THE COLLIERY GUARDIAN AND JOURNAL OF THE COAL AND IRON TRADES. Vol. CIX. FRIDAY, FEBRUARY 12, 1915. No. 2824. Centrifugal Pumping Plant By E. G. IZOD and In May 1911 it became necessary to investigate fully the pumping plant of the Durban Roodepoort Deep. It was decided to equip the new plant with pumps of the centrifugal type, and two units were chosen, each of 375 galls, per minute guaranteed delivery. The details of the complete plant are as follow :— Pumping plant— Nounal quantity of water to be handled per month.............. 10,000,000 galls. Number installed ................. Two sets. Pumps— Type................................ Sulzer centrifugal. Guarantee i quantity of water for each set, per minute ............ 375 galls. Revolutions per minute .......... 1,470. Number of cylinders to each pumping set .................... 2 (.1 high pressure), (1 low pressure). Number of fliers to each cylinder... 8. Total number of fliers to each pumping set .................... 16. Total head against which pumps would have to deliver the water (including friction, &c.) ...... 2,490 ft. Lengt h of each pumping set ..... 20 ft. 1| in. Width do. ...... .. 4 „ Height do. .... 4 „ 5^-,, Weight do. (complete with motor and bed-plate) ................. 28,0001b. Pump motors— Number of motors per pumping set 1. Make of motors...............,.... A..E.G. R.P M. of motors................. 1,470. B.H.P. do........................ 550. Voltage do. ..................... 2,000/ COPPER RING Fig. 1.—Details of Joints in Discharge Piping. GIRDERS MAIN SUPPOR SUPPORTING PIPES Ju INTERMEDIATE SUPPORTS r &. CLAMPS---------- _................. Fig. 2.—Method of Supporting and Clamping v 5 Pipes in Shaft. Piping. Duplicate pipe lines were installed from pump station to collar of shaft, and the piping and valves in the pump station were so arranged that either or both of the two pumping sets could deliver through either or both of the two pipe lines. No. 1 shaft, through which the dis- charge piping was taken to the surface, is a five-com- partment compound shaft, the depth in the vertical being 1,586ft. and the length on the incline 1,174ft. ."*he piping is Mannesmann solid drawn, the internal dian. 'ter being 8 in. throughout, wood lined, bin. * Fr< m a paper read before the South African Institution of Engineers. at a South African Mine.* A. P. ROUILLARD. thickness, thus making the effective diameter 6 in. The thickness of the piping is 7 mm. in the lower half of the shaft or that p^rt subjected to the highest pressure. The piping in the upper half of the shaft is 6 mm. thick, the guaranteed factor of safety on the material of the piping is not less than 3 75 on the elastic limit when under the actual working head of water. The piping was supplied in standard lengths of 21 ft., and the pipe joints used were the dou ble-bordt r type shown in fig. 1. At every 500 ft. in the vertical and incline the piping was carried on two rolled steel channel bearers, 12 in, X 4in. x t in., the ends of which were hitched into the 6 6- Fig. 3.—Retaining Valve. 6' ROLLED STEEL JOIST I2'.4’.«’ HITCHED INTO SHAFT ROLLED STEEL JOIST I2'.4'.%' HITC H E0 INTO SHAFT Fig. 4.—Steel Supporting Pipe. These pipes are fitted every 500 ft. sides or the foot wall or hanging of the shaft. The arrangement is shown in fig. 2. Retaining valves, shown in fig. 3, were fitted in each pipe line at the bottom of the vertical and at the, bottom of the incline. Cast-steel supporting pipes (shown in fig. 4) were Inserted in the pipe line and bolted to these channels, thus ensuring that the weight of the piping was not carried in any way by the timbering of the shaft. Between the main supports mentioned above, light steel joists every 90 ft. were hitched info the shaft, and the pipe clamped to these with wrought iron st» aps. In the incline the space between the clamps was reduced from 90 to 20 feet. . The design of the sump was given particular atten- tion, and is as shown in fig. 5. The mine water is turned into either of the two settling sumps C or D ; if it flows into C it settles the mud in C, flows into A, then through E to the pump. If it flows into D it settles the mud in D, flows into B, then through E to the pump. , This method of using complete duplicate sumps has two great advantages—viz., it allows one side to be cleaned without interfering with the settlement of the grit or the operation of pumping, and also gives a large storage capacity in case of a breakdown of the pumping system. In the sump as first designed it was thought that the settling sumps C and D would be sufficient to settle the grit without going to any further elaboration in design, .and it was considered that the weir between the settling and main sumps would be sufficient to prevent grit getting into the main sump. A great improvement was made on the original arrangement referred to above. When the Crown Mines pumps started, trouble was experienced owing to the fact that the pumps were drawing their water from the old sump, which was not arranged for . complete settlement of the sand and grit. ■The settling sump was on the small side, and a careful inspection of the water flowing over the weir from the settling sump to the main sump showed that the water appeared cloudy, but there was no tangible trace of any sand or grit which would do harm to the pumps. A sample of this water, however, was taken, and when put through a filter paper a very fine residue was left, which, when examined under a microscope,, showed that what really appeared as discoloration in the; , water Were very fine particles of rock with sharply defined points, calculated in the best possible way to cause cutting action on the bushes or working parts of the pump. A further examination of the water in the settling sump showed that these minute solids remained for a considerable time in suspension in the water, and hardly ever came to the surface, but appeared to circulate just below the surface. Mr. Watts, of the Crown Mines, then suggested the application of overflow launders to the settling sump for skimming the water from the surface, which, as mentioned above, was to all intents and purposes free from any solids. It was then found that under normal conditions, and in spite of the fact that the settling sump was not laid out for complete settlement, almost the whole of the grit was prevented from getting into the main sump. As a result of this experience the settling sumps at the Durban Roodepoort Deep were designed and equipped with complete over- flow launder system. The arrangement is shown in fig. 6, from which it will be seen that the water falls into either of the two settling sumps through a quietening box ; then it flows