D643 (H, Y, F, X) - PN 6, 10, 16, 25 three eccentric multi-level metal hard seal/PTFE seal pneumatic transmission flange butterfly valve is suitable for regulating flow and cutting off fluid on medium pipelines such as metallurgy, power, petrochemical, air, and water supply and drainage with medium temperature s65C. Its sealing performance is reliable, and it is an extension and development of general butterfly valves to the medium pressure and medium high temperature fields.