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GT Outlet / HRSG Inlet Cycling Joint (Cold Casing)

Cold casing duct systems are the modern approach to the need of power plants to be cycling more frequently.

DEKOMTE has developed many solutions for cold duct systems, with the emphasis on integration into the duct design. The adjacent duct internal insulation, cladding and flow plate arrangement need careful attention to ensure no gaps of interface.

The insulation system is the most important point. There must be a seamless insulation between the duct and the expansion joint bolster.

The steel frame upstand of the expansion joint must not be heated by the flue gas, after compression and degradation of insulation.

DEKOMTE has retrofit and OEM solutions which will meet the operational criteria required.


DEKOMTE fabric expansion joint 10W as base load solution - suitable for GT applications with cold casing exhaust system
DEKOMTE Membrane expansion joint ME suitable for changeover from hot to cold casing exhaust system with large duct movements
DEKOMTE High tech expansion joint 3Wa as cycling solution - suitable for changeover from hot to cold casing exhaust system with large duct movements and high cycling impact

Design Issues

  • Lining interfaces
  • Insulation integrity
  • Gas paths

Short Term Solution

  • Re-insulate missing pockets
  • Plate gaps to duct flange
  • Reconfigure bolsters
  • Install flow plate
  • Upgrade clamping system

Long term Solution

  • Designed steel parts
  • Improved duct interface
  • New seamless internal insulation
  • New fabric and bolster design
Example of operating parameters for the cold casing design of a fabric expansion joint
Dimension inside 7000 x 8000 mm
Temperature max. 670 °C
Pressure 50 mbar
Movement axial: -200 mm
lateral: 100 mm
Thermal transient cyclic operation
Maximum stress 400 N/mm²
Load cycles 250 000

Thermographics for thermical analysis

Installed DEKOMTE design solution