Injecting Hydrogen into the Gas Network- A Literature Search

Hydrogen injection into the GB gas network is a likely consequence of using excess offshore wind generated electricity to power large-scale onshore electrolysis plants. Government and DECC in particular now have a keen interest in supporting technologies that can take advantage of the continued use of the gas networks. HSE can contribute to the government’s Growth and Green agendas by effectively regulating and safely enabling this technology.
This report will allow HSE to regulate effectively by pulling together scientific and engineering knowledge regarding the hazards of conveying hydrogen/methane mixtures in network pipes and its use in consumer appliances, into a single ‘state-of-play’ report. It enables Energy Division to consider and assess submissions for ‘gas quality’ exemptions to the Gas Safety (Management) Regulations 1996 (GSMR).
In particular, the report has examined the following hazards:

• conveyance of H2/CH4 mixtures in network pipes
• use of H2/CH4 mixtures in consumer appliances (domestic/commercial/industrial)
• explosion and damage characteristics (and ignition likelihood) of H2/CH4 mixtures
• effects on odourisation

It identifies that the flame profile in gas appliances will increasingly flatten as hydrogen content rises. For modern appliances fitted with flame failure devices this may cause the appliance to shut down (and default to a safe condition). For some older types of gas appliance (1970s and older) not fitted with flame failure devices there may be an increased risk of flame failure leading to internal gas escapes. At the concentrations of hydrogen in methane likely to be considered by the industry (between 0.5 and 10%) this effect is not significant. Where exemptions for higher concentrations are sought HSE will insist on the identification and modification of vulnerable appliances. The report concludes that concentrations of hydrogen in methane of up to 20% by volume are unlikely to increase risk from within the gas network for from gas appliances to consumers or members of the public.