M c G r a w - H i l l C o m p a n y , I n c . Devoted to the Operating, Technical and Business
J a m e s H . M c G r a w , President -r» ui .c ¿i, n . 1 -n/i- • t j i. R- D a w s o n H a l l
E . J . M e h r e n , Vice-President Problems of the Coal-Mining Industry E ngineering E ditor
Volume 28 N EW YORK, OCTOBER 15, 1925 Number 16
You Cannot Browbeat an E conom ic Law
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F C O U R SE , th e a n th r a c ite o p e ra to rs serio u sly f e a r a p o ssib le w ag e in c re a se o r an y c h an g e in w o rk in g co n d itio n s w h ich w ill ra is e th e p ric e of a n th r a c ite coal.T h ey a re h a v in g tro u b le now in h o ld in g th e ir m a rk e t.
Oil, coke an d b itu m in o u s coal a r e com ing in w h e re th e y n e v e r cam e in b efo re. A ny in c re a se in p rice w ill m ake a n th r a c ite s till h a r d e r to sell an d w ill n a rr o w its m a rk e t. T h e public w ill b u y th e c h e a p e r a rtic le w hen th e p ric e goes low enough to offset, in its opinion, th e a d v a n ta g e s o f h a r d coal.
In o th e r w ords, th e o p e ra to rs a re up a g a in s t an econom ic law . M oreover, th e y know t h a t th e y a re “ up a g a in s t it.” H ow long b e fo re th e m in e rs w ake up to th e f a c t t h a t th e y too a re up a g a in s t th e sam e econom ic la w ? I ts o p e ra tio n is in e v ita b le : L ess sales, less m in in g ; less m in in g , less w o rk . A nd ev en tu ally th e re s u lt w ill be, if p ric e s co n tin u e to r is e : no sales, no m in in g ; no m in in g , no w ork.
E v e n u n d e r p re s e n t c o n d itio n s, w ith o u t a n y new in c re a se in w ag es o r a d d itio n a l b u rd en so m e w o rk in g co n d itio n s, th e o p e ra to rs, in o rd e r to hold w h a t m a rk e ts th e y have, m u s t secu re th e u tm o st econom ies in o p e ra tio n . B u t th e m a jo r econom ic law t h a t s ta r e s th e in d u s try in th e fa c e is th e th in g t h a t c a n n o t be escaped a n d m u s t be a p p re c ia te d by b o th p a r tie s to th e in d u s
t r i a l p a r tn e r s h ip — o p e ra to rs a n d m in e rs. T h e o p e ra to r s h a v e a n a p p re c ia tio n o f it. T h e m in e rs need to w ake up.
L a b o r u n io n s m a y be able to fo rce ex em p tio n s fro m leg islativ e bodies, b u t th e y c a n n o t b ro w b e a t an econom ic law .
Day W age and the P u b lic
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H E N E V E R COAL S T R IK E S a g ita te th e public, as w ell th e y m ay, th e q u estio n asked is : W h a t do m in e rs rec e iv e ? ’ T h e a n sw e r is n o t a n y too s a tis f a c to ry . T h e in q u ir e r is told th a t th e low est day w ag e is$4.62 or $7.50 as th e case m ay be, b u t h e becom es su sp icio u s w hen th e in fo rm a n t c a n n o t give a c tu a l daily w ag es f o r th e m o st n u m e ro u s bodies of w o rk e rs—
m in e rs, m in e la b o re rs a n d lo ad ers. “ T h e re is som e
th in g q u ee r a b o u t th is ,” h e feels. “ I know th e w ag es o f b ric k la y e rs a n d p la s te re rs , w hy th is difficulty in a s c e rta in in g m in e rs ’ w ag e s ?”
So h e is q u ite g re e d y to h e a r w h a t M r. L ew is, th e m in e w o rk e rs’ cham pion, h a s to say. M r. L ew is q u ite p lau sib ly b a ses h is s ta te m e n t on th e U. S. Coal Com
m issio n re p o rt, overlooking th e f a c t t h a t th is Com m is
sion w as u n ab le to follow th e m in e r fro m jo b to jo b an d so show s f a r m o re m en a t w o rk in m in in g th a n th e m in es c o n ta in a n d th e w ages p e r m a n p e r y e a r m uch low er th a n th e m in e w o rk e rs ac tu a lly receive.
I f each m an h a d a d ay w ag e th e re w ould be less d isp u te an d t h a t is w h a t wre a re com ing to, as m ach in es a re b e in g in tro d u c e d . W hen th e m in es a r e m echanized so as to m ake th e w o rk easy all m en w ill be paid, i t is
to be hoped, a d ay w age. W hen a n y one is asked w h a t is th e w age, th e a n sw e r w ill be fo rth c o m in g w ith o u t a n y dubious note o r le n g th y ex p lan atio n .
Some have doubted w h e th e r a d ay-w age m in e can be m ade successful, b u t th e a tte m p t to r u n a m in e t h a t w ay h as been trie d , an d bo th m en a n d m a n a g e m e n t a re e n th u sia stic . N o t a to n n a g e m an is on th e job, and every m an em ployed is s u re t h a t w h e th e r th e m in e c a rs come or fail- to come p ro m p tly h e is a ssu re d of a c e r
ta in d ay ’s pay. T he o p e ra to r h a s accepted th e u n c e r
ta in ty in place o f th e m in e r, an d th e r e is no sig n th a t h e re g re ts h is choice.
Clean Up Airways
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N M IN E S w h ere m en a r e allow ed to tra v e l th e h au l- agew ays, th e o th e r a i r p assag es, w h e th e r in ta k e o r r e tu r n a irw a y s, a r e p e rm itte d too o fte n to becom e c lu tte re d w ith fa lle n rock, m a k in g th e b u rd e n on th e fa n unduly heavy. In m a n y cases th is rock is 1 rem ovable only w ith difficulty because th e ra ils hav e been lifte d , and concrete sto p p in g s m ake th e a irw a y s re la tiv e ly inaccessible. T hey become u n s a fe and difficult to tra v e l so th a t a f te r a w hile no one c a re s to tr a v e rs e th em . E v e n tu a lly th e ir co n d itio n becom es so b ad th a t th e fa n h as to be speeded up.
I t would be m o re p rofitable to keep such places p ro p erly cleared. T h e fa lls b e in g rem oved, th e a irw a y would be en larg ed , an d v e n tila tio n w ould be aid ed r a th e r th a n h in d e re d . M any a m in e becom es p ro g re s sively difficult to v e n tila te because o f th e co n tin u ed decrease in th e c a p a c ity o f th e a irw a y s ow ing to fa lls and to th e h e a v in g of th e floor. A s th e c le an in g of such a i r p a ssag es is expensive th e w o rk on th em is delayed in tim e o f low coal p ric e so as to c u t cost. W hen th e re is a dem and f o r coal, th e jo b a lre a d y h a s becom e too la rg e f o r a n y one to a tte m p t w ith o u t ris k o f r u n n in g up th e cost unduly. M oreover, th e h a n d lin g o f rock re q u ire s th e lab o r o f m en who m ig h t o th e rw ise pro d u ce coal an d ab so rb s th e ca p a c ity o f c a rs t h a t m ig h t be used f o r th e h au lag e. F u r th e r m o re , th e ro ck c a rs ab so rb th e cap acities o f th e h au lag ew ay , s h a f t, a n d m o tiv e pow er an d cau se delays on th e su rfa c e . So th e jo b is a g a in delayed an d in th e end is n e v e r p e rfo rm e d .
C leaning up a irw a y s is a p a r t of n o rm a l o p e ra tio n an d should be so re g a rd e d . D elay in - p e rfo r m in g such w o rk should n o t be to le ra te d u n less e ith e r thex-e is a p ro sp ect t h a t a new s h a f t w ill be su n k t h a t w ill m ake th e a irw a y useless o r th e r e is a likelihood th a t th e a i r w ay will s h o rtly be d isp en sed w ith an d th e p illa rs draw n . E ven th e n a clear a irw a y w ill m ak e th e p illa r d ra w in g e a s ie r a n d w ill en ab le th e coal to be rem oved fre e of pieces o f b ro k e n d e b ris.
V e n tila tio n is a c o n tin u in g o p e ratio n , a c o n s ta n t d ra in on th e o p e ra to r’s pocket, a n d should be m e t by p e rs is te n t v ig ilan ce. I n m o st m in es fe w see th e con
d itio n of a i r co u rses. T h e y a r e n o t places t h a t m a n a g e rs or executives v is it, and it is in th em , o ften , t h a t 519
520 C O A L A G E VOL. 28, No. 16 h u n d re d s of d o lla rs of w a ste d po w er a r e concealed in
th e in te r e s t o f te m p o ra ry a n d fa n c ie d economy. C lean
in g up a irw a y s is one of th o se lo n g er-v isio n ed econ
om ies t h a t su b o rd in a te s a re a p t to overlook in th e ir effo rts to keep dow n th e c h a rg e s on th e d a ily c o st sheet.
“ M en come a n d go,” s a y th ey , “w h y w o rry a b o u t f u tu r e v e n tila tin g p ro b le m s? ”
W ith in s tru m e n ts t h a t m e a su re w a te r g a g e an d p o w er consum ption, how ever, th e p ro g re ssiv e w a ste s in a irw a y s w h ich becom e c lu tte re d w ith rock can be w a tc h e d an d a p p ro p ria te ac tio n ta k e n .
Sm all Cars, Low Profits
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O N IG G A R D L IN E S S is m ore expensive th a n to use c a rs sm aller th a n ro o f co n d itio n s m ak e n ecessa ry . A ra ilro a d u s in g th e eq u ip m e n t of tw enty-five y e a rs back w ould be in th e b a n k ru p tc y c o u rts, b u t m an y m in es a re still s tr u g g lin g alo n g w ith th e e q u ip m en t th a t w as m o d ern a q u a r te r c e n tu ry ago, w h en c a rs w e re b u ilt, h ig h , s h o rt an d n a rro w . A m o d ern c a r red iices g a th e r in g ch a rg e s, gives th e m in e r a b e tte r o p p o rtu n ity f o r lo ad in g a n d low ers m a in -h a u la g e costs. A m in e w ith a n a rro w g ag e can m ake no b e tte r in v e stm e n t th a n to re la y th e tra c k , sc ra p th e c a rs an d locom otives a n d buy s ta n d a rd eq u ip m en t, la rg e enough to j u s tif y in tro d u c in g th e new c o n stru c tio n a l im p ro v em en ts such as housed w heels, s p rin g d r a f t rig g in g , ro ller b e a rin g s, etc., t h a t go w ith such cars.
T h e re a re lim its, of course, especially in g aseo u s m in es a n d in th o se w ith w eak ro o f. W h ere b r a ttic e cloth is used a t th e face of e n trie s a w ide c a r m a y leave insufficient room f o r th e in ta k e o r r e tu r n c u r r e n t and fo r th e p o sts b y w h ic h th e b r a ttic e is su sta in e d , p a r tic u la rly w h e re th e ro o f is such a s to m ak e th e e n tr y an d c ro ssc u ts n a rro w . B u t i t is e v id en t th a t sm all c a rs a re o fte n used w h e re th e re a re no su ch rea so n s f o r k eep in g t h e ir size dow n to e x is tin g lim its.
W h ere a com pany h a s a n a rro w g a g e all its new ly p u rc h a se d eq u ip m en t a s w ell a s its old m u s t co n fo rm w ith s ta n d a rd s o u t-o f-d ate, u n d u ly expensive a n d u n p ro fitab le in o p e ra tio n . H ence a ch an g e m u s t be m ade sooner o r la te r in th e in te r e s t of economy, so w h y n o t m ake i t now ? B y n o t delay in g , th e a d v a n ta g e can be o b ta in e d a t once. S u re ly if th e m in e is g o in g to con
tin u e p ro d u c in g f o r y e a rs u n d e r p re s e n t m e th o d s i t does n o t p a y to delay m a k in g th e change, th u s d e f e r r in g th e p ro fit a n d m a k in g th e rev isio n , w hen i t does come, th e m ore expensive. U nless m eth o d s o f m in in g a re ra d ic a lly ch an g ed n e v e r w ill th e tra c k a g e be s h o r te r th a n now, n e v e r w ill th e n u m b e r of c ars, fro g s a n d sw itc h e s be less th a n today.
W ith m echanical a id s comes a d em and f o r la r g e r car’s an d a n o p p o rtu n ity fo r co n c e n tra tio n . T h e la t t e r a s su re s a re d u c tio n of tra c k a g e , a n d w hen t h a t is m ad e i t is a good tim e to ch an g e g a g es if th e y a re too n a rro w . N o one w ho tr ie s o u t m echanical a id s in lo ading, w h e th e r lo ad ers o r conveyors, re a lly know s w h a t th e se can do if th e te s ts a re m ad e w ith in a d e q u a te c a rs.
Som e y e a r s back, S am uel D ean, a n E n g lis h e n g in ee r, long dom iciled in A m erica, sa id to h is B ritis h f rie n d s in a te ch n ic al p a p e r delivered in E n g la n d t h a t th e re a so n fo r A m eric an efficiency could be fo u n d in th e la rg e car.
H is su g g e stio n is s till good, th o u g h he h a s b een dead m a n y y e a rs. W hy trifle w ith p roblem s o f loading, tra n s p o rta tio n , h o is tin g an d d u m p in g by u sin g c a rs o f in a d e q u a te siz e?
P o o lin g E xperien ce
T
H E a n n u a l m e e tin g of th e W e st V irg in ia -K e n tu c k y A sso ciatio n of M ine, M echanical an d E le c tric a l E n g in e e rs w ill p ro b ab ly n o t be held th is y e a r. T h is can cellation is to be re g re tte d . I n a tim e like th e p re s en t, w hen ro ck -b o tto m costs a re e sse n tia l, conferences o f m in e m ech an ics a n d e le c tric ia n s a r e of t h e i r g r e a te s t value.O p e ra to rs a re d ep en d in g on developm ents of m ech an ical an d e lectric al eq u ip m e n t to reduce p ro d u c tio n cost.
S election, in s ta lla tio n , in sp ectio n an d m a in te n a n c e of t h a t eq u ip m en t a re all h ig h ly im p o r ta n t fa c to rs con
tr ib u tin g to th e overall n e t re s u lt— low er co st p e r ton.
T h e o ry is v aluable b u t ex p erien ce is ab so lu tely neces
sa ry , a lth o u g h so m etim es costly. M en w ho m u s t le a rn e v e ry th in g first-h a n d in ste a d of p ro fitin g b y th e f a il
u re s a n d successes of t h e ir n e ig h b o rs a re lim ite d in th e serv ice th e y can re n d e r.
M eetin g s of v irile asso c ia tio n s of tech n ical m en offer th e m o p p o rtu n itie s to in c re a se t h e i r value to them selves an d th e ir em ployers. O p e ra to rs th e c o u n try over should see to it t h a t such asso c ia tio n s are k e p t v irile . T hey can do th is by sen d in g one o r m o re m en fro m each m in in g com pany in s tru c te d to c o n trib u te fre e ly o f th e com pany’s experience— a n d to b rin g back w o rth -w h ile ideas. T h e cost o f s e n d in g th e se m en should be a sound in v estm en t.
P u t Y ourself in H is P lace
P P O S IT IO N TO M A C H IN E R Y is n o t u n n a tu ra l.
T he m in e r w ho sees a m ach in e w h ich enables one m a n to do tw o m en ’s w o rk n a tu r a lly a n tic ip a te s t h a t one m a n is likely to be d ropped a n d is opposed to th e im p ro v em en t. C lever m a n a g e rs a r r a n g e t h a t th is sh all n o t happen.
A t m o st m in es m en a re d r if tin g a w ay all th e tim e.
