BEHAVIOR OF CIRCUMFERENTIALLY ALIGNED CORROSION PITS

During service, pipelines are exposed to various forms of surface corr osion which, under adverse conditions, can affect their integrity. Cor rosion defects can be in the form of individual pits, closely spaced p its, small pits joined together to yield an overall wall loss or isola ted pits within thin areas of relatively uniform metal loss. Unfortuna tely, application of codes such as ANSI\ASME B31G and CAN\CSA-Z184-M86 to some complex corrosion geometries can be ambiguous. The technique embodied in these codes, based on the overall length and depth of the corroded areas can lead to overly conservative assessments of very lon g defects. In this technique, corrosion profiles which overlap are pro jected onto a longitudinal plane, and the extent of the defect in the circumferential direction is not considered, nor is the effect of long itudinal loadings. This paper summarises the results of experiments in vestigating the burst strength of pipes with multiple corrosion pits a ligned circumferentially. In addition, the finite element method is us ed to investigate geometric parameters not considered experimentally.