Steam Boilers

A PRACTICAL AND AUTHORITATIVE DISCUSSION OF BOILE R

D E GN AND C N RUC ON AND T HE D E E LOP SI O ST TI , V ME NT OF MOD E RN TY PE S

REV ISED BY

. E . R BE R H KUS M . O T S ,

C O NSU L TING MECH ANICAL ENGINEER F O M LY L M D MO O I O O M P Y H I O R ER SA ES ANAGER , E GE R R N C AN , C CAG AMERICAN SO CIETY O F MECH ANICAL ENGINEERS

ILL USTRA TE D

AME RICA N TE CHN ICA L SOCIE TY

Copyrighted in Great Britain

a era e m an . one ere to s a o er an he oul v g If w vi it big p w pl t, w d probably b e ﬁrst ushered into a clean engine room and shown the Corliss engine with its trim and stately lines or the stocky steam ur ne of a aren s er cons ru c on e en n u on a t bi pp tly impl t ti , d p di g p wh t

’ k n of a r o r h n i d p ime m ve t e pla t possessed . At first thought the uninitiated layman might think that he had seen the best part of the an the w se m an o e er oul now a ere was pl t ; i , h w v , w d k th t th another power behind this mechanical throne and he would ask h r ro H r h to b e shown to t e boile om . e e e woul d find a long line of boilers trembling with the energy pent up within them and with the res un ernea roar n os o nous r n fi d th i g m t mi ly . Afte seei g the mechanical stokers mysteriously carry the fu el to the fires with au o a c re u ar a c in the di a s of a e er n num er t m ti g l ity, w t h g l b wild i g b of a es and ear n the a en an discourse on the r ues of the g g , h i g tt d t vi t superheaters which increase the temperature and pressure of the e s ea he oul e n to a e a o eso e res ec for ese liv t m , w d b gi h v wh l m p t th n o ers and ou rea i e ore c ear e r or ant func on di gy b il w ld l z m l ly th i imp t ti .

ea o ers are at eas as old as the s ea en ne s f S ! e q t m b il l t t m gi it l , and since the first boiler was conceived there have been many In n s ressur no t o changes. days whe team p es did t exceed w pounds er s uare nc cer a n e o s of cons ru c on ere er ss e p q i h, t i m th d t ti w p mi ibl , b ut at the present time when steam pressures are often carried as as 150 to 250 oun s er s u are nc the s r c es a en on high p d p q i h , t i t t tt ti u s b e a to e er r n e ai of es n and cons ruc on m t p id v y t ifli g d t l d ig t ti , in n N o s an n the order to i sure safety of the stru cture. twith t di g enormous increase in the size of our industrial plants and the corre s ondin n crease in the nu er of o er orse o er re u re the p g i mb b il h p w q i d , actu al design of the modern boiler has not changed materially w in T he sec ona ea has een carr e out ith the last few years . ti l id b i d to a point where a boiler plant 18 merely a combination of a number of uni s the ac u a num er of uni s e n e erm ne the s e t , t l b t b i g d t i d by iz of th o er es r e b il d i ed . q The aim of this little volum e is to cover in a very practical manner and yet with sufficient detail the m ethods of constru ction of the cu es of o ers the ro er es n of the a er a s diffi lt typ b il , p p t ti g m t i l use the e o s of r e n and s a n and na l a carefu d , m th d iv ti g t yi g, fi l y l discussion of the difficult types of stationary and marine boilers n i h of the u is ers a the s c o the market . It s t e hope p bl h th t impli ity of style and the freedom of involved technical discussions will a ea pp l to the readers. BOILER INSTALLATION WITH AMERICAN ST OKERS AT PLANT O F KIRKMAN K N EW Y RK AND SO N , BRO O LY , N O ew Courtesy of Combustion E ngineering Corporation, N York CO NTENTS

‘ PART 1

CONSTRUCTION O F BOILERS

PAG E BOILER MATERIALS

o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o

Standard testing regulations . BOILER MANUFACTURING PRO CE SSE S

Riveted j oints .

i Types of .

Calking . Welded j oints Arrangements of plates and j oints M anholes Location

Handholes

Stays .

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Loa on d stay bolts . Areas of segments of heads to b e stayed Boiler tub es and ﬂu es ac n of u Sp i g t bes .

Types of tubes

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o CONTENTS PAGE BOILER RE !UIREMENTS

i rs Factors in designing b o le .

Boiler horsepower . n General requireme ts . Water evaporation per pound of fuel Boiler rating

Steam space . n ur a Heati g s f ce . Allowable pressure Furnace ﬂues Boiler inspection during m anufacture

PART II

TYPES O F BO ILERS

MODERN FLUE BOILERS

C r o nish b oiler. Path of !h ot gases n f n n Taki g care o expa sio . h r r Lancas i e b oile . — — - - Horizontal two flue internally fired . w b i r Gallo ay o le . . — — — Horizontal two-flu e mternally-fired Galloway tubes T wo

FIRE - TUBE BOILERS Comm on horizontal type

rt c Ve i al type .

- Single tube boiler .

- Throu gh tube boilers . Fire- b ox Locomotive boilers r r Stationa y boile s .

- — R eturn tubular ﬁre b ox boiler Cochrane vertical boiler r Shapley boile . Brady Scotch boiler D irecturn CONTENTS

PAG E WATE R-TUBE BOILERS

Horizontal types . Babcock and Wilcox

Root .

0 0 0 0 0

E rie City .

Hazelton or Porcupine

MARINE BOILER TYPE S Rectangular types - r Wet and dry bottom boile s .

- r M arine water tub e b oile s .

Comparison with cylindrical typ e .

o n s ea s s Standard boiler U . S. wo de t m hip

Almy boiler . Variations from standard types

BOILE R D E SIGN

Importance of good c irculation Eﬁectiveness of heating surfac es Acc s b e si ility . n f Replaceme t o tubes .

Plant features inﬂu encing b oiler design Size of plant

CONST RUCT ION O F BO IL ERS

INTRO DUCTIO N

i Essential Principles of Boiler Act on. A steam boiler is a closed vessel used for generating steam from water by the applic ation of

The o e of the e - e e e e e heat . b il r part st am g n rating quipm nt must b clearly distinguished from the part having to do with the genera

ff h o e for tion of the heat whic h is o ered to t e b il r absorption . The place or space in which heat is liberated from fuel by ﬁre is c alled

h ce i e o e oc e the of e t e furna and , wh l cl s ly ass iat d with art st am

e o oe not e o e e of the gen rati n , d s , in this pap r, f rm an ss ntial part H ec e e en . o e e e o e e subj t und r tr atm t w v r , boil r constructi n is inﬂu nc d to a considerable degree by the conditions imposed by highly heated

e to e ee e e e ce b e e to co c gas s , and this d gr r f r n will mad nstru tion f n n o c o o allow s oL ex a sio e e etc . m diﬁ ati ns t p , pr ssur ,

c a c ce o e s are onl ﬁl e e the In a tu l pra ti b il r y partly l d with wat r,

of the o e e remaining portion interi r b ing ﬁll d with steam . M ore o e c e b e o e for e to e ce v r, fa iliti s must pr vid d supplying wat r r pla that which evaporates into steam ; for the proper control and delivery of the steam generated ; for the safe operation of the boiler by the aid of easy and reliable means for determining the height of the water therein ; for the automatic release of steam to prevent excessive pressure ; and for the removal of accumulated m uda nd other impuri th h f ties in e water without disturbing t e continuity o operation .

D c o of e e ec the e e o c of o e o e o is ussi n th s subj ts and r lat d t pi s b il r p “rati n , r h o Bo ce eco o co o etc . b e o t e o e fu na n my and ntr l , , will f und in b k, il r ” c ce o e e the e e A ss ri s , issu d by sam publish rs

Sc e of W k. The e o e of c e to e e op or int nti n , th n , this arti l is pr s nt an explanation of the characteristic s of boiler c onstruction without any attempt to meet c onditions imposed by special branches of

e - e e n e ce for e o o e c e the st am g n rati g s rvi , as , instanc , l c motiv pra tic ,

o e the c e of c o c o th ught b ing that prin ipl s nstru tion , if w rthy, must

e und r all circumstances b e preserved . 2 CONSTRUCTION OF BOILERS

e e In accordanc with this int ntion, three elements of prime

e b e o e e e materials desi ns importanc will c nsid r d ; nam ly, , g , and o w rkmanship. It must b e understood that these elements are

e c e . e e e are e clos ly asso iat d To illustrat , th r many d signs which ,

ec e of the e e e t e r b aus xc ll n mat rials and workmanship , a e service

e e b t c e o able and r liabl , u whi h with inf ri r material and workman

b e e c . L e e e ship would not saf constru tion ik wis , it is f asible and right to use certain kinds of materials in c ertain places and parts to

are e b ut are no which they adapt d , which t to b e considered in other places and parts .

it not e to f n Finally, is possibl lay down a course o boiler c o struction which could b e unl v ersally adopted ; the de5 1gn must b e modiﬁed and adjusted to meet the facilities of the shop in which

e the boiler is mad .

B O I L E R M AT E RI A L S PRO PERTIES O F M ETALS

The materials of which boilers are constructed are exposed to conditions which Weaken them and thus shorten the life Of the

ile . t e e o are o o o e e bo r Among h s conditi ns c rr sion, b th xt rnal and

e e e c du internal , high pr ssur , and xpansion and ontraction, e to varying temperatures and pressures . h Cast Iron. Cast iron was t e material of which the earliest

O e e e e on O low e e forms f boil rs w r mad but , account f its t nsil strength

e it b ut e e e ce or and unreliable natur , is now littl us d , x pt f small

f e - e e o e e for the e O low parts o wat r tub boil rs , and s m tim s nds f

e c c o e for . e o o pressur ylindri al b il rs , and ﬁttings It r sists c rrosi n but ,

‘ O e e e the b e on account f its unr liability and brittl n ss, parts must

o m ade thick and theref re heavy .

Wr u ht r n. e 1870 the o g I o Wrought iron, as lat as , was principal

o material used for boiler plates . It is a pure iron prepared fr m “ ”

o e e e c e Me . pig iron by a pr c ss call d puddling, d s rib d in tallurgy

o t o e e use o e Wr ugh ir n is w ll adapt d for in b il r construction, as it is

o e e e e strong, tough , and ﬁbr us, and combin s high t nsil str ngth with

e the e e men ductility and freedom from brittleness . Wh n prop rti s ti n d r e e e e due to o e a e well combin d , wrought iron will r sist str ss s

e . B e e e e un qual expansion oil r fast nings , stays , and oth r parts mad CONSTRUCTION O F BOILERS 3

TABLE 1

Spec iﬁc atio ns f or Chem ic al Co m positio n o f O pen =Hearth Steel

o o by welding are sometimes made Of wr ught ir n . It is customary to c onsider that a bar loses about one- quarter of its strength by

e o O e o e the e o the w lding , alth ugh it is ft n str ng r in w ld , wing to h working of the metal during t e welding process .

- teel. S ee e e ce e S t l has ntir ly displa d iron for boil r shell work .

B e ee e the e - e e oil r st l is mad by op n h arth proc ss, and contains for

i hic e e of 1 or I e er e e ord nary t kn ss s i inch s p c nt carbon , whil

e of s o c o e r thinner plat s inch h uld not ntain ov r pe cent carbon .

e e ce e of e c co n e e Larg r p r ntag s carbon , whil a mpa i d by an incr ase in

- - h e e e en the d c . T e o o e tensil str ngth , l ss u tility f ll wing prop rties show

ee b e the e o e e at e e : e e e e st l to b st b il r mat rial pr s nt gr at t nsil str ngth ,

c o o e e e ee e du tility, h m g n ity, toughn ss, fr dom from blist rs and inter

B e e r nal unsoundness . list rs and unsoundn ss a e faults sometimes

o - m et with in wr ught iron plates .

a om osit - Chemic l C p ion . Open hearth steel c omes in three grades

e for o e use e ﬁre- b ox l - o e e . suitabl b il r ; viz , ﬂang , , and b i r riv t It is customary to stipulate the requirements as to chemic al c ompo

e . sitiou , as in Tabl I The percentages given show that a very small amount Of the

ee e of e e o e e o st l is mad up matt r oth r than ir n ; th s small am unts ,

e e e n e e on the e e o how v r , hav a striking i ﬂu nc r lativ ductility, t ugh

e le f th n ss, and tensi strength o e steel .

- T O determine whether the boiler material c onforms to any

e e e m c e e b e . r quir m nt such as giv n , a ch i al analysis must made

ee o i o the e e e e h All st l ing ts com ng fr m sam ladl , as pr par d by t e

e - e e a e not o or o o e eou c e op n h arth proc ss , r of unif rm h m g n s stru tur , different parts Of the l adle producing steel of the three different

r e e f h f g ad s m ntioned . The position o t e several grades o steel in 4 CONSTRUCTION OF BOILERS

the e of e e e e e e e e ladl is , cours , known by xp rim nt and xp ri nc , and ,

b e e e e e e e e f as will xplain d h r aft r , th r is no sharp line o demarcation

e ee e ee fire- ee e fire- b tw n flang st l and box st l , or b tween box steel

- and boiler rivet steel .

r Coppe . Copper in many respects is superior to wrought iron

e . e e e for boil r construction It is homog n ous , r sists oxidation (the

e O t ee e i corrosiv action f mos f d wat rs) , and ncrustation . It is more

e e e e e of e n ductil and mall abl , and is a b tt r conductor h at, which ot ' e it e e e e e b ut also e e only giv s a high r vaporativ us fuln ss, nabl s it to

e the f h last longer und r intense heat o t e furnace. Its disadvantages are its low tensile strength (about pounds per square inch)

e e e of e e e f and its d cr as str ngth with an incr as o temperature. In

‘ heating from the freezing point to the boiling point it loses 5 per

of e at 550 e ee . it o t t n cent its str ngth, and d gr s F has l s abou o e

e of e at ee t. e e e on quart r its str ngth fr zing poin For th s r asons, and

f e it e m e int b oiler e account o its high pric , is now s ldo us d work xcept

e e e in v ry sp cial plac s .

Brass. Brass is an alloy of copper and zinc in which the pro

s e ed e e o portions vary con id rably . R brass is b tt r and m re expensive

s e e ce f than yellow bras as it contains a larg r p r ntage o copper .

B e e e e . e ee rass is us d for valv s, gag s, and oth r ﬁttings Int rnal f d

e e e e of e o and oth r piping is pr f rably mad brass , as it r sists corrosi n

of and can b e kept free scale incrustation .

Br n e. B o e of o e adv anta o z r nz is an alloy c pp r and tin , and is

l e e of v e e e the geous y used for valv s and s ats alv s wh r wear is great .

PHYSICAL TESTS

In order to determine the strength and other qualities of the

ec e are e e the e the e materials, sp im ns t st d , r sults showing ultimat

e c e o . tensile strength , lastic limit , contra tion of ar a, and elongati n These quantities as well as the rules and terms used in the text may b e the better understood by a careful study of the following def

initions .

tr ss h e of of e e D eﬁnitions. S e . T e numb r pounds forc appli d

the 1e e 18 e e per square inch is called the stress . If p c und r dir ct

e o the e e e e tension or compr ssi n , str ss is consid r d uniformly distribut d and is equal to the load divided by the area of the transverse sec CONSTRUCTION OF BOILERS 5

" 7 the e of the e 1 the tion. Thus , if s ction plat is by 1 3 and actual

the e er e stress is pounds , str ss p squar inch is

17 750 . x , lb (appro ) 4 375

at tren th The e Ultim e S g . maximum str ss a test piece will stand

c e e e F r c per square in h is call d its ultimat str ngth . o du tilemate rials the breaking stress is considerably less than the ultimate

That ' is he the o are h o strength . , w n l ads gradually applied t e t tal

o e c e the e e e o l ad will r a h a maximum , and th n m tal str tch s s that at

h o e of e the o c e h t e m m nt ruptur l ad is mu h l ss than t e maximum . The strength of iron and steel depends somewhat upon the rate at which the load is applied ; the more rapid the applic ation the higher the stress as recorded by the scale beam .

ra the e c er f St in . Strain is str t h p unit o length O f the test

e e . the e h L th piece wh n in t nsion If original l ngt is , and e stretch

B the eco e or elongation is , strain b m s L B

lastic Limit. e e ece the E Wh n t sting a pi , at ﬁrst stress and

The o c h strain are proportional . p int at whi h t e strain or stretch begins to increase more rapidly than the stress is c alled the elastic

t not e e b e e e e limit . This limi is d ﬁnit ; it can d t rmin d approximately

e e the e o ce e only . A load gr at r than lastic limit will pr du a p rmanent

o elongati n .

m t The e c the e c th Stretch Li i . str t h limit is str ss at whi h e sc ale beam Of the testing machine will fall while the! straining head is at rest .

duction o Area. e e ece e the Re f Wh n a t st pi ruptur s , area at

c e the e or e o e e that point is mu h l ss than plat bar b f r t sting . This reduction shows the ductility of the material ; it also shows the property of changing shape without actual rupture. This is impor tant in boiler c onstruction .

lon ation . D e e e c e e E g uctil mat rials str t h b fore br aking . To

h e e o the o e e e ar measure t e ultimat longati n , two br k n pi c s e placed in a straight line with the broken ends in c ontact and the length

e e e th b tween p oints is then m asur d . As e prick punch marks are

e e e e thee o o e e e e Th mad b for t sting, l ngati n is asily d t rmin d . e ratio 6 CONSTRUCTION OF BOILERS of the elongation to the original length is called the ultimate elonga

o tion . Supp se the distance between the extreme prick punch ? 8 e e e e 9 marks is inch s b for t sting and 3 inches after . Then the bar

e e c e 1 e The e o or plat has str t h d % inch s . ultimate l ngation is 1%

8 or 2 34 or er , , p cent .

D ia ram e e g s . Th s various properties of materials may b e shown

1 h o h by diagrams . Fig . s ws t e diagram for wrought iron and steel

e e te Th t r wh n und r nsion . e uni stresses a e taken as ordinates and the t e o For e uni l ngations as abscissas . each str ss the correspond

e o o h m t e te e O ff. Th ing l ngati n , as found by sting achin , is laid e

e o t e E e o n curv is drawn thr ugh h se points . ach sp cimen has its w

Un it f longa ﬁ ons

Fi e h n r n g. 1 Curv s S owi g E longation of Steel and Wrought I on U der Various Stresses

e o e o . 1 e o e curv , th s sh wn in Fig b ing pl tted from average valu s .

S e e e o are o the e s inc str ss and longati n prop rtional up to la tic limit , the e the O i curv from r gin to the elastic limit is a straight line. At the elastic limit the curve changes suddenly and the elongation

e e incr as s rapidly . From the elastic limit to the point at which the

e e e the t e is no h end pi c br aks s r ss t proportional to elongation . T e

Of the e e the t of the curv indicat s poin rupture. Curves show prop erties of o s m n vari u aterials . It is seen that the elastic limit is ot

e e e b ut b e e e e w ll d ﬁn d can stimat d v ry nearly . These c urves may b e plotted from results of tests or they may b e drawn automatically b the te t m y s ing achine. CONSTRUCTION OF BOILERS

Testing Machines. The simplest way to test a piece of iron

or e e e e b e e e bar plat for t nsil str ngth would to susp nd a bar v rtically, ﬁxing it ﬁrmly at the upper end and hanging weights on the other

en the e . hi c e e o d until bar is brok n T s is a rud m th d , and in order that the elastic limit and elongation may b e determined at the same

e e c e are e . e e are tim , t sting ma hin s us d Th r many kinds . of testing

Fi 2 . an ar e in achine g. St d d T st g M iehle ro h e n e R B t ers T sti g M achin Company, P hiladelphia

“ chi e e e the e e e ma n s , adapt d for various mat rials , but g n ral principl s h are t e same.

The e e c s of e e to hic t sting machin on ists a fram and two h ads , w h the e the e r e nds Of t st piece a e fast ned by wedges or other devices . By means of steam or hydraulic power one head is drawn away from th The t e other for tensile tests . pull is transmi ted to a weighing 8 CONSTRUCTION OF BOILERS

e e e e e e the e device, usually l v rs and knif dg s lik b am of an ordinary

e the b e e platform scale. In small machin s pull may appli d by a

lever .

e are e e e O f e : e e Testing machin s mad for all vari ti s . t sting t nsil ,

e e e o for e ec of e and compressiv , and sh aring str ngth ; als d ﬂ tion b ams ,

‘ for e oo c e e c o e. . 2 o str ngth Of w d , m nt , bri k , and st n Fig sh ws a Riehle testing machine designed for tensile and c ompressive tests of

iron and steel .

i h c e Standard Test ng Regulations. While t e prin ipl s of testing materials are simple it is essential that the methods of applying them

b e o c e e ee t the e ma unif rm and as pra tic d by ngin rs , so tha r sults y

b e comparable . For this reason regulations supported by engineer

o e e e ee e c e not e e e ing s ci ti s hav b n na t d , by l gislation n c ssarily, but

h e by t e soci ties or boards themselves . These regulations have all the force of legislative enactments s1nce they are Observed by persons h dealing with t e subj ect . The essential features Of all the rules pertaining to boiler steel and the testing of it are contained in the following rules which are essentially those O f the American Society Of Mechanical Engineers .

the e t of e see o e e e the So e For complet lis rul s , th s pr par d by ci ty " o and f und in all engineering libraries .

RULES FOR TESTING BOILER STEEL

SE CTION 1

BOILER S HELL MATERIAL

1 . All materials used in the constru ction of boilers shall conform to s ec ca ons ereun er en p iﬁ ti h d giv . 2 : nl the es u a of o en- r a u O y b t q lity p hea th steel sh ll b e sed .

C HE M ICA L C OM P OSITION

' 3 . All steel shall conform to the following requirements as to comp osition

a e ca L s : an anese to er cen ( ) Ch mi l imit m g , p t ; p per cen (b) Analysis

sentative.

10 CONSTRUCTION OF BOILERS

ro T h n i r from the g ove . e specime s b oken at the other two grooves in the sam e nn T he o of s es i t n n n m a er. bj ect thi t t s o ope a d re der visible to the eye any seam s due to fa ure to we u or to n er ose ore n a er or an c a es il ld p i t p f ig m tt , y viti

due to as u es in the n o . er ru ure one s e of eac rac ure is g b bbl i g t Aft pt , id h f t

F 3 . tee ecim en for ension est ig. S l Sp T T

a ne a oc e ens e n u se necessar and the en s of the seams ex mi d , p k t l b i g d if y, l gth and c avities are determined .

6 . Bend Tests .

- n n h a r (a) Cold be d tests shall b e m ade o t e m te ial as rolled . b uenc - en es s ec ens e ore en n s a b e ea e to a ( ) ! h b d t t p im , b f b di g, h ll h t d light cherry red as seen in the dark (about 1200 degrees and quenched

in a er the e era ure of c is a ou 80 e rees F . w t , t mp t whi h b t d g (0) Specimens for cold- bend and quench- bend tests from plates shall bend

throu gh 180 degrees without fracture on the outside . of the

en or on as o ows : For m a er a , 1 nc and un er in c ness b t p ti , f ll t i l i h d thi k , ﬂat on se for m a er a o er 1 nc in c ness aroun a in the it lf ; t i l v i h thi k , d p , - u h c ness of the n diameter oI which is eq al to t e thi k specime . (d) Specim ens for cold- bend and quench-bend test of boiler- rivet steel shall bend cold throu gh 180 degrees ﬂat on themselves without fracture

on the outside of the bent portion .

(e) Bend tests m ay b e made by pressure or by blows.

est ecimens . 7 . T Sp

ens on and en - est s ec ens for a es and race ars ﬂat or (a) T i b d t p im pl t b b , u are s a b e a en ro the n s e ro u c and s a b e of the sq , h ll t k f m ﬁ i h d p d t, h ll

i 4 an r est Piece for Ri ets F g. . St da d T v

ens ones s ec ens s a b e full thickness of material as rolled . T i t t p im h ll

- 3 . Ben es s ec ens of the form and dim ensions shown in Fig. d t t p im — nc es to 2 nc es w e and s a a e the s eare shall b e i h 5 i h id , h ll h v h d

edges milled or planed . CONSTRUCTION OF BOILERS 1 1

For ens on es s r e s b e este to a a e en of not ess an t i t t , iv t will t d gg l gth l th fo r ur h a e e wn in i . 4 es t e as s o F . tim di m t , h g R e s fro eac lot offere se ec e the ns ec or s a s an the iv t m h d , l t d by i p t , h ll t d following tests : 1 Bend r n o r u 1 e r ( ) Tests . T he ivet shanks shall be d c ld th o gh 80 d g ees f ﬂat on e se es as s own in Fi . 5 ou rac ure on the th m lv , h g , with t t ou s f n n ide o the b e ortio . t t p p 2 Flat n le hot to tenin Tests . T he r e ea s s a a e a ( ) g iv t h d h ll ﬂ tt , whi ,

am e er 2 es the am e er of the s an as s own in Fi . di t % tim di t h k , h g

6 ou crac n at the e es . , with t ki g dg

3 Finish. R e s s al b e rue to or c oncen r c and free fro ( ) iv t h l t f m , t i , m

n ur ous scale ﬁns seam s and o er e ec s . i j i , , , th d f t 4 e ectio i to mee the re u re en s s eci e ( ) R j n . Rivets wh ch fail t q i m t p ﬁ d in 1 and 2 b e re ec e and re urne to the anu ac urer ( ) ( ) will j t d t d m f t ,

who shall pay return freight .

ection of Ri et i i 6 . e ec ti 5 . F . t o Fig. S v g R v S n Shank After Bend Test After Flattening Test

FIN ISH AND M AR KIN GS

ariation in Ga e. T he hic ness of eac s eare a e s a not 8 . V g t k h h d pl t h ll vary

ore an 0 . 01 nc un er a or ere . m th , i h d th t d d er l s al b e ree fr n 9 . T he nis e a a o ur ous efec s and s all a e ﬁ h d m t i h l f m i j i d t , h h v

a es and o er a er als use in the c ons ru c on of 1 0 . All pl t th m t i d t ti steam boilers and other pressure vessels shall b e tested at the mill or place where su ch r a s are m anuf ac ure and the m anu ac urer s a a e all es s and mate i l t d , f t h ll m k t t urn s su c recor s of sa e as s a b e re u re ese ru es and s a eac f i h h d m h ll q i d by th l , t mp h a e the na e of su c anufac urer ere anu ac ure and the ea pl t with m h m t , wh m f t d , h t nu er fro hic su c a es ere a e the ens e s ren and the c mb m w h h pl t w m d , t il t gth, thi k Four su c s a s s a b e ace on eac a e a n an area of 25 ness . h t mp h ll pl d h pl t h vi g s u are ee orun er a ou 6 nc es fro the e es at a onal corners and one q f t d , b t i h m dg di g , u the cen er of the a e of as m a b e rec e the ns ec or as desi abo t t pl t , y di t d by i p t , g nated by the boiler maker in his order for the plates . Plates over 25 squ are fee area s a a e ﬁv e su c s a s a ou 12 nc es fro the e e at the four t , h ll h v h t mp , b t i h m dg

cor ers and one a ou the m e of the a e. n , b t iddl pl t E ach head or plate to b e ﬂanged shall b e distinctly stamped by the m anu facturers on o s es as rec e the urc aser of the m a er a or the b th id di t d by p h t i l, by 12 CONSTRUCTION OF BOILERS

o er a er the nam e of the m anu ac urers ace w ere anuf ac ure b il m k , with f t , pl h m t d, owes ens le s ren and the hic ness s a s to b e so oca e as to b e l t t i t gth, t k ; t mp l t d plainly s e en the ea is n s e and in os on in o er r ressur vi ibl wh h d ﬁ i h d p iti b il o p e vessel .

1 1 . Ins ecti e e p on and R j ction .

a T he ns ec or s a a e ree en r at all im es e or i ( ) i p t h ll h v f t y, t whil w k s being ’ er or e to all ar s of the anu ac urer s w or s w c c n p f m d , p t m f t k hi h o cern the m anufacture of the m aterial ordered for boilers or other pres

sure esse s. T he anuf ac urer s all affor the ns ec or free of v l m t h d i p t , cos all reasona e ac li es to sa sf him a the m a er t, bl f i ti ti y th t t ial is n i e in acc or an ce ese s ec c a n bei g furn sh d d with th p iﬁ tio s. All tests and inspections shall b e made at the place of manufacture prior n to shipme t . b M a er a c su se uen to the a o e es s at the ( ) t i l whi h, b q t b v t t mills and its acce ance ere e e o s ea s o s r eness crac s or o er pt th , d v l p w k p t , b ittl , k , th er ec ons or is oun to a e n ur ou s efec s m a b e re ec imp f ti , f d h v i j i d t , y j ted at the shO and s a en b e re ace the anu ac urer a p, h ll th pl d by m f t t

his own cost .

