Check valve also known as one-way valve, reverse valve, back pressure valve. This kind of valve is automatically opened and closed by means of the force generated by the flow of the medium itself in the pipeline. It is an automatic valve. The function of check valve is to prevent the backflow of medium, prevent the reverse of pump and drive motor, and prevent the discharge of medium in the container. Check valves are suitable for pipe lines of various media according to the material of shell and inner parts. Check valves can be classified into the following types according to their structure.

1. The swing check valve closes the check valve

Swing check valves with single disc check valves and multiple multi-disc check valves; There are also shrink - diameter swing check valves and full - diameter swing check valves. Single-valve swing check valve structure, generally used for nominal size DN50~DN500; Multi - valve swing check valve 300 is generally used for nominal size of DN600 or greater. The structure of the reduced diameter swing check valve is shown in figure 2-79, and that of the full diameter swing check valve is shown in figure 2-80.

2. Lift check valve

Lift check valve is a check valve in which the disc moves parallel to the axis of the seat hole. This check valve can only be installed on the horizontal pipe line. For the pump suction tube bottom lift check valve also called bottom valve, its function is to prevent the pump when the medium backflow, to maintain the suction required water column