Institution of Gas Engineers & Managers
Hydrogen in Multi-occupancy Buildings Feasibility Study - Final Report
Mar 2026
Publication
There is a requirement for gas distribution network (GDN) operators to understand the cost safety and practicality of converting network pipelines from Natural Gas to Hydrogen in multi-occupancy buildings (MOBs). Previous work undertaken during project ‘MOBs Work Pack 2 Asset Information Review’ considered the requirements for converting MOBs to Hydrogen and identified gaps in technical evidence. SGN is leading a feasibility project with some applied testing to address the evidence gaps identified.
This report summarises the work which has been undertaken as part of Work Pack 3 – QRA and Testing. This includes the development of Quantitative Risk Assessments (QRAs) for Hydrogen MOBs conversion and an overall impact review of the conversion of MOBs.
Work Pack 3 included the development of a Quantitative Risk Assessment (QRA) for Hydrogen MOBs conversion which should:
• Easily integrate with wider network QRAs (e.g. GB QRA) to help complete understanding of safety across the entire system
• Take account of the network and end user parts of the system in the building
• Provide a record of underlying evidential basis or where this is lacking the justified assumptions or simplifications made in reviewing existing evidential basis (e.g. can it be assumed that occupants will react to a Hydrogen leak in the same way as Natural Gas?)
• Provide a quantified assessment of risk either in the form of:
o Absolute risk
o Comparative risk
o ALARP (“as low as reasonably practicable”)
• Obtain agreement from HSE on conclusions of QRA.
Work Pack 3 also included a review of the overall impact of conversion of MOBs considering:
• The cost and practicality of converting the MOB stock
• The safety of Hydrogen in MOBs vs alternatives
• This study could draw on feasibility type studies – i.e. feasibility review of the conversion of a limited number of real MOBs
• Overall recommendation for the suitability of Hydrogen versus alternatives with potential split between different categories of building
• Further recommendations for transition NIA to SIF project:
o Trials
o Further confirmatory evidential work
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.
This report summarises the work which has been undertaken as part of Work Pack 3 – QRA and Testing. This includes the development of Quantitative Risk Assessments (QRAs) for Hydrogen MOBs conversion and an overall impact review of the conversion of MOBs.
Work Pack 3 included the development of a Quantitative Risk Assessment (QRA) for Hydrogen MOBs conversion which should:
• Easily integrate with wider network QRAs (e.g. GB QRA) to help complete understanding of safety across the entire system
• Take account of the network and end user parts of the system in the building
• Provide a record of underlying evidential basis or where this is lacking the justified assumptions or simplifications made in reviewing existing evidential basis (e.g. can it be assumed that occupants will react to a Hydrogen leak in the same way as Natural Gas?)
• Provide a quantified assessment of risk either in the form of:
o Absolute risk
o Comparative risk
o ALARP (“as low as reasonably practicable”)
• Obtain agreement from HSE on conclusions of QRA.
Work Pack 3 also included a review of the overall impact of conversion of MOBs considering:
• The cost and practicality of converting the MOB stock
• The safety of Hydrogen in MOBs vs alternatives
• This study could draw on feasibility type studies – i.e. feasibility review of the conversion of a limited number of real MOBs
• Overall recommendation for the suitability of Hydrogen versus alternatives with potential split between different categories of building
• Further recommendations for transition NIA to SIF project:
o Trials
o Further confirmatory evidential work
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.
SNG Safety Management Framework: Managament Procedure for Converting Natural Gas Installations in Multi-occupancy Buildings to Hydrogen
Mar 2026
Publication
This procedure details the process of how riser and lateral installations currently supplying Natural Gas to domestic accommodation within multi-occupancy buildings (MOBs) are selected and converted to Hydrogen or identified for decommissioning and the provision of an alternative option.
This procedure describes the requirements for conversion of existing Natural Gas installations in multi-occupancy buildings to Hydrogen operating at pressures not exceeding 75 mbar. For gas installations deemed unsuitable for conversion it provides guidance for decommissioning and alternative energy solutions. The gas supplied is assumed to be 100% Hydrogen as specified by IGEM/H/1 and therefore does not cover blends of Hydrogen and Natural Gas.
This procedure covers guidance for:
• The identification selection and commissioning of network risers and laterals installed in existing multi-storey buildings deemed suitable for repurposing to Hydrogen as they currently are.
• The requirements to identify buildings that are not suitable for repurposing in their current form and outlines the necessary replacement or partial replacement renovation alteration or repair of existing riser and lateral installations from the pipeline isolation valve (PIV) through to the supplier’s emergency control valve (ECV) to enable Hydrogen conversion.
Note: Where an existing Natural Gas installation is to be repurposed for Hydrogen it will have been subjected to a pre-conversion survey and risk assessment to ensure components are suitable for use or otherwise replaced.
• The identification isolation and decommissioning of network risers and laterals installed in existing multi-storey buildings not deemed suitable for conversion to Hydrogen.
• The provision of alternative arrangements in the form of an energy centre or an alternative option such as heat electrification heat pump or heat network.
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.
This procedure describes the requirements for conversion of existing Natural Gas installations in multi-occupancy buildings to Hydrogen operating at pressures not exceeding 75 mbar. For gas installations deemed unsuitable for conversion it provides guidance for decommissioning and alternative energy solutions. The gas supplied is assumed to be 100% Hydrogen as specified by IGEM/H/1 and therefore does not cover blends of Hydrogen and Natural Gas.
This procedure covers guidance for:
• The identification selection and commissioning of network risers and laterals installed in existing multi-storey buildings deemed suitable for repurposing to Hydrogen as they currently are.
• The requirements to identify buildings that are not suitable for repurposing in their current form and outlines the necessary replacement or partial replacement renovation alteration or repair of existing riser and lateral installations from the pipeline isolation valve (PIV) through to the supplier’s emergency control valve (ECV) to enable Hydrogen conversion.
Note: Where an existing Natural Gas installation is to be repurposed for Hydrogen it will have been subjected to a pre-conversion survey and risk assessment to ensure components are suitable for use or otherwise replaced.
• The identification isolation and decommissioning of network risers and laterals installed in existing multi-storey buildings not deemed suitable for conversion to Hydrogen.
• The provision of alternative arrangements in the form of an energy centre or an alternative option such as heat electrification heat pump or heat network.
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.
Draft Standard for Converting Natural Gas Installations in Multi-occupancy Buildings to Hydrogen
Mar 2026
Publication
This supplement gives additional requirements and qualifications for the conversion of Natural Gas installations in multi-occupancy buildings to Hydrogen and is only to be used in conjunction with IGEM/G/5 Edition 3. This supplement outlines the principles required for the conversion of existing Natural Gas installations in multi-occupancy buildings to 100% Hydrogen. A conversion to Hydrogen should consider the following options:
a) Repurposing existing installations
b) Renovating existing installations; this may involve for example an internal lining being applied to the existing network pipelines.
c) Replacing existing network pipelines with either:
a. New network pipelines or
b. An energy centre.
If following a risk assessment and cost benefit assessment none of the above options are considered suitable the remaining option would be to:
d) Decommission the existing gas installation and install a suitable alternative decarbonisation option (electrification heat pump heat network etc.).
This supplement covers the principles required for the repurposing renovating and replacement of existing gas installations for Hydrogen service and the decommissioning of existing gas installations.
This supplement provides the principles required to identify buildings and gas installations that are not suitable for repurposing and outlines remedial work that may be required prior to repurposing.
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.
a) Repurposing existing installations
b) Renovating existing installations; this may involve for example an internal lining being applied to the existing network pipelines.
c) Replacing existing network pipelines with either:
a. New network pipelines or
b. An energy centre.
If following a risk assessment and cost benefit assessment none of the above options are considered suitable the remaining option would be to:
d) Decommission the existing gas installation and install a suitable alternative decarbonisation option (electrification heat pump heat network etc.).
This supplement covers the principles required for the repurposing renovating and replacement of existing gas installations for Hydrogen service and the decommissioning of existing gas installations.
This supplement provides the principles required to identify buildings and gas installations that are not suitable for repurposing and outlines remedial work that may be required prior to repurposing.
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.
Inclusive Innovation: Safeguarding the Switch to Domestic Hydrogen
Mar 2026
Publication
The UK Government is exploring the possibility of switching some homes from natural gas to hydrogen to help the country reach net zero carbon emissions. Wales & West Utilities commissioned the Energy Systems Catapult to run a project to understand how to enable this transition to work well for vulnerable consumers if it is undertaken.
To do this the Energy Systems Catapult engaged with a series of industry experts and reviewed the available evidence. This helped to understand what a transition of domestic properties from natural gas to hydrogen is likely to entail for consumers and what steps should be considered to enable the transition to go well. Once the process was defined we then engaged with consumers in a variety of vulnerable situations to discuss any challenges the proposed process may present to them. In understanding these challenges the project then sought to further engage with both a range of experts and vulnerable consumers to co-create appropriate packages of support to preserve wellbeing during a transition to hydrogen.
The project was able to successfully map out the key consumer touch points during a transition and identify what demands could be placed on consumers. This enabled appropriate packages of support to be designed that should be considered when seeking to support affected residents during each of the following eventualities - that could occur during a transition to domestic hydrogen.
• Enabling a surveyor to access and conduct a survey at the property prior to the conversion
• What to do if an unsafe gas appliance is discovered during the property survey and must be disconnected until it can be repaired or replaced
• How best to capture important information about the personal circumstances of those who live in the home (e.g. health finances) to understand how best to support them during the conversion
• Occupant expectation if a gas appliance in the home is deemed incompatible with hydrogen so cannot be adapted and must be replaced
• What support is needed if an occupant does not have gas for cooking heating or hot water for a few days
• How best to navigate and safeguard residents if more complex works at required at the property e.g. upgrading the existing pipework
Many concerns were identified when discussing the different consumer touch points. These included issues with increased anxiety the impact of any disruption to important daily routines a range of potential cost implications for residents and the heightened risk of accident or injury due to a variety of impairments. For each consumer touch point three tiers of support were co-created in order to mitigate these issues. The lower tier being offered to everyone with the other tiers used for people with more specific needs. The support offered included the provision of temporary equipment help to access local community support involving 3rd parties to support consumers at certain points and in some instances the offer to take the occupant away from the property whilst the work is ongoing.
The project was further able to establish some of the challenges that may arise if seeking to deploy hydrogen on a larger scale across the UK as well as identifying several key factors that should be considered in parallel to the conversion to ensure it goes as smoothly as possible.
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.
To do this the Energy Systems Catapult engaged with a series of industry experts and reviewed the available evidence. This helped to understand what a transition of domestic properties from natural gas to hydrogen is likely to entail for consumers and what steps should be considered to enable the transition to go well. Once the process was defined we then engaged with consumers in a variety of vulnerable situations to discuss any challenges the proposed process may present to them. In understanding these challenges the project then sought to further engage with both a range of experts and vulnerable consumers to co-create appropriate packages of support to preserve wellbeing during a transition to hydrogen.
