• Dinata, R., Janzen, T., Miller, T., Korolnek, R., Finneran, S. Lee, K., Gajonera, D. (2024). Assessment of Natural Gas Pipeline Materials for Hydrogen Service. Canadian Standards Association, Toronto, ON.

Executive Summary

There is significant interest in pursuing hydrogen as a low-carbon fuel to contribute to decarbonization of Canada’s energy systems. As with other gases, pipeline transportation will enable large volume transportation of hydrogen to end-use locations. And converting existing natural gas pipelines for hydrogen service is viewed as an efficient and cost-effective means to enable large-scale use of hydrogen in Canada. Whether as a natural gas-hydrogen blend or pure hydrogen gas, the suitability of pipeline materials designed for natural gas must be evaluated when converting a pipeline for hydrogen service. Through literature review, industry scan, and analysis, this research provides insights into standard gaps and recommendations for future updates of relevant standards to support operators contemplating conversion of their pipeline infrastructure into hydrogen service.

Most Canadian natural gas transmission pipelines are made of carbon steels, which, when exposed to hydrogen environments, can experience, to varying degrees, material degradation, including reduced fracture toughness and accelerated fatigue crack growth rate. Carbon steel pipelines’ susceptibility to such degradation is influenced by various factors such as steel grade, metallurgical characteristics, hydrogen partial pressure, subsurface anomalies, pipe welds, steel hardness, residual strain, operating temperature, presence of inhibiting compounds, sulfur and phosphorus content, carbon equivalent, existing pipeline defects (e.g., pipe dents), and heat treatment application.

Transporting hydrogen through carbon steel pipelines is not a new concept, with standards in existence. Hydrogen pipeline use has been prevalent in North America for several decades in purpose-built pipelines for hydrogen service, pipelines converted from other services like crude oil gathering pipelines, and numerous hydrogen blending demonstration projects involving the addition of hydrogen to natural gas pipelines.

While carbon steels are predominantly used in natural gas transmission pipelines, other materials such as stainless steels, aluminum alloys, cast iron, copper alloys, and non-metallic materials are also employed within the systems to a lesser extent. The suitability of these materials for hydrogen service varies and requires comprehensive evaluation. In the case of natural gas distribution mains, polyethylene (PE) pipes are commonly used. Significant research demonstrates PE pipes’ suitability for hydrogen service evaluating hydrogen permeation and pipe ageing, but only limited relevant standards for hydrogen service exist.

As of June 2023, Canadian federal and provincial pipeline regulations do not specifically reference hydrogen or hydrogen blended pipelines. These regulations typically incorporate CSA Z662 as a reference for the design, construction, operation, modification, discontinuation, and abandonment of pipelines. The 2023 edition of CSA Z662 includes additional provisions specific to hydrogen gas service through Clause 17, applicable to pipelines used for hydrogen or hydrogen blend service. These provisions require operators to conduct engineering assessments that encompass various topics such as material selection and pipeline design to address the potential adverse effects of hydrogen on pipeline materials. Current CSA Z662 edition also references ASME B31.12 as an additional guidance document for hydrogen service, which is widely regarded as the applicable standard for high-pressure hydrogen pipelines. However, pipelines originally constructed for natural gas service are unlikely to meet the minimum requirements for hydrogen service outlined by ASME B31.12. Various requirements between the current edition of CSA Z662 and ASME B31.12 are compared in this report followed by recommendations on addressing the gaps to accelerate the hydrogen economy development.

In summary, the transition to hydrogen as a low-carbon fuel in Canada is gaining traction, with a focus on repurposing natural gas pipelines for hydrogen transport. This shift necessitates careful evaluation of pipe materials, especially carbon steels, due to potential hydrogen-induced degradation. While established standards exist, gaps between requirements for hydrogen and natural gas services should be addressed to accelerate the hydrogen economy rollout.