McGr a w- Hi l l Co m p a n y, In c.
D e v o te d to t h e O p e ra tin g , T ec h n ical a n d B u sin e ss w
Ja m e s H . McGr a w, P resid en t , , i , , n , T j j. R . Da w s o n Ha l l
E .
J.
Me h r e n, V ice-P residentP ro b le m s o f t h e C oal-M ining I n d u s tr y
E n g in e erin g E d ito rV olum e 28 N E W Y O RK , J U L Y 30, 1925 N um ber 5
T hose T errible M ines?
E VERY ONCE in a while comes the p lain t of th e m iner ag a in st the u n fo rtu n ate conditions under which he works. He really does not w ish to labor in th e open w ith the carpenter and mason, b u t he does w ant e x tra pay fo r toiling underground. I t is true, m ining w ork is done in the d ark and in th e d irt, bu t it is not done under a w iltin g sun or in th e fro st. The carp en ter and m ason have much h ard er physical condi
tions th a n th e m iner. The plasterer, th e g ra d e r and th e trench digger and backfiller have ju s t as d irty work and have to face th e clim atic v ariations also.
The m iner is really fo rtu n ate. He has no hot and no cold days. True, he m ay have a w et place, and if the w a te r falls from above he m ay have to p u t up sheet iron or w ear slickers, b u t carpenters, masons, g rad ers and tren ch diggers often work in the ra in and when it gets beyond th e ir endurance th ey quit w ork and lose pay fo r th e days or p a r t days they are idle.
We all irk som ewhat under th e compulsions of indus
try , w hatever we m ay be doing, and th e m iner is to be excused fo r his long-draw n sigh, b u t th a t is no reason why he should receive sym pathy, instead of the congratulation to which he is entitled. He knows he has the b e tte r fate, fo r he alm ost never leaves th e indus
try , and when he is asked to work outside he refuses or he accepts th e new occupation w ith m ore complaints th an he ever leveled a t h is accustomed job and w ith the intention of g ettin g “below” again as soon as he can.
ing a really responsible position a t th e age of 30. Many a m an by the old ro ute w itho ut college tra in in g and w ith h ard work gets to such a position in less time, bu t such advancem ents are usually m ade in small cor
porations, and the men th a t g et them usually stay fo r th e re st of th e ir lives eith er ju s t w here they are or find employment with a company of no la rg e r size.
B efore or A fter Taking
C ONTACT w ith the actual problems of m ining before or a f te r receiving collegiate tra in in g in engineering is necessary if a m an would be a success
ful and com petent m ining engineer. The technically train ed m an m ust eith er s ta r t from th e ea rth or come down to e a rth before he can be successful a t sup er
vision. I t is tru e th a t the young m an who has worked in the m ines is som etimes so enamored of his job th a t he resents being sent to college “to cram ” as he expresses it and th a t the m an who goes to college first w ants to s it behind th e m ahogany and issue orders as soon as he re tu rn s. B ut n eith er plan gives good results.
Not only technological tra in in g specific to th e indus
try but inform ation th a t can be attain ed only from personal contact w ith the actual w ork is necessary fo r the m an who walks around and gives orders. I t is ju s t as well to m ake up one’s m ind to th a t. Even in Europe actual experience of th is kind is custom ary.
One would say th a t the “physical tra in in g ” should be as long as th e academic and th e closer it is to the actual w ork th e better, th e m ore th e atm osphere is absorbed and th e closer are th e observations th a t are made.
Six to eight years, h alf academic and h alf in actual field contact, is not too long a period in which to make a real s ta rt. A m an thus tra in e d should be occupy
Less than One in a Thousand
G REAT B R ITA IN R EPO R TS th a t the fa ta lity rat'e per thousand in its coal m ines is lowered to 0.98.
L ast year it was 1.06. In th e same y ear the fa ta lity ra te in the U nited S tates was 2.87 p e r thousand em
ployees or nearly th ree tim es as high as in G reat B ritain, and th a t in a y ear of relative depression. I t m ust be remembered, however, th a t G reat B rita in also suffered from a depression and th a t th e num ber of w orking hours in a day is only seven.
Perhaps it would be best to m ake a com parison per thousand 2,000-hr. w orkers. The B ritish ra te in 1924 we figure as 1.20, w hereas our ra te d u rin g 1923 was 3.63 or about th ree tim es as g reat.. Many believe the B ritish m iner is exposed to more n atu ra l hazards th an the American. T h a t is always difficult of proof, bu t the figures given are disquieting, to say the least, and only b y an investigation of the ra te p er million tons produced can any relieving consideration be found.
The fa ta lity ra te p er million tons of coal m ined in this country was 4.15, w hereas in G reat B rita in it
■rfas 4.36, so the tonnage was obtained in th e U nited S tates at a lower blood cost p er ton. In the m a tte r of ease of production A m erica certainly has the advantage, so it can hardy be wondered th a t it has a lower ra te per million tons mined. The m arvel is th a t we have not been able to make th e difference m ore considerable.
If Coal Cutting Failed This Is the Reason
S AYS John L. Lewis, th e president of the U nited Mine W orkers, in his book “The M iners' F ig h t fo r American Standards,” which should read fo r “ S tandards H igher than Those Normal to Am erican L ab o r:”
“F ifty years have passed into h isto ry [it should be only a little over half th a t length of tim e b u t let th a t pass]
since the first undercutting coal m achine designed to relieve the strength-sapping s tra in
o nth e m iner’s body and [to a ttain ] m aterially lowered production costs was
in tro d u c e d ;yet coal m ines continue to be
o pened,the owners of which have n eith er the capital no r intention to provide this essential m achine.”
In judging th e conclusion th a t th is is a “sin of managem ent in the bituminous-coal in d u stry ” we will pass by the generally adm itted fact th a t th e mine w orkers opposed th is g re a t innovation and a re still opposing it where it is not introduced, though it saves a “strength-sapping stra in on the m in er’s body,” and we will proceed to call atten tio n to th e fa c t th a t th e
141
142 C O A L A G E Vol. 28, No. 5
m iners through th e ir unions repeatedly have attem pted and alm ost everywhere succeeded in establishing a d if
ferential th a t makes th e introduction of the m achine a doubtful source of profit and the use of th e b etter classes of cutters productive of only indirect gain.
