Threaded check valve refers to a valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back. It is also called check valve, one-way valve, reverse flow valve and back pressure valve. Threaded check valve is a kind of automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, and the discharge of the container medium. The threaded check valve can also be used to supply pipelines for auxiliary systems whose pressure may rise above the system pressure. Threaded check valves can be divided into swing-type threaded check valves (rotating according to the center of gravity) and lift-type threaded check valves (moving along the axis). The function of this type of valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat, thereby cutting off the flow.