The Institution of Mining Engineers. VOL. XXIV PLATE VI. To illustrate Messrs AH.Meysey Thompson and Lupton's Paper on DUTIES OF DIFFERENT SYSTEMS OF PUMPING WATER EXPRESSED IN MILLIONS OF FOOT-POUNDS OF WORK PER 1 CWT. Plate VI. shews the duties of different systems of pumping water, expressed in millions of foot-pounds of work per 1 hundredweight of coal burnt. The light figures are taken from plants under ordinary working conditions, and the dark figures are the average duties of the different systems of pumping. Mr. HENRY LAWRENCE (Newcastle-upon-Tyne) asked what class of boilers were used at the Bradley and Moat engines, and whether there was anything to account for the large difference between the cost of repairs of the respective boilerplants-the costs at Bradley being stated to be 4s. 10d. and at Moat to be only 1s. 9d. per continuous pump-horsepower per annum. In his opinion the most economical way of pumping water from great depths, was to have a series of small pumps delivering round the circle of the crank, or what would be the crank. He differed from the opinion expressed by the writers in the beginning of the paper as to the use of a flywheel, but they afterwards stated that under certain conditions a flywheel attached to a pumping-engine placed underground was a source of economy, enabling them to cut off and to work the engine expansively, and he accepted the latter as the correct view. Prof. HENRY LOUIS (Durham College of Science) said that he did not think that the authors had treated quite fairly the application of electric driving to pumping machinery; he did not believe that any great danger could arise from the dynamo or leads seeing that it was not customary to place a pumping-engine in the return-airway. In the usual position it might be considered fairly safe, and there would be little danger from sparking. He was convinced that much higher efficiencies had been repeatedly recorded for electrical machinery than those given in the paper, and the writers did not refer to the more modern type of pumps driven electrically. The Riedler express pump had been introduced lately, with mechanically-governed valves, which could be worked at a high speed, against fairly high lifts; and he believed that high efficiencies had been recorded for this pump. Several electrical plants claimed an efficiency of 60 per cent. or over. It was obvious that at a colliery having a lengthy range of coke-ovens, the waste-gases could be utilized for the generation of electricity, which could be economically applied in driving a pumping-plant, in which case a much lower efficiency could be admitted than would be the case if they had to use coal; and the convenience of carrying electricity to a considerable distance was a factor that should not be overlooked. If danger from sparking at the commutator did exist, they could always fall back upon the triphase system. So far as his (Prof. Louis') limited experience went, he was not particularly in favour of this system, because if anything happened, and it was necessary to stop the pumps, one had to run off the water from the rising main before restarting the pumps, although he understood that a means had been devised for overcoming this difficulty. Mr. T. Y. GREENER (Crook) said that, having regard to the fact that electricity at the present moment was being largely utilized for power-purposes, he did not think that any statement should be allowed to go forth uncontradicted that its application underground was unsafe. He asked the authors, whether the statement that among the dangers arising from the use of electricity an explosion might be caused by sparking, was merely an opinion or whether it was based upon actual knowledge, as he had heard the point frequently denied. Mr. J. C. B. HENDY (Etherley) said that he had had some experience with hydraulic pumps, and for the particular conditions which prevailed at the Etherley collieries the hydraulic pump had certainly proved successful. He was not able to state the efficiency, as the boilers were heated by the wastegases from the coke-ovens. A Hathorn-Davey hydraulic pump had been working for about three years, placed about 1,400 feet from the shaft-bottom; it was pumping from various distances, from three different points in the dips; and, since it had been erected, he did not think that it had cost more than £1 or £2 per year for repairs. This was a case where the conditions were suitable for the use of hydraulic pumps; but if they had to place pumps at a considerable distance inbye, he thought that nothing could equal the efficiency of electricity. In the case of another hydraulic pump, there was a sudden inrush of water, which drowned out the workings; but the hydraulic pump worked for seven days under water and eventually it overcame the feeder and removed the water. This was one of the especial advantages attending the use of an hydraulic pump, which, if kept in order, would pump water, even when completely immersed. Mr. F. R. SIMPSON (Ryton) said that he had employed an hydraulic pump when working to the dip in a heavily-watered colliery: it was situated 1,800 feet from the shaft-bottom, and had worked in a very satisfactory manner. Mr. J. K. GUTHRIE (Preston Colliery) said that he had had an opportunity of seeing a Riedler pump at the Cramlington collieries, and it seemed to work in a highly satisfactory It had only two valves of large area (one suction-valve and one delivery-valve). Indicator-cards had been taken, which showed great efficiency, and there was no "slip" or "hammer." manner. Mr. T. E. FORSTER (Newcastle-upon-Tyne) asked the authors to give further particulars of the installation of the electric pumping-plant in the North of England which gave the results quoted in their paper. Underground pumping could be divided into two heads, namely, shaft pumping and inbye pumping, and one method might be very good for one case, while another was the best for the other case. He thought that the use of electricity for underground pumping was very handy, and that it was probably as cheap as any other method. For pumping heavy feeders he was bound to agree that pumpingengines on the surface were generally the most economical, with possibly underground engines as a stand-by. In some pits, there was not much water, and where they could erect an underground electric pump, working in conjunction with dynamos and haulage and inbye pumping-plants, it might be, even supposing the efficiency to be little less, that it would prove the cheaper system. The idea that because a motor would spark it would therefore fire gas had not been proved, and the only experiments of which he had heard had pointed to the opposite conclusion. It was a point not yet satisfactorily settled, and it was very desirable that they should receive exact information upon the question. Mr. C. W. MARTIN (Newbottle Collieries) wrote that the first note struck by the writers of the paper was a correct one. The day had gone by for the question of fuel-economy, even at collieries, to be regarded as of small importance. of ever-increasing importance, and it was this fact which made even first cost a secondary consideration. The authors had shown It was |