SE CTION 2

M ISCELLANE OUS M ATER IAL

m s u s ra s ea s c o us on c a ers urna 1 . S el s ru ces or h l , d , b tt t p , h d , mb ti h mb , f , a re u re s a n or ﬂan in s al b e of O en- ear s ee as s e any plates th t q i t yi g g g, h l p h th t l p ci

in ec on 1 Para ra s 2 3 4 5 and 6 of ese rul es. ﬁed S ti , g ph , , , , , th u es s a b e m a e of sea ess hot or co rawn s ee for a er- u e 2 . T b h ll d ml ld d t l w t t b

L a - e e - ee u es s a not b e ur er u se in new wa er- u e boilers . p w ld d st l t b h ll f th d t t b " — boilers nor in retub ingOld water tub e b oilers . e s s a o s and races s al b e of o en- ear e ra so s ee 3 . Riv t , t y b lt , b h l p h th xt ft t l,

as speciﬁed in these rules . as s ee for u se in o ers and s eam su er ea er m oun n s an o e 4 . C t t l b il t p h t ti g , m h l ea e in s s e u s or an o er ar s of o ers or su er ea ers frames, st m pip , ﬁtt g , id l g , y th p t b il p h t ee is u se s a a e the fo ow n c emi c a and s ca ro er es : where c ast st l d , h ll h v ll i g h l phy i l p p ti (a) Chemic al Composition : T he steel shall c onf orm to the following requ irements as to c hemical c omposition

not o v er er en Phosphoru s . 0 05 p c t not o er er c en Sulphur . v p t

(b) Chemical Analyses : T o determine whether the material conforms to h re u re ents as to c e c a c o os on s ec e in a an t e q i m h mi l mp iti p iﬁ d ( ) , analysis shall b e m ade by the manuf acturer from a test ingot taken ac D r n for ana s s al durin g the p ouring Of e h melt . illi gs ly i sh l b e h n taken not less than i inch beneath the surface of t e test i got . A copy of this analysis shall b e given to the purchaser or his repre

sentativ e. A check analysis of c astings m ay b e made by the purchaser from ens on or en - es s ec en in w c c ase an e cess of a broken t i b d t t p im , hi h x

’ 20 per cent above the requ irements as to phosphorus and sulphur

a w b e a owe . the s ec en has een annea e speciﬁed in ( ) ill ll d If p im b l d , the drillings for anal ysis shall b e taken not less than i inch beneath

the surface. CONSTRUCTION OF BOILERS 1 3

i n T he stee for c as n a c nf Tens o Tests . l ti gs sh ll o orm to the following in u r u r n r m im m eq i eme ts as to tensile p operties .

i ren h lb er in ens le st t . s . T g , p q to E longation in 2 in 2 2 per eent Redu c tion of area

Bend Tests : The test specimen shall b end cold through 1 20 degrees for sof cast n s and 90 e rees for e u c as n s ar n a 1 - nc t i g d g m di m ti g , ou d i h

in w ou frac ure on the ou si e of the en ort on . Ben ests p , ith t t t d b t p i d t a ressure or ow m ay b e m de by p by bl s. Alternative Tests to D estru ction : In the case Of sm all or unimportant c as n s a es to estruc on on ree c as in s fro a lot m a b e ti g , t t d ti th t g m y u e for th ens on and n a sub stit t d e t i b e d tests . This test sh ll show the a er al to b e u c e ree ro n ur ous efec s and su a e m t i d til , f f m i j i d t , it bl

for the purpose intended . A lot shall consist Of all castings from nn in th furn h sa e e a ea e e sa e ac e c ar e. t e m m lt, l d m h g Test Specimens : Test b ars shall b e attached to all c astin gs w eighing un or o er ro e the es n Of the c t n will 00 o s as s er i . 5 p d v , p vid d d ig i g p m t If the castings w eigh less than 500 p ounds or are Of su ch a nature a es ars c ann o b e a ac e tw o es ars s a b e cas to re th t t t b t tt h d , t t b h ll t p resent each melt; or the qu ality of the castings shall b e determined by tests to destru ction as sp eciﬁed in All test b ars shall b e h as n r r h anuf ur annealed with t e c ti gs they ep esent . T e m act er and urc aser s a l a ree e er es ars can b e a ac e to c as n s p h h l g wh th t t b tt h d ti g , and also on the loc ation of the b ars on the castings and the method

n - of c asting unattached b ars . Be d test specimens shall b e 1 by

‘ (g) Number of Tests : O ne tension and one b end test shall b e mad e from an es ec en S ows efec e ac nin eac h melt . If y t t sp im h d tiv m hi g or e e o s a s or if a ens ones s ec en rea s ou si e the a e d v l p ﬂ w , t i t t p im b k t d g g en m a b e iscar e an d the anuf ac urer and the ur l gth, it y d d d ; m t p chaser or his representative shall agree up on the selection of another i specimen in ts stead . as ron for use in o er oun n s s ea - e n s s e u s or 5 . C t i b il m ti g , t m pip ﬁtti g , id l g , er ar s of o ers ere cas ron is er e to b e use s a not a e any oth p t b il wh t i p mitt d d , h ll h v r n less than p ounds tensile st e gth . ross es conn ec n the Ste a and w a er ru s of w a er- u e 6 . C pip ti g m t d m t t b boil ers and cross boxes shall b e of wrou ght or c ast steel when the w orking pres n su re exceeds 125 p ounds per squ are i ch .

- u d ru s O f w a er u e o ers and all ressu re arts o er 2f nc 7 . M d m t t b b il p p v i h e s e or e u a en cross- sec ona area on an oi er S a b e O f wrou or pip iz , q iv l t ti l , y b l , h ll ght c ast steel when the w orking pressure all ow ed on the b oiler exceeds 125 pounds gage per squ are inch . f rhea ers a ac e to o ers or se ara e r 8 . Pressure ar s o su e p t pe t , tt h d b il p t ly ﬁ d , shall b e of wrou ght or c ast steel .

9 . Bo er an d su er ea er oun n s su c as no z es cross es s ea il p h t m ti g , h z l , pip , t m es n s al es and e r onne s s a b e of wrou or c as s ee w en pip , ﬁtti g , v v th i b t h ll ght t t l h r expo sed to steam which is su perheated over 80 deg ees F .

- - - 1 0 . a er le and oor fram e r n s of ert ca ﬁre u e oi ers 36 nc es W t g d i g v i l t b b l , i h

or o er in ia e er s a b e of wrou or cas s ee or wrou ron . wrou v d m t , h ll ght t t l, ght i A ght 14 CONSTRUCTION OF BOILERS

on m ud r n s all b e use at the o o in w a er e s of o ers and s ir i g h d b tt m t l g b il , thi water ' leg shall not b e formed by bending in the plates and riveting together at the edges . 1 - - 1 . Water leg and door frame rings of locomotive type boilers shall b e of

wrou or cas s ee or wrou ron . ght t t l, ght i

SECTIO N 3

STAMPING O F BO ILERS

1 . In a n out s e a es urnace s ee s and ea s in the o er s o l yi g h ll pl t , f h t , h d b il h p , care s a b e a en to ea e at eas one of the s a s S ec e in ec on 1 h ll t k l v l t t mp , p iﬁ d S ti ,

Par. 10 of ese ru es so ocate as to b e a n s e w en the o er is com , th l , l d pl i ly vi ibl h b il plated ; except that the tube sheets of a vertical fire-tube boiler shall have a or on at eas of suc s a s s e su c en for en ca on en the p ti , l t, h t mp vi ibl ffi i t id tifi ti wh o e i b il r s completed .

2 . E ac o er s a conf or in e er e a w ese s an ar ru es and h b il h ll m v y d t il ith th t d d l , s a b e s nc s a e a e er of the s a e o er e ar en or an h ll di ti tly t mp d by m mb t t b il d p tm t, ns ec or o n a cer ca e of co e enc as an ns ec or of s ea o ers i p t h ldi g tiﬁ t mp t y i p t t m b il , and w o is not rec or n rec n eres e in the anu ac ure or sa e of h , di tly i di tly, i t t d m f t l s eam o ers b ut in the e o of an nsurance co an au or e to nsure t b il , mpl y i mp y th iz d i

o ers in s a e. E ac o er s a b e s a e the u er in the res b il thi St t h b il h ll t mp d by b ild , p ” ence of the ns ec or a ser a nu er and the na e of the u er i p t , with i l mb with m b ild either in full or abbreviated and the builder Shall submit a facsimile of his pro o r n for r h p sed style of stamping to the state boiler dep a tme t app oval . T e height ]l of e er n not b e ess an n l tt s a d ﬁgures used In stamping shall l th 1 i ch .

3 . In nu er n ser a eac u er s a co ence the nu er mb i g i lly, h b ild h ll mm with mb 1 and c on nue n r r ti umbering In consecutive o de .

4 . L ocation o t m s he oca on of s a s is to b e as o ows f S a p . T l ti t mp f ll — a O n or on a re urn- u u ar o ers on the fron ea a o e the ( ) h iz t l t t b l b il t h d , b v

central rows of tubes. — b O n or on a ﬂu e o ers on the ron ea a o e the ﬂues . ( ) h iz t l b il f t h d , b v — (c) O n locomotive type or starwater-tube boilers ou the furnace

end a o e the an o e. , b v h dh l — (d) O n vertical ﬁre-tube and vertic al submerged- tube boilers ou the

s e a o e the urnace oor. h ll, b v f d e O n wa er- u e o ers a coc and co r n He ne and ( ) t t b b il , B b k Wil x , Sti li g, i , — Robb- Mumford standard types on a head above the manhole

O en n refera on the ﬂan in O the an o e O en n . p i g, p bly g g f m h l p i g — O n er c a o ers a or H a e on e on the to ea . (f v ti l b il , Clim x zl t typ p h d — (g) O n Cahall or Wickes vertical water-tub e boilers on the upper h ru a o e t e an o e o en n . d m , b v m h l p i g — h O n co c ar ne o ers ou the fron ea a o e the cen er or ( ) S t h m i b il t h d, b v t r - ndf urn ight ha ace . i O n E cono c o ers—on the rear ea a o e the cen ra rows of ( ) mi b il h d , b v t l

tubes . — ( 7) For other types and new designs in a lo cation to b e approved by r n c r the board of boile i spe to s . ’ n ar a n h i r a not b e cov 5 . T he sta d d st mp a d t e boiler bu lde s stamps sh ll

" n n r m r ered by i sulati g o other ate ial . CONSTRUCTION OF BOILERS 15

o er s o s in whic o ers are cons ru c e for n a a on in 6 . All b il h p h b il t t d i st ll ti this S a e s a be o en to the e ers of the s a oi er e ar en and ns ec ors t t h ll p m mb t te: b l d p tm t i p t o in cer c a es of c o e enc as ins ectOrs of s ea o lers at all reason h ld g tiﬁ t mp t y p t m b i , a e ours for ns ec on of a er al e o s of anu ac ure or m anshi bl h , i p ti m t i , m th d m f t , w k p, and testing .

BO IL E R MA NU PAcreRlNo PRO CESS ES

Sh E ui ment. ee e o e the e op q p As has b n pr vi usly stat d , d sign an

' engineer m ay submit for boiler c onstruction is dependent upon the

the facilities offered by shop in which the boiler is built . Boiler shops are equipped with the foll owing tools : plate

o e e e e e c e o e r lls, plat plan rs, sh ars, drill pr ss s , pun h s , c unt rsinking

c e ﬂan in c e e e e ma hin s , g g ma hin s , hydraulic and st am riv t rs , and a

o e e - e for o e e c e c mpr ss d air syst m p rating pn umatic ma hin s , such as

o calkers and chippers . They also have machine Shops for d ing

c e o as e e c etc . su h machin w rk is r quir d for ﬁttings , furna e fronts , , and a system of cranes for handling and transporting material .

the o e o e of f c e e In connection with ab v is a st r room su ﬁ i nt siz , a

o e e o e for the f rge shop , and an ngin and b il r supplying Shop with the power necessary to operate it .

RIVETED JO INTS

PREPARATION FO R RIVETING

i l the D rilled vs. Punched R vet Ho es. In boiler work drilling

chi e e of riv et holes is gradually displacing punching . Pun ng is ch ap r

o e o to the e not cc than drilling , but it is m r injuri us plat s and so a u

e e see e o e e e e are rat . It is asy to that drilling riv t h l s , v n if tw nty

e e at O ce o e e o n the e b ing drill d n , is d n with l ss strain plat s than when done by a punch .

orc r n The o ce e e to ch F e Required fo Punchi g. f r r quir d pun a

e e plate gives the best idea of the harm done to the plate. Exp rim nt shows that the resistance of a plate to punching is about the same

S o e to b e as its resistance to tensile tearing . upp s this pounds per square inch ; then the force required to punch the plate is the

e c ut out h e ar a times t e shearing str ngth , or

in which d is diameter in inches and t is thickness in inches . 1 6 CONSTRUCTION OF BOILERS

For o e 7 c e e - c e the o ce a h l 2 in h in diam t r in a é in h plat , f r will b e 1 2X X 2 X lb .

A oo c e e e e g d , du til plat is but littl injur d by punching, but

of ee e e b e e r if a hard , st ly natur , it is lik ly to s riously injured . Fo this reason wrought- iron plates are usually punched and steel plates

are e . O n the e e e e o e drill d whol , a drill d plat is som what str ng r than e e of o t e e a punch d plat for any kind j in with plat s of lik thickness .

ea ed l s R m Ho e . Some boiler makers punch the rivet holes

e the e e l ze h small r than d sir d S and then ream them out. By t is

o e f th pr c ss most o e Injured metal around the holes is cut away . ’ Annealing. Another method to overcome the injurl ous eﬂects

O f th Th f punching is to anneal e plate. e ordinary process o annealing consists Of heating the plate to red heat and then allowing

o o . B e e or stee it to co l sl wly y this m ans , hard and brittl iron l is

e t . e the m e the urfac e e mad sof and tough Whil tal is hot, s e b com s

e . m t r e e e n t h oxidiz d For os pu pos s this oxid scal is o armful , but

e e b e e o e . e e e a e in som cas s it must r m v d As this is xp nsiv , proc ss

The c of of annealing in illuminating gas has been devised . a tion the gas is to reduce the oxide without altermgthe properties of the

' The e ts O e o e e e o the piece. r sul btain d fr m ann aling d p nd up n kind

o or ee the e e e to c e the e of ir n st l , t mp ratur whi h it is rais d , and rat

e e to ee o e o of cooling . It is a gr at advantag all st l Of v r p unds

er e c e e e o e ee are e e e p squar in h in t nsil str ngth , but s ft r st ls littl b tt r

for the process . The Shops that do the best boiler work proceed in the following manner :

H r Standard Practice. oles for rivets in ﬂat plates a e drilled “ ” w e are c e o e e o the e e hile plat s ta k d t g th r by b lts, drills b ing guid d

c e o e the e e e are e by small pun h d h l s in upp r plat only . Plat s tak n

e c e ee O reassem apart aft r drilling, s rap d fr f all burrs and chips, and

bled for riveting .

‘ e are rOlled c e f r r1v tin the Sh lls in ylind rs and assembled o e g, and 1 plates and butt straps are drilled in place 1 3 inch larger than the rivet .

he o e c o c e o e the e T f r going nstru tion insur s true h l s, and hol s in

e ch o e c c both plat s must mat with abs lut a cura y, thus avoiding all

ce for the use O c o O e ce i ne ssity f a driftpin, whi h s ft n produ s injur ous strains which materialize only after the boiler has been placed in

service.

18 CONSTRUCTION OF BOILERS

TABLE 1 1

Dim en sio n s o f Rivets

C ONE HEAD C OU N TERSU NK BU T T O N HEAD

e o e e e e to use o e plat s , but many b il r mak rs pr f r ir n riv ts in all c ases .

ee e of e Use are o . 8 e Thr typ s riv ts in Sh wn in Fig , Tabl II , giving the dimensions .

ri in ivets. Hand Method M ethods of D v g R . Formerly all o e e e e but now e boiler j ints w r riv t d by hand , most riv ting is done c e e c e t t e e to c a by ma hin s, x p hos riv ts whi h machine cannot b e

n - e . e the red hot e e e the o e appli d If do by hand, riv t is ins rt d in h l ,

the eco liead e two e e o and s nd form d by riv t rs w rking with hammers . This head is either made conical by the hammers alone or ﬁnished “ ” - Th with a cup shaped die called a snap . e latter is the more usual

h e r method . T e disadvantages Of hand riv ting a e slowness and a

e e c o e e e the e the o t nd n y to form a Sh uld r b for riv t ﬁlls h le.

c Machine Method. Ma hine riveting is preferable to hand rivet

the e e e e o e c c e the ing , as work is don b tt r, fast r, and m r a urat ly ;

e e c o on the e e e o e e c om pr ssur ming gradually ntir riv t, c mpr ss s it

l l th o e e o e th e o e B o e ete o e e . e e p y int h l b f r h ad is f rm d f r riv ting ,

e o b e e the e are c o e e e so car sh uld tak n that plat s l s tog th r, that a Shoulder will not b e formed between the plates and prevent a good

R e o b e e red- hot for joint . iv ts sh uld always put in whil , in this

o e are o e e o e e e e conditi n th y m r asily w rk d , and wh n th y cool th y

c the e o e e o . contra t, nipping plat s t g th r in a tight j int

H - e o e e e e e e ydraulic riv ting is m r gradual , and is g n rally pr f rr d

Th e e o the e e e e to steam riveting . e pr ssur fr m st am riv t r oft n comes as a sudden blow and does not allow time for the rivet to

e e c e the e b e e completely ﬁll the hole. In ith r as riv t should h ld under pressure until black . CONSTRUCTION OF B OILERS 1 9

o Rivets with Countersunh Heads Use f . It is sometimes desir

e r1v et c o e e the e oe not abl to with a unt rsunk h ad ; that is , riv t d s h h proj ect above t e plate. T e countersunk head is formed by hammering down the end O f the rivet into the c ountersink in the D o . 7 . hi e plate. This form is sh wn at , Fig T s joint is Oft n used in shipbuilding and in boiler making when it is necessary to attach

. It oul b e o e o e on co mountings Sh d always av id d , if p ssibl , ac unt

e e s and e ec e the o ce c the of its w akn s , sp ially wh n pulling f r a ts in

c o of the e of the e the e e e e dire ti n l ngth riv t, as h ad has a v ry ins cur

i e to b e l e o the o hold and is l k ly pu l d thr ugh h le.

eratu re o Rivets or D rivin ee Temp f f g. St l rivets Should not b e

to hi e e o e are to red heated a w t h at , as ir n riv ts , but a bright cherry ,

e o hi o e Th ﬁr i for if heated b y nd t s p int th y will burn . e e in wh ch steel

r o b e hic h a e e e e t e o e e . rivets h at d sh uld k pt t k, and draft m d rat

Shaping Butt Straps. Butt straps should b e bent into true parts of cylinders Of a radius equal to that of the ﬁn ished boiler drum . Under no circumstances is it c onsidered good practice to bend butt “ ” n straps by a series of ki ks to give them an approximate true bend .

The edges of plates should b e bevel planed to fac ilitate calking .

r o f e f Flanging. The const ucti n o practic ally every d sign o boiler manufactured from sheets requires the ﬂanging Of some Of

- - i e of e e e ﬁre e o e . the parts . Th s is tru wat r tub as w ll as tub b il rs

f o er o e o e o e e u e so c NO other part o b il w rk, wh n pr p rly d n , r q ir s mu h

- o m as ﬂan in o o careful design and w rk anship g g, alth ugh in many Sh ps

h eet to b e e. t c e t e this would not appear tru As a ﬁrs prin ipl , sh

e SO the r e e e should not b e ﬂang d that radius Of cu vatur is small , sp “ ” cially where there is a possibility of breathing action being c on “ ” B e i e the centrated at the ﬂanged portion . y br ath ng is m ant

‘ periodic c hange Of shape between the ﬂat Or main portion of the

e e e due to c e e e or to the Sheet and its ﬂang d dg , hang s Of pr ssur

deformation of other portions of the boiler exerting stresses upon the

ﬂanged section .

one o the e The next item , and fully as imprtant , is that ﬂang d sheet must b e un iformly heated to a c herry- red temperature and

o the work completed b efore this temperature is l st by radiation .

A second heating sets up loc al stresses which c an b e only partly

R e e the ee o e removed by annealing . ath r than h at sh t m r than

r of e t be e e e e e . once, some other fo m d sign mus s l ct d if n c ssary 2 0 CONSTRUCTION OF BOILERS

If it is impracticable to heat anentire metal piece for a small

e for t ce the end e ce of o ﬂang , as , ins an , at Of an int rnal furna a Sc tch

e the e e o b ut the e b e c boil r, h at is appli d l cally, whol must arefully

e e the ﬂan in 1 anneal d aft r g g s done. Some boiler Shops perform all simple ﬂange work without

h t t c o heating t e Sheets . I may b e s ated that this practi e sh uld always b e discouraged when intended for u se in c onstructing high

o e o e c e c i e pressure b il rs . An th r pra tic whi h s in disfavor is hamm r ing by hand ; in fact ﬂanging by any other process than by the u se Of suitable machinery should b e avoided in building high- pressure

boilers .

TYPES O F RIVETED JOINTS

in Efﬁciency of a Jo t. It is Obvious that a plate is weakened

f c of by removing the metal o rivet holes . It is ustomary to speak the strength Of a riveted joint in terms of the percentage of the strength preserved of the original plate ; the ratio Of the j oint strength

t t of the eet e e e ec e the to ha original Sh , xpr ss d in d imals, is call d ‘ nc f the t R e e l oints I eﬁicie y o join . iv t d j may fail n several ways :

2 B e (1) By shearing the rivets . ( ) y t aring the plate at the 3 reduced section between the rivets . ( ) By crushing the plate or 4 rivets where they are in c ontact . ( ) By cracking the plate

h he f the c ce between t e rivet hole and t edge o plate. As in pra ti

b e e ffi e ee e e the lap c an always mad su ciently wid , a joint n d n v r

- fail in the last named way .

Classiﬁcation. The names given to the several kinds of joints “ ” e e for e the e o e are d scriptiv , as , instanc , t rm lap j int is appli d to a

h f h o e joint in which t e edges o t e sheet to b e j ined ov rlap . A butt ” j oint is the name given to a j oint in which the edges of the jom ed

n t e eet e c e e e on e the e sheet do o ov rlap but m a h oth r dg , whil fast n ing is accomplished by the use of straps which overlap the edges

to b e united . The number Of rows of rivets parallel to the length of the joint “ ” “ ” “ ”

e e the e e o le e e etc . are expr ss d in t rms singl , d ub , tr bl , In butt-joint seams the word designating the number of rows of rivets refers to the number of rows on one side of the j oint only ; thus a treble-riveted butt joint has actually six longitudinally rows of

n e of the mee e of the e ee . rivets, three o each sid ting lin join d Sh ts CONSTRUCTION OF BOILERS 2 1

Lap Joints . Circumf erential or girth seams are usually lap j oints since the tendency to rupture at these seams is only one- half as great as at the longitudinal seams . Longitudinal lap seams are

o e e e for usually d ubl riv t d , and

hi e e e e e e e . gh r pr ssur s , tr bl riv t d

9 o the o e o Fig , sh ws m st simpl f rm of this j oint and is c alled a single

o - riveted lap j int . D ouble riveted lap j oints may have the riv ets 1 arranged as shown in Figs . 0 and - i 9 . in e i ete L a Joint F g. S gl R v d p 1 h o e o 1 . T e f rm r j int is called a

o e- e e o e the e o e d ubl riv t d lap j int with chain riv ting , and latt r a d ubl

e e o e e e The e e e riv t d lap j int with stagg r d riv ting . stagg r d riv ting

e e e the c the o e is a littl w ak r than hain , but j int is usually tight r and less lap is required .

E lcienc Th f of he c ﬁ y. e e ﬁc iency lap j oints depends upon t pit h

e e the e the c e the e the and diam t r Of riv ts , thi kn ss Of plat s , and

- Fi 1 1 oub le-Ri eted L a Joint Fi . 1 0 . ou b l i e ed L a Joint . . , g D e R v t p , g D v p m Chain Riveting Staggered Ri v et g

he ef c e c o o e e e the number Of rows . T ﬁ i n y is als s m what alt r d if

e e e are c o plates are drilled instead Of punch d . As th r so many ndi

nc e tions we c an give only rough average eﬂicie i s.

L a o n s n e r e e eflicienc a ou 56 p j i t, i gl iv t d, y b t % L a o n ou e r e e ef c enc a ou 70 p j i t, d bl iv t d, fi i y b t % L a o n re e r e e e c enc a ou 72 p j i t, t bl iv t d, ffi i y b t %

It is well to remember that the efﬁciency ﬁgures are calculated without referenc e to the c reation Of an eccentric load on the sheets

h c e are ec b e and t e rivets . The true efﬁcien y ﬁgur s appr ia ly l ss than 22 CONSTRUCTION OF BOILERS

TABLE III

Pro po rtio ns o f Riveted Lap J o ints

e e for o e W e o o thos calculat d , it is imp ssibl h n using lap j ints to av id the tendency of the sheet to pull into a curved line of a radius equal

t of the c e of c o to tha ylind r whi h it f rms a part . Table III gives the proportions of riveted lap joints for average

e e of t 150 practic in boil rs up to abou pounds pressure. The probable efﬁciency of joints may b e calculated by mathe

e b ut the c ef c e b e e e of mati s , a tual ﬁ i ncy can obtain d only by m ans

t f t e th of t m e. e e e o e e the esting achin In sting , a pi c uncu plat , Siz f e e o the c o the c e t te e . which d p nds up n capa ity ma hin , is ﬁrs st d of Then a portion of the j oint approximately the same Size is tested . The ratio of the breaking strength of the joint to that of the uncut plate is its efﬁciency .

utt ints. L e m e e t for e e B Jo ongitudinal s a s, xc p small diam t rs ,

' h e e r eldom are almost always made wit butt joints . Th s joints a e s single riveted bec ause as such they are not much stronger than a

- n n r e e t a d a e e e e e. e e e double riv t d lap joi mor xp nsiv If, how v r, th y

e t r e e e e the aremade with doubl but straps and double o tr bl riv t d ,

f e The two e of the j oint Shows a high e ﬁci ncy . butt straps may b 12 o same width or the inner may b e wider than the outer . Fig . sh ws

- e e- e e a double riveted butt joint with two butt straps . A tr bl riv t d

11 1 . butt j oint is shown 1 Fig . 3 ‘ i c The o are x e eﬂi ciencies Eﬁlc en y. f llowing appro imat

Bu o n s s n e r e e e c enc a ou 65 tt j i t , i gl iv t d , ffi i y b t % Bu o n s ou e r e e ef c enc a ou 75 tt j i t , d bl iv t d, fi i y b t % Bu o n s re e r e e e c enc a ou 85 tt j i t , t bl iv t d, ffi i y b t %

Butt straps should b e at least ﬁv e-eighths the thickness of the

of the o e the o e shell plates . In all butt j ints illustrat d ut r strap is CONSTRUCTION O F BOILERS 23

the e o e to o e made narrower than insid strap , In rd r pr vid a calking edge on the outside with as little pitch or distanc e between the rivets

- Fi . oub le Ri ete Bu Joint g 1 2 . D v d tt as possible ; the effectiveness of c alking is dependent upon the ability h the e o h ee c ose c o c . o t e Of riv ts to h ld t e Sh ts in l nta t Obvi usly,

13 T re le- ete Butt Jo nt Fig . . b Riv d i

e th the c e e the e e it is farth r apart e rivets are along alking dg , asi r for the sheet edge to spring away from its companion sheet . 24 CONSTRUCTION OF BOILERS

TABLE IV

fﬁc ienc es of D o b le=Butt=Stra ou b le- i e e o n s E i u p, D R v t d J i t

Bu tt and ou e- tra Jo nts ou e eted in Whi h the it h of i v ets in O uter D bl S p i , D bl Riv , c P c R h e n w R ow Is T wice the Pitch of Rivets in t e S co d R o .

” e f a Plat ” s Butt Straps (or thicker) ” g, Rivet (before driving)

h in a l T he letters B or G show the m anner in whi ch t e jo t will f i . = n ter row B Strength o f plate b etw een rivet holes i o u . n f wo 2 ri ets us the shearin stren th o f one G =C ru shing strength o f plate in fro t o t ( ) v , pl g g in l shear ( 1) rivet in s —g e . ﬁ ures NOTE T he highest emciency in each c olum n is show n in heav y g .

26 CONSTRUCTION OF BOILERS

e e the o e the sometimes driven by car less workm n into j int , w dging

1 e e e e e Ve plates open as Shown in Fig . 5 . S v r and car l ss calking is ry

the e e e o injurious to boilers . On insid it oft n caus s gr oving and

e the e O e e the e of fractur , and fractur f plat s th n follows lin calking rather than the line Of rivet holes . WELDED JOINTS

i n e Advantages and D sadva tag s. Welded joints for boiler work

e e e e e e h e B would b e desirable if th r w re gr at r c rtainty in t e r sults . y their use deposits which accumulate on and around rivet heads and

o o e e e e e o joints , c rr sion caus d by l akag , and loos riv ts and calking w uld

Mo e e a e ec e e t o e b e done away with . r ov r, p rf tly w ld d join is str ng r

t e e t e e the than the bes riv t d join , and approximat s n arly to original

e e e e e o e strength of the plat . W ld d st am drums are us d f r wat r

B Fi W c m ot e re ox . 1 7 l ri al lde . 1 6 e in o o . E ect c l e B iler l Fig . ld L iv Fi g y W d o F ues Courtesy Of C 0 E lectric and Man Cou rtesy of Railway M aster M echanic ufacturing Company

t e o e of the e e the c c o of c o ub b il rs marin typ and in onstru ti n r ss pipes ,

m etc . U o e it 1S 1m oss1ble e e mud dru s, nf rtunat ly p , from xt rnal

o e the o e of e e o h c e t . T e f appearan s , judg s undn ss a w ld d j int lack o tests on such j oints and the small amount of information on s the

he e e subj ect render t r sults Of exp riments of little value. The weld

1 e e e the e e of the e are e at red 3 b st mad wh n dg s plat s ups t, heat, to

the e t c e f nearly double plat hi kn ss , and beveled to an angle o about

The e are t e e e e e the e 45 degrees . edg s h n h at d tog th r, and w ld made

the t the c e h by hammering join down to original thi kn ss of t e plate. Welding in boiler work ﬁnds its greatest usefulness in repal r

o e ec e e e e me of e w rk , sp ially in such cas s wh r any oth r thod r pair

e the e o of o e ee or ce e e would necessitat r m val b il r Sh ts, in pla s wh r

iff B t ar any other work is d icult owing to lack of room . oiler ubes e CONSTRUCTION O F BOILERS 27 sometimes welded to the tube sheets after the usual expanding is f 1 17 are o O o . done . Figs . 6 and illustrati ns cases in p int It is to b e said in connection with welding Of cracked b oiler

e e e e the ee e e c e she ts , that th r is dang r that Sh t m tal may hav rystalliz d so much as to b e unsuitable for good welding work . Many repair

" o re o c e c e e o e j bs a failures fr m this aus , whi h mak s w lding in b il r

o The e f, work less attractive than it otherwise w uld b e. w lding o tubes into tube Sheets of boilers makes it difﬁ cult to replac e the tubes whenthey fail at a different place than the weld ; it has been for this reason that welding for this purpose has made very little progress except in very special

h o e boil er designs . On t e th r

the e of o ece hand , w lding sh rt pi s

the e O e e the to nds f tub s , aft r ends have been c ut Off for re

o o o e o ee m val fr m b il rs , has l ng b n

suc c essfully practiced .

