Anonymous
The refinery I worked for did have heater tubes that were carburized but this took a very long time, something like 20 years. We had a heavy scale buildup both inside and outside due to long term over firing. We started seeing heavy scale every time we needed to repair tubes. We also started seeing bulges at some areas. We used visual inspection because this buildup was so bad. We did have what is called “Thick Lip” tube failures in some tubes. I hope this may help.