Standards and codes for hydrogen in pipeline infrastructure: testing, qualification, and integrity assessment

• Framework with Gaps : Current standards provide foundational guidance for qualifying materials and infrastructure in hydrogen service but are insufficient for addressing the unique challenges of hydrogen blending, revealing significant gaps and ambiguities. • Harmonization Need : There is an urgent call for harmonization of testing and assessment methods across the EU and globally to ensure consistent methodologies for evaluating materials under hydrogen-natural gas mixtures. • Challenges in Retrofitting : Existing design standards for repurposing natural gas infrastructure to hydrogen service are hindered by high costs and limited scope, necessitating economically viable testing and evaluation strategies for large-scale applications. • Degradation of Aged Infrastructure : A lack of detailed understanding of the mechanical properties and degradation in vintage pipelines poses a significant challenge, highlighting the need for nuanced classification systems that consider age-related defects and operational history. • Future Research Directions : The review identifies key areas for targeted research to inform updates to standards, including the development of cost-effective methods for testing and assessing materials and infrastructure for hydrogen blending. This paper presents a comprehensive review of standards and codes for testing, qualifying, and assessing metallic materials and pipeline infrastructure for hydrogen service, with a view to shed light on the gaps and limitations of current procedures for repurposing EU natural gas infrastructure to hydrogen service. Current standards provide a foundational framework for the qualification of materials in hydrogen-rich environments; however, significant gaps persist in addressing the unique challenges posed by hydrogen-natural gas mixtures. This review explores standards for material testing, qualification methods in codes and standards, and design criteria for hydrogen service, with a critical emphasis on structural integrity assessment. Through a detailed analysis of the different documents, the study has identified limitations in existing testing methods and protocols, including insufficient harmonization, vague testing specifications, and an absence of guidelines for evaluating materials in blended environments. Findings highlight an urgent need for harmonization of procedures to facilitate consistent methodologies across different countries in the EU and beyond, as well as for providing the necessary knowledge in terms of design, testing and assessment methods for the hydrogen-natural gas infrastructure. To address these gaps, this review proposes targeted research areas that can support future updates of standards and codes, contributing to safer, more efficient, and globally aligned approaches to hydrogen blending.