Session: MF-22-01 3D Crack Growth Simulation Using FEA

Paper Number: 122643

122643 - Circumferential and Off-Axis Crack Fatigue Growth Susceptibility in Buried Steel Pipelines 

While the industry generally discounts fatigue growth of circumferential cracks in mainline pipe as being a credible threat, it has occurred. Three instances of girth weld crack fatigue growth are examined in this presentation and modeled for fatigue growth due to internal pressure fluctuation effects. Metallurgical findings for these incidents are presented with potential root causality elements. Cutouts indicating circumferential crack growth dormancy are likewise modeled to assess model realism. Fatigue growth susceptibility is compared to initial fitness for service criteria for common susceptibility elements, including monotonic strain. Sensitivity to superimposed axial tensile stress is projected based on the family of da/dN curves produced using the Walker theory. A practical risk framework is proposed to assist operators determine if fatigue growth of circumferential cracking merits consideration. Commercial off-the-shelf software is employed leveraging publicly available pipeline steel da/dN data and API-579 stress intensity solutions, illustrating universal availability, which has only recently emerged, of this level of fatigue growth forensic capability. The vast experience associated with axial crack fatigue susceptibility is examined to determine what conclusions can be reached relative to circumferential and spiral weld oriented cracking susceptibility. Relative susceptibility for circumferential and spiral weld imperfection fatigue growth and risk treatment options are proposed with recommendations for future work.

Presenting Author: Lyndon Lamborn Enbridge LP

Presenting Author Biography: With more than 35 years of experience in fracture, fatigue, structural design, stress and loads analysis, testing, incident investigation, and 6 years as Crack Threat Subject Matter Expert at Enbridge Liquids Pipelines, Lyndon is now a consulting contractor. Lyndon holds a bachelor of science degree in Mechanical Engineering and two Masters degrees: Aeronautical Engineering and Secondary Education, and was employed in the aerospace industry at Boeing for 30 years. Lyndon is a Professional Engineer in the province of Alberta, Canada, holds eight US Patents, and is heavily involved in advancing pipeline integrity science.

Authors:

Lyndon Lamborn Enbridge LP
James Hogan University of Alberta
James Ferguson Stantec Energy
Jason Skow Integral Engineering