Pneumatic butterfly valve, as a component used to control pipeline flow and make and break, has been widely used in many fields such as petroleum, chemical industry, metallurgy, hydropower and so on. Among the known pneumatic butterfly valve technologies, the sealing forms of pneumatic butterfly valves include soft sealing and hard sealing. The sealing materials of soft sealing surfaces are mostly rubber, polytetrafluoroethylene, etc., while the hard sealing materials are mostly various alloys and metal materials. Metal sealed valves generally have longer service life than elastic sealed valves, but it is difficult to achieve complete sealing.

Introduction of non-metallic contraction joint and precautions for its device
The non-metallic contraction joint, also known as non-metallic compensator and fabric compensator, is a kind of compensator. The data are mainly fiber fabrics, rubber, and other high-temperature resistant data. It can compensate the vibration of fan and air duct operation and pipeline deformation.
1、 Use of non-metallic contraction joint:
The non-metallic contraction joint can compensate the axial, transverse and angular directions. It has the characteristics of no thrust, simplified support design, corrosion resistance, high temperature resistance, noise elimination and vibration reduction, and is especially suitable for hot air pipes and soot pipes.
2、 Connection mode of non-metallic contraction joint:
1. Flange connection
2. Receiving connection
3、 Type of non-metallic contraction joint:
1. Straight cylinder type
2. Compound form
3. Angular type
4. Square