Transformation and decarbonization of existing energy systems are a key part of global energy transition efforts to meet targets set in the COP21 Paris Agreement. In effort to reduce greenhouse gas emissions and decarbonize the existing energy systems, hydrogen has emerged as an attractive fuel option for energy storage and transportation. One key aspect considered is the potential for blending and transporting hydrogen in existing natural gas pipelines. It is recognized that the introduction of hydrogen in existing carbon steel pipelines may present a myriad of effects including hydrogen embrittlement, increases to fatigue crack growth rate, and reductions in ductility and yield strength when exposed to susceptible steels under stress. These potential effects may vary based on the vintage, strength of steel, weld type, and other specific pipeline characteristics, therefore the specific threats and severity of each should be evaluated for numerous pipeline configurations.

Establishing a standard and consistent approach for evaluation compatibility of pipeline materials with hydrogen service would be beneficial to the industry. The existing practice of assessing defects in hydrogen service is based on guidance from ASME B31.12. However, the guidance provided in ASME B31.12 is based on the response of hydrogen at higher concentrations and pressures than will be expected in typical transmission or distribution pipeline systems.

This paper provides a recommended approach to performing testing and analysis for existing and new pipe steels under various hydrogen blends. This would provide a framework across the industry for which a consistent approach for assessing compatibility could be assessed, and allow for improved alignment and compilation of material test data to establish a broader understanding of material compatibility.

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