly  heat  resisting,  has  little  insulating  value  in 
s  natural  rock  form  (see  Fig.  179).  Not  until  the  hbers  are  separated  and 
lanufactured  into  felts,  in  which  they  entrap  a  large  numher  of  finely  divided 
ir  spaces,  does  asbestos  become  an  efficient  insulating  material. 


Fig,  179.     Rock  Asbeitoe. 


ib.  Google 


Is 


II 


ib.Google 


INSULA  TI  ON  3S7 

Asbestos  will  withstand  temperatures  up  to  about  1500  (leg.,  but  the 
fibers  become  brittle  when  subjected  continuously  to  temperatures  above 
1200  degrees.  The  limit  for  the  fire-felt  type  o(  asbestos  insulation,  whicli 
consists  principally  of  asbestos  fiber  and  a  binding  material,  is  about  1200  de- 
grees. The  limiting  temperature  for  laminated  forms  of  asbestos  insula- 
tion is  about  700  degrees.  The  limit  for  the  cellular  types  of  asbestos  insula- 
tion is  about  300  deg.,  on  account  of  the  organic  matter  used  in  the  asbestos 
felt  from  which  they  are  built. 

Carbonate  of  Magnesia.  Next  in  importance  to  asbestos  is  hydrated 
magnesium  carbonate  [4MgC0i.  Mg(OH),.  5H,0].  This  material  in  the 
form  manufactured  for  insulating  purposes  is  light  and  porous  and  has  good 
insulating  value.  Tiie  necessary  mechanical  strength  and  durabiliLy  are 
secured  by  mixing  about  IS  per  cent  of  asbestos  fiber  and  85  per  cent  of 
hydrated  magnesium  carbonate ;  from  this  the  name  "85  per  cent  magnesia"  is 
derived. 

The  natural  rock  from  which  the  magnesium  carbonate  is  obtained  is 
hard  and  dense,  resembling  marble.  In  this  original  form  the  material  has 
practically  no  insulating  value.  The  high  insulating  value  of  85  per  cent 
ma^esia  is  due  to  the  process  of  manufacturing.  The  magnesium  carbon- 
ate is  separated  from  the  other  ingredients  in  the  original  stone,  the  rinished 
product  having  one-tenth  of  the  density  and  less  than  one-twentieth  of  the 
conductivity  of  the  natural  rock. 

The  85  per  cent  magnesia  is  not  ada^ited  to  temperatures  above  500 
degrees.  At  higher  temperatures  the  material  is  calcined,  loses  CO^  shrinks 
and  loses  strength  rapidly. 

Dialomaceotts  Earth  (.Kieselgukr)  is  a  naturally  occurring  mineral  of 
high  heat  resistance.  It  consists  of  practically  pure  silica  (SiOi),  which  is 
finely  divided,  owing  to  the  manner  in  which  the  deposits  were  built  up  under 
water  in  prehistoric  times  from  the  skeletons  of  microscopic  organisms 
known  as  diatoms. 

The  insulating  value  is  less  than  that  of  asbestos  or  magnesia,  but  it 
will  withstand  higher  temperatures  than  either  of  these  materials.  In  molded 
forms  it  is  usually  strengthened  by  being  mixed  with  asbestos  fiber.  Blocks 
manufactured  from  diatomaceous  earth  will  withstand  temperatures  up  to 
2000  degrees. 

Cork.  For  the  insulation  of  larger  surfaces  at  low  temperatures,  as  in 
refrigeration  work,  cork  is  the  moit  desirable  material.  The  source  of  cork 
is  the  bark  of  the  cork  oak  tree.  The  cork  is  ground  and  molded  into 
sheets  by  the  application  of  heat  and  pressure.  No  binding  material  is  re- 
quired as  the  natural  gum  of  the  cork  cements  the  particles  firmly,  and  serves 
as  a  moisture  proof  coating  as  well.  The  use  of  cork  is  confined  almost 
exclusively  to  refrigeration  and  cold  storage  work. 

Hair  Felt.  This  has  the  highest  insulating  value  of  any  commercial 
insulating  material.  It  is  widely  used  for  the  insulation  of  brine  and  cold 
water  pipes,  and  is  then  sealed  in  with  waterproof  membranes  to  prevent 
access  of  moisture  from  the  air. 

On  outdoor  steam  lines,  hair  felt  is  also  used  outside  of  other  insula- 
tions. The  inner  layer  of  asbestos  or  magnesia  protects  the  hair  felt  from 
the  high  temperatures,  while  the  high  insulating  value  of  the  hair  felt  in- 
creases the  cffictency  of  the  combination.  The  maximum  temperature  to 
which  hair  felt  can  be  subjected  is  about  250  degrees. 

Miscellaneous  Materials.  Wool,  silk,  and  cotton  have  insulating  value, 
but  this  is  principally  used  in  clothing.  Wood  and  paper  are  of  vahie  as 
insulations,  and  are  used  in  building  construction. 


ib.  Google 


I! 


If 

13 


ib.Google 


INSULA  TI  ON 


Heat  TransmisBion  Througli  Inaulation. 
The  factors  in  determining  the  rate  at  which  heat  will  be  transmitted 
through  unit  area  of  an  insulating  material  are: 

(1)  The  conductivity  of  the  material, 

(2)  The  temperature  difference  between  its  two  surfaces. 

(3)  The  thickness  of  the  insulation, 

(4)  The  form  of  insulated  surface. 

Of  lesser  importance  are  the  finish  of  the  surface  and  the  velocity  of 
air  currents  over  the  surfaces. 

Table  4S  shows  how  greatly  the  conductivities  of  materials  vary.  The 
figures  in  the  table  are  surface-to-surface  conductivities.  Fig.  178,  however, 
compares  approximately  equal  thicknesses  of  insulating  materials,  the  ordi- 
nates  being  actual  rates  of  heat  transmission  per  square  foot  per  hour  per 
degree  temperature  difference  between  hot  surface  and  surrounding  air. 


J 

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ib.Google 


Effect  of  Temperature  on  Heal  TratumutioH,  Fig.  180  shows  that  the 
rate  of  heat  transmission  per  degree  is  not  the  same  at  all  temperatures. 
However,  the  loss  at  any  temperature  can  be  found  by  multiplying  the 
transmission  factor  given  in  the  chart  for  any  temperature  difference 
between  hot  surface  and  surrounding  air,  by  that  temperature  difference. 

Efficiency.  Insulations  are  often  compared  in  terms  of  their  "insulating 
efficiencies,"  As  thus  used,  the  term  "efficiency"  is  the  percentage  of  the 
uninsulated  surface  loss  saved  by  a  given  insulation.  It  is  bare  surface 
loss  minus  loss  from  insulated  surface,  divided  by  bare  surface  loss;  both 
losses  apply  to  the  same  area  and  arc  for  the  same  temperature  difference. 

Thickness  and  Heat  Transmission.  Fig.  180  shows  the  variation  of  heat 
transmission  from  different  thicknesses  of  material  on  flat  surfaces.  The  loss 
through  material  2-in.  thick  Is  greater  than  one-half  of  that  through  material 
1-in.  thick,  even  ttiough  the  litres  are  for  flat  surfaces,  for  which  the  re- 
sistance of  the  2-in.  material  is  exactly  double  that  of  the  1-in.  material. 
The  "surface  resistance"  is  practically  the  same  for  the  1-in.  as  for  the  2-in. 
thickness.  Consequently,  the  resistance  of  2  in.  of  material  plus  one  surface 
ince  is  not  double  that  of  the  1  in,  of  material  plus  one  surface  re- 
ce.  and  heat   transmission  is  inversely  proportional  to  total   i 


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Fig.  181  shows  the  effect  of  the  thickness  on  heat  transmission  for  pipe 
surfaces.  The  loss  through  material  2-in.  thick  is  even  more  above  one-half 
of  that  through  the  l-in.  thickness,  than  it  was  for  the  flat  surfaces.  In 
addition  to  the  surface  resistance  effect,  the  second  inch  of  insulation  is 
applied  over  a  larger  area  than  the  first  inch,  so  that  it  does  not  offer  as 
much  resistance  to  heat  flow. 

Pipe  Sisc  and  Heal  TransmissioH.  Fig.  182  shows  how  the  rate  of  heat 
transmission  through  a  given  thickness  of  insulation  varies  with  pipe  size. 
By  comparing  this  chart  with  Fig.  180,  the  losses  through  different  thicknesses 
on  pipes  are  found  to  be  greater  than  through  the  same  thickness  of  the  same 
insulation  on  flat  surfaces;  also,  as  shown  in  Fig.  163,  the  losses  are  greater 
on  small  than  on  large  pipes,  other  factors  being  the  same. 


ib.  Google 


I  N  S  U  L  A  TI O  N 


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nominal  Diomtttr  «f  Plpc,lnchti 
Fig.  183.     Comparinn  of  Heat  Losa  from  Vadoua  Sizea  of  Pipe. 


In  flat  surface  insulation  all  the  heat  flows  straishl  through  in  parallel 
lines,  but  in  pipe  insulation  the  heat  has  a  continually  widening  path  into 
which  to  spread  as  it  flows  outward.  Consequently  more  heat  will  flow  from 
a  given  area  of  pipe  surface  than  from  the  same  area  of  flat  surface.  The 
smaller  the  pipe  the  more  rapidly  the  path  for  heat  flow  spreads  out;  there- 
fore the  greater  is  the  rate  of  heat  loss  for  a  given  pipe  area  and  thickness 
of  insulation. 


Is  and  Surface  Finish.  Air  currents  greatly  decrease  the  sur- 
With  bare  surfaces  the  losses  can  be  Increased  by  the  elTect 
of  wind  to  several  times  the  values  In  still  air.  When  efficient  insulations 
are  applied  so  that  they  are  sealed  against  the  effect  of  air  blowing  through 
the  jomts,  the  maximum  increase  in  heat  transmission  due  to  wind  velocity 
varies  from  about  10  per  cent  for  an  insulation  3-in.  thick  to  about  30  per 
cent  for  a  l-in.  thick  insulation.  These  figures  are  only  approximates 
because  the  more  efficient  the  insulation,  the  less  affected  it  is  by  wind 
velocity. 

If  the  insulation  is  loosely  applied  so  that  air  can  circulate  through  the 
joints  and  crevices  or  between  the  Insulation  a[id  the  pipe,  wind  can  in- 
crease the  loss  upward  of  100  per  cent.  Painting  the  surface  of  Insulation 
usually  decreases  the  loss  of  heat  slightly  and  is  desirable  because  the  sur- 
face is  thus  sealed  against  circulation  of  air. 


D,g,tze:Jbi  Google 


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si 

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■ss 
2s; 


ib.Google 


INSULATION 


Thickness  of  Insntatio'i.    The  thickness  it  will  pay  to  use  depends  upon : 

(1)  The  temperature  difference  between  hot  surface  and  air, 

(2)  The  value  of  the  heat  units  to  be  saved  by  insulation. 

(3)  The  size  of  pipe, 

(4)  The  kind  of  insulation  used, 

(5)  The  cosi  of  insulation. 

The  last  increment  of  insulation  put  on  should  save  enough  to  pay  a 
good  return  on  its  cost.  The  minimum  allowable  return  is  usually  taken  at 
about  14  per  cent,  which  covers  interest  and  depreciation. 


s 

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loo        200       300       400        500       600 


T«fiip«raiur«  Diffentncs.OagrMS 


ib.Google 


ib.Google 


INSULATION  365 

Fig.  184  is  a  chart  for  determining  llie  most  econoniical  thickness  of  85 
per  cent  maimesia.  It  can  also  be  used  in  selecting  the  thickness  of  other 
materials.  However,  the  actual  saving  should  be  checked  to  determine 
whether  the  return  on  the  investment  is  satisfactory. 

The  data  given  in  Figs.  178  to  184  can  be  used  to  determine  the  most 
economical  thickness  of  insulation,  as  follows:  Required  to  find  whether  2 
or  ZYi  in.  thickness  of  asbestos  sponge  felted  insulation  should  be  used  on 
a  boiler  drum.  Steam  pressure  is  150  lb.  gage;  cost  of  coal.  $5  per  ton; 
cost  of  insulation,  30  cents  per  sq.  ft.  1  in.  thick ;  boiler  room  temperature, 
80  degrees.  (All  heat  losses  and  savings  are  expressed  in  B.t.u.  per  de- 
gree  of  temperature   difference.) 

Steam  temperature  at  ISO  lb.  gage  pressure .- J66 

Room   temperature  —  80 

Temperature  difference  „ - - -286 

Heat  loss  per  sq.  ft  per  hour  through  2-in.  thick  asbestos  sponge  felted 

(Fig.  180)  „ „ _ „ _-a2l 

Heat  loss  per  sq.  ft.  per  hour  through  ZYt  in.  thick  asbestos  sponge 

felted  _„ _- .ai7 

Saving  per  sq.  ft.  per  hour  per  deg.  temp.  diff.  by  use  of  2^-in.  thick- 
ness - — - _ JQM 

Saving  per  sq.  ft.  per  hour  =  286  X    0.04  =  _ „11.44 

Saving  per  sq.  ft  per  year  =  8760  X  11-44  =  100,300 

Saving  in  lb.  of  coal  per  sq.  ft. 

100.300  .nn, 

'""=" T5ooo  = '™ 

Saving  in  dollars  per  sq.  ft. 

10.03  , 

"20000 

Cost  of  2yi  in.  insulation  per  sq.  ft.  =  I'/i  X  0.30  =  -0.75 

Cost  of  2      in.  insulation  per  sq.  ft.  =  2      X  0.30  =  0.60 

Cost  of  additional  J4  in.  of  insolation  t=  _ 0.15 

Above  saving  expressed  as  percentage  return  on_ 
additional  cost  - -. - lOOX^^^  =  I&7 

This  is  a  satisfactory  retam  so  that  the  use  of  2yi  in.  thick  insulation  is 
a  paying  investment 

(On  such  surfaces  as  boiler  drums  and  heaters,  the  '/i  in.  of  insulation 
is  usually  applied  in  the  form  of  a  plastic  insulating  cement.) 

In  like  manner,  Figs.  182  and  184  can  be  used  to  check  the  most 
economical  thicknesses  of  pipe  insulations. 

Innilat'wn  of  Boiler  Druntt  and  Piping.  In  insulating  steam  and  hot 
water  pipes  and  boiler  drums,  the  correct  thickness  (see  Fig.  134)  should  be 
applied  so  that  there  are  no  crevices  or  open  joints.  Asbestos  cement  can 
be  used  to  seal  openings,  and  a  layer  of  asbestos  cement  can  be  applied  over 
the  outside  of  sheet  or  block  insulation,  to  give  a  smooth  hard  finish. 


per  year - J^X  $5.00  ^ .a025 


ib.  Google 


II 

ll 
1^ 


li 
"I 

Is 


JO 

it 


as 


ib.Google 


INSULA  TI  ON  367 

Boiler  IVall  Insulation.  By  insulation  of  boiler  walls  about  one-half  of 
the  heat  transmission  through  them  can  be  prevented.  This  saving  alone 
would  make  the  insulation  pay.  but  the  saving  can  be  still  larger  if  the  in- 
sulation -seals  the  wall  effectively  against  air  infiltration.  To  accomplish  this 
the  insulation  should  be  applied  in  large  sheets  and  finished  on  the  outside 
with  about  Yi  in.  of  asbestos  cement. 

The  application  of  insulation  on  the  outside  of  a  brick  wall  is  quite 
different  from  applying  it  to  a  steam-heated  surface  at  the  same  temperature. 
The  steam-heated  surface  remains  at  about  the  same  temperature  as  it  was 
before  the  insulation  was  applied;  for  the  temperature  is  only  a  little  below 
that  of  the  steam.  On  the  other  hand,  the  blanketing  effect  of  insulation 
holds  the  heat  in  the  brick  wall.  The  temperature  of  the  wall  surface  is 
greatly  increased,  the  outer  surface  of  the  wail  being  at  a  temperature  far 
below  that  of  the  source  of  heat.  This  temperature  increase  may  amount 
to  500  deg.  on  the  portions  of  the  wall  opposite  the  furnace,  varying  with 
the  thickness  of  wall  and  the  thickness  and  kind  of  insulation.  Consequently 
an  insulation  more  than  90  per  cent  efficient  on  a  steam-heated  surface  saves 
only  from  40  to  50  per  cent  of  the  heat  radiated  from  a  brick  wall.  The 
insulation  itself  is  not  any  less  efficient,  but  the  difference  is  due  to  the 
increased  temperature  of  the  wall  surface. 

Reference  should  also  be  made  to  Chapter  4  on  FURN.ACES  AND 
SETTINGS. 

Brccckins  Insulation.  If  Ihe  breeching  leads  directly  to  the  stack  the 
heat  saved  by  insulation  does  not  find  its  way  into  the  steam.  However,  the 
draft  is  increased  when  this  heat  is  retained  in  the  gases.  With  an  econo- 
mizer the  heat  is  returned  to  the  boiler.  Insulating  the  breeching  helps  to 
cool  the  boiler  room,  which  otherwise  might  he  unbearably  hot. 

Breechings  are  insulated  either  by  an  inside  lining  or  by  insulation  ap- 
plied to  ihe  outside  surface.  An  inside  lining,  finished  with  a  coating  of  re- 
fractory cement,  protects  the  steel.  On  the  other  hand  more  efficient  insula- 
tion can  be  used  on  the  outside  of  the  breeching,  and  then  does  not  obstruct 
the  draft  area.  ' 

Overhead  Outdoor  Lines.  When  outdoor  lines  are  run  overhead  they 
can  be  insulated  with  the  same  materials  used  on  similar  lines  indoors.  The 
insulation  must  be  thicker  on  account  of  the  lower  temperatures  and  the 
exposure  to  wind.  (See  Hair  Felt.)  It  must  also  be  protected  from  the 
weather  by  sheet  iron  or  asbestos  roofing  jacket.  Hair  felt,  with  an  inner 
lining  of  asbestos  or  magnesia,  is  used  successfully  for  outdoor  lines. 

Underground  Lines  in  tunnels  can  be  treated  just  as  if  they  were  indoors, 
except  that  the  canvas  must  be  thoroughly  painted  as  a  protection  against 


Lines  running  in  covered  trenches  should  be  treated  in  the  same  manner 
as  overhead  outdoor  lines. 

Lines  running  underground  can  be  insulated  by  enclosing  them  in  vitrified 
tile  conduit  and  placing  an  efficient  filling  material  in  the  space  between 
the  pipe  and  tile.  All  joints  must  be  sealed.  Thorough  drainage  must  be 
provided  by  a  tile  underdrain  and  crushed  stone,  which  should  be  brought 
well  above  the  center-line  of  the  conduit. 

Cold  Water  Lines.  These  can  be  insulated  with  hair  felt  or  cork.  Mois- 
ture condenses  easily  from  the  air  on  a  cold  pipe,  and  the  moisture  greatly 
reduces  the  insulating  value.  Therefore,  all  insulations  on  cold  water  lines 
should  be  so  thoroughly  sealed  that  moisture- laden  air  cannot  penetrate  them. 


ib.  Google 


11 


9s 


ib.Google 


CHAPTER  11 


HEAT  AND  COMBUSTION 

Theory  of  Heat 

HEAT  is  n  form  of  energy  convertible  in  exact  quantitative  relations  into 
otlier  forms  of  energy.  When  two  bodies  at  different  temperatures  are 
placed  in  communication,  the  temperature  of  the  warmer  body  falls  while 
that  of  the  colder  rises  until  the  two  bodies  attain  the  same  temperature.  To 
account  for  this  phenomenon,  we  say  that  heat  flows  from  the  hotter  to  the 
colder  body.  The  fall  of  temperature  of  the  one  is  due  to  a  loss  of  heat, 
while  the  rise  in  temperature  of  the  other  is  due  to  a  gain  in  heat. 

In  the  caloric  theory,  heat  or  caloric  was  assumed  to  be  a  fluid  which 
could  flow  from  one  body  to  another  and  thus  cause  changes  of  temperature. 
But  the  experiments  of  Rumford,  Davy,  and  Joule  invalidated  the  old  caloric 
theory  and  established  the  modern  mechanical  theory. 

Heat  may  be  generated  by  the  expenditure  of  mechanical  work,  by 
chemical  reaction,  or  by  the  electric  current.  Famdiar  examples  are  the 
heating  of  liearings  due  to  friction,  the  heat  generated  by  the  combustion  of 
coal,  and  the  heat  produced  in  an  electric  lamp  filament. 

Useful  work  can  be  done  by  the  expenditure  of  heat,  as  in  the  steam 
engine.  The  law  of  definite  relationship  between  work  done  and  heat  ex- 
pended has  been  firmly  established  by  the  experiments  of  Joule.  AccoMing 
to  Joule,  heat  is  not  a  fluid  substance  like  caloric,  but  is  a  form  of  energy  due 
to  the  motion  or  configuration  of  the  molecules  in  a  body  or  system. 

Thermometry 
n^HE  measurement  of  the  quantity  of  heat  abstracted  from  or  added  to 
■^  a  body  depends  primarily  upon  the  measurement  of  temperatures ;  that 
is,  upon  thermometry.  The  temperature  of  a  body  is  a  measure  of  the 
intensity  of  its  heat,  or  its  ability  to  impart  heat  to  cooler  bodies  or  to 
abstract  heat  front  warmer  ones. 

Temperature  is  expressed  in  units  called  degrees,  which  are  subdivisions 
of  the  temperature  range  between  the  temperature  of  melting  ice  and  that 
of  boiling  water.  There  are  three  temperature  scales  in  use ;  the  scale  of 
Fahrenheit,  which  is  used  in  nearly  all  engineering  work ;  that  of  Celsius, 
called  the  Centigrade  scale,  which  is  used  generally  in  scientific  laboratory 
work;  and  that  of  Reaumur,  which  is  used  to  some  extent  in  Europe. 

The'  Fahrenheit  scale  is  practically  the  only  one  used  in  American  power 
plant  practice.  When  no  scale  is  mentioned  in  this  book,  the  temperatures 
are  given  in  degrees  Fahrenheit. 

Conversions  of  temperature  readings  from  one  scale  to  another  are  quite 
simple,  as  may  be  seen  from  the  following  table : 


ib.  Google 


Table  47.     Temperature  Scalea. 


Kxpl.n.tion 

'           Der^H 
Fihrenheit 

Centigrade 

Ru^'r 

0' 
100= 
100" 

5 

0' 

q 

4 

Conversions  a 

e  made  as  follows : 
(CX 

^)+i2  =  F 

(30) 

(RX 

-J  )  +  32  ^  F 

(31) 

(F  — 32)  X 

T  =^ 

(32) 

RX 

-J-  -^ 

(33) 

(F~3Z)X 

4="  - 

(34) 

cx 

4=« 

(35) 

Absolute  Temperature 

INVESTIGATIONS  with  gases  show  that  as  they  are  cooled  the  pressure 
they  exert  is  diminished  [iniformly.  The  temperature  at  which  the  pressure 
would  vanish  is  called  "absolute  zero."  This  point,  which  has  been  closely 
approached  in  practice,  is  expressed  as  ^460  deg.  Fahr.  The  "absolute 
lemperatvTe"  of  a  body  is  therefore  its  temperature  above  absolute  zero, 
that  is,  the  regular  scale  reading  plus  460,  and  is  often  used  in  calculations 
relating  to  expansion  and  radiation. 

Thermodynamic  Temperature  Scale 

THE  only  standard  of  temperature  which  depends  solely  upon  the  nature 
of  heat  and  is  independent  of  the  nature  of  any  measuring  substance  is 
the  "Thermodynamic  Temperature  Scale."  By  this  scale,  the  ratio  of  any 
two  temperatures  is  equal  to  the  ratio  between  heat  absorbed  and  emitted 
\w  a  reversible  thermodynamic  engine  working  between  the  same  tempera- 
tures. Again,  these  temperatures  are  numerically  equal  to  those  that  would 
be  indicated  by  an  ideal  gas  thermometer,  obeying  exactly  Boyle's  law, 
Fl'  ^  RT.  Con  Slant- volume  gas  therraomelers,  employing  gases  whose  devia- 
tions from  the  properties  of  perfect  gases  are  known,  are  used,  therefore,  to 
calibrate  instruments  for  actual  temperature  measurement.  Hydrogen  is  used 
for  calibrating  when  the  temperatures  do  not  exceed  600  degrees.  From  600 
to  2800  deg.  nitrogen  is  preferable,  as  it  has  less  tendency  to  diffuse 
through  the  walls  at  the  higher. temperatures.  The  temperatures  are  observed 
as  functions  of  the  pressure  increment,  and  a  calibration  thus  determined 
for  simpler  forms  of  thermometer  exposed  to  the  same  temperature. 

Thermometers  and  Pyrometers 

FIXED   points   have   been   determined   b^   comparison   with    standard   gas 
thermometers,  and  are  used  in  calibrating  instruments  for  high  tempera- 
ture readings.    These  are  expressed  in  degrees  Fahrenheit  as  follows : 


ib.  Google 


Table  48.     Fixed  Points. 


Naphthalene  boils  at  760  mm. 

pressure  

Benzophenone  boils  at  760  mm. 
Cadmium  melts  or  solidifies  Jn  i 

Zinc  melts  or  solidifies  in  air. 

Sulphur  boils  at  760  r 


(29.92  in,  of  mercury)... 


Antimony  melts  or  solidifies  in  COi_..... 

Aluminum  solidilies  in  COt , 

Silver  melts  or  solidifies  in  CO. 

Gold  melts  or  solidifies  in  CO^ 

Copper  melts  or  solidifies  in  CO* 

Lithium  metasilicate  melts  in  air 

Diopside,  pure,  melts  in  air. 

Nickel  melts  or  solidifies  in   H  and   N 

Cobalt  melts  or  solidifies  in  H  and  N 

Palladium  melts  or  solidifies  in  air 

Anorthite   melts  in   air 

Platinum  mclls  in  air 


^4.4 
582.5 
609.4 

re6.7 

832.0 
1165.6 
12173 
1760.0 
1944.3 
1980J 
2193.8 
2526.2 
264S.6 
2713.6 
2820.6 
2821.1 
3136.0 


Instruments  for  measuring  temperature  are  classified  by  /.  A.  Moycr  in 
Table  49,  which  also  gives  the  temperature  range  and  degree  of  accuracy 
niuaUy  obtainable. 

Table  49.    Thermometer*. 


Type 

Range  D»g.   F. 

Accuracy  Deg.  F. 

(a)   Ordinary  Type 

0-1-575 

From  1.0  deg.  in  common 
instruments  up  to  0.01  deg. 

(b)  Jena  Glass,  cap- 

Higher  ranges  accurate  to 

illary  tube  filled  witV 

1  deg. 

(c)  Quartz    Glass 

—  37  1 

0 -1-1500 

Higher  ranges  accurate  to 

capillary    tube    filled 

Ideg. 

with  nitrogen. 

2.  Alcohol  or  Petrol-ether 

—  325i 

o+lOO 

Accurate  to  1  deg. 

3.  Electrical  Resistance 

—  -100  to  +  2200 

Accurate  to  0.01  deg.  for 

4.  Thermo-electric 

—  400i 

0-1- 3500 

5.  Metallic-expansion, 

-1-  300to  -1-  1000 

Uncertain 

mechanical 

-{-95   to  -1- 1350 

7.  Radiation 

deg. 

(a)  Thermo-couple 

-1-  3001 

0-1-4000 

Reliable  to  about  nearest 

in  focus  of  mirror. 

20  deg. 

(b)  Bolometer 

-400 

0  temper- 

Reliable  to  about  nearest 

atur 

20  deg. 

to  temper- 

Reliable   to   about  nearest 

20  deg. 

9.  Seger  Cones 

-1-  1100 

to -1-3600 

Reliable  to  about  nearest 
20  deg. 

ib.Google 


ib.Google 


Mercury  Tkcrmomeiers.  Because  of  the  iiniform  expansion  of  mercury, 
and  its  sensitiveness  to  heat,  it  is  commonly  used  as  the  fluid  for  thermometric 
measurement  within  tiie  ranges  given  in  Table  49.  Up  to  temperatures  of 
about  575°,  the  ordinary  type  of  thermometer  has  a  vacimm  in  tlie  capillary 
tube  above  the  mercury,  while  for  higher  temperature  ranges  the  capillary 
tube  is  filled  with  nitrogen  or  carbonic  acid  gas  under  high  pressure.  Re- 
searches carried  on  at  Jena  have  resulted  in  the  production  of  a  special  glass 
for  thermometers,  known  as  the  Jena  normal  glass ;  this  glass  has  practically 
the  same  coefficient  of  expansion  as  mercury,  and  hence  is  particularly  suit- 
able for  thermometers. 

Correction  for  Stem  Exposure.  Thermometers  are  usually  graduated 
to  read  correctly  for  total  immersion ;  that  is,  with  the  bulb  and  stem  at 
the  same  temperature.  However,  in  general  power  plant  measurement  work 
it  is  seldom  that  the  bulb  and  stem  are  at  the  same  temperature :  therefore. 
in  order  to  obtain  the  correct  temperature  a  "stem  correction"  must  be 
applied.    The  stem  correction  (K)  may  be  calculated  from  the  formula: 

K  =  0.000088  n  ((,—/)  (36) 

in  which  n  is  the  number  of  degrees  of  the  scale  reading  not  immersed.  (, 
the  indicated  temperature,  and  t  the  mean  temperature  of  the  air  surrounding 
(he  stem  as  shown  by  a  second  thermometer. 

Calibration  of  a  Thermometer.  When  a  thermometer  is  intended  for 
exact  work,  its  two  fixed  points,  viz :  the  freezing  point  and  boiling  point, 
should  be  veriBed,  and  the  graduations  calibrated.  To  test  for  the  accuracy 
of  the  graduations,  a  short  column  of  the  mercury  in  the  stem,  say  15  or 
20  dt^rces  in  length,  is  detached  by  jarring,  and  its  length  measured  in  suc- 
cessive positions  through  the  entire  length  of  the  stem  by  means  of  the  scale 
marked  thereon.  Where  the  capillary  tube  is  relatively  narrow,  the  thread 
of  mercury  will  be  correspondingly  long,  and  thus  by  its  changes  in  length 
the  irregularities  in  the  thermometer  tube  can  be  determined  and  a  calibra- 
tion curve  deduced. 

Thermometer  Weils.  A  thermometer  well  is  used  in  measuring  the 
temperature  of  steam  or  water  when  it  is  impossible  to  immerse  the  ther- 
mometer bulb  directly.  A  well  generally  consists  of  a  hollow  plug,  threaded 
at  the  upper  end.  It  is  screwed  into  a  threaded  hole  in  the  top  of  the  hori- 
zontal pipe  through  which  the  steam  or  water  flows,  the  lower  part  of  the 
well  extending  vertically  into  the  interior  of  the  pipe  as  far  as  the  center, 
if  practicable.  The  inside  diameter  of  the  well  should  be  slightly  larger 
than  the  outside  diameter  of  the  thermometer  tube,  The  well  should  be 
filled  with  mercury  or  high  grade  mineral  oil  for  temperatures  below  SOO". 
and  with  soft  solder  for  higher  temperatures.  For  superheated  steam,  the 
immersed  portion  of  the  well  should  preferably  be  fluted  so  as  to  increase 
the  area  of  absorbing  surface. 

Alcohol  Thermometers.  The  low  limit  for  mercury  thermometers  is 
about  — 33  degrees  Fahr.  Hence,  when  it  is  necessary  to  measure  lower  tem- 
peratures, the  alcohol  thermometer  is  employed,  in  which  alcohol  or  petrol 
ether  is  substituted  for  mercury  as  the  expanding  fluid. 

Electrical  Resistance  Thermometers  are  based  on  the  variation  of  the 
electrical  resistance  of  certain  metals  with  the  temperature.  Platinum  has  a 
uniform  resistance,  and  withstands  high  temperatures,  hence  is  often  used 
for  this  work.  The  resistance  thermometer  is  made  of  a  coil  of  pure  annealed 
platinum  wire  wound  upon  a  mica  framework.  The  variation  in  resistance 
is  measured  by  a  Wheatstone  bridge.  Inasmuch  as  small  currents  are  used 
with  this  device,  delicate  galvanometers  are  required. 

Thermo-eleclric  Pyrometers,  Fig.  185,  are  based  upon  the  fact  that  when 
wires  of  two  different  metals  are  joined  at  one  end  and  heated,  an  electro- 
motive force  will  be  set  up  between  the  free  or  cold  ends  of  the  wires.  The 
combination  of  two  such  wires  is  known  as  a  thermo-couple.    The  voltage 


ib.  Google 


so  set  up,  when  the  "hot"  end  is  at  a  higher  lemperalure  than  the  "cold" 
end.  usually  increases  as  the  temperature  difTerence  increases  and  may  be 
measured  by  a  sensitive  galvanometer  or  voltmeter. 


Fig.  185.     Thermo-electric  Pyrometer. 

There  are  two  general  types  of  thermo-couples,  viz:  high  resistance 
and  low  resistance.  The  high  resistance  couple  is  formed  of  platinum  and 
platinum-rhodium  wires  of  small  diameter  and  is  often  called  a  rare  metal 
couple.  Base  metal  or  low  resistance  couples  are  made  of  iron  versus  con- 
stantan,  chromel  versus  alumel  and  various  other  special  patented  alloys 
that  are  obtainable  in  sizes  of  No.  6  or  8  B.  W.  G.  Platinum  and  platinum- 
rhodium  couples  may  be  used  up  to  a  temperature  of  3500°  F..  while  base 
metal  couples  are  not  suitable  above  2000°  F..  though  their  safe  working 
temperature  depends  on  the  character  of  the  alloys  used. 

Thermo-couples,  whether  of  the  rare  metal  or  base  metal  types,  should 
preferably  be  housed  in  protecting  tubes.  Iron  pipe  will  satisfactorily  serve 
as  a  protecting  tube  up  to  1500°  F.,  but  above  this  temperature,  special  alloy, 
quartz  or  porcelain  tubes  should  be  used. 

Mechanical  Pyrometers.  Fig.  186.  depend  for  their  action  upon  the  dif- 
ferent rates  of  expansion  of  two  different  substances,  that  are  generally  in 
the  form  of  iron  and  brass,  or  graphite  and  iron  rods.  The  movement  of 
the  rods  resulting  from  expansion  is  multiplied  by  gears  and  levers  and  com- 
municated to  an  indicating  dial  graduated  in  degrees.  These  pyrometers 
sometimes  find  application  in  the  determination  of  boiler  flue  gas  tempera- 
tures. They  should  be  frequently  calibrated,  although  at  best  they  give 
unreliable  results. 

A  peculiarity  of  these  mechanical  pyrometers  is  apt  to  be  disconcerting 
if  the  inexperienced  observer  is  not  warned.  On  placing  in  a  flue,  the  outer 
element  expands  first  and  causes  the  pointer  to  indicate  a  very  low  tempera- 
ture, after  which  it  rises  to  the  proper  temperature  as  ths  inner  element 
becomes  heated.  On  withdrawing  the  instrument,  the  outer  element  cools 
first  and  causes  the  pointer  to  indicate  a  very  high  temperature  until  the 
inner  element  cools.  Owing  to  this  peculiarity,  they  are  obviously  unreliable 
where  there  are  wide  temperature  fluctuations. 


ib.  Google 


Fig.  186.     Mechanical  Pyrometer. 


Fig.  187.     Recording  Vapor  Thermometer. 


ib.  Google 


II 


ib.Google 


Vapor  Thermometers,  Fig.  187,  operate  by  the  expansion  of  ether,  mer- 
cury, or  other  liquids  confined  in  a  steel  bulb  and  capillary  tube,  to  which 
is  connected  a  measuring  or  indicating  device.  When  the  bulb  is  heated,  the 
vapor  tension  iiicreases  and  operates  the  indicating  or  recording  mechanism. 
The  capillary  tube  of  such  a  thermometer  may  be  as  much  as  100  ft.  long, 
hence  these  instruments  are  suitable  for  use  when  it  is  desired  to  have  the 
recording  device  located  on  an  instrument  board  at  some  distance  from  the 
point  where  the  temperature  is  taken.  This  type  of  thermometer  is  used 
in  the  boiler  room  for  the  measuremant  of  feed  water  and  superheat 
temperatures. 

Radiation  Pyrometeri  are  instruments  devised  to  measure  temperature 
by  means  of  radiation  from  incandescent  bodies.  In  one  type  of  radiation 
pyrometer  (FiryJ  the  heat  rays  are  focused  by  means  of  a  series  of  mirrors 
upon  the  hot  junction  of  a  thermo-couple  and  the  electromotive  force  so 
generated  is  indicated  by  a  sensitive  galvanometer  graduated  to  read  tem- 
perature directly.  These  instruments,  if  used  correctly,  will  measure  fairly 
accurately  the  temperature  of  fuel  beds  or  furnaces,  but  their  application  in 
the  boiler  room  has   been  limited. 

Optical,  Pyrometers  are  not  used  in  boiler  room  practice,  but  serve 
rather  to  measure  the  temperature  of  small  hot  bodies.  The  F4ry  optical 
or  absorption  pyrometer  measures  temperature  by  focusing  the  heat  rays 
by  means  of  a  series  of  mirrors  and  comparing  the  intensity  of  light  emitted 
from  the  furnace  with  the  light  from  a  small  comparison  lamp. 

Seger  Cones  find  little  or  no  use  in  the  boiler  room,  their  use  being 
restricted  chiefly  to  the  ceramic  industries.  Seger  cones  arc  small  pyramids, 
consisting  of  various  mixtures  of  quartz,  feldspar,  etc.,  and  forming  a  scale 
with  differences  of  SO  to  80  degrees  F.  between  fusion  or  softening  points. 
The  cones  are  numbered  in  such  a  way  that  No.  ]  melts  at  2102  deg.  F.,  No. 
022  melts  at  1094  deg.  F.,  and  No.  42  melts  at  3378  deg.  F.  To  determine  the 
temperature  of  a  kiln  or  furnace,  three  or  four  consecutively  numbered  cones 
are  placed  upon  a  tire  brick  and  introduced  into  the  heated  zone.  The  tem- 
perature indicated  lies  between  the  temperature  of  the  cone,  which  still  stands 
upright,  and  the  temperature  of  the  next  one,  which  has  begun  to  soften. 

Color  ai  a  Temperature  Indicator.  The  color  of  many  highly  heated 
substances  is  an  indication  of  the  temperature.  Results,  however,  obtained 
by  this  method  are  unsatisfactory,  except  for  rough  estimation,  as  the  sus- 
ceptibility of  the  observer's  eye  and  the  surrounding  illumination  are  sources 
of  considerable  error.  Table  50  gives  a  schedule  for  judging  temperatures 
in  this  way. 

Table  SO.     PouiUet  Color  Schedule. 

.\piwaruice  I>cg.  F. 


1290 

1470 

1650 

_ 1830 

Deep  orange..- !  2O10 

Clear  orange 2190 

White  orange I  2370 

Bright  white — (  2450 


Dazzling  whit< 


ib.  Google 


Units  of  Heat  Quantities 

Pl£  BrUish  thermal  tinit  (B.t.u.)  is  the  amount  of  heat  required  to 
raise  a  pound  of  water  one  degree  Fahrenheit  in  temperature-  It  makes 
little  practical  difference  at  what  part  of  the  scale  this  one  degree  hes.  but  the 
"mean  B.t.u.,"  adopted  as  the  standard,  is  Vut  of  the  heat  required  to 
raise  a  pound  of  water  from  32  to  212  deg.,  whidi  is  approximately  equal  to 
the  heat  required  to  raise  it  from  63  to  64  deg. 

The  mechanical  eit«ivalent  of  heal  is  the  amount  of  work  that  can  be 
produced  from  or  is  convertible  to  a  unit  of  heal.  Many  scientists  have  con- 
ducted tests  in  which  mechanical  work  was  entirely  converted  into  frictional 
heat;  these  tests  have  been  checked  by  calculations,  and  it  has  been  determined 
that  1  British  thermal  unit  —  778  ft.-lb.  of  work.  The  more  accurate  value 
is  777.S2,  at  a  point  ( such  as  latitude  45  deg.)  at  which  g,  the  acceleration 
of  gravity,  equals  32.174  ft.  per  second  per  second. 

The  heat  contained  in  a  body  is  a  function  of  its  mass,  its  temperature 
and  its  specific  heat,  or  heat  capacity.  The  specific  heat  of  a  substance  is  the 
amount  of  heat  required  to  raise  a  pound  of  it  1  deg.  in  temperature.  The 
speciiic  heat  of  water  is  therefore  1  B.tu.  at  63  deg.  The  specific  heats  of 
all  other  substances  express  their  capacity  as  compared  with  aivater.  The 
greater  the  specific  heat  of  a  substance,  the  more  heat  is  required  to  increase 
Its  temperature  through  a  given  range,  and  the  more  heat  it  will  give  up 
when  cooled.  The  specific  heat  of  a  solid  body  can  be  determined  by  heating 
it  and  immersing  in  water.  The  heat  lost  (as  measured  by  the  increase  in 
temperature  of  the  water)  divided  by  its  mass  and  its  decrease  in  temper- 
ature, gives  the  specific  heat.  This  is  practically  constant  for  solids,  but 
varies  slightly  with  temperature  for  liquids,  and  considerably  in  the  case  of 
gases.  The  calculation  of  the  British  thermal  units  involved  in  heating  water 
is  therefore  simple ;  more  extensive  data  are  required  to  calculate  the  heat 
for  vaporizing  water,  superheating  steam,  or  that  lost  in  flue  gases. 

The  specific  heats  of  several  common  solid  substances  are  given  tn  Table 
51  by  Lucke. 
Table  51.     Specific  Heat*  of  Solid.. 

Solid  '  SjwcLlic  ileal 

0.1  ITO 

0.1138 


Brick  work,  masonry,  stone 0.1298 

Coal --. 0.16  to  0.18 

Wood   0.4S  to  0.6S 

Glass  02    to  0.241 

Cast  Iron about  02 

"  0.0924 
0.241 


A  discussion  on  the  specific  heat  of  gases  oci 
Heat  Transfer 


A  WARM  body  has  a  constant  tendency  to  pass  over  its  heat  content  to 
a  cooler  one,  and  as  their  temperatures  approach,  the  net  rate  of  trans- 
mission decreases  proportionately,  until  it  reaches  zero.  Heat  is  transferred 
by  three  distinct  processes:  radiation,  conduction,  and  convection. 

Radiation  is  the  direct  passage  of  heat  energy  in  the  form  of  rays  through 
space  or  through  a  dtathermanous  medium.  Solar  heat  travels  by  radiation, 
and  is  converted  into  sensible  heat  on  striking  the  earth.     Heat  is  radiated 


ib.  Google 


from  the  burning  fuel  and  gases  in  a  furnace,  and  the  portion  that  strikes 
the  boiler  tubes  aids  materially  in  evaporation. 

Conduction  is  the  passage  of  beat  between  substances  in  actual  contact 
In  homogeneous  bodies  the  heat  transmitted  varies  directly  as  the  area  and 
temperature  dil^erences  of  the  two  surfaces  under  consideration,  and  in- 
versely as  the  thickness.  Transfer  rates  can  also  be  estimated  or  deter- 
mined experimentally  for  combinations  of  materials,  such  as  metal  coated 
vith  scale,  or  with  grease  and  soot.  All  heat  used  in  evaporating  water 
in  a  boiler  must  necessarily  pass  by  conduction  through  the  clean  or  coated 
metal. 

Conveclion  is  the  transfer  of  heat  by  the  motion  of  the  fluid  containing 
it.  In  traversing  the  heating  surfaces  of  a  boiler  the  hot  gases  give  up  heat 
by  convection  to  the  melal  of  the  tubes  from  which  it  passes  by  convection  to 
the  water  in  circulation. 

Radiation 

RADIATION  takes  place  conttantly  from  all  bodies,  even  though  they 
may  be  cooler  than  their  surroundings.  The  net  gain  or  loss  by  radiation 
is  the  difference  between  the  heat  received  and  that  emitted.  The  standard 
of  comparison  is  the  performance  of  an  ideal  "black  body,"  one  that  would 
absorb  all  radiation  incident  upon  it,  and  would  radiate  heat  at  the  maximum 
rate.  The  British  thermal  units  emitled  by  radiation  from  a  "black  body." 
per  square  foot  per  hour,  by  Stefan's  formula  equal  16007^/10°,  when  T  is  the 
absolute  temperature  of  the  body,  in  degrees  Fahrenheit.  With  all  real  bodies 
receiving  heat  by  radiation,  a  portion  is  reflected,  and  if  the  body  is  at  all 
transparent  to  radiation,  a  portion  is  transmitted.  The  absorption  factor, 
the  ratio  of  the  heat  absorbed  to  that  incident,  is  equal  to  the  emission  factor, 
which  is  the  ratio  of  the  emissivity  (radiating  ability)  to  that  of  a  perfect 
black  body.  The  emissivities  given  below  are  for  use  in  Stefan's  formula, 
the  values  being  substituted  for  the  1600  used  for  a  black  body: 

Table  52.     RndintJon  Conitanti. 


Rough  cast  iron,  oxidized.... 


Dull  wrought  iron,  oxidized 


Slightly  polished  copper— 


1S70 
1540 
1540 
1510 
1120 


278 


The  rougher  a  body  is,  and  the  darker  it  is  when  in  the  cold  state,  the 
higher  is  its  radiative  and  absorptive  power. 

The  net  heat  transfer  between  two  bodies  depends  upon  their  tempera- 
tures, on  the  character  of  their  surfaces  as  affecting  their  emissivities,  and 
on  the  angle  of  exposure.  For  two  "black  bodies"  with  parallel  faces  exposed 
to  each  other,  the  heat  transfer  is 

H=~-(.T,'-Tn  (37) 


ib.Google 


,Google 


The  temp«rature  of  a  point  exposed  to  radiation  in  a  furnace  setting 
can  be  determined  by  thia  law.  Take  foi  example  a  point  so  located  on  the 
side  wall  so  that  its  angles  of  exposure  to  the  fuel  bed  and  to  the  boiler  tubes 
are  equal,  the  bed  and  tube  temperatnrea  being  2S00  and  500  deg.  respect- 
ively. As  the  point  is  at  a  uniform  temperature  and  practically  unaffected 
l^  the  gas  travel,  the  heat  which  tt  reeeivea  by  radiation  from  the  fuel  bed 
will  be  equal  to  that  which  it  emits  to  the  tubes.  Taking  1600,  1500  and 
ISSO  as  the  radiation  constants  of  the  fuel  bed,  firebrick  and  tubes  respectively, 

1600  „_™  isoor    liso-r    isoo^,^. 

T  =  2545  deg.  abs.  =  2065  deg.  F. 

which  is  the  temperature  of  the  given  point  in  the  side  wall,  as  influenced  by 
radiation. 

Heat  radiated  to  and  from  a  surface  in  such  a  manner  is  often  spoken 
of  as  "reflected,"  although  the  bulk  of  it  is  absorbed  and  then  emitted. 

The  total  heat  transmitted  to  the  tubes  depends  upon  the  temperature  of 
the  fuel  bed,  and  upon  the  area  of  the  fuel  b«l  exposed  to  the  tubes,  rather 
than  upon  the  total  tube  surface.  The  glowing  carbon  radiates  beat  at  a 
rate  almost  equal  to  that  of  an  ideal  black  body,  and  while  the  tubes  receive 
radiant  heat  from  the  walls  and  the  flame,  as  well  as  from  the  fuel  bed,  the 
net  transfer  can  be  closely  approximated  by  inserting  the  fuel  bed  and  the 
tube  temperatures  and  the  area  of  the  effective  fuel  bed  surface,  in  the 
"black  b<>dy"  heat  transfer  equation. 

In  a  locomotive  type  furnace,  the  entire  surface  above  and  surrounding 
the  fuel  bed  is  heating  surface,  except  the  fire  door,  which  covers  only  a 
small  angle  of  the  fire.  The  transfer  by  radiation  is  proportional,  therefore, 
to  the  fuel  bed  area.  In  a  furnace  of  this  type  having  40  sq.  ft.  of  fuel  bed 
at  2500  deg.,  the  sheets  being  at  50(1  deg..  the  heat  transferred  by  radiation 
would  be 

](il»x40  /  2960-— gW  J  ^  4,858,240  B.t.u.  per  hour. 

The  height  of  the  fire  box  would  not  affect  the  total  transfer  by 
radiation,  as  the  entire  fuel  bed  is  exposed  to  the  cool  heating  surface.  If 
the  height  was  4  ft.,  and  the  total  sheet  surface  200  sq.  ft.,  the  heat  trans- 
ferred by  radiation  would  be  24,291  B.t.n.  per  hour  per  square  foot  of 
heating  surface. 

With  an  externally  fired  boiler,  each  portion  of  the  hot  fuel  bed  is  ex- 
posed to  hot  walls  as  well  as  to  the  cold  boiler  tubes,  and  the  walls  are 
exposed  to  the  fttel  bed  and  the  tubes.     In  each  view  of  Fig.  188,  the  angle  b 


Pig.     188.     Application  of  RadUtion  Law  to  an  Externally  Fired  B<riler. 


ib.  Google 


represents  the  exposure  of  a  point  on  the  fuel  bed  to  the  heat-absorbing 
tubes,  and  a  and  c  the  angles  exposed  to  surfaces  at  temperatures  approxi- 
mating those  of  the  fuel  bed.  By  taking  an  average  of  b/\SO  at  a  number 
of  points  in  the  fuel  bed  and  the  walls,  a  measure  of  the  effective  radiat- 
ing area  of  the  hot  surfaces  cau  be  ascertained.  The  right-hand  member  o( 
the  formula  37  (for  heat  transfer  between  two  black  bodies)  can  then 
l)e  multiplied  by  this  average,  the  result  being  the  average  net  heat  radiated 
by  the  hot  surfaces  to  the  boiler. 

The  higher  the  fuel  bed  temperature  the  more  heat  passes  to  the  boiler 
surface  as  radiant  energy  instead  of  being  carried  by  the  gases  as  sensible 
heat.  Fig.  189  shows  the  extremely  rapid  increase  at  high  temperatures,  the 
radiation  being  four  to  five  times  as  great  at  3500  deg.  as  at  2500  deg.  abso- 
lute. Each  curve  is  plotted  for  a  constant  temperature  (a»  indicated)  of 
the  soot  coating  on  the  water-heating  plates. 


Temperaturo  of  Fuel  Bed 


Tests  by  the  University  of  Illinois  on  Heine  boilers,  with  and  without 
a  baffle  protecting  the  lower  row  of  tubes,  showed  a  much  lower  ilue-gas 
temperature,  and  3  to  S  per  cent  higher  efficiency  when  the  tubes  were  ex- 
posed to  radiation.  Little  smoke  was  produced  in  this  case,  although  if  the 
amount  of  heat  transferred  by  radiation  is  too  great  the  fire  is  cooled,  and 
combustion  is   incomplete. 

A  fuel  bed  under  the  boiler  gives  greater  transmission  by  radiation 
than  does  a  Dutch  oven. 

Up  to  the  point  where  the  products  of  combustion  are  cooled  below  the 
ignition  temperature,  any  heat  transmitted  by  radiation,  instead  of  being 
carried  by  the  gases,  is  clear  gain.  High  transmission  by  radiation  requires 
a  large  fuel  surface  exposed  at  a  wide  angle  to  the  heating  surfaces,  and 
high  temperature  of  the  fuel  bed  surfaces.  The  latter,  however,  must  not 
be  so  high  as  to  damage  the  furnace  lining  or  fuse  the  ash. 


ib.  Google 


Conduction 
/"Conduction    ihrough    a    homogeneous    solid    is    measured    by    the 
^— '  following  formula : 

//  =,  CO,—  i,)  ^^j 


H  r=Amoiiiit  of  heat  conducted  =  B.t.u.  per  sq.  ft  per  hour 
C  ^  CoefTicient  of  conductivity   =;    B.t.u.   p«r  sq.   ft.   per   hour   per 
degree  difference  hetween  the  temperatures  of  two  parallel  plane 
surfaces  I  inch  apart 
N  =  Distance  between  plane  surfaces  or  thickness  of  substance 
/„  /,  =;  Temperatures  of  the  two  plane  surfaces 
Values  of  C  for  different  materials  are  given  below  in  Table  S3: 

T«ble  53,     Coefficients  of  Conductivity. 

UucrimI  I  CoBdiKtlvtty  C 


.Aluminum  

Wrought  iron.... 


nruugni  iron _.. ti£  i        .   ^,y   , 

Soft  stcel.„ _ 322  f    ^'  ^'^  '^^■ 

Cast  iron..™ 314 

Hard  Bted ,.  180 1 

Firebrick 9,0    at  1300  deg. 

Water  4.35  at  86  deg. 

Glass  (soda,  window  glass) 4.5 

Hydrogen  0.976  at  60  deg. 

Air  _ „ 0165  at  32  deg. 

Lamp  bUck 0215  at  212  d^. 

Vacuum   _ 0 


The  conductivity  of  sulids  varies  slightly  with  temperature,  iron  de- 
creasing by  0.0^9  for  each  degree  Fahrenheit  rise.  With  gases  it  varies 
as  the  "constant-volume''  specilic  heat  and  the  viscosity  at  different  tem- 
peratures. 

That  the  metal  offers  only  a  small  part  of  the  resistance  to  heat  flow  is 
shown  in  boiler  practice  by  actual  rales  of  transmission.  Consider,  for 
instance,  a  boiler  operating  at  the  rate  of  10  sq.  ft  per  equivalent  boiler 
horsepower,  corresponding  to  3350  B.t.u.  per  sq.  ft  per  hour,  with  tubes 
Vu  in.  thick.  The  conductivity  of  iron  at  400  deg.  is  408,  and  substituting 
in  the  conduction  formula,  we  get 


3350  r 


4oe  , 


t,—i,  —  0.82  deg.  Fahr. 

Higher  rates  of  driving  involve  greater  temperature  differences,  but  the  drop 
through  the  meial  never  approaches  the  drop  between  the  gases  and  the 
water.  Scale  and  soot  coatings  add  considerably  to  the  resistance,  but  even  if 
the  combination  offers  ten  times  the  resistai^ce  of  a  clean  lube,  the  temper- 
ature dro()  is  only  8.2  deg.  through  solid  material.  This  serves  to  emphasize 
the  possibilities  of  working  the  surface  at  high  rates. 


ib.  Google 


ib.Google 


In  a  test  on  a  Heine  Boiler,  the  water  surface  of  the  li-in.  thick  tubes 
was  41.5  deg.  below  the  temperature  of  the  gas  surface.  The  heat  conducted 
was,  therefore, 


0.12S 


X  41.5  =  136.000  B.t.n.  per  sq.  ft.  per  hr., 


corresponding  to  4,05  boiler  horsepower  per  square  foot,  or  0.247  sq.  ft.  per 
boiler  horsepower. 

Thermal  resistance  is  the  reciprocal  of  thermal  conductivity,  and  the 
total  resistance  of  several  bodies  through  which  the  heat  must  pass,  one  after 
the  other,  is  the  sura  of  the  individual  resistances.  A  break  in  a  snhstance 
creates  a  surface  resistance,  so  that  boiler  seams  in  contact  with  the  fire 
should  be  eliminated. 

Convection 


While  considerable  work  has  been  done  to  elucidate  the  subject  of  con- 
vection, it  must  be  admitted  that  much  research  is  still  necessary. 

Rankinr't  convection  formula  is  based  on  the  assumption  that  the  rate 
of  heat  transfer  is  dependent  simply  upon  the  square  of  the  dilTerence  in  the 
temperatures  of  the  gases  and  of  the  heating  surface,  and  is  independent  of 
the  velocity  of  the  gases.     This  assumption  is  now  generally  rejected. 

Many  prominent  scientists  and  engineers  have  made  investigations  that 
have  provided  interesting  information.  In  1874,  Professor  Osborne  Reynolds 
formulated  a  law  of  heat  transfer  which  may  be  expressed  as ; 


where  R  ^  B.t.n.  transferred  per  sq.  ft  of  heating  surface  per  hour  per 
degree  difference  between  the  temperatures  a!  gas  and  metal 
If  =  Weight  of  gas  per  hour 
A  =  Area  of  gas  passage 
a  and  b  —  Constants, 

This  law  is  baaed  fundamentally  on  the  rate  of  flow  of  the  gas  over  the 
heating  surface ;  it  has  been  frequently  and  conclusively  confirmed  by  Stanton, 
Nicolson,  Jordan  and  others. 

Jordan  summarized  the  convection  law  of  heat  transfer  as  follows: 

1.  For  a  constant  rate  of  mass-flow,  the  rale  of  heat  transfer  is  pro- 
portional to  the  temperature  difference  between  gas  and  metal. 

2.  For  a  given  temperature  difference,  the  rate  of  heat  transfer  in- 
creases with  increasing  gas  velocity  according  to  a  linear  law. 

3.  For  a  given  gas  velocity  and  a  given  temperature  difTerence,  the 
rate  of  heat  transfer  increases  with  the  absolute  value  of  the  temperature. 

4.  The  rate  of  heat  transfer  depends  upon  the  condition  of  the  heating 
surface. 

5.  The  rate  of  heat  transfer  depends  on  the  si:te  of  the  channel  through 
which  the  gas  is  flowing,  the  smaller  the  ratio  of  the  area  of  the  channel  to 
the  perimeter  of  the  channel,  that  is,  the  smaller  the  hydraulic  depth,  the 
greater  the  ratio  of  heat  transfer. 


ib.  Google 


The  value  of  a  is  influenced  by  the  condition  of  the  heating  surface.  It 
varies  between  1^5  and  22S.  With  reasonably  clean  surfaces,  it  is  generally 
very  close  to  2J),  and  this  remains  the  case  no  matter  what  the  circumstances 

The  value  of  b  is  of  the  most  importance.  It  is  influenced  by  the  hydrau- 
lic depth  of  the  channel,  and  by  the  temperature.  AH  ordinarv  conditions 
are  met  by  writing  b  =  O.OOI.  The  effect  of  tbis,  at  say  2,000  and  4,000 
pounds  of  gas  per  sq.  ft.  of  gas  passage  area  per  hour,  is: 


(2,000  \       .       „ 


Some  take  a  much  higher  value  of  b  with  a  consequently  higher  value  of 
R;  but  as  these  higher  values  of  R  are  not  realized  in  practice  when  the 
ladiation  effect  is  eliminated,  it  is  customary  to  make  an  arbitrary  addition 
to  the  amount  of  heating  surface  so  deduced. 

Investigations  now  in  progress  by  the  Research  Department  of  the 
Heine  Comf>any  have  yielded  some  surprising  information.  Under  certain 
circumstances  the  value  of  ^  may  he  increased  very  considerably, — in  some 
instances  to  as  much  as  0.004.  To  show  the  effect  of  this,  the  same  gas 
rates  as  above  are  taken,  namely,  2.000  and  4,000  pounds. 


'(-T> 


The  amonnt  of  heating  surface  required  is,  of  course,  inversely  pro- 
portional to  R  when  radiant  heat  is  nut  considered.  So  that  when  W/A  ^= 
say  4,000  pounds,  a  boiler  with  /?  :=  18  would  have  a  heating  surface  only 
one-third  of  that  of  a  boiler  with  R  =  6,  the  capacity  and  efficiency  being 
the  same  for  both. 

Lawford  H.  Pry  has  made  a  broad  investigation  of  the  work  of  experi- 
menters in  this  line  and  has  devised  a  formula  which  harmonizes  the  results 
of  a  large  number  of  tests.  This  formula  does  not  directly  express  ihe  rate 
of  heat  transfer,  but  rather  gives  an  expression  for  the  rise  or  fall  of  tem- 
perature of  a  gas  in  its  passage  through  a  flue,  the  wall  of  which  is  at  a 
higher  or  lower  temperature  than  the  gas.  When  the  gas  is  hotter  than 
the  flue, 

hlog  y'  — hlog^^  =Mj  (40) 

where    »  =  Distance  along  the  flue  from  entrance 
Ti  =  Initial  gas  temperature,  deg.  absolute 
Tt  ^^  Exit  gas  temperature,  deg.  absolute 
Ti  ^=  Mean  flue  wall  temperature,  deg.  ab.soliite 
M  =  Coefficient 
lolog  ^=  T.x>garithm  of  the  logarithm 

Coefficient  M  depends  on  the  flue  dimensions  and  the   rate  of 
gas  flow. 


ib.  Google 


Fig.  190  is  drawn  from  Fry's  formula,  and  shows  the  relation  of  gas 
temperatures  to  proportion  of  heating  surface  passed  over,  with  2,S00°  initial 
and  450°  exit  temperatures  in  conjnnctioR  with  a  water  temperature  of  360°. 

The  application  of  the  law  of  high  gas  velocity  to  waste  heat  boilers 
has  been  mentioned  in  Chapter  4  on  FURNACES  AND  SETTINGS. 


2200 
ZOOO 


^1400 
J  I  ZOO 


0         10        20        30        40       50       60        70       80        90 
F^rceniage  of  Heating  Surftee  fiSasse^ 

PiK.  190,    Relation  Between  Temperattire  of  Omm  and 
HeatinK  Surface  Patted  Over. 


ib.  Google 


,  Google 


Temperature  Drop  in  Boilers 

FXG.  191  shows  the  results  of  tests  by  the  Bureau  of  Mines  on  a  Heine 
Boiler,  operating  at  4.4  lb.  per  square  foot  per  hour,  in  which  temperatures 
of  both  sides  of  the  lube  were  taken.    These  tests  also  show  the  large  tem- 
perature drop  between  hot  gas  and  metal,  and  the  small  drop  through  the 
metal  to  the  water;  the  temperatures  at  the  i"4-hour  point  being  as  follows: 
Gases     Gas-side  Surf  ace     Water-side     Water 

.\t  beginning  of  path 2552  400  358  347 

At  end  nf  path 688  352  349  347 


Fig.  191.     Temperature  Rcadingi  in  Conductivity  Teit. 


The  transfer  of  heat  from  metal  to  water,  if  the  circulation  is  sufficient, 
i.s  rapid,  because  of  the  high  specific  heat  of  water.  The  high  rale  of  heal 
transfer  in  condensers,  which  may  be  more  than  1000  B.Lu.  per  sq.  fi.  per 
hour  per  deg.  difference,  ilhistrates  this. 

Combuation 
r^OMBUSTlON  is  the  process  of  oxidation  or  the  chemical  union  of  an 
^^^   element  with  oxygen,  and  takes  place  with  such  rapidity  that  considerable 
light  and  heat  are  produced.     The  principal  combustible  elements  in  fuel  are 
carbon,  hydrogen  and  sulphur. 

The  oxygen  necessary  for  the  combustion  of  fuel  is  provided  by  the  air, 
which  is  a  mechanical  mixture,  not  a  chemical  compound.  Air  consists 
principally  of  oxygen  and  nitrogen  and  contains  small  amounts  of  carbon- 


ib.  Google 


dioxide,  water  vapor,  ai^on  and  other  rare  and  inert  gases.     These  inert 
gases  are  ordinarily  included  with  the  nitrogen,  so  that  the  composition  of 

air  is  generally  given  as : 

Per  Cent  by  Volume        Per  Cent  by  Wei^ 
O,  20.91  23.1S 

N,  79,fB  76.85 

The  chemical  combination  of  oxygen  with  the  combustible  elements  of 
fuels  occurs  in  de6iiite  and  invariable  proportions — a  law  which  may  be 
better  understood  by  the  following  brief  references  to  elementary  chemistry. 

All  substances,  whether  gaseous,  liquid,  or  solid,  are  either  elements, 
compounds  or  mixtures. 

An  element  is  a  substance  which  cannot  be  reduced  to  a  simpler  form. 
Carbon,  sulphur,  oxj^en,  hydrogen,  etc.,  arc  elements. 

A  compound  is  a  substance  which  can  be  reduced  into  simpler  forms  or 
elements  by  chemical  process.  Water,  carbon-dioxide,  iron  sulphide,  etc., 
are  chemical  compounds. 

A  mechanical  mixture  contains  one  or  more  substances  not  held  in 
chemical  combination.  Air,  as  mentioned  above,  is  a  mixture  of  the  elements. 
oxygen  and  nitrogen,  and  the  compounds  carbon-dioxide,   water  vapor,  etc. 

Molecules.  If  an  element  or  compound  be  divided  and  redivided  into 
particles,  until  the  limit  is  eventually  reached  where  the  substance  can  not 
exist  by  itself  without  losing  its  characteristics,  that  particle  is  known  as  a 
molecule.  If  such  a  molecule  be  dissociated  into  its  component  elements, 
these  elements  are  known  as  atoms.  The  elements  are  represented  in 
chemical  nomenclature  by  letters,  such  as  H  for  hydrogen,  C  for  carbon,  Fe 
for  iron,  etc.,  etc.  Compounds  are  represented  by  groups  of  letters  with 
subscripts  which  indicate  the  numbers  and  kinds  of  atoms  contained  in  the 
molecule.  For  example,  the  symbol  HiO  for  water  indicates  that  two  atoms 
of  hydrogen  and  one  atom  of  oxygen  comprise  one  molecule  of  water.  Atoms 
seldom  exist  uncombined,  hence  the  symbols  for  oxygen,  nitrogen,  etc.,  are 
written  Oi  and  N.  which  indicate  that  there  are  two  atoms  in  the  molecules. 
Carbon  exists  in  a  number  of  different  forms  and  hence  there  are  many 
carbon  molecules,  each  containing  a  different  number  of  atoms.  The  latest 
investigations  seem  to  indicate  that  the  least  number  of  atoms  in  any  carbon 
molecule  is  twelve. 

Atomic  Weights.  The  atoms  of  different  elements  have  different  relative 
masses  or  weights.  As  hydrogen  is  the  lightest,  its  atomic  weight  is  generally 
given  as  1  and  the  weights  of  other  atoms  referred  thereto,  but  sometimes 
ox^en  is  given  as  16  and  used  as  the  basis.  Table  54  gives  the  atomic 
weights  of  those  elements  most  frequently  met  with  in  the  combustion  of  fuels. 

Tatile  54.     Atomic  Weights. 


12.005 
3Z07 
16,00 
14.01 


ib.  Google 


Molecular  Weigklt,  When  two  or  more  elements  combine  to  form  a 
compound,  the  relative  weight  of  the  molecule  formed  will  equal  the  com- 
bined  weight  of  the  atoms  which  comprise  it.  For  example,  the  water  mole- 
cule, H,0  consists  of  one  atom  of  oicygen  (atomic  wt,  16),  and  two  atoms 
of  hydrogen   (atomic  wt.  1).  16-|-2=18,  the  molecular  weight  of  water, 

SigtiHieaaee  of  Atomic  and  Molecular  Weights.  When  expressing  any 
chemical  reaction  by  an  equation,  the  relative  weights  concerned  in  the  re- 
action  ar«  obtained  directly  by  using  the  atotnic  or  molecular  weigjits.  For 
example : 

C  +  0,=  CO. 
12  +  32  =44 

These  relative  weights  may  be  expressed  in  kilograms,  tons,  pounds  or 
in  any  other  unit  of  weight. 

Where  gases  are  involved,  the  relative  number  of  molecules  of  the 
gaseous  substance  occurring  in  the  reaction  stand  for  the  relative  volume 
of  that  gas.  Roman  numerals  are  generally  used  to  designate  these  relative 
volumes,  which  may  be  expressed  in  cubic  meters,  cubic  feet,  etc.  For 
example,  in  the  combustion  of  methane,  one  volume  of  methane  unites  with 
two  volumes  of  oxygen  to  form  one  volume  of  carbon-dioxide  and  two 
volumes  of  water  vapor. 

I  II  I  11 

CH,  +  20,  ^CO,  +  2H,0 

Heat  of  Combustion  is  usually  expressed  as  the  B.tu.  generated  by  the 
complete  combustion  of  one  pound  of  fuel.  When  elements  or  compounds 
enter  into  chemical  combination  with  one  another,  heat  is  either  evolved  or 
absorbed;  that  is,  the  reaction  is  either  exiothermal  or  endothermal.  The 
reactions  in  combustion  practice  are  exothermal.  When  one  pound  of  pure 
carbon  bums  completely  to  carbon-dioxide,  14,544  B.tu.  are  generated. 
When  carbon  is  not  supplied  with  sulTicient  air  for  complete  combustion, 
carbon  monoxide  is  formed  and  only  4,351  B.t.u.  are  liberated.  The  presence 
of  even  a  small  amount  of  carbon  monoxide  in  boiler  flue  gases  indicates  a 
waste  of  fuel  since  each  pound  of  carbon  in  this  CO  has  yielded  less  than 
one-third  of  its  available  heat.  The  effect  of  the  presence  of  carbon  monoxide 
in  the  flue  gases  on  boiler  and  furnace  efficiency  is  explained  in  Chapter  15  on 
TESTING  and  Chapter  16  on  OPERATION. 

Table  55  gives  the  weight  and  volumetric  reactions  and  the  heat  evolved 
in  the  combustion  of  those  elements  or  substances  occurring  in  fuels. 

Ignition  Temperature.  As  defined  above,  combustion  is  characterized 
by  the  rapid  chemical  union  of  oxygen  with  the  combustible  substance.  The 
rapidity  or  speed  of  the  chemical  reaction  depends  definitely  on  temperature. 
It  is  a  well  known  fact  that  a  lump  of  coal,  even  though  surrounded  by  the 
requisite  amount  of  oxygen  for  combustion,  will  not  burn,  unless  it  is  at  a 
relatively  high  temperature.  So  also  for  every  combustible  substance  there 
is  a  definite  temperature  below  which  the  substance  will  not  oxidize  or  burn. 
This  temperature,  which  is  known  as  the  ignition  temperature,  is  given  in 
Table  56  for  various  components  of  coal  and  for  CO. 

It  is  to  be  noted  that  the  fixed  carbon  in  coal  ignites  at  a  lower  tempera- 
ture  than  the  volatile  hydrocarbons.  Carbon  monoxide  will  ignite  at  about 
1210  degrees  F.  Therefore,  with  poor  firing,  delayed  or  secondary  combustion 
ma.V  take  place  if  oxygen  is  mixed  with  the  CO  in  the  proper  proportions  at 
a  temperature  of  1210°  or  above. 


D,g,tze:Jbi  Google 


a* 


1-8 

5.1 

.si 
i'i 


ib.Google 


I      -5-4: 


li 


, -o     -o  ; 

+        + 


aO '>o    s6    Eg 


1 

^ 

o 
u 

I 

«■ 

<r 

z 

a 

z 

■    4 

2 

e 

o 

E 

I 

t 

1 

J 

1 

a 

1 
1 

1 

.      ; 

1 

1 

■i 
< 

J 
1 

1 
2 

ib.  Google 


a* 

li 

fl 

Is 

h 
I 


ib.Google 


I-. 

_ 

, 

i<^& 

2- 

S. 

a 

o 

1 

u 

u 

+ 

-1 

» 

^ 

: 

- 

'  - 

-- 

<S 

g 

1 

o 

s 

J 

1 

o- 

+ 

o" 

+ 

i 

* 

If 

= 

in 

-r 

-- 

II! 

1 

1 

u 

c3 

II 

-  ■  IS 
ti" 

ilee 


ib.Google 


Table  56.     Iinition  Temperaturci. 


Fixed  Carbon — Bituminous  Coal„. 
Fixed  Carbon — Anthracite  Coal.... 
Carbon   Monoxide. „ 


1210 

9QO-1200 

1130 


orelieal  Furnace  Temperatures  may  be  calculated  on  tbe  basis  of  the 
.g  formula : 

'  =  '-+w^.  ■  <■"> 

I  =:  Temperature  of  combustion 
(,  =  Temperature  of  air 
//  =  B.t.u,  developed  by  combustion 
JK  =  Weidht  of  products  of  combustion 
c  =  Mean  specific  heat  of  products  of  combustion  between  d  and  t. 
The  use  of  ihit  formula  involves  a  trial  and  error  method  in  the  deter- 
mination of  the  mean   specific  heat  of  the  products  of  combustion.     The 
theoretical  furnace  temperatures  calculated  by  the  above  formula  or  modifi- 
cations of  it  have  but  little  value  to  the  engineer,  as  the  actual  furnace  tem- 
perature is  affected  by  variations  itf  the  rate  of  air  supply,  by  the  complete- 
ness of  combustion,  and  by  radiation   from   the   fuel  bed  and   flame  to  the 
cold  surrounding  surfaces.    Actual  furnace  temperature  will  therefore  always 
be  lower  than  theoretical  temperatures. 

Air  Theoretically  Required  for  CombustioH.  Table  55  gives  the  combus- 
tion reactions  which  occur  in  the  burning  of  fuel.  From  these,  the  amount 
of  oxygen  necessary  and  consequently  the  weight  of  air  theoretically  re- 
quired can  be  readily  calculated  by  means  of  the  atomic  weights  of  the 
substances  involved. 

The  method  of  computing  the  air  required  for  the  combustion  of  carbon 
to  CO,  will  be  given  in  the  following  example,  which  is  typical  of  the  manner 
in  which  the  results  given  in  Table  57  are  calculated. 

From  Table  55  it  is  observed  that  one  atom  of  carbon  unites  with  two 
atoms  of  oxygen  to  form  carbon  dioxide. 


hO,-  CO,. 


veight  of  carlHju  in  12  and  of 


12+  f2xl6)=:44. 

or  twelve  parts  of  carbon  by  weight  unite  with  thirty-two  parts  of  oxygen 
by  weight  to  form  forty-tour  parts  of  carbon  dioxide  by  weight  Now,  if 
we  consider  one  pound  of_  carbon  as  being  burned,  the  weight  of  oxygen 
necessary  for  combustion  will  be  "/^  or  2.66/  lbs. 

Since   air   contains  23.15  per  cent  oxygen  by   weight,   there   will  be   re- 
cjiiired  4J2  lbs.  of  air  to  supply  1  lb.  of  oxygen.    Then, 

2.667  X  4.32  =  11.52  lbs.  air  required. 


ib.  Google 


Table  S7.     Theoretical  Air  Requirements  per  lb.  of  Combustible. 


Cora  pound 

Oxygen 
Required 
Pounds 

Air 
Required 
Pounds 

Air 

Required 

cu.  ft  at  80"  F. 

Carbon  to  CO 

Carbon  to  CO^ 

CO  to  CO^ 

U3 
2.67 
0.57 

5.76 
11.52 

2.47 

78.4 
156.5 
33.5 

&00 
1.00 
1.50 

34.56 

4.32 
6.48 

469.5 

Sulphur  to  SO, 

Sulphur  to  SO, 

58.6 
8a2 

Methane  

4.00 
3.08 
3.43 

17J8 
13.29 
14.81 

234.8 

180.9 

Ethylene  

201.6 

Ethane  

Hydrogen  Sulphide „.. 

3  73 

1.41 

16.13 
6.10 

219.5 
83.0 

The  theoretical  air  requirements  given  in  Table  58  are  calculated  on  tlie 
basis  of  the  approximate  atomic  weights.  The  Bureau  of  Mines  gives  the 
following  formula  for  calculating  theoretical  air  requirements,  based  upon 
the  accurate  atomic  weights. 

W  =  0.11S8  C  +  0.3448 H  —  0.04336  (0—S)  {41a) 

where :      If  =  Ih.  of  air  per  lb.  of  fuel 

C  ^  Percentage  of  carbon,  ultimate  analysis 
H  ^  Percentage  of  hydrogen,  ultimate  analysis 
O  =  Percentage  of  oxygen,  ultimate  analysis 
5  :=  Percentage  of  sulphur,  ultimate  analysis 

The  weight  of  air  will  be  per  pound  of  coal,  per  pound  of  dry  coal,  or 
per  pound  of  combustible,  according  to  the  basis  on  which  the  analysis  is 
reported. 

Air  requirements  of  typical  coals  were  calculated  by  the  Bureau  of  Mines 
formula  as  follows: 

Table  58.     Air  Required  per  lb.  of  Coal. 


Cod  by  Analyrii.  Fn  » 


I    °    I 


ib.Google 


P 

Is 


u  c 

1° 

So. 
SK 


8  6 


,Google 


Table  58  shows  that  while  the  weight  of  air  required  per  pound  of  fuel 
varies  greatly  with  the  composition  of  the  coal,  it  is  nearly  proportional 
lo  the  heat  value.  The  weight  may  run  from  7  lo  12  lb.  per  pound  of  coal, 
;md  averages  about  7.S  lb.  per  10,000  B.t.u. 

Air  Actually  Required  for  Combustion 

IN  practice  it  is  necessary  lo  supply  more  air  than  that  theoretically  re- 
Quired,  owing  to  the  products  of  combustion  getting  in  the  way 
when  combustion  is  nearly  complete.  At  the  beginning  of  combustion  in  a 
theoretically  perfect  mixture  oE  CO  and  air,  CO  and  0,  molecules  will  come 
together  more  frequently  than  when  they  are  impeded  by  COi  molecules 
formed  as  combustion  progresses.  The  last  free  molecules  of  CO  and  0>  will 
probably  not  come  together  until  the  temperature  lias  fallen  below  iheir 
combining  or  ignition  point.  Combustion,  therefore,  is  always  more  intense 
in  the  earlier  part  of  a  flame  and  is  langtiid  at  the  tip.  Mixing,  agitation, 
or  eddying  of  ihe  gases  will  hasten  combustion,  but  an  excess  of  the  Oi  mole- 
cules is  still  necessary  to  ensure  complete  combustion  in  a  reasonable  time; 
ihe  more  thoroughly  the  air  is  distributed  and  mixed  with  the  combustible 
gases,  the  less  excess  will  be  required.  Even  in  gas-burning  installations, 
where  the  air  is  intimately  mixed  whh  the  fuel,  some  excess  air  must  be 
used,  and  appreciable  time  is  required  to  complete  combustion.  This  is 
shown  by  the  CO  present  in  the  flue  gases,  if  the  comparatively  cool  heating 
surface  is  too  dose  to  the  burner  so  that  the  flame  reaches  it  and  its  tip 
is  extinguished.  The  combustion  space  between  the  fire  and  the  heating 
surface  should,  therefore,  he  ample,  and  should  be  so  arranged  that  the  gas 
stream  is  diverted  and  broken  up.  In  coal  burning  furnaces  an  excess  of 
at  least  40  per  cent,  or  1,4  times  the  amount  of  air  theoretically  required,  i5 
usually  necessary. 

Products  of  complete  combustion  o£  fuels  containing  only  carbon  and 
hydrogen  are  carbon  dioxide  and  water,  as  will  be  noted  by  reference  to  the 
reaction  equation  given  in  Table  SS.  The  weights  of  these  products  may  be 
readily  calculated  by  the  use  of  atomic  weights,  and  the  relative  volumes  will 
be  noted  in  the  volumetric  equations  in  Table  55. 

The  volume  of  COi  resulting  from  the  complete  combustion  of  carbon 
is  the  same  as  that  of  the  oxygen  consumed,  because  each  molecule  of 
oxygen,  0>,  takes  up  an  atom  of  carbon  to  form  a  molecule  of  CO,. 
Therefore,  the  CO.  and  the  unused  oxygen  in  the  flue  gases  cannot  possibly 
exceed  the  20.9  per  cent  of  the  oxygen  in  the  atmosphere.  But  Ihe  volume  of 
CO  resulting  from  incomplete  combustion  is  twice  that  of  the  oxygen  con- 
sumed, because  each  atom  of  the  oxygen  molecule  takes  up  an  atom  of  carbon 
to  form  a  CO  molecule,  thus  making  two  molecules  of  CO  for  each  molecule 
of  C  Therefore,  if  CO  is  present,  the  (CO,  -f  O,  -(-  CO)  in  the  flue 
gases  can  exceed  20.9  per  cent.  The  steam  which  results  from  burning  the 
hydrogen  in  the  fuel  condenses  and  does  not  show  in  the  analysis,  conse- 
quently the  oxygen  consumed  disappears,  and  the  highest  possible  propor- 
tion of  CO,  and  O,  in  the  flue  gases  is  less  than  20.9,— being  about  19  per 
cent  with  bituminous  coals. 

The  analvsis  of  the  products  of  combustion  is  discussed  in  Chapter  IS 
on  TESTIN6. 

Combustion  Losses.  In  the  combustion  of  fuel,  certain  losses  occur  which 
vitally  affect  boiler  efficiency.  These  losses  are  (I)  the  loss  due  to  ihe  in- 
complete combustion  of  carbon,  (2)  the  loss  due  to  latent  heat  of  moisture 
formed  in  the  burning  of  hydrogen,  (3)  the  loss  clue  to  unconsumed  carbon 
in  the  refuse,  and  (4)  the  loss  due  to  incomplete  combustion  of  the  volatile 
hydrocarbons.  The  determination  of  these  losses,  together  with  certain  other 
losses,  inherent  in  methods  of  boiler  operation,  such  as  heat  carried  away 
by  chimney  gases,  heat  lost  by  radiation,  etc..  is  discussed  under  the  subject 
of  the  heat  balance  in  Oiapter  15  on  TMSTING. 


ib.  Google 


Properties  of  Gases 
PHE  general  law   for  the  effects  of  temperature  and  pressure  c 
'-    represented  by  the  following  equation : 


(«) 


V  =  Volume,  cu.  ft.  per  lb. 

P  =  Pressure,  lb.  per  sq.  in.  absolute  =  gage  pressure  +  14.696 

R  =;  Constant,  differing  with  the  gas 

T  =:  Temperature  absolute  ^=  deg.  Fahr.  +  46(i 
Equation  42  shows  that  the  volume  increases  with  rise  in  temperature  and 
decreases  with  rise  in  pressure.    With  pressure  unchanged,  at  temperature  t, 
the  volume  is 


For  constant  temperature,  at  P,  the  volume  =  VJ'tlP^  where  P,  and 
P,  can  be  expressed  in  pounds  per  square  inch  absolute,  or  in  inches  or 
millimeters  of  mercurr- 

When  the  desired  value  is  to  be  derived  from  the  volume  under  "standard 
conditions."  Vt  is  the  volume  at  32  deg.  and  atmospheric  pressure,  which 
corresponds  to  492  deg.  absolute  and  14.ffl6  lb.  per  »q.  in.  pressure  (760  mm. 
or  29321  in.  of  mercury). 


Tkble  59.    Phy^cal  Characteristics  of  Oases  Involved  in  Furnace  Work 


« 

AtWF. 

1 

eu-ft,                   — =lb.     DB 

Carbon  Monoxide,  CO 

A.3140 
0.6682 
0.3826 

177.900 
22.372 
12.80e 

0. 00662 
0.04470 
0. or  807 

0.00612 
0.04083 
0.07113 

Nitrogen,  N. 

Average  flue  gas 

0.3824 
0.3701 
0.3566 

12.801 
12.390 
11.920 

0.07812 
0  08071 
0.0S400 

0.07127 
0.07353 
0.07660 

0.3348 
0.2420 
0.1636 

11.208 
8.103 
5.473 

0.08922 
0.12341 
0.18271 

Carbon  ESoride,  CO. . 
Sulphur  Dioxide,  SO,. 

0.11244 
0.16646 

The  density,  which  is  the  reciprocal  of  the  volume,  decreases  with  rise 
in  temperature  and  increases  with  higher  pressure. 

The  changes  in  volume 'and  density  of  the  gases  referred  to  in  Table  59 
.ire  shown  in  Fig.  192. 

Air  containing  the  maximum  amount  of  vapor  for  the  existing  tem- 
perature is  said  to  be  "saturated."  Fig.  193  shows  the  weight  of  pure  dry 
air  for  temperatures  from  0  to  212  deg.  at  standard  atmospheric  pressure 
(14.696  lb.  p;r  sq.  iru),  also  the  weight  of  air  and  vapor  in  a  saturated 
mixture  under  the  same  pressure. 


ib.  Google 


Fig.  192.     Temperature  in  Relation  to  Volume  and  Deniity  of  Oaaes. 

Table  60  gives  the  weight  and  volume  of  air 
and  pressures  up  to  100  Ih.  gage.  Intervening  v 
the  use  of  the  general  laws  explained  above. 

Specific  Heal  of  Gases.  There  is  frequent  necessity  for  the  use  of  the 
specific  heal  of  gases  in  the  computation  of  combustion  data.  As  defined  in 
the  units  of  measurements  used  in  power  plant  work,  the  specific  heat  of  a 
substance  is  the  B.t.u.  required  to  raise  the  temperature  of  one  pound  one 
degree.  The  specific  heats  of  all  substances,  whether  gaseous,  liquid,  or  solid, 
vary  with  temperature.  In  the  case  of  liquids  or  solids,  there  is  little  differ- 
ence between  the  specific  heats  at  constant  pressure  and  those  at  constant 
volume.  However,  for  gases  there  is  considerable  difference  in  the  specific 
heats  under  these  two  conditions.  The  gases  in  combustion  practice  may  be 
assumed  to  be  at  constant  pressure. 

Specific  heats  may  be  still  further  classified  as  being  instantaneous  or 
mean.  The  instantaneous  specific  heat  of  a  substance  is  defined  as  the  amount 
of  heat  required  at  a  definite  temperature  to  raise  the  temperature  of  a 
unit  weight  I  degree.  The  mean  specific  heat  of  a  substance  for  a  given 
temperature  interval,  is  the  specific  heat  by  which  the  temperature  difference 
must  be  multiplied  to  determine  the  amount  of  heat  necessary  to  raise  a  unit 
weight  through  the  given  temperature  interval.  The  mean  specific  heat  is 
generally  used  in  the  calculation  of  combustion  data. 


ib.  Google 


400 

TaUe  60. 

Weigb 

HEAT 
t  and  Virfume  of  Pure  Air  at  Different  Prewures. 

OlO  V 

V 

O-lb. 

Wb.          1         lOJb. 

20-lb.                  HMb. 

IKMb. 

.0SC4 
.084b 

.as2s 

11.60 
11.83 

12.08 

.1160 
.1136 

.1112 

w 

. 

,1.      -l- 

- 

0 
10 
20 

IS 

8.99 

.1455 
,1425 
,  1395 

7.16 

.2040  4.91  .3800 
.1996  5.01  .3720 
.1955   5.12.3645 

3.63 
3.6!) 

