TY - CONF A1 - Nietzke, Jonathan A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas T1 - Experimental and numerical characterization of hydrogen diffusion in thick-walled submerged arc welded joint of S420G2+M offshore steel grade N2 - Offshore wind turbines are an important goal in national energy strategies worldwide. Foundation structures are manufactured from submerged arc welded (SAW) plates with thicknesses up to 200 mm. In that connection, high-strength steels like the S420G2+M are more and more applied offering the possibility for increased stability and load-bearing capacity of the foundations. These offshore steel grades can show a susceptibility for delayed hydrogen assisted cold cracking of the weld joints. For that purpose, a minimum waiting time (MWT) of up to 48 h (dependent on applied standards) is recommended before non-destructive testing is allowed and conducted. But this concept is based on older steel grades that have been used for three or more decades. Nowadays, the metallurgical improvements (clean steels, proper rolling, and heat treatment) of base materials and well as welding consumables must be anticipated. Hence, the MWT concept should be critically discussed as it is assumed to be very conservative. For that reason, the focus of this study was to investigate the diffusion behavior in S420G2+M steel and its multi-layer SAW joint. Electrochemical permeation experiments were carried at room temperature. Boundary conditions were anticipated in terms of using different sample thicknesses. From the experimental data, hydrogen diffusion coefficients and absorbed diffusible hydrogen concentrations had been calculated. It was shown that hydrogen diffusion in the base material is increased compared to the weld metal. In addition, the sample thickness had a significant on the calculated diffusion coefficients. The minimum and maximum diffusion coefficients had been used for numerical modelling of the hydrogen diffusion in the welding joint. It became clear that a MWT must be always regarded together with a critical initial diffusible hydrogen concentration for the evaluation of a possible delayed cracking as diffusion times were mostly > 48 h due to the thick plates. T2 - 4th International Conference on Metals and Hydrogen - Steely & Hydrogen 2022 CY - Ghent, Belgium DA - 11.10.2022 KW - Hydrogen KW - Submerged arc welding KW - Diffusion KW - Minimum waiting time KW - Electrochemical permeation PY - 2022 SP - 1 EP - 11 CY - Ghent, Belgium AN - OPUS4-56075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Hydrogen trap characterization in 200 and 1,000 bar charged CoCrNi medium entropy alloy compared to steel AISI 316L N2 - Multiple principal element alloys (MPEAs) represent a new class of metallic materials. MPEAs, such as the CoCrNi medium entropy alloy (MEA), have attracted considerable research attention as potential materials to replace, for example, austenitic steels in high-pressure hydrogen environments. Due to the relatively new alloy concept, studies on the specific hydrogen diffusion and trapping behavior of high-pressure hydrogen-charged CoCrNi MEAs are rare so far. For this reason, a CoCrNi-MEA was investigated and compared to an austenitic stainless steel, AISI 316L. Both materials were subjected to high pressure hydrogen loading for two different pressures: 200 bar and 1,000 bar. After charging, thermal desorption analysis (TDA) was used with three heating rates from 0.125 K/s to 0.500 K/s to clarify the specific hydrogen desorption and trapping behavior. To the best of our knowledge, this study is the first to characterize hydrogen diffusion and trapping in 1,000 bar high-pressure charged CoCrNi. For this purpose, the underlying TDA spectra were analyzed in terms of peak deconvolution into a metallurgically justifiable number of defined peaks. The individual peak temperatures and activation energies “EA” were calculated. The following conclusions can be drawn from the results obtained: (1) Exposure to 200 bar or 1,000 bar leads to an increase in hydrogen absorption, regardless of the material investigated, expressed by a significantly increased desorption rate at 1,000 bar. However, the effusion peaks typically occur only at high temperatures. The (2) TDA showed that a four-peak deconvolution scenario was sufficient to describe the trapping behavior and the "EA" indicated the dominance of irreversible traps. In addition, the average trapping energy is higher than in the 316L. The (3) charge pressure related hydrogen solubility was in the order of: CoCrNi-MEA < 316L for both pressures and (4) charging at 1000 bar results in an average concentration of 49 wt.ppm (CoCrNi-MEA) and > 75 wt.ppm (316L). In summary, the CoCrNi-MEA was characterized by a reduced solubility, but very deep entrapment compared to the 316L. For this reason, further application potentials of the MEA may arise. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Medium entropy alloy KW - Hydrogen KW - Trapping KW - Diffusion KW - High-pressure charging PY - 2025 AN - OPUS4-64160 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for the assessment of in-service welding on/onto pressurized hydrogen pipelines N2 - Hydrogen is the energy carrier of tomorrow and requires a reliable large-scale transport infrastructure. In addition to new pipelines, the conversion of existing natural gas (NG) pipeline grids is an essential part. