There has been multiple reported and documented external stress corrosion cracking (SCC) of above-ground carbon steel pipelines within the past 5 years for a number of in-situ oilsands operators. Majority of these failures were on pipeline carbon steel grades API 5L or Z245.1 with specified minimum yield strength (SMYS) 52 ksi or higher, but there were also reports of external SCC on A106 Gr B and A234 WPB steel grades. All the cracks manifested on the bare (uncoated) Outside Diameter (OD) surface of the pipe, and all were associated with wet mineral wool insulation. Common features include operating temperature between 70°C and 160°C, intergranular cracking morphology, and exposed to wet mineral wool insulation with vintage post 2005.

Previously, SCC of carbon steel pipelines has been commonly reported and investigated for buried pipelines. There is limited information in the industry however on SCC of above ground carbon steel pipelines. Extensive field and lab tests were performed to understand the mechanism, in conjunction with technical studies/literature reviews. This paper provides a summary aimed at increasing the awareness of the industry with this new damage mechanism, and improve public safety.

Subject
Working electrodes, External stress corrosion cracking, Materials, Piping, Insulation, Intergranular stress corrosion cracking, Pipelines, Inspection, Minerals, Wool, Acidity, Stress corrosion cracking, Residual stress
Keywords:
Stress Corrosion Cracking (SCC), pipelines, in-situ, mineral wool insulation
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2022
Association for Materials Protection and Performance (AMPP)
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