Offset Flange Butterfly Valve

China Offset Butterfly Valve Manufacturers, Suppliers and Factory with Low Price
An Offset Butterfly Valve means that the stem does not pass through the centerline of the disc, but instead behind it (opposite of flow direction) . When the stem is located right behind the centerline of the disc, the valve is called single-offset. This design was developed to reduce the disc contact with the seal before full closure of the valve with the aim of improving service life of the valve. Today, single-offset valves have given way to double offset and triple Offset Butterfly Valves.

In a double-offset or doubly eccentric butterfly valve, the stem is located behind the disc with an additional offset to one side. This double eccentricity of the stem enables the rotating disc to rub over the seat for only about one to three degrees.

A triple Offset Butterfly Valve (TOV or TOBV) is often used in critical applications and is designed similar to a double Offset Butterfly Valve. The third offset is the disc-seat contact axis. The seat surface takes a conical shape which coupled with the same shape at the ridge of the disc, results in minimal contact before full closure of the Offset Butterfly Valve. A triple Offset Butterfly Valve is more efficient and allows for less wear. Triple Offset Butterfly Valves are often made of metal seats to create a bubble-tight shut-off. The metal seats allow butterfly valves to be used in higher temperature ranges.

High performance Offset Butterfly Valve designs use the pressure in the pipeline to increase the interference between the seat and the disc edge. The Offset Butterfly Valves have higher pressure ratings and are prone to less wear.