Butterfly got its name from the “butterfly shape” that occurs when the valve rotates. When the valve is closed, it switches to a position that entirely stops the flow of fluid. When the valve is fully open, the valve rotates a quarter of a circle to open the fluid flow path with almost no obstruction. The valve body may be opened gradually to adjust the flow rate. Unlike ball valves, this throttle valve is in that the valve body is always in the flow channel. This causes pressure loss in the flow regardless of the valve’s open position.

This type of valve is widely used in the chemical industry, sewerage and water supply systems. The valve body is designed so that the fluid does not come into contact with the moving metal parts of the valve. Valve seats can be made from many materials to handle all kinds of fluids. These valves are durable and require very little maintenance. Butterfly is usually medium to very large size (DN 40–600).