Demonstrating in-line inspection (ILI) to monitor cracks assuring compatibility for operation with hydrogen in new and re-purposed offshore natural gas pipelines

Expected Outcome

Current existing natural gas grids are expected to form a substantial part of the future hydrogen transport and distribution system. Current industry initiatives such as the European Hydrogen Backbone Initiative of major TSOs and Ready4H2[1] of the European DSOs is showcasing how this could progress.

While the work to assure the integrity of the pipelines and components in the grid have progressed in previous projects and activities, the main focus has been on onshore infrastructure. Offshore pipelines have specific design rules and different operating conditions and cannot be excavated for maintenance or service purposes in the same manner as onshore pipes. This means that existing infrastructure should maintain longer, without service or exchange of segments. The consequences of fatigue and cracks could endanger the complete business case of the pipeline. Similarly, it is very expensive to retrieve inspections tools if they get stuck and this situation should be avoided by design and by the way of operating and handling the tool. Also, the offshore pipelines have a larger diameter and are operated under higher pressure. Although, it is in the common interest of both onshore and offshore transport grid operators to have In-line Inspection tools that can operate in hydrogen pipelines, higher standards apply for the offshore use case. It has been observed that the most critical points in offshore pipeline integrity are the circumferential welds and seam welds. Therefore, their accurate detection is a key factor in advancing research on the repurposing of gas pipelines for hydrogen transport.

The integrity of offshore pipelines for hydrogen transport cannot currently be guaranteed due to hydrogen's detrimental effect on fracture toughness, ductility as well as the increase of fatigue crack growth rate, especially in regard to stress concentration areas and required performance of ILI-tools are not fully established.

The project results are expected to contribute to all of the following expected outcomes:

• Safe operation of repurposed and new offshore pipelines with hydrogen;
• Maintain European technology leadership in ILI-systems;
• Improve ILI efficiency in stress concentration areas, such as welds and crack like defects;
• Extend the lifetime and reduce costs of pipeline operation (also onshore);
• Support the progress of standardisation of gas grid operation and maintenance.

Project results are expected to contribute to the objectives of the Clean Hydrogen JU SRIA.

Scope

The scope of this topic is to demonstrate In-Line Inspection (ILI) tools to qualify existing natural gas pipelines for hydrogen service and to operate in future offshore hydrogen pipelines (new or re-purposed) by validating that the tool is suitable for detecting crack-like defects, especially in stress concentration areas.

Proposals should consider and build on relevant existing work in this area and results from projects related to hydrogen integrity of high-pressure pipelines, ILI-systems and sensor development, such as from Pipeline Operator Forum (POF), European Pipeline Research Group (EPRG), Pipeline Research Conference International (PRCI) and including projects funded by the Clean Hydrogen JU such as HIGGS[2], SHIMMER[3], PilgrHYm[4], etc. and also relevant national projects on the topic, such as TransHyDe[5]. Successful projects are also expected to review the state of the art during their implementation and to identify additional synergies with these and other ongoing relevant projects.

Proposals should develop acceptance criteria for defects, considering the type and size of defects, loading conditions and hydrogen environment. This will be used to prove that inspection methods have sufficient probability of detection and sizing accuracy to ensure the integrity and to determine acceptance criteria for the inspection. Proposals should demonstrate the ability to detect or monitor crack-type defects with satisfactory resolution and detection probability through In-line Inspection (ILI) in offshore high-pressure pipelines, as well as safe and reliable operation of In-Line Inspection tools reaching TRL 6 or higher.

Validation consists of demonstration of the increased performance of the ILI-tools by conducting test-runs in high pressure pipelines.

The validation should be conducted in a hydrogen environment but may take place onshore. Detection results, modus operandi and the in-line inspection device, as such, should be prepared and as far as possible qualified to operate in the hydrogen conditions of the future offshore pipelines, while the dimensions of the tool may be different. The development should consider the securement of the needed material integrity and safety of operation, while also considering the costs of the tool and inspections of the relevant stakeholders. In order to be able to fulfil this scope, proposals should include at least one In-Line-Inspection tool provider and one gas transport grid operator.

The following aspects are to be addressed in the scope of the project:

• Determine acceptance criteria for defects including critical flaw characteristics and sizes. This will set the required detection sensitivity for the in-line inspection method and device differentiate between categorising the effectiveness in seam welds, girth welds and pipe body according to the wall thickness. However, it should be the minimum ambition that the tool can detect internal surface-breaking circumferential flaws and surface defects not larger than 3×20 mm in the pipeline. The minimum acceptable performance with respect to axially oriented cracks and crack-like defects are:
• Minimum depth at a Probability of Detection (POD) = 90% of a crack of a length of 25 mm: 1 mm or 10% of the wall thickness, whichever value is greater and a minimum crack opening: < 0.1 mm
• Depth sizing accuracy at 90% certainty: ± 0.5 mm or 5% of the wall thickness, whichever value is greater and a length sizing accuracy at 90% certainty: ± 5 mm
• Orientation limits for detectability: ± 10°
• Determine required conditions for the tool and its operation:
• The tool should have long term hydrogen compatibility/stability and consider the operational condition (acceleration, mechanical impact, etc.) of the future offshore hydrogen pipelines. One may consider an increased exchange rate of components by design, in a deliberate trade-off between performance and minimisation of costs, considering tool preparation for inspection and all required maintenance on the tool in preparation of a tool run.
• The tool should be able to negotiate at least 1,5D 90° bends, can collapse and pass bore restriction to 75% of the inside diameter, can pass 1:1 offtakes without pig bars and generally have a low tool drag and friction.
• Furter criteria such as: Low cost by design, be easy to handle and have low risk of failure, should also be considered
• Develop and test ILI-tools to the specifications defined;
• Define guidelines and protocols for the execution, including launch and receive, of in-line-inspections for qualifying existing offshore pipeline and for maintaining pipelines with hydrogen, including velocity control of the ILI tool. Pipeline cleanliness level and cleaning pigging launch protocol between crack detection pigs. Combining other methodologies such as MFL- A/C;
• Identify and provide suggestions for amendments of existing RCS for the secure monitoring of offshore high-pressure grids;
• Validate the reliable operation of the ILI tool according to defined specification, guidelines and protocols under real conditions to qualify the design at TRL 6. It is assumed that validation in hydrogen environment and in high pressure pipelines between NPS 16”/DN 400 and NPS 32”/DN 800 are sufficient with controllable pressure and flow conditions to adapt to requirements for testing.

For additional elements applicable to all topics please refer to section 2.2.3.2

Activities are expected to start at TRL 4 and achieve TRL 6 by the end of the project - see General Annex B.

The JU estimates that an EU contribution of maximum EUR 3.50 million would allow these outcomes to be addressed appropriately.

Technology Readiness Level - Technology readiness level expected from completed projects

Activities are expected to start at TRL 4 and achieve TRL 6 by the end of the project - see General Annex B.

[1] https://www.ready4h2.com/

[2] https://cordis.europa.eu/project/id/875091

[3] https://cordis.europa.eu/project/id/101111888

[4] https://cordis.europa.eu/project/id/101137592

[5] https://www.get-h2.de/en/geth2-transhyde/