Control valve
Sterling Hydraulics
BASIC FUNCTION
Load control valves are usually 3 port metering elements that combine three valve functions in a single cartridge, i.e. a relief valve with a reverse flow check valve and a pilot assisted opening feature on the main relief poppet. As the name implies, they are used to control the movement of a hydraulically supported load, and in doing so, guard against the consequences of hose failure. They are also sometimes referred to as over-centre valves, counterbalance valves and boom lock valves. In operation they are connected to the loaded port of an actuator, firstly to allow unrestricted input flow via the check valve to raise the load, and secondly, to control the outlet flow via the pilot assisted relief valve to lower the load. A cross line pilot supply from the actuator’s other port is connected to the valve’s pilot port to give a feedback signal that causes the valve to modulate the load lowering pressure and so prevent a runaway situation. However, this does not apply to valves described later that have an independent pilot supply.
Other variants are detailed below, plus there are special versions not listed that are available on request.
