A butterfly valve is a type of valve used to regulate or control the flow of liquids, gases, or slurries in a pipeline. It consists of a disc or plate that pivots around a central axis to open or close the valve, resembling the shape of a butterfly's wings when fully open. The valve is widely used due to its simple design, compact size, and fast operation.

Key Features:

Design:
The valve has a rotating disc that moves within the pipe to regulate the flow. When the valve is fully open, the disc is parallel to the flow, allowing for maximum flow. When closed, the disc is perpendicular to the flow, blocking it.

Operation:
It is typically operated by a lever, pneumatic actuator, or electric motor. The disc rotates a quarter turn (90°) to open or close the valve.

Applications:
Butterfly valves are commonly used in a variety of industries, including water treatment, HVAC systems, oil and gas, chemical processing, and food and beverage production.
They are ideal for large volume flow control with quick operation.

Advantages:
Compact Size: They are generally smaller and lighter than other types of valves, such as ball or gate valves.
Quick Operation: The quarter-turn operation makes them faster to open and close than some other valve types.
Flow Regulation: They provide effective control over flow, particularly for throttling applications.

Types of Butterfly Valves:
Concentric Butterfly Valve:
The most common type, where the disc is centered on the valve body, and sealing is achieved by a rubber or elastomer seat.
Double Eccentric (or High Performance) Butterfly Valve:
Features an offset disc that moves away from the seat, providing a tighter seal and better performance in higher-pressure applications.

Triple Eccentric Butterfly Valve:
An advanced version with three offsets, providing even more efficient sealing, particularly for high-pressure or high-temperature applications.

Lug or Wafer Style:
Wafer valves are installed between two flanges, while lug valves can be bolted directly to the pipeline without the need for flanges on either side.

Applications:
Water and wastewater treatment: Butterfly valves are widely used in water distribution systems and sewage treatment plants for controlling the flow of water and wastewater.

HVAC systems: Used for air handling and regulating air flow.
Chemical industries: Regulating the flow of chemicals and gases in processing plants.
Food and beverage industries: For controlling the flow of fluids in food processing pipelines.