Pressure Compensator – Always an Even Flow Across the Directional Valve

When handling varying loads, the displacement and speed of the load are affected. You want the relationship between the control device — for example, a steering wheel or joystick — and the movement speed to be smooth and consistent. To achieve even operation under varying loads, a so-called pressure compensator is used. The flow rate — that is, how fast the load moves — depends on two factors: the throttling area and the pressure drop across the restriction. To eliminate the effect of a varying pressure drop caused by changing loads, a compensator valve is used.

Function of a Pressure Compensator with Compensator Valve

The compensator valve ensures that the pressure downstream of the valve remains constant.
This means that the pressure drop across the directional valve stays constant regardless of the load. The recommended constant pressure drop varies between manufacturers — SUN Hydraulics, for example, recommends 14 bar.
The compensator valve is available with different springs, allowing easy adjustment between different pressures.
When the pressure drop across the directional valve is constant, the speed (flow rate) depends only on the diameter of the directional valve. The speed can therefore be controlled independently of the load pressure.

Pressure Compensator with Fixed-Displacement Pump

If a fixed-displacement pump is used, a bypass-type compensator should be selected.
This means that any excess flow is directed back to the tank.
The valve type for this setup is LR*C and can be found here.
Ready-made sandwich solutions for compensator valves can be found here.

Pressure Compensator with Variable Pump

If a variable pump is used, a restrictive compensator is used.
This type of valve restricts the flow without diverting any to the tank — in this setup, the variable pump itself regulates the flow rate.
The valve type for this configuration is LP*C.
Ready-made sandwich solutions for compensator valves can be found here:
Sandwich blocks for special valves

Examples of Applications for Pressure Compensation

There are many applications that benefit from using a pressure compensator, for example:

• Conveyor belts: Regardless of how much load is on the belt, you know the speed when adjusting the control.
• Cranes: The crane is affected not only by the load weight but also by the position of the load within its reach.
• Excavators: When the bucket moves empty toward the ground and starts digging, you still want consistent joystick response.

Integrated Pressure Compensation in Other Components

Directional valves for mobile applications often have built-in pressure compensators — for example, Bosch Rexroth RM10 and RM15.
Sectional directional valves