The project was able to successfully map out the key consumer touch points during a transition and identify what demands could be placed on consumers. This enabled appropriate packages of support to be designed that should be considered when seeking to support affected residents during each of the following eventualities - that could occur during a transition to domestic hydrogen.
• Enabling a surveyor to access and conduct a survey at the property prior to the conversion
• What to do if an unsafe gas appliance is discovered during the property survey and must be disconnected until it can be repaired or replaced
• How best to capture important information about the personal circumstances of those who live in the home (e.g. health finances) to understand how best to support them during the conversion
• Occupant expectation if a gas appliance in the home is deemed incompatible with hydrogen so cannot be adapted and must be replaced
• What support is needed if an occupant does not have gas for cooking heating or hot water for a few days
• How best to navigate and safeguard residents if more complex works at required at the property e.g. upgrading the existing pipework
Many concerns were identified when discussing the different consumer touch points. These included issues with increased anxiety the impact of any disruption to important daily routines a range of potential cost implications for residents and the heightened risk of accident or injury due to a variety of impairments. For each consumer touch point three tiers of support were co-created in order to mitigate these issues. The lower tier being offered to everyone with the other tiers used for people with more specific needs. The support offered included the provision of temporary equipment help to access local community support involving 3rd parties to support consumers at certain points and in some instances the offer to take the occupant away from the property whilst the work is ongoing.
The project was further able to establish some of the challenges that may arise if seeking to deploy hydrogen on a larger scale across the UK as well as identifying several key factors that should be considered in parallel to the conversion to ensure it goes as smoothly as possible.
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.
Kiwa Energy Hazardous Areas Report
Mar 2026
Publication
As part of the UK’s transition towards net zero carbon emissions by 2050 the possibility of using hydrogen to replace natural gas for heating domestic and small commercial properties is being investigated. One of the areas that needs to be considered is whether the conversion to hydrogen would bring about new issues regarding hazardous areas.
This report presents the results of a literature review which looks at the existing natural gas standards and hazardous area procedures. A comparison is then made to relevant work considering hydrogen including review of the IGEM SR/25 Hydrogen Supplement published by the HSE. Discussion and recommendations are made as to whether existing industry guidance continues to be suitable if the gas being used is hydrogen and not natural gas.
The focus of this work is on domestic and small commercial installations (e.g. single units with simple boiler and hot water installations) operating at gas pressures below 25 mbarg. It is important to note however that most available guidance and standards are for larger commercial environments. Although these are not directly applicable to domestic installations they have been considered as a reference point particularly for estimation of potential leak sizes.
Zoning of hazardous areas is not applicable in a domestic setting. However separation distances between electrical and gas installations within a domestic property are advised within BS 6891. Should a property be converted to hydrogen no changes are recommended to these distances. This is because in a low-pressure domestic situation fires do occasionally occur with copper pipe rubbing on electric cables but as both natural gas and hydrogen will ignite immediately the risk from the leak is essentially independent of the gas being carried. On many (probably most) occasions causing secondary fires. It is also advised that pliable meter connections should be wrapped to reduce the risk of fire from accidental electrical contact and this will be included within PAS4441.
Any workplace (including the small commercial properties discussed within) that has a natural gasinstallation and where explosive atmospheres may occur is required under DSEAR to classify hazardous andnon-hazardous areas within the facility. IGEM SR/25 and UP/16 are available to aid installers to complete hazardous area classification and design safe gas installations. It is recommended that UP/16 should be updated for hydrogen and this is currently underway (April 2023).
From experimental findings at low gas pressures it has been shown that the flammable zone for hydrogen in a vertical direction is 130% that of natural gas. However the values proposed within the SR/25 hydrogen supplement give flammable zones that are between 200% and 350% greater at low pressure. It may be that these are driven by an assumption that general deflagration can occur at the hydrogen published lower explosive limit (LEL) of 4%. In practice such deflagration does not occur below about 6% and does not propagate downwards until 8%. The implications of the move from wind driven ventilation (for natural gas) to buoyancy driven ventilation (for hydrogen) also needs thoroughly exploring. It could be argued (for low and medium pressure releases) that the ‘motive force’ provided by the low density of hydrogen is more reliable at clearing hydrogen concentrations than the wind-driven ventilation used for natural gas. In terms of general compliance with DSEAR acknowledgement should be made that Hy4Heat recommends the use of hydrogen detection and AIV’s in properties with a demand in excess of 20m3/h.
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.
This report presents the results of a literature review which looks at the existing natural gas standards and hazardous area procedures. A comparison is then made to relevant work considering hydrogen including review of the IGEM SR/25 Hydrogen Supplement published by the HSE. Discussion and recommendations are made as to whether existing industry guidance continues to be suitable if the gas being used is hydrogen and not natural gas.
The focus of this work is on domestic and small commercial installations (e.g. single units with simple boiler and hot water installations) operating at gas pressures below 25 mbarg. It is important to note however that most available guidance and standards are for larger commercial environments. Although these are not directly applicable to domestic installations they have been considered as a reference point particularly for estimation of potential leak sizes.
Zoning of hazardous areas is not applicable in a domestic setting. However separation distances between electrical and gas installations within a domestic property are advised within BS 6891. Should a property be converted to hydrogen no changes are recommended to these distances. This is because in a low-pressure domestic situation fires do occasionally occur with copper pipe rubbing on electric cables but as both natural gas and hydrogen will ignite immediately the risk from the leak is essentially independent of the gas being carried. On many (probably most) occasions causing secondary fires. It is also advised that pliable meter connections should be wrapped to reduce the risk of fire from accidental electrical contact and this will be included within PAS4441.
Any workplace (including the small commercial properties discussed within) that has a natural gasinstallation and where explosive atmospheres may occur is required under DSEAR to classify hazardous andnon-hazardous areas within the facility. IGEM SR/25 and UP/16 are available to aid installers to complete hazardous area classification and design safe gas installations. It is recommended that UP/16 should be updated for hydrogen and this is currently underway (April 2023).
From experimental findings at low gas pressures it has been shown that the flammable zone for hydrogen in a vertical direction is 130% that of natural gas. However the values proposed within the SR/25 hydrogen supplement give flammable zones that are between 200% and 350% greater at low pressure. It may be that these are driven by an assumption that general deflagration can occur at the hydrogen published lower explosive limit (LEL) of 4%. In practice such deflagration does not occur below about 6% and does not propagate downwards until 8%. The implications of the move from wind driven ventilation (for natural gas) to buoyancy driven ventilation (for hydrogen) also needs thoroughly exploring. It could be argued (for low and medium pressure releases) that the ‘motive force’ provided by the low density of hydrogen is more reliable at clearing hydrogen concentrations than the wind-driven ventilation used for natural gas. In terms of general compliance with DSEAR acknowledgement should be made that Hy4Heat recommends the use of hydrogen detection and AIV’s in properties with a demand in excess of 20m3/h.
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.
MOBs Phase 3: Task 10 - Pressure Testing
Mar 2026
Publication
There is a requirement for gas distribution network (GDN) operators to understand the cost safety and practicality of converting network pipelines from Natural Gas to Hydrogen in multi-occupancy buildings (MOBs). Previous work undertaken during project ‘MOBs Work Pack 2 Asset Information Review’ considered the requirements for pressure testing commissioning and decommissioning of MOBs following a conversion to Hydrogen and identified the following gap in technical evidence.
A desktop study and testing are required to confirm the applicability of test pressures test criteria and purge velocity with hydrogen to MOBs and the suitability of existing equipment for purging operation in MOBs. SGN is leading a feasibility project with some applied testing to understand the steps needed to convert MOBS to Hydrogen including any testing required to address any evidence gaps.
This report focuses on the pressure testing requirements associated with the conversion of MOBs from Natural Gas to Hydrogen. The purging aspects of evidence gap are being addressed by Steer Energy as part of a separate task. It was proposed that ROSEN review the gas leakage and dispersion modelling of pure Hydrogen undertaken as part of the H21 H100 HyDeploy and Hy4Heat projects to determine the maximum permitted leak rate / pass criterion for pressure testing of network pipelines intended for Hydrogen operation.
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.
A desktop study and testing are required to confirm the applicability of test pressures test criteria and purge velocity with hydrogen to MOBs and the suitability of existing equipment for purging operation in MOBs. SGN is leading a feasibility project with some applied testing to understand the steps needed to convert MOBS to Hydrogen including any testing required to address any evidence gaps.
This report focuses on the pressure testing requirements associated with the conversion of MOBs from Natural Gas to Hydrogen. The purging aspects of evidence gap are being addressed by Steer Energy as part of a separate task. It was proposed that ROSEN review the gas leakage and dispersion modelling of pure Hydrogen undertaken as part of the H21 H100 HyDeploy and Hy4Heat projects to determine the maximum permitted leak rate / pass criterion for pressure testing of network pipelines intended for Hydrogen operation.
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.
MOBs Phase 3: Task 7 - Combined Effect of Hydrogen and Thermal Loading on Material Integrity
Mar 2026
Publication
There is a requirement for gas distribution network (GDN) operators to understand the cost safety and practicality of converting network pipelines from Natural Gas to Hydrogen in multi-occupancy buildings (MOBs). SGN is leading a feasibility project with some applied testing to understand the steps needed to convert to Hydrogen. This report is part of Work Pack 3 and summarises Task 7: combined effect of hydrogen and thermal loading on material integrity.
The aim of this task is to fill the following evidence gaps identified in ROSEN report entitled ‘16357-1 Document Landscape Review Report Issue 1-0’:
♦ Validity of current diameter height lateral length and material limitations and permitted jointing methods.
♦ Susceptibility of low strength steel to hydrogen cracking when subjected to stresses resulting from expansion and contraction and effect of hydrogen on likelihood of failure of risers which do not have the required allowance for expansion and contraction.
♦ Applicability of existing thresholds including minimum permitted wall thickness before isolation and corrosion damage categories for pipe designed to operate at stress levels not greater than 40% SMYS with hydrogen.
Finite Element Analysis (FEA) has been performed to assess the performance of existing carbon steel gas riser configurations when subjected to thermal loading to understand the suitability of converting the existing pipework to hydrogen.
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.
The aim of this task is to fill the following evidence gaps identified in ROSEN report entitled ‘16357-1 Document Landscape Review Report Issue 1-0’:
♦ Validity of current diameter height lateral length and material limitations and permitted jointing methods.
♦ Susceptibility of low strength steel to hydrogen cracking when subjected to stresses resulting from expansion and contraction and effect of hydrogen on likelihood of failure of risers which do not have the required allowance for expansion and contraction.
