Improvements to the ASME B31.8 Dent Strain Equations

[+] Author and Article Information
Chike Okoloekwe

University of Alberta, Edmonton, Alberta, Canada

Nikko Aranas

University of Alberta, Edmonton, Alberta, Canada

Muntaseer Kainat

Enbridge Liquids Pipelines Inc., Edmonton, Alberta, Canada

Doug Langer

Enbridge Liquids Pipelines Inc., Edmonton, Alberta, Canada

Sherif Hassanien

Enbridge Liquids Pipelines Inc., Edmonton, Alberta, Canada

J.J. Roger Cheng

University of Alberta, Edmonton, Alberta, Canada

Samer Adeeb

University of Alberta, Edmonton, Alberta, Canada

1Corresponding author.

ASME doi:10.1115/1.4040096 History: Received September 12, 2017; Revised April 02, 2018


Pipelines used to transport oil and gas products are often subjected to external interferences forces during its construction or operation which can result in the formation of dents in the pipeline. Various pipeline codes have stipulations on how these threats should be assessed in order to prioritize repairs. The most prominent being the depth based criterion which determines the severity of a dent by its depth. The depth based criterion fails to consider the fact that the geometry of the dent can lead to high strain concentration and eventually the failure of the pipeline at the dented section. Codified equations are available for evaluating the strains at the dented region of the pipeline. This technique is implemented assuming the peak strains occur at the apex of the dent. The current implementation of these equations might fail to capture the strains that are not aligned with the most severe deformation profile of the dent and as such a global view of the strain distribution of the dented profile would be more informative as per the localized strain distribution. The study presented herein is the implementation of ASME B31.8 formulations together with the suggested modifications to evaluate the three-dimensional strain state of the dented pipeline. The strain distributions obtained are compared against the strains predicted by finite element analysis (FEA) model. The correlation in the predicted strains indicates the possibility of the rapid strain based characterization of dented pipelines.

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