A butterfly valve is from a family of valves called quarter-turn valves. The butterfly is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway.
When the valve is closed, the disc is turned so that it completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the process fluid. The valve may also be opened incrementally to regulate flow. Unlike a ball valve, the plate is always present within the flow, therefore a pressure drop is always induced in the flow regardless of valve positionThe butterfly valve derives its name from the way a “butterfly-shape image” appears to form as it turns.
The butterfly valve is widely used in the chemical industry, wastewater systems and water supplies.
The valve is designed so that the flowing medium does not have to come in contact with the valve’s moving metal parts. The valve seat can be made from many different kinds of material to cater for every kind of medium.
A butterfly valve is very robust and requires very little maintenance.
Butterfly valves are usually available in medium large to very large sizes (DN 40–600).