Machine coal in many instances is m ore economical th an w hat is term ed “hand-mined coal” (but ra th e r should be called “powder-mined coal”) only because it is not so badly sh attered and because its production re duces the area to be developed and m aintained and saves in the construction of houses.
In cases where the use to be m ade of the coal does not demand the production of large sizes th e advantage of the m achine is slight except in so f a r as it removes the danger of solid shooting. The union is responsible largely fo r th is being a hazard. There is little evidence th a t “powder m ining” is strength-sapping. Its chief disadvantage is its danger, and w here the coal is soft and easily shot and precautions are taken, as in the Connellsville region, which, by the way, is non-union and uses proper methods of shooting, th e statistics show th a t the dangers can be avoided. In union fields, where the union men in sist in overloading th e ir holes and in firing them or having them fired, and w here face sprinkling is unknown, the hazard of “powder m ining”
is extreme.
This charge of Mr. Lewis falls to the ground. We rejoice to see machine m ining develop, but only because of secondary, almost impalpable economies and because of safety and not because the m ining by m achine is
per se any cheaper in most cases than “powder m ining”or tru e “hand m ining.” In th e cost of m achine m ining the cost of powder, repair's, in tere st and depreciation have, of course, to be considered and when they are th e machine has only incidental advantages over hand mining. The union has seen to th at. Y et Mr. Lewis uses the fact th a t the use of machines is only 67 per cent instead of 100 per cent as a club a g a in st th e operator. Being w ith his back to the wall, we suppose he will be excused fo r using w hat weapons come to his hand to the best advantage, even though he cannot prove the rig h t of ownership.
In the anth racite region the use of th e m ining machine has been made practically impossible by the action of the union. I t has introduced into th e contract made with the operators a provision th a t has caused the a rb itra to r in his belief no option bu t to give such a decision to the mine workers as makes th e operation of m ining machines unprofitable. Mr. Lewis has uncovered a m are’s nest. His attack on coal operators calls renewed attention to th e union’s studied opposition to m ine-operating efficiency.
W aiting fo r Others
F ROM COLONIAL times the fa n n e r has w aited fo r others to find a way fo r him. F o rtu n ate, indeed, it is th a t the D epartm ent of A griculture and the sta te ag ricu ltural colleges have developed fertilizers, insect poisons, new systems and p lant varieties so th a t the fa rm er has been able to overcome the steady im pover
ishm ent of his soil, droughts and the attacks of plant plagues.
Coal men have followed a sim ilar course to the farm ers. They have left progress in the use of th e ir product to chance. I t is tru e th a t the early an th racite companies urged and assisted the consumer, or possible consumer, to make use of anthracite. In the early days
the D elaware & Hudson Co. was quite active in inducing steam boat owners, householders and in d u stries to use th a t fuel instead of wood. The an th ra cite companies are fo sterin g the use of fine coal, bu t they have invented few or none of these devices. Eckley Coxe, it is tru e, made im po rtant efforts to p u t the autom atic stoker in the steam field, bu t on th e whole, coal men have le ft to the m anu facturers the w ork of devising new stokers and ascertain ing the best m ethod of employing them .
By and large, the coal men have done little. They w anted the consum er to provide his own expansion of the coal industry, and the development th a t m ade the small sizes saleable slowly came about, th ank s to th e consuming public, not to the operator.
In G reat B rita in th e m ine owners are con tribu tin g to research. They are try in g to expand th e ir narrow ing m arket. As the B ritish and C ontinental in dustries are m ore w asteful of fuel th an ours, th ey have to face a g re ater re stric tio n in the sale of coal th a n we have.
Our operators probably already have encountered the w orst of th e ir troubles, b u t in Europe the long period th a t has passed w ithout m uch advance in combustion methods will m ake conditions desperate when once th e tide sets full fo r economy w ith our progress serving the economizers as a guide. In th e U nited S tates almost the only studies being made are those of the N ational Coal Association and the B ureau of Mines. I t is only a beginning b u t it is suggestive of a b rig h te r fu tu re . It looks forw ard to th e tim e when petroleum will be driven not only from th e steam field bu t also fro m the in tern al combustion and lub ricatin g fields. T his is only a small p a rt of the progress necessary. Coal should have a leading place in ou r organic chem istry field and th a t in du stry should be immensely m ore im p o rtan t th an it is now.
The electrical ind u stry is tak in g tim e by th e fo re lock w ith its Society of E lectrical Development which is finding fux*ther uses fo r electricity. F o rtu n ately th e problems of th e public u tility companies are small com
pared w ith ours, fo r th e irs is largely an attem p t to h u rry the inevitable change in th e hab its of m ankind, w hereas the coal ind u stry is seeking to find new devices fo r the conversion of one chemical substance into an
other. Probably th e coal in d u stry would do well to try also*the method of th a t electrical society, inducing the public to use more heat, to re frig e ra te th e ir houses, offices and public buildings, to cease b u rn in g wood and to use small, instead of large, coal, paying a b e tte r price fo r th e small sizes. The Copper and B rass Research Association and th e Am erican Zinc In s titu te are prom oting th e use of copper and of zinc respec
tively. The brick m an u factu rers are associated in an endeavor to popularize brick. Coal men have a lot of good exemplars to follow and th ey should g et in touch w ith them and learn th e ir ways and, w here possible, co-operate w ith them, especially the Society of Elec
trical Development, in the prom otion of th e re frig e ra tion plan.
The n atu ral m eans fo r doing th is w ork as f a r as the bitum inous field is concerned is the N ational Coal Association. I t can be th e bitum inous coal m en’s Coal Research In stitu te and its Society of Coal Development.
