PROBABILISTIC ANALYSIS OF PIPELINES SUBJECTED TO PITTING CORROSION LEAKS

A methodology is described for the assessment of the service life of liquid carrying metallic pipelines subjected to pitting corrosion. The estimate of pipeline life is based on the loss of liquid through pit holes during transportation. The growth of corrosion pits is modelled by a two-parameter exponential function having time dependency and a decreasing rate of pit growth. Parameters which are related to corrosion, pipeline dimension and liquid flow are treated as probabilistic variables. The first-order reliability method is used to estimate the probability of failure and the relative contribution of the various uncertain parameters to it. Failure is defined in terms of a maximum allowable degree of loss or ingress of fluid. Numerical results are given for a typical example pipeline. A sensitivity study was also carried out for the example pipeline to reveal the effect of the level of variability of some of the random variables on the failure probability. The results show that the probability of failure increases nonlinearly with time and that the contribution of pit hole size and pitting corrosion parameters are very significant for long service lives.