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Projects: Projects for Investigator
Reference Number	NIA_NGGT0186
Title	Assessment of Legacy Gas Pipeline Steels to Hydrogen Embrittlement Effects
Status	Completed
Energy Categories	Fossil Fuels: Oil Gas and Coal(Oil and Gas, Refining, transport and storage of oil and gas) 50%; Hydrogen and Fuel Cells(Hydrogen, Other infrastructure and systems R&D) 50%;
Research Types	Applied Research and Development 100%
Science and Technology Fields	PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials) 40%; ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering) 60%;
UKERC Cross Cutting Characterisation	Not Cross-cutting 100%
Principal Investigator	Project Contact No email address given National Grid Gas Transmission
Award Type	Network Innovation Allowance
Funding Source	Ofgem
Start Date	01 September 2022
End Date	31 August 2023
Duration	ENA months
Total Grant Value	£120,166
Industrial Sectors	Energy
Region	London
Programme	Network Innovation Allowance
Investigators	Principal Investigator	Project Contact , National Grid Gas Transmission (100.000%)
Web Site	https://smarter.energynetworks.org/projects/NIA_NGGT0186
Objectives	The project will focus on the technical feasibility of hydrogen transport within NTS pipelines, taking example material and undertaking in depth studies into the microstructure and make up of the various materials on the NTS. We will select varying ages of X52, X60, X65 and X80 pipeline materials based on their make up on the NTS today undertake baseline materials characterisation and then subject the materials to gaseous hydrogen environments to understand the impact of hydrogen on the microstructures. This work in comparison with the materials testing work underway will provide the reasoning for the results we see and provide greater insight into some of the methods of preventing failure. The method chosen through laboratory testing is the most appropriate for the in-depth microstructure analysis planned to be undertaken as this is not feasible at a larger scale. The initial study will last 9 months and provide us guidance on which areas need further focus.Measurement Quality StatementThe measurement approach used to meet Data Quality objectives will be through the identification of high calibre project partners whom are experts in their given field and the use of real data and materials from National Grid sites. In this instance the project will be limited to lab testing and therefore will combine knowledge from past materials investigations with lab scale testing to inform new insights into the impact of hydrogen on varying ages of NTS materials. The lab tests will be assessed by the Warwick Manufacturing Group and published therefore peer reviewing the final outcomes.Data Quality StatementThe project will ensure that materials and data used is of sufficient quality to deliver project objectives through the development of a robust testing plan, this will take into account all key variables and manage them through the testing. The relevant data and background information will be stored for future access within the National Grid Innovation Sharepoint site and the ENA smarter networks portal. The project will be managed through three work packages detailed below. The purpose of which will provide a clear view of how the ages of steel material grades impacts the compatibility of hydrogen transport through our NTS pipelines. It is thought that older steel grades such as X52 will have less impact from hydrogen however older steel pipelines where not manufactured in the same method as those post the late 1970s causing the materials to contain more inclusions which are susceptible to hydrogen. WP1 Steel homogeneityThe service exposed samples (basemetal, seam and girth weldments) will be characterised in terms of:(i) Inclusion populations – this will be carried out using the SEM-based automatic inclusion analysis facility at WMG so that inclusion distributions, clustering, types and spatial variations through thickness and around weldments.(ii) MicroXRF will be used to give large-scale chemical segregation maps over the same locations as in (i).(iii) Ferrite grain size distributions and second phase volume fraction and size distributions will be determined by SEM-EBSD in the same locations as in (i).(iv) Selected micro- and nano-hardness mapping will be carried to determine local mechanical property variations associated with the microstructural differences noted in (i) – (iii).(v) SEM techniques will be used to identify the range of surface oxide types and thicknesses. WP2 Hydrogen uptakeHydrogen behaviour will be estimated on the basis of current microstructure relationships for the range of microstructures / compositions and inclusion populations identified in WP1. The behaviour of these regions will be determined using acid solution charging for slices extracted from the service-exposed samples given a consistent (clean) surface finish. Following any modification of the microstructure relationships full thickness samples will be treated as a composite with respect to hydrogen behaviour to estimate pipe hydrogen behaviour. This model will be verified using hydrogen charging for full thickness, clean surface samples. After verification / modification of the model, the effect of surface condition will be assessed by hydrogen charging tests for different service-exposed surface conditions over known microstructures already modelled. WP3 Cracking and relation to gaseous environments / new buildSamples from service-exposed materials with a range of hydrogen behaviours will be prepared as tensile specimens and tested to failure with and without hydrogen saturation to determine the extent of hydrogen embrittlement. The mechanism of hydrogen embrittlement will be used to confirm the susceptible microstructure features identified in WPs 1 and 2 by selected X-ray CT on tested but unfractured samples (H saturated) and by SEM fractography. For the service-exposed condition showing the greatest susceptibility to hydrogen embrittlement then samples will be tested in a gaseous hydrogen environment (these tests will be outsourced) with post-test analysis at WMG to confirm comparable behaviour with acid charging tests and any differences in hydrogen uptake for a clean surface so that the model kinetics determined for acid charging can be modified for gaseous hydrogen exposure. New build pipeline is likely to be higher grade, e.g. X80, and so would have a different second phase (as noted above). In order to compare this study and the models determined with new grades then samples of X80 will be characterised; service-exposed material will be heat treated to give a comparable second phase (but the heterogeneities will still be present). The new build X80 and heat treated service-exposed material will be subjected to acid charging to establish the effect of heterogeneities in comparison with the presence of harder second phase. As noted above, the aim of the research is to assess whether established assessments of the likelihood of hydrogen embrittlement are appropriate for service-exposed legacy steel gas (methane) pipeline. The project will involve the sourcing and detailed characterisation of a sufficient number of legacy samples (pipes with welds) to identify the range of microstructural and surface conditions representative of the current gas pipeline population. Hydrogen charging characteristics will be determined for the range of steel conditions and related to expected behaviour from established relationships. These tests will encompass service-exposed surfaces and fresh surfaces to deconvolute the effects of surface and microstructure distributions.
Abstract	The proposed project addresses the call topic area of low-carbon energy carrier roles in accelerating decarbonisaton pathways by characterising the condition of legacy gas (methane) pipeline steels after service exposure. Existing hydrogen embrittlement relationships do not properly consider the effect of steel pedigree on degradation. This research will use the results of detailed characterisation to fully document steel microstructure and rigorously track hydrogen interaction with specific features. The results will be directly relevant to assessing the suitability of the current network for hydrogen gas transport. Moreover, the learnings will inform the design and manufacture of future systems. Support involving the supply of suitable legacy specimens has been obtained from National Grid and EPRI will provide review and input on methods used and aid dissemination of findings.
Publications	(none)
Final Report	(none)
Added to Database	14/10/22