Why w a it fo r others? L et us find a place fo r our coal and instead of th e present ruinous com petition we can find employment fo r all. B ut let us be prac
tical, tackling th e easiest roads to increased demand
most energetically and leaving th e la rg e r and less
obvious problems fo r secondary consideration.
Ju l y 30, 1925 C O A L A G E 143
Air-Lift P u m p in g System Q uickly Raises W ater F ro m Flooded A n th racite Mine Areas
O rdinary D e w a ter in g M eth o d s Could N o t E a sily B e U se d a t F irst — N o w A ir L ifts W a te r P art W a y U p S h a ft and C en trifu gal U n its Pum p to Surface
Bv E. J. Gealy
A s s o c i a t e E d i t o r , C o a l A g e , N e w Y o r k C ity
U NUSUA L M ETHODS are- being employed to reopen the Neilson m ine of th e Sham okin Coal Co. in the city of Shamokin, Pa. F o r m any years th e p roperty had been idle and the w a te r had risen in th e sh a ft to w ith in about 30 ft. of th e ground level. All of those p a rts of the coal beds which had been previously mined were, therefore, full of w a te r and it was necessary to s ta r t any unw atering operations from the outside.
The officials of the company decided th a t the best way to s ta r t unw atering the m ine was by means of an a ir-lift pum ping system. Probably the fa c t th a t the m ine will need air-com pressing equipm ent when it gets into operation had m uch to do w ith selecting th is method of ra isin g the w ater. N evertheless, som ething different from o rdinary m ine-pum ping m achinery had to be used so as to obviate the necessity and expense of providing p relim inary stru c tu re s fo r pum ps and buckets.
On Nov. 9, 1924, one a ir lift was started . I t con
sisted of a 190-ft. column line of 10-in. w rought iron pipe supported in th e old m ine sh a ft. T his length of pipe was considered sufficiently long to obtain satis
facto ry subm ergence, although the sh a ft was 1,200 ft.
deep and th e vertical depth of the w a te r was g re a te r than th is because of th e basins in the steeply pitching beds.
The a ir supply fo r th e lift was furnished by a com-
T h e v i e w i n t h e h e a d p i e c e s h o w s t h e t w o a i r l i f t s in o p e r a t i o n . A t f i r s t t h e w a t e r w a s w i t h i n 30 f t . o f t h e g r o u n d le v e l. B y m e a n s o f t h e s e l i f t s t h e w a t e r w a s l o w e r e d t o a p o i n t 50 5 i t . b e lo w t h e s u r f a c e o f t h e g r o u n d . N o w a i r l i f t s r a i s e t h e w a t e r t o t h e N o . 1 2 le v e l a n d i t i s r e l a y e d t o t h e s u r f a c e b y t w o 1 .0 0 0 - g a l. p e r m i n u t e c e n t r i f u g a l p u m p s .
pressor located in a large building a few fe et from th e shaft. In December an other sim ilar a ir lif t w as installed in th e sh a ft and th e tw o lifts w ere kept in operation as much of the tim e as possible. The a ir lifts w ere stopped only when it became necessary to add ex tra lengths of pipes to m ain tain sufficient subm er
gence to obtain satisfacto ry results.
In th e air-com pressor house two large com pressors driven by 2,300-volt synchronous m otors supplied th e air. One com pressor was a 1,500-cu.ft. p e r m inu te u n it driven by a 300-hp. m otor and th e other a 3,500-cu.ft.
p er m inute m achine connected to a 600-hp. m otor. Both machines w ere directly connected to th e ir respective drives.
The cooling w a te r fo r th e com pressors was circulated to a tan k located on a hillside a sh o rt distance from th e com pressor house w here i t was cooled by being discharged upon a screen m ounted a few fe e t above th e top of th e tank. The w a te r dropped th ro u g h the p e r
forations in the screen and separated into fine stream s which perm itted the particles to cool and th en drop into th e tan k and be conducted back to th e w ater jackets on th e compressors.
P assing from th e com pressors, th e a ir w as conducted th ro ug h an 8-in. w ro ug ht iron pipe. N ear the top of the sh a ft th is pipe was connected to two 4-in. pipes which supplied th e a ir to each lift. Suitable control valves were placed in th e a ir lines so th a t th e qu antity of a ir could be regulated or stopped w henever i t was necessary.
Several novel fe atu res w ere incorporated in th e design and operation of th e lifts by B. C. Osier, super
intendent of th e m ine. The foot piece w as constructed
144 C O A L A G E Vol. 28, NO. 5
F I G . 1
F o o t Piece and F a ste n in g s
T h e a i r w a s b r o k e n u p i n t o s m a l l s t r e a m s b y e n t e r i n g t h e e d u c t i o n p ip e t h r o u g h 1 - in . h o le s . B o t h a j a c k e t a n d a n o z z l e a s s i s t e d in i n t r o d u c in g - t h e a i r i n t o t h e p ip e . A H t h e w e i g h t w a s t a k e n o n w i r e c a b l e s a t t a c h e d t o a f la n g e f a s t e n e d t o t h e j u n c t i o n b e t w e e n t h e l a s t w h o le s e c t i o n o f p i p e a n d t h e f o o t p ie c e .
out of a stra ig h t 5-ft. section of 10-in. pipe drilled full of ¿-in. holes except n ear each end, as shown in F ig. 1.
Around the perforated p a rt of th e pipe a sh o rt section of 12-in. pipe was welded in such a m anner as to form a jacket or chamber. A t diam etrically opposite points in this outer pipe connections were made to the a ir line.
An additional p a rt of the foot piece was a 3-in. bronze nozzle also connected to the 4-in. a ir line. T hus the construction of the foot piece was such th a t a large volume of a ir broken up into m any fine stream s had easy access into the eduction pipe.
The ideal design of an a ir lift eduction pipe or dis
charge line is one which properly tap ers throu gho ut its whole length in proportion to the expansion of the a ir bubbles as they rise in the pipe. Such a tube is hardly practical because the length and ta p e r of th e pipe would be different fo r every different a ir lift.
