Creep failure of cracking heater at a petrochemical plant

After two and half years of operation, a bend tube in a cracking heater at an ethylene plant failed due to creep cracking. Creep damage occurred as a result of metallurgical instability including coarsening of carbides that caused softening and initiation of voids or wedge-type intergranular cracks. This was accelerated due to increasing inner surface temperature during decoking process. Thermal fatigue contributed to the failure as a result of temperature variations due to several shutdown–startup operations. imize such failure in futures, periodic inspection to monitor crack formation was scheduled. Nondestructive tests including dye penetrant test for surface cracking and radiographic test for internal crack were implemented.