Hydrogen transport – conversion, replacement, etc – [Ask the Experts] Answers to questions

Q1) What do you think of the use of hydrogen in the heating sector (distribution network, domestic installation, gas boilers)?

Shane Finneran: In an effort to reduce carbon emissions, the implementation of hydrogen-enriched natural gas in grid gas supply is gaining popularity around the world. Hydrogen, like natural gas, is flammable and can be burned to produce power, but it does not release carbon dioxide during combustion, making it an attractive alternative for gas utilities looking business as usual while meeting decarbonization targets or requirements.
To that end, hydrogen and natural gas blended to power residential heaters and many commercial heaters have been extensively and successfully tested for efficiency, safety and durability with little or no modification. required. The future, however, may see the need for a higher hydrogen blend, or even pure hydrogen fuel. This remains largely unexplored, and further research and testing is needed to assess the necessary modifications (e.g. change of orifice, etc.) to allow interchangeability.

Q2) When we talk about repurposing existing pipelines for transporting hydrogen, are they usable as is or do they need internal lining, compressor modifications or other aspects that could be costly?

Jan Fredrik Helgaker: When repurposing existing pipelines for transporting hydrogen, the challenges and impacts that hydrogen brings must be understood and considered. For steel pipelines, components and associated welds, it is well recognized that hydrogen can promote hydrogen embrittlement, which could adversely affect the integrity of the pipeline system and therefore impact both on the design and operation of these pipeline systems.
Hydrogen piping and piping systems can be designed in accordance with the ASME B31.12 Hydrogen Piping and Pipeline Code. For steel grades typical of onshore pipelines, existing pipelines can be repurposed in accordance with ASME B31.12, which was originally developed for onshore pipelines, as certain mitigation measures are taken and certain tests of materials are made. To better understand the required CAPEX, a detailed study is required.
For offshore pipelines, work is currently underway to develop standards for the safe and reliable design, construction and operation of hydrogen pipelines.

Shane Finneran: Additionally, assessing the readiness of a particular existing pipeline for conversion to hydrogen requires a detailed asset-specific assessment. DNV is currently leading many such studies and is in the process of developing industry guidance on this topic for publication with a number of industry partners.
In brief, hydrogen readiness will depend on the material and construction methods of the existing pipeline (including specific base material properties, weld properties, etc.) as well as the condition and parameters of the pipeline. exploitation.
Where materials are susceptible to hydrogen embrittlement (HE), the effects and impacts of HE will depend on the initial material properties, operating stress, and hydrogen partial pressure. This can be a complicated asset-specific analysis, but we find that some systems may be compatible almost as-is with minimal modifications, while some may require some component modification or upgrade, while other systems may not be practicably converted without significant upgrades. and associated costs.

Q3) How to assess if our existing network is suitable for hydrogen from a material point of view?

Jan Fredrik Helgaker: The requalification of existing pipelines must comply with the same requirements as for pipelines designed specifically for the transport of hydrogen. ASME B31.12 provides guidance for evaluating whether existing pipeline systems are suitable for transporting hydrogen from a materials perspective.
Guidelines for offshore hydrogen pipelines are currently being developed as noted above. A practical problem will be to obtain more information regarding the performance of vintage steel grades in hydrogen gas environments.

Shane Finneran: Network compatibility will require a specific assessment of the asset, considering various factors, from network materials (and records of those materials/properties) to individual components along the network.
As noted, ASME B31.12 provides guidance for evaluating material compatibility. However, B31.12 offers two evaluation options, a prescriptive approach that clearly defines compatible (and incompatible) materials, as well as a performance-based methodology, which considers more network-specific parameters to assess compatibility. where they may not respond. stricter prescriptive limits.

Q4) What risk factors should we consider when switching to hydrogen?

Jan Fredrik Helgaker: Factors that should be considered when switching to hydrogen include, but are not limited to:
– Impact of hydrogen on pipeline material properties
– Safety issues related to hydrogen
– State of the pipeline
– Physical Properties of Hydrogen
– Operating conditions
– Lifetime

Q5) How much mixing with natural gas is safe to start with? How do you decide on the mix percentage?

Jan Fredrik Helgaker: The safe mix percentage will likely be a combination of several factors, including pressure, hydrogen partial pressure, material properties, and operating conditions, and should be determined on a case-by-case basis. Some natural gas specifications allow a limited amount of hydrogen without any limitation (up to 1% – 2%), so such amount of hydrogen is assumed to be acceptable for transporting natural gas.
ASME B31.12 is applicable for a quantity of hydrogen ≥10%. Hydrogen below 10% is supposed to be covered by existing codes for natural gas. However, hydrogen, even at small fractions and low partial pressure, can adversely affect pipeline steel when operating under certain conditions. It needs to be assessed.

Shane Finneran: There is no overall acceptance value defined as “safe for all systems”, because hydrogen compatibility is the product of many factors mentioned above. Therefore, a specific valuation of the asset is required, either following the existing approach set out in B31.12 or similar guidance, or performing a detailed performance-based valuation.
Tests have shown that some materials are susceptible to hydrogen embrittlement, even at low partial pressures. However, the impact of this embrittlement is largely dependent on the original properties of the material, the current condition of the pipe or equipment, and the expected operating conditions. For example, a pipe with high initial toughness, few crack-like defects, and operating at low stress, may be compatible even with some level of embrittlement. However, a different system with higher stress and poor or unknown initial toughness may have little margin for embrittlement before being considered incompatible. Hence the need for a specific valuation of the assets.

Q6) What should be checked in the existing pipelines before mixing hydrogen with natural gas?

Jan Fredrik Helgaker: When you mix hydrogen with natural gas, you change the content of the transported fluid. Therefore, the pipeline will need to be repurposed for use with hydrogen, as noted above. The risk factors when switching to hydrogen must be assessed.
In addition to the current state of the infrastructure, the expected remaining life and the effect of hydrogen on asset integrity, safety and potential revenue must also be assessed. In addition, existing technical specifications, policies and operating procedures will need to be assessed and possibly adapted before the pipeline system is ready for hydrogen.

Do you have other questions about the hydrogen transition? Want to talk to a DNV expert or learn more about our solutions? Submit your questions here or email us at digital@dnv.com.

The experts

Jan Fredrik Helgaker, Principal Engineer, DNV

Jan Fredrik Helgaker works with flow assurance and pipeline operations. He holds a master’s degree in applied physics and a doctorate. in fluid mechanics from the Norwegian University of Science and Technology. He is currently the Project Manager of the H2Pipe JIP, a joint industry project developing standards for offshore hydrogen pipelines.

Shane FinneranShane Finneran, Principal Engineer and Section Head for Hydrogen Services and Modeling Section, DNV

Shane Finneran is a Chartered Professional Engineer (PE). He has been with DNV for over 14 years and oversees computer modeling services for all applications from design, serviceability and forensic analysis. His current role as Head of Hydrogen involves overseeing and developing onshore projects related to hydrogen and low carbon fuels, including the conversion of existing oil and gas infrastructure to transport hydrogen. pure or blended with the aim of decarbonizing utility networks.

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