2.75 

,672 
.658 

,645 

1.49 
1.50 
1..55 

ao 

32 
40 

.0811 
.0809 
.0795 

12.34 
12-38 

12-59 

.1088 
.1084 
.1067 

9.18 
9.23 

.1366 

.I3ac 

.13.38 

7.33 
7.35 

7,47 

.1910    5.22  .3570 
.1909    5.24  .3560 
.1876    5-34  ,3503 

2. 80!. 632 
2.81  ,630 
3.801-619 

1.68 
1.69 

1,62 

50 
GO 
70 

.OJiH. 
.0764 
.0750 

12-84 
13.10 
13-35 

.1045 
.1025 
.1006 

9.57 
9,75 
9,95 

.1310 
,1283 
.1260 

7.04 
7.79 
7.94 

.1839    5.44  .3432 
.1803   r., 55  ,3362 
.1770   5.65.3302 

2,921.607 
2.98.596 
3.03|.584 

1.65 

1.68 

80 
00 

1O0 

"071C 

13.60 
13.83 
14.10 

.0988 
.0970 
.0954 

10.13 
10,32 
10, 6( 

.1239 
.1218 
,1197 

8.oa 

8.21 
8,36 

,1738   fi. 75  .3242 
.1707    5.86  .3182 
.1076    5.97.3122 

3.091.572 
3.14  .561 
3.2l|.551 

1.75 

1.78 
!.S3 

no 

1?0 
130 

;0074 

14.35 

14.58 
14. S6 

.0937 
.0921 

.man 

10^87 
11,07 

.1176 
,1155 
,1135 

8.51 
8.66 
R.82 

.1645   6.08.3070 
.1618   6.18.3018 
.1590   6.29  .2966 

3,261.542 
3.32.533 
3.38|.624 

1.86 
1.88 
1.91 

140 

150 
160 

.060,3 
.0652 
.0042 

15.09 
15.36 
15.60 

.0»39 
.0874 
.0869 

11,27 
11,47 
11,53 

,1115 
.1096 
.1078 

8.97 
9.13 
9.28 

.1565   0.39  .2915 
.1511    6.49.2865 
.1517   6,60.2820 

3.431.516 
3.49.608 
3.551.499 

1.94 

1.97 
2.01 

170 
180 
190 

.0631 
.0622 
.0612 

15.81) 

16.10 
16,37 

.0846 
.0833 
.0820 

12'0i 
12,21 

.1062 
.1W6 
,1029 

ii 

.1493    6.69.2775 
.1468   6.81  .2730 
.1447    6.92  ,2690 

3.611.491 
3.6T.484 
3.72|.476 

2.04 
2.07 
2.10 

200 
220 
340 

-E 

16.60 
17.12 
17.62 

,0809 

.0785 
.0763 

12,38 
12,75 
13,13 

,1014 
.0384 
.095.5 

9.87 
10.17 
10.37 

.1427    7.02  .2666 
.1383    7.24  .2675 
.1345   7-44.2605 

3.7r|.470 
3,8!  -457 
3.8.'-i|,444 

2.13 
3-19 
2.20 

230 
280 
300 

.ft}5;j 

18.  IC 
18.61 
19.13 

.0742 
^0703 

13,50 
13. 8S 

14,25 

!09W 
,0881 

11.37 

.1307    7.62  ,2435 
.1273    7.85  .2370 
.1237    8.09.2300 

4. 111.431 
4.22.420 
4..35|.407 

2.32 
2.38 
2-45 

350 
400 
450 

-0491 

.0463 
,W37 

20.90 

21.65 
22.95 

;0S21 

14,98 

!073.-i 

12.13 
12.85 
13-62 

.1160    8.62  .2160 
.1090   9.18.2036 
.1033    9,68  .1925 

4.641.382 
4.92.360 
5.20|,340 

2.62 
3-78 

2.9,-. 

500 
650 

600 

.W14 
.0394 
.0376 

24.20 
25.40 
26.63 

.Q5CH 

17.73 
18.94 
19, 9C 

!0601 
,0631 

15' 13 
15.87 

-0J78  10-23. 1820 
-0930  10.76.1730 
.0885  11.31  .1650 

5.501.322 

5.78.306 

3.11 
3.27 
3.43 

700- 
800 
900 

.0,'i42 
.0316 
.0293 

29.25 
31-70 
34. IS 

'0124 

.a!93 

23^65 
2.5.50 

,0577 
.053! 

17.35 
18.8.1 
20.35 

.0808  12.38.1509 
.074513.44  .1390 
-0G8H  14.54 -1287 

6.641.267 
7.2q.246 
7.7a|.227 

4!0G 
4.41 

1000 

.0273 

36,  GS 

.0366 

27.30 

.0459 

21.80 

.0643  15.56  .1199 

8, 341,212 

4.72 

orM^ 

Tklue 

■  laabc 

n.»d.p 

b«d 

foot. 

uotir 

-Vatam»ia<!uU<:t.M 

(14.es«  lb.  pa 
p«p<»ul. 

■4.1a. 

There  is  considcralile  disagreenient  lietween  the  ppccilic  heats  o(  gases  as 
detemiinci]  by  niany  investigators.  Prof.  G.  B.  Upton  collaborated  the  work 
of  Mallard,  LcChatelicr,  Holborn  and  limning,  Langen,  Pier  and  others,  and 
derived  the  iormutas  of  Tahle  61,  which  are  sufficiently  accurate  for  engineer- 
ing calculations. 


ib.  Google 


Fig.  193.     Weights  of  Air  or  Water  Vapor. 


Table  61.     Mean  Specific  Meat  Formulaa  (Const.  Ptcm.) 
Range  o"  C  ta  1°  C 


Gas 

Formula 

0, 

0.216+ 0.000014J 

N.  and  CO 

0.243  -f-  O.0O00I9I 

CO, 

Oa»+75X  10-^—21  X  ]0-»P  +  2.2xlO-'V 

H, 

3.369  +  0.00055J 

Air 

0237  +  0.0000191 

Water  Vapor 

0.452  +  7.4  X  lO-"'  +  92.6  X  lO-'C—  20.6  X  lO-'V 

The  curves,  Figs.  194,  195  and  196.  showing  the  mean  specific  heats  at 
constant  pressure  of  those  gases  most  comtnonly  met  with  in  combustion 
practice,  are  based  upon  the  formulas  given  in  Table  61.  .^bove  a  tempera- 
ture of  about  2000°  F„  the  valuea  are  somewhat  uncertain  and  the  results  are 
dependable  only  to  the  first  two  significant  figures  after  the  decimal  point 


ib.  Google 


ib.Google 


/"•*  W"* 


ill 

I 

3 


ib.Google 


ib.Google 


i   i 


ill 
si's 


/""W  W^"* 


ib.Google 


aS 


I* 


ib.Google 


Chapter  12 


STEAM 

Properties  of  \Vater  Vapor 

THE  water  used  i[i  the  generation  of  steam  may  be  present  in  the  boiler 
plant  in  a  number  of  different  forms.  It  undergoes  various  transforma- 
tions in  the  bailer  or  in  the  auxiliary  apparatus  used  in  the  boiler  plant. 
In  this  chapter  the  nature  of  water  vapor  is  explained,  and  tables  of  the 
prop«rties  of  steam  are  given,  accompanied  by  a  demonstration  of  their 
application  to  practical  problems. 

Entropy.  In  solving  thermodynamic  problems  a  mathematical  ratio, 
considered  as  a  property  of  substances  and  known  by  the  name  entropy,  is  of 
value.  .  Most,  if  not  all  of  such  problems,  can  be  solved  without  the  use  of 
entropy,  but  engineers  are  now  generally  convinced  of  its  advantage.  It 
should  be  thought  of,  however,  simply  as  a  mathematical  expression. 

It  is  difficult  to  give  a  comprehensive  definition  of  this  property.  One 
that  will  answer  the  purpose  here  is  that  for  any  reversible  operation  ail 
irfinilesimal  change  of  entropy  is  equal  to  an  infinitesimal  change  in  the 
quantity  of  heat  divided  by  the  absolute  temperature  at  which  that  change 
takes  place,  the  transformation  being  so  small  that  no  change  of  tempera- 
ture can  occur.    Thus  changes  only,  of  entropy,  can  be  measured.  Expressed 

*.  =  4?  (43) 

in  which  ♦  is  the  symbol  for  entropy,  H  (or  quantity  of  heat,  and  T  for 
absolute  temperature.  Any  finite  change  can  therefore  be  found  by  integrat- 
ing this  expression  between  the  proper  limits.  Rewriting  it  in  the  form, 
dl{  =  Tdip,  gives  a  simple  expression  for  heat  in  terms  of  the  temperature, 
an  easily  measured  quantity,  and  of  the  change  of  entropy.  Tables  are  calcu- 
lated or  charts  constructed,  giving  changes  of  entropy.  A  measurement  of 
the  temperature  and  a  knowledge  of  one  other  property,  as  the  quahty  or 
volume,  in  order  to  determine  the  change  of  entropy,  are  all  that  are 
required  to  find  the  quantity  of  heat. 

Isothermal  Expansion.  If  a  substance,  while  expanding,  has  sufficient 
heat  added  to  it  to  keep  the  temperature  constant,  the  process  is  termed 
"isothermal."  The  pressure  and  temperature  of  saturated  steam  will  vary  or 
remain  constant  together,  while  if  an  ideal  gas  expands  with  the  temperature 
constant,  the  pressure  varies  inversely  with  the  volume. 

Adiabaiic  Expansion.  This  is  an  imaginary  change  supposed  to  take 
place  in  a  substance  placed  inside  of  some  vessel,  as  a  cylinder,  all  the 
walls  of  which  are  of  non-conducling  material;  consequently,  no  heat  passes 
through  the  v/Ms  to  the  substance  or  away  from  it.  It  is  isolated  from  all 
outside  heat.  Work  can  be  done,  however,  by  drawing  on  the  energy 
already  stored   in  the  substance. 

A  reversible  adiabatic  is  an  imaginary  change  taking  place  without 
friction  or  other  actual  losses.  When  the  direction  of  such  a  change  is 
reversed,  all  the  accompanying  heat  changes  are  reversed.  Upon  completion. 
everything  affected  by  the  heat  changes  in  the  original  direction  will  be 
returned  to  its  initial  condition  as  far  as  heat  is  concerned.  This  applies  to 
the  working  fluid  and  to  substances  outside  as  well.  An  expansion  or 
compression  of  this  nature  takes  place  at  constant  entropy. 


ib.  Google 


,  Google 


Charaeteritties  of  Vapors.  When  a  sabstance  chan^  from  a  liquid  to 
a  gaseous  state  it  passes  through  an  intermediate  condition  in  which  neither 
the  Uws  of  liquids  nor  those  of  gases  are  applicable.  While  in  this  intenne- 
diate  stage,  the  substance  is  known  as  a  vapor, 

A  saturated  vapor  is  one  that  can  exist  in  contact  with  its  liquid ; 
withdrawal  of  heat,  however  small  the  amount,  will  cause  some  of  the  vapor 
to  return  to  its  liquid  form.  The  saturated  condition  extends  therefore 
from  the  time  when  this  vapor  first  begins  to  form  from  the  liquid  to  the 
time  when  a  state  of  complete  vaporization  is  reached. 

The  vapor  is  dry-saturated  just  at  the  instant  of  complete  evaporation. 
During  the  process  of  vaporization  it  is  known  as  wet-saturaled  vapor. 

When  a  dry-saturated  vapor  is  further  subjected  to  heat,  its  charac- 
teristics gradually  approach  those  of  a  gas  and  it  is  then  said  to  be  in  a 
superheated  state. 


^^^ 


li  a  closed  vessel,  provided  with  the  means  of  measuring  prcssore  and 
temperature,  is  filled  with  saturated  vapor  it  will  be  noticed  that  for  any 
yiven  pressure  only  one  temperature  of  the  vapor  can  exist.  Any  change 
in  pressure  will  cause  a  corresponding  change  in  temperature.  Therefore, 
only  one  of  those  quantities  need  be  known  to  locate  the  others.  This 
condition  applies  only  to  saturated  vapor. 

Formation  of  Vafors.  Imagine  a  free  piston,  of  known  weight,  in  a 
cylinder,  containing  a  pound  of  liquid  (Fig.  19?),  the  whole  apparatus  being 
surrounded  by  a  perfect  vacuum.  Imagine  the  temperature  of  this  liquid  to  be 
that  of  melting  ice,  32  deg.  (This  is  universally  recognized  as  the  datum 
temperature  from  which  such  measurements  as  heat  and  entropy  are  taken). 
The  weight  of  the  piston  will  impose  a  certain  pressure  (.p)  upon  the  liquid. 
If  heat  is  added  to  the  liquid  the  temperature  will  have  to  increase  to  that 
corresponding  to  this  pressure  {p)  before  the  process  of  vaporization  can 
be^n.  A  rise  in  temperature  will  be  the  only  effect  of  this  heat  addition, 
until  this  temperature  is  reached.  (Any  increase  of  volume  is  small  enough 
to  be  negligible  and  the  pressure   (^)  will,  of  course,  remain  unchanged.) 

If  more  heat  is  applied  at  this  point  vapor  will  be  formed.  During 
this  process  the  temperature  will  not  change ;  the  weight  of  the  piston  re- 
mainii^  the  same,  the  pressure  will  be  constant.  The  volume  occupied  by 
the  EU^Unce  will  increase  and  in  so  doing  the  piston  will  be  gradually  raised. 


ib.  Google 


If  a  sufficient  quantity  ot  heat  b«  added,  complete  vaporization  will 
result  and  the  cylinder  will  contain  dry  saturated  vapor,  the  liquid  having 
disappeared.  Beyond  this  point  the  temperature  will  increase,  the  piston  con- 
tinuing its  upward  motion.  The  process  has  now  reached  the  superheating 
stage  and  can  be  continued  indefinitely.  At  first,  as  the  vapor  leaves  the 
condition  of  saturation,  its  characteristics  will  continue  to  show  a  marked 
difference  from  tho^e  of  gases;  as  higher  temperatures  are  reached  this 
difference  lessens  and  finally  the  superheated  vapor  lakes  on  all  the  attri- 
butes of  and  becomes  a  gas.  The  j)ressure  remaina  constant  during  all  three 
processes— the  heating  of  the  liquid,  the  vaporization,  and  the  superheating 
ot  the  vapor. 

Saturated  Vapors.  The  heat  necessary  to  raise  the  temperature  of  one 
pound  of  liquid  from  32  deg.  to  any  higher  temperature  is  known  as  the 
heat  of  the  liquid,    tt  can  be  calculated  tq*  the  equation 


=y:: 


1  which  g  is  the  heat  of  the  liquid,  and  c^  is  the  specific  heat  of  the  liquid. 
The  entropy  of  the  liquid  above  that  at  32  deg.  can  be  found  by  integrating 


J  492 


in  which  «c  is  the  entropy  of  the  liquid  above  that  at  32°  F.  (492  deg.  abs.), 
Ct   is  the  specific  heat  of  the  liquid  as  before,  and  T  is  the  absolute  tempera- 

The  specific  volume  of  a  liquid  (cubic  feet  per  pound)  is  considered 
to  be  a  constant  quantity  for  all  temperatures  and  pressures  and  is  represented 
by  8.  The  density  (pounds  per  cubic  foot)  is  the  reciprocal  of  the  specific 
volume. 

Tables  giving  the  properties  of  saturated  vapors  for  different  pressures 
and  temperatures  contain  those  ot  the  above  quantities  that  are  not  constant 

If  a  pound  ot  liquid  is  completely  vaporised  at  constant  pressure  and 
temperature,  the  heat  necessarily  added  is  Icnown  as  the  "latent  heat  of 
vaporization,"  and  is  expressed  as  L.  This  was  first  found  by  experiment. 
From  such  experiments  empirical  formulas  have  f>een  derived,  by  means  of 
which  the  values  in  the  tables  have  been  calculated. 

The  increase  in  entropy  during  vaporization,  known  as  the  "entropy  of 
vaporization,''  is  found  b^  dividing  the  heat  of  vaporization  by  the  absolute 
temperature.    Its  expression  in  symbols  is  itii  or  L/T. 

The  sum  of  the  heat  of  the  liquid  g  and  the  heat  of  vaporization  L,  is 
known  as  the  total  heat  of  dry  saturated  vapor  and  is  represented  by 
H. 

Il  =  q  +  I.  (46) 

Similarly  the  total  entropy  is 

*^»,-^-^  (47) 

Wet  Saturated  Vapor.  U  sufFicient  heat  is  not  added  to  complete  the 
process  of  vaporization,  liquid  and  vapor  are  mixed.  The  part  of  such  a 
mixture  existing  as  vapor  is  known  as  the  "quality"  and  is  designated  by  the 
symbol  *.  The  part  remaining  as  liquid  is  the  "wetness"  or  moisture.  In 
most  types  of  boilers  the  quality  of  the  steam  produced  is  from  98.0  to  99.5 
per  cent  and  the  wetness  trora  O.S  to  2.0  per  cent.  The  water  is  then  held  in 
suspension  in  the  steam  as  a  sort  of  fog.  It  does  not  affect  the  temperature 
and  can  be  carried  an  indefinite  distance  by  the  steam. 


ib.  Google 


V^^t'e 


The  properties  afTecteU  by  this  partial  vaporization  are  the  tieat  L,  the 
entropy  L/T,  and  the  speci5c  volume.    The  last  can  be  expressed  as  follows-. 

Sp.  vol.  =  *i>+  {\—x)h  (48) 

=  *(!'  — 8)  +  8  t«) 

in   which  v  is  the   specific  volume  of  dry   saturated  steam,   xv  the   volume 
of  the  steam  present,  and  (1— r)  g  that  of  the  wetness.  J  is  small  (0.02  cu,£t) 

Superheated  Vapors.  The  properties  of  superheated  vapors  are  calcu- 
lated principally  from  laws  similar  to  those  applying  to  gases ;  thus  the 
addition  of  heat  during  the  process  is  Cp{ttu-p- — '■at-).  The  increase  in 
entropy  is  Cp'loge'(r8up./T"»at-)i  when  Cp  for  both  expressions  is  a  mean 
specific  heat  for  the  given  range  of  temperature.  The  specific  volume  is  calcu- 
lated by  using  the  characteristic  gas  equation  worked  into  an  empirical  form 
as  the  result  of  experiments.  Tables  for  superheated  vapors  usually  give  the 
total  heat  H,  the  specific  volume,  the  entropy  *  measured  from  that  of 
water  at  32  deg.,  and  include  these  quantities  for  the  liquid  stage  and  for  the 
saturated  vapor  stage. 

The  foregoing  discussion  of  the  properties  of  vapors,  although  intended 
primarily  for  use  with  steam,  is  equally  applicable  to  other  vapors;  for  exam- 
ole,  ammonia  as  a  retrigerative  fluid. 

Properties  of  Steam.  Steam  is  usually  generated  in  a  boiler  in  which  the 
removed  as  fast  as  it  is  formed,  thus  keeping  the  pressure  constant. 
9  pumped  into  the  boiler  and  must  have  its  temperature  raised  to 
that  corresponding  to  the  boiler  pressure  before  vaporization  can  begin.  If 
the  temperature  of  the  water  is  32  deg,  when  it  enters  the  boiler,  the  heat 
of  the  liquid  will  be  added  to  each  pound  previous  to  vaporization.  If,  as  is 
usual,  the  water  is  at  some  higher  temperature  when  it  enters  the  boiler,  then 
the  heat  added  to  each  pound  previous  to  vaporization  will  be  the  heat  of 
the  liquid  at  the  temperature  of  the  boiler  steam  minus  the  heat  of  the 
liquid  at  the  entering  temperature. 

If  more  heat  is  added  to  this  water,  steam  is  formed.  This  process 
may  be  complete,  producing  dry-saturated  steam,  or  partial  when  the  steam 
is  wet-saturated.  The  quantity  of  heat  added  is  the  heat  of  vaporization 
(L),  or  (xL)   respectively. 

The  process  of  superheating  due  to  the  continued  addition  of  heat  at 
constant  pressure  may  take  place  in  a  coil  of  pipe  placed  in  the  path  of 
hot  gases  inside  the  boiler  setting,  called  an  attached  superheater;  or  in  a 
coil  placed  over  a  separate  furnace,  known  as  a  separately-fired  superheater. 
With  either  type  the  heat  per  pound  above  the  point  of  dry  saturation  is 
the  mean  specific  heat  for  the  temperature  range  muhiplied  by  this  increase 
in  temperature.  The  method  of  determining  the  increase  in  entropy  during 
superheating  and  the  specific  volume  of  superheated  steam  is  described  else- 

Sourees  of  Data.  Host  of  the  properties  of  saturated  and  superheated 
Steam  have  been  derived  from  experimental  investigations  extending  over  a 
long  period  of  time.  The  scientists  of  later  years  have  produced  more 
accurate  results  than  did  the  earlier  workers.  No  attempt  will  be  made 
here  to  give  in  detail  the  work  of  these  experimenters,  since  it  is  taken  up  in 
the  standard  works  on  thermodynamics. 

When  authors  of  steam  tables  have  used  dilTerent  equations  as  a  basis 
of  their  computations,  the  results  will  vary  somewhat.  In  recent  tables, 
however,  these  differences  are  negligible   for  ordinary  engineering  work. 

The  following  problems  will  serve  to  illustrate  the  use  of  Tables  62  and 
63,  which  are  extracted  from  "Properties  of  Steam  and  Ammonia,"  by 
■  Prof.  G.  A.  Goodenough, 

Example  1.  How  many  heat  units  will  be  taken  up  by  the  water  in  a 
boiler  per  hour  if  10.000  lb.  are  fed  per  hour  at  a  temperature  of  153  deg.. 
the  boiler  pressure  being  ISO  lb.  absolute,  (a)  if  the  steam  is  dry-saturated; 
(b)  if  2  per  cent  priming  is  present;  (c)  if  by  the  use  of  an  attached  super- 
heater the  steam  is  superheated  70  deg,? 


ib.  Google 


ib.Google 


(a)  Looking  in  the  tables  under  153  deg.  we  find  the  heat  of  the  liquid, 
q  =  120.9  B.t.u.  This  heat  is  already  in  the  water  when  it  enters  the 
boiler.  If  the  steam  leaving  the  boiler  is  dry-saturated  the  heat  H  ■=  q  +  L 
will  be  present     This  we  find   (opposite  150  lb.  in  column  7)   is  1194.7  B,t.u. 

The  heat  taken  up  by  the  water  in  the  boiler  will  be  the  difference 
between  that  in  the  steam  when  it  leaves  and  the  water  when  it  enters. 
This  will  be  q  [150-lb.]  +  L  ItSO-lb.]  —  q  [153  deg.],  or  H  [150-lb.]  — 
q  (153  deg.]  per  pound;  substituting  and  multiplying  by  the  weight  we  have 
10,000  (11947  —  120.9)  =  10,738,000  B.t.u.  per  hour. 

(b)  If  the  wetness  is  2  per  cent  then  *  =  0.96  and  the  expression  will 
he:  q  [150-lb.]  +  0.98  L  [ISO-lb.]  —  q  [153  deg.]  =  B.t.u.  per  pound.  Then 
10,000  {3295  -I-  0^  X  864.9  —  12a9)  =  10,565,000  B.t.u.  per  hour,  when  3295 
and  8645  are  the  values  of  q  and  L  for  ISO-lb.  pressure. 

(c)  If  the  steam  is  superheated  70  deg.  its  tcmperatnre  wiU  be  the 
temperature  of  saturated  steam  at  150  lb.  pressure  plus  70  deg.  Opposite 
150  lb.  the  temperature  is  358.5  deg.,  therefore  the  temperature  of  the 
superheated  steam  will  be  358.5  +  70  =  428.5  deg. 

The  heat  content  of  this  superheated  steam  is  found  in  Table  63  under 
150  pounds  and  opposite  the  4^.5  temperature.  Interpolation  between  420 
and  432  deg.  will  be  necessary. 

H  =  1235  B.t.u. 

The  heat  taken  up  by  the  water  will  now  be, 

H  [150-lb.]  —  a  [153  deg.]  per  pound,  or  10,000  (1235.0  -  120.9)  = 
11,141.000  B.t.u.  per  hour. 

Example  2.  Find  the  number  of  cubic  feet  of  steam  that  will  leave  the 
boiler  per  hour  under  the  three  conditions  given  in  Example  1. 

(a)  If  the  steam  is  dry-saturated  the  volume  of  a  pound  can  be  found 
opposite  150  pounds  in  Table  62,  Column  4,  giving  v  =:  3.02  cu.  ft  Total 
volume  —  10,000  x  3.02  =  30.200  cu.  ft.  per  hour. 

(b)  With  2  per  cent  wetness  the  volume  of  one  pound  will  be  found  by 
the  formula  x  (v  —  0.02)  +  0.02  =  0.98  (3.02  -  0.02)  -|-  0.02  =  2.96  cu.  ft. 

Total  volume  =  10,000  X  2.96  =  29,600  cu.  ft  per  hour. 

(c)  If  the  steam  is  superheated  70  deg.  the  temperature  will  be  428.5 
deg.  as  determined  in  Example  1. 

Using  Table  63  (under  150  lb.  and  opposite  i  —  428.5  deg.)  the  specific 
volume  is  3.36  cu.  ft. 

Total  volume  —  10,000  X  3 J6  =  33.600  cu.  ft.  per  hour. 

Example  3.  Steam  under  a  pressure  of  175  lb.  absolute  and  a  tempera- 
ture of  440  deg.  expands  adiabatically  until  it  is  dry-saturated,  (a)  What  will 
the  pressure  then  be?  (b)  If  the  expansion  is  continued  until  the  pressure 
is  50  lb.  absolute  what  will  be  the  final  quality? 

(a)  During  an  adiabatic  expansion  the  entropy  remains  constant  The 
entropy  of  one  pound  of  the  steam  for  the  first  condition  is  given  in 
Table  63  (under  1/5  pounds  pressure ;  opposite  440  deg.)  as  «  =  1.6045.  This 
must  equal  the  total  entropy  of  dry-saturated  steam  at  some  lower  pressure. 
In  Table  62  the  last  column  is  examined  until  the  same  figure  1.6045  is  found. 
Opposite  this  in  column  2  the  pressure  is  given  as  lOO  lb.  absolute. 

(b)  When  the  expansion  is  carried  to  50  lb.  abs..  the  final  quality  (r) 
can  he  found  by  equating  the  total  entropy  of  this  wet  saturated  steam  to 
that  of  the  steam  in  the  initial  superheated  condition.     Then 

♦,    [50-lbs.]    -I-  x-^r  l50-\h.]  =  1J5045 

In  Table  62  opposite  50  lb.  pressure,  columns  8  and  9  respectively,  we  have 

♦,  =  0.4108,   -^-     =1.2501  a4Ifl8+1.250U=  1.6045 

x  =  OSSS 


ib.  Google 


When  extreme  accuracy  is  not  necessat;,  graphical  charts  can  be  used  in 
place  of  the  tables.  The  use  of  two  of  these  charts,  Figs.  198  and  199,  is  ex- 
plained below. 

Temperature -Entropy  IMagrams 
"  I  HE  diagram,  Fig.  198,  is  given  by  Prof.  C,  H.  Peabody  to  solve  problems 
'■  in  saturated  and  superheated  steam.  The  abscissas  are  units  of  entropy 
and  the  ordinales  are  degrees  Fahrenheit  At  the  left  is  a  scale  of  pressures 
by  aid  of  which  the  nearest  degree  can  be  chosen  for  use  in  the  saturated 
region ;  in  the  superheated  region  constant  pressure  lines  are  drawn  and  are 
numlxred  near  the  saturated  line,  as  lOO-lb.  (pounds). 

The  saturation  line  (which  separates  the  saturated  and  superheated 
regions)  gives  the  entropy  of  dry-saturated  steam,  *e  +  L/T.  The  dotted 
lines  give  the  quality  x;  the  values  are  numbered  at  the  bottom.  In  the 
superheated  region  the  dotted  lines  give  the  superheat  or  excess  temperature 
over  that  of  saturated  steam  at  the  same  pressnre. 

The  heat  contents  q  +  xL  are  given  by  full  lines  lettered  "B.t.n."  which 
slope  toward  the  right  downward. 

The  specific  volumes  are  given  by  full  lines  lettered  "Cu.  Ft.,"  which  have 
a  motlcrale  inclination  from  the  horiionial.  In  the  superheated  region  the 
lines  can  be  distinguished  by  sighting  along  them.  The  use  of  the  diagram 
given  in  Fig.  198  is  illustrated  by  the  following  examples: 

Example  1.  Given  the  absolute  pressure  160  lb.  and  the  wetness  2  per 
cent   fa*  ^0.98):     Find  the  entropy,  heat  content  and  specific  volume. 

The  neare.'t  temperature  is  362  deg.,  and  this  line  mterseets  the  quality 
line  j:  =  0.98  at  entropy  ^  ^=  1.54.  The  B.t.u.  line  intersecting  this  point 
is  117S  B.Lu.  =  q  +  xL  and  the  specific  volume  line  for  2.7  cu.  ft  also 
crosses  this  point.     These  tigures  are  of  course  obtained  by  interpolation. 

Example  2.  Given  the  absolute  pressure  160  lb.  and  100  deg.  superheat: 
Find  the  entropy,  heat  content  and  specific  volume. 

The  pressure  curve  160  lb,  in  the  superheat  region  cuts  the  100  deg. 
superheat  line  at  entropy  1.63.  The  intersection  of  the  heat  and  volume  lines 
give  H  =  1250  and  specific  volume  ^  3.3  cu.  ft. 

(Adiahatic  changes  during  which  the  entropy  is  constant  are  represented 
by  vertical  lines,  while  isothermal  or  constant  temperature  changes  are  hori- 
zontal lines.) 

Example  3.  Steam  at  120  lb.  absolute  pressure  and  100  deg.  superheat 
expands  adiabatically  to  a  temperature  of  142  deg.  Find  the  final  quality  and 
the  final  specific  volume. 

The  120-lb.  line  crosses  the  lOO-dcg.  superheat  line  at  entropy  1.65.  This 
proper^  is  constant  during  the  change,  therefore  following  down  the  vertical 
entropy  line  1.65  until  the  horizontal  temperature  line  142  deg.  is  reached, 
we  read  the  quality  as  0.86  and  the  specific  volume  as  100  cu.  ft 

Mollier  I>iagrain  for  Steam 

THE  Mollier  diagram  for  steam,  as  found  in  Goodcnough's  tables,  is  shown 
in  Fig.  199.  In  this  diagram  lines  parallel  to  the  coordinate  axes 
give  values  of  heat  content  and  entropy,  as  read  on  the  scales  along  the 
margin.  Constant  pressure  curves  slope  downward  and  to  the  left.  In  the 
region  of  superheat  constant  temperature  lines  curve  gradually  toward  the 
left  downward.  These  are  replaced  in  the  saturated  region  by  constant 
quality  lines. 

Any  point  on  the  diagram  represents  a  definite  state  of  the  fluid.  If  the 
point  lies  in  the  region  of  superheat  the  heat  content,  entropy,  pressure  and 
temperature  are  read  directly.  In  the  saturated  region  the  quality  is  given, 
but  the  temperature  must  be  obtained  from  the  pressure. 


ib.  Google 


D,n.tz.:HbyGOO^Ie 
Fig.  198.     Peabody's  Temperature  Entropy  EHagram  for  Steam. 


,Google 


To  prevent  confusion,  the  volume  curves  are  not  given.  This  property 
can,  however,  be  easily  obtained.  If  the  point  lies  in  the  superheat  region, 
read  the  pressure  and  temperature  from  the  diagram  and  look  up  the  corrC' 
spending  value  of  volume  in  Table  63.  If  it  Hes  in  the  saturated  region,  read 
the  pressure  and  quality  from  the  diagram,  look  up  the  specific  volume  of  dry- 
saturated  steam  at  the  same  pressure  in  Table  62  and  multiply  this  by  the 
quality. 

The  following  illustrations  of  the  use  of  this  diagram  are  given  by 
Professor  Goodenough. 

Exampie  1.  Find  the  properties  of  steam  at  a  pressure  of  120  lb.  abso- 
lute and  a  temperature  of  412  deg. 

From  the  diagrams  the  point  that  represents  the  state  of  the  steam  is 
found  at  the  intersection  of  the  curves  />  ™  120  and  (  =:  412.  From  the 
scales  are  read  H  =  1231  B.t.u.,  *  —  1.637.  From  Table  63  the  specific 
volume  is  found  to  be  4.16  cu.  ft.  (These  particular  values  could  be  found 
as  easily  and  more  accurately  from  Table  63.) 

Example  2.  Steam  at  a  pressure  of  120  lb.  absolute  and  a  temperature 
of  412  deg.  expands  adiabatically.  At  what  pressure  does  it  become  dry- 
saturated  ? 

During  this  change  the  entropy  remains  constant;  hence  the  final  state 
is  given  by  the  intersection  of  the  line  *  =  1.637  with  the  saturation  curve. 
The  pressure  indicated  by  this  point  is  68  lb.  per  sq.  in.  absolute. 

Example  3.  Steam  in  the  same  initial  state  as  in  Examples  1  and  2 
expands  adiabatically  to  a  pressure  of  2  in.  of  mercury.  Find  the  volume, 
heat  content  and  quality  in  the  final  state. 

The  entropy  in  the  initial  state  is  1.637;  hence  find  the  intersection  of 
the  line  «  =:  1.637  with  the  curve  ^  =  2  in.  of  mercury.  This  point  gives  the 
values  X  =  0.815,  H  =  913  B.t.u.  From  Table  62,  v  for  1  lb.  absolute 
(which  is  practically  2  in.  of  mercury)  is  333.3  cu.  ft.;  hence  the  volume 
of  the  mixture  with  a  quality  x  =  0.815  is  0.8IS  X  333.3  =  271.6  cu.  ft 

Plow  of  Steam  Through  Nozzles 
The     ordinary     form     of     nozzle     in     which     steam     expands     as     it 
passes     to     the    blades     of     an     impulse     turbine     is     shown     in     Pig. 
200.    Suppose    steam    is    Rowing    through    the    nozzle,    the    pressure   being 


Fig.  300.     Expansion  Kozzle. 


Pi,  Pt,  Pa,  as  indicated  by  the  three  gages.  As  long  as  the  absolute  pressure 
at  Pt  is  less  than  0.58  of  the  absolute  pressure  at  P.,  the  absolute  pressure 
at  Pt — the  smallest  section,  known  as  the  throat — is  exactly  O.SaP,,  When 
P,  is  less  than  Pt  the  weight  of  the  steam  flowing  through  the  nozzle  will 
not  change.  This  weight  is  entirely  independent  of  any  pressure  beyond  the 
throat  as  long  as  it  does  not  exceed  the  pressure  in  the  throat 


ib.  Google 


U.  S.  Realty  Building,  New  York,  N.  Y.,  containinK  1535  H.  P.  of  Heine  B<rilen. 


ib.  Google 


Tbe  formula  for  the  flow  through  such  a  nozzle  is  ai  follows: 


(SO) 


W  =  Steam,  pounds  per  second 
A  =:  Area  of  the  throat  section,  square   feet 

ft=  Velocity  of  steam  passing  the  throat  section,  feet  per  second 

V  =  Specific  volume  of  steam  at  the  pressure  and  quality  in  the 

throat  after  adiabatic  expansion  at  constant  entropy. 

On  account  of  the  rapidity  with  which  steam  passes  through  the  noxzle, 

aot  allowing  time  for  any  appreciable  transfer  of  heat  through  the  walls, 

the  process  can  be  considered  as  adiabatic  and  the  entropy  constant. 

Applying  the  laws  for  the  adiabatic  Row  of  steam,  the  following  formula 
for  the  velocity  of  flow  through  the  throat  section  can  be  deduced: 

Vt  =  224  V«r^«t  (51) 

Vt  =  Velocity  at  throat  section,  feet  per  second 

Hi  =  Heat  content  at  the  absolute  initial  pressure  and  quality  of 

the  steam,  B.tu. 

Ht  :=  Heat  content  at  the  absolute  throat  pressure  and  the  quality 

at  that  pressure  resulting  from  a  constant  entropy  change. 

If  the  part  of  the  nozzle  beyond  the  throat  is  omitted,  leaving  it  as 

shown  in  Fig,  201,  the  result  is  a.  standard  convergent  nozzle,  which  can  be 

used  in  measuring  the  flow  of  steam  within  the  limits  of  ordinary  accuracy. 

The  formulas  for  the  weight  and  the  velocity  at  the  throat  of  the 
expansion  nozzle  can  be  applied  directly  to  the  simple  convergent  nozzle,  con- 
sidering the  dimensions  and  properties  of  the  throat  of  the  expansion  nozzle 
to  be  those  of  the  convergent  nozzle,  the  initial  pressure  for  the  expansion 
nozzle  being  the  pressure  before  the  convergent  nozzle. 

This  makes,  as  will  be  noticed,  a  nozzle  with  a  rounded  approach,  as 
shown  in  Fig.  201.  Other  proportions  can  be  used,  but  those  indicated  have 
given  good  results  in  practice. 


Fig.  201.     Smple  Convergent  Noxxle. 

Tbe  use  of  the  formulas  can  be  explained  by  an  example. 

Steam  at  a  pressure  of  140  lb.  abs.  and  a  temperature  of  400  deg.  flows 
through  a  standard  convei^ent  nozzle,  I'in.  diameter,  into  a  pipe  line  where 
the  pressure  is  60  lb.  abs.  How  many  pounds  will  pass  through  the  nozzle 
per  second? 


ib.  Google 


«  5 

If  I 


t     .9 


D,B,i,.ab,Google 


Using  the  Mollier  chart  we  find  that  steam  P,  at  140  lb,  abs.  and  400  Aeg. 
has  a  heat  content  of  1221  B.t.u.,  and  an  entropy  of  1.61.  The  pressure  in 
the  throat  of  the  nozzle,  Px  will  be  0.58  of  140  lb.  or  81  lb.  abs.  As  the  change 
between  these  two  pressures  is  adiabatic  we  follow  the  1.61  entropy  line  on 
the  chart  until  it  intersects  the  8t-Ib.  pressure  curve.  Here  we  read  the  heat 
content  as  1173  and  the  quality,  x  =  0.987.  The  specific  volume  at  this  pres- 
sure and  quality  is  0.987  X  S.42  =  SJ5  cu.  ft. 

The  velocity  in  the  throat  of  the  nozzle  will  be ; 


Ft  =  224v/  //.  —  Ht  =  224  (/  1221  — 1 173  =  1552  ft.  per  sec. 
a  of  a  1-in.  orifice  =  0.OOS4S  sq.  ft.,  so  that  the  wei^t  per  second 
a,_  AVi  _  0.00545  X  1552  _ 


5.35 


=  1.6  lb. 


In  solving  this  problem  the  final  heat  content  in  the  velocity  formula  is 
taken  at  0,58  of  the  initial  pressure,  which  is  the  pressure  at  the  throat  of  the 
nozzle,  and  not  the  final  pressure  in  the  pipe  line.  These  formulas  can  be 
applied  to  either  superheated  or  saturated  steam. 

As  a  result  of  experiments,  empirical  formulas  have  been  derived  for 
the  flow  of  steam ;  these  are  sufficiently  accurate  for  engineering  purposes. 
Two  sets  are  in  common  use,  one  by  Napier  and  the  other  by  Graikof. 
Napier's  experiments  were  made  on  dry-saturated  steam  and  his  formulas 
apply  only  to  steam  in  approximately  that  condition.    He  found  that : 

W  =  J^  when   P,  =  or  <  OJiP.  (52) 

W  =  0.0292-lP,  (P,  —  P.)  when  P,  >  0,6P.  (53) 

W  ^  Amount  of  steam,  pounds  per  seccMid 

A  ^  Area  of  orifice,  square  inches 

Pi  =  Absolute  pressure  before  oritice,  pounds  per  square  inch 

Pi  =  Absolute  pressure  after  orifice,  pounds  per  square  inch. 


For  a  given  nozzle,  the  weight  discharged  is  greater  for  v 
for  dry  steam.  The  flow  then  is  inversely  proportional  li 
of  xt,  and  Grashof  s  formula  becomes 


A  Pi'" 
60  V. 


"'=^^77r  (55) 


To  find  the  weight  of  steam  discharged  when  P,  is  greater  than  0,58Pi. 
the  curves  in  Fig.  202  arc  convenient.  They  are  plotted  from  the  results 
of  Rateau's  experiments  on  convergent  nozzles  and  thin  plate  orifices.  The 
discbarge  for  the  nozzle  is  first  found  for  the  condition  when  P,  is  less  than 
0.S8P,.  This  is  done  either  by  formula  (52)  or  by  formula  (54).  Then  the 
ratio  "~is  found,  and  the  lower  (abscissa)  scale  of  Fig.  202  entered  with 
this  ratio.     Proceed  vertically  to  the  point  of  intersection  with  curve  for 


ib.  Google 


Everett  Building,  New  York  City,  equipped  with  Heine  Botlera. 

D,g,tze:Jbi  Google 


convergent  nozzles,  and  then  horizontally  to  the  left  (ordinate)  scale  and 
read  the  coefficient  of  discharge.  Multiply  by  this  coefficient  the  discharge 
as  just  found,  and  the  result  is  the  actual  discharge  under  the  conditions 

To  find  the  weight  of  steam  discharged  through  an  orifice  in  a  thin 
plate,  proceed  as  above,  except  that  intersection  is  made  with  the  curve  for 
thin  plate  orifice. 

Example :  By  the  use  of  a  thin  diaphragm  inserted  between  the  flanges 
of  a  jainl  in  the  steam  pipe  supplying  an  auxiliary  engine,  it  is  desired  to 
find  the  weight  of  steam  consumed  by  the  engine.  The  pressures  observed 
are  1S2  and  143  pounds;  and  the  hole  in  the  diaphragm  is  '/»  inch. 

The  area  of  the  orifice  is  0.O767  sq.  in^  and  the  absolute  pressure  P,  is 
]66J   lb.     Then   by  formula    (52) 

w  =  «-xjMJ;  ^  „.,8(s,  ,t.  ^,  „, 

1  P,  is  less  than  O.SSP, 

_  P.  =  157.7  and  157.7/166.7  =  0.946.    Entering  the 

lower  scale  of  Fig.  2(£  with  0.946,  proceeding  vertically  to  intersection  with 
orifice  curve  and  horizontally  to  the  left-hand  scale,  read  as  coefficient  0.31, 
Multiplying  by  the  coefficient  OJI  the  maximum  discharge  0.18088  as  found 
above,  the  discharge  through  the  thin  plate  is  found  to  be  5.6  pounds  per 
sec;  multiplying  by  3,600,  the  discharge  is  202  pounds  of  steam  per  hour. 

The  pipe  on  the  supply  side  of  the  diaphragm  should  be  straight  for  at 
least  10  times  its  bore.  The  diameter  of  the  hole  in  the  diaphragm  should  not 
be  larger  than  one  quarter  of  the  pipe  bore.  If  necessary,  a  larger  pipe  must 
be  put  in  on  the  supply  side  with  a  straight  length  of  not  less  than  10  times 
its  bore. 

If  the  diaphragm  is  thicker  than  '/«  inch,  it  should  be  countersunk  at  an 
angle  of  45°  on  the  downstream  side,  so  that  the  parallel  part  of  the  hole  is 
not  more  than  '/••  '"'^•i  '""K-  On  the  inlet  side  of  the  diaphragm,  burrs 
should  be  removed  and  great  care  taken  not  to  round  away  the  entrance 
comer  which  must  be  left  sharp. 

Owing  to  the  difficulty  of  removing  the  burrs  while  keeping  the  corner 
sharp,  it  is  sometimes  easier  to  use  a  much  thicker  diaphragm  and  form  a 
convergent  nozzle  in  it.  The  thickness  of  the  diaphragm  should  then  be 
about  twice  the  diameter  of  the  hole.  There  should  be  a  parallel  portion 
whose  length  is  about  half  the  diameter  of  Che  hole,  and  a  curved  portion 
formed  to  a  radius  of  about  U2  diameters,  making  a  smooth,  rounded  or 
bell-mouthed  entrance  similar  to  Fig.  201. 

While  the  diaphragm  method  is  a  simple  one  for  finding  the  steam  con- 
sumption of  auxiliaries,  and  so  forth,  it  is  essential  that  great  care  be  used 
in  getting  the  exact  diameter  of  the  hole  and  the  exact  pressures  obtaining. 

The  pressure  gages  used  should  be  connected  within  about  12  inches  on 
each  side  of  the  diaphragm.  To  insure  accuracy,  they  should  be  tested  be- 
fore and  after  taking  the  readings,  and,  as  a  further  check,  the  readings 
should  be  repeated  with  the  positions  of  the  gages  reversed. 

Experimental  data  for  the  flow  of  superheated  steam  through  nozzles 
and  orifices  are  lacking.  One  of  the  latest  formulas,  in  the  form  of  that  of 
Groihof,  is  worked  out  from  experiments  by  Leviieke  and  checked  from 
data  in  possession  of  the  General  Electric  Company.  This  formula  is  as 
follows : 

'*'  ~  60"("r+ a6665~DJ  *^' 

in  which  D  is  the  superheat  in  degrees  Fahrenheit,  and  the  other  symbols 


ib.  Google 


STEAM 
Tabk  63.     Propertie*  of  Saturated  Steam. 


FrMm 

Vel- 

■       ftT 

^rB"rr 

UUat 

BBtrow 

B*t>l 

in.. I 

(.lb*.) 

T«.. 

eiLft. 

^ 

of 

K- 

«l 

etn. 

Bt 

^ 

l^Bld 

B."?. 

Uqald 

P«to- 

• 

' 

' 

1_ 

• 

H 

L 

- 

L 
T 

« 

M.n 

34.66 

2992 

0.000334 

2.56 

1074.2 

1071.7 

0,0052 

2.1687 

2.1739 

MM 

!l474 

44.97 

2036 

.000491 

13.04 

1079.2 

1066.1 

.020^ 

2.1130 

2.1392 

M.Ba 

.1965 

62.67 

1650 

.000646 

20.76 

10S2.8 

1062,0 

.0413 

2.1146 

S8.«9 

5SS3 

1265 

.000797 

26.91 

1086.7 

1058.8 

.0533 

2,0966 

se.89 

!2947 

63.98 

1066 

.000947 

32.06 

10S8.1 

1056.0 

.063^ 

2.0169 

2.0601 

M.a8 

0.3438 

68.43 

913 

0.001096 

36.50 

1090.1 

1053,6 

0.0717 

1.9966 

2.0672 

as.u 

.3929 

72.35 

805 

.001243 

40.42 

1091.9 

1051.5 

.0790 

1,9768 

2.0668 

M.M 

.4421 

75.87 

720 

.001389' 

43.93 

1093.5 

1049.6 

.0856 

1.9602 

2.0458 

SB.98 

.4912 

79.06 

652 

.001534 

47.11 

1O95.0 

1047.9 

.0915 

1.9455 

2.0870 

as.s2 

.5403 

81.08 

696 

.001679 

60.03 

1096.4 

1046.4 

,0969 

1.9320 

2.0290 

as.73 

0.689 

84.68 

549 

0.001823 

52.72 

1097,6 

1044.9 

0.1019 

1.9198 

2.0217 

sB.n 

.639 

87.19 

608.7 

.001966 

55.23 

1098.8 

1043.5 

.1065 

1,9086 

2.0160 

as.BS 

.688 

89.54 

474.3 

.002108 

67.57 

1099,8 

1042.3 

.1108 

1.8980 

2,0087 

».ti 

.737 

91.75 

444.5 

.002250 

69.77 

1100.8 

1041.1 

.1148 

1.8882 

2,0030 

SB.8S 

.786 

93.83 

418,2 

.002391 

61.84 

1101.8 

1040,0 

.iisa 

1.8791 

1.9976 

».as 

0.836 

95.80 

395.0 

0.002632 

63.81 

1102,7 

1038.9 

0,1221 

1.8705 

1.9926 

as.i8 

.884 

97.67 

374.3 

.01^672 

65.68 

1103,6 

1037.9 

.1254 

1.8624 

1,9878 

SB.OS 

.933 

99.46 

355.7 

.002811 

67.46 

1104.3 

1036.9 

.1286 

1.8647 

1.9833 

S7.n 

.982 

101.17 

338.9 

.002950 

69.16 

1106.1 

1036.0 

1316 

1.8474 

1.9790 

S7.8M 

1 

101.76 

333.3 

0.00300 

69.76 

1106.4 

1035,6 

0.1327 

..J 

1.977S 

97.82 

1.031 

102.80 

323.7 

0.00309 

70.79 

1105.9 

1036.1 

0.1345 

1,8404 

1,9760 

>7.7« 

1.081 

104.37 

309.8 

.00323 

72.36 

1106.6 

1034.2 

.1373 

1,8338 

1,9711 

a7.«s 

1.130 

105.88 

297.1 

.00337 

73.86 

1107,2 

1033.4 

.1400 

1,8274 

1.9674 

ST.OS 

1.179 

107.33 

2S5.5 

.00360 

76.30 

1107.9 

1032.6 

,1426 

1.8213 

1.9639 

ar.w 

1.228 

108.73 

274.7 

.00364 

78.70 

1108.5 

1031-8 

.1450 

1.8165 

1.9605 

a7.ss 

1.277 

110.08 

264.7 

0.00378 

78.05 

1109,1 

1031.1 

0.1474 

1.8090 

1.9573 

S7.a> 

1.326 

111.39 

256.6 

.00391 

79.36 

1109.7 

1030.4 

.1497 

1.8015 

1.9641 

a7.u 

U75 

112.66 

246.9 

.00405 

80.62 

1110.3 

1029.7 

.1519 

1.7992 

1.9511 

S7.SS 

1.424. 

113.89 

23a9 

.00419 

81.86 

1110.8 

1029.0 

.1540 

1.7942 

1.9482 

X.8S 

1.474 

116.08 

231.4 

.00432 

83.04 

1111,4 

1028,3 

.1661 

1.7893 

1.9464 

M.83 

1.623 

116.24 

224.4 

0.00446 

84.19 

11U.9 

1027.7 

0.1581 

1.7840 

1.9427 

98.78 

1.572 

117.37 

217.8 

.00469 

85.32 

1112,4 

1027,0 

.1601 

1.7800 

1.9401 

ae.M 

1.621 

118.47 

211.6 

,00473 

86.41 

1112,9 

1026.4 

.1620 

1.7756 

1.6376 

98.S8 

1.670 

119.64 

205.7 

.00486 

87.48 

1113.3 

1026.8 

.1638 

1.7713 

1.9361 

M.«S 

1.719 

120.68 

200.S 

.00500 

88.521113.8 

1026.3 

■"* 

1.7671 

1.0327 

ib.Google 


Table  «3 

Propertie*  of  Saturated  Suam— Coat. 

PiMon 

T«LP, 

ta.tt. 

"Ti^B'sr* 

SsrSr 

«poti- 

BDtnnr 

b.  ol 

■iw^ 

d 

U,^ 

cm- 

« 

• 

' 

' 

1_ 

1 

H 

L 

♦. 

L 

* 

9B.sa 

M.8S 

M.U 
MM 

asM 

1.768 
1.817 
1.866 
1.916 
1.965 

121.60 
122.5a 
123,67 
124.KS 
125,44 

196.0 
190.0 
185.3 
180.8 
176.6 

0.00613 
.00526 
.00640 
.00563 
.00666 

89.53 
90.62 
91.49 
92.44 
93.37 

1114.2 
1114.7 
U15.1 
1116.5 
1U6.9 

1024.7 
1024.2 
1023.6 
1023.1 
1022.6 

0.1673 
.1690 
.1707 
.1723 
.1739 

1.7631 
1.7691 
1.7563 
1.7515 
1.7478 

1.9304 
1.9281 
1.9260 
1.9238 
1.9217 

8 

126,10 

173.6 

0.00676 

94.02 

1116.2 

1022.2 

0.1750 

1.7452 

1.9203 

88.89 

as.TS 

S6.M 

as-ss 

3.014 
2.063 
2.112 
2.161 

126.36 
127.25 
128.12 
128.97 

172.5 
168.7 
165,0 
161,6 

0.00580 
.00593 
.00606 
.00619 

94.28 
96.  IS 
96.03 
96.89 

1116.3 
1118.7 

1117.1 
U17.6 

1022.0 
1021.6 
1021.1 
1020,6 

0.1755 
.1770 
.1785 
.1799 

1.7442 
1.7407 
1.7373 
1.7340 

1.9197 
1.9177 
1,9168 
1.9139 

S6.U 

2S.8S 

SB.as 

S6.U 
BB.89 

2.211 
2.280 
2.30B 

2.358 
2.407 

129.81 
130.64 
131.44 
132.24 
133.02 

158.1 
154.8 
151.7 
148.8 
145.9 

0.00633 
.00616 
.00659 
.00672 
,00685 

97.73 
08.56 
9935 
100.14 
100.92 

1117.8 
1U8.2 
1U8.6 
1118,9 
1119.2 

1020.1 
1019.7 
1019.2 
1018J 
101&3 

0.1813 
.1827 
.1841 
.1864 
.1867 

1.7307 
1,7275 
1.7244 
1.7214 
1.71S4 

1.9121 
1.9103 
1.9066 
1.9068 
1.9051 

M.8S 
S8.SS 

2.456 
2.947 

133.78 
140.80 

143.2 
120.7 

0.00698 
.00829 

iiaas 

10a69 

1119.6 
1122.8 

1017.9 
1013.0 

0.1880 
.1008 

1.7164 
1.6888 

1.9084 
1,8886 

S 

141.49 

118.7 

0.00843 

100.38 

1122.9 

1013.6 

0.2009 

1.6862 

1.8871 

u.ra 

si.n 

3.438 
3.929 

146.88 
162,26 

iia4 

92.1 

0.00968 
.01085 

U4.8 
120.2 

1126,2 

1127,6 

1010.5 
1007.4 

0.2008 
.2187 

1.6661 
1.6464 

1.8760 
1.8661 

21.776 

i 

162.99 

oao 

0.01104 

120.9 

1127.9 

1007.0 

0.2199 

1.6438 

1.8637 

i8.8S 

4.421 
4.912 

167.10 
161.50 

82.6 

74,8 

0.01212 
.01338 

126.0 
129.4 

1129.6 
1131.4 

1004.6 
1002.1 

0.2285 
.2336 

1.6290 
1.6134 

1.8666 
1.8470 

18.74 

B 

162.26 

73.6 

0.01360 

13ai 

1131.7 

1001.6 

0.2348 

1.6107 

1.8466 

U.88 
17.88 

5.403 
5.8M 

166.56 
160.30 

68.4 
63.0 

a01463 
.01587 

133.4 
137.2 

1133.1 
1134.7 

900.7 
997.6 

0.2401 
.2461 

1.6902 
1.6862 

1.8393 
1.8323 

17.7M 

« 

170.07 

62.0 

0.01614 

137.9 

1136.0 

997.1 

0.2473 

1.5836 

1.8308 

U.«9 
18.08 

8.39 
6.88 

172.79 
176.06 

5S.S 
64.6 

0.01710 
.01833 

140.7 
143.9 

1136.1 
1137.6 

995.5 
993.6 

0.2616 
.2668 

.16742 
1.6630 

1.8268 
1.8198 

18.87 

' 

176.86 

63.7 

0.01864 

144.7 

1137.8 

993.1 

02681 

1.6603 

1.8184 

ib.Google 


TmUe  61.     Propcrtlw  of  Saturated  Steam. — Cont. 


Phmm 

T«^. 

CO.  ft. 

•£t 

H«^cc«t«t 
laB.t.a. 

LaMet 

XDtnpr 

la. of 

Lb.». 

A 

at 

B.t.a. 

11^ 

oln- 

•Sir 

of 

' 

' 

' 

_i_ 

' 

H 

L 

«• 

L 

T 

* 

1A.9S 

7.37 

179.14 

51.14 

0.01956 

147.0 

1138.8 

991.7 

02817 

1.5626 

1.8143 

18.M 

7.86 

182.06 

48.14 

.02077 

149.0 

11400 

990.0 

Ji662 

1.6429 

1.8091 

lS.fS 

8 

182.87 

47.35 

0.02U2 

150.8 

1140.3 

989.5 

0.2675 

1JH02 

1.8077 

U.8S 

a.36 

184.83 

46.49 

0.02198 

152.7 

1141.1 

988.3 

02705 

1.6337 

1.8012 

U.M 

8.84 

187.46 

43.12 

.02319 

155.4 

1142.1 

9807 

.2746 

1.5250 

1.7996 

U.M 

• 

188.28 

42.41 

0.02368 

166.2 

1142.6 

986.3 

0.2769 

1.6223 

1.7983 

10.M 

9.33 

186.97 

40.99 

0.02439 

157.9 

1143.1 

986.3 

02785 

1.5168 

1.7963 

•.M 

9.S2 

192.38 

39.08 

.02559 

1003 

1144.1 

983.8 

.2822 

1.6089 

1.7012 

».H 

14 

193.21 

38.43 

0.02802 

161.1 

1144.4 

0S3.3 

0.2836 

1.6062 

1.7807 

8.98 

1031 

194.68 

37.34 

0.02678 

162.6 

1145.0 

082.4 

0.2858 

1.5016 

1.7873 

7.98 

10.81 

196.89 

35.75 

.02797 

164.8 

1146.9 

981.1 

.2892 

1.4944 

1.7836 

7.58 

U 

197.75 

35.16 

0.02844 

165.7 

1146.2 

980.5 

O2005 

1.4916 

1.7821 

6.98 
5.98 

11.30 
11.79 

199.03 
201.09 

34.29 
32.96 

002916 
.08035 

167.0 
160.0 

1146.7 
1147.6 

979.8 
97a5 

0.2924 
.2956 

1.4876 
1.4816 

1.7800 
1.7766 

5.49 

U 

201.96 

32.41 

003086 

160.9 

1147.9 

978.0 

02999 

1.4783 

1.7762 

4.98 
S.88 

12.28 
12.77 

203.08 
206.00 

31.71 
30.57 

003163 
.00271 

1701 
173.0 

1148.3 
1149.1 

9n.3 
976.1 

0.2986 
.3015 

1.4747 
1.4687 

1.7733 
1.7708 

S.«5 

18 

206.88 

30.07 

003326 

173.8 

1149.4 

976.6 

0.3028 

1.4660 

1.7887 

8.98 
1.98 

13.26 
13.76 

206.87 
208.67 

29.61 
28.63 

003388 
.03505 

174.8 
176.6 

1149.8 
1160S 

974.9 
973.8 

0.3043 
.3070 

1.4629 
1.4572 

1.7671 
1.7842 

1.48 

14 

209.56 

28.06 

003664 

177.6 

11508 

973.3 

0.3083 

1.4546 

1.7628 

6.98 

14.24 

210.43 

27.61 

003622 

178.4 

1151  Ji 

872.7 

0.3096 

1.4618 

1.7614 

6.4 

14.697 

8U 

26.81 

003730 

180.0 

1151.7 

971.7 

O3120 

1.4469 

1.7589 

- 

14.74 

212.13 

26.76 

0.03739 

1801 

1151.8 

971.7 

03122 

1.4465 

1.76S7 

ib.Google 


STEA  M 
Table  63.    Propertlet  of  Saturated  Steam. — Cont. 


Pf^nn 

HMteoaMot 

EDtrap; 

Lb.p« 

q.ln. 

Vol- 

T^ 

laB.t.a. 

Latnt 

h«to( 

T«mp.. 

uim. 

TUOri- 

•F. 

en.  ft. 

ndcn 

m™- 

o( 

Ow 

"• 

per  lb. 

liquid 

™POT 

la 
B.I.U. 

Uqtiia 

^^ 

' 

• 

' 

_l_ 

• 

" 

L 

*t 

L 
T 

♦ 

9A 

16 

213.0 

26.30 

0.03802 

181.0 

1162.2 

971.2 

0.3135 

1.4438 

1.7673 

SJ 

90 

228.0 

20.10 

0.0498 

196.0 

1157.7 

961.7 

0.3366 

1.3987 

1.7343 

10.8 

85 

240.1 

16.32 

O.0613 

20S.2 

1162.1 

963.8 

0.3631 

1.3633 

1.7164 

UA 

80 

250.3 

13.76 

0.0727 

21&6 

1165.7 

M7.1 

0.3679 

1.3340 

1.7019 

ao.3 

85 

259^ 

11.91 

0.0840 

227.7 

1168.7 

941.0 

0.3805 

1.3090 

1.6806 

at.3 

M 

267.2 

10.61 

0.0951 

235.8 

1171.3 

935.6 

a3917 

1.2871 

1.6788 

a»A 

15 

274.4 

e.41 

0.1062 

243.1 

1173.6 

930.5 

0.4017 

1.2677 

1.6694 

»A 

60 

28 1.0 

8.53 

a  1173 

249.8 

1175.6 

926.9 

0.4108 

1.2501 

1.6609 

«.s 

55 

287.1 

7.80 

0.1283 

266.9 

1177.5 

921.5 

0.4190 

1.2342 

1.6532 

«B.» 

80 

2^7 

7.18 

0.1392 

281.7 

1179.1 

917.4 

0.4287 

1.2195 

1.6462 

60.8 

85 

298.0 

6.66 

0.1501 

267.1 

1180.6 

913.6 

0.4338 

1.2058 

1.6397 

BB.8 

70 

302.9 

6.22 

0.1609 

272:2 

1182.0 

909.8 

0.4405 

1.1931 

1.6336 

00.8 

75 

307.6 

5.82 

0.1717 

277.0 

1183.3 

906.2 

0.4468 

1.1812 

1.6280 

S5.8 

80 

312.0 

5.48 

0.1824 

281.6 

1184.4 

902.8 

0.4527 

1.1700 

1.6227 

70.8 

86 

316.3 

6.18 

0.1932 

286.0 

1185.6 

899.6 

0.4583 

1.1595 

1.6178 

75.8 

« 

320.3 

4.906 

0.2039 

290.1 

11S6.6 

896.4 

0.4636 

1.1496 

1.6131 

80.8 

85 

324.1 

4.663 

0.2145 

204.1 

1187.5 

893.4 

0.4687 

1.1400 

1.6087 

88.8 

108 

327.8 

4.442 

0.2261 

297.9 

1188.4 

890.5 

0.4736 

1.1309 

1.6046 

00.8 

185 

331.4 

4.240 

0.2358 

301.6 

1189.2 

887.6 

0.4782 

1.1222 

1.6004 

85.8 

110 

334.8 

4.067 

a2465 

305.1 

1190.0 

884.8 

0.4827 

1.1138 

1.5966 

U0.8 

m 

338.1 

3.889 

0.2672 

308.6 

1190.7 

882.1 

0.4870 

1.1068 

1.6928 

U5J 

190 

341.3 

3.735 

0.2678 

311.9 

1191.4 

879.5 

0.4911 

1.6893 

1M.8 

188 

344.4 

3.693 

a2783 

316.1 

1192.0 

876.9 

0.4950 

lJiS68 

115.8 

ISO 

347.4 

3.461 

0.2889 

318.2 

1192.8 

874.4 

0.4989 

1.5825 

1903 

186 

360.3 

3.340 

0.2994 

321.2 

1193.2 

872.0 

0.5026 

1.0767 

1.6793 

U5.8 

IM 

363.1 

3.228 

0.3100 

324.2 

1193.7 

869.6 

0.6062 

1.0700 

1.6762 

180.8 

146 

356.8 

3.120 

0.3206 

327.0 

1194.2 

867.2 

0.5097 

1.0636 

1.6733 

185.8 

150 

368.5 

3.020 

0.3311 

329.8 

1194.7 

864.9 

0.5131 

1.0573 

1.5704 

1U.8 

156 

361.1 

2.927 

03417 

332.5 

1196.2 

862.7 

0.6164 

1.0512 

1.6676 

1«5.8 

1«D 

363.6 

2.838 

0.3622 

336.2 

1196.7 

860.6 

0.6196 

1.0453 

1.6649 

150.S 

165 

366.1 

2.767 

0.3627 

337.8 

1196.1 

858.3 

0.5227 

1.0B95 

1.5622 

185.8 

178 

368.6 

2.679 

0.3733 

340.3 

1196.5 

866.2 

0.5258 

1.0339 

1.6597 

U0.8 

175 

370.8 

2.606 

0.3838 

342.S 

1196.9 

854.1 

0.5287 

1.0284 

1.6572 

U5.8 

ISO 

373.1 

2.636 

0.3943 

345.2 

1197.2 

862.0 

0.5316 

1.0231 

1.6547 

170.8 

185 

376.4 

2.470 

0.4048 

347.6 

1197.6 

849.9 

0.6344 

1.0179 

1.5523 

ib.Google 


Tmble  63.     Fropertie*  of  Saturated  Steam. — Coat. 


L..^ 

T-. 

r^. 

v«l- 

PMlb. 

sr 

^B^' 

EBtMpj 

Om* 

*.5r 

^ 

at 

Uqtdd 

^ 

o( 

r 

• 

' 

_i 

H 

L 

*( 

L 
T 

* 

MM 
US.8 
U6.S 

UO 

IK 

800 

aoo 

8U 

377.a 
37B.7 
381.9 
383.9 
386.0 

2.40S 
2.348 
2.202 
2.238 
2.180 

0.4164 
ati69 
a4364 
0.4469 
0.467 

36ao 

362.2 
364.5 
366.7 
368.8 

1197.0 
1198.2 
1198.6 
1198.7 
1199.0 

847.9 
846.0 
844.0 
842.1 
840.2 

0.5372 
a63B0 
0.5426 
0.6461 
0.5477 

1.0128 
1.0079 
1.0030 
09983 
09936 

1.5500 
1.5478 
1.5466 
1.5434 
1.6413 

aw.3 

IDB.S 

»o.a 

SIB 
ISO 
88ft 
900 
888 

388.0 
390.0 
391.9 
393.8 
395.6 

2.137 
2.090 
2.046 
2.002 

1.061 

0.468 
0.478 
0.489 
0.400 
0.610 

381.0 
363.0 
306.1 
367.1 
369.1 

1199.2 
1199.6 
1190.7 
1199.9 
1200.1 

838.3 
836.5 
831.6 
832.8 

831.0 

a56Q2 
0.5626 
0.5560 
0.6573 
0.5597 

0.9890 
09846 
D.9802 
0,9760 
0,9717 

1.5392 
1.6372 
1.6368 
1.5333 
1.5314 

sa6.s 

180.S 

9M.3 
MK.3 

9M 

au 

■SB 

900 

397.6 
399^ 
401.1 
402.9 
404.6 

1.021 
1.883 
1.846 

1.811 
1.777 

0.521 
0.631 
0.642 
0.662 
0.603 

371.0 
378.0 
374.9 
370.7 
378.6 

1200.3 
1200.5 
1200.6 
1200.8 
1201.0 

829.3 
827.5 
826.8 
824.1 
822.4 

0.6619 
0.5641 
a6663 
0.5686 
0.5706 

09676 
09635 
09596 
0,9556 
0,9517 

1.6205 
1.5Z76 
1.6258 
1.5241 
1.5223 

SH.3 

a65.3 
170.8 

885 

970 
S7S 
800 
98B 

406.2 
407.9 
409.6 
41 IJ 
412.8 

1.746 
1.713 
1.683 
1.664 
1.625 

0.573 
0.684 
0.694 
0.605 
0.615 

38a4 
382.2 
383.9 
385.7 

387,4 

1201.1 
1201.2 
1201.4 
1201.6 
1201,6 

820.7 
819.1 
817.4 
816.8 
814.2 

0.5727 
0.5747 
0.5767 
0.5787 
0.5806 

09479 
0,9442 
0.9405 
0,9369 
09333 

1.5208 
1.5189 
1.5172 
1.6166 
1.5139 

87B.3 

9B6J 
iOM 

880 
9BB 
880 

SOB 
810 

414.4 
41S.9 
117.6 
419.0 
42a5 

1.508 
1.671 
1.646 
1.620 
1.496 

0.626 
0.036 
0.947 
0.658 
0.068 

389.1 
390.8 
303.4 
394.1 
396.7 

1201.7 
1201.8 
1201.9 
1202.0 
1202.0 

812.6 
8X1.0 
800.4 
S07.9 
806.4 

0.6828 
a5845 
0.6803 
a6882 
0.5900 

09298 
09263 
09229 
0.9195 
09102 

1.5123 
1.610B 
1.50» 
1.6077 
1,6062 

800.8 
80S^ 

8U^ 
880^ 

815 
890 

880 

aao 

421.0 
423.4 
424.9 
426.3 
427.7 

1.473 
1.460 
1.428 
1.407 
1.386 

a670 
0.690 
0.700 
0.711 
0.721 

397.3 
398.9 
400.4 
402.0 
403.5 

1202.1 
1202.2 
1202.2 
1202.3 
1202.3 

804.8 
803.3 
801.8 
80a3 
798.9 

0.5918 
0.5936 
05053 

0.5970 
06987 

0912B 
O9097 
0,9065 
O9034 
O9003 

1.6047 
1.6082 
1.6018 
1,5004 
1.4090 

880'.8 
880J 

8U 
845 
800 

429.1 
430.5 
431.9 

1.366 
1.346 
1.327 

0.732 
a743 
0.763 

405.0 
406.5 
40B.0 

1202;4 
1202.6 

797.4 
795.9 
794.6 

0.6001 
0.6020 
06036 

0.8972 
0.8942 
0.8912 

1.4976 
1.4062 
1.4049 

800.8 
88B^ 

878 
«00 

438.6 
444.8 

1.230 
1.162 

0307 
0.860 

416.1 
422.0 

1202.6 
1202.5 

787.5 
780.6 

06116 
0.6100 

0.8768 
0.8031 

1.4S84 
1.4821 

ib.Google 


Tabic  03. 

Ptopertie*  of  Superheated  Steam. 

429 

f 

IM  [S27.8I 

105  [S3 1.4] 

no  [334.81 

lis  1338.1) 

•F. 

Y 

* 

H 

V 

* 

H 

T 

* 

H 

T 

. 

H 

Smt. 

1 

i 

440 

i 

490 

1 

7»» 

1:S? 
iiil 

11 

a.i; 

III 

6.M 

11 

a.se 

7.17 

i.eois 

...,„ 

I:SJ8? 

:::: 
ifj 

1.0820 

is! 

■if 

1.8363 

ii»e.2 

Kl 

1227.8 

1238:^ 

SSi 

1254.0 
1204!^ 

'SI 

1278.0 

III 

1404.7 

4.30 
4.37 

i 

4.70 
4:9c 
ft.02 

si 

S.33 

II 

0.82 

1,«>04 
1.6066 

i:S 

1.6270 

IS 

1.6402 

i:6684 

1.6644 

.6760 

:ii 

1.7035 
1.8107 

1104.1 

lis 

227.0 

237: 
342. 

ZS3.3 

263:? 

SI 

1379.0 
1364:s 
1404.5 

4.00 
4.10 
4:3; 
4.48 

'is 

4.73 

4.79 

11 
l;St 

5.67 

S;Si 

0.B1 

1. 5966 
1.6002 

Iffli 

liii 

.6536 

;K 
:Sffi 
S. 
S 
El 

1.8145 

1100  0 
11S2.B 

iil 

1226.1 

IS 

1203.1 

sm 

1278.6 
1303.9 

ill 

3.80 
3.00 
3.97 

li 

4.27 

iZ 

4.67 

ti 

6:06 

a.23 

■  51.1. 

i.eoia 

\B 

1.6689 
1.6647 

ilsl 

1.6871 
.6925 

:;i 

1.8004 

1100.7 

1191.8 

1107.5 
120S.3 

12U:I 
226.< 

|:I 

Sn 
Ei 

1278.0 
1338:8 

li?l:8 

1404.1 

P* 

1M  1341.31 

135  1344.41 

1»  1347.41 

13S  1350.3] 

•F. 

V 

* 

H 

V 

« 

H 

, 

* 

" 

Y 

* 

H 

Sat. 
IS* 

1 

i 

5M 

530 

i 

;s8 

3.7( 
1.00 

ill 

4:82 
4:4c 

J:?! 
Ill 
:!S 

.41 

:oi 

i-E 

LOsao 

i.asM 

11 

.687J 

:703i 

.7083 

i:804f 

11014 
106,4 

218;b 

226  it 
235.3 

24b!o 

256!e 

261.J 

1277,4 

1292:B 
1207.0 

isl 

1403:9 

3.63 
3.00 

11 

3:97 
4:14 

4:3 

4:66 
4.62 

;;L 

In 

1.68B9 

i;sf?t 
III 

i:6484 

1.6824 

1.SB78 

IS 

l,70Bi 
i:8000 

1212:. 

1218.0 

1223.8 
1229.1 

ill 

1260, Q 

1276.9 

1282:* 

ill 

1403:3 

3.48 

3:0; 

|I5 

3:97 

4:08 
4.13 

4.28 
4.6H 

11 

1.582S 
I.6S44 

i:eo64 

i:62B0 
1:0434 

i.aeio 

1.6776 

i:603( 
1.8987 

1,7031 

i:7B5i 

ill 

1244:5 

ill 

276.3 
291:9 

is; 

1403:s 

3.39 

Is 

3:37 

4:02 

4.17 

4:32 

!;I2 
11 

.5863 
.593' 

1.B32S 
1.6386 
1.6446 

i-i 

:894; 

,72  1 
.74  5 

.7693 

1SS:S 

iil 
ills 

1181 

1254.0 

ill 

Si 
201.4 

296.6 

ii 

D  preoureH  knd 


indlug  ■ftt«T>t«d  itoun 


ib.Google 


Table  63.     PropertiM  of  Superheated  Steam — Cont. 
I  [3«S.I|  I'  I4S  I3SC.8I  I  I59I3AS.G1 


1.6813  i: 
l.SftM  i: 
i.sgs3 1: 


i.esss  i: 

1.0949  i: 
l!7433  li 


1.<M3S  i: 
1.6102  i: 
1.616S  i: 

l.A22fl  i: 

1^6346  l! 

i^Mei  ti 
i.flGis  i: 
i!efl2H  li 

t!eT35  li 
1.8787  i; 


1.5622  t 

1.56SI  I 
1.5723  l; 

1.G704  i: 

1. 6883  i: 
1. 6931  i: 

1.6997  l; 
1.6061  I! 


1.6697  IS 
1.6740  1! 


•  To  the  right  of  (P)  aDpeu  bI 


taniperaturea;  llTa  latter  arn  ta  brkcketi 

P  uid  T  are  rnpectlrely  the  al 
<>  and  H  are  the  entropy  and  ton 


6  3 

6  a 

3  3 
I  3 

4  8 

0  3 
6  3 

1  3 

6  3 

g  3 

3  3 

7  3 

0  3 

3  3 

0  8 
Q  3 

1  3 

3  3 

1  * 

7  4 


1.8148  i: 
1. 8307  1! 
1.8267  l: 


1.8712  1| 

l!7Z04  li 
1.7431  i; 
1.7847  !■ 

1.7864  1. 


wpoodlDg  (aturatad  M 


ib.Google 


Table  63.    ProperticB  of  Superheated  Steam — Cont. 


F*  IS*  [373.1] 


1.S55R  11 

i.sesi  11 

1.ST02  1-. 

lisssfi  li 

I.B905  II 


1.IUI2G  i: 
1,5«94  i: 
1.6761  r. 

1.B82T  i: 


P  knd  T  are  reapecUvely  tbe  tbsoluM  premire  and  the  volume  tn  cb.  tt.  per  lb 


«  the  entropy  aod  total  heat  of  aupeiheMBd 


n  measured  mm  an  deg. 


ib.Google 


432 

Table  63. 

Propertie. 

P* 

Mt  1300.01 

115  1391.91 

2M  1393.81 

J3S  [396.61 

•r. 

, 

* 

H 

T 

<)> 

H 

. 

« 

n 

* 

* 

H 

Sat 
«•• 

!iS 

430 
4S« 

i 

BIO 

MO 
15* 

800 

2.09 

1 

2.31 

s!3S 

rti 

i 

,64 

!70 

li 

3.3- 

1.8372 

iIbsbi 

1.572'i 

1.67B4 

i:6045 

i;65»u 

iiae.5 
i20fi.g 

122*;.'! 
1330.6 

111 

26412 
126B.a 

1266.0 

III 

iil 

III 

2.0s 

III 
2!3:; 

S.2( 

2:35 

li 

2:54 
2.57 

2.60 

11 

2.73 
3:30 

i 

;«96 

1.B782 

.8074 
,813a 

:SIS 

1.83S9 
i:B46fl 

.6822 

:7531 

1199.7 

1217.6 

I23B.8 

,2S3:5 
1269.3 

:270> 
278.3 

293.0 

:303:s 

II? 

436:3 

3.00 

sloe 

2.16 

2-20 

til 
II 

2.B2 

2:01 

2.07 
2.81 

3:33 

1.6333 

.8379 
.5463 
.5.'i2€ 

:B684 

.B731 

:5B23 

:8I04 

:6376 
.8331 

;|? 
■HI 

:7S06 

11B9.0 

i2i«:( 

1235,0 

ill 
III 

1292.6 

i308:a 

1346:6 
1435:1 

1.96 

11 

2-15 

2:37 
2.40 

2.46 
2:52 

1:11 

II 

8:i8 

1.6314 

i:6633 

:5766 

15894 
.5966 

i:6134 

IS? 

i:6516 

:7047 

1200,1 

1203,9 
1209.4 

iiis 

234.3 
240.3 

287:9 
1283,7 

:28o:8 

III 

308:5 
1313.9 

if 

V 

140  1397.61 

1 

U  [399.31 

»•  1401.11 

159  1402.91 

■F. 

, 

« 

n 

T 

* 

n 

1.846 

i!a42 
1.974 

2.006 

IS 

2:129 

11 

2:278 

2.30G 
2.333 
2.    81 

2.  89 

2.   17 

2,444 

2.S7t 

2:068 

* 

n 

T 

* 

H 

Smt. 

JS 

440 

i 
1 

IIS 

i 

1.92 

li 

2:  IS 

11 

2.41 

II 

11 

1.620S 

11 

.saro 

S 

:S 

.0384 
.0437 
.0489 

III 

1227^3 
124B:( 
1283. 

lis 

isisis 

III 

1.88 

is 

2.05 
2:1: 

II 

2.3« 
2:41 
2.60 

2.«; 

3:0; 

1.6367 

i;6572 

I.Be40 
1.6707 

1.B772 
1.B836 

i.esaa 

III 

1.8248 

1200.5 

IS! 

!238:8 

1274:0 

290.B 

307:5 

.6258 

■if 

.:6870 
:8050 

::ai66 

.8222 

:8384 

:S 

1206.5 

1225:7 

1   44:0 
1  55:9 

aei-B 
279:1 

384.S 

1298:S 

1345:1 

1,835 
i:B32 
1,963 

ii 

2:201 

i 

risi 

2:527 

2.857 
2:0m 

!:S 

1-5442 
1.8682 

i:S77B 
.5904 

:E 
s. 

.6359 
.6412 

1.6464 

i:694a 

1200.8 

il 

224:g 
231.1 

'f:3 
ill 

289.8 

1301:? 
1306.6 
1313.1 

1317,6 

ill 

•  Td  the  right  of  (P)  a 


1  prenunn  mnd  corrMpondlng  ■Murklei)  al 


(empsratures;  iSe  latter  are  la  bracketa.' 

P  and  T  are  mpectlTely  the  abaolute  preaaure  and  the  volume  In  cb,  ft,  per  lb.;  Bnd 
#  and  H  are  the  entropy  and  total  heat  ol  auperlieated  steam  measured  from  33  dec. 


ib.Google 


Table  63. 

ofSui 

433 

^ 

»•  (404.51 

I4S  1408.2) 

J7»  [407.91 

17»  [409.61 

•r 

, 

<» 

H 

, 

. 

H 

» 

• 

H 

T 

0. 

H 

Sat. 

1.777 

1.5223 

1201.0 

1.74S 

i.saoa 

laoi.i 

1.713 

1.518B 

1301.2 

1.683 

1.5172 

1201.4 

410 
420 

4*0 

lisg] 

1.5413 
I.54S4 

204.1 
224.0 

i!7ag 

f.ll! 

11 

il! 

ii 

il 

iill 

1:71 

!:?S 

i:632e 

1221.4 

4S« 

1 

1.S22 

i;| 

1.5553 
1.5021 

i-ii 

242: 
254!t 

i;Si 

IS, 

i;il 

iil:l 

l:l?i 

!:iSJ 

1.5032 

il 

:iS 

.864 

:S 

1:S 

Si 

^1 

li 

S40 

2.erji 

lilM 

.5877 
.5938 

S 

IZflO.l 

1278:o 
1283.7 

ii 
2:141 

i-ili 

lioosi 

|!:i 

383:1 

2:098 

!:S 

1.5948 
I.eOOfi 
1.6063 

il 

282:6 

!:S! 

3.004 
2:05t 

1.5981 
1.6088 

383.0 

5M 
600 

1 

11 

300.  e 

1??;? 

li 

2^274 

i:625£ 

1288.8 
1294.5 

iisi 

.125 
.230 

i:iy 

1.0338 

38S.3 
294.0 

3.081 

Ii 

3.  88 

.6091 

i|i 

2873 

i:l 

310.3 

3.347 

11 

11 

344: 

2.301 

i 

.8415 

i3ia.7 

i!il 

2.268 
2.383 

2.60« 
2.637 
2.7*8 

1.8391 

1318.3 

iiii 

3.213 
2.33t 

Hi 

1.6387 
1.6620 

is 

si!:! 
il 

us 

2.974 

'■'"• 

1460.1 

2.917 

1.7544 

■"" 

2-863 

1.7622 

1449.7 

2.810 

1.7.01 

'"«•» 

p* 

»•  1411.31 

185  1412.8) 

19*  [414.41 

»5  I4IB.9I 

•F 

• 

« 

H 

V 

* 

H 

T 

• 

H 

V 

•     1    H 

Sat. 

I.as4 

i.sin 

1201.S 

1.625 

1.613B 

iaoi.8 

1.508 

1.8133 

1301.7 

1.571 

i.5in 

1201.8 

440 

if!! 

ill 

ill 

i;707 

1:5344 

1308.5 
1219:7 

\M 

i:6317 

121S:9 

1.683 

i:64i 

i:li 

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•    To  the  right  of  (P)  ■pptBr  Iteam  Il._.ui»  m-M  <.u>id>i>uuuuib  ••i.ui.anxj  •niBiii 

tempsnturai  the  latMr  mnUt  tir»ckew. 

PandrarereBpectivelr  the  absolute  pi«aure  and  (he  Toluiiielticb.lt.  per  lb.;  and 
*  and  H  are  vbe  eoUvpr  and  total  heat  o(  Buperbeated  Bteam  nrawured  tn>m  33  deg. 


ib.Google 


434 

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o  tbe  Bntrc>i>7  mad  toul  bwt  Of  si^MlieKted  ■! 


ib.  Google 


CHAPTER  13 


FUEL 

COAL  in  its  difFerent  forms  is  the  principal  fuel  used  in  boilers,    Its  appli- 
cation, analysis  and  purchase  have  been  most  highly  developed.     The 
use  of  oil   is   increasing   rapidly,   and   other    fuels   are   employed   when 
foctorg    of   economy   or   delivery   warrant.      Natural   gas    and   crude   oil   or 
petroleum  have  the  highest  heat  value  of  die  commercial  gaseous  and  liquid 
fuels ;  and  because  of  their  ease  of  operation,  gas  and  oil  are  highly  regarded 

Classification  of  Coals 
/'^^AL  is  a  dark  brown  or  black  mineral  substance,  found  in  the  carbonif- 
^-^  erous  geological  formation.  All  coals  are  formed  from  vegetable  growth 
fossilized  by  moisture,  heat,  pressure  and  time,  and  can  be  itidlvidually  dis- 
tinguished by  the  physical  structure  as  well  as  by  the  chemical  peculiarities. 
A  broad  class iticati on  includes  wood  hber  or  cellulose,  which  is  the  lowest  of 
the  group,  followed  in  order  by  peat,  lignite,  bituminous  coal,  semi-bituminous. 


' 

0 

a           IS          SO          SS          30         3 

5          4 

0      as 

A     /      A     A     A     A      A     / 

A    A 

•? 

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/ 

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/ 

*>         )3         »        «5         »        i 

i — 5 

i      « 

Fig.  303.     QrouiHng  Coala  according  to  Chemicttl  Constituenti. 

semi -anthracite,  anthracite  coal  and  graphite.  The  differences  in  composition 
are  shown  in  Fig.  203,  based  on  data  prepared  by  the  Bureau  of  Mines.  Start- 
ing from  the  lowest  in  the  group,  each  succeeding  variety  of  coal  is  distin- 
guished by  an  increase  in  carbon  and  a  decrease  in  oxreen.  The  hydrogen 
remains  practically  constant  for  the  lower  part  of  the  group  but  decreases 
rapidly  in  the  higher  part.  The  curve  is  plotted  from  analyses  computed 
on  a  basis  of  coal  free  from  moisture,  ash,  nitrogen  and  sulphur.  Therefore, 
the  sum  of  the  carbon,  hydrogen  and  oxygen  content  as  given  equals  100 

Wood  is  the  representative  of  the  organic  substance  from  which  coal  is 
derived.  The  extreme  variations  of  its  properties  explain  the  differences  found 
in  coal.  The  term  wood  includes  trees,  small  plants,  and  mosses,  which  are  com- 
posed chemically  of  cellulose,  or  of  tiber  and  sap  or  sap  deposits  t>etween  the 
^bers.  Actual  wood  has  a  higher  carbon  content  than  cellulose  or  moss. 
It  contains  from  IS  to  25  per  cent  of  moisture  even  when  air  dried.  The 
ash  content  may  be  from  2  to  3  per  cent.  Dry  wood  has  a  heat  value  of 
8000  to  9000  B.t.u.,  and  ordinary  fire  wood  of  5000  to  6000  B.t.u.  per  pound. 

Peat  is  organic  matter  in  the  first  stages  of  conversion  to  coal.  It  is 
found  in  swamps  and  bogs  and  consists  of  roots  and  fibers  in  every  stage 
of  decomposition,  these  containing  70  to  8S  per  cent  of  moisture.  Its  color 
varies  from  yellow,  through  brown,  to  black.  Its  percentage  of  nitrogen  and 
oxygen  is  large  and  :ts  volatile  matter  poorly  combustible.    Peat  is  valuable 


ib.  Google 


as  a  fuel  only  after  having  been  thoroughly  dried.  Air-dried  peat  has  a 
heat  value  of  9000  B.t.u.,  and  when  completely  dry  the  value  may  be  over 
10,000  B.tJi.  per  pound. 

Lignite,  sometimes  called  brown  coal,  is  the  next  step  from  peat 
in  the  formation  of  coal.  It  contains  from  30  to  50  per  cent  of  water,  this 
being  reduced  by  air-drying  to  from  10  to  20  per  cent.  Lignite  is  of  a 
woody  'texture  and  does  not  coke  on  being  carbonized.  Us  heat  value 
is  between  7000  and  8O00  B.t.u.  per  pound,  while  the  ash  content  varies 
from  5  to  10  per  cent.  As  it  disintegrates  rapidly  on  exposure,  lignite 
cannot  be  shipped  any  distance  except  in  cold  weather  when  frozen. 

Sub-bituminous  coal  is  next  to  lignite  in  order  of  age.  The  chemical 
difference  between  it  and  lignite  is  not  clearly  deRned  and  so  it  is  sometimes 
called  black  lignite.  However,  the  physical  difference  is  marked.  The  sub- 
bituminoui  coal  is  black  and  shiny,  has  only  a  small  trace  of  woody  structure, 
contains  less  water  and  has  a  higher  heat  value  than  Hgnite,  It  differs  from 
bituminous  coals  by  the  slacking  it  undergoes  when  exposed  to  the  weather. 

