1.Valve body and valve seat of tri-eccentric hard sealing butterfly valve are combined component. Build up weld temperature, corrosion resistant alloy material on the valve seat sealing surface layer. 
2. Tri-eccentric: the centerline of shaft offsets centerline of the sealing surface, the shaft centerline is slightly deviated from centerline of the pipeline, and centerline of valve body sealing face (oblique circular cone) and centerline of pipeline form an angle of β.
3. The multi-layer sealing ring is made of soft and hard laminated sheet metal. It has advantages of both of metal hard seal and soft seal. Sealing performance of zero leakage is guaranteed in low and high temperature.