♦ Applicability of existing thresholds including minimum permitted wall thickness before isolation and corrosion damage categories for pipe designed to operate at stress levels not greater than 40% SMYS with hydrogen.
Finite Element Analysis (FEA) has been performed to assess the performance of existing carbon steel gas riser configurations when subjected to thermal loading to understand the suitability of converting the existing pipework to hydrogen.
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.
MOBs Phase 3: Task 9 - Fire Protection Measures
Mar 2026
Publication
There is a requirement for gas distribution network (GDN) operators to understand the cost safety and practicality of converting network pipelines from Natural Gas (NG) to Hydrogen in multi-occupancy buildings (MOBs). SGN is leading a feasibility project with some applied testing to understand the steps needed to convert to Hydrogen.
This report is for work pack 3 Task 9: Fire Protection Measures. The objective of this task is to review the applicability of current requirements for fittings and components relating to the permissible leakage rate during and after a high temperature event where Hydrogen is the gas being distributed.
The objectives of this task are to:
• Confirm the applicability of the test temperature of 650°C (currently specified in BS EN 1775 Procedure B and which corresponds to the self-ignition temperature of a Natural Gas / air mixture) with Hydrogen self-ignition temperature.
• Confirm the applicability of the specified leakage rate of 150 dm3/h for pipework components during and after a test in accordance with the requirements of BS EN 1775 Procedure A.
• Confirm the applicability of the specified leakage rate of 150 dm3/h for pipework components following a resistance to high temperature test in accordance with the requirements of BS EN 1775 Procedure B.
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.
This report is for work pack 3 Task 9: Fire Protection Measures. The objective of this task is to review the applicability of current requirements for fittings and components relating to the permissible leakage rate during and after a high temperature event where Hydrogen is the gas being distributed.
The objectives of this task are to:
• Confirm the applicability of the test temperature of 650°C (currently specified in BS EN 1775 Procedure B and which corresponds to the self-ignition temperature of a Natural Gas / air mixture) with Hydrogen self-ignition temperature.
• Confirm the applicability of the specified leakage rate of 150 dm3/h for pipework components during and after a test in accordance with the requirements of BS EN 1775 Procedure A.
• Confirm the applicability of the specified leakage rate of 150 dm3/h for pipework components following a resistance to high temperature test in accordance with the requirements of BS EN 1775 Procedure B.
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.
MOBs Phase 3: Task 8 - Electrical Safety Report
Mar 2026
Publication
There is a requirement for gas distribution network (GDN) operators to understand the cost safety and practicality of converting network pipelines from natural gas to hydrogen in multi-occupancy buildings (MOBs). Previous work undertaken during project “MOBs Work Pack 2 Asset Information Review” [1] considered the requirements for domestic electrical safety in MOBs following a conversion to hydrogen and identified gaps in technical evidence.
SGN is leading a feasibility project with some applied testing to understand the steps needed to convert MOBS to Hydrogen. Task 8 relates to potential electrical safety requirements associated with the conversion of MOBs from natural gas to hydrogen. It was proposed that ROSEN review the projects “EUSE – Hazardous Areas Within Buildings” [2] and “ATEX Equipment & SR/25 Modification Assessment” [3] to confirm their applicability to MOBs. The objectives of this review are to:
1. Confirm whether the standards to which electrical equipment is currently specified relates to natural gas only or to any flammable gas
2. Determine whether requirements for electrical equipment are impacted by hydrogen being gas group IIC versus gas group IIA for natural gas
3. Investigate whether the existing separation distance between natural gas pipes/meter and electrical equipment remains the same with hydrogen.
ROSEN has reviewed the outputs from these research projects as well as relevant standards to determine electrical safety requirements for the conversion of MOBs from natural gas to hydrogen.
The review of standards and research projects undertaken has drawn the following conclusions in regards to electrical safety.
1. To comply with the requirements of DSEAR meter banks energy centres and common areas within MOBs must be risk assessed to determine the location and extent of explosive atmospheres and their classification once repurposed for use with hydrogen. The risk assessment includes hazardous area classification of the pipework and components.
2. For pure hydrogen the necessary air change rate per hour to allow classification as Zone 2 NE is increased from 0.5 (for natural gas) to 1.5 air changes per hour (ACH). Where this cannot be achieved uncertified electric lighting and other electrical equipment will need to be relocated or replaced with certified gas group IIC equipment.
3. There will be no requirement for a hazardous area classification for hydrogen in a domestic environment (individual dwellings) as DSEAR does not apply.
4. The minimum separation distances between electrical equipment and gas equipment are independent of the gas being transported and research projects have concluded that these do not need to change.
5. Lightning protection requirements are independent of the gas being transported and are in place to protect the pipe structure from damage and existing IGEM/G/5 guidance can remain unchanged.
6. Research indicates that most incidents relating to electrical safety are due to non-compliance with current standards.
7. Any electrical equipment located in the vicinity of gas installations should be assessed for compliance by a competent person prior to the conversion of MOBs to hydrogen.
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.
SGN is leading a feasibility project with some applied testing to understand the steps needed to convert MOBS to Hydrogen. Task 8 relates to potential electrical safety requirements associated with the conversion of MOBs from natural gas to hydrogen. It was proposed that ROSEN review the projects “EUSE – Hazardous Areas Within Buildings” [2] and “ATEX Equipment & SR/25 Modification Assessment” [3] to confirm their applicability to MOBs. The objectives of this review are to:
1. Confirm whether the standards to which electrical equipment is currently specified relates to natural gas only or to any flammable gas
2. Determine whether requirements for electrical equipment are impacted by hydrogen being gas group IIC versus gas group IIA for natural gas
3. Investigate whether the existing separation distance between natural gas pipes/meter and electrical equipment remains the same with hydrogen.
ROSEN has reviewed the outputs from these research projects as well as relevant standards to determine electrical safety requirements for the conversion of MOBs from natural gas to hydrogen.
The review of standards and research projects undertaken has drawn the following conclusions in regards to electrical safety.
1. To comply with the requirements of DSEAR meter banks energy centres and common areas within MOBs must be risk assessed to determine the location and extent of explosive atmospheres and their classification once repurposed for use with hydrogen. The risk assessment includes hazardous area classification of the pipework and components.
2. For pure hydrogen the necessary air change rate per hour to allow classification as Zone 2 NE is increased from 0.5 (for natural gas) to 1.5 air changes per hour (ACH). Where this cannot be achieved uncertified electric lighting and other electrical equipment will need to be relocated or replaced with certified gas group IIC equipment.
3. There will be no requirement for a hazardous area classification for hydrogen in a domestic environment (individual dwellings) as DSEAR does not apply.
4. The minimum separation distances between electrical equipment and gas equipment are independent of the gas being transported and research projects have concluded that these do not need to change.
5. Lightning protection requirements are independent of the gas being transported and are in place to protect the pipe structure from damage and existing IGEM/G/5 guidance can remain unchanged.
6. Research indicates that most incidents relating to electrical safety are due to non-compliance with current standards.
7. Any electrical equipment located in the vicinity of gas installations should be assessed for compliance by a competent person prior to the conversion of MOBs to hydrogen.
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.
Great Britain Distribution QRA Risk Predictions
Mar 2026
Publication
The natural gas distribution system has operated safely across Great Britain for around 50 years. It is an established means of supplying fuel for heating and cooking to residential dwellings and non-domestic buildings and is also used in some industrial processes. In order to meet environmental targets set by the UK Government multiple gas industry projects have been completed or are in progress to investigate the conversion of the existing natural gas system to carry hydrogen. This would make use of a valuable national asset and would help to meet carbon emissions targets.
As part of this programme of work across the gas industry DNV has carried out a Quantitative Risk Assessment (QRA) of the gas distribution system across Great Britain. Note that the ‘distribution system’ in this report covers a wider scope than the common meaning of the ‘distribution network’. Here the system includes the gas distribution network operating at up to 7 bar upstream of the Emergency Control Valve (ECV) and gas use within customer properties downstream of the ECV. The primary aim of the assessment is to quantify the risks posed by a repurposed hydrogen system and the benefits of risk mitigation measures where necessary. To put these results in context the risk associated with the equivalent natural gas distribution system is also quantified.
This report contains the results of the risk predictions. Separate reports gives details of the following:
• A DNV report describes the methodology reviews and modelling updates that were carried out as part of this QRA of the Great Britain distribution system.
• A DNV report describes a separate project carried out to investigate the risks associated with hydrogen use in Multi Occupancy Buildings (MOBs).
• A report produced by the Gas Distribution Networks (GDNs) evaluates each potential risk mitigation measure and justifies their adoption or rejection.
The risk predictions cover the Great Britain gas distribution system and end use within buildings for heating and cooking. The study does not consider hydrogen production or storage gas transmission at pressures above 7 bar industrial use of gas or vehicle refuelling stations.
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.
As part of this programme of work across the gas industry DNV has carried out a Quantitative Risk Assessment (QRA) of the gas distribution system across Great Britain. Note that the ‘distribution system’ in this report covers a wider scope than the common meaning of the ‘distribution network’. Here the system includes the gas distribution network operating at up to 7 bar upstream of the Emergency Control Valve (ECV) and gas use within customer properties downstream of the ECV. The primary aim of the assessment is to quantify the risks posed by a repurposed hydrogen system and the benefits of risk mitigation measures where necessary. To put these results in context the risk associated with the equivalent natural gas distribution system is also quantified.
This report contains the results of the risk predictions. Separate reports gives details of the following:
• A DNV report describes the methodology reviews and modelling updates that were carried out as part of this QRA of the Great Britain distribution system.
• A DNV report describes a separate project carried out to investigate the risks associated with hydrogen use in Multi Occupancy Buildings (MOBs).
• A report produced by the Gas Distribution Networks (GDNs) evaluates each potential risk mitigation measure and justifies their adoption or rejection.
The risk predictions cover the Great Britain gas distribution system and end use within buildings for heating and cooking. The study does not consider hydrogen production or storage gas transmission at pressures above 7 bar industrial use of gas or vehicle refuelling stations.
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.
Great Britain Distribution QRA Methodology Updates in CONIFER
Mar 2026
Publication
The natural gas distribution system has operated safely across Great Britain for around 50 years. It is an established means of supplying fuel for heating and cooking to residential dwellings and non-domestic buildings and is also used in some industrial processes. In order to meet environmental targets set by the UK Government multiple gas industry projects have been completed or are in progress to investigate the conversion of the existing natural gas system to carry hydrogen. This would make use of a valuable national asset and would help to meet carbon emissions targets.
As part of this programme of work across the gas industry DNV has carried out a Quantitative Risk Assessment (QRA) of the gas distribution system across Great Britain. Note that the ‘distribution system’ in this report covers a wider scope than the common meaning of the ‘distribution network’. Here the system includes the gas distribution network upstream of the Emergency Control Valve (ECV) and gas use within customer properties downstream of the ECV. The primary aim of the assessment is to quantify the risks posed by a repurposed hydrogen system and the benefits of risk mitigation measures where necessary. To put these results in context the risk associated with the equivalent natural gas distribution system is also quantified.
