RESIDUAL STRENGTH ANALYSIS OF CORRODED PIPELINE WITH INTERACTING DEFECTS SUBJECTED TO INTERNAL PRESSURE AND LONGITUDINAL COMPRESSIVE STRESS

Failure due to corrosion defects has been the major problem in maintaining pipeline’s integrity. The loss of metal due to corrosion usually results in localized pits with various depth and irregular shapes which occur on its external and internal surfaces. At a certain point of corrosion, the wall of the pipe become thinner and starts to lose its mechanical resistance. An interacting defect is one that is located sufficiently close and able to interact with neighboring defects in an axial or circumferential direction. Methods for assessing metal loss defect have been available for many decades but they are known to be conservative. Therefore, a comprehensive analysis is required by the application of the nonlinear finite element simulation during the analysis. The objective of this study is to estimate the failure pressure of corroded pipelines with interacting defects subjected to internal pressure and longitudinal compressive stress. The analysis was focused on failure pressure by the available code which is DNV-RP-F101 code and Finite Element Analysis (FEA). The FEA showed that the failure pressure results of the corroded pipeline with interacting defects were higher compared to the empirical values obtained from DNV-RP-F101 code. The FEA with the application of longitudinal compressive stress to the models showed that the interaction effects of the defects decrease as the longitudinal spacing increase.