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For the safety assessment of complex engineering systems, fault tree analysis (FTA) is a widely used method and can be performed only when all its basic events (BEs) have their corresponding failure data. However, in many applications, obtaining precise quantitative failure data of all the components of the system is not feasible due to changing environment, insufficient data or new components. The present research develops a novel FTA to identify the best estimate and bounds of system failure probability through qualitative data processing. The failure data of BEs are uncertain therefore expert elicitation method is used incorporating intuitionistic fuzzy (IF) set theory to evaluate the top event failure probabilities. The novelty of the proposed work comes with the use of linguistic values as failure possibilities of the system components and utilizing triangular intuitionistic fuzzy numbers (TIFNs) to quantify the linguistic terms into mathematical form to assess the best‐estimated value of the system failure probability, and also the lower bound and the upper bound of the system failure probability. To exemplify the appropriateness of the proposed study, the case studies Combustion Engineering Reactor Protection System (CERPS) and Emergency Core Cooling System (ECCS) are carried out and a comparison between computed results and outcomes from the previous methods is demonstrated. The results are exceptionally near to the outcomes of conventional FTA, which confirms that the proposed procedure is a real substitute in the IF environment when components have imprecise quantitative failure data. [ABSTRACT FROM AUTHOR]

Reliability and safety are very critical in complex engineering systems such as chemical and nuclear industries. Fault tree analysis (FTA) has been widely applied to evaluate the reliability and safety of complex engineering systems. This approach assumes that systems always have exact component failure probabilities. However, this assumption is not always true in real‐world applications. To deal with this, a number of scholars have integrated fuzzy approach into FTA of engineering systems whose component exact probabilities cannot be collected. Furthermore, simple fuzzy arithmetic operations on membership function have also been proposed to quantify Boolean gates for propagating uncertainties from basic event fuzzy probabilities into the top event fuzzy probabilities. In this study, fuzzy arithmetic operations on α‐cuts, as opposed to simple fuzzy arithmetic operations, are proposed. The significance of the α‐cut is that each α‐cut can uniquely represents each fuzzy probability. In order to verify the applicability of the proposed approach, the reliability of the long‐term cooling system of the Westinghouse AP1000 to mitigate a large break loss of coolant accident is evaluated and the results are compared to the reliability of the same system quantified by conventional FTA published in qualified scientific journals. The results of the benchmarking confirm that the proposed approach can be practicably implemented to estimate the reliability and safety of complex engineering systems whose basic event reliability are characterized by fuzzy probabilities. To be applied in other complex engineering systems, safety analysts have to concern for some steps, which are particularly developed for a specific application, such as failure possibility distribution and its corresponding fuzzy probability distribution and the selection of a defuzzification technique. [ABSTRACT FROM AUTHOR]

In order to accurately evaluate the overall risk of falling from height in building construction and solve the problem of fuzziness and uncertainty of accident causing factors, a fault tree analysis method based on fuzzy set theory was proposed. First, the fuzzy fault tree model was used to identify the key causative elements from qualitative and quantitative perspectives, and the failure probability is obtained. Then, the risk analysis matrix was used to evaluate the risk consequences. Finally, the method was applied to an example for verification. The research results show that the fault tree analysis method based on the fuzzy set theory solves the inaccuracy of probability and the inaccuracy of engineering. The comprehensive risk assessment combined with the failure possibility and consequence severity of falling from height provides a theoretical reference for the formulation of preventive measures. And it has convenient and efficient application value in reliability engineering. [ABSTRACT FROM AUTHOR]

Ensuring high reliability and availability of draglines is imperative for the economic sustainability of a highly productive surface mining project. Draglines are very complex in design and consist of hundreds of components. Reliability modelling of a large complex system is difficult with conventional reliability analysis techniques. The dragging mechanism is a critical subsystem for the smooth operation of the draglines. This study uses the Bayesian Network (BN) model, mapped from the Fault Tree (FT), for the reliability analysis of Dragline. Sensitivity analysis identifies the critical components – helpful information for reliability management. The results demonstrate that three components of the dragging mechanism, namely, the drag motor system, drag brake and drag socket are primarily responsible for the poor reliability of the case study system. This study provides valuable information for maintenance planning of operating draglines and reliability blueprint of future dragline design. [ABSTRACT FROM AUTHOR]