This work has been carried out in partnership with Cadent Northern Gas Networks and SGN. Additional information has been supplied by Wales and West Utilities and several of the Independent Gas Transporters thereby covering almost all the Great Britain distribution system.
This report contains the details of methodology reviews and modelling updates that were carried out as part of the Great Britain distribution system QRA. A separate report details the risk predictions. The updates include some made in response to review by the Evidence Review Group within the HSE and some that take make use of outputs from other gas industry projects. Major updates made as part of this work include:
• Introduction of non-domestic buildings and Multi Occupancy Buildings (MOBs) into the risk predictions. This report is primarily concerned with defining their characteristics and modifying the risk assessment models to represent their features that are not found in houses.
• Updates to the failure frequencies applied to all parts of the system from governor kiosks through the distribution network to end use.
• Modifications to the model that predicts gas movement through the ground following a leak from a main or service.
• Changes to the methodology used to predict gas dispersion movement and accumulation within a building.
• Updates to the treatment of gas explosions inside buildings.
• Several other minor changes and investigations into the sensitivity of various inputs.
This report also contains the risk calculation methodology for governors and benchmarking of the risk predictions against natural gas operational experience.
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.
As part of this programme of work across the gas industry DNV has carried out a Quantitative Risk Assessment (QRA) of the gas distribution system across Great Britain. Note that the ‘distribution system’ in this report covers a wider scope than the common meaning of the ‘distribution network’. Here the system includes the gas distribution network upstream of the Emergency Control Valve (ECV) and gas use within customer properties downstream of the ECV. The primary aim of the assessment is to quantify the risks posed by a repurposed hydrogen system and the benefits of risk mitigation measures where necessary. To put these results in context the risk associated with the equivalent natural gas distribution system is also quantified.
This work has been carried out in partnership with Cadent Northern Gas Networks and SGN. Additional information has been supplied by Wales and West Utilities and several of the Independent Gas Transporters thereby covering almost all the Great Britain distribution system.
This report contains the details of methodology reviews and modelling updates that were carried out as part of the Great Britain distribution system QRA. A separate report details the risk predictions. The updates include some made in response to review by the Evidence Review Group within the HSE and some that take make use of outputs from other gas industry projects. Major updates made as part of this work include:
• Introduction of non-domestic buildings and Multi Occupancy Buildings (MOBs) into the risk predictions. This report is primarily concerned with defining their characteristics and modifying the risk assessment models to represent their features that are not found in houses.
• Updates to the failure frequencies applied to all parts of the system from governor kiosks through the distribution network to end use.
• Modifications to the model that predicts gas movement through the ground following a leak from a main or service.
• Changes to the methodology used to predict gas dispersion movement and accumulation within a building.
• Updates to the treatment of gas explosions inside buildings.
• Several other minor changes and investigations into the sensitivity of various inputs.
This report also contains the risk calculation methodology for governors and benchmarking of the risk predictions against natural gas operational experience.
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.
H21 Phase 2: Ignition Considerations for Network Procedures
Mar 2026
Publication
The objective of the H21 programme is to reach the point whereby it is feasible to convert the existing natural gas (NG) distribution network to 100% hydrogen (H₂) and provide a contribution to decarbonising GB’s heat and power sectors with the focus on decarbonised fuel at point of use. This report is one of a series of reports that look to address the work areas previously identified following a review of network procedures. It looks at the difference between the ignition sensitivities of natural gas and hydrogen primarily regarding electrostatics and friction and how they impact on network procedures. Equipment currently used by NGN was reviewed for its suitability for use with hydrogen. A number of further precautions have been identified for hydrogen and the main findings are summarised below.
Ignition topics that should not require alteration with hydrogen.
The LEL based criteria (20% LEL for the use of non-ATEX equipment when deciding upon evacuation and other safety precautions 70% LEL for switching off electrics under emergency conditions and 5% LEL and falling for reoccupation of buildings) remain fit for purpose with hydrogen; however these do require accurate hydrogen gas detection. Damp rag earthing of PE pipe was demonstrated experimentally to be effective in preventing electrostatic discharges and is suitable for use with hydrogen. Protection against electrostatic discharges extends 10 cm beyond the damp rag. The continuity bonds used for natural gas remain fit for use with hydrogen. The cathodic protection remains suitable for hydrogen from an electrostatics point of view although the location of impressed current cathodic protection (ICCP) systems should be in Zone 2 NE (Negligible Extent) areas. There is little change in the risk of pyrophoric ignition and electrostatic discharge remains the greatest ignition risk with “black dust”.
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.
Ignition topics that should not require alteration with hydrogen.
The LEL based criteria (20% LEL for the use of non-ATEX equipment when deciding upon evacuation and other safety precautions 70% LEL for switching off electrics under emergency conditions and 5% LEL and falling for reoccupation of buildings) remain fit for purpose with hydrogen; however these do require accurate hydrogen gas detection. Damp rag earthing of PE pipe was demonstrated experimentally to be effective in preventing electrostatic discharges and is suitable for use with hydrogen. Protection against electrostatic discharges extends 10 cm beyond the damp rag. The continuity bonds used for natural gas remain fit for use with hydrogen. The cathodic protection remains suitable for hydrogen from an electrostatics point of view although the location of impressed current cathodic protection (ICCP) systems should be in Zone 2 NE (Negligible Extent) areas. There is little change in the risk of pyrophoric ignition and electrostatic discharge remains the greatest ignition risk with “black dust”.
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.
H21 Phase 2A: Finding and Accessing Leaks
Mar 2026
Publication
In line with the UK government’s de-carbonisation strategy Northern Gas Network’s (NGN) H21 project aims to demonstrate the feasibility of converting the existing <7barg gas distribution network to 100% hydrogen. After conversion of the gas networks hydrogen is transported from various sources through new and existing gas networks to industrial and domestic customers.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network components and operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. Firstly a review of all NGN operating procedures was conducted by HSE Science and Research Centre (HSE S\&RC). From this review various recommendations for changes to some procedures were made for their application to a hydrogen network. Of these proposed changes some required more investigation and demonstration. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network parameters and typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE R\&SC and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current report details the work conducted in the H21 testing facility WBS5 downstream of the H21 demonstration facility herein referred to as the “Microgrid” in relation to finding and accessing buried leaks. The programme included consequence tests where live leaks and pockets of gas under various ground surfaces were ignited manned live leak finding operations (barholing/rockdrilling) and accessing leaks on gas saturated ground locations over an isolated section of leaking pipe.
This report details the experimental set-up instrumentation (if any) and test procedure used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5. Appendixes at the back of the document contain photographs diagrams and further details for each test.
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.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network components and operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. Firstly a review of all NGN operating procedures was conducted by HSE Science and Research Centre (HSE S\&RC). From this review various recommendations for changes to some procedures were made for their application to a hydrogen network. Of these proposed changes some required more investigation and demonstration. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network parameters and typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE R\&SC and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current report details the work conducted in the H21 testing facility WBS5 downstream of the H21 demonstration facility herein referred to as the “Microgrid” in relation to finding and accessing buried leaks. The programme included consequence tests where live leaks and pockets of gas under various ground surfaces were ignited manned live leak finding operations (barholing/rockdrilling) and accessing leaks on gas saturated ground locations over an isolated section of leaking pipe.
This report details the experimental set-up instrumentation (if any) and test procedure used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5. Appendixes at the back of the document contain photographs diagrams and further details for each test.
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.
H21 Phase 2B: Planned Live Gas Operations
Mar 2026
Publication
In line with the UK government’s de-carbonisation strategy Northern Gas Network’s (NGN) H21 project aims to demonstrate the feasibility of converting the existing <7barg gas distribution network to 100% hydrogen. Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2b evaluates network operational procedures in use with 100% hydrogen. Conducted on a repurposed part of the natural gas distribution network and identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration facility centred around an existing part of the gas network was built at South Bank Middlesbrough to accommodate operations within low pressure network parameters and typical network components. A Master Test Plan (MTP) for Phase 2 was subsequently developed by NGN in collaboration with the HSE and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding Leaks
♦ Accessing Leaks
♦ Assessment of repair techniques
♦ Planned live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each practical test was derived from one of the above subcategories within the master test plan. This report details the work conducted within the Planned Live Gas Operation remit completed at the NGN H21 testing facility at South Bank. The programme included eight live gas operations undertaken on the buried hydrogen low pressure network within the South Bank test facility the network contained both metallic and PE mains with different diameters throughout the grid. This allowed operations to be undertaken in conditions mirroring real life as they would be completed out on the network. The objective of these experiments is to prove routine operations that are undertaken on a day-to-day basis on the NG distribution network can be completed on 100% hydrogen networks. This report details the experimental set-up operation procedures and method statements used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5.
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.
♦ Emergency Response and bad practice demonstrations
♦ Finding Leaks
♦ Accessing Leaks
♦ Assessment of repair techniques
♦ Planned live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each practical test was derived from one of the above subcategories within the master test plan. This report details the work conducted within the Planned Live Gas Operation remit completed at the NGN H21 testing facility at South Bank. The programme included eight live gas operations undertaken on the buried hydrogen low pressure network within the South Bank test facility the network contained both metallic and PE mains with different diameters throughout the grid. This allowed operations to be undertaken in conditions mirroring real life as they would be completed out on the network. The objective of these experiments is to prove routine operations that are undertaken on a day-to-day basis on the NG distribution network can be completed on 100% hydrogen networks. This report details the experimental set-up operation procedures and method statements used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5.
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.
H21 Phase 2B T&M: Isolation
Mar 2026
Publication
In line with the UK government’s de-carbonisation strategy Northern Gas Network’s (NGN) H21 project aims to demonstrate the feasibility of converting the existing <7 barg gas distribution network to 100% hydrogen. After conversion of the gas networks hydrogen is transported from various sources through new and existing gas networks to industrial and domestic customers. Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2b evaluates network operational procedures conducted on a repurposed natural gas network. Identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration facility was built at South Bank Middlesbrough to accommodate low pressure network parameters and typical network components. A Master Test Plan (MTP) for Phase 2 was subsequently developed by NGN in collaboration with the HSE and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding Leaks
♦ Accessing Leaks
♦ Assessment of repair techniques
♦ Planned live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each practical test was derived from one of the above subcategories within the master test plan. This report details the work conducted within the Isolation Operations remit completed at the NGN H21 testing facility at South Bank. The programme included four isolation operations utilising different isolation techniques and was undertaken on the buried hydrogen low pressure network within the South Bank test facility. The network contained both metallic and PE mains with different diameters throughout the grid. This allowed operations to be undertaken in conditions mirroring real life as they would be completed out on the network. The objective of these experiments is to prove routine operations that are undertaken on a day-to-day basis on the NG distribution network can be completed on 100% hydrogen networks. This report details the experimental set-up isolation procedure and method statement used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5. Appendixes at the back of the document contain photographs diagrams and further details for each test.
