The valve disc of the swing check valve is disc shaped and rotating around the seat channel. Because the valve channel is streamlined, the flow resistance is smaller than the lift check valve. It is suitable for a large aperture with low flow velocity and unchangeable flow, but it is not suitable for pulsating flow, and its sealing performance is less than the lifting type. The swing check valve is divided into three types, single valve, double valve and multi half. These three forms are divided mainly according to the valve diameter. The purpose is to prevent the hydraulic shock from stopping the flow or reverse flow of the medium.