Excessive temperature on carbon steel casing

[91RepairGuy]

We recently performed thermal imaging on the area around our HRSG inlet expansion joint. The exterior carbon steel casing adjacent to the expansion joint was 850F for about 2/3 around the 21' diameter duct. Several feet away from the expansion joint, the temperature was 135F. We are assuming the insulation has failed between the liner and the casing. We are looking for a reference document that indicates what temperature carbon steel is good for. The ductwork is exposed to excessive temperatures for extended periods of time (this is a peaker plant). Is there risk of cracking or catastrophic failure?

 

[metengr]

91RepairGuy;
Carbon steel sheet/plate in this environment and application is designed for maximum metal temperatures of 850 deg F because this is not pressure retaining. In reality, lower metal temperatures will prolong service life because there will be less oxidation damage at lower temperatures.

In reality what will happen is that repeated exposure to service temperatures above 850 deg F will result in surface oxidation and eventual loss of wall thickness. You will experience gas leaks through the expansion joint well before you have a significant problem.
I would search for past EPRI documents related to “Carbon Steel Handbook”. There is good information in this handbook related to exposure temperatures for carbon steel and limits imposed by boiler OEM’s.

http://mydocs.epri.com/docs/public/000000000001014670.pdf