f Hydrogen Conversion Strategy-Pipework – Literature Review and Interim Report

The purpose of this study is to consider, identify, and mitigate risks associated with a conversion (repurposing) of a natural gas (NG) installation to a 100% hydrogen (H2) installation within the current UK gas network. The scope of this project focuses on domestic gas installations, downstream of the ECV to the appliance inlet.
The report analyses accident and leak data to explore the types of leak that occur in current NG domestic pipework. The differences in the physical properties of hydrogen and methane are tabulated and the differing behaviour of hydrogen and methane leaks is analysed.
This report concentrates on spontaneous leaks in the gap between small and the large which will trip the EFV. The dispersion of gas from the different types of leak and available ventilation models are discussed in detail.
British Standard and IGEM guidance documents are discussed in detail along with previous studies of hydrogen and NG leak behaviour.
The review recommends modifications to the original project work programme. In particular, WP3 will be modified to examine methods of testing internal pipework to ensure that it is suitable for repurposing to hydrogen. This is an essential output from this project. This will include consideration of a range of options:
• Visual inspection of visible pipework
• Low pressure tightness testing
• Higher pressure strength testing
• Novel techniques such as thermal imaging or visual inspection using borescopes
• The use of other gases (helium) to check pipework soundness.
This report was submitted to HSE for their assessment of the safety evidence for 100% hydrogen heating, which can be found at Hydrogen heating: HSE assessment of the safety evidence - GOV.UK.
Queries should be directed to DESNZ: https://www.gov.uk/guidance/contact-desnz.