The control lever must only be rotated 90° in order to close off the pipe because butterfly valves are quarter turn valves.
Flanged butterfly valves may be made of stainless steel, cast iron, plastic or other materials, although metal is the most common. The diameter of flanged valves ranges from a few inches to a few feet because they are used for a variety of applications. Butterfly valves are able to completely shutoff a pipe quickly and easily while withstanding high volumes, pressures and temperatures. There are different kinds of butterfly valves that are designed specially to work with different materials and in specific applications.
Flanged butterfly valves can be classified as rotary, pneumatic and hydraulic valves and are used in water distribution, chemical services, ventilation applications and other situations involving a liquid or gas. They are particularly beneficial in settings that require pipe shutdowns quickly and efficiently, in case of an emergency.
Flanged butterfly valves rely on a round vane or disc for operation. The disc is centrally mounted on a shaft or stem, which acts as the axis for the rotating disc. When the valve is open the gas, liquid or slurry flows through the pipes and through the valve. The disc lays parallel to the pipe and the direction of the current. When the lever or crank wheel is engaged, the disc is rotated and stands upright, securely plugging the pipe.
Unlike other valves, butterfly valves do not trap volumes of liquids or gases between valve components because there is only one part that creates the seal. Flanged butterfly valves have at least one flange that allows it to be added in between pipes in a line or system. The flanges are part of the enclosure that contains the valve so flanged butterfly valves are actually short pipes in and of themselves. Lug and wafer butterfly valves are two other methods of integrating the valve.
Lug valves are installed using a set of bolts that screw into the flanges on pipes. This setup allows one side of the pipe line to be disconnected without affecting the other side. Wafer valves are narrow valves that are designed to seal against bidirectional pressure to prevent backflow.