ARRANG EMENTS O F PLATES AND JOINTS

Transverse and Longitudi=

nal Seams. The tendency Of a cylindric al Shell c arrying internal pressure to fail longitudinally

t ce c c e e is wi that ir umf r ntially .

i . M h S e hi the se o F . 18 et o o f Handlin Jo int when inc t s is c a , lap j ints g d g Three o r M o re Plates M eet are used for transverse or g1rth

e o e o o n s r f r s ams , and str ng r f rms (butt j i t ) a e used o the l ongitudinal

seams .

’ Co lica ed i . the c o h ee or o e e mp t Jo nts At jun ti n Of t r m r plat s ,

e e the c c u e e o o ee o wh r ir mf r ntial and l ngitudinal j ints m t, rdinary

e e o ul b o e too c . O e co e fﬁc l riv t d j ints w d thi k T ov r m this di u ty, two

‘

or o e e ar o h . e e t e o o . 18 m r plat s f rg d thin at j int, as sh wn in Fig

The l o o ee e c o c o o one ce i lustrati n sh ws a n dl ss mpli ati n Of j ints at pla ,

e to e e c arﬁn but is giv n mphasiz s gas a means Of Obtaining strength .

e e e o e ee the e o Wh n v r l ngitudinal and girth s ams m t, plat s sh uld “ ” b e e e o one e o arrang d to br ak j ints ; that is, longitudinal s am sh uld 28 CONSTRUCTION OF BOILERS

not b e c f The a ontinuation o another . proper arrangement is shown

1 . in Fig . 9

In both vertical and horizontal boilers the inside lap is made to ce o so not o e e for the fa d wnward , that it will f rm a l dg c ollection of sediment .

! r f B i r hel h M ho o f Br n 19 . o le w n et ea i J in Fig. Pa t o S l S o i g d k g o ts

l = i Joints in Interna ly Fired Bo lers. The belts of plates which

e the e of the are e e e mak up l ngth drums som tim s arrang d conically ,

the e eet c e t the e o of with out r sh pla d oward dir cti n natural drainage.

e the o e c e t the t end t Wh n b il r is slightly in lin d oward fron , his conic al

e e t c e e the arrangm n fa ilitat s draining and cl aning, as dirt is removed at the end s e a l n -ﬁr front . This i a gr at dvantage internally ed

' e r fﬁc e a e to e e e . boil rs, as th y di ult cl an m any v nt

in i il r Jo ts in Vert cal Bo e s. In long vertical boilers the ring

e are e the e o so not to s ams arrang d with insid lap facing d wnward , as

e e e for e o h co o hav a l dg s diment . S metimes t e belts of lo m tive

e are e te e c the e t e e at the boil rs arrang d l scopi ally, with larg s diam t r

ﬁr - n e box e d. Of late years the best makers use larger plates than

- o e . e e ec e e ﬁred f rm rly This is advantag ous, sp ially in xt rnally , multi

e the e se e o e the e e e tubular boil rs, as singl am is plac d ab v wat r l v l,

e and th refore is away from the ﬁre. ‘ = - Water Leg Construction. The portion of internally ﬁred

b oilers between the shell and the furnace is c alled the water leg.

. 20 to 26 e e the e of the Figs , inclusiv , illustrat m thod constructing CONSTRUCTION OF BOILERS 29

h o the 2 te le t e ce o . . 0 21 wa r g and j ints around furna do rs Figs , , and

ee e o of c c th e l . 20 th 22 show thr m th ds onstru ting e wat r eg In Fig . e exterior plate and the furnace plate are riveted to the ring D by

f l e of o o e . means long riv ts This ring is usual y mad wr ught iron ,

21 the but in many cheap boilers it is of cast iron . In Fig . two plates

- - . 2 orm of ater Le Con Fi . 2 1 . orm f a r Le Con Fig 0 . F W g g F o W te g stru ction stru ctio n

the D c o c e are riveted to ﬂanged ring . This nstru tion is b tter than the o - on co of e the o f s lid cast iron ring , ac unt ﬂ xibility, but juncti n o th e D 0 o o e e e e plat s and f rms a c rn r in which s dim nt is deposited .

22 t e e B e e e C. In Fig . h plat is ﬂang d and riv t d to This arrange

h ne o . 21 e e e e e t e o . m nt r quir s l ss riv ting than sh wn in Fig Figs .

20 21 22 ee u the , , and also show thr forms of constr ction of joints 30 CONSTRUCTION OF BOILERS

the e . 2 around furnac door In Fig . 0 both the exterior plate and the furnace

ee are e e e o e e sh t ﬂang d and riv t d t g th r .

e e e This is shown in an nlarg d vi w in Fig .

o 21 23 . The o . constructi n sh wn in Figs ,

24 25 not oo t . , and is as g d as tha in Figs

20 2 ec e of the e e and 3, b aus xtra riv ting ;

e B C for the also , it has two corn rs , and ,

. 22 deposit of sediment . Fig shows a somewhat different form of furnace- door

o c the e e e e c nstru tion , two plat s b ing riv t d

- o to a cast iron ring . This f rm is better

2 I e 6 . t t shown in Fig . mak s this par

f th e too b ut it the o e boil r rigid , has advantage of not having rivet heads in

h oo e e off. e e t e d r op ning to w ar In g n ral ,

‘ the ﬂanged- ring method is preferable to

- e e of e e the cast iron ring , b caus gr at r

e the e freedom for xpansion , but ﬂang d

/ ring form s undesirable corners for sedi

ment accumulation .

n r i Corner Joint Co st uct on. In al

o e e b e most every b il r, plat s must con

- nected at t e . e e of F . 22 or f ig . F m o Water L eg righ angl s An xampl C onstru ction this is seen where the end plates are

e e e are ee joint d to the shell plates of cylindric al boilers . Th r thr principal methods : riveting both plates to

e e o e an angl iron , riv ting b th to a ﬂang d

ﬂan n n i . ring, and g g the e d plate In 2 h Fig . 7 t e two plates are riveted to an

e o e f o or angl ir n , which is mad o wr ught cast iron . This construction is too rigid ; the constant variations of temperature c e e e e c e of o c e aus r p at d hang s f rm , whi h t nd to c rack the angle iron on the inside of the

e the C o o c e e th plat at joint . orr si n in r as s e e a c vil , as it rapidly tta ks iron which has n l d Section Fig. 2 3 . E arge

e of oor Jo int . Fig. 20 onc been cracked or broken . There is no D CONSTRUCTION OF BOILERS 3 1

deﬁnite rule for the dimensions of these

e e to e the angl irons, but it is saf mak mean thickness a little greater than that f h o t e plates . h 2 2 T e forms shown in Figs . 8 and 9 h are better . T e head is ﬂanged and riv

e th h ﬂan in et d to e shell plates . T e g g

e o mak s a m re ﬂexible joint . The radius of the c urve of the ﬂange should b e at

e o h l as t f ur times t e thickness of the plate.

The e e are o e e c on i o f J in h ad and sh ll s m tim s 24 . E nlar e ect on o t Fig . g d S

C onstru ctio n in Fig. 2 1 nected e o to a ﬂang d ring, as sh wn in Fig . 30; the extra row of rivets makes a more

e o the o c ce compl x j int, and c nstru tion , sin

ee b e e b e o . it n d not us d , should av ided In vertical boilers the external ﬁre

E nl r ection of Join 2 n r e i n f in a ed t Fi 6 . E la ed c t o o Jo g S g. g S t

n in Fi . 2 1 C onstru ctio g Constru c tio n in Fig. 2 2

o e the o 1 box is j in d to cylindrical shell by riveted j ints . Figs . 3 and

32 o o Fi 1 n the e e on c of sh w two f rms , that in g. 3 bei g b tt r a count the e c o o co t c o of the ﬂang d ring, whi h all ws expansi n and n ra ti n

e shell and furnac plates .

Fi 2 C o r n e r 2 8 o r n e r . 9 . 2 n Fi . . C Fig 7 . C o r e r g g . m t Wi th lan e Joint with Angle Jom t with Flanged Joint Wi th Flanged Jo F g Plate Head Head Ri ng 32 CONSTRUCTION OF BOILERS

Sometimes the case occurs of connecting two plates which are

e e At h o of the parall l and n ar together . t e bott m locomotive ﬁre box a connection must b e made between the inner and outer shells of the ﬁre are box . Several methods for this construction shown in

° - Fi . 3 1 . E xterna ire Bo Con 2 - g l Fig. 3 E xterna ire Box C on 0 F x l F nec i n Wi h t o t Flanged Ri ng nection with Angle Plate

F i . 33 . . 33A too o c e e g Fig is c mpli at d and is und sirable, both on acc of the e o e e o on ount num r us riv ts and angl ir ns , and account of the i e o c b t e c e . . 333 e e insid j ints, whi h canno alk d Fig is b tt r, since it

one e iro e e the has but angl n ; it has , how v r, undesirable inside joint .

- 3 . iff er nt rm s of i e r B x i ns Fig . 3 D e Fo Locom ot v Fi e o C onnect o

D h f e c . 33 t t e o e e Fig is a good join , form conn cting ring b ing hann l

E e . . 33 we e ee oo e iron Fig , as hav s n , is a g d ﬂ xibl joint , but it has

h e o t e und sirable c rner where sediment lodges . It is to b e remembered that the use of structural steel in the

of - e e o b e e construction high pr ssur b ilers should avoid d , and to this extent the forms of water-leg c onstruction illustrated cannot b e universally used .

34 CONSTRUCTION OF BOILERS

lan ed d r Construction with F g E ges . Manholes a e sometimes

e ﬂan in the e e of the e o u f mad by g g dg hol inwardly, thus f rming o t o f h the sheet itself a reinforcing ring o great rigidity . T e ﬂanged edge f h is faced off to offer a suitable seat or t e manhole plate. When this

o of is e e ec - e e e con f rm construction us d , sp ially in high pr ssur boil r

o e e e shrimk the e structi n , a r inforcing ring is som tim s around ﬂang d

hi n r n e e o are e e off. T s c o st uctio e dg , and b th th n fac d , wh n prop

e e the e e . rly don , is probably b st possibl form to build

l ar Handholes. Handho es e needed to give ac cess to the inside of e the e l of e e for the c e boil rs for r mova s dim nt , washing, and , in as

- f r h c f f w e e o e o t e e e c o e . The o at r tub b il rs , l aning and r pla ing tub s

c e of o c are the e for handholes o prin ipl s c nstru tion sam as for manh les ,

o th use of e o i rm s 1s not e o e e e e th ugh e r inf rc ng g r s rt d to b caus , b ing

e the e of the eet not e o small r , str ngth sh is so s ri usly impaired as

e r e e c with manholes . Th y a e always mad llipti al in shape except in

” e - e o e c e e b e of orof irre u wat r tub b il rs , in whi h cas th y may round g

Th c th f lar shape. e ellipti al shape has e advantage o permitting th e b e e e e e e at the e e plat to ind p nd ntly r movabl , same tim carry

o c th T ing the pressure by f r ing e handhole plate upon its seat . he ﬂanging of the handhole openings l n water- tube boilers is rapidly ﬁnding greater u se on ac count of the greater stiffness of the plate

' and for the o e e around the hole th r advantag s just mentioned .

STAYS

Necessit of Sta in Flat Surfaces. e e e y y g Wh n und r st am , a cylindric al shell is under stress due to internal pressure in two direc

e e e b c e e e due the tions , nam ly, transv rs ly, y a cir umf r ntial str ss to

e e e t the e e e e pr ssur t nding to burs sh ll by nlarging its circumf r nce,

th e h o e e on t e e . e c o e and , l ngitudinally, by pr ssur nds A sph ri al b il r

o e e ec e e e e e te e w uld r quir no stays , b aus a sph r subj ct d to in rnal pr s

e e not c e ce sure tends to nlarg but to hang its shape. All ﬂat surfa s

o e b e e e e the e e e o in b il rs must stay d , oth rwis int rnal pr ssur w uld

t e to e T o bulge them ou and t nd make th m spheric al in shape. avoid stays the ends of steam drums on high-pressure water-tube

r de e e c or o e a e e . boil rs ma h misph ri al , n arly s The ﬁrst and most important requirement in staying is to have

c e e of e e e o the e a sufﬁ i nt numb r stays , so th y will ntir ly supp rt plat

n h e without regard to its ow stiffness . T e s cond is to have them so CONSTRUCTION OF BOILERS 35

e as to e e the e o c o to ee ec o plac d pr s nt l ast bstru ti n fr insp ti n , and ,

to e e so r n e to o ee c rcul o of third, hav th m ar a g d as all w fr i ati n

T oo c c e c o b e e ce water . mu h ar ann t tak n in ﬁtting stays and bra s ,

- e are out of for o e o o e e of he as th y sight l ng p ri ds , and a kn wl dg t ir

ﬁre- e exact condition is not always easy to b e obtained . In tub

oil e the c ce e are : the e c o eets b rs prin ipal surfa s stay d ﬂat nds , r wn sh ,

e e of oco o e e c o o c e of c lin wat r l gs l m tiv b oil rs , and mbusti n hamb rs y

r cal e th d i marin boilers. In e case of m ost Scotch marine

o e the e b il rs , diam ter is large compared to the length ; hence there is c onsiderable

ﬂat surface. All the plates that are not cylindric al or

emi e c b e e h sph ri al must stay d . The details should b e ar ranged for each boiler ; a few general methods and cautions

35 . M e hod f nin a H g. t o Faste g St y Ro ds e e b e . may, how v r, given Simple Stay The most common and simple form of stay

r d o . i is a plain It is used to stay the ﬂat ends of short bo lers . This stay is a plain rod passing through the steam space and having the e e e to the h are e e the e nds fast n d heads . T e ends fast n d and l ngth

e b y e of the e e on o adjust d a vari ty methods, simpl st b ing nuts b th

e of the e The co e e a b o . 5 . sid s plat , as sh wn in Fig 3 pp r wash rs and

e e th h str ngth n e plate and prevent abrasion by t e nuts . In place of the th r e hic are e e nuts e od is often b olted to angl irons, w h riv t d to the e l the one n . hi c s e e o plat s In t s a , turnbuckl s simi ar to sh w

. 36 ar in Fig e used for adjusting the l ength .

kle se to i hten ta Rods Fi . 3 nb u c g 6 . Tur U d T g S y

f o or ee o e The stays are made o wr ught iron st l , with an all wabl

the e are stress of 5000 to 7000 pounds per square inch . If nds

o the co e e of the v e fastened to riveted angle ir ns , mbin d ar a ri ts is

f the rod made a little greater than that o . 36 CONSTRUCTION OF BOILERS

usset Sta . e sa e t n 20 ee G y If a boil r is long, y, mor ha f t , through stays would sag in the middle and not take up the full stress on the

end e . For e et r plat s long boil rs, guss and diagonal stays a e used .

- The form of boiler stay shown in Fig . 37 is made of wrought iron

e e e to e the e e e plat riv t d angl irons , angl irons b ing riv ted to the end

s e . B e of th C L e and G o and h ll oil rs e ornish, ancashir , all way types

Fi . 37 orner o f Boiler ith G u sset ta g . C w S y

e t of s e e e are e re often hav his kind tay. Th s boil rs int rnally ﬁ d and ,

th n of te e e es e o as e variatio mp ratur caus xpansion and contracti n , ‘ h great care should b e used in placing t e gusset stay . If the stay is

e or too are e the e too near the ﬂang if many stays us d, h ad will b e

too rigid and have a tendency to crack .

Fi 8 nal ta s n An e Irons g. 3 . Diago S y U i g gl and Pins

i n l f D ago a Stays. A form o diagonal stay is shown in Fig . 38.

f The The plain rod is c onnected to angle irons by means o pins .

r angle irons are fastened to the shell and end by rivets o bolts .

o e of o e the o oo o . An th r form diag nal stay, call d cr wf t , is sh wn in Fig

r e h nd e . 39 . The two ends a e bolted or riv ted to t e e and sh ll CONSTRUCTION OF BOILERS 37

The angle between the shell plate and stay rod should be small — not e 30 e ee h f mor than d gr s . T e rod itself is designed or tensile

e ce the o ul b e l e c to str ngth, sin diag nal p l may easi y r du ed an eq uiv a

c lent dire t pull . A large factor of safety is used to provide for

e o o futur c rrosi n .

Fi . 3 orm of C row oo ta g 9 . F f t S y

F r o 4 i o e o e o e o e c o o . 0 s marin b il rs , a m diﬁ d r wf t stay , Fig , ft n

Th n e used . e e d passing through the head is suppli d with nuts and t e e the he o e e to o the ap r wash rs , washers having t pr p r tap r all w

to b e set nuts up tightly against them .

o b e a e o e e are e e e It sh uld _ dd d that b il r h ads furth r stiff n d by channel bars or an les laced along the line of holes for the through g t p

i ete R v d Stay Bolts . In loco motive ﬁre b oxes and in the c om b ustion chambers of marine boil

ers e e' are or , th r two ﬂat slightly c urved surfaces whi ch must b e

e o e e e e re stay d t g th r . Th s a riv e e o t d by sh rt screw stay bolts .

The o 41 b lts shown m Figs . and

42 are c e e e the s r w d in plac , and

Fig 40 f ﬂ f a ‘ e M arine e e e e . e nds riv t d ov r In marin nge gf ci jvfgzgsfg, boilers these stays are fastened

e e . So e o Fi . 43 n e e with nuts , as sh wn in g , i st ad of b ing riv t d m

e th h e e Fi . 41 or tim s e b olt is threaded t e entir l ngth, as in g ,

2 he oo 4 . T r e off oo he ce e . is tu n d sm th in t nt r , as in Fig sm th sur

ce es c o o o e e to c e the e ed fa r ists rr si n , and is l ss lik ly fra tur than thr ad

o e the end the b lt . Sometimes a small hole is drill d in , so that if 38 CONSTRUCTION OF BOILERS

o t e the e e e . b l br aks , scaping st am will giv warning This 18 shown

a . 42 . e e are c or 1 at Fig Th s bolts in h inch in diameter . . The stresses whi ch come on a stay b olt are not the same as the

e e on e or on e of str ss s riv ts ordinary stay rods ; as a matt r fact, stay

4 1 . ete o omot e Fi . 42 . ril e orm of e Fig . Riv d L c iv g D l d F Riv ted Stay Locom otive Stay

e e e e c e t bolts fail by a b nding str ss, and g n rally fra tur jus inside the

ee due to the e e s e ee o outside sh t, un qual xpan ion b tw n combusti n

r e the e o e e . O to chamber, o furnac , and outsid b il r sh ll wing this

c of e o e e o e ee e e differen e xpansi n , ﬂ xibl stay b lts hav b n d sign d , but

o e e e u se nor are e e to e c have not c m into g n ral ; th y lik ly , as th y oc upy considerable space and are much more complic ated than the simple

o are e o the e of e e stay b olt . Stay b lts mad fr m b st quality r ﬁn d

bee o the e e of e e e iron , which has n f und to stand str ss s alt rnat h ating

- o o ar and cooling better than mild steel . Ir n stay b lts e more dura

l ec e of the o n e of the . b e, b aus ﬁbr us atur iron

Stiffemn l g Ang es. Where the size of the boiler shell is not large and the pressure is not

e ec e e sp ially high, it is p rmissibl to u se stiffening angles in lieu of stays to prevent the end sheets of cylindric al shells from bulg

111 The a om an l n ll . cc i u s Fi M ar ne a e w th Nuts g p y g g. i St y H ld i

tration . 44 o the de , Fig , sh ws

c o c o ee The tails of such a nstru ti n and n ds no further explanation . illustration can b e studied to advantage in other particulars as it

e the e c the e of a o e the giv s tub spa ing , siz and location handh l ,

o e e e of the e oc the e the oc o of pr p r l v ls gag c ks and wat r, and l ati n a

th c e of 36- c o o o e fusible plug in e as a in h h riz ntal tubular b il r .

Crown Sheet Supports. The crown sheets of ﬁre, boxes and

f o o c e are e o tops o c mbusti n hamb rs usually stay d by cr wn bars, 4 h th o the ce . 5 t e e e on e which extend acr ss ﬂat surfa s, Fig , nds r sting CONSTRUCTION OF BOILERS 39

Fi 44 M etho of ta in Boiler Hea s with teel An les g. . d S y g d S g

h M arin e Boiler ig 4 r wn heet u o rt for Comb ustion Chamb er in cotc F . 5 . C o S S pp S 40 CONSTRUCTION OF BOILERS

Bo side plates . lts about 4 inches apart connect the crown sheet to

e . The e b e a o or it a this gird r gird r may s lid bar, m y b e made

of ﬂat es e or e e e e up two plat bolt d riv t d tog th r, as shown in the

e the e e e e th e ﬁgur , stay bolts b ing plac d b tw en e plat s at intervals

E o r e m a of about 4 inches . ither b lts o riv ts y b e used to keep the

es o m the e e o ec plat which f r gird r from spr ading . Pr j tions are

o e e e on the of the e so t the s m tim s forg d bottom gird r, tha stay bolts

b t e the may e screwed up tightly withou b nding plate. The depth of the plates which make up thegirder varies from

5 3 ’ 7 4 t c e are to t e . If b ol o 6 in hes . Th y from 8 1 inch in hickn ss ts 3

c e e are e the t e e ee the e 1s in h m diam t r us d , dis anc b tw n plat s usually

1 c b ut o s 1 m e e are u e the e in h , if b lt inch diam t r s d , distanc should

. 46 rown hee r Us f n Fig . C S t Suppo t b y e o Sli g Stays

1 b 1 c e The e of th t o the e e e in h s . nds e bars which res up n sid plat s

b e e e e the e should car fully ﬁtt d to make a good b aring , and ar a

l ff c n The shou d b e su i ient to prevent crushing of the e d plates . distance between the crown sheet and the girder should b e at least

1 c e so e e b e o c o the e be in h s, th r will go d cir ulati n and plat s may

c readily leaned . In some cases the girder is supported from the shell by sling

he o . 46 . Th are ec e t stays , as sh wn in Fig e sling stays conn t d to

- h e e e or T o c e e t e . gird r and to an angl iron, ir n , whi h is riv t d to sh ll

h e o of The angle iron stiffens t e shell . In d signing this f rm stay it is usual to make the girder strong enough to support the crown

o t e are e c sheet with u any sling stays , and thes stays us d for addi

tional support .

42 CONSTRUCTION OF BOILERS

TABLE VI !

llowab le Loads on a Bo l s w i h V=T hread s 10 hread er l nc A St y t t , T s p h

N E T CR o ss O U TSI D E DIA METE R DIAM ETER AT SE O T IO N A L BOTTOM O F AREA (A T TH READ BO TTOM O F D ( In . ) TH REA ) In . . S . IN (Sq ) ! .

ad on Sta B lts. e e n e e of Lo y o Flat surfac s , o th r tha s gm nts

e b e - e or e e e or e e h ads, must stay bolt d , stay d by w ld d w ldl ss mild

ee or - e e or or or c o st l wrought iron h ad to h ad through , diagonal r w foot stays . The maximum allowable stress per square inch net cross

‘ sectional area of stays and stay bolts should b e as given in Tables V VI VII L , and

h f se Areas of Segments of Heads to b e Stayed. T e area o a g ment of a head to b e stayed is the area enclosed by lines drawn 3

h 2 e the e . inches from t e shell and inch s from tub s , as shown in Figs 4 47 and 8.

e o e the e of c When a ﬂat head has a manhol p ning , ﬂang whi h is formed from the solid sheet and turned inward to a depth of not h f he e e 2 c e e less than twice t e thickness o t h ad , an ar a in h s wid all

b e e c e he o e o e o . 49 around t manh l p ning , as sh wn m Fig , may d du t d

the e of e c o e e to b e e . from total ar a h ad , in luding manh l op ning , stay d

BOILER TUBES AND FLUES

he of e o e the ee Spac ingof Tub es. Just as t placing riv t h l s in sh t of a shell boiler reduces the strength of the shell against longitudinal

e oe the of o e for the e o of e e e ruptur , so d s drilling h l s ins rti n tub s w ak n

o of e - e e the e e the plate. In s me forms wat r tub boil rs st am and wat r drums are connected by water tubes which enter the drums along It longitudinal lines or parallel with the longitudinal seams . is

the e of c o t the obvious that , should r sult su h a construction sh w tha CONSTRUCTION OF BOILERS

O O O C O O

M ethod of Determining N et Area of Segm ent o f a Head

0 0 0 0 0 © 0 0 0 0

Hea Fi 48 . M etho f n Ne Are of I r ar e m en t o f a g. d o D etermi ing t a r egul S g d

C O M M

f n of H ntainin 49 . M ethod of etermining N et Area O egm e t ead Co g D O S M anhole Opening 44 CONSTRUCTION O F BOILERS

shell is weaker along the tube line than along the longitudinal" rivet

e the e c e of the s ee t t e s l b e e for s am, fﬁ i ncy h t along he ub s hou d us d determining the allowable pressure on the boiler rather than that of the e e h ee two e t riv t d joint. T e material remaining betw n adjac n

0 1 w l th e L 0 9 lad a l .

Fi . 5 ia ram of T u e a n g 0 . D g b Sp ci g with Pitch o f Holes E qual in E very Row tubes expanded into either the cylindrical or the ﬂat part of a e c th m boil r onstruction is termed e liga ent.

E cienc o ﬁ y Li ament. The o c e f g “ f rmulas whi h follow, as w ll as e e are xampl s, taken from the Preliminary Report of the Committee

5 . a am of u e acin wi h ch Fig. 1 Di gr T b Sp g t Pit o f Ho les U nequ al in E very Second R ow of The Americ an Society of Mechanical Engineers to Formulate ” Standard Spec iﬁc ations for the Construction of Steam Boilers

When a shell or drum is drilled for tube holes in a line parallel to the

i i r o f T ub e cin w h f H oles ar in E er ec on F . 5 2 a am a t itch o g . D g Sp g i P V y g v y S d and Third R ow

of the e or the ef c e c of the e e ee the axis sh ll drum , ﬁ i n y ligam nt b tw n tube holes shall b e determined as follows

1 hen the itc h t les er row is e u al Fi . . W p of the ube ho on ev y q ( g the formula is

p p d efﬁciency of ligament CONSTRUCTION OF BOILERS 45

c c of e o e c e d in whi h p is pit h tub h l s in in h s , and is diameter of tube

o e h l s in inc hes .

a m P c - Ex ple . it h of the tube holes in the drum of a water tube boiler e u a s 5 nc es or in D a e q l % i h ches . i m ter of tu be holes equ als 3 kinches or

inches . p d efﬁmency of ligament

When the tch b e 2 . pi of tu e hol s on any one row is not u niform

5 1 or the (Figs . formula is

P —n d - efﬁciency of ligament P in which P is unit length of ligament in inches ; n is number of tube

o e e cl e e of e o e h l s in l ngth P ; and is diam t r tub h l s in inches.

Exam ples . P —nd 1 . efﬁcienc of i a en P y l g m t

P —nd —5 X 3 2 5 ef ci enc of h am ent P ﬁ y g

en a s e or ru is 3 . Wh h ll d m drilled for tu be holes in a line diagonal w the a s of the s e or ru as ith xi h ll d m , f th in Fi . 53 the e c enc o e a g , fﬁ i y lig ment between the tube holes shall b e determined as follows : P—d efﬁciency of ligament P in which P is diagonal pitch of tube holes in inches ; d is diameter of tube G zrfh L ine Fi 53 i m o f b . . a ra T holes in in ches ; and p is distance b e g D g u e Spacin g with Tub e Ho les in Diagona l Lines w n r I ll ee ows of u es lon tudm a . t t b , g y n f u he ru of a wa er- u 4 . D iago al pitch o t be holes in t d m t t be boiler equ als

nc a er of u e o es e u a s 4 nc es . D s ance e ween row i hes . Di met t b h l q l i h i t b t s

of u es on u na e ua s nc es . t b , l git di lly q l i h —4 efﬁcienc y of ligament

‘ b lat ater Le s The c o t c Spacing of Tu es in F W g . ns ru tion of stayed b ox-header water-tube boilers requires that considerable attention b e paid to the tube spac ing judged from the standpoint of o ee the e e of the btaining strength in k ping with r maind r boiler .

b e ec o e o the e e the o e It will r gniz d that , sh uld ligam nt ruptur , wh l

e c e e are e boil r head may have to b e dis ard d , as r pairs v ry difﬁcult 46 CONSTRUCTION OF BOILERS

TABLE VI ]!

