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

In mine work, the displacement pump is especially useful in hand- ling the accumulated water in sumps, dips, entries, etc., its require- ment of complete submergence being borne in mind. It is also pecu- liarly effective in subways and tunnels, in automatically discharging the seepage or leakage water which accumulates in a sump. It may also serve in the basements of factories and warehouses which are subject to occasional inundations by floods or high water, its utter dis- regard of dirt and small debris being of peculiar value in such cases. The same apparatus, but in a slightly modified form, is employed in manufacturing establishments for elevating acids and heavy chem- ical solutions, or for pumping marl, paints and other semi-fluids. In these cases the air valve is so located that it is not affected by contact with the liquid, or by corrosive fumes arising from it. The device has also been successfully employed in elevating sewage. The capacity of the displacement pump is determined by the size of the cylinders or chambers, and the volume of air available. Using air at ordinary pressure from a common single stage air compressor and with a lift not exceeding 250 feet, the efficiency of the displace- ment pump is certainly higher than that of the usual direct-acting plunger pump, under the same conditions of lift and pressure. No plunger pump can handle as much water as the displacement pump, with equal pressures and volumes of air. In the latter machine, 1 cubic foot of free air compressed to 90 pounds pressure is easily the equiva- lent of 175 foot-gallons, or 1.450 foot-pounds of work. In preliminary calculations, it may be taken that, for each cubic foot of water pumped to an"elevation of 210 feet, 9 cubic feet of free air will be required, compressed to a pressure of 90 pounds. This includes a fair allowance for losses in leakage, air absorbed by the water, and the small excess required to start the flow. Direct-Acting Piston or Plunger Pumps. The direct-acting piston pump, of simple or duplex type, lias a most unenviable reputation as a “steam-eater.” It is one of the most uneconomical devices known. Generally speaking, the simple pump is a little more economical than the duplex, but even the pump builder figures at 150 pounds of steam per horse power hour in his pumps. Some claim only 125 pounds. Others, in strictest confidence, will con- fess to from 175 to 250 pounds. The facts are elusive, but the first figure is a happy medium, and will serve the purpose in emphasizing the utterly wasteful character of the direct-acting pump, especially when it is remembered that the ordinary automatic steam engine, itself no miser of steam, requires 30 to 35 pounds of steam per horse power hour. Experiments have shown that under average conditions hardly 50 per cent, of the indicated horse power of the driving cylinder is 49