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Fault trees are a popular industrial technique for reliability modelling and analysis. Their extension with common reliability patterns, such as spare management, functional dependencies, and sequencing-known as dynamic fault tree...
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Fault trees are a popular industrial technique for reliability modelling and analysis. Their extension with common reliability patterns, such as spare management, functional dependencies, and sequencing-known as dynamic fault trees (DFTs)-has an adverse effect on scalability, prohibiting the analysis of complex, industrial cases. This paper presents a novel, fully automated reduction technique for DFTs. The key idea is to interpret DFTs as directed graphs and exploit graph rewriting to simplify them. We present a collection of rewrite rules, address their correctness, and give a simple heuristic to determine the order of rewriting. Experiments on a large set of benchmarks show substantial DFT simplifications, yielding state space reductions and timing gains of up to two orders of magnitude.
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摘要 :
Fault trees are a popular industrial technique for reliability modelling and analysis. Their extension with common reliability patterns, such as spare management, functional dependencies, and sequencing-known as dynamic fault tree...
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Fault trees are a popular industrial technique for reliability modelling and analysis. Their extension with common reliability patterns, such as spare management, functional dependencies, and sequencing-known as dynamic fault trees (DFTs)-has an adverse effect on scalability, prohibiting the analysis of complex, industrial cases. This paper presents a novel, fully automated reduction technique for DFTs. The key idea is to interpret DFTs as directed graphs and exploit graph rewriting to simplify them. We present a collection of rewrite rules, address their correctness, and give a simple heuristic to determine the order of rewriting. Experiments on a large set of benchmarks show substantial DFT simplifications, yielding state space reductions and timing gains of up to two orders of magnitude.
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The manual construction of fault trees for complex systems is an error-prone and time-consuming activity, encouraging automated techniques. In this paper we show how the retrenchment approach to formal system model evolution can b...
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The manual construction of fault trees for complex systems is an error-prone and time-consuming activity, encouraging automated techniques. In this paper we show how the retrenchment approach to formal system model evolution can be developed into a versatile structured approach for the mechanical construction of fault trees. The system structure and the structure of retrenchment concessions interact to generate fault trees with appropriately deep nesting. We show how this approach can be extended to deal with minimisation, thereby diminishing the post hoc subsumption workload and potentially rendering some infeasible cases feasible.
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Fault tree analysis (FTA) is a widely used method for analyzing a system's failure logic and calculating overall reliability. However, application of conventional FTA has some shortcomings, e.g. in handling the uncertainties, allo...
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Fault tree analysis (FTA) is a widely used method for analyzing a system's failure logic and calculating overall reliability. However, application of conventional FTA has some shortcomings, e.g. in handling the uncertainties, allowing the use of linguistic variables, and integrating human error in failure logic model. Hence, Fuzzy set theory has been proposed to overcome the limitation of conventional FTA. Fuzzy logic provides a framework whereby basic notions such as similarity, uncertainty and preference can be modeled effectively. The aim of this paper is to present a review of the concept of fuzzy theory with fault tree analysis and their applications since 1981, to reflect the current status of Fuzzy fault tree analysis (FFTA) methodologies, their strengths, weaknesses, and their applications. This paper explains the fundamentals of fuzzy theory and describes application of fuzzy importance for using FFTA. The concept of the failure possibility and uncertainty analysis by using FFTA is discussed, and concludes with discussion on the application of FFTA in different fields. The review reveals the effectiveness of the FFTA in comparison with conventional FTA, when there is inadequate amount of accurate reliability oriented information.
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Fault tree analysis (FTA) is a powerful technique that is widely used for evaluating system safety and reliability. It can be used to assess the effects of combinations of failures on system behaviour but is unable to capture sequ...
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Fault tree analysis (FTA) is a powerful technique that is widely used for evaluating system safety and reliability. It can be used to assess the effects of combinations of failures on system behaviour but is unable to capture sequence dependent dynamic behaviour. A number of extensions to fault trees have been proposed to overcome this limitation. Pandora, one such extension, introduces temporal gates and temporal laws to allow dynamic analysis of temporal fault trees (TFTs). It can be easily integrated in model-based design and analysis techniques. The quantitative evaluation of failure probability in Pandora TFTs is performed using exact probabilistic data about component failures. However, exact data can often be difficult to obtain. In this paper, we propose a method that combines expert elicitation and fuzzy set theory with Pandora TFTs to enable dynamic analysis of complex systems with limited or absent exact quantitative data. This gives Pandora the ability to perform quantitative analysis under uncertainty, which increases further its potential utility in the emerging field of model-based design and dependability analysis. The method has been demonstrated by applying it to a fault tolerant fuel distribution system of a ship, and the results are compared with the results obtained by other existing techniques. (C) 2016 Elsevier Inc. All rights reserved.
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Over the last 50 years, advances in technology have led to an increase in the complexity and sophistication of systems. More complex systems can be harder to maintain and the root cause of a fault more difficult to isolate. Downti...
