Testing of materials for natural gas/hydrogen grid

The current natural gas grid could be used for hydrogen transport in a future Hydrogen Society. Before that scenario, it is planned to be used to transport natural gas/hydrogen mixtures. As hydrogen is a gas with high diffussivity special attention has to be paid on the study of materials used in natural gas grid. Two groups of tubes have been disposed to perform material testing with natural gas/hydrogen mixtures. At the moment several trials are being performed with three different materials used in natural gas transport: carbon steel, used for high pressure natural gas grid, polyethylene, for medium pressure grid and Copper, used at the consumer point. Both new and used pipe are being used in the trials. Besides tubes themselves, several components used in natural gas grids are also being tested: valves, pressure regulators, filters, flow meters, etc. The aim of this project is to measure possible hydrogen losses from a natural gas/hydrogen mixture in a pipeline and pressure of the gas in the pipe is recorded along the time. Trials are being performed at open atmosphere (outside a building) and temperature is also recorded in order to take into account its effect on pressure. Another objective of the project is to study the behaviour of materials in contact with gas in order to check potential sensitivity to hydrogen embrittlement. Several gas natural/hydrogen mixtures will be tested. First of all, pipelines are being filled only with pure hydrogen in order to perform the test at the hardest conditions. Mixtures with 30% hydrogen and also up to 50% hydrogen will also be tested. Materials will also be tested under stress (flexure stress) and under natural gas/hydrogen atmosphere. Samples will be visually inspected (possible cracks) and also metallographic techniques will be used. Mechanical testing (Charpy test, tensile strength test) will be performed before and after exposing materials to natural gas/hydrogen mixtures.