Abstract

A multi-year collaborative project with the Natural Sciences and Engineering Research Council (NSERC) of Canada and the University of Alberta Edmonton (UoA) was launched in October of 2022. The project considers the potential effects of emerging commodity transport demands in support of Canadian Net Zero 2050. The project seeks a deeper understanding of the mechanisms that govern the long-term fatigue behavior of spiral welded pipelines towards informing maintenance scheduling and design. Multi-scale testing and modelling approaches involving materials, fluids, and their interactions are to be pursued. Methodologies developed and knowledge gained have cross-over applicability to seamless and long-seam welded pipe.

Recent full-scale pipeline fatigue testing for various geometric deformations was found to be sufficient to develop preliminary governing S-N curves for pipeline steels in air. A projection of a governing S-N curve family for pipeline steels which are subject to diffusible hydrogen is baselined through correlation with testing under diffusible hydrogen conditions. Full-scale fatigue tests of stress concentrators in carrier pipe steels indicate that a large percentage of the useful fatigue life consists of the crack initiation portion of the life cycle and may be leveraged in making integrity management decisions.

Finally, in this work, the governing S-N curve is resolved into a safe-life plot versus the spectrum severity indicator cycles. This allows operators to project a practical lower bound safe life horizon for line pipe with typical stress concentrators. The study concludes that a multi-year project remains a prudent approach in the event some pipeline operators begin hydrogen or CO2 transport service before the project concludes in 2026.

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