The ball used to fix the pneumatic ball valve is fixed in the middle of the valve body through the upper and lower valve stems, and will not move when pressed. Sealing of fixed pneumatic ball valve The difference between fixed pneumatic ball valve and floating pneumatic ball valve is that the plate spring or cylindrical compression spring on the sealing valve seat provides sufficient preload to ensure sealing, which belongs to double side forced sealing. The ball is supported by upper and lower bearings to reduce friction, eliminate excessive torque caused by the huge sealing load formed by the ball and seal seat driven by the inlet pressure, and save operation effort. The fixed pneumatic ball valve is double-sided and double-sided sealing, which will form the sealing cavity between the two sealing valve seats. To avoid danger, the fixed pneumatic ball valve must be designed with an automatic pressure relief function, that is, when the pressure of the stagnant medium in the valve cavity rises abnormally and exceeds the preload of the spring, the valve seat retracts from the ball to achieve the effect of automatic pressure relief, and the valve seat automatically recovers after pressure relief. The fixed pneumatic ball valve is widely used in various process pipelines with large diameter and high pressure due to its structural characteristics. As the upper and lower valve stems need to be assembled, only DN50 or above nominal diameter pneumatic ball valves can be produced, and the nominal diameter is too small for assembly.

2、 Function of pneumatic ball valve Pneumatic ball valve is mainly used to cut off, distribute and change the flow direction of medium on the pipeline. The pneumatic ball valve with V-shaped opening also has good flow regulation function. The pneumatic ball valve is not only simple in structure and good in sealing performance, but also small in size, light in weight, low in material consumption, small in installation size, small in driving torque, simple in operation, and easy to realize quick opening and closing within a certain range of nominal diameter. It is one of the fastest growing pneumatic ball valves in recent decades. Especially in the United States, Japan, Germany, France, Italy, Spain, Britain and other industrial developed countries, pneumatic ball valves are widely used. The variety and quantity of use continue to expand, and they are developing towards high temperature, high pressure, large mouth diameter, high sealing, long life, excellent regulation performance and one valve with multiple functions. Their reliability and other performance indicators have reached a high level, It has partially replaced gate valve, stop valve and regulating valve. With the technical progress of pneumatic ball valves, they will be more widely used in the foreseeable short term, especially in oil and gas pipelines, oil refining and cracking units and the nuclear industry. In addition, pneumatic ball valves will also become one of the leading types of pneumatic ball valves in the fields of large and medium-sized caliber, medium and low pressure in other industries.