Structural Significance of Mechanical Damage

Overview

Main Objective

The primary objective of the project is to establish a detailed experimental database to support the development and validation of improved burst and fatigue strength models for assessing the interaction of mechanical damage with secondary features (gouges, corrosion, and welds). The use of this data to develop and validate mechanistic models will produce reliable tools to assess a wide range of mechanical damage forms, thereby increasing safety, reducing unnecessary maintenance, and supporting the improvement of pipeline standards and codes of practice.

Public Abstract

The pipeline industry has identified mechanical damage as a key issue facing the industry as a whole. Analyses of the occurrence of damage to pipelines, in the US and elsewhere, have highlighted mechanical interference as the most frequent source of reported pipeline leaks and ruptures, either immediately on impact or after a period of further operation.

Mechanical damage (dents) formed by a third party or rock indentation can occur in conjunction with secondary features including corrosion, welds, gouges or cracking. Research and engineering studies have clearly shown that these secondary features have a significant impact in promoting dented pipe segment failure as follows:

• Immediately after damage formation or an extreme load event (e.g., a gouge formed during excavation failing as the pipe re-bounds with the removal of the indenter); and
• Gradual damage accumulation due to post-defect loading events (e.g., cyclic re-rounding of dent due to pipeline internal pressure fluctuations).

The primary objective of the project is to establish a detailed experimental database to support the development and validation of improved burst and fatigue strength models for assessing the interaction of mechanical damage with secondary features (gouges, corrosion, and welds). The use of this data to develop and validate mechanistic models will produce reliable tools to assess a wide range of mechanical damage forms, thereby increasing safety, reducing unnecessary maintenance, and supporting the improvement of pipeline standards and codes of practice.

While the studies completed to date have provided valuable data, the number of mechanical damage defects studied as well as the level of detail needs to be expanded to address identified gaps. Given the wide range of mechanical damage defects resulting from the combination and interaction of numerous variables (i.e., pipe, dents, and secondary features), there is a strong need to supplement the initial work with additional defects, as well as additional pipe grades.

Electricore serves as the prime contractor of the project, while PRCI provides overall project guidance. The technical work will be carried out jointly by BMT Fleet Technology Ltd, Gaz de France, and other PRCI member companies.

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