Gas Turbine and CCGT Plants

Penetration Seals

Both metallic as well as fabric expansion joints can technically fulfil the requirements of a penetration seal. However, technical and physical harmonization of all parameters, material and design is required.

The case study shows examples of damages on OEM-designs and the DEKOMTE retrofit solution "steel to fabric".


  • Tension-free expansion joint sealing between processing pipe and boiler wall to compensate for movements
  • Minimum maintenance costs
  • High functionality and availability


  • Boiler penetrations seals in power plants and industrial plants
  • Wall penetration seals with fire protection requirement

Original Designs: Metal Expansion Joints

Operational Failures of Penetration Seals

Characteristic failures at metal expansion joints in different installation positions:

Tension crack corrosion
Mechanical damage due to external effects
Corrosion residues and localised corrosion
Uncontrolled temperature influences
Plastic deformation due to uncontrolled influences by movement

Causes of Damages

  • Basic material choice: Material is frequently subordinated to a budget
  • Chemical processes: Due to flue gas/steam/sulphurous acid/chloride
  • Assembly faults: Damages caused by welding or mechanical effects
  • Incorrect expansion joint design: Lacking review of operating parameters

Original Designs: Fabric Expansion Joints

Operational Failures of Penetration Seals

Characteristic failures at fabric expansion joints in different installation positions:

Sooting caused by inappropriate material composition
Defective sealing
Malfunction due to incorrect expansion joint design
Assembly fault
Internal/external diffusion

Causes of Damages

  • Basic material choice: Thermal functional area of the fabric is not taken into account
  • Incorrect expansion joint design: Standard compositions are inoperative for higher requirements
  • Assembly faults: Insufficient fixing with clamp and tightening straps

Retrofit "Steel to Fabric"

According to experience high tech fabric expansion joints are most suitable for pipe penetration compensation. The higher flexibility and the facile replaceability in combination with the individual design of a fabric expansion joint bring besides functional reliability also considerable long-term cost benefits.
Due to the problematic replaceability of metal expansion joints, DEKOMTE developed a procedure to retrofit metal to fabric expansion joints.
These retrofits are cost-effective, fast and no test or heat treatments are necessary

Preserve the original metal expansion joint

Provided that the deficient metallic bellows do not turn out to be fixed points or being too stiff, they can frequently be preserved.

Covering of the original expansion joint
DEKOMTE fabric expansion joint

Replacement of the original metal expansion joint

Alternatively, a replacement is suitable in which the process pipes remain untouched.

Original design metallic bellows
Removal of the metallic bellows
Fitting of the supporting rings
Mounting of the flanges at the boiler wall and process pipes
Installation of the static insulation at the process pipes
Insulation of the process pipes
Mounting of the cross-pipe moveable insulation
Closure of the fabric expansion joint
Mounting of the flanges and screwing

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