Hydrogen diffusion, permeation through pipeline walls
Land transport of green hydrogen from production to consumption sites is considered to be more economical in pipelines but faces several challenges. API 5L pipeline steels are known to be susceptible to hydrogen embrittlement (HE) in contact with gaseous hydrogen. The optimisation of steel composition and microstructure can help reduce the loss of ductility associated with HE but effects such as the increase of fatigue crack growth rate, especially in weld joints, is more challenging. Whilst it is feasible to design a steady pressure hydrogen pipeline, it is more challenging to design a pipeline used to store as well as transport hydrogen.
The presentation explores the absorption and diffusion kinetics of mobile absorbed hydrogen in steel for daily cyclic storage, such as for a pipeline working in high pressure packing followed by de-packing on daily basis. In an API 5L steel the inner layers of the pipeline would experience strong variations of mobile hydrogen concentration, but deeper into the steel the diffusion will continue in a steadier regime. Permeation still happens in a similar way to a steady averaged condition. However, when looking at a bi-layered pipeline, the situation can be very different. If the inner layer is made of a low diffusivity material and is thick enough, the inner layer can effectively screen the second layer from hydrogen exposure. All the daily variation is absorbed within the inner layer and the concentration gradient is such that the second API 5L layer is exposed to very low levels of concentration. When compared to the equivalent partial pressure using the Sievert law, pressures are well below the level admitted to cause HE. As a result, the mechanical design of the pipeline could be done per the usual pipeline codes.
The presentation explores the absorption and diffusion kinetics of mobile absorbed hydrogen in steel for daily cyclic storage, such as for a pipeline working in high pressure packing followed by de-packing on daily basis. In an API 5L steel the inner layers of the pipeline would experience strong variations of mobile hydrogen concentration, but deeper into the steel the diffusion will continue in a steadier regime. Permeation still happens in a similar way to a steady averaged condition. However, when looking at a bi-layered pipeline, the situation can be very different. If the inner layer is made of a low diffusivity material and is thick enough, the inner layer can effectively screen the second layer from hydrogen exposure. All the daily variation is absorbed within the inner layer and the concentration gradient is such that the second API 5L layer is exposed to very low levels of concentration. When compared to the equivalent partial pressure using the Sievert law, pressures are well below the level admitted to cause HE. As a result, the mechanical design of the pipeline could be done per the usual pipeline codes.
Monday 8 June 2026 6:00 PM - 8:00 PM (UTC+08)
Location
East Perth North Metro Tafe
140 Royal Street, East Perth WA 6004
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Hydrogen diffusion, permeation through pipeline walls
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