As one of the most important components within a vehicle, diesel engines have high requirements for reliability due to the harsh operating environments. However, previous studies have mainly focused on the reliability assessment of diesel engines, while less research has been conducted on the modeling of the diesel engine reliability analysis and its management. For this reason, this paper proposes a comprehensive method for reliability analysis and its management based on the use of 4F integration technology in the early stages of diesel engine design. First of all, an expert group used FEMCA (failure mode, effects and criticality analysis) and FHA (functional hazard analysis) to find the most harmful level of fault mode. At the same time, a new method for the repair of dynamic fault trees to find the weak links at the component level was developed. Finally, a FRACAS (fracture report analysis and corrective action system) was used during the above analysis process. By applying this method to the reliability assessment of a diesel engine in the design stage, the problems of failure information feedback and the reuse of failure information in the actual reliability assessment can be solved. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Specialist literature indicates a large share of the human factor among the causes of failure of technical systems at the level of 70 to 90%, which depends on the sector studied. The collective water supply system is an anthropotechnical system, i.e., it is a complex connection between man and the technical system resulting from the deliberate influence of man on the technical system. Methods: The work presents an assessment of operator reliability of a selected water treatment process based on the fault tree analysis (FTA). Elementary events are determined by the operator's error probability. Results: A failure tree was prepared for the peak event of the filter station failure, resulting from an operator's error during the filter washing procedure. The probability of a peak event occurring is 0.0580. Conclusions: The developed fault tree allows for the identification of elementary events leading to an emergency event. The operator fulfills its task of maintaining the continuity of water treatment. [ABSTRACT FROM AUTHOR]

Clarifying the causes of subway construction accidents has an important impact on reducing the probability of accidents and protecting workers' lives and public property to a greater extent. A total of 138 investigation records of subway construction accidents from 2000 to 2020 were collected in this study. Based on a systemic analysis of 29 well-known accident causation models and the formative process of the subway construction accidents, we extracted the causative factors of subway construction accidents from the collected records. Furthermore, a causation analysis index system of subway accidents was proposed based on fault tree analysis (FTA), where we considered subway construction accidents as the top event and the five dimensions, i.e., human, equipment, environment, management, and safety culture, as first-level intermediate events. Moreover, 17 causative factors were considered to be related to the severity of subway construction accidents. It is found that human factors are prone to be critical to high-risk accidents. Finally, a Bayesian network (BN) was formed to explore the causative factors of high-risk subway construction accidents. Based on the combined application of FTA and BN, this study discusses the complex influence factors and their action routes to unsafe accidents in subway construction sites, and makes efforts to correspond safety decision basis for the management of China subway construction. [ABSTRACT FROM AUTHOR]

Subway transportation is one of the most prevalent urban transportation methods globally. Millions of people around the globe use this medium as their mode of transportation daily. However, subway stations may be highly prone to fire, smoke, or explosion accidents. The safety of people using subway stations demands a robust and practical framework to assess fire hazards and risks. This study provides a methodology to assess fire risk at a subway station. This study integrates fault tree analysis (FTA) and fuzzy analysis to conduct a comprehensive fire risk assessment. An integrated numerical model of fire temperature and fatality rate was developed using probit correlations for various fire exposure scenarios. The fire dynamics simulator (FDS) provides the probability distribution of casualties caused by fire. To demonstrate the operationalization of the model, Line 1 of the Harbin Metro, located in China, is used as a case study. Results show a probability of 42% of having fire risk in the subway station. Results reveal the highest fatality rate is 6.2% when evacuation time exceeds 200 s. The research helps us to understand the spread of smoke and temperature distribution due to a fire in a subway station. This study is helpful for fire protection engineers, safety managers, and local fire departments to develop a contingency plan to deal with fire in a subway station. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the possible causes of collision accidents by using Fault Tree Analysis (FTA). In this study, we were able to examine the potential cause of collision accidents, then develop a fault tree model of the root causes of the accidents using the FTA approach, and finally provide the probability of basic event combinations leading the occurrence of accidents. A total of 62 collision accident reports providing detailed information about the causes of accidents were obtained by Marine Accident Investigation Branch (MAIB) between 2005 and 2020. The study found that most of the factors (E1/Misuse of navigational tools, E3/COLREG Rule-5 (Look-out)) that had the greatest effect on the collision were mainly due to the inadequacy to keep a safe navigation watch. For that reason, the findings of the study are very important in terms of determining the strategies to eliminate the risks for future accident prevention. For future studies, it should collect more accidents data on varying types of ships to improve their prediction performance, incorporate expert opinions with fuzzy evidence into the model to minimize uncertainties, and enhance model expressiveness. In addition, alternative risk assessment methods should be applied considering other types of vessels for better comparisons. [ABSTRACT FROM AUTHOR]

Root cause analysis techniques are often applied to problems in the workplace; however, they may also prove very useful when applied to home projects. This research explores the application of root cause analysis techniques in three home projects: (1) Cause-and-Effect diagram to remove Palmetto bugs in a condo dwelling, (2) Five Whys method to repair a sunroof water leak in a car, and (3) Fault Tree Analysis to repair a Toro string trimmer that starts, then dies. The effective use of root cause analysis techniques can have a meaningful impact on resolving home project issues resulting in a restoration of homeowner issues as well as reduced homeowner anxiety, repair time, and repair cost.

One of the company's efforts in implementing the commitment to customer satisfaction is carried out through continuous improvement activities. All indicators are evaluated to determine the level of quality stability against process variations that will impact non-compliance with predetermined product specifications. One of the quality problems found in the tire manufacture industry is the out-percentage of tire uniformity, which suddenly increases, one of which is the value of static balance. This study analyses the process variation factors that occur to take corrective and preventive actions through a series of Root Cause Analysis (RCA), Fault Tree Analysis (FTA), and Failure Mode and Effect Analysis (FMEA). Refers to the analysis result, it was found that there was a problem with the rubber film gauge variation at the manufacturing step of the steel breaker, one of the material components in the tire construction. Two main factors cause rubber film thickness variation: rubber sticky with roll calendar, Radial Run Out (RRO) Roll Calendar out standard, and viscosity compound variation with 12 root problems found. The results of the improvements that have been made can effectively improve rubber film thickness variation, increase the Cpk level of steel breaker material from 0.82 to 1.91 and reduce the out percentage ratio of static balance by 54.65%.

• A method to evaluate the post-earthquake functionality of communication base stations using Bayesian network is developed. • The dependence between the equipment and its hosting building structure, and the impact of power outages are considered. • The method is validated using seismic damage data from the Ludian Earthquake. • The main causes of base station functional failure are analyzed. • Seismic functional fragility curves for typical communication base stations are provided. The reliability and resilience of communication base stations are critical to the post-earthquake performance of the communication system, and consequently influence the communication, rescue, and emergence management after an earthquake. There is a lack of models that can fully evaluate the post-earthquake functional states of base stations with the consideration of the dependencies between different components. This paper proposes a Bayesian network method to evaluate the post-earthquake functionality of communication base stations. The method considers the dependence between the equipment and its hosting building structure, and the impact of power outages. This model produces seismic functional fragility curves for typical base stations that enable both qualitative and quantitative evaluations of base station functionality. The model is validated using seismic damage data from the Ludian Earthquake. It was found that the proposed model can reasonably predict the post-earthquake functional failure of base stations, in good agreement with the observed seismic damage data. The application of this model provides support for the operation and maintenance of communication base stations, and insights for managing seismic risk and resilience of the communication system. [ABSTRACT FROM AUTHOR]

Clarifying the causes of subway construction accidents has an important impact on reducing the probability of accidents and protecting workers’ lives and public property to a greater extent. A total of 138 investigation records of subway construction accidents from 2000 to 2020 were collected in this study. Based on a systemic analysis of 29 well-known accident causation models and the formative process of the subway construction accidents, we extracted the causative factors of subway construction accidents from the collected records. Furthermore, a causation analysis index system of subway accidents was proposed based on fault tree analysis (FTA), where we considered subway construction accidents as the top event and the five dimensions, i.e., human, equipment, environment, management, and safety culture, as first-level intermediate events. Moreover, 17 causative factors were considered to be related to the severity of subway construction accidents. It is found that human factors are prone to be critical to high-risk accidents. Finally, a Bayesian network (BN) was formed to explore the causative factors of high-risk subway construction accidents. Based on the combined application of FTA and BN, this study discusses the complex influence factors and their action routes to unsafe accidents in subway construction sites, and makes efforts to correspond safety decision basis for the management of China subway construction.

