Pilot pressure reducing valve circuit

Pressure reducing

Here the pilot pressure reducing circuit is shown in diagram form

Pilot pressure reducing valve are the only pressure control valves that are normally open. The valves may be either direct operated or pilot operated.

In contrast to pressure relief valves which affect the input pressure (pump pressure), pressure reducing valve are used to influence the output pressure (actuator pressure).

Nowadays I revise my old article, service report and I remember my experiences on board commercial or offshore vessels as hydraulic troubleshooter

Pilot pressure reducing valve

In this circuit show next clamp B has to be at lower clamping force than clamp A. This circuit comprise a normally open pressure reducing valve.

Cylinder extend motion

When the 4/3 directional control valve is switch in position to extend the cylinders the fluid pressure is sensed by the pressure reducing valve that is placed in the line to the cylinder cap end of clamp B.

Pilot pressure reducing valve in open position

As both cylinders begin to clamp the pressure in the system rises. The pilot pressure reducing valve senses the pressure.  As the valve setting is reach the spool partially closes causing a throttling  the flow channel.

The desired reduced pressure is attained once a balance is present between the pressure in flow channel and the pressure set at spring. Pilot oil from the spring chamber via control line is connect to the tank and therefore flows to the tank.

Another aspect is when pressure drop in the hydraulic system. During cylinder extend spool will open and pressure is build once more until the desired reduced pressure setting is reached.

Cylinder retract motion

To retract the cylinder a check valve is build into the reducing valve and allows fluid to return to the tank via directional control valve.

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