McGr a w- Hi l l Co m p a n y, In c. D e v o te d t o t h e O p e r a tin g , T e c h n ic a l a n d B u s in e s s
Ja m e s H . McGr a w, President _ , , „ , „ R. Da w s o n Ha l l
E . J . Me h r e n, Vice-President P r o b le m s O f t h e C o a l-M in m g I n d u s t r y Engineering Editor
Yolume 25 NEW YORK, MARCH 6, 1924 Number 10
W e a n d T liey
I
N V O LV ED in th e oil scandal a re m any m en who have been fo rem o st in condem ning th e coal-m ining in d u s try . I t w as McAdoo w ho believed t h a t th e coal m en p ro fiteered unduly, and loudly did he proclaim it.I t a p p e a rs th a t th e p rice m ay be too h ig h fo r coal b u t c a n n o t be too h ig h fo r influence a t th e Capital. Some- one h a s well said t h a t “McAdoo w ould sooner be in r ig h t th a n P re s id e n t.” I t w as P a lm e r and D a u g h e rty also who lam en ted th e lack of p a trio tis m of m ine oper- a to rs. T hese g o v ern m en t officials, p a st and p re sen t, m ay be su ffe rin g fro m u ndue public suspicion, and th e coal m an, h im self too o ften suspected w ith little reason , w ill do well to t r e a t th ese m en w ith a ca u tio n in ju d g - m e n t and a tem p eran ce in s ta te m e n t t h a t P a lm e r an d D a u g h e rty too o ften have fa ile d to evidence.
A J o b o f G lo o m
O
N LY a few y e a rs ago o u r thick-w alled fa c to rie s w ith th e ir sm ali w indow s w ere places of d u st and d irt, w h ere m en w orked u n d e r a co n sid erab le handicap.D id th e y w a n t to see a n y th in g clearly th e y took i t to a w indow — an open w indow , th e d ir t on th e w indow s h id in g th e sun ra y s — o r to an open door. N ow we have la rg e r w indow s and a t n ig h t b r ig h t lig h ts. E v e ry th in g can be insp ected an y w h ere in th e b uilding. By n ig h t o r day w ork goes on unim peded by gloom, and m an u- fa c tu r e r s have found t h a t lig h t h as p aid dividends.
T he m ines alone h av e co n tin u ed d ark . T hey have w ith fe w exceptions re lie d on th e u n c e rta in lig h t of cap an d h an d lam ps— in th is co u n try p rin c ip a lly th e fo rm e r, in E u ro p ę m ostly th e la tte r. S u rely th e tim e is com ing w hen th e p ra c tic e a t som e m in es of illum i- n a tin g face as well as ro a d w ay s w ill be s ta n d a rd .
In th e p re s e n t g lu tte d s ta te of th e m a rk e t clean coal is needed. T h eo retically , th e o p e ra to r w eig h s th e coal and re fu s e th a t th e m in e r loads, th ro w s aw ay th e re fu se and p ay s th e m in e r f o r all he sen d s out. As a m a tte r of fa c t a t som e m in es h e p ro b ab ly docks th o se sen d in g p a r tic u la rly b ad coal so heavily t h a t he comes m ore n e a rly even w hen he com p ares h is ra ilro a d w ith h is m in e-car ra te s .
H ow ever, it is n o t j u s t to d is tr ib u te all th e clean in g b u rd e n on th e evil d o er an d in some cases th e loss fa lls larg ely , if n o t e n tire ly , on th e o p e ra to r. In conseąuence he w ill do well to give th e m in e w o rk e r of h o n e st in te n tio n s a good lig h t w h e re b y to clean h is coal. H e m ay save co n sid erab le losses a t th e tip p le by so doing.
The g r e a te r lig h t w ill cause less m a te ria ł to be w asted , w ill m ake i t e a s ie r to w a tc h th e roof, w ill speed up th e w ork an d w ill m ak e th e m in e r m o re ch e ery an d less d isco n ten ted .
M in in g is gloom y w o rk a t b e st. A little lig h t a t th e fa ces w ill b rig h te n th e d a y ’s toil. In th e ro a d w ay s w hen th e m en w a tc h th e ro o f f o r Iow w ire s an d tim - bers, th e y fre q u e n tly fa li by s tu m b lin g over coal an d slate, u p s ta n d in g tie s and tr a v e r s in g ra ils. S im ila rly
w hen th ey w a tc h th e floor th e y s trik e t h e ir heads a g a in s t w ire and tim b e rs. A lig h t in th e ro ad w ay will p re v e n t such acciden ts w hich a re serio us, especially w h ere locom otives a re a b o u t to ru n dow n th e fallen m a n —a tr ip rid e r, fo r in stan ce.
T en y e a rs fro m now, we shall be w o n d erin g , as we look back, th a t in th ese days we w ere co n ten ted to lig h t o u r m ines w ith only th e m e a g e r lig h t of cap lam ps.
The chang e su g g ested is n o t a la rg e one, no la r g e r th a n th e change in fa c to ry illu m in atio n in th e p a s t few y ea rs.
L ig lit Is L ig lit
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O M A T T E R th e source of advice, if it is good, it is well to heed it. T he Coal C om m ission w as in m any m a tte rs no t f a ir , b u t th is a t le a s t is tr u e o f i t : I t ex pressed th e public m ind, an d a f te r all, i t is th e reac- tio n s of th e public t h a t th e coal o p e ra to r h a s to m eet and appease. L e t us re g a rd its p ro n u n c ia m en to s, th e re fo re , as re v elatio n s of th e p o p u la r a p p ra is a l of th e coal in d u s try and, n o t seek in g in a n g e r to m e e t its false ju d g m e n t, endeavor to find a w ay to m e rit p o p u lar ap p ro b atio n .The fa c t is th e coal in d u s try is n o t p ro p e rly “ sold”
to th e A m erican public. T he coal m an h as a rg u e d in h e a t an d passio n an d n o t w ith due calm ness. T he m an w ho is u p se t an d in d ig n a n t in m ak in g re b u tta l is u su ally n o t p ru d e n t o r convincing. H e in g e n e ra ł only involves h im se lf in h is a rg u m e n t.
H is b e tte r p lan is to ask q u estio n s a n d p u t th e pu blic on its defen se w ith a “ H o w ?” an d a “ W h y ? ” T he a v e ra g e m an th u s co n fro n ted , asked to give an an sw e r, u su ally ends by g iv in g co n vincing evidence t h a t h e does no t know o r a p p re c ia te w h a t he h a s been sa y in g . A t le a st th is is g ain ed fro m th e re p o rt o f th e C om m ission:
t h a t every one concedes t h a t it h a d no solu tio n , h a d no
“ H ow ” an d no “W h y ” to g iv e th e con su m er, th e coal m an o r th e m in e w o rk e r. W h e re no one can pro v id e a rem edy, th e p u blic m u s t needs be p a tie n t.
W h a t is sa id a b o u t th e m a in p a r t of th e re p o rt should be m odified, because som e of its p a r ts , especially th e e n g in e e rin g re p o rt, w as w r itte n by efficiency e n g in e e rs aid ed by m in in g m en. U n fa v o ra b le to o u r m in in g p r a c tice as i t is, it does n o t e r r in th e d ire c tio n of excessive ce n su re. Good m in es w e re picked o u t d e lib e ra te ly fo r in v e s tig a tio n , y e t th e fin d in g s w e re sufficiently d is tre s s - ing. F o rtu n a te ly , th e y w e re m ad e j u s t a t th e tim e w h en in s tru m e n ta litie s w e re co m in g in to b e in g t h a t m ay p ro fo u n d ly m o d ify th e inefficiencies d escribed .
T h e re is hope, b r i g h t hope, t h a t a fe w y e a rs h ence th e m in e r w ill lose n o tim e a t th e face, th e t r i p s w ill n o t s ta n d a t th e p a r ti n g an d th e d aym en w ill n o t idle a t th e tip p le . T h e e n g in e e rin g re p o r t does n o t say m uch a b o u t th e cu re. L ik e m uch w o rk by efficiency e n g in e e rs i t re lie s on c o -o rd in a tio n an d co -o p era tio n to end evils t h a t only m e ch a n ical e n g in e e rin g a d e ą u a te ly can rem ove an d t h a t m a n a g e m e n t' can m e re ly im prove.
