Double Pilot Operated Hydraulic Check Valve, 1/2 NPT Ports, 11 GPM. This double pilot operated check valve is designed to hold hydraulic cylinders and prevent them from drifting down while your directional control valve is in the neutral position. At rest the hydraulic check valves remain seated, blocking flow from entering and exiting the cylinder and locking the cylinder in place. When pressure is applied to either port, the hydraulic check valve will open allowing free flow from the inlet to the actuator port across the check valve. When pressure builds and shifts the cylinder, the internal pilot piston will react quickly to the pressure and will shift against the return check. This action mechanically pilots the valve open to allow return flow to pass through the valve from the actuator back to tank. With both ports now open, the valve is unlocked and the hydraulically powered cylinder is now free to move. When system pressure is shut off to the valve, the valve will then return to the holding condition. Summit Hydraulics carries many different check valves. Benefits: Prevents a load from falling if a hose ever fails. Hardened, precision ground parts for durability. Carbon Steel body with black oxide finish. Features: Flow Rating: 11 GPM. Pressure Rating: 5000 PSI. Crack Pressure: 30 PSI.Pilot Ratio: 4:1.. Port Size: 1/2 NPT Thread.