Standard Pressure Compensator
Variable Displacement Pumps Models 320/42

When this control has been set at the desired pressure, the pump will automatically deliver maximum flow until the preselected pressure has been reached. It will then automatically maintain the output pressure. Simultaneously, the output volume and power requirements are automatically reduced to the amount necessary to maintain this set pressure.

This is how the pressure compensator control operates. When the pump first starts, a starter spring forces the cam reaction plate off-center, to partial pumping position. As pressure builds up, discharge pressure is ported to the compensator spool and the larger of the two control piston bores through an orifice, forcing the reaction plate to the maximum displacement position.

If the preset discharge pressure is exceeded, the compensator spool will open, dropping the pressure on the large control piston. The bore of the lower, or smaller, control piston is also ported to discharge pressure. When the compensator control valve relieves the pressure against the upper control piston, the high pressure against the lower control piston forces the cam reaction plate toward neutral reducing pump flow.

Compensator pressure is adjustable from 500 PSI to maximum design pressure of the unit. Relief valves are recommended in all systems and should be set at 10% over the desired compensator setting. In systems using accumulators or pressure compensated flow control valves, a check valve must be installed at the pump outlet port. This is desirable in all systems.

Note: Contact factory for lower pressure settings.

System Diagram

Cutaway Drawing: Standard Pressure Compensator

Optional Volume Limit Displacement Control Available


Drive Shaft Rotation

Pump Rotation of shaft* Oil Flow lnlet Outlet
PF 320 R (CW only) CW A B
PF 420 L (CCW only) CCW B A

*As viewed from the front or shaft end.
**As viewed from the port end (nameplate up).


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