Types of Butterfly Valves

There are three main types of butterfly valves:

1.Zero Offset Butterfly Valves (Resilient Seat Butterfly Valves)

2.Double Offset Butterfly Valve (High-Performance Butterfly Valves)

3.Triple Offset Butterfly Valve

In zero offset butterfly valves, the stem passes through the centerline of the disc that is centered in the seat; all of this is centered inside the valve body. The valve body, seat, and disc lie concentrically when it is in a closed position.?

Zero offset butterfly valves are used in liquid and gas pipelines, which have pressure and temperature ratings of 250 psi and 4000F, respectively.

In double offset butterfly valves, the stem axis is offset behind the centerline of the seat and the body (first offset), then the stem axis is further offset from the vertical centerline of the valve (second offset). When the disc is opened, the seat is lifted from the seal;

Double offset butterfly valves are typically used in water purification, wastewater treatment, HVAC, and fire protection systems (e.g., fire sprinklers). For increased temperature resistance, the amount of soft seat material is reduced by backing it with a layer of metal.

In triple offset butterfly valves, an angular offset in the body sealing cone axis is made in addition to the first two offsets (third offset). This is accomplished by using the right-angled conical profile of the seat coupled with a matching profile at the disc edge. This offset eliminates the contact of the seat and the disc during valve opening and closing, hence, friction is also eliminated. Contact only occurs during the full closure of the butterfly valve; this also acts as a mechanical stop to prevent the disc from rotating further.

Triple offset butterfly valves are ideal in handling high-pressure and superheated steam, high-temperature liquids and gases, and corrosive chemicals that cannot be handled by butterfly valves with soft seats. These valves are commonly used in power plants (e.g., on-and-off valves for boilers), oil and gas processing, chemical manufacturing, pulp and paper manufacturing, and offshore pipelines.