Butterfly valve has been in the chemical industry, metallurgy, petroleum and other industries have been widely used. Of course, mostly soft-sealed butterfly valve. However, in recent years, in some areas of high temperature; high pressure, strong corrosion, three eccentric metal seal butterfly valve is widely used. Three eccentric metal seal butterfly valve structure is characterized by body and valve seat is Siamese member, seat sealing surface layer surfacing temperature, corrosion resistant alloy material. Multi-layer soft stacked ring fixed to the valve plate, this butterfly valve compared with the traditional butterfly valve with high temperature, light operation, opening and closing without friction, closed with the torque of the transmission mechanism to compensate for increased sealing, improved butterfly valve The sealing performance and extend the service life of the advantages. Of course, this three-eccentric metal sealing butterfly valve also has its inherent disadvantages: 1, the valve plate structure is relatively thick, large flow resistance, it is not suitable for DN200 small diameter pipe; 2, normally open pipe, valve seat sealing surface by Front flushing, affecting the fixed in the valve plate on the multi-layer hard laminated ring, a long time will affect the sealing performance; 3, three eccentric structure principle, the sealing surface between the valve plate and the valve seat is sealed by the transmission Torque valve plate to the seat. The positive flow state, the higher the media pressure seal squeeze tight. When the flow medium countercurrent media pressure increases with the pressure between the valve plate and valve seat unit pressure is less than the medium pressure, the seal began to leak. There is now a new type of three eccentric butterfly valve: It is characterized by: the seat ring by the soft T-ring seal on both sides of multi-layer stainless steel sheet. The sealing surface of the valve plate and the valve seat is an oblique conical structure, and a temperature-resistant and corrosion-resistant alloy material is deposited on the oblique conical surface of the valve plate; the spring fixed between the adjusting ring plate and the adjusting bolt on the pressure plate is provided with the structure. This structure effectively compensates for the tolerance band between the sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure and solves the sealing problem existing in the process of transporting the valve in the bidirectional interchangeable medium. The soft T-shaped multi-layer stainless steel sheet on both sides of the seal ring, with the advantages of both metal seal and soft seal, both in low temperature and high temperature conditions, have zero leakage of sealing performance. With the development of mechanical technology, butterfly valve space is also more and more widely used, many shortcomings have also been improved.
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