Evaluation of Analyses for Different Hydrogen/Natural Gas Blends

Hydrogen (H₂) gas concentrations between 1 and 20% are most proposed for blending, and such concentrations have been used in pilot projects worldwide. The pipeline industry is also interested in higher concentrations. H₂ blending is a complex challenge involving social, economic, and technical considerations. Various research organizations, industry organizations, commercial entities, and communities have contributed to the knowledge developed to date. However, each project has its particular focus and objectives. Combined research is not readily available.

The objective of this review was to describe how different H₂/natural gas (NG) blends affect pipeline integrity management intervals.

The following conclusions were formulated based on the results:

1. Laboratory testing shows that exposure to H₂-blended NG has a detrimental effect on the material properties of pipeline steels. The extent to which these effects affect pipeline integrity has not been fully studied, particularly for high-stress pipelines.
2. No lower bound has been established in laboratory testing where H₂ blending has been found not to have a detrimental effect on material properties.
3. Global practical experience with blended H₂/NG of different concentrations shows that using H₂-blended gas is feasible and that the detrimental effects of H₂ on steel may not greatly impact pipeline integrity. This experience is based on low-stress and distribution pipelines. More experience needs to be established with H₂ blending on high-stress pipelines. However, the fatigue life of defects in pipelines carrying H₂/NG may be shorter than for NG alone, warranting a shorter reinspection interval for those pipelines.
4. Based on a review of databases and other sources with information on H₂‑related incidents and accidents, H₂ production and distribution pilot projects, blending facilities, and pipelines to transport H₂-containing gas blends, there were no counter-indications toward the successful use of H₂/NG blending. However, most project descriptions provided little technical information.
5. In the absence of shared integrity management, component performance, and material property data from operators who have run pilot or small-scale projects with blended H₂/NG systems, it is not possible to reliably estimate the remaining life of such systems with postulated or known flaws.