42 



AIR COMPRESSORS 



provided with a tight-fitting screw cap. A screen prevents any 

 dirt in the oil being carried into the cylinder. When the 

 handle is turned, a cavity in the key, which normally forms 

 the bottom of the oil cup, deposits a definite amount of oil in 

 the air cylinders, at the same time pre- 

 venting back pressure from reaching the 

 oil chamber. The bracket may be attached 

 to the top head of the compressor, or placed 

 in the locomotive cab, to suit the conve- 

 nience or standard practice of any railroad. 

 To oil the low-pressure air cylinder, open 

 its oil cup and blow out all dirt, close and 

 fill it with valve oil, and on the down stroke 

 of the piston open the cup to allow the oil 

 to be drawn into the cylinder, closing the 

 cup before the beginning of the up stroke. 

 This is most easily done when the speed is moderate and 

 the air pressure low. To oil the high-pressure air cylinder, 

 open its oil cup and blow out all dirt, then close and fill with 

 valve oil and screw on the cover. Now open the cup and leave 

 it open for a short time so as to permit the oil to find its way 

 into the cylinder, after which it should be left closed. Valve 

 oil only should be used in the air cylinder, a lighter oil will 

 not last and is dangerous; a heavier oil soon slogs and restricts 

 the air passages, causing the compressor to heat and com- 

 press air slowly. A swab well oiled, is essential on each 

 piston rod. 



OUTPUT OF AIR COMPRESSORS 



In the accompanying tables are given the cubic feet of free 

 air compressed and delivered per minute for different diameters 

 of air cylinders. These tables also give the delivery air 

 pressures for different steam pressures when the 8-in. and 

 9$-in. compressors operate at the rate of 120 single strokes 

 permin. and the 11-in. compressor at the rate of 100 single 

 strokes per min. 



