The basic principle.
A non-return or check valve permits flow in one direction and resists it in the other. A ball, poppet or another closing element moves away from its seat when the opening pressure difference is sufficient.
Cracking pressure is the pressure difference at which opening begins under stated conditions. A check valve is not the same as a pressure regulator, and its flow capacity and leakage characteristics matter.
After the pump stops.
A check valve in a suitable lift circuit can prevent fluid returning through the pump path. Lowering uses a separate controlled path rather than requiring flow backwards through that check valve.
Follow the relationship.
- Forward pressureOvercomes the closing force.
- Valve opensAllows the intended flow.
- Reverse tendencyPushes the closing element towards its seat.
Connect it to the lift.
Load holding depends on the complete hydraulic arrangement, including other paths and seals. A closed check valve should not be treated as proof that the entire installation has no leakage. An engineer considers all possible routes when investigating settling.
A closer look
Pilot-operated check valves can be deliberately released by a separate control pressure. Their behaviour differs from a simple unpiloted check valve.
Check your understanding
Is a check valve a way to freely control flow in either direction?
Reveal the explanation
No. Its basic function is directional prevention of reverse flow; other valve functions control lowering or metering.