A s a ru le th e se d r if te r s a re n o t th e m o st d e sira b le m en, an d if no a tte m p t is m ade to h ire new em ployees th e fo rc e g ra d u a lly d ecrea ses au to m a tic a lly . M en, in fa c t, soon cease to ap p ly f o r w ork. T h e w o rd goes aro u n d t h a t none a r e b ein g h ire d , a n d th e y look else
w h ere, p e rh a p s in som e o th e r p ro m is in g in d u s try . Now, w ith th e fo rce a lre a d y decreased , so th a t m ach in e o p e ra tio n is n e cessary to fill o rd e rs, th e m ach in es can be in tro d u c e d w ith o u t o pposition. N o one sees th e m a s a t h r e a t b u t a s a p ro m ise o f s te a d ie r w ork, b ecause of th e low -cost p ro d u c tio n th e y assu re . T he m ac h in es a re s ta r te d w ith o u t a n excess o f m en b ein g em ployed on th em , an d th e y w o rk a t m a x im u m efficiency. T h e psychological c o n d itio n s consequently a re r ig h t. B ecause o f th e w ay i t is in tro d u c e d th e r e is no a n tip a th y to th e m ach in e a n d as i t in s u re s s te a d ie r w ork an d lig h te n s to il everyone is pleased.
E v e ry o p e ra to r should p u t h im se lf in th e m in e r’s place. W h a t w ould h e do i f he h an d led pick a n d shovel ? H e th e n w ill use excellent ju d g m e n t in m a k in g in n o v a
tio n s a n d see t h a t th e y help in ste a d o f h a rm th e em ployee.
In fa c t, w ould i t n o t be w ell a t tim e s o f low p ro d u ctio n (to d ecrease th e n u m b e r of m in e rs ? I t is tr u e a la rg e fo rce of m en in s u re s a speedy lo ad in g of c a r s an d less delays in tr a n s p o r ta tio n , b u t on th e o th e r h a n d i t in c re a se s th e a re a t h a t m u st be k e p t u n d e r devel
opm en t a n d i t d e stro y s m orale. A f te r all, t h a t l a tte r f a c to r is n o t to be u n d erv alu e d . One m ay a s well r u n a m ach in e w ith o u t lu b ric a n t a s to h an d le h u m a n ity w ith o u t m orale.
Oc tober 15, 1 9 2 5 C O A L A G E 521
Face Conveyors Work Better in Longwall Mining Than with Half-V Plan at Sweetwater
C
O N V E Y O R H A U L A G E of coal fro m face to e n try is g e ttin g an in te r e s tin g t r ia l in th e S w e e tw a te r m ine o f th e G unn-Q uealy Coal Co., in W yom ing.F o r a y e a r conveyors h av e been used u n d e r sev eral e x p e rim e n ta l sy ste m s, g e ttin g 100-per c en t ex tra c tio n . A m odification of th e V sy ste m w as tr ie d first, and lately, a plan of longw ell m in in g . R oof tro u b le s, h a n d i
capped the. first schem e because th e h a lf-V ’s could n o t be w orked f a s t enough. T he longw all m ethod, how ever, cleared up ro o f difficulty because of g r e a te r concen
tr a tio n of m in in g and s w if te r p ro g re ss. A b o u t 10 p e r c e n t o f each fa ll is sh o t d ire c tly onto th e conveyors, th u s le ssen in g h a n d w ork. T he com pany is s till p e rfe c t
in g its sy ste m . Glenn A. K nox, s u p e rin te n d e n t o f th e com pany’s o p e ra tio n s, a t th e la s t m e e tin g of th e Rocky M o u n tain Coal M in in g I n s titu te d escrib ed h is e x p e ri
m e n ts th u s :
“ T h e coal in th is m in e h a s a n a v e ra g e th ic k n e ss of 6 f t., 3 in., and lies on an a v e ra g e p itc h of 5 deg. The ro o f is a san d y shale o f m edium h a rd n e ss and h a s been g e n e ra lly c o n sid ered a s good to p f o r th e room and p illa r m eth o d of m in in g .
“W hen o u r com pany becam e in te re ste d in conveyors, I v isite d m o st of th e m in es in th e E a s t w h ere conveyors an d o th e r m ethods of m echanical m in in g a re in use, and decided t h a t a m odification o f th e V -system in use a t th e N o rto n , W. V a., m in e w ould be th e m o st fea sib le f o r o u r conditions. W e in sta lle d 300 f t. of conveyor a s an e x p e rim e n t to see w h e th e r o u r ro o f could b e handled on long faces. T h is 300 f t . w as in sta lle d a s tw o se p a r a te conveyors, one a s a fa c e conveyor 100 f t. long, th e o th e r as a h e a d in g conveyor d e liv e rin g coal in to m ine c a rs on th e m ain e n try .
T h e h ea d p iece sh o w s S w e e tw a te r v illa g e , so u th o f R o ck S p rin g s, W y o ., w h ere c o n v ey o r h is to r y Is b e in g m ade. T h e c o a l c o m e s to th e tip p le b y a lo n g e n d le ss rope, w h ere it is lift e d b y a n ap ron co n v e y o r to th e r e q u isite lo a d in g h e ig h t. F o r u se a t t h is m ine th e su p e r in te n d e n t, Glejjn K n o x , In v en ted th e b o x -c a r load er w h ic h g o es b y h is n a m e. I t w a s d esc rib ed in C oal A g e , J u ly 2, 1925, p a g e 17. T h is lo a d er is a n o rd in a ry p ic k in g a n d lo a d in g boom ly in g b e tw e e n th e r a ilr o a d tr a c k s w h ic h ca n d e liv e r to open ca rs, if n e c e s sa r y , or to a n o th e r b oom r e s tin g b etw e e n th e tr a c k s a n d so d e sig n e d th a t it ca n in tu rn d e liv e r th e co a l th r o u g h the open door o f a b o x c a r in to th e h op p er o f a b o x -c a r lo a d er w h ich d u ly d e liv e r s th e co a l on th e ca r floor.
“T h is face, show n a t A in th e accom panying d ra w ing, w as w orked d ire c tly on th e s trik e a n d dow n th e pitch. T h is did n o t prove to be a success as th e cav in g o f th e ro o f c a rrie d over to th e w o rk in g fa ce an d neces
sita te d p ro p p in g betw een th e conveyor an d th e face. I t w as also n ece ssary to shovel coal onto th e conveyor up th e p itch . A f te r w o rk in g th is fa c e f o r 200 f t. w e in stalled tw o conveyors a t a place a d jo in in g th e w orked- o u t block, b u t on a h a lf V -shaped face a s show n a t B on th e d raw in g . T h is block of coal w as 60 ft. w ide.
T h is m ethod p roved to be successful. W e c u t a place, moved th e conveyor a g a in s t th e face b e fo re sh o o tin g an d c a rrie d tw o row s o f c rib s betw een th e conveyor and th e cave. T he ro o f w as caved ev ery second cut.
“ A f te r w o rk in g o u t th is block we w ere satisfied th a t th is system w as fe a sib le f o r o u r m ine. W e th e n o rd ered 1,200 ft. m ore conveyor o f th e sam e ty p e as th e t r ia l section w ith a few m odifications. W e th e n in sta lle d th is 1,500-ft. u n it on th e f o u r faces, C, D , E a n d F on th e sketch, w ith a p p ro x im a te ly 100 f t. to each face, 200 ft. on each h e a d in g and 300 f t. on th e m a in con
veyor lines t h a t d eliv ered th e coal in to th e p it c a rs a t th e p o in ts G an d H . W e also h ad a h e a d sectio n a n d a r e a r section f o r each o f th e f o u r a d v a n c in g places show n.
“As sections w ere ta k e n o u t of th e h e a d in g conveyors th e y w ere in sta lle d on th e face conveyors, and, w hen th e faces ap p ro ach ed it, th e m a in conveyor w as ta k e n o u t and in stalled in th e n e x t u p h ill o r m ain-conveyor place.
T he ro o f caved very w ell in th e s tr a ig h t line o f th e p o in ts a n d w as b ro k en a b o u t ev ery 20 f t . W e encoun
te re d no tro u b le unless we p e r m itte d one o f th e p o in ts to g e t behind.
“T h e m a x im u m possible p ro d u c tio n by th is m ethod w as e stim a te d a t 725 to n s a day, a ssu m in g t h a t all places w ere c u t a n d cleaned up in one s h ift, a n d th is we a tta in e d f o r sev eral consecutive days.
