Net zero and the energy system transition
High Pressure Venting and Flaring Demonstration for Net-Zero Gases Transportation
National Gas Transmission (NGT) own and operate the UK’s National Transmission System (NTS) transporting natural gas from terminals to end users. NGT have ambitions to repurpose the existing asset to transport hydrogen and hydrogen blends. Understanding the impact of hydrogen on our existing assets is a key enabler for this.
This project will conduct design of flare for hydrogen and its blends and vent system for hydrogen its blends and carbon dioxide and offline physical testing to provide evidence that hydrogen / hydrogen blends could be flared and vented safely and environmentally in for NTS.
Fatigue Rig Post Test Inspection and Mechanical Testing of Hydrogen Charged Materials
High pressure steel pipelines are essential in enabling a safe natural gas transportation network an overly engineered solution tried and tested over several decades proving the NTS to be a robust nationwide asset. The National Transmission System is used to flow gas every day to keep the lights on and our homes heated by connecting large scale industry cities and towns where the network is dynamic allowing for flexibility and adaptability to various flow demand scenarios. This is done so by utilising over 5000 miles of varying grades and differing sizes of pipelines where the gas can flow build line pack for high energy demand areas and provide a mass energy storage solution.
The NTS is used to limit gas loss manage flow direction facilitate maintenance repair modification testing and commissioning to enable safe and effective start-up and shutdown of our pipelines. We now must further evidence pipeline steel material integrity when subjected to high pressure hydrogen gas this can be done by expanding upon the existing fatigue rig standalone testing at DNV Spadeadam.
Although some pipelines materials that we use today have seen blends and 100% hydrogen within the HYNTS Phase 1 test facility what we have not done is post hydrogen fatigue cycling non destructive testing of materials that have been subject to prolonged high pressure hydrogen. One of the welds that make up the fatigue rig has a known weld defect within it NGT aims to have the welds and the weld defect analysed through various methods of testing such as magnetic particle inspection followed by if necessary standard ultrasonic testing.
In 2022 small scale mechanical characteristic tests were conducted to characterise the mechanical properties of the materials used within the construction of the fatigue rig this testing commenced outputting a standard mechanical property data set the new end of test data post hydrogen exposure will be compared to the original data set from 2022 at the end of fatigue cycling. Testing will establish the effect of trapped hydrogen on ‘standard’ mechanical properties measured To facilitate this DNV will remove all girth welds selected seam welds and fitting welds and store them at low temperature to mitigate loss of hydrogen from within the trap sites..
A technical note will be prepared comparing the results of the weld inspections (internal and external inspections). The note will be used to confirm defect removal for metallographic examination.
A technical report will be prepared summarising the macro and microscopic examinations undertaken confirming defect size (to that reported by UT) and whether the defect was an original feature else created due to the pressure cycle duty of the test vessel and the hydrogen environment.
Blending Management Approach Phase 2
The conversion of the National Transmission System into a hydrogen transmission network has been widely discussed and it is recognised that blending of hydrogen and natural gas in the network is an important intermediary step towards that goal. It is therefore important to understand how the NTS will operate with a mix of natural gas and variable blends up to 20% hydrogen.
The Blending Management Approach (BMA) Phase 2 project will explore the operational safety and strategic implications of introducing low-level hydrogen blends into the National Transmission System (NTS) with a particular focus on storage interactions emergency response scenarios and long-term network management strategies. This phase aims to deepen understanding of how hydrogen blends interact with existing infrastructure and protocols.
Carbon Dioxide Repurposing Procedure for the NTS
The project described in this FEN report covers the development of a new repurposing process for NTS assets to transport gaseous phase carbon dioxide. The approach for repurposing the National Gas Transmission System (NTS) to transport carbon dioxide will need an innovative approach to meet the timelines for the net zero transition. There have been several projects undertaken to date to determine the interactions of carbon dioxide with the network assets. We are looking to determine if these activities are providing all the relevant data and evidence required for our network to transition.
Innovative approach to Policy document management
As part of National Gas’s Three Molecule strategy the technical evidence for the transportation of hydrogen and carbon dioxide through the National Transmission system is being gathered through the HyNTS and CO2 programmes. This technical evidence will feed into the updates of NGT’s suite of policies and procedures which are used to demonstrate compliance with the Gas Safety (Management) Regulations (GSMR) Pipeline Safety Regulations (PSR) and Pressure System Safety Regulations (PSSR).
This project will develop the approaches to compliance with regulations for hydrogen hydrogen blends and CO2 considering both new build and repurposed assets. The project will also define how the NTS Safety Case of the future will look including modular design and digitalisation to streamline access to information.