• Merged FTA, SPAR-H, and RCM for comprehensive nuclear plant risk assessment. • Applied Fussell-Vesley criterion to pinpoint crucial system events. • Uniquely quantified the effectiveness of risk mitigation measures. Probabilistic Safety Assessment (PSA) provides a systematic and quantitative approach to assess the risk associated with different components and systems within a nuclear power plant. By quantifying the impact of risk mitigation measures, decision-makers can prioritize and implement solutions that have the most significant impact on reducing risk. Fault Tree Analysis (FTA) is employed as a systematic method within PSA, encompassing all modes of failure across equipment and associated support systems, including unavailability due to maintenance (UDM), human errors (HEs), and common cause failures (CCFs). In the present research, the Extra Borating System (EBS) and the Chilled Water Operating Circuit System (CWOCS) of essential loads are modeled in the SAPHIRE code using VVER-1000 design data. Through importance analysis employing the Fussell-Vesley criterion, the most significant basic events for these two systems are identified. Subsequently, the outcomes of the importance analysis are examined using diversity, SPAR-H, and Reliability Centered Maintenance (RCM) techniques. Recommendations such as the enhancement of diversity, increasing staff training, promoting Human Machine Interface (HMI), reduction of maintenance time, and improvement of power supply reliability are proposed for the most crucial basic events. The ensuing impact of these measures on the reliability of the EBS and CWOCS is subsequently assessed. Through a comparison between the new failure probability and the previous, it is determined that improvements in CCFs contribute a 30% effect; HEs have a 14% effect and UDMs have a 5% effect, with a cumulative impact of 35% on the failure probability of the EBS system. Similarly, for the CWOCS system, enhancements in CCFs contribute 20%, UDMs 17%, and improved power supply reliability 19%, with a cumulative impact of 29%. [ABSTRACT FROM AUTHOR]

A shortage of chemical cargo on tanker ships refers to a situation where the declared cargo amount by the shipper is lower than the declared terminal cargo amount, or the amount specified in the Bill of Lading. As the chemical cargoes are high purity and expensive products, any shortage claims may cause high commercial loss even in small amounts. Despite the chemical transportation industry conducting some technical researches on shortage prevention, no systematic, academic and methodological study has yet been proposed which is capable of comprehensively revealing the underlying causes, their contributions to the risk of shortage. In this study, contribution of all human factor-related structural, technical and operational root causes to risk of shortage are identified. Their failure probabilities are determined by utilising Intuitionistic Fuzzy Integrated Fault Tree Analysis (IFFTA). Accordingly, the probabilistic risk of chemical cargo shortage is obtained and found to be 0.0731 and this number is validated with two different methods. It is found that direct or indirect human factors lead to cargo shortages, accounting for approximately 84% of all factors. It is believed that the proposed model provides an effective solution to mitigate the related risk by systematically revealing notable underlying human related causes. • 86% of the top 50 MCSs are found to be directly or indirectly related to human factor. • Contribution of MCSs caused by human factor to chemical cargo shortage incident is 0.842. • Continuous training and evaluation system will be the most cost-effective solution to reduce the risk of cargo shortage. [ABSTRACT FROM AUTHOR]

Growing concerns over the CO2 footprint due the exponential demand of the aviation industry, along with the requirements for high aerodynamic performance, cost saving, and manoeuvrability during different phases of a flight, pave the path towards adaptable wing design. Morphing wing design encompasses most, if not all, of the flight condition variations, and can respond interactively. However, functional failure of the morphing wing might bring devastating impacts on the passengers, crew, and/or aircraft. In the present work, the dynamic characteristics of a re-configurable modular morphing wing developed in-house by a research group at the Toronto Metropolitan University, are investigated from the perspective of a functional hazard assessment (FHA). This modular morphing wing, developed based on the idea of a parallel robot, consists of a number of structural elements connected to each other and to the wing ribs through eye-bolt joints. Timoshenko’s bending beam theory, in conjunction with the finite element method (FEM), is exploited to model the structural members. Possible hazards, assumed here to be the structural failure of the beam components, have been identified and their failure conditions are assessed. Numerical simulations have been presented to show the impact of various combinations of the identified hazards on the vibration signature of the morphing wing in unmorphed and morphed configurations. Identification of changes in the wing’s vibration signature is a vital component in the fail-safe structural and aeroelastic design of an aircraft. The present study is geared towards the structural response of the system in the absence of any aerodynamic loads.

Copyright of Railway Signalling & Communication Engineering is the property of Railway Signalling & Communication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sand casting explosion accidents will cause serious casualties, and measures should be adopted to prevent these consequences. The purpose of this study was to investigate the evolution mechanism of sand casting explosion accidents. The temperature variations in sand molds were investigated based on on-site testing and numerical simulation. The evolution characteristics of sand casting explosion accidents were analyzed by fault tree analysis, chaos theory and synthetic theory model. The results showed that the temperature at the monitoring point rose rapidly once the energy of molten steel was transferred to the sand mold and then dropped slowly. The closer the monitoring point is to the interface of the casting, the higher the temperature is at the monitoring point. The moisture content in the sand mold is a key factor for sand casting explosion accidents. Sand casting explosion accidents exhibit sensitivity and inherent randomness and are affected by employee, object, environmental and management factors. The organizational factors of sand casting explosion accidents are remote causes, and social factors are basic causes. The findings with respect to sand casting explosion accidents can be regarded as the foundation of accident prevention in practice. [ABSTRACT FROM AUTHOR]

This paper proposes a dynamic reliability analysis approach based on fault tree (FT) and new process capability index (PCI). This work has three contributions. First, new PCIs, namely, Cp‐R, Cpk‐R, Cpm‐R, and Cpmk‐R, are proposed on the basis of traditional PCI prototypes, and the data stability analysis results converge to (0∼1] interval. These new PCI advantages and defects are compared, and the result shows that Cpmk‐R can identify the stability of the dynamic data effectively. Second, fault risk index (FRI) based on Cpmk‐R index, namely, Rpmk‐R, is proposed to approximate the probability of basic events (BEs) for FT. Third, FRI and FT are used to analyze fault transmission and assess dynamic fault risk of equipment. A circulating cooling water heat exchange system is used for simulation to verify the practicability of the approach. Results show that the FT based on Rpmk‐R can assess the dynamic fault risk of equipment accurately. [ABSTRACT FROM AUTHOR]

Sand casting explosion accidents will cause serious casualties, and measures should be adopted to prevent these consequences. The purpose of this study was to investigate the evolution mechanism of sand casting explosion accidents. The temperature variations in sand molds were investigated based on on-site testing and numerical simulation. The evolution characteristics of sand casting explosion accidents were analyzed by fault tree analysis, chaos theory and synthetic theory model. The results showed that the temperature at the monitoring point rose rapidly once the energy of molten steel was transferred to the sand mold and then dropped slowly. The closer the monitoring point is to the interface of the casting, the higher the temperature is at the monitoring point. The moisture content in the sand mold is a key factor for sand casting explosion accidents. Sand casting explosion accidents exhibit sensitivity and inherent randomness and are affected by employee, object, environmental and management factors. The organizational factors of sand casting explosion accidents are remote causes, and social factors are basic causes. The findings with respect to sand casting explosion accidents can be regarded as the foundation of accident prevention in practice. [ABSTRACT FROM AUTHOR]

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical–CO2–cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

This study deals with fault tree analysis algorithms based on an ontology-based approach in a fuzzy environment. We extend fuzzy fault tree analysis by embedding ontology-based fault tree structures. The ontology-based approach allows conducting advanced analyses grounded on rich domain knowledge. Two approaches as the conventional approach and rule-based method are applied for the calculations of failure probability and analysis of the fault tree. Collision and grounding of an autonomous ship are investigated in two scenarios. The structural design, probability calculations, and sensitivity analyses prove that the proposed system is applicable, robust, accurate and reliable. Thus, the propounded ontology-based fault tree algorithms fill a gap in safety engineering by its capability of comprehensiveness.

In order to reduce the failure rate of Integrated Modular Avionics (IMA) partition software, due to the reliability block diagram (RBD) method, fault tree analysis (FTA) method and GO method cannot describe the state transition process of partition software, according to the ARINC 653 standard and the actual running status of the partition software, this paper determines the state machine and conversion delay of the partition software, and establishes the stochastic Petri nets (SPN) reliability quantitative model of the partition software. By proving that each transition in the SPN model of the partition software approximately obeying exponential distribution, and according to the reachable state tree of the SPN isomorphic to a homogeneous Markov chain (MC), the steady-state probability of the partition software in the fault state is calculated to be 5.2778*10-9 by using MC stochastic process theory. The factors affecting the reliability of the partition software are obtained, and the sensitivity of each factor to the model is studied. Finally, the relevant conclusions are drawn to provide guidance for improving the reliability of partition software.

In this paper, an extensive reliability analysis of wind energy conversion systems (WECS) is presented. Elaborate the analysis is presented starting from the subassembly level to the subsystem level, then the system or the overall WECS. The fault tree method with a Weibull probability distribution function is introduced as a complete model for estimating the wind turbine subassemblies’ reliability. The model was tested using a massive dataset of failure rates of various wind turbine subassemblies derived from relevant literature, comprising various operating concepts and the different climate conditions. In addition, ranking for various subassemblies of wind energy conversion systems concerning their impact on the overall system reliability is also presented in this paper to identify the weak items and subsystems. This identification guides the designers and planners in setting the appropriate maintenance strategies to increase the overall reliability of the considered systems and achieve a desired level of reliability. The results indicate that the model has practical applications for managing wind turbines, and the implementation demonstrates the proposed approach’s effectiveness and efficiency, which may significantly enhance the WECS reliability.

Runway excursion (RE) is recognized as one of the main Airport Safety Issues. It can be defined as an event in which an aircraft veers-off or overruns the runway surface during either takeoff or landing. In this paper an application of Fault Tree Analysis (FTA) method on RE events is presented. FTA belongs to quantitative class of causal methods. It estimates the risk of incident or accident according to estimation of probability of occurrence of each cause of an event. It might be restricted to pure statistical analysis based on the available data or combine these data with expert judgment on the accident causes. The aim of this paper is to identify potential causal factors. In order to illustrate FTA application on RE, two models were developed: one for landing and other for take-off. Application of FTA has shown what are the most critical causal factors whose knowledge allows developing certain measures to reduce the risk of RE.

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The lubricating oil systems are essential for ensuring the safe and reliable operation of the cruise ships power plants as demonstrated by recent incidents. The aim of this study is to investigate the safety enhancement of a cruise ship lubricating oil system by employing safety, reliability, availability and diagnosability analyses, which are based on the system functional modelling implemented in the MADe™ software. The safety analysis is implemented by combining a Failure Modes, Effects and Criticality Analysis and the systems functional Fault Tree Analysis. Subsequently, Reliability Block Diagrams are employed to estimate the system reliability and availability metrics. The MADe™ toolbox for determining sensors locations is employed for a more advanced diagnostic system development. A number of design modifications are proposed and the alternative configurations reliability metrics are estimated. The derived results demonstrate that the suction strainer and the lubricating oil pump are the most critical system components. Seven additional sensors are proposed to enhance the original system design. Compared with the original system design, the investigated alternative designs exhibit significantly lower probabilities of failure and higher values of availability. [ABSTRACT FROM AUTHOR]

The present article reflects on a few issues regarding the on-going trend in theory and applications of Statistics. The aspect of applications and the problems with sample surveys in several domains have been emphasized. [ABSTRACT FROM AUTHOR]

An Anti-icing system is a system that aims to prevent the formation of ice when the plane is in the air. The formation of ice in aircraft is of great concern because an airplane flight will pass through the atmosphere, which will experience the formation of the ice at a certain altitude. The formation of such ice will cause a hazard to the aircraft. So that the ice protection system, namely the anti-icing system, is very concerned so that it is always in a serviceable condition. In this study, direct observation and fault tree analysis were used to determine the cause of failure of the Boeing 737-800 NG anti-ice system engine and anti-icing cowl inlet. The results of the analysis using the fault tree analysis method obtained essential events, namely: actuator fails, electrical connector disconnected, Control Selenoid Trouble, Regulator Trouble, Sense Line Connector Trouble, Engine Fault, Engine Control Trouble, Engine Duct Trouble, Panel Buttom Problem, EICAS Module Problem, No Source Electricity, Negative Electrical Source, Wiring Problem. [ABSTRACT FROM AUTHOR]

For an effective integrity assessment of marine robotic in offshore environments, the elements’ failure characteristics need to be understood. A structured probabilistic methodology is proposed for the operational failure assessment (OFA) characteristics of ROV. The first step is to assess the likely failure mode of the ROV system and its support systems. This captures the interaction and failure induced events during operation. The identified potential failure modes are further developed into logical connectivity based on the cause-effect relationship. The logical framework is modeled using the fault tree analysis technique to predict the ROV operational failure probability in an uncertain harsh environment. The fault tree analysis captured the logical relationship between the primary, intermediate, and top events probability. The importance measure criteria were adopted to identify the most probable events, links, and their importance on the failure propagation. The model was demonstrated with an ROV for deep arctic water subsea operations. The result identified the control system, communication linkages, human factor, among others, as most critical in the ROV operational failure. The methodology’s application provides core information on the Mean time between failure (MTBF) of the ROV system that could aid integrity management and provides a guide on early remedial action against total failure. [ABSTRACT FROM AUTHOR]