T h e con veyo r t h a t h a s rev o lu tio n ized m a n y in d u s trie s 341
342 C O A L A G E Vol. 25, No. 10
is on h an d to re c o n s tru c t o u rs. B adly is th is tool of in d u s try needed, fo r th e m echanical load er h as com- p letely b ro k en dow n o u r alre a d y fa u lty tra n s p o r ta tio n sy stem .
T he fa ilu re s to g e t th e a n tic ip a te d to n n a g e s fro m m echan ical lo ad ers a r e co n v in cin g evidence t h a t th e C o m m ission’s s tr ic tu r e s on ir r e g u la r m in e-c ar serv ice a r e ju stifie d , a n d th e only w ay to m ake loaders do a good d ay ’s w o rk w ith b ro k en ro o f b eh in d th e lo ad in g m ach in es is to have a conveyor to rem ove th e coal to som e place w ith an u n b ro k e n roof, w h ere c a rs can be filled stead ily . W h ere several m echanical loaders a re used, th e only w ay to p re v e n t th e cong estio n in ev itab ly co n se ąu en t on th e use of sev eral conveyors fe e d in g to sev eral tr ip s is to have an a g g r e g a tin g conveyor receiv- in g fro m sev e ral g a th e r in g conveyors an d fe ed in g to a sin g le t r i p o r c a rry in g th e coal d ire c t to th e tipple.
T he m ain Coal C om m ission re p o rt h as told w h a t th e p ublic th in k s . T he e n g in e e r’s p o rtio n o f it h a s re- vealed th e g la rin g inefficiencies t h a t e x is t u n d e rg ro u n d . L ig h t is lig h t, even if i t comes fro m a com m ission of w h ich a fe w a t le a st w e re m en w ho could no t ru n a m in e them selves w e re th e y given it w ith o u t an y d eb t or o th e r encum brance.
T h e C om m ission m ay h ave fe a re d to tell th e whole t r u t h ab o u t th e unions, m ay have p alliated w h a t ca n n o t be excused or fo rg iv e n , b u t it told us som e m a tte rs we w ould do well to ta k e to h e a rt. T ho u g h good counsel w as m a rre d o fte n by bad logie, m an y a tr u e w ord slipped in and a poor p lan i t would be to le t th e evil o v ersh ado w th e good.
P r ic e s a n d tlie W a g e C o n tra ct
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E M A R K A B L E an d alm o st im possible to fo re c a st . h a s been th e tre n d of re c e n t ev en ts in th e b itu - m inous-coal in d u s try . I t w as th o u g h t t h a t th e w e ste rn P e n n sy lv a n ia coal o p e ra to rs would n o t a p p e a r in Jack- sonville to n e g o tia te a settlem en t, b u t p re s su re fro m P re s id e n t Coolidge an d H e rb e rt H oover b ro u g h t th em th e re .I t seem ed alm o st in cred ib le t h a t w ith b u sin ess b eing lo st alm o st beyond reco v ery b y re a so n o f a h ig h w age scalę th e o p e ra to rs would co n sen t to sig n fo r th e p re s e n t w age, even th o u g h th e irre s is tib le th o u g h m ore in d ire c t logie of th e s itu a tio n p o in ted th a t w ay. B u t sig n th ey did.
In d ic a tio n s po in ted to a long fig h t on th e p erio d of c o n tra c t. B u t even th e re a g a in th e needle p o in ted in th e w ro n g d irec tio n . T he c o n tra c t w as sig n ed fo r th e th r e e y e a rs, th e m in e rs w a n tin g a fo u r-y e a r co n tra ct, a n d m an y — p e rh a p s m o st— o f th e o p e ra to rs w a n tin g to sig n f o r a sin g le y ea r.
N ow t h a t th e w ag e scalę h a s been approv ed fo r a p e rio d of th r e e y e a rs by th e subcom m ittee of m in e rs a n d o p e ra to rs th e public w ill be w o n d e rin g w h a t effect th e s e ttle m e n t will h ave on th e price of coal. T h a t is a n a tu r a l ą u e stio n b u t one n o t easily answ ered . T he se ttle m e n t w ill r e s u lt in a g lu tte d m a rk e t f o r coal, an d lo w er p ric e s m ig h t be expected as a re s u lt if th e y had no t a lre a d y a tta in e d th e irre d u c ib le m in im u m f o r th e p re s e n t u n io n w a g e scalę. T he losses in c u rre d by th e o p e ra to rs o f u nio n b itu m in o u s-co al m ines a re ra p id ly d ra w in g th e m in to b a n k ru p tc y .
H ow ever, th e p rice m ay be som ew hat h ig h e r r a th e r th a n low er. C o n tra c ts fo r coal deliv ery a r e lap sin g . I t w as well know n t h a t th e s e c o n tra c ts w e re all t h a t e n a b le d som e o p e ra to rs to keep go in g . W hen th e y come
to an end th e m ines th a t relied on th e m w ill have to suspend o r g e t a h ig h e r p rice fo r sp ot coal. T h a t w ill ten d to stiffen th e m a rk e t. T he rem oval o f th e w e a k e r b re th re n w ill m ake it possible fo r th o se w ho re m a in in th e field to ask fo r th e ir coal so m eth in g a little n e a re r cost, enough in sh o rt to m ake it m o re pro fitab le to face th e losses of o p e ra tio n in p re fe re n c e to th e g r e a te r losses of sh u td o w n in an in d u s try w h ere sh u td o w n s a re extrem ely expensive. T h a t hope m ay be b la ste d by th e Iow prices of a non-u nion field re ad y to c u t w ag es to any figurę th a t w ill keep its m in es ru n n in g .
Those who close th e ir m ines w ill do so f o r a long tim e. They w ill d isb an d t h e ir fo rces, b o a rd up t h e i r houses and in som e cases le t t h e ir m in es flood i f th e y a re shallow an d re la tiv e ly ea sily d ra in e d . I t w ill be elear to them th a t only a m easu rab le in e re a se in p rice will m ake it w o rth w hile to u n d e rta k e th e h ig h costs of resu m p tio n. In fa c t t h e ir finances d u rin g th e in te rim becom ing m ore involved m ay p re v e n t th e m fro m re su m - ing. The low-cost m ines, th e re fo re , w ill g e t th e b en e iit of th e b usin ess of tho se o p eratio n s w h ich ca n n o t con- tin u e to w ork.
A n o th er elem ent in th e s itu a tio n m ay e n te r, how ever, to g et th e public c h e ap er coal— th e conveyor an d th e m echanical loader. T he p ro sp e ct of cheap coal f o r a long period will fo rce m ore econom ical m eth o d s o f production. I t w ill be reco gn ized th a t c h e a p e r o p e ra tion and b e tte r p re p a ra tio n w ill be th e only w ay to keep in th e m ark et. T he m in e rs w ill be am en ab le in view o f th e financial s tre s s an d th e y w ill n o t oppose com- plete m ech an ization of th e m in es. T h is w ill h av e its effect in red u cin g p rice. So a f te r all is said it is diffi- cult to fo re c a st th e ups an d dow ns o f th e ind ex of p rice s, sw ayed as i t is by m an y ad v e rse influences o f a n im - ponderable c h a ra c te r.