♦ Emergency Response and bad practice demonstrations
♦ Finding Leaks
♦ Accessing Leaks
♦ Assessment of repair techniques
♦ Planned live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each practical test was derived from one of the above subcategories within the master test plan. This report details the work conducted within the Isolation Operations remit completed at the NGN H21 testing facility at South Bank. The programme included four isolation operations utilising different isolation techniques and was undertaken on the buried hydrogen low pressure network within the South Bank test facility. The network contained both metallic and PE mains with different diameters throughout the grid. This allowed operations to be undertaken in conditions mirroring real life as they would be completed out on the network. The objective of these experiments is to prove routine operations that are undertaken on a day-to-day basis on the NG distribution network can be completed on 100% hydrogen networks. This report details the experimental set-up isolation procedure and method statement used in Section 3; the results and main observations in Section 4 followed by interpretation of results and conclusions in Section 5. Appendixes at the back of the document contain photographs diagrams and further details for each test.
H21 Phase 2A Testing - Part A: Planned Live Gas Operations and Isolation Techniques
Mar 2026
Publication
In line with the UK government’s de-carbonisation strategy Northern Gas Network’s (NGN) H21 project aims to demonstrate the feasibility of converting the existing <7barg gas distribution network to 100% hydrogen. After conversion of the gas networks hydrogen could be transported from various sources through new and existing gas networks to industrial and domestic customers.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Development to accommodate full scale network parameters including typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE Science and Research Centre (HSE S\&RC) and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities (i.e. purging)
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current report details the work conducted on the H21 demonstration grid herein referred to as “Microgrid” in relation to planned live gas operations and isolation techniques. The programme included assessing the effectiveness of existing flow stopping techniques by measurement of the let-by rate downstream of the flow stopping device. The flow stopping techniques demonstrated included: a metallic stopple squeeze off ALH bag off and an MLS bag off. These techniques were performed by third parties according to Method Statements and Risk Assessments modified for the application to hydrogen. Principally the outcome of the Procedural Review conducted by HSE S\&RC1 was that flammable atmospheres within and around the tools pipework and vents as currently operated could not be tolerated as for hydrogen operations. As such the techniques were all conducted with the introduction of nitrogen inerting steps to avoid hydrogen and air mixing within any confined geometries.
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.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Development to accommodate full scale network parameters including typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE Science and Research Centre (HSE S\&RC) and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities (i.e. purging)
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current report details the work conducted on the H21 demonstration grid herein referred to as “Microgrid” in relation to planned live gas operations and isolation techniques. The programme included assessing the effectiveness of existing flow stopping techniques by measurement of the let-by rate downstream of the flow stopping device. The flow stopping techniques demonstrated included: a metallic stopple squeeze off ALH bag off and an MLS bag off. These techniques were performed by third parties according to Method Statements and Risk Assessments modified for the application to hydrogen. Principally the outcome of the Procedural Review conducted by HSE S\&RC1 was that flammable atmospheres within and around the tools pipework and vents as currently operated could not be tolerated as for hydrogen operations. As such the techniques were all conducted with the introduction of nitrogen inerting steps to avoid hydrogen and air mixing within any confined geometries.
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.
H21 Phase 2: Assessment of Repair Techniques
Mar 2026
Publication
In line with the UK government’s de-carbonisation strategy Northern Gas Network’s (NGN) H21 project aims to enable the conversion of the UK gas networks to pure hydrogen. After conversion of the gas networks hydrogen is transported from various sources through new and existing gas networks to industrial and domestic customers.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network components and procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network parameters and typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current technical note details the work conducted in the H21 demonstration grid herein referred to as “Microgrid” in relation to assessment of repair techniques. Six used cast iron (CI) spun iron (SI) and steel (ST) assets purposedly made to present leaks or leak paths were repaired using six commonly used techniques in the current natural gas network including: muffed encapsulation anaerobic repair two-part joint injection polyform repair clamp repair and heat shrink repair. The repairs were then leak checked with nitrogen buried and connected to the H21 microgrid and commissioned with hydrogen. Weekly over the course of five months whilst the rest of the testing programme was being carried out the assets were individually isolated and checked for re-appearance of leakage over time and under service conditions by means of pressure decay tests.
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.
Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2a evaluates network components and procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network parameters and typical network components. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the HSE and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding leaks
♦ Accessing leaks
♦ Assessment of repair techniques
♦ Live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each of these areas of testing and assessments were then divided in individual tests or tasks and identified with a unique ID name.
The current technical note details the work conducted in the H21 demonstration grid herein referred to as “Microgrid” in relation to assessment of repair techniques. Six used cast iron (CI) spun iron (SI) and steel (ST) assets purposedly made to present leaks or leak paths were repaired using six commonly used techniques in the current natural gas network including: muffed encapsulation anaerobic repair two-part joint injection polyform repair clamp repair and heat shrink repair. The repairs were then leak checked with nitrogen buried and connected to the H21 microgrid and commissioned with hydrogen. Weekly over the course of five months whilst the rest of the testing programme was being carried out the assets were individually isolated and checked for re-appearance of leakage over time and under service conditions by means of pressure decay tests.
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.
H21 Phase 2B: Finding and Accessing Leaks
Mar 2026
Publication
In line with the UK government's de-carbonisation strategy Northern Gas Network's (NGN) H21 project aims to demonstrate the feasibility of converting the existing GB gas distribution network to 100% hydrogen. Following progress on Phase 1 of the H21 programme Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB distribution networks to transport 100% hydrogen.
Phase 2 consisted of several project phases which evaluated operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve Phase 2a aims a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network OPERATIONS and typical network components. Phase 2b continued from Phase 2a with demonstrations undertaken in a public setting. A section of existing NGN gas distribution network was adopted and developed utilising existing buried ductile iron gas mains which once served now demolished terrace housing. These mains were interconnected by installing new 180mm PE pipe sections at South Bank Middlesbrough. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the Health & Safety Executives Science & Research Centre (HSE S\&RC) and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations (ER)
♦ Finding leaks (FL)
♦ Accessing leaks (AL)
♦ Assessment of repair techniques (R)
♦ Planned live gas operations (LG)
♦ Isolation techniques (IS)
♦ Commissioning and decommissioning activities (PU)
♦ Pressure regulation and maintenance procedures (MA)
♦ Pressure and flow validation modelling (MO)
This report details the work conducted in relation to the finding (FL) and accessing leaks (AL) tasks within Phase 2b of the MTP. The NGN procedures reviewed and demonstrated being EM72 and EM74 respectively. The programme included manned operational demonstrations of leak finding operations (bar holing/rock drilling) prior to accessing leaks operations (using various excavation techniques) on hydrogen gas-saturated ground locations near to live leaks. In a change to current natural gas procedures; the initial excavations were conducted away from the live leak location following recommendation from the HSE S\&RC's procedural review conducted during H21 Phase 2a¹. The recommendation is such that no work should be conducted in flammable atmospheres on hydrogen distribution networks where the potential for ignition is unknown and likely greater than that of natural gas. After completion of various finding leaks operations and exploratory excavations around the live leaks had been carried out excavations directly onto the leak were carried out in the gas-saturated ground after remote isolation of the buried pipework.
All testing was conducted at Middlesbrough Test Site (MTS) South Bank Middlesbrough TS6 6LF which was constructed specifically for the H21 Phase 2B program.
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.
Phase 2 consisted of several project phases which evaluated operational procedures identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve Phase 2a aims a gas demonstration network was built at DNV Spadeadam Research and Testing to accommodate full scale network OPERATIONS and typical network components. Phase 2b continued from Phase 2a with demonstrations undertaken in a public setting. A section of existing NGN gas distribution network was adopted and developed utilising existing buried ductile iron gas mains which once served now demolished terrace housing. These mains were interconnected by installing new 180mm PE pipe sections at South Bank Middlesbrough. A Master Test Plan (MTP) was subsequently developed by NGN in collaboration with the Health & Safety Executives Science & Research Centre (HSE S\&RC) and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations (ER)
♦ Finding leaks (FL)
♦ Accessing leaks (AL)
♦ Assessment of repair techniques (R)
♦ Planned live gas operations (LG)
♦ Isolation techniques (IS)
♦ Commissioning and decommissioning activities (PU)
♦ Pressure regulation and maintenance procedures (MA)
♦ Pressure and flow validation modelling (MO)
This report details the work conducted in relation to the finding (FL) and accessing leaks (AL) tasks within Phase 2b of the MTP. The NGN procedures reviewed and demonstrated being EM72 and EM74 respectively. The programme included manned operational demonstrations of leak finding operations (bar holing/rock drilling) prior to accessing leaks operations (using various excavation techniques) on hydrogen gas-saturated ground locations near to live leaks. In a change to current natural gas procedures; the initial excavations were conducted away from the live leak location following recommendation from the HSE S\&RC's procedural review conducted during H21 Phase 2a¹. The recommendation is such that no work should be conducted in flammable atmospheres on hydrogen distribution networks where the potential for ignition is unknown and likely greater than that of natural gas. After completion of various finding leaks operations and exploratory excavations around the live leaks had been carried out excavations directly onto the leak were carried out in the gas-saturated ground after remote isolation of the buried pipework.
All testing was conducted at Middlesbrough Test Site (MTS) South Bank Middlesbrough TS6 6LF which was constructed specifically for the H21 Phase 2B program.
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.
HyNTS Pipeline Dataset SIF Project Discovery Phase: Final Report
Mar 2026
Publication
Rosen,
Cadent and
National Grid
HyNTS is a programme of work that seeks to identify the opportunities and address the challenges that transporting hydrogen within the National Transmission System (NTS) and Local Transmission System (LTS) presents. This will unlock the potential of hydrogen to deliver the UK’s 2050 Net Zero targets. The programme is being executed alongside other ongoing UK hydrogen initiatives such as National Grids Project Union and Cadent’s HyNet projects.
A key element of repurposing feasibility and therefore central to the overall HyNTS initiative is the requirement to have an improved understanding of the ‘fingerprint’ of pipeline assets prior to hydrogen injection. The Pipeline Dataset SIF project has two primary objectives:
♦ Defining and gathering the data necessary to ultimately facilitate repurposing of above 7 bar pipelines on the NTS and LTS
♦ Developing the tools and processes to store align and visualise data
Split into 3 phases the first ‘Discovery’ phase aims to develop the high-level data and data management requirements for repurposing as well as the current data availability across the NTS and LTS to meet these requirements. Subsequent Alpha and Beta phases involve detailed planning and subsequent execution of the data collection and data management activities identified in the Discovery phase.
