Due to the pressure of the medium at the inlet end of the pipeline, the valve is opened or closed by overcoming the spring resistance. When the medium pressure at the inlet end is lower than that at the outlet end, the spring pushes the valve core to the valve seat and closes the valve, preventing the medium from flowing backwards, so it plays a non-return role. Vertical check valves are widely used in chemical, liquefied petroleum gas, fluid and other industries. According to the structure, the check valve can be divided into three types: lifting check valve, swing check valve and butterfly check valve.