Strain Based Analysis for Dented Pipelines

• Author / Creator

  Mehranfar, Mahyar

• Abstract
  It is easier and cheaper to transmit oil and gas by pipeline, but their failure can cause considerable environmental and societal consequences. The denting of pipelines is one of the significant challenges faced by those in the oil and gas industry. The formation of dents in the wall of the pipeline can cause lower pressure capacity. Analytical and numerical models, such as the finite element method (FEA), can predict this issue.
  The traditional way for recognizing the seriousness of the dent is to test the dent depth. But unfortunately, this method cannot predict the probability of failure accurately. Based on previous research, there are two ways to assess the seriousness of the dents. The first method is to model the pipe by finite element method. While very accurate, the finite element method is very computationally demanding and time consuming. The second method utilizes the dent profile to perform strain-based analysis. While very fast, the method suffers from lack of accuracy particularly in predicting the strains in the longitudinal direction.
  The first objective of this research was to develop a technique that takes into consideration the membrane strains in the longitudinal direction. The second objective was to test the performance of the new technique on a variety of pipeline dents. The developed method is based on the three-dimensional mathematical model proposed by Okoloekwe et al.
  In the original model proposed by Okoloekwe et al, it was assumed that the displacement in the mid-line of the pipeline is zero, but we found this displacement and added it to the displacement in the horizontal direction. Our study found that the modification yielded significantly better longitudinal strain distribution than the conventional procedure. The newly developed methods provide an increase in accuracy and speed of the analytical process without sacrificing accuracy.
  A number of two-dimensional and three-dimensional models were examined to verify the method. Contrary to the longitudinal results, these results were very accurate in the circumferential direction. With respect to the FEA results, our proposed technique is much faster, more accurate, and more reliable than previously developed analytical methods.

• Subjects / Keywords

  • Strain Based Analysis

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-fhv0-n391

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.