Lap=Welded Bo iler T u b es

to make between tubes expanded into a ﬂat plate. The fact that stay b olts are a necessary part of this construction imposes greater difﬁculties than is the case of expanding tubes in the head of a hori

h e e o zontal tubular boiler . T e best boiler mak rs r s rt to using tube

ee t c e ee b e e e c l o of ef c e c sh ts hi k r than s m to r quir d by cal u ati ns ﬁ i n y, thus using high factors of safety for this important part of the con

c o stru ti n .

ub e H les and Ends. e e are e e or e T o Tub hol s drill d full siz , th y

b c e not to e ee c e e e may e pun h d xc d é in h l ss than full siz , and th n

e e or e e ro c e . drill d , ream d , ﬁnish d full siz with a tating utt r The edges of tube holes should b e chamfered to a radius of 1 about 1 6 inch .

ﬁre- e e the e of the e e e e e A tub boil r has nds tub s b ad d , whil wat r

e e l e the e of e e o e tub boil rs shou d hav nds all tub s , susp nsi n tub s , and nipples ﬂared not less than t inch over the diameter of the tube CONSTRUCTION OF BOILERS 47

The e of e e o e nds all tub s , susp nsi n tub s, and nipples of water

tube boilers must not proj ect through the tube sheets or headers

e c nor o e l ss than i in h m r than inch .

e ece to ce e Wh n it is n ssary pla a fusibl plug in a tube, an extra

c e b e o e for thi k tub must pr vid d that purpose .

es of ub e Typ T s. Boiler tubes are given the names t hey would

e so to b e o e c e h naturally hav , as m st d s riptiv , t e most usiIal grades

e - e e ee c co - o hot- o e e e b ing lap w ld d st l , har al ir n , r ll d s aml ss steel , and

c o -d se e s e Th ld rawn aml s ste l . e most c ommonly used tubes are

e e ec e e are the e lap w ld d b aus th y ch apest. All grades are manu fa t r c u ed in the gages most usually demanded ; the outside diameter of the e e to e e tub is us d d signat its size.

La - e e e are o e o h f p w ld d tub s f rm d fr m a ﬂat plate, t e edges o whic are se e e o h up t , th n b nt ar und until the thickened edges lap s f c e u ﬁ i ntly . It is then heated successively about 8 inches at a time

Fi g. 54 . T ype of Prosser E xpander

Cou rtes o J ose h erson nd o y f p T . Ry a S n , Chicago

e e e e hic c - o and w ld d ov r a mandr l , w h is a ast ir n arm with a slightly

e i c o e to o c the e ce . e V e h nv x p, v r wh h tub is pla d Tabl III giv s t e

o of - e dimensi ns standard lap w lded tubes .

th f andin ub e M e ods o Exp gT s . Tubes are fastened to the tube

e the e of the e o the o sheets by xpanding m tal tub int tube h le. This

o e o c e e e of c e e are two c o is d n by a to l all d an xpand r , whi h th r mmon forms .

r The o n e c o of P osser E xpander. Pr sser expa d r nsists a steel

e e of ee e e e c e tap r pin and a numb r st l s gm nts , h ld in pla by a spring .

‘ The outside of the segments have the form to b e given to the e e e the e o o c o e o c xpand d tub , and insid is a straight h ll w n , int whi h

h 4 The e e are o ce t e ee e . 5 . st l tap r pin ﬁts, Fig s gm nts f r d apart by

er the e of the hammering on the steel pin . In ord that m tal tube

‘ no b re the hamm erin should b e o e may t e inju d , g d n gradually and

e the e e e e e . car fully, and xpand r turn d fr qu ntly 48 CONSTRUCTION OF BOILERS

D ud eon x and r The E e . D e e e . 55 g p udg on xpand r , Fig , has a set of rolls that are forced against the inside of the tube by turning the

. 5 5 T e o f u eon E x an er Fig . yp D dg p d o J Courtesy f oseph T . Ryerson and Son , Chicago

The e the n t e . i e th ap r pin pin and rolls rotat as p is driv n , and e

e the e t th rolls gradually xpand tub agains e tube plate. the effe t of a e of Fig . 56 shows c using Prosser typ expander f h h o o o t e t e e e e . 5 though t e dist rti n ub is gr atly exagg rat d Fig . 7

h ffe t of D e t e of shows t e e c using a udg on yp expander .

e the t e are e e the e are e e e Aft r ub s xpand d , nds b ad d ov r as f h n 56 57. h e o t e co shown in Figs . and This adds to t e str ngth n n ee the t e n t e e I not ectio betw n ub a d ube sheet. B ading ov r s

or o e usually res ted t “wh n expandingwater tubes . Stay Tub es. Stay tubes are not used as extensively at the

e o e e o o present time as they w re f rm rly . They were v ry c mm n at a time when the holding power of expanded tubes had been

6 ec tion p f Prosser E x ansion . 5 7 . u eon E x an sion Fig. 5 . S p Fig D dg p with Distortion E xaggerated

I now e t e t the mented on but little. t is appar n from such t sts tha

e of e e e I . 56 e th holding pow r tub s xpand d , as shown n Fig , is mor an

50 CONSTRUCTION OF BOILERS

he and stiffen it against c ollapse . T methods of building furnaces

0 1 are not o i e e oo th shown in Figs . 6 and 6 c ns d r d as g d as e Adamson

e e . The e o . 60 too oe arrang m nt m thod sh wn in Fig is rigid , and d s f not a o e e o . 61 on the e ll w xpansion , whil that Fig , oth r hand , is elastic ; both have the fault of exposing a double thickness of plate

f e the ﬁre e o h and two rows o riv ts to at ach j int . T e ring sections

are usually 18 inches in length .

Th M o e ﬂue 2 o e I . 6 IS oris n corrugat d shown n Fig p pular and ,

e o e IS e e e . e e I ee o for furth rm r , xc ll nt Th r s fr d m expansion through

i 62 . M or son Bo er ue F g. i il Fl

Courtes o J ose h T . R erson and Son Chica o y f p y , g

out e e e e e c the e on the o e . its whol l ngth , th r by r du ing str sses b il r

The e b e e e e t the c plat s should thick nough to pr v n sagging , thi k

e s ar o Co e ce are n s usually v ying fr m ﬁt to 3 inch . rrugat d furna s riveted to the rear tube sheet in a return- tubular boiler of the marine

e the end of the c e e e the o the e of typ , furna b ing ﬂang d at fr nt ; h ad

the e e o the o e c ut for the ce c boil r is flang d ar und p ning furna , whi h h fits well into t e flange .

BO IL E R RE!U I REMENT S

FACTO RS IN D ESIGNING BOILERS

n r l o e e e are Ge e a Statement. In designing a steam b il r th r many o the o o c onsiderations that must b e kept in mind . Am ng m st imp r

r c the e e o tant a e strength , durability, capa ity to furnish r quir d am unt

f e e for e re al rm and ins ection o steam, conveni nc cl aning, p g, p , sim

licit e e o o of n t o . p y in d tail , and con my b th ru ning and ﬁrs c st

The or e to b e e e e o the o to b e kind , typ , us d d p nds up n w rk

e the o an the e e e e e ce of the don , l cality, d availabl spac and pr f r n

o e e e the e wner . The work to b e done 18 d t rmin d by numb r and

of e h c e the e kind ngines , t e c onstancy with whi h th y run , and pr s

the of the e sure. In choosing a boiler for any locality, purity wat r, CONSTRUCTION OF BOILERS 5 1

the of e the c kind fu l , and laws whi h govern inspection and allowable

o k e e b e co e e h w r ing pr ssur must nsid r d . T e available space greatly inﬂuences the type and sometimes prevents a desirable c hoice in

o e c l . For ce oc o th r parti u ars instan , l motive and marine boilers

b e e to ce . For o o e must adapt d small spa s stati nary b il rs , if the

oo e e e e e e ﬂ r ar a is limit d, but th r is ampl h ight , some type of vertical

b e boiler may chosen .

B iler H se er o or pow . The term boiler horsepower is mislead

t a o e oe not e e o o ing, in h t a b il r d s d v l p p wer but simply acts as a means for absorbing heat energy in one place and transferring it to — o e e the e e e to th a st rag m dium wat r and st am suppli d e b oiler .

The o e e e e e e o th p w r l m nt , wh n it app ars , is f und in e power produc

o of the e e c th e H e e . o e e h ti n ngin s in whi h st am is us d w v r, t e mean ing of the term has become so well understood by frequent u se that n ec c o Th n n o sp ial nfusion arises . e u it known as o e boiler horse power is the equivalent of the evaporation of pounds of water

o at 2 12 e ee c c ou of e fr m and d gr s F . Sin e ea h p nd wat r evaporated under the c onditions given above represents the absorption of

B e n one o e o e o e e the ab sor ritish th rmal u its, b il r h rs p w r is qual to p

f n e o e h B. . B o e o e o o e t e tion o t 11 . y b il r h rs p w r h ur is m ant equivalent performance of a b oiler horsepower during a period of

o the e e c e e ee an hour. This explanation is given s that diff r n b tw n e e o e o e o e o e b e o e ngine hors p w r and b il r h rs p w r will b rn in mind , as

r no of e e nor of ec e the e they a e t qual magnitud , pr is ly sam physical signiﬁc ance.

l e General Requirem ents. A b oi er should hav

fﬁc e of e to the e e o of 1 . Su i nt area grat burn r quir d am unt

2 o u c e to o the e of c o o . En ugh heating s rfa abs rb h at mbusti n o c econ mi ally . e ﬂue e e e o to c om 3 . Combustion c hamb r and ar a larg n ugh pletely burn and c arry off the products of c ombustion . e e _ 4 f c e e . Water space su ﬁ i ntly larg so that a sudd n d mand will not c ause too great a variation in water level . 0 o e f e . e c o e to o e 5 . Surface o wat r larg mpar d v lum , In rd r that

steam may b e readily disengaged . g o to e e 6 . Steam space large en ugh supply an Irr gular d mand

without c ausing a great change of pressure. e to the e i e 7. Steam outlet large enough to supply st am ng n

without wiredrawing . 52 CONSTRUCTION OF BOILERS

the e suﬂicientl r e e of e If outl t is not y la g to supply pl nty st am , the demand will b e greater than the supply and the steam will b e

o e or e . o e e e e . thr ttl d wir drawn that is , it will l s som pr ssur

o o e e the o e h For all c mm n typ s of boil rs , pr portions b tween t e

e e ee e e above requisit s hav b n d termin d by experiment .

o r e f the e Area f G ate. Grat s o same ar a will burn different

e of e e e e e on the e of quantiti s fu l in a giv n tim , d p nding int nsity the the c e of the e the e b ed the draft, chara t r fu l and fu l , and kind “ -ﬁre e th e of grate. For hand d grat s e xtreme length is usually from

6 7 ee the e e e e the of the ce to f t , width b ing d t rmin d by width furna

r o e -ﬁre h ﬂue or boiler setting . Fo st k r d boilers t e rate per square foot at which the fuel will burn III a unit time may b e very much

- ﬁr h h higher than for hand ed grates with t e same draft . If t e mechanical stoker is of a type that removes the refuse accumula

o e e e ee the e b ed o e tion as rapidly as f rm d , th r by k ping fu l in an p n c o im dim ents ﬂow o the bed are e ce onditi n , m to air thr ugh r du d

h h u to a minimum and t e rate at which t e fuel will burn ses. ’ The main factor in determining the rate of combustion for a given furnace construction is the quantity of air forced through the fuel

l c o e of o e h re b ed. Co e e e e t e e a ns qu nt y, sin in s m typ s b il rs grat s

e e e to o not e of e for r strict d in siz owing fact rs capabl chang , as ,

ce oco o e eco e e to c e for instan , in l m tiv s , r urs is tak n artiﬁ ial m ans creating an intensity of draft much higher than would b e obtained h f by t e use o a chimney . It has been established as a fundamental truth that boilers absorb prac tically the same percentage of heat of the amount

' e e e to e o e to the c o e pr s nt d th m with ut r gard a tual quantity, th r h c o c e e e i the e. e e o e t e fa t rs , su h as pr ssur , r main ng sam Th r f r , way

” in which the fuel is burned has a great deal more to do with the over- all ec onomy of the boiler unit with its grate and furnace than

h e r t the t e o o e o e e . o it o e o b il r h at abs rb r its lf Als , is p ssibl burn

e so low e the co o oc e ineﬂicient fu l at a rat that mbusti n pr ss is , although the degree of c ombustion may b e practic ally c omplete . The area of the grate for a given boiler performance determines

h f o e are e t e ec o o e o ce . too e e th n on my p rf rman If larg , c rtain l ss s

e e for e o e o e in vitabl a giv n draft, and if too small , th r l ss s may

h of e e occur or t e boiler may not deliver enough steam . Out th s

the o o c o e : facts f ll wing con lusi ns may b e arriv d at If, having CONSTRUCTION OF BOILERS 53

e e e ce e e o th s l ct d a rtain grat ar a, it is f und that e operating per form ance 1 ec o o c the e e o be s un n mi al, grat ar a sh uld changed,

e e e or e e e making it ith r small r larg r, d p nding on the steam require ments and draft facilities . It is true that such an expedient is

e o e ec e o ce e rar ly ad pt d , b aus , in m st instan s , th re is more than one unit and facilities are offered for operating the units in service

o to c e or ec e the acc rding fair standards by in r asing d r asing number . A certain degree of elastic ity is afforded by the use of boiler ” dampers Which make it possible to change one of the main factors

e o the e of o m e o e . nt ring int rat c mbusti n , na ly, draft

e e e o e are e o e Wh r m chanical st k rs mpl y d , it is usually best to

o the e of the e to e o foll w sugg stions manufactur rs as siz s , th ugh in

n e e be e the e ce such i stanc s th y must appriz d of availabl draft , furna

t e to e co c e e e o . nstru tion , and oth r fac ors , in ord r giv int llig nt pinions i Water Evaporat on per Pound of Fuel. The number of pounds of water a pound of fuel will evaporate depends upon the heat

e of the e the e e of the o e to e valu fu l , inh r nt ability b il r absorb h at, the ef e c of the o e e the c e e of the e ﬁci n y _ b il r furnac , l anlin ss h ating

b ee ce the e ure of e o . e e surfa , and pr ss op rati n It can asily s n that

c b e c e e e of the e e con so many fa to rs, a h ind p nd nt oth rs , may, wh n f sidere o e e e l ec o c o . For o e o d t g th r, r su t in incorr t c n lusi ns purp s s comparison between different installations the actual evaporation is converted into terms of equivalent evaporation for feed water ° W e o e 212 o e c e e. at F . into steam at atm sph ri pr ssur h n a b il r is selected the usual practice is to ﬁnd out what the results are

e of e c c e the e c with fu l a giv n hara t r, judging from r sults a tually obtained in several installations ; by the application of good judg

e o e o o o the e the t m nt, it is p ssibl to so pr p rti n grat s and draf facilities that equal or better results are obtained . The amount of water evaporated per pound of fuel is inﬂu

n c o c o for ce e ced by the character of the boiler nstru ti n , as , instan ,

o o e ce e ec e a b iler with good circulati n , with its h ating surfa ff tiv , is sure to give a better evaporative result than one not so well

e “ c the o e c o e the d signed . The manner in whi h b il r is in l s d , that is ,

e h e o the e tightn ss of t e setting , plays a v ry imp rtant part in boil r

e o p rf rmance .

B i e o e c o e are e o ler Rating. The hors p w r at whi h b il rs rat d may or may not have any relation to the actual boiler horsepower 54 CONSTRUCTION or BOILERS

— produced . The horsepower output of a boiler is dependent upon the amount of fuel burned and the efﬁciency of the boiler and furnace combined . It is quite desirable to rate boilers prior to their actual

' t e ee e to e installa ion, and ngin rs hav come stablish arbitrary quan

e of e e the titi s h ating surfac as basis for rating boilers . The areas so selected have varied from time to time until at present it is generally accepted that 10 square feet of heating surface shall b e

e e One e e o e o c consid r d boil r hors p w r rating in stati nary pra tice.

am / Ste Space. It is beginning to b e realized that boiler space devoted to steam plays less of a factor in the successful operation

e e e e b e the e e a h of a boil r than was b li v d to cas y ars go . If t e

e are e the n e d signs fairly simpl , such as in cyli drical boil r, then the computations which are made regarding steam space are just as e e but e e - valid as v r ; for complicat d d signs, as in water tube

e the e ce e e e not boil rs, st am spa r quir m nts do apply as rigidly as

f e for boilers with large bodies o water . In th se instances it seems more important to pay strict attention to the places where violent e e e e at the o t f bullition tak s plac , as, for instanc , fr n throat o a

e - e e to the e e e horizontal wat r tub boil r, than actual spac d vot d to

th . o e e steam . Also e surface fr m which steam may b lib rated plays th a larger part in these boiler types than e actual water content .

No set e b e the e e rul s can laid down for complicat d d signs, but,

o e o e e for cylindrical b il rs , an illustration of how to c mput st am space will familiarize the student with a number of the problems involved in the subj ect . The steam space is frequently designed as some fraction of the

e o e the e o e e is int rior v lum of boil r, usually ab ut A b tt r way to

n h S e he design it from the steam consuI ption of t e engine . uppos t engine uses 30 pounds of steam at 75 pounds pressure per horse

Th o e e e e 90 o e power per hour . e abs lut pr ssur th n is p unds (n arly) and the speciﬁc volume at that pressure is (from steam

e o e o tables) . As steam is being generat d at an appr ximat ly c nstant

e the e on ee not b e e . the ce rat , supply k pt hand n d gr at If surfa

he e e e of e f c e the o of the e for t dis ngag m nt st am is su ﬁ i nt , rati st am

c h f th e 1 spa e to t e volume o e cylind r is from to ,

E e e o depending upon the speed of the engine. xp rim nt sh ws that if the steam space is equal to the volume of steam consumed by

h c e the e e 20 e o f e . t e e ngin in s c nds, it is su ﬁci nt If spa is qual only CONSTRUCTION OF BOILERS 55

t the e e 12 eco o e o st am us d in s nds , a c nsid rable quantity of water

b e c e e the e . the e e o may arri d ov r with st am If ngin is sl w speed ,

e 60 e o o er e the that is , l ss than r v luti ns p minut , steam space should

be larger .

The volum e of the steam space per horsepower will be the

e of o of e e er o e o e 20 e o numb r p unds st am us d p h rs p w r in s c nds ,

e ec c o e or multipli d by its sp iﬁ v lum ,

. 81 c u . . e er ft (n arly) p h. p.

the e e of 75 o e o e the e e If ngin is h rs p w r , st am spac will b e

c u . ft .

Heating Surface. The portion of a boiler that is exposed to

the e hot e c e the e ﬂam s and gas s is all d h ating surface. This is

e of the o o of the e e o the c o the mad up p rti ns sh ll b l w bri kw rk ,

e o e e the e ce of the e ﬁre- e xp s d nds , and int rnal surfa tub s in tub

he h - o e . t o e of t e e e e the e e o ce b il rs If b il r is wat r tub typ , xt ri r surfa

of h t e tubes is taken in place of the interior surface. The ability of heating surface to transmit heat to water

e e on e e c c o e e e of the e . d p nds up cl anlin ss , ir ulati n , and t mp ratur gas s In designing it is safe to follow proportions of heating surface to grate area in the various types which experience has shown to

e th H - ﬁre e for o c ce e e e l . d giv b st r su ts and grat s , stati nary pra ti , vary from 45 to 60 square feet of heating surface for each square

oo f f c oco o e o e. o e e o o e f t grat In th r typ s b il rs , su h as l m tiv s and

o e s c the o o o e e o th s u ing artiﬁ ial draft, pr p rti ns vary a gr at d al fr m

e e h f e e fﬂe e th s ﬁgures . If t e boiler is o a typ r quiring ba s to c aus

the h e ce e - e gases to impinge up on t e h ating surfa , as in wat r tub

o e the effec e e of the ce b e e c e b il rs , tiv n ss surfa may v ry mu h impair d

the by construction . It is evident that some portions of the heating surface of a

o e For ce o e e r . b il r a e more useful than others instan , m r h at will

o h c o ee ec e of pass thr ugh t e r wn sh t , as it is in dir t lin radiant

e the few ee of the e . h at , than through last f t tub s If a cylindric al multitubular boiler is c onsidered divided into

" e ec o th e o e e the ﬁre e o e o e qual s ti ns , e s cti n n ar st will vap rat m r

e h h e end the e e e wat r than t e one at t e oth r , as gas s hav a high r

” e S o e the o e b e e t mperature at the ﬁrst section . upp s b il r divid d 56 CONSTRUCTION OF BOILERS

e of e e the t e o 1 into six s ctions qual l ngth, and call otal vap ration 00

er p cent . Then the per cent of evaporation per section will b e approximately as follows

the e of e c e e o e ec the ev a o If l ngth a boil r is in r as d an th r s tion , p

b e e e a e the e ration will incr as d littl , but radiating surfac is increased at the same time. In c ase the addition of a section for evaporation causes a loss by radiation nearly equal to the gain in e o o e th e o t vap rati n , it is not conomical to add e s ction on acc un of

the e c of the o e . o e e the e xtra ost b il r If f rc d draft is us d , boil r may b e made longer without danger of impairing the draft . ’ ll able Pressure. c c Law A ow A ording to Pascal s , liquids and

e e e e e o S e e gases ex rt pr ssur qually in all dir cti ns . t am in a boil r f h h exerts the same pressure on all portions o t e shell . As t e pres sure inside a boiler is considerably greater than the pressure out

e the o e e e e e a te e to the sid ( atm sph ric pr ssur ) , th r is nd ncy burst h h e e t e t e e . shell . This tendency is r sist d by plates of boil r e e the e o to e e u e e A sph r is strong st f rm r sist pr ss r , for sinc

e e e e o e e e e t pr ssur is qual in all dir cti ns , th r is a t nd ncy oward

h n But e e enlarging t e sphere and ot to rupture . b cause a spher has the smallest area for a given volume and a large heating sur

e e e o on cc o of ec f e fac is d sirabl , and als a unt m hanical di ﬁculti s , a

Th c spherical boiler is never used. e boiler is made cylindri al to o e e e e the s e e btain gr at r h ating surfac , and lo s in str ngth is mad up by staying .

c o e the e of e to e In nsid ring str ngth cylind rs , it is usual divid the rupturing stresses into two classes : those which tend to rup

u e the c e o o e c e e t r ylind r l ngitudinally, and th s whi h t nd to ruptur

The e e to b e it c ircumferentially or transversely . maximum pr ssur allowed on a steel or wrought- iron shell or drum of a boiler shall b e determined from : the minimum thickness of the shell plates ;

' the lowest tensile strength stamped on the plates by the plate manufacturer ; the efﬁciency of the longitudinal j oint or ligament

e ee the e o e c e e the e the e e e b tw n tub h l s, whi h v r is l ast ; insid diam t r of the outside c ourse ; and a factor of safety of not less than 5 .

58 CONSTRUCTION OF BOILERS

e c e c turer should b ar fully onsidered . If a factory employs more

one of e than standard workmanship , th n it is highly important ,

the e k e e e c for if b st wor is d sir d , to hav fa ilities knowing that the

e the c o e o e on the b st standard of fa t ry is mpl y d boilers ordered .

c e can e o the e of All manufa tur rs mpl y b st kind workmanship ,

e e the ece e ul m ent for e ee assuming th y hav n ssary q p b nding sh ts ,

e e e of ee o e e ﬂ n in e a . b v ling dg s sh ts , p w r riv ting , and g g The only way to b e sure that a boiler is receiving the best workmanship is to engage someone to inspect the work as the Th r are e . e e o e e ec o pa ts fabricat d insuranc c mpani s hav such Insp t rs , but they make a practice of inspecting the sheets for defects

e are e e e the e ole are e the ee and rar ly pr s nt wh n riv t h s mad , sh ts h Th are e t e e e o e . e e of b nt , and riv ting p rf rm d advantag having

e ed of o one a boil r manufactur in a shop nly standard , and that

the e 1 e . f c e the o of b st, s manif st It is di ﬁ ult to judg w rkmanship a f o e e o e e. e e the e o b il r wh n nc mad If th n , as is tru , liv s many people may b e j eopardized by poor workmanship in a high

e e o e no e o b e e to e n t pr ssur b il r , ff rt should spar d saf guard agai s a nee e e e o e e o e e e dl ss hazard, v n th ugh consid rabl additi nal xp ns has to be m et in ofder to do so .

The inspection and testing of sheets as stipulated by the. engi neering societies are extremely important and the data coming

o e e e b e e ec e c o e e fr m th s t sts should car fully insp t d by ! mp t nt

e . e e e e e e e o p rsons Wh r v r possibl , aft r a boil r is fabricat d, it sh uld

e of b e tested in the shop . It frequently happens that c rtain parts

' th o e a boiler may b e so tested without assembling . After e b il r

ee e e e the e e or o e has b n r ct d in ﬁ ld , without its s tting c v ring, a " c o to 50 pressure test should b e applied . It is ust mary apply per c ent more pressure than that allowed by the boiler construc ° Th e o b e the c of 60 tion and laws . e wat r sh uld in vi inity to ° “ wee o b e c e o e 70 F . e , and all l aks or pings sh uld ar fully n t d ,

th e e off the e e c e o e . e pressur tak n , and n c ssary alking p rf rm d The pressure should then b e applied again and repeated until no

the o ee o e o e leakages occ ur . If w rk has b n pr p rly d n , usually very few leaks appear at the ﬁrst application of pressure.

T YPES O F BOILERS

INTRO DUCTIO N i Funct on of a Simple Boiler. A steam boiler is a closed metallic vessel in which steam is generated from water by the applic ation of heat . Only that part of a complete c ontriv anc e used for generating steam from water which is employed in the

o f h f absorpti n o heat is known as t e boiler . All o that portion of the arrangement in which the fuel releases its heat by ﬁre is h H h f o t e ce . e ce t e c o o the r c e kn wn as furna n , fun ti ns fu na and the boiler are exactly opposite ; the former generating or lib erat

e the e o of e o th ing h at , and latt r abs rbing a part this h at fr m e furnace . The purpose of a steam- generating equipment is to c onvert the e e e e o e e e c e e so availabl n rgy of fu l int h at n rgy arri d by st am ,

b e e o e e e e e e e e e the c e that it may mpl y d ls wh r , ith r in an ngin in r a f o o ec nic e e or e o co e o e . ti n m ha al n rgy us d , with ut nv rsi n , as h at Where the heat energy of the steam is to b e converted into mechan ic al energy it is necessary to generate the steam at a greater pres

the o e sure than that of the atmosphere . It followsthat b il r must b e e o to the e re e e mad amply str ng withstand pr ssu int nd d , and

o b e o ec e the c o e e ce of c e e must als pr t t d against ns qu n s ar l ss , unskill

e o o e e o . ful , and dang r us p rating m th ds

econom Boiler Acc essories . T o operate a boil er safely and icall e e be ce c ce o e o e of c y th r must rtain ﬁttings and a ss ri s , s m whi h are e the c e of the o e e o e e e to c e e us d in ar b il r, whil th rs s rv in r as

the o m o of e e are the fol its economy . Among m st i p rtant th s lowing :

Feed Pu m or In ecwrf A ee or i ec o e p, j f d pump , nj t r, with valv s ,

h e . etc . e e to t e o piping , , suppli s wat r b il r

W G e coc e e Gage Cocks and ater Gage. ag ks and glass wat r gag

the e the e of e or the e e e show att ndant h ight wat r , wat r l v l as it is

e the e . call d , in boil r 2 TYPES OF BOILERS

e e e e the ~ Pressure Gage. A pr ssur gag indicat s pressure of steam

The e e e e r in the boiler . pr ssur is usually m asur d in pounds pe square inch

a t a S fe y V lve. A safety valve allows steam to escape from the

e h e e e boil r when t e pressur xce ds a certain ﬁxed amount . This attach b e e e e e e e e. m nt, b ing a saf ty d vic , should automatic and r liabl

Blow- 0 i e A -off e e e 1? P p . blow pip , with its valv s , is us d to blow

ut e e t the e e e the t of e the o s dim n from boil r , r duc amoun wat r in

le or e . boi r , mpty it m i Stea e. A e e e the P p st am pip , with its valv s, conducts h h steam from t e boiler to t e place where it is to b e used .

Mankoles and andholes M o e handholes H . anh l s and , with covers,

are e e e e or c e . us d for making xaminations , and wh n r pairing l aning ! ibl lu s e are e e to Fus e P g . Fusibl plugs d sign d give warning when the water lev el becomes too low . ! i Low- ater Alar - H gh and W ms . High and low water alarms

e th give warning wh n e water level is too high or too low . ! Heaters . A heater is a device for raising the temperature of the feed water to a point as nearly equal as possible to that of the

water in the boiler.

Columns Lu s or Brackets . C or e are , g , olumns, lugs , brack ts sup

ports for the boiler .

Masonr M e e the o e ee y. asonry is us d for nclosing b il r and k ping

e for ee the hot e i n c it in position , and in many cas s k ping gas s ontact

with the heating surface.

Fu r F nace Fittin s . e e e g urnac ﬁttings includ grat bars , bearer

ﬁr - - - e oo e e o e etc . bars , doors, ash pit d rs , d ad plat s, do r lin rs ,

D am er Frame and D am r The e e p pe . damper fram and damp r are used to control the draft by varying the size of the opening through whic h the gases are allowed to esc ape from the boiler setting .

Breechin Th i the e the e g. e breech ng carries gas s from boil r or

e h c its s tting to t e himney .

imne s T he e ie the e e Ch y . chimn y carr s away wast gas s and

e e cr at s draft .

