Validation to Confirm Threats Result from Hydrogen Service
This Task 7 report was prepared by Kiefner and Associates, Inc. (Kiefner) as part of the research project titled “Investigate Damage Mechanisms for Hydrogen (H2) and Hydrogen/Natural Gas Blends to Determine Inspection Intervals for In-Line Inspection (ILI) Tools” for the U.S. Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA), under Contract 693JK32310011POTA.
This report supports PHMSA by validating whether observed pipeline integrity threats in hydrogen service are directly attributable to hydrogen or influenced by other mechanisms. The study confirms that hydrogen can significantly reduce fracture toughness and accelerate fatigue crack growth, thereby shortening the remaining life (RL) of defects and requiring more conservative integrity management, including reduced inspection intervals.
Hydrogen-related threats—including embrittlement, hydrogen-assisted cracking, and hydrogen-induced cracking—were evaluated alongside interacting mechanisms, including fatigue and stress-corrosion cracking (SCC). No single ILI technology can detect all hydrogen-related threats; a combination of inspection methods and improved data standardization is recommended.
The study also evaluates hardness as an indicator of susceptibility to hydrogen damage. Results show that while automated hardness mapping provides broader coverage, it may miss peak hardness in narrow weld regions, where manual measurements are more reliable. Overall, effective integrity management in hydrogen service requires integrated inspection strategies, refined threat definitions, and careful assessment of weld properties.