Concentric (zero offset) butterfly valves
The disc and stem sit on the centre line of the body, and the disc seals against a soft resilient seat or rubber lining. These valves are economical and give tight shut-off at low to moderate pressure and temperature — typical for water, cooling water and general utility service.
Double offset (high-performance) butterfly valves
The stem is offset behind the seal and from the pipe centre line. The disc lifts off the seat as it opens, reducing seat wear and operating torque. Double offset valves handle higher pressures and temperatures than concentric designs, often with a PTFE or reinforced soft seat or a metal seat.
Triple offset butterfly valves
A third, conical offset gives a cam action: the metal disc seal contacts the metal seat only at final closure, without rubbing. Triple offset valves are used for tight shut-off at high temperature and pressure — steam, hot gas, hydrocarbons and critical isolation.
Comparison
| Concentric | Double offset | Triple offset | |
|---|---|---|---|
| Seat | Resilient / rubber lined | Soft or metal | Metal |
| Pressure & temperature | Low to moderate | Moderate to high | High |
| Typical service | Water, utilities | Process lines, throttling | Steam, hot gas, critical isolation |
| Cost | Lowest | Medium | Highest |
Lined butterfly valves for corrosive media
PTFE- or PFA-lined butterfly valves isolate the body from aggressive chemicals, offering corrosion resistance at a lower cost than exotic alloy bodies.
Body styles
Wafer bodies clamp between flanges and are the lightest; lug bodies allow dead-end service and removal of downstream piping; double-flanged bodies suit large sizes and pipelines.
Actuation
Butterfly valves are quarter-turn, so they pair with gear operators, pneumatic rack-and-pinion or scotch-yoke actuators, or electric part-turn actuators.
Frequently asked questions
Can a butterfly valve be used for throttling?
Yes, within limits — high-performance designs throttle better than concentric valves. For demanding control, a characterised control valve may be the better choice.
Which valve for slurry?
Slurries are often better served by knife gate, diaphragm or pinch valves; discuss the media with us.
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