Session: MF-11-01 Small-Scale and Miniature Mechanical Testing (Joint with CS-19)

Paper Number: 106270

106270 - Characterization of Hydrogen Embrittlement of Line Pipe Steels Using Sub-Size Specimens 

With the increasing demand for gaseous hydrogen, it is envisaged to convert existing natural gas pipelines to deliver blends of natural gas and hydrogen or pure hydrogen. It is, therefore, necessary to check the fitness-to-service of these existing pipelines for hydrogen transportation, as hydrogen is known to embrittle steel. The existing gas transportation networks are made of various steel pipes. Some parts consist of « vintage » steels from the '60s or '70s, while others are more recent. A possible solution to check the fitness-to-service of existing pipeline steels for hydrogen transport is to extract small coupons without interrupting supply operations. These coupons can then be used to machine small specimens to characterize ductility and toughness. In this study, it is proposed to use smooth and notched tensile specimens (minimum diameter 1.2 mm, total length 11 mm) and Disk Compact Tension specimens (DCT: thickness 4mm, diameter 10.8 mm).

This study investigates a « vintage » X52 line pipe steel and a modern E355 steel. In order to test the specimens under pressurized hydrogen, a new testing machine was designed. It can reach a pressure of 250 bars and apply low displacement rates  (minimum 0.3mm/min). The maximum load is 5 kN. The volume of the chamber has been reduced so that an ATEX environment is not needed. The chamber has two large sapphire windows to install cameras and backlights. An optical extensometer using an Edge Tracing technique outside the chamber was then developed to control the machine displacement during mechanical tests. Load is measured with a cell located within the chamber. The setup allows conducting tests on DCT specimens using the ASTM E1820 procedure. Crack advance is measured using the unloading compliance method to determine the J-R curve. Due to their reduced size, tests on DCT specimens are not valid according to the standard unless the material is highly embrittled by hydrogen. However, results can be used to compare and rank materials with respect to hydrogen embrittlement.

Presenting Author: Clément Soret GRTGAZ

Presenting Author Biography: Clement Soret has 6 years of experience in pipeline integrity within GRTgaz at the R&D center. With expertise in fracture mechanics and finite element simulations, his main focus is on the improvement of pipeline defects assessment approaches, repair methods, and material properties characterization techniques. He has been involved in most of GRTgaz projects related to integrity and hydrogen for the last years. He is a representative of GRTgaz at the Design committee of the European Pipeline Research Group (EPRG) and at the Design, Materials and Construction committee of the Pipeline Research Council International (PRCI). He works closely with academics on multi-year R&D programs such as the industrial chair Messiah, funded by the French National Research Agency (ANR), which aim is to develop very small-scale specimens to measure mechanical properties of steel structures at lower costs.

Authors:

Clément Soret GRTGAZ
Magali Polo GRTGAZ
Jacques Besson Mines Paris PSL -- Centre des Materiaux --- CNRS UMR 7633
Yazid Madi Mines Paris PSL -- Centre des Materiaux --- CNRS UMR 7633
Said Belkacemi Mines Paris PSL -- Centre des Materiaux --- CNRS UMR 7633
Luciano Meireilles Santana Mines Paris PSL -- Centre des Materiaux --- CNRS UMR 7633
Francis Bourguignon Mannesmann Precision Tubes France
Pierre-Jean Marchais Mannesmann Precision Tubes France