The Butterfly valve, also known as flap valve, is a kind of control valve with simple structure. Its main function is to cut off the circulation of the medium in the pipeline, or adjust the flow rate of the medium in the pipeline. Secondly, butterfly valves can also be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. In addition, when the butterfly valve is installed, it should be installed on the pipeline that is completely sealed and has zero leakage in the gas test.