Butterfly valves are versatile, cost-effective flow-control devices widely used in industries like chemical processing, water treatment, oil and gas, and HVAC. Their simple design, quick operation, and compact size make them ideal for large-diameter pipelines and systems requiring efficient shutoff or throttling. Below is a comprehensive guide to butterfly valves, covering their types, design, applications, advantages, and key selection criteria.

1. What is a Butterfly Valve?

• Design: A circular disc (the “butterfly”) rotates 90° around a central shaft to control flow.

  • Open position: Disc aligns parallel to flow, allowing maximum throughput.

  • Closed position: Disc rotates perpendicular to block flow.

• Key Components:

  • Body (cast iron, stainless steel, PVC, etc.).

  • Disc (often metal or resilient-coated).

  • Seat (elastomeric or metal for sealing).

  • Shaft (connects disc to actuator).

  • Actuator (manual lever, gearbox, electric, pneumatic, or hydraulic).

2. Types of Butterfly Valves

A. By Seat Material

1. Resilient-Seated Butterfly Valves:

   • Seat: Soft elastomers (EPDM, Nitrile, Viton®) for tight shutoff in low-pressure/temperature applications.

   • Use: Water, air, mild chemicals.

2. High-Performance (HP) Butterfly Valves:

   • Seat: Metal (stainless steel, Inconel) or PTFE-lined for high-pressure/temperature or abrasive fluids.

   • Use: Oil and gas, steam, corrosive chemicals.

3. Triple-Offset Butterfly Valves:

   • Design: Metal seat with conical geometry for zero leakage in critical applications (e.g., cryogenics, refineries).

   • Use: High-pressure/temperature, fire-safe systems.

B. By Connection Type

• Wafer-Style: Clamped between flanges (lightweight, cost-effective).

• Lug-Style: Threaded inserts for bolt connections (allows valve removal without disassembling pipelines).

• Flanged: Integral flanges for direct bolting.

• Double Flanged: For high-pressure systems.

C. By Actuation

• Manual: Hand lever or gear-operated.

• Electric: Motorized actuators for automation.

• Pneumatic/Hydraulic: For rapid response in hazardous areas.

3. Key Applications in the Chemical Industry

• Flow Regulation: Adjusting chemical dosing rates.

• Isolation: Shutting off pipelines during maintenance.

• Slurry Handling: Resilient-seated valves for abrasive mixtures.

• Corrosive Fluids: Valves with PTFE or Hastelloy components.

• High-Purity Processes: Sanitary butterfly valves for pharmaceuticals.

4. Advantages of Butterfly Valves

• Compact & Lightweight: Easier to install than gate/ball valves.

• Quick Operation: 90° rotation enables fast shutoff.

• Cost-Effective: Lower material and maintenance costs.

• Low Pressure Drop: Minimal flow restriction when fully open.

• Versatility: Suitable for liquids, gases, and slurries.

Conclusion
Butterfly valves are indispensable in the chemical industry for balancing performance, cost, and reliability. Selecting the right type—resilient-seated, high-performance, or triple-offset—depends on fluid characteristics, pressure/temperature conditions, and compliance needs. Always prioritize material compatibility and certifications (e.g., API, ATEX) to ensure safety and longevity.