Safety

Hydrogen embrittlement (HE) remains a pressing issue in materials science and engineering given its significant impact on the structural integrity of metals and alloys. This exhaustive review aims to thoroughly examine HE covering a range of aspects that collectively enhance our understanding of this intricate phenomenon. It proceeds to investigate the varied effects of hydrogen on metals illustrating its ability to profoundly alter mechanical properties thereby increasing vulnerability to fractures and failures. A crucial section of the review delves into how different metals and their alloys exhibit unique responses to hydrogen exposure shedding light on their distinct behaviors. This knowledge is essential for customizing materials to specific applications and ensuring structural dependability. Additionally the paper explores a diverse array of models and classifications of HE offering a structured framework for comprehending its complexities. These models play a crucial role in forecasting preventing and mitigating HE across various domains ranging from industrial settings to critical infrastructure.

Canada’s commitment to be net-zero by 2050 combined with ATCO’s own Environmental Social and Governance goals has led ATCO to pursue hydrogen blending within the existing natural gas system to reduce CO2 emissions while continuing to provide safe reliable energy service to customers. Utilization of hydrogen in the distribution system is the least-cost alternative for decarbonizing the heating loads in jurisdictions like Alberta where harsh winter climates are encountered and low-carbon hydrogen production can be abundant. ATCO’s own Fort Saskatchewan Hydrogen Blending Project began blending 5% hydrogen by volume to over 2100 customers in the Fall of 2022 and plans to increase the blend rates to 20% hydrogen in 2023. Prior to blending ATCO worked together with DNV to examine the impact of hydrogen blended natural gas to twelve Canadian appliances: range/stove oven garage heater high and medium efficiency furnaces conventional and on demand hot water heaters barbeque clothes dryer radiant heater and two gas fireplaces. The tests were performed not only within the planned blend rates of 0-20% hydrogen but also to higher percentages to determine how much hydrogen can be blended into a system before appliance retrofits would be required. The testing was designed to get insights on safety-related combustion issues such as flash-back burner overheating flame detection and other performance parameters such as emissions and burner power. The experimental results indicate that the radiant heater is the most sensitive appliance for flashback observed at 30 vol% hydrogen in natural gas. At 50% hydrogen the range and the radiant burner of the barbeque tested were found to be sensitive to flashback. All other 9 appliances were found to be robust for flashback with no other short-term issues observed. This paper will detail the findings of ATCO and DNV’s appliance testing program including results on failure mechanisms and sensitivities for each appliance.

To contribute to a more diverse and efficient energy infrastructure large quantities of hydrogen are requested for industries (e.g. mining refining fertilizers…). These applications need large scale facilities such as dozens of electrolyzer stacks from atmospheric pressure to 30 bar with a total capacity ranging from 100 up to 400 MW and associated hydrogen storage from a few to 50 tons.

Local use can be fed by electrolyzer in 20 feet container and stored in bundles with small volumes. Nevertheless industrial applications can request much bigger capacity of production which are generally located in buildings. The different technologies available for the production of hydrogen at large scale are alkaline or PEM electrolyzer with for example 100 MW capacity in a building of 20000 m3 and hydrogen stored in tube trailers or other fixed hydrogen storage solution with large volumes.

These applications led to the use of hydrogen inside large but confined spaces with the risk of fire and explosion in case of loss of containment followed by ignition. This can lead to severe consequences on asset workers and public due to the large inventories of hydrogen handled.

This article aims to provide an overview of the strategy to safely design large scale hydrogen production facilities in buildings through benchmarks based on projects and literature reviews best practices & standards regulations. It is completed by a risk assessment taking into consideration hydrogen behavior and influence of different parameters in dispersion and explosion in large buildings.

This article provides recommendations for hydrogen project stakeholders to perform informed-based decisions for designing large scale production buildings. It includes safety measures as reducing hydrogen inventories inside building allocating clearance around electrolyzer stacks implementing early detection and isolation devices and building geometry to avoid hydrogen accumulation.

We combine state-of-the-art thermo-metallurgical welding process modeling with coupled diffusion-elastic– plastic phase field fracture simulations to predict the failure states of hydrogen transport pipelines. This enables quantitatively resolving residual stress states and the role of brittle hard regions of the weld such as the heat affected zone (HAZ). Failure pressures can be efficiently quantified as a function of asset state (existing defects) materials and weld procedures adopted and hydrogen purity. Importantly simulations spanning numerous relevant conditions (defect size and orientations) are used to build Virtual Failure Assessment Diagrams (FADs) enabling a straightforward uptake of this mechanistic approach in fitness-for-service assessment. Model predictions are in very good agreement with FAD approaches from the standards but show that the latter are not conservative when resolving the heterogeneous nature of the weld microstructure. Appropriate mechanistic FAD safety factors are established that account for the role of residual stresses and hard brittle weld regions.

The publication presents methods and pre-test results of a stand for testing CHSS in terms of resistance to open fire. The basis for the conducted research is the applicable provisions contained in the UN/ECE Regulation R134. The study includes an overview of contemporary solutions for hydrogen storage systems in high-pressure tanks in means of transport. Development in this area is a response to the challenge of reducing global carbon dioxide emissions and limiting the emissions of toxic compounds. The variety of storage systems used is driven by constraints including energy demand and available space. New tank designs and conducted tests allow for an improvement in systems in terms of their functionality and safety. Today the advancement of modern technologies for producing high-pressure tanks allows for the use of working pressures up to 70 MPa. The main goal of the presented research is to present the requirements and research methodology verifying the tank structure and the security systems used in open-fire conditions. These tests are the final stage of the approval process for individual pressure vessels or complete hydrogen storage systems. Their essence is to eliminate the occurrence of an explosion in the event of a fire.

