4CK30 Series Single Pilot Operated Cartridge Check Valve, 29 PSI Cracking Pressure, Pilot Ratio, Nitrile Seals

In a lock valve circuit, a single pilot operated check like the 4CK30 is used to hold a cylinder without leakage while the control valve is in neutral. It lets flow go to the cylinder, then blocks reverse flow until pilot pressure is applied to unlock it, which helps keep a load from moving when the pressure source is inactive.

Lock valves like this one are built exactly for that situation. When the control valve goes to neutral, the 4CK30 blocks reverse flow out of the cylinder with no leakage, holding the load in place. Flow can still pass through to the cylinder normally, but nothing comes back until pilot pressure is applied to release it. One thing worth knowing: a 4-way control valve is required in the circuit, even on single-acting setups, so the pilot can get the pressure it needs to unlock. Also make sure your control valve uses a free-flow (motor) spool. That prevents pressure from building up between the lock valve and the control valve, which can cause problems in service.

This 4CK30 series valve is rated for a maximum operating pressure of 5000 PSI, so it should handle high-pressure applications.