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".
Task
- Tension-free expansion joint sealing between processing pipe and boiler wall to compensate for movements
- Minimum maintenance costs
- High functionality and availability
Applications
- Boiler penetrations seals in power plants and industrial plants
- Wall penetration seals with fire protection requirements
Original Designs: Metal Expansion Joints
Operational Failures of Penetration Seals
Characteristic failures at metal expansion joints in different installation positions:
- Tension crack corrosion
- Corrosion
- Mechanical damage due to external effects
- Uncontrolled temperature influences
- Corrosion residues and localised corrosion
- 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
- Assembly fault
- Defective sealing
- Internal/external diffusion
- Malfunction due to incorrect expansion joint design
- Malfunction
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
- Mounting of the flanges at the boiler wall and process pipes
- Mounting of the cross-pipe moveable insulation
- Removal of the metallic bellows
- Installation of the static insulation at the process pipes
- Closure of the fabric expansion joint
- Fitting of the supporting rings
- Insulation of the process pipes
- Mounting of the flanges and screwing