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the effects of hydrogen embrittlement, the material compatibility (low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines e.g. require maintenance or the need for installation of additional outlets with the necessity of welding on/onto the pipelines while they are still in service, i.e. with gas flow under high pressure, such as the well-known "hot tapping". This in-service welding poses challenges for hydrogen operations. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity compared to room temperature. In addition, possible surface reactions of the present iron oxides (e.g. magnetite or hematite) with the hot hydrogen should be considered. In this context, the knowledge of hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study presents a specially designed mock-up / demonstrator concept for the realistic assessment of the welding process conditions. The mock-up was designed to allow in-situ temperature measurement during the welding process as well as ex-post sample extraction for quantification of the absorbed hydrogen concentration. For safety reasons, the required volume of pressurized hydrogen was limited by inserting a solid cylinder to ensure a 1 cm thick layer of hydrogen gas. Welding experiments on the DN60 and DN200 pressurized mock-ups showed the possibility of safe welding on or onto pressurized hydrogen pipelines. Indeed, the austenitizing temperature was reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding parameter recommendations. This corresponded to an increased hydrogen uptake in the welded area of several ppm. From this point of view, the suggested component concept is a viable strategy for the screening of several materials and welding parameter combinations under realistic operational conditions. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - In-service welding KW - Pipeline KW - Hydrogen KW - Component test PY - 2025 AN - OPUS4-64159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining technologies for hydrogen components: current need and future perspectives N2 - The study provides an overview of the aspects of joining and its importance in manufacturing of components for the more and more important field of hydrogen as key factor for the energy transition to a decarburized future. To this end, the fundamentals of the technology fields of hydrogen production, storage, transport, and application are presented and the state of the art of manufacturing of components for hydrogen technologies by joining is summarized. Based on representative examples from practice, research and development, the importance of joining technology in hydrogen technologies is clearly highlighted and perspectives for the future are derived. From a macroeconomic perspective, the focal points, or trends of joining technologies here include: the erection of new infrastructure for hydrogen storage and transport, and the safe conversion of existing natural gas infrastructure and its challenges for welded materials. In addition, we show the problems that are anticipated with in-service repair welding of hydrogen pipelines. In hydrogen applications, the efficient mass production of fuel cells and electrolysers is becoming increasingly important. For that reason, the importance of additive manufacturing is highlighted. Finally, the challenges for technical regulations and standardization by using hydrogen are shown. T2 - AJP 2023: 3rd International Conference on Advanced Joining Processes 2023 CY - Braga, Portugal DA - 19.10.2023 KW - Hydrogen KW - Infractstructure KW - Joining KW - Welding KW - Research PY - 2023 AN - OPUS4-58674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Kromm, Arne A1 - Mente, Tobias A1 - Brackrock, Daniel A1 - Czeskleba, Denis A1 - Kannengießer, Thomas T1 - Component test for the assessment of delayed hydrogen-assisted cracking in thick-walled SAW joints for offshore applications N2 - Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods, or jackets. These components are typically constructed using submerged arc welding (SAW) with high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen-assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicates the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam/layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with over 20 passes and a seam length of 1000 mm. Additional welded stiffeners simulated the effect of a high restraint, to achieve critical HAC conditions. The necessity of a minimum waiting time (MWT) before the NDT can be conducted (to exclude HAC) was critically verified by the application of ultrasonic testing of the welded joint at different time-steps of the NDT of up to 48 h after the completion welding. The residual stresses were determined by a robot XRD goniometer. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modeling allowed the qualitative estimation of the hydrogen diffusion in the weld. No noticeable HAC occurrence was identified and confirms the high cracking resistance of the investigated material. Finally, the applicability of the MWT concept should be critically discussed. KW - Hydrogen KW - Cold cracking KW - Minimum Waiting Time KW - Offshore steel grade KW - Component test PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-591981 DO - https://doi.org/10.1007/s40194-023-01658-5 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-59198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Welding of in service hydrogen pipelines for repair and maintenance purposes Concepts and Challenges N2 - Hydrogen will make a decisive contribution to a sustainable large-scale energy supply, the transport of which will be based on long-distance pipeline grids. Previous material compatibility studies have shown that the currently used low-alloy pipe steels are generally suitable for hydrogen pipelines. However, this cannot be directly transferred to the case of repair welding. For technical and economic reasons, welding work on hydrogen pipelines in service is usually carried out during operation under continuous pressure and gas flow. In this context, concepts such as hot tapping and stoppling are well established in natural gas (NG) grids and crude oil transportation. In hot tapping, a pressurized pipeline is drilled by flanging a sealed, pressure-tight system consisting of a shut-off valve and drilling equipment. For this purpose, sleeves (made of preformed cylindrical half-shells) must be welded by longitudinal seams and then welded to the product-carrying pipeline by circumferential girth welds. Preheat temperatures of approximately 100 °C must be maintained for most manual metal arc (MMA) / shielded metal arc welding (SMAW) and 250 °C for the interpass temperature in multi-pass welding. This is particularly important for thin-walled pipelines because the austenitizing temperature is exceeded on the inside of the pipeline when the girth welds are welded. As a result, significantly higher hydrogen absorption in the pipeline steel is expected, with possible degradation of mechanical properties or cracking. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - Hydrogen KW - Repair welding KW - Pipelines KW - In-service PY - 2024 AN - OPUS4-61155 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Standardization and examples for R & D activities on hydrogen technologies with respect to testing procedures in Germany N2 - This contribution briefly summarizes the standardization activities in accordance with the "Nationale Roadmap Wasserstofftechnologien" and presents selected results on the activities in Germany with scope on hydrogen transport in pipelines. The talk was given during a panel discussion to set-up a steering committee for standardization for hydrogen pipelines and welding , coordinated by the International Institute of Welding. T2 - IIW Annual Assembly, Meeting of Commission XI CY - Singapore DA - 19.07.2023 KW - Hydrogen KW - Welding KW - Pipelines KW - Standardization KW - Research PY - 2023 AN - OPUS4-57976 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Intended weld repair of in service hydrogen pipelines N2 - In the course of tomorrow's hydrogen-based energy transition, the construction of the corresponding infrastructure will play a central role. In that context, large diameter long-distance transmission pipelines for hydrogen will be the backbone in the European Union with service pressures from 70 to 90 bar (e.g., de-pending on national regulations). It is a major goal to repurposing the existing natural gas (NG) infrastructure despite the necessity of new pipelines. From that point of view repair welding or further welding of branch pipe etc. can be necessary during in-service, i.e., permanent flow of pressurized hydrogen. The reason is that a shut-down of large diameter pipelines is not easy or sometimes merely impossible. At the moment, it is entirely open if current repair welding procedures for NG pipe-lines can be transferred to pure hydrogen pipelines. For that reason, a collaborative project between BAM, DVGW (German Association for Gas and Water Professions) and a large number of gas grid operators, pipeline manufacturers and construction companies was initiated in 2023 to answer questions on: (1) How many hydrogen is additionally absorbed during the preheating and maintaining at interpass temperature under remaining operational pressures? (2) Is the hydrogen concentration sufficient to reach a critical condition? (3)Which material and weld microstructure are the most susceptible? (4) Is there a difference in the repair welding behavior of NG pipelines with materials in “used” condition? (5) Which welding parameters and joint dimensions must be ensured for safe repair welding? The final aim of this project is the publication of a recommended practice for repair welding of in-service hydrogen pipelines. For that reason, the present study gives an overview on: (A) current practice in repair welding of in-service pipelines and (b) plans for hydrogen pipelines and first results of international research projects. T2 - IIW Annual Assembly, Meeting of Commission XI CY - Singapore DA - 19.07.2023 KW - Hydrogen KW - Repair Welding KW - Pipelines KW - Research PY - 2023 AN - OPUS4-57975 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Schaupp, Thomas A1 - Zavdoveev, Anatoly T1 - Challenges for testing hydrogen-assisted cold cracking in weld seams of high-strength steel grades N2 - Hydrogen can cause weld cold cracking even days after fabrication. In this respect, higher strength steels present a challenge to established cold crack testing. In general, the tolerable hydrogen concentration for crack prevention decreases with increasing material strength. In