This series of butterfly valve plate movement mechanism adopts double eccentric structure, soft seal with rubber seals to pay (D47X-2.5) and the metal seal (D47H-2.5) two kinds. Sealing surface when opening and closing force uniform, with opening and closing moments, good sealing performance, long life and other characteristics. The valve for air, gas and other gas medium pipeline to do with the regulation and closure. Apply more stringent requirements on the amount of leakage pipeline. D47H-2.5 type with "Ω"-shaped stainless steel elastic ring, can be used for high temperature gas and other low corrosive gas pipeline to do cutting medium. This series of butterfly valves are widely used in metallurgy, chemical, power, municipal gas, industrial gas, environmental protection and other industries. The valve connecting flange dimensions conform to GB2555-81 standards. Length of the structure dimensions conform to GB12221-89, the first 13 series of standards. Detection methods conform GB/T13927-92 standards.