Working principle of pneumatic butterfly valve Pneumatic butterfly valve is a kind of valve whose valve plate rotates around a fixed axis perpendicular to the channel. It is composed of a piston type double action or single action (spring return type) pneumatic actuator and butterfly valve. It is a rotary high-performance regulating or shut-off valve. Its principle is as follows:

Netting layer
The ideal netting not only needs to wrap the tube under pressure, but also reduces the possibility of hose twisting. Appropriate netting shall comprehensively balance the requirements of hose pressure bearing and hose flexibility. The optimized netting design can make the net sleeve of the hose close to the wave crest of the ripple. Tiled netting
Flat weaving is to combine several single steel wires into one strand, and then weave each strand of steel wire into a mesh sleeve with a tetrafluoro compensator. The mesh sleeve will be tensioned automatically when it is stretched by external forces.
The structure of the flat woven fabric is expressed as: (number of spindles) × (number of steel wires per share) × (diameter of steel wire). For example, in 24 × 8 × 0.3, 24 means the number of spindles of the knitting machine is 24, 8 means the number of steel wires per share is 8, and 0.3 means the diameter of a single steel wire is 0.3 mm.
Teflon hose polytetrafluoroethylene is a polymer of tetrafluoroethylene. The English abbreviation is PTFE. The basic structure of PTFE hose is- CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 -. Polytetrafluoroethylene (PTFE) is widely used in various needs of acid and alkali resistance and organic solvents. It is not toxic to humans, but one of the raw materials used in the consumption process, ammonium perfluorooctanoate (PFOA), is thought to have carcinogenic effect.
The relative molecular weight of PTFE hose is relatively large, ranging from hundreds of thousands to more than 10 million, which is usually millions (polymerization degree is 104, while polyethylene is only 103). The general crystallinity is 90~95%, and the melting temperature is 327~342 ℃. CF2 units in PTFE molecule are arranged in zigzag shape. Since the radius of fluorine atom is slightly larger than that of hydrogen, adjacent CF2 units cannot be completely oriented in trans interpenetration, but form a spiral twisted chain, and fluorine atoms simply cover the appearance of the entire polymer chain. This molecular structure explains the various properties of PTFE. When the temperature is lower than 19 ℃, 13/6 spiral is formed; The phase transition occurs at 19 ℃, and the molecule is slightly untied to form a 15/7 helix.
Although the breaking demands of carbon carbon bond and carbon fluorine bond in perfluorocarbon compounds absorb 346.94 and 484.88 kJ/mol of energy respectively, it only takes 171.38 kJ of energy to depolymerize tetrafluoroethylene into 1 mol tetrafluoroethylene from tetrafluoroethylene hose. Therefore, during pyrolysis at high temperature, polytetrafluoroethylene is mainly depolymerized into tetrafluoroethylene. The weight loss rate (%) of PTFE at 260, 370 and 420 ℃ is 1 × 10-4, 4 × 10-3 and 9 × 10-2 per hour respectively. It can be seen that PTFE can be used for a long time at 260 ℃. Due to the highly toxic by-products such as fluorophosgene and perfluoroisobutylene produced during pyrolysis at high temperature, special attention should be paid to safety protection and prevent polytetrafluoroethylene from contacting open fire.