addition, advanced welding processes require changes in weld geometry and heat input. This directly influences the formation of crack-critical microstructures, e.g. in hardened areas of the heat-affected zone. The limits of use and application of modern cold cracking tests are evaluated by (1) the externally loaded Implant-test and (2) the self-restraint Tekken-test. In particular, external mechanical stresses, which cause additional mechanical loads on the components during welding, must be considered due to the component-specific stiffness of high-strength steels. Accompanying test methods for determining hydrogen concentration and diffusion in welds are presented, such as carrier gas hot extraction for determining hydrogen concentration (ISO 3690) or temperature-dependent diffusion coefficients. These values are of great importance for a holistic approach to the evaluation of the cold cracking sensitivity of high strength steels. KW - Hydrogen KW - Welding KW - Cold cracking test KW - High-strength steel PY - 2024 DO - https://doi.org/10.37434/tpwj2024.08.01 SN - 0957-798X VL - 2024 IS - 8 SP - 3 EP - 9 PB - International Association "Welding" CY - Kyiv, Ukraine AN - OPUS4-60946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian A1 - Erxleben, Kjell A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Repair Welding of In-Service Hydrogen Pipelines - Concepts and Challenges N2 - Hydrogen is set as the energy carrier of tomorrow for a more sustainable fossil fuel free future. As this necessitates a reliable transport infrastructure, repurposing of the existing natural gas grid is planned. With regards to the well-known effect of hydrogen embrittlement, the compatibility of utilized materials must be investigated. First comprehensive studies on pipeline material hydrogen compatibility indicate that these materials can be applied to a certain extent. Nonetheless, the material compatibility is currently of high interest and focus of numerous research projects worldwide. However, pipelines require frequent maintenance and repair work. As part of these, in some cases it is necessary to do weldments onto pipelines while they are pressurized. This in-service welding introduces additional challenges for the material compatibility. Due to the resulting high temperatures, the metallurgical changes in the material and of course the presence of high-pressure hydrogen in the pipeline, additional investigations need to be conducted to ensure that no critical material degradation because of increased hydrogen absorption occurs and an overall material compatibility is given. For this reason, the present paper introduces in-service welding on pipelines. An overview of current research projects that deal with the application of in-service welding specifically on hydrogen pipelines and the emerging problems when applying these techniques on hydrogen pipelines is given. Methods of material testing, their limits and possible solutions are presented and discussed. T2 - 2024 15th International Pipeline Conference CY - Calgary, Alberta, Canada DA - 23.09.2024 KW - Hydrogen KW - Pipeline KW - Welding KW - In-Service PY - 2024 SN - 978-0-7918-8856-8 DO - https://doi.org/10.1115/IPC2024-133052 SP - 1 EP - 6 PB - The American Society of Mechanical Engineers (ASME) CY - New York AN - OPUS4-62262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengiesser, Thomas A1 - Kromm, Arne T1 - In-service and repair welding of pressurized hydrogen pipelines–a review on current challenges and strategies N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed. KW - In-service KW - Hydrogen KW - Repair welding KW - Pipeline PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638944 DO - https://doi.org/10.1007/s40194-025-02127-x SN - 0043-2288 SP - 1 EP - 24 PB - Springer Science and Business Media LLC AN - OPUS4-63894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Diffusion and trapping of gaseous hydrogen charged CoCrFeMnNi-HEA vs. austenitic steel AISI 316L at pressure up to 1000 bar N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s). The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - High-entropy alloy KW - Hydrogen KW - Trapping KW - Diffusion KW - High-pressure charging PY - 2024 AN - OPUS4-61156 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian A1 - Rhode, Michael T1 - Repair welding of pressurized in-service hydrogen pipelines: A review on current challenges and strategies N2 - As energy carrier of the future, green hydrogen can make a decisive contribution to a sustainable energy supply. Particularly important is the decarbonization of heavy industry. Therefore, a reliable supply of hydrogen must be guaranteed. A hydrogen pipeline grid can achieve this purpose. In Europe concrete plans for a hydrogen pipeline grid already exist, as the so called “European Hydrogen backbone”. As building a completely new pipeline grid is economically not justifiable, a dual-way strategy of repurposing natural gas (NG) pipelines and newly built pipelines is intended. Long distance pipeline grids require regular maintenance and repairs. For NG pipelines in-service welding is state of the art. Concepts such as hot-tapping (drilling into pressurized pipelines) and “stoppling” (sealing off pipeline sections after installing bypasses or pressure relieves) allow the repair of damaged pipeline sections or the installation of