Valves are indispensable and important equipment for safe operation, maintenance, transformation and development of gas transmission and distribution and storage systems. In the process of gas production, purification, storage, transportation and application of urban gas, valves must be installed whenever cutting off, diversion, diversion, check, pressure relief, pressure stabilization and bypass are needed. Valves are widely used. According to authoritative statistics of petrochemical industry, the proportion of valves in the total investment of engineering projects reaches 8%. Because natural gas is flammable and explosive, it is particularly important to ensure the safety and reliability of valves in operation.