Remaining life assessment of service exposed reactor and distillation column materials of a petrochemical plant

Mechanical property evaluation is a powerful tool for estimating the residual life of in-service components and health monitoring. In the present investigation such an assessment was carried out to estimate the remaining life of in-service plain carbon steels that had been in use for 45 years in a feed processing unit (FPU) of a petrochemical plant. Health assessment of both base and weld joints of the material has been carried out through accelerated stress rupture tests and other mechanical property evaluation. At the operating conditions, it is noted that the materials still have about 10 years of residual life. However, surprisingly weld joints of the column of this unit exhibited poor notch toughness (5–10 J). It could not be proved beyond doubt, if the weld developed poor notch toughness during fabrication or degraded during service. Annealing of weld joints at 530 °C for 1.5 h improved the notch toughness significantly, hence is recommended accordingly.