This paper proposes an Internet-of-Things-based (IoT-based) safety barrier warning system to achieve a safer underground construction site. A focus of this paper is to establish a hazard energy ...monitoring system and use IoT to generate early warnings and alarms as dynamical safety barriers for hazard energy on underground construction sites. To ensure the performance of the proposed system, the hazard energies and their coupling mechanisms was analyzed to provide safety barrier strategies and scenarios for avoiding unsafe behaviors and unsafe status of construction equipment and workers' environment. The IoT technologies, such as meter-level of RFID-based location and tracking technology, centimeter-level of ultrasonic detection technology, and infrared access technology and so on, were developed in three-tier network architecture to help workers change their risky behaviors and avoid accidents on the changing construction site. The implementation in Yangtze River-crossing Metro Tunnel Construction site has shown the safety performance was improved and the occurrence of accident caused by hazard energy on site could be prevented.
•An Internet-of-Things-based (IoT-based) safety barrier warning system was proposed.•The concept of hazard energy and coupling mechanism on site were introduced.•The system is a proactive controlling system for isolating hazard energy in real time.•The system has applied in Yangzte River-crossing Metro Tunnel Construction site.
This paper presents safety barrier certificates that ensure scalable and provably collision-free behaviors in multirobot systems by modifying the nominal controllers to formally satisfy safety ...constraints. This is achieved by minimizing the difference between the actual and the nominal controllers subject to safety constraints. The resulting computation of the safety controllers is done through a quadratic programming problem that can be solved in real-time and in this paper, we describe a series of problems of increasing complexity. Starting with a centralized formulation, where the safety controller is computed across all agents simultaneously, we show how one can achieve a natural decentralization whereby individual robots only have to remain safe relative to nearby robots. Conservativeness and existence of solutions as well as deadlock-avoidance are then addressed using a mixture of relaxed control barrier functions, hybrid braking controllers, and consistent perturbations. The resulting control strategy is verified experimentally on a collection of wheeled mobile robots whose nominal controllers are explicitly designed to make the robots collide.
•Bow-Ties in QRA do not account for degrading safety barriers in complex systems•Multistate Bayesian Networks allow to account for barriers actual condition•We specifically tailor KPIs to be used to ...assess safety barriers health conditions•Failure Probability is evaluated conditioned on the barriers health conditions•QRA can be updated by incorporating new Knowledge, Information and Data into the BN framework
In this paper, a multistate Bayesian Network (BN) is proposed to model and evaluate the functional performance of safety barriers in Oil and Gas plants. The nodes of the BN represent the safety barriers Health States (HSs) and the corresponding conditional Failure Probability (FP) values are assigned. HSs are assessed on the basis of specific Key Performance Indicators (KPIs) related to the barrier characteristics (i.e., technical, procedural or organizational, continuously monitored or event-based characterized). FP values are estimated from failure datasets (for technical barriers), evaluated by Human Reliability Analysis (HRA) (for operational and organizational barriers) and assigned by expert elicitation (for barriers lacking data or information). For illustration, the multistate BN model is developed for preventive barriers and applied to a case study related to the potential release of flammable material in the slug catcher of a representative O&G Upstream plant which may lead to major accident scenarios (fire, explosion, toxic dispersion). The results from the case study demonstrate that the multistate BN model is able to account for the safety barriers HS and their associated functional performance.
•A quantitative method to study spatial-temporal evolution of fire-related domino effects is developed.•The temporal change of escalation vectors in domino propagation is investigated.•The burnout ...state of process units is introduced to carry out a dynamic risk assessment of domino effects.•High-risk units are identified by a posterior probabilities analysis, and are validated by graph theory.
