1 Classification of pneumatic ball valves Pneumatic ball valves are divided into two categories: floating type and fixed type?
1.1 Floating ball pneumatic ball valve The ball of the pneumatic ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and press on the sealing surface at the outlet end to ensure the sealing of the pneumatic ball valve. The floating ball pneumatic ball valve has simple structure and good sealing performance, but the load of the working medium borne by the ball is all transferred to the outlet seal ring. Therefore, it is necessary to consider whether the seal ring material can withstand the working load of the ball medium. This structure is widely used for middle and low pressure pneumatic ball valves.
1.2 Fixed Ball Pneumatic Ball Valve The ball of the pneumatic ball valve is fixed and does not move after being pressed. The fixed ball pneumatic ball valves are equipped with floating valve seats. After the pressure of the medium, the valve seats will move, making the seal ring tightly press on the ball to ensure sealing. Generally, bearings are installed on the upper and lower shafts of the ball, and the operating torque is small. It is suitable for valves with high pressure and large diameter. In order to reduce the operating torque of pneumatic ball valves and increase the reliability of sealing, oil sealed pneumatic ball valves have appeared in recent years, which not only inject special lubricating oil between the sealing surfaces to form an oil film, frequently enhance the sealing performance, but also reduce the operating torque, and are more suitable for high-pressure and large diameter pneumatic ball valves. This paper mainly discusses the sealing opening and closing torque of the floating pneumatic ball valve, hoping to help the application of the pneumatic ball valve.

Performance characteristics of pneumatic ball valve:
1. The pneumatic ball valve has simple structure, small volume and light weight. The sealing surface material of the ball valve is widely used with tetrafluoro, the deposited welding has good sealing performance, abrasion resistance and erosion resistance, and has also been widely used in the vacuum system.
2. The pneumatic ball valve is easy to operate, fast to open and close, and rotates 90 ° from full open to full close for remote control. It is easy to maintain, the pneumatic ball valve is simple in structure, the sealing ring is generally movable, and it is easy to remove and replace.
3. When the pneumatic ball valve is fully opened or closed, the sealing surface of the ball and valve seat is isolated from the medium, and the medium will not cause erosion of the valve sealing surface when passing through. It has a wide range of applications, ranging from a few millimeters to several meters in diameter, from high vacuum to high pressure.
4. As the power source of pneumatic ball valve is cylinder dependent gas, the pressure of pneumatic ball valve is generally 0.4-0.7MPa. If the pneumatic ball valve leaks, the gas can be discharged directly compared with the hydraulic and electric valves.
5. Compared with manual and turbine rotating ball valves, pneumatic ball valves can be configured with large caliber. Manual and turbine rotating ball valves are generally below DN300 caliber, and pneumatic ball valves can reach a larger caliber.