However, to approach such a characteristic the a ir lift discharge lines a t the Neilson mine w ere m ade of th ree different size pipes. When the a ir lifts were stopped from pum ping directly to the outside surface they con
sisted of a lower section of 10-in. pipe 200 ft. long to which was attached another 200-ft. section of 11-in.
pipe and a t the top was still another section of 12-in.
pipe about 240 ft. long.
The ultim ate total w eight of one of these eduction pipes was nearly 20 tons and, consequently, required
F I G . 2
Pipe and Rope Clamp
T o k e e p t h e e d u c t i o n a n d a i r p ip e s p r o p e r l y a l i g n e d , c l a m p s w e r e p l a c e d a t v a r i o u s p o i n t s a l o n g t h e lin e . I n t h i s m a n n e r t h e to t a l , w e i g h t o f t h e p ip e s w a s s u s p e n d e d o n t h e c a b l e s .
strong supports. In addition to suspending th e a ir and discharge pipes, arran gem en ts had to be such th a t extra pieces of pipe could be added and th e whole column line lowered as the w a te r level receded.
One of the m ost essential fe a tu re s effecting th e suc
cessful operation of an a ir lift is the subm ergence of the eduction pipe. Obviously, as th e level of the w ater in th e Neilson sh a ft became lower the pipes had to be dropped so as to m ain tain sufficient subm ergence. To accomplish such ad ju stm en ts as efficiently and quickly as possible, all ex tra sections of pipe were added to the top and th e whole eduction pipe was suspended on 3-in. steel hoisting cables.
A t the junction of th e foot piece and bottom section
F ig . 3— S ketch Showing A ir L ift and S h a ft
T w o c o m p a r t m e n t s e x t e n d to t h e N o . 11 l e v e l a n d t w o t o t h e b o t t o m le v e l. T h e a i r l i f t w a s f i r s t u s e d t o d i s c h a r g e t h e w a t e r t o t h e g r o u n d le v e l a s s h o w n h e r e . N o w p u m p s a r e l o c a t e d o n t h e N o . 12 le v e l a n d t h e a i r l i f t h a s b e e n m o v e d d o w n t h e s h a f t s o t h a t i t d i s c h a r g e s I n t o a b a s i n in t h e N o . 12 l e v e l f r o m w h ic h i t i s r e l a y e d t o t h e s u r f a c e b y t w o 1 ,0 0 0 - g a l . p e r m i n u t e , c e n t r i f u g a l p u m p s .
of pipe a large round collar or flange was inserted.
Sufficiently spaced from th e outer edge of th is rin g two eye-bolts w ere attached as shown in F ig. 1. To these bolts th e 3-in. supporting ropes w ere attached.
A t various positions along th e discharge pipe, clamps sim ilar to those shown in F ig . 2 w ere used to hold the pipe to the ropes and also tie the 4-in. a ir line to the large pipe.
The support a t the top of the sh a ft was as shown
in F igs. 4 and 5. Two rope clamps 10 in. long were
attached to each rope and the w’eight of the pipes w as
supported on a yoke or cross m em ber which in tu rn
rested on heavy beams. Each rope extended over th e
headfram e onto a reel from which it was unrolled as
required.
W hen it became necessary to attach additional sec
tions of pipe and lower th e column line, other clamps w ere placed on th e ropes fa rth e r up n ear th e top.
When th is was done th e w eight of the pipe w as placed upon large pulley blocks which operated th ro u g h a cable connected to a small hoisting engine. In th is m anner the pipes w ere lowered until th e ir w eight again rested on the new clamps. See F ig. 4.
D uring the period between Nov. 9, 1924, and Feb. 19, 1925, one or the other or both of the a ir lifts were in alm ost continuous operation. As a m a tte r of fact, only about 65 h r. of operating tim e was lost in m aking th e various changes to the lifts.
On Feb. 19, when the lifts w ere stopped from pum p
ing to th e outside surface, th e eduction pipes w ere 640 ft. long and the w a te r had been lowered about 475 ft. This indicates th a t the w ater level dropped at the ra te of about 44 ft. every 24 h r. I t has also been estim ated th a t during p a r t of the tim e 5,000 gal.
per m inute was pumped and a total of about 335,000,000 gal. was raised to the surface.
F ig. 5— Rope C lam ps P re v e n t Cables from S lipping
T w o l a r g e c l a m p s w e r e f a s t e n e d t o e a c h w i r e a n d t h e w e i g h t o f t h e p ip e s s u p p o r t e d o n c r i b b i n g w h i c h s p a n n e d t h e - m i n e s h a f t .
other hoisting com partm ents extend to a point 1,200 ft.
from the surface. An airw ay also goes to the bottom level. In all, probably sixteen coal beds are cut by the whole shaft.
The dew atering of th e m ine having reached the point attained on Feb. 19, a ir-lift pum ping to the su rfa ce was discontinued so as to finish th e job as efficiently as possible. Since th en two 1,000-gal. per m inute pumps have been set up in th e No. 12 level and the a ir lift discharges to these u n its which in tu rn relay the w a te r to th e surface. In tim e, two m ore cen trifu gal pumps will be located in th e No. 11 level and th e w a te r relayed
F I G . 6
C om pressors for Air L ifts
B o t l i o f llie s e u n i t s w o r k e d t o g e t h e r to -su p p ly a i r t o t h e tw o a i r li f t s . A n 8 -in . p ip e c o n v e y e d I lie a i r to t h e s h a f t a n d f r o m t h e r e i t w a s <1 l o p p e d i n t o t h e s h a f t t h r o u g h tw o 4 -in . a i r p ip e s . E a c h a i r l i n e w a s a t t a c h e d to t h e o u t s i d e o f t h e d i s c h a r g e p ip e .
July 30, 1925 C O A L A G E
The discharge from the a ir lifts varied, as would be expected, depending upon the am ount of subm ergence and depth from which the w ater had to be raised. Best results were obtained when the subm ergence was ab o u t 200 ft. and th e lift about 100 ft. A veraged over th e whole range of operation the cost of ra isin g the w a te r was slightly over 6.5c. per 1,000 gal.