The development of liquid hydrogen storage systems is a key aspect to enable future clean air transportation. However safety analysis research for such systems is still limited and is hindered by the limited experience with liquid hydrogen storage in aviation. This paper presents the outcomes of a preliminary safety assessment applied to this new type of storage system accounting for the hazards of hydrogen. The methodology developed is based on hazard identification and frequency evaluation across all system features to identify the most critical safety concerns. Based on the safety assessment a set of safety recommendations concerning different subsystems of the liquid hydrogen storage system is proposed identifying hazard scopes and necessary mitigation actions across various system domains. The presented approach has been proven to be suitable for identifying essential liquid hydrogen hazards despite the novelty of the technology and for providing systematic design recommendations at a relatively early design stage.

Hydrogen is a promising carbon-free energy carrier for large-scale applications yet its adoption faces unique safety challenges. Microscopic physicochemical properties such as high diffusivity low ignition energy and distinct chemical pathways alter the safety of hydrogen systems. Analyzing the HIAD 2.0 incident database an occurrence-based review of past hydrogen incidents shows that 59% arise from general industrial failures common to other hydrocarbon carrier systems. Of the remaining 41% only 15% are unequivocally linked to the fuel’s unique properties. This study systematically isolates hazards driven by hydrogen’s intrinsic properties by filtering out confounding factors and provides an original clear characterization of the different failure mechanisms of hydrogen systems. These hydrogen-specific cases are often poorly described limiting their contribution to safety strategies and regulations improvement. A case study on pipeline failures illustrates how distinguishing hydrogen-specific hazards supports targeted risk mitigation. The findings highlight the need for evidence-based regulation over broadly precautionary approaches.

The increasing adoption of liquid hydrogen (LH2) as a clean energy carrier presents significant safety challenges particularly in confined underground spaces like tunnels. LH2′s unique properties including high energy density and cryogenic temperatures amplify the risks of leaks and explosions which can lead to catastrophic overpressures and extreme temperatures. This study addresses these challenges by investigating the diffusion and explosion behaviour of LH2 leaks in tunnels providing critical insights into disaster prevention and structural resilience for underground infrastructure. Using advanced numerical simulations validated through theoretical calculations and experimental analogies the study analyses hydrogen diffusion patterns overpressure dynamics and thermal impacts following an LH2 tank rupture. Results show that LH2 explosions generate overpressures exceeding 50 bar and temperatures surpassing 2500 ◦C far exceeding the hazards posed by gaseous hydrogen leaks. Mitigation measures such as suction ventilation and high humidity significantly reduce explosion impacts underscoring their value for tunnel safety. This research advances understanding of hydrogen safety in confined spaces demonstrating the importance of integrating mitigation measures into tunnel design. The findings contribute to disaster prevention strategies offer insights into optimizing safety protocols and support the development of resilient infrastructure capable of accommodating hydrogen technologies in a rapidly evolving energy landscape.

Numerical simulations reveal the combustion dynamics of hydrogen-blended natural gas (H-BNG) in semi-open spaces. In the typical semi-open space scenario increasing the hydrogen blending ratio from 0% to 60% elevates peak internal pressure by 107% (259.3 kPa → 526.0 kPa) while reducing pressure rise time by 56.5% (95.8 ms → 41.7 ms). A vent size paradox emerges: 0.5 m openings generate 574.6 kPa internal overpressure whereas 2 m openings produce 36.7 kPa external overpressure. Flame propagation exhibits stabilized velocity decay (836 m/s → 154 m/s 81.6% reduction) at hydrogen concentrations ≥30% within 2–8 m distances. In street-front restaurant scenarios 80% H-BNG leaks reach alarm concentration (0.8 m height) within 120 s with sensor response times ranging from 21.6 s (proximal) to 40.2 s (distal). Forced ventilation reduces hazard duration by 8.6% (151 s → 138 s) while door status shows negligible impact on deflagration consequences (412 kPa closed vs. 409 kPa open) maintaining consistent 20.5 m hazard radius at 20 kPa overpressure threshold. These findings provide crucial theoretical insights and practical guidance for the prevention and management of H-BNG leakage and explosion incidents.

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature combined with its lack of color taste and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor like sensing material sensing element and signal conditioning as well as the electronic protection and signaling module of the critical concentrations of H2. The sensing material consists of a catalyst type Vulcan XC72 40% Pt from FuelCellStore (Bryan TX USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode an ion-conducting membrane type Nafion 117 from FuelCellStore (Bryan TX USA). and an anode electrode mounted in a coin cell type CR2016 from Xiamen Tob New Energy Technology Co. Ltd (Xiamen City Fujian Province China). The electronic block for electrical signal conditioning which is delivered by the sensing element uses an INA111 from Burr-Brown by Texas Instruments Corporation (Dallas TX USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater maximum amperometric response time of 1 s fast recovery time of maximum 1 s and extended range of hydrogen concentrations detection in a range of up to 20%.