“W hile th is w as a success fro m a cost sta n d p o in t, w e f e lt t h a t we could g e t a g r e a te r to n n a g e fro m th e sam e le n g th of conveyor i f w e chan g ed oyer to a longw all m ethod, u sin g one face 250 f t. long w ith n o t m o re th a n
522 C O A L A G E V o l . 28, No. 16
Conveyor-
Conveyor
Mine Workings Where Sectional Conveyors Are Being Tried
T r ia ls w ere first con d u cted on a S m all fu lly . A cco r d in g ly , m ore co n v e y o r w a s ou t, a ll bu t so m e s m a ll stu m p s, an d a lo n g - sc a le to t e s t roof a c tio n . A fte r w o r k in g tw o procured an d m in in g w ith it sta r te d on a w a ll f a c e w a s t.ried a t J. A t p resen t a p la ces sh o w n a t A an d B it w a s b eliev ed fa r m ore a m b itio u s sc a le , fo u r fa c e s , C, D , lo n g w a ll fa c e is b e in g w ork ed a t M an d th a t th e roof cou ld be con tro lled s u c c e ss - E an d F b e in g w ork ed . T h e se w ere w o rk ed a n o th e r s im ila r fa c e m ad e rea d y a t N .
day f o r th e p a s t m o n th an d th e m ine h a s w orked every d ay except S u n d ay s. One long face w ith n ec essary developm ent w o rk o p e ra te d every d ay h a s yielded enough coal to ta k e c a re of o u r b u sin ess.
“ I t is m y o p in io n t h a t th is m eth o d o f m in in g should be k e p t g o in g ev ery day if possible. I f it is p e rm itte d to s ta n d s till f o r a few days th e ro o f w ill g ra d u a lly s e ttle an d b re a k along th e face. T h is is tr u e also o f th e h a lf-V m ethod. W e d id n o t g e t along well by w o rk in g it only tw o or th re e days a w eek. T he longw all sy stem is a m ore flexible p ro p o sitio n , f o r e ith e r one o r m ore faces, as th e m a rk e t m ay d ic ta te , can be w ork ed con
tin u o u sly .
“ W e h av e 1,000 f t . of conveyor te m p o ra rily o u t of use w hile i t is b ein g in stalled in tw o o th e r places, one of w hich is show n on th e sk etch a t N .
“W e firs t b eg an p ro d u c in g coal fro m th e tr ia l con
v eyor on S ept. 6, 1924. Since th a t tim e we have p ro duced a to ta l of 64,804 to n s w ith o u t h u r tin g a m an.
T h e recovery h a s been 100 p e r cent, as we hav e av er-
Apron Conveyor Brings Coal to Required Elevation
R e tu r n in g run ca n be se e n b e n e a th th e c o n v e y in g run. A ll s iz e s a re ca r r ie d ui> to g e th e r rea d y fo r s iz in g on th e tipple.
Tipple and Screen House a t Sw eetw ater
Coal is dum ped o v e r a n en d dum p o n to a b u c k e t con v ey o r.
M a n y o f th e c a r s n ow h a v e en d a n d sid e p la te s, so th a t th e to n n a g e th e y w ill c a r r y w h e n m a c h in e -lo a d e d is in c r e a se d 33 per c e n t or from 3,000 to 4,000 lb.
500 f t. o f conveyor in use. W e have been w o rk in g on th is p lan f o r th e p a s t fo u r m onths.
“ W e s ta r te d th is m eth o d a t th e p o in t J, an d tr ie d to keep th e cave fro m 20 to 25 f t . fro m th e face. T h is did n o t prove to be a success a n d a f t e r w e h a d gone only a b o u t 50 f t. th e ro o f ro d e over th e c rib s to th e face, fo rc in g us to a b a n d o n it. W e th e n in sta lle d tw o fa c e conveyors o f 250 ft. each in th e place m a rk e d K , one fa c e w o rk in g o u t to L w h e re som e coal h a d to be a b a n doned a n d th e o th e r m o v in g in th e o pposite d ire c tio n to M . W e ad o p ted th e p lan o f ca v in g th e ro o f every second c u t an d hav e been w o rk in g on t h a t p la n ever since w ith good success w ith th e roof.
“W e s e t a row o f b re a k e rs w ith p ro p s 8 in. o r la r g e r in d ia m e te r, a b o u t 18 in. a p a r t in a s tr a ig h t lin e th e e n tire le n g th o f th e face. C rib s m ade o f re je c te d r a il
ro a d tie s w ere placed a b o u t 15 f t. a p a r t th e e n tire le n g th o f th e face. T h is g iv es us a c rib 2 f t. 8 in.
squai-e. T h ese c rib s a re s e t on a b o u t 6 in. o f b u g d u st.
I t is seldom t h a t th e y ta k e any w eig h t. T hey a re used only w hen some u n u su a l co n d itio n causes th e ro o f to rid e ov er th e p ro p s to th e face. In such cases th e y a re em ployed only to p ro te c t th e m a c h in e ry a n d m en. W e have p roduced an a v e ra g e o f 359 to n s ev ery w o rk in g
Oc t o b e r 1 5, 1 9 2 5 C O A L A G E 523
The Tipple Has Four Load Tracks at the Sweetwater Mine
T h e p rin cip a l com m e rcia l siz e s in th e R ock S p rin g s a r e a are 8-in. lum p, 8-in. m in e run ( a ll b elo w 8 in .) ; 5-in. or 3 -in . lum p c o a l; 5 x 3-in. s to v e co a l, 5 x l i - i n . and a 3 x l i - i n . nut coal : l i - i n . sla c k an d l i x i- in .
p e a c o a l or p rep ared sla c k an d 3 x 0 d u st. T h e d u st g o e s to sm e lte r s.
ag ed betw een 1,600 and 1,700 to n s p e r fo o t p e r acre.
T he expense of m a in ta in in g th e se conveyors h a s been p ra c tic a lly n o th in g .
“E a c h face, h e a d in g an d ad v an cin g conveyor is ru n a t a speed o f 30 f t. p e r m in u te a n d d riv e n w ith a 15-hp., h ig h -s ta rtin g -to rq u e ty p e m otor, th e speed of w h ich is 900 r.p.m . T h e speed is c u t down by a rig h t-a n g le speed red u cer. T h e m a in conveyor, w hen used on th e h alf-V m ethod, w as d riv e n a t a speed o f 90 f t . p e r m in u te a n d w ith a 50-hp. m o to r of th e sam e ty p e. T he conveyors a re m ade u p of 6-ft. sections an d all sections in h ea d in g , fa c e and m a in conveyors a re of one type an d a r e in te rc h a n g e a b le .
“ In sh o o tin g a lo n g face , w e b eg in a t th e u p p e r end.
T he holes a r e placed 10 ft. a p a r t and we th e n s t a r t th e conveyor a n d fire th e sh o ts one m in u te a p a rt, k e e p in g th e conveyor ru n n in g continuously. W e find th is p ra c tic e to be h ig h ly s a tis fa c to ry . W hen w o rk in g it on th e
Freak R esults fro m a H igh-T ension G round in Illin ois
T h e acco m p an y in g illu s tra tio n show s th e re s u lt of one p h a se of a h ig h -te n sio n lin e com in g in co n tact w ith th e g ro u n d . D u rin g a th u n d e r sto rm in A u g u st, 1923, one w ire of th e 33,000-volt p o w er line ex te n d in g b etw een m in es N os. 11 and 16 o f th e Old B en Coal C o rp o ra tio n , lo cated a t C h ris to p h e r a n d S esser, 111., re sp e c tiv e ly b ro k e a t a n in su la to r* a llo w in g b o th ends to fa ll to th e g ro u n d . T h e c u r r e n t seem ed to p a ss fro m th e end of one w ire th ro u g h th e e a r th to th e end of th e o th e r a n d th en c e on th ro u g h th e line.
A t se v era l p o in ts each of th e fa lle n w ire s r e s te d on sm all tr e e stu m p s t h a t th u s fo rm e d a connection b etw een th e m a n d th e g ro u n d . T h ese stu m p s p ro ceeded to b u rn o u t an d th e p e c u lia r fo rm a tio n h e re show n w as th e re s u lt of th e sa n d an d soil f u s in g a t its c o n ta c t w ith th e stu m p ro o ts. A s f a r as th is fu se d fo rm a tio n ex ten d ed in to th e e a r th th e ro o ts w ere com ple tely b u rn e d aw ay. Below th is p o in t th e wood w as b ad ly c h a rre d w hile s till f a r t h e r dow n i t ap p e a re d to be little h a rm e d , r e ta in in g its w oody c h a ra c te ris tic s .