BHuminout  coal  includes  the  so-called  soft  coals,  which  vary  in  color 
from  dark  brown  to  pitch  black.  The  important  divisions  of  this  group  are 
the  caking  and  the  non-caking  coals ;  both  bum  with  a  yellowish  flame,  and 
give  off  smoke.  Caking  coal  has  a  tendency  to  fuse  and  swell  in  size  during 
heating.  Its  high  volatile  content  and  richness  in  hydrocarbons  make  it  valu- 
able in  the  manufacture  of  coal  gas.  Non-caking  coal  bums  freely  without 
fuging,  is  therefore  well  adapted  to  burning  on  grates  without  interfering 
with  the  air  supply  required  for  combustion,  and  is  used  extensively  under 
steam  boilers.    The  heat  value  is  between  14,000  and  15.000  B.t.u.  per  pound. 

Semi-bituminoui  coal  is  brighter  in  appearance,  and  somewhat  harder 
than  bituminous  coal,  more  nearly  resembling  anthracite.  It  is  generally 
free  burning,  without  smoke.  It  burns  with  a  short  flame  and  has  a  high 
heat  value. 

Semi-atitkracite  coal  is  harder  than  semi -hi  luminous.  It  burns  freely 
with  a  short  flame,  yielding  great  heat  with  little  clinker  and  ash.  It  swells 
considerably  in  size  but  does  not  cake,  and  tends  to  split  up  on  burning. 
Semi -anthracite  when  newly  fractured  will  soil  or  soot  the  hand,  while 
pure  anthracite  will  not.  There  is  only  a  small  amount  of  this  coal  in  the 
United  States. 

Anthracite,  commonly  called  hard  coal,  is  practically  all  fixed  carbon.  It 
generally  occurs  with  slate  streaks,  has  a  deep  black  color,  and  a  shiny 
semi-metallic  luster.  It  contains  little  hydrocarbon,  is  slow  to  ignite,  and 
bums  with  a  short  yellowish  flame  which  changes  1o  a  faint  blue,  but  with 
little  or  no  smoke.  Anthracite  does  not  sotlen  or  swell,  but  breaks  into 
small  pieces  when  rapidly  heated.  Because  the  price  of  the  coal  decreases 
with  the  size,  anthracite  of  less  than  ij-in.  diameter  is  generally  used  for 
steam  purposes.  The  smaller  sizes  often  contain  slate  which  cannot  be  dis- 
tinguished, so  that  the  ash  content  is  high.  Anthracite  has  a  specific  gravity 
varying  from  1.3  to  1.8. 

Graphite  is  the  highest  of  the  coal  group  but  is  not  available  for  fuel 
because  of  the  high  temperature  required  for  its  ignition.  While  practically 
pure  carbon  it  can  be  burned  only  with  difficulty  in  the  hottest  fire  and 
when  mixed  with  other  coals. 

The  classification  of  coals  by  name,  as  above,  is  only  a  convenience. 
The  different  coals  overlap  to  some  extent  and  a  technical  description  is 
necessary.  For  this  purpose  the  chemical  properties  of  the  coals  have 
generally  been  used,  as  shown  in  Table  64,  by  C.  E.  Liicke.  Camfibcll  proposes 
a  classification  on  the  ratio  of  the  total  carbon  (O  to  the  total  hydrogen  (H) 


ib.  Google 


of  the  ultimate  analysis.  The  coals  are  divided  into  twelve  groups,  but 
suflicient  data  to  fix  the  values  marked  (?)  are  not  available.  Frater  sug- 
gests the  fixed  carbon  (f.  c.)  divided  by  the  volatile  combustible  matter 
(v.  m.)  of  the  proximate  analysis,  while  Muck  recommends  the  total  carbon 
content  of  dry  and  ash  free  coal,  as  a  standard.  Another  classification  is 
based  on  the  fixed  carbon  in  the  combustible,  as  in  the  last  column  of  the 
tabulation. 

Table  64.     Claswfication  of  Coal  by  Compoaition. 


CnU 

C^PUU 

Pn»r 

Mua 

-    0«Bmd 

<Stm. 

H 

Lc 

■^ 

^i■■ 

A 

«  to? 

Anthracite 
100 

12 

Anthracite 
95 

Anthradte 

?to30 

97  to  92.5 

Anthracite 

30  to  26 

D 

Semi-anthracite 

26  to  23 

12  to  8 

92.6  to  87.5 

E 

23  to  20 

8  to  5 

Common 
Coal 
82 

87.6  to  75 

20  to  17 

S 

to 
0 

Eastern 

17  to  14.4 

H 

Bituminous 

14.4  to  12.6 

Western 
65  to  50 

1 

Bituminous 

12.6  to  11.2 

11.2  to  9.3 

70 

K 

Peat 

9.3  to? 

69 
50 

L 

Wood  or  Cellulose... 

7.2 

Cannti  coal  differs  from  the  general  group  of  coals  and  is  therefore  not 
included  in  the  previous  classification.  It  lies  somewhere  between  bituminous 
and  sub-bituminous  but  is  considerably  higher  in  hydrogen  than  either.  It 
is  said  that  the  name  is  derived  from  the  fact  that  this  coal  burns  like  a 
candle.  Cannel  coal  is  hard,  dull  black,  easily  broken,  and  gives  a  large 
amount  of  gas  when  heated.  It  is  valuable,  therefore,  as  an  "enricher"  in 
gas  making. 

Location  of  Coal  Deposits  in  the  United  States 
"  I  "HE  map,  Fig.  204,  shows  the  areas  in  which  coals  are  mined,  the  older  dc- 
*•  posits  being  grouped  into  seven  fields.  Some  graphite  coal  is  found  in 
Rhode  Island;  most  of  the  anthracite  comes  from  Eastern  Pennsylvania! 
semi -bituminous  comes  mainly  from  the  noriheast  section  of  the  Appalachian 
field;  bituminous  coals  are  found  in  the  remaining  larger  fields;  sub-bitumi- 


ib.  Google 


ib.Google 


-Afpalac^iia 
-Ntrfftorn /rr, 


T^Gcuthtitef  fnfff'ft^ 


FiK-  204.    Coal  Field*  of  the  United  States. 

nous  is  found  mostly  in  the  western  stales,  and  lignite  comes  (roin  the 
South  and  Northwesi.  The  coals  from  all  these  localities  have  been  analyzed 
by  the  Bureau  of  Mines,  the  compositions  being  listed  in  Table  65. 

Composition  of  Coals 

IN  burning  coal,  first  the  moisture  is  driven  off.  next  the  volatile  matter,  and 
then  the  remaining  fixed  carbon  ignites.  leaving  a  residue  of  ash.  These 
four  constituents  of  coal  are  ordinarily  determined  by  the  "proximate 
analysis."  which  gives  information  snSicient  for  all  practical  purposes.  The 
chemical  elements  are  accurately  determined  by  the  "ultimate  analysis"  which 
gives  the  percentage  of  carbon,  hydrogen,  nitrogen,  sulphur  and  ash.  The  per- 
centage of  oxygen  is  taken  as  the  difference  between  100  and  the  sum  of  the 
other  five  constituents  because  there  js  no  simple  direct  method  of  deter- 
mining it. 

The  results  for  both  analyses,  Table  6S,  are  for  coal  "as  received,"  which 
means  that  the  weight  of  moisture  in  the  actual  sample,  as  received  at  the 
laboratory  or  in  the  coal  at  the  point  of  sampling  in  the  mine,  is  included  in 
the  test  samples.  However,  both  proximate  and  ultimate  analyses  can  be 
made  or  computed  to  a  dry  or  "moisture  free"  condition  or  to  a  basis  of 
"moisture-and -ash- free"  coal.  The  moisture-free  analysis  gives  the  compo- 
sition and  heat  value  of  dry  coal  while  the  moisture-and -ash -free  analysis 
gives  the  approximate  composition  and  heat  value  of  the  dry  combustible 
matter.    Table  68,  for  a  typical  coal  sample,  indicates  the  three  values. 

Commercial  Sizes  of  Coals 

FOR  commercial  purposes,  coals  are  classified  by  trade  names  that  desig- 
nate the  size,  but  the  names  and  sizes  vary  in  different  localities.  In 
bituminous  helds  this  variation  is  marked,  while  in  the  anthracite  trade  a 
fair  standard  exists,  as  indicated  in  Table  66. 


ib.  Google 


FUEL 

Table  65.     Comporition  and  Heat  Value  of  United  State*  Coah. 
UltiiiHte  Analvifa 


CoaM7,B«d  or  Lol  Nuh 


■uluut*  Aiulyila 


d 


Bay,  Tharapwii  VmUmy . . 

Barlnv  Riror,  HutUn* 

Cook  iDlM,  Fort  Gnhun. . 


SaMstian,  GrwBwood 

Hwtanjr.  Ston*  Cuiran. . 


S.SS   tO.M    GT.08 


>.el  S2.M  58M     6Ae    < 
t.tX  34.18   M.ll      9.09     I 


J  WSJ   4S.M   14.ST 


SE.I8    a.«8 
4t.se  lo.ei 


S.81    TB.M     B.80 


1>.1G  tO.Sl 

ze.£D  Zt.AT 

4.4fi  4Z.0E 

S.8>  87.01 

28.M  Z8.«S 


44.27  G.16 

87.87  tAt 

49.  ES  S.»4 

48. U  IZ.G! 

87.ZE  G.02 


0.70  4.M  GG.27  0.81  2S.G7 
0.B3  3.14  BG.S8  l.Si  10.77 
O.GE   G.S1   49.GS  i.n   S4.8T 


4.48 

0.M  S.IZ 

I.IZ  G.4Z 

2.79  4.0E 

1.74  S.SE 

8.12  8.7G 

4.17  6.28 


BG.S8  1 

49.68  i,._  _ 

70.78  1.41 

41.79  0.87  4G39  . . 

^.00  1.18  19.71 

78.71  1.46  8.96 

80.28  1.47  8.69 

78.S7  l.SZ  8.96 

68.01  1.17  1«,14 


0.48  6.04  48.SB   « 


8.80    1G.8B  6G.8S   1 

11.46   87.24  47.01     4.80     < 

11.86   84.62  40.88   1 

11.82   27.86  GG.ID 

1Z.S9  88.89  41.80 

18 .64  SS.69  4D.08   1 

12.70  86.86  41.47 

0.96   84.78  4K.06   1 

18.81   88.62  41.84  1 

11.^  86.70  S9.4E   1 

6.01  82.87  64.82 

18.00  82.41  87  .BE  1 

9.18  27.30  86.40 

8.80  29.86  68.83 

16.91   26.86  88.^    1 

18.68  82.07  46.20     .... 

12.08  S2.48  44.42   11.02 


I  61.29  1.00  19.01 

I  68.69  0.96  19.8E 

1  60.91  0.99  19.1E 

i  69.M  1.04  16.91 

9  69.07  0.96  19.81 


0.90   G.IO  88.46   1 


1.89    6.48   62.97   1.01  21.28 
0.91    6.66   68.SS   1.42   20.84     ' 
S.66   6.84   80.46   0.89   18.66 


3.78   6.63   63.01 


9.69   88.69   41.04   10.B8 


.79   G.S9   82.88    1.23  16.80     : 


8.24  30.74  48.02  16.00 

2.60  S3.B0  61.26  t2.4i 

4.36  38.68  62.62     9,10     < 

11.10  S6.E1  40.69  12.70 

9.04  29.69  46.86  1E.T2 


4.26  G.S7  £8.49  0 

S.19  6.74  66.81  1 

6.16  G.82  M.6S  0 

G.03  4.81  69.82  0 


3.99   6.30  80.72   1.18    _    _ 
S.72   S.01   60.B9   1.06   18.60 


>r  tMtnria;  bU  ot 


ib.  Google 


FUEL 
Table  65.    Comporition  and  Heat  Value  of  United  Sutci  Co«l» — Cont. 


Coonty,  BmI  or  Ldal  N 


llhl 


JWiuM  ABdnb 
"AaBaniTMl" 


41 


If nUadbtn ,  Ctotnl  C^   . 

Oao,UtBmiT 

FIh«.B«ms 

Vtbtttr,  WhMtciDn 

AU«VB7.  luSart^. 

AllacuViFroMbuig 

AUacanr.  Lofd 

AU«ur.Uld);0d 

AlMfany,  Vamnfttfi 

Satfjuw,  SbcIuw 

Aitair,  EbkniUt 

C^waH.  BunUtoD 

Htary,  InHlBr 

Lalvatt^  Napolaoa 

Umod,B*tW 

Rur,  nAinaDd 

CiwbaD,  Boar  Cr«k 

CuoHl*,  Geynr 

CibMt.UUm 

FMia,  l^nristown 

Ubi«)>.UtaiNU 

YtOoKntcaak  MnawWiliBll . . . 
NawHok* 

Coittx,  lUtoa 

Une^,  WUtaOtb 

WKiBiaf.BlMAnA 

NartkDakMa 

Morton,  Liitk 

U'tmn.iVataa 

StaA,*l«bMi ... 

muiwu.  •miMai 

Bdmaot.  *B«IMi> 

Ouarany,  *Dadliird 

jBdwa.  •WalWoB 

Jiff>ni>D,Autorduii 

Nobta,  Brila  Taller 

Pny.'DlzIa 

OUnbMB 

Cod.L*hteh 

HuMUUKIurtalii 

ntuboii.  Carbon 

nttiboii.  UeAbator 

CoaB,BaaTar^ 

AU^any,  Brueatao 

All«hanr.O>k8tatloa 

Boilofd,  Hopinid 

CambtU,  BaavardalB 

Cainbiia,  CarrdltowD  Knod  . 

Cambria,  Fallal  Tlmbar 

Cambria,  "-^"^ 


S.64   G.ST   OJtl    IM   IB.U 


t.TD    U.SO   T4.00 

SJD  1«.B0  7G.M      -    - 

t.ie   K.OE  TG.g8      K.88 


11.11   SLM  4S.TE     S.U 


H.IS  tS.TT  2G.aS  S.TQ 

36M  Sl.K  Z4.ST  7.7t 

ILSB  tB.S>  SG.88  >.AG 

ae.7B  S8.1S  2»JT  "" 


3.60  STM  SI. a 


lt,SM 
ll,ft4f 
ll;37t 


1S,>1S 
U.100 


1.04  4.as  8a.ee  iJ«  s.aa 
U4  I.M  8s.se  Listens  : 
4.11  e.»o  sp.M  a.s4 

4.81  us  S0.40  1.18 

4.08  G.S9  E8.16  O.SS  1S.6S     : 

5.05  S.81  G6.83  0.B8  20.S0  : 
1.41  K.7K  S8.1S  l.DS  11.14  : 
S.77  S.8G  e8.U  1.04  1>.8> 


».18  2S.S1  SO.Sl  1S.08 

tE4S  S8.2T  4SJ)S  SJO 

14.70  2e.Sl  18.11  1S.8S 

1S,8S  17.8S  4S.0T  T.41 

S.IE  IS.Oe  B0.12  11.80 


l.EO  B2.e7   GS.41 


S.44   18.18  78.48     8.«2 


1.08   O.H  18.18 
.18   Ml   81.lt   D.71   19.88 

i.as  E.se  88.04  -■■ 


10,127 

«,eet 

10,816 

lolue 


).68   8.78   89.4E    DJM  4S.8I 
LIE  B.E4  41.48   1.11   41.>r 


0.48   8.98   41.87   0.8B  44.S4 


4.el    G.41    81.40   1.11    14.48 


8.00   6.48  78.89   l.._      _.__ 
2.H   6.42   70.S1    l.GO   11.12 


11,179 
tl,61G 
18,288 


9  ST.Ol   1.29  lE.OO 


8.84   6.18  84.88   1.44 


S   82.11   t»M     SSJ 
1S.10   81.10   89.e3    18.17 


0.E8    6J1   77.11    1.62  10-18     . 
0.81    G.SS   E1.07   1.19  18.28 


T   8.89  TS.ie   1.4E     8.91 


1S41B 
18.700 
14,086 


1.83  4.04   80.81    1.10     4.80 
1.30  4.81   81.S4   1.38     4.81     : 


1.67  4.Z8   81.19   1.S9     2.T8    I 


ib.  Google 


42  FUEL 

Table  65.     Compodtion  »nd  Hot  Value  of  United  Statem  Coali — Cont. 


CoBBtir,  Bad  or  Local  tttmi 


Cambria,  Nantr  u 

Cambria,  P«Hati 

Candirta,St,BBadM.., 


C«wrqw«l«  MQk 

Chiiim,  BhM  Ban  Btatlm . 
ClMuMd,  BoanlmaB 


GkBCvB 


lAdmwauna,  DoDmara., 

LDWtnaJft&tim 

SekayPA  UliMnTaia. . . 
BokurUn,  Tomr  Citr. . 


l,Uwiaiuia 


Hawpoit,  Ponaoouth . 

FM«M«uia,Cn»taa  . 

flaMk  Dalmta 

Parking  Loditpob. .. . 

TaaacaaM 
Aaimaa,  BrIerriUa. . , 
Campb«ir.La(oUMta.. 


Houatiw,  CnckKt. . 

WoodiHoyt 

Hub 
Carbon,  Soaoyaida^ , 


Bvirieo,  GavtoD 

Laa.DarbyAk 

BiiwelT.  Daata 

TaiwuU.  PoeabontM  . . 


KJBL  Conb^aDd, 
KitJma.Bariyn... 
PlHoa,  Caifa^mado. 
Tbnntvo,  C«>tralli 
Waal  TlMfa 
n]Frt*a,C>rlUa... 
raiFatla.PayatM... 
Ti^atta,  Hawki  Na 


s.u  la.n  toM  «^s 

S.ES  lT.St  ra^ti  BJ> 

a.M  is.a  10^  «.«T 

K.TS  U.M  M.M  a.«G 

l.M  IB^   Tl.ff>  S.M 


2.H  14 .4S  U.M     TM 


MS     B.GB   TB.M   10.17 


22.M     t.TB   SSJT   16.1 
4.M     S.01   TB.e>   IS.^ 


l.TB  27. BB  40.17  SOJl 


SS.71   Z8.EG  ZS.78      1.1B 

S.H  8B.BB  4B.7T      _.._ 
S.8S  40.91  48.11      E.SS 


T.SS  B7.a9  4G.BS     8.SS 


3.81  16.80  48.BS  20.18 

ZS.OS  ai.16  B4.01  8.88 

4.16  U.18  18.76  S.H 

B.£l  81.18  11.(8  S.8S 

6.00  24.80  (7.20  8.80 

S.IT  16.11  88.81  2.S1 

8.22  11.83  78.48  1.19 1 


1.88    4.87   B0.S3   1.B1 


l.n   4.W  80.69   1.S8 

1.04   4.48   81.86   1.21     6.26 
1.99   4.n  80.68   I.10      ■  - 


I  72.49   1.31      8.B> 


2.19  6.08  T9.S9  1.19  4.78 
1.29  4.99  7(.7t  1.11  140 
1.82    6.01  18.91   1.81     8.96 


0.48    2.E2   7S.BB  0.11     6.87     : 
0.67    Z.70  B«.81  0.91     8.66     : 


0.90   4.17   79.48    IM     4.19     : 


0.87  8.41  79.49  1.19  6.10 
0.78  6JS  78.78  l.M  1.81 
1.17    6.01  78.88   1.88     8.SB 

0.10  2.84  88.48  O.IB  21.49 
0.87    0.48  I —      -  — 

2.22    8.80   a 

I.Oe  4.97  16JZ  1.80  6.71 
1.14  8.19  74.91  1.81  10.19 
0.49   4.61   88.14   1.19     e.1i 

0.79  8.93  89.18  S.T2  41.11 
0.61  (.79  42.62   0.19  42.09 

1.71  6.48  71.28  1.62   18.46    1 

0.39  6.62  18.01  1.26   11.89 

6.St  6.1B  61.24  0.96   11.24 

1.41  6.79  81.40  1.09  26.11     : 

1.43  4.90  18.66  1.81     8.29 

0.68  6.16  71.98  1  —      "  ■■ 

0.63  6.82  80.13  1 

0.71  4.11  88.38  1 

0.62  G.69  79.89  1 

0.46  6.S0   84.79  1.(3   19.09    ; 

OJT     l.HI     SZ.1T     1.30     14JE8 

11.67 
8.6S 
36.99 


14,274 
18.180 
1S,»01 


(8.66  1 
83.86  I 
47.26 


0.89   6.01  83.86   1.91 


6.09   82.69   1.83     1.28 
6.01    84.11    1.68      E.89     : 


14,102 
14  «0 
14,884 


ly  Google 


T«Ue  6S.     Coropodtion  and  Heat  Value  of  United  State*  Coats — Cont. 


II  ll 


a.32  2t.SS  ti.n     tM 


3.80  14.60   TT.40     G.SS 

Z.30  1S.S8   TS.21      4.B1 

2.  IB  18.91   76.26 

tM  lajl   TS.36 

S.ZE  14.4e   TS.06 

£.66  1S.44  T8.BT 

2.SS  l«.n  «S.SO  1 

S.0O  11.00   TS.SO     6.ES 


1.40  2R.40   62.91     »xa 


1.12   20.74  70.88 


16.se   3S.01   4T.M     1.74 


UltlBMta  Analnla 
■■Am  RsMivS" 

till! 


0.80  6.2B  7B.7S  1.17     7.78 

1.86  4.70  77.ee  1.46      ■  '" 

O.ra  S.lfl  78.87  t.l« 

0.64  4.60  S8.3B  l.OS 

O.Se  4.80  B6.00  1.20     4.27 


.06  l.ll     6.4  S 


.02    1.48     6.04 


0.8S   6.64   60. 


0.88   e.29   64. 


G6.SI   0.76  83.17 
62.01   1.20  26.28 


B 


18,0*6 
14,687 
14.671 
14,600 
18,614 


18,087 

18,608 
14,400 


Table  66.     Commercial  SUeo  of  Anthracite  Coal. 


Pr«pu*l«iUi<u|au«- 

Prapwad  with  rooDd- 

atam 

'S- 

^■ 

■£§-■ 

4 

2H 

2 

m    '     .'ii^ 

Em 

Stove 

3W 

l^ 

Nut  (chestnut) . . 

Pea 

Buckwheat  No.  1 


IS  a  No.  4  Buckwheat  has  been  marketed ;  and  some  mines 
supply  "Birdseye"  which  is  practically  a  mixture  of  Nos.  2  and  3  Buck- 
wheats,  or   "through   ■/«   and   over   '/«." 


ib.  Google 


Hotel  Claridge,  New  York  City,  equipped  with  Heiiie  BoUen. 

.Google 


Society  of  Mechanical 

EASTERN  BITUMINOUS 
Lump  coal  must  pass  over  a  lJ4->n<  mesh  bar  screen. 
Nut   coal   must  pass   through   a    1^-in,   mesh,   and   over   a   H-'m. 

Slack  coal  must  pass  through  a  ^-in.  bar  screen. 

WESTERN  BITUMINOUS 
Lump  coal  comes  in  6-in.,  3-in.  and  Ij^-in.  sizes,  and  the  respective 
lumps  must  pass  over  circular  openings  of  corresponding  size.   Where 
the  lump  coal  is  sized  as  6  by  3  in.  and  3  by   I'A,   in.,  the  coal  must 
pass  through  the  larger  opening  and  over  the  smaller. 

Steam  nut  of  3-in.  si;!e  must  pass  through  a  3-in.  circular  opening 
and  over  a  Ij^-in.  mesh.  Nut  of  1'4-in.  size  must  pass  through  a 
I>^-in,  and  over  a  ^-in.  opening,  and  ^-in.  coal  musi  pass  through  d 
jii-in.  mesh  and  over  a  5^-in.  opening. 

Coal  screenings  must  pass  through  a  \%-'m.  round  mesh. 
In  the  coal  fields  "run-of-mine"  is  the  name  given  to  the  unscreened 
coal  taken  from  the  mine,  and  "culm"  is  the  residue  from  screenings,  in- 
cluding "silt"  and  other  anthracite  dust. 

Sampling  Coal 

SAM'PLES  taken  at  the  mine,  says  C.  S.  Pope,  are  generally  of  higher 
grade  than  those  obtained  from  the  average  commercial  shipments.  The 
former  contain  a  lower  percentage  of  ash  and  have  a  higher  heat  value. 
Persons  without  experience  generally  select  a  sample  better  than  the  average 
run  of  the  coal  delivered.  However,  an  experienced  collector,  by  using  good 
judgment,  can  obtain  samples  so  fairly  representative  that  the  results  of 
the  analyses  are   reasonably  accurate.. 

The  value  of  laboratory  analysis  has  been  questioned  largely  because  of 
ignorance  or  carelessness  in  taking  the  samples.  The  laboratory  test  makes 
use  of  one  gram— about  Vm  of  an  ounce — of  coal.  The  particles  of  roal  in 
this  sample  should  have  been  a  considerable  and  equal  distance  apart  in 
the  original  bulk  shipment.  A  representative  sample  can  be  obtained  only 
by  repeated  and  systematic  crushing,  dividing  and  discarding — such  as  is 
described  below. 

The  sample  should  contain  about  the  same  proportions  of  fine  and 
coarse  coal  as  well  as  foreign  matter,  such  as  slate  and  bone,  in  order  to 
show  the  quality  of  the  coal  delivered  as  a  whole.  To  this  end  portions  of 
coat  are  selected  from  all  parts  of  the  wagon,  car,  or  sbii>,  then  mixed  and 
systematically  reduced  to  the  quantity  required  for  analysis.  The  original 
or  gross  sample  should  weigh  500  lb.  or  more,  preferably  1000  to  2000 
pounds.  The  Bureau  of  Mines  has  established  a  lOGO-Ib.  sample  as  sufficient 
to  give  reliable  results  for  coal  comparatively  free  from  impurities.  For 
other  coals  a  larger  sample  is  required.  Increasing  the  size  of  the  gross 
sample  tends  toward  accuracy,  but  the  possible  increase  is  limited  by  the 
cost  of  collection  and  reduction.  A  separate  sample  should  be  taken  from 
each  500  tons  or  less  of  coal  delivered.  The  gross  sample  is  usually  reduced 
to  quantities  varying  between  2  to  S  lb.  and  then  sent  to  the  laboratory. 

Representative  samples  can  best  be  taken  during  the  time  when  the  coal 
is  being  loaded  or  unloaded.  Portions  of  10  to  30  lb,,  depending  upon  the 
Mze  and  weight  of  the  largest  pieces  of  coal,  should  be  systematically  taken 
with  a  shovel  or  a  specially  designed  tool.  The  mechanical  method  is  Pre- 
ferred to  shovel  sampling,  as  it  eliminates  the  personal  equation.  Care 
should  be  exercised  to  secure  equal  amounts  of  coal  from  near  the  top,  the 
middle  and  bottom  of  the  load.     Clean  boxes,  buckets  or  ash  cans  may 


ib.  Google 


be  used  for  holding  the  portions  o£  coal  that  make  up  the  gross  sample.  The 
receptacles  should  have  light-iitting  lids  which  can  be  locked,  to  prevent 
gain  or  toss  in  moisture  and  to  preserve  the  integrity  of  the  sample. 

The  next  step  is  to  prepare  the  1000  lb.  gross  sample  for  shipment  to 
the  laboratory.  Three  operations  are  involved :  crushing,  mixing  and  reduc- 
tion in  quantity.  These  can  be  done  by  mechanical  means,  using  a  so-cailed 
sample  grinder,  or  else  by  the  hand  method  described  by  the  Burean  of  Mmet, 
which  involves  six  stages.  Fig.  205,  to  obtain  the  final  5  lb.  sample. 

In  this  procedure  the  coal  must  be  broken  down  to  the  sizes  given  in 
Table  ^,  before  division  into  equal  parts.  The  lumps  can  be  crushed  with 
a  tamper,  maul  or  sledge,  on  a  hard,  clean,  dry  floor  free  from  cracks.  Other 
tools  required  are  a  shovel,  broom  and  rake ;  also  a  blanket  measuring  about 
6  by  8  ft.  The  coal  is  raked  while  being  crushed,  so  that  all  lumps  will  be 
broken.  The  floor  or  blanket  is  swept  clean  of  discarded  coal  after  each 
sample  has  been  divided  into  equal  parts.  The  space  where  this  is  done 
should  be  protected  from  rain,  snow,  wind  and  direct  sunlight. 


TaUe  67. 

Laigeat  Siiei  of  Coal  Allowable  in   Sample*. 

pSSSU 

B>unpkLb. 

Co>l.bi(tw 

1 

1,000 

I 

2 

^ 

3 

250 

4 

126 

6 

60 

0 

30 

A 

to  about  250  pounds.  Before  each  reduction  in  quantity  the  sample  should 
be  crushed  to  the  fineness  prescribed  in  Table  67. 

The  crushed  coal  is  shoveled  into  a  conical  pile  as  in  diagrams  2  and  7, 
by  depositing  each  shovelful  of  coal  on  top  of  the  preceding  one,  and  then 
formed  into  a  long  pile  as  follows : 

The  sampler  takes  a  shovelful  of  coal  from  the  conical  pile  and  spreads 
it  out  in  a  straight  line  as  in  diagrams  3  at  A  and  8  at  A.  the  width  being 
that  of  the  shovel  and  the  length  from  5  to  10  feet.  His  next  shovelful  is 
^read  directly  over  the  top  of  the  first  shovelful,  hut  in  the  opposite  direc- 
tion, and  so  on  back  and  forth,  the  pile  being  occasionally  flattened  until 
all  the  coal  has  been  formed  into  one  long  pile,  as  shown  in  diagrams  3  and 
Sat  B. 

The  sampler  then  discards  half  of  his  pile,  and  beginning  at  one  side 
of  the  pile,  at  either  end,  and  shoveling  from  the  bottom  of  the  pile,  takes 
one  shovelful  (No.  1,  in  diagrams  4  and  9)  and  sets  it  aside;  advanc- 
ing along  the  side  of  the  pile  a  distance  equal  to  the  width  of  the  shovel,  he 
takes  a  second  shovelful  (No.  2)  and  discards  iti  again  advancing  in  the  same 
direction  one  shovel  width,  he  takes  a  third  shovelful  (No.  3),  and  adds 
it  .to  the  first.  Shovelful  No.  4  is  taken  in  a  like  manner  and  discarded, 
the  fifth  shovelful  (No.  5)  is  retained,  and  so  on,  the  sampler  advanc- 
ing always  in  the  same  direction  around  the  pile,  so  that  its  size  will  be 
reduced   uniformly.    When   the   pile    is   removed,   about   half  the   original 


ib/Google 


coal  should  be  contained  in  the  new  pile  formed  by  the  alternate  shovelfuls 
which  have  been  retained.  The  retained  halves  are  shown  at  A  and  the 
rejected  halves  are  shown  at  B,  in  diagrams  5  and  10,  Fig.  205. 

After  the  gross  sample  has  been  decreased  by  the  above  method  to 
about  250  lb.,  the  quantity  is  further  reduced  by  the  quartering  method. 
Before  each  quartering,  the  sample  should  be  crushed  to  the  fineness  de- 
scribed in  Table  67. 

Quuitities  of  125  to  250  lb.  should  be  thoroughly  mixed  by  conbig  and 
reconing,  as  in  diagrams  12  and  13 ;  quantities  less  than  125  lb.  should  be 
placed  on  a  cloth  or  blanket,  measuring  about  6  by  8  ft.;  mixed  by 
raising  first  one  end  of  the  cloth  and  then  the  other,  as  in  diagrams  18,  24 
and  30,  so  as  to  roll  the  coal  back  and  forth ;  and  after  being  thoroughly 
mixed,  formed  into  a  conical  pile  by  gathering  the  four  comers  of  the 
cloth,  as  in  diagrams  19,  25  and  31. 

The  conical  pile  is  quartered  by  flattening  the  cone,  its  apex  being  pressed 
vertically  down  with  a  shovel  or  board.  The  flattened  mass,  which  must  be 
of  nnifonn  thickness  and  diameter,  is  then  marked  into  quarters,  as  in 
diagrams  14,  20,  26  and  32,  by  two  lines  that  intersect  at  right  angles  directly 
under  a  point  corresponding  to  the  apex  of  the  original  cone.    The  diagonally 


Fig.  206.     Bureau  of  Mines  Coal  Sample  Cotitainers. 

opposite  quarters,  B  in  diagrams  16,  22,  28  and  34,  are  shoveled  away  and 
discarded  and  the  space  that  they  occupied  brushed  clean.  The  co^  remain- 
ing is  successively  crushed,  mixed,  coned  and  quartered  until  two  opposite 
quarters  equal  approximately  10  lb.  of  Virinch  size.  This  10-lb.  quantity  is 
divided  into  two  equal  parts.  Each  part  is  immediately  sealed  into  a  container 
for  transportation.  One  of  the  samples  ii  forwarded  for  analysis  to  the 
laboratory  and  the  other  held  in  reserve,  should  the  sample  forwarded  be 
lost  or  damaged  in  transit. 

One  or  more  containers  can  be  used  for  this  purpose,  depending  upon 
the  quantity  they  will  hold.  Glass  jars  or  metal  cans  of  one  or  two-quart 
size  are  ordinarily  employed. 

The  Bureau  of  Mines  has  developed  two  sample  holders,  Fig.  206,  one 
8  ^Ivanized  iron  can  and  the  other  a  double  container  consisting  of  a  wooden 
dipping  box  and  an  inclosed  pressed-paper  case.  The  metal  can  is  II  in. 
long  and  i%  i"-  diameter,  inside  dimensions,  with  a  screw  cap  2  in.  diameter. 
The  capacity  is  lYi  to  3  lb.  of  coal,  so  tliat  two  cans  are  used  for  the 
laboratory  sample.  Before  filling,  each  can  should  be  carefully  inspected  as  to 
tightness  and  freedom  from  rust.  The  coal  should  then  be  carefully  packed 
in,  so  as  to  occupy  as  much  of  the  space  as  possible  and  exclude  the  air. 
This  can  be  accomplished  by  shaking  or  jarring  the  container  repeatedly  and 
vigorously  while  filling  it.  The  screw  cap  is  then  closed  against  a.  rubber 
washer.  To  insure  tightness,  the  cap  when  screwed  down  in  place  is  wrapped 
carefully  with  electrician's  rubber  or  adhesive  tape,  the  first  layer  of  which 
completely  covers  the  joint,  as  at  a  In  Fig.  206.  At  b  the  can  is  shown 
properly  sealed  and  ready  to  be  wrapped  for  mailing.  Solder,  paraffin  or 
seating  wax  should  not  be  used,  l>ecause  some  of  it  may  become  mixed 
with  the  coal,  either  when  it  is  applied  or  when  the  cap  is  removed. 


ib.  Google 


Fig.  205.     Preparation  of  Coal  Sample  by  Hand. 
(  Rfd  ttnitht  ten—  both  ptgn. ) 


ib.  Google 


Fig.  205.     Preparation  of  Coal  Sample  by  Hand. 
<  R—d  traighf  ickih  bath  pmie: ) 


D,g,tze:Jbi  Google 


In  the  double  container  shown  at  the  right,  Fig.  206^  f  is  the  pressed 
paper  case,  d  and  e  sections  of  the  wooden  box,  and  f  the  assembled  con- 
tainer. The  paper  case,  5%  in.  diameter  and  7  in.  long,  has  a  capacity  of 
S  to  7  lb.  of  coal.  The  shipping  box  is  made  of  well-seasoned  basswood 
with  lock-jointed  comers,  fully  reinforced.  Two  suit-case  catches  are  placed 
near  opposite  corners,  inside  the  box,  to  operate  in  either  of  the  two  possible 
ways  of  assembly.  Small  holes  are  drilled  through  opposile  sides  of  the 
box,  as  at  g,  and  through  a  small  part  of  the  catch  lug.  By  releasing  the 
catches  with  a  nail  inserted  in  the  two  holes,  the  box  is  easily  opened.  In 
using  this  container,  the  sample  of  coal  is  placed  in  the  paper  case  and  the 
edge  of  the  cap  is  seated  tight  with  adhesive  tape. 

With  each  container  sent  to  the  laboratory  for  analysis,  there  should  be 
a  ticket  bearing  the  name  and  address  of  the  plant,  the  date,  the  kind  and 
size  of  coal,  the  number  of  tons  represented  by  the  sample,  and  other  similar 
information.  This  form,  properly  Ailed  in,  can  be  placed  inside  the  container 
or  preferably  around  the  container  on  the  outside,  before  wrapping  for 
mailing.    A  copy  should  be  retained  for  reference  or  checking. 

Fuel  Analyus 

^T^HE  term  m^stnre,  as  used  in  fuel  analyses,  represents  the  loss  in  weight 
-'-  of  a  coal  sample  when  dried  for  a  given  time  at  a  given  temperature,  'nis 
is  taken  as  the  total  moisture  in  the  coal  received  at  the  laboratory. 

Volatile  matter  is  the  gaseous  combustible  matter  of  the  coal  and 
represents  the  hydrocarbons  and  other  gaseous  compounds  which  distill  o& 
on  application  of  heat,  as  well  as  some  incombustible  gases. 

Fixed  carbon  is  the  solid  combustible  matter  represented  by  the  uncom- 
bined  carbon  in  the  coal  or  the  carbon  remaining  after  distillation.  It  is 
not  pure  carbon  nor  is  it  the  total  carbon  in  the  coal,  for  a  part  of  the 
carbon  is  expelled  as  volatile  matter. 

Ash  is  the  incombustible  remaining  after  the  moisture  and  volatile  matter 
have  been  driven  from  the  coal  and  the  fixed  carbon  burned ;  it  is  the 
residue  left  from  complete  combustion  of  the  coal. 

These  four  items  are  set  forth  in  the  proximate  analysis,  which  may 
,  show  them  in  either  of  three  different  ways.  The  whole  four  items  may 
be  given  in  one  statement,  as  in  the  second  column  of  Table  68,  known  as 
"as  received."  The  moisture  may  be  stated  separately  or  ignored,  and  the 
other  three  items  given  as  in  the  third  column;  and  this  is  known  as 
"moisture  free"  or  "dry  coal."  The  ash  also  may  be  stated  separately,  and 
the  other  two  items  given  as  in  the  fourth  column,  known  as  "combustible" 
or  "moisture  and  ash  free." 

Table  68.     Proximate  Coal  Analysis  Statements. 


ICSf- 

^in^r 

"sr^"" 

10 
30 
60 
10 

100 

33.^ 
55.56 
11.11 

lOO.OO 

The  following  instructions  for  the  proximate  and  ultimate  analyses  of 
coal,  and  for  the  analyses  of  liquid  fuels  are  taken  from  the  1915  Code  of 
the  American  Society  of  Mechanical  Engineers. 


ly  Google 


Proximate  Analytis  of  Coal.  The  apparatus  re<iuired  for  proximate 
analysis  consists  of  a  mill  for  grinding  coal,  chemical  scales  sensitive  to 
Vhh  of  the  amount  weighed,  drying  apparatus,  a  platinum  crucible,  a  Bun- 
sen  burner  and  blast  lamp,  a  supply  of  oxygen  gas,  and  such  chemicals  and 
chemical  apparatus  as  may  be  required.  The  elements  to  be  determined  are 
moisture,  volatile  matter,  fixed  carbon,  ash  and  sulphur. 

Determine  the  loss  from  air-drying  and  the  total  moisture  in  the  ash 
as  received,  as  explained  elsewhere. 

To  determine  volatile  matter,  place  about  one  gram  of  the  air-dried 
powdered  coal  in  the  crucible  and  heat  in  a  drying  oven  to  220'  F.  for 
one  hour  (or  longer  if  necessary  to  obtain  minimum  weight),  cool  in  a  desic- 
cator and  weigh.  Cover  the  crucible  with  a  loose  platinum  plate.  Heat  7 
minutes  with  a  Bunsen  burner  giving  a  6  to  8  in.  flame,  the  crucible  being 
supported  3  in.  above  the  top  of  the  burner  tube  and  protected  from  outside 
air  currents  by  a  cylindrical  asbestos  chimney  3  in,  diameter.  Cool  in  a 
desiccator,  remove  the  cover,  and  weigh.  The  loss  in  weight  represents  the 
volatile  matter. 

In  the  V.  S.  Bureau  of  Mines  practice  a  1-gram  sample  of  fine  (60- 
mesh)  air-dried  coal  is  heated  to  a  temperature  of  1750°  F.  in  a  plat- 
inum crucible  with  a  close-fitting  cover  for  seven  minutes  over  a  No,  3 
Ueker  burner  giving  a  flame  16  to  IS  cm.  high.    The  crucible  is  placed 
so  that  its  bottom  is  2  cm.  above  the  top  of  the  burner.    To  protect 
the  crucible  from  the  effects  of  drafts  it  is  surrounded  by  a  sheet  iron 
chimney  of  special  design.     The  loss  in  weight  minus  the  weight  of 
moisture  determined  at  220°  F.  represents  the  volatile  matter. 
To  ascertain  the  ash,  expose  the  residue   in  the  crucible  to  the  blast 
lamp  until  it  is  completely  burned,  using  a  stream  of  oxygen  if  desired  to 
hasten  the  process.    The  residue  left  is  the  ash. 

The  Bureau  of  Mines  determines  the  ash  in  the  residue  from  the  mois- 
ture determination.  The  moisture  is  determined  by  heating  1  gram 
of  the  60-mesh  air-dried  coal  in  a  porcelain  crucible  for  one  hour  at 
220°  F.  in  a  constant  temperature  heating-oven.  To  determine  the 
ash,  the  crucible  is  heated  slowly  in  a  muffle  furnace  until  the  volatile 
matter  is  driven  off.  Ignition  in  the  muffle  is  continued  at  a  tempera- 
ture of  1380°  F.,  with  occasional  stirring  of  the  ash  until  all  the  par- 
ticles of  carbon  have  disappeared.  The  crucible  is  cooled  in  a  desic- 
cator, weighed,  heated  again  for  half  an  hour,  and  weighed  again. 
The  process  is  repeated  until  the  variation  in  weight  between  two 
successive  ignitions  is  0.0005  gram  or  less. 
The  difference  between  the  residue  left  after  the  expulsion  of  the  volatile 
matter  and  the  ash  is  the  fixed  carbon. 

To  determine  sulphur  by  Eschka's  method,  which  is  the  one  com- 
monly used,  a  sample  of  60-mesh  coal  weighing  1.3736  grams  is  mixed  in  a 
30  cc.  platinum  crucible  with  about  2  grams  of  Eschka  mixture  (2  parts 
light  calcined  magnesium  oxide,  1  part  anhydrous  sodium  carbonate)  and 
about  1  gram  of  the  Eschka  mixture  is  spread  over  it  as  a  cover.  The  mixture 
is  carefully  burned  out  over  a  gradually  increasing  alcohol  or  natural  gas 
flame.  When  all  black  particles  are  burned  out  the  crucible  is  cooled,  the  con- 
tents digested  with  hot  water,  filtered,  washed,  and  the  solution  treated  with 
saturated  bromine  water  and  hydrochloric  acid,  boiled,  and  the  sulphur  pre- 
cipitated as  barium  sulphate  by  adding  a  solution  of  barium  chloride. 

Ultimale  Analysis  of  Coal.  The  apparatus  required  for  ultimate  analysis 
consists  of  a  mill  and  other  apparatus  for  grinding  and  pulverizing  the  coal; 
chemical  scales  sensitive  to  '/«■  of  the  amount  weighed;  drying  apparatus; 
combustion  apparatus,  embracing  a  combustion  furnace,  a  glass  combustion 
tube  one  end  of  which  is  filled  with  copper  oxide  and  chromate  of  lead  and 
the  other  end  with  a  roll  of  oxidized  copper  gauze,  a  porcelain  boat,  a  set  of 


ib.  Google 


ib.Google 


bulbs  containing  hjrdrate  of  potassium,  a  U-tube  filled  with  chloride  of 
calcium,  and  a  supply  of  pure  oxygen  and  pure  air;  together  with  suitable 
chemicals  and  chemical  apparatus  required  for  the  various  processes.  The 
elements  to  be  determined  are  moisture,  carbon,  hydrogen,  oxygen,  sulphur, 
nitTMcn,  and  ash. 

The  moisture  is  determined  in  the  manner  as  pointed  out  above. 

The  carbon  and  hydrogen  are  obtained  by  the  use  of  the  combustion 
apparatus.  One-half  gram  of  the  pulverized  oven-dried  coal  is  placed  in  the 
porcelain  boat,  which  is  introduced  between  the  copper  roll  and  the  copper 
oxide  within  the  combustion  tube.  After  the  contents  within  have  been  thor- 
oughly dried  out  by  a  sufficient  preliminary  heating  aided  by  a  current  of 
dry  air,  the  furnace  is  set  to  work  and  the  coal  burned  by  first  passing  air 
through  the  tube  and  finally  oxygen,  conducting  the  products  of  combustion 
through  the  potash  bulbs  and  the  chloride  of  calcium  tube.  The  carbon 
dioxide  produced  by  the  combustion  of  the  carbon  is  absorbed  by  the  potash, 
and  the  water  formed  by  the  combustion  of  hydrogen  is  taken  up  by  the 
chloride  of  calcium.  The  quantity  of  carbon  is  determined  by  weighing  the 
bnlbs  before  and  after,  thereby  obtaining  the  weight  of  the  carbon  dioxide 
produced,  and  then  calculating  the  weight  of  carbon  from  the  known  compo- 
sition of  the  dioxide.  Likewise,  the  quantity  of  hydrogen  is  determined  by 
weighing  the  calcium  tube  before  and  after,  which  gives  the  amount  of  water 
produced,  and,  dividing  by  9,  the  amount  of  hydrogen. 

Sulphur  is  found  by  the  method  described  above  under  the  heading 
Proximate  Analysis. 

To  determine  nitrogen,  a  certain  weight  of  coal  is  mixed  with  strong 
sulphuric  acid  and  permanganate  of  potash  and  heated  until  nearly  colorless. 
This  process  converts  the  nitrogen  into  ammonia  and  then  into  sulphate  of 
ammonia,  and  the  amount  of  sulphate  is  determined  by  making  the  solution 
alkaline  and  then  distilling  it  The  nitrogen  is  found  by  calculation  from  the 
known  composition  of  ammonia. 

The  ash  is  found  by  weighing  the  refuse  left  in  the  combustion  boat 
after  the  coat  is  completely  burned. 

The  oxygen  is  the  difference  between  the  sum  of  the  elements  previously 
determined  and  the  original  weight  of  coal. 

The  ultimate  analysis  of  coal,  as  will  be  seen  from  the  above  descrip- 
tion, requires  the  use  of  so  much  chemical  apparatus,  and  at  best  it  is  so  com- 
plicated that  it  is  not  likely  to  be  done  except  in  a  fully  equipped  chemical 
laboratory.  It  should  not  be  undertaken  by  one  who  is  not  entirely  familiar 
with  all  the  details  of  the  work. 

Analysit  of  Liquid  Fuels.  The  determination  of  carbon  and  hydrogen 
in  liquid  fuels  is  made  in  the  same  manner  as  that  concerning  the  solid  fuels 
above  described,  using  special  means  for  preventing  loss  in  the  various 
processes  on  account  of  the  volatile  characteristics  of  the  fuel. 

To  determine  the  sulphur,  the  oil  or  other  liquid  is  heated  with  nitric 
acid  and  barium  chloride.  The  quantity  of  sulphate  of  barium  thus  produced 
is  ascertained  by  filtering  and  weighing,  and  the  sulphur  calculated  from  the 
known  com^sition  of  the  compound. 

The  ullimate  analysis  of  Ikjuid  fuel,  like  that  of  coal,  should  be  under- 
taken only  by  a  person  familiar  with  all  the  necessary  details. 

Heat  Value  of  Coal 

'The  heat  value  of  coal  is  represented  by  the  heat  units  liberated  by 
'■  perfect  combustion  and  is  usually  expressed  in  British  thermal  units 
per  pound  of  fuel.  This  value  can  be  approximated  from  either  the  proxi- 
mate or  ultimate  analysis. 

From  its  proximate  analysis  the  B.t.u.  value  of  one  pound  of  coal  is 
given  by  Lucke  as: 


ib.  Google 


B.tu.  =  14.544  c  + 27.000  w(  -^  +  OS    ) 


CS7) 


in  which  e  and  v  are  the  [raciianal  weights  of  fixed  carbon  and  volatile, 
respectively,  in  the  coaL 

From  its  ultimate  analysis  the  B.tu.  value  of  coal  can  be  approximated 
by  the  Dulong  formula : 

B.t.u.  =  14,544 C  + 62.028  ^W—-|-)+  MSfi  S  (58) 

in  which  C  is  carbon,  H  is  hydrogen.  0  is  oxygen  and  S  is  sulphur,  expressed 
as  the  fractional  part  of  one  pound  of  coaL 


Rg.  207.     Heat  Value  of  Coal  by  Proximate  Analyiii. 

Based  on  the  proximate  analysis  of  samples  of  coals,  Wm.  Kent  has  estab- 
lished a  relation  between  the  heat  value  and  the  fixed  carbon  as  well  as  the 
volatile  matter  in  the  combustible,  as  shown  in  Fig.  207.  The  figures  give  a 
useful  approximation  and  are  correct  within  the  indicated  limits. 


Fig.  308.     Heat  Value  of  Coal  by  Ultimate  Anoly^. 


ib.  Google 


A  graphical  method  of  determining  the  heat  value  of  coal,  developed  by 
(f,  C,  Siripe,  is  shown  in  Fig.  208.  The  diagram  is  based  on  the  ultimate 
analysis  and  corresponds  with  the  formula  by  Dulong,  given  above.  Knowing 
the  constituents  of  the  coal  from  the  ultimate  analysis,  connect  the  values  on 
the  left-hand  scale  with  the  diagonals  as  shown  by  the  dotted  lines,  and  read 
the  results  on  the  lower  scales.  The  sum  of  the  three  determined  values  wilt 
give  the  total  approximate  heat  value  of  the  coal. 

Fig.  208  is  for  a  coat  containing  79.9  per  cent  carbon ;  4.98  per  cent 
hydrogen;  4.31  per  cent  oxygen;  1.8S  per  cent  nitrogen;  1.13  per  cent 
sulphur ;  7i<3  per  cent  ash  and  2.91  per  cent  moisture.  The  dotted-arrow 
lines  show  that  the  carbon  represents  11,660  B.t.u. ;  the  hydrogen,  for  the 
oxygen  content  given,  represents  2,750  B.t.u. ;  and  the  sulphur  represents 
45  B.t.u.  Adding  these  values  gives  14,455  B.t.u.  as  the  approximate  heat 
value  of  the  coal. 

A  more  direct  and  accurate  method  of  determining  the  heat  value  of 
coal  ij  by  a  fuel  calorimeter  of  the  "bomb"  type.  A  sample  of  the  coal  is 
burned  in  the  bomb  or  combustion  chamber,  which  is  immersed  in  water.  The 
heat  of  combustion,  transmitted  to  the  water,  raises  its  temperature  and  from 
this  rise  the  heat  value  of  the  coal  is  calculated. 

Mahler  Coal  Calorimeter 
T^HE  Mahler  coal  calorimeter  consists  essentially  of  a  strong  cylindrical 
■^  vessel  having  a  capacity  of  about  800  cc,  which  is  closed  at  the  top 
and  filled  with  oxygen  gas.  under  a  pressure  of  300  lb.  per  sq.  in.  A  sample 
of  finely  powdered  coal  which  will  pass  through  a  100-mesh  sieve,  weighing 
about  1  gram,  is  placed  in  a  pan  suspended  within  the  interior  vessel  pro- 
vided with  two  electrodes  through  which  an  electric  current  from  a  battery 
can  be  passed.    The  whole  is  immersed  in  an  outer  vessel  containing  about 


Pig.  209.     Mahler  Bomb  Calarimeter. 

2500  grams  of  water,  thoroughly  stirred,  the  temperature  of  the  water  ob- 
served,  the  coal  set  on  fire  by  completing  the  electric  circuit,  the  water 
again  stirred,  and  the  temperature  observed  at  intervals  of  half  a  minute 


ib.  Google 


ib.Google 


until  the  thermometer  ceases  to  rise.  The  difference  between  the  initial 
and  final  temperatures  thus  determined  is  corrected  for  radiation,  the  latter 
being  found  by  observing  the  rate  at  wbicb  the  temperature  changes  before 
and  after  the  coal  is  fired. 

The  weight  of  water  contained  in  the  outer  vessel  is  added  to  the  water 
e<iuivalent  of  the  apparatus,  and  the  sum  of  the  two  is  multiplied  by  the  cor- 
rected rise  of  temperature  expressed  in  deg.  cent.  The  heat  generated  in 
burning  the  fuse  wire,  the  heat  due  to  the  formation  of  aqueous  nitric  acid, 
and  that  due  to  the  combustion  of  sulphur  to  sulphuric  acid,  are  subtracted 
fiom  this  product.  The  remainder,  divided  by  the  weight  of  fuel  expressed 
in  grams,  is  the  heat  of  combustion  expressed  in  gram-calories  per  gram. 
This  result  is  multiplied  by  1,8  to  convert  to  heat  of  combustion  expressed 
m  B.tu.  per  lb.  ' 

The  correction  for  iron  fuse  wire  is  1.6  calories  per  milligram.    The 
c  acid,  which  is  obtained  by  titrating  the  washings 
a  solution  (0.0Q587  ^rams  of  NH.  per  cc)  is  5 
;.  of  the  ammonia  solution.    The  correction  for  sul- 
s  barium  sulphate  is  13  gram- 

The  sample  used  for  the  calorimeter  test  should  be  powdered  and 
air-dried  at  the  temperature  of  the  room.  A  duplicate  sample  should  be  taken 
for  the  determination  of  the  moisture  in  this  air-dried  coal  by  heating  in  a 
drying  oven  to  220°  F.  for  one  hour  (or  longer. if  necessary  to  obtain  mini- 
mum weight),  cooling  in  a  desiccator  and  weighing.  The  results  obtained 
on  the  calorimeter  test  should  be  corrected  for  the  moisture  thus  found 
and  reported  as  being  referred  to  dry  coal. 

Ash 
A  SH  is  a  mechanical  mixture  of  silicates,  oxides  and  sulphates.  The 
^*-  composition  of  ash  in  different  coals  is  given  in  Table  69,  due  to 
/.  S.  Cosgrove.  The  amount  of  ash  in  coals  varies  with  the  locality  of  the 
mine,  and  for  coal  from  the  same  district,  with  mining  conditions.  Depend- 
ing on  the  kind  and  size  of  coal,  the  ash  content  is  from  3  to  25  per  cent. 
The  nominal  amount  of  ash  is  that  contained  in  the  face  sample  of  coal 
taken  from  the  seam  proper ;  this  amount  is  usually  increased  by  ash  added 
from  the  roof  or  bottom  in  the  course  of  mining. 


Table  69.     Compotition  of  ConatituenU  In  Percentage  of  Total  Aah. 


S«iii- 

BltnmiDou. 

(■)                 (b> 

ISrsiSS".'""'':: 

0.17 
25.66 

l.M 
27.03 
42.83 

11.83 

1.00 
54.80 

1.40 
29.20 
6.80 

o.eo 

2.10 
1,00 
7.50 

0.10 
47.30 

1.20 
34.60 
9,80 

0.40 

2.50 
2.10 
17.40 

28.90 
16.20 

18.10 
8.60 
13.30 

10.00 

1.80 
5.30 
8.20 

0.40 
53.20 

1.00 
26.00 
15.80 

0.70 

1.60 
0.30 
11.40 

12,60 

Calcium  Oxide  (Lime) 

Iroa Oxide  (FeiO,).... 
MasneAum  Oxide 

24.08 
3.80 

Sodium  Oxide  (NaiO) 
Toul  Ash,  per  cent  . . 

'■7;26  ' 

0.10 
16,60 

ib.Google 


Run  of  mtM  and  prepared  sizes  of  coal  made  over  a  l^>in.  screen  can 
be  improved  by  removing  the  excess  ash  by  hand.  Impurities  amounting 
to  12  per  cent  have  been  taken  out  in  this  manner.  It  is  advisable,  therefore, 
to  wash,  screen  or  hand-pick  the  impurities  before  shipping  the  coal. 
According  to  L.  J.  Joffray,  the  washing  of  coal  at  the  mine  will  reduce 
the  excess  ash  in  screenings,  so  that  the  heat  value  approaches  that  of 
lump  bituminous,  as  shown  by  these  figures : 

Ash  per  cent.     B.tu.  per  lb. 

Dry  or  unwashed  screenings „...       22.61  8.K>5 

Washed  screenings. _„ 14.0S  10,085 

Lump 12.39  10.499 

These  are  actual  values  and  refer  to  coal  taken  from  one  mine  in  the 
Central  West. 

The  relation  between  ask  eonlcnl  and  heal  valve  can  be  established  for 
any  particular  coaL  fig.  210  has  been  determined  by  M.  B.  Smith  on  a 
basis  of  1800  samples  of  Hocking  Valley  slack  coal.  The  samples  came 
from  20  different  mines  and  were  tested  over  a  long  period.  It  is  staled  that 
the  figures  in  the  diagram  agree,  within  10  to  50  B.tu.,  with  actual  calo- 
rimeter tests.     The  average  proximate  analysis  of  this  coal  is: 

_ 52j60 

34.20 

13  20 


I4p00 

~ 

~ 

~ 

~ 

~ 

, 

' 

N 

HOOO 

s 

58 

S.1%000 

S 

\ 

V 

s 

s 

s 

S 

0 

0 

5 

3 

0 

29 

At*  if  Ory  Coa/,  ^remt 
Fig.  210.     Relation  between  Heat  and  Ash  Content. 


ib.  Google 


The  ei-at'oralton  is  related  to  ash  content  as  shown  in  Fig.  211,  due  to 
W.  N.  Polakov.  With  an  increase  of  ash  the  evaporation  falls,  rapidly  at 
first  and  more  slowly  when  the  percentage  is  high.  Large  excess  of  air 
and  additional  losses  due  to  frequent  cleaning  accompany  the  use  of  coal 
of  high  ash  content. 


4' 

\ 

"   c 

i  u    V 

c*              '  >— 

f ..      C 

'        V 

I         J      . . 

1 ''        c  ^^ 

?  ..         i 

^               ^ 

in                A     ^ 

S                                             -o-  t_                                                                       1 

f «          ^ 

-.s 

,..          -.^^     ^  _ 

11                 ^s 

s^ 

70  t— 1— 1 "^--^ 

Alh  in  Dry  Coal,    percent. 


Clinker 

/"^LINKER  is  formed  by  the  mechanical  adhesion  of  the  particles  of  ash, 
^^-'  or  by  the  fnsion  of  the  ash  to  form  slag.  Some  of  the  constituents  of 
ash  act  as  alloys  and  form  a  fused  mass  of  clinker  known  as  "running 
ashes,"    Clinker  can  be  classified  as  "hard"  and  "soft"  by  these  character- 

Hard  clinker  is  the  result  of  the  direct  melting  of  the  ash  or  some  of 
its  components.  When  due  to  the  fusing  of  the  ash,  the  clinker  will  form 
a  large,  hard  cake.  When  due  to  the  melting  of  some  of  the  ash  constit- 
uents the  clinker  will  be  distributed  throughout  the  ash  in  the  form  of  small 


ib.  Google 


ib.Google 


hard  chunks.  Harii  clinker  hardens  while  in  the  ash  on  the  grates.  It  is 
usually  the  direct  result  of  bad  firing  methods. 

Soft  clinker  is  not  directly  chargeable  to  poor  firing,  but  poor  firing 
may  start  the  formation  and  hasten  the  spread  of  clinker.  Soft  clinker  is 
caused  by  the  slagging  of  the  ash,  that  is,  the  silica  of  the  ash  combines 
with  the  base  having  the  lowest  fusing  temperature.  After  having  formed, 
the  clinker  continues  to  grow  until  the  whole  grate  is  covered.  In  appearance 
it  is  not  unlike  hard  clinker,  having  a  crust  on  top  although  fluid  beneath 
the  surface.  Soft  clinker  varies  in  consistency  from  a  thick  paste  to  a 
heavy  oil ;  the  more  fluid  it  is,  the  faster  it  spreads,  remaining  molten  while 
on  the  grate  but  hardening  when   the  temperature  is  lowered. 

Fusion  of  Ask.  For  the  constituents  of  ash,  the  fusing  temperatures  (in 
degrees  Fahrenheit)  are  as  follows : 


Sulphur  (S)... 


....2840    Magnesium  oxide  (MgO).-.38S2 

s  (except  sulphur)  are  higher  than  those  found 


All  the  fusing  lemperatur 
in  a  boiler  furnace. 

The  effect  of  clinker  is  shown  in  Fig.  212,  due  to  /.  P.  Sparrow.  The 
tests  were  made  on  boilers  equipped  with  standard  stokers.  The  efficiency 
remained  constant  up  to  2335  degrees.  Above  this  the  efficiency  increased 
rapidly  with  a  small  rise  in  temperature,  but  beyond  2475  deg.,  the  efficiency 
remained  constant  up  to  2900  degrees.  The  critical  point  of  ash-fusion  is 
between  2400  and  2S0O  degrees.  If  the  ash-fusion  temperatures  are  balow 
2400  deg.,  the  coals  are  classed  as  clinkering,  and  if  above  2500  deg?,  as 
non-cltnkerin^.  The  standard  ash-fusion  temperature  is  taken  as  2450  deg.. 
with  a  variation  of  50  deg.  plus  or  minus. 


^^D 

0 

il 

o 

r" 

/ 

o 

■ 

/ 

"  ^ 

o 

£ 

/ 

1 
J" 

/ 

/ 

"1201)      2100  1400 

Ath  Fusion  Tempcrafi 


Z700 
deg.  Fshr. 
Fig.  311.     Effect  of  CUnker  on  BfRdency. 


The  clinkering  behavior  of  coal  is  indicated  in  Table  70,  due  to  L.  J. 
Joffray,  which  gives  results  from  bumtRE  tests.  The  coals  with  non-dinkering 
ash  listed  in  the  table  were  low  in  sulphur  and  in  lime,  and  did  not  clinker 
at  2900  deg.  in  a  dazzling  white  fire.  The  ash  in  the  clinkcring  coals  fused 
at  a  temperature  of  2200  deg.,  because  the  sulphur  and  lime  content  were 


ib.  Google 


high  in  proportion  to  the  silica,  alumina,  and  the  iron  oidde.  Stilplinr 
content  alone  does  not  indicate  that  the  coal  may  clinker,  although  with 
normal  ash  content  and  4  per  cent  or  more  sulphur,  the  coals  listed  have 
such  a  tendency. 

Table  70.     Aah  Behavior  of  Coal  from  I1Uq<^  and  Indiana  Mine*. 


T«( 

A<hta 
DryCo^. 

PWMlt. 

SuMutf. 
par  not. 

>r 

CUnkw 

Color  of  A*k 

1  9.63 

2  10.30 

3  10.00 

0.64         '        12,325 
1.30         1         12,136 
1 .  19         1        12.368 

No              White 
No         1    White 
No         1    Light  Gray 

4 
5 
S 

12.73 
11.80 
13.85 

2.96 
4.43 
4.02 

12.389 
11,768 
11.842 

Ye. 

Slightly 

Reddish  Gray 
Reddbh  Gray 
Reddish  Gray 

7  1       12.80 

8  17.96 

9  '         8.48 
10     ]       12.49 

4.52 
4.58 
1.47 
4.50 

11,693 
11.124 
12,251 
11,921 

Y«, 

Ves 
No 
Yes 

Reddish  Gray 
Reddish  Gny 
White 
Dark  Gray 

Investigations  of  the  Bureau  of  Minct  on  the  fusibility  of  ash  have 
been  compiled  in  Table  71.  The  softening  temperatures  represent  the 
average  point  of  fusion.  In  making  the  tests,  the  ash  samples  were  molded 
into  solid  triangular  pyramids  ^-in.  high  and  ii'isi.  along  (he  base.  These 
were  mounted  in  a  vertical  position  and  fused  down  to  a  spherical  lump. 
The  values  thus  obtained  in  the  laboratory  are  said  to  be  comparable  witti 
those  obtained  in  the  actual  boiler  furnace. 

The  softening  temperatures  in  Table  71  vary  from  1900  to  3100  degrees. 
Above  2400  deg.,  little  trouble  should  be  experienced  from  clinkering.  The 
temperatures  have  been  grouped  into  three  classes,  as  follows:  (1)  Refrac- 
tory ashes  softening  above  ^00  deg.  (2)  Ashes  of  medium  fusibility,  soft- 
ening between  2200  and  2600  deg.  (3)  Easily  fusible  ash,  softening  below 
2200  deg.  The  coals  of  high  softening  temperatures  are  from  the  lower  or 
older  beds.  The  bituminous  fields  of  Pennsylvania,  however,  give  a  more 
refractory  ash  than  similar  beds  in  West  Virginia.  The  ash  from  the  anthra- 
cite districts  is  very  refractory  and  the  softening  temperatures  are  usually 
above  3000  degrees. 

The  softening  or  fusing  temperature  of  ash  is  a  measure  of  its  clink- 
ering qualities,  although  seldom  included  in  coal  specifications.  This  is 
undoubtedly  due  to  the  many  difficulties  surrounding  the  temperature  deter- 
mmation.  and  to  the  fact  that  no  definition  of  melting  temperature  has  been 
accepted  as  standard. 

Clinkering  in  boiler  furnaces  is  due  to  thick  or  heavy  fires,  excessive 
stirring  of  fuel  beds,  live  coals  in  ashpit,  too  much  slack  in  the  coal, 
closed  ashpit  doors,  or  to  the  admission  of  pre-heated  air  under  grates. 

With  thick  fires  the  air  supply  is  decreased,  so  that  the  ash  becomes 
heated.  In  an  atmosphere  furnishing  oxygen,  the  melting  point  of  ash  is 
higher  than  if  it  is  heated  in  a  reducing  atmosphere.  A  considerable  thick- 
ness of  ash  is  mixed  with  the  burning  coal  in  the  thick  fuel  bed,  and  on 
account  of  the  lower  air  velocity,  a  reducing  zone  exists  near  the  grate. 
In  the  thin  (ire  the  reducing  zone  is  confined  to  the  last  inch  or  two,  at  the 
top,  where  the  few  ash  partides  are  separated  and  cannot  fuse  into  clinker. 


ib.  Google 


Table  71. 

FiwiUlity  of  Aoh  from  the  Co«U  of  the  United  State*. 

ALABAMA 

P«ro«ntia 

LocMteD  ud  B>d 

¥ 

Dry  Cod 

Luotkai  ■Bd  IM 

^Sr  ;i 

.A. 

ot 

of 

Sulphur 

Black  Cieek 

2^0     3.31 
2.3S0     8.68 
2,250     4.35 
2,240     6.M 
2.460   11.61 
2,430      S.91 
2,690      9,81 
2,120      7.45 
2,830      9.90 

0.83 
1.06 
I.IG 
0.73 

1.67 
0.46 
0.67 
2.80 
0.74 

Maykne 

Montevailo 

Nickel  Plate 

2,350 
3,330 
2.620 
2,430 
2.230 
2.340 
2.370 
3,130 

8.29 
7.24 

4.73 
5.49 
8.85 
7.45 
13.90 
8-62 

0.4S 

CoalCily 

0.75 

HarkDMH 

Upper  Straven. , 
YeflowCrwk.... 
Youi^blood 

0.52 

j^on;.;.;::; 

MmryUt 

I. OS 

Hartahorne. . 

No.  1  Bed , . . 
No.  2  Bed. . . 
No.  6  Bed... 

No.  3  Bed... 
No.  4  Bed... 
No.  6  Bed... 

Bevier 

Cherokee 


2,lia  11.74 
9.97 
10.84 


2,120      9.80      2.99 


KKNTUCKY 


No.  6  Bed 
No.  9  Bed 
No.  to  Bed 
No.  11  Bed 
No.  12  Bed 

Alum 

EUdwrn.... 
FuvClay... 

Flag 

Ibrian 

Hazard 


2.97  Jellico 

3,67  Kelliota...... 

4. 18  Lower  Boiling. 

4.08  Lower  H«nite 

2.3U  LowerStandiford 

O.ei  Mason 

0.68  Miller  Creek... 

0.82  Poplar  Lick.... 

0,83  Raw) 

0.85  Straight  Creek. 

0.79  ThacTrer 

1.07|  Upper  Hance. . . 
U    .       


ib.  Google 


¥ 

STcU? 

Lontlvo  ud  B«l 

a,^,^          DfT(iu 

LotrtloD  ud  B«d 

^ 

Sulpbu 

X^   ^ 

or 

BakerMown 

Btuebaugh 

Bnuh  Cnxk.  .  .  . 

3.560 
2.770 
2,470 
2.2S0 
2,410 
2,140 
2.490 
3.010 
2,1«0 

10.26 

12.09 
9.61 
9.61 
8.48 

12.16 
8.23 
7.96 

20.51 

1.70 
1.03 
1.26 
2.42 
1.36 
3.33 
1.22 
1.18 
4.11 

Lower  Kituning. 

Mercer 

Pittrf>ursh 

Quakertown 

Split-Six 

Upper  Freeport.. 
Upper  Kittaning. 
Upper  Scwickky. 

2.440    10.76 
2,020    18.14 
2,930     7.67 
3.010    17.x 
2.220    12  Ai 
2,600   10.72 
3,010     9.60 
2,840     6.06 
2.410    13.76 

2.26 
3.28 
1.03 

Franklin 

Gallitzen 

Grantsville 

Uttle  Pittsburgh 
Lower  Freeport. . 

2.66 
2-08 
0.86 
1.00 
2.58 

Bevier 

Cainaville 

Cherokee 

LexinKton 

Lower  Richhill 


Lower- Wdr- 
Pittrinirgh 

Mulberry 

Milky 

Richhill 

Tebo 

Waveriy 


1.940 

10.78 

1.9ff 

14.5* 

1,941 

U.K 

1.971 

15.4^ 

2,041 

11.64 

2,020 

17.43 

4.45 
3.18 
S.25 
6.12 
4.66 
8.29 


^Mahoning. . . 
Meigs  Creek, 
Middle  Kittaning 


2.120 
2.280 
2,120 
2.040 
2.330 
2.450 


9.56 
0  24 
6.69 
13.02 


Pittsburgh 

2.210 

8.47 

Uniontown 

16.  iq 

Upper  rreeport.. 
Wayn«£urg 

2.280 
2,520 

8.4a 

21.90^ 

2.400 

15.92^ 

Henryetta . . , 
Lehi^  Coal. 
Lower  Hart- 
McAllister.  . . 


8.05 
8.08 
11.46 


McCurtain. 

Pananui 

Stigler 

Upper  Hart' 


PENNSYLVANIA  (] 


Bl0«B 

Broakville 

Fuhon 

Little  Pittaburgh. 
Lower  Freeport. . 


Lower  Kittaning. 
Middle  Kittaning 

Pittsburgh 

Upper  Freeport. . 
Upper  Kittaning. 


1.43 
2.13 
2.16 


ib.  Google 


Table  71.    PurilMlity  of  Ash  from  the  Cool*  of  the  United  States— Cont. 


^^S^" 

Sotfa- 

^^^? 

A 

^ 

^ 

.4^ 

East  Schuylkill.. 

Hazelton 

Pitt9ton 

Plymouth 

2.990 
2.960 
3.010 
3.010 

n.19 

14.50 
6.08 
12.52 

0.84 

Scranton 

Shamokin 

West  Schuylkill.. 

3,010 
2,960 
2.730 
3.010 

12.39 
16.59 
18.0? 
13,17 

0,79 
0.90 
0.82 
0.78 

TENNESSEE 


No.  4  Bed... 
No.  10  Bed... 

Angel 

Battle  Creek. . 

BillyKoat 

Blue  Gem 

Bon  Air  No.  2. 
Caatle  Rock... 

Coal  Creek.'. . ! 
Frozen  Head . . 
Grassy  Ridge  , 

m^.'.'.'.'.'.'.. 

Kelly"-'.."!!! 
Lower  Dean... 
Mingo 


2.220  9.08 
2,150  11.42 
6.80 


10.27 
10.78 
7.11 


2.320 
2,63r 
2.3401     3.69 


Monarch 

Morgan  Spring, 
Mud  Slip 

OldEagie.'.'.!!! 

Old  Etna 

Paint  Rock... 
Poplar  Lick. . . . 

Red  Ash 

Rex  Bed 

Richland 

Rich  Mountain 
Sandstone  Part- 
ing  

Soddy. ..".!!!!! 

Upper  Dean — 
WaUon  Ridge.. 


1.16 
2.29 
0.92 


No.  4  Bed.  . 


Big  Bed 

Big  A.,  No.  2.. 
BigTownhitl... 

"C'  Bed 

Clintwood 

Duncan 

Glamorgan 

Imboden 

Jawbone 

Kennedy 

Laree  Bed 

Little  Townhill. 


I  2,180{  6.68 
2,42q  17.73 
2,420  19.89 
2,32ffl  6.34 
2,240  11.84 
2.210  10.26 
2.67(H  3.26 
"  '  6.65 
6.86 
2.420  11.47 
19.86 
,  7.95 
i  20.19 
8.40 


Little  Bed 

Lower  Banner. . . 
Lower  Btnling... 

Meadow 

Milner 

Mohawk 

Pardee 

Pocahontas  No.3 
Pocahontas  No.5 
Red  Ash 

Splash  Dam 

Upper 

Upper  Banner.. . 


3.010 
2.2S0 
2.72C 
2,480 


2,240 
3,010 
2,720 
3,010 
2,420 


8.74 
12,92 
5,89 
3,4,9 
8,04 
4,26 
5,19 
6-96 
42,98 
6.77 
29,72 
6.43 


0,49 
0.72 

1.12 


0.64 
0,34 
0.65 
0,38 
0.67 


ib.  Google 


Table  71.     FiuiUlity  of  A*h  from   the  Coala  of  the   United  Statea — Cont. 


3ott—        I»vCo.l 

LoaUoDiBdBod 

Soft—         D^cU? 

LowUon  ud  Bad 

SolphOT 

€^   A 

of 

S«lpbar 

No.2Gaa. 

2,760     5.86 
2,800     4.76 
2,610     6.83 
2.960     8.80 
2,940     4.40 
2,540      6-60 
2,090     984 
2,660     7.64 
2,160      6.62 
2,110    10.93 
2.170     7.20 

0.88 
0.65 
1.07 
0.76 
0.77 
0.84 
3.14 
1.76 

4:06 
2.24 

Pocahontas  No.  3 
Pocahontas  No.  4 
Pocahontas  No.  5 
Pocahontas  No.  6 

Redstone 

Sewell 

Sewickley 

Winifrede 

3,440      4.70 
2,480      6.31 
2.700      6.23 
2,400      2.88. 
2.120     6.96 
2,560     3.93 
2,080     9.51 
2,190     6. 17 
2.840     7.41 
2,970     8.44 

0.59 

Cedar  Grove.... 

Coalburg 

Eagle. 

0^70 

Fire  Creek 

Lower  r  recport. . 
Lower  KitUning. 

Mahoning 

Middle  Kittaning 

0.72 
3.99 
1.97 
0.62 
0.S3 

Avoiding  Clinker.    The  following  suggestions  are  offered  by  the  Btireau 

Use  thin  fires  and  keep  the  fuel  bed  level  by  placing  fresh  coal  on  thin 
spots.     Do  not  level  fire  wilh  rake  or  stir  it  with  splice  bar. 

Fire  coal  in  small  charges,  especially  if  it  contains  much  slack.  This  will 
prevent  crust  formation  and  the  need  of  breaking  it. 

Do  not  bum  coal  in  the  ashpit.  Keep  water  in  tight  ashpits,  otherwise 
blow  in  steam.  In  heating  and  decomposing,  the  steam  will  absorb  heat  as  it 
passes  through  the  grate,  ash  and  fuel  bed. 

Keep  the  ashpit  doors  open  and  regulate  the  draft  by  dampers. 

When  the  coal  contains  clinkering  ash,  an  increase  of  the'  draft,  states 
L.  J.  Joffray,  gives  better  combustion  and  reduces  the  slag.  The  air  added 
through  the  fire  keeps  the  temperature  of  the  ash  below  the  fusing  point. 
Should  clinkering  continue,  relief  can  be  had,  according  to  L.  Rankin,  by 
spreading  over  the  grate  a  few  shovelfuls  of  limestone  crushed  to  the  siie 
of  a  walnut ;  this  should  be  done  when  the  fire  is  banked  or  after  it  is 
cleaned.  More  heat  may  be  lost  by  the  frequent  cleaning  of  the  lire  than 
because  of  its  clinkering,  especially  with  coals  that  fu^c  into  large  masses. 
Frequently  the  combustion  is  almost  entirety  stopped  while  the  clinker  is 
being  removed. 

StoraEC  of  Coal 

COAL  in  a  compact  or  solid  mass,  has  the  following  approximate  weights 
per  cubic  foot  of  space  occupied:  Anthracite,  85  to  9S  lb.;  bituminous, 
70  to  80  lb. ;  lignite.  65  to  75  lb.  Peat  weighs  between  25  and  35  lb.,  while 
briquetted  fuel  weighs  40  to  45  lb.  per  cubic  foot.  Table  72  gives  the  approxi- 
mate weights  of  coals  in  storage. 

The  variation  in  weight  of  different  grades  of  coal  is  not  due  solely  to 
the  specific  gravity  of  the  solid  coal.  The  quantity  of  surface  moisture,  the 
proportions  of  coarse  and  fine  coal,  and  the  amount  of  sliaking  or  settling 
also  influence  its  weight  as  delivered  or  as  stored.  Coals  of  high  fixed  carbon 
are  relatively  heavy,  while  increased  ash  content  lowers  the  weight  per  cubic 
foot  The  younger  coals  and  those  of  high  moisture  content  are  relatively 
of  low  weight. 


ib.  Google 


Table  72. 

Approximate  Weights 

of  Coali. 

NUM 

N«- 

Ut./ea.lt. 

Cb-IWIob 

LkVca-K. 

Cu.<Wtan 

Broken 

70 
65 

60 
65 

28 
31 
33 
36 

fc:::::;;: 

Slack 

Run  of  mine .  , . 

60 
66 
60 
45 

f. 

Bucki^heat 

« 

Deterioration  in  Storage 
/'^AL  nrdergoea  a  change  in  heat  value  and  weight  due  to  weathering 
^1—'  when  stored  in  the  open,  indoors  or  under  water.  Usually  the  volume 
and  sometimes  the  weight  is  increased.  Coal  stored  under  fresh  or  salt  water 
may  retain  from  2  to  12  per  cent  moisture,  but  its  heat  value  is  practically 
unchanged.  Exposure  of  coal  to  the  air.  cither  in  the  open  or  under  cover, 
reduces  its  heat  value.  The  quantity  of  carbon  and  disposable  hydrc^en  is 
diminished,  while  the  quantity  of  oxygen  and  in  disposable  hydrogen  is 
increased. 

Extensive  experiments  by  5.  IV.  Parr  on  Illinois  coal  showed  that  the 
most  rapid  loss  in  heat  value  occurred  during  the  first  ten  days.  After  this 
the  rate  of  loss  diminished,  although  the  loss  continued  indefinitely.  The 
total  loss  in  the  open  was  substantially  the  same  as  in  covered  bins,  ranging 
from  1  to  3  per  cent  after  exposure  for  one  year. 

Fine  coal  suffers  a  greater  loss  in  heat  value  than  do  the  larger  sizes. 
The  loss  of  volatile  matter  is  negligible  in  its  effect  on  heat  value.  After 
being  exposed  to  air  for  one  year.  West  Virginia  slack  lost  less  than  1  per 
cent  in  heat  value;  run-of-mine  only  O.S  per  cent;  Pittsburgh  run-of-minc 
0.4  per  cent ;  and  Wyoming  sub-bituminous  about  3,5  per  cent  This  last 
coal  deteriorated  5.3  per  cent  in  heat  value  after  an  exposure  to  air  for  2^ 
years. 

Coal  in  transit  will  lose  in  heat  value  because  of  oxidation  of  its  new 
surface  after  mining.  The  loss  increases  with  the  hydrogen  content,  ranging 
from  0.1  per  cent  for  semi -bituminous  to  1.3  per  cent  for  sub-bituminous 
and  lignite. 

Spontaneous  Combustion  of  Coal 

IN  the  storage  of  coal,  spontaneous  combustion  must  be  provided  against. 
Anthracite  coal  is  not  subject  to  spontaneous  combustion  and  can  be 
safely  stored  in  any  quantity.  Soft  coal  may  ignite  and  disintegrate  unless 
stored  under  water. 

Spontaneous  combustion  of  coal  is  due  to  slow  oxidation  in  an  air  supply 
sufficient  to  support  the  oxidation,  but  insufficient  to  carry  away  all  the  heat 
formed.  The  friability  of  the  coal,  or  its  tendency  to  break  up  into  iinc 
particles  and  dust,  as  well  as  its  chemical  nature,  are  the  major  causes  of 
spontaneous  combustion. 

Dust  and  small  sizes  of  coal  are  dangerous  in  a  coal  pile  containing 
larger-sized  coat,  because  the  resultant  openings  permit  the  flow  of  a  mod- 
erate amount  of  air  to  the  interior.  The  amount  of  volatile  matter  in  the 
coal  does  not  of  itself  increase  the  liability  to  spontaneous  heating,  and 
there  is  no  assurance  of  safety  in  the  storage  of  low  volatile  or  smokeless 
coals.    Pittsburgh  run-of-mine  has  shown  a  greater  tendency  to  spontaneous 


ib.  Google 


nnance  BuUding,  Philadelpbia,  Pa.,  equipped  with  Heine  BeUen. 

D,slz.:liyGOOglC 


combustion  than  have  high  volatile  gas  coals.  Western  coals  with  a  high 
amount  of  volatile  are  usually  liable,  but  this  is  due  particularly  to  (he  high 
ox^en  content  Such  coals  become  heated  readily  t^  oxidation  faster 
than  the  heat  can  be  dissipated. 

The  iniluence  of  moisture  and  sulphur  on  spontaneous  combustion  has 
not  been  definitely  determined.  The  Bureau  of  Mines  has  not  found  a  single 
instance  of  moisture  causing  heating,  although  laboratory  tests  by  Riehter 
ihow  that  moist  coal  oxidizes  rapidly.  While  there  are  no  conclusive  data  on 
the  action  of  sulphur,  experiments  indicate  that  it  is  only  a  minor  factor. 

According  to  the  Bureau  of  Mines,  the  following  precautions  should  be 
observed  in  storing  coal : 

1.  Do  not  pile  in  cones;  pile  evenly  not  over  12  ft,  and  so  that 
any  point  in  the  interior  will  not  be  over  10  ft.  from  an  air  cooled 

2.  If  possible,  store  oijly  screened  nut  coal. 

3.  Keep  out  the  dust  as  much  as  possible  by  reducing  the  handling 


I  that   lump  and   fine   sizes   are   distributed   evenly,   not 
allowing  lumps  to  roll  to  the  bottom  and  form  air  passages. 

5.  Rehandle  and  screen  after  two  months. 

6.  Do  not  store  near  outside  heat  sources,  even  though  moderate 

7.  After  mining,  allow  six  weeks'  seasoning  before  storing. 

8.  Avoid  alternate  wetting  and  drying. 

9.  Prevent  air  reaching  the  interior  of  the  pile  by  avoiding  inter- 
stices around  timbers  and  brick  work,  or  through  porous  bottoms, 
such  as  coarse  cinders. 

10.    Do  not  attempt  to  ventilate  with  pipes  as  they  may  do  more 
harm  than  good. 
In  practice  coal  that  has  been  stored  six  to  eight  weeks  and  has  even 
become  heated  will  seldom  again  heat  spontaneously  if  rehandled  and  thor- 
oughly cooled  by  the  air. 

The  drenching  of  the  coal  pile  will  not  extinguish  a  fire,  because  the 
crust  that  forms  over  the  fire  prevents  the  water  from  reaching  it  It  is 
necessary  to  remove  the  coal  from  around  the  burning  part  Euid  to  spread 
out  the  coal  before  water  can  be  used  with  effect 

Briquets 

COAL  dust,  culm,  slack  and  similar  waste  due  to  mining  of  the  coals 
and  low  grade  fuels  unsuitable  for  transportation  can  be  used  as  fuel 
by  briquetting  or  pressing  into  solid  blocks.  Domestic  experiments  and  the 
experience  of  foreign  manufacturers  indicate  that  briquetting  increases  the 
commercial  value  of  low  grade  coals  sufficiently  to  more  than  cover  the 
cost  of  production. 

Undoubtedly  on  account  of  the  low  cost,  briquetted  fuel  is  used  in 
European  countries.  In  the  United  States,  the  difference  In  cost  between 
steam  sizes  and  slack  is  small  and  the  cost  of  manufacturing  the  briquetted 
fuel  is  high,  so  that  its  use  is  limited  to  locomotive  furnaces  and  to  house 
heaters  or  stoves.  However,  tests  by  the  U.  S.  Geological  Survey  with 
briquetted  coal  in  hand-fired  furnaces  of  Heine  Boilers  have  repeatedly 
shown  satisfactory  economy,  with  no  smoke. 

Briquets  are  generally  machine  made.  Coal  dust  and  small  pieces  of 
coal  are  mixed  with  a  binding  substance  to  hold  the  particles  together,  are 
heated,  and  are  subjected  to  heavy  pressure  in  molds.  The  fuel  material 
is  sometimes  mixed  with  clay,  rolled  into  balls  by  hand,  and  then  air-dried. 
They  are  made  in  shapes  and  sizes.  Fig.  213,  weighing  from  I  oz.  to  sev- 
eral pounds.  Rectangular  briquets  measuring  6>j  by  S]/i  by  A]6  in.  and 
having  rounded  comers,  weigh  about  7  pounds.  Smaller  briquets,  of  6^4  by 
4i4  by  2^4  in,  weigh  about  4  lb.  each. 


ib.  Google 


12     3     4     5     6     7 


Fig-  3 13.     Different  Stylet,  Shape*  and  Sizes  of  Coal  Briquets. 

As  the  coal  resources  of  the  countnr  diminish,  the  economic  importance 
of  briquetted  fuel  will  be  better  realized.  Further  development  should 
also  lead  to  methods  for  the  recovery  of  valuable  by-products  from  the 
coals  used  in  making  briquets. 

The  size  and  shape  of  a  briquet  determine  the  extent  of  its  use.  Heavy 
rectangular  blocks  are  convenient  for  storage.  According  to  /,  E.  Mills, 
the  French  Navy  estimates  the  weight  of  briquets  that  can  be  stored  in  a 
given  space  as  10  per  cent  more  (han  that  of  lump  coal.  The  British 
Admiralty  reports  a  gain  as  high  as  20  per  cent.  To  hasten  combustion  large 
briquets  are  broken  up  when  fed  into  the  furnace. 