Although the total depth of the sh a ft a t th is mine is about 1,200 ft., the mine workings extend about 200 ft.
lower. Obviously, th e work of unw atering the mine was not complete when, on Feb. 19, the a ir lifts were stopped from pum ping to th e surface.
Fig. 3 shows the arran gem en t of the sh aft. Two com partm ents go down to th e No. 11 level which is about 700 ft. from the surface a t th is point. The two
d a m p s
P I G . 4
S u p p o rtin g th e Pipes
A t t h e to p o f t h e s h a f t , h e a v y c l a m p s h e l d t h e r o p e s . W h e n e v e r i t b e c a m e n e c e s s a r y t o l o w e r t h e c o l u m n p ip e , t h e w e i g h t w a s t a k e n o n a s m a l l h o i s t a n d c l a m p s w e r e a t t a c h e d i n a n e w p o s i t i o n . T h e h o i s t w a s t h e n u s e d t o l o w e r t h e p ip e t h e r e q u i r e d d i s t a n c e . '
or cf/schargt
Supporting cahlz
146
C O A L A G E
Vol. 28, No. 5F ig. 7— U nits for P erm an e n t Mine Service
T h e s e a r e tw o o f t h e c e n t r i f u g a l p u m p s w h i c h w i l l b e p e r m a n e n t l y l o c a t e d I n s id e t h e m i n e to t a k e c a r e o f t h e r e g u l a r in flo w a f t e r t h e c o a l b e d s a r e u n w a t e r e d .
to them by the a ir lift. In th is m anner it is intended to carry xne unw atering plan until the a ir-lift system will be im practical fo r fu rth e r use here.
The success of the Shamokin Coal Co. w ith the a ir-lift method of ra isin g w ater recalls to memory th ree other im portan t applications of the system in the an th ra cite region. These were made by th e Glen Alden Coal Co.
a t Hampton W ater Shaft, the Hudson Coal Co. near Carbondale, Pa., and the M adeira, Hill & Co.
N atal M ines F ou r M illion T o n s O f Coal Y early
Seams A re T hin and in M ost Cases S p lit
—V o la tile M atter V aries W id e ly but Is A lw ays L ow — D o lerite S h eets and D y k es
Coal was discovered in N atal in the year 1838, but beyond th is bare statem ent no fu rth e r inform atio n is obtainable. “On Aug. 20, 1842,” says W. J. W ybergh in his small m onograph on “The Inland Coalfields of N atal,” Vol. II of “The Coal Resources of the Union of South A frica,” published by Geological Survey o i th a t commonwealth, “ C aptain Sm ith, w ritin g from P ieterm aritzb u rg to S ir George N apier, stated th a t th ere was no doubt th a t coal existed in consider
able quantities about 130 miles from th e coast and advocated the form ation of a company to w ork it.”
In 1888 a num ber of mines w ere opened, of which the Newcastle Colliery, E landslaagte Colliery and Dundee Coal Co. mine still exist.
D uring the first year the coal was tran sp o rted by bullock wagon, bu t before th e y ea r was over a branch was constructed by the company from Glencoe to Dundee, since taken over by the Governm ent and made p a rt of the Glencoe-Vryheid-Piet R elief Ry. In th a t year the bunker tra d e was successfully in au g u rated on a commercial scale, a total of 686 tons being taken by six steam ers. The total tonnage, coal and rock mined in 1923 was 5,618,404, of which 1,124,947 sh o rt tons was classified as waste. The total coal sold was 4,302,892 sh ort tons fo r which $8,251,390 was received, or $1.92 p er ton.
There are th ree main fields—the Klip River, the Vryheid and th e U trecht. In the Klip River are only two seams of commercial value the “Top” and the
“Bottom.” In only a few collieries can both seams be worked over the whole area, though in m ost cases a t least a portion of both have been considered workable
under existing economic conditions. The coal is quite usually gaseous, even in some cases where it is covered by only 70 ft. of cover.
Some have ascribed th is to th e action of igneous sheets which are from 25 to 380 ft. thick and are found from 60 to 398 ft. above th e coal. Some declare th a t these sheets prevent th e gas from escaping, b u t the au th o r quotes Mr. S te a rt to the effect th a t th e sand
stones and shales are m ore im pervious th an the dolerite sheets. The effect of the dolerite on the p e r
centage of volatiles in th e coal does not seem to accord w ith any rule, certainly not w ith th e rule th a t the effect will be found to vary w ith the thickness of the sheet ( T ) and inversely as th e thickness of intervening m easures (D ). In one place D ~ T = 1.8, th a t is, the protecting m easure is th icker th an the molten sheet. H ere the percentage of volatile m a tte r is 8.48 and th e coal is practically an anthracite. In another place the D -h T — 0.7, th a t is the protecting m easure is th in n e r th an the molten sheet, yet the percentage o f volatile m a tte r is 20.77. The thickness of the sheet is 310 ft. and th e thickness of the in te r
vening s tra ta only 206 ft. Nevertheless, th e coal is distinctly sem i-bitum inous and not an th racite.
As th e au th o r states “I t is m ore th an likely th a t not merely the ra tio D - r T bu t th e absolute distance from th e coal irrespective o f thickness” m u st be considered.
“Of course,” says Mr. W ybergh, “where th e p er
centage of volatiles is unexpectedly low, th is may, in some cases, be due to the proxim ity of a vertical or highly inclined dyke not disclosed by th e borehole, or conceivably, b u t improbably, to th e existence of an o th er sheet below th e coal.” A t th e New Campbell colliery a dyke over 1,200 ft. thick was stru ck about 100 ft.
from the shaft, a t which point the coal contained 4 per cent of volatile m atter. A t a distance of 1,200 ft. from th e dyke it had 15 p er cent of volatile m a tte r and at 1,400 ft. it had 19 p er cent, and th e coal showed indi
cations of coking.
