A butterfly valve is a type of flow control device, typically used to regulate a fluid flowing through a section of pipe. The valve is similar in operation to a ball valve. A plate or disc is positioned in the center of the pipe. The disc has a rod passing through it that is connected to an actuator on the outside of the valve. Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow; therefore a pressure drop is always induced in the flow, regardless of valve position.
