Below is a list of Flanged Butterfly Valves manufacturers from Allentown, Pennsylvania. Flanged butterfly valves are mechanisms that control the flow rate of a fluid as it moves through a piping system. The outside edges of the valve are raised and have holes so that the valve may be bolted onto a pipe. Butterfly valves consist of a seal around the wall of a pipe, a round or elliptical disc and a control lever. The control lever must only be rotated 90° in order to close off the pipe because butterfly valves are quarter turn valves.