new branches without shutting the pipeline down, which in most cases isn’t possible from an economic standpoint. The EIGA 121/14 guideline already pointed out in 2014 that “A hydrogen hot-tap shall not be considered a rou-tine procedure, […]”. This shows that the determination of the transferability of these repair concepts to hydrogen pipelines is of utmost importance. Due to the degrading effects of hydrogen on mechanical properties, commonly referred to as “hydrogen embrittlement” it is necessary to understand and investigate the occurring effects. In the special case of repair welding on in-service hydrogen pipelines an increased hydrogen uptake due to a large heat input and microstructural changes in the material needs to be considered. Therefore, material degradation must be investigated to determine whether modifications of repair procedures are necessary to ensure a reliable and safe hydrogen transportation via pipelines. For this reason, this paper gives an overview on existing weld repair concepts and its risks and limitations in terms of hydrogen absorption and possible embrittlement effects when transferred to hydrogen pipelines. The complexity lies in a large variety of materials (low alloyed steels), pipeline diameters and corresponding weld-ed joints. The material compatibility of materials in used (repurposed NG-pipelines) and new condition must be investigated. Particularly for repurposed/used pipelines the effect of a pre-matured/corroded inner surface and sometimes insufficient documentation of the material “history” needs to be considered. An overview on ongoing and completed R&D-projects with respect to repair concepts for hydrogen pipelines and hydrogen effects on pipeline materials is given. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission II-A "Metallurgy of Weld Metals" CY - Ixia, Rhodes Island, Greece DA - 07.07.2024 KW - Hydrogen KW - Pipeline KW - In-Service Welding PY - 2024 AN - OPUS4-60757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Quantification of hydrogen uptake during in-service hydrogen pipeline welding N2 - Hydrogen must be transported on a large scale from producers to consumers to ensure the energy transition. The necessary pipeline grid is achieved by conversion of the natural gas (NG) grid and building new pipelines. Welding during service as part e.g. of “hot-tapping” is unavoidable for maintenance/repair/expansion. Based on existing studies, the basic material compatibility of (low-alloyed) pipeline steels with hydrogen is postulated. However, this cannot be assumed for the case of in-service welding on pipelines in pressurized condition. The reason is the increased temperature e.g. by preheating and (in particular) during welding of the single passes. As a result, the inner pipeline surface undergoes multiple short-term heating but to high temperatures. In particular, the first passes can result in a temperature close to the austenitic transformation of the material for small wall thicknesses. Both increase the hydrogen uptake into the welded joint. If hydrogen embrittlement is likely to occur, depends on the hydrogen uptake, which must be quantified. For this purpose, welding experiments on pressurized demonstrators were conducted. The hydrogen uptake at 100 bar was compared to reference experiments with nitrogen. A new sample extraction routine for the quantification of the weld-zone specific hydrogen uptake was established. Comprehensive experiments with different steels (P235, L360, L485), wall thicknesses (4.1 mm to 7.8 mm) and diameters (DN50 and DN200) were conducted. In addition, the influence of the welding layer sequence on the hydrogen uptake between single- and multi-layer welds was investigated. Analytical approaches were used to approximate the hydrogen uptake in the respective weld zones. The main findings were that the layer sequence and especially the wall thickness have a large influence on the hydrogen uptake. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 12 AN - OPUS4-63166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Characterization of hydrogen trapping in a CoCrFeMnNi high-entropy alloy charged up to 1000 bar high-pressure hydrogen N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s), see Fig. 1a to d. The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. In addition, the trap occupancy rate must be considered in terms of a pressure-related hydrogen absorption. The derived apparent hydrogen solubility was in the order: 316L < CoCrFeMnNi-HEA for both charging pressures. Especially, the 1,000 bar values lead to noteworthy results with > 70 wt.ppm for the AISI 316L and >130 wt.ppm for the CoCrFeMnNi. In fact, both the hydrogen diffusion and trapping data on gaseous high-pressure hydrogen charged HEAs are rare so far. The results of the present study allow a deeper understanding of hydrogen trapping in the regarded CoCrFeMnNi-system. T2 - 78th IIW Annual Assembly and International Conference CY - Genoa, Italy DA - 26.06.2025 KW - Hydrogen KW - Thermal desorption analysis KW - High-pressure charging KW - Trapping KW - Diffusion PY - 2025 AN - OPUS4-63542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Component test concept for evaluation of in-service welding on pressurized hydrogen pipelines N2 - Hydrogen is set as the energy carrier of tomorrow and most countries will achieve large-scale hydrogen