Temporal Variability in Corrosion Modeling and Reliability Updating

Many parameters influencing corrosion degradation are time variant and the corrosion process is thus subject to temporal variability, the real characteristics of which are commonly neglected in reliability assessment. After a short overview on the quantitative modeling of corrosion loss, a comparison is made between different temporal models of corrosion degradation and the consequences of applying an inappropriate model are investigated. The effect of temporal variability is then investigated in detail and illustrated in an example considering CO 2 corrosion in pipelines. It is demonstrated how the time-variant corrosion process can be consistently represented by time-invariant random variables, using equivalent values of the corrosion rate. Finally, the influence of temporal variability on reliability updating following inspections is investigated and it is shown how this effect can be accounted for in inspection planning.

[1]  Daniel Straub,et al.  Generic Approaches to Risk Based Inspection Planning for Steel Structures , 2004 .

[2]  C. Guedes Soares,et al.  Reliability of Corrosion Protected and Maintained Ship Hulls Subjected to Corrosion and Fatigue , 1999 .

[3]  John Dalsgaard Sørensen,et al.  Cost Optimal Reliability Based Inspection and Replacement Planning of Piping , 1999 .

[4]  Robert E. Melchers,et al.  Probabilistic Models for Corrosion in Structural Reliability Assessment—Part 2: Models Based on Mechanics , 2003 .

[5]  K. J. Moerk,et al.  A probabilistic approach to prediction of CO{sub 2}-corrosion, and its application to life cycle cost analyses of oil and gas equipment , 1995 .

[6]  R. Melchers.  Corrosion uncertainty modelling for steel structures , 1999 .

[7]  Jae-Myung Lee,et al.  A Time-Dependent Corrosion Wastage Model for the Structures of Single-and Double-Hull Tankers and FSOs and FPSOs , 2003 .

[8]  C. D. Waard,et al.  Predictive Model for CO2 Corrosion Engineering in Wet Natural Gas Pipelines , 1991 .

[9]  Sankaran Mahadevan,et al.  Model uncertainty and Bayesian updating in reliability-based inspection , 2000 .

[10]  Michael Havbro Faber.  Uncertainty Modeling and Probabilities in Engineering Decision Analysis , 2003 .

[11]  Robert E. Melchers,et al.  Reliability estimation of pressurised pipelines subject to localised corrosion defects , 1996 .

[12]  I. S. Cole,et al.  Recent Progress in Modelling Atmospheric Corrosion , 2002 .

[13]  C. D. Waard,et al.  Carbonic Acid Corrosion of Steel , 1975 .

[14]  R. Melchers.  Modeling of Marine Immersion Corrosion for Mild and Low-Alloy Steels—Part 1: Phenomenological Model , 2003 .

[15]  Peter Friis-Hansen,et al.  Reliability Analysis of a Midship Section , 1994 .

[16]  Emanuel Parzen,et al.  Stochastic Processes , 1962 .

[17]  Michael Havbro Faber,et al.  Epistemic Uncertainties in Decision Making , 2005 .

[18]  Pierre R. Roberge,et al.  Atmospheric corrosivity modeling — a review , 2002 .

[19]  Niels C. Lind,et al.  Methods of structural safety , 2006 .

[20]  A. Turnbull.  Review of modelling of pit propagation kinetics , 1993 .