Learnings

Outcomes

WP1-3 Summary

The existing high purity hydrogen pipeline systems have shown decades of incident-free operation. These systems would be subject to coating and CP performance specifications applicable to oil and gas transportation systems, and current at the time of pipelines’ design stage and/or during their operation. Two such pipeline systems (located in Texas, USA) were originally operated as crude oil pipelines and then repurposed for successful transportation of hydrogen.

No standards were found with specific recommendations regarding coatings and cathodic protection (CP) for hydrogen transportation systems and only one study was found (using extreme aqueous charging conditions) relating to the behaviour of coatings on steel to permeated hydrogen. ASME B31.12-2019 is currently the most widely recognized standard for hydrogen pipeline systems. The standard does not provide general specifications on external coatings but refers to the use of typical protective coatings for repairs. Similarly, the best industry practice applicable to natural gas systems is being considered regarding CP. The same approach, i.e. the best industry practice, is also being adopted in guidelines for new hydrogen pipeline systems, as evident in publications prepared by International Gas Consortium / European Gas Producers Association; i.e. CGA G5.6-2013.

Review of the scientific literature related to hydrogen absorption by X50 – X100 grade pipeline steels from both aqueous and gaseous media indicates that very low concentrations of sub-surface atomic hydrogen (0.15 w ppm) would be expected for steel exposed to pure hydrogen at up to 100 bar. This hydrogen level is below the value expected to cause significant harm to external pipeline coating systems.

No studies were reported that had assessed (legacy) coal tar enamel coating behaviour. The other materials used for external coatings were reported to show no degradation on exposure to molecular hydrogen at levels used in hydrogen transportation systems. In addition to the lack of work on coal tar coatings the behaviour of coatings with permeated atomic hydrogen requires confirmation.

No evidence was found that hydrogen permeation affected CP efficacy for charging from aqueous systems although impressed voltages caused more hydrogen to be retained in the steel (still at the low level noted above). Nevertheless, in the absence of published work a theoretical hypothesis on the potential impact that hydrogen may have on CP, specifically at disbonded/defective coating locations was postulated. It was proposed that under given conditions, permeated surface-adsorbed atomic hydrogen may be consumed though hydrogen evolution reactions, which would result in pipeline depolarization, i.e. consumption of electrons supplied by the applied CP. Confirmation of the above for gaseous hydrogen through experimentation is recommended.

The project value tracking is listed below:  

·         Maturity

o  TRL 2-3 – Desktop study on impact of hydrogen on existing below-ground corrosion management systems (coatings and cathodic protection).

·         Innovation Opportunity

o  100% or multiple asset classes – Scope covers all existing below-ground corrosion management systems - external barrier coatings and cathodic protection systems.

·         Deployment Costs

o  £0.00 – No direct deployment costs as this is a research project. However, costs might need to be incurred to ensure hydrogen readiness of assets with corrosion management.

·         Innovation Cost

o  £ 73,131.00 – Cost of innovation project.

·         Financial Saving

o  £ 0.00 – No direct financial savings as this is a research project. However, understanding of corrosion management processes in hydrogen might enable life extension or avoidance of replacement of assets.

·         Safety

o  0% – No direct safety improvement as this is a research project. However, understanding of corrosion management processes in hydrogen is paramount to ensures safety via avoidance of significant corrosion.

·         Environment

o  0.0 tonnes CO2e – No direct environmental benefits as this is a research project. However, understanding of corrosion management processes in hydrogen might enable life extension or avoidance of replacement of assets with associated avoidance of environmental harm.

·         Compliance

o  Ensures compliance – Work supports transition to hydrogen.

·         Skills & Competencies

o  Individuals – Work will augment knowledge of individuals involved in project.

·         Future Proof

o  Supports business strategy – Work will inform hydrogen repurposing and future new build strategies (e.g. procurement requirements).

Lessons Learnt

The project proceeded very much as expected. The inclusion of the FutureFuels CRC at the workshops provided a broader prospective of researcher / user experience and gave useful feedback. Furthermore, the combination of an industrial (ROSEN) and academic (WMG) partner to conduct joint research was deemed successful as this enabled a broad view of the topic. It would be recommended to consider this approach for future research projects

Follow on work will focus on filling identified knowledge gaps via an experimental testing programme.