Penetration seal
metal expansion joints

Penetration seal
metal expansion joints

Penetration seal<br/>
metal expansion joints
Penetration seal (with telescopic covers option)
area cross section.

Item Description
1 Bellows
2 Outside ring
3 Inside ring
4 Drain plug (optional)
5 Cover ring (optional)
6 Inside cover (optional)
7 Outside cover (optional)
8 Boiler wall*
9 Penetration pipe*

* Shown for illustration only.

Penetration seal
metal expansion joints


  • 100 % airtight solution to boiler penetration.
  • Permits axial and lateral movement without causing high stresses in penetration pipe and boiler wall.
  • Maintenance-free
  • Used in heat recovery steam generators (HRSGs).


  • Improved boiler efficiency through zero gas seepage.
  • Improved boiler efficiency through reduced heat loss.
  • No emissions
  • Noise reduction

Operating range

Diameter: 75 mm (3”) ... 750 mm (30”) bellows inside diameter
Process temperature: Up to 650 °C (1,200 °F)
Pressure: Up to 1 bar (15 PSI)
Typical axial movement limit: ±200 mm (±8”)
Typical lateral movement limit: 200 mm (8”)
Typical angular movement: 0°

Movements are non-concurrent.


  • Bellows material options: 1.4301(ANSI 304), 1.4404 (ANSI 316/L dual-certified), 1.4541 (ANSI 321), Inconel® 600, Inconel® 625, 254 SMO®, Incoloy® 25-6HN.
  • Bellows basics: formed by punch mandrel, thin-wall ply thickness ≤1.5 mm (0.060”).
  • Rings, bands: carbon steel, chrome-moly.
  • Metal covers: carbon steel, stainless steel.

Standards and approvals

  • GE Specification
  • Expansion Joint Manufacturers Association (EJMA)
  • ISO 9001:2008

Functional description

Metal expansion joints are used in pipelines to compensate for thermal growth, typically in applications with high internal temperatures; or to prevent vibrations from being transmitted beyond the expansion joint.


Standard quality control and testing:
  • Air and soap bubble leak check.

  • Skilled field service teams can provide site support.
  • Expert clamshell (split bellows, for in situ repair) bellows welders.
  • Experienced supervision by our field service personnel available.