Water Lifted By Compressed Air
For Municipal, Manufacturing, Irrigation or Other Water Supply

now under full control of the engineer in the main plant, who visits the pumps perhaps once a day to fill the oil cups. If still higher economy is desii'ed a small reheater of simple form may be installed at the pump and the fire maintained in it by the fireman from the main plant, in a few visits daily. These represent instances in which a saving will be secured by the use of compressed air even in an uneconomical piston pump. But the greatest economy- will be secured only when the compressor is designed for the work, the pump cylinders properly proportioned and the details of transmission and reheating correctly planned. While it is thus seen that it pays well to abandon the pump boilers and install air compressors in an old plant, in new installations a much greater saving can be effected by the use of air. For the first cost of boilers, settings and buildings is eliminated, going far toward paying for the air compressors. Power-Driven Pumps. The greatest advantage in the use of the power-driven pump when air is the driving power lies in the fact that it permits the expansive use of the air and makes possible the saving resulting. One instance of the expansive use of air for pumping was mentioned above, where the direct-acting crank-and-flywheel pump is employed. But greater possibilities along this line lie in the use of high grade expansive air engines direct-connected, belted, or geared to some form of duplex or triplex plunger pump, or to the simple, compound or turbine types of centrifugal pump in its various forms. Pumps of the first class are suitable to all duties where the direct-acting type could be used. But in connection with an economical air engine they are capable of an economy far beyond that of the second class. Centrifugal pumps have come into prominence in recent years, and in the large modern compounded types are capable of lifts up to 2,000 feet. They have the advantage, shared with the displacement pump, of easily handling dirty, gritty water and that containing debris. Indeed, they have been extensively employed as suction dredges in harbor and drainage work. Nor are they limited to water in their application. They are compact and reliable, and in every way satisfactory. Used in connection with expansive air engines, they assure a high degree of economy in pumping operations. Where the magnitude of the operation justifies it, the use of the return pipe” system with expansive engines on pumps of this class will, in connection with reheaters, secure the very highest efficiency. In any case, where expansion is employed, and the location permits it, reheaters should be used. The extent to which reheating may be carried is a mooted question, but most recent investigations seem to indicate that initial cylinder temperatures of from 500 to 700 degrees 5.3