Stored  briquets  are  not  subject  to  spontaneous  combustion  or  to  notice- 
able weathering  due  to  exposure.  Briquets  not  over  2  lb.  in  weight  are 
favored  abroad.  The  most  common  forms  are  prismatic  with  round  edges 
or  ovoid  shapes.  These  briquets  are  easily  handled,  cause  little  dust  and 
minimum  breakage.  The  rounded  edges  permit  good  air  circulation  and 
therefore  thorough  combustion. 

The  properties  of  briquetted  fuel  depend  largely  upon  the  grade  and 
amount  of  binder  used  with  the  coal  mixture.  The  most  common  binder 
used,  states  C.  L.  Wright,  is  a  pitch  made  either  from  coal  tar  or  water-gas 
tar,  although  starch,  lime  and  sulphite  liquor  are  sometimes  used. 

With  the  correct  binder  smokeless  combustion  can  be  expected.  Other 
advantages  of  this  fuel  are  regularity  in  size,  uniform  condition  of  fuel-bed, 
no  etinker,  minimum  attention  to  ^res,  high  heating  value,  high  rates  of 
combustion,  small   loss   from  breakage,  and   tittle  weathering. 

Anthracite  briquets  have  been  made  from  coal  dust  mixed  with  dry  pitch. 
According  to  E.  F.  Loiseau,  the  pitch  represents  10  per  cent  of  the  bulk  of 
the  briquet  and  is  prepared  from  tar  at  572  deg.  by  separating  the  volatile 
The   fuel   mixture   is   continuously  heated  by   steam   so 


ib.  Google 


as  to  maintain  a  temperature  of  212  deg,,  at  which  the  pitch  acts  as  a  binder. 
It  is  then  passed  between  rollers  made  of  semi-oval  molds,  in  which  the 
briquets  are  formed.  The  pressed  fuel,  about  the  size  of  an  egg,  drops  on 
to  a  belt  conveyor;  this  carries  it  to  a  screen  in  eight  minutes,  the  briquets 
then  being  cool  enough  for  handling  and  delivery. 

Carbocoal  briquets  are  made  in  sizes  ranging  from  1  to  5  oz.  and  repre- 
sent about  72  per  cent  of  the  raw  coal.  As  described  by  C.  T,  Malcolnuon, 
the  raw  coal  is  first  crushed  and  then  distilled  at  a  temperature  of  about  90O 
deg,,  yielding  gas,  tar  and  "semi-carbocoal,"  which  is  rich  in  carbon.  Pitch 
obtained  from  the  tar  is  then  mixed  with  the  semi-carbocoal  and  formed  into 
briquets.  These  are  in  turn  distilled  at  a  temperature  of  about  1800  deg., 
resulting  in  the  recovery  of  additional  coal-tar  products  and  the  production 
of  the  carbocoal  fuel.  The  fuel  is  dense,  uniform  in  size  and  quality,  and  of 
grayish  black  color.  Analysis  shows  from  1  to  3  per  cent  moisture ;  0.75  to 
3.S  per  cent  volatile  matter ;  82  to  90  per  cent  fixed  carbon  and  7  to  12  per 
cent  ash.    It  is  said  that  carbocoal  requires  no  greater  draft  than  bituminous 

Lignite  briquets  can  be  made  without  a  binding  material,  according  to 
the  Bureau  of  Mines,  Lignite  briquets  burnt  in  furnaces  of  steam  boilers  have 
proved  equal  to  good  Middle  West  bituminous  coal.  They  will  endure 
handling  and  resist  weathering  better  than  raw  lignite,  and  manual  labor  is 
not  required  from  the  time  the  lignite  is  loaded  into  die  mine  car  until  the 
briquets  are  delivered  to  the  consumer. 

The  lignite  after  mining  is  crushed  and  screened  and  then  dried  to  re- 
duce the  high  moisture  content.  Closed  conveyors  carry  the  powdered 
lignite  to  hoppers  that  feed  the  molds,  where  it  is  subjected  to  a  pressure 
of  about  20,0(X)  lb.  per  sq.  in.  The  heat  developed  during  compression 
liberates  the  tarry  matter  from  the  material  and  cements  the  fuel. 

Lignite  yields  gas,  ammonia,  oils  and  tar  on  carbonizing.  The  residue 
can  be  made  into  briquets  by  the  addition  of  a  binding  material.  In  one 
plant,  states  /,  B.  C.  Kershaw,  the  ovens  or  retorts  take  a  10-ton  charge  of 
lignite  and  heat  it  for  two  hours  at  about  900  deg.  The  yield  of  by-producti 
at  this  temperature  include  10,000  cu.  ft.  of  gas,  13  gal.  of  tar  oil,  and  2.5  lb. 
of  ammonium  sulphate  per  ton  of  lignite.  After  the  distillation  is  completed 
the  residue  is  mixed  with  pitch  and  other  binders  to  form  the  briquets. 
Analysis  of  these  lignite  briquets  shows  1.34  per  cent  moisture;  7.6  per  cent 
volatile  matter ;  84.04  per  cent  fixed  carbon ;  7.02  per  cent  ash,  and  a  heat 
value  of  14,000  B.t.u.  per  pound. 

Peal  briquets  are  possible  commercial  fuel  for  steam  boilers.  The  peat 
used  abroad  as  a  domestic  fuel  is  not  as  rich  in  combined  nitrogen  as  the 
peat  of  the  United  States.  By  gasification  the  latter  will  yield  ammonia,  tar 
and  other  chemical  compounds  of  value. 

Peat  produces  a  large  amount  of  gas  of  good  quality  when  consumed 
in  a  gas  producer.  The  gas  can  be  used  in  engines  or  for  the  firing  of  boil- 
ers. With  by-product  gas  producers,  sufficient  ammonia  can  be  recovered 
to  pay  for  most  of  the  operating  costs,  so  that  the  gas  and  power  it  furnishes 
are  practically  free. 

Technical  success,  says  F.  P.  Coffin,  has  been  attained  by  several  pro- 
cesses but  commercial  success  in  peat  manufacture  has  not  yet  been  demon- 
strated. Of  the  several  plants  that  have  at  times  operated  in  the  United 
States,  one  uses  a  centrifugal  pump  for  removing  the  peat  from  its  bed. 
According  to  Wm.  Kent,  the  pump  discharges  into  storage  bins,  and  after 
some  of  the  water  in  the  peat  has  drained  away,  the  material  is  further 
dried  by  exhaust  steam  and  stack  gases.  When  dry,  the  peat  is  reduced 
to  powder,  and  conveyed  to  a  press  where  it  is  compressed  into  regularly 
shaped  blocks.  The  briquetled  peat  is  clean  and  withstands  handling  as 
well  as  transportation. 


ly  Google 


as 

1'^ 


If 

is 


ib.Google 


Solid  Fueis  Other  Than  Coal 

yV/OOD  fuel  consists  ai  sawdust,  shavings  or  other  refuse  (troduced  in 
'"  quantity,  as  in  wood- working  plants  and  saw  mills.  Cord  wood  is 
used  to  a  limited  extent,  when  timber  is  plentiful  and  other  fuels  expensive. 
Wood,  of  course,  is  used  in  starting  coal  fires. 

Table  73.      Weights  and  Comporitions  of  Air-Dried  Wood*. 


Wood 

IJ>.p<.r 
eo-RT 

Y-^ 

C 

H. 

0. 

N 

Adi 

B.tD. 

p-rlb. 

Ash 

Beech 

Bin* 

Elm 

46 
43 
45 
35 

3,620 
3,250 
2,880 
2,350 

49.18 
49.36 
50.20 
48.99 

6.27 
6.01 
6.20 
6.20 

43.91 
42.60 
41,62 
44.25 

0.07 
0.91 
1.15 
0.06 

0.57 
1.06 
0.81 
0.50 

5,420 
5,400 

6,680 
6,400 

Oak 

Kne 

Poplar 

Willow 

52 
30 
36 

25 

3,850 
2.000 
2,130 
1,920 

49.64 
50.31 
49.37 
49.96 

6.92 
6.20 
6.21 
5.96 

41.16 
43.08 
41.60 
39.56 

1.29 
0.04 
0.96 
0.96 

1.97 
0.37 
1.86 
3.37 

5.480 
5,700 
6.660 
6,830 

Freshly  cut  wood  contains  about  45  pet  cent  of  water  by  weight.  After 
air-drying  the  moisture  content  is  15  to  25  per  cent  The  average  heat  value 
of  dry  wood  is  about  770O  B.t.u.  per  pound.  The  weights  and  com- 
positions of  air-dried  wood  are  given  in  Table  73.  As  fuel,  1  lb.  of 
wood  is  assumed  to  equal  0.40  tb.  of  coal,  or  1  lb.  of  coal  equals  I'/i  lb.  of 
wood.  Measuring  in  bulk,  2  cords  of  wood  are  considered  the  equal  of  1  ton 
of  CcraL  Sometimes  1  lb.  of  wood  is  said  to  give  an  evaporation  of  6  lb.  of 
water  from  and  at  212  deg.,  which  represents  a  heat  value  of  5794  B.tu. 
per  pound.  By  weight,  shavings,  sawdust  and  refuse  lumber  have  the  same 
heat  value  as  the  original  wood. 

Charcoal  is  made  by  heating  wood  in  a  closed  vessel.  Distillation  begins 
at  about  400  deg.,  leaving  a  residue  of  common  black  charcoal.  Other  grades 
of  charcoal  are  obtained  at  higher  carbonizing  temperatures.  The  wood 
melts,  and  at  about  620  deg.  yields  a  mass  similar  to  soft  coal  coke.  At 
temperatures  over  2000  deg.  a  blade  dense  solid  charcoal  is  formed. 

Wood  will  yield  about  18  per  cent  charcoal  and  82  per  cent  volatile  matter 
hj  weight  at  high  temperature,  and  68  per  cent  charcoal  and  32  per  cent 
volatile  at  low  temperature.  The  carbon  content  varies  then  from  85  to  55 
per  cent.  The  heat  value  is  generally  about  11,000  B.Lu.  per  pound.  Char- 
coal absorbs  moisture  rapidly  up  to  15  per  cent  It  is  seldom  used  in  boiler 
practice  except  when  it  is  a  by-product,  as  in  the  manufacture  of  wood  alcohol 
or  turpentine. 

Coke  is  the  solid  substance  remaining  after  coals  are  distilled  in  retorts 
or  partl]^  burned  in  ovens.  The  bituminous  coals  are  used  extensively,  al- 
though Ignite  and  peat  offer  commercial  possibilities.  In  gas  retorts,  a  large 
yield  of  gas  of  high  illuminating  value  is  desired,  so  that  the  coke  is  a  by- 
product. In  beehive  coke  ovens  high-grade  coke  is  produced  for  use  in 
metallurgical  processes.  In  by-product  coke-ovens,  good  coke,  a  large  coke 
yield  or  else  gas  and  chemical  by-products  may  be  desired.  The  coke 
yield  varies  between  35  to  90  per  cent  of  the  weight  of  coal.  Cokes  are 
generally  rough  and  may  be  dense  and  soft,  or  porous  and  hard.  The  color 
varies  from  silvery,  light  gray  to  dark  gray  and  black.  They  readily 
attract  and  retain  moisture  and  if  not  properly  protected  may  contain  20 


ib.  Google 


per  cent  by  weight.  Coke  bums  without  flame  or  smoke  and  makes  an  in- 
tense fire  when  forced.  The  heat  value  is  between  12,000  and  14,000  B.t.u. 
per  pound.  Analysis  gives  an  average  of  1.3  per  cent  volatile  matter;  88  per 
cent  fixed  carbon;  0^  per  cent  sulphur;  1.5  per  cent  moisture;  and  8.4 
per  cent  ash.  The  average  weight  of  solid  coke  is  about  45  lb.  per  cubic 
foot.  Heaped  coke  weighs  about  30  lb.  per  cubic  foot,  or  75  cubic  feet  to 
the  long  ton.  Coke  generally  costs  as  much  as  coal,  so  that  it  is  not  used 
to  any  extent  as  a  boiler  fuel. 

Coke  hrette  consists  of  the  fine  particles  left  when  the  coke  is  drawn 
from  the  ovens,  or  of  the  screenings  from  coke  prepared  for  blast  furnaces. 
It  represents  about  2  to  ZYi  per  cent  of  the  coal  originally  used  in  the  coking 
process.  Generally,  it  is  considered  as  waste,  but  by  burning  coke  breeze 
under  boilers,  its   fuel  value  can  be  utilized. 

Corn  has  been  used  a^  fuel  when  the  crop  was  plentiful  and  the  price 
low.  At  15  cents  a  bushel  corn  would  be  as  cheap  a  fuel  as  coal  at  about 
$8  per  ton.  It  is  sometimes  used  as  an  emergency  fuel  in  grain-growing 
localities.  Boiler  tests  by  C.  R.  Richards  showed  thai  bituminous  coal  gave 
1.9  times  as  much  heat  per  pound  as  corn  on  account  of  the  difference  in 
heat  value  of  the  fuels.  Calorimeter  tests  place  the  heat  value  of  corn  and 
cob  at  about  8000  B.t.u.  per  pound,  the  cob  alone  at  7500  B.t.u.,  and  dry 
corn  at  9000  B.tu.    Corn  weighs  about  56  lb.  per  bushel. 

Straw,  used  in  some  localities  as  fuel,  consists  of  the  stems  or  stalks  of 
grain.  Its  composition  is  about  36  per  cent  carbon ;  S  per  cent  hydrogen : 
38  per  cent  oxygen;  0,5  per  cent  nitrogen;  15.75  per  cent  moisture;  and  4.75 
per  cent  ash,  which  gives  a  heat  value  of  5411  B.t.u.  per  pound.  Dry  straw 
will  average  from  56O0  to  6700  B.t.u.  per  pound.  Straw  when  compressed 
weighs  about  7  lb.  per  cubic   foot. 

Tan  bark  is  the  fibrous  portion,  known  as  spent  tan,  which  is  left  from 
ground  bark  employed  as  a  leather  tanning  agent.  The  raw  bark  is  usually 
air-dried  oak  or  hemlock  but  in  the  process  it  absorbs  sufficient  moisture  to 
make  the  spent  tan  weigh  more  than  twice  the  raw  material,  two-thirds  of 
Ibis  weight  being  water.  The  waste  heat  of  the  chimney  gases  can  be  used 
for  drying  the  fuel. 

Fig.  214  gives  heat  values  of  tan  bark  for  different  moisture  contents, 
derived  from  Table  74.  The  net  heat  value  cannot  be  measured  directly,  so 
that  the  total  calorific  value  should  be  determined  by  combustion  In  a  fuel 
calorimeter.  At  best,  the  useful  heat  of  a  liquid,  gaseous  or  wet  fuel,  can  be 
determined  only  approximately,  for  it  involves  the  ultimate  analysis  and 
assumptions  depending  upon  operating  conditions. 

Table  74.     Calorific  Value  of  Tan  Bark  with  varioua  Percentagea  of  Moisture. 


B.t.u. 

LoMH  ol  BtiDt  dua  to 

NeCHeaC 

VllH, 

B.t.n. 

^?ss:- 

"V^ar- 

M<4Mim        Wm 
Tin. 

MoMure 

Bin  Fuel 

HotlncAir 

^. 

0.20 
0.30 
0.40 

6,336 
5,544 

4,752 

261 

392 
522 

564 
493 
423 

1,446 
1,266 
1,085 

4,065 

3,393 

2,772 

64.2 

61.2 
57.3 

4.19 
3.50 
2.81 

0.50 
0.60 

0,70 
0.60 

3,960 
3,16S 
2,376 
1,584 

653 

784 
914 

1,045 

352 
282 
211 
141 

904 

723 
542 

362 

2,051 

1,379 

709 

36 

51.8 
43.5 
29.8 
2.5 

Z.ll 
1.42 
0.73 
0.03 

ib.Google 


Mfiiturt  in  FuH,  Ptrfnt 
Fig.  214.     Heat  Value  of  Tan  Bark. 

Dry  tan  bark  consists  of  about  50  per  cent  carbon ;  6  per  cent  hydrogen ; 
40  per  cent  nitrogen ;  and  4  per  cent  ash,  giving  a  heat  value  of  8000  B.t.u. 
per  pound.  Dry  tan  bark  with  15  per  cent  ash  has  a  heat  value  of  about 
6100  B.t.u.;  and  with  1.5  per  cent  ash,  about  9OO0  B.t.it.  per  pound.  Wet 
tan  bark,  as  used  for  boiler  firing,  has  a  heal  value  of  about  5S0O  B.t.u. 
per  pound  with  30  per  cent  moisture;  and  3500  B.t.u.  with  GO  per  cent 
moisture.  An  evaporation  from  and  at  212  deg.  of  2  to  3  !b.  of  water 
per  pound  of  wet  fuel  can  be  expected  in  specially  designed  furnaces. 

Bagasse,  or  megass,  that  part  of  the  sugar  cane  remaining  after  the  ex- 
traction of  the  juice,  is  widely  used  as  fuel  for  boilers  on  sugar  plantations. 
The  refuse  resulting  from  the  treatment  of  ihc  raw  cane  by  the  sugar  mill 
rolls  is  known  as  "mill  bagasse,"  while  the  product  remaining  after  a  series 
of  soaking  processes  of  the  raw  chopped  cane  is  known  as  "diffusion  bagasse," 
The  fuel  value  of  baga:ise  depends  upon  the  amount  of  woody  fiber  it 
contains  and  upon  the  amount  of  combustible  matter,  such  as  sucrose, 
glucose  and  gum,  retained  in  the  liquid.  Louisiana  bagasse,  according  to 
E.  C.  Freeland,  consists  of  about  40  per  cent  fibre,  7  per  cent  sucrose  and 
otiier  constituents,  the  remaining  53  per  cent  being  water.  Bagasse  obtained 
from  tropical  cane,  according  to  L.  A,  Becucl,  contains  37  to  45  per  cent 
woody  fiber ;  9  to  10  per  cent  combustible ;  and  46  to  53  per  cent  water. 
The  composition  of  dry  bagasse  ranges  between  43  and  47  per  cent  carbon ; 
5.4  and  6.6  per  cent  hydrogen;  45  and  49  per  cent  oxygen;  and  5  and  3 
per  cent  ash.  Its  average  heat  value  as  determined  by  test  is  8300  B.t.u. 
per  pound.  Owing  to  the  usual  moisture  content  of  the  fuel  as  fired,  its 
heat  value  then  is  only  4000  B.t.u.  or  less.  One  pound  of  the  fuel  will 
evaporate  about  2  to  3  lb.  of  water  from  and  at  212  deg.  By  utilizing 
waste  gases  and  drying  the  bagasse  before  firing,  better  results  can  be  ob- 
tained. The  fuel  yield  from  sugar  cane  can  be  taken  as  25  per  cenL  One 
ton  of  cane  as  ground  will  therefore  give  500  lb.  or  more  of  wet  bagasse. 

Table  75  gives  the  calorific  values  of  diffusion  bagasse  of  varying  per- 
centages of  moisture. 

Table  76  gives  the  calorific  value  of  one  pound  of  mill  bagasse  at  dif- 
ferent extractions,  based  upon  a  cane  of  10  per  cent  fiber  and  juice  of  15 
per  cent  total  solids. 


ib.  Google 


^8 


If 


ib.Google 


Table  75.     Fad  Value*  of  One  Pound  of  DiffuMon  Bagaue  at  Various 
Degrees  of  Mmsture. 


■"^'is"- 

H«t  Dmrdoped  per 
B.t.u. 

Number  at  Poancb 

of  Bunma 

Egulvklut  to 

1 1£.  of  C«l  of 

14,000  B-tu. 

0 

20 
30 

8.325 

6,660 
5,827 

8,325 
6,420 
51468 

1.68 
2.18 
2.56 

40 
50 
60 

4,995 
4,162 
3,330 

4,516 
3.563 
2,611 

3.10 
3.93 
5.41 

70 

75 

2,497 
2,081 

1,658 
1,183 

8,44 
11-90 

Table  76.     Fud  Values  of  One  Pound  of  Hill  Bagaaae  at  different  Extrac- 
tions upon  Cane  of  10  per  cent  Fiber  and  Juice  of  15  per  cent  Total  Solids. 


Heat  Value  of  Wet  Fuels 
""PHE  useful  heat  liberated  hy  fuels  tired  wet  is  lower  than  the  total  heat 
■^  value  determined  by  calonmeter  tests.  The  calorific  power,  as  fired,  o( 
green  wood,  tan  bark  and  bagasse,  is  termed  the  gross  heat  value.  By  de- 
ducting from  this  gross  value  the  heat  required  to  evaporate  the  moisture 
and  raise  it  to  the  tetnperature  of  the  gases  leaving  the  boiler,  the  net  heat 


ib.  Google 


Fib-  315.     Heat  Value  of  BagasM. 

value  absorbed  by  the  boiler  water  is  obtained.  Therefore,  a  dry  sample 
having  a  total  of  7000  B.t.u.  per  pound  by  calorimeter  test  will  have  a  gross 
heat  value  of  5600  B.t.u.  per  pound,  if  it  contains  ^  per  cent  moisture. 

To  compute  the  net  heat  value  of  wet  fuels,  the  following  formul.i  can 
be  used: 

hj.=  (9 If  +  IV)  X  1(212  — t)  +9721  +  [0.48  ft,  —  212)  ]  (59) 

in  which  ft.  /.  is  the  B.t.u.  lost  per  pound;  H  is  the  hydrogen  conlenl;  {■'.' 
the  water;  t  and  (■  ace  the  temperatures  of  the  air  supply  and  the  chimney 
gases.  The  result  is  the  heat  lost  in  the  superheated  steam  formed  by  the 
combustion  of  the  hydrogen  and  from  the  water  in  the  wet  fuel. 

If  green  wood  contains  6  per  cent  hydrogen  and  24  per  cent  water  as 
fired,  and  the  air  supplied  for  combustion  is  at  72  deg.,  resulting  in  a  stack 
temperature  of  462  deg,,  the  loss  is: 

(9  X  0,06  +  0.24)  X  [  (212  —  72)  +  972]  +  (0.48  (462  —  212)  ]  =  987  B.t.u. 
Assume  that  this  wood  sample  has  a  heat  value  of  6987  B.t.u.  by  calorimeter 
test.  The  net  heat  value  is  found  by  deducting  the  loss  due  to  hydrogen  and 
water,  which  gives  6000  B.t.u.  per  pound  for  steaming  purposes. 

Liqtiid  Fuels 

FUEL  oil  consists  practically  of  petroleum  or  of  its  residue  after  the  more 
volatile  oils  have  been  removed.  The  petroleum  or  crude  oil  is  a 
viscous  mineral  oil  varying  in  color  from  light  brown  through  shades  of 
green  to  black.  The  specific  gravity  is  generally  belween  0.80  and  0.98, 
corresponding  to  45  and  12  deg.  Baume,  respectively. 

Fuel  oil  at  10  deg.  Baume  has  a  specific  gravity  of  1.00,  the  same  as  that 
of  water.  The  gravity  of  oil  is  usually  measured  on  the  Baume  scale.  This 
can  be  converted  by  the  following  Bureau  of  Standards  formula,  for  liquids 
lighter  than  water : 

,.      ..    ^      .  140  (60) 

Specific  Gravity  =     130  +  deg.  W 


ib.  Google 


Crudt  oil  is  a  mixture  of  hydrocarbons  thai  often  contain  a  small  per- 
centage of  sulphur,  oxygen  and  nitrogen.  It  can  be  distilled  into  gasoline. 
benzine,  kerosene  and  other  oils,  which  diifer  considerably  physically  and 
chemically,  depending  upon  the  locality,  the  source  of  supply,  and  upon 
the  treatment  or  distillation  process.  After  the  kerosene  has  been  run  off, 
the  oils  remaining,  of  from  12  to  25  deg.  Baume,  are  available  as  fuel  for 
steam  boilers. 

Gasoline  is  a  petroleum  product  of  about  74  to  64  deg,  Baume,  Benzine 
is  a  distillate  of  about  55  deg.  Baume,  while  kerosene  ranges  from  about 
48  to  .IS  deg.  Baume.  However,  the  high  price  of  these  lighter  distillates 
prevents  their  use  as  a.  boiler  fuel. 

Oils  are  classified  by  their  flash  point,  the  temperature  at  which  they 
give  off  intlammable  vapors ;  viscosity,  the  tendency  of  the  oil  particles  to  hold 
together,  thus  retarding  the  flow;  moisture,  in  the  form  of  an  emulsion  in 
the  heavier  oils;  sulphur,  which  produces  obnoxious  gases  and  has  a  cor- 
roding effect  if  condensed  on  boiler  tubes  and  slack;  density;  and  heat  value. 
The  properties  of  fuel  oils  from  different  localities  are  given  in  Table 
77,  by  C.  E.  Lucke. 


Table  77. 

CompoMtion  and 

Heat  Value  of  Oil  Fuels. 

,a 

UltlBUU  u»ly«>^  p«  «c 

H-t 

C. 

H.       1     O-HN. 

S. 

jwrlb. 

California  fuel  oil 

Calif  ornia  crude 

14,93 
16.24 
31.67 

38.  SB 
23.18 
21.25 
21.66 
36.47 

81-52 
86.30 
85.40 

85.00 
86.10 
83.28 
84.60 
84.30 

11.61 
16.70 
13.07 
13.80 
13.90 
12.41 

6.92 

0.55 
0.80 

18,026 
21.723 

0.60 

■3:83" 

0.60 
0.60 
0.50 
1.63 

PennaylvanU  crude. . , 
Texas  fuel  oil 

20,949 
19,654 

18,977 
20,809 

West  Virginia  crude. . , 

14,10 

1.60 

The  heat  value  of  oil  can  be  determined  accurately  by  calorimeter  test. 
An  approximate  method  proposed  by  J.  N.  LeConle  gives  the  value,  free 
from  moisture,  as  17,680  -|-  (60  X  deg.  Bi)  B.tu.  per  pound. 

Another  method  utilizes  the  Dvlong  formula: 


t.  -  14,544  C  +  62,028^//  _  _2  \  -f.  4050  S 


(62) 


in  which  C  is  carbon,  H  is  hydrogen,  0  is  oxygen  and  S  is  sulphur,  as  ob- 
tained from  the  ultimate  analysis.  This  formula  gives  a  heat  value  of 
about  5  per  cent  higher  than  that  of  California  oils,  as  determined  by  calo- 
rimeter. Fig,  216  shows  other  heat  values.  These  indicate  that  per  pound  the 
lighter  oils  have  a  higher  calorific  value  than  the  heavier  fuels,  but  a  lower 
value  per  gallon,  A  barrel  of  heavy  petroleum  will  therefore  have  a  higher 
heat  value  than  a  barrel  of  lighter  oil. 

The  average  California  oil  has  a  specific  gravity  of  about  0.96,  which 
corresponds  to  15.16  deg.  Baume  at  a  -temperature  of  60  deg.  The  average 
weight  of  a  gallon  of  oil  is  8.03  pounds.  As  it  usually  comes  in  barrels  of 
42  gal.,  the  average  weight  of  a  barrel  of  fuel  oil  is  337  pounds.  The 
heat  value  is  about  18,700  B.t.u,  per  pound,  which  should  easily  give  an 
equivalent  evaporation  from  and  at  212  deg.  of  about  14.5  lb.  of  water  per 
pound  of  fuel. 


ib.  Google 


People*  Oat,  idKl)t  ^  Coke  Co.,  Chicago,  111*.,  operating  Heine  Boilen. 

;    C.OOgIC 


Fig.  21«.     HeatiDB  Value  of  Fuel  Oil. 

Coal  tar  is  a  by-product  of  coking  processes.  Its  commercial  value 
usually  prevents  its  use  as  a  fuel.  This  black,  viscous  liquid  must  be  heated 
and  strained  before  it  can  be  used.  The  coa.1  tar  yield  is  from  4%  to  6yi 
per  cent  of  the  weight  of  the  coal  used  in  gas  or  coke  manufacture.  The 
specific  gravity  is  about  125,  so  that  a  gallon  weighs  10.4  pounds.  It  is 
lower  in  hydrogen  and  higher  in  carbon  than  petroleum,,  an  ultimate  analysis 
showing  89.21  per  cent  carbon;  4.9S  per  cent  hydrogen;  1.05  per  cent  nitrogen; 
4.23  per  cent  oxygen ;  0.56  per  cent  sulphur ;  and  a  trace  of  ash.  Coai  tar  has 
a  heat  value  of  about  15,800  B.t.u.  per  pound. 

Tar  oils  include  pitch,  creosote,  anthracene  and  other  residuum  fron: 
distillation.  Oil  tar  produced  in  gas  apparatus  has  a  specific  gravity  of  1.15, 
is  less  viscous  than  coal  tar,  and  can  be  handled  much  like  other  fuels.  Its 
composition  is  92.7  per  cent  carbon;  6.13  per  cent  hydrogen;  0.11  per  cent 
nitrogen;  0.G9  per  cent  oxygen;  0.37  per  cent  sulphur;  and  a  trace  of  ash, 
giving  a  heat  value  of  17,100  B.tu.  per  pound. 

Colloidal  fuel  was  developed  by  the  Submarine  Defense  Association 
to  meet  war  conditions.  It  is  an  emulsion  of  powdered  solid  fuel  and  oil 
fuel.     A  so-called  fixateur  is  used  to  stabilize  the  elements  of  the  mixture 


ib.  Google 


482  FUEL 

that  have  different  specific  gravities,  and  thus  maintain  a  homogeneous 
product.  Most  oils  in  Iheir  natural  state  can  be  mixed  with  putvertzed 
solids  to  make  the  smokeless  colloidal  fuel.  Dried  and  pulverized  bituminous 
and  antbracite  coals  can  be  used,  as  can  li^ite,  peat,  coke,  charcoal  or  wood, 
so  long  as  two-thirds  of  the  dry  solid  fuel  is  combustible. 

The  colloidal  fuel  is  fired  with  the  same  equipment  used  for  oil  burning. 
A  marine  boiler  test  gave  an  equivalent  evaporation  of  13.6  lb.  of  water 
per  pound  of  colloidal  fuel  at  an  elTiciency  of  76.8  per  cent,  while  straight 
Mexican  oil  gave  an  equivalent  evaporation  of  13.97  lb.  of  water  per  pound 
of  oil  fuel  at  an  efficiency  of  73J2  per.'ccnt.  With  coal  of  13,500  B.t.u. 
per  pound  and  crude  oil  of  18,200  B.t.u.  per  pound,  the  colloidal  fuel  has 
a  heat  value  of  17.000  B.t.u.  per  pound,  with  25  per  cent  solid  fuel  in 
suspension ;  and  16,300  B.t.u.  per  pound  with  40  per  cent  of  solids  in  the 
mixture.  It  is  possible  to  combine  4S  per  cent  oil,  20  per  cent  tar  and  30 
per  cent  powdered  coal  and  still  obtain  a  stable  colloidal  fuel  that  can  be 
stored  for  a  month  or  more  without  the  solids  settling.  With  such  mixture 
it  is  said  at  least  50  per  cent  of  the  oil  fuel  now  used  can  be  saved,  and  equal 
if  not  greater  heat  value  per  barrel  obtained  at  a  lower  cost 

Gaseous  Fuels 

IN  gas   fuels   each  constituent   has  a  known  heating  power.     The  total 
heat  value  of  a  cubic  foot  of  gas  can  be  determined  by  multiplying  the 

fractional  constituents  and  the  corresponding  heating  powers  per  cubic  foot, 
and  by  adding  the  products.  The  low  heat  values  are  given  by  C.  E.  Luekr 
as  follows: 

B.tu.  per  cu.  ft. 


Hydrogen 


Methane 959 

Ethyler 


-  341 


Natural  gas  is  often  held  at  high  pressure  in  huge  natural,  underground 
reservoirs  that  are  tapped  by  sinking  wells.  The  gas  is  piped  and  distributed 
over  long  distances,  and  delivered  at  working  pressures  of  2  to  8  ounces. 

The  principal  combustible  components  of  natural  gas  are  methane  (marsh 
gas)  and  hydrogen.  The  incombustible  gases  are  carbon  dioxide,  nitrogen 
and  oxygen.  Table  78,  compiled  by  G.  A.  Burreli,  gives  the  average  heat 
value  and  the  composition  for  different  samples. 

ArliScia!  gases  are  made  principally  from  coal  or  oil.  Natural  gas 
costs  10  to  30  cents  per  1000  cu.  ft.,  while  coal  and  water  gases  cost  $1  or 
more.  With  coal  at  $5  per  ton,  producer  gas  will  deliver  35,000  B.t.u,  for 
one  cent,  while  natural  gas  at  20  cents  gives  50,000  B.t-u.  for  one  cent. 

The  compositions  and  heating  values  of  gas  fuels  are  compared  in  Table 
79.  Owing  to  the  variations  in  heat  values,  different  quantities  of  gas  are 
required  to  generate  one  boiler  horsepower. 

Junker  Gaa  Calorimeter 

THE  heat  value  of  gaseous  fuels  is  generally  determined  with  the  Junker 
Gas  Calorimeter  illustrated  in  Fig.  217. 

This  instrument  consists  of  a  vertical  cylindrical  water  chamber  contain- 
ing vertical  tubes,  which  is  heated  by  the  gas  burned  in  a  Bunscn  Uimp 
beneath.  The  products  of  combustion  pass  upward  through  a  combustion 
chamber  and  downward  through  the  tubes,  while  the  water  passes  in  at  the 
bottom  and  out  at  the  top  in  a  continuous  current.  The  quantity  of  gas  is 
measured  by  a  gas  meter,  and  the  quantity  of  water  by  collecting  the  overflow 


ib.  Google 


2B.M  in. 

SP«^ 

LoaUoD  of  W<dli 

nr 

N,^ 

UMhaiH 

Ethue 
CH. 

Armstrong  Co.,  Pa. 
Omm  Co.,  OUa. . . 
Kiefer,  Okla 

0.05 
1.10 
2.40 

0,0 
0.0 
0.0 

1.45 
4.6 
1.8 

81,6 
94.3 
64.1 

16.9 
0.0 
31.7 

1,184 
1,004 
1,272 

0.64 
0.58 
0.74 

Barron  Co.,  Ky.... 
Barron  Co.   Ky — 
Moab,  Utafi 

2.5 
2.6 
3.6 

0.0 
0.0 
0.0 

1.3 

5.1 
5.6 

23.6 
44.1 
90.8 

69  7 

48.2 
0.0 

1.548 

1,367 

967 

0,91 
0.84 
0.61 

Moab,  Utah 

Northwestern  Ore  . 
Crawford  Co.,  Pa. . 

3.S 
3.0 
0.0 

0,0 
0.0 
0.0 

6.5 

0.9 
2.3 

90.0 
96.1 
6.6 

0.0 
0.0 
91.1 

959 
1,023 
1,766 

0.62 
0.58 
l.OI 

Northwestern  Ore. 

Tillamook,  Ore 

Stillwater,  Nev.... 

0.5 
0.1 

1.3 

0,0 
0.0 
0.0 

12.5 
97.9 

3.1 

87.0 
2.0 
95.6 

0.0 
0.0 
0.0 

927 
21 

1,018 

0.60 
0.96 
0.58 

Forest  Co.,  Pa 

Clarion  Co.,  Pa.,.. 

0.0 
0.0 
0.0 

0.0 
0.0 
0.0 

1.1 
1,0 
1.7 

96.4 

70.8 
80.5 

28.2 
17.8 

1,073 
1,279 
1,189 

0.57 
0.70 
0.65 

Kings  Co..  Cal . . . . 
Grey  bull  Field.  Wyo 

0.0 
30.4 
0.2 

0.0 
0.0 
0.0 

0.9 
2.4 
0.8 

53.3 
66,2 
81.7 

45.8 
1.0 
17.3 

1,420 

724 

1,192 

0.78 
0.85 
0.64 

Casing  head  gas.  .  . 
McKeanCo.,  Pa.. 

0.0 
O.S 
0.0 

0.0 
0.0 
0.0 

1.3 
3.1 
1.0 

51.5 
64.1 
86.0 

47.2 
32.3 
13.0 

1,427 
1,282 
1,159 

0.77 
0r68 
0.59 

Caddo  Parish  Field, 

0.9 
0,0 

0.0 
0.0 

1.5 
1.8 

97,6 
94.4 

0.0 
3.8 

1,039 

1,076 

Park  County,  Okla. 

0.59 

Bradford,  Pa 

Nortonville.  N.  D.. 
SchuUo  Field,  Okla. 

0.0 

1.3 
0.5 

0.0 
0.0 
0.0 

8.9 
13.6 
1.5 

18.9 

85.1 
76.4 

72.2 
0.0 
21.6 

1,534 

907 

1,215 

1.00 
0.62 
0.67 

Casing;     head     gas 
used  for  produc- 
tion of  gasoline.  . 

0.0 

0.0 

3.3 

78.7 

18.0 

2,424 

1.38 

From  Pittsburg  gae 

0.0 
0.0 

0.0 

0,0 

1.2 
1.6 

79.2 
80.3 

19.6 

18.1 

1,208 
1.193 

From  Columbus  gaa 

""ppiy 

0.64 

Table  79.     Composition  of  Oas  Fuels,  by  Percentages. 


ff 

Hydnw. 

MtUuiH 

— 

M^SSl 

S^. 

0>ytM  JNitros™ 

cTft. 

Natural  gas 

Coal  gas 

Water  gas 

1.7 
39.78 
21.8 

94.16 
45.16 

30.7 

0.30 
6.38 
12.9 

0.55 
7.04 
28.1 

0.29 
1.08 
3.8 

0.30 
0.06 
0.5 

2.80 
0.50 
2.2 

1,000 
730 
700 

Coke  oven  gas... 
Blast  furnace  gas 
Producer  gas. , ,  . 
Oil  gas 

53.2 
3.0 
2.81 

32.0 

35.0 

2.0 

6.0 

27.5 
14.34 

2.0 
10.0 
10.5 

0.5 

2.0 
59.4 
66.7 

3.0 

620 

5.56 
48.0 

"ie^s 

110 
850 

ib.Google 


ib.Google 


Fig.  317.    The  Junker  Oaa  Calorimeter. 

discharged  from  the  apparatus.  Thermometers  are  inserted  at  the  points  of 
entrance  and  exit.  The  heat  of  combustion  of  a  cu.  ft.  of  gas  is  determined 
by  multiplying  the  rise  of  temperature  in  deg.  F.  by  the  weight  of  water 
in  lb.,  and  dividing  the  product  by  the  volume  of  gas  in  cu.  ft.  The  result 
thus  found  after  being  corrected  for  moisture  and  reduced  to  the  equivalent  at 
32  deg.  and  14,696  lbs.  per  sq.  in.,  is  what  is  termed  the  "higher  value,"  and 
this  is  the  value,  unless  otherwise  stated,  which  is  generally  employed. 

The  "low  value"  is  obtained  by  multiplying  the  weight  of  the  con- 
densed vapor  resulting  from  the  combustion,  expressed  in  lb.,  by  the  total 
heat  of  atmospheric  steam  above  the  temperature  of  the  condensed  vapor, 
dividing  the  product  by  the  volume  of  the  gas  in  cu.  ft.,  and  subtracting  the 
quotient  from  the  higher  value. 

Heat  Value  of  Liquid  and  Gaseous  Fuels 

THE  healing  jwwer   of  a  fuel,  as  used  in  calculating  boiler  trials,  is  the 
value  determined  by  calorimeter  test.    Some  fuels  contain  hydrogen,  and 
others  moisture,  thus  reducing  the  heat  available  for  steam. 

Most  liquid  fuels  and  some  gases  contain  a  high  percentage  of  hydrogen. 
Their  calorific  power  as  determined  by  calorimeter  test  is  called  the  "high" 
heat  value,  while  the  available  heat  is  known  as  the  "low"  heat  value. 
The  difference  between  the  two  is  equal  to  the  latent  heat  of  steam  formed 


ib.  Google 


by  the  burning  of  the  hydrogen,  which  cannot  be  absorbed  by  the  water  in 
the  boiler.  As  hydrogen  combines  with  eight  times  its  weight  of  oxygen, 
the  result  is  9  lb.  of  water  for  the  combustion  of  1  lb,  of  hydrogen.  The 
latent  heat  of  steam  being  971.7  B.t.U.  per  pound,  this  combustion  represents 
a  total  of  8745  B.t.u.  per  pound  of  hydrogen.  Deducting  this  from  60,626 
B.Lu.,  the  high  heat  value  of  hydrogen,  gives  51,892  B.t.u.  as  the  low 
heat  value  per  pound  of  hydrogen.  On  a  volumetric  basis  the  high  heat 
value  of  hydrogen  can  be  taken  as  340  B.t.u.  per  cubic  foot  and  the  low 
heat  value  as  290  B.t.u.,  leaving  50  B.t.u.  per  cubic  foot  that  is  not  absorbed 
by  the  boiler  water. 

If  a  calorimeter  test  gives  the  high  heat  value  of  oil  as  18,500  B.t.u. 
per  pound  and  the  fuel  contains  10  per  cent  hydrogen,  then  the  low  heat 
value  is  18,500  —  (O.IO  X  8745)  =  17,625  B.t.u.  per  pound  approximately. 

If  a  sample  of  gas  fuel  containing  20  per  cent  hydrogen  by  volume  has  a 
high  heat  value  of  710  B.tu.  per  cubic  foot  as  determined  by  calorimeter, 
then  the  low  heat  value  is  710  —  (0.2  X  SO)   =  700  B.t.u.  per  cubic  foot. 

Buying  Fuels  Under  Contract 

THE  purchase  of  fuels  under  contract  and  specification  involves  expense  in 
sampling  and  analysis,  but  many  engineers  believe  the  advantages  gained 
are  worth  the  cost  Large  consumers  of  coal  and  oil  have  adopted  the  con- 
tract and  specification  method,  because  it  guarantees  economy  when  quality 
and  price  are  considered.  Power  reports  a  saving  of  520,000  in  the  coal 
bills  of  18  plants,  the  fuel  having  been  tested  at  a  central  laboratory  at  a 
cost  of  $1,500  for  the  year. 

Spec  ill  cations  insure  a  more  uniform  grade  of  fuel  than  can  be  other- 
wise obtained.  Boiler  plant  operation  can  be  studied  more  carefully  and 
adjustments  made  to  secure  the  highest  efficiency  with  the  grade  of  fuel 
delivered.  However,  sampling  and  analyzing  are  expensive.  Fuel  contractors 
hold  that  many  s^cifications  are  unreasonable,  and  sometimes  add  5  to  10 
per  cent  to  the  price  to  cover  contingencies. 

Specifications  for  Coal 

THE  following  specification  for  the  purchase  of  coal  on  a  heat  value  basis 
is  given  by  /.  E.  Woodtvell,  as  typical  of  central  power  slalion  practice: 
A.     The    company    agrees    to    furnish    and    deliver    to    the    consumer, 


JuantiticB  as  ordered  by  the  consumer  for  consumption  at  said  premises 
uring  the  term  hereof,  at  the  consumer's  option,  either  or  all  of  the  kinds 
of  coal  described  below ;  said  coals  to  average  the  following  assays : 

Coal  of  size  passing  through 
screen  having  circular 
perforation  in  diam in.    in _in. 

Coal  of  size  passing  over 
screen  having  circular 
perforation  in  diam in.    in .-in. 

Moisture  in  coal  as  de- 
livered — _____ %    % % 


From  following  coun^..~ 
From  following  state 


ib.  Google 


Coal  of  the  above  respective  descriptions  and  specified  assays,  not  aver- 
a|:e  assays,  to  be  hereinafter  known  as  the  contract  grade  of  the  respective 

B.  The  consumer  agrees  to  purchase  from  the  company  all  of  the  coal 
required  for  consumption  at  said  premises  during  the  term  of  this  contract, 
except  as  set  forth  in  paragraph  C  below,  and  to  pay  the  company  for  each 
ton  of  2000  lb.  avoirdupois  of  coal  delivered  and  accepted  in  accordance  with 
all  of  the  terms  of  this  contract  at  the  following  contract  rate  per  ton  of 
each  respective  contract  grade,  at  which  rates  the  company  will  deliver  the 
following  respective  numbers  of  B.t.u.  for  one  cent,  the  contract  guarantee: 
Kind  of  Coal  Contract  Rate  per  Ton  Contract  Guarantee 
Equal  to —net  B.t.u.  for  1  cent 


Said  B.t.u.  for  one  cent  being  in  each  case  determined  as  follows : 

Multiply  the   B.tu.  per   lb.   of  dry  coal  by  the   per  cent 

moisture,  expressed  in  decimals,  and  subtract  the  product  so 
found  from  the  B.t.u.  Then  multiply  tiie  remainder  by  2000 
and  divide  this  product  by  the  contract  rate  per  ton  plus  one-half 
the  ash  percentage,  both  expressed  as  cents. 

vided  that  the  consumer  may  purchase  for  .. 


sumption  at  said  premises  coal  other  than  herein  contracted  for  test  purposes, 
it  being  understood  that  the  total  of  such  coal  so  purchased,  shall  not  exceed 
5  per  cent  of  the  total  consumption  during  the  term  of  this  contract. 

D.  It  is  understood  that  the  company  may  deliver  coal  hereunder  con- 
taining as  high  as  3  per  cent  more  ash  and  as  high  as  3  per  cent  more  mois- 
ture  and  as  low  as  500  fewer  B.Lu,  per  pound  dry  than  specified  above  for 
contract  grades. 

£.  Should  any  coal  delivered  hereunder  contain  more  than  the  per  cent 
of  ash  or  moisture  or  fewer  than  the  number  of  B.Lu.  per  pound  dry 
allowed  under  paragraph  D  hereof,  the  consumer  may,  at  its  option,  either 
accept  or  reject  the  same. 

F.  All  coal  accepted  hereunder  shall  be  paid  for  monthly  at  a  price  per 
ton  determined  by  taking  the  average  of  the  delivered  values  obtained  from 
the  analysis  of  all  the  samples  taken  during  the  month,  said  delivered  value 
in  eadi  case  being  obtained  as  follows : 

Multiply  the   number  of  B.t.u,  delivered  per  pound  of  dry 
coal  by  the  per  cent  of  moisture  delivered,  expressed  in  decimals, 
and  subtract  the  product  so  found  from  the  B.t.u.  delivered  per 
pound  of  dry  coal.     Then  multiply  the  remainder  by  2000  and 
divide  this  product  by  the  contract  guarantee.    From  the  quotient, 
expressed  as  dollars  and  cents,  subtract  one-half  of  the  ash  per* 
centage  delivered,  expressed  as  cents. 
How  such  a    rule   works   is   illustrated   in   the   diagram,   Fig.  218.    in 
which    the    standard    is    9    per    cent    moisture,   8   per    cent   ash    and    I3,S00 
B.t.u.  per  pound  of  dry  coal  at  S3  per  ton.    Coal  of  500  B.t.u.  and  3  per 
cent  each  of  moisture  and  ash,  either  below  or  above  the  specification  base, 
is  tiie  minimum  acceptable  and  the  maximum  practicable,  respectively,  as 
shown  in  the  diagram.     On  this  basis  the  average  premium  or  penalty  is  3 
little  over  5  cents  for  each  lOO  B.t.u.  above  or  below  the  standard. 

An  Ohio  street  railway  company  has  specifications  drawn  on  a  basis 
of  a  graded  scale  of  premiums  and  penalties.  The  established  standard  for 
heat  value  ranges  from  12,610  to  12,759  B.t.u.  per  pound  of  dry  coal.  The 
standard  for  ash  is  from  0  to  IS  per  cent  and  for  sulphur  from  0  to  3.5  per 
cent  The  premiums  on  heat  value  are  graded  to  a  maximum  of  21  cents 
per  ton,  above  the  basic  price,  for  13,960  B.t.a  and  over.     The  penalties 


ib.  Google 


ib.Google 


=.-       _     . 

"->.   ^. 

«     '^,  ^s^ 

\ 

-      ^^-^; 

i    ~ 

^i    i 

~^ 

^^  ,^-__    . 

^^->i. 

..'"^;  ^. 

Ct^frm^t,    <i„ 

^           ^1 

^' 

1 

' 

i 

-jB-" 

,'' 

' 

SU      »        to.       1  .    '   J.    '   n 

g-'-ir-'-ib     ill     tr^ 

are  also  graded  to  as  high  as  50  cents  per  Con  for  heating  powers  of  10,660 
to  10,809  B.LH.  There  is  no  premium  for  the  minimuni  ash  content,  but 
there  is  a  penalty  for  excess  ash,  amounting  to  SO  cents  per  ton  when  the 
ash  is  29.1  per  cent  and  higher.  The  penalty  for  sulphur  above  the  standard 
is  graded  to  4S  cents  per  ton  when  the  content  is  10  per  cent  or  more. 

This  contract  provides  that  should  the  coal  company  or  contractor  fail  at 
any  time  to  supply  the  quality  and  quantity  of  coal  specified,  the  consumer 
may  purchase  a  supply  In  the  open  market,  at  prevailing  rates,  and  collect 
from  the  contractor  any  difference  in  cost.  The  company  reserves  the 
right  to  cancel  and  relet  the  contract  should  the  coal  company  fail  to  meet 
all  the  terms  specified. 

The  contract  of  a  New  York  transit  company  gives  an  average  premium 
and  exacts  an  average  penalty  of  about  2  cents  for  every  100  B.t.u.  above  or 
below  the  standard.  Its  standard  is  14,201  to  14,250  B.t.u.,  20  per  cent 
or  less  volatile  matter;  9  per  cent  or  less  ash,  and  V/i  per  cent  or  less  sulphur. 
For  heat  values  above  the  standard  the  premium  reaches  26  cents  per  ton  for 
15,505  B.t.u.  per  pound  of  dry  coal.  For  values  below  it  the  penalty  is  a 
maximum  of  45  cents  per  ton  at  12.000  B.Lu,  or  lower.  The  other,  penal- 
ties are  highest  at  18  cents  a  ton  for  24  per  cent  or  more  of  volatile  matter; 
23  cents  for  \Z'/i  per  cent  or  more  of  ash,  and  12  cents  for  a  maximum  of 
2yi  per  cent  sulphur. 

The  U.  S.  Ctrvcmment,  a  large  user  of  coal  for  power  and  heating  pur- 
-  poses,  buys  fuel  under  specifications  that  merge  the  heat  value,  ash,  moisture 
and  price,  into  a  single  unit  of  cost  per  1,000,000  B.t.u.    Provisions  are  made 
for  penalties  and  premhims  with  respect  to  the  contract  standard. 


ib.  Google 


The  intent  of  the  specifications  is  to  insure  a  coal  delivery  similar 
within  reasonable  limits  to  the  standard  of  the  contract  and  not  continually 
to  make  corrections  in  price  for  shght  variations  in  heat  value.  A  2  per  cent 
variation  from  the  standard  is  allowed  before  the  price  is  corrected,  as  it  is 
recognized  that  the  quality  of  the  coal  cannot  be  controlled  within  narrow 
limits.  Orders  of  50  tons  or  less  are  sampled  only  at  the  discretion  of 
the  Government,  because  the  collecting  and  preparing  of  a  representative 
sample,  and  the  cost  of  analysis,  would  considerably  increase  the  cost. 

Under  these  specifications  it  is  possible  to  utilize  the  output  from  a 
group  of  coal  mines.  Anthracite  for  power  and  heating  purposes  includes 
the  pea  and  buckwheat  sizes  from  the  mines  in  the  counties  of  Susquehanna, 
Lackawanna,  Luzerne,  Carbon,  Schuylkill,  Columbia,  SuUivan,  Northumber- 
land and  Dauphin,  in  the  state  of  Pennsylvania.  Coal  accepted  as  bitumi- 
nous includes  the  usual  bituminous  grades,  as  well  as  semi-bituminous,  sub- 
bituminous,  and  lignite. 

All  the  coals  are  analyzed  and  tested  by  the  Bureau  of  Minet,  on  the 
basis  of  its  specifications.    The  main  provisions  for  bituminous  and  anthra- 


specified  herein  a.t  may  be  required  for  use  of  the 

,  will  be  received  tmtil 


.,  at  the  office  of  the,.- 


and  then  opened. 

Each  bidder  shall  have  the  right  to  be  present,  either  in  person  or  by 
attorney,  when  the  bids  are  opened. 

Proposals,  in  duplicate,  must  be  forwarded  to  the ,. , 

postage  prepaid. 

Proposals  must  be  made  in  duplicate  on  the  form  provided,  and  must 
be  signed  by  the  individual,  partnership,  or  corporation  making  the  same. 
When  made  by  a  partnership,  the  name  of  each  partner  must  be  signed.  If 
made  by  a  corporation,  proposals  must  be  signed  by  the  officer  thereof 
authorized  to  bind  it  by  contract,  and  be  accompanied  by  a  copy,  under 
seal,  of  his  authority  to  sign. 

The  proposals  must  be  accompanied  by  cash  or  by  certified  check  drawn 

payable  to  the  order  of  the ,  in  the  amount  equal 

to  2  per  cent  of  the  estimated  amount  involved  for  the  fuel  for  which  bids 
are  submitted,  the  minimum  amount  in  any  case  to  be  $10.  This  requirement 
is  solely  to  guarantee,  if  the  award  is  made  on  the  proposal,  that  within  10 
days  after  notice  is  given  that  an  award  has  been  made,  the  bidder  will 
enter  into  a  contract  in  accordance  with  the  terms  of  the  proposal  and  execute 
a  bond  for  the  faithful  performance  thereof,  with  good  and  sufficient  sure- 
ties as  hereinafter  required.  In  the  event  of  the  failure  of  the  bidder  to 
enter  into  contract  or  execute  bond,  the  cash  or  check  guarantee  will  be 
forfeited. 

Bond.  Each  contractor  shall  be  required  to  give  a  bond,  with  two  or 
more  individual  sureties  or  one  corporate  surety  duly  qualified  under  the 
act  of  Congress  approved  Aug,  13,  1894,  in  which  the  contractor  and  the 
sureties  shall  covenant  and  agree  that,  in  case  the  said  contractor  shall  fail 
to  do  or  perform  any  or  all  of  the  covenants,  stipulations,  and  agreements 
of  said  contract  on  the  part  of  the  said  contractor  to  be  performed  as  therein 
set  forth,  the  said  contractor  and  his  sureties  shall  forfeit  and  pay  to  the 
United  States  of  America  any  and  all  damages  sustained  by  the  United  States 
by  reason  of  any  failure  of  the  contractor  fully  and  faithfully  to  keep  and 
perform  the  terms  and  conditions  of  his  contract,  to  be  recovered  m  an 
action  at  law  in  the  name  of  the  United  States  in  any  proper  court  of 


ib.  Google 


competent  jurisdiction.  Such  sureties  (except  corporate  sureties)  shall  justify 
their  responsibility  by  affidavit  showing  that  thej"  severally  own  and  possess 
property  of  the  clear  value  in  the  aggregate  of  double  the  amount  of  the 
above-mentioned  forfeiture  over  and  above  all  debts  and  liabilities  and  all 
property  by  law  exempt  from  execution.  The  affidavit  shall  be  sworn  to 
before  a  judge  or  a  clerk  of  a  court  of  record  or  a  United  States  attornM-, 
who  must  certify  of  his  own  personal  knowledge  that  the  sureties  are  suffi- 
cient to  pay  Che  full  penalty  of  the  bond. 

If  the  estimated  amount  involved  in  the  contract  does  not  exceed  the 
sum  of  $200,  then  the  bond  may  be  waived  with  the  consent  of  the  depart- 
ment involved, 

ReservalioHs,  The  right  is  reserved  by  the  Government  to  reject 
any  and  all  bids  and  to  waive  technical  defects.  Bidders  are  cautioned 
against  guaranteeing  higher  standards  of  quality  than  can  be  maintained  in 
delivered  coal,  as  the  Government  reserves  the  right  to  reject  any  and  all 
bids,  if  the  Government  has  information  regarding  analyses  and  test  results 
that  indicate  that  higher  standards  have  been  offered  than  probably  can  be 
maintained. 

The  right  shall  be  reserved  by  the  Government  to  purchase  for  the 
purpose  of  making  boiler  tests,  other  coal  than  that  herein  contracted  for,  pro* 
vided  the  amount  so  purchased  shall  not  exceed  10  per  cent  of  the  estimated 
consumption  during  the  period  covered  by  this  agreement. 

If  it  should  appear  to  be  to  the  best  interests  of  the  Government  to  do 
so,  the  right  is  reserved  to  award  the  contract  for  supplying  coal  at  a  price 
higher  than  that  named  in  a  lower  bid,  or  in  lower  bids. 

If  the  bidder  to  whom  the  award  is  made  shall  fail  to  enter  into  a 
contract  as  herein  provided,  then  the  award  may  be  annulled  and  the  con- 
tract let  to  the  next  most  desirable  bidder  without  further  advertisement, 
and  such  bidder  shall  be  required  to  fulfill  every  stipulation  expressed  therein, 
as  if  he  were  the  original  party  to  whom  the  contract  was  awarded;  pro- 
vided, however,  that  such  bidder  is  notified  of  said  award  within  60  days 
after  the  date  on  which  the  bids  on  this  contract  were  opened.  If  such 
notice  should  not  be  given  within  said  60  days,  then  the  acceptance  of  the 
award  will  be  optional  with  the  said  bidder. 

No  contract  can  be  lawfully  transferred  or  assigned. 

No  proposal  will  be  considered  from  any  person,  firm,  or  corporation 
in  default  of  the  performance  of  any  contract  or  agreement  made  with  the 
United  States,  or  conclusively  shown  to  have  failed  to  perform  satisfactorily 
such  contract  or  agreement. 

Quanlily.    The  estimated  quantity  of  coal  in _..  tons 

of  2,000  lb.  to  be  purchased  is  based  Upon  the  previous  annual  consumption, 
but  the  right  will  be  reserved  to  order  a  greater  or  less  quantity,  subject  to 
the  actual  requirements  of  the  servine. 

Delivery.  The  coal  shall  be  delivered  in  such  quantities  at  such  times  as 
the  Government  may  direct.     (Place  of  delivery  to  be  stated.) 

All  the  available  storage  capacity  of  the  Government  coal  bunkers  shall 
be  placed  at  the  disposal  of  the  contractor  to  facilitate  delivery  of  coal 
under  favorable  conditions.  When  an  order  is  issued  for  coal,  the  contractor 
upon  commencing  a  delivery  on  thai  order  shall  continue  the  delivery  with 
such  rapidity  as  not  to  waste  unduly  the  services  of  the  Government 
inspector. 

After  verbal  or  written  notice  shall  have  been  given  to  deliver  coal 
under  this  contract  a  second  notice  may  be  served  in  writing  upon  the 
contractor  to  make  delivery  of  the  coal  so  ordered  within  a  reasonable 
lime,  to  be  determined  by  the  Government  official  in  charge,  after  receipt 
of  said  second  notice.    Should  the  contractor  for  any  reason  fail  to  comply 


ib.  Google 


ib.Google 


with  the  second  request,  the  Government  shall  be  at  liberty  to  buy  coat  inde- 
pendent of  this  contract,  and  for  coal  so  purchased  to  charge  against  the  con- 
tractor and  his  sureties  any  excess  in  price  over  the  price  which  would  have 
heen  paid  to  the  contractor  had  the  coal  been  delivered  by  him. 

The  contractor  shall  be  allowed  to  deliver  coal  during  the  usual  hours 
of  teaming — that  is,  between  8  a.  m.  and  5  p.  m. 

Weighing.  (To  be  statetf,  by  whom  and  where  the  coal  shall  be 
weighed.) 

Sampling.  The  contractor  shall  have  the  privilege  of  having  a  repre- 
sentative present  to  witness  the  collection  and  preparation  of  the  samples  to 
be  forwarded  to  the  laboratory. 

The  samples  shall  be  collected  and  prepared  in  accordance  with  the 
method  given  iD  the  appendix,  attached  hereto  as  a  part  of  these  specifica- 
tions and  proposals. 

Analyses.  The  samples  shall  be  immediately  forwarded  to  the 
Bureau  of  Mines,  Department  of  the  Interior,  Washington,  D.  C.,  and  they 
shall  be  analyzed  and  tested  in  accordance  with  the  method  recommended 
by  the  American  Chemical  Society  and  by  the  use  of  a  bomb  calorimeter. 
Such  analyses  and  tests  shall  be  made  at  no  cost  to  the  contractor.  The 
results  shall  be  reported  by  the  Bureau  of  Mines  in  not  more  than  fifteen 
days  after  the  receipt  of  the  sample.  If  more  than  one  sample  is  received 
from  the  same  delivery,  the  fifteen  days  shall  date  from  the  receipt  of  the 
last  sample  taken. 

Description  of  Coal  Desired.    The  coal  must  be  a  good  coal 

(kind  and  size  to  be  specified),  and  must 

be  adapted  for  successful  use  in  the  particular  furnace  and  boiler  equipment. 

Bidders  are  required  to  specify  the  coal  offered  in  terms  of  moisture  in 
the  coal  "as  received,"  and  of  ash,  volatile  matter,  sulphur,  and  B.t.u.  in 
"dry  coal."  such  values  to  become  the  standards  for  the  coal  of  the  successful 
bidder.  In  addition,  the  bidders  are  required  to  give  the  trade  name  of 
the  coal  offered,  and  other  designation ;  Uiis  information  shall  be  furnished 
in  spaces  provided  hereinafter. 

Coal  of  the  description  and  analysis  specified  is  herein  known  as  coal  of 
the  contract  grade.  Bidders  are  cautioned  against  specifying  higher  stand- 
ards than  can  be  maintained,  for  to  do  so  will  result  in  deductions  in  price 
and  may  result  in  the  rejection  of  the  delivered  coal  or  the  cancellation  of 
the  contract.  In  this  connection  it  should  be  recognized  that  the  small 
"mine  samples"  usually  indicate  a  coal  of  higher  economic  value  than  that 
actually  delivered  in  carload  lots,  because  of  the  care  taken  to  separate 
extraneous  matter   from  the  coal   in  the  "mine  samples." 

Award.  In  determining  the  award  of  this  contract  consideration  will 
be  given,  to  the  quality  of  the  coal  (expressed  in  terms  of  moisture  in  coal 
"as  received,"  of  ash  in  "dry  coal,"  and  B.t.u.  in  "dry;  coal"),  offered  by 
the  respective  bidders  and  to  the  operating  results  obtained  with  the  same 
and  with  similar  coals  on  previous  contracts  or  by  test,  as  well  as  to  the 

Bids  may  be  rejected  from  further  consideration  if  they  offer  coals 
regarding  which  the  Government  has  information  that  they  possess  unsatis- 
factory physical  characteristics  or  volatile  matter  or  sulphur  or  ash  con- 
tents, or  that  they  are  unsatisfactory  because  of  clinkering  or  excessive 
refuse,  or  because  of  having  failed  to  meet  the  requirements  of  city  smoke 
ordinances,  or  for  other  cause  that  would  indicate  that  they  are  of  a 
character  or  quality  that  the  (jovemment  considers  unsuited  for  the  storage 
space  or  the  furnace  equipment  of  the  particular  contract. 


ib.  Google 


The  method  used  shall  be  to  merge  the  four  variables— moisture,  con- 
tent, ash  content,  heating  value,  and  price  bid  per  ton — into  one  figure, 
the  cost  of  1,000,000  B.Lu.  The  procedure  under  this  method  shall  be  as 
follows : 

(a)  All  bids  shall  be  reduced  to  a  common  basis  with  respect  to 
moisture,  by  dividing  the  price  quoted  in  each  bid  by  the  difference  between 
100  per  cent  and  the  percentage  of  moisture  guaranteed  in  the  bid.  The 
adjusted  bids  shall  be  figured  to  the  nearest  tenth  of  a  cent. 

(b)  The  bids  shall  be  adjusted  to  the  same  ash  percentage  by  selecting 
as  the  standard  the  proposal  that  offers  coal  containing  the  lowest  percentage 
of  ash.  The  difference  in  ash  content  between  any  given  bid  and  this 
standard  shall  be  divided  by  two  and  the  price  in  such  bid,  adjusted  in 
accordance  with  the  above,  multiplied  by  the  quotient.  The  result  shall  be 
added  to  the  above  adjusted  price.  The  adjusted  bids  shall  be  figured  to 
the  nearest  tenth  of  a  cent. 

(c)  On  the  basis  of  the  adjusted  price,  allowance  shall  then  be  made 
for  the  varying  heat  values  by  computing  the  cost  of  1,000,000  B.LU.  for 
each  coal  offered.  This  determination  shall  be  made  by  multiplying^  the 
price  per  ton  adjusted  for  ash  and  moisture  content  by  1,000,000,  and  dividing 
the  result  by  the  product  of  2.000  multiplied  by  the  number  of  B.tu.  guar- 
anteed. If  the  coat  is  purchased  on  the  basis  of  2,240  lb.  to  the  ton,  the 
factor  of  2.240  should  be  used  instead  of  2.000. 

After  the  elimination  of  undesirable  bids,  the  selection  of  the  lowest 
bid  of  those  remaining  on  the  basis  of  the  cost  per  1,000,000  B.tu,  may  be 
considered  by  the  Government  as  a  tentative  award  only,  the  Government 
reserving  the  right  to  have  practical  service  test  or  tests  made  under  the 
direction  of  Ihe  Bureau  of  Mines,  the  results  to  determine  the  final  award 
of  contract.  The  interested  bidder  or  bis  authorized  representative  may 
be  present  at  such  test. 

Coal  Subjert  to  Rejection.  It  is  understood  that  coal  containing  3 
per  cent  more  moisture,  or  4  per  cent  more  ash,  or  3  per  cent  more 
volatile  matter,  or  1  per  cent  more  sulphur,  or  4  per  cent  fewer  B.t.u.  than 
the  specified  guaranties  as  to  the  standards  for  the  coal  hereunder  contracted 
for,  or  coal  furnished  from  a  mine  or  from  mines  other  than  herein  speci- 
fied by  the  contractor,  unless  upon  written  permission  of  the  Govemnient, 
shall  be  considered  subject  to  rejection,  and  the  Government  may,  at  its 
option,  either  accept  or  reject  the  same.  Should  the  Government  have  con- 
sumed a  part  of  such  coal  subject  to  rejection,  such  consumption  shall  not 
impair  the  Government's  right  to  cause  the  contractor  to  remove  the  remain- 
der of  the  delivered  coal  subject  to  rejection. 

It  is  agreed  that  if  the  contractor  shall  furnish  coal  in  three  consecu- 
tive deliveries,  or  in  case  more  than  20  per  cent  of  the  coal  delivered  to 
any  date  during  the  life  of  this  contract  shall  contain  3  per  cent  more  mois- 
ture, or  2  per  cent  more  ash,  or  3  per  cent  more  volatile  matter,  or  I  per 
cent  more  sulphur,  or  2  per  cent  fewer  B.t.n,  than  the  specified  guaranties 
as  to  the  standards  for  the  coal  hereunder  contracted  for,  or  if  the  coal  is 
furnished  from  a  mine  or  from  mines  other  than  herein  specified,  unless 
upon  written  permission  of  the  Government,  then  this  contract  may,  at 
the  option  of  the  Government,  be  terminated,  or  the  Government  may,  at  its 
option,  purchase  coal  in  the  open  market  until  it  may  become  satisfied  that 
the  contractor  can  furnish  coal  equal  to  the  standards  guaranteed,  and  the 
Government  shall  have  the  right  to  charge  against  the  contractor  any  excess 
in  price  of  coal  so  purchased  over  the  corrected  price  that  would  have  been 
paid  to  the  contractor  had  the  coal  been  delivered  by  him. 

Removal  of  Rejected  Coal.  The  contractor  shall  be  required  to  re- 
move, without  cost  to  the  Government,  within  48  hours  after  notifica- 
tion, coal  that  has  been  rejected  by  the  Government  Should  the  contractor 
not  remove  rejected  coal  within  the  said  48  hours,  the  Govenunent  ^lall  then 


ib.  Google 


lelivery  f 

«ith  all  t 


be  at  liberty  to  have  the  said  coal  removed  from  its  oremises  and  to  dispose 
of  such  coal  by  sale,  as  the  Government  shall  elect.  The  proceeds  from  such 
sale,  less  all  costs  incidental  to  its  removal  and  to  the  sale,  shall  be  paid  over 
to  the  contractor. 

Delermitiaiiott  of  Price.  The  Government  hereby  agrees  to  pay 
the  contractor  within  thirty  days  after  the  completion  of  an  order  or 
f  for  each  ton  of  2,000  lb.  of  coal  delivered  and  accepted  in  accordance 
.1  the  terms  of  this  contract,  the  price  per  ton  determined  by  taking 
the  analysis  of  the  sample,  or  the  average  of  the  analyses  of  the  samples  if 
more  than  one  sample  is  analyzed,  collected  from  the  coal  delivered  upon 
the  basis  of  ihe  price  herein  named,  adjusted  as  follows  for  variations  in 
heat  value,  ash  content,  and  moisture  content  from  the  standards  guaran- 
teed herein  by  the  contractor. 

Heat  Unit  Adjustment.  Considering  the  coal  on  a  "dry  coal"  basis, 
no  adjustment  in  price  shall  be  made  for  variations  of  2  per  cent  or 
less  in  the  number  of  B.t.u.  from  the  guaranteed  standard.  When  the 
variation  in  heat  units  exceeds  2  per  cent  of  the  guaranteed  standard,  the 
adjusted  price  shall  be  proportioned  and  shall  be  obtained  as  follows: 
B.t.u.  delivered  coal  ("dry-coal"  basis)  y  i;j    q.:,., 

B.tu.  ("dry-coal"  basis)  specified  in  contract 

The  adjusted  price  shall  be  figured  to  the  nearest  tenth  of  a  cent. 

As  an  example,  for  coal  delivered  on  a  contract  guaranteeing  14.000 
B.t.u.  on  a  "dry-coal"  basis  at  a  bid  price  of  $3  per  ton,  showing  by  calo- 
rific test  res,ults  varying  between  13,720  and  14,^  B.t.u.,  there  would  be 
no  price  adjustment  If,  however,  by  way  of  further  example  the  delivered 
coal  shows  by  calorific  test  14,350  B.t.u.  on  a  "dry-coal"  basis,  the  price 
for  this  variation  from  the  contract  guaranty  would  be,  by  substitution  in 
the  formula; 

Ash  Adjustment.  No  adjustment  in  price  shall  be  made  for  varia- 
tions of  2  per  cent  or  less  below  or  above  the  guaranteed  percentage  of  ash 
on  the  "dry-coal"  basis.  When  the  variation  exceeds  2  per  cent,  the  adjust- 
ment in  price  shall  be  determined  as  follows : 

The  difference  between  the  ash  content  by  analysis  and  the  ash  content 
guaranteed  shall  be  divided  by  two  and  the  quotient  shall  be  multiplied  by 
Uie  bid  price,  and  the  result  shall  be  added  to  or  deducted  from  the  B.t.u. 
adjusted  price  or  the  bid  price,  if  there  is  no  B.t.u.  adjustment,  according 
to  whether  the  ash  content  by  analysis  is  below  or  above  the  percentage 
guaranteed.  The  adjustment  for  ash  content  shall  be  iigured  to  the  nearest 
tenth  of  a  cent. 

As  an  example  of  the  method  of  determining  the  adjustment  in  cents 
per  ton  for  coal  containing  an  ash  content  varying  by  more  than  2  per  cent 
from  the  standard,  consider  that  coal  tor  which  the  above-mentioned  heat 
unit  adjustment  is  to  be  made  has  been  delivered  on  a  contract  guaranteeii^ 
10  per  cent  ash,  and  shows  by  analysis  an  ash  content  of  7.5  per  cent.  The 
adjustment  in  price  would  be  determined  as  follows : 

The  difference  between  10  and  7.5  which  is  2.5  would  be  divided  by  2, 
and  the  quotient  of  1.25  multiplied  by  $3,  resulting  in  an  adjustment  of  3.7 
cents  per  ton,  which  in  this  case  would  be  an  addition.  The  price  after 
adjustment  for  the  variations  in  heating  value  and  ash  content  would  be 
$3,075  plus  $0,037,  or  $3,112. 

Moisture  Adjustment.  The  price  shall  be  further  adjusted  for  mois- 
ture content  in  excess  of  the  amount  guaranteed  by  the  contractor,  the 
deduction  being  determined  by  multiplying  the  price  bid  by  the  percent- 


ib.  Google 


age  of  moitture  in  excess  of  the  amount  guaranteed.  The  deduction  shall 
b«  figured  to  the  nearest  tenth  of  a  cent. 

As  an  example,  consider  that  coal  for  which  the  above-mentioned  beat 
unit  and  ash  adjustments  are  to  be  made,  and  as  having  been  delivered  on  a 
contract  guaranteeing  3  per  cent  moisture,  and  that  the  coal  shows  by  analysis 
4.5  per  cent  moisture  i  then  the  bid  price  would  be  multiplied  by  1.5  (repre- 
senting excess  moisture),  giving  4.5  cents  as  ihe  deduction  per  ton.  The 
price  to  be  paid  per  ton  for  the  coal  would  then  be  (3.112,  less  $0,045.  or  $3,067. 

Partial  Payment.  If  the  coal  on  visual  inspection  by  the  Govern- 
ment inspector  appears  to  be  acceptable  coal,  the  Government  shalt  have  the 
right,  immediately  on  the  completion  of  an  order,  to  make  payment  on  90 
per  cent  of  the  amount  of  the  bill,  based  on  the  tonnage  delivered  and 
the  bid  price  per  ton.  The  10  per  cent  withheld  is  to  cover  any  deduction 
on  account  of  the  delivery  of  coal  that  on  analysis  and  test  is  subject  to  an 
adjustment  in  price.  If  the  10  per  cent  withheld  should  not  be  sufficient  to 
:  the  deduction,  then  the  amount  due  the  Government  may  be  taken 


from  any  money  thereafter  to  become  due  to  the  contractor,  or  may  be 
collected  from  the  sureties.  Because  of  the  distance  of  the  point  of  delivery 
from  the  laboratory,  requiring  several  days  for  the  transmittal  of  samples 
and  the  return  of  analytical  report,  because  of  loss  of  the  original  sample. 
necessitating  the  forwarding  of  the  reserve  sample,  or  for  any  other  reason 
that  would  result  in  delayed  payment,  should  such  be  withheld  until  receipt 
of  analytical  report,  the  Government  may,  as  circumstances  in  its  opinion 
warrant,  exercise  the  foregoing  right 

Information  to  be  Supplied.  The  following  spaces  should  be  filled 
in  by  the  bidder  for  each  bid,  for  if  the  information  called  for  is  not  sup- 
plied, the  proposal  may  be  regarded  as  informal  and  rejected: 

The  undersigned  agrees  to  furnish  to  the - - 

the  coal  described  below,  in  tons  of  2,000  lb.  each,  and  in  quantity  as  may  be 
required  during  the  fiscal  year  ending,  in  accordance  with  the  foregoing 
specifications ;  the  coal  to  be  delivered  in  such  quantities  and  at  such  times  as 
the  Government  may  direct. 


(a)  Kind  and  size 

(b)  Commercial  n 
(c) 


(e) 

(0 

(g)       Name  of  operator  of  mine  or  mines.,^ 

(h)  Percentage  of  moisture  in  coal  "ai  received"-^ 

(i)         Percentage  of   ash  in   "dry   coal" „_„__ 

(j)        Percentage  of  volatile  matter  in  "dry  coaI"~ 

(k)  Percentage  of  sulphur  in  "dry  coal"_ 

(1)    - 

(in) 


d  price  p«r  too  of  2,000  p 


ib.Google 


specifications  for  Oil 

FUEL  OILS  are  commonly  specified  according  to  their  density.  While  this 
is  accepted  trade  practice,  it  is  not  an  accurate  gage  of  the  fueL  The  heavy 
oils  are  of  an  asphalt  base,  viscous,  jsluggish,  and  of  relatively  low  beating 
power.  The  light  oils  are  fluid  at  ordinary  temperatures,  are  volatile,  rich  in 
hydrocarbons  and  high  in  heating  power.  The  heating  power,  however,  de- 
pends mainly  upon  the  hydrogen  and  carbon  content,  and  when  reduced  to 
ultimate  analysis  these  values  are  about  the  same  for  both  heavy  and  light 
oils.  The  commercial  value  of  fuel  oil  depends  upon  how  easily  it  can 
be  handled,  or  how  completely  it  can  be  atomized  by  the  burner  equip- 
ment, and  these  features  are  controlled  by  the  viscosity  of  the  fuel. 

Viscosity  can  be  defined  as  molecular  friction  or  the  resistance  to  inter- 
nal movement  of  a  liquid.  It  is  generally  measured  by  the  scale  of  a  visco- 
meter, such  as  the  Saybolt,  Redwood  or  Englcr,  which  indicates  the  time 
required  for  an  amount  of  oil  to  flow  through  a  standard  orifice  or  short 
tube  under  fixed  conditions  of  head  and  temperature.  The  result,  some- 
times expressed  in  "degrees,"  is  simply  a  time  ratio.  The  type  of  viscometer 
should  always  be  named  in  specifying  viscosity,  because  the  standards  vary 
in  difierent  i 


As  the  viscosity  is  materially  lessened  as  the  temperature  increases,  the 
fuel  oil  in  power-plant  practice  is  heated  to  about  160  deg.  before  being 
ted  to  the  burners.  At  this  temperature,  California  oils  have  a  vis- 
cosity between  3.S  and  8.S  deg.  Engler,  Many  of  the  lighter  oils  are 
sufficiently  mobile  at  ordinary  leropcrafures  and  do  not  require  pre-heating. 
In  general,  oil  fuel  is  heated  to  within  SO  deg.  of  the  flash  point  for  boiler 
operation  with  mechanical  burners. 

The  flash  point  of  the  fuel  indicates  the  temperature  at  which  inflammable 
gases  or  vapors  are  given  off.  For  oil  fuels,  it  ranges  from  Z20  to  280  d^ 
For  safehr  in  handling  this  should  not  be  below  150  deg.  When  stored  m 
tanks  and  at  ordinary  temperatures,  there  is  practically  no  danger  as  the 
oil  does  not  form  any  appreciable  amount  of  gas  at  temperatures  below  the 
flash  point.  The  flash  point  is  determined  by  heating  the  oil  fuel,  usually 
in  a  dosed  container,  and  testing  with  a  spark  or  flame.  The  vapor  or  gas 
is  driven  off  and  flashes  or  ignites.  The  temperature  at  which  ignition 
takes  place  is  called  the  flash  point  In  the  so-called  open  test  an  open 
vessel  prolongs  the  flash  point,  the  temperature  being  higher  than  with 
the  closed  instruments  of  Abel,  Pensky  or  Marten,  which  are  considered 
standard. 

By  continuing  the  heating  beyond  the  flash  point  until  the  ftash  becomes 
permanent  and  the  fuel  continues  !o  burn  a  temperature  known  as  the 
bttming  point  is  reached.  As  a  free  supply  of  air  is  required  in  this  test,  the 
open-cup  method  is  used.  For  Kern  River  oil,  the  bummg  point  can  be  taken 
as  between  260  and  270  degrees. 

The  properties  of  oil,  as  outlined,  are  of  prime  importance  in  the  pur- 
chase of  the  fuel,  and  are  therefore  included  in  commercial  specifications. 

Naval  Speci&catiom  for  Oil.  The  British  Navy  specifies  a  flash  point 
not  lower  than  1?5  deg.,  closed-cup  test.  The  water  content  must  not  exceed 
0.5  per  cent ;  sulphur  not  over  3  per  cent ;  and  acidity  expressed  as  oleic  acid, 
a  maximum  of  O.05  per  cent 

The  U.  S.  Navy  requires  a  hydrocarbon  oil  of  best  quality,  free  from 
grit,  acid  and  other  foreign  matter,  A  barrel  of  42  gal.,  each  gallon  of  231 
cu.  in.  at  60  deg.,  is  the  standard.  For  a  variation  of  10  deg.  from  the 
standard  temperature,  0.4  per  cent  is  added  or  deducted  to  correct  the  meas- 
ured quantity.  The  oil  must  not  contain  more  than  1  per  cent  water  and 
sediment.  If  over  1  per  cent,  the  excess  is  either  deducted  from  the  volume 
or  else  the  fuel  is  rejected. 


ib.  Google 


Viscosity  at  100  deg.  must  not  be  higher  than  200  Engler  or  7000  seconds 

SaybolL  The  flash  paint  must  not  be  below  150  deg.  as  the  minimum 
by  ihe  Abel  or  Pensky-Marten  closed-cup  test,  or  175  deg.  by  the  Taghabuc 
open-cup  method.  For  acceptance  it  should  not  be  lower  than  the  temper- 
ature at  which  the  viscosity  is  8  deg.  Engler.  As  water  is  unity  on  the 
Engler  scale,  an  oil  having  a  viscosity  of  8  deg,  Engler  at  a  temperature 
of  180  deg.  will  have  a  »ash  point  of  180  deg.  The  equivalent  of  8  deg.  Engler 
is  taken  as  2iS0  sec  Saybolt. 

Railroad  Fuel  Oil.  The  contract  form  of  a  large  railroad  system  u^g  oil 
as  fuel,  calls  for  the  following: 

Fuel  oil  should  have  a  density  ranging  between  13  and  29  deg.  Baumi 
at  60  deg.  It  should  contain  no  sand  or  other  foreign  matter,  such  as 
sticks,  waste  and  stone.     The  moisture  content  should  be  a  r  '   '  '^'' 


containing  over  2  per  cent  water  and  other  impurities  will  be  rejected. 

Viscosity  to  be  so  low  that  the  fuel  oil  will  flow  readily  through  a  4-in. 
pipe  at  70  deg.  temperature. 

Oil  will  not  be  accepted  when  the  flash  point  is  less  than  110  deg.  as 
tested  by  the  Tagliabue  open-cup  method.  The  fuel  is  to  be  heated  at  the  rate 
of  5  deg.  per  minute  and  the  test  flame  applied  at  one-minute  intervals  after 
90  deg.  has  been  reached. 

Govemmeiil  Oil  Fuel.  For  the  purchase  of  oil  fuel  for  the  diflerent 
departments  of  the  U.  S.  Government,  the  Bureau  of  Mine*  has  outlined 
the  main  features  controlling  the  efficient  utilization  of  fuel  oil  under 
steam  boilers,  as  follows: 

Fuel  oil  should  be  either  a  natural  homogeneous  oil  or  a  homogeneous 
residue  from  a  natural  oil;  if  the  latter,  all  constituents  having  a  low  flash 
point  should  have  been  removed  by  distillation;  it  should  not  be  composed 
of  a  light  oil  and  a  heavy  residue  mixed  in  such  proportions  as  to  give  the 
density  desired. 

It  should  not  have  been  distilled  at  a  temperature  high  enough  to  bum 
it,  nor  at  a  temperature  so  high  that  flecks  of  carbonaceous  matter  began 
to  separate. 

It  should  not  flash  below  140  deg.  in  a  closed  Abel-Pensky  or  Pensky- 
Marten  test. 

Its  specific  gravity  should  range  from  0.85  to  0.96  at  59  deg.;  the  oil 
should  be  rejected  if  its  specific  gravity  is  above  0,97  at  that  temperature. 

It  should  be  mobile,  free  from  solid  or  semi-solid  bodies,  and  should 
flow  readily,  at  ordinary  atmospheric  temperature  and  under  a  head  of 
1  ft.  of  oil,  through  a  4-in.  pipe  10  ft.  in  length. 

It  should  not  congeal  or  become  too  sluggish  to  flow  at  32  degrees. 

It  should  have  a  heating  value  of  not  less  than  18,000  B,t,u.  per  pound; 
18.450  B.t.u.  to  be  the  standard.  A  bonus  is  to  be  paid  or  a  penalty 
deducted  according  as  the  fuel  oil  delivered  is  above  or  below  this  standard. 

It  should  be  rejected  if  it  contains  more  than  2  per  cent  water  or  more 
than   1  per  cent  sulphur. 

It  should  not  contain  more  than  a  trace  of  sand,  clay,  or  dirt 


ib.  Google 


w 


CHAPTER  14 


FEED  WATER 

ATER,  the  most  widely  distributed  liquid  in  nature,  is  the  fluid  gen- 
erally employed  for  converting  heat  energy  into  work  by  its  expansion 
in  the  form  of  steam. 

Properties  of  Water 

CHEMICALLY  pure  water  is  a  chemical  combination  of  the  two  elements, 
hydrogen  and  oxygen,  in  the  proportion  of  two  parts  hydrogen  by 
volume  to  one  part  oxygen  CH,0).  or  one  part  hydrogen  by  weight  to  eight 
parts  of  oxygen.    Distilled  water  may  be  generally  regarded  as  chemically 

Water  reaches  its  maximum  density.  62.425  lb.  per  cu.  ft  at  39.1  deg.. 
and  expands  if  this  temperature  is  either  raised  or  lowered.  Fig.  219  shows 
its  variation  in  weight  and  volume  at  temperatures  from  20  to  250  deg- 
The    values    given    are    those    at    saturation    pressure ;    that    is.    the  pres- 


Flg.  119.     Variation  of  Weight  and  Volume  of  Water  with  Temperature. 

sure  at  which  liquid  and  vapor  in  contact  at  the  same  temperature  will  remain 
in  equilibrium.  For  temperatures  between  32  and  212  deg..  the  weights  and 
volumes  at  atmospheric  pressure  are  practically  indistinguishable  from  those 
at  saturation  pressure,  as  water  is  almost  incompressible.  The  dotted  lines 
beyond  these  ranges  represent  the  volume  and  weight  of  water  in  contact 
with  steam  at  the  pressures  (above  or  below  ordinary  atmospheric)  corre- 
spondbg  to  the  temperatures  given. 

The  specitic  heat  of  water  at  63  deg.  is  taken  as  unity,  that  is,  it  requires 
1  B.t.u.  to  raise  a  pound  of  water  from  63  to  64  deg.  The  specific  heat 
varies  slightly  at  other  temperatures,  being   ISH  at  20  deg.;  reaching  its 


ib.  Google 


FEED    WATER 

.  .  .1,  0.99S,  at  100  deg.;  and  rising  to  1.18  al  600  deg.  The  term,  "mean 
specific  heat"  is  applied  to  Che  difference  in  heat  capacity  per  pound  at  two 
different  temperatures,  divided  by  the  temperature  difference.  The  mean 
specific  heat  of  water  from  32  to  175  deg.  is  0.999,  and  for  greater  ranges  it 
gradually  rises,  reaching  1.062  for  the  range  from  iH  to  600  deg.  For  many 
engineering  purposes,  the  specific  heat  of  water  can  be  regarded  as  constant, 
and  the  heat  liberated  or  absorbed  taken  as  1  B.t.u.  per  pound  per  degree 
of  temperature  change. 


^ 


Fig.  220.    Variation  of  BoUing  Point  of  Water  with  Prewure. 

