The inside of the wafer check valve is composed of two semicircular springs and a disc. The spring is fixed on the valve body with a pin to close the valve disc, and the medium pressure makes the opening spring deform quickly, which can protect the pipeline from damaged by water hammer. It is suitable for various pipelines with nominal pressure PN1.0MPa～42.0MPa, Class150～2500; nominal diameter DN12～1200mm, NPS1/2～48; working temperature -196～540℃, used to prevent medium backflow. By choosing different materials, it can be applied to various media such as water, steam, oil, nitric acid, acetic acid, strong oxidizing medium and urea.

The swing check valve is a check valve in which the valve flap rotates around the rocker shaft in the body cavity. The opening and closing principle of the swing check valve is the same as that of the lift check valve. It also depends on the action of medium pressure and the self-weight of the valve disc. The inlet direction of the valve should be on the side that can impact the rotation of the disc.

The closing part of the swing check valve is a disc or disc with the same diameter as the pipeline, which is suspended in the valve cavity. When the fluid is flowing forward, the disc opens under the action of the fluid pressure. It closes under the action of its own weight and the pressure of the countercurrent fluid.

Swing check valve consists of valve body, valve cover, valve disc and hinge. The valve disc is disc-shaped and hinge around the pin shaft outside the valve seat channel. The channel in the valve is streamlined, and the flow resistance is smaller than that of the straight-through lift check valve, which is suitable for large-diameter pipelines. But at low pressure, its sealing performance is not as good as the lift check valve. In order to improve the sealing performance, an auxiliary spring or a weight structure can be used to assist the sealing.

Due to the weight of the disc, when the swing check valve is opened, the resistance to the medium is relatively large. In addition, because the valve flap is suspended in the medium, the medium can be turbulent. This also shows that the fluid pressure drop across the swing check valve is greater than that across other types of check valves. When the flow direction changes suddenly, the valve disc will be violently closed on the valve seat, which will cause great wear on the valve seat and produce water hammer along the pipeline. To overcome this problem, a damping device can be installed on the valve disc, and metal Seat reduces seat wear.