Center line butterfly valve is a kind of component used to realize on off and flow control of pipeline system. It has been widely used in petroleum, chemical industry, metallurgy, hydropower and many other fields.In the butterfly valve technology known to the public, its sealing form USES the sealing structure, the sealing material is rubber, polytetrafluoroethylene and so on. Due to the limitation of structural characteristics, it is not suitable for high temperature, high pressure, corrosion resistance, wear resistance and other industries. Existing a more advanced butterfly valve is a three-eccentric metal hard seal butterfly valve, valve body and seat for the conjoined components, seat seal surface layer surfacing welding temperature, corrosion resistant alloy materials. The multi-layer soft folding sealing ring is fixed on the valve plate. Compared with the traditional butterfly valve, this kind of center line butterfly valve has the advantages of high temperature resistance, light operation, no friction when opening and closing. When closing, the torque of the transmission mechanism increases to compensate the sealing, which improves the sealing performance of the butterfly valve and extends its service life.