In the implementation of dam construction, there are usually many problems at the stages of work, therefore careful planning is needed so that the project can run smoothly and be completed on time. The method used in this study is the fault tree analysis (FTA) method which is used to find the root cause of the dominant risk factor (major risk). Data collection was carried out using a literature study approach, namely references to journals and similar research in the latest editions as well as field studies in the form of expert interviews and distributing questionnaires to stakeholders involved in implementing this project. From the results of the risk analysis, there are 5 dominant risk variables, namely unfinished land acquisition (R2), changes in drawings/designs (R9), material availability (pile) less than the volume requirement (R11), damage to work equipment and equipment (R18), and the effect of weather on the execution of work (R21). From the fault tree analysis (FTA) obtained 54 basic events that are the cause of the dominant risk. Knowing the root cause of the dominant risk can be information for all parties involved in the Package 1 Temef Dam Development Project (stakeholders) to be able to minimize the occurrence of risks. [ABSTRACT FROM AUTHOR]

The probability of the correct performance of the activities required by the system over a given period of time and the working conditions specified by a person is called human reliability. Human reliability is seen in all industries, and it can affect the performance of the system or results in unpleasant events. In electrical power systems, the human errors of maintenance groups are one of the most important factors in the failure of electrical equipment. In this paper, a new method based on the combination of Fault Tree Analysis (FTA) and Human Factors Analysis and Classification System is presented in order to calculate and analyze the human reliability in electrical power systems. In this method, the basic causes (roots) of human errors are comprehensively identified in all aspects. The relationship among the causing roots, and also between the human errors and these roots are established logically. Finally, human reliability can calculate easily. Since the data available in this study are mostly linguistic, the fuzzy logic is used to eliminate the inaccuracy of the evaluation and to improve the FTA technique. The validity and the accuracy of the presented method are assessed by the results of human reliability analysis in Fars Electricity Maintenance Contractor Company as a case study. Results show the accuracy of the proposed method for human reliability analyses of maintenance groups in power transmission grids. [ABSTRACT FROM AUTHOR]

One of the important steps in designing and implementation of tunneling projects is analyzing and managing the risks from the viewpoint of geotechnical risks. Second part of the Emamzadeh Hashem tunnel is one of the greatest civil projects in Iran that has faced with serious and important challenges in design because of the poor geological structure and geotechnical condition in excavation track. In this research, try to be after the geological studying in the tunnel excavation track, the overall risk amount be assessed by fault tree analysis. During this study, 4 important event including damage to the personnel, damage to the TBM, damage to the restraint system and deflection from the excavation track was identified and studied by using the geotechnical hazards like: encounter to fault and comminuted areas, squeezing, water inrush and tunnel instability. Results of the analysis show that reasons of the higher risk in this project are damage to the TBM and damage to restraint system. So, the higher risk should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification. According to the results, in this project, damage to the TBM and damage to restraint system have the highest risks and their risks should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification.

Semua proyek konstruksi pasti memiliki risiko. Salah satunya adalah risiko terjadinya kecelakaan. Masalah Keselamatan dan Kesehatan Kerja (K3) pada sektor konstruksi masih belum menjadi perhatian utama. Hal itu dapat dilihat dari angka kecelakaan kerja di sektor konstruksi adalah yang paling tinggi di antara bidang kerja lainnya. Berdasarkan Laporan Insiden HSE Project, terdapat tujuh insiden pada proyek Office Tower J-Box Jakarta Pusat, sehingga prinsip zero accident pada proyek tersebut tidak tercapai. Tujuan dari penelitian ini adalah untuk mengidentifikasi pekerjaan yang berisiko menimbulkan bahaya pada pekerja proyek, menilai tingkat risiko, menilai efektivitas pengendalian risiko, dan menentukan pengendalian risiko yang tepat pada proyek tersebut. Data yang digunakan dalam penelitian ini adalah data primer berupa kuesioner pada responden dan data sekunder berupa Laporan Mingguan K3, Laporan Bulanan K3, dan Laporan Data insiden. Penelitian ini menggunakan kombinasi metode Fine dan Fault Tree Analysis. SPSS V22 digunakan untuk menguji validitas data primer. Metode Fine digunakan untuk menghitung nilai risiko kecelakaan kerja. Metode Fault Tree Analysis dipakai untuk menganalisis nilai risiko sehingga diketahui penyebab dasar dari suatu kejadian yang berpotensi bahaya dan merekomendasikan tindakan spesifik yang dapat dilakukan kontraktor dalam meminimalisir bahaya tersebut. Analisis hasil penelitian menunjukkan bahwa nilai efektivitas risk control pada pekerja proyek konstruksi pembangunan Office Tower J-Box Jakarta berada pada tingkat risiko

