Pressure relief valve, piloted

With the help of a pilot actuated pressure relief valve, pressure can be limited for larger volumetric flow rates than would be possible with a directly actuated valve. Fundamentally, the valve consists of 3 components: a directly actuated pressure-relief valve as pilot stage, a pressure balance as primary stage and a throttle nozzle for limiting control oil.

Oil flows from port P through the throttle nozzle to port X. The pilot valve limits pressure at X to the desired value. At the same time, this pressure acts upon the pressure balance. The pressure balance limits pressure from port P to port T in accordance with the spring, and pressure applied to X. Pressure within the valve’s working ranges drops via the throttle nozzle only by an amount equal to differential pressure resulting from the spring (opening pressure p0_M) and the primary stage.

The pilot stage can be bypassed using port X. In this way a pressure shut-off and a pressure switching can be realized.

The pressure regulation range dp_P is the pressure increment above the opening pressure p0_P of the pilot stage, at which the pilot stage is fully open.

The pilot stage starts to open, when pX > p0_P. It is fully open, when pX > p0_P + dp_P.

The pressure regulation range dp_M is the pressure increment above the opening pressure of the main stage, at which the main stage is fully open.

The main stage starts to open, when pP > pX + p0_M. It is fully open, when pP > pX + p0_M + dp_M.

The hydraulic resistances relate to the fully open stages. A leakage for each stage can be specified.