Check valves -also known as non-return valves- are valves that allow flow in only one direction. Reverse flow is prevented using mechanical components (springs etc.), or, back-pressure from the flowing medium itself.
Lift check valves are often installed in series with globe valves and seat in the same manner. This type of valve is suitable for many flow applications although it is commonly installed within high flow systems. Typical applications include steam, air, gas, water and vapour systems.
Lift check valves must always be installed so that the flow inlet is on the lower side of the valve seat, otherwise the valve will not operate correctly.
Lift check valve discs are of the plug or ball design. Flow from the underside of the seat lifts the disc off the seat and allows flow through the valve. The ball or plug is kept aligned during opening and closing by guides. When flow reduces, the valve closes slightly, when flow stops, the valve closes; back flow also moves the lift check valve to the closed position.
This 3D model contains all common parts of a diaphragm valve, these include: