Butterfly valve

Butterfly valve is a type of valve used for regulating or isolating the flow of a liquid. The mechanism of a butterfly valve is similar to that of a ball valve, which allows for a quick shut off. Butterfly valves are generally favored because they are lower in cost and lighter in weight than other types of valves.

Design and Operation

The butterfly valve derives its name from the disc that is centrally located in the flow path of the valve. This disc, which is the main operating element of the valve, is similar in appearance to a butterfly's wings, hence the name. The disc is attached to a rod, which is connected to an actuator on the outside of the valve. When the actuator is turned, the disc turns as well, either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, therefore a pressure drop is always induced in the flow, regardless of valve position.

Types of Butterfly Valves

There are different types of butterfly valves, each adapted for different pressures and different usage. The most common types are:

• Concentric butterfly valves - This is the simplest and most common type of butterfly valve, in which the disc is centered in the middle of the pipe. The disc's diameter is equal to the pipe's diameter.

• Double-eccentric butterfly valves (also known as high-performance butterfly valves) - In these valves, the disc is not centered in the pipe, which allows it to seal against the seat without friction.

• Triple-eccentric butterfly valves (also known as triple offset valves) - These valves have a metal seat, which allows them to be used in high temperature applications.

Applications

Butterfly valves are used in a wide variety of applications, due to their robustness and simplicity. They are commonly used in water supply, wastewater treatment, fire protection and gas supply. In the industrial sector, they are used in oil, gas, and power generation plants. They are also used in process applications such as chemical and food processing.

See Also

• Valve
• Ball valve
• Gate valve
• Globe valve

References

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