transport through the conversion of the natural gas (NG) grid and the construction of new pipelines. The interaction between hydrogen and the pipeline materials differs fundamentally from that of NG, as hydrogen is readily absorbed into the material. Considering the possible hydrogen embrittlement (HE), the compatibility of the pipeline materials (low-alloyed steels with a wide strength/thickness range) must be investigated. However, pipelines require intervention for maintenance, repair, or grid expansion with welding on/onto the pipelines while in service, i.e. the well-known "hot tapping" and "plugging" or “stoppling”. The challenges compared to NG can be broadly divided into the possible austenitization of the inner pipe material exposed to hydrogen and the welding itself. Both result in a significant increase in hydrogen solubility and could potentially pose challenges in terms of HE. Emphasis is placed on the word "could" because knowledge of "hot tapping" on hydrogen pipelines is scarce due a lack of service experience. To this end, this study proposes a concept for a component-like demonstrator with the objectives: (1) safe feasibility of "hot tapping" on pressurized model hydrogen pipeline sections, (2) facilitate ex-post sample extraction for the purpose of quantifying the absorbed hydrogen concentrations, and (3) ensure in-situ temperature measurement during welding to monitor the pipeline surface temperature. For safety reasons in the event of an unintentional "burn-through", a solid cylinder was inserted in the demonstrator to restrict the hydrogen gas volume to a small, pressurized layer. Reference pipeline surface temperature measurements were ensured on comparable, unpressurized geometries. The investigated range of welding conditions was investigated for representative material/thickness combinations (DN50 to DN200), suggesting the feasibility of the demonstrator for the determination of reliable in-service welding conditions for both installed and new pipelines for hydrogen service. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 11 AN - OPUS4-63168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Development of a component test for assessment of delayed hydrogen assisted cracking susceptibility of thick walled submerged arc welded high strength offshore steels N2 - Offshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever-increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time-delayed hydrogen assisted cracking (HAC) may occur. The evaluation of this crack susceptibility is very complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry was developed to transfer the real stiffness conditions to laboratory (i.e. workshop) scale. The 350 kg mock-up studied consisted of heavy plates (thickness 50 mm, seam length 1,000 m) joined by a 22-pass submerged-arc weld. Additional stiffeners simulated the effect of high restraint or shrinkage restraint of the weld. Extreme scenarios of hydrogen absorption during welding were simulated by using flux in dry (HD < 5 ml/100g Fe) and wet (HD > 15 ml/100g Fe) conditions. Weld residual stresses were determined using a robotic X-ray diffractometer. Areas of critical tensile residual stress (at the level of the yield strength) were found in the weld metal and in the heat affected zone, suggesting that these weld sub-zones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were tested by phased array ultrasonic testing (PAUT) after welding, 6 h, 12 h, 24 h, and a maximum of 48 h. Summarized, no significant occurrence of HAC was detected, indicating the high crack resistance of the welded joint, i.e., a suitable combination of base material, welding consumable and parameters. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - Hydrogen KW - Offshore wind turbine KW - Component test KW - Submerged arc welding KW - Minimum waiting time PY - 2024 AN - OPUS4-61154 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Assessment of in-service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow. This requires a reliable transport infrastructure with the ability to carry large amounts of hydrogen e.g. for steel industry or chemical industry. The conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. In this context, the transportation of hydrogen is fundamental different from NG as hydrogen can be absorbed into the pipeline material. Given the well-known effects of hydrogen embrittlement, the compatibility of the materials for the intended pipelines must be investigated (typically low alloy steels in a wide range of strengths and thicknesses). However, pipelines require frequent maintenance, repair or the need for installation for further outlets. In some cases, it is necessary to perform welding on or onto the pipelines while they are still in service, i.e. with active gas flow under high pressure, e.g. such as the well-known “hot tapping”, see Fig. 1a. This in-service welding causes challenges for hydrogen operations in terms of additional hydrogen absorption during welding and the material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study introduces a specially designed mock-up / demonstrator concept for the realistic assessment of the welding processing conditions, see Fig. 1b. The mock-up was designed to enable in-situ temperature measurement during welding as well as ex-post extraction of samples for the quantification