TY - CONF A1 - Erxleben, Kjell T1 - Component test for the assessment of in-service welding on/onto pressurized hydrogen pipelines N2 - Hydrogen is seen as the energy carrier of the future. Therefore a reliable infrastructure to transport hydrogen in a large scale is needed. A so called European hydrogen backbone out of long distance transmission pipelines is planned by European countries to create a hydrogen transport infrastructure. Due to economic reasons this will be achieved by new build pipelines such as repurposed natural Gas (NG) pipelines, converted to hydrogen useage. A general suitability for hydrogen service of low alloyed pipeline steel, as it is used for NG service today, is given. But in case of necessary in-service welding procedures in terms of e.g. hot-tapping and stoppling, the risk of a critical hydrogen uptake into the pipe materials due to much higher temeperatures while welding and the possibility of hydrogen embrittlement (HE) needs to be closely investigated. The presentation gives an overview of the current H2-SuD project, investigating the feasability of in-service welding on future hydrogen pipelines. Therefore, component-like demonstrators were developed to test (I) the additional hydrogen uptake due to in-service welding under hydrogen pressure and (II) to measure the temperature field due to different welding parameters and demonstrator geometries, especially on the inner pipe wall surface. Collected data will be used to validate a numerical simulation of the thermal field and additionally the hydrogen diffusion in the pipeline material. T2 - Presentation at The University of Manchester CY - Manchester, United Kingdom DA - 12.09.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Welding PY - 2025 AN - OPUS4-64129 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 - Erxleben, Kjell 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 AN - OPUS4-63170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell 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 AN - OPUS4-63165 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 - 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 - Erxleben, Kjell T1 - Assessment of in-service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow for a fossil-free future. This requires a reliable transport infrastructure capable of transporting large quantities of hydrogen. In addition to the construction of new pipelines, the conversion of existing natural gas (NG) networks is an essential part of global hydrogen strategies. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the known effects of hydrogen embrittlement, the compatibility of the materials for the proposed pipelines (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines require frequent maintenance, repair, or the need to install additional outlets. In some cases, it is necessary to perform welding on or to the pipelines while they are in-service, i.e. with active gas flow under high pressure. This in-service welding poses challenges for hydrogen operations in terms of additional hydrogen absorption during welding and 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 of the respective materials compared to room temperature. In this context, knowledge about welding on hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from natural gas to hydrogen pipeline networks. For this reason, the present study presents a specially designed demonstrator concept for the realistic assessment of the welding process conditions. The demonstrator was designed 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. Welding experiments on the DN50 and DN200 pressurized demonstrators showed an increased hydrogen uptake in the welded area of several ppm. T2 - Materials Week/Steel Innovation CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - Component test PY - 2025 AN - OPUS4-62941 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test for safety assessment of in-service welding on / onto pressurized hydrogen pipelines N2 - Hydrogen is the energy carrier of tomorrow for a fossil-free future. This requires a reliable transport infrastructure capable of transporting large quantities of hydrogen, e.g. for the steel and chemical industries. In addition to the construction of new pipelines, the conversion of existing natural gas (NG) networks is an essential part of global hydrogen strategies. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the known effects of hydrogen embrittlement, the compatibility of the materials for the proposed pipelines (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines require frequent maintenance, repair, or the need to install additional outlets. In some cases, it is necessary to perform welding on or to the pipelines while they are still in service, i.e. with active gas flow under high pressure, such as the well-known "hot tapping". This in-service welding poses challenges for hydrogen operations in terms of additional hydrogen absorption during welding and 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 operational experience. Fundamental experimental investigations are required to investigate the transferability from natural gas to hydrogen pipeline networks. For this reason, the present study presents a specially designed mock-up / demonstrator concept for the realistic assessment of the welding process conditions. T2 - Materials Week 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding PY - 2025 AN - OPUS4-62874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test to simulate critical conditions of hydrogen assisted cracking in submerged arc welded offshore steel 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. For this reason, a minimum waiting time (MWT) of up to 48 h must be considered before NDT is conducted. The evaluation of the crack susceptibility is complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry has been developed to transfer the real stiffness conditions to laboratory (i.e. workshop) scale. The 350 kg mock-up 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 yield strength level) were found in the weld metal and in the heat affected zone, suggesting that these weld subzones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were inspected 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 - Materials Week/Steel Innovation CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - Cold cracking KW - Component test KW - Hydrogen KW - Minimum waiting time KW - Offshore steel grade PY - 2025 AN - OPUS4-62873 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 - CONF A1 - Erxleben, Kjell T1 - Challenges and difficulties in repair welding procedures on in-service hydrogen pipelines N2 - Hydrogen as an energy carrier plays a key role in tomorrow's energy transition. For effective use of hydro-gen as energy carrier the construction of the corresponding infrastructure is of utmost importance. In that context, large diameter long-distance transmission pipelines will form the so-called hydrogen backbone in the European Union with service pressures up to 100 bar (e.g., depending on national regulations). From an economically and ecologically point of view, a major goal is to repurpose the existing natural gas (NG) infra-structure to minimize the need to install new pipelines. To ensure the safety, reliability and integrity of this future hydrogen infrastructure repair welding or further welding of branch pipes etc. can be necessary at in-service conditions, meaning a permanent flow of pressurized hydrogen while executing the repair procedure. The reason is that a shut-down of large diameter pipelines is not easy or sometimes merely impossible. In fact, as long, as no oxygen enters the pipeline, there will neither be any combustion nor (in the worst-case scenario) explosion. The special techniques like hot tapping or stoppling are state-of-the-art for NG and oil pipeline grids. Currently, it is not finally clarified if repair welding procedures for NG pipelines can be trans-ferred to pure hydrogen pipelines. In opposite to NG, hydrogen can be way easier absorbed to the pipeline steels and diffuses through the material. If it accumulates in susceptible regions, i.e., in the welded joint or heat affected zone, hydrogen assisted embrittlement could occur and lead to loss of integrity or even cata-strophic failure of the pipeline. For example, requires the planned welding procedure a preheating and maintenance of the weld joint of up to 300°C for up to several hours at the outer. This temperature is way higher compared to the typical service temperature of max. 60°C at operational pressures of up to 100 bar. In accordance to API 941, these low-alloyed pipeline steels are subjected to short-term service loads, which they are not designed for. Another considerable fact is that if the weld seam is attached to the pipeline, the temperature especially for small wall thickness can be easily above the austenitization temperature. It is well known that austenite has a way higher hydrogen solubility compared e.g. to ferrite/bainite microstructure of the low-alloyed steel. Current studies indicate a remarkable increase of the hydrogen ingress dur-ing the austenitization from the inner pipe wall. It must be answered if a critical material degradation because of increased hydrogen uptake due to in-service welding procedures is likely to occur. T2 - MPA Seminar 2024 CY - Stuttgart, Germany DA - 08.10.2024 KW - In-service KW - Pipeline KW - Hydrogen KW - Welding KW - Repair PY - 2024 AN - OPUS4-61468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Challenges in repair welding of in-service h2-pipelines N2 - Hydrogen will be one of the most important energy carriers of tomorrow. For the necessary large-scale and long-distance transportation, a reliable pipeline infrastructure is required. It is meanwhile in the most countries accepted to follow a two-way strategy by (I) repurposing the existing natural gas (NG) grid combined with (II) the installation of new pipelines. For example, in Europe a so-called European Hydrogen Backbone (EHB) is planned for 2040. Currently, 28 countries work together to establish a hydrogen pipeline grid of several thousands of kilometers. In that connection, a wide number of materials are used with different thicknesses, strength levels, chemical composition, surface conditions and so on. Worldwide research projects suggest the general compatibility of the currently applied pipeline steels e.g., in Germany the “SysWestH2” project. Nonetheless, the hydrogen gas grid will require regular inspections, repair, and maintenance. In addition, sometimes pipeline tees are required to connect new grids or pipelines the existing infrastructure. From that point of view, existing