The Discovery phase comprises four Workpacks as shown in the diagram below designed to cover the project objectives.
ROSEN and Cadent have partnered with National Grid (NGG) to deliver the Discovery phase. Close collaboration between NGG Cadent and ROSEN has been required to conduct all Workpacks particularly in terms of appraising the current data held and current Data Management arrangements within both organisations.
This report presents the findings from the Discovery Phase as well as providing recommendations to feed into shaping subsequent Alpha and Beta phase activities.
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.
A key element of repurposing feasibility and therefore central to the overall HyNTS initiative is the requirement to have an improved understanding of the ‘fingerprint’ of pipeline assets prior to hydrogen injection. The Pipeline Dataset SIF project has two primary objectives:
♦ Defining and gathering the data necessary to ultimately facilitate repurposing of above 7 bar pipelines on the NTS and LTS
♦ Developing the tools and processes to store align and visualise data
Split into 3 phases the first ‘Discovery’ phase aims to develop the high-level data and data management requirements for repurposing as well as the current data availability across the NTS and LTS to meet these requirements. Subsequent Alpha and Beta phases involve detailed planning and subsequent execution of the data collection and data management activities identified in the Discovery phase.
The Discovery phase comprises four Workpacks as shown in the diagram below designed to cover the project objectives.
ROSEN and Cadent have partnered with National Grid (NGG) to deliver the Discovery phase. Close collaboration between NGG Cadent and ROSEN has been required to conduct all Workpacks particularly in terms of appraising the current data held and current Data Management arrangements within both organisations.
This report presents the findings from the Discovery Phase as well as providing recommendations to feed into shaping subsequent Alpha and Beta phase activities.
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.
FutureGrid Phase 1: Facility, Closure Report
Mar 2026
Publication
The National Transmission System (NTS) is a cornerstone of the Great Britain’s (GB) energy infrastructure transporting over 800 TWh of energy annually across 5000 miles of pipelines in the UK.
This system provides GB with a significant opportunity to decarbonise various industries by transporting low-carbon gases such as hydrogen biomethane and various synthetic fuels. Transitioning this system would also pave the way for industrial emitters to decarbonise either through fuel switching or transporting carbon dioxide to potential storage sites around the United Kingdom (UK). Recognising the imperative to transition to a low-carbon future the FutureGrid project sought to explore the feasibility of repurposing the NTS to transport hydrogen. This project an essential part of the National Gas HyNTS programme endeavours to align the NTS with GB’s net zero ambitions by demonstrating the operational viability of the system with varying hydrogen blends using decommissioned assets typical of the natural gas network today ultimately aiming for 100% hydrogen conveyance.
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.
This system provides GB with a significant opportunity to decarbonise various industries by transporting low-carbon gases such as hydrogen biomethane and various synthetic fuels. Transitioning this system would also pave the way for industrial emitters to decarbonise either through fuel switching or transporting carbon dioxide to potential storage sites around the United Kingdom (UK). Recognising the imperative to transition to a low-carbon future the FutureGrid project sought to explore the feasibility of repurposing the NTS to transport hydrogen. This project an essential part of the National Gas HyNTS programme endeavours to align the NTS with GB’s net zero ambitions by demonstrating the operational viability of the system with varying hydrogen blends using decommissioned assets typical of the natural gas network today ultimately aiming for 100% hydrogen conveyance.
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.
Inhibition of Hydrogen Embrittlement Effects in Pipeline Steel - Technical Report
Mar 2026
Publication
Rosen and
National Gas
National Gas has identified the need to understand the effects of hydrogen on various pipeline materials commonly found in the UK National Transmission System (NTS) to determine their potential for a hydrogen use case. Accordingly National Gas is interested in investigating the potential use of oxygen as a mitigation of hydrogen embrittlement (HE) the detrimental effect of hydrogen on the mechanical properties of metallic materials. This report presents the laboratory findings part of the project “Inhibition of hydrogen embrittlement effects in pipeline steels” in which ROSEN has been requested to investigate the potential use of oxygen as a mitigation of hydrogen effects.<br/>Three pipe materials were investigated which included a ERW X52 commissioned in 1993 a DSAW X60 commissioned in 1973 and a DSAW X80 constructed in 2004. The test programme aimed to characterise the effectiveness of oxygen on mitigating hydrogen embrittlement and included an in-air baseline characterisation and three main hydrogen tests: threshold stress intensity factor KIH fracture toughness and two types of fatigue crack growth rate tests (frequency scans and Paris curve). Fracture toughness and fatigue crack growth rate tests were performed in pure hydrogen and at various oxygen concentrations ranging from 50 to 1000 ppm.<br/>The baseline in-air characterisation showed that some of the mechanical properties of the X52 and X60 were below the T/SP/PIP/1 requirements. For the X52 the yield strength of transverse parent material specimens was below the 360 MPa required by its designation. For the X60 both the longitudinal and transverse yield strength of the parent material were below the 415 MPa required for this grade. Furthermore CVN energies were also below the T/SP/PIP/1 requirements for parent metal and seam weld metal for the X60 pipe. The X80 was within specifications.<br/>Threshold stress intensity factor KIH tests were performed on the three investigated materials on base and weld metal in pure hydrogen. Crack extension was not seen in any of these tests for the applied stress intensity factors as high as 73 MPa√m. The absence of crack growth was verified by means of SEM examination which showed the direct transition from the fatigue pre-crack region to the final fracture region. For this reason KIH tests with oxygen additions were not conducted.<br/>Fracture toughness testing showed that the fracture resistance was reduced when testing in pure hydrogen. This was seen in X60 specimens that had a fracture resistance JQ of 31 kJ/m2 35% of that in air. The addition of oxygen resulted in an increase of the average JQ which at 250 ppm O2 was 85% of the in air value. At concentrations above this value the fracture resistance continued to approach in-air values although at a decreased rate. Increasing the oxygen concentration also resulted in smaller standard deviations of the fracture resistance decreasing from 13 to 2 kJ/m2 as the O2 concentration was increased from 50 to 500 ppm. These findings indicate there is a smaller variability of the performance when oxygen is added. The recovery of the fracture resistance was consistent with the SEM examination of fracture surfaces of tested specimens. In pure hydrogen fracture surfaces were consistent with a quasi-cleavage fracture characterised by planar facets with visible river marks. As oxygen was increased the fracture surface became more dimpled and areas with signs of plastic strain became evident. At concentrations of 250 ppm O2 the fracture surface resembled those obtained in air suggesting the same ductile failure mode. Obtaining quantitative fracture toughness data for the X52 and X80 specimens in oxygen additions was not possible due to material related challenges. However fractographic examination showed that in pure hydrogen and low oxygen concentrations e.g. 50 ppm the failure mode was predominantly brittle while at 250 ppm O2 and in air the failure mode was ductile and was accompanied of limited crack growth.<br/>The inhibiting effects of oxygen were also seen in fatigue crack growth rate tests. Frequency scan tests on X60 showed that the exposure to hydrogen resulted in high crack growth rates up to 2 orders of magnitude above the BS7910 in-air mean depending on the testing conditions. Crack growth rates were affected by the choice of the frequency. For the test performed with a Kmax of 45 ksi√in (49 MPa√m) crack growth rates continued to increase above 1 mm/cycle as the frequency was reduced to 1E-4 Hz. For the test performed with a Kmax of 38 ksi√in (42 MPa√m) crack growth rates reached a plateau at a frequency of 0.1 Hz. The additions of oxygen resulted in a reduction of crack growth to values a few times above the BS7910 in-air mean. Furthermore the effect of frequency was visibly reduced in 250 ppm O2 as reducing the frequency 40000 times resulted only in a 2 times increase of the crack growth rates. The effect of oxygen was also seen in Paris curve types of tests. In pure hydrogen crack growth rates were comparable with ASME B31.12 and Sandia National Laboratories reference curves and were in general up to an order of magnitude above the BS7910 in-air mean depending on ΔK and other parameters. The additions of oxygen at concentrations as low as 50 ppm resulted in reductions in fatigue crack growth rates to values closer to those in air. Further increases in the oxygen concentration resulted in slight reductions of crack growth rates that were more noticeable at higher ΔK and Kmax. The recovery of the fatigue performance was consistent with the fractography observations. The addition of oxygen resulted in an overall increase of the plastic strain seen on the fracture surfaces. In pure hydrogen fracture surfaces were consistent with quasi-cleavage failure and had planar cleavage facets with river marks and very fine striations that were mostly visible at high frequencies and ΔK under high magnifications (55800x). The fracture surfaces of specimens tested in presence of oxygen resembled those seen in the in-air fatigue pre-crack region especially at high frequencies and high ΔK. At low frequencies and low ΔK the fracture surfaces resembled that of quasi-cleavage fracture although they had a ‘fibrous’ aspect with visible signs of plastic strain. Striations were readily visible on the fracture surfaces of all specimens tested in presence of oxygen and were more defined than those seen in pure hydrogen.<br/>Based on the data generated in this work a concentration of 250 ppm O2 is recommended as the minimum value to achieve inhibition of hydrogen effects. This concentration provided a recovery of 85% of the in-air fracture resistance and resulted in crack growth rates close to in-air levels. The fracture surfaces of specimens tested at this oxygen concentration generally showed ductile features consistent with higher toughness failure mechanisms.
NTS Materials Testing to Enable Hydrogen Injection in High Pressure Pipelines, Technical Summary Report
Mar 2026
Publication
DNV and
National Gas
National Gas is aiming to demonstrate the potential use of hydrogen in high pressure transmission pipelines and associated equipment through the FutureGrid NIC programme. This involves construction and operation of a realistic high pressure transmission system using decommissioned National Gas assets. The linepipe for the facility will be X-52 and X-65 grade steels. A key parameter for the facility is to operate at the current NTS pressure tier.
The most applicable pipeline design code is ASME B31.12 used in the USA and currently used by UK HSE for evaluating hydrogen pipeline designs. Hydrogen supplements to the IGEM/TD/1 and IGEM/TD/13 codes also refer to this standard. The code has prescriptive design methods for allowable pressures which would reduce the FutureGrid maximum allowable design pressure (MAOP) to below current NTS pressure. The code does however allow less prescriptive methods if the linepipe has been tested for fracture toughness and fatigue performance in hydrogen using a protocol as defined by ASME VIII Section 3 Article KD-10. This would potentially allow a higher MAOP for FutureGrid1.
A materials test programme has therefore been established to evaluate the fracture toughness and fatigue properties of the actual linepipe used for the FutureGrid facility. The X-52 and X-65 linepipe being used to construct the facility has been tested in hydrogen including realistic seam welds and girth welds. This data has been used to confirm an appropriate maximum operating pressure for the FutureGrid test facility by carrying out fracture mechanics analyses in accordance with the above standards.
