The figure above shows XCOMB display of EGT patterns. The lines are as follows:
  • The dotted red circle = maximum EGT spread.
  • The dotted yellow circle = the minimum EGT spread.
  • The solid white circle = average EGT value for all the thermocouples.
  • The dotted white line = the actual EGT pattern.
  • The solid magenta line = expected EGT pattern.
The system also displays the actual and the expected EGT spread value. The fault index, which is the percentage deviation of the EGT spread value from the expected spread value is also displayed.

The fault index is a very good indicator of the onset of combustion problems.

Click for more information on  gas turbine combustion diagnostics (XCOMB)

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