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July 20, 2020

Several sealing principles of butterfly valve


Sealing schematic diagram of double eccentric sealing BUTTERFLY VALVE

On the basis of single eccentric Butterfly Valve, the rotary center of butterfly plate (i.e. the center of valve shaft) is offset with the center line of valve body to form dimension B. during the opening process of butterfly valve, the sealing surface of butterfly plate will break away from the sealing surface of valve seat faster than that of single eccentric sealing butterfly valve. When the butterfly plate is rotated to 8 ° to 12 °, the sealing surface of butterfly plate will completely break away from the valve seat seal. When the butterfly plate is fully opened, the shape between the two sealing surfaces will be formed The design of this kind of butterfly valve greatly reduces the mechanical wear and extrusion deformation between the two sealing surfaces, and improves the sealing performance of the butterfly valve.

Since the rotating center (i.e. the center of valve shaft) of butterfly plate and the sealing section of butterfly plate are set eccentrically according to a, the sealing surface of butterfly plate is gradually separated from the sealing surface of valve seat during the opening process of butterfly valve. When the butterfly plate is rotated to 20 ° to 25 °, the sealing surface of butterfly plate is completely separated from the sealing surface of valve seat. When the butterfly plate is fully opened, a gap x is formed between the two sealing surfaces, which makes the two sealing surfaces of butterfly valve in the process of opening and closing The relative mechanical wear and extrusion are greatly reduced, thus ensuring the sealing of butterfly valve.

3. Sealing principle of triple eccentric sealing butterfly valve



Sealing schematic diagram of triple eccentric sealing butterfly valve

Because the center line of the valve seat and the center line of the valve body form a β angle offset on the basis of the double eccentric butterfly valve, the sealing surface of the butterfly plate will immediately break away from the sealing surface of the valve seat at the moment of opening, and will contact and compress the sealing surface of the valve seat at the moment of closing. When the valve is fully opened, a gap y is formed between the two sealing surfaces, which is the same as that of the double eccentric sealing butterfly valve. The design of this kind of butterfly valve completely eliminates the mechanical wear and scratch between the two sealing surfaces, and greatly improves the sealing performance and service life of the butterfly valve.

4. Sealing principle of variable eccentric sealing butterfly valve



Sealing schematic diagram of variable eccentric sealing butterfly valve

The unique feature of the variable eccentric butterfly valve is that the stem shaft of the butterfly plate is a three section shaft structure. The two shaft sections of the three section shaft type valve rod are concentric, and the center line of the central section shaft deviates from the axis at both ends by a center distance, and the butterfly plate is installed on the intermediate shaft section. The eccentric structure makes the butterfly plate become double eccentric when the butterfly plate is fully open, and single eccentric when the butterfly plate rotates to the closed position. Due to the action of eccentric shaft, the butterfly plate moves a distance into the sealing cone surface of the valve seat when it is close to closing, and the sealing surface of the butterfly plate and the valve seat are consistent to achieve reliable sealing performance.
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