T h e m a te ria l o f w hich th is fo rm a tio n is com posed is a n im p u re g la ss o r sla g so m ew h at re se m b lin g th e f u lg u r ite s so m etim es fo rm e d w h e re lig h tn in g s trik e s in san d . T h e soil, do u b tless, a c te d a s a flux f o r th e sa n d i t co n tain ed th u s a s s is tin g th e f u s in g process.
h a lf-V sy stem , w e sh o t th e coal dow n onto th e con
veyor th e fu ll le n g th o f th e 100-ft. face w hile th e con
veyor w as s ta n d in g still. W e h ad no tro u b le in s ta r tin g th e conveyor w ith th is load. U n d e r o u r p re s e n t long- w all plan a p p ro x im a te ly 10 p e r cen t o f th e c u t is loaded o u t w ith o u t b e in g h an d led w ith shovels. T h e conveyor is placed d ire c tly a g a in s t th e face b e fo re sho o tin g .
“T he conveyor now in u se is c o n stru c te d along r a th e r heavy lines and w ill w ith s ta n d a reaso n ab le fall. W e never have dam aged a section by sh o o tin g th e coal onto it. W e a re w o rk in g th is sy stem u n d e r 500 ft. of cover.
T he su rfa c e h as show n no d isp lacem en t o r sig n of s e ttlin g .
“I do n o t believe th e p e rc e n ta g e o f th e d iffe re n t g ra d e s o f coal p roduced by o u r v a rio u s m eth o d s v a rie d m uch, as th e a d v a n ta g e in sh o o tin g o r w o rk in g th e long faces is overcom e by th e b re a k a g e in h a n d lin g it w ith th e conveyors.”
In c id en tally , a f t e r th e sto rm w as over a n d th e line w as b ein g re p a ire d , a n opossum w as fo u n d dead b e tw een th e p o in ts w h e re th e w ire s touched th e g ro u n d . To all ap p e a ra n ce s, b e in g in ex p erien ced in th e m a n ip u la tio n o f h ig h -te n sio n tra n s m is s io n lin es, h e cam e o u t to in v e s tig a te w h a t all th e fu s s w as ab o u t. A nd, like th e in q u isitiv e dog who once sm elled o f a th ir d ra il, he “g o t a nose fu ll of in fo rm a tio n ;”
" “Juices” Wild Did This
W h en a h ig h - te n sio n p o w er lin e broke, e a ch end fe ll on a little tree stu m p . T h e cu r- r e n t a p p a r e n tly p a sse d th r o u g h th e g ro u n d fro m stu m p to stu m p fo r a p eriod u n til pow er w a s s h u t off. E ach stu m p w ith m o st o f it s r o o t s w a s b urned o u t and sa n d in th e so il w a s m elted in to s tr a n g e s h a p e s su c h a s th is, the d irt a c tin g a s a
flux.
524 C O A L A G E "VOL. 28, NO. 16
A lth o u g h th e h o is t is o p era ted in b a la n c e th e h o r s e p o w er req u ired is la r g e . T h e d ep th o f th e s h a f t is 989 ft.
a n d th e m a x im u m dru m sp ee d 60.5 r.p.m .
Large Electric Hoist Has Air-Operated Contactors
2 0 0 0
S y ste m o f C ontrol I s S im ilar to th a t U se d in R ailroad E lectrifica tio n
— S w itc h e s A re C lo sed b y C o m p ressed A ir A c tin g A g a in s t a P o w e r fu l O p en in g S p rin g — H a s C o m p lete S e t of P r o te c tiv e D e v ic e s
B y J. E . B orlan d
G en era l E n g in e e r , W e s tin g h o u se E le c tr ic an d M a n u fa c tu r in g Co., E a s t P ittsb u r g h , P a .
F
OR M A N Y Y E A R S e lectric d riv e h a s been g e n e ra lly recognized a s th e m o st s a tis fa c to ry and econom ical m eth o d of o p e ra tio n f o r m in e h o ists, a n d th e re a re now h u n d re d s of electrically d riv e n h o ists o f ' all c a p acities in service. F o r new in s ta lla tio n s th e electric d riv e h as becom e m o st com m on a n d m a n y e x istin g ste a m h o is ts have been a d v a n ta g e o u sly rem odeled to use e lectric pow er. I t is only u n d e r ex ceptional condi
tio n s t h a t a n y a d v a n ta g e can be fo u n d fo r o th e r possible fo rm s of drive.
T h is g e n e ra l use of electric h o ists h a s been b r o u g h t about- la rg e ly th ro u g h th e ex ten sio n o f p o w e r service, a n d th e re s u ltin g w id esp rea d use of e lec tric po w er in th e m in in g in d u s try . Im p ro v em en ts in m eth o d s o f con
tro l, also, hav e c o n trib u te d g re a tly to w a rd th e p re v alence of electric o p e ra tio n of h o ists.
T he th re e g e n e ra l sy ste m s o f e le ctric h o is tin g a r e : (1 ) th e w o u n d -ro to r in d u c tio n m o to r w ith rh e o s ta tic control. (2 ) T h e d ire c t-c u rre n t m o to r w ith v a ria b le vo ltag e co n tro l a n d supplied by a sy n ch ro n o u s m o to r- g e n e ra to r set. (3 ) T he d ire c t-c u rre n t m o to r w ith v a ria b le v o ltag e co n tro l and supplied b y an in d u ctio n m o to r-g e n e ra to r s e t p ro v id ed w ith a flywheel fo r load equalization.
T h e in d u c tio n m o to r w ith rh e o s ta tic co n tro l is th e sim p le st ty p e o f eq u ip m e n t fo r a n e le ctric m in e h o ist, an d u n d e r o rd in a ry c o n d itio n s th e m o st econom ical in o p e ratio n . M ag n etic co n tro l e q u ip m en t h a s p ro v ed su c
c essfu l in th e c a p a c ities f o r w h ich i t h a s been developed.
F o r la rg e m o to rs, how ever, v a ria b le v o ltag e control,
F ig. 2—Pedestal Type H oist Motor
T h e s h a f t o f th e ro to r ig m ad e lo n g so th a t in sp e c tio n o f th e rotor or s ta to r w in d in g ca n be m a d e r e a d ily b y m o v in g th e sta to r in a n e n d w ise d irectio n .
w ith th e added expense of a m o to r-g e n e ra to r set, o ften h a s been co nsidered n ece ssa ry because o f th e m a g n itu d e of th e m a in c u rre n ts , even th o u g h o th e r con d itio n s fa v o re d th e use o f an in d u c tio n m o to r. Such co n d itio n s w ill g e n e ra lly be fo u n d w ith la rg e c a p a c ity h o is tin g cycles w ith a h eav y load p e r t r ip fro m a deep level.
In such cases th e a c c e le ra tin g an d r e ta r d in g p e rio d s a re a c o m p a rativ ely sm all p a r t of th e to ta l h o is tin g cycle. On h o is ts o f th is c h ra c te r, m o to r r a tin g s o f fro m 1,000 hp. to 2,000 hp. o fte n a r e re q u ire d , an d con
ta c to rs o f h ig h ca p a c ity a re n e c e ssa ry i f th e m a in m o to r c u r re n ts a re to be controlled d irectly .
A novel and in te r e s tin g ap p lic atio n of co n tro l f o r a la rg e m in e h o ist is th e eq u ip m en t re c e n tly in sta lle d a t S h a f t No. 4 of th e L e h ig h Coal a n d N a v ig a tio n Co.
T he d u ty cycle .upon w hich th e ca p a c ity of th e electrical eq u ip m en t w as based is show n by F ig . 1.