Vapor  rises  from  water  at  all  temperatures,  unless  the  vapor  pressure 
in  the  space  in  contact  with  the  water  exceeds  the  saturation  pressure.  The 
boiiing  point  for  any  particular  pressure  ii  the  highest  temperature  which 


ib.  Google 


FEED    WATER  SOI 

can  be  reached  with  the  water  and  vapor  in  contact  with  it  at  that  pressure, 
any  heat  added  to  the  water  resulting  only  in  the  formation  of  additional 
vapor.  In  the  generation  of  steam  tor  practical  purposes,  the  ebullition 
is  of  course  much  more  pronounced  than  is  the  formation  of  vapor  at  low 
temperatures,  but  the  phenomenon  is  similar  in  its  nature. 

The  boiling  point  rises  and  falls  with  the  pressure,  so  that  daily  changes 
in  the  barometer  have  a  slight  effect  on  the  boiling  point;  these  must 
be  allowed  for  in  calibrating  thermometers.  The  boiling  point  is  reduced 
at  points  of  high  elevation  and  consequent  low  average  barometric  pressure. 

As  long  as  heat  is  supplied  to  a  boiler  producing  steam,  the  temperature 
remains  at  the  boiling  point  corresponding  to  the  momentary  pressure,  so 
that  the  temperature  of  boiler  water  in  contact  with  saturated  steam  can  be 
judged  from  the  pressure.  Fig.  220  indicates  the  boiling  point  for  pressures 
up  to  400  lb.  gage.  The  divisions  to  the  right  indicate  the  corresponding 
pressures  in  absolute  units,  eqnal  to  14.696  plus  the  gage  pressure  in  pounds 
per  square  inch.  Absolute  pressures  in  pounds  per  square  inch  are  converted 
into  "standard  atmospheres  by  dividing  by  standard  or  normal  atmospheric 
pressure  (14.696  lb.  per  sq.  in.),  which  is  the  pressure  that  will  support  a 
column  of  mercury  760  mm.  (29.921  in.)  in  height.  Koughly,  2  in.  of  mercury 
correspond  to  each  pound  of  pressure. 

Pure  water  boils  at  212  deg.  under  standard  atmospheric  pressure.  For 
boiling  points  lower  than  212  deg.,  the  pressures  are  less  than  atmospheric. 
They  are  expressed  as  absolute  pressures,  in  pounds  per  square  inch  or  in 
head  of  mercury;  or  by  the  amount  of  "vacuum,"  that  is,  the  difference 
between  the  absolute  head  of  mercury  and  the  standard  atmospheric  head  of 
29.921  inches.  For  engineering  purposes,  the  barometer  is  arranged  so  that 
the  reading  is  subtracted  from  30  instead  of  from  29.921,  so  that  stand- 
ard atmospheric  pressure  when  "referred  to  a  30-in.  barometer"  would  be 
recorded  as  0.08  in.  of  vacuum. 

Impuritiea  in  Water 
A  LL  known  substances  are  more  or  less  soluble  in  water,  so  that  natural 
'^  water  supplies   other  than  rain   water  are  always   contaminated,   and 
contain  in  solution  organic  matter  or  traces  of  the  solids  with  which  they 
have  come  in  contact.     In  a  boiler,  the  solids  remain  behind  when  steam 
is  produced,  and  the  impurities  are  precipitated  when  their  maximum  con- 
centration  is   reached,   that  is,   when  the   volume   of  water   is   sufficiently 
reduced  to  become  saturated  with  the  particular  substance.     These  precipi- 
tates cause  scale  and  accompanying  troubles,  the  seriousness  of  which  depends 
upon  the  nature  and  amount  of  the  original  impurities. 

The  characteristics  of  a  boiler  feed  water  may  be  described  by  one  or 
of   the    following   terms :    temporary   hardness,   permanent   hardness, 
irity,  causticity,  acidity,  and  dis    "      '  '  ...... 

purities   being   generally   expressed   i 

Temporary  hardness  is  the  term  applied  to  water  containing  the  bicar- 
bonates  of  calcium,  Ca(HCOt)b  and  magnesium,  Mg(HCOi)b  which  are 
held  in  solution  by  an  excess  of  carbon  dioxide.  Boiling  at  212  degrees 
expells  the  carbon  dioxide.  In  the  one  case,  calcium  carbonate,  CaCOi,  pre- 
cipitates out  directly.  In  the  other,  magnesium  monocarbonate  is  formed. 
This  is  soluble  and  requires  further  treatment  with  calcium  hydroxide, 
Ca(OH),  to  reduce  to  the  precipitate  Mg(OH), 

Sodium  bicarbonate,  NaHCOi,  and  sodium  carbonate,  NaiCOi,  are  found 
in  the  water  in  some  localities.  The  former  can  be  converted  to  the  car- 
bonate by  the  use  of  calcium  hydroxide,  Ca(OH)r 

Permanent  hardness  refers  to  those  waters  which  contain  sulphates,  the 
most  common  of  which  is  calcium  sulphate,  CaSOt. 


ib.  Google 


■a 


D,B,i,.ab,GoOglc 


FEED    WATER  503 

Solid  caldum  sulphate,  CaSO^  is  known  as  plaster  of  Paris,  or  as 
gypsum  when  containing  a  larger  amount  of  water  of  crystallization.  It  is 
highly  soluble  in  water,  138  grains  per  gallon  at  60  deg,,  and  over  30  grains 
at  300  deg.,  but  when  concentrated,  deposits  a  hard  scale  on  the  boiler  tubes. 
It  can  be  converted  by  the  use  of  soda  ash  (sodium  carbonate,  Na,CO,), 
forming  calcium  carbonate,  CaCOi,  and  sodium  sulphate,  Na.SO..  The 
CaCOt  can  be  precipitated  before  the  water  enters  the  boiler,  but  the  NatSO* 
remains  in  solution,  and  does  not  interfere  with  boiler  operation  unless  it 
becomes  highly  cci'.cei  it  rated. 

Magnesium  sulphate,  MgSOi,  is  decidedly  soluble,  but  tends  to  read 
with  any  calcium  salts  present,  forming  hard  calcium  sulphate  scale.  Water 
containing  MgSOi  can  be  treated  by  introducing  calcium  hydroxide,  Ca(OH)i, 
forming  insoluble  magnesium  hydroxide,  Mg(OH)i,  and  calcium  sulphate, 
CaSOi.  which  can  be  corrected  by  soda  ash. 

Iron  oxides,  FeO,  Fe.0.  and  FeiO.;  aluminum  oxide  or  alumina,  AUO,; 
and  silicon  oxide  or  silica.  SiiOi.  are  scale- forming  substances  sometimes 
found  in  solution. 

Alkalinity,  a  term  often  used  confusedly  wilh  temporary  hardness,  refers 
more  particularly  to  waters  containing  impurities  which  will  neutralize  acids. 

Causticity  describes  waters  that  contain  hydrates  which  react  to  the 
phenol phthale in  indicator.  This  test  is  important  in  connection  with  waters 
which  may  give  caustic  embrittlement  trouble. 

Acidity,  as  the  term  implies,  refers  to  waters  containing  free  acid.  In 
mining  districts  the  water  often  contains  sulphuric  and  sulphurous  acids. 
Organic  acids  are  found  in  swamp  water  and  in  water  contaminated  with 
sewage.  Chlorides  and  acids  present  in  boiler  feed  water  are  neutralized 
by  the  reagents  used  to  correct  sulphates  and  carbonates. 

Calcium  chloride,  CaCIi,  and  magnesium  chloride,  MgCli,  are  found  in 
boiler  feed  water.  The  latter  is  troublesome,  as  at  boiler  temperatures  it 
tends  to  form  hydrochloric  acid,  which  causes  corrosion. 

Solid  matter  such  as  mud  and  silt  are  often  present  in  boiler  water,  par- 
ticularly if  the  feed  water  is  obtained  from  rivers  and  streams. 

Dissolved  gases,  or  air  entrained  or  in  solution,  in  boiler  feed  water  is 
recognized  as  a  source  of  corrosion. 

Water  Analysis 
'T'ABLE  80  gives  some  representative  analyses  of  water  from  various  locali- 

Melhods  of  Water  Analysis.  Where  it  is  proposed  to  prescribe  a  method 
of  feed  water  treatment  for  a  boiler  plant,  it  is  obvious  that  water  analyses 
should  be  carried  out  in  a  laboratory  equipped  especially  for  the  purpose. 
However,  there  are  a  number  of  simple  tests  which  can  be  performed  in  the 
boiler  room  with  a  minimum  outlay  for  apparatus,  and  which  will  indicate 
to  the  plant  engineer  the  advisability  of  installing  feed  water  treatment 

Test  for  Hardness.  A  100  cubic  centimeter  sample  of  the  water  tor 
analysis,  together  with  a  standard  soap  solution,  is  shaken  in  a  flask ;  the 
soap  solution  being  added  a  tittle  at  a  time  until  a  permanent  lather  is  formed. 
The  number  of  cubic  centimeters  of  the  standard  soap  solution  required  to 
form  the  permanent  foam  will  be  equivalent  to  the  hardness  in  parts  per 
100.000.  or  in  degrees  "U.  S."  hardness  depending  upon  the  standard  to 
which  the  soap  solution  is  made  up.  One  degree  "U.  S."  hardness  is  equiva- 
lent to  I  grain  of  calcium  carbonate  per  U.  S.  gallon  (1  part  in  58.349). 
Standard  soap  solutions  may  be  obtained  from  chemical  dealers.  If  this 
soap  test  is  made  on  unboiled  water,  the  total  hardness  will  be  determined, 
and  if  on  boiled  water,  the  permanent  hardness  will  be  obtained,  the  difference 
between  the  two  being  the  temporary  hardness. 


ib.  Google 


FEED    WATER 


Table  80.     Water  Analytea. 

("BflUer  Water*"  by  W.  W.  Chrittie) 

OraiM  per  U.  S.  Oalloo  of  231  Cubic  Inchea. 


mmmWrtm 

I!! 

J!i 

II 

i 

1"- 

h 

Buffalo,  N.  y,  Lake  Erie 

Pittsburgh,  Allegheny  River.. . . 
Pittsburgh,  Monongahela  River 

5.66 

0.37 
1.06 

3.32 
3.78 
5.12 

0.58 
0.58 
0.64 

"h'.'ii 

0.78 

3.20 

9,74 
6.60 
10.80 

Pittaburgh,  Pa.,  artesian  well . . 
Milwaukee,  Wisconwo  River. . . 
Galveston.  Texas.  1 

23.45 
6.23 
13. 6« 

5.71 
4.67 

13.52 

18.41 

1.76 

326.64 

1,04 
20.14 
Trace 

0.82 
6.50 
Trace 

49.43 
39.30 

353.84 

21.79 
20.76 

2.87 

29.15 
11.74 

3.27 

398.99 
7.02 
Trace 

"oiss 

0.36 

4.00 
6.50 
2.10 

Washington,  D.  C,  city  supply. 

8.60 

Baltimore,  Md.,  city  supply 

Sioux  City,  Iowa,  city  supply . . 
Los  AngeleB.  Cal.,  1 

2.77 
19.76 
10.12 

iJJ 

Trace 
1.17 
3.51 

0.10 

in 

3.80 
4.40 
4.10 

7.30 
27.60 
26.20 

3.72 

8.47 
4.84 

12.59 
10.36 
33.66 

126.78 

•1 

6.00 
8.74 
10.92 

Bay  City,  Mich..  River 

179.20 

Cincinnati,  Ohio,  River 

3,88 
1.47 
8.78 

0.78 
4.51 

6.22 

1.79 
1.76 
3.51 

Trkce 

1.59 

Trace 
1.78 
10.98 

6.73 

Fort  Wayne,  Ind 

31.08 

10.04 
14  14 
12.99 

6,02 
25  91 

7.40 

4.29 
24,34 

1.97 

8,48 
"2.19 

6.17 
2.00 

8.62 

SprinRBeld.  III.,  i 

33.17 

5.47 
14.56 
4.32 

4.31 
2.97 
16.15 

1.56 
2.39 
1.20 

4.28 

5.83 
Trace 
5.12 

Pueblo,  Colo 

28.76 

Long  Island  City,  L.  1 

Mississippi  Riverabove  Missouri 
River 

4.0 
8.24 

28,0 
1.02 

16.0 
0.50 



1.0 
5.25 

39.0 
15.01 

Mississippi  River  below  mouth 

10.64 
9.64 

7.., 
6,4 

1.36 
1.54 

1.22 
1.57 

Water  Works 

9.85 

29.54 

Hudson    River    above    Pongh- 
keepsie.N.  Y             

1.06 
4-57 

o.ie 

O.U 
0.40 

10.76 
1.92 

0.77 
0.67 

12.70 

Croton     River    above    Croton 
Dam,  N.  Y 

7.72 

Croton  River  water  from  service 

pipes  in  New  York  City 

Schuylkill    River   above    Phila 

2.36 
2.16 

1.36 
1.30 

0.29 

0.49 

quantities  of  other  salts  present  ._  _ 
Magnesium  carbonate  X  L19 
Magnesium  sulphate  X  0333 
Magnesium  chloride  X  1.05 
Calcinn)  sulphate  X  0735 

Calcium  chloride  X  0.901 


o  a  calcium  carbonate  basis. 

Hardness  as  calcium 
:  carbonate  per 
U.  5.  gallon. 


ib.  Google 


FEED    WATER 


A  water  containing  more  than  20  grains  of  calcium  carbonaie,  masnesiuin 
carbonate  or  magnesium  chloride  per  U.  S.  gallon,  or  more  than  5  grains  of 
calcium  or  magnesium  sulphate  per  U.  S,  gallon,  is  considered  undesirable 
for  boiler  feed. 

Table  81  rougbly  classifies  the  desirability  of  bard  waters  for  boiler  use. 

Table  81.    ClatdRcation  of  Boiler  Peed  Watcn. 


0  to  10  gr. 
10  to  IS  gr, 
15  to  20  gr. 
20  to  30  gr. 
Over  30  gr. 


0  to  2.5  gr. 
23  to  4.0  gr. 

4  to  S,0  gr. 

5  to  7.S  gr. 
Over  7.5  gr. 


Very  Good 

Fair. 

Bad. 
Very  Bad. 


j4lka!iniiy  Test.  A  50  cubic  centimeter  sample  of  the  water  to  be 
tested  is  titrated  with  a  standard  solution  of  sulphuric  acid,  using  methyl 
orange  as  an  indicator.  The  degree  of  alkalinity  will  be  represented  by  the 
number  of  cubic  centimeters  of  acid  used  to  neutralize  the  solution,  as  will 
be  indicated  when  the  color  of  the  solution  just  turns  from  pink  to  pale 
yellow.  The  required  standard  sulphuric  acid  solution  can  be  obtained  from 
chemical  dealers. 

Causlicfly  Test.  A  SO  cubic  centimeter  sample  of  the  water  is  titrated 
with  a  standard  solution  of  sulphuric  acid,  using  phenolphthalein  as  an  indi- 
cator. The  degree  of  causticity  will  be  represented  by  the  number  of  cubic 
centimeters  of  acid  used  to  satisfy  the  reaction,  as  will  be  indicated  when 
the  solution  turns  from  red  to  colorless. 

The  alkalinity,  hardness  and  causticity  of  a  properly  treated  boiler  water, 
as  expressed  in  grains  per  U.  S.  gallon  by  analysis,  should  stand  in  the 
approximate  relation  of  6,  5  and  4. 

Concentration  Test 

THE  total  conccniratioH  of  soluble  sails  in  a  boiler  fed  with  softened 
water  can  be  estimated  from  the  amount  of  sodium  chloride  or  common 
salt  (NaG)  in  solution,  which  can  be  determined  as  follows :  After  blowing 
down  the  boiler,  a  sample  is  drawn  from  the  water  column,  allowed  to  cool 
and  settle,  and  100  cc.  of  the  clear  liquid  measured  off.  A  drop  of  phenol- 
phthalein solution  is  added  to  the  latter,  turning  it  pink;  then  just  sufficient 
N/20  sulphuric  acid  (about  'A  per  cent  strong)  from  a  burette  to  destroy 
the  pink;  and  four  drops  potassium  chromate  indicator  (containing  20  grains 
per  100  cc).  Silver  nitrate  solution  is  then  added  slowly  from  another 
burette,  while  stirring  the  sample,  until  a  permanent  reddish  precipitate  is 
formed.  If  the  silver  nitrate  solution  is  of  a  strength  of  4.976  grains  AgNO, 
per  liter,  each  cubic  centimeter  of  the  solution  consumed  represents  1  grain 
of  sodium  chloride  per  gallon  in  the  boiler  water. 

Water  Treatment 

'ATER  treatment  may  be  roughly  classified  into  three  separate  divisions, 

viz:  mechanical  treatment,  thermal  treatment  and  chemical  treatment. 

Mechanical  Treatment.    Raw  water  from  rivers  very  often  contains  mud 

silt  in  suspension,  and  if  used  directly  in  boilers  will  cause  the  deposi- 


W 


ib.Google 


II 


ib.Google 


FEED    WATER  507 

lion  of  mud  on  the  heating  surfaces,  resulting  in  lowered  heat  transmission, 
burned  tubes  and  bagged  plates.  Such  solid  matter  may  be  removed  by 
settling,  filtering  or  by  a  combination  of  these  two  methods.  Heavy  mud 
and  sand  can  be  eliminated  by  allowing  the  water  to  stand  in  settling  basms, 
but  suspended  matter  which  will  not  gravitate  must  be  removed  by  filtration. 
Settling  basins  are  generally  constructed  of  concrete.  They  should  be  ar- 
ranged in  duplicate  so  that  while  one  basin  is  settling  the  other  may  be 
drawn  upon  as  the  supply.  The  size  of  such  basins  will  depend  upon  the 
characteristics  of  the  particular  water  as  regards  sedimentation,  which  may 
be  roughly  determined  by  experimental  tests  conducted  on  not  less  than 
barrel  samples.  Filter  beds  may  be  constructed  of  coke,  excelsior,  crushed 
stone  or  sand,  and  they  should  be  arranged  in  duplicate  to  allow  for  clean- 
ing. 

Thermal  Treatment.  As  stated  above,  the  carbonates  of  lime  and  mag- 
nesia are  precipitated  by  boiling,  hence  it  is  obvious  that  any  type  of  feed 
water  heater  will  act  to  a  certain  extent  as  a  puriAer  or  softener.  A  descrip- 
tion of  the  various  types  of  heaters  and  of  economiiers  is  given  in  Chapter 
9  on  AUXILIARIES. 

Chemical  Treatment 
""The  chemical  methods  used  for  softening  boiler  feed  water  have  been 
*■  practically  unchanged  for  more  than  50  years,  except  for  special  methods 
devised  to  obtain  softened  cold  water.  Hydrate  of  lime  in  the  form  of  lime 
water,  or  of  milk  of  lime,  is  still  the  most  economic  means  for  neutralizing 
acids,  absorbing  carbon  dioxide,  and  converting  bicarbonates  to  carbonates 
or  hydrates.  Likewise,  soda  ash  is  preferred  for  transforming  sulphates, 
chlorides  and  nitrates  to  carbonates.  While  the  chemical  methods  have  not 
been  changed,  the  engineering  appliances  for  performing  the  softening  process 
have  undergone  a  radical  evolution.  The  improvements  have  consisted  prin- 
cipally in  the  proper  use  of  heat  for  accelerating  the  chemical  reaction,  the 
more  accurate  feeding  of  chemical  reagents,  and  the  reduction  in  the  labor 
required  in  handling  chemicals  aad  in  removing  precipitates. 

Two  general  types  of  lime-soda  processes  are  used  in  power  plants.  In 
all  essential  respects,  these  two,  the  hot  continuous  and  the  cold  continuous; 
processes,  are  similar.  The  treatment  consists  of  adding  to  the  raw  water 
softening  agents  in  carefully  controlled  amounts  (which  must  agree  with  the 
composition  of  the  water),  mixing  these  thoroughly  wiihin  the  water,  and 
perniitting  sufficient  time  to  elapse  for  the  separation  of  the  "sludge"  before 
the  water  is  fed  into  the  bailer.  In  the  first  process,  the  heat  increases  the 
rapidity  of  the  chemical  reactions,  so  that  the  storage  space  required  is 
less  than  with  the  cold  continuous  process.  The  hot  process  expels  the  air 
from  the  water  and  so  reduces  corrosion.  The  cold  process  is  used  mainly 
when  cold  water  is  required  for  some  special  purpose,  such  as  process  work. 

Most  softeners  are  of  the  continuous  type.  In  intermittent  softeners, 
two  or  more  tanks  are  intermittently  filled  with  raw  water  and  chemicals. 
The  treated  water  is  then  drawn  off  from  one  tank,  while  the  other  is  filled 
and  agitated  by  a  revolving  paddle  so  as  to  insure  mixing  and  to  stir  up  old 
sludge,  which  assists  in  settling  out  the  new  precipitate. 

The  water  softening  apparatus  tisually  includes  some  method  of  mixing 
the  raw  water  with  the  chemical  reagents;  the  chemical  reactions  occur  and 
the  impurities  are  precipitated  in  a  sedimentation  tank.  Sometimes  the  raw 
water  is  then  passed  through  a  filter  tank. 

Chemical  Feed.  Chemicals  must  be  fed  to  a  softener  accurately  in  pro- 
portion to  the  amount  of  water  and  to  the  impurities  in  the  water.  Other- 
wise the  water  will  deposit  scale,  or  will  contain  an  excess  of  unused  reagents. 
In  some  softeners  the  raw  water  flowing  to  the  softener  turns  a  water  wheel 
or  operates  a  tilting  bucket.    This  in  turn  operates  dipper*  in  which  the  re- 


ib.  Google 


see  FEED    WATER 

agents  are  ladled  out  to  be  mixed  with  the  raw  water.  In  one  design  part 
of  the  water  is  separated  from  the  main  supply  by  orifices  or  weirs,  and 
flows  through  chambers  containing  the  reagents.  In  another  ^e,  the  water 
displaces  the  reagent  from  the  tank,  at  the  same  time  diluting  that  which 
remains  in  the  tank.  The  raw  water  is  sometimes  passed  through  a  hydraulic 
motor,  which  drives  a  small  chemical  pviap.  The  feed  can  also  be  controlled 
by  hand,  an  operator  adjusting  the  chemical  pump  to  deliver  the  required 
amount  of  solution  each  hour.  Results  are  more  satisfactory,  however  with 
the  automatic  feed. 

SedimetilalioM  Tankt  usually  have  a  conical  base,  into  which  the  precipi- 
tates settle.  The  hot  water  and  softening  reagents  arc  delivered  at  the  top, 
and  settle  to  the  bottom,  where  the  clarified  water  is  withdrawn.  In  some 
designs  (see  Fig.  221)  an  open  feed  water  heater  is  placed  above  the  sedimen- 
tation tank.  The  heating  chamber  of  the  softener  can  be  divided  into  two 
compartments,  one  for  heating  the  raw  water,  and  the  other  the  pure  water 
supply,  the  latter  passing  directly  to  the  boiler  feed  pump. 

Filltft.  In  some  installations  a  separate  filter  is  often  dispensed  with, 
the  sedimentation  tank  removing  the  impurities.  Under  other  conditions  a 
low^ressure  sand  filter  is  placed  between  the  sedimentation  tank  and  the 
bailer  feed  pump  or  meter,  the  water  flowing  through  by  gravity.  The  water 
delivered  should  be  crystal  dear,  containing  no  solids  except  those  in  solu- 
tion, and  practically  no  mud-forming  properties.  This  clarified  water  will 
leave  no  troublesome  deposit  in  the  feed  lines,  pumps  or  meters,  and  i> 
especially  suitable  for  boilers  operated  at  high  ratings. 

In  the  hot  process  water  softener,  Fig,  221,  the  raw  water  flows  over 
heating  trays,  where  it  is  heated  by  exhaust  steam  purified  of  oil  to  a  tem- 
perature within  a  few  degrees  of  the  Steam  itself.  The  water  falls  from 
the  trays  into  the  sedimentation  tank.  Immediately  after  the  water  is  heated 
to  the  boiling  point  or  near  it,  the  softening  chemicals  are  added.  In  certain 
waters,  they  may  be  added  above  the  heating  trays.  A  precipitate  is  formed, 
which  settles  toward  the  bottom  of  the  sedimentation  tank,  traveling  much 
faster  than  the  water.  Due  to  the  lower  viscosity  of  hot  water,  the  precipi- 
tation is  much  more  rapid  than  in  cold  water.  As  a  result  the  precipitate 
passes  to  the  conical  bottom,  from  which  it  is  removed  by  opening  the  blow- 
off  valve. 

A  chemical  proponioner  is  used  to  regulate  the  proportion  of  lime  and 
soda  ash  to  the  raw  water.  A  thin  plate  with  a  restricting  orifice,  is  placed 
in  the  raw  water  tine  between  the  regulating  valve  and  heater.  A  differential 
pressure  is  set  up  on  the  two  sides  of  the  plate,  proportional  to  the  square  of 
the  flow.  This  pressure  is  continually  translated  to  an  effective  direct  pres- 
sure on  the  chemical  orifice.  The  chemical  solutions  and  the  raw  water 
each  pass  through  their  respective  orifices  at  exactly  the  same  effective  pres- 
sure, so  that  the  chemicals  are  always  accurately  proportioned  to  the  raw 

Tht  chemical  treatment  is  controlled  by  drawing  a  sample  of  the  treated 
water  from  time  to  time  and  titrating  with  standardized  solutions,  the  whole 
operation  requiring  about  ten  minutes.  The  titration  readings  are  obtained 
and  then  located  upon  a  chart  supplied  with  the  softener,  from  which  the 
correct  chemical  treatment  is  immediately  read.  Thus  the  operator  sees  at  a 
glance  what  change,  if  any,  is  required  in  the  amounts  of  the  chemicals. 

Zeolite  Process.  This  process  gives  a  water  of  lero  hardness.  The 
softening  agent  is  an  artificial  material  (permutit)  composed  largely  of  sodium 
compounds,  which  are  exchanged  for  the  incrusting  (scale- forming)  material 
of  die  water.  The  hard  water  flows  over  the  permutit  which  is  packed  in 
a  cylinder,  or  is  forced  through  and  flows  from  it  with  all  scale-forming 
material  removed.  The  softener  must  be  regenerated  from  time  to  time  by 
allowing  a  solution  of  salt  to  flow  over  it,'thus  restoring  its  original  com- 


ib.  Google 


FEED    WATER 


ib.  Google 


510  FEED    WATER 

position  and  activity.  If  the  water  i»  of  a  high  desree  of  temporary  or 
carbonate  hardneu,  the  zeolite  process  introduces  a  large  amount  of  aodiwn 
salt,  and  foaming  may  occur.  With  such  waters  the  zeolite  process  is  modified, 
an  intermittent  or  continuous  equipment  being  connected  throughi  a  filter 
to  a  zeolite  softener.  Only  lime  is  used  in  the  tank,  the  soda  compound  being 
secured  from  the  zeolite.  The  filter  is  placed  between  the  tank  and  the 
zeolite  softener  to  avoid  any  sludge  coating  the  permutit  particles,  and  thus 
impairing  its  efficiency. 

Bailer  Compounds.  Boiler  compounds  for  scale  prevention  are  tX' 
tensively  used  in  small  isolated  plants  where  the  expense  of  a  water-soften- 
ing plant  would  not  be  warranted.  While  it  is  to  be  admitted  that  all 
chemical  reactions  necessary  to  prepare  a  feed  water  should  preferably  take 
place  outside  of  the  boiler  itself,  there  is  no  doubt  but  that  a  compound  suit- 
able for  particularly  bad  conditions  and  correctly  used  is  to  be  preferred  to 
no  treatment  at  all. 

Results  of  Poor  Water  oil  Boiler  Operation 

"DRIMING  describes  that  phenomenon  occurring  in  steam  boiler  operation,  in 
^    which  water  is  delivered  in  belches  with  the  steam. 

Foaming  of  boilers  is  the  production  of  large  quantities  of  babbles  in 
the  steam  space. 

If  this  water  is  carried  out  of  the  boiler,  it  erodes  turbine  blades, 
increases  the  steam  consumption  and  causes  waste  of  lubricating  oil  in 
reciprocating  engines,  while  if  the  steam  passes  to  a  superheater,  the  water 
may  carry  solids  to  accumulate  there  as  scale. 

Foaming  and  priming  is  encouraged  by  the  presence  of  finely  divided 
suspended  matter,  such  as  carbonate  of  lime,  or  of  oil  or  soluble  salts,  such 
as  sodium  sulphate,  either  originalljr  present  or  produced  by  the  action  of 
water-softening  chemicals.  At  maximum  capacity,  water-tube  boilers  will 
stand  a  concentration  of  200  to  300  grains  of  sodium  sulphate  per  gallon; 
when  foaming  begins,  the  impurities  can  be  removed  by  the  use  of  the 
surface  and  bottom  blow-offs.  Even  though  some  heat  is  lost,  the  removal 
of  sediment  and  the  stopping  of  foaming  increases  the  efficiency. 

Foaming  is  also  encouraged  when  oil  is  contained  in  the  feed  water 
introduced  mto  boilers.  The  oil  tends  to  collect  on  the  tubes,  to  interfere 
with  heat  transmission,  and  to  break  down  into  corrosive  acids.  Oil  carried 
in  the  exhaust  steam  from  reciprocating  engines  or  auxiliaries  is  removed 
by  passing  the  steam  through  a  separator  rather  than  by  skimming  or 
filtering  the  condensate.  The  latter  method  is  ineffective  when  the  conden- 
sate contains  oil  in  an  emulsified  or  finely-divided  state. 

Corrosion  of  boiler  plates,  tubes  and  rivets  may  be  almost  uniform  tn 
effect,  in  which  case  the  action  is  difficult  to  detect,  or  it  may  be  manifested 
by  visible  grooving  and  pitting. 

Corrosion  of  boiler  metal  is  an  electrolytic  phenomenon  by  which  a 
neutral  iron  atom,  in  contact  with  two  positive  hydrogen  ions  in  the  water, 
takes  up  their  positive  charges  and  becomes  subject  to  oxidation.  The 
hydrogen  film  formed  tends  to  reduce  the  speed  of  the  reaction  almost  to 
jero  unless  ox^en  from  the  air  or  from  acid-forming  compounds  is  present 
in  the  water.  The  removal  of  carbon  dioxide  or  other  acids  by  chemical 
treatment,  and  the  de-aeration   of  the   water  by  pre-heating  will  prevent 


Electrolysis  or  galvanic  action  with  its  resultant  corrosion  of  the  boiler 
metal,  occurs  frequently  in  marine  practice,  due  principally  to  the  presence  of 
salt  (NaCl)  and  air  in  the  feed  water.  Zinc  plates  are  therefore  placed  in 
the  drum  to  act  as  the  electro-negative  element,  thus  hindering 
See  the  description  of  the  Heine  Marine  Boiler  in  Chapter  I. 


ib.  Google 


FEEDWATER  '  SU 

Causlie  Embrittlement  is  a  phenomenon  which  has  lately  received  con- 
siderable study,  but  as  yet  its  action  is  not  definitely  established.  In  certain 
localities  in  which  boiler  waters  are  of  an  alkaline  character  the  development 
of  cracks  around  seams  and  rivet  holes  below  the  water  line  have  caused 
failures  which  can  not  be  attributed  to  faulty  materials  or  design.  In- 
vestigation of  the  subject  seems  to  disclose  the  fact  that  these  failures  are 
due  to  an  embrittlement  of  the  boiler  metal.  This  embrittlement  is  pre- 
sumably caused  by  the  metal  absorbing  nascent  hydrogen  in  such  a  way  as 
to  impair  its  physical  properties.  This  effect  has  been  decidedly  pronounced 
in  boilers  using  water  containing  a  considerable  amount  of  caustic  soda, 
which  has  been  present  either  due  to  over-treatment  of  the  water,  or  as  the 
result  of  the  decomposition  of  the  sodium  bicarbonate  NaHCOi  occurring  in 
the  raw  water. 

Scale  Formation 

SOLUBLE  carbonates  and  sulphates  when  concentrated  in  the  boiler  are 
precipitated  as  Rolids,  which  tend  to  accumulate  and  become  baked  into 
hard  layers  known  as  "scale,"  which  hag  a  high  heat  insulating  value.  As  a 
result,  fuel  is  wasted,  and  the  metal  becomes  overheated.  Expansion  and  con- 
traction strains  follow  and  may  greatly  shorten  the  hfe  of  the  tubes.  Reports 
from  boiler  insurance  companies  show  that  the  majority  of  boilers  inspected 
—  J,™ 1  /-~m  impure  feed  water  by  scale  or  by  corrosion  and  pitting. 


It 


r  Surface 

Fig.  313.     Effect  of  Scale  on  Heat  Transmi^on. 

Fig,  222,  by  E.  Rcutlinger,  shows  the  high  temperature  difference  neces- 
sary in  operating  boilers  with  variation  of  heat  transmission  and  of  scale 
thickness.  For  the  clean  heating  surface,  the  rate  of  transmission  was  166 
B.t.u.  per  sq.  ft.  per  hour  per  degree  difference  between  the  metal  and  the 
water ;  for  the  plate  coated  with  Scale  No,  2,  which  was  0.217  in.  thick,  oi 
conductivity  23.85,  the  rate  was  reduced  to  67  B.t.u. ;  and  for  the  plate 
coated  with  Scale  No.  3,  of  the  same  thickness,  but  of  conductivity  8.06, 
.1.-  . :— 1-_  --. 5  ^jjiiy  3[  g(y     puj.  g  pi^jg  ^^^uii  ^  heavy  grease 


ib.  Google 


512  FEED    WATER 

coating  the  rate  was  13.5  B.t.n.  The  necessary  temperature  differences 
can  be  read  on  the  scale  to  the  left,  which  shows  that  with  scale  the  metal 
must  be  maintained  at  a  temperature  several  hundred  degrees  above  that  of 
the  water,  when  the  boiler  is  driven  at  the  rates  now  common. 

The  heat  losses,  which  may  be  as  great  as  10  per  cent,  the  damage  to 
the  boilers  themselves,  the  cost  of  repairs  and  cleaning;  all  these  emphasize 
the  importance  of  preventing  the  formation  of  scale.  Distilled  water  if 
used  exclusively  is  prohibitive  in  cost.  The  only  practical  method,  when 
scale-forming  matter  is  present  in  the  water,  is  to  form  soluble  salts  or 
non-scale  producing  precipitates.  Sodium  carbonate  (soda  ash)  can  be  used 
for  transforming  sulphates,  chlorides  and  nitrates  to  carbonates,  while 
calcium  hydroxide  (lime  water  or  milk  of  lime)  will  correct  acids  and 
bicarbonate  s. 


Two  200  H.  P.  Heine  Crosa-Drum  Marine  Boilers  on  the  Dredge-boat  "Dixie". 
Board  Qf  Port  CommiMiooeri,  New  Orleana,  L,a. 


ib.  Google 


CHAPTER    15 


BOILER  TESTING 


B". 


results  are  to  be  expected.  The  whole  matter  should  be  thoroughly 
understood  both  theoretically  and  practically. 

Accurate  tests  depend  very  largely  upon 
observers.  It  is  much  easier  to  make  mist 
who  are  not  familiar  with  practical  testing. 

Boiler  tests  are  run  to  compare  different  boilers,  stokers,  etc;  different 
kinds  o(  fuel;  different  methods  of  operation,  and  so  forth j  but  the  object 
of  the  trial  in  every  instance  is  to  determine  capacity,  or  efficiency  In  relation 
to  capacity.  To  more  definitely  check  the  results,  and  to  find  the  cause  of 
unusually  low  or  high  efficiency  by  investigating  the  losses,  the  performance 
of  the  test  and  the  analysis  of  the  observations  become  more  elaborate. 

The  Rules  for  Conducting  Evaporative  Tests  of  Boilers,  formulated  by 
the  American  Society  of  Mechanical  Engineers,  29  West  ,19th  Street,  New 
York,  should  be  obtained  and  studied.  All  boiler  tests  should  be  made  and  re- 
ported in  conformity  with  these  rules,  so  that  intelligent  comparison  with 
other  boiler  tests  may  be  made. 

A  new  edition  of  the  A.  S.  U.  E.  Code  will  be  available  about  the  time 
this  book  is  published.  If  the  following  directions  for  conducting  boiler 
tests  conflict  with  the  new  Rules,  the  Rules  must  be  followed  in  preference; 
but  it  is  not  expected  that  any  serious  differences  will  occur.  In  several 
instances  where  it  was  considered  appropriate,  parts  of  the  A.  S.  M.  £.  Code 
of  1915  have  been  copied. 

To  facilitate  understanding  the  preparations  for  and  making  of  boiler 
trials  and  computing  the  results,  the  subject  will  be  treated  in  two  parts. 
In  the  first  part,  the  simpler  tests  will  be  considered  where  the  capacity  only, 
or  the  efficiency  and  capacity,  are  wanted.  In  such  instances,  only  the  useful 
work  done  is  measured,  and  the  observations  may  be  restricted  to  those 
necessary  to  attain  this  end.  In  the  second  part,  the  further  observations  and 
calculations  necessary  to  prepare  heat  balances  will  be  discussed.  This 
work  Includes  finding  the  amount  and  cause  of  the  losses  as  well  as  the 
amount  of  useful  work  done. 

Personnel 

'T'HE  person  conducting  the  test  should  have  sufficient  assistance  to  enable 
-*■  him  to  oversee  at  all  times  everything  connected  with  the  test.  He 
should  satisfy  himself  from  time  to  time  that  the  weighing  scales,  instru- 
ments, etc.,  are  giving  correct  indications  and  that  all  readings  are  being 
correctly  and  punctually  recorded.  He  should  continually  be  on  the  alert 
for  any  change  in  conditions,  such  as  an  unusual  demand  for  steam,  stoppage 
of  stokers,  fans,  feed  pumps,  and  so  forth.  His  assistants  should  be  chosen 
for  their  enthusiasm  no  less  than  for  their  ability;  and  it  may  prove  wiser 
to  abandon  and  repeat  the  test  rather  than  tMsntinue  with  an  assistant  who 
shows  contempt  for,  or  lack  of  interest  in,  the  proceedings. 


ib.  Google 


ib.Google 


TESTING  SIS 

Condition  of  Boiler 
"T^E  condition  of  the  boiler  and  furnace  should  first  be  ascertained,  and 
■^  described  in  the  report  of  the  test.  If  it  is  desired  to  demonstrate  the 
value  of  improved  operating  conditions,  then  a  test  should  be  run  without 
any  change  whatever,  followed  by  another  before  which  defective  brickwork, 
bafHes,  etc.,  should  be  repaired,  soot  and  scale  removed  and  the  boiler 
put  in  generally  clean  and  first-class  working  condition.  If  the  expected 
capacity  or  efficiency  is  not  realized,  the  heat  balance  will  probably  show 
the  cause ;  and  if  the  necessary  observations  for  calculating  a  heat  balance 
have  not  been  made,  then  another  test  must  be  run  for  this  purpose.  Changes 
can  then  be  made  in  whatever  direction  the  losses  in  the  heat  balance  point, 
and  other  tests  run  until  the  results  expected  are  realized.  Sometimes 
several  tests  are  run  to  enable  an  efficiency  curve  to  be  drawn  at  different 
loads  or  to  enable  comparison  to  be  made  of  operating  under  different 
working  conditions. 

Duration 

THE  duration  of  the  test  must  be  sufficient  to  insure  accuracy,  and  this 
is  governed  by  the  closeness  with  which  the  amount  of  fuel  and  water 
involved  at  start  and  stop  can  be  ascertained.  With  oil,  gas,  etc.,  there  is  no 
store  of  fuel  in  the  furnace,  and  four  or  five  hours  is  generally  suflicient- 
With  coal,  the  amount  of  fuel  in  the  furnace  must  be  judged  at  start  and 
stop;  and  as  this  is  often  little  better  than  guesswork,  a  much  longer  period 
is  necessary  because  the  error  in  this  judgment  may  be  a  noticeable  per- 
centage of  the  total  fuel  burned. 

With  mechanical  stokers  carrying  a  steady  load,  10  hours  may  be  suf- 
ficient, but  if  there  is  much  variation  in  load  this  should  be  greatly  increased. 
With  hand  firing,  the  duration  should  not  be  les«  than  &  hours  for 
anthracite  or  10  hours  for  bituminous  coal.  The  trial  should  be  long  enough 
for  at  least  2S0  pounds  of  coal  to  be  burned  on  each  square  foot  of  grate 
area.  If  an  accurate  efficiency  test  is  desired,  it  should  be  continued  for  34 
hours ;  but  for  capacity  only,  3  or  4  hours  is  sufficient. 

Simple  Test  Data 
TF  the  capacity  only  is  wanted,  the  coal  need  not  be  weighed  or  analyzed; 
*■  but  such  tests  are  unusual  since  they  give  so  little  information.     There- 
fore, only  those  tests  will  be  discussed  in  which  both  capacity  and  efficiency 
are  to  be  ascertained. 

Observations  are  necessary  to  obtain  the  following  quantities: 
Weight  of  Feed  Water 
Weight  of  Coal 
Heat  Value  of  Coal 
Temperature  of  Feed  Water 
Pressure  of  Steam 
Quality  of  Steam 
Particular  accuracy  is  essential  in  determining  the  first  three  items.    If 
any  of  these  are  incorrect,  the  test  is  useless. 

Weighing  Feed  Water 

THE  usual  plan  for  weighing  feed  water  is  to  have  one  or  more  tanks 
on  scales  at  a  high  level,  discharging  by  gravity  to  a  single  tank  below. 
The  lower  tank  should  be  larger  than  either  of  the  others,  and  have  no  pipe 
Ions  except  the  suction  line  to  the  feed  pump.     The  level  of  the 
1  the  lower  tank  should  be  noted  at  the  commencement  of  the  test 


ib.  Google 


and  be  broaght  back  to  this  level  at  the  end.  The  upper  tanks  may  have 
overflows,  but  irare  must  be  taken  that  the  overHow  water  cannot  fall  into 
the  lower  tank.  The  upper  tanks  must  be  large  enough  so  that  there  is 
ample  time  for  operating  the  Riling  and  dumping  valves,  weighing  the  water 
and  recording  it.  A  simple  rule  will  prevent  mistakes — record  immediately 
the  time  of  dumping  each  tank;  and  if  there  are  more  than  one  tank,  number 
them  and  record  the  time  of  dumping  in  separate  columns. 

Water  Meters  are  not  considered  sufficiently  accurate  or  reliable  for 
boiler  testing;  but  in  some  instances  it  is  almost  impossible  to  avoid  using 
them.  They  should  be  carefully  calibrated  before  and  after  the  test  hj 
weighing  water  metered  into  suitable  tanks.  When  calibrating  meters, 
care  must  be  taken  that  all  readings  are  from  the  same  part  of  the  cycle  of 
motions  operating  the  counter.  As  water  meters  measure  volume,  the 
temperature  of  the  water  during  calibration  must  be  taken,  and  the  weight 
of  water  at  that  temperature  used  in  the  calculations.  Water  meters  of  the 
Venturi  type,  or  weirs,  are  reliable;  but  should  be  calibrated.  Automatic 
water-weighers  are  installed  in  many  large  plants,  and  their  readings  may 
be  used  after  calibration  and  examination  aa  to  reliability. 

Water  Gage,  A  scale  should  be  mounted  close  to  the  boiler  gage  glass  so 
that  the  height  of  the  water  can  be  easily  read.  Note  should  be  made  of  the 
position  of  the  scale  and  then  it  can  be  replaced  accurately  if  the  glass 
breaks  during  the  trial.  The  position  of  the  scale  relative  to  the  boiler  must 
be  definitely  determined,  so  that  the  volume  of  water  in  the  boiler  cor- 
responding to  any  distance  on  the  scale  can  be  computed  if  necessary,  as 
explained  below. 

Water  gages  should  not  be  blown  down  for  at  least  one  hour  before 
starting  and  stopping,  as  this  changes  the  water  level  in  the  glass,  because 
the  temperature  and  consequently  the  density  of  the  water  in  the  gage  and 
connecting  pipe,  is  changed. 

The  feed  should  be  so  managed  that  the  water  will  be  at  the  same  level 
in  the  boiler  at  the  end  of  the  test  as  it  was  at  the  start.  If  this  is  not  done, 
the  difference  in  level  must  be  allowed  for  by  calculating  the  volume  of 
water  in  the  boiler  between  the  two  levels.  The  weight  of  water,  calculated 
at  the  temperature  in  the  boiler,  must  then  be  added  or  deducted  as  required. 
The  correction  for  difference  in  level  must  always  be  made  in  this  manner. 
Pumping  in  more  water  or  blowing  down  are  not  permissible. 

Leakage.  Care  must  be  taken  that  all  valves  and  fittings  are  tight.  Blow- 
off  pipes  should  be  blanked  off,  or  disconnected  so  that  any  leakage  can 
be  seen  and  measured.  Where  the  feed  pipe  connects  with  other  boilers,  it 
may  not  be  necessary  to  blank  off  these  branches  if  they  are  provided  with 
two  valves  with  a  drain  cock  or  plug  between,  which  may  be  kept  open  dur- 
ing the  test  to  insure  that  no  water  is  passing  through  leaky  valves.  Un- 
avoidable leakage  from  pump  stuffing  boxes  and  so  forth,  must  be  weighed 
and  deducted. 

Boiler  leakage  may  be  ascertained  by  closing  all  valves,  maintaining 
pressure  by  means  of  a  very  slow  fire,  and  noting  the  fall  of  water  in  the 
gage  glass.  Readings  of  this  description  should  be  taken  every  ten  minutes 
and  continued  until  they  show  a  constant  rate. 

Leakage  from  tubes  in  the  feed  water  heater  must  be  looked  for,  and 
any  such  leakage  either  measured  or  cured. 

Where  drainage  from  heating  systems  is  automatically  returned  to  the 
boiler,  arrangements  must  be  made  to  disconnect  the  system  and  discharge 
the  condensate  elsewhere  during  the  test. 

The  fundamental  condition  to  keep  in  mind  is  that  no  water  shall  enter 
the  boiler  during  the  test  except  that  which  is  being  weighed;  and  that  all 
the  water  which  is  weighed  enters  the  boiler  and  leaves  by  way  of  the  steam 
space  only. 


ib.  Google 


Weighing  Coal 

COAL  should  be  weighed  only  about  as  fast  as  required,  but  the  supply 
must  always  be  ample.  In  this  way  the  amount  on  the  firing  Roor  can 
easily  be  estimated  at  any  time,  such  as  hourly.  The  same  simple  rule  recom- 
mended for  feed  is  desirable  here — record  immediately  the  time  of  dumping 
each  wheelbarrow  load. 

Never  trust  to  marks  or  tallies  for  weighing  coal  or  feed  water. 

IVeighing  Scales  for  coal  and  water  should  be  examined  carefully  to 
see  that  they  swing  freely,  and  should  be  tested  to  see  that  they  balance 
at  zero  and  with  standard  weights  of  about  the  amount  at  which  they  will 
be  used.  Platform  scales  are  generally  most  convenient  for  weighing  feed 
water  tanks  and  wheelbarrows  of  coal  and  ash. 

Heat  Value  of  Coal 
fjEAT  value  of  coal  is   fully  treated  in  Chapter   13  on   FUEL,  where 
'-  -''   methods  of  working  down  samples  and  of  analysis  are  described,  and 
representative  analyses  of  fuels  are  given. 

A  imall  sample  should  be  taken  from  each  wheelbarrow  of  coal  be- 
fore weighing.  The  amount  taken  should  be  about  1  per  cent  with 
small  anthracite  and  2  per  cent  with  bituminous  coal.  The  bulk  sample  thus 
obtained  should  be  worked  down  to  about  10  lbs.  as  described  in  Chapter  13. 
Half  of  this  is  to  be  sent  to  the  laboratory  in  an  airtight  fruit  jar  or  similar 
airtight  package,  and  the  remainder  kept  for  reference  or  to  replace  loss. 

The  moisture  in  the  coal  is  an  important  item  and  is  difficult  to  get  with 
accuracy. 

The  moisture  in  the  sample  as  received  at  the  laboratory  can  be  deter- 
mined with  fair  accuracy.  But  since  coal  readily  absorbs  or  gives  off  moisture 
according  to  the  humidity  of  the  atmosphere,  different  analysts  will  often 
obtain  different  results  from  the  same  sample. 

Unless  the  bulk  sample  while  being  collected  during  the  test  and  while 
being  worked  down  to  a  laboratory  sample  is  kept  in  a  cool  place,  it  will  not 
be  representative  as  to  moisture.  If  the  sample  is  collected  and  worked 
down   in  a  warm  and  drafty  place,  it  may  possibly  lose  as   much  as  2  per 

Therefore,  it  is  often  preferable  to  determine  the  moisture  during  the 
test,  and  for  this  purpose  a  small  pair  of  scales  ia  required,  sensitive  to  about 
f4  oz.  when  weighing  about  20  pounds.  A  sample  of  about  20  lbs,  (separate 
from  the  main  bulk  sample)  is  carefully  selected  to  be  representative  as  to 
moisture,  shortly  after  commencement  of  the  test ;  and  after  weighing,  it  ia 
spread  out  on  a  sheet  iron  tray  and  exposed  to  a  temperature  of  about  250° 
F.  for  several  hours.  Care  must  be  taken  to  protect  the  sample  from  strong 
drafts  which  might  blow  away  some  of  the  dry  dust ;  and  it  is  advisable  to 
cover  the  tray  with  a  perforated  sheet  iron  cover,  leaving  a  space  of  an  inch 
or  two  between  it  and  the  coal.  The  tray  may  be  placed  on  a  flue  or  breech- 
ing; but  it  must  not  be  allowed  to  get  too  hot  or  some  of  the  volatile  matter 
will  be  distilled  off,  thus  giving  an  erroneous  result.  It  may  be  necessary 
to  support  the  tray  on  bricks  or  the  like  to  prevent  the  sample  getting  too 
hot.  For  this  determination,  the  coal  should  be  crushed  down  so  that  the 
largest  pieces  are  not  over  !4  inch.  The  sample  is  carefully  weighed  before 
and  after  drying  for  about  four  hours  and  then  weighed  every  hour  after* 
wards  until  two  consecutive  weighings  agree.  The  loss  in  weight  divided 
by  the  weight  before  drying,  multiplied  by  100  is  the  percentage  of  moisture 
referred  to  coal  "as  fired.'' 

Feed  Water  Temperature 
T^EED  water  temperature  must  be  taken  with  a  thermometer  having  the 
■*■    scale  graduated  on  the  glass  stem.    There  should  be  several  Spare  ther- 
mometers so  that  breakage  will  not  cause  stopple  of  the  test 


ib.  Google 


The  thermometer  is  placed  in  a  thermometer- well  screwed  in  the  feed 
pipe.  The  well  should  be  deep  enough  to  reach  to  the  center  of  the  pipe, 
or  at  least  well  into  the  flowing  water.  It  should  not  be  in  a  packet  where 
the  flow  is  sluggish.  The  well  may  be  tilled  with  mercury  or  oil.  Response 
to  changes  of  temperature  is  not  as  quick  with  oil  as  with  mercury;  but  unless 
there  are  unusually  rapid  changes  of  temperature,  oil  is  quite  good  enough. 

Recording  thermometers  are  desirable  when  there  is  much  fluctuation, 
but  they  should  be  checked  against  the  regular  indicating  thermometer 
readings. 

Thermometers  and  thermometer- wells  are  described  in  Chapter  11  on 
HEAT,  to  which  reference  should  be  made  as  to  care  and  methods  of  use. 

Steam  Pressure 
'Pressure  gages  should  be  tested  with  a  dead-weight  tester  with  both 
'•    rising  and  falling  pressure,  and  the  case  should  he  tapped  gently  to  see 
that  the  mechanism  is  free.     Allowance  must  be  made  for  head  of  water 
in  the  connecting  pipe  if  there  is  any. 

Recording  gages  are  useful  for  boiler  testing,  but  their  accuracy  must 
be  established.  The  pen  or  other  recording  device  most  be  quite  free  to 
move  with  slight  pressure  fluctuations.  The  clock  error — fast  or  slow — in 
relation  to  the  clock  or  watch  used  for  the  test,  must  be  ascertained  and 
recorded. 

Ample  syphons  must  be  provided  to  prevent  steam   reaching  the  gages. 

Care  of  g3,ges  and  methods  of  use  are  described  in  Chapter  16  on 
OPERATION. 

Quality  of  Steam 

IF  the  steam  is  not  superheated,  it  must  be  tested  for  the  amount  of  moisture 
or  entrained  water  present.  For  this  purpose  the  throttling  calorimeter  is 
used  when  the  moisture  does  not  exceed  4  per  cent,  and  the  separating  calo- 
rimeter for  wetter  steam. 

Tke  Throhling  Calorimeter  was  invented  by  Prof.  C.  H.  Peabody,  and  has 
long  been  used  with  complete  satisfaction.  It  is  dependent  upon  the 
adiabalic  expansion  of  steam  through  a  nozzle.  The  heat  converted  into 
work  as  velocity  of  the  steam,  is  returned  to  the  steam  as  sensible  heat  when 
the  steam  loses  its  velocity  in  the  expansion  chamber.  As  the  total  heat  in 
the  steam  is  the  same  after  expansion  to  atmospheric  pressure  as  it  was 
at  boiler  pressure,  it  is  obvious  that  some  or  all  of  the  moisture  present  in 
the  high  pressure  steam  will  be  evaporated.  If  too  much  moisture  is  pres- 
ent, the  resulting  mixture  will  have  a  temperature  of  212°  F.,  while  with  dry 
steam  the  temperature  will  be  much  higher,  showing  considerable  superheat. 
From  the  amount  of  superheat  of  the  expanded  steam,  the  amount  of  moisture 
present  in  the  steam  before  expansion  can  be  readily  calculated. 

Taking  dry  saturated  steam  of  150  lbs.  gage  pressure,  the  total  heat  per 
pound  is  1196.1  B.t.u.  The  total  heat  per  pound  at  atmospheric  pressure  is 
1151.7,  and  the  difference  or  44,4  B.t.u.  is  used  in  superheating  the  steam  at 
atmospheric  pressure. 

If  the  steam  contains  2  per  cent  of  moisture  the  total  heat  is,  for  the 
steam; 

0.98  X  1196.1   =  1172.18 
for    the    water: 

0.02  X     337.8  =        6.77 

1178.95  B.t.u. 
The  total  heat  in  one  pound  of  dry  steam  at  atmospheric  pressure  and 
212°  F.  is  1IS1.7,  and  the  difference. 

1178.95  —  1151.7  =  27.25  B.t.u., 
is  available  to  superheat  the  steam  after  the  moisture  has  been  evaporated. 


ib.  Google 


TESTING 


=  59°  R 


As  the  speciiic  heat  of  steam  is  0.46,  the  amount  of  superheat  will  be: 
2725  _ 
0.46 

The  temperature  of  the  expanded  steam  will  be  shown  by  the  thermom- 
:r  as: 

212  +  59  =  271'  F. 
If  a  regular  or  standard  instrument  is  not  available  for  making  the 
<t,  one  may  be  made  up  of  pipe-fittings  as  illustrated  in  Pig.  223. 


Kc-  333.    Throttling  Calorimeter. 


ib.  Google 


1 

i 

ii 


!>  c  d 


•sis 

S.SiE 


1 5^ 

5  is 

Iffio 

if. 


U  a 


ib.  Google 


TESTING  S21 

A  piece  of  4-in.  pipe,  10  to  12  in.  long,  and  screwed  caps  on  each  end 
niake  up  the  body  of  the  calorimeter.  Openings  in  the  end  are  provided  as 
shown — steam  inlet  at  A  usually  J^-in.  pipe,  thermometer  and  gage  con- 
nections at  T,  exhaust  outlet  at  N  of  at  least  1-in.  pipe.  Care  must  be 
taken  to  offset  the  pipes  A  and  N.  The  whole  calorimeter  is  heavily  lagged 
to  prevent  radiation.  The  nipple  A,  through  which  the  steam  enters  the 
calorimeter,  is  made  of  composition,  cut  with  pipe  thread  and  provided  with 
an  orilice  for  reducing  the  pressure  and  gaging  the  flow  of  steam.  It  is 
shown  in  detail  at  (b).     The  orifice  may  be  made  V«  inch. 

Steam  passes  from  the  main  through  the  oriAce  xn  A,  in  which  it  expands 
and  enters  the  chamber  K  at  atmospheric  pressure.  If  the  calorimeter  is 
properly  lagged  so  that  no  heat  is  lost  by  radiation,  the  heat  content  of  one 
pound  of  steam  at  the  lower  pressure  in  the  calorimeter  will  be  the  same 
as  that  at  the  boiler  pressure. 

Kent's  formula   for  reducing  the  observations  of  the  throttling  calo- 

"""'"  '"  «  =  .00  X    H  -  1151.7 -0.«(,.- 2.2)  (^, 


Jlf  =  Percentage  of  moisture  in  the  steam 
H=  Total  heat  of  the  high  pressure  steam,  P, 

ta^  Temperature  of  the  steam   in  the  expansion   chamber  of  the 
calorimeter 

L  =  Latent  heat  of  the  high  pressure  steam,  P, 

With  low  pressure  steam,  the  outlet  N  of  the  calorimeter  may  be  con- 
nected to  the  condenser.  In  that  case  the  latent  heat  llSl.7  and  the  specific 
heat  0.46  in  formula  (63)  are  replaced  by  those  due  to  the  lower  pressure 
in  the  expansion  chamber  K. 

The  Mollier  diagram  given  on  page  416  is  particularly  applicable  to  the 
solution  of  this  problem.    Its  use  is  illustrated  below : 

Example  1.  Boiler  pressure,  100  lb.  abs. :  calorimeter  pressure,  20  lb. 
abs. ;   calorimeter  temperature,  250   deg.     Find   the  percentage   of  wetness 

Locating  on  the  diagram  the  intersection  of  the  20-lb.  line,  and  that  for 
the  temperature  2S0  deg..  we  find  the  heat  content  to  be  1173  B.t.u.  Follow- 
ing this  B.t.u.  line  until  it  intersects  the  100  lb.  pressure  line,  we  read  the 
quality  as  0.98.    The  priming  will  be  (1  —  0,98)  tOO  —  2  per  cent. 

The  range  of  use  of  the  calorimeter  depends  upon  the  heat  available  to 
superheat  the  steam.  This  in  turn  depends  upon  the  boiler  pressure  and  the 
drop  in  pressure.  To  get  sufficient  accuracy,  not  less  than  10  deg.  super- 
heat in  the  calorimeter  is  necessary. 

The  following  is  taken  from  the  "Description  of  Steam  Calorimeters" 
in  the  A.  S.  M.  E.  1915  Code. 

"The  percentage  of  moisture  is  determined  by  observing  the  number  of 
degrees  of  cooling  that  the  thermometer  in  the  low-pressure  steam  shows 
below  the  'normal'  reading  for  dry  steam,  and  dividing  that  number  by 
the  'constant'  number  of  degrees  representing  1  per  cent  of  moisture. 

"To  determine  the  'normal'  reading  of  the  low-pressure  thermometer 
corresponding  to  dry  steam,  the  instrument  should  be  attached  to  a  horizon- 
tal steam  pipe  in  such  a  way  that  the  sampling  nozzle  projects  upwards  to 
near  the  top  of  the  pipe,  there  being  no  perforations  and  the  steam  entering 
through  the  open  top  of  the  noiile.  The  test  should  be  made  when  the  steam 
in  the  pipe  is  in  a  quiescent  state,  and  when  the  steam  pressure  is  maintained 
constantly  at  the  point  observed  on  the  main  trial.  If  the  steam  pressure  falls 
during  the  time  when  the  observations  are  being  made,  the  test  should  be  con- 
tinued long  enough  to  obtain  the  effect  of  an  equivalent  rise  of  pressure. 


ib.  Google 


522  TESTING 

To  find  the  'constant'  for  1  per  cent  of  moisture  divide  the  latent 
heat  of  the  steam  supplied  to  the  calorimeter  at  the  observed  pressure  or 
temperature  by  the  specific  heat  of  superheated  steam  at  atmospheric  pres- 
sure (0.46)  and  divide  the  quotient  by  100. 

"Finally  ascertain  the  percentage  of  moisture  by  dividing  the  number 
of  degrees  of  cooling  by  the  constant,  as  above  noted. 

"To  determine  the  quantity  of  steam  used  by  the  calorimeter  it  is  usually 
sufficient  to  calculate  the  quantity  from  the  area  of  the  orifice  and  the  absolute 
pressure,  using  Napier's  formula  for  the  number  of  lb.  which  passes  through 
per  second;  that  is,  absolute  pressure  in  lb.  per  sq.  in.  divided  hy  70  and 
multiplied  by  the  area  of  orifice  in  sq.  in.  To  determine  the  quantity  by 
actual  test,  a  steam  hose  may  be  attached  to  the  outlet  of  the  calorimeter, 
and  carried  to  a  barrel  of  water  on  platform  scales.  The  amount  of  steam 
condensed  in  a  certain  time  is  determined,  and  thereby  the  quantity  dis- 
charged per  hour." 

Separating  Calorimeter,  When  the  percentage  of  moisture  is  too  lai^e 
for  the  throttling  calorimeter,  the  separating  calorimeter.  Fig.  224,  is  used. 
In  this  the  moisture  is  mechanically  separated,  just  as  it  is  in  the  ordinary 
power-plant  separator.  Steam  enters  as  indicated,  passes  down  into  the 
perforated  basin  from  which  dry  steam  escapes  through  small  openings 
near  the  top,  while  the  moisture  is  deposited  in  the  bottom  of  the  calorimeter. 
The  dry  steam  passes  through  the  jacket  surrounding  the  water,  from  which 


Fig.  3J4.     Carpenter  SeparBting  Calorimeter, 


D,g,tze:Jbi  Google 


TESTING 

it  is  discharged  throug[h  an  orifice.  This  orifice  can  be  used  to  i 
the  dry  steam,  or  the  discharge  can  be  led  to  a  condei^ser  and  the  condensed 
steam  weighed.  The  quantity  of  water  separated  in  the  reservoir  can  be 
determined  by  reading  the  special  scale  provided  on  the  gage  glass.  The 
weight  of  water  collected  divided  by  the  sum  of  the  weights  of  this  water 
and  of  the  dry  steam  for  the  same  period  of  time,  gives  a  result  which  is  the 
percentage  of  wetness.  In  practice  the  results  obtained  with  the  separating 
calorimeter  are  only  approximately  correct,  because  of  the  difficulty  of  draw- 
ing a  representative  sample  from  the  pipe  line. 

The  calorimeter  connection  with  the  steam  main,  from  which  the  sample 
of  steam  to  be  tested  is  taken,  should  be  made  according  to  A.  S.  M.  E. 
recommendations.  The  ^i-in.  pipe  should  extend  across  the  main  to  within 
)-i-in.  of  the  opposite  side,  the  end  being  plugged.  Around  the  circumference 
of  this  sample  pipe  should  be  drilled  not  less  than  twenty  J^-in.  holes, 
spaced  irregularly.  The  nearest  hole  should  be  at  least  J^-in.  from  the  side 
of  the  main. 

Superheated  Steam.  Use  a  gas  filled  thermometer  with  enlarged 
bore  at  the  upper  end.  The  thermometer  well  should  contain  mercury  or 
lott  solder,  and  the  immersed  portion  of  the  well  should  be  fluted  to  cause 
quicker  response  to  fluctuations  of  temperature. 

Where  extreme  accuracy  is  essential,  make  the  stem  correction  aa 
described  on  p.  373. 

St; am  Tables 

"T^E  report  of  the  test  should  state  which  steam  tables  the  calculations 
■*■  were  based  on.  Goodenough's  tables  are  given  on  page  424  and  are 
used  throughout  this  hook.  If  Marks  and  Davis's  or  Peabody's  tables  are 
used,  care  must  be  taken  to  adopt  their  values  as  constants  in  the  formulas 
where  they  occur,  such  as  in  finding  the  factor  of  evaporation. 

Starting  and  Stopping 

SPECIAL  consideration  of  the  methods  to  be  used  in  starting  and  stopping 
the  test  is  necessary.  These  must  be  well  thought  out  beforehand,  and 
be  suitable  for  the  particular  conditions  to  be  encountered.  Sufficient  error 
to  render  the  test  useless  is  easily  introduced,  unless  the  proper  observations 
are  made  quickly  and  simultaneously  and  immediately  recorded. 

With  hand  fired  boilers,  in  order  that  the  fire  may  be  as  nearly  as  pos- 
sible in  the  same  condition  at  start  and  at  stop,  the  hre  must  be  burned  low 
and  cleaned  both  before  the  beginning  and  before  the  end  of  the  test,  so 
that  a  clean  fire  is  left  on  the  grate  in  each  instance.  Thin  fires  are  more 
easily  judged  than  thick  ones.  Bituminous  coal  tires  should  be  2  to  4  in. 
thick  at  start  and  stop,  and  small  anthracite  fires  may  be  1  to  2  inches. 
Colored  spectacles  should  be  used  in  examining  fires,  particularly  so  with 
forced  draft  and  soft  coal,  for  little  is  to  be  seen,  much  less  judged  with  any 
accuracy,  without  them. 

To  start  the  test,  rote  quickly  the  condition  of  the  fire,  the  water  level  in 
the  gage  glass,  the  water  level  in  the  lower  or  suction  tank  of  the  feed 
water  tanks,  and  the  time.  Record  these  observations  with  the  time  as  the 
start  of  the  test.  Record  the  first  steam  pressure  reading  and  the  first  teed 
water  temperature  reading  immediately  afterwards. 

To  end  the  test,  watch  the  fire  when  and  after  being  cleaned,  and  as 
soon  as  it  is  in  the  same  condition  as  at  the  start,  note  the  water  level  in 
the  gage  glass,  the  water  level  in  the  lower  feed  water  tank  (preferably 
stopping  the  feed  pump)  and  the  time,  and  record  these  as  the  end  of  the 
test. 


ib.  Google 


ib.Google 


TESTING  S25 

If  there  is  any  difference  in  the  gage  gtaaa  level  at  start  and  st(^, 
allowance  is  to  be  made  later  by  calculation.  If  the  water  level  is  low  in 
the  lower  feed  water  tank,  weigh  the  amount  necessary  to  make  up  the  de- 
ficiency and  add  it  to  the  total  water  fed;  and  if  the  water  level  is  high, 
bale  out  and  weigh  the  excess  and  deduct  it  from  the  total. 

When  a  water  meter  is  used,  the  procedure  at  both  start  and  stop  is  to 
note  the  condition  of  the  fire,  the  water  level  in  the  gage  glass,  the  reading 
of  the  meter,  and  the  time.  Record  these  observations  with  the  time  as  the 
starting  and  stopping  times  respectively. 

Weigh  back  any  excess  coal  left  on  the  firing  floor  and  deduct  it  from 
the  total. 

In  a  plant  containing  several  boilers  where  it  is  not  practicable  to  clean 
them  simultaneously,  the  fires  should  be  cleaned  one  after  the  odier  as 
rapidly  as  may  be,  and  each  one  after  cleaning  charged  with  enough  coal 
to  maintain  a  thin  fire  in  good  working  condition.  After  the  last  fire  is 
cleaned  and  in  working  condition,  burn  ail  the  fires  low  (say  4  to  6  in.), 
note  quickly  the  thickness  of  each,  also  the  water  levels,  steam  pressure,  and 
time,  which  last  is  taken  as  the  starting  time.  Likewise  when  the  time 
arrives  for  closing  the  test,  the  fires  should  be  quickly  cleaned  one  by  one, 
and  when  this  work  is  completed  they  should  all  be  burned  low  the  same  as 
at  the  start,  and  the  various  final  observations  made  as  noted. 

In  the  case  of  a  large  boiler  having  several  furnace  doors  requiring  the 
fire  to  be  cleaned  in  sections  one  after  the  other,  the  above  directions  per- 
taining to  starling  and  stopping  in  a  plant  of  several  boilers  may  be  followed. 

Mechanical  Stokers.  To  obtain  the  desired  equality  of  condition  of  the 
fire  when  a  mechanical  stoker  other  than  a  chain  grate  is  used,  the  procedure 
should  be  modihed  where  practicable  as  follows : 

Regulate  the  coal  feed  so  as  to  burn  the  fire  to  the  low  condition  re- 
quired for  cleaning.  Shut  off  the  coal- feeding  mechanism  and  fill  the 
hoppers  level  full.  Clean  the  ash  or  dump  plate,  note  quickly  the  depth  and 
condition  of  the  coal  on  the  grate,  the  water  level,  the  steam  pressure,  and 
the  time,  and  record  the  latter  as  the  starting  time.  Then  start  the  coal- 
feeding  mechanism,  clean  the  ashpit,  and  proceed  with  the  regular  work  of 
the  test 

When  the  lime  arrives  for  the  close  of  the  test,  shut  oiif  the  coal-feeding 
mechanism,  fill  the  hoppers  and  bum  the  fire  to  the  same  low  point  as  at  the 
beginning.  When  this  condition  is  reached,  note  the  water  level,  the  steam 
pressure,  and  the  time,  and  record  the  latter  as  the  slopping  time.  Finally 
clean  the  ash  plate  and  haul  the  ashes. 

In  the  case  of  chain  grate  stokers,  the  desired  operating  conditions  should 
be  maintained  for  half  an  hour  before  starling  a  test  and  for  a  like  period 
before  its  close,  the  height  of  stoker  gate  or  throat  plate  and  the  speed  of 
the  grate  being  the  same  during  both  of  these  periods. 

Report  of  Simple  Test 

Obtcn'ationt  should  be  made  punctually  and  immediately  recorded.  When 
it  is  essential  that  a  number  of  instruments  be  read  simultaneously,  there 
should  be  an  observer  at  each  one.  A  signal  should  be  given,  such  as  by  a 
bell  or  whistle,  when  the  readings  are  to  be  taken. 

The  frequency  of  taking  the  readings  of  steam  pressure  and  feed  water 
temperature  depends  upon  the  extent  and  rapidity  of  the  fluctuations.  Usually, 
half  hourly  observations  are  sufficient;  but  if  there  is  considerable  variation, 
readings  should  be  taken  every  15  minutes. 

Records.  The  observations  should  be  recorded  on  separate  sheets  so  that 
different  observers  are  not  hampered  by  having  to  write  in  the  same  book. 
The'  plan  of  the  test  must  be  arranged  beforehand  and  the  duties  of  each 


ib.  Google 


S26  TESTING 

observer  dearly  defined.  In  important  and  complicated  tests,  one  or  more 
preliminary  runs  as  rehearsals  arc  very  desirable. 

Make  a  note  of  every  incident  connected  with  the  test  together  with  the 
time  of  its  occurrence,  however  unimportant  or  unnecessary  it  may  appear 
at  the  time. 

The  record  sheets  should  either  be  printed  or  made  Up  by  hand  before  the 
test,  and  the  original  sheets  should  be  kept,  no  matter  how  dirty  they  may 
be.  Each  record  sheet  should  be  dated  and  signed  by  the  observer.  As  soon 
as  possible  after  completing  the  test  or  even  during  its  progress,  the  whole 
of  the  observations  and  remarks  should  be  written  up  in  a  log  book  having 
pages  not  less  than  letter  paper  size — 11  in.  by  S'/i  inch. 

It  is  desirable  that  the  records  show  the  coal  and  water  consumption 
each  hour.  This  is  easily  done  by  allowing  for  the  coal  on  the  firing  door  and 
for  the  height  of  the  water  in  the  gage  glass  at  the  end  of  each  hour.  But 
this  is  only  incidental  and  the  orderly  procedure  of  weighing  full  tanks  of 
water  and  of  the  regular  quantity  of  coal  must  not  be  disturbed. 

Chart.  Where  there  are  fluctuations  of  load,  steam  pressure  and  so  forth, 
it  is  advisable  to  plot  a  chart  of  the  test.  This  may  well  be  done  white 
the  test  is  in  progress.  Unlooked  for  conditions  are  shown  at  a  glance.  Fig. 
225  is  a  chart  reproduced  from  the  A.  S.  M.  E.  1915  Code. 

The  form  of  report  shown  in  Table  82  is  suitable  for  the  simpler  kind  of 
test  which  has  been  described.  Items  may  be  added  to  record  other 
observations  if  desired,  such  as  draft  in  uptake  and  at  other  points,  weight 
of  water  actually  evaporated  per  hour,  smoke,  etc. 

Sketches,  photographs  and  descriptions  should  be  attached,  giving  any 
particular  information  such  as  condition  of  boiler  and  furnace,  arrangement 
of  baffles  and  so  forth. 


Table  82. 

Evaporative 

Te«. 

Description  of 

Boiler 



-Rated  H.  P 

Grate,   Type 

„-.Jirea 

....- draft - 

(  I  )     Steam  pressure,  lb.  per  sq.  in 

(  2  )     Percentage  of  moisture  in  steam — or  superheat,  ' 

(  3  )     Factor  of  correction  for  quality  of  steam„ 

(4)     Feed  water  temperature,  °F. — — — . — 

{  5  )     Factor  of  evaporation _ 

(  6  )  Equivalent  evaporation  per  hour,  from  and  at  212*  F.,  lb.... 

(  7  )  Equivalent  evaporation  per  hour,  from  and  at  212'  F. 

per  sq.  It.  of  heating  surface,  lb— .... ~~ — 

(8)     Percentage  of  rated  capacity  developed 

(  9  )     Percentage  of  moisture  in  coaL 

(10)  Dry  coal  per  hour,  lb 

(11)  Dry  coal  per  sq.  ft.  of  grate  surface  per  hour,  lb„ 

(12)  Equivalent  evaporation  from  and  at  212°  F.  per  lb. 

of  dry  coal,  lb_ . 

(13)  Heating  value  per  lb.  of  dry  coal,  B.t.u 

( 14)  Efficiency,   per   cent - - 


ib.  Google 


TESTING 


^1  I  I  I  I  I  I  I  i  I  I 


li 


j|  1 1 1 1 1 1  !  I  I  I  1 1  I  1 1  i 


,Google 


528  TESTING 

Calculation  of  Simple  Test 

THE  heading  of  the  report  should  be  filled  in  first.  No  explanation  of 
this  part  IS  necessary,  except  to  mention  that  the  grate  area  is  the 
horizontal  area  between  furnace  walls,  so  that  the  grate  area  is  the  same 
whether  the  grate  is  horizontal  or  sloping.  In  the  following  discussion,  the 
numbers  at  the  commencement  of  paragraphs  are  those  of  the  items  in 
Table  82. 

(1)  This  is  the  average  of  the  observations. 

(2)  Methods  of  linding  the  percentage  of  moisture  in  saturated  steam 
have  been  discussed.  With  superheated  steam,  the  temperature  of  saturated 
steam  due  to  the  pressure  is  found  from  the  Steam  Tables  in  Chapter  12 
on  STEAM,  and  deducted  from  the  temperature  of  the  superheated  steam, 
giving  the  number  of  degrees  of  superheat. 

(3)  When  the  percentage  of  moisture  is  less  than  2,  it  is  sufficient 
merely  to  deduct  the  percentage  from  the  weight  of  water  fed,  in  which 
case  the  factor  of  correction  for  quality  is: 

1        per  cent  moisture  _y, 

ater  than  2,  or  it  extreme  accuracy  is  required, 

\-M^f^'  (65) 

in  which  M  is  the  proportion  of  moisture,  H  the  total  heat  of  I  )b.  of 
saturated  steam,  q,  the  heat  in  water  at  the  temperature  of  saturated  steam, 
and  q  the  heat  in  water  at  the  feed  temperature. 

When  the  steam  is  superheated,  there  is  no  factor  of  correction, 

(4)  This  is  the  average  of  the  observations.  If  there  is  an  economizer 
and  the  test  is  of  the  boiler  and  economizer  together,  then  this  item  is 
the  temperature  of  the  feed  water  entering  the  economizer.  If  the  test  is  of 
the  boiler  only,  this  item  is  the  temperature  of  the  feed  water  entering  the 
boiler,  whether  there  is  an  economizer  or  not 

(5)  The  factor  of  evaporation  may  be  described  as  ths  amount  of  heat 
transferred  to  each  pound  of  feed  water  passed  through  the  boiler,  divided 
by  the  heat  necessary  to  evaporate  a  pound  of  water  from  and  at  212°. 
Therefore : 

''=w  (*' 

F  =  Factor  of  evaporation 

H  ^  Total  heat  of  steam  at  boiler  pressure  or  at  pressure  and  tem- 
perature of  superheated  steam 
q  ^  Total  heat  in  water  at  feed  temperature. 

No  allowance  is  to  be  made  for  moisture  in  the  steam,  as  this  is  taken 

(6)  The  total  weight  of  feed  water  is  first  corrected  tor  differences 
in  level  of  boiler  water  gage  and  in  feed  suction  tank  if  necessary.  If 
there  is  no  superheater,  this  total  weight  is  multiplied  by  item  3  to  find  the 
total  water  actually  evaporated.  This  is  multiplied  by  item  S  'to  find  the 
total  equivalent  evaporation  from  and  at  212°  F.,  and  divided  by  the  duration 
of  the  test  in  hours. 

(?)     This  is  item  6  divided  by  the  actual  water  heating  surface. 

C8)  Item  6  divided  by  34.5  gives  the  B.H.P.  developed.  The  B.H.P. 
developed,  divided  by  the  rated  H.P.  of  the  boiler  gives  the  percentage  of 
the  rated  H.P.  developed. 


ib.  Google 


(9)  This  does  not  require  further  explanation. 

(10)  The  total  coal  weighed  out  is  Rrst  corrected  for  diRerences  in 
quantity  in  furnace  at  start  and  stop  if  necessary,  and  for  any  coal  re- 
maining unused  at  end  of  test.  The  total  weight  of  moisture  as  found  by 
item  9  is  deducted,  leaving  the  total  weight  of  dry  coal.  Dividing  this  by 
the  duration  of  the  lest  in  hours  gives  the  dry  coal  per  hour. 

(11)  This  is  item  10  divided  by  the  grate  area. 

(12)  This  is  item  6  divided  by  item  10. 

(13)  This  is  entered  from  the  laboratory  report. 

(14)  This  is  item  12  multiplied  by  971.7  and  by  100.  and  divided  by 
item  13. 

Complete  Test  Data 

A  COMPLETE  evaporative  test  includes  several  other  observations  in  ad- 
dition to  those  already  described.  These  observations  are  directed 
mainly  to  finding  the  parasitic  losses  by  means  of  a  heat  balance.  To  begin 
with,  an  ultimate  analysis  of  the  coal  will  be  required,  and  this  will  be 
stated  as  in  item  25  of  Table  86. 

Temperature  of  Exit  Cases  may  be  taken  with  a  gas  filled  thermometer. 
To  get  the  average  in  a  large  flue,  specially  long  thermometers  are  made  to 
reach  to  the  center  or  at  least  well  into  the  gas  current.  An  0il  pot,  or 
large  thermometer-well  may  be  arranged  to  hang  into  the  flue,  and  the 
thermometer  will  then  have  to  be  lifted  out  of  the  oil  each  time  it  is  read. 


Electric  pyrometers  of  the  thermo-couple  type  are  the  handiest  in 
ments  for  the  purpose.  The  portable  instrument  shown  in  Fig.  226  is 
convenient,  for  it  may  be  connected  to  several  "hot  ends." 

Various  thermometers  and  pyrometers  are  described  in  Oiapter  1 
HEAT. 


ib.  Google 


ib.Google 


TESTING  S31 

The  temperature  of  the  air  entering  the  ashpit,  item  16  of  Table  86, 
may  be  taken  as  that  of  the  boiler  room  in  natural  draft  plants.  With  forced 
draft,  the  temperature  should  be  taken  near  the  fan  inlet.  Inexperienced 
observers  should  be  warned  against  the  danger  of  accident  unless  the  fan 
inlet  is  screened.  If  air  heaters  are  installed,  the  temperature  should  be  taken 
both  entering  the  heater  and  entering  the  ashpit,  and  so  reported. 

Particular  care  must  be  taken  that  the  thermometer  is  not  exposed  to 
radiation  from  nearby  hot  surfaces. 

Flue  Gas  An(dysis.  The  average  composition  should  be  represented  in 
the  samples  collected.  For  use  in  computing  heat  balances,  the  sample  should 
be  taken  so  as  to  include  air  leakage  into  the  setting,  and  the  sampling 
tube  should  be  placed  in  the  uptake.  Even  in  good  commercial  settings,  the 
COi  may  drop  as  much  as  3  or  4  per  cent  between  the  combustion  chamber 
and  the  stack.  This  inleakage  may  not  be  excessive,  but  nevertheless  the 
conditions  should  be  known.  The  efficiency  of  firing  operations  can  be 
studied  by  analysing  "grab"  samples  taken  from  the  furnace  or  from  amons 
the  tubes,  and  plotting  the  results  as  shown  on  page  575. 

Perforated  sampling  tubes  are  sometimes  used,  but  a  plain,  open-end 
pipe,  drawing  from  the  center  of  the  flue,  is  generally  favored.  A  radial 
"spider"  is  also  recommended  by  the  Bureau  of  Mines.  Fig.  227  shows  a 
sampling  tube  inserted  in  a  Heine  boiler.  The  tube  should  be  placed  at 
least  3   ft  below   the   damper   and   I   ft.   above   the   steam   drum,   through  a 


Fig.  337.     Method  of  Inserting  Sampling  Tube. 


ib.  Google 


hole  drilled  in  the  brick  wall  and  closed  with  asbestos  packing.  By  con- 
necting an  ejector  to  the  pipe,  a  small  stream  of  gas  is  constantly  drawn  out 
with  the  steam  or  water,  and  a  representative  sample  can  be  drawn  at  any  time 
from  the  current  moving  toward  the  ejector.  A  continuous  or  average 
sample  representing  one  to  six  hours  operation  can  be  secured  by  the 
arrangement  shown  in  Fig,  228.     The  upper  2-gal.  bottle,  initially  full  of 


water,  is  slowly  emptied,  drawing  in  the  Hue  gas.  Such  a  sample  produces 
an  average  upon  the  basis  of  time,  rather  than  load,  and  is  reasonably  repre- 
sentative it  the  difference  between  the  two  water  levels  is  2  ft.  or  more, 
so  as  to  maintain  the  effective  head  nearly  uniform.  If  the  sample  is  to 
stand  over  the  water  for  more  than  two  hours,  or  if  it  is  subject  to  much 
variation  in  COj  content,  it  should  be  collected  over  a  saturated  brine  solution 
(one-fourth  salt  by  weight)  to  minimize  absorption  by  the  liquid.  All  joints 
in  the  pipe  connections  should  be  tight  and  coated  with  asphaltum  paint. 
The  line  can  be  cleaned  more  easily  if  crosses  having  removable  plugs  are 
used  instead  of  elbows,  but  the  liability  of  leakage  is  increased. 

A  water-cooled  or  quartz  tube  is  desirable  tor  the  part  ot  the  sampler 
extending  into  the  gas  current,  although  a  ^  to  ^-in.  metal  tube  is  satis- 
factory. For  securing  "grab"  samples  for  combustion  control,  a  \ii  in,  bore 
copper  tube  is  preferable.  Tt  has  less  capacity  for  the  same  nominal  size, 
and  two  or  three  rapid  fillinRS  of  the  burette  suffice  to  clear  it  of  air. 
It  can  be  easily  inserted  through  cleaning  holes,  so  that  samples  can  be  taken 
from  different  points  in  the  boiler. 

Gat  Analysis  Apparatus.  For  determining  the  composition  of  flue  gases 
in  ordinary  boiler  work  one  ot  the  simplest  and  most  convenient  instru- 
ments is  the  Orsat  apparatus.  This  instrument  can  easily  be  used  by  the 
person  conducting  a  test,  or  by  some  assistant  whom  he  directs. 

.  Orsat  Apparatus.  The  principal  constituents  of  flue  gas  CCO„  0,  and 
CO)  can  be  measured  in  the  Orsat  apparatus  by  parsing  a  sample  of  the  gas 
successively  into  three  solutions,  each  having  a  high  absorptive  capacity  for 
one  of  the  constituent  gases. 

The  apparatus,  Fig.  229.  consists  ot  a  measuring  burette,  leveling  bottle, 
three  absorption  pipettes  and  the  connections.  The  burette  is  filled  with  water 
by  raiting  Ihe  leveling  bottle.    The  flue  gas  is  then  admitted  to  the  header. 


ib.  Google 


TESTING 


^g.  329.     Onat  Apparatua  for  Analyxing  Flue  Oa*. 


drawn  into  the  burette,  and  rejected  to  the  atmaspliere.  This  b  repeated 
several  times  until  the  water  is  saturated  with  COi  and  the  system  is  filled 
with  gas.  A  100  cc.  sample  is  then  taken  into  the  burette  by  lowerinR 
the  bottle  until  the  surface  of  the  water  in  the  burette  reaches  the  lowest 
graduation  when  it  b  at  the  same  level  as  the  water  in  the  bottle,  thus 
subjecting  the  sample  to  atmospheric  pressure.  Next  comes  the  actual 
measuring. 

The  gas  supply  is  shut  off,  and  the  sample  forced  into  the  right-hand 
pmette,  where  the  COt  is  absorbed  by  a  solution  of  KOH,  caustic  potash. 
The  sample  is  passed  back  and  forth  several  times  until  its  volume  ceases  to 
decrease,  when  the  solution  is  drawn  to  its  original  level  in  the  upper  neck 
of  the  pipette  and  isolated  again.  The  residual  gas  is  then  measured  under 
atmospheric  pressure,  that  is,  with  the  water  in  the  bottle  and  in  the  burette 
at  the  same  level,  and  the  loss  in  volume  represents  the  percentage  of  COi 
in  the  original  sample. 

The  connection  is  now  opened  into  the  second  pipette,  which  contains 
an  alkaline  solution  of  pyrogallic  acid.  The  oxygen  in  the  remainder  of 
the  sample  is  absorbed  and  the  percentage  determined  in  the  same  manner 
as  was  that  of  the  CO,. 

The  third  pipette  contains  an  ammoniacal  solution  of  cuprous  chlo- 
ride, CutCl),  which  absorbs  the  CO,  and  the  loss  in  volume  in  this  third  opera- 
tion gives  the  percentage  of  CO.  The  cuprous  chloride  absorbs  both  CO 
and  oxygen,  and  would  thus  give  an  erroneous  indication  if  all  free  oxygen 
was  not  first  removed.  The  oxygen  is  determined  primarily  in  order  to 
ascertain  the  CO  content.  The  analysis  for  O,  and  CO  is  not  ordinarily 
made  unless  the  presence  of  CO  is  suspected,  as  when  the  COi  percentage 
is  high  and  the  supply  of  air  may  be  dcRcient. 

To  prevent  sudden  temperature  changes  while  the  sample  is  being  exam- 
ined, the  measuring  burette  is  encased  in  a  water  jacket.  The  front  legs 
of  the  pipettes  are  filled  with  small  glass  tubing,  to  afford  large  contact 
surface  between  the  solutions  and  the  gas,  while  the  rear  legs  of  the  0< 
and  CO  pipettes  are  closed  to  prevent  contact  of  the  solution  with  the  air. 


ib.  Google 


ib.Google 


TESTING 


This  is  not  necessary  with  the  KOH  solution  used  for  the  CO, 
measurements. 

