Creep failure of reformer tubes in a petrochemical plant

This paper investigates a failure in HP-Mod radiant tubes in a petrochemical plant. Tubes fail after 90,000 h of working at 950 °C. Observed failure is in the form of excessive bulging and longitudinal cracking in reformer tubes. Cracks are also largely branched. The microstructure of service-exposed tubes was evaluated using optical and scanning electron microscopes (SEM). Energy-dispersive X-ray spectroscopy (EDS) was used to analyze and characterize different phases in the microstructure. The results of this study showed that carbides are coarsened at both the inner and the outer surface due to the long exposure to a carburizing environment. Metallography examinations also revealed that there are many creep voids that are nucleated on carbide phases and scattered in between dendrites. Cracks appeared to form as a result of creep void coalescence. Failure is therefore attributed to creep due to a long exposure to a high temperature