S a fe ty a M a jo r C o n s id e r a tio n
N E of th e firs t th o u g h ts w hen b u sin ess g e ts un - profitable is to c u t off all in d ire c t e x p e n d itu re s — those w h ich do n o t prod uce im m e d ia te p rofit. E x p en d i- tu re s on s a fe ty a re am o ng th ese, b u t th e cost of r u n n in g risk s is too h eav y to m ake such econom ies p ro fitab le and sav in g s o f th is k in d a r e c e rta in ly n o t m o ra ł.-
In fa c t, a t no tim e is s a f e ty m o re n eg lected by th e m ine w o rk e rs an d fo rem en th a n d u rin g a tim e of Iow profits. T h e m in e r a n x io u s to m ake a b ig day d u rin g an u n ste a d y r u n fa ils to p u t up a p ro p if th e re b y he can th e m o re p ro m p tly fili a ca r. T h e m o to rm a n and his t r ip rid e r, h a r rie d to tr a n s p o r t a la rg e to n n a g e and so c u t th e c o st o f h a u la g e , r u n ris k s in co u p lin g cars, in o pen in g doors an d in ta k in g sw itch es. T he fo rem an seeks to re d u ce co sts b y b r in g in g p re s s u r e to b e a r on th o se w ho w ould re p o r t places fo r gas. H e seeks to have all h is m en en g a g ed in d ire c tly p ro fitab le labo r an d n o t a t w o rk th a t, a s he would p u t it, m ere ly a ssu re s sa fe ty .
A t such tim e s it is m o re th a n ev er n e c e ssa ry to rem em b er th e co st o f p h y sic a l h a z a rd an d to h av e s a f e ty m en a ro u n d th e w o rk s w hose w hole s ta n d in g w ith th e com pany lies n o t in th e ch e ap n ess o f coal b u t in th e freed o m fro m accid en t. E v e ry d a y ’s coal sho uld be c h a rg ed w ith th e accid en t co sts o f o p e ra tin g th e m in e so th a t th e h a z a rd alw ay s w ould be re m e m b ered as p a r t of th e co st to be low ered. A c cid en ts a r e n o t unav oid able c h a rg e s in m in in g . T h ey a re co sts w hich good m a n a g e m e n t w ill m uch redu ce, an d to overlook th em is to involve th e m in e in difficulties so on er o r la te r .
M arch 6, 1924 C O A L A G E 343
Lewis Minę Provides Against Electrical Shutdown And Uses Błock System of Deyelopment
A lternating Current Used for E verything E xcept H aulage— M ain- Line H aulage Eąuipm ent Pressed In to Seryice to Gather Cars—
Gob on Tw o Sides o f Pillar Coal D oes N o t Prohibit Extraction
By Al p h o n s e F . Br o s k y A s s is ta n t E ditor, Coal Age
F
E W o p e ra tio n s in th e E a s t u tilize a lte r n a tin g ca p acity fo r all p u rp o ses o th e r th a n hau lag e.T he L ew is m in ę of th e H udson Coal Co., located a t W olf S um m it, W. V a., is one of th ese. As a re s u lt th e electrical sy ste m em ployed a t th is m in e is well w o rth y of c a re fu l co n sid e ra tio n .
A doption of a lte r n a tin g c u r r e n t fo re sta lls m an y of th e tro u b les to w hich d ire c t-c u rr e n t e ą u ip m e n t is sub- je c t. A t th e p re s e n t tim e , how ever, th is m in e is no t developed so ex tensively t h a t ap p reciab le line losses would be in c u rre d if d ire c t c u r r e n t w e re em ployed.
C onseąuen tly no n ec essity a t p re s e n t would e x is t fo r an excessive y a rd a g e of copper feed cable. T he officials of th is com pany are, how ever, a n tic ip a tin g th e f u tu r ę needs of th is deyelopm ent an d p ro v id in g fo r th e tim e w hen th e w o rk in g s w ill be sufficiently ex ten d ed to w a r- r a n t th e use o f a n o th e r u n d e rg ro u n d s u b sta tio n , one alre ad y h a v in g been in stalle d . W h en such tim e shall a rriv e th e fo re s ig h t of th e officials w ho h ave recom - m ended th e p re s e n t u se of a lte r n a tin g c u r r e n t w ill become a p p a re n t.
B riefly, f u t u r ę p lan s cali fo r th e s te p p in g dow n of a
N o te — H ea d p iece sh o w s th e tipple o f I ^ w is M ine o f th e H u d so n Coal Co. B e ca u se circu la r p ic k in g ta b le s are u sed th e building; is m orę n ea rly sq u are th a n m o st str u c tu r es o f th is kind. A b elt con veyor b rin gs th e co a l fro m th e un d ergrou n d w o r k in g s to th e preparator.
22,000-volt in co m in g lin e p o te n tia l in a b a n k of tr a n s - fo rm e rs to be located n e a r th e tip p le . T h ese w ill redu ce th e v oltag e to 2,200. B ra n c h lin es c a rry in g th is p o ten tia l w ill ra d ia te fro m th e p rim a ry tra n s f o rm e rs to v a rio u s p o in ts on th e p ro p e rty , w h e re th e y w ill e n te r th e u n d e rg ro u n d w o rk in g s th ro u g h boreholes. A t these v a rio u s p o in ts, u n d e rg ro u n d tr a n s f o r m e r s ta tio n s w ill be in sta lle d to feed th e d ire c t-c u rr e n t h a u la g e lines.
S ev eral p re c a u tio n a ry m e a s u re s h av e been ta k e n a t th is o p e ra tio n to o b v iate p o ssible sh u td o w n s, e ith e r m o m e n ta ry o r p ro lo n g ed , as w ell as to su rm o u n t th e difficulties e n ta ile d b y flu c tu a tin g lin e v oltage. Such m e a su re s cali f o r th e ex e rc ise of co n sid erab le s tu d y an d in g e n u ity in o rd e r to a d a p t th e m to th e re q u ire m e n ts o f an y p a r tic u la r p la n t. J . P . R o sier, th e electrical a d v is e r a t th is in s ta lla tio n , h a s solved th e difficulties w ith w hich h e w as c o n fro n te d in a m a n n e r t h a t in v ite s th e ad o p tio n of s im ila r p la n s a t o th e r developm ents.
Al l Eq u i p m e n t No w Us e s 4 4 0 Vo l t s
I n th e p re s e n t a lte r n a tin g - c u r r e n t sy ste m an incom in g p o te n tia l o f 22,000 v o lts is step p ed down to 440 v olts by m ean s of a b a n k o f th r e e 50-kva. tr a n s f o r m e r s in a s u rfa c e s ta tio n n e a r th e tip p le . In c id e n ta lly , th is w ill becom e th e p r im a r y tr a n s f o r m e r s ta tio n , w h en prop osed e x te n sio n s an d a lte r a tio n s to th e sy stem a re
344 C O A L A G E Vol. 25, No. 10
m ade. Ali e ą u ip m e n t now in stalled , both on th e su rfa c e an d below g ro u n d , is ra te d a t 440 volts. A t th e p re se n t tim e th e m ain conductors a re ta k e n down th e a ir s h a f t to th e u n d e rg ro u n d d is trib u tio n c irc u it. In o rd e r to p ro te c t th e 440-volt lines and th e e ą u ip m e n t connected to th e m fro m sin g le-p h asin g and line b u rn -o u ts, w hich m ig h t re s u lt fro m fa lls of ro o f o r fro m o th e r causes, an a lte r n a tin g - c u rr e n t b re a k e r is employed.
A sin g le-p h ase and re v e rs e -c u rre n t re la y o p erates in serie s w ith th e fa n c irc u it, so t h a t single- or re v erse- p h a sin g in th e h ig h -ten sio n incom in g lin es re s u lts in s h u ttin g down th e 50-hp. in d u ctio n m otor, by w hich th e 5 -ft. re v ersib le c e n trifu g a l fa n is d riv en . T h is re la y a u to m a tic a lly opens th e m ain -lin e a lte rn a tin g - c u r re n t cicu it b re a k e r and holds it open u n til such tim e a s th e p h a sin g difficulty is co rrected , a f te r w hich th e b re a k e r closes au to m atically . T he fa n m u st, how ever, be r e s ta r te d by hand .
W ith in th e m ine th e a lte r n a tin g - c u rr e n t lines of 4 /0 b a re copper a re s tru n g on glass in s u la to rs fa ste n e d to th e rib s of th e e n trie s. W h e re th ese lin es cross h a u la g e ro a d s and m anw ays th e y a re su ita b ly p ro tec ted .
