Session: 09-04-02 fracture and toughness for H2 pipelines

Paper Number: 133907

133907 - Engineering Assessment of Hydrogen Embrittlement Susceptibility at Defects in Hydrogen Pipelines by Numerical Modeling 

Abstract: 

Conversion of existing natural gas pipelines to transport hydrogen and hydrogen blending gas is increasingly recognized as an effective method to decarbonize the energy system and accelerate the achievement of the net-zero emission goal in 2050. However, aged pipelines typically exhibit various defects such as corrosion, cracking, and mechanical damage. These defects can lead to uneven stress and strain distribution, and plastic deformation, which can serve as hydrogen traps to accumulate hydrogen atoms, thereby increasing hydrogen embrittlement risk at defects during hydrogen services. Extensive research has been conducted globally, aiming to understand the degradation of the mechanical properties of pipeline steel and assess existing pipelines' compatibility through theoretical and experimental methodologies and techniques, however, there are few studies on hydrogen atoms diffusion and accumulation behavior and the influence on the local degradation of material properties of steel at the defects. In addition, current industry standards and codes, such as ASME B31.12-2019 and CSA Z662-2023, lack detailed guidelines for the hydrogen pipeline defects engineering assessment.  For corrosion defects, the B31G code may not be fully applicable for hydrogen pipelines as mentioned in Clause 1.3-Exclusions in the ASME B31G-2012, the hydrogen embrittlement risk would be significantly enhanced in some scenarios due to local hydrogen accumulation at corrosion defects, which may have brittle fracture initiation characteristics. API RP 1183-2021 is not applicable to evaluate the dents for hydrogen pipelines as mentioned in Clause 4.1.1-Exclusions. API 579-2021 Clause 9F.4.6.2 highlights that the assessment of flaws in hydrogen-charged materials should be treated with extreme caution and excludes the factors that if a material remains in a hydrogen-charging environment, a subcritical crack may grow over time to critical size and unstable fracture will occur, and long exposure to hydrogen may produce irreversible damage (e.g., micro-cracks) in the material. This deficiency in current research and industry standards underscores the urgent need for in-depth research and the development of reliable methodologies to assess the integrity of defects in hydrogen pipelines. This paper will demonstrate a novel multiphysics field numerical modeling approach to study the time-dependent atomic hydrogen diffusion, accumulation, and hydrogen/steel interactions at pipeline defects (such as corrosion, cracks, and dents) and evaluate the locally enhanced hydrogen embrittlement risk at defect sites. It is expected that this research will contribute to the further development of defect engineering assessment methodologies for hydrogen pipelines.

Presenting Author: Luyao Xu DNV Canada Ltd.

Presenting Author Biography: Luyao Xu is a Principal Engineer in Hydrogen and Modeling Services group at DNV. He received his M.Sc. and Ph.D. degrees in mechanical engineering from University of Calgary. He has over 15 years of research and industry experience in pipeline integrity, specialized in fracture mechanics, materials and FEA. Before joining DNV, Luyao was awarded NSERC research fellowship and worked as research scientist at CANMET focused on pipeline SCC and FEA. Then he served as a Pipeline Integrity Engineer and Technical Leader at Stantec in charge of the development of FFS assessment models, procedures, guidelines, and providing trainings and SME reviews for the department. His expertise also encompasses the integrity assessment of hydrogen blending pipelines. He has developed advanced FEA models to study the diffusion and accumulation behavior of hydrogen at pipeline defects and evaluate the risk of hydrogen induced cracking. He currently serves as an editorial board member of Journal of pipeline Science and Engineering and has published over 30 research papers related to pipeline integrity and FEA modeling.

Authors:

Luyao Xu DNV Canada Ltd.
Shane Finneran DNV USA Inc.