This project is to determine the suitability of the existing PE network for 100% hydrogen conversion, addressing the knowledge gap of existing operational assets. While testing has concluded current specification PE pipework is suitable for 100% hydrogen conversion, no research has been conducted on PE subjected to prolonged exposure to natural gas under pressure, adversely effecting material properties over time, in some instances up to 50 years.
This project will expand the evidence generation programme of PE assessment to include permeation testing, slit defect leakage rate, stress cracking susceptibility, fracture toughness and leak tightness of house fittings for pre-1976 specification PE.
Benefits
CO2 Reduction
The project is part of the wider future hydrogen conversion projects, including the H21 Project to potentially convert the gas distribution network to hydrogen, therefore assisting with the government aim, and the new legislation committing the UK, to a target of Net Zero emission by 2050
Cost Saving
A review of the suitability for conversion of PE networks will allow mitigation to be planned and implemented proactively rather than reactively.
Time
This project will provide the evidence needed to determine whether the development and replacement of network components is required to meet the future hydrogen conversion planning programmes.
Customer
Minimise future disruption and duplication of cost, by ensuring that potential issues are assessed and mitigated efficiently.
Learnings
Outcomes
The following reports were created as part of this project:
- Final report: summarising the findings from the whole programme.
- Permeation of Hydrogen: This report shows the findings from the permeation tests used to determine the hydrogen permeation rates on Aldyl-A.
- Slow Crack Growth: This report details the effect of hydrogen on the slow crack growth failure mechanism in Aldyl-A pipes.
- Leaks from Representative Defects: This report shows the findings on the hydrogen leakage rates on Aldyl-A through representative defects found on the network.
- Fracture Toughness: This report shows the findings from Charpy Testing to determine the impact of hydrogen on the fracture toughness of Aldyl-A.
- Soil Temperature Study: This report summarises a desktop study to determine the average soil temperature in the UK and how this variable can affect permeation.
The above reports highlight how Aldyl-A behaves in hydrogen, compared to:
- Its performance in natural gas
- The performance of modern-grade PE in hydrogen
Since modern grade PE has been deemed suitable with hydrogen, comparing Aldyl-A with both metrics described above would allow the HSE to determine whether Aldyl-A is ideal as a material in a hydrogen gas distribution network.
Lessons Learnt
Project Timelines
The project's Timeline underestimation was a significant challenge. It was initially planned for completion within 14 months, but it took 28 months. These delays were attributed to various factors, including issues with sourcing components, testing rigs, and underestimation of test duration. The project's high testing programme complexity underscores the importance of accounting for uncertainty from the project's outset. This can be achieved by providing sufficient float for potential issues, fostering a culture of continuous improvement.
Involvement of the HSE
The HSE played a crucial role throughout the project, particularly in advising on the effectiveness and robustness of the novel testing setups. These setups, designed to provide accurate and representative data, were 'peer reviewed' by the HSE at various intervals. This proactive approach allowed for any feedback to be implemented ahead of project completion, ensuring the generation of good-quality testing data.
Recommendations for exploiting the learnings further
This project has provided a significant dataset on the performance of vintage-grade pipelines installed in the 1960s/70s. The next step would be to feed this data into a quantitative risk assessment to understand the risk to society of converting these pipelines to hydrogen. This work is planned and will be incorporated into the GB QRA (NIA 437).
Effectiveness of R&D undertaken
The R&D undertaken in this work program was highly effective. It set out to create evidence specific to the UK network. The data created, unique and not existing anywhere else, can be directly applied to understanding the impact of conversion to hydrogen on the UK networks. This uniqueness of the data underscores its significance in providing the HSE with the evidence needed to understand the impact of conversion.
