Crack Threat Management Transition From Hydrostatic Test to In-Line Inspection for an Aging Pipeline

A vintage North American pipeline has been transitioned from periodic hydrostatic test to periodic crack in-line inspections (ILI’s) to manage the cracking threat. Historic crack incidents were reviewed to determine if the hydrostatic testing was likely to have been a contributing factor in the incidents. A real-world application of surviving flaw analysis and interim pressure-based management as crack ILI’s could be planned and executed is described. Reliability improvement strategies, as they pertain to the specific asset, are reviewed and the decision-making process supporting the threat management method change is described. After selecting periodic crack ILI for long-term crack threat management, the process for selection of crack ILI technology and preparing for response to likely inspection findings is defined. After in-line inspections were completed and field result comparisons became available, meaningful interactions between the ILI provider and operator were required to manage ILI and NDE discrepancies. The scope and depth of these interactions have advanced the collaboration environment and led to deeper understanding of ILI methods in managing aging pipelines. The economics of the legacy hydrostatic test and crack ILI management methods are compared. As an integral part of managing the cracking threat on vintage pipes, emerging guidance on toughness inputs was evaluated on this asset and compared to ASTM 1820 compact tension specimen J-R integral test results.