Tools e e e e e . Tools include shov ls , slic bars , scrap rs , tub brush s ,

e e o etc . soot blow rs, gask t m ld s,

! A thou h desirab le the are not a so utel ne essar as a o er c an b e su essfu l g , y b l y c y, b il cc lly o r Wi hou h pe ated t t t em . TYPES OF BOILERS 3

CLASSIFICATION i l iﬁ i Bas s of C ass cat on. The almost endless variety of boilers

h now in use is due largely to the many conditions under which they

e for h e o are used . Another r ason t e num rous f rms is the resource

l e of e e ee the ce e fu n ss d signing ngin rs, who , during last ntury , hav

o to ce o e e e e e r s ught produ , at m d rat cost , st am g n rators which a e mi e e e e o . at onc saf , durabl , and con cal A proper grasp of the subj ect requires that an orderly classi

ﬁ i n of e ‘ b e f cat o boil rs e attempted . A numb r o different methods are e e for hi o e o e o o e mploy d t s purp s , but nly thos m st c mmonly us d

are e e e . o e the e h r giv n F rtunat ly, many of names appli d to b oilers are c e e e so e f c l b e suffi i ntly d scriptiv , that littl di fi ulty wi l found in loc ating a b oiler in its particular field when once its proper name is

. M c e e b e e e e known u h valuabl tim may sav d, and a bett r und r

of the ec e e e one e f standing subj t gain d , by s l cting d sign o boiler to

e e e e . o e r pr s nt a giv n class Again, a classiﬁcati n t nds to bring out interesting and important features . All boilers possess one or the other of the following pairs of characteristic s Fire Tube and Water Tube Vertical and Horizontal Stationary and N on-Stationary or Portable E xternally Fired and Intern ally Fired

There are some designs which empl oy both characteristics of

an for e e m a e o ﬁre e e a p ; instanc , a boil r y hav b th tub s and wat r

e not b e e e e c or o e tub s ; may distinctly ith r v rti al horiz ntal , but hav

a position midway between these two . Boilers are also classiﬁed ac cording to the pressure at which

o e e are e o e e hi h- ressu re or low they p rat , and th n kn wn ith r as g p

r The e e c o e e e o e pressu e boil ers . pr ssur at whi h a b il r is int nd d to p r

e nl how o the b e ee not ate det rmines o y str ng parts must , and n d h affect the selection of the scheme of putting t e parts together .

low- e e oi e - e e o l e b e Consequently, pr ssur b l rs and high pr ssur b i rs may exactly alike in external appearance though their c onstruction details and the materials of which they are made may b e radically

ff e o e s e e to b e e e e are e e . Be di r nt sid s , b il r d sign d us d at high pr ssur

f th c e e. e o e e frequently used at low pr ssur In vi w for going , a lassi ﬁc ation based on pressures alone would not b e especially service

e e i e f c e e ee the e es abl , ven though to bo l r manu a tur rs and ngin rs xpr 4 TYPES OF BOILERS sions high- pressure and low-pressure at once bri ng to mind

c f c o c c to characteristi s o nstru tion pe uliar each group . i Scheme of Classiﬁcat on. The scheme of classiﬁcation ac cord ing to use and form is given as follows :

Cornish (Single- Flue) Flue Boil L ancashire (T wo- Flue) Stationary G alloway E x erna - Fired Mult1tub ular t lly { InternalIy- Fired (Return-Tubular) Horizontal Fl re- BO X Boilers Vertical

Straight- Tube Curv ed- T ll b e IIorizontal Water-Tube Boﬂers Vertical Sectional N on—Sectl onal Mixed Types Peculiar Forms

Multitubular Fire-Box (Common F orm ) Wootten Type L ocomotive Corru gated Furnace Peculiar Forms

E arly Forms (Box or R ectangular) Scotch or D rum R eturn- Tubu lar Throu gh- Tube Marine Water- Tube

L aunch Boilers

E arly Forms Cornish (Single- Flue) L ancashire (T wo- Flu e) G allow ay Single Flue (E xternally- Fired)

Horizontal (Common F orm) Vertic al Fire- Tube Return-Tubu lar (Multitubular) Throu gh-Tube Fire-Box Peculiar Form s

Sectional ' l e Hor on Non- Sectional iz t ggfiigffil fi a er- u e W t T b - Straight Tube Verti cal Curved- Tube Peculiar Form s Mixed Types

6 TYPES OF BOILERS

r B it was called the Haystack o alloon boiler . It was of wrought

e e to e T iron and had a h misph rical p and arch d bottom . he ﬁre was

e de e the c e the e plac d un rn ath ar h d portion , hot gas s surrounding the l ower part of the b oiler . An improved form of the Haystack

. 1 S e e the ﬁr i boiler is shown in Fig . m aton plac d e nside the shell and arranged internal ﬂues for conducting the hot gases to the

e . e e e e the e e chimn y This arrang m nt incr as d h ating surfac and ,

h e the o t e e . consequently, conomy of b il r

a n il W go Bo er. T o increase

the e e re h ating surfac still mo , James Watt introduced his

e Th . 2 e Wagon boil r, Fig . top was semicylindrical and the

e e h sid s curv d inward . T e curved plates assisted in the formation f o e ﬂues. The hot e , sid gas s passed from the grate beneath

the o e the e o b il r to r ar, thr ugh

he e - ﬂue to the o t l ft hand fr nt , then through the right- hand ﬂue

the e e e the to r ar, and th nc to

n e the chl m ey. This was call d “ ” heel dra t bec ause the gases w f . h passed entirely around t e boiler . In the large sizes a ﬂue was

i he a stack Boi er e the e . The F g . 1 . T H y l plac d in boil r prod nets of combustion returned

through this ﬂue to the front after passmg under the boiler to the

the ﬂue the the e . o rear, as in small siz s On issuing fr m at front , the gases divided and passed to the chimney at the rear by means

o of e the of the ﬂues in the brickwork . This f rm draft was call d “ ” split draft . Watt used a column of water in the vertical feed pipe as a pres

sure gage; the rise and fall of this column also c ontrolled the damper .

The feed was regulated by a ﬂoat . h H o o e e e Although such boilers as t e aystack, Wag n , and th rs w r

e e e e e e fairly satisfactory at the time th y w r inv nt d, th y could not

withstand the higher pressures which soon bec ame common . TYPES OF BOILERS 7

h c n About the beginning of the nineteenth century t e yli drical the c lin boiler was introduced The earliest forms were plain y ” - The diﬂerence the drical boiler and the egg end boiler . was in — of c s form of the ends those of the former were ﬂat and a t iron, m de of r while the ends of the latter were hemispherical and a w ought

“ ” ’ a on Bo i er ia ramm tic ketch of Watt s W g Fig 2 . D g S l

or c ec e its he e -end o e e e no iron . T gg b il r r quir d staying bra ing b aus the o e to e e a the e ce o of e e, form is, with x pti n a sph r str ng st r sist int rn l

pressure. f e of The c c e c o o Cylindrical Boilers. ylindri al boil r nsists a sh ll e e i or of c wrought-iron boiler plate and ends of the sam mat r al ast 8 TYPES OF BOILERS

h set . 3 . T e iron . It is in brickwork as shown in Fig boiler is about

- e e the e o th two thirds ﬁll d with wat r, r maining third f rming e steam

ec e the e e h space. To coll t and stor st am as it ris s from t e water a

e e e . The e e c e the e st am dom is add d st am pip is atta h d to dom , to h which the safety valve is connected also . T e hot gases from the

ﬁr h e the e e th e pass under t e boil r to r ar and th n to e chimney . The heating surface of this type is small for a given diameter ‘ unless the boiler is very long . As all sediment collects in the bottom

h t e e the e r e o e t e e a e t b e e . wher h at is mos int ns , plat s lik ly burn d

Se e c e e c of e the e e dim nt and s al b ing poor condu tors h at, h at r mains

e of in the plates and burns th m instead passing to the water .

Fi 3 C lin r ca Boi er and ettin g. . y d i l l S g — The disadvantages the small heating surface and the collee — e o e the c tion of sediment do not seem so s ri us wh n simpli ity, dura b ilit e of o the e e of e y, and str ngth c nstruction , and as cl aning and

making repairs are c onsidered . T he plain c ylindric al boiler is adapted for mining districts and other places where fuel is abundant and where skilled boilermakers

o e e e to the are not readily found . This b il r is mad v ry long obtain

e the e e e e cee eet. required heating surfac , l ngth som tim s x ding ﬁfty f Some of these boilers are still in use where relatively low operating

r e e are e e . pressures a e allow d , but th y b ing rapidly displac d TYPES OF BOILERS

MO D ERN F L UE BO I L ERS

In order to get the necessary heating surface in the cylindrical boiler without making it exces siv el o de yl ng , it was ma with an internal ﬂue through which the hot gases passed

o he c e ﬂue t t himn y . This was quite large and ex tended from end to end of th the boil er . In e United

S e e E e tat s, Oliv r vans us d

e e 1 this typ as arly as 800.

E led the In ngland , it to internally- ﬁred ﬂu e boilers

c e e are whi h w r , and still , e e e e xt nsiv ly us d,

CO RNISH BO ILER — H o riz o n ta l Single=

— rn l l =F Fl u e In te a y ired. When it was found that a large proportion of the total heat of combustion was lost by radiation and air inﬁl

tration Co e ee , a rnish ngin r named Trevithick c onceived the idea of placing the ﬁre inside of a large internal ﬂ h ue. T e type he intro duced is known as the Cor

ni e sh boil r .

Pa th of Hot G ases. The products of combustion pass from the ﬁre on the

e C . 4 grat bars , Fig , through . 10 TYPES OF BOILERS

the ﬂue to end e its back , wh re they divide and return to the front end e of the e ﬂues L the c by m ans lat ral in bri kwork . At the

t the hot e fron gas s pass downward and , unit

t the ﬂue F ing , pass hrough in contact with

the o of the o e b ttom b il r . On leaving the

e e the c e boil r th y go to himn y . This arrange ment of ﬂues reduces the temperature of

a l Fu r the e e e e me o ct Fig . gas s b for th y co in c nta with fiacffififlsiifictii)? the o o of the o e e b tt m b il r, wh re sediment h n th collects . T e grate bars rest o e dead plate D at one end and on h B 4 h . t e e t e o e . e tw o e e bridg at th r, Fig If mad in l ngths , as is oft n the c e e are o e the e e ~ c The as , th y supp rt d at c nt r by a ross bearer .

e of fire the e e flues are fire bridg is built brick, and xt rnal lined with

The e are s e to the' e et E E brick . h ads tay d sh ll by guss stays .

6 e t n f M n B r h r te Fig. . S c io o oriso oile S owing Cor uga d Flue Cou rtes o J ose h T on o y f p . Ryerson <9: S , Chicag

Takin Care f n h g o Expa sion. The large internal ﬂue is t e

e t the e e r For hott st par of boil r b c ause it contains the ﬁ e . this re the ﬂue e e th e e ason has gr at r linear expansion than e sh ll, and , wh n TYPES OF BOILERS 1 1 '

the ﬂue is c e the c e e e a plain ylind r, in r as in l ngth c auses the ends to

h o e e. e t e c o the ﬂue e to o e . bulg Wh n b il r is ld , r turns its n rmal l ngth

’ This lengthening and shortening will soon l oosen the ﬂue at the

e . e o e the ﬂue f e nds To ov rc m this, is sometimes made up o sev ral short rings ﬂanged at the ends and joined by being riveted to a plain

. o c o o ec o . 4 o e ring This c nstru ti n is sh wn in s ti n in Fig . An th r

e o o ec o Th m th d is sh wn in s ti n in Fig . 5 . e plain rings are riveted to the c e the e e the e c e e urv d rings ; latt r tak up xpansion, slightly in r as the e ce e e the ﬂu e e e h ating surfa , and str ngth n e against xt rnal pr s “ ”

e. o o the The e sur This f rm is kn wn as Adamson Ring . sam

e b e o e the u se of the c o e ﬂue one o r sults may btain d by rrugat d , f rm

f 6 The c e ﬂue adv an o o . o which is sh wn in Fig . rrugat d has many

e o e the e ce 4 5 e e e tag s v r d vi s shown in Figs . and ; it is fr qu ntly us d

I 1nt rn ll -ﬁred n e a y boilers .

LANCASHIRE BO ILER

— = l — = H riz ntal Two F ue Internall Fired. b e e , o o — y It can prov d e e i e c c o t e e both by xp r m nt and by al ulati n, tha with a giv n thickn ss of material cylinders of large diameter cannot withstand as much

e e e For e o on co of the e . pr ssur as small r on s this r as n, and ac unt

o ce o c o c c e the Co sh rt distan a ﬁreman can thr w al a urat ly, rnish

f e too e the boiler is suitable or small powers only . If it is mad larg ,

flue e to o e on the o e the e e of is lik ly c llaps ; but , th r hand , if diam t r the flue too the e b e f c e e . e is small , grat will insu fi i nt in ar a Wh n

o f to b e e e e o ﬁe this f rm o boiler is us d in a larg siz , it is m di d by using

f n c e the L c e o e . two ﬂu es instead o o e. This is all d an ashir b il r It

o ﬂues of o e two is like the Cornish except that it has tw and , c urs , furnac es . n The ﬂues are sometimes c ontinued separately to the e d. If

' n e flue c o the c omb ustion c they merge into o e larg , whi h f rms ham “ ” - b er c e the eec e flued or e c e o e . e e , it is all d br h s dupl x furna b il r Th s furnaces are fired alternately ; the unburned gases set free from the freshly-fired c oal are burned on meeting the hot gases from the

ce e e inc andescent c oal of the other furna . This arrang m nt aids in preventing the esc ape of partly burned gases . The main disadvantage in the design of the Lancashire

‘ boiler is the diffi culty in finding room for the two flues without h e of the e . o t e greatly increasing the diameter boil r Als , small furnac 1 2 TYPES OF BOILERS

e e the e e o of the e t spac is unfavorabl to compl t c mbustion gas s , he

e c Th space for mixing and burning b ing restri ted . e combustion

e of the ee e -ﬂued o e 1ncreases the e b ut th chamb r br ch s b il r spac , e construction at the junction of the two ﬂues is weak and has been

o responsible for many expl sions .

GALLO WAY BO ILER

= l rn ll =Fire ll Horizontal Two F ue Inte a y d Ga oway Tub es.

o e o e of the e e e o the G o o An th r b il r sam g n ral f rm is all way , sh wn in

e e o e e to o h . 7 8 9 . e t e Figs , , and It was d v l p d with a vi w v rcoming

Fi . 7 G a ow a Boi er. Br c t n i g . ll y l i k Set i g Part ally Rem o ved shortcomings of the Lancashire boiler by providing obstructions

the flues c e e f h of c o to aus an intimat mixture o t e gases mbustion , at the same time adding efficient heating surface; the cross flues also serve to create a circulation of water around the bottoms of the

ﬂues e c m e o ec the c e main , thus ov r o ing a s ri us obj tion to Lan ashir

o e c is e c e b il r , whi h d ﬁ i nt in this respect .

Two Types. There are two different forms of Galloway boilers

‘ t e ﬂues t v two e hos having two distinct , and hose ha ing furnac s

TYPES OF BOILERS

F IRE =T U BE BO I L ERS

CO MMON HO RIZO NTAL TYPE — - = b E t rnall Fired. Sin le Flue B iler. Single Fire Tu e x e y In g “ o e G o o e the e 1nternal the Cornish, Lancashir , and all way b il rs, larg

' e e e e flue o e flue serv ed as a fire box . Th r was, how v r , a b il r having

The e s . 10 e e e the ﬁre external to the shell . boil r hown in Fig r s mbl s

e e . 3 o e e the plain cylindrical boil r , illustrat d by Fig , b th in app aranc

ut it one or o e e ﬂues e te o end to and setting , b has m r larg x nding fr m

e the e ce c e e t t the end. This increas s h ating surfa to su h an xt n tha b oiler can b e c onsiderably shorter than the plain cylindrical !b oiler . nd Note that the gases leave the setting on the front e .

Boi er Fi 1 0 . ection o f C in rica ue g. S yl d l Fl l — an Small Fire Tu bes E xternall Multitub ular Boiler. M y y

' ” e o the internal ﬂue adv an Fired. When engine rs f und that was an

e e the e oo e m o e e . the e , tage, th y s n add d r tub s As numb r incr as d

size diminished until they bec ame of the size used at present . This

is a brief statement of the development of the multitubular boiler . for For many years this type of boiler has been commonly used

e e o e e for stationary work , and , although oth r typ s p ss ss advantag s

c e e ec o o c e e, e certai n conditions , it is still onsid r d n mi al , r liabl asily

e c o c e of oo e o e e handled , and saf , if nstru t d g d mat rial and p rat d

- with c are and intelligence; i n small and medium sized plants oper

ated at moderate pressures . TYPES OF BOILERS 1 5

D cr 1 1 t 1 r e i o e . es i tion . o 4 a e e e e p . Figs s l ct d to illustrat th s b il r

T 1 1 . s he boiler without the brick setting is shown in Fig . It consi ts of a steel cylindrical shell and num erous small tubes extending from

n n re t 4 nc e e e are e d to e d. These tubes a 3 o i h s in diam t r and

e e the two e e e ee ex an the fast n d to nds , call d tub sh ts , by p ding

The tubes into the sheet and beading them over on the outside.

e e of ee e in e e e on sh ll is mad st l plat s i to 51 inch thickn ss , d p nding th he o th e e e e e e e e e. t e diam t r and pr ssur At fr nt, sh ll plat s xt nd beyond the tube sheet and are c ut away to allow the waste gases to

h o one- the o e of th e enter t e uptake. Ab ut third v lum e boil r is occupied by the steam ; the other two-thirds is ﬁlled with water and

Th a e t e e b e tubes . e w t r line is a shor distanc (from 3 to 8 inch s) a ov the f e top row o tub s .

. 1 1 . M u titu u ar Boi er w thout Its ett n Fig l b l l i S i g ‘

r e e e o The ﬂat ends a e pr v nt d fr m bulging by stays , which may

12 b e o . o . or e b e of the form sh wn in Fig , th y may diag nal stays The through stays are fastened to the tube plates by means of nuts

12 Be o o S . 1 1 . . and washers as sh wn at in Fig , and also in Fig l w

e e the end e e the e . e of the water l v l , plat is stay d by tub s This typ boiler may b e supported by brackets B riveted to the shell or by 4 Th w . 1 . e o means of beams and columns , as sho n in Fig fr nt

th e the e c et bracket is often ﬁxed in e sid wall , but r ar bra k should

e e t the of the e b e placed on rollers . This will pr v n straining plat s

ce b e e during expansion and contraction . A small spa must l ft

between the rear tube sheet and the brick wall to allow for

expansion . 1 6 TYPES OF BOILERS

he e o . 1 1 has e h T boil r sh wn in Fig two st am nozzles N . If t e

me the e o e ce e e or e the boiler has a do , st am n zzl is pla d ith r at n ar

to f h p o the d ome. T e feed pipe may enter either at the

o or I fr fr nt at the rear . t e quently terminates in a per forated pipe below the water

- line. The blow off pipe is at

the e the o e r ar of b il r , as

o . 13 . e sh wn in Fig A valv ,

e the - off v alv e re call d blow , g ulates the ﬂow and may b e

" opened to blow out sediment

e c e The and d ta h d scale. boiler is usuall slight

manholes 1 1 shows a ma top near the handhole near the front tube holes may b e p

M o e man . anh l holes are made

e are o t 1 1 c e 15 c e shape. The form r ab u in h s by in h s the latter about 4 inches by 6 inches . TYPES OF BOILERS 17

f Th ce the ce e o e Heating Su r ace. e heating surfa is surfa xp s d

h ce e t hot e . e t e e o gas s In this typ , h ating surfa is mad up of

9 - 9 N01!

o th e the e - of he e e ab ut half e sh ll , tub s , and about two thirds t r ar tub

h is e o the e e. ee . e e t e e e sh t In g n ral , all h ating surfac b l w wat r lin 18 TYPES OF BOILERS

n The o e e Form of Setti g. c mpl t multitubular boiler is shown i n

c ettin in . 14 and e o of h e its bri k s g Fig , a longitudinal s cti n t e s tting

h c e o of 13 . T e s e r in Fig . bri k tting c nsists brick laid in c ment o

The e and the of the e e e h mortar . bridg portions furnac xpos d to t e

r r e fir fire- The e fi e a e lin d with e brick, laid in clay mortar . bridg is built at the rear of the grate and forms a support for the grate bars ; Th it also directs the flames upward . e arrows show the direction

of the of hot e . The e i e the e the ﬂow gas s furnac s form d by bridg ,

nd th o e t of the T o e a e e t . he e t sid walls, l w r par boil r fron b il r fron

f the e e r is usually o cast iron with low r part lin d with ﬁ e brick . The front has doors which lead to the

e it nd m e a e . Th furnac , ash p , s ok box space below the grate is called the ash

t o t r pit, and hr ugh i s doors ashes a e removed and a large portion of the air

for e e re combustion nt rs . Both the ﬁ doors and the ash- pit doors have draft

e or to e h plat s, grids , r gulate t e supply

f h o o air . T e do rs to the smoke b ox give ac cess to the tubes for cleaning n a d repairs .

VERTICAL TYPE

Upright boilers are used when ﬂoor space is valuable and there is

fﬁc su ient height . Small sizes are

e for e e us d pil driving , supplying st am

for pumps and similar work , and in hoisting engines ; large sizes are used if it is necessary to have a powerful - Fi . 15 Vertica x g . l Fire Bo Boiler

e e. e e batt ry in a small spac In g n ral , they are not so economical as horizontal multitubular boilers unless

e ar e of the e th y e car fully designed and considerable height . If tub s h are t e es e c e be o e e e c e e . short , hot gas s ap f r th y giv up mu h of th ir h at = il Single Tub e Bo er. O ne of the simplest forms of upright

15 . e boiler is shown in Fig . It has a cylindrical sh ll with a large

n ﬁre e the ﬁre b ox at its lower e d. This box is form d by inner cyl

h ter s e b s o t s t inder, which is fastened to t e ou h ll y h r crew s ay bolts TYPES OF BOILERS 1 9

as shown . A flanged ring c onnects the fire box with a large flue

c co c the hot e T whi h ndu ts gas s away . he necessary handholes,

e e e etc . are o i e gag s , saf ty valv s, , pr v d d . This form is not ec onom

b ut e on cco of the ical is us d a unt little attention required .

ultitub ular B iler M o . More economical forms of the small

t o e are ll e . 16 1 h uprigh b il r i ustrat d in Figs and 7. T e b oiler shown

Fi . 16 co o o e e e e the in g is a mm n f rm , xt rnally b ing lik boiler repre

e e Fi . 1 5 o s nt d by g , but having a s mewhat different inside construc

Fi ic al M u l i 1 7 . ert t tub u lar il g. V Bo er with Upper E nds o f Tu bes Below i e ic al M ul i ular il ate r ine F . 1 6 V rt t tub Bo er g . W L

e ul e ce on end. The tion . It resembl s a m titubular boil r pla d ﬁre

the b ox is made of an inner cylinder stayed to outer . The top of the ﬁre b ox e the o e e ee c o e e the e , call d l w r tub sh t, is nn ct d to upp r

h he hot e the e e o c t o e e. h ad by tub s, thr ugh w i h gas s pass to sm k pip

e 1 he e e of the It will b e readily s en from Fig . 6 that t upp r nds tubes are surrounded by steam while the lower portions are covered f e . e oo c o o e the t es With wat r As st am is a p r condu t r h at, ends of h e

e tubes are liable to injury from overh ating. 20 TYPES OF BOILERS

_ In the class of boiler shown in 1 Fig . 7 the upper ends of the

e are e the e ev tub s b low wat r l el ,

o the thus av iding fault just ,

e c e c e d s rib d in onn ction with Fig . 1 6 . The upper tube sheet is

e e subm rg d , and is ﬂanged and riveted to the frustrum of the

co e c o m the x n whi h f r s smoke b o . The chief defect in this boiler is that the lower part of the c one is often placed too near the shell ;

o e o e e this is d n to admit m r tub s . This c onstfuction restricts the space so much that there is not sufﬁc ient room for the steam to

i e it n r s as is formed o the tubes .

The e c ec e to con , whi h is subj t d

e e e e e e xt rnal st am pr ssur , is lik ly to b e weak and should b e care

fully stayed . These small upright boilers

e e c e the r quir no bri k s tting , as ﬁre box is within the boiler and the cast- iron foundation forms

the ash pit .

oil Th n Manning B er. e Ma

ning boiler is illustrated in Fig .

to the 1 . e e 8 It is , in g n ral , similar 1 w . 6 upright boiler sho n in Fig , but in order to get a large heat

ce e 20 to 30 ing surfa , it is mad

the o e o o feet high . At l w r p rti n , the shell is of greater diameter than at the top in order to pro

The vide a large grate area .

8 M annin Boiler e to the 1 . x Fig . g inner ﬁre b o is stay d Courtesy of The Bigelow Company A shell by screw stay bolts . s

22 TYPES OF BOILERS

e the e o the o e th just ov r furnac d or, and at b ttom n ar e foundation

f r . e e are no o e o c e the o ring As th r manh l s l aning , b iler is suited to good feed water only . The feed pipe enters the shell at the side near the middle of the

e e e e o the o e e o e t wat r spac , and xt nds acr ss b il r ; it is p rf rat d o dis tribute the water . The heating surface c onsists of the inside of the ﬁre b ox and the h e the e e e t e e ee . t of the tub s up to wat r l v l , and tub sh t That par

e e the e e the e e u ce t the tub s abov wat r lin is sup rh ating s rfa ; tha is , heat from the gases passes through the metal of the tubes to the

e e e e t i i its e . st am , thus raising its t mp ratur withou ra s ng pr ssure ” S e e e e c e e team heat d und r th s onditions is call d sup rheated steam . In small vertic al boilers this superheating surface is not desirable because the work of the small boiler does not require superheated

h e are e b e e h steam and t e tub s lik ly to burn d by t e intense heat .

h e of the M the e are not With t e long tub s anning, gas s as hot when

e e the to o e t e e th y r ach p, and as this b il r is buil in fairly larg siz s ,

2 e o the e e e are 00 horsepower b ing comm n , ngin s suppli d built for

e e e e e e . economy , and r quir dry if not sup rh at d st am

INTERNALLY=FIRED MARINE TYPE

RET URN=T UBULAR BOILERS

— ll ir u Horizontal Many Sma F e T b es. The boilers hitherto

r for the e ce described a e used mainly stationary work, x ptions being

e ee not b e e e e e . H e e e so few that th y n d v n m ntion d ow v r , th reis another modiﬁcation of the ﬁre-tube boiler which is now extensively

Th of h - used in marine work . e parts t e return tubular boiler are essentially the same as those of ﬂue boilers (Cornish and Lancashire)

f the l e . e are e e and o multitubu ar boil r Th y , how v r, arranged

b e differently in order to used on board ship .

E arliest Forms . The e e o e e arli st f rms of marin boil rs , working “ e 15 30 er e e e e r with pressur s of to pounds p squar inch , w r squar o

- e e of o for box shaped . They wer conomical and convenient f rm

e e e e e e e e e the ships . Wh n high r st am pr ssur s b cam n c ssary, ﬂat surfaces required so much staying that they were abandoned and

th ce the e the e cylindrical type was introdu d , as this form is b st of

practical shapes to resist internal pressure. The cylindrical form TYPES OF BOILERS 23

not b e c e e o e a may as onv ni ntly st w d aboard ship , but it will st nd Th much higher pressures . e cylindric al marine boiler is frequently

f r 200 o er e o built o p unds p squar inch w rking pressure.

= in le=Flu - Single Ended S g e Type. T he single ended return

o e o . 2 1 co e the e c ﬂ tubular b il r, sh wn in Fig , mbin s int rnal furna e ue of the Cornish type and the numerous small ﬁre tubes of the multi

The c c e e of e e e o e e tubular . ylindri al sh ll is mad up plat s riv t d t g th r

f th o e r h h e o e c a e e t e e . and to t e flat nds b il r, whi h flang d to fit sh ll

The e c c 3 4 eet e e e. Fu rnac furnac is ylindri al , to f in diam t r , Th n and about 7 feet in length . e front e d of the furnace ﬂue is

nd e h o e e o e. riveted to the fr nt plat , which is ﬂang d for t e purp s

e e the o or The back end is riv t d to combusti n chamber plates . F

e the ﬂue e c e e m rly, was a plain cylind r, but as a plain ylind r , unl ss of e e c o c e e e e oo small diam t r, ann t stand mu h xt rnal pr ssur , it s n

e of the became necessary to strengthen it . This was done by m ans th curved ring shown in Fig . 5 and other methods ; at present e ﬂ n o e ue e o e o e . 6 . c rrugat d is us d , f rm b ing shown in Fig

a Th ce th c f h f Gr te. e grate is pla d at about e enter o t e height o the furnace ﬂue; the space above this grate is oc cupied by the ﬁre

h h b e ee o th ot e e e o t e . e and gas s , whil b l w is ash pit As will s n fr m ‘

o 21 he ho e ﬁl - h e h ﬁre th . t t l t e ce t e e arr ws in Fig , gas s spa abov , h c e t e e the e. combustion hamb r, tub s , and uptak

Combustion Chamber. The c e the combustion hamb r, in which

od ts m st are u e m ﬂ and u e pr uc of co bu ion b rn d, is for ed of at c rv d 24 TYPES OF BOILERS

e e o e Th plates ﬂanged at the edges and riv t d t g ther . e shape of the

- e o Fi . 2 1 c sec o e of e e plat s is sh wn in g , whi h is a ti nal vi w a singl nded

The c e eet o the o of h m marine b oiler . ba k tub sh f rms fr nt t e c o b u s

The ce the e ﬂ o e . ce ue com ti n chamb r spa around tub s , furna , and b usti n c e e e the e e e e o hamb r is ﬁll d with wat r, wat r l v l b ing 6 to 8

f The ce inches above the top row o tubes . spa above the water level is called the steam space.

ta Rods the e - e e e S y . As r turn tubular boil r has s v ral ﬂat surfaces,

The ﬂa e this type requires careful staying . t nds above the water

22 eturn-T u u ar Boi er with T hree lu es Fig . . R b l l F level are prevented from bulging by long stay rods similar to those i h Be o the e e e th ﬂ n t e e. e ce ue multitubular typ l w wat r l v l , furna

the e o the e o o . o eo e and tub s aid in h lding ﬂat plat s in p siti n M r v r, “ f f e c c e 21 r ew o the e o the e . a e e a tub s , sh wn by h avi r ir l s in Fig , mad

c e so e b e on the e c are s e e thi k r that a thr ad may cut nds, whi h cr w d

The c o st o ch into the tube sheets and held by thin nuts . mbu i n am b er plates are stayed to the rear end plate and the shell by short sc e The of the c o e r w stay b olts . ﬂat top mbustion chamb r is sup ported by girders or crown bars . TYPES OF BOILERS 25

= = l i l l e. Th Single Ended Mu t p e F ue Typ e boiler shown in Fig.

