Both twin-ferrule and single-ferrule fittings seal by controlled ferrule deformation, no welding, no thread sealant. The difference is how the two jobs of a tube connection, sealing and gripping, are divided.
The short answer
A twin-ferrule fitting separates the functions: the front ferrule forms the metal-to-metal seal against the body, the back ferrule swages onto the tube for retention. A single-ferrule fitting does both with one ferrule.
When to specify twin-ferrule
- Severe vibration (compressor packages, offshore topsides)
- High cyclic or pulsating loads
- High pressure or safety-critical service
- Lines that will be re-made repeatedly through maintenance
When single-ferrule is enough
- General instrumentation and utility service at moderate pressure
- Instrument air, pneumatics, lubrication, water distribution
- OEM machinery where cost and simplicity matter
| Property | Twin-ferrule | Single-ferrule |
|---|---|---|
| Sealing & gripping | Independent | Combined |
| Vibration resistance | Excellent | Good |
| Component count | 4 (body, 2 ferrules, nut) | 3 (body, ferrule, nut) |
| Typical duty | Critical / severe service | General instrumentation |
Read the full technical pages: TwinFerrule™ Tube Fittings and SingleFerrule™ Tube Fittings.