Comparison Between In-Line Crack Detection and Hydrostatic Testing in IPL’s Line 3

Abstract

The BG Elastic Wave in-line crack detection vehicle was used to inspect 213.5 km (133 miles) of Interprovincial Pipe Line Inc’s (IPL’s) Line 3. Rigorous analysis of the inspection data, concentrated on the seam weld and surrounding region, identified 73 sites for excavation. Pressure retaining sleeves were fitted at 17 locations. Of these, the most severe defect noted was a 25 mm (1 inch), 40% through wall long seam shrinkage crack. This was the only feature exceeding a size predicted to possibly fail under hydrotest to 100% SMYS. Twelve other cracks were sleeved, all of which were measured to be between 20% and 35% through wall. Minor imperfections were found at the majority of those reported locations which were not sleeved. Following completion of remedial work, 198 km (124 miles) of Line 3 was hydrostatically tested at pressures up to 100% SMYS, including 156 km (98 miles) that had been inspected by the Elastic Wave vehicle. There were no leaks or ruptures under hydrotest, demonstrating the ability of the tool to reliably detect cracks in the seam weld and surrounding region that were smaller than would have been found by hydrostatic testing alone.