Butterfly valves are versatile, cost-effective, and widely used in fluid control systems—from municipal water plants to HVAC systems and oil refineries. Their simple design (a rotating disc inside a pipe) makes them lightweight and easy to install, but not all butterfly valves are created equal. The right type depends on pressure, temperature, fluid type, and pipe size—whether you’re working with a compact 1 inch butterfly valve or a large-diameter 12 inch model.
In this guide, we’ll break down the most common types of butterfly valves, their unique features, and practical applications. We’ll also highlight key considerations like size, material, and compliance, with a nod to brands like Eagle that excel in durability across diverse industries.
1. Concentric Butterfly Valves (Zero Offset)
What They Are: The most basic and affordable butterfly valve design. The disc center aligns perfectly with the valve shaft (hence “concentric”), creating a simple on/off flow control mechanism.
Key Features:
- Lightweight and compact, ideal for low-pressure systems.
- Elastic seat (usually EPDM or NBR rubber) for tight shutoff at low pressures.
- Limited to temperatures below 200°F (93°C) due to rubber seat constraints.
Common Sizes: 1 inch butterfly valve, 2 inch butterfly valve, up to 24 inches.
Best For: Residential plumbing, HVAC systems, and low-pressure water treatment. Example: A 2 inch concentric butterfly valve might regulate flow in a commercial building’s heating loop.
Limitations: Not suitable for high pressure (over 150 PSI) or abrasive fluids—rubber seats wear quickly under stress.
2. Eccentric Butterfly Valves (Single Offset)
What They Are: A step up from concentric valves, with the disc shaft offset slightly from the centerline. This reduces friction between the disc and seat, extending lifespan.
Key Features:
- Metal or reinforced elastomer seats for higher pressure tolerance (up to 300 PSI).
- Better throttling capabilities than concentric valves (ideal for partial flow control).
- Handles temperatures up to 400°F (204°C) with PTFE seats.
Common Sizes: 3 inch butterfly valve, 4 inch butterfly valve, up to 36 inches.
Best For: Industrial process lines, wastewater treatment, and medium-pressure HVAC. Eagle’s 4 inch single offset butterfly valve, for instance, is popular in food processing plants for its easy maintenance and tight seal.
Pro Tip: Look for models with a “lug-style” design for easy installation between flanges.
3. Double Offset Butterfly Valves
What They Are: Engineered for high-performance applications, with two offsets: one for the shaft (like single offset) and a second for the disc’s sealing surface. This minimizes contact between the disc and seat until fully closed, reducing wear.
Key Features:
- Metal-to-metal seating for fire safety and high temperatures (up to 1000°F / 538°C).
- ANSI Class 600 pressure rating (suitable for oil, gas, and steam).
- Bubble-tight shutoff, meeting API 607 fire-test standards.
Common Sizes: 6 inch butterfly valve, 8 inch butterfly valve, up to 48 inches.
Best For: Oil refineries, chemical plants, and power generation. A 6 inch double offset valve might control heavy crude flow in a pipeline, where reliability is critical.
Why Eagle Stands Out: Eagle’s double offset valves feature precision-machined discs and Inconel seats, making them a top choice for offshore drilling rigs.
4. Triple Offset Butterfly Valves
What They Are: The most advanced butterfly valve design, with three offsets: shaft, disc, and a conical seat geometry. This creates a “cam action” that ensures the disc only contacts the seat at full closure—eliminating friction entirely.
Key Features:
- Zero leakage (meets ISO 5208 Class VI standards).
- Handles extreme pressures (up to ANSI Class 900) and temperatures (1500°F / 816°C).
- Ideal for toxic, corrosive, or high-purity fluids.
Common Sizes: 10 inch butterfly valve, 12 inch butterfly valve, up to 60 inches.
Best For: Petrochemical pipelines, LNG facilities, and pharmaceutical manufacturing. A 12 inch triple offset valve could isolate a section of a natural gas pipeline during maintenance.
5. Wafer vs. Lug vs. Flanged Butterfly Valves (By End Connection)
Beyond design offsets, butterfly valves are categorized by how they connect to pipes:
- Wafer Butterfly Valves: Slim, lightweight, and clamped between two flanges. Best for low-to-medium pressure (up to 200 PSI). Common in 1 inch to 10 inch sizes for HVAC and water systems.
- Lug Butterfly Valves: Have threaded lugs (bolt holes) for direct flange mounting. Can be installed in dead-end service (one end closed) and are popular in 2 inch to 24 inch sizes for industrial applications.
- Flanged Butterfly Valves: Integral flanges for bolting to pipe flanges. Ideal for high-pressure systems (300+ PSI) and large diameters (12 inch+).
How to Choose the Right Type: 4 Key Questions
- What’s the pressure rating? Low-pressure (concentric), medium (single offset), high (double/triple offset).
- Fluid type? Corrosive fluids need stainless steel or Hastelloy construction; abrasive slurries may require metal seats.
- Temperature range? Rubber seats (up to 200°F) vs. PTFE (400°F) vs. metal (1000°F+).
- Pipe size? 1 inch butterfly valve for residential lines, 12 inch+ for industrial pipelines.
Final Thoughts: Match the Valve to the Job
Butterfly valves are a workhorse, but choosing the right type is critical. For simple on/off in low-pressure systems, a 2 inch concentric valve works. For high-pressure oil lines, a triple offset valve is non-negotiable. Brands like Eagle simplify this by offering a full range—from budget-friendly concentric models to rugged triple offset valves—all engineered for reliability.