Orsat  connections  consist  either  of  rubber  tubings  closed  by  pinch  cocks, 
or  of  glass  tubing  with  ground-glass  cocks.  The  latter  system  is  considered 
more  reliable  and  operates  satisfactorily  when  the  cocks  are  clean  and  well 
lubricated. 

If  momentary  samples  are  obtained,  the  analyses  should  be  made  as 
frequently  as  possible,  say  every  15  to  30  minutes,  depending  on  the  skill  of 
the  operator,  noting  the  furnace  and  firing  conditions  at  the  time  the  sample 
is  drawn.  If  the  sample  drawn  is  a  continuous  one,  the  intervals  may  be  made 
longer. 

For  determining  the  hydrogen  and  other  unbumed  combustible  matter 
in  the  flue  gases,  and  for  general  gas  analysis,  the  Hempel  apparatus,  or 
some  modilicatioii  thereof,  is  required.  Work  of  this  kind  should  bt  entrusted 
to  a  person  who  is  familiar  with  all  phases  of  the  subject. 

The  Hemfet  Apparatvi  works  on  the  same  principle  as  the  simple  form 
of  Orsat  apparatus  described,  so  far  as  the  latter  is  applicable,  except 
that  the  absorption  may  be  hastened  by  shaking  the  pipettes  bodily,  bringing 
the  chemical  into  most  intimate  contact  with  the  gas.  It  is  less  portable  and 
in  some  particulars  it  requires  more  careful  manipulation  than  the  Orsat, 
while  for  general  analysis  it  is  not  adapted  unless  used  in  a  well  equipped 
chemical  laboratory.  The  absorption  pipettes  are  made  in  sets  which  are 
shaped  in  the  form  of  globes,  and  a  number  of  independent  sets  are  required 
for  the  treatment  of  the  different  constituent  gases.  A  simple  pipette  of  the 
Hempel  type  is  shown  in  Fig.  230. 


Fig.  330.     Hempel  Hpette. 

The  method  of  carrying  on  an  analysis  with  the  Hempel  apparatus 
is  as  follows : 

A  sample  of  gas  measuring  100  cc.  is  drawn  into  the  burette,  and  then 
transferred  to  the  first  pipette,  which  contains  potassium  hydrate  dissolved  in 
twice  its  weight  of  water.  This  solution  absorbs  carbon  dioxide  (COi). 
The  gas  is  then  passed  into  the  second  pipette,  containing  saturated  bromine 
water,  which  absorbs  the  heavy  hydrocarbons  (C1H4);  then  into  the  third 
pipette,  containing  a  solution  of  pyrog^llic  acid  and  potassium  hydrate  in  the 


ib.  Google 


proportion  of  5  grains  ot  acid  to  100  cc.  of  hydrate,  which  absorbs  oxygen 
(O);  then  into  the  fourth  pipette,  containing  ammoniacal  cuprous  chloride, 
which  absorbs  carbon  monoxide  (CO),  and  finaliy  into  the  fifth  pipette, 
which  is  of  large  size  and  provided  with  exploding  wires  and  galvanic 
battery,  for  the  determination  of  marsh  gas  (CH.)  and  hydrogen  (H),  A 
measured  quantity  of  oxygen  gas  is  added  to  this  pipette  and  the  contents 
exploded  by  an  electric  spark  from  the  battery,  resulting  in  a  mixture  of 
carbon  dioxide,  nitrogen  and  free  ox^en.  The  quantity  of  carbon  dioxide  ij 
determined  by  passing  the  gas  into  Ihe  pipette  containing  potassium  hydrate, 
and  the  quantity  of  oxygen  by  subsequently  passing  it  into  the  pipette  con- 
taining potassium  pyrogallate,  finally  determining  the  quantity  of  marsh  gas 
and  hydrogen  from  the  known  reactions  which  occur  during  this  process, 
and  the  composition  of  the  resulting  gases. 

For  each  of  these  processes  the  pipettes  are  shaken  to  hasten  the  absorp- 
tion, and  the  quantity  absorbed  is  determined  by  returning  the  gas  into  the 
measuring  burette  and  observing  the  successive  differences. 


The  ashes  and  refuse  withdrawn  from  the  ftrnace  and  ashpit  during  the 
progress  of  the  test  and  at  its  close  should  be  weighed,  so  far  as  possible, 
in  a  dry  state.  If  wet,  the  amount  of  moisture  should  be  ascertained  and 
allowed  for,  a  sample  being  taken  and  dried  for  this  purpose.  This  sample 
may  serve  also  for  analysis  for  the  determination  of  unburned  carbon  and 
for  fusing  te.iits. 

When  the  ashes  and  refuse  are  to  be  reported,  the  ashpit  and  combustion 
chamber  must  be  cleaned  at  the  beginning  and  end  of  the  test,  and  the 
amount  found  at  the  end  of  the  test  weighed. 

The  dust  and  ash  from  the  combustion  chamber,  tubes  and  flues,  should 
be  weighed  separately.  With  heavy  forced  draft  there  may  be  a  considerable 
amount  In  some  instances  endeavor  is  made  to  determine  the  amount 
carried  up  the  stack.  But  it  is  practically  impossible  to  ascertain  these 
quantities  with  any  precision. 

The  temperatures  tn  the  furnace  and  combustion  chambers  may  be  taken 
by  means  of  electrical  or  optical  pyrometers.  These  instruments  are 
described  in  Chapter  11  on  HEAT. 

Draft  gages  should  be  connected  between  each  boiler  and  its  hand- 
damper,  and  as  near  the  damper  as  practicable.  In  the  case  of  a  plant  con- 
taining a  number  of  boilers,  a  gage  should  also  be  connected  to  the  main 
fiue  between  the  regulating  damper  and  the  boilers.  It  is  desirable  also  to 
have  gages  connected  to  different  points  of  the  gas  passage  through  the 
boiler;  to  the  furnace  or  furnaces,  and  in  the  case  of  forced  draft,  to  the 
ashpits  and  blower  ducts.  If  there  is  an  economizer,  a  gage  should  be  con- 
nected to  the  flue  at  each  end  of  it. 

The  same  draft  gage  may  be  used  for  all  the  points  mentioned,  provided 
suitable  pipes  are  run  from  the  gage  to  each,  arranged  so  as  to  be  readily 
connected  to  either  point  at  will. 

Draft  gages  are  discussed  in  Chapter  16  on  OPERATION. 

The  height  of  the  barometer  should  be  observed  during  important  tests 
and  the  average  given  in  item  15.  It  is  common  to  add  14.7  lb.  to  the 
gage  pressure  to  find  the  absolute  pressure ;  but  the  actual  Etmospheric  pres- 
sure as  read  from  the  barometer  should  be  added  instead  if  extreme 
accuracy  is  desired. 

The  humidity  of  the  atmosphere  should  be  observed  for  particularly 
accurate  work.  The  usual  wet  and  dry  bulb  thermometer,  preferably  of  the 
sling  type,  is  suitable  for  this  purpose.  Table  83  gives  the  relative  humidity 
from  the  wet  and  dry  bulb  thermometers,  Table  84  gives  the  weight  of 
moisture  present,  and  Table  85  gives  the  weight  of  saturated  air.  The 
relative  humidity  is  entered  as  item  16. 


ib.  Google 


TESTING 


T.^,. 

Dia«»»b«tww>  Dry  ud  WM  Tbamoa, 

Mw^IJ^BWir. 

1 

2 

S 

« 

s          s 

^ 

8 

• 

06.8 
78.1 
84.9 

34.0 
66.6 
70.0 

1.5 
35.3 
55.2 

14.3 
41-0 

26.9 

12,9 

30 
40 
50 

89.1 
91,6 

78.3 
83.4 
87.0 

67-5 
76,3 
80.6 

56.8 
67.5 
74.3 

46.6 

68^0 

36,4 
62.4 

61.9 

26.3 
46.0 

65.8 

16.5 

37,7 
50,0 

6,8 
30,6 
44,3 

60 
70 
80 

94.6 
96.3 

06.8 

89.0 
00.6 
91.7 

83.6 
86.0 

87.7 

78.3 
81.6 
83.7 

73.1 
77,2 
79,9 

68.1 
73.9 
76.1 

63.1 
72^3 

68,3 
64,4 
68.6 

63.6 
60.4 
65,0 

90 
100 
110 

96.1 
96.6 
96.7 

92-3 

03.0 

88.7 
89.7 
90.3 

85,1 
86.4 
87.2 

81.7 
83,2 
84,2 

78,3 
80.0 
81.2 

75,0 
77,0 
78.3 

71.7 
74.0 
75.6 

7l!o 
73.9 

120 
130 

07.0 
97.1 

94.0 
04.2 

01.0 
01. 3 

88.0 
88.5 

86.1 
85.7 

82.3 
83,1 

79.6 
80.6 

76.9 
78.1 

74.3 

75.7 

!    10 

11 

12 

IB 

1* 

16     1      16 

IT 

IB 

23.6 

38.7 
49.1 

16.6 
33.2 

44.6 

9.7 
27.8 
40.1 

3.0 
22-4 
35.7 

50 
60 

17,2 
31,4 

13.1 
27.1 

7.0 
22.8 

2,0 
18.6 

u.h' 

70 
80 

90 

56.4 
61.5 

65.3 

52.6 
68.1 
63.1 

48.7 
54.8 

59.1 

44,9 
51.5 

56.1 

41.1 
48,3 
53,2 

37,4 
44.9 
50,2 

33,8 

41.7 
47.4 

30.3 
38.6 

44.7 

26.9 
36.6 
42.0 

100 
110 
120 
130 

68.0 
70.2 
71.8 
73.4 

85,1 
67.6 
69.4 
71.1 

62.3 
65.0 
67.0 
68.8 

59,6 

64^6 

66,6 

66,8 
60,0 
62,3 

64,5 

64.3 

57.5 
60.1 
62.4 

51.6 
55.1 
67.9 
60-3 

49.1 
52.8 
55.7 
58,3 

46.7 
50.6 
63.6 
56.3 

19 

20 

11 

22 

33 

U 

2G 

2« 

2T 

10.5 
32^6 

6.5 
20.2 

2.6 
17.0 
27.0 

70 
80 

14,0 
24,3 

11,0 
21.6 

8.0 
19.0 

6.0 
16.4 

2.1 
13.9 

'ii'/i 

(90 

too 

110 
120 
130 

39.4 
44.4 
48.3 

38.8 
42.1 
46.1 

34.3 
44!o 

31.9 
37,6 
42,0 

29,5 
35,6 
40,0 

27.2 
33.4 
38.0 

24.9 
31.3 

36.1 

22.6      30.5* 
29.3     27.4 
34.2      32.4 

51.6 
54.4 

49.6 
62.6 

47.6 
50.6 

45,6 

48.7 

43.7 
46.9 

41.8 
45.1 

40.0 
43.4 

38,2     36.4 
41.7      40,0 

<S 

E« 

ao 

1 

80 
90 
100 

9.0 
18.3 
25.5 

6.7 

16.2 
23.6 

4.4 
14.1 
21.7 

, 

i      i 

110           1  30.6 
120              34.7 
ISO           1  38.3 

28.9 
33.0 
36.7 

27.2 
31.4 
35,2 

1 

ib.  Google 


ib.Google 


TESTING 


T«ble  84.     WeiKht  of  Moisture  per  1,000  Lb.  of  Dry  Air. 

in  Pounds. 

Dty 

Mwmry 

0 

1 

2 

8 

« 

« 

« 

■ 

0.0383 
0.0631 
0.1026 

0.8 
1.3 
2.1 

0.5 
1.0 
1.8 

0.3 
0.8 
1.5 

0.0 
0.5 
1.2 

0.2 
0.9 

20 

0.6 

0,3 

30 
40 
50 

0.1640 
0.2477 
0.3625 

3.4 
5.2 

7.7 

3.0 
4.8 
7.2 

2.7 

4.4 
6.7 

2.3 
3.9 
6.2 

1.8 
3.5 

5.7 

1.6 
3.1 
6.2 

1.2 
2.7 

4.7 

0.9 
2.3 

4.3 

60 
70 
80 

0.6220 
0.73flG 
1.0290 

11.0 
15.8 
22,2 

10.4 
15.0 
21.2 

9.8 

14.2 
20-2 

9.2 
13.6 

10.3 

8,7 
12,8 

18,4 

8.1 
12.1 
17,5 

7.5 
11.4 
16,7 

7.0 

10,7 
15,8 

80 
100 
110 

1.4170 
1.9260 
2.5890 

30.9 
43.3 

60.6 

29.7 

41.6 
67.5 

40^0 

65.4 

27.3 
38.4 
53.4 

28.1 
36.8 

SI. 5 

25.0 
35,4 

49.6 

23,9 
34  0 

47,8 

22.8 
32,6 
45,9 

120 
130 

3.4380 
4.5200 

82.5 
112.5 

79.7 
108.9 

76.8 
105.3 

74,1 
101.7 

71,4 
88.3 

84-S 

68,3 
81. 7 

63.9 
88.6 

S 

S 

TO 

11 

12 

IS 

11 

IS 

IS 

0,6 
1,9 
3.8 

0.3 
1.6 
3.4 

1.2 
2.9 

0.8 
2.5 

0.8 
2.1 

0,2 
1.7 

1.3 
3.4 

60 

0.9 

0,5 

60 
70 
80 

6.4 
10.1 
15.0 

5.9 
9.4 
14.2 

6.4 
8.8 

13.5 

4.8 
8.2 
12.7 

4.4 
7.6 
11.9 

3.9 

7,0 
11,2 

0.4 
10.4 

16,0 

2.9 

6.8 
9,7 

2,5 
6.2 

9,0 

90 
100 
110 

21.8 

31.2 
44.1 

20.8 

29.9 
42.4 

19,8 
28.6 
40.7 

18,8 
27-3 

38.1 

17.9 
26.2 
37.6 

16,8 
25,0 
36,0 

23.9 
34,5 
49.0 

15,2 
22-8 

14.3 
21.7 
31.6 

120 
130 

61.5 
86.7 

69.3 
82. S 

57.1 
79.9 

65.1 

77.1 

53.0 

74.3 

61.0 
71.6 

68,0 
85.3 

47.0 
66.2 

45.1 
63.6 

" 

IB 

» 

20 

It 

£2 

28 

U 

iS 

0.1 
2.0 

4.7 

60 

1.6 
4.1 

1.1 
3.6 

0.7 
3.1 

6.3 
2.6 

70 

2.1 

1.6 

1.1 

0.7 

80 
90 
100 

8,4 
13.5 
20.7 

7.7 
12.7 
19.7 

7.1 
11.8 
18.7 

6.5 
11. 1 
17.7 

6.9 
10.3 

16.8 

6.3 
9,6 
15,8 

4,7 
8,9 
14,9 

4.1 
8,1 

13,9 

3.5 

7.4 
13,0 

no 

120 
130 

30.1 
43.2 
61.1 

28.8 
41.4 
58.6 

27.5 
56'3 

26.3 
38.0 
54.1 

25.0 
36.5 
52.0 

23.8 
35.0 
50.0 

22.6 
33.5 
48.0 

21,5 
32,0 
46.2 

20,3 
30,5 

44,4 

IS 

2T 

£B 

» 

30 

80 
00 

2.9 
6.7 

2.4 

6.1 

1.9 
5-4 

1.3 

4.8 

21 

100 

no 

120 
130 

12.1 
19.2 
29.1 
42. a 

11.3 
18.1 

27.7 
40.9 

10.6 
17.0 
26.3 
38.2 

9.7 
16.0 
25.1 
37.5 

8.9 
16.0 
23,8 
35,9 

ib.  Google 


S40  TESTING 

Table  85.     Wdsbt  in  Pound*  of  One  Cubic  Foot  of  Saturated  Air. 


Drr 

'V 

S« 

„ 

tt 

» 

■0 

0 
10 
20 

0.0750 
0.07338 
0.07180 

0.07788 
0.07620 
0.07466 

0.08077 
0.07903 
0.07733 

0.08366 
0.08185 
0.0S009 

0.08064 
0.08468 
0.08286 

30 
40 
60 

0.07027 
0.06879 
0.06732 

0.07297 
0.07143 
0.06992 

0.07569 
0.07409 
0.07262 

0,07839 
0.07675 
0.07612 

0.08110 
0.07942 
0.07773 

00 
70 
SO 

0.06588 
0.06442 
0.06297 

0.06S43 
0.06602 

0.06642 

0.07098 

0.06943 
0.06789 

0.07353 
0.07193 
0.07034 

0.076O9 
0.07440 
0.07280 

BO 
100 
110 

0.06146 
0.05991 
0.05828 

0.06388 
0.06228 
0.06060 

0.06629 
0,06465 

0.06293 

0.06870 
0.06703 
0.06528 

0.07112 
0.06939 
0.0B769 

120 
130 

0.05663 
0.05467 

0.05882 
0.05692 

0.06111 
0.06917 

0.06339 
0.06142 

0.06669 
0.00367 

Report  of  Complete  Test 

TABLE  86  contains  the  items  necessary  for  recording  a  complete  evap- 
orative test  The  sequence  of  the  items  has  been  chosen  so  as  to  keep  the 
same  numbers  as  were  used  in  the  short  report,  and  so  avoid  confusion  in 
explaining  the  different  items.  The  actual  form  of  report  used  should  be 
that  prescribed  in  the  A.  S.  M,  E.  Code. 

Table  86.     Complete  Evaporative  Tett. 


...Duration Conducted  by__ 


Heating  surface,  boiler™ 


....economizer.... 


(1) 
(2) 
(3) 
(4) 
(5) 
(6) 
(7) 

(8) 
(9) 
(10) 
(11) 
(12) 


...^r  superheat,  'F.... 


Factor  of  correction  for  quality  of  stcam_. 

Feed  water  temperature  "F 

Factor  of  evaporation ™ , 

Equivalent  evaporation  per  hour,  from  and  at  212'  F.,  lb,... 
Equivalent  evaporation  per  hour,  from  and  at  212°  F. 

per  sq,  ft.  of  heating  surface,  lb. 

Percentage  of  rated  capacity  developed — _. 

Percentage  of  moisture  in  coal - 

Dry  coal  per  hour,  lb.... 


Dry  coal  per  sq.  ft.  of  grate  surface  per  hour,  lb. 

Equivalent  evaporation  from  and  at  212*  F.  per  lb. 
of  dry  coal,  lb 


ib.  Google 


TESTING 


(15)  Barometer,  in.  of  mercury. 

(16)  Relative  humidity  of  air  for  combustion,  per  cent.... 

(17)  Temperature  of  air  for  combustion,  T, 

(181     Furnace  temperature,  °F__ ;. 

(19)  Temperature  of  gases  leaving  boiler,  'F. 

(20)  Draft  pressure  in  ashpit,  in,  of  water. 

(21)  Draft  in  furnace,  in.  of  water 

(22)  Draft,  leaving  boiler,  in.  of  water 

(23)  Refuse,  per  cent  of  dry  coal , , 

(24)  Combustible  in  refuse,  per  cent — 

(25)  Ultimate  analysis  of  dry  coal: 

(a)  Carbon,  per  cent 

(b)  Hydrogen,  per  cent 

(c)  Oxygen,  per  cent . 

(dj    Nitrogen,  per  cent , — 

(e)  Sulphur,  per  cent . 

(f)  Ash,   per   cent — 

(26)  Fusion  temperature  of  ash 

(27)  Analysis  of  flue  gases  by  volume: 

(a)     Carbon   dioxide .— 

Cb)     Oxygen  — — - 


(28)     Heat  balance  based  on  dry  fuel: 


Description 

B.tu. 

Percent 

(b)    Loss  due  to  evaporation  of  moisture 

(c)    Loss   due    to   heat   carried   away   by 
steam    formed  by  the   burning   of 

(d)    Loss  due  to  heat  carried  away  in  the 

(f)    Loss  due  to  combustible  in  ash  and 

(e)    Loss  due  to  healing  moisture  in  air 

(h)    Loss  due  to  unconsumed  hydrogen  and 
hydrocarbons,  to  radiation,  and  un- 

1 

(■)    Total  heating  value  of  1  lb.  of  dry  coal. 
Item    13 

loao 

Calculation  of  Complete  Test 
In  the  following  explanation,  the  item  numbers  are  given  at  the  com- 
mencement of  the  paragraphs: 

(1  to  14)    These  are  the  same  as  in  the  short  report. 

(15)  This  is  the  average  of  the  observations.  It  is  to  be  converted 
into  lb.  per  sq.  in.,  and  added  to  the  gage  pressure,  item  1,  to  find  the 
absolute  pressure  wilh  which  to  enter  the  steam  tables. 

(16)  This  item  will  be  used  in  computing  item  £  of  the  heat  balance. 


ib.  Google 


542  TESTING 

tl?)  This  is  the  average  of  the  observations.  It  is  osed  as  the  basic 
temperature  in  findins  the  losses  set  forth  in  items  b,  c,  d  and  g  of  the 
heal  balance. 

(18)  This  item  is  not  used  in  the  calculation  of  any  of  the  results. 
It  is  necessary  in  researches  into  the  transfer  of  heat  hy  radiation  and 
convection.  It  may  also  have  some  value  in  iavestisationi  as  to  any  unusual 
formation  of  clinker  in  conjunction  with  item  26. 

(19)  This  item  is  used  as  the  higher  temperature  in  finding  the  losses 
set  forth  in  items  b,  c,  d  and  g  of  tilM  heat  balance. 

(20,  21  and  22)  These  items  are  recorded  for  comparison  with  other 
tests. 

(23)  This  item  is  used  to  compute  the  weight  of  air  required  and  the 
weight  of  gases,  in  computing  items  d  and  g  of  the  heat  balance. 

(24)  This  item  is  used  in  the  calculation  of  item  f  of  the  heat  balance. 

(25)  This  is  the  laboratory  report. 

(26)  This  is  the  laboratory  report,  and  is  of  service  in  investigating 
instances  of  unusual  clinker  formation.     See  also  the  remarks  on  item  18. 

(27)  This  is  the  average  of  the  observations,  and  is  used  in  the  calcu- 
lation of  items  d  and  e  of  the  heat  balance. 

The  value  of  this  analysis  in  promoting  economy  is  discussed  in  Chapter 
16  on  OPERATION. 

Heat  Balance 
IJAVING  given  attention  to  the  rest  of  the  items,  the  construction  of  the 
'■  *■  heat  balance  can  now  be  proceeded  with.  The  heat  balance  may  be 
made  on  the  basis  of  coal  as  fired  or  of  dry  coal.  The  usual  basis  is  dry 
coal,  and  the  calculations  will  be  studied  in  this  manner.  When  the  general 
method  is  understood,  it  is  easy  to  make  the  heat  balance  in  either  of  the 
ways  mentioned.  The  letters  at  the  commencement  of  the  paragraphs  are 
those  of  the  items  in  the  heat  balance  28. 

(a)  Heat  absorbed  by  the  boUer.    Item  12  X  9717. 

(b)  Loss  due  to  evaporation  of  moittvre  in  coal.  This  moisture  is  heated 
from  the  lire-room  temperature,  item  17,  to  212  deg.,  evaporated,  and  super- 
heated to  the  flue  gas  temperature,  item  19.  The  latent  heat  of  evaporation 
is  9717,  and  the  specific  heat  of  the  superheated  steam  is  0.47. 

The  percentage  of  moisture,  item  9,  is  always  reported  on  the  weight 
of  coal  as  fired.  As  the  heat  balance  is  based  on  dry  coal,  the  moisture 
should  be  converted  to  this  basis,  though  if  the  amount  is  small,  the  error 
is  n^iigible.  Thus  2  per  cent  of  moisture  becomes  2  X  100/98  =  2.04  per 
cent ;  and  10  per  cent  becomes  10  X  100/90  =  11,11  per  cent. 

If  coal  containing  2  per  cent  of  moisture  is  tired  at  60  deg.,  -and  tbe 
gases  Irave  the  boiler  at  500  deg.,  then  each  pound  of  water  takes  up : 

212  —  60=    152.0  (Heating  to  212  deg.) 

9717  (Latent  heat  of  evaporation) 
500—212  =  288,  and288x0.47=    136.0  (For  superheating) 

Total  =  12S97  B.t.ii.  per  pound. 

Each  pound  of  dry  coal  is  accompanied  by  0.0204  lb.  of  water  and  this, 
multiplied  by  12597,  gives  26  B.t.u. 


ib.  Google 


(c)  Loss  due  to  heal  carried  away  by  sleam  formed  by  Ike  burning  of 
kydrosen.  This  is  dealt  with  similarly  to  the  moisture  loss,  except  that  the 
Steam  resulting  is  9  times  the  weight  of  the  hydrogen.  Assuming  the  same 
fire-room  and  flue  gas  temperatures  as  before,  the  loss  will  again  be  12S97 
B.Lu.  per  pound  of  steam  formed.  With  dry  coal  containing  4  per  cent  of 
hydrogen,  there  will  be  0,04  X  9  =  0.36  lb.  of  steam  formed  per  pound  of  dry 
coal )  this  multiplied  by  12597  gives  453  B.t.u. 

id)  Losi  due  to  heat  carried  away  in  the  dry  flue  gases.  This  is  nearly 
always  the  largest  single  item  of  loss.  The  temperature  of  the  gas  is  raised 
from  that  of  the  (ire-room,  item  17,  to  the  exit  temperature,  item  19.  This 
rise  of  temperature  multiplied  by  024  (the  assumed  specific  heat)  is  the 
B.t.u.  loss  for  each  pound  of  gas.  From  a  fire-room  temperature  of  60 
deg.  to  a  flue-sas  temperature  of  500  deg.,  the  loss  is  440  X  0-24  =  tOS.ti 
B.t.u.  per  pound  of  Hue  gas. 

The  weight  of  gas  is  computed  from  the  flue  gas  analysis.  An  example 
is  worked  out  in  Table  87  to  facilitate  understanding  the  method. 


Tkble  87.     AnalyM*  of  a  Sample 

of  Flue  Ou. 

•SSff 

"^■r 

Vdchu 

EVrcotby 

Cuban 

Ctaytm 

Gil 

PwOMlt 

N— M 

1    \^ 

U/UslCOt 

mnd 
12/3801CO 

ttLI*MCOt 
16/*»o(C0 

> 

.. 

12-1- (16X2)  =44 
12+ 16          -2S 
16X2            =32 
14X2            -2^ 

IV        1         V 

VI 

VII 

VIII 

CO, 
CO 

o 

N 

14.0 
1.0 
3.0 

82.0 

016 

28 

96 

2,296 

20.29 
0.B2 
3.16 

76.63 

6.53 

14.76 
0.63 
3.16 

76.63 

100,0 

5.92 

IS. 45 

The  lotal  amount  of  carbon  in  the  gases  (column  VI)  is  5.92  per  cent. 
Therefore  the  weight  of  dry  gases  is  100/5.92  =  16.89  lb.  per  pound  of 
carbon.  If  the  dry  coal  contains  80  per  cent  at  carbon  and  the  carbon  lost 
to  the  ashpit  is  2  per  cent  of  the  dry  coal,  then  the  carbon  burned  is  78 
per  cent  of  Che  dry  coal,  and  the  weight  of  dry  gas  is  16.89  X  0.78  =  13.17  lb. 
per  pound  of  dry  coal.  As  shown  above,  105.6  B.tu.  are  used  to  heat 
one  pound  of  dry  gas  from  60  to  500  deg..  and  13.17  X  105.6  =  1390  B.t.u. 

Study  of  Table  87  will  show  that  the  molecular  weights  may  be  can- 
celed and  the  following  formula  derived  for  the  weight  of  dry  flue  fas 


W- 


1 1  CO. -I-  80,  -H  7tCO  +  N.) 
3  iCO^  +  CO) 


(^+il33) 


(67) 


iV  =  Weight  of  dry  gas  per  pound  of  dry  fuel 
CO,,  CO,  Oi,  N,  ^  Percentages  by  volume  in  flue  gas  analysis 

C,  S  =  Percentages  by  weight  from  ultimate  analysis  of  dry  fuel. 
C  is  the  carbon  actually  burned,  that  lost  in  ashes  and 
refuse  being  deducted. 


ib.  Google 


■32 

«3 


ib.Google 


(e)  Lots  due  to  carbon  monoxide.  When  carbon  is  burned  to  CO,, 
14,540  B.t.u.  are  evolved  per  pound,  as  against  4,350  B.t.u.  when  burned  to 
CO.  Tlie  diiTerence — 10,190  B.LU. — is  the  loss  due  to  each  pound  of  carbon 
burned  to.  CO, 

Table  87,  column  VI,  shows  that  0.39  lb.  of  carbon  are  burned  to  CO 
out  of  5.92  lb.  of  carbon  present  in  the  gases.  The  proportion  of  carbon 
burned  to  CO  is  0.39  X  100/5.92  ■=  6.59  per  cent ;  the  carbon  present  in  the 
gases  is  ?8  per  cent  of  the  dry  coal,  so  that  0.0659  X  0,78  =  0.OS14  lb.  of 
carbon  are  burned  to  CO  per  pound  of  dry  coal.  The  loss  per  pound  of  dry 
coal  is  0.0514  X  10.190  =  S24  B.t.u. 

Without  proceeding  according  to  Table  87.  the  CO  loss  may  be  found 

1-=    ^o';°.-n  XI  C+Vkr  |X10,1M  (68) 


'^(^+-iia-)> 


=  Loss  in  B.t.u.  due  to  unbumed  CO 
10,190=  Difference  between  the  heat  generated  by  burning  1  jioutid 
of  carbon  to  COt  and  CO  respectively, 
and  the  rest  of  the  symbols  are  as  in  equation   (67). 

With  bituminous  coals  the  presence  of  CO  generally  indicates  the  presence 
of  unbiirned  hydrocarbons  also,  so  that  the  whole  loss  due  to  combustible  in 
the  gases  may  be  assumed  to  be  about  double  that  due  to  the  CO  loss.  With 
the  anthracites,  the  CO  loss  will  be  the  whole  loss  under  this  head. 

(/)  Loss  due  to  combustible  in  ash  and  refuse.  The  combustible  in  the 
ash  is  the  main  part  of  this  loss.  Sometimes  the  amount  is  assumed  as  the 
difference  between  the  percentage  of  ash  as  weighed  up  during  the  boiler  test 
and  that  found  by  the  coal  analysis.  Or  a  representative  sample  of  the  ash 
can  be  analysed;  if  it  contains  213  per  cent  of  combustible,  and  the  ash  is  10 
per  cent  of  the  dry  coal,  then  0.2  X  O.I  =  0.02  lb.  of  combustible  in  the  ash 
per  pound  of  dry  coal.  This  can  be  considered  as  coke  and  valued  at  14.540 
B.t.u.  per  pound.  The  loss  will  be  14.S40  X  0.02  —  291  B.t.u.  per  pound  of 
dry  coal. 

(c)  Loss  due  to  heating  moisture  in  air.  With  the  readings  of  the  wet 
and  dry  bulb  thermometers  the  weight  of  moisture  per  pound  of  air  may  be 
found  from  Table  84. 

The  weight  of  air  per  pound  of  dry  fuel  is; 

A  =  ir  +  lUO  —  C  (69) 


A  =:  Weight  of  air  per  pound  of  dry  fuel 
W  =  Weight  of  dry  gas  per  pound  of  dry  fuel 
f/,0  =  Weight  of  water  vapor  in  Item  28c,  or  9  X  Item  2S(i 
C  =  Weight  of  fuel  per  pound  of  dry  coal  in  products  of  c 

.     ..       ,       Item  23 
busfon,  1  -  -jg^— 


13.I7  +  0J6  — 0J8=I2.7Slb. 

The  weight  of  saturated  vapor  per  pound  of  dry  air  at  60  deg.  is  found 
from  the  hygrometric  tables  to  be  0,011  ;  if  the  humidity  is  75  per  cent,  the 
weight  of  vapor  will  be  0.011  X  0.75  =  0.008  lb.  per  pound  of  dry  air.  As  the 
weight  of  air  per  pound  of  dry  coal  is  12,75  lb.,  the  weight  of  vapor  in  the 
air  is  12JS  X  0.008  =  0.102  lb.  per  pound  of  dry  coaL  The  rise  in  tempera- 
ture by  the  specific  heat  of  the  vapor  is  440  X  0.47  =  207  B,t.u.  per  pound 
of  vapor,  and  207  X  0.102  =  21  B.t.u.  per  pound  of  dry  coal. 


ib.  Google 


very  small  anil  is  usually  ii 


(A)  Lnji  due  lo  nneoniumed  hydrogen  and  hydrorarboni,  to  radialii/n, 
and  tmaccouuted  for.  The  flue  gas  analysis  rarety  includes  a  determination 
of  the  unconsumed  hydrogen  and  hydrocarbons,  and  the  losses  due  thereto 
are  usually  included  in  this  general  item. 

The  loss  due  to  radiation  is  from  3  to  8  per  cent  of  the  heat  value  of 
the  fuel.  When  the  boiler  is  driven  hard  and  the  temperature  within  the 
setting  is  high,  the  actual  radiation  loss  is  larger  but  is  a  smaller  percentage 
of  the  heat  generated ;  whereas  at  very  low  rates  the  actual  loss  is  less,  but 
■s  a  larger  percentage.  Accurate  measurement  is  impracticable:  the  radiation 
and  "unaccounted-for"  losses  are  usually  lumped  in  one  item,  which  is  simply 
the  difl^erence  between  the  sum  of  the  rest  of  the  items,  and  the  heat  value 
of  the  dry  coal,  item  f. 

A  heat  balance  may  now  he  made  up  as  an  example  with  the  figures 
assumed,   and   Table  88   will   ilhmtrate   the   method. 


Table  B8.     Heat  BaUnce. 


Heat  absorbed  by  bcnler  ••equivalent  evaporation  from 
and  at  212  deg.  per  pound  of  dry  coal  X  971.7(a) 

Loss  due  to  evaporation  of  moisture  In  the  coal  (b) 

Loss  due  to  heat  carried  away  in  the  steam  formed  by 
combustion  of  hydrc^en  in  the  coal  (c) 

LoM  due  lo  heat  carried  awair  in  the  dry  flue  gasea  (d) . . . 

Loss  by  incomplete  combustion  of  carbon  to  CO  (e) 

combustible  in  ash  and  refuse  (f) 

heating  moisture  in  air  (g) 

-"''''"■•""   unconsumed  hj^rogenand  hydro- 


Loss  due 


carbons,  and  unaccounted  for  (h)  . 


Total  calorific  value  of  onepoundof  drycnal.  Item  13  (i)     13,850 


The  second  column  is  filled  in  first,  and  hy  dividing  the  different  numbers 
of  B.t.u.  by  their  total,  the  percentages  to  be  written   in   the   third   column 

EfRciency 

THE  efficiency  shown  by  item  a  of  the  heat  balance  is  the  same  as  item  H. 
It  is  the  combined  efficiency  of  the  whole — boiler,  auperheater,  furnace! 
grate— and  is  frequently  called  the  overall  efficiency.  The  consensus  of 
opinion  is  that  this  is  the  only  efficiency  which  should  be  reported. 

Attempts  liave  been  made  to  separate  the  overall  efficiency  into  boiler 
efficiency  and  furnace  efficiency,  and  have  resulted  in  much  confusion.  At 
present,  it  is  absolutely  impossible  to  decide  what  proportion  of  the  losses 
due  to  unburned  combustible  gases  and  to  radiai.on  should  be  charged  to 
the  boiler  and  furnace  respectively;  and  this  proportion  would  very  properly 
vary  according  to  the  relative  poorness  of  design  of  the  boiler  and  stoiter. 
While  it  would  be  valuable  to  know  the  furnace  and  boiler  efficiencies  sep- 
arately, it  must  be  ailmitted  that  up  to  the  present  no  method  of  finding 
them  has  been  proposed  which  is  not  highly  c—— *■ — 


ib.  Google 


TESTING  547 

Accuracy 

THE  absolute  accuracy  of  the  results  of  a  boiler  test  even  when  conducted 
with  the  greatest  care  is  doubtful,  but  there  is  as  yet  no  common  agree- 
ment as  to  what  the  probable  limits  might  be.  It  is  generally  conceded, 
however,  that  there  are  several  sources  of  indeterminate  error,  ili»  iiiuii.  im" 
poflant  -of  ff hich,-are  dism^sed-Jariowr  The  limits  of  accuracy  of  a  test 
migKt  very  reasonably  be  taken  to  be  within  plus  or  minus  3  per  cent. 

One  of  the  sources  of  probable  error  is  the  sampling  of  coal.  Even  when 
the  greatest  care  is  taken  to  obtain  a  representative  sample,  there  may  be  an 
indeterminate  error  in  ascertaining  the  heat  value  of  the  coal,  even  though 
the  laboratory  analysis  is  most  reliable.  With  modern  apparatus  these 
laboratory  detcrminnlions  should  be  substantially  correct  as  regards  the 
sample  tested;  but  the  question  as  to  how  truly  the  sample  represents  the 
whole,  is  always  present.aiid  etuumrliiranswtieJ  iiidHbitablr. 

Another  is  the  moisture  contained  in  the  coaL  As-eitplaiHed~jnJhc-pw- 
«(ling  r'""'fl'"'pfl  t*"  sampling  is  more  or  lesS'^incertain.  It  is  contended 
by  some  that  if  the  attempt  is  made  to  determine  the  moisture  during  the 
test,  ths  methods  of  drying  and  weighing  are  unreliable;  while  others  con- 
tend that  though  the  moisture  as  determined  in  the  laboratory  is  accurate 
so  far  as  the  sample  delivered  to  the  laboratory  is  concerned,  this  sample 
probably  does  not  represent  the  bulk  of  the  coal  actually  burned  since  there 
must  inevitably  have  been  more  or  less  loss  of  moisture  during  the  collec- 
tion, preparation  and  handling  of  the  sample. 

Similarly,  it  is  problematical  whether  the  samples  collected  for  the  r 
determination  of  the  moisture  in  steam  and  for  gas  analysis  are  representative  ' 
of   the   bulk,   although    the   testing   of   the   samples    obtained   may   be   quite 


It  is  not  unusual  for  heat  balances  to  be  reported  to  the  nearest  B.t.u. 
and  to  the  nearest  one-tenth  of  1  per  cent.  But  the  present  state  of  the  art  of 
bailer  testing  does  not  provide  means  for  attaining  anything  like  this  ac- 
curacy. In  general,  results  should  be  reported  only  to  the  nearest  significant 
figure.  Reporting  results  of  any  kind  in  small  units  is  likely  to  convey  an 
erroneous  idea  as  to  the  real  accuracy  of  the  figures. 

It  is  therefore  quite  logical  in  the  case  of  guarantee  tests,  that  a  sub- 
stantial compliance  with  the  guarantee  be  accepted  as  full  compliance  there- 
with, although  preferably  a  limit  of  tolerance  should  be  agreed  upon  before- 
hand by  the  parties  to  the  test.  The  amount  of  this  tolerance  might  well 
hear  some  relation  to  the  care  exercised  in  arranging  the  details  of  the  test 

Steam  Consumption  by  Auxiliaries 

THE  steam  or  power  used  in  generating  forced  or  induced  draft,  reducing 
smoke  by  means  of  steam  jets,  driving  stokers,  atomizing  liquid  fuel. 
oil  heaters,  oil  pumps,  and  so  forth,  should  be  determined  and  specifically 
reported.  No  deductions  on  this  account  are  to  be  made :  but  they  may 
conveniently  he  reduced  to  a  percentage  of  the  steam  generated. 

The  method  of  finding  the  steam  consumption  of  auxiliaries  by  means 
of  the  rate  of  flow  of  steam  through  a  nozzle  or  an  ori5ce  in  a  thin  plate  is 
described  on  page  421, 


SOOT  accumulations  are  seldom  accounted  for,  as  the  quantity  is  small 
during  an  ordinary  trial.  The  quantity  of  combustible  carried  oflf  in  the 
gases  as  smoke  is  determined  only  rarely.  A  prepared  surface  of  21  sq.  in.  in 
area  suspeiided  in  a  stack  has  been  found  to  collect  9  to  184  milligrams 
per  hour. 


ib.  Google 


Smoke 

NO  wholly  satisfactory  methods  for  either  quantitative  or  qualitative  smoke 
detennina lions  have  yet  come  into  use,  nor  have  any  reliable  methods 
been  established  for  delinicely  lixing  even  the  relative  density  of  the  sniokc 
issuing  from  chimneys  at  different  times.  One  method  commonly  employed, 
which  answers  the  purpose  fairly  well,  is  that  of  making  frequent  visual  ob- 
servations of  the  chimney  at  intervals  of  one  minute  or  less  for  a  period  of 
one  hour  and  recording  the  observed  characteristics  according  to  the  degree 
of  blackness  and  density,  and  giving  to  the  various  degrees  of  smoke  an 
arbitrary  percentage  value  rated  in  siome  such  manner  as  that  expressed 
in  Table  89. 

Table  89.     Smoke  Percentases. 

Dense  black  100 

Medium  black „ „._ - 80 

Dense  gray _ _ 60 

Medium  gray  „ 40 

Light  gray - 20 

Very  light 5 

Trace  1 

Clear  chimney 0 

The  color  and  density  of  smoke  depend  somewhat  on  the  character  of 
the  sky  or  other  background,  and  on  the  air  and  weather  conditions  obtaining 
when  the  observation  is  made,  and  these  should  be  given  due  consideration 
in  making  comparisons.  Observations  of  this  kind  are  also  subject  to  errors 
of  judgment.  Nevertheless,  these  methods  are  useful,  especially  when  the 
results  are  plotted  according  to  the  percentage  scale  determined  on  so  that 
a  graphic  representation  of  the  chatiges  can  be  shown. 

Various  forms  of  charts  and  clouded  glasfi  arrangements  for  comparing 
and  £xing  smoke  densities  have  been  proposed  and  to  some  extent  used  i 
but  these  have  proved  more  or  less  unsatisfactory  and  they  are  subject  to 
personal  errors,  and  to  sky,  wind,  and  weather  conditions,  the  same  as  the 
simpler  method  above  described. 

Among  the  chart  methods  referred  to,  the  use  of  the  Ringelmann  smoke 
chart  is  perhaps  the  most  familiar.    This  is  shown  in  Fig.  231. 

To  use  this  chart,  four  cards  are  ruled  like  those  shown,  though  covering 
a  much  larger  area,  and  placed  in  a  horizontal  row  about  50  ft.  from  the 
.  observer,  and  in  line  between  him  and  the  chimney,  together  with  two  other 
cards,  one  of  which  is  white  and  the  other  solid  black.  The  observer  glances 
rapidly  from  the  chimney  to  the  cards  and  judges  which  one  corresponds 
with  the  color  and  density  of  the  smoke.  He  makes  these  observations  every 
minutei  or  oftener  if  desired,  recording  the  number  of  the  card  representing 
the  character  of  the  smoke  at  the  instant  of  observation.  The  results  arc 
then  plotted  on  a  chart,  and  the  variations  shown  graphically. 

The  lines  in  cards  1  to  4  are  respectively  1,  2.3,  3.7,  and  5.5  mm.  thick, 
and  the  spaces  9,  7.7,  6.3,  and  4.5  mm.  The  lines  should  be  made  with  black 
India  ink. 

A  convenient  method  of  recording  and  presenting  smoke  reports  is 
illustrated  on  page  65. 

Another  method  of  smoke  determination  consists  in  the  use  of  a  nar- 
row flat  metal  plate  suspended  in  the  flue,  the  character  of  the  smoke  being 
indicated  by  the  amount  and  quality  of  the  soot  and  dust  deposited  upon  the 
plate  in  a  given  time.  This  method,  like  others,  is  useful  in  furnishing  a 
means  of  comparison  in  different  cases  rather  than  a  means  of  exact  de- 


ib.  Google 


TESTING 


No.  3.  No. 

Fig.  231.     RinKdnumn  Smoke  Chart. 


ib.  Google 


SSO  TESTING 

Among  the  latest  tiiethoijs  brought  out  (or  indicating  and  recording 
the  density  of  smoke  is  one  depending  on  the  variations  in  the  electrical 
conductivity  of  the  metal  selenium  due  to  variations  in  the  intensity  of  light 
shining  upon  it.  Openings  are  provided  on  either  side  of  the  flue  directly 
opposite  each  other.  The  selenium  is  located  at  one  opening  and  a  strong 
light  at  the  other.  The  intensity  of  the  light  rays  falling  on  the  selenium 
varies  with  the  density  of  the  smoke.  A  milliampere  meter  in  circuit  with 
the  selenium  cell  registers  the  variations. 

Liquid  and  Gaseous  Fuels 
Tests  with  liquid  and  gaseous  fuels  follow  the  same  general  lines  as 
those  with  solid  fuels.    Liquid  fuel  tests  are  reported  on  weight  of  fuel  as 
in  solid  fuel  tests,  while  gas  tests  are  commonly  reported  on  a  volumetric 


ib.  Google 


T 


CHAPTER  16 


OPERATION 

'HP.  methods  and  apparatus  concerned  in  the  operation  of  boiler  plants 

may  be  divided  into  two  classes — necessities  and  money  savers.    The 

' '      '  which  the  plant  either  cannot  be  operated  at  all  or 


cannot  be  operated  with  safety,  will  generally  be  considered  first  Discussion 
of  the  money  savers,  which  either  reduce  the  cost  of  operation  or  assist  in 
reducing  it,  will  follow.  The  latter  might  be  divided  further  into  two  classes 
— those  which  directly  save  money  such  as  feed  water  heaters  and  coal 
conveyors,  and  those  which  show  where  waste  occurs  such  as  COt  recorders 
and  coal  weighers. 

Boiler  Fittings 

THERE  are  several  necessary  items  of  equipment  which  must  be  attached 
to  a  steam  boiler  before  it  is  placed  in  service,  among  which  are  a  water 
column,  safely  valves,  steam  gage  and  blow-off  valves. 

Water  Colnmn.  The  water  column  usually  consists  of  a  cast  iron  body 
connected  at  the  bottom  with  a  pipe  to  the  boiler  below  the  water  level  and 
at  the  top  to  the  steam  space  of  the  boiler.  It  is  provided  with  three  or  more 
trycocks,  one  placed  at  about  the  mean  or  normal  water  lins  and  the  others 
above  and  below.  The  gage  glass  is  connected  through  gage  cocks  at  its  top 
and  bottom  to  the  water  column ;  and  if  both  gage  cocks  are  open,  the  water 
will  stand  in  the  glass  at  the  same  height  as  it  is  in  the  column  and  in  the 
boiler.  Both  gage  glass  and  water  column  should  be  provided  with  drain 
corks,  so  that  they  may  be  blown  out.  If  valves  are  placed  in  the  pipes 
connecting  the  water  column  with  the  boiler,  particular  care  must  be  taken 
to  lock  them  or  otherwise  prevent  absolutely  their  closure  by  unauthorized 
persons.  Long  pipe  connections  from  the  boiler  to  the  water  column  should 
be  avoided,  as  there  is  always  the  possibility  of  such  long  runs  of  pipe  be- 
coming clogged  with  sediment  or  scale,  thus  causing  the  water  column 
to  become  inoperative.  In  these  pipes  crosses  are  preferable  to  elbows,  for 
when  the  plugs  are  removed,  the  pipes  can  easily  be  cleaned  and  looked 
through. 

Fig.  231  shows  the  type  of  water  column  used  as  standard  equipment  on 
all  Heine  boilers.  This  column  is  provided  with  copper  floats  which  operate 
a  whistle  when  the  water  level  is  too  high  or  too  low. 

Safely  I'alJ-es.  The  function  of  a  safety  valve  is  to  prevent  the  pressure 
in  the  boiler  to  which  it  is  attached  from  rising  above  a  definite  point  called 
the  working  pressure.  The  working  pressure  of  a  new  boiler  is,  of  course, 
dependent  upon  the  design  and  thickness  of  materials  used  in  its  construction. 
The  working  pressure  of  a  boiler  which  has  been  in  service  for  some  time 
is  dependent  upon  its  age  and  physical  condition,  and  is  usually  governed  by 
the  report  of  a  municipal  or  insurance  boiler  inspector. 

The  A.  S,  M.  E.  Boiler  Code  (1918)  requires  that  the  safety  valve  capac- 
i^  for  a  boiler  shall  be  such  that  the  safety  valve  or  valves  will  discharge 
all  the  steam  that  can  be  generated  by  the  boiler  without  allowing  the  pres- 
sure to  rise  more  than  6  per  cent  above  the  maximum  allowable  working 
pressure,  or  more  than  6  per  cent  above  the  highest  pressure  to  which  any 
valve  may  be  set.    Th;  total  relieving  capacity  of  the  »afet>-  valve  or  valvej 


ib.  Google 


ib.Google 


OPERATION  553 

required  on  a  boiler  shall  be  determined  on  the  basis  of  6  lb.  of  steam  per 
hour  per  sq.  ft  of  heating  surface  for  water  tube  boilers.  Charts  for  de- 
termining safety  valve  siies  are  given  in  Chapter  8  on  PIPING. 


Water 
Fig.  331.     Reliance  Water  Column  equipped  with  Self-Closing  Oage. 

When  two  or  more  safety  valves  are  used  on  a  boiler,  thej;  may  be 
either  separate  or  twin  valves,  which  are  made  by  mounting  individual 
valves  on  a  Y  base.  Duplex,  triplex  or  multiplex  valves  are  those  '^vhich 
have  two  or  more  valves  in  the  same  body  or  casing. 

The  blow  down,  or  difference  between  opening  and  closing  pressure  of  the 
safety  valve  shall  not  be  more  than  4  lb.  on  boilers  carrying  less  than  100 
lb.  gage  pressure,  not  more  than  6  lb.  on  boilers  carrying  between  100  lb. 
and  200  lb.  pressure,  and  not  more  than  8  lb.  on  boilers  carrying  over  200 
lb.  pressure. 

The  use  of  weight  lever  safety  valves  or  dead  weight  valves  is  not  per- 
mitted under  the  A.  S.  M.  E.  Code,  hence  only  spring  loaded  pop  safety 
valves  will  be  described  here. 

Fig.  232  illustrates  a  typical  pop  safety  valve  for  use  with  saturated 
steam,  in  which  the  boiler  pressure  acting  upon  the  under  side  of  the  valve 
is  resisted  by  the  helical  spring.  When  the  boiler  pressure  exceeds  the 
spring  resistance,  the  valve  lifts  from  its  seat  and  the  steam  escapes  into 
the  atmosphere. 


ib.  Google 


SS4  OPERATION 

The  valve  is  provided  with  a  skirt  which  becomes  filled  with  steam  when 
the  valve  is  open,  so  that  the  effective  area  of  the  valve  i,s  increased.  As 
soon  as  Ihe  valve  lifts,  this  increased  area  immediately  takes  effect;  and  the 
greater  load  on  the  spring  compresses  it  more  than  would  be  the  case  with 
a  plain  valve,  and  the  vaivs  opens  wider.  Once  open,  the  valve  will  remain 
open  while  the  pressure  drops  below  that  which  opened  it,  because  of  the 
effect  of  the  increaped  area.  The  pressure  per  sq.  in.  on  the  added  area  is 
less  than  the  boiler  pressure,  and  is  dependent  upon  the  freedom  with  which 
the  steam  can  escape  from  under  the  skirt.  Passages  conned  this  part  with 
an  annular  space  called  the  '  huddling  chamber,"  and  this  chamber  is  pro- 
vided with  an  adjustable  outlet.  If  the  huddling  chamber  outlet  is  closed, 
the  pressure  under  the  skirt  will  be  greater,  and  the  boiler  pressure  will 
drop  very  low  before  the  spring  can  close  the  valve.  If  the  huddling  chamber 
outlet  is  wide  open,  the  pressure  in  it  and  under  the  skirt  will  be  small,  and 
the  valve  will  close  with  very  little  drop  of  boiler  pressure.  The  difference 
of  pressure  between  that  necessary  to  open  the  valve  and  that  at  which 
the  spring  ran  close  it,  is  called  the  "blow  down,"  and  is  adjusted  by  con- 
trolling the  huddling  chamber  outlet. 


Fie.  333.     Ashton  Pop  Safety  Valve  for  Saturated  Steam. 

It  has  been  explained  how  the  effect  of  the  skirt  is  to  cause  the  valve 
to  open  wide  immediately  upon  opening  at  all.  In  closing,  this  action  is 
reversed,  for  when  the  boiler  pressure  drops  sufficiently  to  allow  the  spring 
to  begin  closing  the  valve,  the  pressure  under  the  skirt  drops  and  allows 
the  spring  to  close  the  valve  further,  so  that  the  action  is  cumulative  atld 
the  valve  closes  quickly.  Owing  to  the  rapidity  with  which  these  valves  open 
and  close,  they  are  called  "pop"  valves. 

The  valve  may  be  opened  to  discharge  at  any  pressure  less  than  the 
Teaeving  pressure  by  operating  the  hand  lever. 


ib.  Google 


OPERATION  SSS 

Every  superheater  should  be  equipped  with  a  safety  valve  at  its  outlet, 
set  to  blow  at  a  lower  pressure  than  the  boiler  safety  valves,  in  order  that  a 
flow  of  steam  may  be  maintained  through  the  superheater  if  fo'  any 
reason  the  main  steam  flow  is  stopped;  and  this  will  avoid  damage  to  the 
superheater  tubes  by  burning. 

Fig.  233  shows  a  type  of  valve  designed  for  superheated  steam  service. 
The  spring  is  exposed  to  the  air,  so  that  high  temperature  steam  does  not 
affect  its  elasticity  by  coming  in  contact  with  it. 


Pig,  333.     Consolidated  Pop  Safety  Valve  for  Superheated  Steam. 

Suam  Pressure  Cages,  Every  boiler  must  be  equipped  with  a  steam 
gage,  which  may  be  connected  directly  to  the  boiler  steam  space  or  to  the 
water  column  or  its  steam  connection. 

These  gages  are  generally  of  the  round-pattern,  indicating  type.  They 
consist  mainly  of  a  pressure  element  in  the  form  of  a  tube  spring  or  a  dia- 
phragm, and  of  a  movement  to  operate  the  indicating  mechanism.  The  styles 
differ  chiefly  in  the  details  of  construction,  such  as  material,  mountings, 
trimmings  and  Bnish. 

The  Bourdon  pressure  element  is  an  oval  metal  tube,  closed  at  one 
end  and  bent  In  an  arcuate  form  to  give  the  single  or  double  spring,  as  in 
Fig.  234.  The  free  end  of  the  tube  is  connected  by  one  or  more  levers 
to  a  toothed  sector  or  segmental  rack,  which  actuates  a  small  pinion  on  the 
pointer  shaft.    Lost  motion  is  taken  up  by  a  hair  spring  attached  to  this  shaft 


ib.  Google 


SS6  OPERATION 

For  marine  and  portable  work  ar  in  siaiionary  installations  where 
vibrations  would  jar  the  sensitive  mechanism,  the  double-tube  gage  is  recorn- 
mended.  This  gage  is  not  so  easily  alTected  by  rapid  fluctuations  of  pres- 
sure. The  two  free  ends  of  the  pressure  tubes  are  connected  to  a  multi- 
plying mechanism  similar  to  that  in  the  single-tube  gage,  but  the  needle 
movement  ts  much  greater. 


Singlt  Tube.  Dial.  Double   Tube. 

Fig.  334.    Bourdoa  Tube  Steam  Oagea. 

When  measuring  pressure,  gages  show  the  difference  between  the  inside 
pressure  actuating  the  device,  and  the  pressure  on  its  outside.  Therefore, 
when  the  gage  indicates  rero.  the  pressures  inside  and  outside  of  the  spring 
are  the  same;  when  it  indicates  SO  lb.,  then  the  pressure  inside  the  spring  is 
50  lb.  greater  than  the  pressure  on  its  outside.  The  absolute  pressure  is 
the  sum  of  the  atmospheric  pressure  (14.7  lb.)  and  the  gage  reading;  thus 
50  lb.  gage  is  equivalent  to  64J  lb.  absoltile.  Pressure  is  usually  expressed  in 
pounds  per  tquare  inch. 

In  selecting  n  gage,  the  size  and  unit  of  the  scale  required  should  be 
specified,  and  the  scale  selected  should  not  exceed  one  and  one-half  times 
the  working  pressure.  Round  pattern  gages  used  on  the  steam  plant,  range 
from  3  to  12-in,  diameter.  The  dials  of  indicating  gages  are  usually  silver 
finished  brass,  having  figures  and  graduations  filled  with  black  enamel ;  or 
they  may  be  black  with  silver  figures.  The  casings  are  iron,  brass  or  nickel- 
Gages  should  be  located  so  that  they  are  accessible,  can  be  easily  read, 
reeled   as   to   insure   correct    readings.      Standard   gages   have   i 


■4  in.  pipe-thread  male  connection  and  are  generally  provided  with  a  stop 
CQck.     For  dark  or  obscure  places,  illuminated  dial  gages  should  be  used. 

Gage  tubes  may  become  softened  when  subjected  to  temperatures  of 
more  than  150  deg.,  so  that  steam  or  very  hot  water  should  not  come  in 
direct  contact  with  the  tube.  A  goose-neck  siphon  or  loop.  Fig.  235.  is  used 
to  maintain  a  protective  water  seal  between  the  gage  and  the  steam  supply. 

When  the  gage  is  exposed  and  subject  to  freeiring,  a  pet  cock.  Fig.  23Sd, 
should  be  provided  for  draining  the  water  from  the  siphon.  Freezing  might 
burst  the  connection  or  damage  the  gage  spring.  This  pet  cock  should  not 
be  opened  when  the  pressure  gage  is  in  service,  as  then  the  water  seal  would 
be  lost  and  the  gage  tube  be  liable  to  be  damaged  by  contact  with  the  steam. 

If  a  gage  is  placed  below  a  pipe  line.  Fig.  235e,  allowance  must  be 
made  for  the  head  of  water  in  the  seal  to  obtain  correct  readings.  Such 
a  correction  can  be  made  by  multiplying  the  head  of  water  in  feet  by  .433, 
thus  reducing  it  to  lbs.  pressure  per  sq.  in.,  which  should  be  deducted  from 
the  gage  readings. 


D,g,tze:Jbi  Google 


OPERATION 


Gages  should  be  attached  securely  to  minimize  the  effects  of  vibration. 
Repeated  jarring  will  cause  wear  of  the  rack  and  pinion,  resulting  in  in- 
accurate pressure  indications.  Gages  subject  to  vibration,  or  placed  high 
up  and  in  hot  boiler  rooms,  should  be  frequently  tested.  As  the  spring  of 
the  gage  has  only  a  slight  motion,  the  least  interference  with  it  will  produce 
a  noticeable  error  because  of  the  greater  movement  of  the  needle  or  pointer. 


ions  for  Steam  Gages. 


A  gage  can  be  calibrated  by  comparison  with  a  standard  test  gage,  or 
by  trial  on  a  dead  weight  tester,  or  on  a  mercury  column  tester.  Where 
testing  devices  are  not  available,  as  in  the  small  plant,  ^ages  siiould  be 
sent  to  the  factory.     A  typical  dead  weight  tester,  Fig.  236,  consists  of  a 


Pig.  336.     Dead  Weight  Oage  Tester. 


stand  on  which  is  mounted  an  oil  reservoir,  plunger  pump  and  cylinder 
htted  with  a  piston  to  receive  the  weights.  The  gage  to  be  tested  is  attached 
to  a  ihrce-way  cock.  Each  test  weight  is  marked  with  the  pressure  in 
pounds  per  square  inch  that  it  will  show  on  the  gage.  The  weights  are 
placed  on  the  disk,  one  at  a  time ;  and  they  should  be  whirled  while  taking 
the  reading,  so  as  to  eliminate  the  error  caused  by  the  friction  of  the 
plunger.  If  the  gage  is  at  variance  with  the  dead  weight  applied,  it  may 
be  corrected  by  removing  the  pointer  with  a  gage-jack  and  pressing  it  back 
on  the  spindle  at  the  proper  indication. 


ib.  Google 


,Google 


-# 


Fig.  237.     EverlBiting  Blow-ofT  Valve. 


Pig.  338.     Yarway  SeatlcM  Blow-ofT  Valve. 


ib.  Google 


560  OPERATION 

Blow^ff  I'alfes,  All  boilers  ihnuld  be  equipped  with  one  or  more  blow- 
off  pipe^.  tvith  one  or  more  cocks  or  valves  on  each  pipe.  The  A.  S.  M.  £. 
Code  (1918)  provides  that  blow-off  piping  shall  not  be  less  than  1  inch  or 
larger  than  2^'^  inches,  and  that  globe  valves  should  not  be  used.  The  re- 
quiremenis  of  a  good  blow-off  valve  are  that  it  shall  provide  a  clear  passage 
for  water,  mud  and  scale,  and  that  it  shall  open  easily  and  close  tightly. 

Fig.  237  illustrates  the  Everlasting  Blow-off  Valve,  which  consists  of  a 
top  and  bottom  bonnet  and  a  disc  which  swings  between  seats  on  the  faces 
of  the  bonnets.    The  disc  is  actuated  by  a  lever. 

Fig.  238  illustrates  the  Yarway  Seatless  Blow-off  Valve.  A  plunger  V 
is  operated  by  a  hand  wheel  and  screw.  In  closing  the  valve,  the  shoulder 
S  on  the  plunger  V  engages  the  loose  follower  gland  F,  compressing  the 
packing  P  above  and  below  the  port,  thus  making  a  tight  closure. 

Fusible  Plttst,  see  Fig.  239,  are  intended  to  protect  a  boiler  in  case 
of  low  water.  At  best,  these  plugs  are  unreliable,  but  the  law  in  some 
states  requires  their  use,  even  in  water  tube  bailers. 


Fig.  139.     Pvirible  Plugs, 


The  fusible  plug  consists  of  a  brass  or  bronze  fitting  which  may  be 
screwed  into  the  shell,  furnace  crown  sheet,  or  watcrleg  of  a  boiler.  The  fit- 
ting is  bored  out  and  filled  with  pure  tin  or  some  composition  metal  which 
has  a  melting  point  but  little  above  the  temperature  of  the  steam  in  the 
boiler.  The  metal  of  the  plug  transmits  the  heat  to  the  water  so  rapidly  that 
its  temperature  does  not  rise  if  it  is  covered  with  water;  but  if  the  water 
level  falls  below  the  plug,  the  fusible  metal  in  the  core  will  melt  out,  allowing 
the  steam  to  escape,    ff  heard  or  noticed,  this  will  serve  a$  an  indication  of 

Methods  of  Hand  Firing  Coal 

HAND-FIRING  is  not  only  hard  work,  but  requires  considerable  judg- 
ment and  skill  if  waste  of  coal  is  to  be  avoided.  The  method  of  firing 
depends  upon  the  kind  and  quality  of  coal. 

Biluininous  Coal,  Inasmuch  as  bituminous  coals  vary  widely  in  comiKi- 
sition,  it  is  difficult  to  state  definite  rules  for  handling  which  will  fit  all 
casef.  The  most  suitable  method  of  (iring  a  particular  coal  is  best  determined 
by  experimenting  with  it,  and  a  careful  fireman  soon  learns  how  to  produce 
the  best  results. 

There  are  three  general  systems  of  firing,  known  as  alternate,  spread- 
ing and  coking. 

In  the  allernate  system,  fresh  coal  is  fired  first  on  one  side  of  the  furnace 
then  on  the  other,  or  through  3llern,ite  doors  when  there  are  more  than 
two,  so  that  the  entire  fire  is  not  blanketed  with  green  coal.  This  system 
is  used  where  the  grates  are  wide  or  when  two  or  more  furnaces  have  a 
common  combustion  chamber. 


ly  Google 


OPERATION  561 

The  spreading  system  consists  in  charging  a  amall  amount  of  coal, 
spreading  it  in  a  thin  layer  over  the  entire  grate  at  each  firing ;  usually  it 
is  spread  from  the  bridge  wall  toward  the  door.  Although  it  means  nwre 
work  for  the  fireman  because  the  furnace  must  be  tired  frequently,  the  use 
of  this  system  is  increasing.  It  gives  an  air  supply  which  is  always  more 
nearly  proportional  to  the  fuel  supply. 

Tn  the  coki»s  system,  the  fresh  coal  is  piled  up  on  the  dead  plate  or  on 
the  front  of  the  grate,  so  that  the  mass  can  become  nearly  or  wholly  coked. 
It  is  then  pushed  back  toward  Che  bridge  wall,  and  spread  evenly  over  the 
grate  to  make  room  for  the  new  charge.  When  no  dead  plate  is  provided, 
about  one-third  of  the  grate  at  the  front  is  left  bare  and  receives  fresh  coal 
at  each  firing.  This  ^stem  is  adapted  to  furnaces  in  which  the  gases  pass 
horizontally  over  the  fire. 

The  spreading  and  alternate  methods,  as  compared  with  the  coking 
system,  give  higher  efficiency,  higher  COi  and  lower  temperature  of  exit 
gases.  Because  of  the  greater  uniformity  in  furnace  temperatures,  steam 
is  generated  more  uniformly.  In  the  coking  method  less  of  the  refuse  appears 
as  clinker  and  more  as  ash,  but  the  combustible  lost  through  the  grate  is 
about  the  same  in  the  three  methods  of  firing.  The  amount  of  slicing  and 
raking  is  equal  with  all  three,  but  the  coking  method  also  requires  time  and 
labor  for  leveling. 

The  spreading  and  alternate  methods  of  firing  are  widely  used  in  hand 
firing  non -caking  and  high  volatile  bituminous  coals.  In  the  alternate 
method  the  volatile  matter  given  off  by  a  fresh  change  of  green  coal  on  the 
one  side  of  the  grate,  is  mixed  with  some  air  which  has  been  heated  by 
passing  through  the  fuel  bed  on  the  other  side ;  but  care  must  be  taken  to 
make  provision  for  thoroughly  mixing  the  gases  from  the  two  sides  of  the 
fire,  and  there  is  the  difficulty  of  getting  one  side  of  the  fire  heavier  than 
the  other.  Spreading  over  the  complete  fuel  bed  is  perhaps  more  extensively 
used  than  even  the  alternate  method,  and  has  the  advantage  over  the 
alternate  method  that  the  whole  fuel  bed  can  be  kept  of  more  uniform 
thickness,  thus  minimizing  the  possibility  of  holes  occurring  in  the  fire. 

The  coking  method  is  most  applicable  to  those  bituminous  coals  which 
cake  or  melt  and  run  together  upon  heating.  With  this  method  the  hydro- 
carbons must  pass  over  the  hottest  part  of  the  fire  which  is  near  the  bridge 
wall,  on  their  way  to  the  boiler  heating  surface.  The  back  part  of  the  fire 
should  be  kept  thicker,  as  the  character  of  the  coke  bed  is  much  more  open 
here  than  at  the  front 

Two  disadvantages  of  the  coking  method  of  firing  are  that  the  fire  doors 
must  be  kept  open  relatively  long  in  order  to  work  the  fire,  which  results 
in  large  quantities  of  excess  air;  and  the  fire  is  being  continually  disturbed, 
a  fact  which  will  result  in  excessive  dinkering  with  coals  containing  fusible 

Following  are  a  few  general  rules  which  have  been  formulated  by  the 
Coal  Stoking  and   Anti-Smoke  Committee  of  the   Illinois  Coal  Operators' 

Association  for  the  hand-firing  of  Illinois  and  Indiana  coals. 

(1)  Break  all  lumps,  and  do  not  fire  coal  into  the  furnace  of  a  size 
larger  than  the  fist.  Large  pieces  do  not  ignite  quickly  and  their  presence 
results  in  the  formation  of  holes  in  the  fire,  with  consequent  losses  due  to 

(2)  Keep  the  ash  pits  bright  at  all  times.  If  they  become  dark  it  is 
an  indication  that  the  grates  are  becoming  covered  with  clinkers  and  that 
the  fire  needs  cleaning. 

(3)  Do  not  fire  the  coal  in  heaps  on  the  grate  unless  filling  up  a 
hole.    Spread  the  coal  as  it  leaves  the  lip  of  the  shovel. 


ib.  Google 


562  OPERATION 

(4)  When  firing,  spread  the  coal  from  the  bridge  wall  forward, 

(5)  Do  not  allow  the  fire  to  burn  dull  before  charging. 

(6)  Do  not  allow  holes  to  form  in  the  Are.  Should  one  form,  it  should 
be  filled  by  leveling. 

(7)  Regulate  the  draft  by  the  ash  pit  doors  rather  than  by  the  manipu- 
lation of  the  stack  damper.  When  the  fitack  damper  is  closed  the  intensity 
of  the  draft  is  diminished,  but  by  closing  the  ash  pit  doors  the  air  supply 
is  reduced. 

Referring  to  rule  (7),  general  opinion  is  against  regulating  the  draft 
by  the  ashpit  doors.  The  air  supply  is  reduced,  whether  it  is  the  damper 
or  the  ashpit  doors  that  are  partly  closed.  Closing  the  ashpit  doors  is 
generally  believed  to  result  In  unduly  heating  the  grate  bars ;  and  it  reduces 
the  boiler  efficiency  by  causing  an  increase  in  the  leakage  of  air  through 
defects  in  the  setting. 

Anlhraeilc,  Anthracite  should  be  fired  by  the  spreading  method,  in 
small  quantities  and  at  frequent  intervals.  For  large  sizes  of  anthracite 
such  as  ''stove"  or  "e^,"  almost  any  type  of  hand-fired  furnace  is  suitable. 
However,  the  larger  sizes  of  anthracite  are  now  almost  exclusively  used  for 
domestic  purpose;:,  and  because  of  their  high  cost  are  but  little  used  under 
steam  bailers.  The  smaller  grades  of  anthracite  do,  however,  find  extensive 
use  as  boiler-fuel,  and  their  successful  burning  depends  upon  several  factors. 

The  small  sizes  of  anthracite  pack  closely  together  on  the  grates,  which 
makes  the  employment  of  a  strong  draft  necessary  to  secure  the  proper 
amount  of  air  for  combustion.  Mechanical  draft  is  usually  employed,  which 
is  obtained  by  the  use  of  steam  jet  blowers  or  by  fans.  As  the  fine  grades 
of  anthracite  run  higher  in  ash  than  the  larger  grades,  there  is  considerable 
tendency  toward  clinker  formation ;  and  the  employment  of  steam  jet  blowers 
for  forced  draft  is  desirable,  as  the  introduction  of  steam  into  the  ash  pit 
decreases  formation  of  clinker. 

It  is  desirable  to  disturb  the  fuel  bed  as  little  as  possible  with  the  firing 
tools.  With  n  little  practice,  the  fuel  can  be  spread  very  thinly.  The  fire 
should  be  kept  of  even  thickness,  and  if  necessary  it  may  he  levelled  occa- 
sionally with  a  lee-bar.  This  can  be  a  light  tool  made  of  a  length  of  ii 
or  1  in.  pipe  screwed  into  the  branch  of  a  tee,  with  pieces  of  pipe  about  6  in. 
long  screwed  into  the  "runs."  The  fire  is  simply  to  be  leveled  with  this 
tool,  and  not  stirred  up.  Some  firemen  get  good  results  by  levelit^  the  fire 
with  a  tee-bar  between  each  firing. 

There  is  a  limit  to  the  forced  draft  pressure  when  small  anthracites  are 
burned,  owing  to  the  liability  of  lifting  the  fuel  off  the  grate.  This  makes 
holes  in  the  fire  and  carries  some  of  the  fuel  into  the  combustion  chamber 
and  flues.  Owing  to  the  necessarily  slower  rate  of  combustion,  the  grate 
area  for  small  sized  anthracite  is  made  larger  than  for  bituminous  coal  in 
order  to  develop  the  same  horsepower.  The  relation  of  grate  area  to  boiler 
heating  surface  to  develop  the  rated  capacity  of  a  boiler  is  given  in  Table  f9. 


Tabic  89.     Rclatdon  of  Orate  Area  to  Boiler  Heating  Surface. 


No. 

1 

Buckwheat 

No. 

2 

No. 

;( 

No. 

4 

" 

ib.Google 


OPERATION  563 

On  account  of  the  large  amount  of  ash  in  small  hard  coal,  there  will 
be  a  considerable  depth  of  ash  on  the  grate  just  before  cleaning.  The  ashpit 
pressure  is  small  Just  after  cleaning,  but  as  the  ash  thickens  on  the  grate, 
the  pressure  must  be  greatly  increased  to  maintain  an  even  combustion  rate. 
Therefore,  forced  draft  blowers  should  be  chosen  which  have  characteristics 
showing  that  their  efficiency  is  maintained  over  a  wide  pressure  range. 

The  "free  burning"  varieties  of  anthracite  are  burned  satisfactorily  when 
the  above  directions  are  followed.  But  with  the  harder  coals— those  con- 
taining very  little  volatile  matter — it  is  usually  necessary  to  mix  from  10  to 
15  per  cent  of  bituminous  coal.  The  bituminous  coal  should  be  fine  "slack," 
not  lumpy. 

Tools  for  Hand  Firing.  The  hoe,  slice  bar,  rake  and  shovel  are  the 
necessary  hand  firing  tools,  and  Fig.  240  illustrates  those  designed  for  a 
6  ft.  grate. 


"\^ 


Fig.  340.     Tools  for  Hand  Firing. 

For  best  results  in  hand-firing,  the  equipment  must  be  so  arranged 
that  the  shovel  and  other  (iring  tools  can  be  handled  freely  wiUiout  hitting 
bumps  and  rivets.  This  implies  sufficient  firing  space,  a  smooth  floor  to 
receive  the  coal,  or  stil!  better,  a  hand  or  industrial  coal  car  similar  to  the 
tj'pe  shown  in  Fig.  241. 

In  the  firing  procedure  recommended  by  the  Bureau  of  Mines,  the 
fireman  lakes  the  position  indicated  in  Fig.  242,  in  which  he  can  see  the  thin 
spots  in  the  fire  and  can  throw  the  coal  on  without  exertion.  He  stands 
4S4  to  5  ft.  in  front  of  the  furnace  at  about  12  to  18  in.  from  the  center 
line  of  rtie  firing  door.    The  coal  pile  is  about  2  ft  away. 

If  the  coal  is  less  than  6  to  7  ft.  from  the  boiler  front,  the  fireman  is 
crowded.  To  avoid  the  intense  heat,  he  stands  to  one  side  of  the  door,  and 
throws  the  coal  in  by  guess.  The  room  for  handling  the  scoop  is  not  suffi- 
cient so  it  travels  in  the  arc  of  a  circle,  scattering  some  coal  in  its  path,  and 
dumping  the  remainder  in  a  heap  on  the  dead  plate  or  on  the  grate  just 
inside  of  the  firing  door.  The  result  is  an  uneven  fire  that  requires  raking 
and  sprea<Iing  over  the  grate. 


ib.  Google 


"is 


si 


«•!. 


f2S 


ib.Google 


OPERATION 


For  economy,  coal  should  be  burned  rapidly  and  at  high  temperatures. 
This  means  light  tiring  or  the  frequent  charging  of  small  amounts  ol  coal 
to  prevent  the  thin  places  from  burning  through  and  admitting  too  much 
excess  air.  The  amount  of  coal  and  time  of  firing  depend  upon  the  grate 
surface  for  the  available  draft.  A  draft  of  1  in.  in  the  uptake  will  give 
good  results  with  2  to  IVi  lb.  of  coal  to  a  sauare  foot  of  grate  at  each 
tiring.  A  boiler  with  a  grate  6  by  8  ft.  would  then  require  six  to  nine 
shovelfuls  of  coal  at  each  tiring  period,  about  every  5  minutes.  For  a  higher 
draft  the  interval  might  be  3  minutes,  and  for  a  lower  draft  the  firing  time 
might  be  8  minutes. 

The  facilities  for  handling,  care  in  charging  and  cleaning  fires,  and  the 
suitability  of  the  type  of  grate  to  the  fuel  burned — all  may  cause  loss  or 
waste  of  coal.  With  poor  facilities  or  management  the  total  may  run  as 
high  as  10  per  cent  of  the  coal  consumed,  while  under  fair  operation  the 
loss  will  average  from  2  to  3  per  cent. 


Fig.  341.     Steel  Coal  Cars. 


-^- 


f^S'—-\—2'-' 
Fig.  242.     Proper  Pontion  for  Hand-firing. 


ib.  Google 


566  OPERATIOM 

The  thicknesa  of  foel-bed  re<]uirecl  depends  to  a  \atgt  extent  upon  the 
grade  of  coal,  available  dcaft,  firing  periods  and  the  experience  of  the  fire- 
man. For  a  ^iven  operatiiif;  condition  and  boiler  setting,  Uie  thicknesa  giving 
maximum  efficiency  can  be  determined  by  test.  If  the  fuel-bed  is  too  thin 
excess  air  will  result.  If  it  is  too  thick  the  air  supply  wilt  be  insufficient 
for  proper  combustion.  In  either  case  the  boiler  efficiency  will  be  decreased. 
Generally  a  thin  tire  is  to  be  favored,  but  with  iroarse  coal  the  fire  bed 
should  be  thicker.  Far  the  larger  sizes  of  anthracite  a  fuel-bed  of  6  to  10  in. 
can  easiW  be  carried ;  a  2-in.  bed  will  give  good  results  with  barley  and  rice 
coals.  The  free-burning  bituminous  coals  can  be  easily  handled  with  a  6 
to  lO-in.  bed;  the  poorer  grades  give  good  results  with  a  fuel-bed  4  to  6  in. 
thick. 

Lignite.  Lower  grades  of  lignhe  disintegrate  and  crumble  readily  when 
heated.  The  packing  of  this  finely  divided  fuel  on  the  grate  increases  the 
resistance  of  the  fuel  bed  to  the  flow  of  air,  hence  a  high  draft  pressure 
is  required  for  even  moderate  rates  of  combustion.  This  crumbling  causes 
intenfe  combustion  near  the  grate  where  the  air  enters,  and  the  high  tem- 
perature at  this  point,  coupled  with  the  low  fusion  point  of  the  ash,  results 
in  the  formation  of  clinkers.  The  fuel  bed  should  be  disturbed  as  little  as 
possible  during  firing,  because  of  this  tendency  to  form  clinker.  Special 
types  of  overlapping  grates  with  small  air  spaces  should  be  used  to  prevent 
the  disintegrated  lignite  from  sifting  into  the  ash  pit.  The  thickness  of  the 
fuel  bed  may  vary  from  4  to  S  inches  with  natural  draft,  and  up  to  20 
inches  with  forced  draft  in  the  semi-producer  type  of  furnace.  Either  the 
alternate  or  spreading  type  of  firing  may  be  used  with  lignite. 

Wood.  Cord  wood  or  slabs  may  be  successfully  burned  on  herring-bone 
grates  with  natural  draft  When  stacked  in  a  furnace  they  form  an  open 
Rre  through  which  the  friction  draft  loss  is  slight,  and  htmce  the  fud  bed 
may  be  as  much  as  from  lyi  to  3  feet  in  depth.  Double-deck  fire  doors  on 
the  fire-fronts  are  convenient  for  feeding  slab  wood. 

Hog  wood,  or  the  refuse  resulting  from  the  maceration  of  logs  and 
tnill  ends  in  a  hogging  machine,  may  be  fed  to  the  grates  through  chutes 
or  by  hand.  It  is  generally  burned  in  a  Dutch  oven  on  herring-bone  or 
Tupper  grates.  The  fuel  bed  may  be  from  two  to  four  feet  deep.  Care 
should  be  taken  to  avoid  too  much  excess  air  coming  in  through  fuel 
chutes  or  by  parts  of  the  grates  being  uncovered.  The  bed  of  fuel  should 
not  be  disturbed  with  firing  tools  of  any  kind;  but  even  then  a  large  amount 
of  linconsumed  wood  particles  are  carried  away. 

Forced  draft  under  the  grates  is  not  desirable,  because  of  increasing  the 
amount  of  "fly  ash"  and  unconsumed  particles  of  wood  carried  up  into  the 
breechings,  etc.,  where  secondary  combustion  may  cause  damage. 

Excellent  results  are  being  obtained  in  burning  this  fuel  on  Laclede- 
Christy  Chain  Grate  Stokers  under  Heine  standard  boilers.  Compared  with 
hand  operation,  these  stokers  give  much  higher  boiler  efficiency  and  entirely 
eliminate  smoke  and  the  carriage  of  unburned  particles  out  of  the  furnace 
and  combustion  chambers. 

Wet  or  green  tati'dust  is  satisfactorily  burned  on  hollow  blast  grate  bars 
with  forced  draft.  Inasmuch  as  the  character  of  the  sawdust  as  regards  its 
resinous  properties,  moisture  content  and  sire  of  particles,  vary  in  different 
localities,  no  general  thickness  of  iirc  can  be  recommended,  but  usually  it 
will  be  less  than  twelve  inches.  It  is  preferable  to  tire  the  sawdust  over  the 
grate  surface  evenly  by  hand.  Heaps  or  cones  formed  when  the  sawdust  is 
fed  into  the  furnace  through  chutes  should  be  constantly  leveled. 

Shavings  and  fine  dust  from  polishing  machines  are  not  usually  available 
in  sutticient  quantities  to  burn  alone.  They  are  generally  used  in  conjunction 
with  coal  fired  grates,  often  set  in  an  extension  furnace.    As  this  material 


D,g,tze:Jbi  Google 


OPliRATION  S67 

is  generally  very  dry.  care  must  be  taken  that  there  is  a  vacuum  in  the  fur- 
nace, for  if  not,  the  furnace  brick  work  and  cast  iron  fronts  will  be  damaged 
by  the  intense  heat. 

Tatt  Bark.  Tan  bark  may  be  satisfactorily  burned  in  a  Ehitch  oven  or 
extension  type  furnace  equipped  with  horizontal  or  inclined  stationary  grates. 
The  grates  usually  have  from  20  to  30  per  cent  air  space,  with  the  actual 
opening  between  bars  not  more  than  '/«  to  V<  inch,  thus  preventing  the  tan 
bark  from  falling  into  the  ash  pit.  The  ratio  of  grate  surface  to  boiler 
heating  surface  is  generally  about  1  to  30. 

The  thickness  of  fuel  bed  varies  with  the  character  of  the  bark,  furnace 
design  and  available  draft.  In  the  usual  practice,  the  tan  bark  feed  chutes 
are  located  in  the  top  of  the  extension  furnace  arch,  and  the  material  builds 
up  on  the  grates  in  the  form  of  cones.  These  cones  will  vary  in  depth,  and 
where  they  meet  will  be  from  6  to  18  inches. 

Tan  iMirk  is  sometimes  fired  with  bituminous  coal  in  a  Dutch  oven  fur- 
nace equipped  with  dumping  or  shaking  grates.  The  grate  surface  in  such 
a  case  will  range  between  1  to  35  and  1  to  SO. 

Cleaning  Fires 

CLEANING  a  tire  is  made  necessary  by  the  accumulation  of  clinker  and  ash, 
which  impede  the  air  for  combustion.  The  intervals  between  cleaning 
depend  upon  the  proportion  of  ash  in  the  coal  and  its  fusibility,  and  upon 
the  type  of  grate.  If  the  coal  contains  much  ash,  or  ash  that  is  fusible, 
the  fires  must  be  cleaned  frequently.  Less  clinker  forms  with  light  tires, 
which  can  often  be  run  through  a  12-hour  shift  without  cleaning.  Fires 
should  he  cleaned  thoroughly,  all  clinker  and  ash  being  removed  so  that  they 
cannot  fuse  and  adhere  to  the  side  and  bridge  walls.  Accumulations  of 
dinker  melted  onto  the  furnace  walls  reduce  the  grate  area;  and  the  brick- 
work is  damaged  when  they  are  eventually  broken  off. 

The  more  quickly  fires  are  cleaned,  the  less  coal  is  wasted.  The  damper 
should  be  partly  closed  while  it  is  being  done. 

There  are  two  general  methods  of  cleaning  fires,  the  side  and  the  front 
to  rear  methods. 

In  the  side  method,  one  side  of  the  fire  is  cleaned  at  a  time.  The  good 
coal  on  the  top  of  the  fuel  bed  is  scraped  and  pushed  to  one  side,  large 
clinkers  are  broken  uj)  with  a  slice  bar,  and  the  refuse  drawn  out  of  the 
furnace.  After  one  side  is  cleaned,  all  the  burning  coal  from  the  other 
side  is  moved  back  and  spread  evenly  over  the  cleaned  part  of  the  prate, 
after  which  a  few  shovels  of  green  coal  are  added.  This  adding  of  fresh 
coal  is  necessary  in  order  to  have  enough  live  coal  to  cover  all  tht  gr.itc 
when  the  cleaning  is  completed.  The  refuse  is  then  removed  from  the  other 
half  of  the  grate  and  the  burning  coal  spread  over  the  whole  grate. 

In  the  front  to  rear  method,  the  burning  coal  is  pushed  liack  with  a  lioe 
against  the  bridge  wall  and  the  exposed  clinker  removed.  The  burning 
coat  is  tlien  pulled  forward  and  formed  into  a  narrow  ridge  across  the 
bare  grate.  The  clinker  from  the  back  of  the  fire  is  "jumped"  across  the 
ridge  with  the  hoc,  and  pulled  out  through  the  fire  door.  The  ridge  of  live 
coal  is  then  spread  evenly  over  the  grate.  With  this  method  it  is  difficult 
to  get  a  really  clean  fire  without  wasting  a  lot  of  unburned  coal. 

An  improvement  on  the  front  to  rear  method  is  to  form  the  front  of 
the  bridge  wall  into  a  shelf  or  cleaning  table.  The  live  coal  is  pushed  onto 
the  cleaning  table,  giving  every  facility  for  thorough  cleaning  without  waste 
of  unburned  coal.  After  the  ash  and  clinker  have  been  removed,  the  live 
coal  is  drawn   forward  from  the   cleaning  table  and  spread  over  the  grate. 

The  height  of  the  cleaning  table  above  the  grate  should  be  such  that 
it  is  about  level  with  the  top  of  the  layer  of  ash.  This  will  naturally  vary 
with  the  quality  of  coal  and  with  the  length  of  time  between  cleanings,  but 
about  6  in.  will  meet  general  conditions. 


ib.  Google 


OPERATION 


With  anthracite,  dumping  grates  are  frequently  used.  The  fire  is  burned 
very  low  on  one  section  by  not  feeding  coal  to  it,  and  that  section  is  then 
dumped.  Burning  fuel  is  pushed  onto  the  clean  grate  and  fresh  fuel  added. 
Other  sections  are  similarly  treated  until  the  whole  fire  is  cleaned. 

Stand-by  Bmlers  and  Banked  Fires 

POWER  plants  which  operate  under  changeable  load  conditions  must  always 
be  ready  to  carry  the  maximum  or  peak  load,  and  in  order  to  meet  these 
sudden  demands,  steam  pressure  must  be  maintained  on  the  boilers  held  in 

The  length  of  time  that  stand-by  boilers  are  held  in  reserve  depends 
entirely  upon  the  service.  Boilers  are  held  in  reserve  in  public  utility  plants 
to  meet  the  peak  load  demands  of  morning  and  evenii^  rush  hours  wlitcli 
come  on  at  delinite  times;  and  are  also  held  for  long  periods  to  meet  un- 
expected demands,  such  as  are  due  to  thunderstorms,  fire  protection  serv- 
ice, etc. 

