What is a butterfly valve?

A butterfly valve is a commonly used pipeline for conveying fluids in industrial applications. It has a wide range of applications, such as in chemical processing, metallurgy, gas generators, coal gas, natural gas, liquefied petroleum gas, and hot/cold air systems.

The working principle of a butterfly valve involves regulating the flow of fluid medium through a butterfly plate. The butterfly plate is positioned vertically within the pipeline. It is disc-shaped and rotates around an axis within the valve body. By operating the valve stem, the angle of deflection of the butterfly plate can be adjusted to control the flow rate of the fluid medium.

There are many different types of butterfly valves, such as concentric butterfly valves, single-offset butterfly valves, double-offset butterfly valves, and triple-offset butterfly valves. The characteristic of a concentric butterfly valve is that the valve stem axis, the center of the circular butterfly plate, and the valve body center are all at the same point. This type of butterfly valve has a simple structure and is easy to manufacture. However, its drawback is that the butterfly plate is constantly in friction with the valve seat, leading to rapid wear. The single-offset butterfly valve addresses this issue. It separates the valve stem axis from the butterfly plate center, alleviating the compression between the butterfly plate and the valve seat. By offsetting the valve stem center from both the butterfly plate center and the valve body center, we obtain a double-offset butterfly valve. This structure effectively reduces friction between the butterfly plate and the valve seat, minimizing wear and significantly extending the valve's service life. However, double-offset butterfly valves also have drawbacks when handling high-temperature fluid media. If high-temperature-resistant hard seals are used, the medium is prone to leakage. On the other hand, if soft seals are used, they cannot withstand high temperatures. To address this issue, the triple-offset butterfly valve was developed. The third offset separates the axis of the conical butterfly plate's sealing surface from the axis of the cylindrical valve body, transforming the butterfly plate's sealing cross-section from circular to elliptical. This changes the original positional seal to a torque seal, achieving sealing through the contact pressure of the valve seat.