All You Need to Know About Butterfly Valves
Butterfly Valve is used for opening, closing and regulation purposes. It has 2 ports for inlet and outlet and it is bi-directional. It generally works by rotating the built-in handle with a 90 degree turn. This feature helps to open/close the flow quickly. The flow of liquid or gas that passes through the butterfly valve can be regulated by adjusting the angle of the handle from the open to the close position. As it has super-fast opening and closing speed, water hammer effect can occur. Water hammer effect is a phenomenon that occurs when the valve closes quickly and the flowing water inside the pipe hits the closed valve abruptly. This results in extremely high pressures in pipes and causes the water to flow backwards. Pipes may burst and joint leaks can happen when the pressures in the pipe are too high.
Types of Butterfly Valves
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Rubber-lined: Suitable for lower temperature applications.
Plastic-lined: Suitable for corrosive chemicals and sanitary applications.
Metal: Suitable for high pressure-temperature and fire-resistant applications.
• Wafer type butterfly valve has two or more holes on the outer body of the valve to ease the installation.
• This type of valve is designed to prevent backflow in the system.
• Not suitable for pipe end or end-of-line service.
Semi Lug Type
• Semi lug type butterfly valve has bolt holes that match with the pipe flanges.
• Metal inserts are placed in the valve’s bolt holes.
• Suitable for pipe ends or end-of-line service.
• Lug Type has more bolt holes around its circumference than Semi Lug Type that match with pipe flanges.
• Metal inserts are put in the valve’s bolt holes.
• Suitable for pipe ends or end-of-line service
Double flanged Type
• This type of butterfly valve has flanges on both sides of the valve.
• This type of valve is connected to th piping flanges by bolts.
• Suitable for dead-end service in heavy—duty applications
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Fully Opened & Closed Butterfly Valve
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For butterfly valves that have a handle, when the built-in handle on top of butterfly valve is rotated, the butterfly disc of the valve turns slowly and becomes parallel to the flow of liquid or gas. This condition allows the flow of liquid or gas to pass through. To close the butterfly valve, the handle must be rotated in another direction, which causes the butterfly disc to slowly turn and become perpendicular to the flow of liquid or gas. In this condition, the flow of liquid or gas is blocked by the butterfly disc. By adjusting the degree of turning for the handle, the butterfly valve is able to control the flow of liquid or gas. Moreover, the butterfly disc will stay in the middle of the valve regardless of the open or close position. Therefore, cleaning or inspection through pigging is not allowed.
The different designs of the butterfly valves have different uses in different industries like food manufacturing, water, marine and oil and gas refineries. The following are some typical applications for butterfly valves:
● Water and steam applications
● Compressed air or gas applications
● Slurry applications
● Agricultural or wastewater treatment that has large amount of liquid applications.
-Butterfly valves can operate quickly.
-They have a low pressure drop.
-They can deal with slurries and high-volume water applications.
-Butterfly valves have poor sealing ability.
-Pipelines that have butterfly valves is cannot be cleaned using scrapers. (pigging)
-They have low maintenance requirements.