The  quantity  of  fuel  nsed  in  banking  fires  does  not  contribute  directly  to 
the  power  output  of  a  station,  but  rather  represents  the  losses  due  to  radia- 
tion, leakage,  etc.,  called  the  stand-by  losses.  Stand-by  losses  vary  widely  in 
different  plants  and  under  different  operating  conditions,  as  is  indicated  in 
Table  90  which  shows  the  fuel  required  for  tanking  fires. 


Table  90.     Fuel 

Consumed  by  Banked  Fiiet. 

Type  of  l-lanl 

Method  o!           '              Kind  of 
Fifing                                Co.[ 

RUfld 
B.H.P. 

Loicth 

CiMlPcr 
Hr. 

Public  Utility 
Public  Utility 
I^blic  Utility 

Chain  Grate  Stoker 
Chain  Grate  Stoker 
Underfeed  Stoker 

III.  Bituminous 
Bituminous 

m 

608 
600 

2 
24 
24 

130 

490 
330 

Industrial 
Industrial 

Industrial 

Hand  Fired 
Hand  Fired 
Side  Feed  Stoker 

W.Va.  Bituminous 

No. 3  Anthracite 
III  Bituminous 

640 
600 
4«. 

8 

192 
200 
260 

It  is  obvious  that  the  coal  required  per  hour  for  a  short  bank  will  not 
be  as  high  as  that  required  for  a  loni;  bank,  due  to  the  fact  that  the  setting 
remains  hot  from  the  previous  operating  period. 

When  burning  oil,  about  2  per  cent  of  the  fuel  used  when  operating  the 
boiler  at  rating,  will  maintain  the  full  steam  pressure  for  a  long  banking 

Quick  Steaming  Prom  Banked  Fires 
T3  OILERS  which  may  be  called  upon  to  carry  sudden  heavy  loads  must 
'-^  have  tree  and  definite  circulation,  as  the  water  must  get  in  motion 
quickly.  Boiler  circulation  is  not  positive,  but  is  induced  by  "bubble  pump" 
action,  wherein  the  upward  travel  of  the  steam  bubbles  due  to  their  buoyancy, 
sets  the  water  in  motion  in  the  same  direction.  The  unrestricted  water  passage 
offered  by  the  spacious  Heine  walerleg  is  particularly  favorable  to  starting 
circulation  quickly. 

The  curve  of  Fig.  243  by  G.  W.  Perkins,  of  a  quick  steaming  test  on  a 
950  H.P.  Heine  boiler,  demonstrates  rapid  response  to  sudden  heavy  loads 
by  attaining  300  per  cent  of  rating  in  4  minutes  and  23  seconds,  or  3000  H.P. 
in  5  minutes,  from  a  banked  fire. 

Forced  draft  fires,  oil  or  powdered  coal,  can  handle  these  unexpected 
loads  more  rapidly  than  natural  draft.  The  curve  tn  Fig.  243  is  of  a  trial 
with  a  Sanford  Riley  Underfeed  Forced  Draft  Stoker. 


D,g,tze:Jbi  Google 


OPERATION 


Fig.  243,    Quick  SteamiiiE  from  Banked  Fire«. 

Load  Signals 
"TT  is  often  convenient  for  the  firemen  to  know  what  load  ts  being  carried 
■•■  in  the  engine  room,  especially  in  stations  where  the  load  is  variable.  This 
may  be  readily  accomplished  by  the  use  of  a  simple  signal  system.  A  box 
with  three  rows  of  numbers  painted  on  its  glass  front,  each  row  from  0  to  9 
with  a  small  lamp  back  of  each  number,  may  be  placed  prominently  i 

boiler  room.     The  upper   row  of  figures  will  represent  the  load  in  te _ 

thousands  of  kilowatts,  the  middle  row  thousands,  and  the  lower  row  hun- 
dreds. A  bank  of  twenty-nine  switches,  each  switch  corresponding  to  a 
ber  on  the  signal  box  in  the  boiler  room,  will  be  placed  in  the  engine  : 
The  lamps  in  the  signal  box  will  light  and  inform  the  boiler  room  operators 
of  the  load  being  carried,  as  the  switches  are  turned  on. 

In  very  long  boiler  rooms  the  signal  may  be  composed  of  a  number  of 
lamps  arranged  as  in  outdoor  electric  signs. 

Quite  elaborate  systems  of  load  dispatching  have  been  worked  out  in 
large  inter-connected  power  stations. 

Prevention  of  Smoke 

SMOKE  consists  of  small  particles  of  unconsumed  carbon  which  give  to 
the  gases  a  color  ranging  from  light  grey  to  dense  black.  It  is  caused  by 
the  lack  of  sufficient  air  at  the  proper  temperature  at  the  point  where 
the  volatile  gases  from  the  coal  should  be  burned,  with  the  result  that  the 
gases  arc  only  partly  burned  and  carbon  is  set  free. 


ib.  Google 


ib.Google 


OPERATION  S71 

The  dentitf  of  imoke  may  be  measured  in  several  ways  and  the  most 
popular  method  is  by  means  of  the  Ringelmann  charts,  whidi  are  described 
in  Chapter  15  on  BOILER  TESTING. 

Many  cities  enforce  ordinances  providing  penalties  to  be  inflicted  upon 
those  plants  which  arc  consistent  smoke  producers.  Hence  it  is  the  engineer's 
concern  to  know  of  the  possible  methods  for  eliminating  smoke. 

Smoke  may  be  caused  by  (1)  character  of  fuel,  (2)  improper  method 
of  firing,  (3)  poor  furnace  design,  (4)  lack  of  sufficient  draft,  and  (5) 
insufficient  furnace  capacity. 

In  general  it  may  he  stated  that  bituminous  coals  of  high  volatile  content 
are  more  difficult  to  burn  smokelessly  than  those  of  a  low  volatile  content. 

When  the  various  methods  of  firing  were  discussed  earlier  in  this  chap- 
ter, it  was  mentioned  that  the  particular  method  selected  would  depend  upon 
the  type  of  fuel.  In  general,  smokeless  combustion  will  be  more  completely 
attained  by  firing  the  coal  in  small  quantities  and  at  frequent  intervals.  It  is 
due  principally  to  this  fact  that  mechanical  stokers  usually  accomplish  smoke- 
less combustion. 

Much  depends  upon  proper  furnace  design.  The  problem  of  attaining 
efficient  and  smokeless  combustion  resolves  itself  into  three-  requirements, 
vii.:  the  mixing  of  the  unbumed  gases  with  the  proper  amount  of  air  for 
combustion,  the  allowance  of  time  for  combustion,  and  the  maintenance  of 
high  furnace  temperatures,  all  of  which  depend  upon  correct  furnace  design. 

The  converse  of  proper  mixing  is  stratification  or  laneing,  which  occurs 
commonly  in  hand-tired  furnaces,  and  is  the  more  objectionable  where  the 
gases  rise  directly  from  the  fuel  bed  into  the  tubes  as  in  the  case  of  vertically 
baffled  boilers.  The  installation  of  wingwalls,  mixing  piers,  arches,  and 
steam  jets  is  often  necessary  to  effect  smokeless  combustion.  But  it  is  diffi- 
cult to  construct  such  arches  and  piers  to  stand  up  satisfactorily  under  the 
intense  furnace  heat,  and  some  of  these  mixing  devices  take  up  room, 
diminish  the  combustion  space  in  the  furnace  and  also  reduce  the  available 
draft. 

The  preferable  way  to  reduce  smoke  and  still  obtain  the  proper  mixing 
effect  in  &e  furnace  is  to  employ  horizontal  baffles,  with  a  curtain  wall  added 
for  high  volatile  cods.  Fig.  20  on  page  93  shows  such  an  arrangement 
which  is  highly  successful. 

Time  is  also  an  important  element  in  smokeless  combustion  and  depends 
upon  the  length  of  gas  travel  and  the  volume  of  the  combustion  chamber. 
Horizontal  baffling  meets  this  requirement,  as  has  been  shown  in  experiments 
by  the  U.  S.  Bureau  of  Mines  with  a  Heine  boiler  in  which,  with  a  combustion 
rate  of  64.S  lbs.  of  coal  per  square  foot  of  grate  area  per  hour,  only  1  per 
cent  of  the  total  unconsumcd  combustible  was  present  when  the  products  of 
combustion  had  traversed  160  cubic  feet  of  combustion  space. 

The  higher  tire  furnace  temperature  the  more  rapid  and  complete  is  the 
combustion  with  absence  of  smoke,  as  is  shown  by  tests  made  on  a  Heine 
boiler  at  the  University  of  Illinois.  This  boiler  was  equipped  with  a  bottom 
horizontal  baffle  of  C  tile  which  completely  encircled  the  tubes  of  the  lower 
TOW  over  the  furnace.  It  was  "almost  impossible  to  make  smoke  with  this 
setting  under  any  condition  of  operation." 

Inasmuch  as  part  of  the  air  for  the  complete  combustion  of  bituminous 
coal  must  be  drawn  through  the  fuel  bed  and  the  rest  admitted  above  the 
fire,  it  is  obvious  that  smoke  will  result  if  there  is  a  lack  of  sufficient  draft. 
The  brgesi  quantity  of  secondary  air  is  required  just  after  firing,  and  much 
less  is  needed  for  the  rest  of  the  cycle  until  the  next  firing. 

A  well  designed  and  operated  furnace  will  burn  a  given  fuel  without 
smoke  up  to  a  certain  critical  combustion  rate.  Beyond  this  rate  the  efficiency 
will  decrease  and  smoke  will  result,  owing  to  the  lack  of  air  and  of  furnace 


ib.  Google 


572  OPERATION 

capacity  in  which  to  mix  the  gases.  This  is  the  nason  why  hand^lired 
furnaces  usiully  smoke  when  they  are  being  forced  to  carry  much  overload. 
When  fires  are  being  kindled  or  when  banked  tires  are  being  forced, 
smoke  is  almost  unavoidable,  and  most  city  ordinances  provide  exceptions 
to  their  rules  to  cover  these  e 


Cinders.  In  large  central  stations  operating  boilers  at  high  ratings  with 
stokers  and  forced  and  induced  draft,  there  ia  often  a  nuisance  caused  by 
cinders  discharsed  from  the  stacks.  Attempts  have  been  made  to  reduce 
this  by  installing  cinder  catchers  in  the  stack,  but  these  have  not  been  par- 
ticularly effective.  A  cinder- separating  induced  draft  fan  which  is  claimed  to 
be  successful,  has  recently  been  placed  on  the  market 

Meaning  of  Carbon  Dioxide 

THE  proportion  of  Cd  in  flue  gas  is  a  ga^  of  the  success  realized  in  pre- 
ventmg  inleakage,  and  in  securing  combustion  of  the  fuel  with  the  minimum 
amount  of  air.  The  more  nearly  the  maximum  value  is  approached,  the 
greater  the  success  in  keeping  down  the  excess  air  and  the  consequent  heat 
losses  up  the  chimney.  This  maximum  value  runs  from  about  18.5  with  high 
volatile  bituminous  coals  to  about  20.0  with  anthracite.  Assuming  an  all- 
carbon  fuel,  the  percentage  of  excess  air  used  can  be  calculated  directly  from 
the  COi  percentage,  and  equals: 

100  m-?.  <™, 

in  which  D  b  the  percentage  of  Cd  by  volume  in  the  exit  flue  gases.  As 
each  volume  of  COi  present  is  produced  by  the  consumption  of  an  equal 
volume  of  oxygen,  the  numerator  in  the  fraction  represents  the  unconsumed 
or  excess  oxygen  remaining  in  the  gas,  and  the  denominator  the  oxygen 
actually  consumed;  that  is,  the  amount  theoretically  required  for  combustion. 

Fig.  244  indicates  the  amount  of  excess  air,  and  the  preventable  fuel 
loss  corresponding  to  observed  percentages  of  COi  based  upon  average  coals. 
Good  practice  is  represented  by  15  per  cent  CO^  which  corresponds  to  40 
per  cent  excess  air,  with  practically  no  preventable  loss  up  the  stack.  In 
the  absence  of  effort  to  maintain  high  values  of  COi,  a  usual  average  in 
a  great  many  power  plants  is  as  low  as  5  per  cent 

Of  course,  the  exact  amount  of  excess  air  and  the  preventable  fuel  loss 
will  depend  upon  several  circumstances.  The  chart  Fig-  245,  by  Haylelt 
O'Neill,  shows  the  effect  of  the  flue  gas  temperature  on  the  efficiency  with 
different  proportions  of  CO*  These  corves  are  typical,  although  they  were 
drawn  for  the  following  specific  conditions; 

Coal,  B.  t  u.  per  lb _ „ „ 14,500 

Combustible,  per  cent 90 

Volatile  hydrogen,  per  cent 5 

Moist 


Relative  humidity  of  air,  per  cent- 
Temperature  of  air,  deg. 

CO  in  flue  gases,  per  cent 

Steam  pressure,  lb.  per  sq.  in_ 

Combustible  in  ash,  per  cent 


The  overall  efficiency  decreases  as  the  COi  content  is  reduced,  and  as 
the  exit  temperatures  are  increased,  except  with  low  flue  temperatures.  These 
correspond  to  low  rates  of  driving,  with  high  radiation  losses  and  low 
efficiency. 


ib.  Google 


OPERATION 


btf 

«w 

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,i-^ 

.s™  ' 

5            ^-- 

^3«                       r       -           -           

A 

r 

-           5^"                        I 

( 

•' ' '  4 ' ' ' ' ' '  ^ ' '  J  ^ ''''m 

Carbon  DiOKida.PercBnt 


A  high  value  of  COi  is  constantly  sought  in  boiler  operation.  Few 
boilera  are  operated  with  an  air  supply  even  approaching  the  minimum,  and 
the  amount  of  CO  in  the  flue  gas  becomes  objectionable  only  when  the  air  is 
so  reduced  that  the  COi  is  above  15  per  cent  The  CO,  is  generally  low  when 
surplus  air  is  introduced,  and  is  increased  by  adjusting  the  draft  and  fuel-bed 
resistance,  by  closing  holes  in  the  setting,  and  by  avoiding  holes  in  the 
fire.  With  complete  Cd  records  the  work  of  different  firemen  can  be 
checked.  When  these  records  cannot  be  kept,  special  tests  can  be  made 
and  the  conditions  under  which  they  were  produced  studied,  so  as  to  fix 
a  standard  of  operation.  Samples  of  such  studies  are  given  in  Fig.  246. 
A  com^rison  of  samples  from  different  passes  indicates  leakage  through 
the  setting. 


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OPERATION 


FIb.  345.    Bdler  Efficiency  u  affected  by  Plue-Oaa  Tempemtttrea. 
Effects  of  Firing  on  Carbon  IMoxide 


__    _.._  ;  by  pli       „    ._   „_„ 

samples  against  time,  indicates  the  effect  of  different  operations  on  furnace 
efficiency.     Fig,  246  illustrates  the  method. 

In  A.  which  is  hand-firing,  the  fire  was  dirty  and  the  COi  was  down  to 
5  per  cent ;  but  after  cleaning,  it  rose  to  13  per  cenL 

Record  B  was  made  with  a  sloping  grate  stoker,  and  shows  how  the 
COi  fell  as  the  fire  was  cleaned,  and  rose  as  soon  as  the  dump  grate  was 
cloi^ed.  It  was  customary  to  poke  coal  down  from  the  hopper  soon  after 
each  cleaning,  and  this  was  accompanied  by  a  big  drop  in  COi,  which  indicated 
the  entrance  of  much  excess  air  due  to  the  upper  part  of  the  grate  being  cov- 
ered with  unignited  coal.  As  this  new  coal  became  ignited,  the  COa  again 
rose. 

The  latter  part  of  C  shows  good  hand-firing;  the  CO,  rises  after  each 
firing  and  falls  slowly.  The  first  firing  was  uneven,  and  quickly  burned  into 
holes,  which  reduced  the  CO,  to  3  per  cent. 

The  effect  of  leveling  a  fire  which  was  full  of  holes  is  shown  in  D. 


ib.  Google 


OPERATION 


A — Dirty  •*.  dcaa  Sra,  hand  Brine 


B — Slopini  gntt  itokir 


C— Good  huHl  Bclos  I>— Efbet  of  levelios  An 

Fig.  246.     Variaticm  of  COi  with  Different  Method*  of  Firins. 

Fig.  247,  by  M.  Gensch,  shows  the  general  effect  of  excess  air.  The 
fuels  for  which  results  were  plotted  are  typical  high-grade  and  low-grade 
coats,  so  that  values  for  other  coats  would  lie  in  the  bands'  betweeti  the 
different   pairs   of  curves.     The   combustion   temperature   and   the  efficiency 


5' 

h 

E 


»| 


Excess  Air. Percent 
Fit-  347-     Effect  of  ExceH  Air  on  the  Combuition  of  High-Orade  and 
Low-Qradc  Coali. 


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,Google 


OPERATION  577 

iiiioimt  at  air  increases.  At  the  same  tinie  the  flue  gas  volume 
suiting  in  greater  load  on  the  draft  fan  and  on  the  chimney. 

The  admission  of  undue  excess  air  through  the  fire  bed  is  corrected 
by  adopting  standard  methods  of  firing.  Air  leakage  through  the  setting 
can  be  eliminated  only  by  testing  every  point  where  air  might  possibly  get 
in  and  by  slopping  up  the  cracks.  The  flame  of  a  lighted  candle  held  next 
to  the  cracks  will  indicate  whether  any  air  is  being  drawn  in,  or  the  sudden 
closing  of  the  damper  when  the  fire  is  operating  at  a  high  rate  will  cause 
smoke  to  issue  from  the  cracks. 

Cracks  can  be  caulked  with  a  mixture  of  fire-clay  and  waste,  or  with 
magnesia  covering  made  into  a  paste.  Several  coats  of  asphal turn-base  paint 
should  be  applied  to  leaking  settings. 


Carbon  Monoxide 

'T'HE  presence  of  CO  or  carbon  monoxide  in  flue  gas  indicates  partly- 
■^  burned  carbon ;  the  cause  may  be  insufficient  air,  poor  mixing  of  the  air 
with  the  combustible  gas,  reduced  furnace  temperature,  or  the  rapid  distilla- 
tion of  volatile  after  firing,  with  insufficient  secondary  air  to  consume  it. 
The  CO  may  be  present  even  with  high  Oi,  as  when  the  fire  is  clogged  at 
some  points  and  air  is  coming  through  large  holes  at  others. 

Any  CO  produced  in  a  furnace  results  in  the  loss  of  70  per  cent  of  the 
heat  of  the  carbon  involved,  and  furthermore  the  presence  of  CO  indicates 
Ihat  other  combustible  gases  such  as  hydrogen  and  hydrocarbons,  are 
escaping  unconsumetl. 

Carbon  Dio^de  Recorders 

PIE  method  of  analyzing  flue  gas  by  means  of  the  Orsat  apparatus  is 
described  on  page  532.  While  hand  indicators,  such  as  the  Orsat,  can 
be  used  as  a  means  of  studying  air-supply  conditions,  or  for  occasional  tests, 
as  discussed  on  page  574,  they  do  not  answer  the  purposes  of  daily  plant 
operation,  since  the  COi  content  of  the  flue  gases  varies  widely,  due  to  the 
fact  that  the  proportions  of  air  supply  through  and  above  the  fire  are  easily 
unbalanced  by  the  firing  of  fresh  coal,  open  fire  doors,  holes  in  the  fire, 
damper  manipulation,  etc.  Hence  a  number  of  instruments  have  been  de- 
veloped that  will  test  automatically  the  quality  of  the  flue  gases  and  make 
a  continuous  graphic  record  of  the  percent^es  of  COi  they  contain.  These 
furnish  a  definite  and  permanent  record,  which  assists  not  only  in  correcting 
improper  combustion,  but  also  has  a  moral  effect  in  maintaining  the  right 

The  recording  instruments  depend  for  their  operation  upon  the  absorp- 
tion of  COi  from  a  sample  of  the  flue  gas,  usually  by  means  of  a  solution 
of  caustic  potash,  though  sometimes  it  is  used  in  the  solid  form.  In  one 
instrument  it  is  replaced  by  ordinary  quick  lime  which  has  similar  absorbent 
properties. 

Several  different  methods  are  used  to  measure  the  sample  of  gas,  and 
to  bring  it  into  contact  with  the  absorbent  In  one  ^e  of  instrument  a 
flow  of  water  trickles  continuously  into  a  container.  When  this  container 
becomes  full,  it  is  suddenly  emptied  by  a  siphon  action  which  draws  in  a 
measured  sample  of  the  flue  gas.  This  is  then  put  into  communication  with 
the  chamber  containing  the  caustic  solution.  The  diminution  of  its  volume 
by  the  absorption  of  the  C0»  is  measured  by  the  descent  of  a  gas  holder  in 
which  it  is  contained.  The  motion  of  this  holder  causes  a  pen  to  draw  a 
line  on  a  chart,  the  length  of  the  line  being  proportioned  to  the  CO*  percent- 
age. This  cycle  of  operation  takes  place  every  few  minutes,  according  to 
the  rate  of  flow  of  the  water. 


ib.  Google 


OPliRATION 


}  indicate  the  percentage.  By  means  of  a  steam 
jM  aspirator,  a  small  current  of  flue  gas  is  drawn  continuously  through  a 
chamber  containing  the  absorbent  When  the  COi  is  eliminated,  the  pressure 
in  the  chamber  is  reduced,  and  the  reduction  is  measured  by  a  manometer  or 
other  farm  of  pressure  gage.  This  method  provides  a  continuous  record, 
and  the  recording  instrument  can  be  placed  at  a  distance  from  the  boiler 
room.  In  an  alternative  plan,  flue  gases  are  drawn  through  a  chamber  in 
which  the  absorbent  is  covered  by  a  porous  pot  The  reduction  of  pressure 
inside  this  pot  is  utilized  to  operate  the  manometer.  In  both  these  types, 
however,  more  absorbent  is  consumed  than  in  an  intermittent  test,  and  the 
steam  used  by  the  jet  may  be  considered  as  wasted. 

In  a  third  method  of  detertnining  COi,  the  flue  gases  pass  through  two 
ordinary  gas  meters,  one  before  absorption  and  one  after.  The  second  one 
will  work  more  slowly,  as  it  naturally  has  less  gas  to  measure.  The  differ- 
ence in  their  speed  is  recorded  by  a  differential  gear,  which  operates  the 
pen  producing  the  record.  In  this  type  of  instrument,  dry  calcium  hydrate 
forms  the  absorbent,  and  the  gases  are  drawn  through  the  meter  by  a 
water  jet 

A  CO,  recorder  should  run  indefinitely,  and  the  only  attention  required 
should  be  to  change  the  chart,  renew  chemicals,  and  change  the  filtering  ma- 
terial in  the  gas  line.  The  instrument  should  compensate  automatically  for 
temperature  changes,  changes  of  volume  and  specific  gravity  in  absorbent 
solution,  and  changes  of  draft  in  boiler.  It  should  have  a  minimum  number 
of  moving  reciprocating  parts.  It  is  desirable  to  have  a  recorder  for  each 
boiler,  but  if  one  recorder  is  used  for  a  battery  of  boilers,  the  piping  should 
be  arranged  so  that  the  firemen  will  not  know  which  boiler  is  connected. 
This  can  be  accomplished  by  running  the  gas  pipe  from  the  boiler  to  a 
common  header,  and  then  boxing  the  valves  on  the  header. 

A  COi  recorder  made  by  the  Mono  Cnrf>oral'on  of  America,  is  shown 
in  Fig.  248,  which  may  be  operated  with  either  water  or  compressed  air  at 
a  minimum  pressure  of  8  lbs.  The  manufacturers  state  that  it  will  make 
records  of  up  to  40  analyses  per  hour.  The  pressure  medium,  by  which  the 
apparatus  is  driven,  passes  through  a  regulating  valve  and  the  receiver  into 
a  bottle  containing  mercury.  This  forces  the  mercury  from  the  bottle  up 
through  a  system  of  tubes,  of  which  one  leads  to  the  volumeter  and  another 
to  the  gas  release  outlet  When  all  the  mercury  is  thus  displaced,  the  pres- 
sure in  the  bottle  is  released  through  contact  with  the  atmosphere.  Then 
the  mercury,  which  was  forced  up  the  tubes,  recedes  to  the  bottle,  sealing  the 
receiver,  and  the  cycle  is  repeated.  In  this  way  an  alternating  rising  and 
falling  movement  is  employed  in  drawing  in  the  flue  gas  for  analysis  and 
letting  off  excess  gas. 

As  the  mercury  falls  in  the  volumeter,  the  gas  to  be  anal3^ed  is  drawn 
in  through  the  gas  inlet  and  mercury  seal.  When  the  mercury  rises,  the 
gas  in  the  volumeter,  which  contains  100  cc,  is  forced  through  the  tubes  anil 
a  second  mercury  seal  to  the  caustic  potash  container,  which  is  filled  with  the 
absorption  liquid  and  through  which  the  gas  bubbles,  thus  making  the 
absorption  of  COi  complete.  The  remainder  of  the  gas  passes  into  the 
gasometer,  which  is  suspended  in  a  glycerine  solution,  where  it  is  measured 
again  at  the  same  temperature  as  in  the  volumeter.  As  the  gas  enters,  the 
gasometer  rises,  turning  the  pulleys  from  which  the  recording  pen  is  sus- 
pended. When  the  pen  has  come  to  a  stop  on  the  chart,  the  mark  indicates 
the  percentage  of  gas  absorbed.  Then  the  gas  in  the  gasometer  is  released  to 
the  atmosphere,  and  the  apparatus  is  ready  for  a  new  analysis. 

The  CO.  record  furnishes  a  good  index  of  furnace  performance,  but  a 
knowledge  of  the  percentage  of  CO  in  the  escaping  flue  gases  is  also  valuable. 
Records  of  CO  can  be  secured  from  an  instrument  consisting  of  a  Mono  COi 
recorder  and  a  special  CO  attachment.    The  COt  recorder  is  of  the  usual  ab- 


D,g,tze:Jbi  Google 


OPERATION 


Fie.  348.     Mono  COt  Recorder. 

sorption  type,  operated  either  by  air  or  water  pressure.  When  CO  is  to  be 
measured,  a  chamber  containing  an  electric  furnace  and  the  chemicals  to 
carry  on  the  reactions  is  mounted  on  the  wall  next  to  the  recorder.  Either 
CO  or  CO,  can  be  shown  on  the  chart,  but  the  two  cannot  be  recorded  simul- 
taneously. The  usual  practice  is  to  supply  CO.  instruments  for  each  boiler 
and  one  complete  CO  recorder,  arranged  to  be  connected  to  any  unit,  for 
each   plant. 

Draft  Instruments 

THE  difference  of  pressure  causing  the  flow  of  gaaes  through  fuel  bed 
and  boiler  Is  referred  to  as  "draft,"  although  the  term  is  sometimes 
loosely  applied  to  the  motion  of  the  gases.  These  pressures  are  measured 
by  instruments  called   draft  gages,   and   are  usually   expressed   in   inches  of 

Draft  gages  may  be  simply  glass  tubes  bent  into  U  form  and  half 
filled  with  water.  The  differences  in  level  are  frequently  so  small  that  they 
are  difficult  to  read  accurately.  The  bore  of  the  tube  should  be  the  same 
in  both  legs,  or  error  is  introduced  as  may  be  seen  by  the  liquid  standing 
at  dififerent  levels  in  the  two  legs  when  both  are  open  to  the  atmosphere.    If 


ib.  Google 


sat  OPERATION 

the  inside  of  the  tubej  is  not  dean  and  free  from  grease  when  water  is  used, 
the  water  will  not  freely  "wet"  the  glass,  and  the  surfaces  in  the  two  legs 
will  not  be  similar  in  height  or  shape  when  the  gage  is  "free."  Readings 
should  be  taken  from  the  lowest  part  of  the  meniscus  with  liquids  which 
wet  the  glass,  such  ai  water ;  and  from  the  highest  part  of  the  meniscus  with 
liquids  which  do  not  wet  the  glass,  such  as  mercury. 

When  the  pressure  fluctuates  so  rapidly  as  to  interfere  with  observation, 
the  pulsations  may  be  damped  in  a  plain  U-gage  by  putting  a  few  snuU 
stones  or  some  sand  in  the  lowest  part  of  the  tube. 

To  facilitate  reading  the  gage  when  the  differences  in  level  are  small, 
verniers  are  sometimes  provided. 

Various  devices  are  used  to  exaggerate  small  pressure  differences,  though 
some  are  delicate  and  only  suitable  for  laboratory  work.  In  gages  for  the 
boiler  room,  flexible  diaphragms,  slanting  lubes,  and  non-miscible  liquids 
in  combination  with  small  bore  tubes  connecting  the  U-gage  legs,  are  used. 
In  the  slanting  tube  gages,  mineral  oil  of  a  sp.gr.  less  than  unity  is  generally 
used ;  and  it  is  highly  colored,  bright  red  or  blue,  so  that  the  instrument  can 
be  easily  read. 

A  simple  draft  gage  indicates  the  difference  in  pressure  between  the 
point  to  which  it  is  connected  and  the  atmosphere,  while  a  differential  gage 
indicates  the  difference  in  pressure  between  two  points  in  the  gas  passages. 
Fig.  249  illustrates  a   Hays  differenlial  draft   gage. 


Compound  and  triple  types  of  differential  gages  are  composed  of  two 
and  three  single  instruments  respectively.  With  these,  the  draft  can  be  read 
simultaneously  at  different  points  in  the  setting.  For  forced  or  balanced 
draft,  the  scale  of  a  single  instrument  can  be  divided  with  the  zero  point 
about  midway.  The  liquid  then  moves  to  the  right  under  a  vacuum  and  to 
the  left  under  a  positive  pressure. 

The  gage  should  be  located  so  that  it  can  be  seen  by  the  fireman  when 
he  is  setting  the  damper.  The  connections  from  the  gage  are  usually  of 
^-in.  pipe,  this  being  led  through  a  larger  pipe  into  the  furnace,  pass  or 
flue.  The  connection  should  merely  project  through  the  wall,  to  prevent 
the  burning  off  of  the  end.  The  piping  Into  the  furnace  should  be  as 
close  as  possible  to  the  front  and  to  the  top  of  the  chamber,  to  avoid  slag 
accumulation. 

An  indicating  instrument  of  the  diaphragm  type.  Fig.  25H  is  used  for 
forced  draft  installations.  This  has  three  scales,  reading  from  0  to  2  in.  of 
water  for  the  flue  connection,  1-in,  vacuum  to  1-in.  pressure  for  the  com- 


D,g,tze:Jbi  Google 


OPERATION  581 

buation  chamber,  and  0  to  6  in.  pressure  for  the  ash  pit.  The  varying  pres> 
sures  are  transmitted  by  diaphragins  to  plungers,  which  are  attached  to 
horizontal  shafts  by  links  or  levers.  The  indicating  pointers  are  carried  on 
these  horizontal  shafts. 


The  StgttHiranci:  of  Draft,  Efficient  combustion  requires  that  a  certain 
quantity  of  air  be  supplied  for  each  pound  of  fuel  burned.  Therefore,  the 
quantity  of  gases  passing  through  the  boiler  setting  will  be  almost  in  direct 
proportion  to  the  load  on  the  boiler  when  combustion  is  progressing  properly. 
And  inasmuch  as  the  boiler  heating  surface  interposes  a  resistance  to  the 
flow  of  gases,  a  differential  draft  gage  indicating  the  pressure  drop  or  draft 
loss  between  furnace  and  up-take,  will  act  as  a  gas  flow  meter  and  indicate 
whether  or  not  the  proper  quantity  of  air  is  being  supplied  for  the  given  load. 
A  differential  gage  so  located  will  also  indicate  the  cleanliness  of  the  gas 
passages,  since  an  undue  increase  in  draft  loss  will  mean  that  they  are  be- 
coming clogged. 

A  differentia!  draft  gage  connected  so  as  to  show  the  draft  loss  through 
the  fuel  bed,  in  conjunction  with  one  showing  the  drop  through  the  boiler, 
will  indicate  any  change  in  the  furnace  conditions.  A  relative  increase 
in  the  fuel  bed  drop  will  indicate  that  the  fire  is  becoming  thicker,  or  that 
it  is  becoming  clogged  with  clinkers  and  ash.  Similarly,  if  the  pressure  drop 
becomes  less,  it  indicates  that  there  are  holes  in  the  fire  or  that  the  fuel  bed 
is  too  thin.  The  above  principles  are  made  use  of  in  so-called  combustion 
meters  and  efficiency  indicators  in  which  fixed  points  are  set  by  test  on  the 
gage  scale  representing  the  best  draft  relations  for  the  particular  unit. 
Deviation  from  these  points  warns  the  operator  of  unfavorable  conditions. 


ib.  Google 


Union  Tnut  Building,  CindiUMti,  Ohio,  eqnlppwl  with  Hdne  Standard  BoUen. 

D,3,tze:Jb.GOOg[e 


LU    Y 


Blov  Off 
Pig.  251.    Mason  Damper  Regulator. 


ib.  Google 


584  OPERATION 

Draft  Regulalion.  Combustion  can  be  controlled  automatical^  by  vary- 
ing the  supply  of  air  or  fuel  passed  through  the  boiler  furnace.  For  natural 
draft  the  control  is  secured  through  movements  of  the  breeching  or  stack 
damper.  For  forced  draft,  the  supply  of  air  can  be  varied  also  by  varying 
the  fan  spwd,  or  by  adjuiting  a  damper  placed  where  the  air  eaters  the 

The  twdraulic  damper  regulator  is  used  in  natural  draft  plants.  As 
shown  in  Fig.  2SI,  this  is  operated  by  the  variation  of  steam  pressure  in  the 
boiler,  but  water  pressure  is  used  as  motive  power.  The  change  in  steam 
pressure  moves  a  lever,  which  opens  a  pilot  valve  controlling  the  supply 
and  discharge  of  water.  The  piston  contained  in  the  regulator  cylinder  is 
moved  when  water  is  admitted,  the  damper  movement  being  controlled  by 
connections  from  the  piston  stem.  As  the  piston  moves,  it  displaces  the 
fulcrum  of  the  pilot  valve  lever  and  closes  the  pilot  valve.  Consequently,  the 
piston  does  not  make  a  full  stroke,  but  graduates  the  damper  opening  to 
the  load. 

In  small  forced  draft  installations,  where  the  stoker  and  fan  are  driven 
by  the  same  engine,  both  fuel  and  air  supply  can  be  controlled  by  the  stand- 
ard hydraulic  regulator,  according  to  the  variations  in  steam  pressure.  In 
larger  installations,  when  separate  units  drive  the  fan  and  stoker,  the  speed 
of  the  former  can  be  controlled  by  a  balanced  valve  on  the  steam  line.  The 
speed  of  the  stoker  engine  can  be  controlled  by  the  pressure  in  the  wind-box. 

When  variable  speed  motors  are  used  for  the  stoker  or  fan  drive,  they 
can  be  controlled  automatically  by  rheostats  operated  from  the  hydraulic 
regulator. 

In  so  called  "balanced  draft"  systems  it  is  the  aim  to  keep  the  furnace 
chamber  automatically  at  atmospheric  pressure,  and  this  is  usually  accom- 
plished by  means  of  a  regulator  with  a  relay  which  controls  two  hydraulic 
cylinders,  one  operating  the  air  supply  damper  and  the  other  the  stack  damper. 

Economical  Operation 

WITHOUT  suitable  instruments  and  organization,  it  is  impossible  to  tell 
whether  the  boiler  efficiency  is  50  or  75  per  cent,  or  why  it  is  so. 
Unless  the  management  knows  what  should  be  done,  it  cannot  reasonably 
complain  that  the  boiler  room  force  does  not  do  it.  The  operation  of  gener- 
ating steam  should  be  investigated  and  controlled  by  intelligent  planning, 
as  much  as  is  the  case  with  other  manufacturing  operations. 

Control  Boards.  The  necessity  of  installing  instruments  for  controlling 
combustion  and  boiler  operation  is  gaining  recognition  and  many  modern 
plants  have  these  assembled  on  an  instrument  or  control  board.  These  boards 
may  be  of  two  general  types,  the  one  containing  instruments  which  serve  a 
whole  boiler  room  and  the  other  containing  instruments  which  serve  only 
one  individual  boiler  or  battery.  In  small  plants  the  first  type  is  satis- 
factory, but  in  large  plants  the  individual  control  board  is  to  be  preferred. 

Such  boards  carry  indicating  and  recording  steam  flow  meters,  recording 
pressure  gage,  recordii^  thermometers  for  feed  water,  superheated  steam,  exit 
gases  from  boiler  and  from  economizer,  direct  and  differential  draft  ga^es 
with  selecting  valves,  stoker  and  fan  speed  controls;  and  COi  recorders  and  in- 
dicating and  recording  water  meters  are  nearby.  The  design  and  equipment  of 
these  boards  is  entirely  dependent  upon  the  particular  conditions  to  be  met. 

A  desk  and  chair  should  be  provided  for  convenience  in  keeping  a  log, 
and  in  calculating,  tabulating  and  comparing  data. 

Fig.  252  illustrates  an  instrument  and  control  board  with  Venturi  indi- 
cating, recording  and  integrating  meter  conveniently  near. 


ib.  Google 


OPERATION  S8S 

Efficient  Operation.  With  an  installation  of  this  kind,  used  with  reason- 
able intelligence  and  enthusiasm,  there  i^  no  reason  why  the  boiler  plant 
should  not  be  run  continuously  under  "test  conditions." 


Fig.  252.     Instrument  and  Control  Board  by  W.  N   Polakov  and  Co. 

The  control  board  shown  in  Fig.  252,  combined  with  a  course  of  training 
and  assisting  the  boiler  room  force,  and  a  system  of  secondary  paynient 
for  actual  economy  effected,  resulted  in  the  following  drop  in  cost  of  gener- 
ating steam  while  the  cost  of  coal  rose  30  per  cent  and  of  labor  nearly  50 
per  cent.  The  figures  of  Table  91  were  supplied  by  W.  N.  Polakov  as 
representative  of  a  number  of  plants  whose  operation  has  been  similarly 
improved. 


ib.  Google 


ib.Google 


OPERATION 


Table  91.     Rrdncing  Coat  of  OcneratiiiB  Steam. 


1919                   1            T  „i  r  ..           1        Toi.1  Wright  ol 

Con  of  looo 

Lb*,    of  Stum 

January                      1          $24,086.27 
February                               22.345J8 
March                        1           21^5.90 

25,381.000 
23.400.000 
24,571,000 

$0,951 
953 
J593 

April 

18.985.05 
16.340.47 
18,142.36 

29.741,066 

26,900.000 
26,476,000 

.637 
.572 
.685 

August 
September 

16,98725 
18,983.40 
16.384.33 

36.127,000 
36.166,000 
33.527,000 

.468 

.525 
.488 

Measuring  Water 

THE  principal  methods  used  (or  measuring  water  are  given  in  outline  forn 
in  the  following  table : 

Table  92.     Methods  of  MeaaurinB  Water. 


General   Method 

Examples 

Gravimetric  or  Actual  WeiKhing 

Tanks  and  Scales 
Tilting  Weighers 

Tanks 
Tank  Meter 
Piston  Type  Meter 
RoUry  Type  Meter 
Disk  Type  Meter 

Weirs 

V-Noleh 
Cycloidal 
Trapezoidal 

Velocity  of  Flow 

Venturi  Tube 
Orifice 
Pilot  Tube 
Pitometer 

The  volumetric  and  gravimetric  methods  are  accurate  and  useful  when 
the  flow  does  not  need  to  be  continuous.  When  the  liquid  must  flow  in  a 
continuous  stream,  the  pitot  tube,  orifice,  venturi  tube,  or  weir  methods  must 
be  employed.  The  first  three  of  these  can  be  conveniently  and  quickly  applied 
for  measuring  liquids  flowing  in  closed  pipes  under  pressure.  In  these  Uiree 
methods,  however,  the  pressure  is  the  factor  actually  measured,  and  it  varies 
as  the  square  of  the  rate  of  flow.  Accuracy  is  secured  therefore  only  for 
flows  between  the  maximum  for  which  the  instrument  is  designed  and  say 
!^  or  ^  of  this  maximum.  At  smaller  flows  the  head  is  extremely  small, 
and  any  friction  in  the  moving  parts  of  the  instrument  introduces  a  serious 
error. 


ib.  Google 


OPER AT [ON 


Fig.  3S3.     Worthinston  Water  Weigher 


Pis.  254.     Hammond  Volumetric  Meter. 


ib.  Google 


OPKRATION  589 

The  plain  orifice,  either  submerged  or  discharging  into  free  air,  presents 
the  same  difficulty  at  small  heads.  The  ordinary  rectangular  weir  is  better, 
but  each  size  of  weir  requires  a  different  device  for  converting  head  to  flow 
in  a  recording  and  integrating  instrument.  In  the  V-notch  or  trianjtular 
weir,  the  cross-section  of  the  issuing  stream  is  a  similar  figure  at  all  heads, 
so  that  the  relation  of  flow  to  head  is  fairly  constant 

Gravimetric  meters  depend  upon  the  actual  weighing  of  the  water.  Two 
tanks  are  arranged  so  that  they  can  be  filled  until  a  definite  weight  is  balanced. 
They  are  then  dumped  alternately,  a  record  being  made  of  the  number  of 
dumpings.  This  same  method  is  ujed  in  testing  work,  except  that  the  tanks 
used  rest  upon  platform  scales.    Fig.  253  shows  a  gravimetric  meter. 


Pig.  355.     Valve  Gear  of  Hammond  Volumetric  Meter. 

The  Hammond  volumetric  meter,  made  by  the  Alberger  E^imp  and  Con- 
denser Co.,  is  illustrated  in  Fig.  254  and  255,  Two  chambers  are  alternately 
filled  and  emptied,  and  the  cycle  recorded  on  a  counter.  The  valve  gear  is 
operated  by  the  pressure  exerted  on  the  discharge  valves  and  timed  by  the 
movement  of  the  floats ;  and  it  swings  the  guide  which  directs  the  water  into 
either  of  the  compartments.  The  valve  gear  is  shown  in  Fig.  255.  An 
outstanding  feature  is  the  ease  with  which  the  vital  parts  cati  be  seen  and 
the  accuracy  of  operation  checked.  For  instance,  a  needle  gage  is  provided 
for  each  compartment,  and  this  may  be  observed  at  any  time  to  see  that  the 
gear  trips  exactly  at  the  right  level.  The  error  between  lero  and  maximum 
rated  capacity  is  guaranteed  to  be  within  J^  of  1  per  cent. 

In  a  V-notch  meter  designed  primarily  for  use  with  open  feed-water  heat- 
ers (see  Fig.  168,  pa^e  32S).  a  float  operates  the  recording  and  integrating 
mechanism.  The  motion  of  the  float  is  communicated  to  a  cylindrical  drum. 
which  is  attached  to  a  disk  provided  with  a  spiral  slot.  This  slot  forms  a 
cam,  the  motion  of  which  is  imparted  through  a  follower  to  the  indicating, 
recording  and  integrating  mechanism.  The  meter  and  recorder  shown  in 
Fig.  168  is  accurate  to  within  less  than  \'/i  per  cent. 


ib.  Google 


OPERATION 


Adjusfi'ng  Sfop 
4-Ikiy[ningraH'ria      \ 

Aluminum  )i/te  ' 

•Comflolltr 

Support-  ior 

fndkatorDial—    t 

Zero  Lint 

Cam 

MainShaft  — 


Capillary  Pan 


© 


Pig.  256.     Vcnturi  Metering  Tube  and  Meaauring  Mcchaniam. 


ib.  Google 


OPERATION  a 

The  theoretical  discharge  over  a  V-notch  weir  is  given  by  the  formula 


3=(fs-j2^X') 


where        Q  :=  discharge  in  cu.  ft.  per  sec. 

H  =  height  of  water  above  bottom  of  notch 
B  =  half  the  breadth  of  notch  at  water  level 

«  =  slope  of  the  notch,  or  the  quotient.  B/H. 

For  a  right-angled  notch,  the  slope  e  becomes  unity.    Combining  a 
efficient  of  discharge  with  the  constant  part  (assuming  g  to  be  const 
of  the  above  equation,  the  formula  for  discharge  over  a  ri^-angled  V-notch 
weir  with  sharp  edges  may  be  written 


H.  W.  King  made  a  thorough  investigation  at  the  University  of  Michi- 
gan, supplemented  his  results  by  the  experiments  of  Thompson  and  Ban,  and 
deduced  the  following  expression  as  the  mean  of  experimental  results : 

Q  =  2.52  H-"  (73) 

Venturi  meters  for  measuring  hot  water  are  generally  made  in  from  2 
to  12-in.  sizes.  Fig.  256  shows  a  typical  arrangement  of  meter  tube  and 
measuring  mechanism.  The  meter  actually  registers  in  gallons,  but  is  usually 
calibrated  to  read  in  pounds.  Table  93  shows  the  measuring  capacities  of 
standard  meter  tubes.  For  hot  water,  extra  heavy  meter  tubes  with  American 
Extra  Heavy  Standard  flange  ends  are  usually  selected.  The  meters  are 
graduated  for  a  standard  temperature  of  62  deg.,  so  that  the  correction  curve 
furnished  by  the  manufacturers  must  be  used  for  other  temperatures.  If  the 
nieter  tube  is  p1;<ced  in  a  pipe  line  subject  to  pulsations  from  the  pump,  an  air 
chamber  must  be  installed. 

The  formula  for  measuring  the  flow  of  water  through  a  Venturi  meter 
( Fig.  256)  is 


C=C.J 


(fy- 


(71) 


where        Q  =  discharge  in  cu.  ft  per  sec 

C  =  a  constant,  usually  taken  as  0.97,  but  Coadenough  gives  0.96 
for  the  meters  now  on  the  market 

A  =  area  in  sq.  ft.  at  entrance  to  meter  (A) 
a  =  area  in  sq.  ft.  at  throat  (B) 

H  =  difference  in  heads  at  entrance  (A)  and  throat  (B),  re- 
in the  flow  meter  shown  in  Fig.  257.  cither  a  pitot  tube  or  an  orifice  is 
inserted  into  the  pipe  where  the  flow  is  to  be  measured.  The  pressure  differ- 
ences created  by  the  flow  are  transmitted  to  a  murcury  column  in  the  meter 
body.  The  rise  and  fall  of  this  column  are  made  to  engage  and  disen^ge 
conductors  which  vary  the  electrical  current  flowing  through  a  circuit.  The 
measuring  mechanism  is  included  in  this  circuit.  The  indicating,  integrating 
and  recording  mechanism  really  measure  electrical  quantities,  although  these 
are  proportional  to  similar  quantities  (flow,  amount,  etc.)  for  the  fluid  pass- 
ing through  the  pipe. 


D,g,tze:Jbi  Google 


m 


Is* 
■iii 


11-: 
lis 


o  5  " 


ib.Google 


OPERATION 


(O 


Table  93. 

Measuring  Capacitiea  ofVenturi  Hot  Water  Meter 

Dt^ 

Tab* 
n.      In. 

InlH 

O01b.perhp.pvbr.) 

W.tarnow, 
PoVDda  par  Hour 

T.t« 

Fl™, 

laeba 

.rr 

3 

I 

1 
1 

11'^ 

3 

45 
66 
115 

5M 

850 

1,600 

.30 
1,960 
3,470 

17,600 
26.400 
46,100 

3 
4 

7 

35 
50 
90 

'2H 

2 
2 
1 

4H 
3 

2 

85 
115 
180 

1,150 
1.600 
2,350 

2,660 
3,470 
5,420 

34,500 
45.100 
70,400 

6 
7 
11 

70 
90 
140 

3 

2 
2 
2 

11 

4H 

2 

116 
ISO 
260 

1,500 
2,350 
3,380 

3.470 
5.420 
7,820 

46,100 
70.400 
102,000 

7 
11 
16 

90 
140 
205 

4 

4 
3 
3 

.28 

6 

■i 

180 
SOS 
465 

2,350 

4,000 
6,000 

5,420 
9,170 
13,000 

70.400 
119,000 
181,000 

11 
18 
28 

140 
240 
360 

5 

6 

4 
4 

Si 

a 

306 
405 
726 

4.000 
6,000 
9,400 

9.170 
13.900 
21.700 

119,000 
181,000 
282,000 

18 
28 
43 

240 
360 
560 

6 

5 

5 

4 

11 

4H 
10 

3 

466 
725 
l.MO 

6,000 
0,400 

i3,eoo 

13,900 

21,700 
31.300 

181.000 
282,000 
406.000 

28 
43 
63 

360 
560 
810 

8 

7 
6 
6 

2 

4 

870 
1530 
1.850 

11.300 
16,000 
24.100 

26,500 
36,600 

55,600 

344,000 
476.000 
722.000 

53 
73 
111 

680 
950 
1,440 

10 

9 
8 

7 

6 

5 

1.230 
1350 
2,900 

16,000 
24.100 
37.60q 

36.600 
55,600 

86,900 

4T6.000 

722.000 

1,129.000 

73 

111 
174 

050 
1,440 
2,260 

12 

11 
9 
8 

0 
11 
10 

0 

1^60 
2,900 
4,200 

54.200 
37.600 
64,200 

65,600 
86.900 
125,000 

722.000 
1.129,000 
1,626.000 

HI 
174 
250 

1,440 
2,280 
3,260 

Inlminn  IbsUh  i 

nto-tliouldDol 


not  b«1iu«rted 


iM  ^^     Gita  vain*  or 


ib.  Google 


OPERATION 


Fi(.  257.     Republic  Flow  Meter  for  Measuring  Water  or  Steam. 

Practically  all  of  the  so-called  (low  meters  on  the  market  are  appli< 
with  certain  moditications  to  either  steam  or  water  measurement.  O 
types  of  flow  meters  are  described  under  "Metering  Steam." 


ib.  Google 


OPERATION  595 

Metering  Steam 
\^OST  practical  Gleam  meters  are  based  upon  one  or  the  other  of  two 
^"'-  principles,  both  depending  on  the  velocity  of  flow.  Either  there  is  a 
constriction  inserted  in  the  steam  pipe  so  as  to  cause  a  small  pressure  di£Fer- 
encc,  which  will  vary  with  the  amount  of  steam  passing,  or  the  velocity  of 
the  flowing  steam  is  measured  by  a  pitot  tube,  or  else  the  steam  in  flowing 
through  an  orifice  impinges  against  a  movable  pari  which  assumes  different 
positions  for  different  rates  of  flow. 

The  actual  measuring  instrument  can  be  placed  at  any  convenient  dis- 
tance from  the  steam  pipe  and  is  connected  to  it  by  two  small  copper  lubes 
filled  with  water  of  condensation.  These  tubes  transmit  the  differential  pres- 
sure to  the  instrument.  The  latter  can  either  indicate  on  a  dial  or  scale 
the  rate  of  flow  of  the  steam  at  any  instant,  or  record  the  rate  of  flow 
graphically  on  a  chart,  or  integrate  numerically  by  means  of  a  counting 
mechanism  the  quantity  which  has  passed  in  any  given  time.  All  these 
functions  can  be  combined  in  one  instrument. 

In  instruments  using  the  con  strict  cd-pipe  principle,  the  quantity  of  steam 
passing  per  unit  time  is  taken  as  being  directly  proportional  to  the  square 
root  of  the  difference  of  pressure  on  the  two  sides  of  the  constriction.  This 
proportion  holds,  however,  only  if  the  pressure  and  the  superheat  of  the  steam 
are  constant.  In  the  simplest  form  of  pitot  apparatus,  two  tubes  are  inserted 
through  the  side  of  the  steam  pipe,  one  being  cut  off  flush  with  the  inner 
wall  of  the  pipe  and  the  other  bent  so  that  its  open  end  faces  the  flowing 
steam.  Both  tubes  are  submitted  to  the  static  pressure  of  the  steam,  but 
the  bent  one  measures  also  the  dynamic  pressure  due  to  the  velocity.  The 
difference  in  pressure  in  the  two  tubes  is  therefore  a  measure  of  the  rate 
of  flow  and  can  be  employed  to  operate  an  instrument.  The  disturbance  of 
the  flow  due  to  the  presence  of  the  pitot  tube  itself  must  be  reekrned  with. 

An  alternative  to  the  fixed  orifice  consists  of  a  variable  orifice  designed 
to  create  a  constant  pressure  drop.  The  steam  passes  upward  through  the 
seat  of  an  automatically  lifting  valve,  which  is  held  in  a  higher  or  lower 
position  according  to  the  rate  of  flow.  A  lever  mechanism  connects  the 
valve  with  the  pointer  of  the  instrument  At  low  velocities  the  forces  acting 
are  so  small  that  the  readings  are  unreliable.  In  instruments  depem'ing  upon 
the  drop  of  pressure  across  an  orifice,  this  difficulty  can  be  overcome  either 
by  inserting  a  smaller  orifice,  or  by  using  a  butterfly  valve  which  can  be  locked 
in  one  of  several  positions  according  to  the  rate  of  flow.  Thus  the  range 
of  the  instrument  can  be  altered  without  interfering  with  the  steam  pipe.  In 
every  type  of  instrument  referred  to,  however,  accurate  metering  is  difficult 
when  the  density  of  the  steam  varies. 

The  best  steam  meters  working  under  commercial  conditions  are  correct 
within  plus  or  minus  2  per  cent  at  loads  ranging  from  three-quarters  to  full 
load.  At  half  load  the  accuracy  will  be  within  ZJ^  per  cent,  and  from  one- 
quarter  to  one-sixth  load  it  will  be  within  4  per  cent.  Such  accuracy  can  be 
obtained  only  by  calibrating  each  instrument  under  conditions  similar  to 
those  under  which  it  will  have  to  work. 

In  the  simplest  instruments,  namely,  those  that  merely  indicate  the  rate 
of  flow  at  an  instant,  the  differential  pressure  acts  upon  liquid  in  a  U-tube. 
the  liquid  rises  in  one  limb  and  indicates  by  its  height  the  rate  of  Row.  This 
is  read  off  a  graduated  scale  placed  alongside  the  liquid  column.  Water  is 
sometimes  used  as  the  indicating  liquid,  partly  on  account  of  the  ease  with 
which  it  is  automatically  su^qtlied  by  condensation,  and  partly  because  of 
the  open  scale  obtained  with  small  pressures.  Mercury,  however,  is  fre- 
quently adopted. 


ib.Google 


■So- 
Is 


l!i 


11 

IS-- 


ib.Google 


OPERATION  597 

The  instrament  shown  in  Fig.  261  uses  the  orifice  principle  at  a  constant 
difference  of  pressure,  the  size  of  orifice  being  varied  to  allow  different 
amounts  of  steam  to  pass.  This  is  accomplished  by  a  float  set  in  the  orifice, 
so  shaped  that  its  motion  changes  the  effective  area  of  the  orifice.  The  float 
movement  is  transmitted  to  an  arm  carried  by  a  horizontal  shaft  projecting 
through  tjie  casing,  and  carrying,  at  its  outer  extremity,  the  recording  pencil 
and  indicator  pointer. 


Fig-  361.     Mechanism  of  Variable  Orifice  Type  of  Steam  Flow  Meter. 

Some  of  the  instruments  used  to  measure  water  (see  Fig.  2S7)  can  also 
be  used  to  measure  steam.  In  the  latter  service,  however,  a  condenser  must 
be  used  so  that  the  steam  does  not  come  directly  into  contact  with  the 
internal  mechaniim  of  the  instrument  In  some  designs  the  steam  flow  meter 
b  combined  with  other  instruments.  Fig.  262  consists  of  a  steam  flow 
meter,  to  record  the  amount  of  steam  generated;  an  air  flow  meter,  to  record 
the  amount  of  air  supplied  to  th^  furnace;  and  a  recording  thermometer,  to 
record  the  temperature  of  the  uptake  or  the  escaping  chimney  gases.  All 
these  readings  are  shown  on  a  single  chart  The  steam  flow  is  measured 
by  the  use  of  a  special  orifice,  placed  between  two  flanges  in  the  pipe  line, 
and  corrugated  to  form  its  own  gasket.  Holes  are  drilled  on  either  side 
of  the  flange  Jii  which  the  orifice  is  inserted,  and  are  connected 
with  the  pressure  recording  device  in  the  instrument    The  air  flow  part  of 


ib.  Google 


OPERATION 


ib.  Google 


OPERATION  599 

the  meter  is  operated  by  the  difference  between  pressures  in  fire  box  and 
in  smoke  boTc.  The  flue  gas  temperature  is  obtained  by  the  aid  of  a  nitrogen- 
lilled  bulb,  extending  across  the  path  of  the  gases  where  they  leave  the 
boiler  heating  surface.  The  average  temperature  of  all  gases  is  thus  obtained, 
and  the  condition  of  the  boiler  heating  surface  and  baffles  can  be  checked. 
The  record  of  steam  flow  is  made  in  red  ink,  and  that  of  air  flow  in  blue 
ink.  The  latter  is  calibrated  so  that  under  ideal  conditions  the  blue  and 
red  records  coincide  on  the  chart.  When  the  air  Flow  pen  reads  more  than 
the  steam  flow,  there  is  an  excess  of  air  passing,  and  when  it  reads  less, 
the  air  supply  is  insufficient;  thus  improper  conditions  can  be  easily  rectified. 


r 


Weighing  Coal 
HE  equipment  for  this  work  may  be  divided  into  three  classes— that  for 

weighing  the  coal  received,  that  for  weighing  the  total  amount  of  coal 
consumed,  and  that  for  weighing  the  coal  consumed  by  each  boiler  unit 

For  checking  the  amount  of  coal  received  at  a  plant,  there  are  several 
types  of  equipment, — track  scales,  wagon  scales,  weighing  hoppers  with  hand- 
operated  or  automatic  scales,  conveyor  weighers,  and  coal  meters.  For  de- 
termining the  quantity  of  coal  used  each  day  in  a  boiler  room  the  same  tjrpei 
of  weighing  or  measuring  devices  can  be  used,  and  also  the  movable  weigh- 
ing hopper  or  traveling  Tarry  equipped  with  scale. 

Track  scales  are  set  in  the  car  track  so  that  a  section  of  the  rails  is 
carried  by  the  scale  platform,  and  the  railroad  cars  can  be  run  upon  the  plat- 
form and  weighed.  The  wagon  scale  is  similar.  The  coal  may  be  handled 
in  small  hand-operated  industrial  cars,  automatic  railway  cars,  or  cars 
operated  by  electricity  or  a  cable  system.  Track  scales  can  be  provided  to 
weigh  the  coal  handled  by  such  cars,  and  if  the  amount  handled  justifies  the 
expense,  the  scales  can  automatically  record  the  weight  as  the  car  passes 
over  the  scale  platform  without  stopping.  The  recording  device  of  one  of 
these  scales  consists  of  a  wheel  having  the  numbers  in  type  on  its  periphery, 
and  when  a  lever  is  moved  by  the  attendant  or  is  tripped  automatically  as  the 
car  passes  over  the  platform,  the  wheel  revolves  a  distance  depending  on  the 
weight,  and  then  prints  the  amount  on  a  tape  which  is  fed  from  one  roller 
and  wound  up  on  another.  The  weights  of  the  different  loads  are  thus 
recorded  on  the  tape,  which  can  be  taken  off  whenever  desired. 

Track  scales  are  also  used  for  overhead  tracks,  usually  of  the  monorail 
type.  A  separate  section  of  rail  or  rails  is  supported  on  the  scale  beam  so 
that  the  larries  or  trolleys  carrying  the  loads  can  be  stopped  and  weighed, 
or  if  an  automatic  recording  scale  is  installed,  the  loads  can  be  weighed  as 
they  pass  over  this  section  of  track. 

Fig.  258  illustrates  an  automatic  receiving  scale  of  75  tons  hourly  capac- 
ity. This  type  of  scale  is  very  satisfactorily  adapted  to  use  in  those  plants 
where  track  scales  cannot  be  installed.  It  operates  by  the  gravity  of  the 
coal  which  must  be  delivered  from  some  point  above  the  scale,  and  thus 
can  take  its  charges  from  a  hopper,  bunker,  elevator  or  conveyor  and  dis- 
charge into  a  hopper,  chute,  conveyor  or  elevator  boot,  depending  upon  the 
service  required  and  the  local  conditions  of  handling. 

A  crusher  is  necessary  to  reduce  run  of  mine  coal  to  reasonably  uniform 
sizes  for  the  successful  operation  of  an  automatic  hopper  scale.  Where  this 
is  not  done,  or  where  coal  is  handled  on  a  belt,  bucket  or  pan  conveyor,  a 
conveyor  scale  is  applicable,  and  is  recommended  where  head  room  will  not 
admit  of  a  hopper  scale.  In  one  type  of  conveyor  scale  a  section  of  the 
conveyor  is  suspended  on  a  floating  platform  balanced  through  a  compound 
leverage  system  by  an  iron  float  in  a  cylinder  of  mercury.  For  varying 
weights,  the  float  takes  up  dilTerent  positions,  and  its  movement  offers  a 


ib.  Google 


Inttallation  of  2500  H.  P.  oT  Heine  Standard  Boilers  ii 
Ridgewood  Pumping  Station,  Brooklyn,  N.  Y. 


ib.  Google 


OPERATION 


Fig.  358.     Richardion  Automatic  Receiving  Scale. 


Fig.  359.     Traveling  Weigh  Hopper. 


ib.  Google 


OPERATION 


For  keeping  a  record  of  the  coal  used  under  each  separate  boiler  the 
devices  ordinarily  employed  are  the  automatic  scale  and  the  coal  meter. 
The  automatic  scale  may  be  stationary  if  the  coal  bunkers  are  located  above 
the  boiler  fronts  or  may  be  installed  on  a  traveling  larry  if  the  coal  bunkers 
are  located  at  the  ends  of  the  firing  aisle.  When  stationary,  each  individual 
scale  is  mounted  on  a  frame  directly  beneath  the  overhead  bunkers  from 
which  It  receives  the  coal ;  and  it  discharges  the  coal  after  weighing,  into 
the  spout  which  leads  down  to  the  stoker  hopper. 

Fig.  259  illustrates  a  traveling  larry,  which  consists  of  a  four-wheeled 
carriage  or  truck,  upon  which  is  mounted  a  hopper  and  scale.  The  truck 
moves  upon  an  I-beam  track  by  hand  operation  of  the  chain  wheel  geared 
to  one  truck  axle.  The  scale  beam  is  located  so  as  to  be  balanced  and  read 
from  the  floor.  In  large  central  stations  where  traveling  larries  are  used. 
they  are  usually  driven  by  an  electric  motor  and  equipped  with  automatic 
scales.  The  operator  rides  in  a  cage  on  the  larry  and  keeps  a  record  of  the 
coal  delivered  to  each  boiler. 

The  spouts  leading  from  the  overhead  bunkers  are  sometimes  fitted  with 
a  helical  vane,  Fig.  260,  which  is  calibrated  30  that  its  rotation  is  a  guide 
of  the  amount  of  fuel  used  by  each  boiler.  The  rotation  of  the  vane  is 
transmitted  by  shafts  and  gears  to  a  counter  registeriog  on  a  dial. 


F^.  360.     Coal  Meter  of  the  Helical  Vane  Type. 


When  stoker  fired,  the  amount  of  coal  used  by  each  boiler  may  be 
roughly  determined  by  installing  revolution  counters  on  the  stoker  ^aft. 
With  chain  grate  stokers  the  r.p.m.  of  the  stoker  sprocket  must  be  used  in 
conjunction  with  the  depth  of  fire  and  width  of  grate  to  get  a  rough  check 
on  the  coal  consumption.  In  underfeed  stokers  of  the  Riley,  Taylor  or 
Westinghouse  type,  about  17  to  18  lbs.  of  coal  per  retort  Is  fed  to  the  furnace 
with  each  revolution  of  the  crank  shaft 


ib.  Google 


OPERATION  603 

Handling  Coal 
""THE  handling  of  coal  and  ashes  resolvea  itself  into  the  following  stages: 
J-    (1)  Unloading  of  coal  as  received,  either  by  land  or  water;    (2)    Its 
transfer  to  bunkers  or  other  storage;  (3)  Its  movement  to  boilers  ready  for 
ftring;  and  (4)  Removal  and  final  disposal  of  ashes. 

Unloading  of  Coal.  When  the  plant  is  not  large  enough  to  warrant  a 
railroad  siding  the  coal  is  delivered  by  truck  and  unloaded  by  hand.  If 
bottom-dumping  cars  are  available,  the  coal  can  be  discharged  directly  into 
hoppers  or  into  the  storage  space  provided.  With  water  delivery  a  clam- 
shell bucket,  operated  by  a  locomotive  crane  or  from  a  tower,  can  be  used 
to  move  the  fuel  from  the  barge. 

Methods  of  Storing  Coal.  In  small  plants  the  coal  may  be  stored  in 
bins,  bunkers  or  piles  inside  the  boiler  room ;  but  in  larger  plants  the  quan- 
tities of  coal  used  each  day  are  so  large  that  the  inside  bunkers  hold  only 
a  few  days'  supply  and  outside  storage  is  necessary, 

A  convenient  storage  system  often  employed  is  that  in  which  the  storage 
space  is  adjacent  to  the  boiler  room  and  the  whole  served  by  a  continuous 
tnicket  conveyor.  This  bucket  conveyor  runs  horizontally  in  a  tunnel  beneath 
the  coal  storage  space  and  boiler  room  floor,  rises  vertically  at  the  far  end 
of  the  boiler  room,  returns  horizontally  on  a  bridge  over  the  boiler  coal 
bunkers  and  outside  storage  space  and  finally  descends  at  the  outer  end  of 
the  storage  pile  to  the  tunnel,  thug  completely  encircling  the  boiler  room 
and  storage.     Chutes  below  the  coal  storage  bin  deliver  the  coal  to  the 


Fig.  263.    Circular  Co«]  Storage  System 


ib.  Google 


<53 


ib.Google 


by  a  t 

which 


OPERATION  60S 

buckets,  which  then  carry  it  up  sbove  the  boiler  bunkers  where  a  tripping 
device  overturna  the  buckets  and  discharges  the  coal  to  the  bunkers.  A  con- 
tinuous bucket  conveyor  installation  of  this  type  usually  handles  ashes  as 
well  as  coal. 

The  Circular  Storage  Sytlem,  Fig.  263,  is  often  used  for  storing  coal 
for  power  plant  use  and  is  suitable  for  capacities  ranging  from  5000  tons  up. 
It  consists  of  a  long  radius  locomotive  crane  equipped  with  self-filling  bucket. 
running  on  a  circular  track  around  a  central  track  hopper  into  which  coal 
is  dumped  from  railroad  cars.  The  coal  to  be  stored  is  taken  from  this 
central  pit  or  hopper  by  the  bucket  and  delivered  to  the  pile.  This  system 
has  a  handling  capacity  of  from  40  to  250  tons  per  hour,  according  to  the 
size  of  the  bucket  and  crane  employed. 

RectangMiar  Storage.  A  few  large  plants  store  their  coal  in  a  pile  spanned 

a  traveling  bridge.  The  coal  is  received  in  hopper  bottom  railroad  cars 
mich  discharge  into  a  pit  running  lengthwise  of  the  pile,  from  which  it  is 
removed  by  a  grab  bucket  operated  from  the  bridge  and  placed  on  the  storage 
pile.  The  capacity  of  a  storage  of  this  type  is  determined  by  the  span  of  the 
bridge  and  length  and  height  of  pile.  Economical  handling  capacities  of 
storage  systems  of  this  type  are  from  100  to  300  tons  per  hour. 

Submerged  Storage,  Bituminous  coal  which  is  subject  to  spontaneous 
combustion  is  sometimes  stored  under  water.  Storage  bins  for  this  purpose 
may  be  constructed  of  concrete,  the  inside  surfaces  being  treated  with  a 
waterproofing  compound.  A  6000  tons  submerged  storage  pit  has  been  con- 
structed by  ihe  Omaha  Electric  Light  and  Power  Company.  The  pit  is  built 
of  concrete  with  walla  22  ft.  high  on  three  sides.  The  fourth  wall  is  16  ft. 
higher  and  serves  as  the  support  for  one  rail  of  the  crane  runway.  The 
other  rail  is  carried  by  a  girder  along  the  side  of  the  power  house.  Two 
SO-ton  receiving  hoppers,  also  of  concrete,  are  located  at  the  power  house 
end  of  the  submerged  storage. 

The  storage  and  spontaneous  combustion  of  bituminous  coal  are  dis- 
cussed on  page  466. 

Transfer  of  Coal  from  Storage  to  Boiler  Room.  Where  mechanical 
storage  systems  are  in  use,  the  transfer  of  the  coal  from  storage  pile  to  car 
is  accomplished  by  means  of  grab  buckets  operated  from  locomotive  cranes 
or  bridges  as  described  above.  However,  where  mechanical  storage  systems 
arc  not  used,  and  where  storage  piles  are  at  some  distance  from  the  boiler 
room,  portable  loaders  are  used  to  transfer  the  coal  from  pile  to  car  or  wagon. 
These  loaders  may  be  either  of  the  bucket  or  belt  type  and  may  be  driven 
by  electric  motor  or  gasoline  engine. 

Coal  can  be  transferred  to  the  boiler  bunkers  by  small  hand  or  power- 
operated  cars,  or  by  a  conveyor  system.  Conveyors  may  be  of  several  dif- 
ferent types,  the  selection   depending  upon  the  conditions. 

Screw  Conveyors  may  be  used  for  horizontally  conveying  coal  of  J^ 
inch  or  less,  a  distance  of  100  or  150  ft.  The  conveyor  or  screw  consists  of 
sections  of  a  stamped  or  rolled  steel  helix  mounted  on  hollow  steel  shafting, 
carried  by  hangers.  The  screw,  which  is  driven  by  gears  or  sprockets  at 
one  end,  revolves  in  a  steel  box  through  which  the  fuel  is  conveyed. 

Scraper  or  Flight  Conveyors  may  be  used  for  conveying  tine  sizes  of  coal 
horizontally  or  on  inclines  up  to  about  45  degrees.  Single  strand  conveyors 
of  this  type  consist  of  a  single  chain  to  which  are  bolted  steel  flights  or 
plates.  Double  strand  conveyors  have  the  flights  suspended  from  two  chains, 
and  are  used  whert  the  conveyors  are  long  and  subjected  to  heavy  service. 
Either  type  may  be  equipped  with  sliding  blocks  or  rollers.  The  troughs 
through  which  the  coal  is  conveyed  are  made  of  steel  plate  or  of  wood  lined 
with  plates. 


ib.  Google 


dl/i. 


OPERATION 


^^^^^ 


ib.Google 


OPERATION  607 

Apron  Conveyors  »Tt  often  used  tor  conveying  coal  horizontally  or  on 
inclines  up  to  about  30  degrees.  larger  sizes  of  coal  may  be  handled  with 
this  type  than  with  screw  or  flight  conveyors.  The  apron  conveyor  consists 
of  two  strands  of  roller  chain  separated  by  overlapping  apron  plates  with 
sides  from  2  to  6  inches  high.  These  apron  plates  carry  the  coal ;  and  as  the 
coal  is  carried  instead  of  being  dragged,  less  power  is  required  and  maut' 
tenance  costs  are  less  than  with  scraper  or  screw  conveyors. 

Pivoted  Bucket  Conveyors.  Fig.  264,  are  frequently  used  in  power 
plants.  Their  use  in  handling  coal  from  storage  to  bunkers  is  discussed 
in  a  previous  paragraph.  This  type  of  conveyor  will  handle  comparatively 
large  sizes  of  coal  at  capacities  ranging  from  15  to  200  tons  per  hour. 

Bell  Conveyors  will  handle  coal  satisfactorily  on  horizontal  runs  or  on 
inclines  up  to  20  degrees  at  capacities  up  to  500  tons  per  hour.  This  type  of 
conveyor.  Fig.  265,  consists  of  an  endless  belt  driven  by  suitable  pulleys 
and  carried  upon  Idler  pulleys  so  arranged  that  the  "carrying"  side  of  the 
s  trough-shaped  in  cross- section.  The  loaded  or  carrying  side  may 


CfcM    H    H    ho* 

Fig.  265.    Belt  Conveyor. 

be  supported  by  three  or  five  troughing  idlers  as  may  be  required,  while  the 
empty  side  is  carried  on  straight  return  idlers.  The  idlers  are  carried  bv  iron 
or  wooden  stands,  spaced  from  3  to  6  ft,  centers  on  the  troughing  side,  and 
from  6  to  12  ft.  on  the  return  side.  The  belts  generally  used  consist  of 
plies  of  coiion  duck  cemented  together  with  a  rubber  compound  and  protected 
from  moisture  and  abrasion  by  ^  rubber  cover.  Tripping  devices  placed  at 
the  required  points  discharge  the  coal  from  the  belt.  These  trippers  are 
mounted  on  a  carriagie  and  consist  essentially  of  two  pulleys,  one  above  and 
slightly  in  advance  of  the  other,  so  that  the  belt  runs  over  the  upper  one  and 
under  the  lower  one,  thus  throwing  the  coal  into  a  chute  on  the  first  I'own- 
ward  turn  of  the  belt.  The  trippers  may  be  fixed  so  that  the  coal  will  always 
discharge  at  one  point,  or  movable  when  it  is  desired  to  discharge  the  coal 
into  di^erent  bunkers.  Movable  trippers  may  be  propelled  by  a  hand-crank 
or  automatically  propelled  by  gearing. 

Coal  Crushers.  When  coal  is  handled  by  screw  or  scraper  conveyors  it 
is  necessary  to  crush  the  coal  down  to  about  ^  inch  size.  Belt  or  bucket 
conveyors  will  satisfactorily  handle  larger  sizes. 

Coal  crushers  are  generally  installed  beneath  or  adjacent  to  the  receiving 
hoppers,  see  Fig,  263. 

A  type  of  crusher  satisfactory  for  reducing  run  of  mine  bituminous  coal 
to  a  size  suitable  for  stoker  use,  consists  of  two  rolls  provided  with  solid  cast 
steel  or  renewable  steel  teeth.  The  rolls  are  mounted  in  a  heavy  frame  and 
arc  gear  driven.  Relief  spring  bearings  are  provided  for  one  of  the  rolls, 
so  that  they  may  separate  in  case  tramp  iron  enters  the  crusher. 


ib.  Google 


«8  OPERATION 

Coal  BunkcTt  are  ^nerally  overhead  when  mechanicat  coal  handling 
systems  and  stokers  are  installed.  Usually,  overhead  bunkers  should  hold  not 
less  than  one  day's  supply  of  coal.  In  lar^  stations  where  there  are  no 
facilities  for  outside  storage,  the  overhead  bunkers  may  hold  as  much  as  a  ten 
days'  supply. 

Coal  bunkers  may  be  arranged  so  that  each  boiler  or  each  batter)  has 
its  individual  bunker,  or  there  may  be  one  continuous  bunker  for  all  the 
boilers.  Catenary,  parabolic  and  V-shaped  bunkers  are  generally  of  the  con- 
tinuous type.  The  angle  of  repose  of  coal  varies  from  35  to  40  <legrees;  liut 
due  to  convenience  in  fabricating,  the  45  degrees  slope  is  generally  used  for 
hopper  bottoms.  Overhead  bunkers  raay  be  constructed  of  unlined  steel 
plate,  of  structural  steel  lined  with  concrete  or  of  reinforced  concrete. 

Down  spouts  with  a  shut-olf  gate  convey  the  coal  from  the  bunkers  to 
the  firing  floor  or  the  stoker  hoppers. 

Where  overhead  bunkers  are  not  installed  immediately  over  the  boiler, 
traveling  larries.  Fig.  258.  ur  traveling  buckets,  carry  the  coal  from  the 
distributing  bunker  or  coal  storage  to  the  boiler  fronts. 

Ash  Handling  Systems 

IN  all  Ixiilers  the  ashes  are  either  raked  out  onto  the  firmg  floors  or  are 
dropped  into  ash  pits.  The  design  and  construction  of  ash  pits  of  different 
types  of  boiler  settings  is  discussed  in  Chapter  4  on  FURNACES  AND  SET- 
TINGS. 

The  pits  often  discharge  into  small  push  or  electric  cars,  which  carry 
the  ashes  to  a  conveyor  or  elevator  system,  from  which  they  are  carried  to 
the  ash  bunkers.  The  coal  handling  system  is  used  sometimes  for  carrying 
ashes,  although  it  is  considered  that  the  two  should  be  separated,  because  of 
the  abrasive  action  of  the  ashes.  When  the  systems  are  combined,  the 
pivoted-bucket  conveyor  has  the  advantage  that  the  parts  can  be  replaced 
easily  as  they  wear  or  corrode. 

The  bucket  and  chain  elevator,  with  rigid  buckets,  is  a  common  method 
of  elevating  ashes.  The  ashes  are  fed  into  a  boot  forming  the  bottom  part 
of  the  elevator,  are  scooped  up  by  the  buckets  and  carried  inside  a  casing 
to  the  top  of  the  elevator,  where  they  are  discharged  into  a  spout  leading 
to  the  point  of  disposal.    This  may  be  an  ash  bunker,  a  truck  or  a  railroad  car. 

The  skip  hoist  is  another  well  known  method  of  ash  removal ;  it  con- 
sists of  a  bucket  running  on  inclined  or  vertical  tracks,  and  hoisted  by  a 
steel  cable  attached  to  a  motor-driven  winding  machine.  The  bucket  and 
chain  elevator  is  recommended  for  small  plants,  where  the  lift  is  40  ft.  or 
less.  For  larger  plants  the  skip  hoist  is  said  to  have  the  advantages  of 
simplicity,  low  power  consumption,  and  ability  to  handle  the  large  clinkers 
often  produced  by  forced  draft  stokers  at  high  overloads. 

Pneumatic  Ash  Conveyors.  These  consist  primarily  of  a  pipe  through 
which  a  current  of  rapidly  moving  air  carries  the  ashes  to  any  desired  point. 
Inlets  to  receive  the  ashes,  consist  of  tees  which  are  plugged  when  net  ia 
use;  and  are  provided  wherever  convenient,  such  as  in  front  of  the  ashpits. 
The  conveyor  may  discharge  onto  the  ground  or  into  a  hopper  from  which 
cars  and  wagons  may  be  filled.  The  commencement  of  the  pipe  should 
have  an  open  end,  so  that  there  is  an  ample  flow  of  air  along  the  pipe  at 
the  first  ash  inlet. 

In  vacuum  conveyors,  a  vacuum  is  produced  in  a  closed  tank,  either  by 
means  of  a  motor-driven  or  a  steam  jet  exhauster.  When  steam-jets  are 
used,  they  may  either  be  arranged  to  exhaust  from  a  hopper  as  just  described, 
or  may  be  introduced  at  some  point  or  points  after  the  last  inlet,  generally 
at  a  bend  in  the  conveyor  pipe.  Steam-jet  conveyors  may  either  discharge 
into  the  open  or  into  vented  tanks. 


ib.  Google 


OPERATION  609 

Since  the  ash  travels  at  a  high  vdocity,  the  abrasive  action  is  considerable, 
especially  at  changes  of  direction.  Therefore,  bends  are  provided  with  easily 
replaceable  "wearing-backs,"  and  the  ash  is  generally  discharged  against 
some  form  of  target  to  protect  the  hopper  wall. 

Fig.  266  shows  one  end  of  the  boiler  room  of  No.  2  plant  of  the  Heme 
Company.  The  inlets  of  the  ash  conveyor  are  flush  with  the  firing  floor, 
and  offer  no  impediment  when  closed.  The  ashes  are  removed  very  rapidly 
and  the  boiler  room  is  kept  free  from  dust  and  dirt. 


Fig.  366.     Detrick-Hagan  Steam- Jet  A*h  Conveyor. 

With  hopper  ashpits,  the  conveyor  pipe  may  be  laid  on  the  basement 
floor  or  hung  from  the  underside  of  the  tiring  floor  as  is  most  convenient. 
Connections  may  also  he  made  to  the  combustion  chambers. 

Clinkers  should  he  broken  up  and  ashes  and  dust  should  be  dry  when 
fed  to  the  conveyor  to  avoid  clogging,  particularly  at  bends.  Water  sprays 
are  frequently  placed  in  the  conveyor  pipe  near  the  discharge  end,  or  in  the 
ash   Unk. 

Steam-jet  conveyors  are  less  noisy  than  vacuum  systems  with  a  steam- 
jet  exhauster  drawing  from  the  ash  tank.  It  is  difficult  to  muffle  these 
latter,  owing  to  the  abrasive  or  "sandblast"  action  of  the  fine  dust  quickly 
perforating  metal  baffles. 

Flumes.  In  some  plants  where  there  is  a  plentiful  supply  of  water, 
lliimes  are  constnicteil  beneath  the  bailer  setting,  into  which  the  stokers 
discharge  their  refuse.  A  stream  of  water  flowing  through  the  flume  washes 
the  ashes  into  a  pit  from  which  an  elevator  discharges  them  to  a  railroad 
car  or  wagon. 


ib.  Google 


610  OPERATION 

The  ash  bins  used  with  mechanical  conveying  systems  may  be  made  of 
steel,  coDcrete-Hneil,  or  of  concrete  on  a  steel  skeleton.  On  account  of  the 
corrosive  action  of  the  wet  ashes,  concrete  or  brick  bins  are  often  rsed. 
They  should  be  ventilated  to  prevent  gas  explosions.  The  discharge  is  from 
the  bottom  to  wagons  or  railroad  cart. 

Handling  of  Fuel  Oil 

THE  use  of  fuel  oil  requires  special  provisions  for  storage.  While  a 
gravity  system  of  boiler  feed  is  sometimes  permissible  in  small  plants  or 
in  places  where  large  outdoor  areas  are  available  for  the  location  of  distant 
tanks,  the  usual  practice  is  to  place  properly  vented  cylindrical  steel  tanks 
under  ground  or  at  least  below  the  level  of  the  furnace. 

The  arrangement  adopted  is  governed  in  most  instances  by  local  and 
insurance  regulations. 

The  use  of  a  continuous  circulating  system,  that  is,  with  the  surplus  oil 
returned  to  the  tank  by  means  of  a  release  valve  or  by  the  use  of  a  stand- 
pipe,  prevents  choking,  and  is  especially  important  with  highly  viscous  oils. 
The  pumps,  which  are  preferably  installed  in  duplicate  to  protect  against  in- 
terruption of  service,  can  be  either  rotary  or  reciprocating,  although  the 
former  insures  a  more  even  pressure. 

Live  or  exhaust  steam  heaters  are  ordinarily  used  in  the  pressure  line, 
with  additional  coils  in  the  storage  tank  if  very  heavy  oils  are  used. 

Some  satisfactory  systems  for  handling  fuel  oil  are  the  Rogers-Higgim, 
Staples  and  Pfeifer,  Koertitig,  Coen  and  Moore.  Fig.  267,  illustrating  a 
Roger j-Higgins  Oil  SyJteni,  shows  the  general  principles  involved.  One 
of  two  duplex  oil  pumps,  mounted  on  an  exhaust  steam  heater,  serves  to 
draw  the  fuel  from  the  storage  tank  and  to  force  it  through  the  heater  and 
strainer  to  the  burners  in  front  of  the  furnace,  where  it  is  atomized  by  steam. 
The  relief  valve  above  the  heater  carries  back  the  excess  oil  to  the  tank 
by  a  separate  line. 


Diagram  of  Typical  Oil  Handling  Installation. 


i  shown  in  Fig,  51, 


Cleaning  Boilers 

THE  sticcessful  and  efficient  operation  of  a  boiler  demands  thst  the  heat- 
ing surface  be  clean  both  externally  and  internally.  External  cleaning  of 
the  Heine  boiler  by  means  of  an  efficient  mechanical  soot  blowing  system 
has  been  discussed  in  Chapter  1  on  HEINE  PRACTICE.     In  water  tube 


ib.  Google 


OPERATION  «1 

boilers,  the  waterlegs  of  which  are  not  equipped  with  hollow  staybolts,  or 
in  vertically  baffled  boilers,  the  external  heating  surface  is  cleaned  with  a 
hand  lance,  or  the   ■rotating  element"  type  of  mechanical  soot  blower. 

If  boilers  are  to  be  stored  out  in  the  weather  for  even  short  periods, 
the  exterior  surfaces  should  be  protected  wilh  a  good  grade  of  red  lead  or 
black  paint. 

To  remove  the  grease  and  oil  which  remain  from  the  operation  of  manu- 
facture, new  boilers  should  be  boiled  out  twice  over,  with  a  charge  of  2 
to  5  lb.  of  soda  ash  each  time. 

The  effect  of  scale  on  heat  transmission  has  been  discussed  in  Chapter 
14  on  FEED  WATER.  It  is  obvious  that  the  preferable  way  to  keep 
internal  heating  surfaces  clean  is  to  avoid  scale  formation  by  proper  treat- 
ment of  the  water  before  it  is  fed  to  the  boiler.  However,  all  boiler  plants 
are  not  equipped  with  water  treating  systems ;  and  often,  under  bad  water 
conditions,  it  is  not  possible  to  purge  the  water  of  scale-forming  materials 
entirely  even  with  chemical  treatment.  Hence  all  boilers  are  subject  in  a 
greater  or  lesser  degree  to  scale  formation. 

When  scale  has  once  formed  on  the  heating  surface,  it  is  usual  to  remove 
it  by  washing  out  or  by  turbining.  If  chemical  compounds  are  used,  care 
must  be  taken  to  see  that  the  resulting  mud  or  sludge  is  blown  off,  as 
otherwise  there  is  a  tendency  for  it  to  lodge  again  on  the  heating  surface 
and  cause  bagged  or  blistered  tubes. 

Where  the  scale  is  of  a  very  soft  nature,  or  where  mud  deposits  on  the 
tubes  without  baking,  the  heating  surface  may  be  effectively  cleaned  by 
washing  out  with  water.    But  where  the  scale  is  hard,  turbining  is  necessary. 

There  are  several  types  of  turbine  tube  cleaners  on  the  market,  the  most 
satisfactory  of  which  is  the  water  turbine.  This,  as  Fig.  268,  usually  con- 
sists of  a  cylindrical  casing  containing  a  small  hydraulic  turbine,  with  the 
necessary  guide  plate  and  turbine  wheel.     On  an  extension  of  the  turbine 


Pig.  268.     Roto  Tube  Cleaner. 

shaft,  arms  are  mounted  to  which  cutters  are  attached.  These  arms  revolve 
at  high  speed  and  the  cutters  bearing  upon  the  scale,  chip  it  off  the  tube  in 
small  pieces.  The  stream  of  water  flowing  from  the  turbine  envelopes  the 
cutlers,  keeps  their  edges  cool,  and  washes  away  the  scale  as  it  is  loosened. 

