Dent severity in the pipeline industry has historically been characterized through parameters including depth, length and width. Other approaches utilize techniques that estimate the strain in a dent based on the longitudinal and circumferential curvature. However these methods have shortcomings as they degenerate the geometry to a series of curve fits in two planes. Dents interacting with other anomalies and those that have atypical characteristics present particular challenges to both operators and in-line inspection vendors, as they do not fit the traditional analysis molds described above. Advances in high-resolution caliper tools offer an improved means of dent assessment through the use of finite element analysis, which can be performed on anomalies of any shape and size including those with interactions. This paper presents a case study where a plain dent was generated in the lab and characterized with an optical scanner and ROSEN’s high-resolution geometry tool. Both sets of data were analyzed using the general purpose finite element code ABAQUS to predict stress concentration factors and expected strains under internal pressure. The analysis results were benchmarked to lab tests where strain gages were used to measure the peak strains. The paper concludes by presenting how the process of conducting finite element analysis has been streamlined to the point where it can be automated and stress concentration factors rapidly provided to operators in conjunction with standard ILI reports. This streamlined process now allows finite element analysis to be used as a primary means of assessment to rank, prioritize and mitigate dents.
Dotson, R. L., Ginten, M., Alexander, C., Bedoya, J., Schroeer, K., “Combining High Resolution In-Line Geometry Tools and Finite Element Analysis to Improve Dent Assessments”, Pipeline Pigging & Integrity Management Conference, PPIM 2014, PPIM-ILI2-16, February 10-13, 2014, Houston, TX.
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