Sanitary butterfly valve is widely used. Compared with other valves, it is more convenient and more affordable. At present, the sealing data of butterfly valve can be divided into soft seal and hard seal. Soft seal can be divided into rubber, polytetrafluoroethylene and so on. But soft seal used in sanitary butterfly valve is more. Due to the limitation of structural characteristics, it does not conform to the industries of high temperature, high pressure, corrosion resistance and wear resistance.

Sanitary butterfly valve body and butterfly plate are processed by high precision CNC lathe. Sanitary butterfly valve has the advantages of small volume, light weight, simple composition, and only a few components. Secondly, it is easy to use. The valve can be opened and closed quickly only by 90 ° rotation of butterfly plate. At the same time, the valve has good fluid control characteristics.

When the sanitary pneumatic butterfly valve is in the complete open position, the thickness of butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is very small, so it has good flow control characteristics. Sanitary butterfly valve has two seal types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be inlaid on the valve body or attached to the periphery of butterfly plate.

The existing butterfly valve is a three eccentric metal hard sealing butterfly valve. The valve body and valve seat are connected components, and the surface layer of the valve seat is overlaid with temperature resistant and corrosion resistant alloy data. Compared with the traditional butterfly valve, this kind of butterfly valve has the advantages of high temperature resistance, heavy operation, no friction in opening and closing, and compensates for sealing with the increase of torque of transmission mechanism when closing, which improves the sealing performance and prolongs the service life of butterfly valve.

However, the following problems still exist in the application of this sanitary butterfly valve:

1、 Due to the multi-layer soft and hard laminated seal ring fixed on the valve plate, when the valve plate is normally open, the medium forms a positive scour on its sealing surface, and the soft sealing band in the metal interlayer is scoured, which directly affects the sealing performance.

2、 Limited by the structural conditions, the structure does not comply with the valve diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

3、 Due to the principle of three eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat depends on the driving installation torque to make the valve plate press towards the valve seat. In the positive flow state, the higher the medium pressure, the tighter the seal extrusion. When the medium flow counter current, with the increase of medium pressure, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.