Take you to understand the sealing principles of various types of eccentric butterfly valves

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　　A butterfly valve is a type of valve in which a valve stem is used to rotate the valve disc 90 degrees to open or close it, and its working principle is simple. There are many types of butterfly valves. Based on the design of their valve seats, they can be classified as single-eccentric butterfly valves, double-eccentric butterfly valves, and triple-eccentric butterfly valves. These valves can be used in various applications. But how should we determine which type of eccentric butterfly valve to choose when making a selection? First, we need to understand the sealing principle of eccentric butterfly valves. 1. Sealing principle of the single-eccentric butterfly valve: The single-eccentric butterfly valve is also known as the centerline butterfly valve. Its structural feature is that the axis of the valve stem, the center of the butterfly disc, and the center of the valve body are all in the same position. It has a simple structure and is easy to manufacture. To overcome compression and scraping and ensure sealing performance, the valve seat is generally made of elastic materials such as rubber or polytetrafluoroethylene; however, the sealing materials are limited by temperature in terms of their usability, which is why butterfly valves are traditionally considered unsuitable for high-temperature environments. 2. Sealing principle of double-eccentric sealed butterfly valves: By offsetting the rotation center of the butterfly disc (i.e., the center of the valve shaft) from the centerline of the valve body by a distance b, based on the design of single-eccentric butterfly valves, the sealing surface of the butterfly disc separates from the seat sealing surface more rapidly during the opening process. When the butterfly disc rotates to 8°–12°, its sealing surface is completely separated from the seat sealing surface; at full opening, a larger gap y is formed between the two sealing surfaces. This design reduces mechanical wear and compression deformation between the sealing surfaces, thereby improving the sealing performance of the butterfly valve. 3. Sealing principle of the triple-eccentric sealed butterfly valve: By offsetting the center line of the valve seat by an angle β relative to the center line of the valve body, based on the design of the double-eccentric butterfly valve, the sealing surface of the butterfly disc separates from the sealing surface of the valve seat immediately at the moment of opening, and it comes into contact with and presses against the valve seat sealing surface only at the moment of closing. When fully opened, a gap y is formed between the two sealing surfaces, similar to that in double-eccentric sealed butterfly valves. The design of such butterfly valves eliminates mechanical wear and scratching between the two sealing surfaces, thereby **improving** both the sealing performance and service life of the butterfly valve.