Sp l it s Red u c e Va l u e o f Se a m s
The coal is extensively faulted and th e p a rtin g between the Top and Bottom coals varies from a few inches to 40 or 50 ft., and even in a single colliery from one foot to 50 ft. The thicknesses of these splits vary from less th a n 2 ft. to 10 ft. or more bu t in th e g re a te r p a rt of the area are between 3 ft. and 5 ft. thick. The ash percentage in the coal as used a t Capetown varies from 9.89 to 15.60.
In the V ryheid d istric t are fo u r commercial seams, the Alfred, Gus, Dundas and Coking seams and others of lesser im portance. The Gus seam is usually unsplit and ru n s from 4 ft. to 6 ft. 8 in. The Coking seam is th in and ru n s from f ft. 2 in. to 2 ft. 6 in. The A lfred and Dundas seams frequently split, b u t in one place the la tte r contains two layers 4 ft. 7 in. and 4 ft. 3 in, respectively, w ith a shale p artin g . The sulphur in these seams is quite low, 0.50 to 1.20 p er cent. The ash run s fro m 7.44 to 15.95 p er cent and the volatile m a tte r from 10.22 to 26.06 p er cent. Here, also, are igneous sheets, dykes and faults.
The U trecht coal field has no railroad, but it contains some of the best coal in N atal. The same seams are found as in the V ryheid district. Thus a t th e U trech t colliery th e A lfred seam is 6 ft. 1 in. thick, th e Gus seam 5 ft. and th e Dundas seam 2 ft. A t Dumbe M ountain these seams are 6 ft., 3 ft. 6 in. and 6 ft. 5 in.
respectively, w ith th e 1 Coking seam 3 ft.
Ju l y 30, 1925 C O A L A G E 147
A ltern ato rs S upplying Mine Loads A re Easily an d Safely P aralleled an d O p erated
F lu c tu a tin g L o a d s M ake S p ecia l P reca u tio n s N e ce ssa r y — S y n ch ro sco p es Can B e M ade from L am p s and V o ltm ete r s— D ia g ra m s E x p la in B ad
, E ffe c ts o f P o o r P ow er F actors
B y J. A. Erskine
P i t t s b u r g h T e r m i n a l C o a l C o., P i t t s b u r g h , P a .
T H E IN C R EA SED use of electricity in the work
ing of m ines necessitates in many cases a power plan t comparable in size w ith th a t fo r supplying lig h t and power fo r a fa irly large sized town. The colliery electrician has, therefore, to take charge of a plant w here altern ato rs frequently are required to run in parallel and connected to a load which is certainly not helpful to good parallel operation. The aim of th is article is to show how th is difficulty can be overcome.
The w ork of paralleling altern atin g -cu rren t machines is a m ore difficult operation th an is the case w ith con
tinuous-current generators. W ith direct-current gen
erato rs th e only im portant point is th a t th e voltage of the incom ing m achine should be the same as the busbar voltage.
W ith altern atin g -cu rren t m achines not only m ust the voltage be the sam e b u t the periodicity also. F u rth e r than this, the machines m ust be in phase; th a t is to say, i t is not sufficient fo r the periodicity of the m achines to be exactly th e same, but the voltage of th e machines , m ust rise and fall a t the same instant.
The process of b rin g in g machines into phase is called synchronizing. “Synchronous” m eans th a t the p re s
sures and c u rren ts rise and fall exactly a t th e same tim e. Two altern ato rs to be connected in parallel, m ust both be of the same pressure and c u rre n t a t th e same in s ta n t; each m u st-b e a t the positive maxim um of pressure and c u rren t a t the same in sta n t; each m ust be a t zero pressure and c u rre n t a t the sam e in stan t. A t any in sta n t the pressure fu rn ish ed by each m achine m ust be exactly the same.
W hen connecting three-phase machines in parallel, like phases m ust be connected to g eth er; th a t is to say, re fe rrin g to F ig. 1, phase 1 of th e two m achines to be paralleled m ust be connected to g eth er; phase 2 of the two m achines connected together, and so also w ith phase 3. I f phase 2 of one m achine is connected to phase 3 of the other machine, and, say, phase 3 of the first m achine to phase 2 of the second machine, the m achines will not parallel, and large cu rren ts will pass between them.
F ig. 1 shows diagram m atically the th re e phases of
.yscto rd io g ra m o f N o .Im a c h in e j-j-'No.I_p h o s e term in a l j^ V e c io r o/iagram Voltaqe o f No. / p h a se Voltage o f o f No. 8 machine
9 No. ¡phase*''
, -Voltage o f WMa9 * o f No. ¿phase.,A N o 3 p h a se
Vo/faqe o f No. 2
D irection o f \
.■’V oltage o f ' No. 3 p h a s e
two machines th a t are to be paralleled, and how the connections should be made. It will be noticed th a t phase 1 of the left-hand m achine is connected to phase
1 of the right-hand m achine, phase 2 of th e left tophase 2 of the righ t-han d m achine, and phase 3 to phase
3.Fig. 2 shows diagram m atically th e same two machines, b u t w ith th e ir phases connected incorrectly.
From this diagram it will be seen th a t while phase 1 of the left-hand machine is connected as before to phase 1 of th e rig h t-h an d m achine, phase 3 of the left- hand m achine is connected to phase 2 of th e righ t-h and m achine; and phase 2 of th e left-hand to phase 3 of the right-hand.
The difference in the arrang em ent of the phases be
tween the right-hand m achine and the left-hand one will be recognized as th a t which is used to reverse the direction of ro tation of an induction m otor. And this provides the te st fo r en su ring th a t the phases are in proper sequence. B efore connecting two altern ato rs to ru n in parallel, if th ere is any doubt as to th e sequence of th e phases of th e two machines, each of them should be trie d upon an induction m otor. I f the m otor runs in th e same direction w ith th e cu rren ts from both machines, they m ay be safely connected in p arallel;
if not, it will be necessary to alter the connections of one of the alternators, so as to b rin g them into the proper sequence as shown in Fig. 1.
