What Is a Butterfly Valve & How Does It Work?
1. What Is a Butterfly Valve?
A butterfly valve is a quarter-turn (90°) rotary valve used to start, stop, or regulate flow. A metal disc rotates from fully open (parallel to flow) to fully closed (perpendicular to flow). When open, the disc remains in the flow path, creating minimal pressure drop.
Key advantages: lightweight, compact, low cost, fast operation, excellent for large diameters (2" to 80"+).
2. Main Components
| Component | Function |
|---|---|
| Body | Housing, connects to pipe |
| Disc | Rotates to open/close flow |
| Stem | Transmits torque to disc |
| Seat (Liner) | Seals against disc – bubble-tight |
| Actuator pad | ISO 5211 for lever/gear/auto |
3. How It Works – Simple Steps
| Position | Disc Angle | Function |
|---|---|---|
| Open | 0° (parallel to flow) | Maximum flow, low pressure drop |
| Throttling | 30°–70° | Flow regulation |
| Closed | 90° (perpendicular) | Bubble-tight shut-off |
Sealing is pressure-assisted: line pressure pushes the disc into the seat.
4. Three Common Types of Butterfly Valves
| Type | Design | Pressure | Temp | Best For |
|---|---|---|---|---|
| Concentric (Rubber-lined) | Stem center, rubber seat | ≤250 PSI (PN16) | ≤120°C | Water, HVAC, air |
| Double Offset (HP) | Two offsets, cam action | ≤740 PSI (Class 300) | ≤400°C | Chemical, steam, oil/gas |
| Triple Offset (Metal-seated) | Three offsets, metal-to-metal | ≤1500 PSI (Class 600) | ≤800°C | High temp, cryogenic, fire-safe |
5. Butterfly Valve vs Ball Valve vs Gate Valve (6" Size)
| Parameter | Butterfly | Ball Valve | Gate Valve |
|---|---|---|---|
| Weight | ~8 kg | ~25 kg | ~35 kg |
| Length | Short (wafer) | Long | Long |
| Cost (large dia) | Low | High | Medium |
| Throttling | Excellent | Fair | Poor |
| Pressure drop | Low | Very low | Very low |
| Best size range | 2"–80" | ¼"–24" | 2"–48" |
6. End Connections – Quick Reference
| Connection | Standard | Key Feature |
|---|---|---|
| Wafer | ASME B16.34 | Sandwiched between flanges – lowest cost |
| Lug | ASME B16.34 | Dead-end service, removable downstream pipe |
| Flanged | ASME B16.5 / EN 1092-1 | High pressure, easy disassembly |
| Clamp (Tri-Clamp) | ISO 2852 / 3A | Sanitary, quick-open |
7. Seat Material Selection (Concentric Valves)
| Material | Temp Range | Best For |
|---|---|---|
| EPDM | -40°C to +120°C | Water, air, dilute acids |
| NBR | -20°C to +90°C | Oil, fuel, grease |
| Viton (FKM) | -15°C to +200°C | Chemicals, solvents |
| PTFE | -40°C to +230°C | Corrosive media |
| Silicone | -60°C to +200°C | Food, pharma |
8. KINKO Butterfly Valve Series – At a Glance
| Series | Type | Size | Max Pressure | Applications |
|---|---|---|---|---|
| KBF-LT | Concentric (rubber-lined) | 2"–24" | 250 PSI | Water, HVAC, wastewater |
| KBF-HP | Double offset | 2"–36" | 740 PSI | Chemical, steam, oil/gas |
| KBF-TO | Triple offset (metal) | 3"–48" | 1500 PSI | High temp, cryogenic, fire-safe |
| KBF-SAN | Sanitary (clamp) | 1"–12" | 150 PSI | Food, dairy, pharma |
9. Advantages & Limitations
| Advantages | Limitations |
|---|---|
| Lightweight (80% less than gate valve) | Disc stays in flow path |
| Low cost per inch (large diameters) | Lower pressure rating (rubber-lined) |
| Fast operation (1–3 seconds) | Seat erosion in abrasive throttling |
| Good throttling capability | Limited temp with soft seats |
| In-line seat replacement (wafer/lug) | — |
10. Procurement Checklist – 5 Questions
-
Size? (Butterfly excels at ≥6")
-
Pressure/Temp? (≤250 PSI → rubber-lined; higher → double/triple offset)
-
Media? (Water, chemical, slurry, food, steam)
-
Dead-end service? (Yes → lug type)
-
Actuation? (Lever, gear, pneumatic, electric)
11. KINKO Quality – What You Get
-
100% hydrotest + low-pressure air test (zero bubble leakage)
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PMI material verification on all stainless steel
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EN 10204 3.1 certificates + signed test reports
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ISO 5211 direct mount for all actuators
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Optional: FDA, 3A, ATEX, fire-safe (API 607), NACE
12. Conclusion
The butterfly valve is the most economical and space-efficient choice for large-diameter, low-to-medium pressure applications. KINKO offers a full range from rubber-lined concentric to triple offset metal-seated valves – all with full traceability and test documentation.
Send your specs (size, pressure, media, end connection) for a quick quote.
Ivan (Mobile:+86-18968769287)
WhatsApp：+86-13579991606
Wechat:+86-18968769287
Website：www.kinko-flow.com
ZHEJIANG KINKO FLUID EQUIPMENT CO.,LTD
