PROBABILISTIC ANALYSIS OF PIPELINES SUBJECTED TO PITTING CORROSION LEAKS

A methodology is described for the assessment of the service life of l iquid carrying metallic pipelines subjected to pitting corrosion. The estimate of pipeline life is based on the loss of liquid through pit h oles during transportation. The growth of corrosion pits is modelled b y a two-parameter exponential function having time dependency and a de creasing rate of pit growth. Parameters which are related to corrosion , pipeline dimension and liquid flow are treated as probabilistic vari ables. The first-order reliability method is used to estimate the prob ability of failure and the relative contribution of the various uncert ain parameters to it. Failure is defined in terms of a maximum allowab le 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 variabil ity of some of the random variables on the failure probability. The re sults 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.