Transportation of hydrogen gas in offshore pipelines: H2Pipe

A joint industry project to develop a recommended practice for transport of hydrogen gas in existing and new offshore pipelines.

Hydrogen can play a significant role in decarbonizing the world’s energy supply to mitigate climate change and hence is becoming an important part of many companies’ strategies to build a clean-energy business. In this regard, several industry players are currently exploring ways of transporting hydrogen gas as an addition or replacement for natural gas.

The potential for hydrogen embrittlement and the risk of adverse effects on the integrity of steel pipelines are widely recognized. The actual effects of hydrogen and its blends on the mechanical properties of these materials, however, are less well understood. This may significantly affect how we design, re-qualify and operate our pipelines for hydrogen transportation.

Challenge

Several industry players are currently exploring ways of transporting hydrogen gas (either pure hydrogen or a hydrogen and natural gas blend) as an addition to or replacement for natural gas. In this context, both new pipelines and utilization of existing infrastructure (re-qualification of pipelines) are viable options. A large-scale deployment of pipelines for hydrogen transport, however, requires that the best possible balance between safety and cost-effectiveness can be established to allow for optimal design of new pipelines, or possibly assessment of the use of existing pipeline infrastructures.

Solution

The need for developing a pipeline code for design, construction and operation of offshore hydrogen pipelines is therefore well recognized and supported by the industry. The DNV standard for submarine pipeline systems (DNV-ST-F101) is a well-recognized standard for safe and reliable design and operation of submarine pipelines. First published in 1976, DNV-ST-F101 celebrates 50 years of service to the energy industry. Even though the standard includes hydrogen as a listed transport product, additional considerations are required to meet the target safety level. Consequently, it is important to ensure that DNV-ST-F101 has reliable design and material requirements that do not compromise the pipeline integrity and safety.

To meet the above challenges, DNV in 2021 started the first phase of a joint industry project (JIP) with the long-term objective to develop a recommended practice (RP) for offshore hydrogen pipelines. Initially, a project specific guideline was developed and delivered to participants in late 2021. Due to limited available data related to how hydrogen gas may affect the material properties, the first revision of the guideline included many functional requirements.

Phase 2 of the JIP started in 2023 and consisted of a comprehensive mechanical test program to investigate the influence of hydrogen gas on typical line pipe steels and welds. In addition, tasks on feasibility design of offshore hydrogen pipelines and a risk assessment study to look at safety aspects of offshore hydrogen pipelines were performed. At the end of Phase 2, the guideline developed during Phase 1 and knowledge gained during the JIP was combined to develop the first public RP for offshore hydrogen pipelines, DNV-RP-F123. While the RP is developed as a supplement to the DNV offshore pipeline standard DNV-ST-F101, many of the design principles are relevant to onshore pipelines.

Phase 3 of the JIP is planned to start in Q2 2026 and will have a 2-year duration. Phase 3 will consist of a large-scale test of an actual pipe to validate small-scale mechanical test data and integrity assessment schemes, allowing DNV and participants to further develop DNV-RP-F123. The primary objective of the H2Pipe JIP Phase 3 is to evaluate if subcritical/constant load crack growth can occur in a full-scale pipe and further how the results from the large-scale tests impacts the fatigue and fracture limit state used in integrity assessments.

Benefits

The key benefits of performing this JIP are to:

• Enhance the general understanding on how hydrogen gas affects the material properties (both as 100% H2 and a blend with natural gas) and further the real design limitations
• Provide a better understanding of how a pipeline system can be designed for safe hydrogen gas transportation, and if necessary, which mitigation measures that should be put in place
• Ensure less conservative design and material requirements
• Provide a better understanding of how third-party interference may affect the pipe integrity
• Enable possibly higher pressure and flow capacity
• Ensure a better utilization of the pipeline system
• Ensure better economy

Value

It is essential to develop more accurate, reliable, and possibly less conservative code requirements for hydrogen pipelines and to have a better understanding of the real design limitations. Cost-efficient hydrogen delivery is a key, and both newbuilt and requalification of existing natural gas transportation pipelines will play an important role in this respect. 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.

JIP participation

If you would like to join this JIP, kindly contact us.

The cost for Phase 3 is NOK 1 500,000.

New companies joining Phase 3 will also pay NOK 1 000,000 to get access to Phase 1 and 2 results.