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Modeling the Burst Pressure of Offshore Pipelines with Extensive Internal Corrosion in the Free Span

Samadi Mal Amiri, Farzam | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54508 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Raie, Mohammad
  7. Abstract:
  8. Internal corrosion is one of the most common defects in pipelines. In recent decades, the use of offshore natural oil and gas resources has increased dramatically, followed by the use of offshore pipelines to transport products. At the same time, numerous accidents and explosions in offshore pipelines and their economic and environmental consequences underscore the importance of ensuring safe operation. Pipeline integrity management has been developed to ensure the safe and correct operation of pipelines. Integrity management starts with planning, then leads to inspection, then evaluation, and finally to corrective action, and this loop is repeated regularly. In this loop, the importance of evaluation is twofold due to the complexity of the analysis. In offshore pipelines, due to the corrosive environment and high internal pressure, pipeline burst is one of the major accidents. Previous research has only examined the effect of external corrosion on burst pressure and has not explicitly examined internal corrosion. Also, the existing regulatory relations for evaluating the burst pressure, only the effect of internal pressure is examined, and the effect of bending moment is not considered. Free spans are formed in the seabed, which causes the pipeline to have a sizeable bending moment due to its weight. The results show that bending moments in pipelines with extensive corrosion significantly reduce up to fifty percent of the internal pressure capacity. The focus of this study is on internal corrosion. Before numerical modeling was done, the design of experiments (DOE) was performed to obtain the most critical parameter on the burst pressure of pipelines to reduce time and cost. Then, in the next section, by considering other parameters, the main parameter was examined in more detail. The interaction effect of these parameters was also investigated. After modeling, statistical analysis was performed on the data, and based on these parameters; an equation was obtained that presents the burst pressure in the corrosion domains studied in this study. Finally, to verify the accuracy of finite element analysis, the results were compared with the laboratory results on the burst pressure of the pipeline, which differed by an average of thirteen percent of the burst pressure presented. Finite element analysis was compared with regulatory relations and valid recommended practices such as DNV RP F101 and ASME B31G. The percentage difference was obtained with each of the recommendations that had the modeling results closest to the DNV RP F101 recommended practices
  9. Keywords:
  10. Burst Pressure ; Finite Element Analysis ; Free Span ; Bending Moment ; Statistical Analysis ; Internal Corrosion ; Offshore Pipeline Integrity Management

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