DD643 pneumatic flange multi-level metal hard seal butterfly valve adopts the three-dimensional eccentric principle design, so that the spatial motion trajectory of the sealing surface is idealized, the sealing surface has no friction and no interference between each other, and the sealing material is properly selected, so that the sealing, corrosion resistance, high temperature resistance and wear resistance of the butterfly valve have been reliably guaranteed. Using precision J-shaped elastic sealing ring and three-eccentric multi-level metal hard seal structure, it is widely used in industrial pipelines such as metallurgy, electric power, petrochemical, water supply and drainage and municipal construction with a medium temperature of 425 °C, for adjusting flow and carrying fluids. The valve adopts three eccentric structure, the valve seat and the sealing surface of the disc plate are made of different hardness and stainless steel, with good corrosion resistance, long service life, the valve is used two-way sealing function, the product meets the national GB/T13927-92 valve pressure test standard.