Bsudhakar – are you still operating a fuel oil fired coker heater? There are not many that I have encountered these days?
High heat values and burner/draft issues make hot spots more likely with these types of heaters. All of the causes you mention can lead to hot spots and accelerated creep rates. If you don’t have a TMT there or have good visibility with IR camera, you might never know there was hot spot there. We always advocated for more TMT’s and better peep doors for just this reason.