Coal Age : devoted to the operating, technical and business problems of the coal-mining industry, Vol. 29, No. 17

M c G r a w - H i l l

P u b l i s h i n g C o m p a n y , I n c . J a m e s H . M c G r a w , President

E . J . M e h r e n . Vice-President

Devoted to the Operating, Technical and Business

Problems of the Coal-Mining Industry

P rev en tin g S u b stitu tio n in M ark etin g Coal

/C O M M E N T W A S M A D E in a re cen t ed ito rial on V _>the evils of s u b s titu tio n in m a rk e tin g coal an d its u n fo rtu n a te re p erc u ssio n s on th e produ cer, w hole­

saler an d re ta ile r. No one in th e in d u s try can re g a rd such p ra c tic e s w ith indifference even th o u g h his own p ra c tic e is in every w ay honorable. A com m uni­

cation w as received fro m G eorge R. P r a t t of Coal

G overnm ent of th e P ro v in ce o f A lb e rta endeavors to establish f a ir - tr a d e conditions in coal m a rk e tin g . The foundation of th e se m ethods is f a ir price, h ig h coal quality, co n su m er s a tis fa c tio n an d good will.

A special a c t called th e Coal S ales A ct of 1925 p ro ­ vides f o r r e g is te r in g th e tra d e nam es of th e coals which th e sev e ral m in es produce. No coal can be ad ­ v ertised o r sold except u n d e r its re g iste re d tra d e nam e, and th e invoices an d sh ip p in g bills m u st give th e nam e of th e m ine, th e coal field in w hich it is located, th e size of coal sh ip p ed an d th e re g is te re d tra d e nam e of the coal.

E v ery d e a le r is re q u ire d to keep a re co rd o f h is coal purchases w h e th e r fro m A lb e rta o r outside sources.

This reco rd is open to in sp ecto rs w ho have th e pow er to inspect invoices an d s h ip p in g docum ents, and, w h ere these do n o t con fo rm to th e coal in question, th e y m ay stam p upon th e d o cum ent a s ta te m e n t to t h a t effect. A penalty is p ro v id ed f o r fa ilu re to com ply w ith th e law or fo r false s ta te m e n ts in th e invoice docum ents.

In advices to th e re ta il coal d ea le r th e follow ing ex­

cellent ru le s a r e offered f o r h is a d o p tio n : T h a t th e value of th e coal shall be equal to th e a d v e rtise d v alu e;

th a t in th e ev en t of d isp u te o f value no re b a te in m oney (unless a c o n tra c t to th e c o n tra ry h a s been m ad e) shall be given b u t th e offer shall be m ade to rem ove th e coal w ithin 24 h o u rs a n d to re fu n d th e p u rc h a se m oney;

th a t th e Golden R ule sh all g o v e rn in all d ealin g s be­

tween d ealer an d consum er.

I t is recognized t h a t w h e re th e “q u a lity firs t” d ealer pays th e p ric e f o r q u a lity coal an d sells in com p etitio n w ith secon d-quality coal sold a t th e q u a lity price, th e result is a b u y in g p u blic d issa tisfie d w ith th e price, d is­

satisfied w ith th e q u a lity an d of c ritic a l m in d to w a rd all engaged in th e in d u s try . A d v e rtis in g a n d selling e f­

fo rts enhance coal values, b u t by su p p ly in g coal below the estab lish ed q u a lity s ta n d a rd , o r o f d iffe re n t sizes, or by s u b s titu tin g coals of d iffe re n t class, in fe r io r to the prom ised s ta n d a r d an d re b a tin g to one cu sto m er ou t of ten who com plains fo rc e fu lly enough, good w ill an d confidence a re u n d erm in e d .

To overcom e th e difficulty o f th e fe w d ea le rs w ho do not w ish to deal on th e sq u a re , th e g o v e rn m e n t office offers to all d ealers w ho a g re e to o bserv e th e fo re g o in g rules th e p riv ileg e of a tta c h in g a seal to each c u sto m e r’s delivery slip an d su pp lies th e sea ls to th e d ea le rs. T he

seals a re ab o u t th e size of a postage stam p an d con tain th e w ords— “Coal on th e S q u are.”

E v id ently th e A lb erta coal in d u s try h as w orked out a p ra ctical m ethod to in su re s a tis fa c to ry tra d e p ractice m d is trib u tin g th e ir product. No doubt o th e r m ethods would serve th e sam e ends b u t sim ila r problem s a rise in m any c o a l-d istrib u tin g ce n te rs an d need th e a tte n ­ tio n of producers, w holesalers and re ta ile rs in e sta b lish ­ in g “coal on th e sq u a re ” p ractices.

W ater o n Cutter Bits

T } A P ID P R O G R E SS is being m ade in th e app licatio n X V of je ts of w a te r to th e b its of c u ttin g m achines, th e purpose being to keep down coal d u st w hich would otherw ise be suspended in th e a i r an d c a rrie d co n sid er­

able distances ou tb y th e face. W here places a re w etted down by a hose and a w a te rlin e is th e re fo re convenient th e sp ra y pipe of th e c u ttin g m achine should, o f course, be connected to th e line. A bsence of th is la s t prov isio n in th e m a jo rity of m ines should not r e ta rd th e sp read of b it sp rin k lin g , fo r it is e n tire ly p ra cticab le to c a rry a ta n k of w a te r on a tr a ile r tru c k , to w hich p re ssu re m ay be applied by a sm all a i r com pressor. In o th e r cases a pum p m ay be used.

A t th e last m eetin g of th e Coal M ining In s titu te of A m erica, In sp e cto r E. G irod o f th e T w e n ty -th ird B itum ino us D istric t, p a r t of th e coke reg io n o f P e n n ­ sylvania, sta te d th a t five m ines in h is t e r r ito r y d u rin g th e la st ten m onths of 1925 adopted th is m easu re. H e added th a t he expected a ra p id g ro w th in th e p ractice.

Solely as a sa fe g u a rd a g a in s t th e d an g e r fro m coal du st, it ou g h t to be re g ard e d as being w o rth w hile b u t tho se not so stro n g ly influenced by th is sa fe ty fe a tu re should be won over by th e p ecu n iary g ain w hich m ig h t pos­

sibly accom pany it.

A je t of w a te r play in g on th e b its n o t only lay s th e d u st b u t d issip a tes th e h e a t g e n e ra te d d u rin g c u ttin g . W hen th e m a te ria l cu t is h a rd th e te m p e r w ith in th e po inted section o f th e b it is likely to be lo st a t le a st to skin depth by ex trem e rise s of te m p e ra tu re , an d th e effectiveness o f th e tool m ay soon become lessened by th e g re a te r ra te of w e a r of th e c u ttin g edge. M ining m en g enerally, including several m a n u fa c tu re rs of c u t­

tin g m achines an d c u tte r-b it steel, say th a t th is actio n does no t ta k e place. T h e ir co nten tio n a s applied to th e absence of such action in b its m ade o f alloy steel is no doubt tru e . H ow ever, a re th e y even re aso n ab ly s u re th a t th e ir co ntention re s ts on solid g ro u n d as re g a rd s carbon steel, o f w hich p ra ctically all th e b its now in use a re m a n u fa c tu re d ?

