Comparative Fracture and Fatigue Testing of Selected Pipeline Microstructures in Gaseous Hydrogen Environment

Abstract An ongoing study is assessing the suitability of line pipe materials for use in gaseous hydrogen transmission pipelines. Previous publications present fracture and fatigue testing of the parent and seam weld centre line microstructures of an offshore 1970’s API 5L X60 grade SAW material from a 36″ diameter pipe joint. This paper offers further results from this study, expanded to include a variety of other materials commonly present in Shell pipelines that are anticipated to be repurposed for use in hydrogen service, tested in near-pure H2 pressures up to 172 bara. This includes the heat affected zone of the same vintage X60 material, a 2010’s era sour rated seamless X65 pipe (SMLS 12″ OD) that has been strained and aged, with tests carried out on both the parent pipe and girth weld, and finally the parent pipe microstructure of a late 1960’s X60 high frequency electric resistance welded pipe sample (HF-ERW, 12″ OD). The fracture performance of the SMLS material was found to be very similar to the parent pipe of the vintage SAW material in comparing the Kth values, however the slopes of the JR curves were very different after crack initiation. The HF-ERW material showed lower Kth values. Fatigue crack growth results were more similar among the materials and match trends already reported. The impact of the results on hydrogen pipeline design, pipeline reuse, and integrity management is also discussed.