Below is a list of Pneumatic Butterfly Valve manufacturers from St. Clair, Missouri. A pneumatic butterfly valve is a mechanism that controls the flow of gas by using a rotating disc within a pipe. Butterfly valves use a disc held in the valve to provide a tight seal that prevents any liquid or gas from seeping past it. The disc is controlled by a lever or hand wheel; in many cases, only a quarter turn is required to completely shutoff the line. Electric actuators are also available.