The materials test programme also includes a task to generate similar fracture toughness and fatigue data for a wider range of materials within the NTS as described in Table 1 below. This report provides test results for all of these materials along with analysis and interpretation of the results. It therefore satisfies the reporting requirements associated with a number of milestones as follows:
• Task 7 “Update of Data Analysis/Design using additional X60 results”
• Task 19 “Completion of Task 3 Reporting”
• Task 20 “Completion of Task 4 & Associated Reporting”
At present the report does not include details of tests carried out within Task 17 “Sub-critical crack growth testing” as some of those tests are still ongoing. The report will be updated to include these data when the tests are complete.
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.
The most applicable pipeline design code is ASME B31.12 used in the USA and currently used by UK HSE for evaluating hydrogen pipeline designs. Hydrogen supplements to the IGEM/TD/1 and IGEM/TD/13 codes also refer to this standard. The code has prescriptive design methods for allowable pressures which would reduce the FutureGrid maximum allowable design pressure (MAOP) to below current NTS pressure. The code does however allow less prescriptive methods if the linepipe has been tested for fracture toughness and fatigue performance in hydrogen using a protocol as defined by ASME VIII Section 3 Article KD-10. This would potentially allow a higher MAOP for FutureGrid1.
A materials test programme has therefore been established to evaluate the fracture toughness and fatigue properties of the actual linepipe used for the FutureGrid facility. The X-52 and X-65 linepipe being used to construct the facility has been tested in hydrogen including realistic seam welds and girth welds. This data has been used to confirm an appropriate maximum operating pressure for the FutureGrid test facility by carrying out fracture mechanics analyses in accordance with the above standards.
The materials test programme also includes a task to generate similar fracture toughness and fatigue data for a wider range of materials within the NTS as described in Table 1 below. This report provides test results for all of these materials along with analysis and interpretation of the results. It therefore satisfies the reporting requirements associated with a number of milestones as follows:
• Task 7 “Update of Data Analysis/Design using additional X60 results”
• Task 19 “Completion of Task 3 Reporting”
• Task 20 “Completion of Task 4 & Associated Reporting”
At present the report does not include details of tests carried out within Task 17 “Sub-critical crack growth testing” as some of those tests are still ongoing. The report will be updated to include these data when the tests are complete.
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.
NGT Compressor Station FMEA for Hydrogen: FMEA Summary Report
Mar 2026
Publication
DNV and
National Grid
The project between DNV and NGT innovation is exploring the future impact of introducing hydrogen into the National Transmission System (NTS) network and specifically looking at the impact on the compressor station equipment. The consequent failure modes associated with the introduction of hydrogen will be assessed through Failure Mode Effect Analysis (FMEA).
The work scope includes:
• Perform a staged approach FMEA study Qualitative assessments determining the risk levels associated with the various components of the compressor trains.
• Perform the FMEA on each selected train type assessing the operational safety and environmental impact of H2 introduction.
Assessment has been made for two potential network gas types:
• 25% H2/NG blend
• 100% H2
The output is an FMEA on each generic compressor stations indicating the risk areas from H2 operation. This output will allow NGT to identify areas which require further assessment / action before H2 is introduced.
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.
The work scope includes:
• Perform a staged approach FMEA study Qualitative assessments determining the risk levels associated with the various components of the compressor trains.
• Perform the FMEA on each selected train type assessing the operational safety and environmental impact of H2 introduction.
Assessment has been made for two potential network gas types:
• 25% H2/NG blend
• 100% H2
The output is an FMEA on each generic compressor stations indicating the risk areas from H2 operation. This output will allow NGT to identify areas which require further assessment / action before H2 is introduced.
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.
Safe Venting and Recompression of Hydrogen - Final Technical Report
Mar 2026
Publication
This document summarises The Safe Venting and Recompression of Hydrogen project (NIA_NGGT0205) project carried out by Wood PLC for National Gas Transmission from Feb 2023 to Feb 2024. The project explored the possible impacts of transition from natural gas fuel to hydrogen (or to hydrogen/natural gas mixtures) on the requirement to depressurise transmission pipelines and associated equipment for maintenance or other purposes. NGT currently employ gas recompression or venting to atmosphere as a means of achieving safe conditions for intrusive work. The project investigated the impact of the presence of hydrogen on these and other potential technologies for providing safe conditions of work. Details of the work carried out is recorded in Technical Notes TN01 to TN04. High level summaries of each technical note are included at the end of this Executive summary.
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.
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.
Oxygen Ingress - Interim Report 2
Mar 2026
Publication
There was an event at the Redcar EcoHouse where after the isolation of the hydrogen pipework for 27 days over the Christmas break 2023/2024 and shortly after initiation of the flame in a hydrogen gas fire appliance a minor ignition event occurred. Visual investigation led to a discovery that the gas meter was damaged.
Air ingress into the isolated hydrogen pipework (causing a flammable mixture in this pipework) followed by the flame propagation from the ignition system of the hydrogen gas fire were considered to be the most likely reasons for the aforementioned event.
The aim of the work presented in this report was to complement the work undertaken by Steer Energy and to:
• investigate the possibility of the above phenomena to occur in domestic hydrogen installations with main focus on hydrogen appliance design
• to conclude whether there are plausible explanations of the event observed at the Redcar EcoHouse
• to propose possible mitigations which are likely to prevent similar events in the future.
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.
Air ingress into the isolated hydrogen pipework (causing a flammable mixture in this pipework) followed by the flame propagation from the ignition system of the hydrogen gas fire were considered to be the most likely reasons for the aforementioned event.
The aim of the work presented in this report was to complement the work undertaken by Steer Energy and to:
• investigate the possibility of the above phenomena to occur in domestic hydrogen installations with main focus on hydrogen appliance design
• to conclude whether there are plausible explanations of the event observed at the Redcar EcoHouse
• to propose possible mitigations which are likely to prevent similar events in the future.
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.
SIF Discovery Project - Hydrogen Barrier Coatings for Gas Network Assets, Technical Summary Report: Hydrogen Barrier Coatings
Mar 2026
Publication
This report is the Technical Summary Report of the SIF Discovery project (10022648) Hydrogen Barrier Coatings for Gas Network Assets. This report summarises the hydrogen barrier coatings work packages undertaken in the project which were led by Ultima Forma Ltd with inputs from National Grid Gas Transmission.
Around 23 million homes in UK are currently heated by natural gas supplied via the National Transmission System. Green hydrogen generated via renewable energy has potential to be a zero-carbon replacement for natural gas for heating. Re-purposing the existing National Transmission System for the transmission of hydrogen gas in lieu of natural gas would provide resilience and storage rather than relying on transient production. However hydrogen has been shown to embrittle certain pipeline materials thereby reducing allowable operating parameters. Hydrogen barrier coatings applied to the internal surface of the pipeline assets could prevent the need to replace the assets and/or enable the operation of the network in a flexible and optimised manner.
This report builds on and summarises the recommendations arising from project deliverables D1: Potential Coating Materials Their Properties And Application Technologies D2: Use Cases Summary Report and D3: Analysis of Potential Coating Solutions. From D1 zinc cadmium copper tin aluminium and nickel were identified as strong candidate materials. From D2 pipework girth welds valves and filters were identified as high-priority assets able to provide diverse requirements. From D3 electroplating metal spraying and hot-dipping were identified as candidate coating technologies. These are all therefore further explored within this report but brought together to find solutions for the use cases and the technologies best suited for the candidate materials. Additionally due to the importance of the underlying surface quality prior to coating a section within the report was devoted to looking at surface preparation methods. This included paint removal chemical treatment and epoxy coating.
After bringing the various elements together it is clear that different technologies are suitable for different use cases. As zinc is suitable for all proposed coating technologies coating zinc is very mature and zinc is cheaper than tin it is recommended that further research be carried out on the hydrogen permeability of zinc. As hot-dipping is only suitable on the uncoated or paint striped steel and is unsuitable for many candidate materials it should likely not be a priority for further investigation and the focus should instead be on electroplating and cold spraying. For these technologies copper tin cadmium and nickel are suitable. Cadmium has a risk of toxicity tin is more expensive and nickel has a risk of embrittlement when not part of an alloy therefore promoting copper as the next most suitable candidate material for further research.
This Discovery phase has identified a number of candidate materials and application processes in order to successfully mitigate the risk of hydrogen to the existing National Transmission System and to allow for a greener hydrogen transition. A detailed plan for validating these processes and technologies has been made and set out in the follow-on Alpha phase application.
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.
Around 23 million homes in UK are currently heated by natural gas supplied via the National Transmission System. Green hydrogen generated via renewable energy has potential to be a zero-carbon replacement for natural gas for heating. Re-purposing the existing National Transmission System for the transmission of hydrogen gas in lieu of natural gas would provide resilience and storage rather than relying on transient production. However hydrogen has been shown to embrittle certain pipeline materials thereby reducing allowable operating parameters. Hydrogen barrier coatings applied to the internal surface of the pipeline assets could prevent the need to replace the assets and/or enable the operation of the network in a flexible and optimised manner.
This report builds on and summarises the recommendations arising from project deliverables D1: Potential Coating Materials Their Properties And Application Technologies D2: Use Cases Summary Report and D3: Analysis of Potential Coating Solutions. From D1 zinc cadmium copper tin aluminium and nickel were identified as strong candidate materials. From D2 pipework girth welds valves and filters were identified as high-priority assets able to provide diverse requirements. From D3 electroplating metal spraying and hot-dipping were identified as candidate coating technologies. These are all therefore further explored within this report but brought together to find solutions for the use cases and the technologies best suited for the candidate materials. Additionally due to the importance of the underlying surface quality prior to coating a section within the report was devoted to looking at surface preparation methods. This included paint removal chemical treatment and epoxy coating.
After bringing the various elements together it is clear that different technologies are suitable for different use cases. As zinc is suitable for all proposed coating technologies coating zinc is very mature and zinc is cheaper than tin it is recommended that further research be carried out on the hydrogen permeability of zinc. As hot-dipping is only suitable on the uncoated or paint striped steel and is unsuitable for many candidate materials it should likely not be a priority for further investigation and the focus should instead be on electroplating and cold spraying. For these technologies copper tin cadmium and nickel are suitable. Cadmium has a risk of toxicity tin is more expensive and nickel has a risk of embrittlement when not part of an alloy therefore promoting copper as the next most suitable candidate material for further research.
This Discovery phase has identified a number of candidate materials and application processes in order to successfully mitigate the risk of hydrogen to the existing National Transmission System and to allow for a greener hydrogen transition. A detailed plan for validating these processes and technologies has been made and set out in the follow-on Alpha phase application.
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.
Iron mains and fittings in hydrogen service
Mar 2026
Publication
Distribution Network Operators have investigated the potential to utilise iron mains and fittings in hydrogen service.
