f H21 ATEX-SR25 Summary Technical Report

In order to utilise the existing gas transmission and distribution network to transport 100% hydrogen, the effects of the changes in characteristics of hydrogen from natural gas need to be reviewed and the resultant effect on the network assessed. Hydrogen features a substantially larger range of flammable concentrations than natural gas, which could cause safety concerns if the existing network is not reviewed.
By surveying the electrical and instrumentation assets on site, it was identified that many of the existing instruments currently in operation are not certified for the hydrogen environment (minimum Gas Group IIC) and require replacement.
There are a large quantity of instruments not suitable for the hydrogen environment due to asset condition / age and the effect of corrosion overtime affecting instruments, such as missing or illegible faceplates resulting in being unable to verify ATEX certifications. A smaller percentage of existing instrumentation are in good condition but not certified for the hydrogen environment.
Equipment without a faceplate have been considered as not suitable for Hydrogen, pending a review of certification for validation within a hydrogen atmosphere, a replacement may not be required.
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.