The function of swing type check valve is to prevent medium backflow in pipeline. Check valves belong to automatic valves. The opening and closing parts are opened or closed by themselves by the force of flowing media. Check valves are only used in pipelines with one-way media flow to prevent media backflow in order to prevent accidents. The American standard check valve is designed and manufactured according to ANSI B16.34 standard. Varieties are: swing type check valve, lift check valve, lift vertical check valve; Class 150lB-900Lb; NPS 1-28 working temperature-40-570 degrees C; valve body materials are: WCB, WC1, WC6, WC9, C5, CF3, CF8, CF3M, CF8M, etc. Swing check valves are suitable for medium: water, steam, oil, nitric acid, strong oxidizing medium and urea, etc. It is widely used in power plants, petroleum, chemical industry, pharmaceuticals, food and other industries. It can be used directly with imported equipment. Clamp check valves are suitable for nominal pressure PN1.0MPa-42.0MPa, Class150-2500; nominal diameter DN12-1200mm, NPS1/2-48; working temperature-196-540 C pipelines to prevent medium backflow. By choosing different materials, it can be used in water, steam, oil, nitric acid, acetic acid, strong oxidizing medium and urea and other media.