Development of screening software tool for evaluation of pipeline lateral buckling

Abstract

During its lifetime a pipeline is subjected to an increase in internal pressure and temperature from its as‐installed condition. These loads cause the pipeline to expand at its “free” end, and induce stresses and forces in the pipe wall. If the pipeline is not allowed to expand, this will result in buckling if the magnitude of the loads is large enough, to overcome external restraining forces. The scope of this thesis is to develop a Screening Software Tool for Evaluation of Pipeline Lateral Buckling; a tool for evaluation of pipeline integrity based on survey results. The main purpose of the software is the identification and evaluation of locations that have undergone lateral buckling. This is done by first of all creating a software tool that can import text files; files such as the design route, as‐laid data and survey data. With this information the software is able to print all three pipeline routes, and a visual comparison between design/as‐laid and the survey route can be performed. Further, the lateral offset between design/as‐laid and the survey route is plotted in order to get a better overview on locations that may have undergone global lateral buckling. From this plot the user can select a section for further investigation. The survey data is the data set to be analyzed, it is not fully accurate; noise often occurs and needs to be reduced/ eliminated. Noise reduction is done by smoothing the data set. After this smoothing is carried out and the user feels the smoothed curve is realistic; this part of the work is finalized. With this smoothed curve the screening tool can now calculate the curvature, and multiplying it with the bending stiffness of the pipe; the result is the bending moment. This is not a fully accurate result, but it gives a good indication on where the pipeline might be operating under a high degree of utilization, and that a better and more thorough FE‐analysis should be run. The verification work on this screening tool has been applied in the program SIMLA, where self‐established routes have been tested with the Lateral Buckling Screening Software. The Lateral Buckling Screening Software (LBSS) has shown to be a good tool for the evaluation of pipeline lateral buckling. It has developed into an easy and effective tool for import of data files. And it contains a great smoothing function that makes the results realistic and sufficient to obtain a good estimate for further curvature calculations. The LBSS has its limitations when calculating the bending moment; it only takes the horizontal position into consideration. So any effect from an uneven seabed or upheaval buckling is not included, this is why the LBSS will always give lower stress results than a FE‐analysis software.