As for sealing, pneumatic butterfly valves have two types of seals: elastic seal and metal seal. The former is for the purpose of valve sealing. Generally, the seal ring will be embedded around the butterfly plate or on the valve body. As for the valve with metal seal, its service life will be longer than that of elastic seal, but it cannot be completely sealed. In the working environment with high temperature, metal sealing is a very practical method, while elastic sealing is subject to temperature restrictions. 　　　　

The existing advanced butterfly valve is a tri eccentric metal hard seal butterfly valve. The valve body and valve seat are integral components, and the sealing surface layer of the valve seat is welded with heat-resistant and corrosion resistant alloy materials. The multi-layer soft laminated seal ring is fixed on the valve plate. Compared with the traditional butterfly valve, this butterfly valve has the advantages of high temperature resistance, easy operation, no friction when opening and closing, and compensation sealing with the torque of the transmission mechanism when closing, which improves the sealing performance of the butterfly valve and extends its service life. Since multi-layer soft and hard laminated seal ring is fixed on the valve plate, when the valve plate is normally open, the medium will form a frontal erosion on its sealing surface. After the soft seal belt in the metal sandwich is washed, the sealing performance will be directly affected.