I n te r ru p tio n s to pow er supply and th e b u rn in g out of th e v e n tila tin g -fa n m o to r a re im m in e n t causes of w o rry to th e m in e m a n a g e r i f he is n o t p re p a re d to m eet such em ergencies. S team , gasoline o r oil engines a r e in m any cases in stalled as s ta n d -b y s to pro vide a g a in s t such co n tingencies. T he H udson Coal Co., how ever, h a s em ployed a d iffe re n t ty p e of a u x ilia ry eą u ip m e n t in th e fo rm of a 20-hp. d ire c t-c u rre n t m o to r t h a t can be d riv en fro m th e s to ra g e b a tte r y of a g a th e r in g locom otive in th e event of a la s tin g pow er in te rru p tio n or fro m a m o to r-g e n e ra to r in th e u n d e r
g ro u n d s u b sta tio n in case th e m ain fa n m o to r should b u rn out.
T h is a u x ilia ry d ire c t-c u rre n t m o to r is in stalled d ire c tly below th e fa n pulley, as m ay be seen in one o f th e accom panying illu stra tio n s. I t is provided w ith a te n sio n o r b elt tig h te n e r in ad d itio n to th e d rive pulley on th e m o to r sh a ft. T h is ten sio n m ay be a d ju s te d by m ean s of a tak e-u p an d com pression sp rin g , w hich fa c ilita te s a ąuick a d ju s tm e n t of th e d riy in g belt b etw een th e a u x ilia ry m o to r and th e fan.
A lead -arm o red , ju te-co v ered cable ex ten d s fro m th is d ire c t-c u rr e n t m o to r down th e a ir s h a f t to a b are 2 /0 c o n d u c to r lead in g to th e m ain sw itch b o ard in th e
F ig . 1— M otor-G enerator Sets U nderground
One o f th ese u n its fu r n ish es direct current a t 275 v o lts to the tr o lle y lin es ; th e oth er fu r n ish es 125 v o lt direct current for battery ch a rg in g , for o p era tio n o f th e sta n d b y fan m otor and for opera- tion o f a sto r a g e b a tte r y and tro lley locom otiye w hen the m ain h a u la g e u n it fa ils.
F ig. 2—A.C. C ircuit B reak er and O u t-o f-P h ase R elay T he upper cab in et co n ta in s th e relay w h ich a u to m a tic a lly opens the circu it breaker and h old s it open u n til th e p h a sin g difficulty h a s been elim inated. The breaker then clo ses a u to m a tic a lly .
u n d erg ro u n d s u b sta tio n . T h ro u g h th is sw itch b o ard , connections m ay be m ade w ith a 60-kw. 125-volt m o to r- g e n e ra to r set. T h is connection w ill be used in case th e re g u la r a lte r n a tin g - c u rr e n t fa n m o to r sho uld fa il.
F u rth e rm o re , a connection m ay be m ad e to th e sto ra g e b a tte r y of a 6-ton g a th e r in g locom otive in th e m o to r b a rn should p o w er fa il on th e in co m in g line.
The cap acity of th e s to ra g e b a tte r y on th e locom otive is 440 am p.hr., w hich is sufficient to d riv e th e fa n fo r ab o u t 5 h r. a t h a lf speed, o r 125 r.p .m . W hen o p e ra tin g a t th is r a te th e f a n w ill g e n e ra te a b o u t 50,000 cu .ft. of a ir p er m in u tę .
In ad d itio n to th e m o to r-g e n e ra to r s e t a lre a d y men- tioned, th e p re s e n t u n d e rg ro u n d s u b s ta tio n houses a 100-kw., 275-volt, 150-kva. sy n ch ro n o u s m o to r-g e n e ra to r fo r c o rre c tin g th e p ow er fa c to r. T h is l a t t e r m achinę is of th e th re e -w ire ty p e an d is used fo r c h a rg in g sto rag e b a tte r ie s and f o r su p p ly in g d ire c t c u r re n t to th e tro lley lines. S hould an ac cid en t b efall th is m otor- g e n e ra to r set, th e 125-volt m o to r-g e n e ra to r can be sw itched to th e tro lle y line an d one of th e storage- b a tte ry g a th e r in g locom otives can d ra w pow er for o peration as a m ain -lin e tro lle y m ach in ę. T h is particu- la r locom otive is specially w ire d an d e ą u ip p e d to meet th is re ą u ire m e n t.
P ro p e r b alan c in g of e ą u ip m e n t an d th e application, in new co m b in atio n s o f p rin c ip le s a lre a d y know n, will confine p erio d s o f sh u td o w n to th e tim e re ą u ire d to change over fro m one sou rce o f p o w e r to an other.
T here can be little d o u b t t h a t b ro a d e r co -o rd in a tio n of electrical lin es a n d eą u ip m e n t can be so ex ecu ted as to serve o th e r s im ila r p u rp o se s.
Mo s t o f t h e Co a l Re c o v e r e d o n Se c o n d Mi n i n g
I t is th e firm b e lie f o f th is coal co m p an y t h a t in first m in in g n o t m o re th a n 10 to 15 p e r c e n t of th e u ltim a te recovery should be rem o ved fro m an y ro om section w here th e ro o f is te n d e r an d fa lls re a d ily . A s a re su lt, th e błock sy stem o f m in in g , th e g e n e ra ł la y o u t o f w hich differs b u t little fro m t h a t o rig in a te d in th e F a irm o n t field an d u sed su cc essfu lly elsew h ere, h a s b een chosen.
A sy stem of o p e ra tio n w a s so u g h t fo r t h is m in e t h a t would in c o rp o ra te n a rro w roo m s an d w ide p illa rs , as th ese p illa rs w e re ex pected to s ta n d f o r a lo n g p erio d w ith a m in im u m o f tim b e rin g . I t w a s n e c e s s a ry also th a t th e p illa rs should be o f su ch d im en sio n s t h a t
M arch 6, 1924 C O A L A G E 345 th e y m ig h t be split, slabbed o r s p lit a g a in to fo rm
w in g p illa rs.
I t w as th e conviction of th e officials of th e H udson Coal Co., t h a t flexibility in th e recovery of big p illa rs would elim in a te some of th e d a n g e rs usually eneoun- te re d in r e tr e a t w o rk in g and m ake possible th e m in in g of gob-encroached p illa rs th a t o th erw ise m ig h t be lost.
F u rth e rm o re , th e system adopted possesses an addi- tio n al a d v a n ta g e, in t h a t it p e rm its p illa r blocks to be m ined if d esired by some m odification of longwall m ethod in co n ju n ctio n w ith m echanical lo aders an d conveyors. N o o th e r sy stem could be fou nd t h a t would m eet th e p re se n t and f u tu r ę needs of th e Lew is m ine, an d as a consequence, no o th e r re co u rse re m ain ed bu t to adop t th e błock system of ro o m -and-pillar w orking, w hich in re a lity is only a m odification of th e alm ost u n iv ersa l sy stem in vogue th ro u g h o u t th is co un try .
Coal is m ined by th e błock sy stem in several o th er o p eratio n s in th e F a irm o n t field, an d a t F lem in g, Ky., th e E lk h o rn Coal C o rp o ratio n is o p e ra tin g in th is w ay in th e th ic k E lk h o rn bed u n d e r th e ty p ically heavy cover of th e K entu cky m o u n tain s, an exceptionally h ig h recovery b eing a tta in e d . I m entio n th e se in stan ce s of th e successfu l u tiliz a tio n of th is system to su b s ta n tia te its p ra c tic a b ility an d to re fu te v a rio u s ru m o rs t h a t have received c irc u la tio n recen tly and t h a t ten d to fo s te r a c o n tra ry belief.
In some cases th is sy ste m h a s been unsu ccessfu l and m uch coal h a s been lost, n o t only by iso latio n of stu m p s and la rg e r p o rtio n s of blocks in th e goaf, b u t by th e squeezing as th e re s u lt of n egligence o f larg e a re a s a lre a d y laid ou t in blocks. T h e p rim e prin cip les g o v ern in g su ccessfu l m in in g by room s and błock p illa rs a re no d iffe re n t fro m th o se th a t m u s t be observed in all o th e r w orkin g-place lay o u ts.
