A flanged butterfly valve is usually cylindrical in shape and is typically installed in a pipe system or as an inlet or outlet to some type of closed system and used to regulate the flow of some material, either liquid or granular, that acts as a fluid with respect to flow. A flange, when the word is used to refer to a valve, is a collar that is used as an anchor point for installation. The flange is typically pre-drilled with holes for bolts to connect the valve to other pipe sections, but some may be designed to connect to the system differently such as with clamps or latches.
A butterfly valve is a cylindrical housing, which can resemble a tube or a disk. A metal rod passes across the cylinder, when viewed from the end, following the diameter line of the circles formed by the ends of the cylinder. A circular, metal disk that fits very precisely within the cylinder is mounted on the rod, and the rod and disk assembly pivot. The disk of metal that forms the valve vaguely resembles a butterfly, with the metal rod representing the body and each half of the metal disk representing the wings, and is the source of the name of this type of valve.
The position of the metal disk in the flanged butterfly valve determines whether the valve is closed or open. When the valve is closed, the disk is rotated to lie in a plane perpendicular to the flow through the valve, which blocks the cylinder, stopping the flow. When opened, the disk lies in a plane parallel to the flow through the valve, allowing liquid or other material to flow. The valve can be manually operated by a lever mechanism or mechanically controlled by actuators or hydraulics.
A flanged butterfly valve has a flange, or collar of material, that extends outward from the body of the valve but is not part of the valve mechanism itself. A butterfly valve, depending on the application, may have one or two flanges, located at one or both ends of the valve. The flange on a flanged butterfly valve serves as an anchor point for the installation of the valve and can be designed in a number of ways to accept various connection hardware, such as bolts, latches, screws or clamps.