Butterfly valve is a type of quarter-turn valve used to regulate or shut off the flow of liquids or gases in a pipeline. The valve consists of a circular disc or plate with a pivot in the center, which is connected to an actuator (such as a lever or gear) outside the valve body. When the actuator is rotated 90 degrees, the disc turns to open or close the valve. Butterfly valves are commonly made from materials such as cast iron, steel, or PVC, and are available in a variety of sizes and pressure ratings to suit different applications. They offer several advantages over other types of valves, including quick and easy operation, low pressure drop, and minimal leakage.