Overcenter valves, also known as counterbalance valves, are designed to prevent uncontrolled forward movement of loads on hydraulic cylinders or hydraulic motors. The actuators are preloaded on the discharge side via the adjustable pressure valve. This preload is released via an internal control bore when required, allowing controlled movement. The valves must always be adjusted for the specific application. The valve enables static and dynamic control of the load by regulating the flow rate TO and FROM the actuator through ports U1 and U2.

The valve consists of two units, each containing a check valve and a pressure relief valve. The pressure relief valves are each opened by the pilot pressure on the opposite side. The check valves allow free flow into the actuator and then block the load against unwanted backward movement. The pilot pressure at D1/D2 reduces the pressure setting of the opposing pressure relief valve proportionally to the specified pilot ratio until the pressure relief valve opens and allows controlled flow from U2 to D2 or from U1 to D1. The spring chambers of the pressure relief valves are relieved toward the respective port D1 or D2.

Due to the pressure-balanced pressure relief valves, their presettings are independent of the backpressure at D1 or D2. However, the pilot behavior of the valves remains dependent on the backpressure at D1 or D2. The setting value of the pressure relief valve should be at least 1.3 times the maximum expected load pressure.

Order 1:

Connection sizes: G 3/8” BSP (D1 + D2 + U1 + U2)

Schemes:

Order 2:

Connection sizes: G 1/2” BSP (D1 + D2 + U1 + U2)

Schemes:

Additional information:

Controlled flow from “U1” to “D1” and from “U2” to “D2”.

Pressure setting must be at least 1.3 times higher than the load pressure.

Normally used when ports A+B are blocked in neutral position on the upstream directional control valve.

The set opening pressure is independent of the back pressure, while the opening pressure is still influenced by the back pressure.