The disc of a butterfly valve is installed in a diametrical direction of a line. In the spherical way of the body, the disc rotates with the axis, and the angle is 0°to 90°. When it rotates to 90°, the valve will be open fully.
A butterfly valve has simple structure, small size, light weight, and is merely assembled by several parts. It’s operation is easy because it can open and close rapidly when it rotates to 90°. And it features good fluid control at the same time.
When the valve opens fully, the thickness of the disc is the only resistance to medium, and the pressure is low when the medium flows through the body. So, it has good fluid control.
There are two types on its sealing form, one the resilient sealing, the other metal sealing. The sealing ring of a resilient sealing valve can be inlaid in the body or attached around the disc.
The service life of a valve with metal sealing is longer than the valve with resilient sealing, but it is hard to seal fully. The metal sealing can adapt to higher temperature, but the resilient sealing is limited by temperature.
If it is used to control fluid, the main problem is how to choose dimension and type of a valve correctly. The structural principal particularly adapts to produce large-caliber valve. The butterfly valve is widely used in some industries, such as petrology, gas, chemical, and water treatment. And, it can be used in cooling water system of a thermal-power plant.
Common butterfly valves can be divided into clip-on butterfly valve and two-flange butterfly valve. The clip-on valve is connected by stud bolts between two flanges, and the two-flange butterfly valve processes a valve in the body, which two-flange valve is connected with the pipe flange with the bolt.