+ M in e s 33-Inch Coal U nd er 2 5 -Foot C over
S
T R I P - P I T o p e r a to rs in th e p a s t h a v e loo k ed a sk an c e a t th in b ed s o f coal ly in g n e a r th e s u rfa c e as b e in g e c o n o m ic ally u n w o rth y o f d e v e lo p m e n t. T h e i r v iew in th is m a tte r w as sen sib le. W h y a tte m p t to s trip - m in e th in coal w h e n b ed s o f c o n s id e rab le th ic k n e s s s u ita b le f o r rem o v a l b y shovel a r e a v a ila b le ? B u t th a t v iew c a n n o t be e x te n d e d f a r in to th e f u tu r e , f o r th e re c e n t w h irlw in d g r o w th o f sh o v el o p e ra tio n s h a s been re sp o n sib le f o r w id e in r o a d s in to th e re so u rc e s o f th is b r a n c h o f coal m in in g .
M a n y im p ro v e m e n ts h a v e been m a d e in s tr ip p in g , b o th in- eq u ip m e n t a n d m e th o d s. T h e s e h a v e g ra d u a lly in c re a se d th e p ra c tic a b le s tr ip p in g ra tio b e tw e e n th e th ic k n e s s e s o f coal a n d co v er. T h is p r o g re s s , com bined w ith th e g r o w in g s c a rc ity o f s tr ip - pable th ic k coal, is p u s h in g a h e a d th e tim e w h e n sh o v e l o p e r a to rs m u s t look to th in coal m e a s u re s f o r th e c o n tin u ance o f th e ir a c tiv itie s. I n fa c t, th a t tre n d a lre a d y h a s a c tu a lly h a d a s ta rt.
T h e M id la n d E le c tr ic C oal Co. is in th e v a n g u a r d o f th is ad v a n c e . I t h as in f u ll o p e r a tio n a t A tk in s o n , 111., a b o u t 150 m iles w e s t o f C hicago, a p la n t w ith a c a p a c ity o f a b o u t 1,500 to n s d aily , w h ic h is s tr ip p in g o n ly 33 in. o f coal u n d e r a c o v e r o f 25 ft.
T h e m in in g o f so th in a bed is m a d e p o ssib le : firs t, by th e lig h tn e ss o f th e c o v e r; se co n d , b y th e u s e o f m o d e rn e q u ip m e n t; a n d , th ir d , b y its p r o x im ity to a la rg e m a rk e t.
T h o s e th r e e f a c to r s a r e closely i n te rre la te d . T h o u g h th e c o v e r is c o m p a ra tiv e ly th in , th e coal also is t h i n ; so th e a d v a n ta g e o f m o d e rn e q u ip m e n t in re la tio n to th e f irs t f a c to r w a s n o t sufficient to w a r r a n t th e p r o je c t. T h e o v erp lu s o f a d v a n ta g e o f th is p la n t is larg ely o n e o f p u r e e c o n o m ic s in v o lv ing fa v o ra b le d is tr ib u tio n o f th e p ro d
-By K. R. BIXBY
General Manager Midland Electric Coal Co.
Atkinson, III.
uct. T h e g e o g ra p h ic lo catio n o f th is m in e en ab les it to se rv e th e n o r th e r n p o rtio n o f Illin o is a n d also Io w a , W isc o n sin , a n d M in n e so ta . W ith in a s h o rt ra d iu s o f th e p la n t a re a n u m b e r o f in d u s tria l c e n te rs w h o se a c tiv i
tie s a r e la rg e ly d e p e n d e n t o n fu el su p p ly . A b o u t 2 0 p e r c e n t o f th e p la n t o u tp u t g o es b y tru c k , o v e r go o d ro a d s, to n e a rb y to w n s.
