What is double eccentric butterfly valve and how does it work?

The so-called double eccentricity, the first eccentricity refers to the valve stem shaft deviates from the center of the sealing surface, that is, the valve stem shaft is behind the butterfly surface. This eccentricity makes the contact surface of the butterfly plate and the valve seat a sealing surface, which fundamentally overcomes the congenital deficiency of the middle line butterfly valve, thereby eliminating the possibility of internal leakage at the upper and lower intersection between the valve stem shaft and the sealing valve seat.
Another eccentricity means that the center of the valve body through the water hole is offset from the stem axis, that is, the stem axis separates the butterfly plate into two parts, one side more than the other. This eccentricity can make the disc quickly detached from or close to the seat during the opening and closing process, reduce the stroke friction between the disc and the seal seat, reduce wear, reduce the opening and closing torque, and extend the service life of the seat.
The outer rim of the butterfly plate and the sealing seat of the double eccentric butterfly valve are processed into a semi-spherical surface, and the elastic deformation of the inner sphere of the sealing seat is achieved by squeezing the outer sphere of the butterfly plate. Double eccentric butterfly valves usually use tetrafluoroethylene material as its sealing seat, and can also use gold seal seat to expand its application in high temperature fields. However, the double eccentric butterfly valve with metal sealing seat still belongs to the position sealing structure, that is, the sealing surface of the butterfly plate and the seat is in contact with the line, so it is not able to withstand high pressure, which will inevitably lead to a large leakage when applied in the high pressure system, so the double eccentric butterfly valve with metal sealing seat should be avoided as far as possible in the high pressure or the system that requires cutting off must be tight.
If you have any question about butterfly valve, just contact us freely.Edited by Shandong RMT