Domino effects are typically high impact low probability (HILP) accidents, whereby escalation effects triggered by fires are most frequent. The evolution of fire-related domino effects depends on synergistic effects and the performance of safety barriers, but those factors usually are time-dependent. In the present study, a methodology is developed to provide more accurate probabilities related to domino effects, by considering the temporal evolution of escalation vectors caused by time-dependent factors. The Dynamic Bayesian Network (DBN) approach is applied both to model the spatial-temporal propagation pattern of domino effects and to estimate the dynamic probabilities of domino chains. The methodology is illustrated with a case study to determine the dynamic aspect of the probabilities of domino effects considering the impact of add-on (active and passive) safety barriers and taking into account synergistic effects. The critical units for facilitating domino propagation have been identified by the analysis of posterior probabilities, and further validated using graph theory. The methodology will be helpful for risk management and emergency decision-making of any chemical industrial area.
This article studies the problem of obstacle-avoidance tracking control for a class of uncertain nonlinear robot systems in multiple-dynamic-obstacles environment. The main challenge focuses on how ...to simultaneously ensure tracking performance and obstacle avoidance. The existing collision-avoidance tracking control schemes cannot guarantee the tracking performance inside the obstacle detection region, since the use of additive Lyapunov-barrier function (LBF) generates the dynamic mismatching. To overcome this difficulty, a novel integral-multiplicative LBF is constructed. The adaptive mechanism is designed to compensate for the mismatching uncertainties. By incorporating the barrier function into backstepping procedure, a secure adaptive tracking control scheme is proposed. Compared with the existing results, the proposed control scheme can simultaneously achieve the obstacle avoidance and tracking performance regardless of being inside the obstacle sensing region and unknown nonlinear uncertainties.
•The paper provides a systematic review of research work on safety barriers in the chemical process industries.•A novel classification of safety barriers, based on the identification and management ...of performance indicators, is proposed.•Safety barrier functions are identified and illustrated using the resilience engineering concepts.•The roadmap for future studies to develop integrated management of safety and security barriers for assurance of the resilience of chemical plants is suggested.
Barriers are used in various forms to assure the safety of chemical plants. A deep understanding of the literature related to safety barriers is essential to tackle the challenges in improving their design and management. This paper first provides an overview of the history of the development of the safety barrier concept. Subsequently, this paper elaborates a systematic review of the definition, classification, evaluation, performance assessment, and management of safety barriers in the chemical process industries. Based on the literature review, this study proposes a practical classification of safety barriers benefiting the identification of performance indicators and the collection of indicator-related data for safety barriers. The safety barrier functions are extended and illustrated by involving the resilience concept. Performance assessment criteria are proposed corresponding to the adaptability and recoverability of the safety barriers. Finally, the management of safety barriers is discussed. The roadmap for future studies to develop integrated management of safety and security barriers to ensure the resilience of chemical plants is suggested.
Regulatory gaps and safety concerns induce uncertainty amongst stakeholders, increases investment risk and impedes the deployment of hydrogen refueling stations (HRS). In this study, a risk-informed ...approach was employed on a potential HRS in Canada, to optimize separation distances, and identify regulatory gaps. This risk assessment improves upon previous ones that assumed uniform hydrogen leak sizes throughout the entire HRS. This analysis considers variable leak sizes based on the varying pipe flow area in different parts of the HRS like the tube-trailer area, hydrogen system area and the dispenser area. For each area, the potential leak sizes of 0.1%, 1%, 10%, and 100% of the pipe flow area were evaluated to cover a range of possible leaks. Leak frequency for 1% and 10% leak sizes were found to be 2.38E-02/year and 2.68E-03/year indicating relatively smaller difference as compared to other leak sizes. Leak frequency and consequence distances were assessed using HyRAM+ (V5.0) and Safeti (V8.9) respectively. Separation distances, which refer to the required spacing measured from the hydrogen process areas beyond which the risks are considered tolerable, were assessed for the tube-trailer area, storage area, and dispenser area at 350 bar and 700 bar dispensing pressures. Results indicated that 700 bar scenario requires substantially larger separation distances up to 39.1 m due to extended harm distances at lower temperatures. This study proposes safety barriers which reduced jet and flash fire frequencies by 100 and 20 events/year, respectively, that enables decreasing separation distances for each area. The comprehensive evaluation of separation distances generates important insights into separation distance criteria and guidelines, addressing the identified gap in existing codes and standards. While the study focuses on a potential HRS in Canada, the methodology, approach, and results presented are broadly applicable and transferable to similar contexts globally.