21 nl one e e - ul e e e e has o y furnac , but r turn tub ar boil rs fr qu ntly hav

hree or e . two, t , four furnac s

. 22 c L r Fig shows a boiler with three furna es . arge furnaces a e more efﬁcient than small ones because the grate area increases

ec the e e e the ce o e the i c e e dir tly as diam t r , whil air spa ab v g ate in r as s

h e of the e e . T he e e c as t e squar diam t r gr at r spa e aids c ombustion . The length of the grate bars is nearly constant for all siz es of ﬂue

e e the di ce ﬁre- r becaus it is limit d by stan a man can th ow c oal . Fur

e ﬂues are o 36 54 c e th nac usually fr m to in h s in diameter . As e

e of ce e the e e e o th f h siz furna s is ﬁx d, numb r d p nds up n e size o t e

o e for e o e t e e e e c c an b b il r , a larg b il r mus hav a larg grat ar a, whi h e Th obtained only by using several furnaces . e various arrange

e are 2 m nts shown diagrammatically in Fig . 3 .

Fi 23 e era Arrangem ents o f M ulti ler Flue Bo er u e heets g. . S v l p il T b S

mbers e- ce o e Arrangement of Combustion Cha . A singl furna b il r

n two- ce o e e has but o e combustion c hamber . A furna b il r may hav a c ombustion chamber for each furnace or it may have a common

I e o o o combustion chamber . t is better to hav a c mm n combusti n c e for the e ec e e e s ee hamb r two furnac s , b aus alt rnat toking k ps

f e e e up a more nearly constant pressure o steam and th r is l ss smoke.

ee- r ce o e e ee o o c e Thr fu na b il rs usually hav thr c mbusti n hamb rs ,

o - r c e o e are e while f ur fu na e b oilers have two . In cas f ur furnac s us d

ee c e the e e u e e to with thr combustion hamb rs , two c nt r f rnac s l ad a n common combustion chamber and each outside furnace has o e.

u = nde - D o b le E d Type. This form of marine return tubular boiler is practically the same as two single-ended boilers placed back to

c h Th f h t . e o t e ba k, but with e rear plates removed e w ight e r ar

e e e e o o ; e plat s is sav d, and th re is l ss loss fr m radiati n This mak s the double-ended boiler lighter and cheaper in proportion to the

TYPES OF BOILERS 27

D o e-e e o e are o e e 1 heating surface. ubl nd d b il rs ft n mad 6 feet in diameter and 18 feet long . There are two distinct classes of double- ended return-tubular — boilers those having all the furnaces open into one combustion chamber and those having

e several combustion chamb rs . The boiler having but one combustion c hamber has the disadvantage that if one ﬁre is being cleaned the whole boiler m ay b e c ooled by the

e e inrush of c old air . It is b tt r to have a c ombustion cham

r or c e or at he f ea h furnac , least to have a combustion chamber for the furnaces of

n The e o each e d. usual m th d

“ of dividing up the c omb us tion chambers is by water

ce s o n . 24 spa s, as h w in Fig which shows sections of a b oiler havin g a c ombustion chamber

e c n c for a h fur a e. Stationary Return=Tu b u lar Type. While the return tubular b oiler is c ommonly

e in e o e us d marin w rk, this typ ,

so e c e e with m hang s in d tail , is

e o us d in stati nary plants . Fig . 25 shows the c onstruction and

e t of arrangem n parts . The

ﬂue is - larger in proportion to the diameter than is the c ase with the marine form ; the co s e e e l to the e i s th mbu tion chamb r is partly xt rna sh ll ; that , e

e e ee o the e end r ar tub sh t is als r ar plate. This arrangement does away with the necessity of staying the ﬂat plates of the ‘ comb ustion 28 TYPES OF BOILERS

Another form of internal-furnace return- tubul ar boiler is shown

2 o e in Fig . 6 . This b il r usually has two ﬂues extending from the h Th front to t e back head . e grate is placed in the corrugated

o e e e h ﬂ c of e p rtion , whil conical wat r tub s support t e ue ba k a bridg Th wall . e large furnaces and the space around the conic al tubes

o e o e of pr vid a c mbustion chamb r ample size.

The o o the ec o th hot e arr ws sh w dir ti n taken by e gases . Aft r

e i the e ﬂue e e e the e e w c are e o l av ng int rnal th y nt r r turn tub s , hi h b l w

the e e o e e the o e th furnac ; b f r l aving b il r, they pass underneath e

- . 26 tat onar Bo er of the eturn u u ar T Fig . S i y il R T b l ype

e h ar th e e shell . By this arrang ment t e hotter gases e near e wat r lin

and the c ooler gases in c ontact with the cold water . Thus there is

e c e the greatest difference in temperature at all times . At a h chang

the ec o of the hot e e e for t in dir ti n gas s , th r is an opportunity dir

- the e e c e and ash to fall by gravity, so that tub s may r main l an and

efﬁcient .

With the exception of the foundation there is no brickwork .

- n n c e . o e The shell is c overed with a o condu ting mat rial This b il r,

h e e e ce like t e Galloway, has a larg st am and wat r spa , thus insuring

dry steam and great reserve power .

30 TYPES OF BOILERS

- lin The usual form of horizontal ﬁre box b oiler c onsists of a cy

' r e e e ec u ﬁre drical shell , o barr l , partly ﬁll d with tub s , and a r tang lar

o o e e the e e eet o box . The shell is pr l ng d b yond r ar tub sh to f rm a

o e of the e e the ﬁre , smoke box . The fr nt nds tub s op n into box

c o o e the e 18 e e of stack or uptake. For lo m tiv work, r a larg numb r

2- c b ut for o the e are small tubes , usually in h , stationary w rk tub s

The e for if e e ce t larger and less numerous . r ason this d f r n is tha in

ce ece to the locomotive boiler a greater heating surfa is n ssary, and obtain sufﬁcient draft to burn the large amount of coal for this

- h n ub e r ss re Box to u ort T i e for 28. o omotive ire Box Boiler owi T A o i pp Fig. L c F S g c F S l Furnace A rc h

ce the e t e e o the o e b ox . heating surfa , xhaus st am is turn d int sm k

The blast of steam c arries the heated gases up the stack and a fresh h supply of air passes through t e grate. The cylindric al shell i s joined to the ﬁre box by riveting to a

- e o o 111 the e c o e . ﬂanged ring or to a cone shap d p rti n , as v rti al b il r

The ﬁre b ox has a rectangular cross section and usually a ﬂat top.

e e e e e e for the Like the vertic al boil r, th r is an inn r and an out r sh ll

the e the e e the o e e e furnace, inn r having sam shap as ut r, xc pt that

The e e e o e e the e o the top is ﬂat . xt rnal sh ll is c nn ct d to inn r by sh rt

h e e ee i s e the e le . The screw stays . T e spac b tw n call d wat r g ﬂat

e e are o e e top is stayed by girders or crown stays . Th s s m tim s The e of the e attached to the shell by sling stays . low r portions tub TYPES O F BOILERS 3 1

sheets are held in place by the tubes ; the upper portions are stayed

by diagonal stays . The c hief differences in the various forms of loc om o tive b oilers are the shape of the ﬁre b ox and the loc ation

of h oc o o e t e grate. L m tiv boil ers are either straight top or

o The o to wagon t p. wag n p

l 2 c o e o e . 8 b i r, Fig , has a n shaped portion by means of which the boiler is larger at

he ﬁr - end con t e box . This struction is to give a greater

e c Th st am spa e. e increase in size of b oilers has raised the top so high above the rails that

“ the wagon top is not now used

e e e the to xt nsiv ly ; straight p,

. 29 o e co Fig , is m r mmon .

e l ir il B pa e Bo er. T he shell and ﬁre tubes of this typ e of b oiler are practically the same as in any other ﬁre box boiler ; the peculiarity lies

the ﬁr b x in e o . The inner and

0 l o o o o o o o lo o o o o m o o o o outer ﬁre- b ox plates are hori

z ontal the to at p, and the sides of the outer ﬁre box are con

t tinued SO that the space above o o o o o o o o o o 0 the crown sheet is rectangular 3

in ec s tion . The advantage to Z ' o :o o: :o o o o o o

b e i e : o ga n d by thi s c onstructi on e o one o o o o o o o o o

the o is that stay b lts, Which

hold the crown sheets and side

ee b e sh ts, can plac ed at right

e to the ee angl s sh ts . This reduces any tendency on thepart of the

ee to e e e Sh ts b nd wh n und r pressure.

34 TYPES OF BOILERS

STATIONARY BOILERS

= - ox e. The ﬁre b ox e G eneral Fire B Typ boil r, usually called

e e e for s o t t the locomotive boil r, is oft n us d tati nary work, rac ion

for e e of t . t e of e s engines , and v ss ls ligh draft This yp boil r, lightly

me e e e e the se m for e modiﬁed , is so tim s us d for g n rating t a h ating

e o c e e e buildings . It is c nomi al and durabl wh n us d with natural

‘ c e f e e e o are e t es ec e draft . The hi f di f r nc s in constructi n larg r ub b aus

a the e due to e of o t. of the dr ft, and chang s m thod supp r A common

i 32 ocom oti e e o f Boi er for tat onar U se F g. . L v Typ l S i y

2 t e e . e ee form is shown in Fig 3 . This typ has b n buil in larg siz s

for e e e so e e e e. high pr ssur , but wh n mad is xp nsiv

PECULIAR FO RMS = = h Return Tub ular Fire Box Boiler. Boilers of t e form shown in

3 e e e the ﬁre- t e b ut e Fig . 3 r s mbl locomotive box yp , in addition hav

Th c h e e s of t e e return tubes . e hot gases rea h t e uptak by m an h s tubes instead of passing to the chimney from the Thus they combine the advantages of the ﬁre-b o

- return tubular type without the brick setting . The

e t e e e . cl arly, fur h r d scription is unnec ssary TYPES OF BOILERS 35

il Cochrane Vertical Bo er. The Cochrane verti c al boiler is somewhat like the return-tubular boiler in point of arrangement of

Fi 3 3 o om oti e ire-Box R eturn- ub ul ar Bo er g. . L c v F T il

e 4 The e . 3 . heating surface. This boil r is shown in s ction in Fig ho e o the ce the o c e e t gas s pass fr m furna to c mbustion hamb r , th n

— ‘ through thet ub es to the uptake. The heating surface consists of tubes and the plates of the ﬁre

hic o n e box, w h is surr u d d by

c h Th water ex ept at t e bottom . e crown of the b oiler and of the

ﬁre box e emi e , b ing h sph rical ,

Th e require no staying . e h mi spheric al crown also allows a large

The e th steam space. ﬂat plat s ( e tube plates) are held together by

he e t tub s . h l S ap ey Boiler. The Shap

le o e o . 35 y b il r, sh wn in Fig , may b e called a return- ﬂue vertical

e The e o o boil r . upp r p rti n is a

e e o for e e r s rv ir wat r and st am , and

the e the ﬁre ox low r contains b .

The f h s eet o t e ﬁre n i n crown bo s , 4 Cochra e ert ca Bo e, h x i Fig 3 , V l 36 TYPES OF BOILERS

to the to The stayed p by through stays . hot gases from the ﬁre rise in the ﬁre box and pass through short horizontal tubes to an annu

e o c h ﬂ lar space. This annular spac is c nne ted to t e ue at the base

e th e by v rtical tubes passing through e wat r space. This boiler has a large combustion chamber ; the ﬁre box is

e e the eet e are e e surround d by wat r, and crown sh and tub s r mov d

th e h ﬁre e e t from e intense h at of t e . This arrang m n increases the

Fi 35 ection of he ha le ertical Bo iler g. . S t S p y V

e ce o oo c o o e e h ating surfa , all ws g d mbusti n , and r sults in a durabl

o h e e so b iler . T e base is partly ﬁll d with wat r , that any sparks

carried over will b e quenched .

Brad c tch B iler. The B S o Bo e . 36 y S o o rady c tch il r , Fig , is a

f - e o e modiﬁcation o the well known standard marin b il r, and com f bines the advantages of internal ﬁring with some virtues o its own .

Th o e e one e o e lower shell contains two c rrugat d flu s, b ing sh wn in part section in the figure ; the flues lead into a chamber at the back

38 TYPES OF BOILERS

The B e e i e -ﬁred e e rady boil r, b ing nt rnally , r quir s no brick

the hot e the ﬂues es are e setting and , as gas s in and tub at all tim s

o e e the e o o are e e surr und d by wat r, loss s fr m radiati n r duc d to a

nho e ndh l r . S ha o es a e e o minimum tandard ma l s and provid d , all w ing a thorough inspection and cleaning of all parts of the boiler

Th r without difﬁculty . e boilers a e suitable for both marine and stationary work . ’ Th Be D ir t rn o D irecturn. e ec u e . 37 gg s b il r, Fig , is , in

e o e e - ﬁred e - u o e bri f, a h rizontal , xt rnally , r turn tub lar b il r in

c hot e o the e e the tubes condu t gas s thr ugh spac b hind bridge.

37 D irectu rn E xterna - ire Return- ub ular Boiler Fig. lly F d T ew ork it Cou rtesy of J am es Beggs and Company, N Y C y

- boiler consists of a shell partly ﬁlled with 3 inch tubes . rear

- of the furnace is a throat sheet in which 4 inch tubes are expanded .

r o the e end e e The other ends a e expanded int r ar plat , which is mad f h h large enough or t e purpose . T e furnace is encased in steel plates lined with ﬁre brick held in place by rods passmg through

n The o e for e e the o e the notches as show . manh l nt ring b il r is

ce the o e e of the e e e o e. pla d in fr nt h ad inst ad in sh ll , as is fr qu ntly d n A number of other makes of this type of boiler have been devel ” the E e C t Th . c e o e . e E c 38 p d onomic , Fig , manufa tur d by ri i y

E e C Pe e e e. Iron Works, ri ity, nnsylvania, is a notabl xampl TYPES OF BOILERS 39

Fi . E cono D il g 38 . mic irecturn Bo er Cou rtesy of E rie City I ron Works

W AT ER=T U BE BO I L E RS

h i i - General C aracter st c s. Water tube boilers differ essentially

o ﬁre- e o e the e c the e o of e fr m tub b il rs , nam s indi ating chi f p ints diff r

h ﬁre— e h r u e e ce. t e e o t e e a e n In tub b il r, tub s, which s rround d by

- e c c the hot e the o e b ox. the e e wat r, ondu t gas s to sm k In wat r tub , the e are ﬁl e e the e e tub s l d with wat r, and hot gas s pass ov r and

o e n to h hi am ng th m o their way t e c mney . Although ﬂue b oilers and the tubular types were introduced at

n e e e o a th e - e et the - e e a arli r p ri d th n e wat r tub , y last nam d typ is 40 TYPES OF BOILERS

new of e e e . A o a e not a form st am g n rator b ut c ntury ago , John

S e e e e e - e e e it to e t v ns inv nt d a wat r tub boil r and ﬁtt d a st amboat .

e . 39 c o e c This boil r, Fig , was a mbination of small tub s onnected at “ ” n n e e he n o e e d to a r s rvoir . Thus t Porcupine was o e of the earli

At e e e est forms . various tim s sinc th n many ideas have been D worked out both for marine and stationary boilers . uring the

e -ﬁv e e e e the e - e e last tw nty y ars , how v r, wat r tub boil r has been

e the e e o e the e f st adily growing in favor, chi f r as ns b ing nec ssity o

e e e e e c e e e el high r st am pr ssur s , larg r apaciti s , gr at r r iability of mate

e e in e and o e e e rials, gr at r skill d sign workmanship , and m r int llig nt

e t managem n . It is not within the province of this article to discuss the

me ﬁre- e te - e e b ut relative rits of tub and wa r tub boil rs, a careful

39 a ramm ati et h of tev ens Bo er Fig . Di g c Sk c S il impartial consideration seems to show that as far as economy of

e e e e e ffe e e o running is conc rn d th r is but littl di r nc , pr viding condi

n f e The ﬁre- e tions exist permitti g the use o eith r type. tub b oiler is reliable and can b e handled by those possessing comparatively little knowledge of engineering ; its chief d efect seems to b e the

Th e - o e . e e o e disastrous results foll wing an xplosion wat r tub b il r,

n e e to e e e o the other hand, is saf , and suit d high r pr ssur s, but in

some cases requires greater manual labor in operation .

n es. Be e e e e e let Adva tag for discussing th s boil rs in d tail , us

consider brieﬂy the salient points .

afet the e e e e the S y. Probably gr at st advantag claim d for .

- e The e c e water tube boiler is its saf ty . boil r contains mu h l ss

e a e the e ed water than does the ﬂu or tubul r boil r, and wat r is divid

42 TYPES OF BOILERS

T f the internal pressure is the same. he thickness o the shell of a

ﬁre- e not e ce e e e of the o e e tube stationary boil r is x ssiv , b caus m d rat

e e the e - e o e the e e for diam t r ; but in r turn tubular marin b il r , sh ll plat s b 1 Th 250 pounds pressure would e about % inches thick . e difﬁculty of working such thick plates and their great weight render the cylindrical b oiler unsuitable for high pressures . The small tubes and drums of the water- tube boiler may b e made quite thin even

e b e for the e e e . e for v ry high pr ssur s In g n ral , it may said that ,

e e e the e of e - e o e sam capacity and pr ssur , w ight a wat r tub b il r is

- f - only about two thirds that o a fire tube . l i i n C ass ficat o . Many attempts have been made to classify “ - B o e e c c o e on water tube boilers . y s m writ rs a lassifi ati n bas d

o or on the c e of o e o c e to b e e o circulati n , prin ipl p rati n , is laim d sup ri r to any division according to c onstruction . On page 4 of this article i s given a classiﬁcation acc ording to features of construction . No classiﬁc ation is altogether satisfactory bec ause boilers overlap into other divi si ons ; a water-t ube boiler

b e ec of the o e- e e e or e may s tional , d ubl tub typ , hav h izontal tub s , f t e ee c o . o e to e o e o o straigh tub s, and fr cir ulati n In rd r hav s m s rt c as o b e e e e o e r lassiﬁcation , and no discussi n will nt r d int r ga ding

e e e the e b e e e o e r lativ m rits , classiﬁcation giv n will h r ad pt d and

o followed as closely as c nditions will permit . — Water- tube boilers are divided into tw o great classes hori

e e e c o e c n zontal and vertical . Und r th se h ads m se tional a nd no

e - e c e — e e- s ctional , straight tub and urv d tub , and singl tube and

- h u e e. t e e are e o c the e do bl tub If tub s n arly h rizontal , su h as is cas of the B o E e Moo He e o e the abcock and Wilc x, dg r, in , and th rs ,

e b e c e o the e are e c or e boil r will all d horiz ntal ; if tub s v rti al , n arly n h e . the c e S etc . t e e b e c e so , as in Wi k s , tirli g , , boil r will lass d as v rtical

o o e b e e e o e Alth ugh m st boil rs can classiﬁ d as alr ady utlin d , there are a few of such peculiar c onstruction and arrangement that “ ” they must b e placed by themselves under Peculiar Forms .

o e to c e of o e few re re As it is imp ssibl dis uss all mak s b il rs, a p

sentativ e forms will b e considered as types of their respective classes .

o e b e e to c o e e as e the e N att mpt will mad h os any mak b ing b st ,

because many conditions must b e c onsidered in selecting a boiler .

e o e e c e e ce few c e are now e e e e Th b il rs d s rib d , x pt in a as s , us d xt nsiv ly

or e in either stationary marin work . TYPES OF BOILERS 43

HORIZO NTAL TYPES Babc ck and il — o W cox. Water Tu bes Nearly Horizontal Steam and Water D ru m Hor — — — izontal Straight Tube Single Tu be Sec

e e e of 4- boil r consists larg numb r inch tubes, 18

Fi - g. 4 1 . ertical Header on itu al din ru m B . Boiler E qui ed with B V L g D pp . Super heater and Chain G rate Sto ker Cou rtes o Babcock and Wilcox Com a n y f p y, N ew York City

ee co ec e f t long, nn t d to one another and to a horizontal steam and e . The e e of the o n Fi . 41 wat r drum arrang m nt parts is sh w in g , c e e of - e f whi h is a sid vi w a much us d form o this boiler . 44 TYPES OF BOILERS

E t e e e e er of the ach ub is xpand d into a h ad form shown in Fig . 42.

The t e a e e e one e e n ub s in v rtical row nt r pi c , a d this vertic al row

e e e t of the e is ind p nd n oth rs, thus

it ec o o e making a s ti nal b il r , with a “ ” staggered arrangement of the t ubes . In the back side of the

t e e the o e fron h ad r, and in fr nt sid

of the e e e e are e r ar h ad r , hol s drill d into which the water tubes are h expanded . In t e front side of the header opposite each tube is a handhole ﬁtted with a handhole h plate. T e details of construction

are o 4 . h sh wn in Fig . 3 T e tops of the headers are connected to the steam and water drum by short

e the c o c o tub s , and same nstru ti n is used for connecting the mud

the e e drum to r ar h ader .

O eration Th p . e grate is at the front end of the boiler under the

e end of th t high r e tubes . The ho

Fi 42 Wrou St e tical ea er fo r e om the ﬁre are e g. . H d gas s fr guid d by t g‘gl ﬁgl e e ”so division plat s and bridg s , that after rising from the grate they pass up between the tubes ; the

” e e a o o the e e e o gas s th n p ss d wnward am ng tub s and , aft r rising a s c nd

e off the e . the e of the tim , pass to chimn y In this way, dir ction currents of hot gases is at all times

o t e to the e t alm st a right angl s tub s, hus impinging upon them instead of passing

e to the e s e parall l h ating urfac s, as in

f the e the case o ﬁre tubes . As gas s impinge three times against the stag

ered e the e ce e g tub s , h ating surfa is v ry

eﬁiCIent. Fig. 43 . H I h( e ittings for B £ VFB0 1Ter ircu lation The ee e e C . f d wat r ent rs

the e e the e o Fi . 44 . st am and wat r drum through , pip sh wn in g

It is thus heated before it mixes with the hot water in the boiler .

46 TYPES OF BOILERS

h e - ee e e e r form . T e forg d st l h ad r boil rs a e used for the higher

e e . The e of e pr ssur s marin form this boil r has a cross drum ; that is , the t t e the t be e f drum is a righ angl s to u s inst ad o parallel to them . It is similar in form to the cross-drum types used for stationary

n fﬁc e m e e t e e ot t e . work . This for is us d in cas h r is su i n h ad room — — o a D Root. Tu bes Nearly Horiz nt l rums Horizontal Straight

— l e e t he R Tube Sectiona . This bri f outline indicat s hat t oot water

W r- B i er Fi 45 . ection of Root ate T u e o g. S b l Cou rtesy of Abendroth and Root Man ufactu ring Company

e o e e e e the B oc . tub b il r is , in its main f atur s, lik abc k and Wilcox In

h e e ce e of . . 45 o fact , t e diff r n is in d tail construction only Fig sh ws

e o the e the a longitudinal section of the boil r . Surr unding tub s is

to the e e e steam and water drum which has attached und r sid , n ar

h n c e on e e e e the t e front e d, a ross box having op nings its fac to r c iv ,

regular connecting bends from the top row of tubes .

he Root e - e e is e of Construction . T wat r tub boil r compos d

- e are e e o t-i e e 4 inch tubes . These tub s xpand d int cas ron h ad rs as TYPES OF BOILERS 47

c one 46 . e c e e shown in A, Fig . A v rti al s ction is form d by pla ing

- f e c B . 46 . One e o pair upon another as shown at , Fig tub a h pair is

e e e e of c connected to one above it by a ﬂ xibl b nd, by m ans whi h an uninterrupted circ ulation from the bottom to the top of the

c c C D and E . 46 section is obtained . A metalli pa king ring , , , , Fig , insures a tight j oint between the bend and the header . To form the boiler several

" “ of these vertic al sections are

The e placed side by side. th ory is that these vertical rows are not to b e rigidly connected

e e because the lower tub s , b ing

h ﬁre e e nearer t e , xpand mor than those above. ti Circu la on . Each section is connected to the cross box of the overhead drum into which the water and steam are dis

h e At the charged from t e tub s . rear of the boiler a plate " is riv eted to the drum and bored to receive the tubes that make the connection between the drum

e The ee and rear head rs . f d water enters at the top of the

o hic the e mud drum , up n w h r ar

h e e s ends of t e tub s r st ( ee Fig . and meets the hot water Fi 46 oot Boi er u e and ea er etai s g. . R l T b H d D l The circ coming from above. u lating water then ﬂows from the top of the m ud drum into the

n f he r o lower e d o t tubes . As these tubes a e surrounded by h t

e the e eco e e e e o the e to the gas s , wat r b m s h at d and ris s thr ugh tub s

steam and water drums . This heated water contains bubbles of

c e e the e c h The steam whi h l av wat r and colle t in t e steam drum . water ﬂows bac k through the steam and water drum and descends

hro the c e e to ee th e e h t ugh ba k h ad r m t e ent ring fe d water . T e water level is kept at about the middle of the steam and water

drums .

50 TYPES OF BOILERS

4 c e the e e are h Fig . 9 shows l arly how h ad rs connected with t e “ ” drums in such a manner as to avoid the construction of a throat through which the steam and water must pass after leavmg the

e c o t o the o e tubes in th ir cir ulati n hr ugh b il rs . This is a distinctive

48. E e M oor Boi er howin u erheaters. Boiler Co nstru ction is tan ar Fig . dg l S g S p S d d : Setting Special d e o r lawar Cou rtesy of E dge M oor I ron Company, E g M o , D e e

No th not o e t feature of the Edge Moor boiler . te that e drums do pr j c h through t eheaders .

the e handholes o e e c e end Fig . 50 shows ﬂang d pposit a h tub and the e c l e e on t of e i e llipti a c ov r plat , which, accoun its shap , is nt r TYPES OF BOILERS 5 1

e e the of e e h chang abl and , with aid a gask t , carri s t e boiler pressure

so the e e hi as to hold plat to its s at . T s construction is unique on account of the ﬂanging fea

e e e the e tur and, b caus m tal is retained between the hand

e e e e hol op nings, p rmits d sir able tube spacmg opposite with the assurance that there is ample strength in the Th handhole sheet . e stays across the header are usually solid . Circu lation and Opera

ion Th c l o of t . e cir u ati n steam and water is identical

Wi t e i o de . 49 ea er D rur i th tha pr v usly Fig . H d n ounect ons in E dge 0 0 1”lg0 1per scribed for the Babcock and

e The of the c o Wilcox boil r . aim constru tion is to pr vide as little internal resistance to circulation as possible by the removal of

etti j ature hi e obstructions . In s ng e s t s boil r has been installed in a great variety of ways ; the normal large boiler is usually similar to that of the Babcock and Wilc ox

41 ec in shown in Fig . ; in sp ial n 4 stances as shown i Fig . 8; and for the smaller sizes as shown in 2 Fig . 5 .

in u bes Nearl Hor He e. T y — izontal D rums Parallel to Tubes

— - l Straight Tu be Non Sectiona . The Heine water- tubeboiler is not

e of e a sectional boiler . Inst ad b ing expanded into small headers

e the grouped to form a boil r, all — e hi are 3 c e tub s, w ch 5in h s in diam - 50 Arran em en f E lli i are e e the e Fig . . g t o pt cal Flanged eter, xpand d into insid Handholes of E dge M oor Bo iler n plates of a water legat each e d.