No scientific stu d ie s o f th e problem have y e t been m ade, fo r w hich reason a p o sitive opinion should be w ithheld. A lread y sev eral m a n u fa c tu re r s ’ en g in ee rs have w ith d ra w n th e ir ad v erse c ritic is m to th e su g g e s­

tio n and, a f te r h e a rin g th e o th e r side o f th e a rg u m e n t,

593

C O A L A G E

VOL. 29, No . 17

h a v e ta k e n a n eu tr a l sta n d . T h e v e r y ^ o‘ h “‘ e^

s te e l is a d m itte d to b e fa r su p e r io r ^ sh a d o w 0 f

r

S S - S

0“ s te e l a re n o t lik e ly to be f a tig u e d and fr a c tu r e d b y ^shoc w ^ en u n ifo r m lo w te m p e r a tu r e is m a in ta in e d . T h e sp n n ^ m g a tta c h m e n t m a y "after all b e th e m e a n , b y w h ich , th e tim e lo st in th e fr e q u e n t c h a n g in g o f b its m a y be re trTeved; a lso it m ig h t en ab le th e b its to cu t coal a t g r e a te r sp eed.

594

L im iting the P eak

n E A K L O A D S are a lw a y s to be avo id ed r e g a r d le s s o f r W hether p o w er fo r m in e o p era tio n is P J r c h a s f ^

g e n e r a te d . I f c u r r e n t is p u r ch a sed th e p ea k load s th e p a ce,” th a t is, d e te r m in e s th e d em and c h a r g e p fo r p ow er fo r th e m on th d u r in g w h ic h th e p eak occu rred a s w eU a s in m an y in sta n c e s fo r th e e lev e n su c c e e d in g m o n th s a s w ell. I f p o w er is g e n e r a te d th e p eak th r o w s a h ea v y and u su a lly an u n n e c e ssa r y load on th e p o w e r- g e n e r a tin g eq u ip m en t.

In ord er to avoid h ig h m o m e n ta r y p ea k s, e s p e c ia lly w h e r e p ow er is p u r ch a sed v a r io u s e x p e d ie n ts h a v e b een em p loyed . A t on e la r g e m in e m so u th e r n I lli­

n o is th e p r e s e n t p ro d u c tio n o f w h ic h is w e ll b elo w its d e m o n stra ted c a p a c ity an d w h e r e c o n se q u e n tly it is n o t n e c e ssa r y to h o is t s te a d ily t h r o u g h o u t th e e n ^ e s h if t in ord er to r a is e th e d a y ’s ou tp u t, a p la in ly v is ib le in d ic a tin g m e te r is p laced n ea r th e h o is t e n g in e e r s p la tfo r m . T h is is m ark ed w it h a p r e d e te r m in e d p eak load w h ich is n o t to be ex ceed ed . T h e h o istm a n w a tc h e s t h is m e te r c lo sely and w h e n t h is m a x im u m d em an d is ap p roach ed h o is t in g is su sp e n d ed u n til th e d em and s u b sid e s w h e n it is a g a in resu m ed .

C er ta in o th e r m in e s a re em p lo y in g c ir c u it b r ea k er s so a r r a n g e d t h a t w h e n th e to ta l load re a c h e s a p r e d e ­ te r m in e d v a lu e th e b r ea k er s c o n tr o llin g on e or m ore o f th e fe e d e r c ir c u its w ill k ick ou t. T h e s e b r e a k e r s w ill a u to m a tic a lly re clo se w h e n th e to ta l d em an d h a s d ecr ea sed to a p r e d e te r m in e d le v el. T h is a r r a n g e m e n t is e x tr e m e ly h a n d y an d e ffe c tiv e p o s s e s s in g th e m a rk ed a d v a n ta g e th a t it is a u to m a tic in o p era tio n , th u s r e ­ q u ir in g n o a tte n d a n c e.

C o n se r v a tio n in m in e c o s ts is a d o m in a n t tr e n d in th e coal in d u s tr y to d a y . O f c o u rse w h a t all m in e o p e r a to r s m o st d e sir e is a m ea n s f o r m a te r ia lly lo w e r in g th e m a jo r e x p e n se in v o lv ed in coal p ro d u c tio n , n a m e ly th e c o st o f lo a d in g , b u t a d v a n ta g e sh o u ld b e ta k e n , n e v e r ­ t h e le s s , o f all o th e r p o s s ib ilit ie s b y w h ic h th e c o s t o f m in in g m a y b e red u ced , ev en th o u g h t h e r e d u c tio n b e sm a ll. N o t a llo w in g th e p o w e r d em an d to e x c e e d a p r e d e te r m in e d a m o u n t is o n e m ea n s o f a c c o m p lish in g th e d e sir e d r e su lt.

T h e t im e h a s p a sse d in w h ic h th e s u p e r in te n d e n t c a lled f o r p ow er, m o re p ow er, r e g a r d le s s o f t h e w a y in w h ic h it w a s u sed . H e n o w t r ie s to m ak e h is u s e s fit a c e r ta in d efin ite h o u r ly su p p ly . H e t r im s h is p o w e r b ills j u s t a s h e h a s lo n g lim ite d h is su p p ly r e q u is itio n s .

Substance and Shadow s

H

O r g a n iz ed la b o r in th e coal in d u s t r y is fir m ly op p o sed to co m p u lso ry a r b it r a t io n . In t h a t «PP03^

w o r k e r s h a v e t h e t a c it or op en s u p p o r t o f t h e m a jo r it y o f th e c o u n tr y . R a is e th e c r y , a s u n io n le a d e r s h a v e done, t h a t co m p u lso r y a r b it r a t io n m e a n s e n f o r c e d lab or, an d o n ly a sm a ll m in o r it y w ill h a v e e ith e r th e c o u r a g e o r th e d e s ir e to e m b ra c e t h a t u n c e r t a in s t r ik e p r e v e n tiv e .

T h e U n ite d M in e s W o r k e r s, h o w e v e r , g o e s s t ill f u r ­ t h e r in fig h tin g th e s u g g e s t io n t h a t t h e fe d e r a l g o v e r n ­ m e n t sh o u ld h a v e th e p o w e r to in te r v e n e m t im e s o f e m e r g e n c y . T h e u n io n o b je c ts to a n y t h in g an d e v e r y ­ t h in g t h a t s m e lls o f a r b itr a t io n . M e d ia tio n an d c o n ­ c ilia t io n i t is r e a d y to a c c e p t— p o s s ib ly b e c a u s e t h e y a lr e a d y a re w r it t e n in to t h e D e p a r tm e n t o f L a b o r law . A n y p ro p o sa l t h a t th e P r e s id e n t b e a u th o r iz e d to c r e a te a fa c t-fin d in g a g e n c y w it h p o w e r t o in q u ir e in to w a g e d isp u te s an d m a k e p u b lic th e r e s u lts o f it s in v e s t ig a t io n s is w h o lly u n a c c e p ta b le to t h e m e n w h o d ir e c t th e d e s tin ie s o f th e m in e w o r k e r s ’ o r g a n iz a tio n .

