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Types of Butterfly Valves (API 609)

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By using a butterfly valve, you can shut off or modulate the flow of a fluid (isolation and regulation). In low-pressure and non-critical applications, API 609 Centric butterfly valves (soft seated) are preferred to gate and ball valves because they are cheaper, lighter, and easier to install. In some applications, eccentric butterfly valves (double offset and triple offset valves) with metal seats are replacing globe and ball valves.


WHAT IS A BUTTERFLY VALVE?

In some applications, a butterfly valve can replace a globe or ball valve as a regulating and shut-off device.


Valve types can be classified based on several parameters:


• There are three types of designs: centric, double eccentric, and triple eccentric

• There are four types of end connections: wafer, lug (semi- or full), flanged, and double-flanged

• Material for the seat: soft (example: Teflon, Buna, rubber, etc) or metal-to-metal (SS304, SS316)

• Body and disc materials (cast iron to high nickel alloys)

• Manuel (lever, gear, worm gear) and actuated (electric, pneumatic, hydraulic, and gas-over-oil types)


 Butterfly valves are used for a wide range of applications, including water supply, wastewater treatment, fire protection, chemical and oil processing, fuel handling systems, and power generation.


As double and triple eccentric designs are introduced, butterfly valves are more and more used in oil and gas applications, where they are beginning to compete with more traditional Valve Suppliers in UAE, such as ball and globe valves.

BUTTERFLY VALVE WORKING PRINCIPLE


Its key component is the disc, a metal ring that is positioned at the centerline of the pipe and connected to an external actuator (manual level or actuator) via a rod.


In comparison to a ball valve, the disc of a butterfly valve is always in contact with the fluid conveyed by the pipeline, which causes a pressure drop.


When the disc is closed, it blocks the bore of the valve, and when it is open, it allows fluid to flow through.


To switch the valve from a fully open to a fully closed position, a quarter turn movement is required (and such a movement can be completed as quickly as a ball valve).


BUTTERFLY VALVE SPECIFICATION


API 609, ASME B16.34 (pressure and temperature rating), API 598 (testing), ASME B16.5 and ASME B16.47 (flanged ends), and ASME B16.25 specify the dimensions and tolerances of butterfly valves for the petrochemical industry and piping applications.


BUTTERFLY VALVE DESIGN

The first classification is between concentric and eccentric butterfly valves:


• Concentric butterfly valve: the stem is centered in the middle of the disc, and the disc is centered in the bore

• Eccentric butterfly valves (double offset and triple offset): have one or more stub shafts (stems) that are offset from the center of the valve. Double and triple offset butterfly valves are also known as eccentric butterfly valves.


CONCENTRIC BUTTERFLY VALVE (CENTRIC)


The concentric butterfly valve is used in water and wastewater treatment plants, fire protection systems, and gas supply systems.


• Water treatment

• Water distribution

• Pumping installations

• Water transmission

• HVAC

• Aeration systems

• Clean wastewater

• Filter Installations

• Pumping installations

•  Membrane installations

• Fire Protection (indoor/outdoor)

• Natural gas and flare gas


DOUBLE ECCENTRIC BUTTERFLY VALVE


Despite the fact that they are lighter, cheaper, and require less excavation, double eccentric butterfly valves find use in underground water supply systems and compete with gate valves (especially in the larger bore sizes).


TRIPLE ECCENTRIC BUTTERFLY VALVE


With remarkable corrosion and high temperature/pressure resistance, butterfly valve supplier in Qatar. Complete with ball valves in mission-critical applications using high-grade materials such as stainless steel and duplex or super duplex steel. Triple offset butterfly valves are the most sophisticated type and are gaining market share.

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