Double offset and triple offset butterfly valves both outperform concentric designs in demanding service. The difference is the seat: double offset is usually soft-seated; triple offset is metal-to-metal. Here is when each one wins.
Double Offset: The Workhorse
Double offset valves have two geometric offsets so the disc swings away from the seat on opening, reducing friction and wear. They typically use soft seats (PTFE, reinforced PTFE) and suit temperatures up to about 230°C, with Class V/VI shutoff.
Best for: oil & gas, chemical and HVAC service where you need better performance than concentric but don't face extreme temperatures.
Triple Offset: Metal-Seated Severe Service
Triple offset valves add a conical seat geometry, so the disc contacts the seat only at the fully closed position — zero rubbing, metal-to-metal sealing to Class V, and temperatures up to 550°C.
Best for: steam, high-temperature gas, LNG, and fire-safe service where soft seats would fail.
Comparison Table
| Aspect | Double Offset | Triple Offset |
|---|---|---|
| Seat | Soft (PTFE etc.) | Metal-to-metal |
| Max temp | ~230°C | 550°C |
| Leakage | Class V/VI | Class V |
| Friction | Low | Zero (at seat) |
| Fire-safe | Optional | Inherent |
| Cost | Moderate | Higher |
Which to Choose
Choose double offset for high-performance soft-seated service up to 230°C. Choose triple offset when the medium is steam, hot gas or flammable and you need metal-seated reliability beyond soft seat limits.
Reguvale manufactures both. See our triple offset butterfly valves or double offset butterfly valves. Send your spec for a recommendation.