F o r th is serv ice a w o u n d -ro to r in d u c tio n m o to r h a v in g a c o n tin u o u s 40-deg. C. r a tin g o f 1,200 hp., 3 00/293 r.p.m . w as selected to o p e ra te fro m a 2,200-volt, th re e - phase, 25-cycle pow er supply. T h e m o to r is o f th e p ed estal b e a rin g ty p e, s im ila r to t h a t show n in F ig . 2.
an d w as su p p lied w ith tw o p e d estal b e a rin g s b u t w ith o u t b a se ; b e in g m o u n ted on an ex ten sio n of th e h o ist bedplate. T he fra m e of th is m o to r is a sin g le c a s tin g and p ro v isio n is m ade f o r s h if tin g i t in a d ire c tio n p arallel to th e s h a f t a sufficient d istan ce to u ncover th e ro to r w in d in g and fa c ilita te in sp ectio n o r re p a ir. T he m o to r is p ro v id ed w ith a s h a f t e x ten sio n w h ich is con
nected th r o u g h a flexible co upling to th e p in io n s h a f t o f th e h o ist.
T h is in s ta lla tio n is of in te r e s t m a in ly in th e ap p lica
tio n o f th e e le c tro -p n eu m atic sy ste m of c o n tro l f o r th e 1,200-hp. in d u c tio n m o to r. E le c tro -p n e u m atic co n tro l h a s been used f o r m an y y e a rs on h eav y tra c tio n , s tr e e t ra ilw a y an d su b w ay service, an d h as g ain ed h ig h re p u ta tio n th ro u g h its s tro n g c o n stru c tio n , p o sitiv e o p e ra -
October 1 5 , 1 9 2 5 C O A L A G E 5 2 5 tio n a n d low m a in te n a n c e . T h is ty p e of e q u ip m e n t is
well a d a p te d to co n tro l o f la rg e in d u c tio n m o to rs on heav y -d u ty service.
T h e m a in c irc u it sw itch es o f th e h o is t c o n tro lle r a r e electro -p n eu m atically o p era ted , each sw itch b e in g closed in d iv id u a lly by a ir p re s s u re a c tin g on a p is to n opposed by a p o w erfu l' sp rin g . C om pressed a i r is a d m itte d to a n d ex h a u ste d fro m th e sw itc h cy lin d e rs th r o u g h elec
tric a lly o p e ra te d valves w h ich a re g o v ern e d by th e m a s te r c o n tro lle r in c o n ju n c tio n w ith a u to m a tic c u rre n t lim itin g and p ro te c tiv e rela y s. S tr o n g fo rc e s a re ex
e rte d w h ich in s u re p o sitiv e a n d ra p id ac tio n of th e sw itch, w ith a quick b re a k on o p en in g a n d heav y c o n ta c t p re s s u re in th e closed p o sitio n . T h e m o vem ent o f th e
C ontrol circu its D.C. A.Ç.
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Fig. 3— Control W iring Is Simplified
M an y fe a tu r e s d e sig n e d to m a k e p o ssib le s a f e a n d q u ick con trol o f th e h o is t h a v e b een in co rp o ra ted h ere. A c c e le r a tin g r e la y s, lim it s w itc h e s , oversp eed r e la y s a n d o th e r n e c e ssa r y d e v ic e s w h ic h h a v e m a d e e le c tr ic h o ists so efficien t a n d s a f e h a v e a lso b een in clu d ed in t h e co n tro l sy s te m .
sw itch co n ta c ts is such t h a t a rc in g occurs m a in ly on th e tip s o f th e co n ta c ts a n d on th e a rc in g h o rn s, th u s leav in g th e c u r r e n t- c a r r y in g su rfa c e s re la tiv e ly sm ooth a n d clean.
T h e m a in co n tro l c irc u it p ro v id in g e x c ita tio n fo r th e m a g n e t valves o f th e m a in sw itch es is ta k e n fro m a s e p a ra te source o f d ire c t- c u rre n t e n e rg y a t low v o lt
age. T h e m a g n e t valves a re sm all an d th e po w er con
sum ed is n eg lig ib le. O p e ra tio n o f th e e lectro -p n eu m atic sw itc h es is e n tire ly in d e p e n d e n t o f an y v a ria tio n of vo ltag e on th e m a in a lte r n a tin g - c u r r e n t line, a n d re li
able o p e ra tio n is o b ta in e d over a w ide ra n g e in a ir p re ssu re .
E a c h e le c tro -p n eu m atic sw itc h is a u n it in itse lf, and m ay be rem oved in d e p en d e n tly fro m th e s u p p o rtin g
Fig. 5—A rc Chute Removed from P rim ary Switch
L o n g tr o u g h s m a d e o f in su la tin g m a te r ia l h old th e a r c from d a m a g in g a d ja c e n t p a r ts or o th e r s w itc h e s an d y e t c a u se th e a r c to b rea k q u ick ly .
s tr u c tu r e w ith o u t d is tu rb in g a d ja c e n t u n its . All p a rt3 su b je c t to w e a r a re located so as to be re a d ily accessible f o r in sp ectio n o r rep lacem en t.
F o r re v e rsin g th e d ire c tio n o f ro ta tio n o f th e h o ist m o to r six p rim a r y u n it sw itc h e s a r e used. T h e d e tailed c o n stru c tio n of th e se sw itch es is show n in F ig . 4. E a c h p rim a ry sw itch h a s a r a tin g o f 500 am p. an d is in su la te d f o r 3,000-volt service. A c o rre c tly p ro p o rtio n e d blow o u t coil, pole pieces an d a rc in g h o rn s on each sw itch in su re p o sitiv e r u p tu r in g o f th e arc. E a c h sw itc h is equipped w ith an a rc in g c h u te o f h e a t- re s is tin g m a te ria l in w hich th e a rc s a re ex tin g u ish e d .
T he p rim a ry re v e rs in g sw itch es a re m o unted in a s u b s ta n tia l s tr u c tu r a l steel fra m e w o rk as sh o w n by F ig . 6. T he six sw itch es a re a r ra n g e d in th r e e tw o-pole elem ents, th e tw o u n its o f each elem ent b ein g m ech an ically connected to g e th e r so a s to o p e ra te sim u lta neously. One two-pole elem ent is closed a t every o p era-
F IG . 4
Electro-Pneum atic Switch
N o r m a l l y th e sw itc h is h eld open b y m e a n s o f a sp r in g an d is clo sed b y c o m p ressed a ir p ressu re. T h e p r i
m a r y sw itc h is p r o v id e d w i t h a rc c h u te s an d b lo w o u t co ils.
526 C O A L A G E Vol. 28, No. 16
Figs. 6 and 7—P rim ary Reversing Switches
Thf -s illu str a tio n s c le a r ly sh o w h o w th e h ig h v o lta g e s w itc h e s a r e grou p ed an d p rotected . A n a ir p ipe e x te n d in g u n d ern ea th th e sw itc h e s c o n n e c ts to th e a ir cy lin d e r w h ic h c lo s e s th e p o w er circu its.
tio n w hile th e o th e r tw o elem en ts a re used to re v e rse one p h ase of th e p rim a ry , and a re closed a lte rn a te ly , fo r th e tw o d ire c tio n s o f ro ta tio n .
A s tro n g m echanical in te rlo c k is p ro v id ed betw een th e tw o tw o-pole sw itch elem en ts used f o r re v e rsin g , an d in a d d itio n a sy ste m of elec trical in te rlo c k in g is used as show n by th e co n tro lle r d iagram .' T h is con
s is ts e sse n tia lly o f tw o sm all tra n s f o r m e r s h a v in g th e ir h ig h -v o lta g e w in d in g s connected a c ro ss one p h a se of th e p r im a r y c irc u its, betw een th e re v e rs in g sw itch es an d th e m otor, and th e low -voltage w in d in g s connected to th e o p e ra tin g coils o f tw o n o rm ally closed re la y s d e sig n a te d as N os. 30 and 31 in th e d ia g ra m . T he n o rm ally closed re la y co n ta c ts a re connected in se rie s w ith th e o p e ra tin g coils o f th e re v e rs in g sw itch e s, so t h a t if a n a rc te n d s to h a n g on a f t e r o p en in g of a p rim a ry sw itch , th e re lay s re m a in en erg iz ed a s lo n g as p o te n tia l e x ists on t h e ir coils, and as th e re la y c o n tacts a re held open u n d e r th is co n d itio n th e co n tro l c irc u it to th e re v e rs in g co n ta c to rs is b ro k en . T h ese fe a tu re s effectively p re v e n t th e closing o f one s e t o f re v e rs in g c o n ta c to rs u n til th e opposite se t h a s opened an d th e a rc h a s been com pletely e x tin g u ish ed .
