Pneumatic butterfly valve is an important execution unit with relatively large usage in industrial pipelines,the compressed air is used as the power source to operate the valve opening and closing, and the execution speed is very fast, usually only takes a few seconds.Pneumatic butterfly valve has simple structure, convenient operation and low cost，it can not only be used for quick cut-off, but also can be used with valve positioner to receive relevant signals to achieve the regulation and control of pipe medium, pressure, flow, temperature and other parameters.

There are many kinds of pneumatic butterfly valves, which can fully meet the requirements of various working conditions, and can also customize the required butterfly valve products according to customer needs.Pneumatic fluorine lined butterfly valve and pneumatic hard seal butterfly valve are two commonly used types,the use of media,pressure and temperature are not the same.The control forms of the two are the same, but the sealing structure is completely different,the pneumatic fluorine lined butterfly valve is applicable to the pipeline that requires sealing and contains corrosive medium, but the pressure and temperature should not be too high,pneumatic hard seal butterfly valve can be used in various pressure and temperature ranges, with long service life, but the sealing effect is poor.

1. From the structure:

Hard sealing butterfly valve refers to that both sides of the sealing pair are made of metal materials or other hard materials.The soft sealing butterfly valve can use soft materials alone or all of the two sealing surfaces in contact，for example, the fluorine lined butterfly valve means that the seat and disc of butterfly  valve are wrapped with PTFE.

2.From the sealing performance：

The advantages of the soft sealing fluorine lined butterfly valve are good sealing performance, while the disadvantages are easy to aging, wear and short service life.Hard sealing butterfly valve has a long service life, but its sealing performance is relatively worse than that of soft sealing.

3.From the use of conditions:

Soft sealing fluorine lined butterfly valve used in normal temperature and pressure environment,hard seal butterfly valve can be used in low temperature, normal temperature, high temperature and other environments, and generally can be used for high pressure,soft seal is not, but fluorine lined butterfly valve has super corrosion resistance.

4.From the manufacture:

As for manufacturing, in principle, there is little difference between the two,the main difference is the valve seat,the soft sealing fluorine lined butterfly valve is the non-metallic structure, while the hard sealing butterfly valve is the metal structure. The hardness relationship between metals, working conditions and  medium should be considered.

The selection between the pneumatic fluorine lined butterfly valve and the pneumatic hard seal butterfly valve is mainly based on medium, temperature and pressure,hard seal butterfly valve is preferred if the medium contains solid particles or the temperature is higher than 200 ℃.