These combine a solenoid valve and a relief valve in one block. De-energised, the valve dumps pump flow to tank at almost no pressure. Energise the coil and the circuit builds to the relief setting.

Two jobs it does well: unloading a pump so the motor starts against no load and idles cheaply, and controlled lowering — opening a path from a cylinder back to tank so a raised load comes down under its own weight at a metered rate.

Normally open or normally closed? Normally open is the safe choice for lowering — lose power and the load stops rather than runs away. Normally closed suits unloading duty where you want no flow until the operator asks for it.

Manufactured by CBF Hydraulic, Montecchio Maggiore, Italy. Recommended oil viscosity 10–420 cSt, working temperature −20 to +90 °C, absolute filtration 25 µm.