Hydrogen Embrittlement in Pipeline Steels and Welds

In the energy transition towards a low carbon economy, the EU strives to provide a hydrogen grid of almost 23000 km by 2040. 75% is expected to be obtained by retrofitting existing pipelines for the transport and storage of hydrogen gas.

However steels are prone to hydrogen embrittlement, i.e., hydrogen reduces their ductility and fracture toughness. The engineering assessment criteria to accept or reject weld imperfections are to a large extent based on those mechanical properties. Therefore, the effect of hydrogen on mechanical properties of welds, and particularly their heat affected zones, needs specific attention in the research on structural integrity of welded joints.

Devoted tensile and fracture toughness test methods are developed and tests are performed on (welded) samples with and without hydrogen charging. Laboratory scale tests are used to calibrate an in-house developed numerical diffusion-degradation-damage model of welded parts. Scale effects in hydrogen embrittlement sensitivity will be investigated by up-scaling the experiments. The numerical model will be validated by component scale, so-called curved wide plate, mechanical experiments. Using the validated model, existing acceptability criteria for (girth weld) flaws will be evaluated and updated for hydrogen transport.