1. Structure of butterfly valve
Butterfly valve is mainly composed of valve body, living body, valve shaft, bearing, sealing device, operating mechanism and ancillary components. The valve body is usually cylindrical, and the living body (valve flap) rotates around the shaft inside the valve seat. The valve flap can be disc-shaped, rotating around an axis, so as to control the passage or blocking of the fluid.
2. Principle of operation
The working principle of a butterfly valve is based on the rotation of the valve stem and the simultaneous rotation of the disk. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, when the butterfly plate reaches 90 °, the valve will be completely open (the maximum allowable fluid flow), and at the same time, the angle of the disc plate can be changed to regulate the flow of media. When the butterfly plate is perpendicular to the centerline of the pipeline, the valve is in the closed position.
3. Operation mode
- Open: When the valve is open, the flapper is located in the path of the fluid and guides it through the valve body, so there is minimal resistance to fluid flow and low pressure drop.
- Closed: When the valve is closed, the flapper seals against the seat and prevents the flow of fluid, thus preventing it from passing through the valve.
4. Classification
- Concentric butterfly valve: stem axis, butterfly plate center, body center in the same position, simple structure, easy to manufacture, but there are problems of extrusion and wear.
- Single eccentric butterfly valve: stem axis away from the center of the butterfly plate, reducing the excessive extrusion of the butterfly plate and the valve seat, but there is still scratching.
- Double Eccentric Butterfly Valve: further improved, eliminating unnecessary excessive extrusion and scraping, improving seat life and sealing performance.
- Triple Eccentric Butterfly Valve: Specially designed to withstand high temperature and pressure environments, using a combination of hard and soft seals, but with high leakage.
5. Advantages
- Good fluid control performance: when the butterfly valve is fully open, the thickness of the butterfly plate is the only resistance to the flow of the medium through the valve body, so the pressure drop through the valve is very small.
- Wide application in the field of large-diameter regulation: when the butterfly valve is opened between about 15°~70°, it can carry out sensitive flow control, which is suitable for the field of large-diameter regulation.
- Lightweight structure and compact body: Butterfly valves use a thin metal disk as the flow control mechanism, which takes up little space but is strong enough to regulate the flow of fluid.
- Fast and efficient sealing: Butterfly valves provide fast sealing on actuation, making them suitable for high-precision flow applications.
- Low pressure drop and high pressure recovery: butterfly valves are designed to allow the fluid to recover energy quickly after leaving the valve, making them suitable for high pressure recovery environments.
