Why are three-eccentric hard-sealed butterfly valves widely used?

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　　Three-eccentric hard-sealed butterfly valves are widely used in industrial pipelines in industries such as metallurgy, power generation, petrochemicals, as well as water supply and drainage and municipal construction, where the medium temperature is ≤425°C, for regulating flow and shutting off fluids. 　　In previous articles, we explained to you the sealing principles of various types of eccentric butterfly valves. As components used to control the flow and shut off pipelines, butterfly valves are widely employed in many fields such as petroleum, chemicals, metallurgy, and hydropower. Due to the limitations of their structural characteristics, single-eccentric butterfly valves and double-eccentric butterfly valves are not suitable for applications that require resistance to high temperatures and pressures, as well as corrosion and wear. Three-eccentric metal hard-sealed butterfly valve, where the valve body and the valve seat are integrated components, and the sealing surface of the valve seat is clad with a heat-resistant and corrosion-resistant alloy material. Multi-layer soft folded sealing rings are fixed on the valve plate; compared to traditional butterfly valves, this type of butterfly valve offers advantages such as high temperature resistance, easy operation, friction-free opening and closing. When closed, the sealing is enhanced as the torque applied by the actuation mechanism increases, which improves the sealing performance of the butterfly valve and extends its service life. The three-eccentric metal hard-sealed butterfly valve is characterized in that: the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of a flexible T-shaped sealing ring. The sealing surfaces of the valve plate and the valve seat are of a slanted cone shape, with heat-resistant and corrosion-resistant alloy materials welded onto the slanted cone surface of the valve plate ； A structure in which a spring fixed between the adjustment ring pressure plates is assembled with the adjustment bolts on those pressure plates. This structure effectively compensates for the tolerance gaps between the shaft sleeve and the valve body, as well as the elastic deformation of the valve stem under medium pressure, thereby resolving the sealing issues that arise during two-way media transfer with this type of valve. A sealing ring is formed using multiple layers of stainless steel sheets on both sides of a flexible T-shaped structure, combining the advantages of both metal hard sealing and soft sealing; it provides zero-leakage sealing performance in both low-temperature and high-temperature conditions. 　　Tests have shown that in the forward flow condition of the tank (where the direction of fluid flow is the same as the direction of rotation of the butterfly valve disc), the pressure on the sealing surface is generated by the torque exerted by the actuation mechanism and the pressure of the fluid acting on the valve disc. As the positive medium pressure increases, the inclined conical surface of the valve plate presses more tightly against the sealing surface of the valve seat, resulting in an improved sealing effect. In the reverse flow condition, the seal between the valve disc and the valve seat is maintained by the torque of the driving mechanism, which presses the valve disc against the valve seat. As the reverse medium pressure increases, when the unit normal pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored in the spring of the adjustment ring under load compensates for the sealing force between the valve plate and the valve seat, thereby providing automatic compensation. Therefore, unlike existing technologies that install multiple layers of soft and hard sealing rings on the valve plate, this utility model installs them directly on the valve body; adding an adjustment ring between the pressure plate and the valve seat represents an ideal method for achieving bidirectional hard sealing. It can replace gate valves, globe valves, and ball valves.