Double eccentric hard seal butterfly valve is gradually improved from the ordinary butterfly valve to adapt to different working conditions (such as working temperature and working pressure). It has the advantages of simple structure, reliable sealing, light opening, long service life and convenient maintenance. At present, with the development of large-scale transformation of blast furnace ironmaking equipment in China, double eccentric hard seal butterfly valve has been widely used in water supply and drainage, building fire protection, metallurgy and other pipeline systems.
The Working Principle:
In theory, the ordinary butterfly valve is sealed as line contact. While for the multi-level double eccentric metal hard seal butterfly valve, the position of the sealing pair forms a wide ring belt from the original linear due to the secondary eccentricity (the position of the valve stem moves up). As long as the surface contact of the sealing pair is in this ring belt, the sealing can be realized without any clamping group when the valve disc is opened.
During the opening of the valve disc, the sealing points of the ordinary butterfly valve disc move along the tangent trajectory of the conical valve seat bus. And there is a relative translation between the sealing pairs. So the friction torque is large. However, the translation between the sealing pairs of the double eccentric metal hard seal butterfly valve is very small. And each point of the surface contact seal is rapidly separated along the tangent trajectory direction of the conical valve seat bus. Therefore, the friction torque is very small, which effectively reduces the wear between sealing pairs.
In the metallurgy system, the double eccentric hard seal butterfly valve is mainly used in the preheating system and dry dust removal system of ironmaking blast furnace with large nominal diameter, low working pressure, low opening & closing differential pressure and high temperature (200°C ~ 350°C).
As the double eccentric hard seal butterfly valve has very good sealing performance, wide applicable temperature, large working pressure, wear resistance, corrosion resistance and long service life. Therefore, its roles are as a combustion air shut-off valve, combustion gas shut-off valve, gas inlet & outlet shut-off valve of heat exchanger system, flue gas inlet & outlet shut-off valve of heat exchanger system and gas shut-off valve of dry dust removal system.