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Over the last 50 years, advances in technology have led to an increase in the complexity and sophistication of systems. More complex systems can be harder to maintain and the root cause of a fault more difficult to isolate. Downtime resultin from a system failure can be dangerous or expensive, depending on the type of system. In aircraft systems the ability to diagnose quickly the causes of a fault can have a significant impact on the time taken to rectify the problem and to return the aircraft to service. In chemical process plants the need to diagnose causes of a safety-critical failure in a system can be vital and a diagnosis may be required within minutes. Speed of fault isolation can save time, reduce costs, and increase company productivity and therefore profits. System fault diagnosis is the process of identifying the cause of a malfunction by observing its effect at various test points. Fault tree analysis (FTA) is a method that describes all possible causes of a specified system state in terms of the state of the components within the system. A system model is used to identify the states that the system should be in at any point in time. This paper presents a method for diagnosing faults in systems using FTA to explain the deviations from normal operation observed in sensor outputs. The causes of a system's failure modes will be described in terms of the component states. This will be achieved with the use of coherent and non-coherent fault trees. A coherent fault tree is constructed from AND and OR logic and therefore considers only component-failed states. The non-coherent method expands this, allowing the use of NOT logic, which implies that the existence of component-failed states and component-working states are both taken into account. This paper illustrates the concepts of this method by applying the technique to a simplified water tank level control system.
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Many construction projects are of long-duration and high value and foreseeing and planning for every eventuality may be impossible. Engineers and managers are expected to solve problems surfacing during the execution stage. Moreov...
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Many construction projects are of long-duration and high value and foreseeing and planning for every eventuality may be impossible. Engineers and managers are expected to solve problems surfacing during the execution stage. Moreover, problems blended with conflict are damaging and manifest as disputes. The authors suggested that construction dispute can be conceptualized as having three basic components: contract provisions, triggering events and conflict. This conceptualization fits nicely with fault tree (FT) framework that is used to evaluate system failures. Furthermore, through the use of a hypothetical case, a fuzzy FT model was employed to analyze the likelihood of construction dispute. This research suggested that complex project delivered in the traditional design then build approach, construction dispute are bound to appear.
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The maintenance of the diesel engine parts in any electric power station contains many problems that lead to stopping. Several reasons lead to such problems; these reasons should be analyzed and evaluated in order to eliminate the...
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The maintenance of the diesel engine parts in any electric power station contains many problems that lead to stopping. Several reasons lead to such problems; these reasons should be analyzed and evaluated in order to eliminate their effects. This paper is based on evaluation of the main causes that lead to diesel engine injector failure as a main part of electric power stations, using fault tree analysis (FTA). The FTA is the most broadly utilized strategies in the industrial area to perform reliability analysis of complex designing frameworks. A fault tree is a logical representation of the relationship of basic events that lead to a given unwanted event (i.e., top event). Starting with introducing the FTA and how it could be utilized in analyzing the reasons of main issues that lead to that the injector stops working, in which the probability of occurrence of each issue is calculated. The application of the root cause analysis principle of diesel engine injector failure in diesels Haditha station is chosen as a case under study. According to the probabilities’ evaluation by using the FTA based on of the causes under the top event its value was (0.80). It is concluded from the analysis that the three largest values of the occurrence of a problem with the diesel engine injector are 0.50 for fuel problems, 0.20 for overloads, and 0.18 for nozzle head corrosion. Plant management can define a specific plan with taking into consideration the calculated value of each cause in order to reduce their impacts and to avoid long downtime hours compared to operating hours. Finally, recommandations are suggested to overcome these causes.
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摘要 :
Fault-tree analysis is commonly used for risk assessment of
industrial systems. Several computer packages are available to carry out
the analysis. Despite its common usage there are associated limitations
of the technique in terms...
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Fault-tree analysis is commonly used for risk assessment of
industrial systems. Several computer packages are available to carry out
the analysis. Despite its common usage there are associated limitations
of the technique in terms of accuracy and efficiency when dealing with
large fault-tree structures. The most recent approach to aid the
analysis of the fault-tree diagram is the BDD (binary decision diagram).
To use the BDD, the fault-tree structure needs to be converted into the
BDD format. Converting the fault tree is relatively straightforward but
requires that the basic events of the tree be ordered. This ordering is
critical to the resulting size of the BDD, and ultimately affects the
qualitative and quantitative performance and benefits of this technique.
Several heuristic approaches were developed to produce an optimal
ordering permutation for a specific tree. These heuristic approaches do
not always yield a minimal BDD structure for all trees. There is no
single heuristic that guarantees a minimal BDD for any fault-tree
structure. This paper looks at a selection approach using a neural
network to choose the best heuristic from a set of alternatives that
will yield the smallest BDD and promote an efficient analysis. The set
of possible selection choices are 6 alternative heuristics, and the
prediction capacity produced was a 70% chance of the neural network
choosing the best ordering heuristic from the set of 6 for the test set
of given fault trees
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The fault tree analysis is one of the most frequent used methods of supporting the safety systems analysis. Real time systems are one of the fields of applications. Information of hazard occurrence in these systems is important as...
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The fault tree analysis is one of the most frequent used methods of supporting the safety systems analysis. Real time systems are one of the fields of applications. Information of hazard occurrence in these systems is important as well as information related to timing aspects. In this chapter the models of gates has been collected, the notation of events for XML file generation has been given and application for analyzing of fault trees with time dependencies, given both numerically and parametrically, has been shown.
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