Iron mains operate at low (<75 mbarg.) or medium (<2 barg.) pressure iron fittings at up to intermediate pressure (<7 barg.) depending on design. No iron mains have been laid since the 1980s although certain grades of iron are still used to construct fittings which includes valves.
The work was conducted by DNV. It examined the impact that hydrogen might have on iron of different grades and also the risk of explosion posed by hydrogen if it escapes from a buried main. In carrying out the analysis no account was taken of additional mitigation measures associated with hydrogen conversion (e.g. in home detection) which would reduce risk to members of the public.
To enhance confidence at the request of Operators IGEM assembled a ‘Peer review panel’ of material science and risk modelling experts from a range of backgrounds. Their role was to express their professional opinion of the findings. The reports produced by DNV and the peer review panel are attached to this report in the appendix.
The conclusion is that iron fittings and most iron mains expected to be in operation after the current replacement programme is completed in December 2032 can operate in hydrogen service.
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.
Iron mains operate at low (<75 mbarg.) or medium (<2 barg.) pressure iron fittings at up to intermediate pressure (<7 barg.) depending on design. No iron mains have been laid since the 1980s although certain grades of iron are still used to construct fittings which includes valves.
The work was conducted by DNV. It examined the impact that hydrogen might have on iron of different grades and also the risk of explosion posed by hydrogen if it escapes from a buried main. In carrying out the analysis no account was taken of additional mitigation measures associated with hydrogen conversion (e.g. in home detection) which would reduce risk to members of the public.
To enhance confidence at the request of Operators IGEM assembled a ‘Peer review panel’ of material science and risk modelling experts from a range of backgrounds. Their role was to express their professional opinion of the findings. The reports produced by DNV and the peer review panel are attached to this report in the appendix.
The conclusion is that iron fittings and most iron mains expected to be in operation after the current replacement programme is completed in December 2032 can operate in hydrogen service.
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.
EUSE Hydrogen Purity - Contaminants Impact Materials in Domestic Installations
Mar 2026
Publication
The EUSE hydrogen purity project is investigating the impact of contaminants in a .pipeline network that has been repurposed from natural gas to hydrogen. With the focus on end users the impact of the contaminants on the pipework and appliance materials downstream of the Emergency Control Valve (ECV) to the appliance is considered and in addition the impact on the combustion of the hydrogen with the contaminants present.
DNV carried out a review using its own experience together with information from IGEM standards and information collated as part of the BEIS Hy4Heat programme to identify the most abundant material types that are present in domestic installations. This data was supplemented by information from Cadent on the surveys that were undertaken as part of the Whitby Village trial.
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.
DNV carried out a review using its own experience together with information from IGEM standards and information collated as part of the BEIS Hy4Heat programme to identify the most abundant material types that are present in domestic installations. This data was supplemented by information from Cadent on the surveys that were undertaken as part of the Whitby Village trial.
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.
Technical Summary of the NGGT and Partners' Feasibility Study of Hydrogen Fuel Gas for NTS Compressors
Mar 2026
Publication
This Networks Innovation Allowance (NIA) funded project (NIA_NGGT0176) comprised a feasibility study on an exemplar National Grid Gas Transmission (NGGT) National Transmission System (NTS) compressor station. The study has examined safety environmental technical operational and economic issues in blending hydrogen/methane for combustion in a gas turbine (GT) driving NTS compression. The project also determined how to establish an innovative green hydrogen production storage and supply facility to fuel GTs on varying hydrogen/methane blends.
This strategic study is preparatory work ahead of demonstration on an NTS compressor station which precedes hydrogen blending in NTS compressors as ‘business as usual’. Higher hydrogen concentrations may be achieved in the GTs in advance of similar blends within the transmission pipes. As such this strategic and innovative project could de-risk the hydrogen transition of GT compression operations and bring forward CO2 and NOx reductions.
For the feasibility study two scenarios have been assessed: co-firing with 25%/75% vol hydrogen/natural gas blend and 100% vol hydrogen.
The study found it is viable to run the Siemens Energy SGT-A20 GTs on blends of hydrogen and natural gas up to 100% hydrogen and there are historic examples of this type of GT doing so without detriment.
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
This strategic study is preparatory work ahead of demonstration on an NTS compressor station which precedes hydrogen blending in NTS compressors as ‘business as usual’. Higher hydrogen concentrations may be achieved in the GTs in advance of similar blends within the transmission pipes. As such this strategic and innovative project could de-risk the hydrogen transition of GT compression operations and bring forward CO2 and NOx reductions.
For the feasibility study two scenarios have been assessed: co-firing with 25%/75% vol hydrogen/natural gas blend and 100% vol hydrogen.
The study found it is viable to run the Siemens Energy SGT-A20 GTs on blends of hydrogen and natural gas up to 100% hydrogen and there are historic examples of this type of GT doing so without detriment.
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
HyNTS Compression, Alpha Technical Report
Mar 2026
Publication
The HyNTS Compression project investigates the key challenges associated with compression of hydrogen and hydrogen blends through NTS assets. The project will determine the most cost-effective technically feasible solution for hydrogen compression on the NTS and develop the strategy for hydrogen compression. The alpha phase of the project has focussed on the following before progression to the beta phase of the project:
• Business case and Requirements for hydrogen compression
• Gas Turbine System
• Compression System
• Ancillary Equipment
• Demonstration Facility Development
The conceptual design development has concluded that it is possible to repurpose existing compression assets to demonstrate their capability of operating with 100% hydrogen. This will obtain the evidence necessary to update the Safety Case to enable deployment across the NTS. This phase of work further reinforces the importance of carrying out a demonstration to gather evidence of how repurposed compression assets would operate and the impact this would have on their performance. If repurposing NTS compression assets for hydrogen service can be proven there is potential for huge savings when realised across the entire NTS compression fleet.
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.
• Business case and Requirements for hydrogen compression
• Gas Turbine System
• Compression System
• Ancillary Equipment
• Demonstration Facility Development
The conceptual design development has concluded that it is possible to repurpose existing compression assets to demonstrate their capability of operating with 100% hydrogen. This will obtain the evidence necessary to update the Safety Case to enable deployment across the NTS. This phase of work further reinforces the importance of carrying out a demonstration to gather evidence of how repurposed compression assets would operate and the impact this would have on their performance. If repurposing NTS compression assets for hydrogen service can be proven there is potential for huge savings when realised across the entire NTS compression fleet.
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.
HyNTS Pipeline Dataset Aplha Phase: Final Technical Report
Mar 2026
Publication
Rosen,
National Gas and
Cadent
HyNTS is a programme of work that seeks to identify the opportunities and address the challenges that transporting hydrogen within the National Transmission System (NTS) presents. This will unlock the potential of hydrogen to deliver the UK’s 2050 Net Zero targets. The programme will feed into a number of ongoing hydrogen initiatives such as Project Union which has the aim of creating a UK hydrogen transmission backbone for the UK using repurposed and new-build infrastructure.
The Pipeline Dataset SIF project has two primary objectives.
♦ Defining and gathering the data necessary to ultimately facilitate repurposing of above 7 bar pipelines on the NTS and LTS.
♦ Developing the tools and processes to store align and visualise data to facilitate effective Integrity Management decision-making during post-repurposing service.
This report provides a summary of the work completed in the HyNTS Pipeline Dataset project Alpha phase to address these objectives.
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.
The Pipeline Dataset SIF project has two primary objectives.
♦ Defining and gathering the data necessary to ultimately facilitate repurposing of above 7 bar pipelines on the NTS and LTS.
♦ Developing the tools and processes to store align and visualise data to facilitate effective Integrity Management decision-making during post-repurposing service.
This report provides a summary of the work completed in the HyNTS Pipeline Dataset project Alpha phase to address these objectives.
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.
Hydrogen Impact on Pipeline Cathodic Protection Performance and External Coating Degradation
Mar 2026
Publication
National Grid Gas Transmission (NGGT) contracted Rosen UK Ltd (Rosen) and The University of Warwick UK (Warwick) to conduct a literature review on the subject of “impact of hydrogen conveyance on the performance of cathodic protection (CP) and pipeline coating degradation”. NGGT’s motivation for this project comes as part of the route to Net Zero with NGGT looking at opportunities to increase the percentage of hydrogen transported within natural gas. As the percentage of hydrogen increases there may be increased risk for the evolution of atomic hydrogen which could permeate through the steel pipe and affect external coatings and the efficacy of CP polarization potentials. Pertaining to the above NGGT’s goal is to gain an appreciation of the work that has been undertaken on coatings and CP systems of hydrogen pipelines and what corrosion protection currently utilized on hydrogen pipelines worldwide as well as reported effects of hydrogen on the behaviour of coating
types with or without impressed voltage. Specifically the focus was to identify potential impacts of hydrogen on coating performance adhesion and CP polarization for differing concentration levels of hydrogen being transported at a range of pressures for:
1. A selection of applied and factory coatings and coating types both for a range of aged and new applications.
2. A selection of coating holiday (coating defect) sizes at varying levels of CP polarization.
The project was divided into three work packages:
1. Work Package 1: Literature Review – Rosen as an Industrial Partner.
2. Work Package 2: Literature Review – Warwick as an Academic Partner.
3. Work Package 3: Reporting – presented as a joint effort between Rosen and Warwick.
During the execution of the projects all parties involved participated in two interactive on-line workshops; Workshop 1 was held on the 20th of December 2022 and Workshop 2 on the 2nd of May 2023. Both workshops served as platforms for sharing work progress and obtained results and their discussion; presentation slides delivered at both workshops can be found in Appendix A – Workshop 1 Presentations and Appendix B – Workshop 2 Presentation.
The current document presents the final stage of the project i.e. Work Package 3.
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.
types with or without impressed voltage. Specifically the focus was to identify potential impacts of hydrogen on coating performance adhesion and CP polarization for differing concentration levels of hydrogen being transported at a range of pressures for:
1. A selection of applied and factory coatings and coating types both for a range of aged and new applications.
2. A selection of coating holiday (coating defect) sizes at varying levels of CP polarization.
The project was divided into three work packages:
1. Work Package 1: Literature Review – Rosen as an Industrial Partner.
2. Work Package 2: Literature Review – Warwick as an Academic Partner.
3. Work Package 3: Reporting – presented as a joint effort between Rosen and Warwick.
During the execution of the projects all parties involved participated in two interactive on-line workshops; Workshop 1 was held on the 20th of December 2022 and Workshop 2 on the 2nd of May 2023. Both workshops served as platforms for sharing work progress and obtained results and their discussion; presentation slides delivered at both workshops can be found in Appendix A – Workshop 1 Presentations and Appendix B – Workshop 2 Presentation.
The current document presents the final stage of the project i.e. Work Package 3.
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.
No more items...