Electricity in Mining.

Thames Star, Volume XXIX, Issue 8606, 10 March 1897, Page 2

Electricity in Mining.

[Conclusion.]

Of course, it, is.- not rational to expect that the early results at Trafalgar should indicate such a high efficiency as our more modern works; —firstly, because Trafalgar was the pioneer of transmission; and (secondly) because efficiency was only a secondary issue, and a saving of 50 per cent, of transmitted power was quite sufficient to convince the Welsh mining engineers of the ultimate triumph of electricity as a transmitter. It has beforo been printed out that the loss of a few horse power, manufactured out of coal valued at 1« per ton, was not a serious matter at the colliery; and as the demands of economy were not stringent as to. whether 70 per cent, or 40 per.cqnt. of power should be recovered, there was no commercial necessity to reduce the loss in transmission to a mathematical minimum. As a matter of fact, the.pe.wer exerted by the under-ground pumps at Trafalgar in 1887 represented only 45 por cent, of the. power emitted to the generator by tne steam engine. In November of that year, Mr Frank Brain, who succeeded his cousin (Cap* tain W. B. Brain) in the management of the colliery, furnished to the §outh Wales Engineers' Institute a number of TABULATED FIGUBES giving the working results obtained at Trafalgar. In order to show the difference between the power given off at the belt of the primaly steam engine and the actual work done, Mr F. Brain compiles the following table :—

H.P. given off to generator... ... 23*C0 Loss in generator 456 H.P. or 20"/ o ") „ cables... 345 „ „ 15*/.f«-», „ motor... 303 „ „ 137. { '' „ pump.. 1-63 „ „ T/.J

The proportion of power given off by belt used to lift water is, therefore, 45 per cent. This is far behind the figures of the present day, but it must be borne in mind that an effete steam engine was used, and the machinery was worked without special regard teobtaining high efficiency of transmission. With carefully adapted conditions and an apparatus of scientific exactitude it would have been an easy matter to recover 75 per cent, of power even below the surface. And it may as well be stated here that in electrical transmission the maximum value of the efficiency is entirely governed by prevailing; conditions and their adaptability to the . engineer's methods. If the natural conditions are not suitable to the .methods, the methods must be made adaptable to the conditions. Therein must lie the genius of the electrician andjthe engineer. A COMPARISON OF COST. • It is almost unnecessary to state, therefore, that when we deal with Trafalgar as the birthplace of electrical transmission in mining, we do not set forth its actual results either as a standard of efficiency or of working costs, for the exceptional cheapness of its primary power is a special feature rarely met with except in the case of collieries and natural water power. As a means, however, of comparing the cheapness of electricity as against the rival systems, the figures supplied by Mr F. Brain are of considerable importance, though they cannot, being an individual test, be regarded as applicable to all conditions. The calculations are extracted from a Berlin paper of 1883 :—

Comparison of cost on 10 effective H.P. hours, trans mltted 1093 yard*:

By Cables .. .. l-77d per effective H.P. per honr „ Electricity .. 221 d „ „ „ „ Hydraulics .. 2'9od „ „ „ „ Compressed air 2*9Bd „ „ „

Comparison of cost «n 60 effective H.P. hour!, trans, mltted the sime distance:

By Cables .. .. l-35d per effective H.P. per hour „ Hydraulics .. 187 d „ „ „ „ Electricity .. 2"07 d „ „ „ „ Compressed air 227 d „ „ „

Comparison of cost on 10 effective H.P. hours, trans' mitted 6465 yards:

By Electricity .. 2-fild per effective H.P. per hour „ Compressed »ir 4-fifld „ „ „ „ Cables .. .. 4-6 M „ „ „ „ Hydraulic!) .. s'2od „ „ „ Comparison of cost on SO effective H.P. hours, trans. tnitted 5465 yards: ■. By Electricfly .. 237 d per effective H.P. per hour ','. Coippremedair: 209 d „ ■■• - " " „ Hydraulic* .. 3<02<l „ „ „'

Steait) wis the prince iqotor used in each instance. From the abo c figures it is inferred that far distances ol about 100) yanla'caUe iromiqtoion'costs least, but that in longer distances electricity takes the lead, and maintains it against all other systems.

When we add to this the fact that the first cost of the electric plant is less,in most cases than that of the mechanical systems, the commercial advantage is evident. . .

EFFICIENCY OF SIECHAITJCAI< METHODS.

It only remains to compare on an equitable basis—if such is possible—» the relative efficiency of the rival methods. Modern investigations have shown that tho loss in electrical transmission rarely exceeds 25 per cent., and is sometimes reduced to a much lower figure, an average test giving, as we have shown, a recovery of 72*56 h.p.'out of 100. On the other hand,, the efficiency of the endless rope system has sometimes—under favorable circumstances —attained a relatively high scale, and though it is not so adaptable to varied conditions as electricity, it is nevertheless chief rival amongst the mechanical methods. Hydraulics and compressed air are practically out of the competition, experience having proved that the recovery of power by air compression in many cases does not exceed 25 ; per cent. It will probably be some time before the endless rope or cable system is totally superseded, for with suitable it possesses many advantages. This principle is largely applied in California and also in Melbourne, where it is used with considerable success in the cable car services. SUMMARY. In the fore-going articles we have endeavored to touch on every point of scientific aud economic advantage which accompanies the use of electricity as au agent of power transmission. The case for electricity is greater efficiency, greater adaptability, and less cost; but as individual circumstances differ so widely, this can only be accepted in the general sense, and cannot be methematicaUy demonstrated except in particular" instances. The great strides accomplished by the practical application of electrical trans- < mission in recent years are proof j positive that it is not mere theory, and the rapidity of its present career of usefulness gives undeniable proof ol a • | brilliant future. An important ke£ to/ the inception of that career has been \ herein disclosed in the history of 1 Trafalgar colliery. The connecting . links of the history are the lecture of 1877, which fore-shadowed the cou- ( etruction of the transmission apparatus; (

the contemporary paper of 1882, which announced the first success on a practical scale; and Mr F. B. Brain's paper of 1887, which reduces tho work at Trafalgar to figures. It is also a matter of history that the Americans, with

YANKEE PUSH AND ADAPTATION, have appropriated the experience of tho English and Continental school, and have passed the idea through many stages of practical perfection. Since 1834 America has far outstripped the older countries in the utilisation o4 the electric current, and to-day tW groat transmission works at Niap^H probably stand unique and u^H proached in tho world of pnu^H science.

AN EXAMPLE TO FOLLOW. 1 There is amplo room fur this col to learn a very useful losson troM

success of America. Writing in To^| Capt. Brai a remarked that eloct ridtywl a transmitter would be highly impertant " where water-power can be obtained either in volume or high pressure, notably in the lake districts of our own country and many parts of America." That was tho koy-note which the American engineers wero quick to learn and appreciate, and it applied—both then and now—with, equal force to New Zealand. We have the best of climatic conditions, plenty ofcnatural water power, ' and splendid forests which—if they are. conserved—wi!l prevent drought and maintain tho "apply? Our duty, then, is clearly to supplement the cyanido process, which las conquered tho rofactoiy ores, with a chMfp motive povreir whfch will save the low grade ©res. We use the word #< supplement" because the two must go nand-in-kand; it-.. is a cheapening and improving of the two great co-operating factors. Nor is there any need to go up from home in oir quest. Natural water power, plus electricity, giTea the cheapest results possible, and this, apart from facilities of ascent or descent, is an unanswerable claim on the intelligence of the mining community.

(Concluded.)