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 LMP value 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.