Metal Expansion Joint -- Axial Bellows SS321
High-Temperature Axial Metal Expansion Joint for Steam and Exhaust Pipelines
Document No.SV-DS-EXP-003
RevisionRev A
DateMay 2026
ManufacturerSupreme Valves India, Ahmedabad, Gujarat, India
This datasheet covers axial metal expansion joints with multi-ply SS321 bellows for absorbing thermal expansion in high-temperature steam, exhaust, and hot gas pipelines.
Technical Specifications
| Parameter | Specification |
|---|
| Size Range | DN50 to DN2000 (2" to 80") |
| Pressure Rating | PN10 / PN16 / PN25 / PN40 / Class 150 / Class 300 |
| Bellows Material | SS321 (UNS S32100) multi-ply hydroformed bellows, 2 to 6 plies |
| End Connection Material | Carbon steel or SS321 flanges / weld ends |
| Temperature Range | -200°C to +600°C (SS321 limit) |
| Movement Capability | Axial: 20-200 mm (size and convolution count dependent) |
| End Connections | Flanged ASME B16.5 / BS EN 1092-1 or butt weld ends |
| Features | Multi-ply SS321 bellows, axial movement, internal liner, limit rods, external cover |
| Internal Liner | SS321 internal liner for high-velocity flow and particle-laden gas streams |
| Accessories | Limit rods, tie rods, external shroud, pre-compression tabs |
Materials of Construction
| Component | Material |
|---|
| Bellows | SS321 multi-ply hydroformed bellows, 2 to 6 plies, solution annealed, 100% dye-penetrant tested |
| End Pieces | Carbon steel or SS321 pipe sections with weld preparation or machined flange faces |
| Flanges | Carbon steel or SS321 slip-on, weld-neck, or lap-joint flanges per ASME B16.5 / BS EN 1092-1 |
| Internal Liner | SS321 thin-wall liner with drain holes and flow directional taper to prevent bellows erosion |
| Limit Rods | Carbon steel or SS321 threaded rods with double nuts and washers for unrestrained installations |
| External Cover | SS304 or carbon steel protective shroud for personnel protection and environmental shielding |
| Gaskets | Spiral-wound SS321 + graphite for flange connections (if flanged ends specified) |
Testing & Inspection
| Test | Requirement |
|---|
| Test Standard | Hydrostatic 1.5x PN; helium leak test on bellows; fatigue cycle test on request |
| Certification | CE, PED, ISO 9001 |
Applicable Standards
| Standard | Description |
|---|
| Design Standard | ISO 10628 / BS 6129 / EJMA Standards |
Notes
- Axial expansion joints must be installed with main anchors and adequate pipe guides to prevent lateral or angular movement that damages bellows.
- For unrestrained installation without anchors, specify limit rods sized for full pressure thrust at test pressure plus safety factor.
- Internal liner is mandatory for steam velocities above 25 m/s or gas streams with particulate; specify flow velocity at order.
- Bellows fatigue life depends on axial movement per convolution; specify total expected axial movement and design temperature at order.
- Pre-compression or pre-extension tabs may be used during installation to set bellows at neutral position; remove after piping is complete.
