3.3 Sealing mechanism of fixed pneumatic ball valve High pressure or pneumatic ball valve with nominal diameter DN ≥ 200mm usually adopts fixed structure. The ball of the fixed pneumatic ball valve does not produce floating amount, which can ensure two-way sealing and reduce the operating torque of the valve; The load fluctuation amplitude on the seal seat is small. Fixed pneumatic ball valves can be divided into ball front sealed (population sealed) and ball rear sealed (outlet sealed) pneumatic ball valves, as shown in Figure 2. Figure 2

In order to reduce the operating torque of the pneumatic ball valve and increase the reliability of the seal, an oil sealed ball valve has emerged. It not only injects special lubricating oil between the sealing surfaces to form an oil film, which not only enhances the sealing performance, but also reduces the operating torque, and is more suitable for high-pressure large caliber ball valves.