Preparations for 100% hydrogen: TÜV AUSTRIA assesses existing natural gas pipeline of Wiener Netze

With the increasing shift from pure natural gas to natural gas-hydrogen mixtures and even 100% hydrogen gas flows, there is a growing need to check existing gas pipelines and networks for their adaptability and resistance to hydrogen molecules. As Austria’s leading testing, inspection and certification service provider, TÜV AUSTRIA is on hand to provide advice and support, with a focus on safety-relevant processes.

From data analysis to evaluation

TÜV AUSTRIA recently provided support in the evaluation of an existing natural gas pipeline of Wiener Netze for the transportation of up to 100% hydrogen. The focus was on researching standards and examining the state of the art. Specifically, the use of materials and welding seams for hydrogen transportation was examined. The special challenge in this project was that essential data had to be extracted from documents that were more than 30 years old using data mining. For this purpose, a separate database was created with all the necessary data for the relevant sections (Simmering to Donaustadt power plant and Donaustadt power plant to Aderklaa). This included the type of various components, their material, age, diameter, wall thickness, heat treatment condition and fracture toughness value. This was followed by comprehensive analysis and evaluation procedures to assess the existing natural gas pipeline and to determine the safety factor of the pipe string and calculate the maximum allowable operating pressure (MOP) based on the available information.

The detail is in the molecule

As hydrogen (H2) is a much smaller molecule than natural gas (CH4), it can penetrate the material more easily and also penetrate seals more easily, for example. In addition, hydrogen can cause limited material defects such as (hairline) cracks and small corrosion spots to grow. The strength properties of materials, such as hardness, tensile strength and impact strength, are impaired and lead to hydrogen embrittlement. Therefore, a thorough investigation and evaluation must be carried out to assess whether existing networks are suitable for the transportation of hydrogen.