Designed for marine engine rooms and deck-level exhaust lines, this stainless steel bellows manages axial growth from hot exhaust while keeping joints gas-tight in salt-laden environments. If you are replacing rubber connectors to reduce maintenance, a stainless solution offers a stable spring rate and consistent backpressure across the service life, which is critical for emissions and fuel efficiency.
Material & Design Rationale
We typically supply 316L for saltwater exposure and 321 where sustained high temperature is the dominant load; 316L improves pitting resistance (chlorides), while 321 stabilizes carbide precipitation above 500 °C. A multi-ply construction keeps the effective bending strain lower than a single-ply design at the same movement, which directly extends fatigue life under engine torsion and hull vibration.
For high-velocity streams or when mounted close to turbo outlets, an internal sleeve can be added to smooth flow and protect the root of the convolution from hot gas impingement. Where vibration is severe, specifying an extra ply or slightly longer face-to-face length reduces the spring rate without increasing backpressure noticeably.
Technical Parameters
| Item | Typical Value / Range | Notes |
| Nominal Diameter | DN50–DN600 (custom larger on request) | Matched to pipe schedule or OD |
| Face-to-Face Length | 150–1000 mm | Set by movement and layout |
| Design Temperature | Up to 600 °C (higher with 321/Inconel) | Continuous exhaust service |
| Working Pressure | 1.5–6 bar | Reinforcement options available |
| Allowable Axial Movement | ±10–±30 mm (per unit) | Validated by EJMA calc & test |
| Materials | 304 / 316L / 321 (Inconel optional) | Inner liner optional |
| End Connections | Weld ends / Loose flange / Clamp collar | Built to print for OEM |
| Leak Test | Helium or air-under-water | 100% unit test |
Marine & Automotive Cross-Over
If you maintain mixed fleets, stainless bellows technology also applies to stainless steel exhaust flex pipe in vehicles, but marine bellows are tuned for larger axial strokes and chloride resistance; this is why they outperform fabric or elastomer couplers on long hot runs near seawater spray.
FAQ
How do I choose between 316L and 321?
316L is the safer choice against chloride pitting in coastal engine rooms; pick 321 when metal temperature stays high for long periods (turbo-proximate sections) because titanium stabilization protects strength above ~500 °C.
Will a metal bellows increase backpressure compared to a rubber connector?
With an inner liner and correct diameter, pressure drop remains low; most increases come from undersized IDs or sharp transitions—match the bellows ID to the adjoining pipe and keep velocity within 45–60 m/s.
Can I clamp this like a sterndrive rubber bellows?
No; this product is welded or flanged. Clamp-on methods suit rubber sterndrive bellows, not stainless axial expansion joints exposed to hot exhaust and pressure thrust.
How do you protect bellows during shipment and installation?
We ship with internal spacers or transport bars to prevent compression; keep them installed until final alignment and remove only after anchors/guides are set, then perform the leak test before insulation.
If you are evaluating a marine exhaust bellows replacement for a genset or considering a stainless steel marine exhaust compensator to reduce maintenance, share your target axial stroke and temperature window so we can size the ply count and liner correctly for cycle life.