4. Sealing of pneumatic ball valve The most important material for sealing ring of valve seat of pneumatic ball valve is polytetrafluoroethylene (PTFE), which is inert to almost all chemicals, and has comprehensive characteristics of small friction coefficient, stable performance, aging resistance, wide temperature application range and excellent sealing performance. However, the physical characteristics of PTFE, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require that the design of valve seat seal must focus on these characteristics. Plastic materials for seat sealing also include filled PTFE, nylon and many other materials. However, when the sealing material becomes hard, the reliability of the seal will be damaged, especially in the case of low pressure difference. In addition, synthetic rubber such as butadiene rubber can also be used as valve seat sealing material, but its applicable medium and temperature range medicine are limited. In addition, if the medium is not lubricated, it is easy to jam the ball with synthetic rubber. In order to meet the requirements of industrial applications such as high temperature, high pressure, strong erosion and long life, metal sealed pneumatic ball valves have been greatly developed in the past decade. Especially in countries with developed industries, such as the United States, Italy, Germany, Spain, the Netherlands, etc., the structure of pneumatic ball valves has been constantly improved, with the emergence of all welded body directly buried pneumatic ball valves, lifting pneumatic ball valves, which has made pneumatic ball valves more and more widely used in long-distance pipelines, oil refining units and other industrial fields, with large diameter (3050mm), high pressure (70MPa) The pneumatic ball valve with a wide temperature range (- 196~815 ℃) enables the technology of the pneumatic ball valve to reach a new level.

Features and technical parameters of large-diameter medium linear rubber butterfly valve Main features of large-diameter medium linear rubber butterfly valve are: low cost, exquisite valve design, reliable performance, replaceable rubber seat (replaceable rubber seat can effectively reduce maintenance costs), midline structure suitable for two-way flow of media, fully rubber lined valve body and valve plate can effectively improve corrosion resistance The light weight valve plate design can make the valve run smoothly