T hese are, (1 ) t h a t no p illa rs m u s t be allowed to lag behind th e line o r f r o n t of r e t r e a t ; (2 ) t h a t every body of coal, la rg e o r sm ali, lo st in th e gob adds to th e difficulty of co n tro llin g th e ro o f and, (3 ) t h a t every p re c a u tio n m u st be ta k e n to m ake th e ro o f b re a k as n e a r as possible to th e r e tr e a tin g p illa rs. Officials of b oth th e E lk h o rn Coal C o rp o ra tio n an d th e H udson Coal Co., believe t h a t success w ith th is sy stem th ro u g h o u t long perio d s o f tim e an d w ith little or no re d u ctio n in recovery is d ep en d en t on th e a b ility of th e m ine fo rem an to m ake h is daily advances re g u la rly and system atically.
T h e L ew is m ine o p e ra te s in th e P itts b u r g h seam w hich h a s an a v e rag e th ic k n e ss a t th is p o in t o f 7 f t.
I t is located in a t r a c t of 1,034 acres. A t th e tip p le, w hich is located a t th e n o rth w e s te rn c o rn e r of th e p ro p e rty , th e th ick n ess o f cover s lig h tly exceeds 50 ft.
C onsequently, as m en tio n ed in Coal A g e o f Dec. 20, 1923, p. 919, th e coal is b ro u g h t to th e s u rfa c e by a b elt conveyor 247 f t. long c e n te r to c e n te r an d in stalle d on an in c lin a tio n o f 18 deg. T h e ,m ain h e a d in g is d riv e n so u th w a rd fro m th e slope b o tto m on th e s trik e of th e coal an d in c id e n ta lly in close p ro x im ity to th e w e ste rn b o u n d a ry of th e p ro p e rty . F iv e e n trie s have been th u s d riv en . One is em ployed f o r h au lag e , one as a m an w ay an d th re e a s a ir co u rses. Two o f th e se passa g es a re in ta k e s a n d th r e e a re re tu r n s . T h ey a r e driv en 10 ft. w ide on 40-ft. c e n te rs an d a r e p ro te c te d by b a r r ie r p illa rs 400 ft. w ide.
F ace h e a d in g s on 350-ft. c e n te rs a r e d riv en ea st- w a rd to th e ris e a t an an g le o f 72 deg. to th e m ain h ea d in g s. Room s a r e d riv e n p a ra lle l to th e m ain h e a d in g on 9 0-ft. c e n te rs an d th e p illa rs b etw een th e m a r e
subdivid ed in to 80 -ft. blocks by crosscu ts on 90-ft.
ce n te rs, th ese cro ssc u ts b ein g d riv en p arallel to th e face head in g s. T he re la tiv e d ire c tio n s of h ead in g s and c ro ssc u ts w ith re g a rd to th e fa ces and b u tts of th e coal have been fixed as describ ed fo r th e reason t h a t th e m a jo r p a r t of th e t ig h t w o rk in g in th e blocks is a g a in s t th e ,faces. Rooms a r e m ade 12 f t. wide.
T he lay o u t d iffers fro m th e błock system as usually em ployed, in t h a t c ro ssc u ts a re d riv en in a d ja c e n t room p illa rs in such a w ay as to s ta g g e r th e p illa r blocks.
By th is m eans, th e ro o f is n o t g re a tly w eakened a t th e co rn ers of th e blocks.
Pi l l a r Co a l Is Ea s i l y Re c o v e r e d
T he p illa r coal is easily recovered by s p littin g a błock in tw o an d by p u llin g th e w in g p illa rs from cro ssc u ts in each h a lf of th e błock. I t is needless to go in to f u r th e r d etails, fo r th e m eth o d s of a tta c k of n ecessity v ary w ith th e con ditio ns encou ntered . M ost o f th e tig h t w o rk is fa c ilita te d by to p c u ttin g w ith arcw all m achines, so th a t, in sh o o tin g , th e ro o f is not d istu rb e d .
Room s and p illa r blocks a r e a t p re s e n t developed in an a re a o f a b o u t 125 acres, o f w hich only a sm ali p o rtio n h a s been com pletely m ined. A p illa r section off No. 2 h ea d in g an d one off No. 6 h e a d in g yield m ost of th e p re s e n t o u tp u t, am o u n tin g to 1,500 to n s daily.
A n o th e r sectio n is b ein g s ta r te d off No. 9 h ead in g , in com pliance w ith th e developm ent p lan w hich calls fo r an u ltim a te daily ca p acity of a b o u t 3,000 to ns. Gob lines a r e m a in ta in e d a t an an gle o f ab o u t 45 deg. to th e h ead in g . W h e re th e y m eet, th e y w ill fo rm an an gle o f 90 deg. E v en tu a lly , w h e n 'th e s e th re e sectio n s a re
F ig . 3— S tan d b y M otor fo r th e F a n
T h is d.c. m otor, in sta lled w ith its p u lle y d ir e c tly u n d er th e fa n p u lley, m a y d ra w cu rren t e ith er fro m th e 125 v o lt m o to r-g en e ra to r s e t in th e u n d ergrou n d su b s ta tio n o r fro m th e sto r a g e b a tte ry o f a g a th e r in g lo co m o tiv e in th e m o to r barn.
346 C O A L A G E Vol. 25, No. 10
F I G . 4
M ain H eading B e ca u se th e bottom in th is m in e sw ells e x c e s s iv e ly u n d e r th e action o f m o is- tu re th e tie s are here so c l o s e l y sp aced a s to a lm o st floor th e track . D ra in a g e d itch es a lso m u st be kept o p e n r elig io u sly . E oth th e rib s of t h i s h ea d in g and th e Steel ro o f b eam s fltted w ith la g g in g h a v e been w h ite- w a sh ed th u s g r e a t- ly a id in g in th e il- lu m in ation . A bun- d a n t lig h t a t poin ts su c h a s th is is a g r e a t aid to a cci- d en t preven tion .
connected th ro u g h th e g o af th e contin u o u s lin e th u s fo rm ed will be in th e shape of saw te e th .
Some en g in ee rs hołd th a t a d d itio n a l ro o f tro u b le is en c o u n te red a t th e p o in t w here gob lines of two a p p ro a c h in g p illa r sectio n s m eet in th e m a n n e r above d escribed. N o d o u b t th is is tr u e to a c e rta in ex ten t, b u t difficulty of th is k in d so f a r experienced h a s not been sufficiently g re a t to induce tho se who have adopted th is plan to a lte r it. N o unu su al ro o f tro u b le is a p p a re n t in e ith e r o f th e tw o a p p ro a c h in g p illa r sec
tio n s, and i t is h a rd ly probable th a t m uch coal will be lo st a t th e p o in t w h e re th e tw o sections m eet.
T he ju n c tio n an g le betw een th e gob lines, how ever, should n o t be less th a n 90 deg. T he ea rly a tta in m e n t o f c a p a c ity p ro d u c tio n n ec e ssita te s such a p ro cedu re, o th e rw ise a sufficient n u m b er of w o rk in g places would n o t be available. A dvocates of th e saw -too th gob line a s s e r t t h a t th e loss of coal in th e tro u g h of th ese te e th is n o t excessive. A lthough th ese p o in ts h av e n o t y e t been c re a te d in th e L ew is m ine, th e m an ag e m en t does n o t a n tic ip a te an y serio u s difficulty w hen th e gob lines close.
T he con d itio n s p re v a le n t in th is m in e a re alm ost ideał fo r th e use of s to ra g e -b a tte ry locom otives fo r g a th e rin g . T h is is because th e m ain h e a d in g is on th e s trik e of th e coal, w hich dips only sufficiently to e sta b lish a n a tu ra l g ra d e of ab o u t 1 p e r cent in fa v o r o f th e loads on th e cross-heading s. I t should be recalled, also, t h a t p ra c tic a lly all th e coal lies e a st of th e m ain h eading .
