PR-214-114500-R01 Fatigue Life Assessment of Dents with and without Interacting Features

The long-term integrity of a dented pipeline segment is a complex function of a variety of parameters, including pipe geometry, indenter shape, dent depth, indenter support, pressure history at and following indentation. In order to estimate the safe remaining operational life of a dented pipeline, all of these factors must be accounted for in the assessment.

The current project provides pipeline operators with a methodology for assessing and managing dent fatigue, thus making it possible to prioritize response and remedial action(s) in an informed manner. The methodology allows the users to carry out dent ranking/prioritization and dent fatigue life assessment. In addition to the development of the plain dent fatigue life assessment methodology, dent weld and dent metal loss interaction criteria have been developed to ascertain their effect on the fatigue life of a dent.

The dent assessment methodology utilizes dent shape information that can be derived from in-line inspection (ILI) data, operating pressure spectra and pipeline material grade. A three-level approach has been developed for assessing the fatigue life or cyclic pressure loading dependent fail-ure of pipeline dents. All three assessment levels draw upon information regarding pipeline operational, material and mechanical damage data. The assessment level selection and accuracy of the results are based upon the complexity of the features, the availability of required data and the level of detail and certainty in the input data. The three levels provide a range of alternatives for integrity management, where the appropriate method to use is dependent on the desired outcome and the available information.