Search Results (6)

The lack of biochemical stability in drinking water increases the secondary contamination risk in water supply systems and hence represents a sanitary threat to consumers. The work presented here assesses the likelihood of such risk. The assessment is based on data obtained from one of the water treatment plants. The assessment of the bio-chemical instability risk combines both approaches: fault and event trees. Additional consideration was naturally given to the events that initiated the contamination at the outlet of the water treatment plant. It is concluded that if it is to protect the water-supply infrastructure representing a kind of critical infrastructure, a water-supply company needs to put more emphasis on the distribution of stable water in terms of its properties and composition, thus having no potentially corrosive properties. The assessment underlines the importance that water supply utilities should equally consider both the supplied water sanitary quality and the water supply service continuity. Full article

To investigate the human-related factors associated with suffocation on ships during docking repair, a comprehensive analysis model composed of a Bayesian network (BN) and a complex network (CN) is proposed in the present study. The principle of event tree analysis (ETA) is firstly applied to identify the hazardous events involved in the accident according to the accident report, based on which the CN would then be developed with the logic relationships among the hazardous events. The improved K-shell decomposition algorithm is utilized to determine the criticality of nodes in the CN, the results of which are then used to develop the BN model within the framework of a human factor analysis classification system (HFACS). Then, the developed BN model can be simulated with the probability distribution of all the nodes within the BN, which are obtained on the basis of node criticality. Finally, the results of the BN simulation are interpreted from the perspectives of a brief analysis, backward analysis and sensitivity analysis. The results are verified with existing studies and the accident investigation report issued by authority, which are presented as evidence to verify the effectiveness of the proposed methodology to evaluate the human-related risk involved in the suffocation on ships. The methodology proposed in this study integrates the advantages of BN and CN to investigate the human-related hazardous events involved in maritime accidents, which can be seen as the main innovation of this work. Full article

The purpose of this paper is to propose a framework for cybersecurity risk management in telemedicine. The framework, which uses a bow-tie approach for medical image diagnosis sharing, allows the identification, analysis, and assessment of risks, considering the ISO/TS 13131:2014 recommendations. The bow-tie method combines fault tree analysis (FTA) and event tree analysis (ETA). The literature review supported the identification of the main causes and forms of control associated with cybersecurity risks in telemedicine. The main finding of this paper is that it is possible, through a structured model, to manage risks and avoid losses for everyone involved in the process of exchanging medical image information through telemedicine services. Through the framework, those responsible for the telemedicine services can identify potential risks in cybersecurity and act preventively, recognizing the causes even as, in a mitigating way, identifying viable controls and prioritizing investments. Despite the existence of many studies on cybersecurity, the paper provides theoretical contributions to studies on cybersecurity risks and features a new methodological approach, which incorporates both causes and consequences of the incident scenario. Full article

Dependability analyses in the design phase are common in IEC 60300 standards to assess the reliability, risk, maintainability, and maintenance supportability of specific physical assets. Reliability and risk assessment uses well-known methods such as failure modes, effects, and criticality analysis (FMECA), fault tree analysis (FTA), and event tree analysis (ETA)to identify critical components and failure modes based on failure rate, severity, and detectability. Monitoring technology has evolved over time, and a new method of failure mode and symptom analysis (FMSA) was introduced in ISO 13379-1 to identify the critical symptoms and descriptors of failure mechanisms. FMSA is used to estimate monitoring priority, and this helps to determine the critical monitoring specifications. However, FMSA cannot determine the effectiveness of technical specifications that are essential for predictive maintenance, such as detection techniques (capability and coverage), diagnosis (fault type, location, and severity), or prognosis (precision and predictive horizon). The paper proposes a novel predictive maintenance (PdM) assessment matrix to overcome these problems, which is tested using a case study of a centrifugal compressor and validated using empirical data provided by the case study company. The paper also demonstrates the possible enhancements introduced by Industry 4.0 technologies. Full article

In an automated systems environment is very important to predicted failures or unexpected situations to achieve system reliability. Failure of such systems can cause serious property damage, the environment, damage to human health or cause death. The essential task is to determine the tolerable and acceptable risk. The required level of risk for safety-critical systems can be achieved by using international technical standards and applying safety functions. Safety functions are implemented using an electrical/electronic/programmable electronics (E/E/PE) safety-related system. Technical standards offer the aspect of balancing risk tolerability according to the relevant, reliable safety functions. Based on the specific architecture of the whole system, it is possible to determine the maximum failure rate of the probability of failure on demand (PFD_SYS) of the selected architecture. Subsequent application of reliability analysis using the event tree analysis (ETA) and fault tree analysis (FTA) methods can optimize the failure rate of the entire system. Application of reliability analysis using event tree analysis (ETA) and fault tree analysis (FTA) methods can only theoretically optimize the failure rate of the entire system with constant initial conditions and constant parameters of the reliability functions. The article proposes a new methodology for dynamic analysis of the state of system reliability as a function of the system operation time, maintenance frequency and system architecture. As a result of the methodology is a library of standard element architectures and simulation models which allows predicting and optimizing the reliability of E/E/PE safety-related systems. Full article

Fault tree analysis (FTA) is frequently applied to deductively evaluate the safety systems of complex engineering systems such as chemical industries or nuclear facilities. To perform this analysis, generic data are commonly used due to the limitation of historical failure data of the system being evaluated. However, generic data have a degree of uncertainty and hence cannot represent the system’s actual performance. In addition, generic data are not applicable to older components due to the aging process, which obviously degrades the reliability of those components. To deal with this limitation, another safety analysis method, called fuzzy fault tree analysis (FFTA), has been proposed. The purpose of this study is to apply FFTA to evaluate the performance of the primary cooling systems of G.A. Siwabessy Multipurpose Reactor (RSG-GAS). RSG-GAS is a research reactor, which belongs to the National Nuclear Energy Agency of Indonesia (BATAN). Expert justifications were used to evaluate the failure occurrences of basic events in the primary cooling system of the RSG–GAS through questionnaires. The assessment by experts is in the form of qualitative data, which are then converted into quantitative data by applying FFTA. Then, the top event probability generated from FFTA was applied to calculate the event probability using event tree analysis (ETA). It was obtained that the highest event probability was 4.304 × 10⁻⁸/year. Since it complies with The International Atomic Energy Agency (IAEA) specified core damage frequency (CDF) limit, i.e., not greater than 10⁻⁵/year of reactor operation, the reactor is safe to operate. Full article