1. Distinctive Central Disc

The defining characteristic of a butterfly valve is the flat, circular disc positioned in the middle of the valve body. This disc rotates around a central shaft, controlling fluid flow by turning the disc to align with or block the flow path.

• Open Position: The disc is parallel to the flow, allowing fluid to pass through.
• Closed Position: The disc is perpendicular to the flow, creating a complete seal to stop fluid movement.

The disc's visibility inside the pipe, even in a partially open state, makes it easy to distinguish from other valve types like ball or gate valves.

2. Slim, Compact Design

Butterfly valves are known for their slim profile and lightweight structure compared to other industrial valves. This makes them easier to install in tight spaces and reduces the need for heavy support structures.

• Wafer-Style: Fits between two flanges, held in place by flange bolts.
• Lug-Style: Has threaded inserts allowing for independent bolting on each side, making maintenance easier.
• Flanged-Style: Comes with its own flanges and bolts directly to the pipe system.

3. Operated by a Lever, Gear, or Actuator

Butterfly valves are typically operated by

• Manual Lever Handles: Small to medium-sized valves often feature a lever that rotates 90 degrees (quarter-turn) for fast opening and closing. The position of the lever often indicates whether the valve is open or closed.
• Gear-Operated Handwheel: Larger butterfly valves require a gear-operated wheel to gradually turn the disc, providing better control over larger pipelines.
• Electric or Pneumatic Actuators: For automated systems, butterfly valves are equipped with actuators for remote operation and precise flow regulation.

4. Visible Lug or Wafer Body

The physical structure of a butterfly valve includes distinct lug or wafer patterns that fit between pipe flanges. This design minimizes the need for excessive material and keeps the valve lightweight.

• Lugged Butterfly Valve: Flange bolts pass through the lugs, allowing removal of downstream piping without affecting the upstream section.
• Wafer Butterfly Valve: Sandwiched between flanges and held by flange bolts without threaded inserts.

5. Variety of Materials and Sizes

Butterfly valves come in different materials depending on the application

• Body Materials: Cast iron, stainless steel, PVC, ductile iron.
• Disc Materials: Stainless steel, aluminum bronze, or rubber-coated metals for corrosive environments.
• Liner Materials (Seats): EPDM, NBR, PTFE (Teflon), and other rubber-like materials ensure a tight seal against the disc.

These valves can range from small diameters (2-12 inches) for basic water systems to huge industrial sizes (up to 100 inches or more) for pipelines in oil, gas, and water distribution networks.

6. Flow Control and Versatility

Butterfly valves are versatile and used for

• On/Off Service: Quickly shut off or allow full flow.
• Throttling/Flow Regulation: By adjusting the disc to various angles, butterfly valves can control the flow rate with precision.
• Bi-Directional Flow: They can regulate flow in either direction, enhancing their usability across multiple industries.

7.How to Differentiate from Other Valves

• Ball Valve: Features a solid ball with a hole through the center. Butterfly valves have a visible disc, while ball valves do not.
• Gate Valve: Uses a wedge-shaped gate that slides vertically. Butterfly valves operate with a rotating disc.
• Globe Valve: Has a linear motion disc or plug, designed for precise flow regulation. Butterfly valves use quarter-turn rotational motion.