•10% leak size optimized separation distance for areas in hydrogen refueling station.•700 bar dispenser required the largest separation distance of 39.1 m•Proposed safety barriers reduced jet fires by 100, flash fires by 20 per year.•Canadian Hydrogen Installation Code lacks guidelines for risk-informed separation.•Regulatory alignment needed with hydrogen requirements in provincial fire code.
•A systematic approach for analyzing safety barriers in a battery pack.•Investigation on the battery degradation and barriers against cascading failures.•Integration of thermal propagation, thermal ...simulations, degradation, and reliability analysis.
Lithium-ion batteries have been widely employed as the principal power source in electric vehicles and other storage systems. However, some critical issues in a battery pack still exist, such as thermal failures on initial cells that impact the temperatures of the surrounding cells. Such cascading failures may significantly affect battery performance and safety. Thermal barriers, as one kind of safety barrier, are therefore installed to prevent failure propagations. This paper focuses on the situation when the temperature of battery cell increases, but the battery pack still can be used in a degradation mode since the barriers are against cascading failures. An approach is proposed to analyze how the deployment and performance of thermal barriers in a battery pack determine their capabilities against cascading failures. The approach includes thermal propagation models associated with the simulations, degradation models, reliability analysis, and barrier analysis. Its application is illustrated with a practical case study. The battery reliabilities are sensitive to many factors of the barriers, such as temperature differences, failed cells, and performance coefficient. The barriers between parallel cells are found to be more effective in mitigating failure propagation. Such findings can be beneficial for barrier optimization and reliability improvement of battery packs.
The extensive population growth calls for substantial studies on sustainable development in urban areas. Thus, it is vital for cities to be resilient to new situations and adequately manage the ...changes. Investing in renewable and green energy, including high-tech hydrogen infrastructure, is crucial for sustainable economic progress and for preserving environmental quality. However, implementing new technology needs an effective and efficient risk assessment investigation to minimize the risk to an acceptable level or ALARP (As low as reasonably practicable). The present study proposes an advanced decision-making framework to manage the risk of hydrogen refueling station leakage by adopting the Bow-tie analysis and Interval-Value Spherical Fuzzy Sets to properly deal with the subjectivity of the risk assessment process. The outcomes of the case study illustrate the causality of hydrogen refueling stations' undesired events and enhance the decision-maker's thoughts about risk management under uncertainty. According to the findings, jet fire is a more likely accident in the case of liquid hydrogen leakage. Furthermore, equipment failure has been recognized as the most likely cause of hydrogen leakage. Thus, in order to maintain the reliability of liquid hydrogen refueling stations, it is crucial that decision-makers develop a trustworthy safety management system that integrates a variety of risk mitigation measures including asset management strategies.
•Proposing an advanced decision-making framework for risk management.•Integrating the Bow-tie analysis and Interval-value Spherical Fuzzy Sets.•Demonstrating the application of study on a real hydrogen generation plant.
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Two natural clay soils are considered as promising materials for creating safety barriers for radioactive waste disposal. Composition indicators that affect the absorbing properties of clays have ...been analyzed. The absorption capacity of the soils is studied in column experiments with respect to Cs, Sr, U, Th, Ba (analogue of Ra), and Nd and Dy (analogues of Am-241 and Cm-244), which can be present in radioactive waste of hazard classes III and IV. The experimentally derived migration parameters (effective porosity, effective dispersion coefficient, and sorption capacity) of soils are used in predictive mathematical modeling for the comparative assessment of the effectiveness of safety barriers made of the materials under study; the possibility of using them for engineering safety barriers is estimated.
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