T h is p la n t w a s s ta rte d in J a n u a r y , 1929. T h e p ro p e r ty e m b ra ce s an a re a w h ich w ill g iv e th e p la n t a life o f 30 y e a rs a t th e p re s e n t p ro d u c tio n ra te . T h e r e is a fo rc e d d iv isio n o f th e p ro p e r ty in to tw o eq u a l p a r ts by th e m a in line o f th e C hicago, R o c k Is la n d & P acific R .R . a n d th e s tr ip p in g o p e ra tio n is confined to o n ly o n e- h a lf th e a re a . T h e coal se am is th e Illin o is N o . 3 a n d th e o v e rb u rd e n c o n sists la rg e ly o f a sh a le y clay w h ich is s e p a ra te d fro m th e coal by 2 ft. o f b la ck sla te a n d co v e red b y 8 ft. o f s u rfa c e loam . B e ca u se o f th e n a tu r e o f th is m a te ria l, th e s tr ip p in g shovel c a n h an d le th e o v e rb u rd e n w ith o u t b la stin g .
Tipple at Midland Stripping
M id la n d is eq u ip p e d w ith tw o M a rio n e le c tric sh o v els, th e s tr ip p in g u n it h a v in g a 13^-y d . d ip p e r a n d th e lo a d in g u n it a 3 -y d . d ip p e r. T h e la rg e sh o v el h a s s trip p e d 18,900 cu .y d . o f m a te ria l in 2 4 h o u r s w h e n tr ip le -s h ifte d a n d th e coal sh o v el h a s lo ad ed a 5 0 -to n c a r in less th a n 8 m in u te s. T h e s e fig u re s a r e n o t u n u s u a l ; th e y a r e g iv e n m e re ly to sh o w th e p o te n tia l c a p a c ity o f m o d e rn s tr ip p in g e q u ip m e n t. M e m o ry is n o t ta x e d in re c a llin g th e tim e w h e n 8,000 cu .y d . o f m a te ria l w a s c o n s id e re d a go o d 2 4 -h o u r r u n f o r a s tr ip p in g sho v el.
I n c o m in g p o w e r a t 3 3 ,0 0 0 v o lts is ste p p ed d o w n th r o u g h th e p la n t tr a n s f o r m e r to 4 ,0 0 0 v o lts, w h ic h is c o rre c t p o te n tia l f o r th e shovels.
G ro u n d cables in p r e f e re n c e to o v e r h ea d lin es w e re se lec ted f o r th e d is trib u tio n o f p o w e r to th e v a rio u s field u n its . T h e s e cables, f u rn is h e d b y th e O k o n ite C o. co m e in 1 ,0 0 0 -ft.
le n g th s. A sm all, p o rta b le w o o d - fra m e ju n c tio n h o u se, eq u ip p e d w ith th r e e se ts o f c u to u ts, is e re c te d a t th e en d o f each cable le n g th . A ll cables
August, 1930 —
C O A L A G E 477
A Mechanical Track S hifter Is a Necessity Where Thin Beds Arc Stripped
Strip Pit, Showing Shovels in Operation
Picking-Table Floor in Midland Tipple
Rope Drive on Main Shaking Screen
473 C O A L A G E —
Vol.35, N o.8a r e jo in e d by ru b b e r-c o v e re d p u ll- ty p e c o n n e c to rs m a d e by th e M in e s E q u ip m e n t Co.
T h e in itia l c o s t o f th e s e ju n c tio n h o u se s w a s lo w a n d th e sim p lic ity o f th e ir c o n s tru c tio n m a k e s th e m fo o l
p r o o f. A s o n e s e t o f c u to u ts c o n n e c ts th e live g r o u n d ca b le w ith th e a d jo in in g 1,000- f t. se c tio n , it is p o s sible, w h e n th e o p e ra tio n is close to th e m a in t r a n s f o r m e r en d , to c u t o u t a n d m o v e th e e x te n s io n s w ith o u t in te r f e r in g w ith th e sh o v el o p e ra tio n . A se co n d se t o f c u to u ts is p la ce d b e tw e e n th e liv e lin e a n d th e fe e d e r f o r th e s tr ip p in g sho v el. T h e th ir d se t is o n th e liv e lin e a n d th e 4 4 0 -v o lt tr a n s f o r m e r f o r th e lo a d in g shovel, c o m p re s s o r, p u m p s, a n d o th e r e q u ip m e n t.
