This example shows how a compound relief valve can be used to limit maximum pressure and unload the pump when the desired accumulator pressure is reached. When this happens, a pressure switch triggers a valve that ventilates the compound relief valve. When the load moves, the accumulator discharges and eventually the pressure switch flips back. This allows the pump flow into the circuit again.

Fig. 1 shows the load position. Fig. 2 shows the state of the pressure switch. In Fig. 3 you can see how the accumulator pressure initially builds up, drops during the cylinder movement, and finally builds up again after the cylinder stopped.


Fig. 1 Load position


Fig. 2 State of the pressure switch


Fig. 3 Accumulator pressure

Reference

Industrial Hydraulics Manual, 5th ed., Maumee, OH: Eaton Hydraulics Training Services, 2008 p. 474.

medium	Value: Oil() Type: Medium Description: Medium in the component
desiredPressure	Value: 20000000.0 * 0.6 Type: Pressure (Pa) Description: Desired accumulator pressure