Predictive Model for Flood Risk Management
This project developed and evaluated a predictive flood monitoring system for Above Ground Installations (AGIs) and pipeline assets using real-time sensor data and 48-hour surface water forecasting. The system was deployed at Goxhill AGI Crieff AGI Hatton Compressor Station and Penicuik Peat Farm pipeline following a a nationwide flood risk survey. The trial assessed the system’s accuracy responsiveness and operational value across diverse environments. The project supports climate adaptation regulatory compliance and asset resilience by enabling early warning and proactive intervention. It aligns with RIIO-2 NIA objectives by reducing flood-related disruption enhancing safety and informing future investment decisions. The project concluded with a technical report and recommendations for wider rollout under RIIO-3.
Standardised Biomethane Connections
Through consultation with the biomethane industry National Gas are looking to offer a cost effective repeatable and simplified Minimum Connection arrangement at greenfield locations with low visual impact by locating the network isolation valves in a pit. Thus avoiding a traditional larger Above Ground Installation with perimeter security fence and internal vehicle access and potential local authority planning permission.
The use of pits to house valves on National Gas AGI’s has historically created operational and maintenance issues such as pipe pit wall transition corrosion pit flooding and access restrictions.
However through consultation with NG Chief Engineer a decision support paper was submitted and approved allowing the development of a valve pit arrangement to align with requests from the biomethane industry and address historic issues.
Following this decision conceptual designs were completed for minimum connections at Oulton Airfield and Manby projects in 2024. These designs included a concept design of a MOC valve arrangement in a pit.
Recompression Solutions for a Net Zero NTS
This project will provide National Gas Transmission (NGT) with a clear technical understanding and strategy for the deployment of recompression solutions for Net Zero gas networks including hydrogen blends 100% hydrogen and Carbon Dioxide transmission.
The NIA Safe Venting & Recompression of Hydrogen innovation project explored the possibility of repurposing natural gas recompression units for hydrogen blends and 100% hydrogen and investigated new solutions for hydrogen pipeline recompression as part of routine maintenance activities.
This project furthered NGT’s knowledge of hydrogen recompression for different scales and applications on the NTS to reduce venting and explore similar solutions for carbon dioxide pipelines.
Deblending Rollout Strategy Phase 2
National Gas Transmission (NGT) are committed to reducing emissions from the operation of the National Transmission System (NTS) and eliminating emissions by 2050. The transition to hydrogen provides an opportunity to reduce carbon and utilise the network for hydrogen refuelling for transport. The HyNTS Deblending for Hydrogen Transport project has involved the development of a UK-wide rollout strategy from ERM that lays out demand clustering and potential locations for deblending supplied refuelling for transportation mapped against the NTS.
The project will aims to obtain further information on NRMM maritime cars LGVs and mobile power to fully understand the hydrogen demand. It will also review the existing rollout strategy to ensure it is accurate and full captures the current hydrogen market given the changes in this landscape
HyNTS Operational Methodologies - Valve Performance Assessments
This project aims to assess and enhance the hydrogen readiness of ball valves within the (NTS) by conducting maintenance strategy evaluation with material performance analysis. It involves reviewing current valve operations diagnostics and OEM maintenance guidance alongside a literature review of commonly used valve materials to understand their behaviour under hydrogen exposure. The project valve performance testing and finite element analysis of existing valve designs to evaluate structural integrity. Findings from these activities will provide actionable recommendations for updating NGT’s valves maintenance strategies diagnostic tools and design standards to support safe and efficient hydrogen service deployment
Hydrogen backbone social economic assessment
Develop credible and independently modelled pathways to test the economic case of developing a H₂ Backbone and prepare NGT for dialogue with NESO DESNZ HMT and a wider group of stakeholders.
Preferential Emissions Study
The characteristics of transmission pressure hydrogen and natural gas blends are not fully understood including relative leakage behaviour. Existing evidence for leak behaviour of hydrogen blends do not extend above 7barg and therefore do not account for the effects of transmission pressures on gas behaviour. This project will test whether or not methane and hydrogen within a blend leak at the same rates or whether due to its small size hydrogen will leak at a ratio greater than its relative concentration and whether it leaks where methane does not.
Understanding the leak behaviour of hydrogen in a natural gas blend will ensure we can operate a blended system safely particularly in enclosed spaces and will ensure that the carbon benefit of hydrogen enrichment is not lost through fugitive emissions. Also as green hydrogen is currently significantly more expensive than natural gas the shrinkage costs associated with hydrogen fugitive emissions could be considerable.
Predictive Tool for Unaccounted-For Gas (UAG) Identification
The Unaccounted-for Gas (UAG) project aims to develop a predictive tool that identifies and quantifies UAG across the National Transmission System (NTS). Leveraging 12-18 months of SCADA data the tool will simulate gas flow and metering behaviour to pinpoint anomalies and reduce losses. UAG currently represents significant financial cost to the consumer; even a 1% reduction could yield practical savings. The project aligns with RIIO-2 NIA criteria and supports regulatory compliance under the Gas Transporter Licence Part J of Special Condition 5.6 (System operator external incentives revenues and costs) requiring National Gas to undertake work to investigate the causes of UAG. It builds on prior research and integrates learnings from international benchmarks. The initiative will enhance operational efficiency improve data transparency and support long-term decarbonisation goals through better system visibility and control.
