Research

With hydrogen transport in transmission pipelines becoming more concrete, the transition to a hydrogen economy is on a fast track. Within a short to medium period, we may face a reality whereby H₂ transport became a routine across the network. Many pending questions relevant to fracture control for natural gas operations will be carried over. Further, there is little doubt that hydrogen operations over the long-term will lead to a new set of questions. Defect assessments tools will be under increased scrutiny as engineers evaluate their suitability and effectiveness to tackle both long-standing and emerging challenges.

The decrease in ductility of line pipe steel due to hydrogen embrittlement as well as the interactions between ductile damage evolution, stress-state and failure leads to consider if models from the 1960s and 70s will still be conservative in H₂, and whether theories developed in the past 15 years could improve our assessment tools. The aim of this research is to demonstrate the effectiveness of the modern ductile fracture models in the context of fracture initiation for natural gas and hydrogen applications through the following phases:

• Conduct a comprehensive literature review of existing fracture models, with a particular focus on damage indicator models recently proposed;
• Implement and assess the performance of most promising model(s) in the context of natural gas operations for which the industry possesses significant amount of data and knowledge;
• Expand the horizon of the model and theory to the context of blends of natural gas / hydrogen mixtures for arbitrary types of defects;
• Validate models’ readiness for the industry, for the steel present in the ground through integration of the experimental plan with other Future Fuels CRC projects as well as dedicated experiments.

A particular emphasis is placed the transfer of knowledge of modern ductile failure theories to current and future engineers. The background and expertise of the industry-based PhD candidate offers a significant opportunity to develop awareness, practice and culture within the engineering community. Better fracture initiation models suitable for current and future energy fuels will allow the Australian Pipeline industry to continue to capitalise on its long and positive safety track record while improving the efficiency of the maintenance schedules and repairs.

The first outcome of this work is to demonstrate the effectiveness of models developed in the past 15 years in the context of fracture initiation for natural gas applications. This activity will be supported by industry data and knowledge gathered over several decades of operations. The second outcome is to expand the horizon of the theory to the context of blends of natural gas / hydrogen mixtures for arbitrary types of defects, thanks to the integration of stress-state history on the evolution of the fracture. Such model would provide a unified approach to handle the transition from natural, through blends, to pure hydrogen operations.

The third outcome of this work is to mature the model to validation and industry readiness. To do so, the work will link with Future Fuels CRC projects conducting the characterisation of Australian line pipe steel in hydrogen environment.  Testing schedule, use of a range of testing and analysis methodologies as well as expansion of data representative of the network will provide benefits across the projects.

Finally, the industry will benefit from the transfer of knowledge of modern ductile failure theories to current and future engineers. The background and expertise of the industry-based PhD candidate offers a significant opportunity to develop awareness, practice and culture within the engineering community.

Douglas Proud

Research & Utilisation Program Coordinator

douglas.proud@futurefuelscrc.com