Butterfly Valves is a valve, which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. These valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight, meaning less support is required. 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.
Lug Type Butterfly Valves have head loss characteristics of a full bore valve. The main variations for Lug Type Butterfly Valve are the methods of sealing the perimeter of the disc in its closed position. The simplest variation is to use an elastomeric lined bore which is an interference fit on the disc. The valve has been developing such that for many duties it now provides optimum solution for a leak tight on-off valve supplanting the gate valve. The butterfly valve can be manufactured as a small valve of 40mm bore and can be made for extremely large sizes up-to 1000mm bore.