The of e le n Construction . construction this wat r g is show in

f e e an . 51 . It e o e ri ted Fig is compos d two parall l plat s ﬂang d d ve . 52 TYPES OF BOILERS

The a e are e e e e to a butt strap . pl t s str ngth n d by short hollow scr w stays similar to those used in the water- leg c onstruction of ﬁre

t the to the e le e o e the box boilers . A p, wat r g is curv d and j in d to

o e e c steam and water drum by riveting . Opp sit a h tube is a circular it the t e or e e e e. handhole for cleaning ub , r placing if d f ctiv

l tion The ee e e e at the o t of th Circu a . f d wat r nt rs fr n e steam

e . 52 o the and wat r drum, Fig , and ﬂows int mud drum, a small n drum shown at the rear of the steam a d water drum . From here

c e oc Th e it passes to the rear header with mu h less v l ity . e wat r

e e o the e e i to the is warm d whil passing thr ugh pip l ad ng mud drum , and as it ﬂows slowly through the mud drum it deposits its sedi

e The c c e d m nt . a umulat d se im ent is blown off by means of the blow- off pipe at the

Th e i e e . e t b r ar wat r, as comes heated in the mud

e and e the drum , ris s pass s to

of the o front mud drum , fr m which it ﬂows in a thin sheet to the rear of the steam and water drum and to the rear

e le th wat r g. From e rear

e le it e e the e Heine Boiler Water L eg wat r g nt rs tub s , in which it is partly con

Th e verted into steam . e mixtur of steam and water enters the

e end of the o the l e ec o high r drum fr m water eg. A d ﬂ ti n plate

’ prevents water from b eing c arried to the perforated steam pipe

at the e t o t of the shown high s p in drum . The ﬂow of hot gases from the ﬁre is directed by tile placed on

the to o o o s of t e o 2 The hot p and b tt m r w ub s as sh wn in Fig . 5 . gases ﬂow nearly parallel with the tubes instead of across them as

n the B h o o i abcock and Wilcox and in t e Edge M or b ilers . ‘ j l — leﬁ h b e ori ljgmMos er. Tu es Nearly Horizontal D ru ms (Cross Typ ) H — zontal Bent Tu be Non- c ona Th e e e e e ee Se ti l. e chi f diff r nc b tw n this boiler and those already described is that it has short bent

e i e o e tub s, thus mak ng a more compact boiler . This type is mor ft n

e h o of us d in marine than in stationary work . T e b iler consists a

a e s e m an e m i . 3 e l rg t a d wat r dru , F g 5 , connected by slightly curv d

TYPES OF BOILERS TYPES OF BOILERS 55 steam pressure on the conical head increases the tightness of the j oint .

i . 4 M osher ru m Plu s F g 5 . D g

- — Thornycroft= MarshalL Tu bes Nearly Horizontal D rurns (Cross — e t e N - ect The Th rn r ft Type) Horizontal B n Tu b on S ional. o yc o Marshall non- secti onal boiler c onsists of a large horiz ontal steam

a e v e c e b ox or e e the e e and w t r drum , a rti al wat r h ad r , and g n r

h the e are e e . e t e o e ating tub s Lik M sh r , tub s b nt slightly, but the header is quite different from that boiler .

Th e f Construction . e general f atures o construction are shown

Th e e e h i 5 . e e o e t e F . 5 in g st am and wat r drum , s m tim s call d

e o e c e e e . The e s parat r barr l , is simply a ylind r with dish d nds wat r

- h f h Th c e o one t e e o t e c e . e e is arri d at ab ut third h ight ylind r tub s ,

c are ~ c e e are co ec e to whi h §i in hes in diam t r , nn t d in pairs a junction b ox at one end and to a water b ox or header at the other th f h end. e c o e two e o t e Thus a h pair f rms a unit , but tub s unit

h The are not in t e same vertical plane . upper tube enters the

e e h o e the o e o e e e low o h ad r as hig as p ssibl and l w r n s nt r d wn , F h f thus giving considerable upward sl ope . rom near t e top o

the e b ox ee o of e e to the e a o e wat r , thr r ws tub s l ad s p rat r barr l

h x Fi . T b o e o . 56 e e c o c o as sh wn in g wat r is simpl in nstru ti n ,

h e t e ﬂat plat s being stayed by short hollow screw stay bolts . The jun ction boxes are not restrained in any way ; this c onstruc

o c o e the c e of the e o ee ti n , mbin d with slight urv tub s , all ws fr

expansion . h h Circu lation . T e feed water enters t e steam and water drum and then passes to the water b ox through the tw o lower sets o f

Fi Th e th e f h e . 55 . e e e e o e o t e o tub s , g wat r nt rs l w r nds vari us h of e o Fi . 56 e t e e e pairs tub s , as sh wn in g , and ris s in tub s whil in h h Th f contact with t e hot gases from t e furnace . e mixture o

e hot e e e e the e e o c e st am and wat r th n nt rs h ad r, fr m whi h it pass s to the steam and water drum by means of the highest row of 56 TYPES OF BOILERS

Th of the e of e tubes . e difference in height two tub s a unit insur s

e e the e o good circulation . A bafﬂe plate pr v nts wat r fr m splashing

he e to t st am pipe .

- M arshal Boi er Fi 55 . ertical ection of T horn croft g. V S y l l

The hot gases pass upward among the tubes which cross so frequently that the heating surface is quite efﬁcient . — e rl orizontal D rurn orizontal Niclausse. Tu bes N a y H H

tr ht — l e e e e o e S aig Tu be Sectiona . This boil r diff rs ss ntially from th s

- e. e e already described in that it is of the double tube typ In g n ral ,

TYPES OF BOILERS 59 is provided at the open end with two cone- shaped parts ; these are

The o e e o about 8 inches apart . first c n fits into a tap r h le flanged

h e of the e e the ec c o outward in t e front fac h ad r, and s ond ne ﬁts

h c of th B h a similar hole in t e rear fa e e header . oth t e holes

the e e e o mi and tubes are ground to sam siz and tap r . Ab ut dway

h o e e e o o c c e the e o e between t e c n s , a third xpand d p rti n o upi s tub h l

mi e of th the i or e e e e . 58. The in d aphragm ddl plat h ad r, “Fig portion of the tube within the header is c alled the lantern At this p oint the tube iscut away so that water may freely enter the

the e e e e o ; Fi . 58 the e tube, op nings b ing abov and b l w In g , upp r

m b ut the e e ee e tube is in its nor al position, low r tub has b n turn d

r o h o through 90 deg ees to sh w t e c nstruction .

Fi 58 . Niclausse Bo er eta ls g. il D i

e e e the e e e the e e To stand high st am pr ssur s, l m nts of h ad rs f are o o ee are o e. . 59 o made wr ught st l and sinu us in shap Fig . sh ws

h f h e e h E c ele t e shape o t e h ad r and t e positions of the tubes . a h

o 2 the ment c ntains 24 tubes in two vertic al rows of 1 each . In f h le o t e e e e e for the e o . midd h ad rs , th r is a“diaphragm dividing int ri r The e e e o n c e for the e the front passag s rv s as a d w om r wat r, and “ ” e the u com er or e for the e of e r ar is p , ris r, mixtur st am and

er wat .

The o e e of the e e are c o e the e e l w r nds h ad rs l s d , and upp r nds

e ec the e e hic 42 ﬂang d to conn t with st am and wat r drum , w h is

e inches in diam ter .

irculation h C . Fig . 58 gives an idea of t e direction of circula

e h tion . Wat r from t e drum descends in the front c ompartment of the e e the c ul e hic co c e h ad r, ﬂows into irc ating tub s , w h mmuni at 60 TYPES OF BOILERS

the c o e t with front mpartm n only, and, after ﬂowing the length of the e e e the e e circulating tub s , nt rs g n rating tubes . The water then comes back through the annular spaces in the generating tubes to the e e t of the e e e r ar compartm n h ad r, b cause the generating tubes

c e the e c e communi at with r ar ompartm nt only, while in the annular

ce it e o e spa is partly vap rat d . The mixture of steam and water

e e the th n ris s to drum .

VERTICAL TYPES Wi k c es. Water Tu bes Ver — tical Straight Tube Non Sec

tional Let . us now consider a water- tube boiler having vertical

o tubes . Fig . 60 sh ws the general arrangement of the parts of the

W e e c e - ick s v rti al wat r tube boiler . At the top is a cylindric al steam and water drum into which the upper ends of the vertic al tubes

are expanded . At the bottom is a cylindric al drum of the same

e e the e The diam t r as upp r drum . tubes are straight and plumb when in position ; they are ar ranged in parallel rows with a clear space between rows to admit a small hoe to remove any

80 0 1: that m a cc e 0 1] the Fi 5 9 Niclausse ea er etails y a umulat g, . H d D f he tube sheet o t lower drum .

' The tubes are divided into tw o c ompartments by heavy ﬁre

The e the ec o e the ce r brick tile. tub s in s ti n adjac nt to furna a e “ ” “ ” e e o e the e are the co e ec e the call d ris rs ; th s in r ar down m rs , b aus

e e e e to the e o the o e h at d wat r ris s st am drum thr ugh fr nt tub s, and

h The ee e t e cooler water ﬂows down those in the rear . f d wat r is ‘ o The e o ﬂow of hot intr duced into the upper drum . dir cti n of

e h gas s is t e same as that of the water . The furnace is extended in front of the boiler setting and built

TYPES OF BOILERS TYPES OF BOILERS 63

hi i e e o e co e drums . As t s p p is ﬁll d with c mparativ ly ol wat r and

e of hot e e the the generating tubes with a mixtur wat r and st am,

- c irc ulation is up in the 4 inch tubes and down in the external pipe .

e the e e o o the The feed water ent rs st am and wat r drum , ﬂ ws d wn

the e e e inthe e e external pipe to low r drum, and th n ris s g n rating tubes to the steam and water drum .

Th ﬁre r e t of the e 111 e is in a brick fu nac in fron boil r, as shown

1 the hot es o the e . The ul o m Fig . 6 , gas rising am ng tub s ann ar f r of the steam drum makes the central space c onic al ; in this space

e ec e or e e the hot e e several d ﬂ ting plat s, bafﬂ s , caus gas s to r main

h e h h hot e . e e t e t e e t e among the tub s Aft r h ating wat r in tub s, gases pass through the opening in the steam and water

m co ct the e o ni the e . dru , coming in nta with m tal c ntai ng st am This thoroughly dries the steam and in many c ases slightly super heats it . Both the steam drum and the lower drum are equipped with

nh ad Th e o e e handholes swinging m a e s. e st am drum als has s v ral

s e e for u e in removing and r placing tub s . — — i arl rt l St rling. Tubes Ne y Ve ic a D rums Horizontal Bent

l 2 on e Non S o e o . 6 c Tub tirling b i r , sh wn in Fig , sists of three cylindrical steam and water drums at the top and a

h Th e c e the mud drum at t e bottom . e low r drum is conne t d to upper drums by three sets of tubes which are c urved slightly at the

The e e o nd e it o e ends . curv d tub s allow for expansi n a mak p ssibl

the e e e the to have tub s nt r drums radially .

The f ee e e e the e e e and d wat r nt rs r ar st am and wat r drum , c oming in contact with the hot gases just before they enter the

‘

e e o e e . e c e o t of uptak , b c m s gradually warm d This h ating aus s m s

h e e to to the o hic it b e o t e s dim nt fall mud drum , fr m w h may bl wn

Th o e h out at intervals . e mud drum is pr tect d from t e intense heat

the of the furnace by bridge wall . Each set of tubes is separated from the others by partition

b aflfles of fire- e the se the walls or brick til , so that ga s from furnace pass along the entire length“ among the first set of tubes ; they are

e e o the ec o set of e e th n guid d d wnward among s nd tub s , and, aft r

o the e of the ir et e c e th him rising again am ng tub s th d s , s ap to e c ney . The ﬁre- brick arch just above the furnace insures an even distri b ution of the gases and promotes combustion ; the arch heats the 64 TYPES OF BOILERS

e e e e e e the nt ring air to a high t mp ratur , thus r ducing danger of f c hilling the tubes by an inrush o cold air .

S e e the e set t am is tak n from middl drum , which is a little

on itu dina Section of tir n Boi er howin ettin and M echanical toker L g l S li g l , S g S g S ew York it Cou rtesy of Babcock and Wilc ox Company, N C y

The higher than the others in order to obtain more steam space . boiler is surrounded on the rear and two sides by the brick setting ;

the o N e o o e fr nt is of cast iron or of pressed steel . um r us p nings in

the brickwork allow entrance for cleaning .

66 TYPES OF BOILERS

this the vertical boiler illustrated in Fig . 63 is made up of straight

e the e e of two of e tub s and four drums, with xc ption rows v rtical

e the t e e the two u e tub s and circulating ub s conn cting pp r drums, h f th f which are bent . T e purpose o e two rows o bent tubes in the

e to e e t for th f e middle s ction is provid a stabl suppor e ba ﬂ wall . When superheaters are used they are located with the elements pro jecting almost up to the top

e e to the r ar drum, clos mid dle bafﬂe w all in the space between the bent tubes and

the straight tubes .

4 on how n How ust Boi er T ub es h Fi 6 . e t e t e e g. S c i S i g R l In ord r that tub s are Set 1nto Dru m may b e m serted 1nto their

es to the e of the the ee are hol normal surfac drums, drum sh ts

e e e e e the ef e t of forg d hot in a hydraulic pr ss ﬁtt d with sp cial di s , f c 4 this forging being shown in Fig . 6 .

= - Bigelow Hornsby. The development of the Bigelow Hornsby boiler is an attempt to satisfy the demand for large boiler capacity

the o e - - without resorting to d ubl and triple deck boiler house design . A section consists of four tube units suspended from structural iron overhead and connected by short tubes to a central steam drum as h . t e e shown in Fig 65 . As main st am drum is the only rigid m em b er e o c are e t e e of m e , xpansi n and contra tion asily ak n car , no att r

re e r ow h how many sections a us d o h long t e central drum is made.

Th e te 125 e e er e so e of e boil rs ra at hors pow r p s ction, that a boil r

e ten e The e 1250 horsepow r has s ctions . wat r circulation is down the rear units and up the front as well as in the individual units

ee e e e h to themselves . The f d wat r nt rs t e p rear unit drums and

e the o c c e o mix s with d wnward cir ulating urr nts , thus pr viding that the ol e e ee the co e O n cco the c d st wat r shall m t ld st gases . a unt of o e c e of the o e e e t e and p n stru tur b il r , it is an asy matt r o insp ct h c e . t e e are e ec one oo o l an it As tub s p rf tly straight , can l k thr ugh

e see e h - e th m and if they ne d cleaning . T e b afﬂe plate arrangem nt is

. 65 the e e ce at the c of shown in Fig , til b ing pla d ba k each unit

e the e i e e o the ot betwe n succ ss v s cti ns, thus making h gases pass

the e of the o to the e so on through tub s f rward unit s cond and .

e e e ce th e e o e e . When us d , a sup rh at r is pla d b l w main st am drum

e e e o the H E e This boiler is d v lop d fr m ornsby, an nglish typ . TYPES OF BOILERS 67

- - Fi . 5 e tion of an F ire B e g 6 . S c H d d ig low Hornsb y Vertical Boiler ou rtes o he ow n C y f T Bigel Compa y, N ew York City 68 TYPES OF BOILERS

be t o e — Co nnelly. Tu s a Vari us Pitch s D rums Horizontal

— - Bent Tu be Sin le Tu be Non Sectional. The Co e e g nn lly boil r , Fi . 66 c c c shown in g , onsists normally of two ylindri al steam and

e one e the to ee f wat r drums and wat r drum at p, all thr o which h c onnect with a mud drum at t e b ottom . When the units are

e e e e of e built sp cially larg , this boil r may consist as many as sev n

B IB / C K

i n ll - l F g. 66 . C o ne y Water Tub e Boi er

Cou rtesy of D . Connelly B oi ler Com pany, Cleveland, Ohio drums arranged by uniting two boilers of the four- drum type into one e e the ce of o e the o to pr ssur unit, pla articulati n b ing fr nt p

e of e c e e e the e ec o of one of wat r drum a h , th r by p rmitting r j ti n

f the o e of e e e the these drums . In any o b il rs this g n ral d sign all tubes are bent to the required shapes so as to enter the drums radially .

70 TYPES OF BOILERS

he ea ce ee e the et e traverse t h ting surfa in thr passag s , outl b ing at h the top rear of t e setting .

W -T B i er r c t n n om ete Fi . 67 E r e C t Vert a ater u e o . B et I g . i i y ic l b l i k S i g c pl , Batﬂes n ot Inserted e P enns lvania Courtesy of E rie City Iron Works, E ri , y

The r e e e the e tubes a e indep ndently r movabl , spacing b ing

" r f e e the so arranged . Also they a e bent in such a orm as to nt r

drums radially . TYPES OF BOILERS 71

6 . o or u ine Bo e nd ettin Fig. 8 Vertical Section of Hazelt n P c p il r a S g 72 TYPES OF BOILERS

PECULIAR FO RMS

l i — Haze ton or Porcup ne. Tu bes Horizontal D rurn Vertical

i ht Tu be The H e e - e o e Stra g . az lton wat r tub b il r differs in many

h L - respects from t e boilers thus far described . ike most water tube

e it of e e m e e boil rs consists a st am and wat r dru and wat r tub s , but the central standpipe is vertical and the short horizontal tubes

r o radiate from the central drum . Ac cording to ou classiﬁcati n it is not a vertical water-tube boiler because the tubes are horizontal ;

not e e e e e e . also, it is a horizontal boil r, as in g n ral app aranc it is v rtical

Fi . i n f rcu ine Boiler how n C enter ub es g 69 . Part Sect o o Po p S i g T

e ' o e o the c e The grat is circular and f rm d ar und ntral drum,

- n c o o o . o e the e which rests o a cir ular cast ir n f undati n Ab v grat , the central drum forms part of the heating surface and is the steam

the c b e e e e reservoir ; below the grate it is mud drum, whi h may nt r d 68 the e. o . by means of a manhole just b elow grat As sh wn in Fig , Th the standpipe above the ﬁre is provided with radial tubes . e “ ” he o e the e Po c e arrangement of these tubes gives t b il r nam r upin .

e f r e The The standpipe is about 3 feet in diamet r o large boil rs .

e e e t out the tubes are about 4 inches in diam t r, and proj c from

74 TYPES OF BOILERS

70 e are e e the - e c e , tub s not us d ; inst ad , wat r is ontain d in hollow

- c e e e . e e . 71 are ast iron sph r s , call d units Th s units , Fig , arranged

e c c e are e e e i e in v rti al rows , all d slabs , which susp nd d sid by s d ,

ne c t o o e o k. The about o in h apar , fr m an ir n fram w r brickwork setting IS merely a c overing to keep the hot gases in contact with

the units . The use of units in place of tubes combines great strength and

r a large heating surface . They a e strong because small and spher

c on cc t of the o of the e o e i al , and , a oun divisi n wat r int small mass s ,

f Th ar the heating surface is e fective . e units e held together by long bolts which pass through

the e e Fi . c nt rs , as shown in g 1 7 . The machined faces make a steam-tight j oint

o without packing . This b iler requires the same ﬁttings as other boilers The great advantage of

this boiler is safety . From

the c uc o onstr ti n , it is appar

Fi . 1 etails of ri i g 7 . D Har son Bo ler Units ent that rupture cannot ex

tend beyond the unit ; thus disastrous explosions c annot occur . They

are e be e e o o c e e e claim d to durabl , c n mi al , rapid st am rs , and asily

e e m . handled . The capacity can b e increas d by mer ly adding ore slabs

MARI NE BO ILER T Y PES

Elements of D esign. Because boilers used in marine work must b e built to meet the special c onditions imposed by the construction

of the c o e ec e o e c ce ships ntaining th m , and b aus b il r pra ti is slightly

e e sea on o e o out the diff r nt at than land , it is th ught b st to p int

e e of e e co e e e o e main f atur s d sign n unt r d in marin b il rs , grouping them together in one part of this article so as to distinguish them

c e e o of e c o the as a lass , v n th ugh all th m must lassify am ng “ ” e e o cco to o for ce ﬁre- e diff r nt gr ups a rding f rm , as , instan , tub , , ” . ' - h h c o o e e etc . T e c e o e t e wat r tub , prin ipl s g v rning nstructi n of marine boilers cannot b e different from those governing the

o o of o e o e e e e e e are c nstructi n all th r b il rs , and what v r diff r nc s shown TYPES OF BOILERS 75 come from the restrictions imposed by the spaces into which the

t o ec e of the e to e ce ﬁre . boilers mus g , and b aus att mpt r du hazard Marine boilers usually take one of the following forms :

1 R ec an u ar or b ox o ers ( ) t g l , b il 2 C n r ca or ru o ers ( ) yli d i l , d m b il (3 ) Water-tub e b oilers

As was pointed out with respect to boilers used in stationary

the te denc is o the e e use e - e o e plants , n y t ward gr at r of wat r tub b il rs o c count of e e e e e e e ec e n a th ir gr at r saf ty und r high pr ssur s , and b aus they are somewhat more c ompact for a given horsepower . It will b e ee o the e - ﬁred e of o e c one s n , als , that int rnally typ b il r, whi h at

e e e e e e o of e o e e e tim supplant d n arly v ry oth r f rm marin b il r , pr s nts the difﬁculty of offering very limited fac ilities in the matter of grate surface ; and this one fact has c ontributed not a little to the adop

- tion of water tube boilers in their stead . From these remarks it must not b e inferred that cylindric al boilers are not now frequently used in marine work ; they are still the most common boilers on

o b ut the n e e e e e ec the e o e b ard ship , w r v ss ls , and sp ially larg r n s , are being equipped with water-tube boilers built particularly for marine use.

RECTANGULAR MARINE FIRE=TUBE BOILERS

F ures of Constructi n. The ec o eat e . o r tangular b il r, Fig 72, is

‘ r b ox- e e h r made square o shap d ; h nce t e sides a e ﬂat . This form

one of the e e e e e o e e use e was arli st us d ; at pr s nt, h w v r, its is r stricted

l w e e e 30 o er to o e . pr ssur , that is, und r p unds p squar inch The reason why this boiler c annot b e used for high pressure is because the e e e o e e e ﬂat plat s t nd to bulg utward wh n und r high pr ssure.

o e to e e the e o e b e e In rd r pr v nt plat s fr m bulging , th y must stay d with

e o o e c num r us l ngitudinal and v rti al stay rods .

Box o e are e e e e b il rs g n rally mad with an int rnal uptake, as

2 co shown in Fig . 7 . This nstruction makes possible a larger steam

and re ce o of e ce . e e ex n spa du s l ss h at by radiation It is , how v r, pe

e e o the e of the siv in ﬁrst cost and r pairs ; als , plat s uptake waste

l e ec e the e e ec e th e n rapid y, sp ially n ar wat r lin , b aus e h at is ot trans

tt e l e mi ed as r adi y by st am as by water . In case the uptake is m e e e oe not o the e h ad s parat and d s f rm a part of boil r, t is obj ection

e is avoid d . 76 TYPES OF BOILERS

The e of the e e are or tub s r ctangular boil r usually horizontal , “ ”

e . e set e or e it e e e n arly so Wh n inclin d with a rak , as is call d , th r

e o e at the e- end The e is mor r om for manhol s smok box . extr mities

the e at the e end are e the e of tub s combustion chamb r n ar furnac ,

t ar h - n The e o t th b u e higher at t e smoke box e d. water lev l is ab u e

e th e the e e e t the c o o sam as with e horizontal tub s, nds n ar s mbusti n

The c chamber having the greater depth of water over them . in lina t o t 1 th o ion is ab u inch to e fo t .

- Fi . 72 W et Bottom e tan u ar M arine Boi er g . R c g l l

= = Wet and D r Bottom B ilers. Rec e are y o tangular boil rs m“ade o the o of o are in two ways , and fr m f rm c nstruction known as wet ” “ ” - o e r bottom and dry bottom . Wet bott m boil rs a e made with the

e e e e t of the e the e furnace wholly insid and ind p nd n sh ll , furnac s

h - being surrounded by water on all sides . T e wet bottom boiler is very difﬁc ult to inspect and repair .

h - o o o er the e e l n th In t e dry b tt m b il , furnac s t rminate e boiler

th hav m e e e the e l shell at e bottom, g a wat r spac call d wat r eg

78 TYPES OF BOILERS

' reason it a e e of e for that ttain d a high stat p rfection . From time

e e ee e to o ce e - e o e to tim , ngin rs tri d intr du wat r tub b il rs in place of the on cc of oo e o o cylindrical , but a ount p r d sign , faulty c nstructi n , or e e the e e e e e e e ce bad manag m nt , xp rim nts w r not ntir ly suc ssful . the e e e e e c e e of ee At pr s nt tim , how v r , an in r as sp d is demanded

. co e e e e e e e are and , ns qu ntly , high r pr ssur s and light r machin ry neces f . W c e e o e e co e e e of e sary ith this in r as pr ssur m s incr as w ight , c o e c e of e o o the c c f st , and damag in as xpl si n , if ylindri al form o E boiler is retained . ngineers have foreseen that the cylindrical

o e e to the e e e c e b il r must giv way st am g n rator whi h is light r ,

o e e . str ng r , and saf r

e - e o e e e e e co c e A wat r tub b il r , if w ll d sign d and w ll nstru t d , h seems to fulﬁll the requirements . Although t e cylindrical boiler

e ce e ef c e c an b e e to e o e is s rvi abl , ﬁ i nt , and mad stand any r as nabl

e e et the e - e o e o e e e pr ssur , y wat r tub b il r p ss ss s many advantag s over it . The principal obj ections to the cylindrical boiler are the great

e c e f c of o o out of e e w ight , thi k plat s , di ﬁ ulty m ving it int and v ss ls , and its small f urnace space. This last disadvantage has already

ee c ed o e the c c o e e o ce b n dis uss , Als , wh n ylindri al b il r is und r f r d

the e o e for the of c o o to e draft , tim all w d products mbusti n giv up their heat is short . Among the advantages of this boiler may b e mentioned econ om e e e e e y and st adin ss in supplying dry st am , and in this r sp ct it

h - o e e e for excels t e water tube boiler . It is als far b tt r suit d salt

e the e - e e e adv an wat r than is wat r tub boil r, but this is not a gr at th tage at e present time .

l i i - r ' i C ass ﬁcat on. Water tube b oilers a e b u lt in a great variety

of e . e b e e o fe e c e d signs Th y may divid d int dif r nt lass s , as straight

e c e e or the o e e o e tub and urv d tub ; dr wn d tub , that is , th s having

’ the e e e e o e the u er e o e upp r nds subm rg d , and th s having pp nds p n ing into the steam space ; or those having a steam drum and those having none .

For c o e e ce let e e two c e nv ni n us divid th m into lass s, straight

h e c e e. t e c we ce o o and urv d tub In ﬁrst lass may pla , am ng th rs , ’ the Be e e B coc W co He e o D Allest Almy, ll vill , ab k il x , in , Yarr w , , f f and Niclausse. A ew o those having curved tubes are the Thorny

No o e f ee W . So e o e e e croft, rmand , M sh r, and ard m th s hav b n TYPES OF BOILERS 79

fe f discussed in the preceding pages . Only a w o these boilers need

e e e the e e to the e hi be describ d h r , purpos b ing show mann r in w ch ordin ary land practice must b e modiﬁed to conform with the requirements for marine use.

M - Fi 3 . e t ona o f g. 7 S c i l d el o Bab coc k and Wil cox M arine Water Tu be Boiler

Babc ck Wil a in r=Tu o 6: cox M r e Wate b e Boiler. In Fig . 73 is shown a sectional view of a model of a marine type of the

B c o e o e o r ab ock Wilcox b il r, lo king from a r ar p sition towa d the ﬁring end. All the essential features of this boiler are clearly

o he e e set for o e of th o c om sh wn, t r b ing up purp s s e illustrati n two

lete e h n f p s ctions united with t e e d o a steam and water drum . 80 TYPES OF BOILERS

Attention is called particularly to the forged-steel rectangular

e e e the e e the e shap d box s, inclin d at sam angl as tub s, lying along side the grate surface and communicating with vertical forged- steel

the e e o the of e headers . With xc pti n of bottom row tub s and the

c e e o e o e cir ulating tub s abov , it is cust mary to mpl y small diam ter tubes expanded into forged- steel serpentine headers in groups of . E c o e c te o of o o . e f ur a h handh l communi a s with a gr up f ur tub s ,

o the u of c of o e the idea being to av id se a multipli ity handh l caps . It will be noted that the transverse method of bafﬂing is

h l w n of the o e oc e e e t e o e d o . mploy d , but that b il r is l at d in fr nt The bottom row of tubes supports tube tile proj ecting upward from the inner end of which is the ﬁrst cross- ﬂam e plate encoun

Th h to o e e tered by the gases . e gas outlet is at t e p fr nt imm diat ly

- Th e behind the cross drum . e boiler is enclos d within a steel c e ﬁre the o e e e com asing lin d with brick , and wh l constitut s a v ry

ec c e . e e t o pact onomi al boil r To pr v n harmful galvanic acti n and,

o e e e c o o to zl ne c ns qu ntly, int rnal rr sion , it is customary install plates with positive metallic contact between these plates and the iron attached to the steam baffle plate within the boiler drum . The plan is to employ an electropositive metal which will receive corrosmn attack in preference to the metal of the boiler when

E e galvanic action takes place. ven though such action ceases aft r

few o of o e o o to e o a h urs p rati n , it is imp rtant mpl y zinc as a protection against corrosion ow1ng to the presence of air in the feed water .

= tandard Water Tub il r . amshi s. S e Bo e , U S. Wooden Ste p In order to expedite the building of boilers for the United States

e c e h . Cor e e e t e U S. S Bo E e e ee m rg n y ﬂ t , hipping ard m rg ncy Fl t

oration c e of th f h or the p , having harg e building o t e ships f

S B e h i 4 . e t e o e e F . 7 hipping oard , d sign d b il r illustrat d by g This is like the Babcock Wilcox marine previously dealt with in being a straight-tube cross- drum boiler but differs from it in several

h e important particulars . T e scheme of design is such as to p rmit the c o of the o e e e e o constru ti n b il r in any w ll quipp d sh p , making it possible for a relatively large number of boiler manufacturers to engage in production rather than c onﬁning the output to the c c e of few o e o h e e o of apa iti s a b il r sh ps only . It was t e pr s rvati n “ ” this production feature which led to the selection of a b ox header

P S OF BOILERSl 82 TY E ,

c e of the e e inﬂ c onstru tion inst ad s ctional typ , which in turn uenced a

h e the e ec o of e e c t e d sign by s l ti n tub siz s and spa ing to ﬁt .

