5、 Applicable scope of pneumatic ball valve Pneumatic ball valve is applicable to nominal diameter from 8mm to 1200mm; Nominal pressure from vacuum to 42MPa; The working temperature ranges from - 204 ℃ to 815 ℃; Generally, pneumatic ball valves are recommended for pipeline systems with dual position adjustment, strict sealing performance, mud, wear, necking channel, rapid opening and closing (1/4 turn opening and closing), high pressure cut-off (large pressure difference), low noise, cavitation and gasification, small leakage to the atmosphere, small operating torque and small fluid resistance. Pneumatic ball valve is also suitable for pipeline systems with light structure, low pressure cut-off (small pressure difference) and corrosive media. Pneumatic ball valves can also be used in low-temperature (cryogenic) devices and pipeline systems. When the adjustment performance is required, the pneumatic ball valve with special structure and V-shaped opening shall be selected. In petroleum, petrochemical, chemical, electric power and urban construction, metal to metal sealed pneumatic ball valves can be selected for pipeline systems with operating temperature above 200 ℃. In the oxygen pipeline system of metallurgical industry, the pneumatic ball valve with strict degreasing treatment shall be used. When the main pipeline in the oil and gas pipelines needs to be buried underground, the full bore welded pneumatic ball valve shall be used. Pneumatic ball valves are widely used in irrigation systems, mainly at the inlet of branch pipes. The pneumatic ball valve is simple in structure, small in volume and small in resistance to water flow. The disadvantage is that it can be opened or closed too quickly, which will cause water hammer in the pipeline (the pressure will rise when the water flow speed in the pipeline changes suddenly). Therefore, the pneumatic ball valve should not be used on the main pipe, but can be used for flushing on the main pipe, branch pipe or its end, with good flushing and blowdown effect. Since the seat sealing ring of the pneumatic ball valve is usually made of plastic, the fire resistance and fire prevention of the pneumatic ball valve should be considered when selecting the structure and performance of the pneumatic ball valve. Especially in the petroleum, chemical, metallurgical and other departments, when using the pneumatic ball valve in equipment and pipe systems with flammable and explosive media, more attention should be paid to fire resistance and fire prevention. Generally, pneumatic ball valves are recommended for pipeline systems with dual position adjustment, strict sealing performance, mud, wear, necking channel, rapid opening and closing (1/4 turn opening and closing), high pressure cut-off (large pressure difference), low noise, cavitation and gasification, small leakage to the atmosphere, small operating torque and small fluid resistance.

Therefore, the braiding angle of the pneumatic butterfly valve mesh sleeve is different from that of the rubber hose wire mesh.
It can be seen from the above that the smaller the local transverse load acting on the metal wire mesh sleeve, that is, the greater the ability of the bellows to accept the transverse load, the smaller the balanced braiding angle. Therefore, unlike the balanced braiding angle of the rubber hose, the braiding angle of the pneumatic butterfly valve mesh sleeve is often set smaller.
Due to the following difficulties in the manufacturing process: metal wire strands gather; Broken wire in strand; Interleaving and uneven stretching of strands; Especially when the joint, mesh sleeve and bellows are connected in a trinity way, if the rolling welding process is adopted, the sectional area of the metal wire will be reduced; If fusion welding process is adopted, the metal wire will produce a certain range of heat affected zone. Therefore, the condition that the metal wire receives the load on average does not exist. It is extremely inaccurate in practice to study the influence of the above elements in an analytical way.
For pneumatic butterfly valves with larger diameters, it would be uneconomical to use metal wires to weave nets in places where flexibility requirements are not high. It is understood that the pneumatic butterfly valve used to compensate the tank foundation subsidence and the pneumatic butterfly valve with small transverse compensation and large bending radius used in other places abroad mainly adopts the structure of corrugated pipe armored steel belt mesh sleeve