When an altern ato r is to be connected in parallel w ith others th a t are running, it is first brou gh t up to about the speed a t which it will run when tak in g its share of the load. The exciting c u rren t of th e field m agnets is then brought up to the stren g th th a t will give the pressure the m achine is to fu rn ish when ru n ning in parallel. The th ird step is to b rin g the m a
chine into exact synchronism . Synchronism is obtained by varying the speed a t which the incom ing altern ato r is running. H aving th e speed n e a r th a t a t which it is it to run, the revolutions are slightly increased or de
creased, until th e phases of th e incom ing m achine are exactly in synchronism w ith the m achine already at work.
The m ain object of synchronism is to prevent the
tVector d ia g r a m o f No. / m a c h in e - ± —No.!phase term in a f
" '¿ v v-/ " Voltage o f
V o lta g e ¿¿— Voltage o f N o ./p h a se No. I phase->C p h a s e :
r o ta tio n j ^ . - N o . 2 phase term inal • Direction o f \
--- 1 r o ta tio n !
i---"O --- J
No. 3 p h a s e te r m i n a l —
F ig. 1— T h ree-P h ase M achines Connected in P arallel
I t is i m p o r t a n t t h a t e a c h p h a s e b e p r o p e r l y a r r a n g e d s o t h a t t h e c i r c u l a t i n g c u r r e n t w i l l b e lo w .
.‘■Vo/taae o f N o .J p h a s e
Voltage o f No. 2 p h a se, t m a c h in e
■Voltage o f
ÿ' No. 2 p h a s e t e r m in a l
~ o ~
No. 3 p h a s e te r m in a l ly .
F ig . 2— In co rre ct P hase A rra n g e m e n t
T h e p h a s e r o t a t i o n i n e a c h c i r c u i t m u s t b e t h e s a m e b e f o r e t h e m a c h i n e s a r e s w i t c h e d t o g e t h e r .
148 C O A L A G E Vol. 28, No. 5
passage of useless cu rren t between two or m ore a lte r
nato rs when running. I f any altern ato r is out of step w ith the others, cu rren ts will pass between th e m a
chines, the power fo r which has to be fu rn ish e d by the prim e movers. These cu rren ts operate a g a in st the successful w orking of the units. The operation of get
tin g the incoming m achine into exact synchronism re quires a certain am ount of nerve to throw in the switch a t th e rig h t moment, and, of course, some form of synchronizing ap p aratu s is required. W hen a lamp synchronizer >is used, it is the usual custom to also have a synchronizing voltmeter. The lamp synchronizer is not so good a guide as the voltmeter, bu t the two to geth er should enable the engineer in charge to know the exact moment to close the switch.
W ith low-tension m achines, the lamp is connected between two sim ilar phases of the two m achines; or say, between a certain phase of the incoming m achine and th e same phase of the busbars. This arran gem en t is shown diagram m atically in Fig. 3, and fo r sim plicity
F ig . 3— Lam p Used to S ynchronize G en erato rs
N o t e t h a t t h e l a m p Is c o n n e c t e d I n to o n e c o n d u c t o r o n ly . I f t h e p h a s e r o t a t i o n , v o l t a g e a n d f r e q u e n c y a r e c o r r e c t , a l a m p in o n e lin e is a l l t h a t is n e c e s s a r y t o d e t e r m i n e w h e n t o c lo s e t n e p a r a l l e l i n g s w i t c h .
the connections between the other phases are om itted.
W hen the m achines are in synchronism, th e pressures delivered by the phases of the two m achines to which the lamp is connected are exactly equal a t all p a rts of the cycle, and therefore no c u rre n t passes th ro u g h th e lamp.
F or high-tension machines, a modification is shown diagram m atically in Fig. 4. A tra n sfo rm e r is wound w ith a prim ary coil fo r each g en erato r; or, say, a prim ary fo r th e busbars and another p rim ary fo r th e incoming machine. The secondary of th e tran sfo rm er is connected to the lamp. The p rim aries are so wound th a t they oppose each o th e r; and when the two machines are in phase, no lines of force are created in th e m ag
netic circuit of the tran sfo rm er. Therefore, th ere is no secondary pressure a t the term inals of th e lamp, and no cu rren t flows.
In a fu rth e r modification of the arran g em en t shown in F ig. 4, the p rim ary coils are so wound th a t when the m achines are in phase, sufficient pressure is induced in th e secondary coil to light the lamp to which it is connected to its full brilliance.
In another arrangem ent connections from th e differ
ent phases are m ade so th a t certain lamps lig h t and
One o f th e a lte r n a to r^ A l te r n a to r to be
a lr e a d y ru n n in g s w it c h e d in
F ig . 5— V o ltm eter A ids W ork of Synchronizing
T h e l i g h t o f a l a m p v a r i e s a n d , t h e r e f o r e , i t is s o m e t i m e s q u i t e d if f ic u lt t o t e l l w h e n i t is a t i t s m a x i m u m b r i l l i a n c e ; a v o l t m e t e r is o f t e n u s e d w i t h a l a m p t o o v e r c o m e t h i s d iff ic u lty .
certain others are d ark when th e machines are in synchronism .
W ith the lamp and voltm eter synchronizer shown in Fig. 5, the m ethod of synchronizing is as follow s; The prim aries pp of th e two step-down tran sfo rm ers are connected, one to the two busbars, and the other to the machine to be synchronized; while th e secondaries ss are joined in series and connected to an incandescent lamp and a voltm eter, as shown in F ig. 5. The lamp should be a carbon-filam ent one, so as to be very sus
ceptible to changes in th e c u rren t th ro ug h it. I t also m ust be suitable fo r the full voltage of s -j- s.
The w indings of the tra n sfo rm e rs are so connected th a t when the voltages in the secondaries are in step, they work to g eth er; but if out of step, they oppose each other more or less. I f the frequency of th e a lte r
n ator to be switched in is not correct, the lamp lights up and goes out a t rapid intervals. The speed of th e m achine m ust then be adjusted until th e lig h t of the
F I G . 6
Rotary
S ynchroscopeT h i s I n s t r u m e n t i n d i c a t e s w h e t h e r t h e m a c h i n e to b e p u t o n t h e l i n e is r u n n in g - to o f a s t o r to o s lo w .