The e of f o e of e syst m ba ﬂing is l ngitudinal inst ad transv rse, dead spaces within the tube region being avoided by gaps in the bafﬂe placements where normally they would meet the header tube

c m e the f e e are ee . c e e sh ts To a com odat ba ﬂ s , full spac s r at d by leaving out horizontal rows of tubes where they would occur in the

- ff h W of the o e e e e. o t e e c cross ba l d typ Als , tub idth b il rs b omes

e the to of the e e e the e e e narrow r as p h ad r is approach d , g n ral shap

the c e e e the - e of ba k h ad r b ing as shown in right hand Vi w, which illustrates a front half elevation of the front header within its

r - he e c o ee c . e e a e 38 3 c e t n l sing st l asing Thus th r , in h tub s in “ lowest and only 24 in the highest full rows of tubes . The standard boiler has a total heating surface of about 2500 square feet and square feet of grate surface and is designed to withstand a working pressure of 200 pounds gage when

' h f h . e c omplying with all t e rules and regulations o t e U S. St amboat Inspection Service applying to marine water- tube boilers for ocean

e e and c oastwise trade. Among special f atures it may b e mention d that the c over plates closing the holes opposite each tube are

ee l e e - e o e e conical st l pugs , h ld in plac by cup shap d y k plat s and

- h are forged steel nuts screwed upon threaded stems . T e j oints

e e of o e e e the e e e of the mad tight by m ans c pp r f rrul s, inn r dg s handholes being rolled with a spec ial expander to allow ﬂaring of

Th e the c opper ferrules . e plates therefore receive the pressur

c e to c e the e o e e ev the e whi h t nds los handhol p nings, thus r li ing plat

e of the st m pressure load . These boilers are equipped with the customary complement of ﬁttings and trimmings suitable for marine practice and are fully

ee e c e o e of ﬁr - st l n as d utsid e brick lining .

lm Water=Tub il ‘ e e B er. i o o A y o In F g. 75 is sh wn a fr nt vi w

‘ e o e e c e of an Almy marin b il r, with its outsid asing , grat s , and

of ﬁttings removed . It will b e noted that the boiler is made up

e e- o e c o ec ec straight mall abl ir n tub s, nn ted by sp ial ﬁttings with one another and with m anifolds at the bottom and top terminals. The sections that extend along the side from the bottom manifolds to the side top manifolds form a loop extending over above the

ﬁr to the o of h ﬁr x Th e e so as form ro f t e e bo . e s ctions arising TYPES OF BOILERS 83

h o o o o tw o oo e e from t e rear b tt m manif ld f rm l ps , ﬁnally nt ring at

c o o c o e e o e h the top front manifold . A ﬂat ntinu us il xt nding v r t e

The o to o c o entire top is a heater section . fr nt p manif ld is nnected

e c e o e or e o the o e end of c to a v rti al st am d m , s parat r, l w r whi h is riveted to a horizontal water reservoir extending across the front

The e c o ec o are e the. to of the of the boiler . st am nn ti ns mad at p

b e o e he e e e o c o ec e down ﬂow s parat r , whil t wat r r s rv ir is nn t d by pipes to the ends of the bottom manifolds in front .

i lm - F . A c i n il g 75 . y Se t o al Water Tub e Bo er Cou rtes o Alm Water- Tu be Boiler om n P ro ce ho e y f y C pa y, viden , R d

No f 1s ce e the e ace the e ec ba ﬂing pla d insid h ating surf , xp ta

o b ein ‘ that the e h ti n g h ated gases will envelop t e tubes throughout . The particular c haracteristic of the boiler is the very large per centage of the heating surface that is in direct line with the

e c o h r radiant h at ming from t e ﬁ e .

D ou ble Tu be Type. This boiler is also made in what is known

‘ the o e— e e the ex ression in c a e e as d ubl tub typ , p this s m aning that a double row of tubes following the same general c ontour is employed

e of one e the o e e in plac tub as shown in illustrati n . This xpr ssion 84 TYPES OF BOILERS

double- tube must not b e confused with that employed elsewhere

in this book where one tube is placed inside another .

Variations from Standard Land Types. The variations from standard land types of water- tube boilers are mainly those con cerned with length of tubes and the use of cross-drums instead of

B e the e are o e e longitudinal drums . ecaus tub s sh rt r th y may be

of e e e e the use of o — small r diam t r as w ll , and cr ss drums is also

permissible for the same reason .

ra re h e G te A a . T e grate area is determin d in a similar manner to that used in designing cylindrical boilers ; but for most types the

e b e e e so the e t b e e e e ar a must gr at r, that h a may distribut d v nly

o e th e over the surface of the tubes . It is not well t hav e h at too

Th o c o of o intense near any of the tubes . e c nstru ti n m st water

h r f r tube boilers allows some space above t e ﬁ e o combustion .

h f the e e o he Steam D rum . T e size o steam drum d p nds up n t f h amount o steam generated by t e b oiler . In order to make it as

o e the e are o e e o e small and as light as p ssibl , boil rs s m tim s w rk d at

e e the e e e o the e e high pr ssur , and pr ssur maintain d c nstant at ngin f by means o a reducing valve. Water- tube boilers having the upper ends of the tubes opening into the steam space have dash plates and internal steam pipes h which separate t e water and steam .

d anta es r C lindri al - o e A v g ove y c Type. Water tube b il rs have the following advantages over cylindrical boilers :

1 e - ( ) Light r (weight about one half that of the cylindrical) .

2 F c e ( ) irst ost l ss on account of less m aterial used .

3 e e of ( ) L ss dang r damage in case of explosion . 4 ( ) Large grate area and large furnace volume for c ombustion .

5 G e e ( ) r at r rapidity in raising steam .

6 o e e e r ( ) M r asily plac d aboard o removed .

7 H e e c c ( ) av a larg r apa ity range.

The last three conditions are of great importance in the navy .

to the e e e o e e c ffe f o As r lativ con my , th r is mu h di rence o opini n as h t e o o c o e . e e the eco o c nditi ns vary nsid rably In g n ral , n my is

e about qual in both types . Th f e ease o making repairs depends upon the type of boiler . The sectional type can usually be repaired more readily than

86 TYPES OF BOILERS

e e e e of the c ﬁre boilers , will s rv as an xampl lass with many tubes . and the considerations entering into its design will apply with

e o e to the Sco c e o e e F . 21 to 2 qual f rc t h marin b il r illustrat d in igs 5 ,

W e e e u e of e are e inclusive . h r a larg n mb r tub s distribut d through

e to o e the e to o a boiler sh ll , it is now customary l cat tub s so as f rm wider lanes for the movement of steam and water than would prevail were the tube spacing uniform throughout . It is more important to provide these larger lanes for water travel in the c ase

' of internally ﬁred boilers built after the pattern of the Scotch f marines than in the c ase o horizontal tubular boilers . Experience teaches that unless such precautions are taken a deﬁnite water c irculation is not set up and the tendency is to create dead zones

the e ce c o e e the Sco e within wat r spa , parti ularly in a b il r lik tch marin ,

hot e o the o which does not have gas s impinging up n utside shell .

2 o how e ce are o e e ee e Fig . 3 sh ws plainly xtra spa s pr vid d b tw n tub

e the e o for the ci shown is e rows . Whil primary r as n spa ng to p rmit

h ' c o c o of the co o c e the e t e nstru ti n mbusti n hamb rs in r ar , it is fortunate for circulation that they exist .

= Tub B ile s. Overcomin esista o W r l Water e o r g R nce t ate F ow . The c irculation within water- tube boilers constitutes one of the

” o o o e c e e e o e e e c e m st imp rtant pr bl ms whi h th y pr s nt , m d rn t nd n i s not onlv c ausing designers to avoid restrictions as much as appears to b e necessary but also induc ing them to afford positive circula tion by inclining the tubes to a greater extent than at ﬁrst would T seem to b e required . o illustrate this it is well to point out the

ec o e two o e of the o o e - e e pr auti ns tak n in b il rs h riz ntal wat r tub typ ,

f - representing the extremes o sectional and b ox header c onstruction .

44 o e c ec In Fig . is sh wn in v rti al s tion that portion of the B & W boiler which is likely to set up the greatest resistance to water ﬂow . It will b e noted that short 4- inch nipples connect the several

e c e e ec o to the o h v rti al h ad r s ti ns b iler drum proper . In t e illustra

o e e e of 4- c e e e e h ti n , tw lv tub s in h diam t r d liv r t e water passing through them through one 4- inch submerged nipple at the front throat ; longer 4- inch tubes provide the facilities for keeping the boiler tubes supplied with water coming from the rear end of the

. e the ﬂow of e o to b e drum Manif stly , wat r, supp sing it all solid , through thenipples must b e twelve times as rapid as the average

e 4 50. e. to . 48 9 ﬂow through any singl tub Turn now Figs , , and TYPES OF BOILERS 87

In these are shown the details of construction of Edge Moor boilers in the particular place known as the throat and previously dealt with in B W boilers . In this instance no nipples are

“ The e of the e le o 1 e o e . oo e mpl y d d pth wat r g is ab ut f t ; th n , su osm the e oo o e o t e e e the pp g Edg M r b il r is als w lv tub s high , space available for water movement on the way to the drums is an area of about 78 square inches as against about 12 square inches for the B W bpiler. There is this difference between the two

o e : the B W o e c e 2 7 c e to the e oo b il rs b il r is pit h d 1 in h s lin ar f t, whereas the Edge M oor boiler tube pitch is 1 inch to the foot ;

e the B o e e co e e , s t e e ns qu ntly whil W b il r may up ‘ a gr at r e to c c o o e e e e to resistanc ir ulati n , it also pr vid s what is b li v d b e a correspondingly greater force to overcome it .

Prevention o Moistu re. So e e of o e th f m typ s b il rs , mainly e

c or e e c o e e o e verti al s miv rti al , pr vid xtra rdinarily larg circulation facilities and sometimes do so to such an extent that the space into which the tubes discharge may b e in a c onstant condition of very h e o . t e e e to e active bulliti n If wat r t nds foam , this viol nt stirring ac centuates the trouble and additional means must b e provided to afford space and time for the water thrown up into the steam ﬂEl space to settle bac k to the general level . Ba es are provided to

ece e e e i e e e e c the r iv wat r and st am mping m nt, th r by ausing water to lose its velocity while the steam may pass to an additional drum 2 Th S o e . 6 o for e e o . e o e e furth r s parati n tirling b il r , Fig , is a g d xampl of this arrangement . i i i Aux liary Circulat ng P pes. It is sometimes necessary to provide special circulating pipes leading from one drum to another 1 or o the e e to o e e . 6 . fr m upp r st am drum a l w r wat r drum , as in Fig This is done because all the tubes of the boiler are intended to c e e to the e e e ffo arry wat r and st am upward st am drum , th r by a rd

‘ ing no way for the water to reach the lower drum except by setting up a counter- circulation resisting that set up by heat trans

h e o e the e c o s . T o c e t e c c o e mi sion fa ilitat ir ulati n , th r f r , pip lumn shown on the left of the illustration is installed and all downward

o m vement of water may take place through this .

o Importance of Good Circulation. Featu res f Boilers Aﬁected.

e e the e of c c f ec two of the In g n ral , matt r ir ulation a f ts most

e h e e important featur s of boilers . If t e circulation is inad quat , it is 88 TYPES OF BOILERS

the the e e e reﬂected in inability of boil r to absorb h at r adily and ,

the e e of the e f fully as important as this , in mat rial curtailm nt lif o

ue o th the parts subj ected to heat . This is d t e fact that steam

are e e on the e e of the e ce pockets cr at d wat r sid h ating surfa and , in as much as steam is a poor absorber of heat as compared with

the e not the e to the e water, plat s will transmit h at st am as rapidly as though solid wetness were presented to the plate ; hence the

he metal may become overheated . If t circulation is such as to

' permit the alternate but rapid formation of steam pockets followed

e e e of the e set c by solid w tn ss , fatigu m tal is up and rystallization

' io o e c c ce is e The e e . ensues . d t r rati n und r such ir umstan s v ry rapid n f Retirement of Old Forms . It is this o e matter of insu ﬁcient circulation that has caused in modern boiler practice the retirement of many of the old forms which formerly were well received . Where a high rate of duty IS expected regardless of what the

e e b e o e c e charact r of wat r may , a b il r su h as that illustrat d in

Th can out of the e o . e e e b e e Fig . 68 is qu sti n sam comm nt mad h e e e e to . 70 e e o t e e with r f r nc Fig , v n supp sing mat rials would with stand modern high pressure and in other respects b e satisfactory .

EFFECT LVENESS O F HEATING S URFACES

rfa Pr l m ifﬁ l Heating Su ce ob e D cu t. Manifestly no good pur

o e e e o e e e c e et the o p s is s rv d by pr viding us l ss h ating surfa , y pr b lem of using all the heating surface provided is not as simple as

of the it may appear . Out accumulated experience of boiler build ers e e e co e oo e of , d sign rs, and us rs has m a fairly g d und rstanding what are the main items to b e considered in employing the heating surfac e properly so that injury in some other particular may not

b e e co e e . Re e to . 41 b e o e n unt r d f rring Fig , it will n t d that

" the boiler is bafﬂed by the placement of two vertical ﬂam e

e oc e e e to h plat s l at d transv rs t e tubes . It is recognized in this instance that possibly the upper portion of the top rows of tubes near the front headers may not b e well employed as heating

The e e surface. sam r mark applies to a less extent to the bottom

of e the e e e e rows tub s in s cond and third gas pass s . Were exp di nts adopted to employ these tubes throughout their length to their

e e e e e h o be full st xt nt , th n so much r sistance to t e draft forces w uld set the e end the m f r It is up that furnac of installation ight su fe .

90 TYPES OF BOILERS

o e e o the e when a p ck t xists , gas circulati n within pock t is of low velocity and the means taken for the blowing out of soot becomes

e e e the e o o e the o t ineffectiv b caus gas s , m ving sl wly, p rmit s ot o fall

e e . e e e no back after b ing stirr d up In oth r words , th r is special

e o oo e e the e e e e difﬁculty in r m ving s t wh r gas s trav l with high v lociti s, but it is almost impossible to remove it unless there is a swift- moving

current to c arry it after it has been dislodged .

Th o f Absorbtion of Heat by Radiation . e m st e fective heating surface that c an b e obtained is that which is in the direct line of radiant heat coming from the fuel b ed. It is this peculiarity of the heating surface of the externally ﬁred shell boiler that has retained this type in such general use as to constitute for moderate pressures the most common boiler m et with . In this instance the boiler shell is located immediately above the ﬁre and the trans

the e e c e e e e mission of heat through r lativ ly thi k sh ll m tal , v n when

- e c o e ec oo e . e ox int rnal cir ulati n is not sp ially g d , is v ry rapid Fir b boilers are a still more striking example of the rapidity of radiant

o e of the e - heat absorption . Those b il rs wat r tube type that present large quantities of heating surface to the radiant heat action of ﬁres are invariably more economical steamers than those which are not so liberally provided with heating surface within range

o e the e c e of of radiant heat . Unf rtunat ly v ry aus s a high rate of radiant heat transmission sometimes set up diffic ulties in other

c o c b e e o e the e i of parti ulars , am ng whi h may m nti n d lik l hood

o e oc e due to c c o c f rming st am p k ts faulty ir ulati n , whi h in turn may c ause tube failures to an excessive degree.

ACCESSIBILITY

Pr i i n ual for ns ti n an i ov s o s Us I pec o d Clean ng. Under this topic the main problems are those of the plant designer rather

f r f than o the boiler designer . There a e practically no m anu ac turers of special boiler equipment that do not provide facilities for

e c e or ec f The e int rnal l aning insp tion o pressure parts . faciliti s

b e c e or e e e o to e o e e are may rud r quir much ff rt mpl y th m , but th y

e present . It is important in selecting a boiler to look into thes

e o ce e e to e ec the o e e e matt rs and , if a ch i is p rmitt d , s l t n s wh r in the e o e o l ast manual lab r is r quired during operation . An imp rtant instance is that of choosing for water-tube boilers the kind of a TYPES OF BOILERS 9 1

handhole c over plate which does not depend too much upon the

skill of the operator to make a tight joint when closed . In other

o eo e ec e has the e e w rds, it is advantag us to s l t a plat that pr ssur

th e o c e e the e e se of e st am f r ing it against its s at rath r than r v r , not only to reduce the hazard but to reduce the labor and tim e f out o service.

e e c o e e oul b e e e e e ei In g n ral, v r plat s sh d s l ct d that hav th r

m e pressure loads sym etrically distributed. Odd shap d plates

e m c e o of e o be o e nle r quiring co pli at d f rms gask ts sh uld av id d , u ss some very decided advantage in some other particular is created

by their u se. It is usually less trouble to remove one manhole plate giving access to a whole bank of tubes than to take off as many plates h ere are e . not a e t e e e as th tub s This is always an dvantag , as m r ’ ' taking oﬂ of the plate does not complete the job and as in most instances where a manhole plate is taken off in order to make the

e ce e e e the dr m i i e the tub s ac ssibl a man must nt r u , wh ch mpos s further necessity that the drum b e cool and free enough from

vapor to permit him to enter to perform his work . I lities i oiler tse . Replacement of Tub es. Faci n B lf It is impor

hic as e e be tant that any part w h may fail , such a boil r tub , removed and replaced without disturbing too many other boiler

e e Th of on l ments . e Stirling boiler is an example e where tube placing is such that even the most remote or interior tube can be Th passed out from its nest without getting down other tubes . e practice of so designing boilers is becoming quite general and is to be commended unless carried so far that the gases do not have th a fair attack at e heating surface.

S ace aciliti e n o e he nl p F es . In d sig ing or installing a b il r t o y safe assumption is that any one of the tube elements may fail and

e ire e l r n nl th e r qu r p acement . Fo this reason ot o y must e boil r permit having its tubes replaced but spaces surrounding the

o m - e b e o e . For i e e e b il r ust also pr vid d nstanc , a straight tub boil r like the horizontal water- tube types will require a space in one

e o e e o c e to the e of the be . dir cti n, ith r fr nt or ba k, qual l ngth tu s

The e e r e of th ﬁre- e b o e sam r ma k appli s to any e tub il rs , such as the o ul h o e e the horiz ntal tub ar and t e Sc tch marines . To r plac

e the o e 4 o tub s, b il r illustrated in Fig . 7 must have a space c vering 92 TYPES OF BOILERS

' a rather large horizontal area . Some forms of vertical boilers

require almost double the installation height in order to replace th tubes without wrecking e boiler setting . — T SHAPES AND SlZES O F TUB ES

u . Straight vs. Bent T b es It is always desirable to retain tubes in a straight condition as manufactured instead of bending

e l e e the e ee no them to som particu ar shap , sinc us r n d t c arry in reserve a number of different shapes and it is also easier to inspect

- e e . e not o e e and cl an th m It do s follow , h w v r , that a bent tube

e e e e b e e e a - e o e boil r is n c ssarily l ss to d sir d than straight tub b il r, for it is more than likely that the bent-tube boiler may b e better able to accommodate itself to the space in which it is to be located .

b o l Fire Tu e B i ers . Tub e D iameters. In the matter of tube

e e e ee of o e diameters th r is l ss fr dom ch ic than as to shape. If the

f the ﬁre- e e t e the e e th boiler is o tub typ , h n diam t r of e tube plays

t the e t e an important par in matt r of draf r duction . The loco motive boiler is a good instance of the use of tubes of small

e e e e o e b e ee e e diam t r b ing _mad p ssibl y xc dingly high draft cr at d h at the exhaust nozzle. If t e attempt were made to apply locomotive tube practice to stationary practice it would b e found

e e the e o b e too o impractical b caus tub s w uld small , w uld rapidly

o oo e e e e o cl g up with s t , and v n wh n cl an w uld impose too much of

h o h ﬁr e o . e e t e e t e e e the a r stricti n In g n ral , l ng r tub , larger its diameter needs to b e.

- Water Tu be Boilers . e e e e In wat r tub practic , tub s of small diameters are not suitable in that the application of intense heat

e to e e e c e e e h t nds cr at st am po k ts within th m , b cause t e circulation

o e o o e o e the e e f rc s cann t v rc m wat r ﬂow r sistance. Tube failures due to o e e e or e v rh ating , fatigu , scal formation may combine to make their c ost prohibitive. It is a fair statement that the greater the rate at which the boiler-heating surface is expected to operate the larger should

e e b e o the o e the e the wat r tub s ; als , l ng r tub s larger the diameter . ! The e e e e e ec ﬁre e r v rs is partially tru with r sp t to tub s, and in this instance the practical limitations are those set up by the avail able draft .

94 “TYPES OF BOILERS

Stokers. The size of the boiler units as well as their number

he determine the feasibility of installing stokers . T latter are not usually serviceable or economical when combined with boilers of

of e less than 150 horsepower . Some types stok rs do not bec ome economic ally worth while until the sizes both of the units and of th e e o e e e the e of e plant as a whol b c m quit larg , charact r labor required for operation and their cost being against the use of the

e e e e the t e most r ﬁn d stok rs unl ss plan has a larg output . The nature of the available fuel determines the type of stoker that can be used economically and by learning the economical size of the stoker of that type in common practice the plant designer may come to ﬁx upon boiler sizes somewhat different than he would

e are select if not considering stokers . If stok rs justiﬁed by other

e o the e e t be e to i consid rati ns , boil r d sign mus mad ﬁt, by which s meant that the dimensions of boilers of any given make may vary

h e ff to ur e e e. t e suit f nac siz and shap Also , boil r ba ling may

o o require m diﬁcati n to get satisfactory results .

Water. One of the troublesome elements in many cases is the

for the character of water that is available plant use. If water

e e e c e e e t to t e it pr cipitat s a v ry hard s al , th n it is usually b s r at

' ’ e it the o e e e s e befor admitting to b il r, but v n with uch pr cautions

r the there a e occasions when some scale will appear . If scale so

o e b e e e e e e e t the en meer f rm d cannot compl t ly liminat d by tr atm n , g is likely to b e justiﬁed in ruling against the adoption of water-tube

e no e the t e of o e e t boil rs, though, matt r what yp b il r, scal of his

e o l b e e c e u e e. he haract r is lik ly to ca s tr ub Or, may justiﬁ d in rej ecting a water-tube boiler in which the labor of making the tubes accessible for cleaning is much greater than In a boiler of

n e e for e h e or e a oth r typ ; instanc , e may choose a v rtical s mi vertical water-tube boiler in place of a horizontal water-tube boiler

f o e e c o o e e . e having a multipli ity handh l plat s It is to b said, h w v r, that unless the water contains common salt in solution there is hardly any reason why water treatment will not permit the greatest

ee the e ec o of h f e e the e fr dom in s l ti n t e type o boiler . Wh r availabl

e n o e - e e e of oo e n is wat r is u satisfact ry, a wat r tr ating quipm nt g d d sig

e e m e t e of o e e ec e . always a paying inv stm nt, no att r wha typ b il r is s l t d

Fuel. e e e c e it is e e e Asid from grat siz s and chara t r, xtr m ly important that the nature of the available fuel b e considered in TYPES OF BOILERS 95

e h m connection with the type of boiler sel cted . In t e ost favorable

t or ﬁne to e e o at the e and furnaces, soo ash is bound d v l p grat

ce e e e o o pass to the heating surfa wh r larg p rti ns may deposit . Since dirty heating surface on the ﬁre side is more costly in fuel

e o o e u e e the e than any oth r f rm of b il r ncl anlin ss, if fu l itself contains a relatively large percentage of volatile or soot-making

e the e ee o e ec e of o e in hi matter, th n ngin r sh uld s l t a typ b il r w ch

the e of oot l d e are e c e e . For e a plac s s o gm nt asily a c ssibl instanc , three-crosspass horizontal water-tube boiler affords less opportunity for soot deposit in the tube chambers thana horizontal boiler with

e . e e oot e o e horizontal pass s In any v nt, s r m ving d mands close

of t he o e t e e study in all stages b il r plan d sign, consid ration being

h e the o e e the e o given to t e furnac , b il r passag s, and spac s ar und

o er e ee in m the n e of the the b il s ttings , k ping ind that atur coal has a direct bearing on the amount of such deposits . Thus the kind of fuel determines to a large extent the kind of stoking or ﬁring h f h e t e e e o t e o e . equipment which, in turn, ﬁx s siz and shap b il r h Availab le Space. Aside from t e very obvious necessity of choosing boiler units that may be installed within the Space

e to th m ere a al e s o t nee e assign d g , th r ss obviou fact rs tha d consid ra

Th t l b e e oe o tion . e fact tha an insta lation may mad d s n t argue

e e r e e the f that it is n c ssa ily good, as is att st d by thousands o instances where sacrifices to space considerations were made in the i first instance for unimportant reasons . If t is remembered that a boiler is only an absorber of heat and that there is also the prob lem of e t e e o e ffi ul e o e e u e h a g n rati n, littl di c ty is nc unt r d m nd rstand ing the reasons for the following points

(1) Under no circum stances compromise with the question o h o of providing combusti n time and space . If t e head ro m is c e e it se ec a t e of o e t t e at ramp d , mak up by l ting yp b il r ha giv s o e e e o e least ample horizontal ro m . A r v rs situati n d mands oppo t e site reatm nt . Sufﬁcient draft combined with furnace design determines the rate at which the fuel may be burned as well as the economy e t e o of heat evolution . A boiler d sign that does not lend i s lf t the chosen space without sound breeching design should be e in hi h o rej cted . L ked up with t s is t e wh le subj ect of boiler f . e de a new t e e e ba ﬂing Wh n signing plan cr at (by ov rprovision ,

s e the t e b e e e . if pos ibl ) , all draf int nsity that may d sir d If looking 96 TYPES OF BOILERS

e e it b for troubl in an xisting plant , will probably e found by an The e of analysis of the draft facilities . siz s gas passages and their e e o e are o the o t r lativ p sitions and shap s am ng imp rtan items . t e o e e e t (3) D o no ov rlo k tub r placem n facilities . 4 S o em e e e or ( ) o t r oval , wh th r don manually by permanent o e e e e e o e e bl w rs , d mands ad quat all y ways around b il r s ttings . Many forms of stokers require side inspection and manipulating N0 e o o ee e e space. oth r c nditi n is so disagr abl as cramp d quarters c o e o o e to et for routine boiler and furna e p rati n . In rd r g adequate space it may b e necessary to reduce setting widths and increase o e e e c oo e o b il r h ights wh n h sing th m , but it is usually w rth while s o e o e o e e to do so unles s m th r imp rtant f ature is advers ly affected . (5) It is a mistake to install more than two boilers in a e e e e o e ce the e o for singl s tting , and , wh r d n by choi , r as ns so doing should b e of the best and it should b e fully appreciated that e th sacriﬁces will b e mad during e life of the plant . (6) Many boilers properly designed as to pressure parts fail to b e e e e ec e of o f e fully ff ctiv b aus faulty supports , p or ba ﬂ s ,

im o r e o o etc . of are e e e m pe xpansion pr visi ns , all which r ﬂ ct d in the creation of cracks in settings attended by uneconomical heat

e ce e e e c o . absorbtion , r du d capacity, and high furnac maint nanc sts This part of the subj ect warrants the c losest study in even the most minute details .

IND EX

Accessibility of boiler parts provisions for inspection and cleaning

r Belpaire boile .

gage coc ks .

manholes

tools .

Bo l er ac on essen a r nc es of . i ti , ti l p i ipl

Boiler constru ction . r allowable pressu e . r area of g ate .

ﬁanging 2 IND EX

PART PAGE 0 Boder constru ct1on (contmued)

heating surface .

m anholes .

m aterials .

a es and o n s arran e en of . pl t j i t , g m t

welded j oints o r es n B ile d ig . r features of individual boile s . accessibility u on c irc lati . eff ectiveness of heating surfaces shapes and sizes of tubes plant features

analysis of problem .

personal element n siz e of pla t . r stoke s . r wate . un Boiler f ction . Boiler inspection during manufactu re

o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o

o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o

on a n el g tio . redu ction of area ru les of American Society of M echanical E ngineers standard regulations strain stress re c st t h limit .

testing machines .

4 IND EX

PART PAGE

D amper frame and damper rs D irecturn boile .

- D ouble ended boiler . - f D ou e u e o er e n on o . bl t b b il , d ﬁ iti Dudgeon expander

Edge Moor boiler.

r E xpande s .

- E erna ﬁred o er e n on of . xt lly b il , d ﬁ iti

Fire-tube boilers

locomotive .

horizontal

peculiar forms .

D irecturn

a e Sh pl y . vertical

Gage cocks

Gun r boat boile . IND EX 5

PART PA GE

Heating surface of boilers . Heine boiler

Inspection of boiler n erna -fired o er e n on of I t lly b il , d fi iti Internally-fired marine boiler

Lentz boiler

Manholes .

location siz e of openin g

Manning boiler . M r n a i e boilers .

locomotive

rectangular wet and dry- bottom

co ar son c n r mp i with yli d ical . launch

an r S. oo en a U . s ea s s St d d , w d t m hip variations from standard land types Masonry M o ern ﬂ d ue boilers . 6 IND EX

PART PA G E Modern ﬂue boilers (continued) Galloway Lancashire Mosher b oiler Multitubular boiler

Niclausse boiler Non-sec ona o er e n on of ti l b il , d ﬁ iti

P an s e of . l t, iz P a es and o n s arran e en of l t j i t , g m t

r P essure of boilers . Pressure gage Prosser expander

R eamed holes . R ectangular marine boilers R eturn-tubular boilers

reamed holes

Root boiler.

Safety valve i n f ec ona o er e n o o . S ti l b il , d ﬁ ti Sections of boilers o r Shapley b ile . Shop equipment

8 IND EX

Water evaporation per pound of fuel Water-leg construction Water-tube boilers advantages circulation in

horizontal .

Babcock and Wilcox . E dge Moor

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

- Thornycroft Marshall .

Worthington .

peculiar form s .

Harrison . Hazelton or Porcupine vertical Bigelow-Hornsby

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

Welded j oints - r Wet and dry bottom boile s .

Worthington boiler