A ca d em ic d is c u s s io n o f c o m p u ls o r y a r b it r a t io n is b e­

sid e th e p o in t. I t is o b v io u s t h a t s u c h c o m p u ls io n is r e p u g n a n t to th e n a tio n w h e n t h e s u r f a c e o f in d u s tr ia l r e la tio n s is r e a so n a b ly ca lm . C o n g r e s s d o e s n o t in te n d to c o n sid e r t h a t q u e stio n . T h e U n it e d M in e W o rk er s, a p p a r en tly , h a s n o in te n t io n o f v ie w i n g f a v o r a b ly an y o f th e v a r io u s h a lf - s t e p s p r o p o se d in th e m a n y “ e m e r ­ g e n c y c o n tr o l” b ills w h ic h h a v e b e e n r e f e r r e d to th e H o u se c o m m itte e . T h a t C o n g r e s s , o f it s o w n v o litio n , w ill r isk b a ttle a g a in s t a m in o r it y a s e ff e c tiv e ly and v o c ife r o u s ly o r g a n iz e d a s u n io n la b o r u p o n a n is s u e in w h ic h th e r e is lit t le p r e s e n t p u b lic in t e r e s t is u n lik e ly . T h u s th e c h ie f e x c u s e f o r f e d e r a l r e g u la t io n o f th e coal in d u s tr y f a lls o f it s o w n w e ig h t .

F ire W ill B u ild , N ot B u rn , O ur H o m e s

P

T h e co a l in d u s t r y w ill n e c e s s a r ily b e n e fit in t h is m o v e m e n t an d sh o u ld f o s t e r it . T h e r e i s n o r e a s o n w h y t h e p r e s e n t h e a v y y e a r ly lo s s f r o m fir e s h o u ld b e s u s ­ ta in e d . F r o m th e p r o g r e s s in t h e u s e o f s t e e l fo r s c h o o lh o u s e s, f a c t o r ie s a n d d w e llin g s , t h e c o a l in d u s tr y m a y d ra w m u c h h elp in t h e f u t u r e . U n f o r t u n a t e ly d w e llin g s n o t e n t ir e ly s t a n d a r d m a k e i t d iffic u lt to co n ­ s t r u c t th e g r e a t v a r i e t y o f s h a p e s n e e d e d f o r r e sid e n c e c o n s tr u c tio n . B u t t h e o x y - a c e t y le n e field w e ld in g ap ­ p a r a tu s w ill p r o b a b ly e n a b le th e a r c h it e c t t o t u r n r ig id sta n d a r d fo r m s in to t h e s h a p e s r e q u ir e d b y t h e eccen ­ t r ic it ie s o f h o m e c o n s t r u c t io n a n d t o do i t w it h a s m uch

e a s e a s a w o m a n c a n r e m o d e l a b o n n e t w i t h a f e w d e ft to u c h e s.

T h e fir e p r o o f e r a w ill b e o n e in w h ic h fir e a n d t h e r e ­ f o r e co a l w ill h a v e in c r e a s e d u s e . F i r e w ill b e m ore a c tiv e in th e b u ild in g a n d le s s a c t iv e in t h e b u r n in g o f o u r h o m e s.

Ap r il 2 9 , 1 9 2 6 C O A L A G E

5 9 5

D e a d E n d s B e s t V e n t ila t e d b y B lo w e r s and C a n v a s T u b in g

— A ir I s S t a tic in W id e P la c e s — S o m e tim e s a F a n Can D e ­ liv e r M ore A ir T h a n M in e W ill P a s s at W a te r G a g e P r o v id ed

B y Carl H . T rik

M i n e V e n t i l a t i o n E n g i n e e r , J e f f r e y M a n u f a c t u r i n g C o ., C o l u m b u s , O h io

I N ALL the studies of the mining of coal by mechanical cutters, loading devices, conveyors and o t h e r means, commonly desig­

nated as “concentrated mining,” little has been written as to the effect of these new methods of “harvesting coal” by machinery on the ven­

tilation problems at the working face. Is it not high time to consider the effect of t h e s e changes on the venti­

lation of the mine?

What effect will they have on the quality and quantity of the air delivered to the face? How will it modify the mine resistance? What effect will it have on the fan and on the cost of operation? Let us consider each of these matters in turn. Theoretical discussion is of little

f a i i e ^ ? PKe(^e s h o w s a f a n d e l i v e r i n g a i r t o a " m i n o r f a c e . ” T h i s e n a i e i n g . s e r v e d b y a s e c t i o n a l c o n v e y o r w h i c h b r i n g s t h e b lnw ot- ¡„a n o i r 9 o n v e y o r o n e n t r y w a y o f t h e p a n e l . T h e tViB rl.,v.VS f ? n t h e o p p o s i t e s i d e o f t h e m a i n c o n v e y o r w a y f r o m D la re P l a c e o r r o o m , s o t h a t t h e a i r r e t u r n i n g f r o m t h e f a c e 1 n o t e n t e r t h e f a n a n d b e r e d e l i v e r e d t o t h e w o r k i n g

value to the practical man, and empirical data are so far difficult to find. However, enough information is now available to allow anyone to arrive at certain definite conclusions.

Ventilation has, for instance, definitely divided itself into two parts, a primary and a secondary system to be compared aptly with the ventilation of a metal mine which has its gangways and tunnels ventilated by a primary system and its “dead ends” such as blank stopes and raises requiring secondary systems supplied with air drawn from the main, or primary, air current.

In those states that permit the driving of a single entry for any number of feet without a crosscut, the problem of secondary ventilation is simply, if not always cheaply, solved. These “minor faces” must have air while they are being driven to open up a panel or block. As they receive conveyors, it will be well to name them “con­

veyor headings,” or “conveyorways,” though “develop­

ment headings” would be an equally satisfactory term.

