The sealing performance of valve refers to the ability of valve sealing pair to prevent medium leakage. This is an important technical performance index of the valve. The sealing pair of butterfly valve is continuously developing and changing. The double-eccentric butterfly valve uses the force exerted by the valve rod between the valve seat and the butterfly plate to produce a certain elastic deformation between the sealing pairs and achieve sealing. There are two sealing surfaces, one is conical and the other is circular. Therefore, double eccentricity is line sealing.
Based on the double-eccentric butterfly valve, the triple-eccentric butterfly valve takes the center of the double-eccentric valve rod as the center and deflects the conical sealing surface to a certain angle. At this time, the sealing face of triple-eccentric butterfly valve is no longer a circular line sealing, but the sealing of an elliptical face, and the sealing surface is asymmetric. In order to prevent excessive closing of butterfly valve, a small part of the sealing surface is parallel to the valve passage. Therefore, triple-eccentric butterfly valve has fundamentally changed the design structure of butterfly valve.
When butterfly valve is closed, the sealing of small pieces of triple-eccentric butterfly valve relies on the specific pressure of valve rod. A sealing ring composed of stainless steel plate and flexible graphite is inlaid around the triple-eccentric butterfly valve. This kind of sealing has the double advantages of metal hard-sealing and non-metal soft seal. The sealing performance index is high. When the butterfly valve works in the ultra-high temperature or ultra-low temperature condition, the temperature change will cause the seal deformation. If the deformation is not effectively controlled and compensated, the sealing pair will have clearance, resulting in leakage. So in general, butterfly valve is not suitable for ultra-high temperature or ultra-low temperature.
In order to expand the application of butterfly valve, we start with the design of sealing structure of butterfly valve. By using the elastic sealing pair or improving the elastic deformation ability of the sealing pair, the deformation caused by the temperature change between the valve sealing pairs can be made up or filled, so as to ensure the reliable sealing of butterfly valve under the ultra-high temperature condition.