What is a lift check valve?
A lift check valve, also known as a non-return valve, one-way valve, reverse flow valve, or back-pressure valve, is an automatic valve. It automatically opens and closes the disc based on the flow of the medium itself, preventing backflow.
How does a lift check valve work?
The lift check valve's operating principle is primarily based on changes in medium pressure. During forward flow, the fluid pressure forces the conical disc to disengage from the valve seat, opening the valve. During reverse flow, the disc's weight (sometimes supplemented by a spring) and the fluid's return pressure force it to return to the seat, closing the valve. This operating principle ensures unidirectional flow of the medium in the pipeline.
Structural Features of a Lift Check Valve:
- Disc Movement: The disc moves up and down along the centerline (or perpendicular to the centerline) of the valve body.
- Valve Body Structure: The structure of a lift check valve is very similar to that of a globe valve. The valve body is identical to that of a globe valve and can be used interchangeably. The disc design is similar to that of a globe valve. A guide shaft and sleeve are installed on the upper disc and lower bonnet. The disc guide shaft can be raised and lowered freely within the bonnet guide sleeve.
- Sealing Performance: Lift check valves, which utilize a metal-to-metal seal, allow for a small amount of leakage and are only suitable for applications where backflow sealing is not critical.
Types and Classifications of Lift Check Valves
Depending on the installation method, lift check valves can be categorized as either straight-through or vertical. The former is generally installed in horizontal pipelines, while the latter is suitable for vertical pipelines. There are also improved lift check valves, such as piston lift check valves and angle lift check valves with a slow-closing mechanism.
