| dc.description.abstract | Research into clean and renewable energy sources is crucial to reducing greenhouse gas emissions and mitigating the issue of global warming. Hydrogen is a highly versatile energy carrier produced from various sustainable processes and used with near-zero emissions. It has the potential to decarbonize the maritime, aviation, and automotive sectors, power production, and manufacturing. However, several safety issues need to be addressed for the widespread rollout of hydrogen technologies. This substance is highly flammable and challenging to transport and store. In addition, hydrogen can interact with metallic materials, degrading their mechanical properties, facilitating crack initiation and propagation, and eventually leading to the loss of integrity of industrial equipment. Although hydrogen-induced degradation, referred to as hydrogen embrittlement, has been widely investigated over the years, it is still responsible for several equipment failures. However, these undesired events are commonly preceded by premonitory signs. The timely detection and interpretation of these precursors could prevent the loss of integrity and avoid potentially catastrophic consequences. Therefore, inspection and maintenance activities are crucial for guaranteeing the operational safety of hydrogen technologies. Effective inspection planning can reduce the inspection frequency and cost while ensuring the plant’s availability under safe conditions.
Most industrial accidents result from incorrect risk management. Therefore, directly correlating the material degradation with the inspection that could reduce the likelihood of loss of integrity would be highly beneficial. In this context, the risk-based inspection approach quantifies the risk associated with each component item and prioritizes the inspection of the most safety-critical equipment. This strategy can reduce the plant’s downtime and minimize inspection costs while guaranteeing safe operations. However, the standardized RBI methodology neglects most hydrogen-induced degradations and has never been implemented on H2 transport and storage equipment. Therefore, this PhD thesis investigates how hydrogen damages can compromise the structural integrity of hydrogen technologies. It explores the predictive strategies to reduce the likelihood of component failures and examines whether RBI approaches can be adopted for equipment exposed to hydrogen environments.
This research presents a semi-quantitative RBI methodology for hydrogen storage equipment and pipelines. It considers the effects of hydrogen-induced cracking and hydrogen-enhanced fatigue, taking into account the synergistic influence of the environmental, material, and mechanical parameters. These lookup evaluations are integrated with quantitative approaches based on experimental data. An extensive testing campaign investigates the susceptibility of pipeline steels to pressurized H2 environments. The hydrogen effect on mechanical properties is evaluated through an alternative in-situ testing technique, considering the influence of the surface finishing and steel’s microstructure. Machine-learning tools are then used to leverage the results of the experimental campaign and predict the magnitude of the hydrogen-induced degradation for several materials. Finally, an ad-hoc inspection planning methodology for hydrogen technologies is developed by integrating the conventional RBI with the predictive models. The proposed approach is validated using real-world case studies. The results show how an ad-hoc inspection planning strategy would significantly improve the operational safety of equipment in the entire hydrogen value chain. Limitations and future challenges are highlighted and discussed. Therefore, the main contributions of this research include:
• Investigation of the causes of loss of integrity of hydrogen equipment;
• Analysis of the effects and susceptibility factors for hydrogen-induced damages;
• Analysis of the possible inspection techniques for hydrogen technologies;
• Evaluation of the damage factor for hydrogen-induced cracking;
• Evaluation of the damage factor for hydrogen-enhanced fatigue;
• Experimental evaluation of the effects of high-pressure hydrogen gas on steels;
• Development of data-driven predictive models for the hydrogen-induced ductility loss;
• Development of data-driven predictive models for the hydrogen-enhanced fatigue crack growth;
• Comparison between RBI and conventional inspection approaches for hydrogen technologies;
• Integration of RBI with predictive models and validation of the methodology.
The application and validation of this research prove its potential impact on the safety and reliability of hydrogen technologies. Nevertheless, even if risk-based inspection and maintenance strategies appear promising, the research on this topic remains nascent. In the future, data-driven models should be trained with additional test results on different materials under various conditions. | en_US |