±_
c
7 q
1Secondary w in d in g
y<— P r im a r y yf- w in d in g .^ ' ^
Iro n core
F I G . 4
Lam p and T ra n sfo rm e r
W h e n a h e a v i e r v o l t a g e t h a n t h e l a m p c a n w i t h s t a n d is u s e d , a t r a n s f o r m e r r e d u c e s t h e l i n e v o l t a g e . C a r e m u s t b e t a k e n t o c o n n e c t t h e t r a n s f o r m e r a n d l a m p , o t h e r w i s e i n c o r r e c t r e s u l t s w ill b e o b t a i n e d .
lamp rises and falls only a few tim es a m inute. This shows th a t the speed and, therefo re, th e frequency also are correct. The m achine is th en switched in a t th e moment the lamp is fully lighted and the voltm eter read
ing is a t its m aximum. T his indicates th a t the m achine is in synchronism w ith the others. B efore closing the switch, th e altern ato r voltage m ust, of course, be ad
justed to correspond w ith th a t of th e busbars.
A more recently developed arran gem ent th a n th a t shown indicates not only synchronism b u t also w hether the incoming altern ato r is ru nn in g too fa s t or too slow, or if i t is simply out of phase.
This type, an example of which is given in F ig. 6,
is term ed a ro tary synchronizer. I t h as a ro ta tin g
pointer which moves in one direction or the other while
the incoming m achine is out of synchronism . I f the
po in ter ro tates clockwise, th e incoming m achine is too
fa s t; if counter clockwise, the m achine is too slow.
Ju l y 30, 1925 C O A L A G E 149
F I G . 8
F ields E sta b lish Speed
T h e r o t o r c i r c u i t d r i v e s t h e i n d i c a t o r n e e d l e b y t h e f o r c e t e n d i n g t o h o l d t h e m a g n e t i c fie ld s t o g e t h e r .
F ig . 9— H igh F u el Econom ies and R eliability H ave Reduced Pow er G en eratin g Costs
O n ly b y u s i n g m o d e r n t y p e g e n e r a t i n g u n i t s c a n a p o w e r h o u s e s u p p l y e l e c t r i c a l e n e r g y a t a n e c o n o m ic r a t e t o d a y . R e c e n t a d v a n c e s i n t h e d e s i g n a n d c o n s t r u c t i o n o f l a r g e t u r b o - g e n e r a t o r u n i t s s u c h a s t h i s h a v e
m a d e t h e m s o h i g h l y e f f ic ie n t t h a t t h e s a v i n g s w h i c h t h e y m a k e o v e r o ld t y p e s j u s t i f y t h e e x p e n s e o f r e p l a c i n g t h e o ld u n i t s
From busbars
F ig . 7— H ow th e S ynchroscope W orks
T h e d e v ic e c o n t a i n s a s im p le s l i p - r i n g m o t o r w h i c h r u n s a t a s p e e d a n d d i r e c t i o n d e p e n d i n g u p o n t h e f r e q u e n c y o f t h e c u r r e n t s u p p l i e d t o i t s s t a t o r a n d r o t o r .
The principle of th is instru m en t is shown in F igs. 7 and 8. The essential pai’t of the app aratu s consists of a m in iatu re slip-ring m otor. The s ta to r and ro to r are both wound fo r tw o phases, and in series w ith these are connected non-inductive resistances R I R2 (in the form of incandescent lam ps) and choking coils Cl C2;
The connections to the ro to r being m ade by m eans of th ree slip-rings m arked SR.
In F ig. 7, th e w indings A1 and B1 produce a ro ta tin g field, the speed of which depends upon the frequency of th e busb ar supply; and w indings, A 2 and B2 also set up a ro ta tin g field, whose speed corresponds to the frequency of th e incoming alternator.
The device is arranged so th a t these two fields, indi
cated by N I S i and N 2 S2 respectively in F ig. 8, shall ro tate in the sam e direction ; and it will be evident th a t owing to m agnetic a ttra ctio n between N i S2 and N 2 S i , th e ro to r field N 2 S2 will always try to follow the sta to r field.
I f the two fields are ro ta tin g a t the same speed, th a t is, if the frequency of th e incom ing m achines is the same as th a t of th e busbars, the ro to r will rem ain
stationary. B ut suppose th e two frequencies are not the same, and th a t N l S i is ro ta tin g at, say, 1,500 r.p.m., and N 2 S2 a t 1,400 r.p.m., when the ro to r is a t a stan d still; then, in order th a t N 2 S2 may still keep pace w ith N l S i , th e ro to r m ust tu rn in the same direction, namely, counter clockwise in F ig. 8, a t the ra te of 100 r.p.m. The pointer which is attached to the ro to r would th u s travel around th e dial in Fig. 6, a t 100 r.p.m. in th e direction m arked “Slow.” On the other hand, suppose N2 S2 is ro ta tin g a t 1,600 r.p.m.
when the ro to r is held statio n ary due to the incoming altern ato r ru n n in g a t too high a frequency; then fo r
N2 S2 still to keep in step w ith N l S I , the ro to r willtu rn backward, or clockwise, a t a speed of 100 r.p.m.
This would be indicated on th e dial by the p ointer indi
cating “F a st.”
Now, in addition to equality of frequency, th e voltage
of th e incoming altern ato r m ust also be in phase w ith
150 C O A L A G E Vo l. 28, N o. 5
F ig. 10— M any D ifferent T ypes of A lte rn a to rs M ust Som etim es Be P aralleled T ogether
A u t o m a t i c v e r t i c a l t y p e a l t e r n a t o r s a r e s t i l l in l a r g e d e m a n d in m a n y i n d u s t r i e s . C o a l m i n i n g c o m p a n i e s a r e t u r n i n g t o t h e u s e o f m o r e a u t o m a t i c e q u i p m e n t b e c a u s e i t u s u a l l y is
m o r e r e l i a b l e t h a n m a n u a l l y o p e r a t e d ty p e s .