HyNTS Operational - Qualification of Pressure Vessels
This project assessed whether a fracture mechanics approach can be used to justify existing gas cleaning scrubbers for future hydrogen or hydrogen blend service. The work focused on a representative Kings Lynn scrubber and considered crack-like flaws hydrogen-affected toughness residual stresses pressure cycling and fatigue crack growth. The results indicate that the approach is viable for demonstrating integrity in large parts of the scrubber particularly the upper vessel and nozzle welds but further evidence is required before it can be applied across the wider scrubber population.
Impact of Hydrogen and on NTS Oils & Greases – Phase 2
Phase 1 of the project compiled a list of oils and greases considered to be gas-facing on the NTS along with identifying functional and material property requirements of these products. Proposed standards and testing methodologies were also outlined to inform the next phase of the project. In Phase 2 the project will proceed with additional required activities to ensure the safe utilisation of NTS oils/greases in a hydrogen pressurised environment. These activities include laboratory testing for lubricants and functional testing for sealants to assess degradation and performance of these products in hydrogen. Subsequently requirements for in-service monitoring will be identified.
NTS Pipeline Assessments Phase 2
This project will build upon previous work to inform decisions relating to the repurposing of National Transmission System pipelines for 100% hydrogen and hydrogen-natural gas blends. New input data will be generated and collated the assessment methodology will be refined and an alternative assessment method probabilistic will be utilised and the resulting network impact will be considered.
This project will generate the following benefits:
- More accurate assessment of the capability of the NTS to transport 100% hydrogen and hydrogen-natural gas blends.
- Data on the impact of low percentage blend hydrogen on pipeline materials.
- Standardised document for Engineering Critical Assessments (ECA) of hydrogen and hydrogen-natural gas blend pipelines and pipework.
Greater understanding on the effect of hydrogen on the design and operation of pipeline systems.
Gas Inhibitors for Hydrogen Pipelines - Phase 3
The Phase 3 project on gas inhibitors for hydrogen pipelines aims to translate lab-scale findings into practical applications for the UK’s National Transmission System. It focuses on validating the effectiveness of oxygen and alternative inhibitors in mitigating hydrogen embrittlement addressing unresolved safety and integrity concerns from previous phases and designing a plan for safe integration into existing infrastructure. The project includes physical demonstration planning and network design to assess technology implementation.
H2 Site Safety Systems
This project will examine the suitability of existing Fire and Gas (F&G) detection and suppression systems for use with hydrogen blends of up to 20%. These systems comprise: fire detection fire suppression gas detection and associated control systems. They are found in compressor cabs and at network terminals.
Through CFD modelling three representative F&G systems will be individually assessed for compatibility with blends and will then be used as examples to make comments on the suitability of other F&G systems on the network. Where assets or control systems are not suitable this project will not design a new system but recommend where changes should be made and demonstrate how those changes safely manage risk – including cost estimation for upgrade or retrofit.
Integrity Management of Hydrogen Pipelines
Existing defect assessments and repair methodologies designed for natural gas service are aligned with the T/PM/P/** and T/PM/P/** management procedures and are adopted to inspect assess and repair pipelines for defects and take suitable measures to mitigate them. However the scope and applicability of the assessment inspection and repair techniques in the presence of high-pressure hydrogen remain uncertain. The key questions which form an outline of the project are:
- What are the different types of defects we may encounter or consider injurious in the presence of hydrogen?
- What is the impact of hydrogen on each defect type? Have the mechanisms of failure changed for each defect type after hydrogen-natural gas blending?
- Will the existing repair techniques be applicable under transmission of high-pressure hydrogen and hydrogen-natural gas blends?
- Can we implement the defect assessment inspection and repair methodologies safely? Are the techniques safe and suitable for the pipeline operations and maintenance teams?
The project seeks to answer the above in addition to understanding the types and extent of repairs across the NTS and assess the impact of hydrogen on the effectiveness of these inspection assessment and mitigation technologies.
Application of Functional Blending - Testing a Market-led Approach
Wales & West Utilities has developed a Regional Decarbonisation Pathway to provide an overarching strategic plan for the network in Wales and the South West of England. To deliver that pathway more detailed assessment and planning is required to facilitate the progression of opportunities in particular areas.
In 2023 WWU supported Cadent as the lead partner in the development and delivery of a Functional Blending Specification (FBS) which has progressed the technical understanding of how blending equipment can be practically applied within the context of existing gas network assets (