Special inclosing covers a re used on th e p r im a r y sw itc h g ro u p to muffle th e noise w hich is c h a ra c te ris tic of all h ig h -v o ltag e a ir-b re a k co n ta c to rs. T he a p p e a r
an c e of th e p rim a ry sw itc h s tr u c tu r e w ith covers in place is show n by F ig . 7.
T w e n ty -fo u r u n it sw itch es a re p ro v id ed f o r accelera
tio n of th e m o to r by s h o rt c irc u itin g sectio n s o f g r id r e s is to r connected in th e ro to r c irc u its. T h ese sw itch es a re of th e sam e g e n era l c o n stru c tio n a s th e p rim a ry sw itches, b u t a re in su la te d f o r 1,500 volts a n d a re fu rn is h e d w ith a rc c h u tes only, blow out coils b e in g u n n ec essa ry , as th e sw itch es do n o t open th e c irc u it. E ac h seco n d ary sw itch h a s a r a tin g of 800 am p., a n d a s th e sw itch es, in g ro u p s o f th re e , a r e connected in d elta on each step , a n effective cap a c ity of 1,200 am p. is o b tain ed . E ig h t ste p s of re s is ta n c e a re used.
T he seco n d ary sw itch es a re assem bled in th r e e s tr u c t u r a l steel fra m e s as illu s tra te d b y F ig . 8. In clo sin g covers a re n o t re q u ire d w ith th e se sw itch es as th e only noise a tte n d in g th e ir o p e ra tio n is th e escape of a ir fro m th e c y lin d e rs upon opening.
O p eratio n of th e h o ist is controlled by m e an s of a sm all re v e rs in g m a s te r c o n tro lle r m o u n ted on th e o p e ra t o r ’s p la tfo rm . B y m a n ip u la tio n of th is m a s te r con
tro lle r th e closing of th e m a in p rim a ry a n d seco n d ary sw itch es is controlled u n d e r th e a u to m a tic p ro te c tio n o f th e in te rlo c k in g an d c u rr e n t-lim itin g f e a tu r e s p r e viously described. T h e m o to r is th u s rev ersed , acceler
ate d in e ith e r d irectio n , r e ta r d e d or stopped, a n d w hen o p e ra tin g u n d e r load a c c u ra te co n tro l is re a d ily obtain ed .
A s in d ic a te d on th e d ia g ra m o f connections, th e m a g n e t valves of th e m a in sw itch es a re en e rg iz e d by successive p o in ts of th e m a s te r c o n tro ller, closing of th e seco n d ary sw itch es b e in g a u to m a tic a lly con tro lled by a c u r re n t- lim it a c c e le ra tin g relay , th e co n ta c ts of w hich a re connected in s e rie s "with th e m a g n e t valves o f each ste p of seco n d ary sw itch es b y in te rlo c k in g con
ta c ts on th e p re c e d in g step . T h is re la y is a d ju s te d to hold its co n tacts open u n til th e c u r r e n t h a s d ecreased to a p re d e te rm in e d value, so th a t if th e m a s te r c o n tro ller h an d le is m oved too ra p id ly th e h o ist is a u to m a tic a lly a c c elerated a t th e p ro p e r ra te , th e re la y d elay in g th e closing of successive seco n d ary sw itch es u n til th e c u r
r e n t h a s decreased to th e d e sire d value.
To p e r m it s ta r tin g th e h o is t u n d e r exceptionally heav y loads w ith o u t c h a n g in g th e s e ttin g o f th e ac
c e le ra tin g relay , a fo o t-o p e ra te d sw itc h is located on th e o p e ra to r’s p la tfo rm . C losing of th e sw itch s h o rt c irc u its th e re la y c o n ta c ts so as to p e r m it closing o f th e p ro p e r seco n d ary sw itch es to o b ta in th e m ax im u m m o to r to rq u e a t s ta r tin g .
T he 2,200-volt incom ing lin e to th e h o is t eq u ip m en t is b ro u g h t th ro u g h d isco n n ectin g sw itch es to a sw itc h b o a rd panel o f s ta n d a rd c o n stru c tio n c o n s is tin g of th re e sla te b ases w ith black m a rin e finish su p p o rte d on 92-in.
p ip e fra m e w o rk w ith a c h an n el-iro n sill. T he p a n e l is pro v id ed w ith a cov erp late an d o p e ra tin g h a n d le f o r a
Oc t o b e r 15, 1925 C O A L A G E 527 m a n u a lly o p e ra te d rem o te controlled oil c irc u it b re a k e r,
w hich is m o u n ted on th e w all a t th e re a r. T h e oil c irc u it b re a k e r is ra te d 500 am p., 7,500 volts, three-'pole, sin g le th ro w .
O verload p ro te c tio n of th e h o ist e q u ip m en t is p ro vided by tw o tr a n s f o r m e r t r ip coils on th e oil c irc u it b re a k e r coverplate, a n d in v e rse tim e lim it a tta c h m e n ts a re used to p re v e n t th e c irc u it b re a k e r fro m open in g on h ig h overloads of s h o r t d u ra tio n re q u ire d to ac
ce le ra te exceptionally heavy loads. T he c irc u it b re a k e r is a rra n g e d to open also in case o f low voltage. T he sw itc h b o a rd is pro v id ed w ith a poly p h ase w a tth o u r m e te r sh o w in g th e pow er co n su m p tio n o f th e h o ist.
A sim ple schem e o f co n tro l connections is used and th e u su al s a fe ty fe a tu re s a re re a d ily included. F o r p ro te c tio n of th e h o ist eq u ip m en t in case o f pow er fa ilu re , a double-pole a lte r n a tin g - c u r r e n t low -voltage re la y is provided, one pole b ein g w ire d in se rie s w ith th e d ire c t-c u rre n t co n tro l c irc u it an d th e o th e r pole in s e rie s w ith th e b ra k e hook m a g n e t so t h a t opening o f th e re la y cau ses all m a in co n tro l sw itch es to be de-energized and th e b ra k e set. A re s e t c o n ta c t on th e m a s te r co n tro lle r is so connected to th is a n d th e d ire c t- c u r r e n t low -voltage re la y th a t th e m a s te r co n tro lle r m u s t be re tu rn e d to th e “ off” p o sitio n b e fo re o p e ra tio n can be resu m ed , follow ing a fa ilu re of pow er. T h is p re v e n ts an ac cid e n tal s t a r t of th e h o is t upon r e tu r n of po w er as th e m a s te r co n tro ller m u st be in th e “off”
p o sitio n to reclose th e low -voltage relays.
Sa f e t y De v i c e Pr e v e n t s Ov e r s p e e d
P ro te c tio n a g a in s t overspeed o r o v e rtra v e l a t th e h o is tin g lim its is fu rn is h e d by a s a fe ty device d riv en fro m th e h o is t d ru m . C o n tacts o f th is device a r e con
necte d in th e a lte r n a tin g - c u r r e n t low -voltage re la y c ir
c u it so t h a t o p en in g of an y s a fe ty c o n ta c t w ill sto p th e h o ist. A sm all d ru m “ b ack -o u t” sw itch is used to p e rm it o p e ra tio n o f th e h o is t in th e re v e rse d ire c tio n only, in case o f o v e rtra v e l a n d o p ening of a n y o f th e lim it sw itch contacts.
A p ro te c tiv e re la y is used to p re v e n t o p e ra tio n of th e h o ist c o n tro lle r if th e a ir p re s s u re should fa ll below th e low est p o in t in th e d esira b le ra n g e of p re s s u re fo r th e e le c tro -p n eu m a tic sw itch es. T h is p re v e n ts closing
of th e m ain sw itch es unless s tr o n g a ir p re s s u re is p re se n t, an d ob v iates th e p o ssib ility o f f a u lty o p e ra tio n u n d er insufficient closing forces.
