The companies have cooperated in Poland and Italy on the first European pipeline certified for pure hydrogen
Hydrogen is becoming the energy source of the future due to its versatility, producibility, and efficiency. The European Union recognises hydrogen's role in the decarbonisation of industry and thus in the energy turnaround within its hydrogen strategy
The strategy's goal is to achieve an annual production of 10 million tonnes of green hydrogen within Europe by 2030, with an additional 10 million tonnes of hydrogen imports. This requires the availability of corresponding infrastructure, specifically a Europe-wide hydrogen transmission grid.
The European Hydrogen Backbone (EHB) will be developed by converting 70% of existing natural-gas pipelines and constructing new hydrogen pipelines for the remaining 30%. Corinth Pipeworks (CPW), a Greek pipe producer, and Dillinger, a German heavy-plate maker, are pursuing the construction of high-pressure gas pipelines for hydrogen of up to 100% purity. An example includes their cooperation in Poland and Italy on the first European pipeline certified for pure hydrogen.
Hydrogen laboratory
CPW established an Emerging Fuels Team in 2020 to define and pursue a strategy for future-oriented development of pipe technology. The team consists of Athanassios Tazedakis, senior operations director and metallurgical engineer with a PhD in Welding, Nikolaos Voudouris, head of Engineering and Technology and chemical engineer with a PhD in Materials Science, and Efthymios Dourdounis, head of Quality Assurance and chemical engineer with a PhD in Metallurgy.
The company developed protocols for hydrogen pipelines based on the ASME B31.12 code published in the United States due to a lack of European standardisation. CPW integrated the code requirements into a standardised testing and qualification procedure for pipes to achieve certification of the product in line with ASME Code B31.12 Option B.
This certification applies to hydrogen pipes used for transmitting hydrogen/natural gas mixtures and pure gaseous hydrogen, with no design restrictions for onshore applications. Apart from the qualification protocol, CPW has developed its testing capabilities.
CPW is currently the only pipe producer to possess an in-house hydrogen laboratory for testing and certifying pipes for pure hydrogen under steady-state and/or rising loading conditions, as well as at high pressures of up to 300 bar.
Testing is based on ASME Code B31.12 and other relevant standards, evaluating the reduction in toughness and ductility caused by hydrogen embrittlement. This understanding of hydrogen-specific phenomena enables the supply of end products with the required level of safety and delivers further insights into the design requirements of gas grid operators.
High-pressure pipeline for Poland
CPW has long served GAZ-System Poland, the Polish gas grid operator. In 2021, the company received an order for an 80km high-pressure pipeline, initially for natural gas but designed for future hydrogen use as part of the EHB.
CPWs' standardised test and certification procedure helped GAZ-System in its decision to adopt the requirements of the ASME Code into its own specifications for the planned high-pressure gas pipeline. Running from Gustoržyn to Wronów, the pipeline is only one section of a larger high-pressure gas pipeline.
The longitudinally submerged arc-welded (LSAW) pipeline has a diameter of 1,016mm and a wall thickness of 22.2mm. Externally, it has a triple-layer polyethylene coating to protect against corrosion, and internally, it contains an epoxy-resin coating. The pipeline's operating pressure of 80 bar conforms to the typical pressure for transmission pipelines used in Europe.
Tazedakis said, "In order to meet and exceed the applicable specification requirements, we must be very cautious and conservative when selecting our partners."
Dourdounis said, "Our choice fell on Dillinger, which supplied 11,000 tonnes of heavy plate in grade L485ME for this section. This is the highest steel grade that may be qualified for hydrogen applications, as per ASME B31.12. Grades L415, L450, and L485 are more commonly used. However, the selection of L485ME grade, as specified by GAZ-System, permits a lower wall thickness due to its high mechanical properties (i.e., yield strength), resulting in less steel being needed for the same design pressure."
Heavy plates for hydrogen pipelines
Dillinger was chosen as the supplier due to data regarding steel properties, the specific requirements CPW set, and Dillinger's track record in the industry.
According to Voudouris, it was Dillingers' capabilities to form plates that met the specifications for hydrogen pipelines that proved decisive.
Voudouris said, "We set strict requirements for the chemical analysis and the mechanical properties of the steel, which we ourselves must guarantee in order to ensure high-quality pipes."
The pipe plate needed to behave predictably during forming, allowing for correct welding preparation. The preceding FEM analysis detailed how each forming station and plate was to be applied for the specific pipe designs.
Voudouris said, "We don't produce standard, off-the-shelf pipes; every project is designed from the ground up. Our customers provide designs for clearly defined applications, with requirements specified in detail."
The steel supplier must therefore design the steel not only to meet customer requirements but also to comply with all relevant technical standards, including those specific to hydrogen.
Certified safety
Tazedakis said, "Hydrogen embrittlement is one of the greatest challenges that we have to overcome in this sector, especially in the case of high-strength steels. For us, it was a decisive factor in the selection of this high-strength material from Dillinger. Only in this way can we ensure that what has been promised will actually be supplied, and not only from Dillinger, but also from ourselves."
Voudouris said, "Our relations with Dillinger are based, however, not only on the quality of the materials supplied, but on the entire package: We are also given an extremely high-quality set of documentation on the steel. Everything is top-level: the metallurgical know-how, the reaction capability, enabling rapid adaptation of specific items to tests, and, not least of all, communications. We speak the same language. This is why frequent meetings are held, to mutually bring projects up to the latest status and to update our own and Dillinger's agendas for these technically demanding projects."
The high-pressure gas pipeline delivered for GAZ-System has been in operation since 2023 and is one of the first European pipelines certified for the transmission of pure hydrogen.
The first hydrogen pipeline of this type was also supplied by CPW for the Italian pipeline-grid operator Società Nazionale Metanodotti (SNAM). This pipeline comprises over 600km of hydrogen-certified pipes produced by CPW.
What's next
Converting existing pipelines will require significant economic sacrifices from gas-grid operators, as they will need to inspect the entire length of the pipeline and reduce the pipeline pressure for the transmission of hydrogen if any defects or suspect areas are found.
Additionally, due to the lower energy density of hydrogen, hydrogen transmission pipelines are only profitable with high flow rates, resulting in the expectation that hydrogen will require high demand for entirely new pipelines. CPW is working to develop the currently missing standards for offshore pipelines.
