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

utilized in the pump cylinder, the rest being absorbed partly by the engine as machine friction, but principally by the friction of the water in passage through valves and chambers. From these facts it follows that when it is attempted to apply com- pressed air in place of steam to direct-acting piston pumps, the result is likely to be a system of air-consumers painful to the manager and ruinous in the reduction of profit. But if electricity were to be adopted in place of steam as a motive agent, the engineer who attempted to apply an electric motor to an old piston pump would do so at a most serious risk to his reputation as a man of sense as well as an engineer. He would more likely replace the old “steam-eaters” by high grade duplex or triplex power pumps, geared to motors and oper- ating at high efficiency. Yet it is a piece of folly as rank as that already cited to apply compressed air, with any hope of economy, to a badly cut and worn steam pump, with driving cylinders probably incorrectly proportioned to the work, and a clearance out of all reason. If the same care and skill is exercised in applying compressed air as in adapting electric power, a pneumatic engineer being retained to select proper compressed air pumps and lay out a correct distribution system, compressed air as a power for pumps will be in much better repute. For the electric pump is characterized by high first cost, fre- quent attention, liability to short-circuits and burn-outs in damp loca- tions, expensive maintenance, and annoying loss of time in repairs Even a properly designed air-driven direct-acting pump may not show such intrinsic high net efficiency, but the compressed air system can- not be drowned out and lends itself more readily than the electric to the securing of economical results; and results are most important and desirable things. In a compressed air pumping system, with power properly produced, delivered and applied, there is no question what- ever as to the saving in net horse power from coal-bin to pump. The subject of pumping with air-driven, direct-acting pumps is a vast and important one, which, be it here confessed, has been sadly neglected not only by engineers in general, but by the manufacturers of air machinery themselves. It is worthy of closest study, and it is encouraging to note that it is to-day receiving the attention it deserves. Where compressed air is to be used for pumping exclusively, sev- eral methods of satisfactorily meeting the conditions are available, the merits of each one to be carefully weighed in the scale of local conditions. One of the simplest and most efficient of these methods is that known as the return pipe” or “closed circuit” system. In this the same air is used over and over again, the exhaust from the pumps being piped back to the compressor under a limited back pressure. Ilie compressed air is a transmitter of power pure and simple, just as is a belt or transmission rope. But the medium never wears out, can 50