Có 80+ tài liệu thuộc chủ đề "bảo trì máy"
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For each sequence of the event tree, the fault trees of the composing events are linked in one large fault tree that follows the logic depicted in the event tree, and the fault tree is then solved with the usual techniques to compute the probability of occurrence of that sequence.. If the probability of the sequence ( I. S 2...
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The cause-consequence diagram is reduced to a minimal form by, firstly, remov- ing any redundant decision boxes and, secondly, manipulating any common failure events that exist on the same path. An algorithm has been developed that will produce the correct cause-consequence diagram and calculate the exact system failure probability for static systems with binary success or failure responses to the...
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the ‘estimated reportable hazard frequency’ arising from functional failure of the item,. the ‘estimated physical condition’ of the item related to its safety.. This is measured according to the contribution of:. the ‘actual disabling injury frequency’ arising from functional failure of the item,. the ‘actual reportable hazard frequency’ arising from functional failure of the item,. the ‘actual physical condition’ of...
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The cost of ensuring the required reliability and safety relative to the selected at- tributes can be formulated as. C f = cost of failure relative to the selected attributes R = risk of a failure incident occurring.. p = the probability of the event occurring c = the consequence of the risk on the estimate.. As a result, it...
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Furthermore, it is always advisable to take into account the level of training and experience of the personnel who will be operating the plant. However, systems modelling approaches have to be adapted to the information that is available at certain points in the design stage.. Thus, the initial model, derived in the early design phases, must be refined by adding...
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e) Critical Risk Theory in Designing for Safety. z k , all of which must function for the system to be able to function, and where the useful life length of the system is Z.. Denoting the survival function of the useful life expectancy of Z by F , and of z i by F i ( i . The...
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3.3.3.4 and illustrated in Fig. The problem with the model, though, is the lack of any detailed data for generic sys- tems, assemblies and components, to provide an adequate assessment of safety in engineering design—especially in the preliminary design phase. A somewhat different approach to the beta factor model has thus been taken in which the beta values are not...
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is obtained by multiplying the p.g.f.s of the random variables together. 5.2.4.2 Cause-Consequence Analysis for Safety Systems Design. Cause-consequence analysis for safety systems design is fundamentally a combina- torial symbolic logic technique, utilising the symbolic logic of fault-tree analysis (FTA), reliability block diagramming (RBD) and event tree analysis (ETA). Fault trees are generated in the failure domain, reliability diagrams are...
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interval Main PCV V1 Stop high-pressure. Sub-PCV V2 Stop high-pressure surge passing through system. ESD valve V3 Stop high-pressure surge passing through system. HIPS1 V4 Stop high-pressure surge passing through system. HIPS2 V5 Stop high-pressure surge passing through system. Pressure sensors. Pr S Indicate the level of pressure to the computer. a high-pressure surge originating from process circulation pumps, to...
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to the point of impracticality where, for example, consideration is given only to sin- gle modes of failure, or only to random failure occurrences, or to maintenance that results in complete renewal and ‘as new’ conditions. At best, the intrin- sic failure characteristics of components of equipment are determined from quan- titative probability distributions of failure data obtained in a...
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Table 5.18 (continued) Component Failure. TLF Low pressure switch fails due to corrosion or mechanical damage. 2 T heoret ical Ov ervi ew of Safet y and R is k in E ngi neeri ng D esi gn 665 Table 5.19 FMECA for process and cost criticality. Fails to open TLF Production Medium. 666 5 Safety and Risk in Engineering...
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Decision trees provide a more formal structure in which decisions and chance events are linked from left to right in the order they would occur. Probabilities of the likelihood of failure events are added to each node in the tree. Such sensitivity analysis is best conducted with the aid of specialised application software such as @RISK c , in which...
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5.49 Detail design model of the scrubber in the layout of a gas cleaning plant. structural and geometric feature of the design. A schematic design model of the gas cleaning plant is graphically illustrated in Fig. After evaluation of the design variables and constraints describing the structural and geometric feature of the design, a detail design model is prepared. In...
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sign variables also adds difficulty to the problem. A numerical scheme is therefore required that produces integer values for these variables, since it will not be appropriate to utilise a method where real numbers are rounded to the nearest whole number. Expected maintenance downtime, for example, can be represented by an explicit function of the design pa- rameters. however, the...
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Ex- amining the artificial neural network itself only shows meaningless numeric values.. The ANN model is fundamentally a black box. Artificial neural net- works have the ability to account for any functional dependency by discovering (i.e.. learning and then modelling) the nature of the dependency without needing to be prompted. The process goes straight from the data to the model...
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The problem is that the fuzzy sets F i and H i are both defined by their membership functions μ , with domain R, the set of real numbers, the input vectors of the training set having infinite elements.. Furthermore, the range of the membership functions are con- tained to the interval [0, 1]. 5.67, draw a semicircle in the...
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One neurode is present in the output layer for each category specified by the user. 5.4, an artificial intelligence-based blackboard model is used to hold shared information in a general and simple model that allows for the representa- tion of a variety of modelled system behaviours. The AIB blackboard system is prescribed for problem-solving in knowledge-intensive domains that require large....
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The simple parallel arrangement of the four blocks 1, 2, 3 and 4 in Fig. 5.88, with a vote number (number of available paths required for success) of 2, would result in the truth table given in Table 5.27.. Figure 5.89 illustrates the use of the fault-tree diagram in determining potential system failures in a parallel control valve configuration of...
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744 5 Safety and Risk in Engineering Design. A typical design problem that is ideal for ANN mod- elling is the formulation and evaluation of stream surge pressures in continuous flow processes, given in the simulation option of the AIB blackboard as illustrated in Fig. The NeuralExpert c (NeuroDimension 2001) program, imbedded in the AIB blackboard, asks specific questions and...
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754 5 Safety and Risk in Engineering Design. The knowledge base consists of facts and functions relating to all the techni- cal data pertaining to process definition, systems definition, performance assess- ment and analysis, conditions and constraints relating to equipment failure modes and effects, the level of risk and mitigating maintenance procedures, as well as an assessment of the required...