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How Does a Butterfly Valve Work?

How Does a Butterfly Valve Work?

China A217 WC6 Butterfly Valve

150LB A217 WC6 Butterfly Valve, 48 Inch A217 WC6 Butterfly Valve, China A217 WC6 Butterfly Valve, Lug Type A217 WC6 Butterfly Valve, Worm Gear A217 WC6 Butterfly Valve Manufacture

A butterfly valve is a quarter-turn rotary valve used to start, stop, or regulate fluid flow in pipelines. It consists of a rotating disc mounted on a central shaft, which controls flow by turning perpendicular (closed) or parallel (open) to the flow direction.

1. Key Components

Part Function
Body Houses the disc and connects to the pipeline (wafer, lug, or flanged).
Disc Rotates 90° to open/close flow (also called the “butterfly”).
Stem Transmits torque from the actuator to the disc.
Seat Provides a tight seal (rubber, PTFE, or metal).
Actuator Manual (lever, gear) or automated (pneumatic, electric, hydraulic).

2. Working Principle

A. Open Position (0°)

  • The disc is parallel to the flow, allowing full fluid passage.

  • Minimal pressure drop (ideal for low-resistance systems).

B. Partially Open (0°–90°)

  • The disc is angled, regulating flow rate (used for throttling).

  • Higher turbulence than gate/ball valves (not ideal for precise control).

C. Closed Position (90°)

  • The disc is perpendicular to the flow, blocking it completely.

  • The seat compresses against the disc for a bubble-tight seal (if elastomeric).

3. Types of Butterfly Valves

Type Design Best For
Wafer Lightweight, clamped between flanges Low-pressure water/air
Lug Threaded inserts for bolt-on installation Dead-end service, easy maintenance
Flanged Integral flanges for direct piping connection High-pressure systems
Double Offset Eccentric stem reduces seat wear HVAC, moderate pressures
Triple Offset Metal seat, zero leakage Oil & gas, high-P/temp

4. Advantages & Disadvantages

✔ Advantages

  • Compact & lightweight vs. gate/ball valves.

  • Fast operation (90° turn).

  • Lower cost for large diameters.

  • Good flow regulation (if designed for throttling).

✖ Disadvantages

  • Higher pressure drop than gate/globe valves.

  • Not ideal for slurries (disc can erode).

  • Limited high-P/temp (unless triple-offset design).

5. Common Applications

  • Water Treatment: Pump control, filtration.

  • HVAC: Chilled water, air handling.

  • Oil & Gas: Tank vents, low-P pipelines.

  • Chemical Processing: Corrosive fluids (with lined seats).

  • Marine/Shipbuilding: Seawater ballast systems.

6. Butterfly Valve vs. Other Valves

Valve Type Best For Butterfly Valve Comparison
Gate Valve On/off, high-pressure Heavier, slower, no throttling
Ball Valve Tight shutoff, high-P More expensive, better sealing
Globe Valve Precise throttling Higher pressure drop

Conclusion

A butterfly valve is a versatile, cost-effective choice for quick shutoff or moderate throttling in large pipes. For high-pressure/temperature or zero-leakage needs, consider triple-offset metal-seated designs.

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