Pilot operated check valves

Pilot operated check valves they are normally used to ensure the static block or a load, not for dynamic or lowering control.  They normally consist of a non-return valve and a pilot piston. Pilot operated check valves they allow free flow in one direction and block it in the opposite direction, until they are opened by pilot pressure sent on the other branch of the circuit, which acts on the pilot piston and creates an opposite reaction to that one of the load. 

 The pilot ratio generally greater than one, is the ratio between the area of the pilot piston and the seatling area of the unidirectional valee. In case they are used in combination with throttle valves. 

These latter ones should be preferably positioned between the actuator and the valve, not between the valve and distributor. In fact, the back pressure created by the downstream throttling of the valve acts in the opposite direction to the pilot pressure. In the case of mounting on the rod side of a cylinder which supports a load, as stabilizer cylinders, the pilot ratio must be substantially greater than the ratio between bottom area and annular area of the cylinder. 

The version with seal on the piston is recommended for use in circuits with open center spools in neutral position. 

The valves are available for single or double effect.

Available example models:

VBPDE 3/8    VBPDE 3/8 L2 CEXC    VBPSE 3/8 L4 VIE    VBPSE 2 CEXC   VBPDE SC   VBPDE CMP/FLV   VBPSE c/RUB   VBPSL   VBPSE A   VBPDE A   VBPSE FL   VBPDE FL