Probabilistic safety assessment (PSA) which plays a crucial role in risk evaluation is a quantitative approach intended to demonstrate how a nuclear reactor meets the safety margins as part of the licensing process. Despite PSA merits, some shortcomings associated with the final results exist. Conventional PSA uses crisp values to represent the failure probabilities of basic events. This causes a high level of uncertainty due to the inherent imprecision and vagueness of failure input data. In this paper, to tackle this imperfection, a fuzzy approach is employed with fault tree analysis and event tree analysis. Thus, instead of using the crisp values, a set of fuzzy numbers is applied as failure probabilities of basic events. Hence, in the fault tree and event tree analysis, the top events and the end-states frequencies are treated as fuzzy numbers. By introducing some fuzzy importance measures the critical components which contribute maximum to the system failure and total uncertainty are identified. As a practical example, under redesign Iranian heavy water research reactor loss of coolant accident is studied. The results show that the reactor protection system has the largest index in sequences lead to a core meltdown. In addition, the emergency core cooling system has a main role in preventing abnormal conditions.

[Introduction] The service water system as the ultimate heat sink is of great significance for the operation and accident mitigation of nuclear power plants. [Method] In this paper, the fault tree was built to model the full power and shutdown modes of the investigated plant under cold and non-cold weather conditions respectively, and then to assess the reliability of service water system as an accident mitigation measure. The Monte Carlo method was used to analyse the operability of the system as an initiating event. Relationships between equipment failure rate, maintenance cycle and the annual average unavailability were also attained via sensitivity analysis. [Result] Quantitative results show the failure rates of service water system for different mission time, particularly under the conditions of non-cold weather at full power the failure rates are 1.47E-01 per year and 4.10E-04 per 72 hours (mission time in accident mitigation process), and at shutdown mode the corresponding failure rate is 6.45E-03 per 96 hours. The frequency of the loss of service water is about 2.0E-03 per year and the annual average unavailability time of the system is about 3.4 hours. [Conclusion] The results suggest that seawater pretreatment system has more significant influence on the unreliability of service water system, of which the operation failure of electric isolation valve at the main pipeline is the dominant contributor due to having no redundant design. In addition, shortening regular maintenance cycle will be a more effective and operable way to reduce the annual average unavailability time compared with reducing the failure rates of components.

Over the years, several approaches have been developed for the quantitative analysis of dynamic fault trees (DFTs). These approaches have strong theoretical and mathematical foundations; however, they appear to suffer from the state-space explosion and high computational requirements, compromising their efficacy. Modularisation techniques have been developed to address these issues by identifying and quantifying static and dynamic modules of the fault tree separately by using binary decision diagrams and Markov models. Although these approaches appear effective in reducing computational effort and avoiding state-space explosion, the reliance of the Markov chain on exponentially distributed data of system components can limit their widespread industrial applications. In this paper, we propose a hybrid modularisation scheme where independent sub-trees of a DFT are identified and quantified in a hierarchical order. A hybrid framework with the combination of algebraic solution, Petri Nets, and Monte Carlo simulation is used to increase the efficiency of the solution. The proposed approach uses the advantages of each existing approach in the right place (independent module). We have experimented the proposed approach on five independent hypothetical and industrial examples in which the experiments show the capabilities of the proposed approach facing repeated basic events and non-exponential failure distributions. The proposed approach could provide an approximate solution to DFTs without unacceptable loss of accuracy. Moreover, the use of modularised or hierarchical Petri nets makes this approach more generally applicable by allowing quantitative evaluation of DFTs with a wide range of failure rate distributions for basic events of the tree.