BUTTERFLY VALVE AND IT'S WORKING PRINCIPLE

WHAT IS BUTTERFLY VALVE?

Butterfly valves are a family of quarter-turn rotational motion valves that are used in pipelines to shut-off flow. It is often said that butterfly valves can be used to regulate the flow. However, we do not recommend doing this, as it can damage the valve disk and have a negative effect on the sealing properties. They are used in a wide variety of process media and industries especially in water supply, collection, and distribution, as well as pumping stations, and have a broad range of use cases especially in flow isolation. A couple of their key advantages over other valve families are their simple construction and compactness, resulting in the end products being of lighter weights and lower cost and with smaller installation footprints and faster actuation speeds.

WORKING PRINCIPLE OF BUTTERFLY VALVE:

The construction of a butterfly valve is relatively simple, with the rotation of the valve disc controlling the fluid flow. In the closed position, the disc blocks the valve bore while in the open position, the disc is oriented perpendicular to the flow direction to allow flow. Butterfly valves generally provide bi-directional flow and shutoff capability. However, they are not full-bore, which renders them unsuitable for pigging or swabbing. The body material is ductile iron with an epoxy powder coat on both internal and external surfaces. The valves are typically operated by handwheels, gears, or actuators, or a combination thereof, according to the specific application requirement and technical specifications. We will be discussing the actuation methods later in the article.

Butterfly valve actuation:

There are multiple ways to operate, or actuate, a butterfly valve - manual, semi-manual, or fully automatic.

Electric: Uses an electric actuator for controlling the valve with a 4-20mA control signal and are typically used for high precision regulation and time-sensitive application.
Pneumatic: Also used for high precision application and uses compressed air for actuation.
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Hydraulic: Typically used for applications requiring large torques for opening and closing the valve, such as high pressure and high viscosity applications.
Manual: Manually operated butter valves make use of a handwheel, crank, or lever to operate the valve. Smaller manual valves are typically fitted with a lever. For larger sizes, hand wheels are provided and are accompanied by a gearbox to transfer the torque with a high mechanical advantage. Another way of manual actuation is in use cases where the valve is buried underground without a manhole; in such applications, actuation is done with an extension spindle, adapter / square cap, and a corresponding T-key from the ground level.

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