of the absorbed hydrogen concentration, see Fig. 1c. For safety measures, the necessary pressurized hydrogen volume was limited by the insertion of a solid cylinder ensuring a 1 cm hydrogen gas layer. Welding experiments on the pressurized mock-ups with the diameters DN50 and DN200 have shown that the austenitization temperature can be reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding practices. This corresponds to an increased hydrogen uptake in the welded area of several ppm T2 - 1st Conference on Hydrogen in Materials Science and Engineering (H2-MSE) CY - Siegburg, Germany DA - 11.02.2025 KW - Hydrogen KW - Pipeline KW - In-service welding KW - Component test PY - 2025 AN - OPUS4-62544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Update on "Call for interested people to contribute to series of comprehensive papers on welding and joining of components for sustainable energy systems" N2 - Based on the initial call in March 2024, an update time-frame is introduced on the working plan for a comprehensive review paper series on joining and welding technologies for the manufacturing of components and parts used in sustainable energy generation, conversion, and transport with focus on hydrogen and wind energy. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission II-A CY - Ixia, Rhodes, Greece DA - 07.07.2024 KW - Review paper KW - Research study KW - Hydrogen KW - Joining KW - Welding PY - 2024 AN - OPUS4-60674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for simplified testing of hydrogen‐assisted delayed cold cracking of high‐strength, submerged arc‐welded offshore steel structures N2 - Offshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever-increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time-delayed hydrogen assisted cracking (HAC) may occur. The evaluation of this crack susceptibility is very complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry was developed to transfer the real stiffness conditions to laboratory (i.e. workshop) scale. The 350 kg mock-up studied consisted of heavy plates (thickness 50 mm, seam length 1,000 m) joined by a 22-pass submerged-arc weld. Additional stiffeners simulated the effect of high restraint or shrinkage restraint of the weld. Extreme scenarios of hydrogen absorption during welding were simulated by using flux in dry (HD < 5 ml/100g Fe) and wet (HD > 15 ml/100g Fe) conditions. Weld residual stresses were determined using a robotic X-ray diffractometer. Areas of critical tensile residual stress (at the level of the yield strength) were found in the weld metal and in the heat affected zone, suggesting that these weld sub-zones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were tested by phased array ultrasonic testing (PAUT) after welding, 6 h, 12 h, 24 h, and a maximum of 48 h. Summarized, no significant occurrence of HAC was detected, indicating the high crack resistance of the welded joint, i.e., a suitable combination of base material, welding consumable and parameters. T2 - MPA Seminar 2024 - Materials, Processes, Applications CY - Stuttgart, Germany DA - 08.10.2024 KW - Hydrogen KW - Offshore wind turbine KW - Component test KW - Submerged arc welding KW - Minimum waiting time PY - 2024 AN - OPUS4-61323 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining Processes in Hydrogen Technologies - Current need and future R&D activites, a review N2 - This study gives an overview on the important field of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the different technological field of hydrogen generation, storage, transport and use. In addition, the emerging field of additive manufacturing is included. Finally, some remarks are given for necessary changes in the standardization and its challenges. T2 - 46th Seminar - Additive Manufacturing, Hydrogen, Energy, Integrity CY - Online meeting DA - 12.10.2021 KW - Hydrogen KW - Joining process KW - Welding KW - Review KW - Research and Development PY - 2021 AN - OPUS4-53554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining processes for components in hydrogen technologies: Current need and future importance N2 - This presentation gives an overview on the importance of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the three technological fields: hydrogen storage, transport and use (in terms of the emerging field of additive manufacturing). Finally, some remarks are given for necessary changes in the standardization. T2 - IIW Intermediate Meeting, Comm. II-A "Welding Metallurgy" CY - Online meeting DA - 17.03.2022 KW - Hydrogen KW - Welding KW - Research KW - Review KW - Additive manufacturing PY - 2022 AN - OPUS4-54488 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kaiser, Sebastian T1 - Repair welding of pressurized in-service hydrogen pipelines: A review on current challenges and strategies N2 - As energy carrier of the future, green hydrogen can make a decisive contribution to a sustainable energy supply. In Europe concrete plans for a hydrogen pipeline grid already exist, as the so called “European Hydrogen backbone”. As building a completely new pipeline grid is economically not justifiable, a dual-way strategy of repurposing natural gas (NG) pipelines and newly built pipelines is intended. Long distance pipeline grids require regular maintenance and repairs. In that conection, for natural gas (NG) pipelines in-service welding is