Judging by the number of companies using the small

auxiliary blower and flexible canvas tubing, as compared

with those using brattice cloth to conduct air to the

face of these conveyor headings, the former method

must be the best means of ventilating these minor

faces. In fact, operators who have installed fans and

tubing declare that this method of providing air is less

costly by far than the erection of brattice cloth. Many

operators would gladly adopt these fans in preference

C O A L A G E

29, No. 17

F ig . 1— O p p osite V iew o f C onveyor, F a n and C a n v a s T u b in g S how n in H ead p iece

T w e l v e - i n c h d i a m e t e r t u b e ^ ‘'J f ^ i o n c a ^ 'r e a d 'T l y " '^ d i s c e r n e d , c o n v e y o r , b e i n g e m p t y , i t s c o n ,s t D o r ts 0 ; t h e c a n v a s t u b e A n e l e c t r i c l a m p s t r u n g f r o m t h e s u p p o r t s ; o ,. t t i o n . l i g h t s u p t h e c o n v e y o r a n d a d d s t o t h e s a t e t y o i u i e w

to older devices if the laws of the states in which they are operating would permit. They believe that these laws should be revised so as to be in harmony wi changing conditions. Of course, there are those who object to the small blower, and they present many rea­

sons for their opposition. But there are also many who take exception to the use of the brattice line, and they have just as many and as cogent reasons for the stand they take. Be that as it may, the conveyor head­

ings must be ventilated. That is true regardless of the system of secondary ventilation that is adopted. Cer­

tainly this ventilation will not be as expensive as in those fields where the state laws and state inspectors insist on having a crosscut driven every 60 to 100 ft.

Even when such rulings are obeyed the operator is left without anything that could be dignified with the term

“secondary system.”

When the decrees of such legislatures and inspectors are followed the resistance of the airways varies greatly according to the degree of their development, and the main current has to be regulated to suit the frictional losses of the most resistant entries. The ventilation is consequently uneconomical and not appreciably safer than when the small blower is used.

entries if these are driven, are completed and connected with each other so as to form a continuous working this section becomes “a major face” and a part of the primary ventilation system in that a true circuit or current is established which can be considered as a separate split of the main current passing to the return or being carried back to the intake air current, diluted and used again, all depending on local conditions. Many operators mining a large acreage on a continuous face (really consisting of a series of small faces

) find themselves forced to consider one of the blocks as a separate split, the law of the state under which the operator is working limiting the number of men allowed on each split. . . .

We are now ready to consider the ventilation of those working places which, for obvious reasons, we have termed “major faces.” In a block consisting of a single face or a series of staggered faces, the conveying and haulage problems may be more or less intricate but the ventilation will be plain sailing from this point on, so that the old cry, “No air at the working face” will

become a thing of the past. ^

We have all heard of operators who have been all

Au x i l i a r i e s or Hig h Wa t e r Gage

The headpiece of this article shows the method of setting the blower that one operator adopted when driving a single entry to connect up with another entry parallel to the one down which we are looking in the picture. The fan is set across the entry so that it will not recirculate the air as it returns from the con­

veyor heading. Here it is entirely out of the way.

A few inspectors have severely criticized the small blower as a source of danger declaring that with it the air might be recirculated. I have even heard one man state that he knew of a small fan handling nothing but gas between the fan inlet and the face. This may be true, it could easily happen, but I fail to see the logic in condemning the small blower. Rather should the operator be taken to task who was so utterly lax as to install a fan in such a position as to permit this to occur. Every tubing company makes right-angle bends of tubing to obviate this very condition. If these were used even the probability of recirculation would be eliminated so long as the main fan continued in op­

eration.

After the narrow conveyor headings or the double

F ig . 2— L o o k in g A lo n g C o n v e y o r w a y T o w a r d F a n

T h e c a n v a s t u b i n g n a t u r a l l y s t r a i g h t e n s i t s e l f a n d g i v e s a f a i r p a s s a g e f o r t h e a i r c u r r e n t . R e s t i n g o n t h e f l o o r o f t h e r o a d w a y i t r e q u i r e s n o s u p p o r t . N o t e h o w l a r g e a c a p a c i t y t h e c o n v e y o r p r o v i d e s .

too eager to get out coal and who in their mad dash for production have dug themselves in until their airways, especially on the return, are mere dog holes and the air current is so feeble that it cannot travel against the high resistance of the mine. But with concentrated mining systems we shall probably hear of them no longer.

Under the new system the ventilation should be much superior to that of the average mine under the old plan, and that is proved by the experience of many companies throughout the land. There is an “if,” how­

ever, in this, as in every flat statement and that is

“ i f

the main airways, both intakes and returns, are

Ap r il 29, 1 9 2 6

C O A L A G E 59 7

F I G . 3

Work in Good A ir E a c h m a n h a s a b o u t 25 ft. o f fa c e . D e s p ite th e a b s o r p ­ tio n o f lig h t b y th e c o a l, s i x m e n c a n be se e n a t w o r k on a b o u t 125 f t . o f fa c e . T h e p h o to ­ g ra p h w a s t a k e n w ith a f la s h lig h t, a te s t im o n y to th e e x c e lle n c e o f t h e v e n t ila t io n d u e to th e g e n e r o u s c u r ­ r e n t t h a t c a n be m a d e to s w e e p a s t r a ig h t fa c e .

kept fre e an d clean a n d th e sectional a re a is am ple fo r the volum e re q u ire d .”

W hen c u ttin g b eg in s on a m a jo r face, th e c u rre n t of a ir flows p a s t th e m en w o rk in g along it in a clean uncontam inated stre a m . F ig . 3 show s how p u re the a ir is a t one of th e se faces. T h is flash lig h t p h otog raph reveals ab o u t 125 f t . of face. S ix loaders can be d is­

tinctly seen th ro u g h th e clean a ir. F ig . 4 show s a n o th e r face im m ediately a f te r shootin g. The a i r h as ra p id ly swept aw ay all fu m es an d smoke.

In fa ct, a t som e m ines, as c u ttin g proceeds and m ore and m ore coal is rem oved, th e space betw een th e w ork­

ing face and th e gob in cre ases to such an e x te n t th a t the a ir is likely to become slu g g ish due to th e g re a te r increase in a re a . P le n ty of a ir m ay be p assing, b u t th e area over w hich it tra v e ls is so w ide th a t th e speed will decline u n less som e m ean s be ta k e n to guide th e a ir to th e place in w hich its sco u rin g effect is needed.

Pu t t in g Br a t t ic e Cl o t h Be h i n d t h e Me n

The b est m ethod is to line b ra ttic e cloth betw een th e men and th e gob a t such a d istan ce as will cause th e air to tra v e l alo ng th e fa ce a t th e re q u is ite speed.

This, in no case, sho uld exceed 500 f t. p e r m in u te n o r be less th a n 50 f t . In fa c t 75 f t. p e r m in u te would be the p re fe ra b le figure.

However, i t w ill be fo u n d t h a t in m ost m ines th e roof will h ave fa lle n s h u t p ra c tic a lly up to th e props or cribbing, an d th e a ir w ill now slow down so m uch

as to m ake th e use of b ra ttic e cloth necessary. A l­

th o u g h th e roo f is down and loose rock is piled up to th e r e a r line of props, th e gob is no t t ig h t an d th e a ir will w ork its w ay th ro u g h an d aro u n d th e caved area, w hich is as it should be. W hen th e coal is m ined out to th e b a r r ie r p illa r and th e la s t c u t h a s been tak en , th e e n tire a re a m ay be sealed off an d fo rg o tte n so f a r as e n te rin g in to th e schem e o f v e n tila tio n is concerned.

