Probabilistic Pitting Corrosion Risk Assessment of Welded Offshore Steel Pipelines

Steel structures continuously exposed to offshore marine environments are prone to corrosion. This can be of major economic and perhaps of environmental significance. The risk of these scenarios occurring can be assessed using good quality data, good quality corrosion and pitting models and structural reliability assessment. Recently, improved models for the prediction of longer term corrosion and pitting of welds have been developed and these are reviewed herein. An example illustrates the application of reliability analysis to a pipeline subject to localized corrosion. The reliability assessment includes parameters related to corrosion, pipeline dimensions and liquid flow, all treated as random variables. The influence of the weld heat affected zone is considered critical in the analysis. The effect of random variable variability is assessed by means of a sensitivity study. The results provide an estimate for long-term reliability, and show the considerable influence on the probability of failure of pit diameter and the corrosion parameters.