HYDRAULIC AIR COMPRESSOR 



707 



The velocity with which fine bubbles rise through still water is 

 approximately 9 inches per second, and it is essential that the velocity of 

 flow be greater than this. Experiments show that velocities of from 

 12 to 16 feet per second give the best results. 



The volume of air compressed per cubic foot of water used, may be 

 determined as in the case of the air lift pump. 



Recently published tests of such a plant as here described are said 



FlG. 341. Hydraulic Air Compressor. 



to have given an efficiency of 82 per cent. 1 Here h d = 71 feet 

 and h s = 261 feet. Three vertical shafts are used, each 5 feet 

 in diameter, and the plant is capable of developing 4000 H.P., com- 

 pressing the air to a pressure of 117 Ibs. per square inch above the 

 atmosphere. 



1 Engineering and Mining Journal, New York, January 19, 1907, p. 125. See also an 

 abstract in "Proceedings Institute Civil Engineers," vol. 169, p. 500. This value is probablj 

 nigh. See also Engineer, Nov. 10, 1911, p. 482. 