It  is  not  advisable  to  operate  turbine  tube  cleaners  by  steam,  because 
the  hot  steam  exhausting  through  the  tube  heats  it  and  causes  it  to  expand 
to  a  greater  length  than  its  cool  companions,  and  this  tends  to  loosen  the 
tube  expansion  in  the  waterleg,  resulting  in  leaks. 

Hammer  type  mechanical  tube  cleaners,  in  which  the  scale  is  loosened  by 
a  series  of  rapid  hammer  blows,  are  applicable  to  either  water  tube  or  fire 
tube  boilers,  but  are  more  generally  used  for  the  latter.  Care  must  be  taken 
that  they  are  not  kept  at  work  in  one  spot  for  any  length  of  time,  as  this 
tends  to  wealien  the  tubes  by  peening  bags  on  them. 

Both  hammer  and  turbine  types  may  be  operated  by  water,  steam  or  com- 
pressed air. 


ib.  Google 


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ib.Google 


OPERATION  613 

Renewing  Tubes 

OLD  tubes  can  be  removed  readily  by  collapsing  the  ends  of  the  tube  with 
a  cold  chisel  and  hammer;  but  care  must  be  taken  not  to  injure  the  seat 
in  the  tube  hole. 

When  the  new  tube  is  in  position  for  expanding,  the  ends  should  not  pro- 
ject through  the  tube  sheet  more  than  Vw  nor  less  than  Vi.  inch.  There  are  two 
types  of  tube  expanders  in  use,  known  as  the  Prosier  and  the  Dudgeon. 

The  Prosier  type,  which  finds  favor  in  locomotive  practice,  consist?  of  a 
number  of  steel  segments  held  together  by  a  rubber  or  spring  steel  ring. 
These  segments  are  of  such  a  size  that  when  the  expander  is  collapsed,  it 
is  of  smaller  size  than  the  bore  of  the  tube,  so  that  it  may  be  inserted  easily- 
The  segments  surround  a  tapered  steel  mandrel,  by  driving  which  the  seg- 
ments are  separated  and  bear  against  the  tube.  By  gradually  driving  in  the 
mandrel,  slacking  and  turning  the  tool  and  driving  again,  the  tube  is  expanded 
into  its  seat  in  the  tube  sheet. 

The  Dudgeon  expander,  which  is  widely  used  in  stationary  water  tube 
practice,  expands  the  tube  by  the  continuovis  pressure  of  steel  rollers  turning 
inside  the  tube.  This  type  of  expander.  Fig.  269,  consists  of  a  hollow  cylin- 
der, with  three  or  more  slots  in  which  are  steel  rollers.  A  tapered  steel 
mandrel  is  inserted  through  a  central  hole  ill  the  cylinder  and  bears  upon 
the  rolls.  By  revolving  the  expander  and  driving  the  mandrel,  the  rolls  are 
forced  outward  as  they  rotate,  thus  expanding  the  tube.  This  expander  can 
be  either  hand  or  power  operated. 


Fig,  269.     Henderer- Ferguson  Self-Feed  Roller  Tube  Expander. 

-4ftet  expanding  the  tube  into  its  seat  in  the  tube  sheet,  the  tube  is 
slightly  flared.  Flaring  can  be  done  with  a  so-called  "belling"  tool  or  by 
using  the  Dudgeon  expander  with  one  steeply  tapered  roll  substituted  for  a 
straight  roll. 

The  tubes  in  water-tube  boilers  are  seldom  beaded.  When  desired  this 
may  be  done  with  a  beailing  tool  or  "boot" 

Care  of  Idle  Boilers 
TF  a  boiler  is  to  be  out  of  service  for  three  or  four  months  it  should  be 
*■  cleaned  thoroughly  both  internally  and  externally,  by  washing  out,  turbin- 
ing  and  soot  blowing.  It  should  then  be  tilled  up  with  water,  to  which  IGO 
or  150  lbs.  of  soda  ash  have  been  added.  A  slow  fire  should  then  l)e  maintained 
until  all  air  has  been  expelled  from  the  boiler,  after  which  the  boiler  should 
be  pumped  full  and  closed  up  tightly.  If  the  stack  is  located  directly  above 
the  boiler,  the  stack  lop  should  be  covered,  or  the  boiler  surface  so  protected 
that  rain  cannot  reach  it. 

If  the  boiler  is  to  be  idle  for  longer  than  three  or  four  months,  it 
should  be  emptied,  turhined,  washed  out.  left  open  to  dry,  and  brushed  with  a 
scraper  or  stiff  wire  brush.  A  tray  of  quicklime  should  then  be  placed  inside 
the  drum  and  the  boiler  closed  up  tightly. 


ib.  Google 


614  OPERATION 

Some  engineers,  before  emptying  a  boiler  that  is  to  be  laid  up,  place 
several  gallons  of  cniile  oil  in  the  shell,  so  that  when  the  blow-off  or  drain 
is  open^  and  the  water  let  out.  the  oil  will  form  a  protecting  film  on  the 
internal  heating  surface.  If  this  method  is  used,  the  boiler  must  be  thor- 
oughly boiled  out  with  soda  ash  before  again  being  placed  in  service,  so  that 
all  traces  of  oil  may  be  removed. 

"Cuttmg-In"  Boilers 

TO  "cnt-in"  a  boiler  or  to  put  it  "on  the  line"  after  it  has  been  out  of 
service,  is  to  place  it  in  free  communication  with  other  boilers  that  are 
nnder  steam. 

In  cutting  in  a  boiler  that  has  been  idle,  the  stop-valve  should  be  kept 
closed  until  the  (team  pressure  in  the  boiler  has  risen  to  the  exact  value 
thai  is  prevailing  at  the  time  in  the  steam  main  to  which  the  boiler  is  to 
be  connected.  It  is  not  sufficient  to  bring  the  pressure  to  within  a  few 
pounds  of  that  in  the  main.  Practice  of  this  kind  should  not  be  tolerated, 
for  it  is  exceedingly  important  that  the  equality  should  be  as  exact  as  the 
engineer  can  make  it  by  the  aid  of  his  pressure  gages.  Then,  when  the 
equality  is  apparently  exact,  the  main  stop-valve  should  be  opened  very 
■lowly  and  carefully.  It  should  be  opened  by  a  mere  crack  at  tirst,  because 
it  will  be  impossible  by  means  of  commercial  steam-gages  to  judge  the 
equality  of  the  pressure  so  closely  that  there  will  be  no  flow  of  steam  in 
either  direction.  The  object  of  opening  the  valve  slowly  is  to  permit  the 
■mall  outstanding  difference  of  pressure  to  become  equalized  very  gradually. 
If  there  is  any  evidence  of  disturbance  in  the  boiler  or  the  piping,  as  indicated 
by  snapping  or  pounding,  or  by  abnormal  vibration  of  the  boiler,  the  stop- 
valve  should  be  immediately  closed  again. 

It  is  safer  to  have  the  pressure  in  the  boiler  that  is  to  be  cut  in.  a  little 
higher  than  that  in  the  steam  main,  rather  than  to  have  it  a  little  lower, 
because  steam  will  then  flow  from  the  boiler  out  into  the  main  instead  of 
in  the  opposite  direction.  Having  the  pressure  in  the  boiler  exceed  that  in 
the  main,  however,  is  nol  recommended.  It  is  far  better  to  have  the  two 
exactly  equal. 

Boiler  Inspection 

THERE  are  many  engineers  who  believe  that  boiler  inspection  is  solely 
the  concern  of  the  state  or  insurance  boiler  inspector.  This  attitude  is 
not  even  justified  from  the  consideration  of  safety  only;  and  it  is  certainly  not 
justified  when  successful  and  efficient  operation  is  considered.  The  engineer 
should  not  only  go  over  the  boiler  with  the  inspector  at  the  time  of  his 
rather  infrequent  visits,  but  should  also  make  it  a  point  to  inspect  the  boiler 
at  intervals  of  a  month  or  two.  The  inspection  of  the  Heine  water  tube 
boiler  will  be  discussed  here,  although  the  methods  of  procedure  in  the  case 
of  other  types  will  be  somewhat  the  same. 

Before  making  the  actual  inspection,  the  engineer  will  Snd  it  to  his  ad- 
vantage to  have  a  blue  print  of  the  boiler  and  setting  so  that  he  may  check 
any  unusual  condition  by  reference  to  the  print.  He  will  find  it  necessary  to 
have  with  him  a  six-foot  rule,  a  pair  of  calipers,  a  stick  of  chalk,  and  a 
pencil  and  note  book.  An  electric  light  in  a  guard  on  an  extension  cord 
is  a  desirable  part  of  his  equipment,  though  in  lieu  of  this,  a  packet  flashlight, 
kerosene  torch  or  candle  may  be  used  to  furnish  light.  A  mason's  hammer 
b  a  desirable  tool  to  carry,  as  it  can  be  used  for  tapping  tubes,  rivets,  etc, 
and  also  for  chipping  scale  from  the  heating  surface,  clinker  from  the  out- 
side of  the  tubes,  etc. 

Inspection  of  the  boiler  must  be  both  external  and  internal.  External 
inspection  covers  the  outside  of  the  setting,  the  inside  of  the  furnace,  and 
the  exterior  of  the  tubes,  waterlegs  and  shells,  while  interior  inspection  refers 
to  the  examination  of  die  interior  side  of  the  boiler  heating  surface. 


ib.  Google 


OPERATION  615 

In  general,  it  is  most  convenient  to  make  the  external  examination  first, 
for  during  this  part  of  the  work  a  helper  may  be  knocking  in  man  hole 
covers,  removing  hand  hole  plates  and  making  ready  for  internal  inspection. 

External  Inspection.  When  examining  the  exterior  of  the  setting,  the 
condition  of  the  brick  work  should  be  noted.  Cracks  and  loose  bricks 
should  be  pointed  up  to  prevent  air  leakage.  Inspection  doors,  fire  doors, 
and  ash  doors  should  fit  tightly.  Buckstays  should  be  close  to  the  brick 
work  or  they  are  not  properly  supporting  the  walls,  which  is  their  only 
function. 

Entering  the  furnace,  the  grates  or  stoker  parts  should  be  examined. 
Warped  or  burned  grate  bars  or  defective  stoker  parts  should  be  renewed. 
That  part  of  the  furnace  brick  work  subjected  to  the  highest  furnace  tem- 
peratures should  be  carefully  examined,  particularly  with  reference  to  erosion 
or  to  excessive  building  up  of  clinker  accumulations.  Note  whether  or  not 
the  brickwork  protecting  the  bottoms  of  the  front  and  rear  waterlegs  is 
intact,  as  these  parts  should  not  be  exposed  to  the  direct  action  of  flame. 
Scrape  the  soot  and  clinker  down  from  the  lower  baffle  and  renew  such 
tile  as  are  faulty.  By  holding  the  light  between  the  rows  of  tubes  near 
each  waterleg,  look  for  evidence  of  leaky  tube  expansions  or  leaky  staybolts. 
If  any  are  evident,  make  note  of  the  location  by  counting  the  row  up 
from  the  bottom  and  over  from  one  side,  and  record  the  same  in  the  note 

Enter  the  setting  above  the  tubes,  and  drop  the  light  down  between  the 
rows  of  tubes  near  the  waterleg  and  look  for  evidences  of  leaky  expansions 
as  was  done  from  below.  Note  also  the  condition  of  the  soot  blower  ele- 
ments, which  should  extend  at  least  ;4  'n-  and  preferably  yi  in.  through 
the  waterleg.  IE  any  are  burned  off  flush  with  (he  waterleg  they  should  be 
replaced,  as  the  effectiveness  of  the  blast  is  lessened  and  erosion  of  the 
staybolt  is  liable  to  result  Look  for  any  soot  accumulations  which  seem  to 
indicate  that  the  soot  blowers  are  not  effective  in  cleaiiing  certain  portions  of 
the  heating  surface.  Examine  the  upper  baffle  and  make  note  of  any  tile 
replacements  needed.  Inspect  the  riveted  throat  connections  and  shell  joints, 
looking  for  incrustations  which  may  be  evidence  of  leaks.  Look  carefully 
for  external  corrosion,  such  as  thinning  of  tubes,  and  for  commencement  of 
cracks  near  joints  in  the  sheets.  Have  the  helper  work  the  damper  rigging 
and  note  the  operation  of  the  damper.  This  completes  the  external  inspec- 
tion of  the  boiler. 

Internal  Ins/-ection.  Before  making  the  internal  inspection  oE  the  boiler 
BE  SURE  that: 

(1)  The  main  stop  valve  is  tightly  closed. 

(2)  The  automatic  non-return  valve  is  screwed  down. 

(3)  The  blow-off  valves  arc  closed. 

(4)  The  feed  water  valves  are  closed. 

(5)  The  water  tender  or  firemen  know  you  are  in  the  boiler. 

Upon  entering  the  drum,  note  the  thickness  or  character  of  the  scale 
deposits,  and  look  for  evidences  of  oil  along  the  water  line.  Chip  away 
the  scale  at  every  seam,  note  the  condition  of  the  rivet  heads  and  look  for 
evidences  of  corrosion  or  grooving.  Examine  the  throat  stays,  and  by  holding 
the  light  down  into  the  waterleg,  note  the  condition  of  the  staybolts.  In- 
spect the  dry  pipe,  deflection  plate  and  mud  drum,  and  see  that  they  are  held 
securely  iti  position.  Examine  the  connections  to  the  water  column  and  see 
that  the  pipes  are  clear. 

Examine  the  staybolts  in  the  waterleg.  Tap  them  with  the  hammer  to 
see  if  they  are  tight  Examine  the  hand  hole  cap  seats,  noting  whether  any 
are  cut  or  grooved,  or  whether  gaskets  are  sticking.  Have  a  helper  hold  a 
light  at  one  end  of  each  tube  while  you  examine  the  tube  from  the  other  end. 
Look  for  piles  of  loose  scale,  which,  unless  removed,  may  lodge  in  the  tube 
and  cause  a  bag  or  blister.    Note  character  and  thickness  of  scale. 


ib.  Google 


616  OPERATION 

After  the  boiler  and  furnace  have  been  inspected,  the  steam  gage  should 
be  calibrated  and  the  water  column,  blow-off  piping  and  valves  should  be 
examined.  If  the  safety  valves  have  been  repaired  or  reground,  they  will 
have  to  be  reset  by  a  responsible  operator  after  the  boiler  is  fired  up. 

A  report  should  be  made  after  each  inspectioi]  and  filed  for  future 
reference.  The  re^rt  will  make  possible  a  comparison  of  the  condition  of 
the  boiler  at  any  time  with  its  condition  at  former  inspections ;  and  wiU  also 
indicate  any  repairs  that  are  liable  to  be  needed  at  the  next  shut-down,  so 
that  the  material  may  be  ordered  and  be  on  hand  when  wanted,  thus  prevent- 
ing unnecessary  delay. 

Cost  of  Generating  Steam 

EVERY  power  plant  is  a  business  in  itself,  whether  it  be  a  large  central 
station  or  a  small  isolated  plant;  and  as  a  business,  its  records   should 
be  kept  in  such  a  manner  that  the  cost  of  producing  power  is  known. 

The  object  of  keeping  records  is  not  only  to  allocate  charges  for  deter- 
mining a  fair  cost  or  selling  price  of  the  power :  but  also  to  enable  the  plant 
manager  to  compare  station  performance  from  time  to  time,  and  tbe  engineer 
lo  analyze  the  various  records  with  a  view  of  reducing  all  losses  to  a  mini- 

Different  methods  of  cost  accounting  are  applicable  to  different  types  of 
power  plants.  A  public  utility  corporation,  which  not  only  generates  power, 
but  distributes  its  product  over  a  wide  area,  will  of  necessity  employ  a  differ* 
ent  cost  keeping  method  than  a  manufacturing  plant  which  uses  its  steam 
for  power,  lighting,  industrial  cooking,  etc.  Many  slates  require  that  public 
utility  corporations  submit  annual  statements  on  printed  forms  provided  by  the 
state,  and  this  governs  the  method  of  cost  accounting  to  be  followed  in  such 
instances.  But  the  owner  of  a  private  plant  is  free  to  use  his  own  method 
of  cost  keeping,  and  the  following  general  methods  of  accounting  the  cost 
of  generating  steam  have  been  outlined  for  such  cases. 

Power  plant  costs  usually  include  the  total  cost  of  power  production, 
with  no  subdivision  of  cost  into  boiler  room  and  engine  room  expense.  For 
example,  the  labor  item  is  seldom  subdivided  so  as  to  cover  the  various 
duties  it  performs ;  yet  the  necessity  of  these  operations  being  performed 
creates  the  expense,  and  unless  it  is  known  how  much  labor  is  required  to 
perform  them,  the  magnitude  and  cause  of  the  expense  is  only  approximate. 
The  cost  of  generating  steam  is  the  largest  factor  in  power  cost,  and  hence 
it  is  essential  for  intelligent  management  that  this  cost  be  kept  separate  from 
engine  room  and  distribution  expenses. 

Costs  can  be  divided  into  tliree  general  classes:  (1)  overhead  or  fixed 
charges,  (2)  operating  costs  and  (3)  maintenance  costs. 

Overhead  Charges 
Overhead  or  lixed  charges  may  include : 

Interest  on  Investment  Taxes 

Depreciation  Insurance 

Rent  Management 

InUrcst  on  Investment.  Expert  accountants  are  not  in  agreement  as  10 
the  propriety  of  including  this  item.  It  is  contended  that  interest  form:)  part 
of  profit,  and  if  included  in  overhead  cost  it  is  virtually  charged  twice  over. 
But  in  comparing  competing  equipment,  interest  on  the  cost  at  prevailing 
rates  for  borrowing  money  should  be  considered,  so  as  to  make  the  compari- 


ib.  Google 


OPERATION  617 

Physical  depreciation  is  defined  as  the  decrease  in  value  of  equipment  due 
to  age  or  wear  and  tear  in  service,  while  functional  depreciation  means  the 
decrease  in  value  of  equipment  due  to  its  becoming  unsuitable  for  use  or 
out  of  date  before  the  end  of  its  estimated  life.  It  is  obvious  that  the  rate 
of  physical  depreciation  can  be  lessened  by  increasing  the  life  of  apparatus  by 
repairs  and  proper  maintenance. 

There  is  considerable  disagreement  between  eugineers  and  between  ac- 
countants as  to  tlie  proper  method  of  computing  depreciation  charges. 
Probably  the  most  commonly  used  is  the  straight-line  method  which  is  based 
upon  the  assumption  that  if  the  investment,  less  th°  salvage  value,  is  divided 
by  the  life  of  the  equipment,  the  resulting  quotient  expresses  the  amount 
which  should  be  allowed  each  year  to  cover  tiie  accrued  depreciation.  Fre- 
quently the  salvage  value  is  not  taken  into  consideration,  as  being  more 


Rental.    A  proportion  of  the  rent  paid  for  land  and  buildings  should  be 
included  in  overhead  charges,  unless  these  are  owned  by  the  concern. 

Taxes.     The  location  of  the  plant  governs  this  item,  which  may  range 

from  0.1  per  cent  to  2.S  per  cent  on  the  assessed  valuation  of  the  equipment 

Insurance  may  include  fire,  employers'  liability  and  boiler  insurance;  the 

amount  being  charged  to  the  cost  of  steam  generation,  being  pro  rated  to  suit 

the  particular  plant  conditions. 

Management  Cost  is  very   frequently  included   in  the  overhead  cliarges, 
and  as  such  may  include  a  proportion  of  the  following; 

Manager's    Time  OfTice  Maintenance 

Chief    Engineer's    Time  Restaurant 

Drafting    Room  Care  of  Grounds 

Office  Help  Miscellaneous 

Operating  Costs 
Boiler    room    operating   costs    include   both    labor    acid    material,    which 
may  be  enumerated  as  follows: 


Fuel 

Water 

Lubricants 

Miscellaneous  Tootj 

Water  Softening  Chemicals  or  Boiler  Compounds 

Rags  and  Waste 

Miscellaneous 


Coal   Unloading  and   Handling 

Feeding  Stokers  or  Furnaces 

Tending  Water 

Cleaning  Fire  Side  of  Boilers 

Cleaning  Water  Side  of  Boilers 

Cleaning  Economizer 

Cleaning  Feed  Water  Heaters 

Qeaning  Bailer  Room 

Ash  Handhng  and  Disposal 

Testing  Boilers 

Miscellaneous 


ib.  Google 


618  OPERATION 

Fuel  is  the  largest  single  item  of  expense  in  boiler  room  operation,  and 
therefore  any  saving  efFecied  in  its  use  is  readily  noted  on  the  cost  sheet. 
Labor  is  the  next  highest  cost  of  operation.  By  keeping  careful  record  o(  the 
distribution  of  labor  in  the  boiler  room,  operating  costs  in  this  regard 
can  be  kept  down  to  the  minimum  necessary  for  the  efficient  handling  of  the 
equipment.  Any  undue  labor  cost  in  the  items  enumerated  above  will  also 
serve  to  indicate  the  advisability  of  installing  more  efficient  apparatus  or  labor 
saving  machinery. 

Uaintcnance  Coat* 

Boiler  room  maintenance  costs  also  include  both  labor  and  material. 
In  some  respects  the  line  drawn  between  maintenance  costs  and  operating 
costs  is  a  fine  one ;  though,  in  general,  maintenance  is  understood  to  refer  to 
the  labor  and  material  cost  on  repairs  to: 

Buildings  Superheaters 

Stacks  and  Breeching*  Feed  Water  Heaters 

Coal  Handling  Machinery  Water  Softeners 

.A.sh   Handling   Machinery  p^  ^„j   Injectors 

Stokers  and  rumaces  r>-  -        u-  .        ^  ^..       ,- 

Fans  and  Ducts  P'Pmg,  Valves,  Traps,  VipK  Covernig 

Motors  and  Stoker  Engines  Tools 

Boilers  and  Settings  Instruments 

Economizers  Miacelbneous 

Maintenance  costs  tend  to  increase  with  the  age  of  equipment.  While 
(derating  costs  are  lowered  by  the  installation  of  labor  saving  machinery, 
maintenance  costs  are  slightly  increased. 


Pour  315  H.  P.  Heine  Standard  BoiteT*  Kt  over  Jooet  Uaderfeed  Stoken 
in  the  Hamilton  Countjr  Court  HousCt  Cinctnaatl,  ^>la> 


ib.  Google 


INDEX 


A.S.M.E,,  boiler  construction  code,  49 
A.S.M.E.,  boiler  testing  rules,  513 
Absolute 
temperature,  370 
Mro  o£  temperature,  370 
Accounts  of  steam  getieration  cost  6\6 
Acidic  of  water,  see  Water 
Adiabatic  expansion,  407 
Peabody's  diagram,  415 
Air 
admission  of  secondary,  90 
carbon  dioxide 

excess  and,  572 

inleakage  of,  and,  573 
combustion 

actual  required,  397 

theoretical  required,  394 
composition  of,  390 
cooled  furnace  blocks,  ISl 
cooling  firebrick  walls,  151 
currents  and  insulation,  361 
excess,  and  weight  of  gases,  179 
gas  weight  and  excess,  179 
heaters,  339 

air  pressure  loss  in,  339 
humidity,  537 
leakage, 

draft  ducts,  236 

settings,  153,  577 
moisture  in.  539 

removal  in  feed  water  beaters,  329 
required 

per  pound  of  coal,  39S 

per  10.000  B.t.u..  189 

with  forced  draft,  227 

grates,  58,  97 
setting  walls,  145 
sped  6c  heat,  403 
water  vapor  and,  weight  of,  401 
weight.  182 
saturated,  540 
volume  and,  400 
Alberger  water  meter,  SS9 
Alcohol  thermometers.  373 
Analyses,  coal,  440 
Analysis. 
ash,  457 
coal,  450 
fuel,  450 
gas,  532 

'    1  of  volumetric,  543 


Analysis—Continued 

gas — Continued 
weight  of  flue  gases  and,  179 
Anthracite.  436 

briquets,  470 

cleaning  fires.  568 

firing  low  volatile.  563 

forced  draft  and  small,  562 

free  burning,  563 

fuel  bed  thickness,  566 

furnace  for  hand  6ring,  95 

grate  bars,  97 

hand  firing.  562 

heating  sur&icc  ratios,  562 

high  setting,  96 

setting  for  hand  firing,  95 

sizes.  443 

specific  gravity,  436 

"on'struction,  153 
flat,  153 

smoke  and  deflection,  93 
Asbestos,  355 
cement  for  boiler  walls,  367 
coating  for  settings,  157 
conductivity,  3S3 
heat  resistance,  357 
Ash.  457 
analysis,  457 
bins.  610 

boiler  testing,  536 
coal,  in 

evaporation  and,  459 

beat  value  and,  458 

reducing,  458 
combustible  in,  loss,  545 
composition,  457 
conveyors,  608 

flume,  609 

pneumatic,  608 

steam  Jet  608 

vacuum,  608 
determination,  coal  analysis,  451 
effect  on  firebrick.   151 
elevators,  608 

fusibility  in  U.  S.  coals,  463 
fusion,  461 

Illinois  coal,  462 

Indiana  coal,  462 
handling,  608 
hoists,  608 
Ashpits,  107 
capacity,  107 


ib.  Google 


Ashpits — Con  tinued 

combustion  in.  111 

doors,  111 

hand  firing,  107,  109 

hopper,  109 

large  capacity,  109 

teaky  doors,  HI 

lining  of  hopper,  III 

side  feed  stokers,  109 

valves,  111 
Atmosphere,  composition  of,  390 
Atomic  weights,  390 
Atomizing  oil  fuel,  119 
Auxiliaries 

exhaust  to  feed  heaters,  326 

regulation  of  exhaust  to  feed  heater, 
326 

steam  used  by,  423,  547 
Auxiliary 

engines,  341 

fuel  bed  (or  blast  furnace  gas,  129 

turbines,  341 


Badger  expansion  joint,  290 
BafHes, 

deflecting,  in  fiues,  217 

divided  pass,  65 

fjues,  in,  217 

forming  furnace  roof,  65 

soot  blowers  and,  65 

tight,  keeping,  65 

tiles.  66 
Baffling,  59 

boiler  efficiency  and,  63 

cliimney  temperature  and,  63 

draft  loss  and,  62 

exit  gas  temperature  and,  63 

extinguishing  action   with  vertical,  93 

flue  gas  temperature  and,  63 

furnace  temperature  and,  87 

head  room  for  vertical,  91 

Heine  boilera,  27 

smoke  and  horizontal,  87 

stack  temperature  and,  61 

verlical,  and  head  room,  91 

waste  heat  boilers,  141 


burning,  137 

composition,  477 

grate  bars  for,  99 

grates,  137 

heat  value,  475 
Bailey  boiler  meter,  598 
lialanced  draft,  584 
Ranked  fires.  568 

fuel  consumption  by,  568 

quick  steaming  from,  568 
Bark,  see  Tan  baric 


Barometer 
boiler  testing  and,  536 
chimneys  and  height  of,  173,  192 
Bends,  expansion  pipe,  2^ 
Best  Calorex  oil  burner,  121 
Birkholt-Terbeck  gas  burner,  130 
Bituminous  coal,  see  Coal,  bituminous 
Blast  furnace  gas,  128 
boiler  setting,  128 
burners,  130 
burning.  128 
composition,  483 
dust.  129 
explosions,   129 
heat  value,  483 
igniting  grate,  129 
Blow  down  of  safety  valves.  554 
Blowing  soot,  39.  41,  610 
Blow-off 
piping,  275 
valves.  274,  560 
Boiler, 
capacity  and  economy,  66 
circulation.  66,  568 

Heine,  35,  43 

quick  steaming  and,  568 
compounds,  510 

construction.  A.  S.  M.  E.  code,  49 
drums,  heat  insulation  of,  157 
efficiency,  546 

baffling  and,  63 

carbon  dioxide  and,  572 

characteristics.   66 

clinker  and,  461 

superheating  and,  69 

with  two  stokers,  105 
feeding,  see 

Centrifugal  boiler  feed  pnmps 

Feed  pumps 

Feed  water  heaters 

Injectors 

Water 
fittings,  551 
Heine  cross  drum,  43 
horsepower,  55 
inspection,  614 

precautions.  615 

report,  616 
operation, 

economical,  584 

under  "test  conditions."  585 

waste  heat  142 
plant  depreciation,  616 
rating,  55 

room  basement,  110 
settings,  85 

air  leakage,  153 

air  leakage  and  CO..  573 

air  leakage,  curing,  577 

air  leakage,  prevention,  157 

air  leakage,  testing  for,  577 


,,  Google 


Boi  1  e  r — Con  tinu  ed 
settings— Continued 
nir  space  in  walls.  ]45 
air-tight,  for  waate  heat,  142 
anchor  rods,  14JJ 
anthracite.  95 
arches  in,  153 
asbestos  coating,  157 
bagasse,  137 
blast  furnace  gas,  128 
brick  required  for,  147 
brickwork,  145 
buckstays,  148 
cargo  boats,  143 
chain  grate  stokers,  100 
classification.  92 
concrete,  147 
down  draft,  95,   100 
draft  loss.  11J6 
dredge  boat,  143 
fireclay  mortar,  147 
foundations,  145 
front  feed  stokers,  101 
gas  burning,  127 
.glazed  brick,  156 
high  smokeless,  91 
insulating,  155 
insulating  brick,   155 
magnesia  coating,  157 
marine.  143 
oil  burning,  117 
over  feed  stokers,   101 
powdered  coal,  III 
radiation,  153 
refuse  burning,  133 
shavings.  134 
side  feed  stokers,  100 
smokeless,  93 
steel  casing,  156 


toker 


,  too 


stokers, 

tic   rods,   148 

underfeed  stokers,  103 

walls.  145 

wall  ties,  155 

waste   heat,   139 

wood  chips.  134 

wood  chips  and  coal.  134 

specifications,  staridard,  49 

testing,  513 
accuracy,  515,  547 
air  temperature,  531 
ashes  and  refuse,  536 
ashes,  combustible  in,  545 
barometer,  536 
calculating  heat  ba  Ian  ire.  542 
calculating  simple  test,  528 
calorimeter,  Carpenter,  522 
calorimeter,  coal,  455 
calortmeter,  sas,  482 
calorimeter,  Junker,  482 
calorimeter,  Mahltr,  455 


•iler — Continued 
testi  n  g— Con  tin  ue  d 

calorimeter.  Peabody,  518 

calorimeter,  separating.  522 

calorimeter,  throttling,  518 

carbon  monoxide  loss,  545 

Car  pettier  calorimeter.  522 

chart.  526 

coal  sampling.  517 

coal  weighing,  517 

condition  of  boiler.  515 

data  required.  515 

draft  gages,  S36,  579 

efficiency,  boiler,  546 

efficiency,  furnace,  546 

efficiency,  overall,  546 

exit  gas  temperature.  529 

factor  for  moisture  in  steam,  ! 

factor  of  evaporation,  528 

feed  water  temperature,  517 

feed  water  weighing,  515 

flue  gas  analysis,  531 

Hue  gas  heat  loss.  54.1 

due  gas  temperature.  529 

furnace   temperature,   536 

gas  analysis,  532 

gas  analysis  apparatus,  532 

gas  analysis,  conversion,  543 

gas  sampling  continuous,  532 

gas  sampling  tubes,  531 

gaseous  fuel.  550 

guaranlee  tolerance,  547 

hand  firing.  523 

heat  balance  example.  546 

beat  balance  form.  541 

heat  losses,  542 

Hemp  el  apparatus,  535 

humidity  of  air,  535 

humidity  tables,   537 

hydrocarbon  loss.  546 

hydrogen  loss,  543.  546 

leakage  of  water,  516 

liquid  fuel,  550 

log  book.  526 

losses  unaccounted  for,  546 

mechanical   stokers,   525 
n  air,  536,  539 
n  air,  loss  by,  545 
n  coal,  loss  by,  542 
...    _  .n  steam,  518 

observations,   525 

Onat  apparatus,  532 

Orsat  operation,  533 

Peabody  calorimeter,  518 

personnel,   513 

radiation  loss,  546 

records.  525     ■ 

report  of  complete  test.  540 

report  of  simple  test,  526 

sampling  coal,  517 

samplit^  gat,  531 


i,  Google 


Boiler — Continneil 

testing — Continued 
sampling  steam,  523 
separating  calorimeter,  522 
starting  and  stopping,  523 
steam  pressure,  518 
Steam  quali^,  518 
steam  ubies,  523 
superheated  steam,  523 
temperature  of  air,  531 
temperature  of  feed  water,  517 
temperature  of  flue  gases,  529 
temperature  of  furnace,  536 
throttling  calorimeter,  518 
unaccounted  for  losses,  546 
water  gages,  516 
water  meters,  516,  587 
weighing  coal,  517 
weighing  feed  water,  515 
weighing  scales,  517 
weight  of  gases,  543 

the  lirst  Htine,  52 

tubes,  conductivity,  383 

wall  insulation,  367 

water  gages,  516,  551 

with  two  stokers,  105 

air-tight  settings  for  waste  heat,  142 
baffling,  59 

waste  heat,  141 
blowing  soot,  610 

Heme,  39.  41 
cleaning,  610 
Heine,  21,  39,  41,  43 
vection  and  heat  transfer,  385 
I  waste  heat,  141 


"cutting  in."  614 
dead  gas  pockets,  59 
draft  loss,  62,  186 

waste  heat,  142 
dusting,  6)0 

dust  in  waste  heat,  142 
fans  for  waste  heat,  142 
feed  water  heating  in  Heine,  35,  45 
gas  pockets  in,  59 
heat  transfer,  389 

waste  heat,  141 
Heine 

cross  drum,  43 

longitudinal  drum,  23 

marine.  47 
high  draft  loss,  142 
high  gas  velocity.  141 
idle,  613 
stand-by,  S68 

steam  separation  in  Heine,  35,  43 
temperature  drop  in,  389 
waste  heat,  139 

water  purification  in  Heine,  19,  35,  45 
zinc  plates  in  marine,  49 


Boiling  point  of  water  at  different  pres- 
sures, 500 
Bomb  calorimeter.  455 
Botmot  powdered  coal  system,  112 
BonrdoH  pressure  gage,  555 
BradthaW'Fraser  gas  burner,  131 
Brady  {HarringtoH)  stoker,  168 
Breechings,  214 

arrangement.  219 

baffles  in,  217 

cleaning  doors.  217 

construction,  217 

design,  215 

draft  loss  through.  187 

example  of.  218 

insulation.  220,  367 

size  of.  214 
Brick 

arches,  153 

boiler  settiiws, 
glazed,  156 
insnlating,  155 
vitrified.  156 

chimneys,  201 

tire.  148 

plastic  fire,  152 
Bricks,  number  of,  for  settings,  147 
Brickwork 

boiler  settings,  145 

smokeless  combustion,  85 
Bridge  wall 

cleaning  table,  567 

^s  passage  area  over,  93 
British  thermal  unit,  378 
Briquets,  469 


inthra 


■-   470 


carbocoal,  471 

lignite,  471 

peat.  471 

weight  of,  466 
BucksUys,  148 
Bunkers,  coal,  608 
Burners, 

gag.  128 

oil.  119 

powdered  coal,  116 

tar,  125 
Burning  superheaters,  76,  555 
Buying  fuels  under  contract,  486 

C 

Calibrating 

pyrometers.  370 

thermometers,  370,  373 

water  meters,  516 
California  oil,  heat  value,  479 
Calorex  oil  burner,  121 
Calorimeter, 

bomb.  455 

Carpenter  separating,  522    ■. 

coal,  455 

formula  for  throttling,  521 


,  Google 


Calorimeter — Continued 

033,482 

Junktr  gas,  482 

Mahler  bomb,  455 

Peabody  steam,  518 

separating,  522 

steam  connection.  523 

throttling,  518 
Campbells  coal  classification,  437 
Cannel  coal,  437 
Carbocoal  briquets,  471 

combustion  data,  393 

determinaiion  in  coal,  451,  453 
Carbon   dioxide 

boiler  efficiency  and,   S?2 

careless  firing  and,  572 

excess  air  and,  572 

desirable  percentage,  572 

dirty  fires  and,  S?5 

leaky  setting  and,  573 

recorders,  5?7 

specific  heat  of,  403 

weight  of  flue  gases  and,  179,  543 
Carbon  monoxide 

combustion  data,  393 

heat  loss  due  to,  545.  577 

recorders,  578 

specific  heat,  403 
Carpenter  calorimeter,  522 
Cast  iron. 

effect  of  heat  on,  97.  252 

for  grates,  96 

strength  of,  97.  271 

superheated  steam  and,  83 
Cast  steel  and  superheated  steam,  83 
Caustic  embrittlement.  511 
Causticity  of  feed  water,  503.  SOS 
Celsius  temperature  scale,  369 
Cement. 

plastic  fireclay,  152 

settings  coated  with  asbestos.  157 
Centigrade  temperature  scale,  370 
Centrifugal  boiler  feed  pumps,  302 

capacity.  305 

characteristics,  303 

DeLavfa,yS6 

efficiency,  305 

horsepower,  305 

hot  water  capacity,  318 

Lta-Co%rtenay,  307 

motor-driven,  313 

regillatu^.  313 

single-stage,  306 

turbine  driven,  305,  345 

with  low'pressure  economizer,  306 
Check  valvfis.  274 
Chimneys,  1/3 

anthracite,  173 

at  altitudes,  192 


Chimneys — Continued 
B.H,P.  and  draft  table,  176 

baffles  in,  217 
brick. 

ladders  on,  206 

lining  for,  205 

radid.  201 
capacity  table,  176 
characteristics,   177 
cinders,  discharging,  _.., 
cleaning  doors,  195,  207 
coal  burned,  weight  of,  185 
coal  burning, 

anthracite,  173 

western.  184 
concrete.  207 

design  of,  209 

erection  of,  210 
connections  for 

fiues.  214 
,  induced  draft  fans.  241 
cost  by  height.  173 
defective,  strengthening.  214 
deflectors  in.  217 
draft 

capacity  and.  181 

H.P.  and,  table,  176 

losses  tabulated,  187 

loss  in.  182 

required,  187 
evas3,  191 
examples,  J 84 
flue  openings  in,  214,  241 
foundations,   193 

sizes.  194 
gas  basis,  design  on.  189 
gas  burning    190 
gases. 

heat  of  fuel  in,  334,  543 

weight  of.  182,  543 

gyed  steel,  197 
P.  and  draft  table,  176 
height, 

anthracite,  173 

cost  and,  173 

economical,   173 
highest,  173,  216 

concrete,  211 
joints  in  steel,  200 
ladders, 

brick,  206 

steel,  195 
lightning  rods,  206 

bride,  20S 

steel,  195 
municipal  refuse,  191 
oil  burning.  189 
power  plant  typical.  184 
pressure  of  wind,  193 


ib.  Google 


Chimneys — Continued 
radial  brick,  201 
refuse,  municipal,  191 
reinforced  concrete,  207 
reinforcing  old  brick,  213 
remodeling,  214 
self-tupporting  iteel,  194 
soot  collectors  in,  207 
steel, 
guyed,  197 


join 


I,  200 


ladders  o  . 

lining  for,  195 

self-supi>orting,  194 
strengthening  defective,  214 
stoker  firing,  184 
table,  draft  and  H.P.,  176 
temperature, 

drop  in,  174 

gases,  average,  181 
typical  power  plant,  184 
velocity  of  gases  in,  189 
venturi,  191 
wind  pressure  on,  193 
wood  burning,  191 
Cinder  separating  fans,  237,  572 
Cinders  from  chimneys,  572 
Circnlation,  see  Bailer  circulalicin 
Geaning 
boilers,  see  Boilers,  cleaning 
coal,  458 
fires,  567 

anthracite.  568 

CO.  and,  575 
Ubie.  567 
Cleveland  stoker,  159 
Clinker,  459 
adherence,  151 
avoiding.  466 
boiler  efficiency  and,  461 
hard,  459 
Illinois  coal,  462 
Indiana  coal,  462 
soft,  461 
sticking,  151 
U.  S.  coals,  463 
Coal, 
air  required,  395 

per  10,000  B.t.u.,  189 
analyses,  440 
analysis,  450 

statements,  450 
anthracite,  436 
ash, 

and  heat  value  of,  458 

fusibility,  463 

reduction   in,   458 
bituminous.  436 

fuel  bed  thickness,  566 

hand  firing,  560 
briquets,  469 


Coal — Continued 
bunkers,  608 

burners  for  powdered,  115 
burning  powdered.  111 
buying  under  contract,  486 
calorimeter,  Mahler,  455 
cannel,  437 
carbon  in.  453 
classification, 

composition,  437 

geological,  435 
clinker,  459,  562 
composition.  435,  440 
consumption, 

banked  lires,  568 

stand-by  boilers,  563 
conveyors,  60S 

apron.  607 

belt.  607 

flight,  605 

pivoted  bucket,  607 

scraper,  605 

screw.  605 
crushers,  607 
draft  for,  185 

evaporation  and  ash  in.  459 
-gas, 

composition,  483 

heat  value  of,  483 
gases,  weight  of  flue,  543 
geological  classification,  435 
hand  firing, 

anthracite.  562 

bituminous.  560 
handling,  603 

see  Coal  conveyors 
heat  value  by 

ana1}>^is.  453 

calorimeter,  455 
hydrogen  in,  453,  543 
location  of  deposits,  437 
meter,  helical  vane.  602 


analysis,  450 

loss  due  to.  5« 

sampling,  517 
nitrogen  in.  453 
oxygen  in,  453 
powdered, 

burners,  115 

burning,  111 
proximate  analysis.  451 
sampling,  445 

boiler  testing.  517 

errors,  547 
semi -anthracite.  436 
semi-bituminous,  436 


ly  Google 


Coal — Con  f  i  nued 
specifications,  486 
spontaneous  combustion  of,  467 
spoats,  608 
storage,  603 

circular,  605 

deterioration,  467 

rectangular,  60S 

submerged,  605 

sub-bituminous,  436 

sulphur  in,  451,  463 


-tar,  s 


E  Tar 


ultimate  analysis,  451 
unloading,  603 
volatile  matter,  451 
volume,  467 
washing,  458 

weighing,  see  Boiler  testing 
continuous,  599 
conveyor  scales,  599 
helical  vane,  602 
hopper  scale,  601 
hopper,  traveling,  601 
stoker  speed,  602 
I  rack  scales,  599 
traveling  hopper.  601 
traveling  larry,  602 
weight  of,  466 
Cochrane  feed  water  heater,  325 
Cnchrane  water  softener.  509 
Coen  oil  burner,  123 
Coke, 
breeze,  474 
composition,  473 
heat  value,  473 
-oven  gas, 
burning.   131 
composition,  483 
heat  valne.  483 
weight  of,  474 
Colloidal  fuel,  481 
Combustion,  389 
air  required, 
actual.  397 
theoretical,  394 
ashpit.  111 

baffle   furnace   roof  and,  65 
chamber.  85 
bhst  furnace  gas,  128 
pas  pas^aitc  areas.  93 
Heine  boilers,  21,  37 
natural  gas,  127 
oil.  117 
shape  of,  90 
size  of,  85 

surface,  oil  burning,  117 
temperature,  86 
chemistry   of,   390 
data.  393 
furnace 
temperature  and,  86 


Combustion — Con  tinned 

f  u  rnace — Con  tinned 
volume  and,  87 

heat  of,  394 

losses.  397 

rate.  57 

requirements,  85 

space, 
grate  area  and,  89 
required.  85,  89 

spontaneous,  of  coal,  467 
Combustion  Eng.  Co.,  Type  "E"  stoker. 

161 
Concrete 

boiler  settings,  147 

chimneys,  207 
Condensers,  heat  transfer  in.  389 
Conduction  of  heat,  379,  383 
Conductivity, 

boiler  tubes,  383 

insulation,  155 

materials.  351 
table  of,  353 

refractories.  15S 
Cones,  Seger,  377 
Continental  stoker,  167 
Control  boards,  584 
Convection,  379,  385 

waste  heat  boilers,  141 
Conveyors,  wood  refuse  and  pneumatic, 
133 

see  Coal  conveyors. 
Copes'  feed  water  regulator,  314 
Cork  heat  insulation.  357 
Corn,  heat  value,  474 
Corrosion, 

feed  pumps.  301 

feed  water  and,  510 

gases  in  feed  water  and,  503,  510 

marine  boilers,  49 
Cost 

accounts  of  generating  steam.  616 

boilers  by  heating  surface,  57 

comparison  of  boiler  feed  pumps,  305 

reducing,  of  generating  steam.  587 

reduction,  Folakov  method  of  power, 
585 
Coxe  stoker,  168 
Crushers,  coal.  607 
Culm,  grate  bars  for,  97 
"Cutting-in"  boilers,  614 

D 

Dampers,  220 
balancing.  222 
design,  221 
details,  222 
forced  draft,  23S 
induced  draft,  241 
operation  of.  222 
regulators,  584 


,,Goog[e 


DfLaval  centrifugal  feed  pump,  306 
Depreciation  of  boiler  plant,  616 
Destructor  chimneys,  refuse,  191 
Detrkk-Hagan  ash  conveyor,  609 
Detroit  stoker,  159 
Diatoniaceous  earth,  357 
DifFerential  draft  gases,  580 
DisengaginS  surface,  steam,  67 
Down  draft  furnace,  9S,  100 
Draft 
anthracite,  small,  173,  562 
balanced,  584 
chimney  capacity  and,  181 
coal  bumiiw,  IsS 
diagrams,  ^3 
ducts,  forced,  235 
air  leakage,  236 
forced,  227 
gases, 
boiler  testing,  536 
choked  passes,  581 
compound,  ^O 
connections,  580 
diaphragm,  580 
differential,  580 
flow  meter,  581 
liquid   for.  580 
multiple.  580 
poor  fires.  S81 
simple,  579 
slanting  tube,  580 
small  pressure  differences,  580 
gas  burning,  190 
induced,  236 

579 


lignite.  566 

accelerating  gases,  187 
air  heaters,  339 
altering  gas  velocity,  187 
baffling  and,  62 
boiler  setting.  186 
chimnevs,  I& 

186 


t  boiler 


142 


losses  tabulated,  187 

mechanical.  223 

oil  burning.  189 

pressures,  forced,  227,  231 

rcKulators,  584 

table,  chimneys.  176 

wood  burning,  191 
Ducts,  forced  draft.  235 

air  leakage  in.  236 
Dudgeon  tube  expander,  613 
Dulong  formula,  454,  479 
Dumping  grates,  97,  568 
Dust 

blast  furnace  gas.  129 


Dust— Continued 
blowers 

baffles  and,  65 

boilers,  39.  41,  610 

economizers,  333 

superheaters,  31 
doors,  leaking,  153 
separating  fans,  237 
waste  heat  boilers,  141 

E 
Earth,  diatomaceous,  357 
Economizers,  331 

counter  flow.  334 

dimensions,  337 

draft 
diagram,  225 
loss  through,  186 

Green,  333 

heating  surface,  337 

heat 

recovery  by,  335 
transfer  rate,  335 

integral.  331 

low  pressure,  306 

performance,  333 

saving  effected  by,  333 

scrapers,  333 

soot  blowers,  333 

steel  tube.  331 

surface.  337 
Electrical  pyrometers,  373 
Electrolysis  and  corrosion,  510 
Embrittlement.  caustic,  SII 
Engines, 

auxili^y,  341 

fan.  343 

pump,  309 

stoker,  343 

superheated  steam,  69 
Entropy,  407 

diagrams,  414 
Peabody,  4!S 
MoUier.  416 
superheated  steam,  69 
Equivalent 

evaporation,  55,  528 

mechanical,  of  heat,  378 
Erosion  of  turbine  blades,  73 
Esehka's  method  for  sulphur,  451 
Evaporation 

ash  in  coal  and,  459 

equivalent.  55,  528 

factor  of,  55,  528 

rate,  57 

rate  and  circulation,  66 
Evase  chimneys,  191 
Everlasting  blow-off  valve,  560 

carbon  dioxide  and,  572 
general  effect,  575 


,,  Google 


Excess  aii^G>Dtuine<l 

weight  of  gases  and,  179 
Exit  gases,  see  Flue  gases 
Expansion, 

adiabatic  407,  414 

firebrick,  149 

force  of,  piping,  286 

isothermal,  407,  414 

joints,  286 

metals,  coefficients.  283 

nozzles,  417 

pipe  bends,  287 

piping,  283 

steam,  407 
Explosion  doors,  129 
Explosions  with  blast  furnace  gas.  129 
Extinguishing  action  with  vertical  baf- 
fling, 93 

F 
Factor 

for  moisture  in  steam,  S28 

of  evaporation,  SS,  528 
Fahrenheit  scale,  370 

characteristics,  229 

chimney  connections  for  induced  draft, 

241 
cinder  separating,  237,  572 
damoers  for 

forced  draft,  235 

induced  draft,  241 
density  of  gases  with  induced  draft, 

239 
dirt  unbalancing,  229,  236 
drives,  238 
ducts,  235 

efficiency,  induced  dr%ft.  240 
engine  and  feed  pump,  3(^ 
engines,  343 

erosion,  induced  draft,  236 
forced  draft,  227 

ducts.  235 
H.P.  output,  235 
inlet  screens,  236 
load  on  induced  draft.  239 
operating  difficulties,  229 
output.  235 
performance.  232 
pitot  tube,  testing.  232 
safe  tip  speed,  232 
screens,  236 
sizes, 

forced  draft.  228 

induced  draft,  237 

induced  draft,  237 
safe.  232 
test.  232 
testing,  232 
induced  draft.  240 
pitot  tube,  232 


Fans — Continued 
turbine  driven,  227,  343 
types  of,  229 
waste  heat  boilers,  142 
water-cooled  bearings,  237 
weakened  by  heat,  239 
weight, 

forced  draft,  228 

induced  draft,  237 
Feed  pumps,  297 
air  chambers,  296 
automatic  regulation,  310 
bronze  fittings,  301 
capacity, 

duplex,  299 

hot  water,  299,  317 

simplex,  298 

single  cylinder,  296 
centrifugal,  see  Centrifugal  boiler  feed 

pumps 
corrosion,  301 
cost  comparison,  305 
direct  acting 

power,  309 

steam,  297 
duplex,  299 
excess  pressure,  297 

regulator,  310 
knocking,  S9 
motor  driven,  311 

regulator,  311 
performance,  301 
piston  speed,  299 
power  driven,  309 
pressure  regulator,  310 
regulation,  313 
"short  stroking,"  298,  299 
simplex,  296 
single  cylinder.  298 
"steam  bound."  299 
steam  consumption,  302,  305 
suction  lift,  317 

hot  water,  317 
suction  piping,  318 
triplex.  309 

volumetric  efficiency.  298 
Feed  water,  see  Water 
constant  excess  pressure,  310 
economy  of  beating,  323 
heaters,  323 

closed,  327 

Cochrane,  325 

filter.  326 

metering,  325 

oil  separating,  326 

open.  323 

PaUerson-Berryman,  327 

regulation  of  exhaust  steam  to.  326 

removal  of  air  in,  329 

■election  of,  330 


ib.  Google 


Feed  water — Continued 

beatii^  in 
Heine  boilers,  35,  45 
ice  plants,  329 

purification  in  Heine  boilers,  19 

quantity  required.  297 

regulators,  310 

steam  required  to  heat,  325 
Felt,  hair,  357 

Ferguson  tube  expander,  613 
Firy  pyrometer,  377 
Filters, 

feed  water  heater,  326 

water  treatment,  508 
Firebrick,  148 

air-cooted  blocks,  151 

arches,  153 

blocks, 
air-cooled.  151 
perforated,  151 

commercial,  149 

compression  of,  149 

effect  of  ash  on.  151 

expansion  of,  149 

fusing  point,  149 

hardness,  149 

mortar  for.  151 

nodules,  ratio  of,  149 

plastic,  152 

plasticity  of,  148 

special  blocks,  148 

standard  shapes,  150 

surface,  oil  burning,  117 

weight  of.  151 
Fireclay,  148 

cements,  plastic,  151 

mortar.  151 

plastic  cement,  151 

ashpit,  in,  Idl 
cleaning,  567 

protection  and  stand-by  boilers,  56S 
sand.  151 
Fires,  banked,  568 

carbon  dioxide  and,  574 

tools.  563 
Flexible  metallic  pipe,  293 
Flooding  superheaters,  76 
Flow  meter 

draft  gage  as,  581 

RepubUe.  594 

steam,  595 

variable  orifice,  597 

water.  594 
Flow  of  steam, 

Grashof.  421 

Napier.  421 

nozzles,  417 

P,>0.S8P„  421 

Raleau,  420 


Flue  gases, 
air  heaters.  339 
analysis,  531 

apparatus,  532 

conversion  to  weight.  543 

OrMt,  532 
heat  of  fuel  in.  334 
loss  due  to  CO  in.  545 
loss  due  to  heat  in,  543 
sampling, 

continuous.  532. 

tubes.  531 

temperature,  178.  529 
baffling  and,  61,  63 
elTiciency  and,  574 
superheating  and.  69 

weight  of,  182,  543 
Flues, 

baffles  in,  217 

cleaning  doors.  217 

construction  of.  217 


defied 


1,  217 


_i  of,  215 
example  of.  218 

draft  loss,  182,  187 

insulation,  220 

size.  184.  214 

underground.  220 
Fluxes  in  fireclay  mortar,  151 
Foaming  and  bad  water,  510 
Foersi  oil  burner,  121 
Forced  draft, 

air  required,  227 

ducts,  235 

fans,  see  Fans 

pressures.  227 
Foundations, 

boiler  settings,   145 

chimneys,  193 
Fraier's  coal  classificati 
Fuel,  435 

air  required,  395 


437 


colloidal,  481 

consumption,  banketl  fires.  568 

errors  m  moisture  in,  547 

gaseous.  482 

heat  value,  see  fuel  in  question 

high,  485 

low,  485 

wet,  477 
hydrogen  loss,  543 
liquid.  478 
loss  due  to 

hydrogen  in.  543 
■■        in,  542 


ib.  Google 


Fuel — Continu  ed 
moisture  in, 
errors,  547 
finding,  450,  517 
loss  by,  542 
oil.  see  Oil 
sampling,  445 
boiler  testing,  517 
errors,  547 
superheating,  extra  for,  69 
weight  of  gases,  543 
wet,  heat  value  of,  477 
Furnaces. 
air-cooled  lining,  151 
arches,  1S3 
baffle  roof,  65 
boiler  settings  and,  85 
chamber,  gas  passage  areas,  93 
desigii  of,  85 
down  draft.  95.  100 
gases  from  industrial,  temperature  of, 

141 
industrial,  temperature  of  gases  from, 

141 
linings,  air-cooled,  151 
oil  burning,  119 

smoke  and  down  draft,  95,  100 
smokeless,  93 
temperature, 
complete  combustion  and,  86 
observing,  536 
theoretical,  394 
tile  roof  and,  87 
volume,  see  fuel  in  question 
Fusible  plugs,  560 
Fusion  of 
ash,  461 
firebrick,  149 

G 
Gage, 
boiler  water.  516,  551 
piping,  boiler  water,  551 
Gages, 


Gas, 
see 
Blast  furnace  gas 

Coal  gas 
Coke-oven  gas 
Flue  gases 
Natural  gas 
Oil  gas 
Producer  gas 
Water  gas 
analysis,  532 
CO  recorders,  S78 
COi  recorders,  577 
Hemp  el  apparatus.  535 
OrMi  apparatus,  532 


Gas — Continued 
burners,  128 
burning,  127 

settings,  127 
call 


.  482 
passage  area,  59,  93 
pockets,  dead,  59 

producer  and  superheated  steam.  83 
sampling, 

errors,  547 

flue.  531 
temperature  drop, 

chimneys,  174 

over  heating  surface,  387 
velocity, 

beat  transfer,  385 

waste  heat  boilers.  141 
Gaseous  fuels,  482 

density  of,  399 

in  feed  water  and  corrosion,  503,  510 

pressure  effect,  398 

properties,  398 

specific  heat  of,  399,  401 

temperature  effect.  398 


to\ar 


.  398 


weight,  ;.  _ 
Gate  valves.  273 
Globe  valves,  273 
Goodenough's  steam  tables,  424 
Graphite,  436 
Grashof,  flow  of  steam,  421 

air  space,  58,  97 
bar  openings,  S8,  97 

anthracite,  97 

bagasse,  137 

cast  iron  for,  96 

culm.  97 

heat  effect  on  east  iron,  97 

herringbone,  97 

hoUow,  99 

slotted,  97 

Tupper.  97 
hand  firing,  96 
inclination,  100 
length,  99 
slope,  100 
surface,  57 

anthracite,  562 

ratio,  5a  562,  567 
water.  95,   100 
Green  economiier,  333 
Green  stoker,  168 
Guys  for  steel  chimneys,  201 

H 

Hagan  ash  conveyor,  609 
Hair  felt.  357 
Hammel  oil  burner,  120 


,,  Google 


Hammond  water  meter,  589 
Hand  firing,  560 

anthracite,  562 
low  volatile,  563 
setting,  95 

ashpit,  107 
large,  109 

CO,  and,  574 

coal  cars,  563 

depth  of  grate.  99 

frequency,  S6S 

grates,  96 

losses,  565 

methods,  560 

rules,  561 

space  for,  563 

thickness  of  lire,  566 

tools,  563 
Handhole  caps.  Key,  27,  47,  54 
Hard  coal,  see  Anthracite 
Harrington  stoker,  168 
Hayt  draft  gage,  560 
Head   room, 

furnace   for   soft   coal,  90 

smokeless  settings,  91 

stolcer  settings,   100 

vertical  baffling,  91,  93 
Heat 

balance, 
calculating,  542 
example,  546 
form  of,  54 1 

combustion,  of,  391 

conduction,  383 


effect  on  strength  of  materials,  97,  239. 

252 
insulation,  347 

air  currents,  361 

breechings,  220,  367 

boiler  drums,  157,  365 

boiler  settings,  15S,  3^ 

cold  water  pipes,  367 

commercial,  354 

conductivity.  156,  353 

cork,  357 

economy,  349 

efficiency.  360 

flues.  220,  367 

hair  felt.  357 

loose,  361 

"magnesia,  8S%,"  357 

painting,  361 

pipe  size  and,  360 

piping,  360 

piping,  outdoor,  367 

piping  in  trenches.  367 

piping  in  tunnels,  367 

piping,  underground,  367 

settings.  155 

surface  finish,  361    ___ 

turf ace  r    * 


Heat— Continued 
insulation — Continued 

thicliness,  360 

uses  of,  355 

walls,  367 

waste  without,  349 

weight  of,  355 
loss, 

bare  surfaces,  348 

CO  in  flue  gases,  54S.  577 

combustible  in  ash,  S4S 

commercial  insulators,  354 

hydrocarbons,  546 

hydrogen,  543^ 

moisture  in  air,  545 

moisture  in  coal,  542 

radiation,  546 

soot   formation,   547 

unaccounted  for,  546 
losses,  see  Heat  balance 
mechanical  equivalent  of,  378 
radiation,  379 
resistance,  385 

asbestos,  357 
specific,  378 

gases,  399 
theory,  369      __ 
transfer,  58,  378 

air  heaters.  339 

boilers.  389 

condensers,  389 

convection,  385 

economizers,  335 

gas  velocity  and,  385 

insulation,  359 

scale  and,  511 

superheaters,  81 

surface  resistance,  347 

waste  heat  boilers,  141 
treatment,  feed  water,  507 
units.  378 
values,  see  fuel  in  question 

Dulong  formula,  454,  479 
Heaters, 
air,  339 

feed  water,  see  Feed  water  hi 
Heating  surface,  57 
cost  of  boilers  by,  57 
economizer,  337 
evaporation  rate,  57 
gas  temperature  drop  over,  , 
ratios,  sis 

anthracite,  5^ 

tan  bark.  567 
Height  of  furnace  chamber  am 
smoke,  90 
stoker  settings.  100 
vertical  baffling,  93 
Heine 
baffle  tile,  66 
boiler,  the  first,  52 


ib.  Google 


Heine — Continued 
boilers, 
baffling,  27 
circulation.  19,  5 
cleaning,  21 
cross  drum,  43 
longitudinal  drui 
:.  47 


23 


overload  capacity,  19,  568 
small  space  re<iuired,  31 
water  purification  in,  19 

by-pass  superheater,  78 

marine  suoerheater,  49 

service.  23 

soot  blowers,  31,  41 

superheat  control.  29,  78 

superheaters,  29,  78 
Heine  reinforced  concrete  chimney,  209 
Hempel  gas  analysis  apparatus.  535 
Henderer  tube  expander,  613 
High 

draft  loss,  waste  heat  boilers,  142 

gas  velocity  heat  transfer.  38S 

heat  value  of  fuels,  485 

pressure  feed  pumps,  301 

anthracite,  96 
smokelessness,  91 
vertical  baffling,  91 

water  signal,  551 
Hog  wood 

firing,  566 

fuel  bed  thickness,  566 
Hopper  ashpits,  109 
Horizontal  bafHing,  61 

flame  travel  and.  93 

furnace  temperature  and,  87 

smoke  and,  87,  93 
Horsepower,  boiler,  55 
Hoi  water  and  feed  pump 

capacity,  299,  317 

corrosion,  301 

suction  lift.  317 
Huddling  chamber,  safety  valves,  554 
Humidity  of  air, 

heat  loss  due  to,  545 

observing,  536 

tables,  537 
Hydrocarbons,  heat  loss  due  to,  546 
Hydrogen, 

combustion   data,  393 

in  fuels.  453 
heat  loss  due  to,  543 

specific  heat,  404 


iriinots  stoker,  169 

Impact  pressiure,  pitot  tube,  233 


Induced  draft,  236 

chimney  connection,  241 

cinder  separating  fan,  237,  572 

dampers,  241 

density  of  gases,  239 

diagram.  ^ 

dirt  untnUancing  fans,  236 

erosion  of  fans,  236 

fan  speeds,  237 

sizes  of  fans,  237 

weights  of  fans,  237 
Infusorial  earth  (Kieselguhr),  357 
Injectors,  319 

"breaking,"  323 

exhaust  steam.  323 

inspirators,  322 

live  steam.  319 

scale  in,  323 

steam  pressure  range,  321 

suction  lift  321 

suction  piping,  323 

superheated  steam,  321 

thermal  efficiency,  323 
Inleakage  of  air, 

see  Air,  leakage  in  settings. 
Inspection  of  boilers,  614 

precautions,  615 

report,  616 
Inspirators,  322 
Instrument  boards.  584 
Insulating  brick,  155 
Isothermal  expansion,  407,  414 


Jet  blowers.  227 
Jones  stoker,  162 
Junker  gas  calorimeter,  482 


Kellog  chimneys,  203 
Kent  chimney  table,  176 
Key  handhole  caps,  27,  47,  54 
Kieselguhr,  357 
Kirkwood  gas  burner,  128 
Kling-Weidlein  gas  burner,  130 
Koerting  oil  burner,  123 
oil  burning  system,  123 


Laclede-Christy  stoker,  170,  566 
Ladders, 

brick  chimneys,  206 

steel  chimneys.  195 
Lance,  steam,  43 
Laning,  or  stratification.  93 
Larry,  coal  weighing,  602 
Lea-Courtenay    centrifugal    feed   pump, 


307 


i,  Google 


632 

INDEX 

Ugnite,  436 

Meters— Continued 

briquets,  471 

water— Continued 

composition,  436 

V-notch  formula,  591 

firing.  566 

volumetric.  589 

forced  draft,  566 

Model  stoker,  161 

fuel  bed  thickness,  S66 

Moisture  in 

heat  value,  436 

air,  536,  545 

moisture  in,  436 

coal,  450,  517 

weight  of,  466 

errors,  547 

Lining, 

fuels,  see  fuel  in  question 

air-cooled  furnace.  151 

loss  due  to,  477,  542 

brick  chimneys,  205 

steam.  518 

steel  chimneys,  I9S 

factor  for.  528 

Lipiak  flat  arch,  153 

Molecular  weights.  391 

Liquid  fuels,  478 

M oilier  diagram,  416 

boiler  tests,  550 

Moloch  stoker,  162 

Load 

Mono  CO,  recorder,  578 

dispatching,  569 

Mortar, 

signals.  569 

firebrick.  147 

Lopulco  powdered  coal  burner,  116 

fluxes  in,  151 

feeder,  115 

fusion  of,  151 

Low 

weight  of  fireclay.  151 

heat  value  of  fuels,  485 

Muck-i  coal  classification,  437 

water  signal,  5SI 

Mud  drum,  internal,  35,  45 

Lubrication  and  superheat,  7S 

N 

Napier,  flow  of  steam,  421 

M 

Marine 

boilers 

National  stoker,  171 

corrosion,  49 

Natural  gas 

Heine.  47 

burners,  128 

settings,  143 

burning,  127 

zinc  plates  in  49 

composition,  483 

superheaters,  49 

heat  value,  483 

Mason  damper  regulator,  583 

working  pressure,  482 

Mechanical 

Navy  oil  specifications.  497 

draft.  223 

Nitrogen 

equivalent  of  heat,  3/8 

in  coal.  453 

stokers.  159 

specific  heat  403 

chain  grate,  167 
front  Feed,  159 

Noizles,  steam,  417 

convergent,  419 

hand  operated,  171 

expansion,  417 

overfeed.  1S9 

P,>0.58P„  421 

settings.  lOO 

Roteau,  420 

side  feed.  159 

underfeed.  161 

O 

treatment  of  water,  SOS 

Oil. 

Megass,  see  Bagasse 

atomizing,  119 

Mercury  thermometers.  373 

burners,  119 

Meters, 

location.  119 

Bailey  boiler,  598 

burning,  117 

coal,  helical  vane,  602 

boiler  tests,  550 

steam  flow.  S9S 

chimney  table,  190 

variable  orifice.  597 

water,  587 

combustion  chamber,  117 

hoiler  testing.  516 

fire  brick  surface,  117 

furnace  design,  119 

(Cravimetric.  589 

consumption,  stand-by  boilers. 
crude,  479 

Venturi  capacities.  593 

Venturi  diagram,  590 

fuel,  478 

Venturi  fonnula,  591 

handling,  610 

V-notch,  589 

,  Google 


INDEX 

Oil— Continued 

Pipe— Continued 

fuel— Continued 

fi  ttings — Cont  inued 

heat  value,  479 

east  iron,  281 

settings,  117 
specifications,  497 

cast  steel,  261 

flange,  263 

specific  gravity,  479 

flange  unions,  267 

gas, 

flanged,  12S  lb.,  265 

flanged,  250  lb.,  268 

heat  value.  483 

general,  261 

heater,  124 

malleable  iron,  261 

and  pump,  124 

names  of.  264 

separation  in 

nut  unions,  265 

feed  water  heaters,  326 

flanges, 

Heine  boilers,  4S 

125  lb,  267 

separators,  293 

250  lb.,  269 

materials,  271 

composition,  481 

hangers,  293 

heat  value,  481 

headers,  cast  steel,  252 

•tar,  481 
Operating 
cost  of  feed  pumps,  305 

insulation,  360 

double  extra  heavy,  2S6 

cost  of  steam  generation,  617 

extra  heavy,  255 

economical  boiler,  584 

large  0.  D..  257 

under  "test  conditions,"  585 

standard,  253 

waste  heat  boilers,  142 

steam,  saturated,  276 

Optical  pyrometer,  377 

steam,  superheated,  281 

Orifice,  steam  flow.  421 

water,  281 

Orsal  apparatus,  532 

strength  of,  257 

operation.  533 

supports,  293 

solutions,  533 

water,  260 

Oxygen 

weight, 
brass,  260 

in  coal.  453 

specific  heat,  403 

copper,  260 

P 

double  extra  heavy,  256 

Pattcrsou-Berryman  feed  water  heater, 

extra  heavy.  255 

327 

large  0.  D.,  257 

Peobody 

standard,  253 

calorimeter.  518 

Pipes. 

entropy  diagram,  415 

flow  of 

Peat.  435      ^ 

steam  in,  275 

briquets,  471 

water  in,  281 

heat  value,  436 
weight,  466 
Peck  pivoted  bucket  conveyor,  606 

friction  pressure  drop,  275 

size' charts.  277 

Pipe 

velocity,  275 

anchors.  286 
brass,  252,  260 

velocity, 

steam.  275 

bursting  pressure,  257 

water,  283 

capacity, 

double  ^xtra  heavy,  256 
extra  heavy.  255 
standard,  253 

/•utt    irnn     7^^ 

Piping, 
blow-off,  275 
boiler  water  gage,  551 
color  identification,  251 

ca3i   iron,  iji 

condensation  and  superheating.  69 
copper.  252, 260 
extra  heavy 

design,  243 
diagram,  251 
drainage  of  steam,  243 

brass,  261 

expansion 

copper.  261 
iron,  255 

and  contraction,  283 
bends,  287 

heat  effect  on  strength  of,  252 

force,  286 

fittings, 

joints,  286 

brass,  263 

of  matenals,  285 

,  Google 


P  ipi  ng — Continued 
feed  pump  suction,  318 
flaage  joints,  267 
identification,  251 
insulation,  360 
materials, 

expansion  of,  285 

moduli  of  elasticity,  286 
saturated  steam,  259 
screwed  flanges,  268 
slope  of  steam,  243 
steam,  draining,  243 
superheated  steam,  69,  83,  259 

duplicate  header,  245 
loop  header,  247 
ring  header,  247 
selection,  244 
single  header,  244 
unit,  247 

unit,  modified,  249 
Van  Stone  joint,  271 
vibration  in  steam.  243 
water  in  steam,  243 
water  hammer  in  steam,  243 
welded  flanges,  271 
wrought  iron,  251 
Pitot  tube,  232 
double,  233 
water  meter,  591 
Plastic 
firebrick,  152 
fireclay  cements,  151 
Plasticity  of  firebrick,  148 
Playford  stoker,  170 
Foiokov  control  board,  585 
Powdered  coal 
burners,  116 
burning.  111 

control  of  air,  116 
equipment,  113 
feeders,  115 
settings,  111 
Power  feed  pumps,  309 
Pneumatic  conveyors, 
ash,  608 

wood  refuse,  133 
Precision  Instrument  Co.,  draft  gage,  581 
Pressure, 
effect  on  boiling  point  of  water,  500 
effect  on  gases,  398 
excess  feed  water,  Z^ 
gages, 

boiler  testing,  518 

correcting,  557 

description,  555 

head  of  water  in  pipes,  556 

location,  556 

siphons,  556 


Pressu  re— Continued 

gages — Continued 
tester,  557 
vibration,  557 
water  seal,  556 

regulators, 
excess  feed,  310 
feed  pump,  310 
Priming,  67 

bad  feed  water  and,  510 
Processes,  industrial 

air  heated  by,  341 

superheated  steam  for,  83 

waste  heat  from,  139 
Producer  gas, 

burning,  131 

composition  of,  483 

heat  value,  483 
Properties  of 

gases,  398 

saturated  steam,  424 

superheated  steam,  429 

water,  499 
Frosser  tube  expander,  613 
Proximate  analysis  of  coal,  451 
Psychrometric  tables,  537 
Pulverized  coal,  see  Powdered  coal 
Pumps,  see  Feed  pumps 
Pyrometers, 

accuracy,  371 

calibrating,  370 

electrical  resistance,  373 

mechanical,  374 

optical,  377 

radiation,  377 

range  of,  ^1 

thermo-electric  373 


Radial  brick  chimneys,  201 
Radiation,  379 

boiler  settings,  153 

heat  loss,  546 

oil  burning,  surface.  117 

pyrometers,  377 

Stefan's  formula,  379 

surface  for  oil  burning,  117 
Rankine's  convection  formula,  385 
Ratfan.  flow  of  steam,  420 
Rated  H.P.  of  boilers,  55 
Ray  rotary  oil  burner,  124 
Reaumur  temperature  scale,  370 
Reboilers  for  ice  plants,  329 
Receiver  steam  separators,  295 
Recorders, 

CO.  577 


ib.  Google 


Recorders — Continaed 

smoke,  550 
Refuse 

bumiDg  settings,  133 

composition  of  municipal,  191 

destructor  chimneys,  191 
Refractories,  148 

perforated  blocks,  151 

thermal  conductivity,  15S 

weights  of,  ISt 
Regulators, 

draft,  584 

excess  feed  pressure,  310 

feed  pump  pressure,  310 

feed  water,  313 

superheat  temperature,  78 
Reinforced  concrete  chimneys,  207 
Reinforcing  old  brick  chimneys,  213 
Renewing  boiler  tubes,  43,  613 
Repubiic  flow  meter,  594 
Resistance, 

heat.  335 

surface,  to  heat  flow,  347 
RichaTdson  coal  scale,  601 
RUey  sfoker,  16S 
Ringeimann  smoke  chart,  549 
Roach  stoker,  162 
Roney  stoker,  161 
Hoss  expansion  joint,  290 
Rust  concrete  chimney,  211 

S 
Safety  valves, 
A.S.M.E.  Code,  55! 
blow  down 
allowed,  553 
control,  554 
discharge  piping  from,  243 
huddling  chamber,  554 
operation  of  pop,  554 
pressure  rise  allowed,  551 
size  chart,  272 
specifications,  271 
superheaters,  75,  555 
Sampling 
coal,  44S 
boiler  testing,  517 
errors,  547 
flue  gases,  531 
tubes,  for,  531 
Sand,  fire,  151 
Sanford  RUey  stoker,  165 
Sawdust 
burning,  566 
fuel  bed  thickness,  566 
grate  bars,  99 
heat  value,  473 
Scale,  boiler 
formation.  Sll 
heat  transfer,  511 


Scale,  boiler — Continued 
injector,  323 
removal,  til  1 
superheaters,  76 
Scales. 
temperature,  370 
conversion,  370 
thermodynamic,  370 
weighing, 
boiler  testing,  517 
continuous,  599 
conveyor,  599 
track,  599 
Secondary  air  admission,  90 
Sedimentation  tanks,  508 
Srger  cones,  377 
Semi-anthracite  coal,  436 
Semi -bituminous  coal,  436 
Separating  calorimeter,  522 
Separator,  feed  water  oil,  326 
Settings,  see  Boiler  settings 
Shavings, 
burning,  133,  566 
burning  dry.  134 
graie  bars,  99 
heat  value,  473 
Signals, 
high  water,  551 
load,  SG9 


r,  SSI 


Smoke, 
baffling,  65,  93 
causes,  571 

combustion  Space,  571 
curtain  walls,  93 
deflection  arch,  93 
down  draft  furnace.  95,  100 
furnace 

design,  571 

temperature,  S7I 

volume,  85 
gas  passage  areas,  93 
height  of  furnace  chamber,  90 
horizontal  baffling,  62.  87,  93 
indicators,  550 
observations,  548 
ordinances,  571 
overloads,  571 
prevention,  569 
recorders,  5S0 
records,  65 
reports,  548 
Ringeimann  chart,  549 
tile  furnace  roof,  87 
vertical  baffling,  93 
Soft  coal,  see  Coal,  bituminous 
Soot 
blowers,  610 

bamea  and,  65 

boilers,  39,  41 


,,  Google 


Soot— Continued 
bl  o  wers — Co  nli  nu  ed 
economizer,  333 
superheater,  31 
collectors  in  chimneys,  207,  208 
heat  loss  by  formation  of,  547 
Sorge-Cochrane  water  softener,  509 
Specific  heat,  378 

sdids,  ^ 
water,  499 

Specifications. 

boiler,  standard,  49 

coal,  486 

oil  fuel,  497 
Navy,  497 
railroad,  498 
Spontaneous  combustion  of  coal,  467 
Stacks,  see  Chimneys 
Staples  and  Pfeifer  oil  burner,  120 
Stand-by  boilers,  568 

fire  protection,  568 

oil  consumption,  568 

quick  steaming,  568 
Static  pressure,  pilot  tube,  232 

calorimeters. 

Carpenter,  SZi 
connections,  S23 
formula,  521 
Peabody,  518 
separating,   522 
throttling,  518 
consumption, 
auxiliaries,  423,  547 
feed  pumps,  3CQ,  305 

accounts,  616 

Potakov  method  of  reducing,  585 
diagram 

Mollier,  416 

Peabody,  415 
disengaging  surface,  67 
entropy,  407 

diagrams,  415,  416 
factor  for  moisture  in,  528 
flow. 

Groihof.  421 

meters,  595 

meters,  variable  orifice,  597 

Napier,  421 

nozzles.  421 

pipes,  275 

Raieau,  420 
generation, 

maintenance  costs,  618 

operating  costs,  617 

reducing  cost  of,  587 


Steam — Contiou  ed 
jet  ash  conveyors,  608 
lance,  43 
meters,  555 
MolUer  diagram,  416 

description,  414 
nozzles,  417 
Peabody  diagram.  415 

description,  414 
pipes,  see  Pipes 

flow  in,  275 

friction  pressure  drop,  275 

size  charts,  277 

sizes.  276 

velocity  in,  275 
piping,  see  Piping 

drainage,  243 

expansion.  283 

slope  of,  243 

systems,  see  Piping  systems 

vibration,  243 

water  hammer,  243 

water  in,  243 
pressure  gages,  see  Pressure  gages 
properties  of,  410 

table,  saturated,  424 

table,  superheated,  429 
quality,  518 
receivers,  295 

separation  in  boilers,  35,  43 
separators,  293 

superheated,  see  Superheated  steam 
superheaters,  see  Superheaters 
tables, 

saturated,  424 

superheated,  429 
Steel  chimneys,  see  Chimneys,  steel 
Stefan's  radiation  formula,  379 
Sleveiu  stoker,  163 
Stokers.  159 
see  Mechanical  stokers, 
settings,  100 
Storage  of  coal,  see  Coal  storage 
Stratification  or  laning,  93 

composition,  474 

heat  value,  474 

weight,  474 
Strengdi  of  materials  and  heat,  97,  239. 

252 
Sub-bituminous  coal,  436 
Suction  lift 

feed  pumps,  317 

hot  water,  317 

injectors,  321 
Suction  piping. 

feed  pumps,  318 

injectors,  323 


ib.  Google 


Sudden  loads  from  banked  lires,  568 

combustion  data,  393 

in  coal,  451 

in  U.  S.  coal,  463 
Superheat, 

accurate  control,  7? 

boiler  load  and,  75 

control  of,  75 

damage  by  fluctuation  of.  7S 

fluctuations,  75 

regulation,  75 

regulator,  78 
'  variation  with 
■      furnace  temperature,  76 
gas  flow,  76 
load,  76 
steam  flow,  76 

weakening  materials,  63 
Superheated  steam,  69 

advantages,  69 

automatic  temperature  control,  78 

boiler  efficiency,  69 

constant  temperature,  77,  78 

Corliss  engines  and,  73 

cylinder  condensation  and,  69,  72 

danger  of  temperature  fluctuations,  75 

economy,  69 

engines  using,  tests  of,  72 

erosion  of  turbine  blades,  73 

European  practice,  73 

extra  fuel  for,  69 

fittings,  83 

flue  gas  temperature  and,  69 

industrial  uses  of,  83 

injectors  and,  321 

limit  of  economy  with  engines,  71 

lubrication  and,  75 

pipe  condensation  and,  69 

pipe  sizes,  281 

piping,  259 

poppet-valve  engines  and,  75 

reciprocating  engines  and.  71 

slide-valve  engines  and,  73 

tables,  429 

taking  temperature,  523 

temperature-entropy  diagram,  69 

tests  of  engines  using,  72 

theoretical  engine  and,  73 

turbines  and.  73 
blade  erosion  of,  73 

variation  of  temperature,  75 

velocities  in  piping,  69,  83 

water  gas  producers  and,  83 
Superbeated  vapors,  411 
Superheaters,  69 

attached,  75 

burning,  76 

by-pass,  77 


Superheate  rs — Cont  inu  ed 
cleaning,  31 
details,  77 


76 


flooding,  76 

heat  transfer  rate.  81 
Heine,  29,  34,  77 
marine,  49 
materials,  83 

weakness  of,  83 
position  of.  76 
protecting,  76 
requirements.  79 
safety  valves,  75,  555 
scale  in,  76 
separately  fired,  7S 
soot  blower.  31 
surface 

efficiency,  69 

required,  79 
types  of,  75 

grate,  57 

heating, 
boilers,  57,  562,  567 
cost  of  boilers  by,  57 
337 


efficiency  of  superheater,  69 

gas  temperature  drop  and,  387 

superheater,  79 
resistance  of  insulation,  360 

to  heat  flow,  347 
steam  disengaging,  67 
waste  of  coal  with  bare  hot,  349 

T 
Tan  bark 
burning,  133 
composition,  475 
firing,  567 

fuel  bed  thickness,  567 
grate  bars,  99 

heating  surface  ratio  with,  567 
heat  value,  474 
moisture  in,  474 
settings  for  burning,  133 
Tar 

burners,  125 

burning,   125 

composition 

coal,  481 

oil,  481 

heat  value 

coal,  481 

oil,  481 

-oil,  481 

specific  gravity,  481 
weight  of  coal,  481 
Taylor  stoker,  164 


ib.  Google 


TemperUttre 

absolate,  370 

absolute  iero  of,  370 

color  schedule.  tP 

-entropy  diagrsm,  415,  416 

lixed  points,  371 

scales,  370 
conversion,  370 
thermodynamic,  370 
Testing  boilers,  see  Boiler  testing 
Thermal  units,  378 

Thermodynamic  temperature  scale,  370 
Thermo-electric  pyrometers,  373 
ThemiometeTs, 

accuracy,  371 

alcohol,  373 

calibratioQ,  370,  373 

mercury,  373 

range  of.  371 

stem  correction,  373 

vapor,  377 

wells,  373 
Thermometry,  369 
Tile 

baiHes,  66 

furnace  roof  and  smoke,  87 

roof  and  furnace  temperature,  87 
Tolerance  in  guarantee  tests,  547 
Treatment  of  water,  see  Water 
Trenches,  insulating  piping  in,  367 
Trials  of  boilers,  see  Boiler  testing 
Triplex  feed  pumps,  309 
Tubes 

beading,  613 

cleaning  boiler,  43 

cleaners, 
hammer  type,  611 
turbine  type,  611 

conductivity  of  boiler,  383 

expanders,  613 

flaring,  613 

pilot,  232 

renewing  boiler,  43, 613 

rolling,  613 
Tunnels,  insulating  piping  in,  367 
Tupper  grate  bars,  97 
Turbines, 

auxiliary,  341 

blades,  erosion,  73 

boiler  feed  pumps  and,  345 

fans  and,  227,  343 

feed  pumps  and,  345 

superheated  steam  and,  73 

tube  cleaners,  611 

U 
Ultimate  analysis  oE  coal,  451 
Underfeed  stokers,  161 
Units, 
British  thermal,  378 


Units — Continued 

heat,  378 

work,  378 
Univertal  stoker,  163 


Vacuum  reboilers,  329 
Valves 
ashpit,  111 

automatic  non- return,  274 
blow-off,  274,  560 
check,  274 
gate,  273 
globe,  273 
safety,  271,  SSI 
safety,  superheater,  75,  S55 
Vapor 
thermometers,  377 
water 
specific  heat,  40S 
weight  of  air  and,  401 
Vapors,  characteristics  of,  409 
Velocity, 
gas, 
chimneys,  189 
draft  loss  altering,  187 
draft  loss  generating,  187 
heat  transfer  and,  385 
waste  heat  boilers,  141 
pressure,  pitot    tube,  233 

nozzles,  417 
pipes,  275 
superheated.  69,  83 
water,  pipes,  283 

chimneys,  191 

capacities,  593 
diagram,  590 
formula,  S91 
Vertical  baffling,  61 
extinguishing  action,  93 
head  room  for,  91 
smoke  and,  93 
Vibration  in  piping,  243 
Vitrified  brick,  156 
V-notch  meter,  589 

formula,  591 
Volatile  matter  in  coal,  451 

W 

Walls, 
air  space  in  boiler,  145 
boiler  setting,  145 
insulation  of  boiler,  153,  367 
leakage  through  setting,  157,  577 
smoke  and  curtain,  93 
ties  for  setting,  155 


ib.  Google 


Washing  coal,  458 
Waste  heat  boilers,  139 

airtight  settings,  142 

bafflins,  141 

dust  in,  142 

heat  transfer,  141 

high  draft  loss,  142 

high  gas  velocity,  141 

industrial  furnaces,  141 

operation,  142 
Waste  of  coal  with  bare  hot  surfaces,  349 
Water 

acidity,  503 

air  in,  removal  of,  329 

alkalinity,  503 
test,  505 

analyses,  table  of,  504 

analysis,  503 

boiling  point  and  pressure,  500 

causticity,  503 
test,  SOS 

characteristics  of  boiler  feed,  501 

chemical  treatment,  SO? 

classification  of  feed,  505 

concentration  lest  of  feed,  505 
510 


-gas, 

composition,  483 

generators  and  sttperheated  steam,  83 

heat  value  of,  483 

tar  burning,  125 
gases  in  feed,  503 
grate,  95,  100 
hardness, 

factors,  504 

permanent,  501 

temporary,  501 

test,  503 
heaters,  see  Feed  water  heaters 
heat  treatment  of,  507 
impurities  in,  501 

permanent  hardness,  501 
piping,  260 

flow  in,  281 

insulating  cold,  367 

sizes  of,  281 

velocity  in,  283 
priming  and  bad,  510 
properties  of,  499 

punlication  in  Heine  boilers,  19,  35,  45 
softening,  see  Water  treatment 
solid  tnatter  in,  503 


Water — Con  tinned 

specific  heat  of,  499 
temporary  hardness,  501 
thermal  treatment,  507 
treatment, 

boiler  compounds,  510 

chemical  feed,  507 

chemical  proportioners,  506 

filters,  508 

hot  process,  508 

Heine  mud  drum  and,  35,  45 

mechanical,  505 

sedimenlation  tanks,  508 

Sorge-Cochrane,   509 

Zeolite.  508 

characteristics,  409 
specific  heat,  405 
weight  of  air  and,  401 

weight, 
maximum  density,  499 
volume  and,  499 
Weir,  formula  for  V-notch,  591 
WesttHghouse-Roaey  stoker,  161 

underfeed  stoker,  164 
Wet  fuels,  heat  value  of,  477 
Wettel  stoker,  161 
Weiderhall  chimneys,  211 
Wind, 

heat  insulation  and,  361 

pressure  on  chimneys,  193 
Will  oil  heater  and   pump,   124 
Wood  fuel,  435,  473 

chimneys,  191 

chips,  134 
coal  and,  134 

composition,  473 

cord,  566 

fuel  bed  thickness,  566 

grate  bars,  99 

heat  value,  435,  473 

hog,  566 

refuse  settings,  133 

sawdust,  566 

slab,  566 
Work,  unit  of,  378 
Wortkinglon  water  weigher,  589 

Y 

Yaraxiy  blow-off  valve,  560 


Zeolite  water  treatment,  508 
Zero  of  temperature,  absolute,  370 
Zinc  plates  in  tnarine  boilers,  49 


ib.  Google 


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D,B,i,.ab,GoOglc 


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