Why it is called butterfly valve?

A butterfly valve is called so because of the shape of its disc or plate, which resembles the wings of a butterfly. The disc or plate is mounted on a shaft, and when the valve is open, the disc rotates around its axis to allow fluid or gas to flow through the valve.

The disc of a butterfly valve can be made of various materials, such as metal or plastic, and can be coated or lined with materials such as rubber or Teflon to improve the valve's performance and durability. The disc is usually mounted between two flanges, and the valve can be actuated manually or through an automated system.

Butterfly valves are commonly used in a wide range of industrial applications, such as water treatment, HVAC, and chemical processing, due to their simple design, lightweight, and low cost compared to other types of valves.