Hydrogen as part of the future energy mix is expected to play a significant role in decarbonizing the world’s energy supply to mitigate climate change, and the push towards establishing an infrastructure to handle this is rapidly increasing. Cost efficient hydrogen delivery is a key, and both newbuilt and requalification of existing natural gas transportation pipelines play an important role in this respect. In order to realize an efficient infrastructure, it is of utmost importance to establish requirements that ensure the combined need for safety and cost-effective design to make hydrogen transportation a viable option. In this paper, this challenge is discussed in light of material related aspects. The existing basis for pipeline design, primarily the ASME B31.12 code, is presented and the issues believed to be the main limitations are pointed out. For steel pipelines in general, it is well recognized that hydrogen may promote hydrogen embrittlement (HE) which potentially could have an adverse effect on the pipeline integrity. Despite the tremendous effort that has been undertaken to grasp the peculiarities with the failure mechanisms associated with HE, there are still several controversial findings currently being debated. The various suggested hydrogen embrittlement mechanisms are reviewed (e.g. HEDE, HELP, AIDE, HESIV), and the perceived main aspect and uncertainties of relevance for hydrogen transport presented. The length scales associated with HE embrittlement are discussed, and it is underlined that in case of more detrimental HE the phenomenon falls in a meso-scale between purely brittle cleavage fracture propagation (ultimately concerning separations at the interatomic length scale) and ductile crack growth ( primarily being plastic deformation controlled at length scale above the grain size of the material). One particular concern in this respect is the lack of clearly defined damage nucleation mechanisms in most of the HE models proposed. &nbsp;A number of observations in the literature pointing to possible special aspect related to HE and H2 are highlighted. An example here is the apparent differences in loading rate sensitivity during fatigue crack growth testing and local hardness when comparing H2 and electrochemical charging. &nbsp;Based on the current knowledge, special implications for design of offshore pipelines are presented, with focus on fatigue loading and potentially increased axial stress levels.&nbsp; In addition, implications for potentially large-deformation failure modes like burst, running ductile fracture, and third-party damage are also addressed. The paper is concluded with a summary of the main challenges/gaps that currently exists in the view of the authors.

Hydrogen’s Peculiar Effect on Material Properties - Do We Need to Be Concerned About Hydrogen Transport in Pipelines?

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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