The closing member of a swing check valve is a disc or disc with a diameter equivalent to that of the pipeline, suspended in the valve cavity. When the fluid flows in the forward direction, the valve disc opens under the action of fluid pressure. When the pressure drops, the valve disc closes under the action of its own weight and the pressure of the countercurrent fluid. This type of valve is composed of a valve body, a valve cover, a valve disc and a rocker. The valve disc is disc-shaped and rotates around the pin shaft outside the valve seat channel. The internal channel of the valve is streamlined, and the flow resistance is smaller than that of the straight-through lift check valve, making it suitable for large-diameter pipelines. However, at low pressure, its sealing performance is not as good as that of the lift check valve. To improve the sealing performance, an auxiliary spring or counterweight structure can be adopted for auxiliary sealing.

The advantages of swing check valves include:
The automatic opening and closing feature eliminates the need for external power or operation, simplifying the operation and enhancing the reliability and safety of the system.
The inner channel of the valve is streamlined, with relatively low flow resistance, making it suitable for large-diameter pipes.
The disadvantages of swing check valves include:
Due to the weight of the valve disc, the resistance to the fluid when it is opened is relatively large. Moreover, the valve disc suspended in the fluid can cause turbulence in the fluid, resulting in a greater fluid pressure drop than that of other types of check valves.
When the flow direction changes suddenly, the valve disc will close violently against the valve seat, causing wear to the valve seat and generating water hammer along the pipeline. To overcome this problem, a damping device can be installed on the valve disc and a metal valve seat can be adopted to reduce valve seat wear.
Swing check valves are widely used in pipeline transportation in petrochemical, pharmaceutical, power and other industries. They can be installed in both horizontal and vertical pipelines.