Evaluating the Impact of Selective Seam Weld Corrosion on Pipeline Integrity

Date
2023-12-15
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Abstract

This thesis examines the impact of Selective Seam Weld Corrosion (SSWC) on the burst pressure of pipelines. This process is caused by factors like galvanic reactions, weld defects, and chemicals like sulfur becoming trapped in the weld material, and results in the longitudinal weld seams being corroded faster than the surrounding pipe material, creating a sharp v-shaped groove that creates a higher concentration of stress. This impact is worsened by the fact that this higher stress is experienced in the Heat Affected Zone, a relatively weak section of material compared to the base metal of the pipe. SSWC is relatively uncommon, seen primarily in ERW and EFW pipes manufactured before 1985, and thus warrants further study this thesis aims to contribute to. This thesis investigates the change in burst pressure when the same pipe sees a varying series of defects, investigating the relationship between this burst pressure and defect dimensions. These results were then compared to values from the Recalibrated PCORRC model, a mathematical model created to predict burst pressure with crack defects. Through this study, it was determined that defect has the largest impact on weakening a pipe's pressure-containing ability, with radius having a smaller but still significant impact. It was also determined that the Recalibrated PCORRC model was most accurate for cracks with a tip radius between approximately 0.7 to 1 mm. For larger radii, these results were further from the FEA results, however, this difference was conservative and predictable. Meanwhile, for radii smaller than 0.7 mm, burst pressures were overstated and inconsistent.

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Keywords
Mechanical engineering, Pipelines, Pipeline integrity, Corrosion, Selective seam weld corrosion (SSWC), Burst Pressure, FEA
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