Valve which blocks the flow rate in one direction and allows it in the opposite direction. They are used to block the hydraulic load lines for directional valves suffering from leaking oil or as hydraulically actuated drain or idle circulation valves.
To keep a hermetic seal in the closed position, the check valves are designed as cone-seated or ball-seated valves. The barrier function is generally performed by a spring, the effect of which is amplified by the system pressure on the barrier element. For certain applications, check valves are built so that the barrier can be lifted by control pressure (releasable check valves).