Ne w Me t h o d s Low er Mi n e Re s is t a n c e

F ro m th e fo reg o in g i t is a p p a re n t w h a t a re m a rk ab le effect th is will have in red u cin g th e w a te r gage, o r m ine re sistan ce. T h is is w h a t every conscientious m a n ­ a g e r is seeking, and th is new m ethod of o p eratio n will com m end its e lf to him fro m th is reaso n alone.

We have now seen th e effect of th e new m etho ds o f m in in g on th e q u ality of th e a ir an d th e re s is ta n c e to its p assage. I t n ex t behooves us to consider its effect on th e fa n . I t is well know n to v e n tila tio n an d fa n sp ecialists t h a t fully 80 p e r cen t of th e fa n s v e n tila tin g coal m ines today a re w o rk in g below th e ir tr u e o r norm al capacity, fo r th e w a te r g age is h ig h e r th a n t h a t fo r w hich th e fa n is designed.

The reason s fo r th is condition are m any, ch ief am ong th em being t h a t th e m ine m a n a g e r o ften tim es w hen o rd e rin g a fa n , o rd ers th a t it be b u ilt to afford “p len ty of ca p acity ” and he g ets it in the fa n , b u t he fa ils to live up to h is end of th e b a rg a in , in t h a t He does n o t give th e fa n a m ine th a t will p e rm it th e n o rm al cap acity

F IG . 4

A fte r a Shot I m m e d ia te ly a f t e r s h o o tin g , th e m e n a r e a b le t o r e s u m e w o r k . T h e c o n ­ v e y o r in a n y e v e n t d o e s n o t n e e d lo a d ­ in g b y h a n d , fo r it is a lr e a d y w e ll- lo a d e d b y t h e e f ­ f e c t s o f th e sh o t.

M uch o f th e c o a l is a b o v e th e c o n v e y o r a n d d o e s n o t h a v e to b e r a is e d . T h e w o r k is t h a t o f lo w e r in g c o a l r a th e r th a n o f lif t in g it a s in lo a d in g a m in e ca r.

598

of the v e n tila tin g u n it to flow th ro u g h th e m ine w o rk ­ ings except a t a w a te r gage en tirely out of all reason.

A gain one finds a t m ines, fa n s th a t fit th e m ine conditions th e first few years of th e ir operation, but as tim e has passed th e o p erato r has been too o p tim istic as to h is ab ility to keep down th e resistan c e of th e m ine to th e sta te d w a te r gage, and as th e w orking s develop th e fa n becomes m ore and m ore u n su ited to th e w o ik it is requ ired to perform . I t is now too larg e and is able to deliver m ore a ir alto g eth er th a n can pass th ro u g h the ag in g m ine a t the orig in al w a te r gage. As r e tr e a t­

in g begins, of course, the fa n is g rad u ally b ro u g h t up to capacity and operates m ore efficiently.

F ig . 5 shows a 12-ft. blow ing reversib le fan , th e norm al capacity of which is abo u t 300,000 cu .ft. per m inute. W hen th e m ine re sistan c e is equal to 3 in.

of w a te r gage th e fa n is 75 p er cent efficient m ech an i­

cally and th e brake horsepow er re q u ired is 140. B u t th e m ine will only p e rm it 200,000 cu.ft. p er m in u te to pass w ith a 3-in. w a te r gage. As a re su lt 140 hp. is re q u ired to o btain th is re su lt.

By cleaning up th e airw ay s and o therw ise relieving th e re stric tio n , th e fa n could be b ro u g h t to efficiency and m ade to deliver th e desired 300,000 cu .ft. of a ir p er m inute w ith o u t a single additional revolution p er m inute, b u t th is is exceedingly difficult and expensive to do once th e airw ay s th ro u g h o u t th e m ine have been allowed to become clu ttered w ith roof falls.

Ch a r a c t e r ist ic Curves of Mu l t iv a n e Fa n

F ig . 6 shows th e c h a ra c te ristic curves of a m odern m u ltiv an e fa n of practically any sta n d a rd m ake w hen ru n n in g a t c o n sta n t speed. I t will read ily be seen th a t w ith th e fa n ru n n in g a t norm al capacity it o perates a t a peak efficiency of 75 p er cent d elivering 150,000 cu.ft. p e r m in u te a t 3.5-in. w a te r gage. Should roof fall in th e airc o u rses so as to re s tr ic t th e a ir p a ssin g th ro u g h th e m ine to one-half th a t volume, th e w a te r gage, as will be noted fro m th e grap h , will show a slig h t increase, b u t th e efficiency of th e fa n w ill be reduced to ab o u t 58 p e r cent. Yet, its speed will have rem ain ed unchanged. T he constant-speed curve illu stra te s clearly th e im p o rta n t economy effected by o p e ra tin g a m u ltiblade fa n a t ra n g e s reasonably w ith in its norm al capacity.

F ig . 7 shows a small m odern all-steel fa n 5 ft. in d iam eter rep lacing a wooden fa n of 20-ft. d iam eter.

T h is s u b stitu tio n saved th e o p erato r ab o u t $3,000 a y e a r in h is pow er bills, because th e new fa n w as op­

e ra te d a t peak efficiency. N ot so m uch of th is tro u b le

will be experienced in a m in e t h a t h a s in tro d u c e d th e new system s of m in in g , fo r th e f a n w ill be over- ra th e r th a n underloaded. As m o st fa n s a r e u n d erlo ad ed th e change to m ore m o d ern m eth o d s of e x tra c tin g coal, w hich will in crease th e load, w ill be fa v o ra b le to g re a te r

m echanical efficiency. ,, . .

W h at ab o u t th e effect of th is c h a n g e on th e cost of v en tila tio n ? My d a ta , o b serv atio n an d exp erien ce lead me to th e conclusion t h a t v e n tila tin g co st w ill be m ate­

ria lly reduced, p a rtic u la rly in th o se s ta te s p e rm ittin g th e d riv in g of e n trie s m ore th a n 80 f t. w ith o u t a cro ss­

cu t T he elim in a tio n of th e d riv in g of m an y crosscuts and of th e b u ild in g and m a in te n a n c e of m an y stoppings will re s u lt in an im p o rta n t re d u c tio n of cost. A positive decrease in th e cost of v e n tila tio n is a s s u re d because of th e red u ctio n in th e re sis ta n c e of th e m ine. The pow er re q u ired to d riv e a m in e fa n v a rie s a s th e square of th e p re ssu re and in creases, o r d ecreases, as th e cube of th e volume, th e velocity or th e n u m b e r o f revolutions p er m in u te of th e fan .

If a m ine needs 200,000 c u .ft. of a i r p e r m in u te and th e w a te r gage is 4.5 in. a 250-hp. m o to r is needed to v en tilate it. T he o p eratio n of th e f a n w ill cost about

$25,000 a year, e s tim a tin g th e co st on th e b a sis of a 24-hr. day, 300 d ays in th e y ea r, a 60-per ce n t overall efficiency an d 2c. p e r k ilo w a tt-h o u r. T h is figu re will be about $19,200 a y e a r w ith e n e rg y a t l i e . p e r un it.

T h is is to ru n th e fa n alone.

O p e r a t o r S a v e s

$13,000

Should th e sam e m in e be able to re d u ce its re sistan ce to 2 in. of w a te r g ag e fo r th e sam e q u a n tity of air, th e pow er bill fo r th e o p e ra tio n of th e f a n w ill be cut to $11,300 on a b a sis of 2c. p e r k ilo w a tt-h o u r an d to

$8,500 if th e cost of en e rg y is only l i e . p e r u n it. I t

NO.

C O A L A G E

Fig. 6—C haracteristics of Mine F an Running at Constant Speed

T h e g r e a t e s t w a t e r g a g e i s n o t f o u n d a t t h e p o i n t o f m a.x .im v * ” } e f f i c i e n c y . I f t h e m i n e d e m a n d s t h e h i g h e r w a t e r g a g e t h e 1 » w i l l f u r n i s h i t i n s o m e d e g r e e b u t a t a l o s s o f c a p a c i t y . IX d e m a n d s l e s s p r e s s u r e m o r e a i r w i l l b e d e l i v e r e d b u t a t a e f f i c i e n c y . A s f a r a s p o s s i b l e t h e m i n e s h o u l d f i t t h e f a n a n d t n o f a n t h e m i n e , b u t t h a t f a c t i s r a r e l y u n d e r s t o o d .

Fig 5 Fan Makes More Air Than Mine Will Take

A l w a y s c o n s i d e r t h e m i n e w h o l l y f r o m t h e ¿ a ; £ c e r t a i n w a t e r g a g e a n d a c e r t a i n r e s i s t a n c e t

c e r t a i n q u a n t i t y o f a i r . T h e d u t y o f t h e y e r i t . l a t . n g

c r e a t e t h a t w a t e r g a g e . H o w m u c h a i r m u s t i t ^ t h a t J u s t a s m u c h a s , a n d n o m o r e t h a n , t h e m i n e

p r e s s u r e .

Ap r il 29, 1926 C O A L A G E 599

is quite evident, th e re fo re , t h a t if th e p e rm a n e n t a i r ­ w ays a re k e p t clean an d open, u n d e r th e new system , the v en tilatio n cost, in so f a r as pow er bills a re con­

cerned, will be reduced appreciably. The com pany u sing th is system of m in in g successfully should be able to show a sa v in g in th e cost of produ ctio n p er to n over its fo rm e r system , and if it can achieve a sav in g of 25c. a ton on th e m in in g alone, it is inclined to re g a rd any sav in g in th e cost of v e n tila tio n as so m uch “velvet.”

The v en tilatio n of th e w orking faces u n d er v ario u s system s of concentrated m in in g p re se n ts problem s all h av in g th e sam e physical aspects b u t th ou gh th ese a s ­ pects are alike th ey cannot all be solved in th e sam e m an n er. The o p erato r in one s ta te m ay have clear sailin g, w hereas his n eigh bo r across th e s ta te line m ay be ham pered in m any w ays by th e laws w ith w hich he is obliged to conform . One s ta te will be fo un d p ro ­ g ressiv e and alive to w h at th ese new m ethods can do and in fra m in g its legislation will give all reasonable assistan ce to its m in in g men. A n o th er will be found to cling to law s m ade fo r a system of m in in g th a t is surely, b ut, of course, g radually, doomed to give place to a new order, th e s ta te being n evertheless u nw illing to recognize th is fact.

I re fe r, of course, to those s ta te s th a t b a r th e use of th e sm all au x ilia ry blow er w ith canvas tu b in g fo r v e n tila tin g m in o r faces an d w hich do not p e rm it an e n try to be driven w ith o u t m akin g a cro sscu t every 60 or 80 ft. T he la s t th in g in m y m ind is to recom m end a step b ackw ard or to undo an y good p ra ctice alre ad y established, b u t th e re a d e r will surely a g re e th a t w ith ­ out jeo p ard izin g th e lives of th e m en employed, a m in in g code m ay be so fra m e d an d w orded as to give p ro g re s ­ sive o p erato rs a chance to w ork th e ir m ines efficiently by one of th e m any system s of con cen trated m in in g now receiving extended application.

Royalties Are Low in Southern Illinois

In v e stig atio n s m ade by L. D. T racy, a coal-m ining engineer of th e U. S. B u rea u of M ines, show th a t since 1910 the a v e ra g e ro y a lty in W illiam son C ounty in southern Illin o is h a s g ra d u a lly in creased fro m ab ou t 3c. per ton fo r ru n -o f-m in e coal to ab o u t 6 ic. In F ra n k ­ lin County, w hich is a d ja c e n t to W illiam son and in th e same sta te , d u rin g th e sam e period th e ro y a lty has risen from a b o u t l i e . to 5c. p e r ton.

In norm al tim e s a piece of coal land in W illiam son County b rin g s ab o u t 8c. p e r to n ro y alty . T h is p re su p ­ poses th a t all co n d itio n s a s to m in in g , sh ip p in g and quality a re fa v o ra b le an d t h a t i t will be m ined in th e course of th e n o rm a l developm ent of th e field. In F ran k lin C ounty th e p ro b a b ilitie s a re t h a t a slig h tly lower ro y a lty w ould be ask ed th a n in W illiam son, although ro y a ltie s a s h ig h as 10c. p e r to n have been received. S u rfa c e o ptions, as g iven in leases in th is district, in d icate th e s u rfa c e as valued a t $85 p e r acre.

General in q u iry w ould in d ic a te t h a t fro m $50 to $75 per acre w as a f a i r p ric e f o r th e s u rfa c e and $100 to

$125 p e r acre fo r th e b ig seam , No. 6, w ith o u t su rface.

F orm erly no m en tio n of s u rfa c e sub sid en ce w as m ade in coal leases, b u t in la te r y e a rs a b o u t 52 p e r ce n t of the leases in W illiam son C ou nty an d 37 p e r cent of those in F ra n k lin C o unty co n ta in a clause w hich ex­

pressly releases th e lessee fro m all lia b ility fo r dam ­ ages to th e s u rfa c e by su b sid en ce cau sed by rem oving the u n d erly in g coal. No differen ce in th e ro y a lty appears to re s u lt fro m in c o rp o ra tin g su ch a clause.

There a re no re c e n t fig u res a t h a n d of ro y a ltie s in other fields o f th e c o u n try b u t G eorge H. A shley gives a few as of 1910. H ow ever, co m p a rin g th e a v e ra g e royalty in F ra n k lin an d W illiam so n a s of 1923 w ith those in th e coal fields as g iv en by A shley it would appear th a t s o u th e rn Illin o is coal is valu ed a t a m uch lower figure by com p ariso n.

As f a r back a s 1910, P itts b u r g h coal ro y a ltie s ra n g e d rom 10 to 15c. p e r to n of ru n -o f-m in e coal. H ock ing

Valley, Ohio, coal b ro u g h t 8c. p er to n ; K anaw ha, W. Va.,

C ounty 8 to 2 7ic. T hese figures of fifteen y e a rs ago a re h ig h e r th a n those of W illiam son C ounty w hich av erag ed a little over 6c. p er to n o r th ose of F ra n k lin C ounty t h a t ru n fro m abo ut 4 to 7c. p e r ton fo r th e p a st few years. T h ere does no t seem to be an y definite reason fo r th is seem ing discrepan cy in values.

T he h ig h e s t price of W illiam son and F ra n k lin C ounty coal land, is $125 p e r acre fo r coal and $75 p e r acre fo r su rfa ce, or a to tal of $200. T he a v e rag e th ick n ess of th e p rin cip al bed is given as 9.2 ft., an d th e av erag e th ick n ess m ined as 7J f t. T hese figures will give an app roxim ate acre-fo ot value of $21.50 an d $26 resp ec­

tively.

C om paring A shley’s m axim um acre-fo ot values of fifteen y ea rs a g o : P itts b u rg h coal is $110 to $170;

K an aw h a d is tric t $6 to $60; P ocah o n tas d is tric t $10 to $40; Colorado $23 to $60. A nd probably in none of those places does th e s u rfa c e value play as la rg e a p a r t as in th e Illinois acre-fo ot value.

T h is Top Cutter O vercom es O bstacles

T u r r e t m a c h in e w it h 8 - ft . c u tte r b a r is u se d b y t h e P h e lp s D o d g e Corp. fo r s p e c ia l c u t tin g in 3 5 -ft. r o o m s w h e r e f a c e s s la n t a t a n a n g le o f a b o u t 32 d eg . T h e r e v o lv in g c u t t in g m e c h a n is m is s e lf- p r o p e llin g w it h in it s w o r k in g a r e a , m a in t a in in g c o n t a c t w it h th e n e a r e s t p o w e r lin e b y m e a n s o f a c a b le reel.

F IG . 7 N ew and Old

A s m a ll f a n s u b s tit u te d f o r a 20 - ft. d ia m e te r w o o d fa n . T h e m o d e r n f a n is a ll ste e l.

C O A L A G E

V ol . 29, No. 17

A T ra n sfo rm er S ta tio n f o r Two B ig M ines U sin g P u rch ased P ow er.

S e v e ra l M ines O w ned by a S in g le C om pany Could, R educe T h eir C osts by Pooling T heir P o w er D em ands.

L oad F a c to r s in Illin o is M in es M ay R u n as L o w as 15 to 18 p e r Cent.

The S m a ll L o a d F a c to r Is D u e L a r g e ly to W orking O n ly One H o u r in S ix D u rin g the S pace of a W h ole Y e a r.

W hy Illin o is Uses P u rc h a s e d P o w e r E x te n siv e ly

Sm all Loads and Irregularity of O peration Favor U se of Purchased Pow er— Load Factor of D iversified Ser­

vice Much Greater Than T hat of A ny S in gle M ine

B y J. P a u l C la y to n

V i c e - P r e s i d e n t , C e n t r a l I l l i n o i s P u b l i c S e r v i c e C o ., S p r i n g f i e l d , 111.

UT of a to ta l a re a of 56,000 sq u are m iles in th e S ta te of Illinois som ew hat over 35,000 sq u are m iles are u nderlaid w ith b itu m inou s coal. W ith an average yearly production of abou t 70,000,000 to n s th is s ta te ra n k s th ir d in th e Union, being exceeded only by P en nsy lv an ia and W est /ir g in ia . The beds of coal now w orked v ary from 3 to 14 ft. in th ick n ess and lie a t a depth ra n g in g from n o th in g a t c e rta in outcrops to as m uch as 1,000 ft. below th e su rface. T he av erag e depth of th e m ines now w orking is ap p roxim ately 400 ft.

L ittle w a te r is encountered in any of th ese o perations.

E a rly developm ent of th e coal deposits of th is s ta te largely utilized hand labor, b u t as th is becam e m ore an d m ore expensive it h as been g ra d u ally supplem ented by m echanical energy u n til a t th e p re sen t tim e m echan­

ical or electrical pow er is used fo r a g re a t v a rie ty of o perations. T he early m ines w ere supplied w ith m echanical o r electrical en erg y fro m sta tio n s located n e a r th e s h a ft or o th er m ine opening. T hese as a ru le w ere sm all a t th e s ta r t and grew by accretio n as pow er dem ands increased. As a re su lt, m any of th ese ea rly m ine pow er p lan ts w ere w oefully inefficient.

I t w as no t u n til abo u t 1912 th a t h ig h -ten sio n t r a n s ­ m ission lines fu rn is h in g pow er to th e m ines m ade th e ir ap pearan ce in Illinois. A t t h a t tim e tw o la rg e m ines w ere b u ilt and com pletely electrified u sin g p u rc h ased pow er fo r th e ir operation. T hese two developm ents a re still am ong th e m ost efficient in th e s ta te fro m th e sta n d p o in t of pow er consum ption. T hey a re likew ise am ong th e la rg e s t producers as re g a rd s a n n u a l to n n ag e.

T he exten sio n of tra n sm issio n lines stead ily p ro g ressed

A b s t r a c t o f a p a p e r e n t i t l e d " P u r c h a s e d P o w e r f o r C o a l M i n e s i n I l l i n o i s , " p r e s e n t e d b e f o r e a m e e t i n g o f t h e M i d - W e s t P o w e r C o n f e r e n c e a t C h i c a g o , J a n . 26 t o 28 , 1 9 2 6 .

u n til, a t p re sen t, p u rc h a se d p o w er is av ailab le in alm ost all th e coal fields of th e s ta te . M ost of th e power fu rn is h e d to th e se fields is g e n e ra te d in la rg e m odern ste a m -tu rb in e s ta tio n s w h e re i t ca n be produced at low cost.

E le c tric service to th e coal m in e s h a s ste a d ily prog­

ressed fro m its h um ble b e g in n in g back in 1912 up to th e p re se n t. T oday n o t less th a n 200 coal operations p u rc h ase all o r a s u b s ta n tia l p o rtio n of t h e ir to ta l power re q u ire m e n ts. T h e re a r e now a b o u t 338 sh ip p in g m ines w ith in th e s ta te , so t h a t a p p ro x im a te ly 60 p e r cent buy p a r t o r all of th e ir pow er. A m a jo r ity of th e fully electrified o p e ra tio n s a r e o f la rg e c a p a c ity so th a t probably a t le a s t 75 p e r c e n t of th e coal m ined w ith in th e s ta te b o rd e rs is p ro du ced in w hole o r in p a r t by the aid of pow er p u rc h a se d fro m c e n tra l s ta tio n companies.

