34 THE COLLIERY GUARDIAiv January 3, 1913. power curve, which shows that the horse-power, between 400 gallons per minute and 630 gallons per minute, only i increases from 17 to 19 brake horse-power. The larger sizes of these low-lift pumps are made with double inlet impellers, as shown on fig. 3, which I represents a pump with a 12 in. delivery and 14 in. diameter suction, and the performance of this pump is represented by the test sheet (fig. 4), from which it will be seen that, when this pump runs at 750 revolutions per minute and delivers 2,500 gallons per minute against a head of 53 ft., the efficiency reached is 80 per cent., which is a very creditable performance for a pump of this capacity. It will also be seen that the efficiency keeps over- 70 per cent, from 1,700 gallons per minute to 3,300 gallons per minute. For higher lifts the “ C ” type pumps have been intro- duced, these being plain centrifugal pumps suitable for lifts up to 150 ft. Fig. 5 shows one of these pumps arranged for a belt drive. The pump is of the hori- zontal spindle type, with double inlet suction. The standard position of thebranches is:—Suction horizontal, delivery vertical, both being on the same side of the pump. The casing and bedplate are of cast iron, the latter being provided with extension to take a motor, or the outer bearing in the case of belt-driving. The covers, which are of cast iron, are provided with a 1000 2000 3000 4000 GALLONS PER MINUTE Fig. 7.—High-lift Centrifugal Pump Arranged foil Electric Drive. Fig. 8.—Section of Multi-stage Turbine Pump. Fig. 9.-—Five-stage Turbine Pump Arranged for Belt-drive. LONDON & READING. .-. ■ — passage to conduct the water from the suction branch to the centre of the impeller, and, where they come in contact with the latter, they are fitted with renewable cast iron slip rings. The impeller is of cast iron of the double inlet balanced shrouded type, machined at the eye of the periphery, where it comes in contact with the stationary part of the pump. The shaft, which is of steel, runs in a bearing carried by a stiff bracket from the pump casing on both sides of the pump, and is fitted with pulleys or a flexible coupling for connecting to a motor shaft. The bearings, which are liberally propor- tioned, are of cast iron, fitted with white metal liners, the Fig. 6. :: 130 IM IZO 16010 HIGH LIT PULSOMETER ceNtriiuga LON DON & READING. ENGINEERING C ? L' 5000 jflO Z4> 16b . Pt?MP eeb~' BOIL 7SS I70L GRAPH IC RE JORL OF I EST OF - SiZiE C IB. 751 2 01 the lubrication being continuous by means of a revolving ring dipping into a large reservoir fitted with oil indicator and drain. The creeping of oil is prevented by rings carried on the shaft. The covers can be removed and the impeller withdrawn without disturbing the pipe connections. The pump shown in fig. 5 has a 10 in. delivery and 12 in. suction. The pulley shown is 18 in. diameter by 20 in. wide, and is capable of transmitting up to 200-horse power. The test sheet, fig. 6, shows the performance of this pump. When running at 760 revolutions per minute and when delivering 2,800 gallons per minute against 138 ft. head, it will be seen that the efficiency reaches 80 per cent., and that the efficiency keeps above 70 per cent, between 1,400 gallons per minute and 4,000 gallons per minute. This particular pump was intended for hydraulic sluicing in mining operations. Fig. 7 shows another “ C ” type pump arranged for electric drive. For heads of 150 ft. and upwards, multi-stage turbine pumps are recommended, and the Pulsometer Engi- neering Company make a very large number of sizes of standard pumps, which cover a very wide range of duties. A section of a multi-stage pump is given in fig. 8, fig. 9 shows a “ T 5 A ” five-stage belt-driven pump, and fig. 10 the same pump opened out. The action of these pumps is as follows :—The water, after passing through the suction pump, enters the “ eye ” (f.e., centre) of the first impeller, and, leaving the periphery at a high velocity, passes between stationary scroll-shaped blades called the “ diffuser,” the function of which is to change velocity into pressure with a minimum loss due to friction and eddies. After leaving the diffuser, the water travels inwards at a low velocity through an s-shaped passage communicating with the eyes of the next impeller, and so on, stage by stage, until the delivery chamber is reached, when the water ultimately finds its way into the discharge pipe. Each chamber contributes its share of pressure, the total pressure being represented by the sum of the pressures generated by the individual stages. The initial cell contains the suction branch, and the terminal cell the discharge branch. The alignment of the pump is automatic, the com- ponent parts being centralised by nipple and recess. End thrust, which is so pronounced in some forms of construction, has been overcome in a very simple manner, and has, in fact, been almost entirely eliminated. As a consequence, no thrust bearing is required, except to provide against such small end thrust as may be caused by the driving gear. All working surfaces within the pump are fitted with renewable liners, as well as the tips of the guide blades, which are exposed to high-velocity water. The bearings are liberally proportioned and fitted with continuous automatic lubrication. The casing is of cast iron and consists of a number of sections or stages held together by long bolts passing through the end covers, which form, respectively, the suction and discharge chambers. This construction obviates the difficulty that exists when the impellers and diffusion rings have to be withdrawn axially through a long barrel. Alignment is secured by the registering or nippling of the component parts. The faces in contact with the bosses of the impellers are of bronze, and renewable. The diffusers are separate from the casing and fit into tooled recesses. The inner portions of the diffuser vanes are made of a hard bronze to present a smooth surface to the high-velocity water, and are easily renewable. The water passages are machined where possible, and the remaining surfaces are carefully finished in order to eliminate eddies and to reduce the frictional losses to a minimum. Bosses are provided for air-escape valves, lifting eyes and drains, also for pressure gauge and charging. The impellers are of special bronze, with accurately-shaped water passages, the outside surfaces being machined to reduce water friction. Each impeller is mechanically balanced, indepen- dently, in order to eliminate vibration, and is secured to the shaft by two keys. End thrust is eliminated by hydraulic balancing ; the bosses are arranged to balance the water pressures on each side and also the axial thrust due to the change in direction of flow. The stuffing boxes are fitted with bronze neck bushes, the glands being of cast iron bored clear of the shaft. The stuffing boxes are water-cooled and water-sealed, and exposed only to the pressure of the first impeller, so that it is impossible for air to be drawn in through the stuffing box at the suction end, even with high suction lifts. The stuffing box on the delivery side is relieved of the heavy pressure in the delivery chamber, and can thus be kept tight without trouble. The shaft is of best hammered steel and is protected by renewable bronze sleeves where it passes through the stuffing boxes, and by the long bosses of the impellers where it passes through the pump, so that all parts in the water space are protected from direct contact with water. The bearings are of cast iron, with renewable liners, and are secured by bolts to the end covers, correct alignment being obtained by means of a register or nipple. The lubrication is continuous, being effected by means of oil rings dipping in large reservoirs which are fitted with hinged lids and arrangements for overflow and emptying. The shaft is fitted with efficient oil- throwing rings. Protection from dirt and grit is provided by detachable covers mounted on the bearing.