Valve is an indispensable important equipment for the safe operation and maintenance, transformation and development of gas transmission and distribution and storage systems. In the process of gas production, purification, storage, transmission and distribution and application of urban gas, valves must be installed whenever it is necessary to cut off, change direction, divert, check return, relieve pressure, stabilize pressure and bypass. Since natural gas is a flammable and explosive substance, it is particularly important to ensure the safety and reliability of the valve in operation and turnover.