F iv e 6-ton s to ra g e -b a tte ry locom otives g a th e r th e coal an d d eliv er i t to th e m ain s id e tra c k located 2,000 f t . fro m th e slope bottom . F ro m th is sid e tra c k th e e n tir e o u tp u t, to ta lin g a t p re se n t 1,500 tons p e r d iv , is h au led to th e ro ta r y dum p a t th e fo o t of th e slope b y an 8-ton duplex tro lley and sto ra g e -b a tte ry locomo- tiv e . In a sm u c h as th is la tt e r m achin ę is equipped w ith tw o m otors, one d ra w in g its en e rg y fro m s to ra g e bat- te r ie s an d th e o th e r ta k in g c u r re n t from th e tro lley w ire , i t is p re p a re d to a s s is t in g a th e rin g w hen not en g a g ed in h aulage.
T h e w isdom o f th is choice of eą u ip m en t is im m e-
diately a p p a re n t. All five g a th e r in g locom otives are k ep t busy th ro u g h o u t th e s h ift, each s e rv in g ab o u t tw en ty w o rk in g places a n d g a th e r in g 300 to n s o f coal and h a u lin g it a d istan ce of a p p ro x im a te ly 1,800 f t. to th e m ain sid etrac k . T he p ro v isio n of a s to ra g e b a tte ry on the m ain-line h a u lag e locom otive re n d e rs th is m a
chinę a self-co n tain ed u n it cap able o f tra v e lin g any- w here in th e m in e re g a rd le s s of w h e th e r th e tra c k is trolleyed and bonded o r o th erw ise . I t th u s ad d s g re atly to the flexibility of th e h a u la g e sy stem an d to th e u tility o f th e m achinę itself.
R o m an s B u r n e d B r i t i s h Co a l.— E x c a v a tio n has proved beyond all d o u b t t h a t coal w as u sed by the R om ans; ash e s and sto re s o f th e u n b u rn t m in erał are being found all along th e W all, a t L a n c h e ste r and E b ch ester, in D u rh am . a t W ro x e te r, in Shropshire, and elsew here. [ T he W all to w hich re fe re n c e is made is th e R om an w ali b etw een th e T yne, n e a r Newcastle, and th e Solw ay on th e w e ste rn co a st.] F o r the most p a rt, it a p p e a rs to have been used f o r w o rk in g iron, bu t it w as possibly also used fo r h e a tin g hypocausts [fu rn ace s w hich h ea te d th e f lo o r s o f R om an b ath h o u ses].
T h ere seem s good re aso n to believe t h a t i t fo rm e d the fuel o f th e sacred fire in th e tem p ie of M in erv a at B ath, as S olinus, w r itin g a b o u t th e en d of th e th ird cen tu ry , com m ents on th e “ sto n y b alls” w hich were le ft as ash es by th is sa c re d fire. T h a t su ch coal as was used by th e R om ans w as o b ta in e d fro m outcrops, w here th e seam s cam e to th e s u rfa c e is m ore th a n p rob able. T h ere a p p e a rs to be no c e rta in evidence of any re g u la r m in in g f o r coal a t th is p e rio d .— E n g lis h I n d u s tries in th e M iddle A ges, by L. F . S alzm an.
W. W. Od e l l, fuel e n g in e e r, U. S. B u re a u o f M ines, h as com m enced th e s tu d y of p e a t as a fu el, an d is spend- in g som e tim e a t th e M in n eap o lis e x p e rim e n t s ta tio n o f th e b u re au , in th e n o r th e m p e a t d is tr ic t. So f a r he h as m ad e p re lim in a ry stu d ie s as to th e b e s t m eth o d s o f a tta c k in g th e p rob lem w ith th e fu n d s av ailable.
M arch 6, 1924 C O A L A G E 347
How the Modern Underfeed Stoker W orks, and Why*
Number of Underfeed Stokers H as Increased R apidly— W hat Special Features in D esign H ave Been Introduced for Burning Western Coals— Progress of Ash in Fire M ust Be G iven Serious Consideration
By Jo s e p h G. Wo r k e rI
I
N A N Y stu d y of fu e l-b u rn in g eąuipm ent, we m u st d isc rim in a te betw een th e o ry and good p ra ctical o p e ra tin g en g in ee rin g . O ur problem in fuel b u rn in g is no t e n tire ly one of selectin g th e m ost efficient th e rm a l system . We m u st consider also tho se physical fa cto rs in th e fuel bed w hich vitally affect its com bustion and d eterm in e its u ltim a te efficiency.Low flue-gas te m p e ra tu re s , p re h e a te d a ir, hollow-wall co n stru c tio n , etc., affect th e overall efficiency of a com
b u stio n sy stem fro m five to te n p e r cent, b u t th ey a re n o t a p a r t of an y one p a r tic u la r com bustion system , a lth o u g h th e y m ay be provided w ith any one of them . In o u r endeavor to find an y given condition w hich will give th e b e st re s u lts fro m a d o llar-and-cents b asis g re a t c a re m u st be ta k e n to see th a t th e re su lts o btained are n o t a ttr ib u te d to th e w ro n g causes.
T h e m echanical sto k er, m ore th a n an y o th e r piece of boiler-room eąuipm ent, h as m ade it possible to d e
sig n b o iler p la n ts of th e p re se n t h ig h capacity, to b u rn
Fig. 1— F u el Bodies of an U nderfeed F ire Bed D u rin g th e coking' process, th e coal sw e lls and fo rm s arch es over the tuyeres. The in ca n d escen t fu e l is on th e top and th e coking- a r ea e x ten d s back in to th e retorts.
th e fu e l efficiently an d ra p id ly an d to o b ta in as m uch as 6 kw. of g e n e ra to r ca p acity p e r b o iler horsep ow er.
Only fifteen y e a rs ago, we w ere obliged to in s ta ll a b o iler h o rsep o w er fo r every 2 kw. g e n e ra te d .
M any ty p e s o f sto k e rs have a s s iste d in th is develop- m en t. T h e u n d e rfe e d s to k e r h a s played its p a r t and h as figu red p ro m in e n tly in th is p ro g re s s. To ap p re- c ia te th e e x te n t to w h ich it is now u sed to b u rn M id- w e st coals, a su rv e y w as m ade an d th e follo w in g fa c ts w e re re v ealed :
A little over 1,000,000 hp. of b o ilers w e re sold in th e U n ited S ta te s d u rin g th e y e a r 1922, by tw e n ty - e ig h t b o iler com panies. T h is includes ab o u t 800,000 hp.
of all ty p es o f m ech an ical sto k ers. O f th ese, 550,000 hp.
•A b s tra c t o f a d d ress d elivered a t C h ic a g o S ection , A m erican S o ciety o f M ech an ical E n g in eers, Jan. 15.
fP re sid e n t, S to k er M a n u fa c tu rers’ A sso c ia tio n .
w ere equipped w ith one ty pe or o th e r of u n d erfeed sto k er, ab o u t 200,000 hp. w ere p rovided w ith some ty pe of c h a in -g ra te sto k e r and a b o u t 50,000 hp. w ith some k in d o f overfeed sto k er. T h a t is, ab o u t 75 p e r cent of th e sto k e rs sold in th e U n ited S ta te s d u rin g th e y e a r 1922 w e re of th e u n d erfee d type.
T ho ug h th e se fig ures th ro w some lig h t on o u r sub- ject, th ey a re p e rh a p s as ex pressiv e o f economic con- d itio n s as th ey a re of efficiencies in th e d iffe re n t com
b u stio n sy stem s. T h ese figu res m ay be su rp ris in g , because only a few y e a rs ago any of us would hąve c o rrectly s ta te d t h a t m o st of th e sto k e rs sold in th e W est w ere of th e c h a in -g ra te type. T he change h a s come ab o u t slowly. I t m ay have been delayed a t tim es, b u t we a re now a t th e p o in t w h ere alm ost as m an y u n d erfee d sto k ers a re b ein g in stalle d in th e W est as in th e E a st.
