Executive Summary

The increasing interest in utilizing hydrogen as a low carbon fuel to help decarbonize the energy system has led to considerations of transporting hydrogen through existing natural gas pipelines, either as natural gas-hydrogen blends or pure hydrogen. However, the potential impacts of hydrogen on pipeline materials and components necessitate an evaluation of material integrity and risk for safe and reliable operations. Knowledge and data gaps can hinder the development of appropriate Canadian standards for repurposing infrastructure for hydrogen service. This study discusses current practices to identify and recommend consideration paths forward to address gaps within Canadian standards and codes specific to hydrogen or hydrogen blend service.

The materials and components of natural gas transmission pipeline systems covered in this study include steel line pipes, fittings, flanges, valves, station piping, compressors, and meters, which are governed by standards such as CSA Z662, CSA Z245.1, CSA Z245.11, CSA Z245.12, CSA Z245.15, API Std 617, and API Std 618. Canadian natural gas pipeline systems typically adhere to the requirements of CSA Z662, which also provides provisions specific to hydrogen or hydrogen blend service through guided engineering assessments. The standard also references other hydrogen standards, such as ASME B31.12, for further guidance. Differences in requirements between natural gas and hydrogen service stem primarily from potential adverse effects of hydrogen on materials, such as hydrogen embrittlement in steels. Hydrogen embrittlement can reduce the material’s resistance to failure and shorten the component’s fatigue life and can be influenced by several factors, including hydrogen partial pressures and pipe grade, based on the material’s specified minimum yield strength. This phenomenon is observed in materials used in the pipeline system, such as high-strength carbon steels commonly employed for natural gas transmission pipelines. Other materials that lack ductility, such as cast iron, can be found in components within natural gas pipeline systems, such as certain parts of meters and compressors, and may be unsuitable for hydrogen service. Additionally, concerns arise about hydrogen leaks for some components utilizing mechanical joints (e.g., flanges) due to smaller hydrogen gas molecules compared to natural gas.

Nevertheless, transporting hydrogen through pipelines is not a new concept, and some materials and components used for natural gas services have been used for hydrogen service in both purpose-built and repurposed infrastructures. However, differences in requirements between natural gas and hydrogen service should be extensively evaluated. This study provides a non-exhaustive list of gaps that need to be addressed, including implementing generally more stringent requirements for hydrogen service, which infrastructures built for natural gas service may not meet. It is also essential to determine the hydrogen blend level and conditions (e.g., system pressure) at which these requirements become applicable. Examples of relevant requirements to be evaluated include Charpy V-notch impact properties, material hardness, material specified minimum yield strength, and material ultimate tensile strength. Further, the availability of data on material properties for existing natural gas infrastructure could be an issue, since hydrogen standards such as ASME B31.12 require an evaluation of parameters not typically mandated for natural gas service such as girth weld Charpy V-notch values.

The discussions on the identified gaps in this report can serve as the starting point for interested parties, such as CSA committees, researchers, operators, regulators, and manufacturers, to further assess the applicability of existing requirements for hydrogen service, develop additional technical basis as required, and provide clear guidelines, including potential alternative provisions to facilitate the conversion of existing Canadian natural gas infrastructure into hydrogen or hydrogen blend service.