Structure of butterfly valve and existing problems in use

&At present, butterfly valve, as a component used to realize on-off and flow control of pipeline system, has been widely used in many fields, such as petroleum, chemical industry, metallurgy, hydropower, etc. In the well-known butterfly valve technology, the sealing structure is mostly adopted, and the sealing materials are rubber, polytetrafluoroethylene, etc. Due to the limitation of structural features, it is not suitable for industries such as high temperature, high pressure, corrosion resistance and wear resistance.

&A more advanced butterfly valve is a three eccentric metal hard seal butterfly valve. The valve body and valve seat are connected components, and the sealing surface of valve seat is overlaid with heat-resistant and corrosion-resistant alloy materials. The multi-layer soft laminated seal ring is fixed on the valve plate. Compared with the traditional butterfly valve, this butterfly valve has the advantages of high temperature resistance, light operation, no friction between opening and closing. When it is closed, it compensates the seal with the increase of the torque of the transmission mechanism, improving the sealing performance of the butterfly valve and prolonging its service life.

&However, the following problems still exist in the use of this butterfly valve:

&First, because the multilayer soft and hard laminated seal ring is fixed on the valve plate, when the valve plate is normally open, the medium will form a positive flushing on its sealing surface, and the soft sealing belt in the metal sandwich will directly affect the sealing performance after being washed.

&Second, the structure is not suitable for valves with a diameter below DN200 due to the restriction of structural conditions, because the overall structure of the valve plate is too thick and the flow resistance is large.

&Third, due to the principle of three eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat relies on the torque of the transmission device to make the valve plate press against the valve seat. In the positive flow state, the higher the medium pressure, the tighter the sealing extrusion. When the medium flow reverses, with the increase of the medium pressure, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, and the seal begins to leak.

&The high-performance three eccentric two-way hard sealing butterfly valve is characterized in that the valve seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped sealing ring. The sealing surface of valve plate and valve seat is of inclined cone structure, and the temperature resistant and corrosion-resistant alloy material is overlaid on the inclined cone surface of valve plate; the spring fixed between the pressure plate of regulating ring is assembled with the regulating bolt on the pressure plate.

&This structure effectively compensates the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the process of two-way interchangeable medium transportation. The sealing ring is composed of two layers of stainless steel plates on both sides of soft T-shape, which has the double advantages of metal hard sealing and soft sealing. It has the sealing performance of zero leakage no matter at low or high temperature.

&It is proved that the pressure of the sealing surface is caused by the torque of the transmission device and the effect of the medium pressure on the valve plate in the positive flow state of the pool (the medium flow direction is the same as the rotation direction of the butterfly plate). When the positive medium pressure increases, the closer the oblique conical surface of the valve plate and the sealing surface of the valve seat are squeezed, the better the sealing effect is. When the reverse flow state, the seal between the valve plate and the valve seat relies on the torque of the driving device to make the valve plate press against the valve seat. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation stored by the spring of the regulating ring after being loaded can compensate the tight pressure between the valve plate and the valve seat sealing surface automatically. Therefore, unlike the prior art, the utility model is directly installed on the valve body instead of installing the soft and hard multi-layer sealing ring on the valve plate, and adding an adjusting ring between the pressing plate and the valve seat is a very ideal two-way hard sealing method. It will replace gate, globe and globe valves.