Co n f u s e Fu e l Bu r n i n g Wi t h Cl e a n i n g
We m ay have been c o rre c t in th e p a s t in claim ing t h a t no sto k e r h and les all g ra d e s of coal w ith th e sam e degree of sa tisfa c tio n . In th a t th o u g h t, how ever, we allowed ourselves to co n sid er difficulties in m echanical o p e ra tio n t h a t w e re in no w ay a p a r t of th e fuel- b u rn in g sy stem , b u t w ere to a la rg e e x te n t a p a r t of th e clean ing process of th e fu e l bed.
T h ere have alw ays been tw o ty p e s of s to k e r d esig n - ers. One h ad ten den cies to w a rd b u ild in g a m ach in ę t h a t would offer th e b e s t co m bu stion p o ssib ilitie s, ir- resp ectiv e of th e clean in g devices. O th e rs m ixed and confu sed th e problem , w ith th e r e s u lt t h a t s to k e rs have been d esig ned w hich, th o u g h th e y w e re n o t th e m o st efficient in th e b u rn in g of coal, h an d led c lin k e rs so s a tis fa c to rily t h a t t h e i r lack of com b ustio n efficiency w as w illing ly overlooked.
W e have h e a rd m an y tim e s t h a t th e u n d e rfe e d w as all r i g h t f o r M iddle-w est coals, except t h a t w h en i t w as used th e clin k ers gave too m uch tro u b le. In m any
F ig . 2— T ay lo r U n d erfeed F u el Bed
T h is illu s tr a tio n sh o w s th e g r a v ity a sh feed . T he fine a sh flo a ts on th e top o f th e fu e l bed and slo w ly w o rk s its w a y dow n in to th e ash p it.
r/vce or ruYtgrcs
348 C O A L A G E Vol. 25, No. 10
F ig . 3— Section T hrough F ire Bed
T he arch ed a r ea s correspond to th e p o sitio n s of th e tu y eres sh ow n in F ig . 1. The fu e i bed is supported by th e green c o a l in the retorts.
in stan ce s th o se who m ade th is sta te m e n t fa ile d to in v e stig a te how th is difficulty could be overcom e w ith - o u t d is tu rb in g th e p rim a ry com bustion system .
Y e ars ago, w hen th e u n d e rfe e d p rin cip le w as b ein g developed, som e o f th e pow er s ta tio n s of th e E a s t h ad a som ew hat s im ila r experience. Some people could n o t see its v irtu e s, and alm ost endless d iscussio n re - su lted . Im p ro v em en ts w ere m ade on one p a r t or o th e r of th e co n tro llin g m echanism , b u t th e u n d e rfe e d m ethod o f b u rn in g coal w as, probably m ore th a n an y o th e r sin g le elem ent, th e re aso n f o r th e success of th e whole system .
M any new sto k e r developm ents w ere s ta r te d in th e W est, b u t ra re ly w ere th e ir problem s finally an d defi- n ite ly w orked out. I f th ey w ere, it w as w hen som e o th e r p a r t of th e c o u n try took up th e problem . E ven th e n , a s th e coal conditions in t h a t section w ere n o t so sev ere as in th e W est, th e solu tion of th e difficulty gave such a n im p etu s to th e sto k e r b u sin ess th a t no f u r th e r effo rt or m oney w as sp en t in m o d ify in g a p a r tic u la r sto k e r to s u it W e ste rn coals.
I t is im p o rta n t to o b ta in a elea r idea of th e p rin - ciples involved in th e b u rn in g of a f uel bed on a m ultip le- r e to r t u n d erfee d sto k er. A n endeavor h a s been m ade to exem p lifv in F ig . 1 som e of th e id eas of Elwood T ay lo r, by whom th is ty p e of sto k e r w as invented.
T h e in v e n to r’s claim , w hen he p etitio n e d f o r p a te n ts on th is device, ex p lain s clearly th e m ovem ent of th e fuel.
Un d e r f e e d Fu e l Be d Is No t Ag i t a t e d
M any hav e th e idea t h a t an u n d e rfe e d fu e l bed is a g ita te d and t h a t th e fuel is pushed acro ss th e sup- p o rtin g s tr u c tu r e fro m th e p o in t w h ere it en te r s th e fu e l bed to th e p o in t w h e re it is d isch arg ed as a s h ; b u t th e in v e n to r s ta te d t h a t in th e o p eratio n o f h is sto k e r, th e fu e l bodies in th e sev eral r e to r ts c o n stitu te d th e legs o f a sin g le fuel bed. T h is bed b u rn e d w ith th e in c a n d e sc e n t fu e l on top an d w ith th e coking fuel u n d e rn e a th ex te n d in g back in to th e re to r ts .
O w ing to th e cohesion and a rc h in g p ro p e rtie s o f th e fu e l as i t sw ells d u rin g th e coking process, th e fuel bed receives its su p p o rt fro m th e w alls of th e r e to r t a n d is fed o u tw a rd ly by th e r e to r t p u sh ers.
I t arch es o v er th e tu y e re faces a n d so is k e p t su b- s ta n tia lly fre e fro m th em as show n in th e sketch.
T his illu s tra tio n also p lain ly show s th e p a r tia lly coked coal e x ten d in g in to th e re to r ts , an en d e av o r b ein g m ade to m ake plain th e w ay in w hich th e coke a rc h e s over th e tu y e re s .' T h is o p e ra tin g p rin c ip le an d th e claim of th e in v en to r h as been d e m o n stra te d in re s e a rc h w ork in connection w ith th is sto k e r. I t h a s also been sub- s ta n tia te d by e x p e rt e n g in e e rin g testim o n y .
Co k e Ar c h e s Ho l d Up Fu e l Be d
F ew have realized th a t th e coke a rc h e s in th e u n d e r
feed sto k e r ac t in th e co m b u stio n p ro cess as th e re fra c - to ry arch es do in th e c h a in -g ra te a n d o th e r sto k ers.
T hese u n d erfeed a rch es a r e m ade up o f p a r tia lly b u rn e d coal and ai-e con tin u o u sly b e in g b u rn e d up an d re- form ed. Im m ed iately o ver th e s e a rc h e s o f p a r tia lly b u rn e d coal is th e in can d e scen t a n d m a jo r fu e l bed ex ten d in g acro ss th e o p ening s of th e r e to r ts .
F in a lly , i t w ill b e n o ted t h a t th e fine a sh floats on top of th e e n tire fu el bed, F ig . 2. T h ese p a rtic le s of a sh a r e sm ali and w ere o rig in a lly in d e p e n d e n t pieces of g re en fuel. T he ash is fed b y g r a v ity dow n th e slope of th e fu e l bed, th e m o vem en t b e in g in d uced by th e period ical in tro d u c tio n o f c a rtrid g e s o f fu e l w hich give a w eavin g m ovem ent to th e fu e l b ed an d a n out- w a rd feed m ovem ent acro ss th e m o u th of th e r e to r t.
O ften th e idea is advanced t h a t th e a g ita tio n of u n d erfeed fu el beds is u n d e sira b le w h e re a h ig h -a sh coal is used. A c a re fu l an a ly sis o f th e s e fu e l beds will show, in fa c t, th a t th e fuel is n o t a g ita te d o r m ixed as is g en erally supposed. T h e in je c tio n o f th e s e c a r t
rid g es o f fuel is so slow t h a t th e m o v em en t a t th e tim e th e coal is in tro d u ce d is h a rd ly p e rc e p tib le to the eye. The a rc h in g o f th e fu el in th e r e t o r t re liev es th e p re ssu re on th e coal p u sh e rs w h en th e y r e tr e a t fo r a n o th e r ch arg e, an d co n seąu en tly th e fu e l m ovem ent is alw ays ou tw ard .
