Chicago Pneumatic CPF 270, Instruction Book

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Unloading
If the air consumption is less than the air delivery of the compressor, the net pressure increases. When the net
pressure reaches the upper limit of the working pressure (unloading pressure), solenoid valve (5) is de-
energized by electronic regulator (1). The plunger of solenoid valve (5) moves downwards by spring force:
Phase Description
1 The plunger of solenoid valve (5) shuts off the supply of receiver pressure towards
chamber (2).
2 Control pressure present in chamber (2) is vented to atmosphere through loading solenoid
valve (5). Unloading valve (7) closes by spring force.
3 Valve (9) is pushed downwards releasing receiver pressure through flexible (6) and
channels (3 and 4) towards the air inlet.
4 A small flow of air remains drawn in through hole (8) and channel (3), and is blown from
receiver (10) via flexible (6) to the air inlet.
5 Air delivery is stopped (0%), the compressor runs unloaded.
Loading
When the net pressure decreases to the lower limit of the working pressure (loading pressure), solenoid valve
(5) is energized. The plunger of solenoid valve (5) moves upwards against spring force:
Phase
1 The plunger of solenoid valve (5) opens the supply of receiver pressure towards chamber
(2). Unloading valve (7) opens against spring force.
2 Receiver pressure also pushes valve (9) upwards, shutting off blow-off channels (3 and
4).
3 Air delivery is resumed (100%), the compressor runs loaded.
Instruction book
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