Check valve that can also be opened against the locking direction if required. This action occurs via a control piston (K 2) that is dimensioned so that it can open the valve cone against the system pressure. A distinction is made between directly controlled check valves and pilot-controlled check valves, which are preferred in larger valves as releasable double check valves.
Directly controlled releasable check valve
Pilot-controlled double check valve
Upon hydraulic release of the valves, the full flow cross section is quickly enabled. To avoid abrupt opening and the relief surges which may arise as a result at high pressures and oil volumes, a releasable check valve with hydraulic release should be used.