A 1 ,0 0 0 -ft. f e e d e r cable fu rn is h e s th e s tr ip p in g sh o v e l w ith p o w e r. T h is le n g th o f cable, w h ic h is g r e a te r th a n u su a l, h a s its a d v a n ta g e s . I t p e rm its th e lo c a tio n o f g r o u n d cab les an d ju n c tio n h o u se s a t le a st 40 0 f t. aw ay fr o m th e fa c e o f th e cu t, allo w in g c o n tin u e d o p e r a tio n th r o u g h o u t th e w in te r m o n th s w ith o u t th e n e c e ssity o f t r a n s f e r r i n g th e tr a n s m is s io n lines d u r in g in c le m e n t w e a th e r.
A p a ra lle lin g ty p e o f o v e rh e a d tr a n s m is s io n lin e w o u ld h a v e e n ta ile d a h ig h m a in te n a n c e cost, o n ac c o u n t o f th e f r e q u e n t s h if tin g o f th e lin e b y re a s o n o f th e lig h tn e ss o f th e co v e r a n d th e th in n e s s o f th e coal s trip p e d . I f a p a ra lle l lin e so m e w h a t rem o v e d f ro m th e fa c e o f th e cu t, w ith la te ra l lin e s a t r e g u la r in te rv a ls , h a d been u sed , th e la te r a ls so o n w o u ld h av e been re d u c e d to j u n k co p p e r.
A th in b ed o f coal p re s e n ts p r o b lem s in s tr ip p in g th a t a r e n o t m e t in coal o f 5, 7, o r 9 f t. th ic k n e ss. In th ic k coal a re a s g r e a te s t e ff o rt u su a lly is e x p e n d e d in re m o v in g th e cover.
B u t in s tr ip p in g a th in seam , in a d d i
tio n to th is p ro b le m , th e o p e ra to r is fa c e d w ith th e p ro b le m o f c o n s tru c t
in g a n d m a in ta in in g th e h a u la g e tra c k . A d a y ’s r u n o f coal a t th is strip p in g w ill n e c e s s ita te th e s id e -s h iftin g o f a
K . R . B i x b y
3 0 0 -ft. tr a c k se c tio n a d is ta n c e c o n fo rm a b le w ith th e ta k in g o f a 4 5 - ft.
cu t. T h e tra c k is s h ifte d by a N o rd - b e r g tr a c k - s h if te r in c o n ju n c tio n w ith a c a te rp illa r tra c to r .
F o r th e p re s e n t, s ta n d a r d ra ilro a d e q u ip m e n t is b ein g u se d in h au la g e . T h r e e 9 0 -to n ste a m lo co m o tiv es a re in se rv ic e a n d h a u l 5 0 -to n d ro p -b o t
to m c a rs o f th e g o n d o la ty p e . T h e s e c a rs a r e to be rep la c e d la te r by s p e cially b u ilt 4 0 -to n a u to m a tic d ro p - b o tto m c a rs. C oal is d u m p e d in to a r e in fo rc e d h o p p e r a n d is e lev a ted to th e to p o f th e tip p le by a 4 2-in. belt c o n v e y o r w h ic h is 2 0 8 ft. lo n g a n d in c lin e d a t 18 deg.
T h e tip p le , d esig n e d a n d e re c te d by- A lle n & G a rc ia C o., h a s a c a p a c ity o f 3 0 0 to n s p e r h o u r a n d is p ro v id e d w ith fac ilitie s f o r th e p re p a ra tio n a n d lo a d in g o f in d iv id u a l a n d co m b in a tio n sizes o n five tra c k s . M in e -r u n coal is s e p a ra te d b y th e m a in s h a k e r sc re e n s in to a p p ro x im a te ly 14.67 p e r c e n t o f 6-in. lu m p , 13.75 p e r c e n t o f 6 x 3 -in . egg, 13.67 p e r c e n t o f 3 x 2 -in . n u t a n d 4 8.18 p e r c e n t o f 2 -in. sc re e n in g s.
