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.

4、 Timing analysis of purchasing quality of raw materials
The timing analysis of the purchase quality of raw materials is an important link that many pneumatic butterfly valve companies tend to neglect. The regular analysis of the purchase quality of raw materials can find out whether the quality of raw materials supplied by suppliers has rules in terms of stability, and also provide the main information and even basis for the quality control of the next production process, the selection and adjustment of suppliers in the future.
Regular analysis of the purchase quality of raw materials. Class A raw materials should usually be stopped once a month; Class B raw materials shall be stopped every six months; Class C raw materials shall be stopped once a year. The analysis mainly includes: statistical analysis of inspection results such as raw material trial and inspection; The supplier's on-time delivery and delivery quantity; Disposal and rectification of abnormal supply quality.
In a word, pneumatic butterfly valve companies should not only focus on production process and efficiency, but also pay more attention to the quality of raw materials purchased. Only by properly handling the quality of purchased raw materials and strengthening the quality control of the purchase process can the pneumatic butterfly valve supplier have a solid foundation and guarantee the quality.