This valve is a pilot to open check valve. It has a sealed pilot, a steel seat, and is non-vented. It allows free flow from the valve (port 2) to the load (port 1) and blocks flow in the opposite direction. Pressure at the pilot (port 3) will open the valve from port 1 to port 2. Pilot pressure needed at port 3 to open the valve is directly proportional to the load pressure at port 1. Pressure at port 2 directly opposes pilot pressure. Provides hose break protection, prevents loads from drifting and positively locks pressurized loads. Extremely low leakage. The seat and poppet are heat treated for long life. If the load drifts due to the valve, the seat has probably been damaged by contamination and the valve should be replaced. Sealed pilot for use in circuits where cross port leakage is undesirable. Note: Available only with 30 psi or 75 psi (2 bar or 5 bar) check valve cracking pressures. Pilot-to-open check cartridges are locking valves, not motion control valves. For motion control applications, use counterbalance valves. For models with manual load release control option, turn load release clockwise to release load. Cartridges configured with EPDM seals are for use in systems with phosphate ester fluids. Exposure to petroleum based fluids, greases and lubricants will damage the seals. Incorporates the Sun floating style construction to minimize the possibility of internal parts binding due to excessive installation torque and/or cavity/cartridge machining variations.