Hydrogen Fracture Toughness Assessment for Gas Networks Ireland Transmission Pipeline System

Project Background

Gas Networks Ireland (GNI) owns, operates, and maintains Ireland’s gas transmission and distribution networks, which include over 2,500 km of high-pressure steel pipelines. This system forms part of a broader 14,725 km national network that delivers reliable energy to more than 720,000 homes and businesses across Ireland every day.

GNI is now pursuing an ambitious goal to fully decarbonise their gas network by 2045. A key part of this vision is the transition from natural gas to 100% renewable gases, such as biomethane and hydrogen. To enable this, existing infrastructure first must be assessed for safe and effective repurposing.

Services

Penspen has been engaged to evaluate whether GNI’s existing gas transmission pipelines are suitable for hydrogen service. This includes assessing the pipeline systems ability to operate at current or planned Maximum Operating Pressures (MOPs) while accounting for the effects of hydrogen on fracture toughness and fatigue crack growth.

The scope of work includes:

• Defining plausible crack-like anomalies that could exist in the system
• Using fracture mechanics to model these anomalies
• Estimating hydrogen-specific fracture toughness values
• Developing operating envelopes based on fatigue life in hydrogen conditions

Another critical aspect of the assessment involves reviewing traceable material records, including hydrostatic test data and notch toughness results, to evaluate material suitability and the potential for defect growth under hydrogen service. This data informs key risks such as hydrogen embrittlement and supports safety-critical decisions by helping to estimate remaining fatigue life and define realistic operating limits for safe repurposing.

Result

Drawing on experience from similar hydrogen projects completed across the UK and Europe, Penspen services will provide GNI with the insights required to repurpose existing energy infrastructure safely and effectively, enabling a lower-cost, lower-disruption transition. By quantifying material performance and structural integrity under hydrogen service, our work supports informed decision-making and the practical next steps toward GNI’s 2045 net zero goals and the development of a global hydrogen economy.