As h Ro l l s Do w n Sl o p e b y Gr a v i t y
T he o p eratio n of th e u n d e rfe e d s to k e r is th u s easily d istin g u ish a b le fro m t h a t of fo rm s o f m echanical stok
ers em ploying inclined g ra te s in w h ich th e g reen fuel is fed by th e o v erfeed p rin cip le. N o g r a te or fuel su pp ort, such as is em ployed by o v erfeed o r chain- g ra te sto k ers, is used in th e u n d e rfe e d ty p es, the fuel in stead b ein g su p p o rted fro m th e r e to r ts . This is m ade elea r by F ig . 3, in w hich all th e s u p p o rtin g stru c
tu re of an u n d e rfe e d fu el bed h a s been ta k e n away.
T his show s how th e u n d e rfe e d fire is s u p p o rte d on legs of coal an d th e m a jo r w e ig h t o f th e fu e l bed is tra n s m itte d to th e re to r ts .
The fo rm a tio n an d p ro g re s s o f th e a sh o f an u n d e r
feed fuel bed is g en e rally m isu n d e rsto o d . N o p u sh e rs o r ram s cornpel th e a sh in an u n d e rfe e d fu e l bed to p ro g ress th ro u g h th e fire. I t can be p ro v ed t h a t th e
F ig . 4— F o rm a tio n of C linker on Side W all
U n le ss th e a sh co n tin u es to flow in it s n a tu ra l co u rse a clin k er q u ick ly bu ild s up and g ro w s la rg er u n til rem oved.
M arch 6, 1924 C O A L A G E 349
F ig. 5— R otary A sh D ischarger W hich P rev en ts F o rm atio n of C linker
T h is is one o f th e la te s t d ev ices ad a p ted to stok ers. The illu stra tio n sh ow s a se r ie s o f a ir baek s and w a te r back s freą u en tly u sed on th e fr o n t fa c e o f th e brid ge ■wali to p rev en t sto p p a g e o f th e a sh in its course to th e clink er
grinder. C lin k erin g coal no longer p resen ts seriou s difflculties to stok er m an u fa ctu rers.
feed o f g re e n fuel induces th e ash to move by g ra v ity down th e slope of th e fu e l bed. A close-up view of th e s u rfa c e of such a bed w ould show clearly t h a t th e fine p a rtic le s of ash tra v e l down th e incline. T he in clin atio n of th e fuel bed m u st be such t h a t th e ash will m ove in th is m an n er.
H a v in g developed th e p rin cip les of a p ro p e r fuel- b u rn in g process, have we given enough th o u g h t to th e m ach in e ry n ecessary to allow a fu el bed to fu n c tio n ac co rd in g to its p rin c ip le s? I f th e re w e re no side w alls n o r b rid g e w alls o r o th e r r e f ra c to ry p a r ts su rro u n d in g an u n d e rfe e d sto k er, an d n o th in g to r e ta r d th e flow of ash fro m th e top o f th e fu e l bed to th e b ottom , would clin k ers fo rm ?
A p a rtic ie of a sh in a fu e l bed, as show n in F ig . 4, if stopped in its p ro p e r course down th e slope ad h e res to th e side w ali an d backs up th e oncom ing ash , th u s com m encing th e fo rm a tio n of clinker. U nless it is s ta r te d on its course ag a in , i t will g ra d u a lly grow u n til it b u ild s o u t u n d e rn e a th th e fu el bed and in some cases down in to th e re to r ts .
In developing th e fu rn a c e co n stru c tio n fo r u n d erfee d sto k ers, side-w all a i r plates, air-cooled c ru s h e r plates, w a te r backs, etc., have been devised and co n stru c te d , all fo r th e p u rp o se of k eep in g th e a sh fro m sto p p in g in its course down th e fuel bed. Side-w all a ir backs a re now ą u ite g en e rally used w ith u n d e rfe e d sto k e rs. T hese p la te s a re w o rk in g ą u ite s a tis fa c to rily and, o f course, a re m uch b e tte r th a n th e r e f ra c to ry m a te ria ł w hich th e y have replaced.
As h e s St o p p e d a t Br id g e Wa l l a n d Cl i n k e r e d
I f we assu m e t h a t th e a sh is n o t stopped in its de- scen t of th e slope o f th e fu e l bed, i t w ill ev e n tu a lly re a c h th e b rid g e wali. W hen m u ltip le -re to rt u n d e rfe e d s to k e rs w e re firs t in stalle d th e y w e re eąu ip p ed w ith dum p g ra te s , an d unless th is p a r t o f th e sto k e r w as handled p ro p erly , th e ash e s w ould stop a t th e b rid g e wali an d g ra d u a lly accu m u late an d back up so t h a t la rg e clin k ers would fo rm . T h ese w ould n o t only lie on th e dum p g ra te s b u t would b u ild up in to th e fu e l bed.
W ith o u t d is tu rb in g th e p rin c ip le s o f th is fu e l bed, th e d e sig n e rs tack led th e problem of th e sto p p a g e and c lin k e rin g a t th e b rid g e w ali and th e re s u lt w as w h a t is com m only te rm e d th e ro ta r y -a s h d is c h a rg e r show n in F ig . 5. T h is device is n e c e ssa ry fo r th e co n tin u o u s
p ro g re ss of th e ash an d clin k er fro m u n d e rfe e d -sto k e r fires.
I t is obvious t h a t u n d e r c e rta in co n d itio n s o f opera- tion , it would n o t be n ec essary to a c tu a te con tin u o u sly th e c ru sh e r in th e a sh well. I t is th e re fo re only oper- ated to keep in tu n e w ith th e fo rm a tio n o f a sh as it proceeds down th e slope of th e fu e l bed. A ir backs and w a te r backs a re used on th e f r o n t fa ce of th e b rid g e w ali to p re v e n t th e ash or clin k er fro m b e in g stopped in its dow nw ard cou rse th ro u g h th e a sh w ells and th ro u g h th e c ru s h e r rolls in to th e a sh p it.
T he W est is now solving some of th e se c lin k e r p ro b- lem s. N o lo n g er a re we in f e a r of w h a t th e ash in th e coal m ay do. A t least, th e c lin k e rin g of W e ste rn coals is no lo n g er allowed to h in d e r good e n g in e e rin g p ro g ress.
M echanizing French Coal Mines
In o rd e r to m eet th e in c re a se d cost of o p eratio n , F re n c h co al-m ining com panies h ave g iv en special a tte n - tio n to m echanical e ą u ip m e n t su ite d to th e con d itio n s in F re n c h m ines. T h is h a s re su lte d in th e in c re a se in th e p e rc e n ta g e of coal pro du ced b y m ach in es in one d is tric t fro m 4.27 p e r ce n t in 1913 to 16 p e r ce n t in 1922, say s C h e ste r Lloyd Jon es, C om m ercial A ttach e , P a r is , in a re p o rt to th e D e p a rtm e n t of Com m erce.
T he c h a ra c te r o f th e d ep o sits is such t h a t c e rta in ty p es of coal m in in g m a c h in e ry a s used in th e U n ite d S ta te s w ill n o t alw ays w o rk w ith efficiency. N e v e rth e - less in th e P as-d e -C alais a n d in th e N o rd m ark e d advance h as been m ad e in re c e n t y e a rs. In th e P as-d e - C alais th e re a re tw o A m e ric a n m ach in e s of special ty p e a n d one b a r coal c u tte r in use o r u n d e r tr ia l. T h e m o st successfu l ty p e em ployed is t h a t o f th e m echan ical p ick -h am m er. O f th e se th e r e w e re in u se in 1911 only 743, in 1913, 1,392; b u t in 1922, 2,872 w e re em ployed.
P e r f o r a tin g h a m m e rs o f th e h a n d ty p e h ave also become p ro m in e n t, th e n u m b e r in use h a v in g ris e n fro m 1,878 in 1913 to 2,343 in 1922.
In th e N o rd th e coal m in ed b y m ech an ical m ean s b e fo re th e w a r w a s a b o u t 2.5 p e r c e n t of th e to ta l, b u t in 1922 th is h ad in c re a se d to 10 p e r cent. S ix coal c u ttin g m ach in e s w e re o p e ra te d d u rin g th e y ea r, bu t, b ecau se o f th e n a tu r ę of th e coal dep o sits, th e y showed a yield o f only som e 17,000 to n s.