A m eans of sto p p in g th e h o ist quickly in a n e m e r
gency is provided in a s a fe ty p u sh b u tto n m o u n ted on a panel on th e o p e ra to r’s p la tfo rm . T h is panel also c a rrie s s ta r tin g b u tto n s fo r th e e x c ite r s e t a n d a ir com pressor m otor, p re s s u re g a g es an d m e te rs in d ic a t
in g o p eratio n of th e h o ist eq uipm ent.
T he co n tro ller includes g rid re s is to rs d esig n ed fo r low to rq u e on th e firs t p o in t w ith p ro p e rly p ro p o rtio n e d a c c e lera tin g step s. R e sisto rs o f sufficient cap acity a re used to avoid undue h e a tin g d u rin g acce lera tio n or speed control of th e m ptor.
Ad v a n t a g e s o f Au t o m a t i c Co n t r o l
F ro m th e fo re g o in g d e sc rip tio n i t m ay be seen th a t electro -p n eu m atic control em bodies a n u m b e r of f e a tu r e s d esirab le in heavy d u ty service, r e lia b ility in o p e ra tio n and low m a in te n a n c e costs a re in su re d by th e use o f m ain control sw itch es, in terlo ck s an d a u x ilia ry p a r ts of s u b s ta n tia l co n stru c tio n , follow ing d esig n s t h a t have been proven u n d e r severe o p e ra tin g conditions.
O p eratio n of th e electro -p n eu m atic sw itch es is ra p id an d positive and is unaffected by o rd in a ry v a ria tio n s in line voltage. T he u n it sw itch es a re assem bled in com
p ac t g ro u p s su p p o rte d on steel fra m e w o rk . T h is fo rm of c o n stru c tio n leaves all p a r ts re a d ily accessible, and a t th e sam e tim e sim plifies in s ta lla tio n o f th e control eq uipm ent. O p eratio n o f th e electro -p n eu m atic sw itch es is q u iet, a s th e re a re no w e ig h ty m o v in g p a r ts . T he noise w hich accom panies th e b re a k in g o f a rc s of th e p rim a ry sw itches is c h a ra c te ris tic of all h ig h -v o ltag e c o n tacto rs and special covers a re pro v id ed on th e re v e rs in g sw itch g ro u p to muffle th is noise. W ith th is p ro vision bo th th e p rim a r y and th e seco n d ary sw itch g ro u p s m ay be located in th e h o ist room w hich avoids th e necessity of c o n stru c tin g a s e p a ra te c o n tro l room an d m ay re s u lt in a m a te ria l s a v in g in b u ild in g con
stru c tio n .
T he selection of th is ty p e o f co n tro l by th e e n g in e e rs of th e L eh ig h Coal & N a v ig a tio n Co. u n d o u b ted ly m a rk s a step fo rw a rd in th e p ra c tic e of c o n tro llin g la rg e induction m o to r m ine h o ists.
Figs. 8 and 9—Views of Secondary Contactors
T he illu str a tio n on th e r ig h t sh o w s a r ea r v ie w o f the se c o n d a r y sw itc h e s , w ith th e ir a ir c y lin d e r s. On th e le ft is a fr o n t v ie w o f th e sw itc h e s .
528 C O A L A G E Vol. 28, No. 16
Triple Shifting Makes Big Stripper Profitable
By Fran k H. K neelantl
A s so c ia te E d ito r, C o a l A g e N e w Y ork C ity
A B O U T F O U R M IL E S , as th e crow flies, n o r th e a s t fro m th e C o u rt H ouse in Boonville, Ind., lies -L A . a body o f coal lan d h a lf a m ile s q u a re w hich a ttr a c ts a tte n tio n because s tr ip p in g ta k e s place th e r e on a ,th r e e - s h if t b a sis th a t h a s re su lte d in m a rk e d econom y o f o p e ratio n . I t is th e S u n lig h t Coal Co.’s p la n t.
T h is is one of th e few coal o p e ra tio n s in s o u th e rn In d ia n a o r in th e M iddle W est, f o r t h a t m a tte r, th a t w orked re g u la rly six days p e r w eek m o st o f th e su m m e r. T h e b ig e le ctric shovel rem o v in g th e o v e rb u rd e n r u n s d ay an d n ig h t. T he sm all lo ad in g shovel, how ever, can load o u t as m uch coal in one s h if t a s th e s tr ip p e r can uncover in th re e .
Two fa c to rs a re m a in ly re sp o n sib le f o r th e o p e ra tin g econom y w hich h a s enabled th is s tr ip m in e to keep w o rk in g in a tim e w hen m o st n e ig h b o rin g p la n ts r a n p a rt-tim e o r n o t a t all. F ir s t, trip le s h if tin g keeps th e s tr ip p e r bu sy th ro u g h o u t th e e n tir e day, th u s c u t
tin g to o n e -th ird th e h o u rly o v erh ead c h a rg e e n tailed by th e co st o f th is m achine. Second, th e use of elec tric po w er g re a tly red u ces th e cost of lab o r n eces
s a r y f o r th is shovel’s o p e ratio n .
T he o v erb u rd e n s tr ip p e d in th is o p e ra tio n c o n sists of sa n d sto n e, shale, sla te an d su rfa c e soil. I t ra n g e s in th ic k n e ss fro m ap p ro x im a te ly 25 to 50 f t. T h e coal uncovered is fro m 6 to 74 f t. th ic k , is f r e e fro m p a r t in g s an d lies ap p ro x im a te ly level, t h a t is, w ith o u t a n y g e n e ra l dip.
To fa c ilita te th e o p e ra tio n o f th e s trip p e r, th e o v er
b u rd e n is d rille d w ith tw o g aso lin e an d one electric
c h u rn drills. S ix -in ch holes a r e p u t dow n to w ith in a b o u t 1 f t. of th e coal. E a c h of th e se is cleaned o u t a n d s lig h tly s p ru n g w ith one s tic k o f 4x8-in. 40-per c e n t d y n am ite. T hey a re th e n loaded w ith a b o u t equal w e ig h ts o f th is d y n a m ite an d F F black b la s tin g pow der, fro m 25 to 50 lb. o f each explosive b e in g u sed in each hole a c co rd in g to th e d e p th of o v e rb u rd e n en co u n tered . F ir in g is done w ith elec tric d e to n a to rs.
T he coal is d rille d by m ean s o f com pressed a i r an d sh o t w ith th e sam e g ra d e o f d y n a m ite a s th e o v er
b u rd e n . In th is case, how ever, th e stic k s o f explosive a re lx 8 -in . w h ile th e holes in to w h ic h th e y a re loaded a re 2 in. in d ia m e te r. A ir c u sh io n in g to som e e x te n t is th u s o b ta in e d a n d th e s h a tte r in g effect of th e explo
sive on th e coal is lessened acco rd in g ly . A f te r sh o o t
in g , th e coal is loaded d ire c t in to r a ilro a d c a rs b y a ste a m shovel fitte d w ith a d ip p e r of l i cu.yd. cap acity . T he ra ilro a d c a rs a re r u n d ire c tly in to th e p it.
T h e s tr ip p in g shovel w o rk s back an d f o r th alo n g th e face ta k in g a w id th o f a b o u t 40 'ft. o f o v e rb u rd e n a t each cu t. T he to ta l le n g th of th e p it is now a b o u t 2,500 ft., th is face ex te n d in g ro u g h ly d iag o n ally acro ss th e t r a c t fro m c o rn e r to c o rn e r— th a t is, fro m n o r th e a s t to so u th w est.
T he s tr ip p e r is o p e ra te d by tw o m e n : a shovelm an a n d a n oiler. T h e fu ll crew , how ever, co n sists o f six m en a n d a n e le c tric ia n w ho w o rk s on i t only p a r t tim e.
One m a n g iv es h is e n tire a tte n tio n to k e e p in g a re c o rd o r log of th e s tr ip p in g shovel’s o p e ra tio n . H e th u s re c o rd s th e lin e a r f e e t o f th e shovel’s ad vance p e r
Uncovering Coal Illustration A shows the big electric stripper of the Sunlight Coal Co. I t runs three sh ifts a day exposing coal fo r the lh-yd. steam loading shovel, B.
Power by Wire A t the le ft is the end of the 4,000 - v o lt pole line. The sled carrying f u s e s and an oil switch advances w ith the w orkings. T h e shot-hole drill is shown also.
