Hydrogen Blending into Gas Pipelines Is Outpacing the Testing Standards Meant to Ensure Safety

Governments and utilities worldwide are piloting hydrogen blending into existing natural gas pipeline networks as a decarbonization pathway. However, existing testing standards for hydrogen embrittlement (ASTM E1681, ASTM G142) were designed for pure hydrogen in new infrastructure, not for hydrogen-natural gas mixtures in aging pipelines. A 2025 comprehensive review found these standards "are insufficient for addressing the unique challenges of hydrogen blending, revealing significant gaps and ambiguities." There are no testing protocols for material behavior under mixed hydrogen-natural gas at varying blend ratios, no assessment standards for vintage pipeline steel under hydrogen exposure, and no standards covering the plastic service lines that serve the "last mile" to consumers.

The hydrogen pipeline code (ASME B31.12) has more stringent requirements than the natural gas code (ASME B31.8), creating a regulatory discontinuity for conversion. Utilities piloting hydrogen blending cannot determine safe blend ratios for their specific pipeline materials without commissioning bespoke testing programs. Common pipeline steels show moderate ductility reduction under hydrogen (elongation drops from 17% to 15%, reduction in area from 56% to 40%), but the safety implications for aging infrastructure with pre-existing microstructural damage, welds, and operational stress cycles are unknown. The hydrogen embrittlement effect varies nonlinearly with pressure and saturates between 0.1 and 7 MPa — a range that encompasses typical distribution pressures.

ASTM E1681 and G142 provide foundational hydrogen embrittlement testing but not for blended environments. ASME B31.12 was updated with rules for pipeline conversion and retrofit, but only covers steel and with limited scope. NREL published a comprehensive technical review (TP-5400-81704) identifying codes and standards gaps. DOE hosted a Hydrogen Infrastructure Strategies Workshop in February 2024 documenting safety challenges. Multiple countries (EU, UK, Australia, Japan) are pursuing hydrogen blending pilots. However, no coordinated international testing standards framework exists. The gap between ASME B31.12 and B31.8 forces pipeline operators into a binary choice — full code migration or no hydrogen — with no intermediate pathway for blending. Machine learning models are being developed to predict embrittlement because testing standards cannot keep pace with deployment decisions. A 2025 review explicitly called for "urgent harmonization of testing and assessment methods across the EU and globally."

A validated, standardized testing protocol for hydrogen-natural gas mixtures at varying blend ratios (5%, 10%, 20%) on representative pipeline steel grades (API 5L X52, X60, X70), including welds and aged specimens. This protocol would need to be adopted by both ASTM and ASME to bridge the B31.8/B31.12 regulatory gap. For plastic service lines, basic material compatibility data under hydrogen exposure is needed — a gap that is almost entirely unaddressed.

A team with access to materials testing equipment could conduct slow strain rate tensile tests on common pipeline steel specimens in hydrogen-nitrogen gas mixtures at varying ratios, generating the material compatibility data the standards bodies need. Even testing one steel grade at three blend ratios would produce a publishable contribution. A complementary approach would be developing a decision framework that maps existing pipeline material documentation to hydrogen readiness criteria, helping utilities triage their networks. Relevant disciplines: materials science, mechanical engineering, chemical engineering.