Creep damage and remaining life assessment of service exposed engineering materials used in petrochemical industry

In this paper creep damage assessment of 55 years service exposed Catalytic Cold Cracking (CCU) reactor vessel and Feed Processing Unit (FPU) distillation column materials of a petrochemical industry while evaluating their remnant life. Uncertainty involved in calculating LMP (Larson Miller Parameter) value has been given prime importance because it is a function of rupture time. The placing of confidence bounds around any failure time prediction requires knowledge of the failure time distribution. Usually, remaining life is predicted from extrapolation of stress vs. LMP plot without incorporating the uncertainty involved in calculation of LMP values. Uncertainty involved in calculating LMPvalue has been given prime importance in this work because it is a function of rupture time. Variability of normalized creep damage for reactor and column materials is well approximated with the aid of Weibull distribution. As expected, it is observed that the distributions shift towards the higher range of damage with increase in service exposure time.