AIR COMPRESSORS 35 



PC. A 7 o. Ref. No. Name of Part 



*2 1,497 Lubricator, bracket, and pipe connections, 



complete, includes one each 99, 103, 104, 

 two of 56, four each 100, 101, 102. 

 21,439 99 Lubricator bracket. 



21.595 Oil-pipe-union connection, complete, in- 



cludes 100, 101, and 102. 



20,470 100 Union stud. 



2,001 101 Union nut. 



1,892 102 Union swivel. 



21,597 103 Oil pipe to low-pressure air cylinder. 



21.596 104 Oil pipe to high-pressure air cylinder. 

 25,848 106 Piston-valve bush. 



25,847 107 Large piston bush. 



36.239 Large piston portion with rings includes 



one each of 28 and 117, and two of 27. 



20.583 Large piston portion, less rings. 



36.240 117 Exhaust-piston portion with rings includes 



one of 118 and four of 28. 

 20,585 Exhaust-piston portion, less rings. 



36.241 118 Small piston portion with rings includes 



28, 29, and 119. 



20.584 119 Small piston portion, less rings. 



36.242 Small piston follower with rings includes 



29 and 120. 

 20,590 120 Small piston follower, less rings. 



Operation of Compressor. While steam is being admitted 

 to the bottom end of the high-pressure cylinder, forcing 

 the piston upwards, the main slide-valve cavity opens the 

 bottom end of the low-pressure cylinder to the exhaust; also 

 the cored passages in the slide valve connect the top end of 

 the high-pressure cylinder to the top end of the low-pres- 

 sure cylinder, thus allowing the steam above the high-pressure 

 piston to expand into the low-pressure cylinder and force the 

 piston downwards. During this time, free air is taken into the 

 bottom end of the low-pressure air cylinder, while that in the 

 top end is compressed into the high-pressure cylinder to about 

 40 Ib. A similar increase obviously takes place in the pressure 

 above the high-pressure air piston, which exerts a downward 

 force on that piston the same as does the steam above the 

 low-pressure steam piston. On the lower side of the high- 

 pressure air piston, the air under compression to the main 



*When air-cylinder lubricator is to be mounted on the boiler 

 head or inside of the locomotive cab, state so and specify Piece 

 No. 21,984 instead of Piece No. 21,497. 