G re a t p ro g re ss h a s been m ad e in th e electrificatio n of th e m in in g in d u s try of Illin o is d u rin g th e la s t fifteen y ea rs.

Ser v ic e s Po w e r Pe r f o r m s

T he m ain p u rp o se fo r w h ich po w er is used a t elec­

trified m in es a re as fo llo w s: H o is tin g , h a u la g e , cuttin g, v e n tila tin g , p u m p in g , p re p a ra tio n , shops, lig h tin g and to a lim ited e x te n t b a tte r y c h a rg in g . In th e larg er fu lly electrified m in es of Illin o is p ra c tic a lly all the h o is tin g is done by m ean s o f flyw heel m o to r-g en e rato r sets w hich ta k e en e rg y fro m th e a lte rn a tin g -c u rre n t supply th ro u g h an in d u c tio n m o to r an d g en erate d ire c t-c u rre n t pow er. A la rg e flyw heel is m ounted on th e sam e s h a f t w ith th e m o to r a n d g e n e ra to r so th a t a n y su dd en d r a f t of p o w er f o r h o is tin g is provided by b oth an in cre ased in p u t fro m th e tra n s m is s io n line to

O

D o u b le-M o to red H o is t A t Orient," N o . 2 M ine. I n o r d e r to a v o id t h e i n s t a l l a ­ tio n o f a m o to r o f e x c e s s iv e s iz e t w o su c h m a c h in e s a r e em p lo y e d to o p e r ­ a te a s in g le h o is t.

W h e r e la r g e o u t ­ p u ts m u s t b e a t ­ ta in e d s p e e d a n d r e lia b ility a r e p r im e r e q u isite s in h o i s t ­ in g e q u i p m e n t . S u c h m a c h in e r y m u st, th e r e fo r e , b e m a s s iv e in d e s ig n .

H o is tin g E le c tr ic a lly H o i s t a t V a lie r . R a is in g c o a l e n t a ils a b ig d e m a n d f o r p o w e r . A fly w h e e l m o to r - g e n e r a t o r is in te r p o s e d b e tw e e n t h e h o is t a n d t h e lin e . T h e in e r t ia o f t h e f ly w h e e l ta k e s p a r t o f t h e lo a d w h e n c o a l is b e in g r a is e d , t h u s c u t t in g d o w n d e ­ m a n d p e a k s.

APRIL 29, 1 9 2 6 C O A L A G E

the m otor an d th e sto re d e n e rg y o f th e flywheel. The hoist its e lf is d riv en by a m o to r d ra w in g its c u r re n t supply fro m th e d ire c t-c u rr e n t g e n e ra to r. An a u x ilia ry a lte rn a tin g -c u rre n t m o to r o f re la tiv e ly sm all cap acity is provided f o r h o is tin g m en an d m a te ria ls w hen th e large m o to r-g e n e ra to r is n o t in o p eration.

T his m ethod of d riv in g th e h o ist, v ario u sly know n as the W ard -L eo n ard an d Ilg n e r sy stem of control, provides a fa irly ste a d y a v e ra g e load upon th e a lte r n a tin g - c u rr e n t supply, sim u ltan e o u sly affo rd in g alm o st u n lim ited pow er for h o istin g p u rp o se s. One of th e a d v a n ta g e s of th is method of co n tro l is t h a t in th e event of an in te rru p tio n to the pow er su p p ly sufficient en e rg y fo r h o istin g is available fo r som e tim e fro m th e flywheel alone. T his control also g ives g r e a t refin em en t of m a n ip u la tio n in hoisting. I t is u n d o u b ted ly th e m o st s a tis fa c to ry method y et devised fo r co n tro llin g m in e h o ists a t o p era­

tions of la rg e cap acity . In sm all m ines or th o se th a t hoist only a s h o rt d ista n c e w h e re th e size o f m otor required does n o t exceed

to

hp. g ea red a lte rn a tin g -c u rre n t m o to rs a re em ployed.

Ha u l a g e Us e s 2 5 0 -Volt Cu r r e n t

P ow er h a u la g e in Illin o is m in es is p e rfo rm e d en tire ly by m eans of d ire c t c u r r e n t a t a p p ro x im a te ly

volts.

To fu r n is h th is e n e rg y sy n ch ro n o u s m o to r-g e n e ra to r sets a re em ployed. A n Illin o is law fo rb id s th e c a rry in g of p o ten tials exceeding

volts on exposed w ires.

C u ttin g an d m in in g m ach in e s a re o p erated both by direct c u rre n t fro m th e h a u la g e sy stem a t a p p ro x im a te ly

volts an d by a lte r n a tin g c u r r e n t a t ab o u t

volts.

A lte rn a tin g -c u rre n t c u ttin g m ach in e s w e re first in tro ­

duced in th is s ta te in 1913 follow ing th e in tro d u c tio n of p urchased pow er. T h e ir use encouraged th e p ra ctice of ta k in g pow er a t 2,300 volts u n d erg ro u n d by m eans of three-p hase, lead-covered, arm o red cables to b an ks of tra n s fo rm e rs located a d ja c e n t to th e w o rk in g faces.

T h is arra n g e m e n t g re a tly reduced th e losses experienced in th e d ire c t-c u rre n t tra n s m is s io n an d m a te ria lly les­

sened re p a irs to th e c u ttin g m ach ines them selves as full voltage w as alw ays supplied to th em . T h e m a jo rity of new m ines developed w ith in th is s ta te d u rin g th e la st te n y ea rs have installed a lte r n a tin g - c u rr e n t c u ttin g m achines.

Pu m p s a n d Fa n s Use Al t e r n a t in g Cu r r e n t

P um ps used fo r voiding w a te r fro m th e m in es a re usually driven by a lte rn a tin g - c u rr e n t m o to rs, alth o u g h some are operated fro m th e d ire c t-c u rre n t h au lag e c ir­

cuits. V e n tilatin g fa n s a r e u sually d riv en by in d u ctio n m otors ta k in g e ith e r 220, 440 o r 2,300 volts. M any m achines of th is kind a r t o p erated a t c o n sta n t speed b u t o th ers a re connected to v ariable-sp eed m o to rs ob­

ta in in g th is v a ria tio n of speed e ith e r by m eans of pole-changing devices o r by som e fo rm of m echanical equipm ent fo r a lte rin g th e speed. T ipple m o to rs a t th e m a jo rity of m ines a re o p erated on a lte r n a tin g c u rre n t of 220 to 440 volts.

D u rin g th e la s t tw o o r th re e y e a rs a n u m b e r of la rg e s tr ip m ines have been developed in Illinois. Some en tire ly sa tis fa c to ry beds of coal lie w ith in 25 o r 30 f t.

of th e su rface. By th e use of la rg e pow er shovels it

has been found possible to s tr ip th e o v erb u rd en fro m

th ese m easures and lay th e coal b are. S m a lle r shovels