state of the art. Concepts such as hot-tapping (drilling into pressurized pipelines) and “stoppling” (sealing off pipeline sections after installing bypasses or pressure relieves) allow the repair of damaged pipeline sections or the installation of new branches without shutting the pipeline down. The EIGA 121/14 guideline already pointed out in 2014 that “a hydrogen hot-tap shall not be considered a routine procedure”. This shows that the determination of the transferability of these repair concepts to hydrogen pipelines is of utmost importance. Due to the degrading effects of hydrogen on mechanical proper-ties, commonly referred to as “hydrogen embrittlement” it is necessary to understand and investigate the occurring effects. In the special case of repair welding on in-service hydrogen pipelines an increased hydro-gen uptake due to a large heat input and microstructural changes in the material needs to be considered. For this reason, this paper gives an overview on existing weld repair concepts and its risks and limitations in terms of hydrogen absorption and possible embrittlement effects when transferred to hydrogen pipelines. The complexity lies in a large variety of materials (low alloyed steels), pipeline diameters and corresponding welded joints. The material compatibility of materials in used (repurposed NG-pipelines) and new condition must be investigated. Particularly for repurposed/used pipelines the effect of a pre-matured/corroded inner surface and sometimes insufficient documentation of the material “history” needs to be considered. An overview on ongoing and completed R&D-projects with respect to repair concepts for hydrogen pipelines and hydrogen effects on pipeline materials is given. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission XI "Pressure Vessels and Piping" CY - Ixia, Rhodes, Greece DA - 07.07.2024 KW - Hydrogen KW - Repair welding KW - Pipelines KW - Study PY - 2024 AN - OPUS4-60673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for simulation of in-service welding on hydrogen pipelines N2 - Hydrogen is set as the energy carrier of tomorrow and most countries will achieve large-scale hydrogen transport through the conversion of the natural gas (NG) grid and the construction of new pipelines. The interaction between hydrogen and the pipeline materials differs fundamentally from that of NG, as hydrogen is readily absorbed into the material. Considering the possible hydrogen embrittlement (HE), the compatibility of the pipeline materials (low-alloyed steels with a wide strength/thickness range) must be investigated. However, pipelines require intervention for maintenance, repair, or grid expansion with welding on/onto the pipelines while in service, i.e. the well-known "hot tapping" and "stoppling". The challenges compared to NG can be broadly divided into the possible austenitization of the inner pipe material exposed to hydrogen and the welding itself. Both result in a significant increase in hydrogen solubility and could potentially pose challenges in terms of HE. Emphasis is placed on the word "could" because knowledge of "hot tapping" on hydrogen pipelines is scarce due a lack of service experience. To this end, this study proposes a concept for a component-like demonstrator with the objectives: (1) safe feasibility of "hot tapping" on pressurized model hydrogen pipeline sections, (2) facilitate ex-post sample extraction for the purpose of quantifying the absorbed hydrogen concentrations, and (3) ensure in-situ temperature measurement during welding to monitor the pipeline surface temperature. For safety reasons in the event of an unintentional "burn-through", a solid cylinder was inserted in the demonstrator to restrict the hydrogen gas volume to a small, pressurized layer. Reference pipeline surface temperature measurements were ensured on comparable, unpressurized geometries. The investigated range of welding conditions was investigated for representative material/thickness combinations (DN60 to DN300), suggesting the feasibility of the demonstrator for the determination of reliable in-service welding conditions for both installed and new pipelines for hydrogen service. T2 - 49th MPA Conference CY - Stuttgart, Germany DA - 06.10.2025 KW - Hydrogen KW - Pipeline KW - In-service welding KW - Component test PY - 2025 AN - OPUS4-64317 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Processing and application properties of multiple principal element alloys (MPEA) N2 - The presentation gives an overview of BAM's activities on processing influences and application properties of MPEAs in the form of joined and machined high and medium entropy alloys (CoCrFeMnNi and CoCrNi). In the case of welding, the focus is on defect-free welded joints with sufficient mechanical properties. In the case of machining, the focus is on the possible influence on the surface quality of the materials through adequate milling parameters. In addition, the hydrogen absorption and diffusion properties as well as the electrochemical corrosion behavior are fundamentally examined. T2 - FAU-Department Werkstoffwissenschaften, Seminar: Aktuelle Probleme der Werkstoffwissenschaften CY - Erlangen, Germany DA - 25.04.2024 KW - Welding KW - Application properties KW - Machining KW - High-entropy alloy KW - Hydrogen PY - 2024 AN - OPUS4-59975 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -