(3) When the storage tank pressure reaches 80 psi, the pressure switch
opens the electrical switch in series with the compressor motor, which does the
(a) Stops the compressor.
(b) Opens the unloader valve, venting the compressor and drying
chamber to the atmosphere.
It should take approximately 40 seconds to build from 0 psi to 80 psi.
This ends the pumping cycle, and the purging cycle automatically
b. Purging Cycle. With the unloader valve open and the drying chamber
vented to the atmosphere, dry compressed air in the storage tank passes through a
bleed hole in the flow control valve where it expands at the controlled rate. Refer to
Figure 1-4. Purging cycle schematic diagram.