How Does A Pneumatic Butterfly Valve Work

1. How does a pneumatic butterfly valve work?
Pneumatic butterfly valve uses the round disc to open and close, which can be designed to have the functions of regulation. In general, it serves as a block valve, but also enable have adjustment ability. At the moment, there are more and more butterfly valves used for pipelines with low pressure and medium large diameter. 

Pneumatic butterfly valve has advantages of simple structure, light weight, low cost. There was little fluid resistance, so the liquid inside the pneumatic butterfly with medium large diameter could cover a large area when fully opened. It is easy to open and close with 90 degrees. Discs on both sides of the rotator have similar medium forces, resulting in opposite torque directions. We could achieve good sealing performance under low pressure due to small torque of opening and closing. Butterfly valve materials include Buna-N rubber (BNR), fluorine rubber, hydrocolloid, PTFE, so it has good sealing performance. Among which hard sealing butterfly valve has stacked soft and hard metal plate, which has advantages of hard sealing and elastic sealing.
 
2. Operating principles and feasible circumstances
A disc is installed on the diameter direction of a butterfly valve. In the cylinder-shape channel of the valve, the disc spins around the center axis with 0-90 degree. When it turns 90 degrees, the valve will be fully opened.

The butterfly valve has simple structure, small size, light weight and is consist of few components. You can quickly open and close the valve for just turning 90 degrees. It is not only easily operated, but also has the characteristic of fluid controlling. When a butterfly valve is fully opened, the thickness of disc becomes the only resistance for the fluid media. The pressure drop inside of the valve is very small, so the valve has good fluid controlling.

There are two kinds of butterfly valves, which includes elastic sealing and metal sealing valves. The gasket can be inset on the valve body or around the disc.

The valve with metal sealing usually has longer service life than that of the elastic type, though it is still hard to achieve completely sealing. A metallic sealing valve works well at high temperature while an elastic seal valve does not.
If you want to use the butterfly valve for fluid control, getting a suitable size and type is the most important thing. The structure principle of butterfly valves particularly suits for manufacturing valves with large diameters. Butterfly valves are not only extensively applied in oil, gas, chemical and water treatment industries, but also in cooling water systems for heating and power plants.
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