f Use of Automatic Isolation Valve (AIV) Systems with Hydrogen, Final Report

Automatic Isolation Valve (AIV) systems are common gas safety systems based around a powered isolation  valve, a control system and some form of measurement input that is often a gas detector or proving system. AIVs are a standard safety system already found in some commercial and industrial Natural Gas installations.
This project investigates their suitability for small commercial installations using hydrogen with a focus on the UK village trial sites. The project scope included a review of commercial installations in the two hydrogen village trial sites, in Whitby and Redcar and assessed the potential benefits of using AIVs as a risk mitigation method in those sites.
A small number of AIV systems were found during the site surveys and the project considers the benefits of adding additional systems to improve installation safety with the hydrogen trials. The project scope also included an investigation of AIV systems suited for hydrogen, and three such units were to be specified and tested.
The initial focus of the project was to assess the performance of AIVs with hydrogen. However, it was later realised that the key to this assessment was the correct placement of detectors, which required an understanding of how hydrogen moves and disperses compared to Natural Gas. The project was therefore refocused to include experimental studies, using methane as a substitute for hydrogen, and computational fluid dynamics (CFD) studies to model the movement and dispersion of hydrogen.
This report summarises the output of the project; additional details on individual elements of work are provided in the appendices. Appendix A gives details of the risk assessment methodology of the project. Appendix B comprises the interim project report and baseline project review. Appendix C has the full experimental programme of work. Appendix D covers the scenario modelling and village trial site visits. Appendices E and F provide manufacturer guidance on detector placement. Appendix G gives the reports on the CFD study.
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.