concepts from NG-grids must be investigated in terms of the transferability to hydrogen service. An overview on occurring challenges for this hydrogen transition, especially for in-service weld repair procedures is given in this presentation. T2 - AMPP 2024 - The Association for Materials Protection and Performance CY - Genoa, Italy DA - 09.06.2024 KW - In-service KW - Pipeline KW - Repair welding KW - High-pressure KW - Hydrogen PY - 2024 AN - OPUS4-60327 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Repair welding 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., depending on national regulations). It is a major goal to rededicate the existing LNG infrastructure despite the necessity of new pipelines. From that point of view repairing of such transmissions pipelines via welding can be necessary. For the LNG infrastructure, it is state of the art that repair welding is conducted at pipelines under service, i.e., the LNG is still flowing as pressurized gas in the steel pipes. The reason is that a shut-down of large diameter pipelines is not so easy or sometimes impossible. In fact, as long no oxygen enters the pipeline, there would be any combustion or (in the worst case) explosion. At the moment, it is entirely open if current repair welding procedures for LNG pipelines can be transferred to pure hydrogen pipelines. In opposite to LNG, hydrogen can be way easier absorbed to the pipeline steels and diffuses through the material. If it accumulates in susceptible regions, i.e., in the welded joint, hydrogen assisted embrittlement could occur. The planned welding procedure requires a so-called preheating and maintenance of the weld joint of up to 300°C for several hours. This temperature is way higher compared to the typical service temperature of max. 40 to 50°C at operational pressures of 100 bar. In accordance to API 941, these low-alloyed pipeline steels are subjected to short-term service loads, which they are not designed for. For that reason, a collaborative project between BAM and DVGW (German Association for Gas and Water professions) was initiated in 2022 to answer the following questions by experiments and numerical simulation of: (1) How many hydrogen is additionally absorbed during the heating of the material to max. 300°C under remaining operational pressures? (2) Is the hydrogen concentration sufficient to reach a critical condition? (3) Which material and weld microstructure is the most susceptible? (4) Is there a significant difference in the repair welding behavior of LNG pipelines that had been already in use for long-term? (5) Which welding parameters and joint dimensions must be ensured for safe repair welding repair of typical pipelines? For that reason, the present study gives an overview on the current practice in repair welding of in-service pipelines, the industrial importance of this topic for the hydrogen-based energy transition and summarizes first results. T2 - Eurocorr 2023 - The European Corrosion Congress CY - Brussels, Belgium DA - 27.08.2023 KW - Hydrogen KW - Repair Welding KW - Pipeline KW - In-service KW - High-pressure PY - 2023 AN - OPUS4-58334 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Hydrogen determination in welded metallic materials: Necessity and challenges N2 - In the course of tomorrow's hydrogen-based energy transition, the construction of the corresponding infrastructure will play a central role. The majority of materials used to date are typically welded for component fabrication. In that context, steels are widely applied and can be prone to hydrogen embrittlement. For the evaluation of any hydrogen effect on, for example, the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. According to ISO 3690, carrier gas hot extraction (CGHE) can be used. In addition to the pure quantification of hydrogen, thermal desorption analysis (TDA) with varied heating rates can be used to determine and evaluate the bonding state at microstructural defects in the material. For both techniques, experimental and measurement influences have to be considered, which have a great effect on the result. For CGHE, for example, ISO 3690 suggests different sample geometries as well as minimum extraction times. The present study summarizes results and experiences of numerous investigations with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding: the influence of the sample surface (polished/welded), measurement accuracies depending on the sample volume. In particular, a deviating extraction temperature to the set temperature, can significantly falsify the measurement results. Based on the results, methods are shown to quickly reach the desired extraction temperature without having to physically interfere with the measurement equipment. This serves to substantially improve the reliability of hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples for the selected heating procedure is advisable to exclude possible unwanted temperature influences already before the measurement. In addition (and way more important), the methods described can be transferred directly to industrial applications. T2 - Eurocorr 2023 - The European Corrosion Congress CY - Brussels, Belgium DA - 27.08.2023 KW - Hydrogen KW - Carrier gas hot extraction KW - Welding KW - ISO 3690 KW - Measurement PY - 2023 AN - OPUS4-58305 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -