In order to meet the UK governments plants of net zero by 2050 there is a need for no carbon heat. Hydrogen for heat provides an opportunity to meet the challenging target while minimizing disruption to customers and therefor, is an attractive alternative to natural gas.
SGN’s H100 project aims to demonstrate hydrogen can be distributed safely to people’s homes. To ensure the highest level of safety on this ‘first of its kind’ hydrogen network, Excess Flow Valves will be installed on every service of the network to avoid risk of hydrogen build up in buildings.
Excess Flow Valves are an essential safety feature within the gas network designed to close and stop gas flow if the service, meter or internal pipework suffers a catastrophic failure. Stopping the flow of gas from a damaged service significantly reduces the risk of a fire, explosion, injury and/or property damage.
Through SGN’s H100 project the EFVs currently used on natural gas services were tested for suitability with hydrogen. The project identified that the higher flow rates of hydrogen caused the EFV to ‘trip’ erratically and therefor deemed them unsuitable.
Objectives
The objectives of his project are to:
· Develop a new Gas Industry Standard and specification for a hydrogen excess flow valve.
· Industry approval of the new standard
· Development of a prototype EFV that has been tested against the new standard and meets the criteria set out in the specification
· Final report outlining the outcomes of the tests
Learnings
Outcomes
A gap analysis exercise was undertaken of the natural gas excess flow valve industry standard: GIS/EFV1:2006. The different characteristics of hydrogen were noted and a new hydrogen specific standard was developed. The standard went through the IGEM approvals process and became an approved IGEM specification. IGEM/H/PRS/1
Prototype hydrogen EFVs were developed and tested against the performance criteria set out in IGEM/H/PRS/1. The results show that the requirements of schedule 3 to 6 of the new EFV test specification IGEM/H/PRS/1 were met by a combination of EFV sample configurations. No one sample configuration met all the test specification requirements. It is recommended, that at least one sample EFV for a given design is tested against all test specification requirements to assess whether any issues are encountered.
In addition to assessing the EFV design, this project also considered the suitability of the test specification, specifically the calculations relating to volumetric flow rate conversion for air and hydrogen. The air to hydrogen volumetric flow rate conversion methodology was found to be unsuitable for tests. Therefore, it has been recommended that at least one sample of each design is tested with air and hydrogen to assess whether any hydrogen specific issues are encountered e.g. flow past the sealing faces meaning that air would not be suitable as a surrogate test gas.
Lessons Learnt
It was discovered that a hydrogen EFV cannot be tested against the existing natural gas standard due to the difference in characteristics between natural gas and hydrogen. Such as, hydrogen velocities caused the EFV to trip at the flow rates set out in the natural gas standard.
Following the development of the hydrogen EFV standard, we demonstrated a flow limiting valve operating in low pressure hydrogen networks is feasible and can be designed to meet the performance criteria set out in the standard. Further lessons are discussed in the Outcomes section of the Closure Report.
