Learnings

Outcomes

SGN now have a recommendation for a plan to modify mechanical and electrical equipment used at offtake sites, for blends up to 20% hydrogen. 

The assessment and review of the sample sites was completed, and a site-specific blueprint design was produced 

This blueprint was delivered to be compliant with TD/13, externally appraised and approved in line with SGN’s PS/6 process, and based on a volume-controlled offtake site.  

When reviewing the equipment at both offtake sites, the following observations were made:

·         Although most valve manufacturers claim that their products are compatible with hydrogen operations, most of them do not currently hold complete lifetime maintenance records or the materials used. It would be advisable to replace these as they get to the end of their asset life. The current research in Europe shows there have been no failures of valve material with blends of up to 20% hydrogen and further research at NG’s FutureGrid facility will either support this or confirm the need to replace the valves.

·         It is advised that the combustion settings on boilers be adjusted, the CO2/O2 content of the combustion checked and brought in line to keep the required heat input (kW) to the appliance. Adjustments should also be made to account for the change in the Wobbe index. The HSE have recently amended the GSMR regulations to lower the emergency limit of Wobbe number to allow for a greater variety of gas resources such as biomethane and blends of hydrogen.

·         In terms of the gas chromatographs, it is recommended that care is taken to ensure they follow Ofgem’s guidance on requirements for new calibration gas mixtures, which will be review as part of the blending implementation. 

·         A number of files and equations that are used in the DANNIT software will need to be changed to include extra data points for hydrogen. Currently gas composition is not passed via telemetry. Some important gas properties such as calorific value and relative density are passed through to DNCC/GNCC and used for billing purposes. There may be a future requirement for hydrogen content to be passed via telemetry. This could be driven by certain customers requiring accurate knowledge of the hydrogen content of their gas (as may be the case in sensitive applications such as food, glass or steel manufacturing), or could come from network operational requirements. In these cases, only minimal changes to telemetry configurations would be required to transfer this data via the same route it currently follows. Any changes to the telemetry points will need to follow the SGN/PM/INE/3 Management Procedure for Selection of Telemetry Points to Operate the SGN Gas Supply System. 

·         Most offtakes either already have ultrasonic meters or are currently planned to be upgraded with ultrasonic meters. With current ultrasonic meters, when the concentration of hydrogen in natural gas changes, it would be necessary to recalibrate the meter to minimise bias from the change in performance due to the addition of hydrogen. In the future, it is expected that corrections will be automatically applied within the ultrasonic meter electronics based on a hydrogen input signal (similar to existing pressure and temperature corrections that are carried out within the ultrasonic meter electronics).

·         Site capacities will also be impacted, as the addition of hydrogen would reduce the calorific value by 1.4% for a 2% hydrogen blend and 14% for a 20% blend. This could mean that offtakes would have to increase their volumetric flow rate to achieve the same calorific value. This could affect offtake sites that are already running close to full capacity. 

·         A venting risk assessment will also be required on most sites. 

·         The pipework at each offtake site will need to be assessed for suitability, according to AIGA/ EIGA and other guidelines for material selection purposes. This is an area where there is ongoing research and evidence is required from large scale projects such as FutureGrid and LTS Futures. 

There is now a clear roadmap for all the necessary equipment calibrations and upgrades needed to make all their offtake sites safe to operate with blends of up to 20% hydrogen.

Lessons Learnt

There were a number of delays due to the limited number of hydrogen qualified engineers available.