Design engineers and developers have been waiting for this for a long time: practical and easy-to-apply design guidelines that allow companies to qualify new components such as fittings, containers, housings, and pipes for use under pressurized hydrogen without time-consuming and costly individual approvals and component tests. Existing design guidelines often lead to oversized components due to blanket specifications, resulting in high materials consumption, or they do not take the influence of hydrogen into account at all, which necessitates individual case testing and thus long development times. In particular, secure weld seams, which are found as connecting elements in almost all machine components and are in direct contact with hydrogen in almost all components of the hydrogen infrastructure, are particularly critical design elements and a limiting factor with regard to the development of the H2 infrastructure in Germany.
This is precisely where the H2WeldEng research project, funded by the Federal Ministry for Economic Affairs and Energy as part of the 8th Energy Research Program, comes in. The aim is to develop design guidelines that are generally applicable to welds and mechanical engineering components and take into account the life-reducing influence of hydrogen.
The FAT classes of the IIW (International Institute of Welding) guidelines are widely used and established for the load-bearing design of weld seams. The FAT classes describe the fatigue strength for a variety of weld details and provide a good starting point for formulating a universal design concept for welded joints under pressurized hydrogen.
The project will further develop these established guidelines to make them suitable for H2 applications. To this end, test concepts will be developed to experimentally determine the fatigue strength of weld seam details within H2 atmospheres. A database with characteristic values for various weld details is being created for strength assessment. The interaction between the mechanical stress on the weld seam and hydrogen diffusion is simulated. FAT classes and assessment guidelines for weld seams are derived mathematically and validated experimentally. These are then tested on various demonstrators from the companies in the project consortium.
The methods developed in the project thus contribute significantly to the efficient and targeted development of the hydrogen infrastructure, to the reduction of development times, and to materials savings. Based on an example calculation for the pipelines of the planned German hydrogen core network with a length of almost 10,000 km, the associated ecological impact amounts to around 2 million tons of CO2 saved, assuming a reduction in wall thickness of up to 30 percent based on optimized design criteria.
Fraunhofer Institute for Mechanics of Materials IWM