Codes and Standards

Revisiting ASME Strain-Based Dent Evaluation Criterion

[+] Author and Article Information
Abu Naim Md Rafi, Hossein Ghaednia, Jorge Silva

Centre for Engineering Research in Pipeline,  University of Windsor, Windsor, Ontario, Canada N9B 3P4

Sreekanta Das1

Centre for Engineering Research in Pipeline,  University of Windsor, Windsor, Ontario, Canada N9B 3P4sdas@uwindsor.ca

Richard Kania, Rick Wang

TransCanada Pipelines Limited, Calgary, Alberta, Canada T2P 5H1


Corresponding author.

J. Pressure Vessel Technol 134(4), 041101 (Jul 27, 2012) (7 pages) doi:10.1115/1.4005890 History: Received April 23, 2011; Revised October 28, 2011; Published July 26, 2012; Online July 27, 2012

Oil and gas transmission pipelines can be subjected to concentrated lateral loads and as a result, a dent can form. A dent is a localized defect in the pipe wall in the form of a permanent inward plastic deformation. This kind of defect is a matter of serious concern for the pipeline operator since a rupture or a leak may occur. Dent may not pose an immediate threat to the structural integrity of a pipeline. However, it can possibly hinder the operational and inline inspection activities. In the long run, it can cause a leak or rupture in the pipeline under sustained or cyclic pressure load. Hence, AMSE B31.8 recommends a strain-based criterion for the assessment of dents. This strain-based criterion was developed based on several assumptions. This study was undertaken using full-scale laboratory tests and finite element analyses to review and revisit the ASME strain-based dent evaluation criterion and its assumptions. It was found that some of these assumptions are incorrect, and hence, this dent evaluation criterion can lead to inaccurate estimations of critical (effective) strain values in dents, which in turn can lead to inaccurate assessments of the dents.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Geometric parameters of a dent (ASME 2007)

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Figure 4

Test setup for small diameter pipe specimen

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Figure 5

Typical load-deformation behavior

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Figure 6

Locations for strain data collected

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Figure 7

A typical FE model for full pipe

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Figure 8

Strain distribution for Line 1

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Figure 9

Strain distribution for Line 3

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Figure 10

Schematic of dent cross-sections

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Figure 11

Effect of dent depth on circumferential membrane strain

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Figure 12

Effect of pressure on circumferential membrane strain

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Figure 13

Effect of pressure on longitudinal membrane strain




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