With the development of natural gas pipeline industry, the amount of gas pipeline valves is increasing, which is different from ordinary valves. Natural gas pipeline valve features the following points: 1, the material pipeline transportation of natural gas before desulfurization contains a lot of hydrogen sulfide (which is a highly toxic and corrosive gas, which reacts with iron to form iron sulfide, can Peeling flake, eroded mechanical equipment). Even after natural gas desulfurization process, there is still residual hydrogen sulfide. Therefore, select the pipeline valve corrosion-resistant materials to be selected anti-sulfur. 2, the amount of leakage Most of the natural gas pipe network built on the edge of the city, unlike the general operation and management of factories, workers often have the operation, maintenance and inspection. Ordinary city gas pipelines are over a hundred kilometers long and can only be patrolled and inspected on a regular basis. Sometimes the pipelines need to go through complicated areas and the loss of media may lead to a serious fire accident. In particular, the pipeline from the city closer to prevent leakage of the valve is particularly important. Gas valve leakage is very strict requirements, usually buried and more important valves are all welded body valve structure. In order to ensure the sealing performance of pipeline valves, sealing pair with excellent corrosion resistance, wear resistance, self-lubrication and flexibility. In recent years, the development of polymer materials for the selection of pipeline valve sealing material provides a vast selection of world, such as PTFE, Nylon, NBR, VITON and other special. 3, the application pipeline once put into operation, not allowed to stop running for a few years, the longer the operation the better, unlike the general chemical plant or refinery, overhaul period. Natural gas transported by the pipeline faces a large number of users in the whole city, and there are residents, enterprises, factories, and the like, and in particular, natural gas-based enterprise users are not allowed to have a brief interruption. Inline pipeline in the pipeline once the valve failure, the consequences could be disastrous. Therefore, the main sealing pipeline valve wearing parts such as valve seat and other parts require long life. General mainline pipeline valve life requirements of more than 30 years. 4, the drive due to high pipeline pressure, large diameter, fast switching time, pipeline valves need to use high-torque drive. Such as electric or pneumatic devices, gas-liquid linkage or electro-hydraulic linkage. Drive also have explosion-proof requirements, requiring EExdIIBT4, protection class IP68. Because of the management and control personnel in the station or the central control room, requiring pipelines in the event of a major accident such as rupture, pipeline valves can be automatically cut off. Pipeline valve requires a small operating force, in the temperature, the impact of changes in external forces, to achieve accurate operation. In particular, emergency shut-off valve, must be able to long-term in a fully open state, if necessary, quickly closed the pipeline. At the same time, require the valve opening and closing position and opening indicator accurate, easy to understand, to meet the appropriate switching speed.