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

simple pump of the same capacity. In some cases this same result may be secured by the use of tlii’ee pumps in series, relieaters being used as before after each expansion and the exhaust from one pump being supplied to the next, with a larger air cylinder. To secure the maximum of economy by this means, the air cylinders must, of course, be properly proportioned. Crank and flywheel pumps, essentially direct-acting and driven by air used expansively, have also been used with great economy in large units. Other methods of applying air expansively to pumps will be discussed under the next classification. A common instance in which air for pumping would effect a mate- rial saving is found in factories and shops where a separate pumping station is maintained at a distant source of supply, to furnish water for the plant. One of two methods is usually employed, either the station contains separate small boilers (often in duplicate) with an attendant, or else a long steam line is run from the factory boiler plant to the pump. In the first method fuel is burned and steam generated in small uneconomical boilers. If the station is inaccessible by wagon or track, the fuel is probably high-priced. A separate attendant is required, combining the functions of engineer and fireman. Oil and waste are required for this little plant. The result is that the net cost of pumping is probably more than the cost of any other feature of the plant. In the second method, with a long steam transmission, two things result : First, there is a heavy condensation in the pipe, increas- ing the already enormous steam consumption charged to the pump; second, the capacity of the pump is reduced under the low steam press- ure and wet steam due to condensation in the pipe. The economy ( ?) by this second method is probably about as high as by the first. Consider now the possibilities of air as applied to these cases. In all probability the factory has already a steam plant where steam is gen- erated in high grade boilers with high economy of fuel. A high grade air compressor installed in the main engine room will use this steam economically. In the first case, an air pipe line will be laid to the pump, and the major expense of fuel and the entire expense of attend- ance and maintenance at the pump station will be removed. For even when a small slide valve compressor is used and the air applied to the old pumps, the actual fuel required to do the pumping with the compressor may be no more, and will probably be less, than under the old scheme, simply because of the greater steam economy of the larger boilers and the fact that the compressor may operate on the return circuit system described. The boilers will be left in place as a reserve when the main boiler plant is shut down. In the second case, the air compressor will be connected to the pipe line already laid, and the loss in pipe condensation and low pump performance is eliminated. The distant pumping station is 52