A butterfly valve is a quarter-turn rotational motion valve that controls fluid flow by rotating a disc. Known for their simple structure, quick operation, low flow resistance, and lightweight design, butterfly valves are widely used in water treatment, petrochemical, power generation, marine, and HVAC applications.
1. Main Components of a Butterfly Valve
The key components of a butterfly valve include:
（1）Valve Body
- Typically made of cast or forged materials such as cast iron (HT200/250), ductile iron (QT450), carbon steel (WCB), stainless steel (CF8/CF8M), or duplex steel.
- Common connection types: Wafer Type, Flanged Type, and Lug Type.
（2）Disc
- Usually a circular plate made of stainless steel, duplex steel, or lined with rubber/PTFE.
- Classified into Centric (Concentric) and Eccentric (Single, Double, Triple Offset) designs based on sealing mechanism.
（3）Stem
- Constructed from high-strength alloy steel (e.g., 17-4PH) or stainless steel (304/316) for corrosion resistance and torque transmission.
- Connected to the disc via a key or pinless design for stability.
（4）Sealing System
- Soft Sealing (Elastomeric Seal): Uses EPDM, NBR, or PTFE, suitable for low-pressure and low-temperature applications (≤1.6MPa, ≤120°C).
- Metal Sealing (Hard Seal): Stainless steel with graphite/alloy overlay, ideal for high-pressure and high-temperature conditions (≤10MPa, ≤600°C).
（5）Actuation Methods
- Manual Operation (Lever, Gearbox)
- Pneumatic Actuator (Single/Double Acting)
- Electric Actuator (On-Off or Modulating)
- Hydraulic Actuation (High-pressure, high-torque applications)
2. Key Technical Specifications
| پارامتر | محدوده | Remarks |
| Nominal Diameter (DN) | DN50~DN3000 | Large-diameter valves are common in water treatment |
| Pressure Rating (PN) | PN6~PN100 (ANSI 150~600) | High-pressure triple-offset valves can reach PN100 |
| Temperature Range | -40°C ~ 600°C | Special treatment required for cryogenic applications |
| Compatible Media | Water, oil, gas, steam, corrosive liquids | PTFE-lined valves for acidic/alkaline fluids |
| کلاس نشتی | کلاس ANSI IV/V/VI | Metal seals can achieve Class VI |
3. Types of Butterfly Valves & Applications
（1）Centric Butterfly Valve
- Design: The disc and seat are concentric, relying on elastomeric compression for sealing.
- Applications:
- Water supply & wastewater treatment (DN100~DN2000)
- HVAC systems
- Food & pharmaceutical industries (Sanitary butterfly valves)
（2）Double Eccentric Butterfly Valve
- Design: The stem is offset from the disc center, reducing friction and extending service life.
- Applications:
- Oil & gas pipelines (PN16~PN40)
- Power plant cooling water systems
（3）Triple Eccentric Butterfly Valve
- Design: The disc, seat, and stem are all offset, enabling metal-to-metal sealing for high-pressure/temperature use.
- Applications:
- Refineries (high-temperature oils, ≤600°C)
- Chemical processing (PTFE-lined for corrosive media)
- Marine ballast water systems (seawater-resistant)
4. Advantages & Disadvantages
✔ مزایا
✅ Compact design, ideal for large-diameter pipelines
✅ Fast operation (90° rotation for full open/close)
✅ Low flow resistance, energy-efficient
✅ Easy maintenance, replaceable seals
✖ Disadvantages
❌ Limited flow control precision (not ideal for fine regulation)
❌ Potential cavitation under high-pressure drops (requires special design)
5. Selection Guide
- Water Supply/HVAC → Centric soft-seal butterfly valve (EPDM/NBR)
- Oil & Gas/Chemical → Double or triple-offset metal-seal butterfly valve
- Food/Pharmaceutical → Sanitary butterfly valve (316L+EPDM)
- Marine/Seawater → Super duplex steel valve (chloride-resistant)
نتیجهگیری
Butterfly valves are cost-effective and versatile, suitable for various industrial applications. For extreme conditions (high temperature, pressure, corrosion), triple-offset metal-seal or PTFE-lined butterfly valves are recommended for long-term reliability.
