A check valve is a valve whose switching parts are disc-shaped and rely on their own weight and medium pressure to produce the effect of stopping the medium from flowing back. It is an automatic valve, also known as a one-way valve, check valve, backflow valve, or isolation valve. The commonly used check valves are as follows. Swing check valve Swing check valves have a disc-shaped valve flap and rotate around the axis of the valve seat channel. Because the internal passage of the valve is streamlined, the flow resistance is higher than that of a lift check valve. Small size, suitable for medium, small diameter, low pressure, and large diameter pipeline (large diameter case flow rate is low and infrequent flow changes). Sealing performance is not as good as lifting type. 1. Swing check valve is divided into three types: single valve, double valve, and multi-flap type. These three types are mainly divided according to the diameter of the valve. The purpose is to prevent the media from stopping or backflowing and to reduce the hydraulic shock. Single-valve swing check valves are usually used in medium diameter applications. When a single-valve swing check valve is used for large diameter pipelines, it is best to use a slow-closing check valve in order to reduce water hammer pressure. Double-flap swing check valves are suitable for medium and large-diameter pipelines. Buttress double-flap swing check valve, small structure, lightweight, is a fast developing check valve; multi-flap swing check valve is suitable for large diameter pipeline. 2.The installation position of the swing check valve is not restricted, it can be installed on horizontal, vertical, or inclined pipelines.