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2009

Hydrogen Impact on NTS Welds

  • Status: Complete
  • Reference: NIA_NGT0253
  • Start Date: 01 April 2025
  • End Date: 01 March 2026
  • Budget: External EPRI – £ 110,629Internal – £ 25,916Total – £ 136,546
  • Funding Mechanism: Network Innovation Allowance
  • Collaborating Networks: National Gas Transmission PLC
  • Project Partners: Gas Network – National Gas Transmission PLC Technical & Industrial Lead – Electric Power Research Institute (EPRI)

Abstract

This project investigates how hydrogen affects the integrity of welded joints (seam welds and girth welds) in the UK National Transmission System (NTS) pipelines, as part of plans to repurpose existing natural gas infrastructure for hydrogen transport.

Specifically, Work Package 4 integrates results from metallurgical characterisation, historical weld procedures, and fracture toughness testing conducted in high-pressure hydrogen. The study examines pipeline steels of different grades and vintages (including X46, X52, X60, X65 and X80), focusing on weld metal and heat-affected zones (HAZ), which are known to be the most vulnerable regions.

The report combines:

  • Detailed metallography and hardness mapping of real NTS welds,
  • Post-test fractographic analysis of specimens tested in hydrogen,
  • Interpretation of fracture toughness data,
  • An overall assessment of risks and uncertainties associated with hydrogen service,
  • Recommendations to support safe decision-making for hydrogen repurposing.

The project will look at:

  • Mapping out the weld procedures used across the NTS overtime and generate key learning on the interpretation of weld test results with respect to pipeline operation in hydrogen.
  • Develop an increased understanding of the impact of hydrogen on different pipeline welds across the age of the NTS
  • Inform update/creation of standards relating to the welding of new pipelines for hydrogen.
  • The overall benefit will be the ability to transport hydrogen in lieu of natural gas thus contributing to greenhouse gas emission reductions.
  • Repurposing existing assets will represent the lowest cost and quickest solution to the end-user.
file format pdf download NIA_NGT0253_Hydrogen_Impact_on_NTS_Welds_Progress_Report.pdf
file format pdf download NIA_NGT0253_Hydrogen_Impact_on_NTS_welds_Closure_Report.pdf
file format pdf download NIA_NGT0253_Hydrogen_Impact_on_NTS_Welds.pdf
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2025-04-01
2026-09-18
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