The air compressor is a 2 stage air cooled type with a centrifugal unloader on Model 20-904, and a pressure switch
unloader on Model 20-911.
The compression cycle Marts with the low pressure piston A at the top of its stroke.
When the piston moves down, it draws air through the air cleaner B and inlet valve C into the cylinder. The air cleaner
On the upstroke, inlet valve C closes and the low pressure piston A pushes air out into the intercooler E through the
Compressing the air heats it up. The intercooler E gets rid of some of that heat before passing the air on to the high
The high pressure stage works the same as the low pressure stage except that the high pressure piston F goes up when
the low pressure piston A goes down. This way, the low pressure piston is drawing air in while the high pressure piston is
pushing air out.
Compressed air from the high pressure stage goes to the air tank through the aftercooler. The aftercooler gets rid of
some more of the heat generated by compression of the air.
Change 1 4-3