1. Basic DefinitionA butterfly valve is a quarter-turn rotational motion valve that uses a disc-shaped closure element to regulate or isolate fluid flow. The disc rotates 90 degrees within the pipe bore to open or close the flow path, resembling the wings of a butterfly - hence its name.
2. Key Components
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Disc: The primary flow control element, typically circular in shape
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Stem: Connects the actuator to the disc for rotational movement
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Seat: Provides sealing between the disc and valve body
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Body: Main pressure-containing structure that fits between pipe flanges
3. Working PrincipleIn operation:
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Open position: Disc aligns parallel to flow direction (minimal pressure drop)
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Closed position: Disc rotates perpendicular to block flow completely
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Intermediate positions: Allow flow regulation (in some designs)
4. Main Types
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Concentric: Most common, with stem centered in disc
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Double-eccentric: Offset stem reduces operating torque
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Triple-eccentric: Advanced design for high-pressure applications
5. Material OptionsCommon materials include:
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Body: Cast iron, ductile iron, carbon steel, stainless steel
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Disc: Stainless steel, aluminum bronze, nickel alloys
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Seat: EPDM, Viton, PTFE, metal-to-metal
6. Advantages
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Compact, lightweight design
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Quick operation (90° rotation only)
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Lower cost compared to other valve types
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Minimal maintenance requirements
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Suitable for large diameter pipes
7. Common Applications
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Water and wastewater treatment
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Chemical processing
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Power generation
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HVAC systems
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Oil and gas pipelines
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Food and beverage industry
8. Selection ConsiderationsWhen choosing a butterfly valve:
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Pressure and temperature requirements
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Flow characteristics needed
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Media compatibility
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Actuation method (manual, electric, pneumatic)
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Industry standards compliance (API, ANSI, ISO)