Selection of Valve Electric Actuator Models
Sep 26,2022Read More
At present, the butterfly valve, as a component used to realize the on-off and flow control of the pipeline system, has been extremely widely used in many fields such as petroleum, chemical industry, metallurgy, and hydropower.
In the existing butterfly valve technology, the sealing structure is mostly adopted, and the sealing material is rubber, polytetrafluoroethylene, etc. Due to the limitation of structural characteristics, it is not suitable for industries such as high temperature resistance, high pressure, corrosion resistance, and wear resistance. One of the more advanced butterfly valves available is the triple eccentric metal hard seal butterfly valve (triple eccentric butterfly valve). Its valve body and valve seat are conjoined components, and the sealing surface layer of the valve seat is welded with temperature-resistant and corrosion-resistant alloy materials. The multi-layer soft stacked sealing 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 when opening and closing, and the sealing performance and the service life of the butterfly valve are improved as the torque of the transmission mechanism increases when it is closed. However, this butterfly valve still has the following problems during its use:
1. Since the multi-layer soft and hard stacked sealing ring is fixed on the triple eccentric butterfly valve plate, when the valve plate is normally open, the medium will flush its sealing surface positively. After being scoured, the soft sealing tape in the interlayer of the metal sheet directly affects the sealing performance.
2. The triple eccentric butterfly valve is restricted by structural conditions. This structure is not suitable for valves with a diameter below DN200. The reason is that the overall structure of the valve plate is too thick and the flow resistance is large.
3. Due to the principle of the triple eccentric butterfly valve structure, the sealing between the sealing surface of the valve plate and the valve seat depends on the torque of the transmission device to press the valve plate against the valve seat. In the positive flow state, the higher the medium pressure, the tighter the seal extrusion. When the flow channel medium flows back, as the medium pressure increases, and the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.
The seat sealing ring of the high-performance triple eccentric butterfly valve is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped sealing ring. The sealing surface of the valve plate and the valve seat is an oblique cone structure, and temperature-resistant and corrosion-resistant alloy materials are bead welded on the oblique cone surface of the valve plate; The structure of the spring fixed between the pressure plate of the adjusting ring and the adjusting bolt of the pressure plate is assembled together, which effectively compensates the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the pressure of the medium, solving the sealing problems during the two-way exchange of the medium conveying process of the valve.
The high-performance triple eccentric two-way hard sealing butterfly valve adopts a soft T-shaped sealing ring composed of multiple stainless steel sheets on both sides, which has the dual advantages of metal-hard sealing and soft sealing, and has zero leakage sealing performance regardless of low temperature and high temperature.
Tests have proved that when the high-performance triple eccentric two-way hard seal butterfly valve pool is in positive flow state (the flow direction of the medium is the same as the direction of rotation of the butterfly plate), the pressure on the sealing surface is generated by the torque of the transmission device and the action of the medium pressure on the valve plate. When the positive medium pressure increases, the tighter the oblique cone surface of the valve plate and the sealing surface of the valve seat are pressed, the better the sealing effect.
When the high-performance triple eccentric two-way hard seal butterfly valve is in the reverse flow state, the seal between the valve plate and the valve seat depends on the torque of the driving device to press the valve plate 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 of the spring of the adjusting ring after being loaded can compensate for the tightness of the sealing surface of the valve plate and the valve seat. The pressure plays a role of automatic compensation. Therefore, unlike the prior technology of installing multiple sealing rings on the valve plate, the multiple sealing rings are directly installed on the valve body, and an adjustment ring is added between the pressure plate and the valve seat, which is a very ideal two-way hard sealing method. It can replace gate valves, globe valves and spherical valves.
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