The difference between the upstream sealing automatic pressure relief valve seat and the double sealing valve seat of the fixed pneumatic ball valve In pipeline valves, two types of soft sealing valve seat structures are usually used, one is the self releasing valve seat, and the other is the double piston effect valve seat. The traditional fixed pneumatic ball valve generally adopts a self discharging valve seat. In recent years, double piston effect valve seats are also increasingly used in pipeline valves.

2、 The inspection procedure is sufficient to check the unstable process of zero electromagnetic flowmeter. First, make a preliminary investigation and judgment according to the process, and then carefully check and try to remove the fault item by item. The sequence of inspection items listed in the process is as follows:; (2) According to the past on-site maintenance experience, those with high frequency and high probability of occurrence in the future are in the first place; (3) The sequence required by the inspection itself. If the causes of the last several failures are confirmed through preliminary investigation, careful inspection can also be carried out in advance.