Abstract
This paper contains the results obtained from a three phase study of the integrity of corroded oil transmission pipelines under combined load conditions. The study was necessary for two reasons. First, the current and potential modified ANSI/ASME B31G criteria for corroded pipe are empirically drawn from experimentations on pipes much smaller in diameter and lower in grade of steel than those used in the oil transmission pipelines. Second, the current criterion does not account for the effects of axial bending that could occur in buried pipes due to settlement, and for the axial compression that could occur because of differences in installation and service temperature. To address these deficiencies, an engineering model was developed based on elastic shell theory. The engineering model was calibrated against full-scale burst tests performed on pipes with simulated corrosion subjected to combined loading. In general, the dimensions of the simulated corroded region and the axial stresses due to constrained thermal expansion were specified at the start of a test. A combination of internal pressure, bending moment, and axial load was then applied to the test section until failure occurred. In order to gain insight into the different failure mechanisms, each of the burst tests was simulated using a three-dimensional elastic-plastic large deformation finite element analysis.