S c re e n in g s a r e f u r t h e r s e p a ra te d b y a n a u x ilia ry s h a k e r sc re en , located below th e m a in sc re en , in to 18.28 p e r
c e n t o f 2x1 £ -in . n u t, 2 3 .4 7 p e r ce n t ' o f H x fly -in . slack a n d 6.43 p e r ce n t o f -fV-in. d u ff. T h e la tte r, co m p o sed o f lo w -g ra d e coal a n d im p u ritie s , is w a ste d w ith th e r e f u s e m a te ria l p ic k e d f ro m th e lu m p , egg, a n d n u t coal o n th e ta b le s. I t c o n s titu te s a b o u t 9.73 p e r c e n t o f th e m in e -ru n .
T h is a u x ilia r y s h a k e r is a h ig h sp e ed w ire sc re e n s u p p o rte d on ro u n d b a rs , o n w h ic h n o t o n ly is th e s c re e n in g a r e a in c re a se d b u t th e te n d e n c y o f th e fine m o is t p a rtic le s to a rc h a n d c o n s e q u e n tly d e s tro y th e efficiency o f th e s c re e n is le ssen e d . T h e sc re e n is a g ita te d f r o m th e u nderside, b y n u m e ro u s fre e - s w in g in g r u b b e r b alls w h ich a r c su s p e n d e d f r o m th e sc re e n fra m e , a s sh o w n in th e a c c o m p a n y in g sk e tch .
A n o th e r f e a tu r e o f th is tip p le is th e g a th e r in g - m ix in g c o n v e y o rs n e a r th e d is c h a rg e e n d s o f th e ta b le s a n d r e ce iv in g e n d s o f th e boom s. T h e s e c o n v e y o rs p r o v id e a n u n c o m m o n ly c o n v e n ie n t a n d efficient m e a n s o f co l
le ctin g , m ix in g , a n d lo a d in g in to r a il
ro a d c a rs v a r io u s c o m b in a tio n s o f p r e p a re d sizes. T h e lo a d in g -b o o m h o ist h o u se is s e p a r a te d fr o m th e b u ild in g p r o p e r in a n a r r a n g e m e n t w h ich g iv e s c le a r v isio n o f th e lo a d in g o p e ra tio n fr o m th e c o n tro l ro o m . I n c o rp o ra te d in th e p la n t is a se rie s o f b in s w h ic h rec eiv e lu m p , eg g , n u t, o r c o m b in ed siz es fro m th e m ix in g c o n v e y o rs f o r local tr a d e r e q u ir e m e n ts. T h e c e n te r lines o f th e s e b in s r a d ia te o u tw a rd ly , a s d o th e sp o k es o f a w h ee l fr o m th e ir h u b , g iv in g a m a x im u m o f sp a ce f o r tr u c k s u n d e r each b in in a m in im u m o v e r-a ll a re a .
B o th s h a k in g s c re e n s a n d s h a k e r p ic k in g ta b le s a r e e q u ip p e d w ith T e x - ro p e d riv e s o p e ra tin g d ire c t f ro m th e m o to rs. T h is ty p e o f d riv e a lso h a s b ee n a p p lie d to th e v a r io u s c o n v e y o rs a n d lo a d in g b o o m s w h o se m o to r s a r e eq u ip p e d w ith c u t g e a rs. T h e a r r a n g e m e n t o f th e s e d riv e s h a s m in i
m ized v ib ra tio n o f th e s tr u c tu r e a n d g iv e n q u ie t, efficient o p e ra tio n o f th e v a rio u s u n its .
Self-Cleaning Auxiliary Shaking Screen
Welded j o i n t s
4 " x £ y
S te e l p la t e
y.--Aufjust, 1930
— C O A L A G E 479
C o a l A g e
S y d n e y A . H a l e , E d it o r
Ne w Yo r k, A u g u s t, 1930