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3.3.2.8 Uncertainty and Incompleteness in Engineering Design Analysis Uncertainty and incompleteness is inherent to engineering design analysis. Uncer- tainty, arising from the complex integration of systems, can best be expressed in qualitative terms, necessitating the results to be presented in the same qualitative measures. An important question is to decide what kind of possibility theory or fuzzy logic representation (in...
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3 .3 A n aly tic De v elo p m en t o f R elia b ility an d P er fo rm an ce in E n g in ee Table 3.16 Extract from FMECA worksheet of quantitative RAM analysis field study: motor RJS pump no. RJS pump no. Motor fails to start or drive pump. TLF...
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It is often more convenient to define an additional covariate, x o = 1, in order to allow the Weibull scale parameter to be included in the vector of regression coefficients, and the proportional hazards model expressed solely by the beta (shape parameter), together with the regression parameters and covariates. The PH reliability function is thus given by the expression...
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The parameter of the exponential distribution can also be estimated using the maxi- mum likelihood estimation (MLE) method. F is the number of groups of times-to-failure data points.. N i is the number of times to failure in the ith time-to-failure data group.. λ is the failure rate parameter (unknown a priori, only one to be found).. T i is...
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ment of the characteristics of failure. A major problem arises, though, when the measures and/or estimates of the Weibull parameters cannot be based on obtained data, and engineering design analysis cannot be quantitative. Credible and statisti- cally acceptable qualitative methodologies to determine the integrity of engineer- ing design in the case where data are not available or not meaningful are...
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The likelihood function is a fundamental concept in statistical inference. For instance, suppose an unknown random variable u that has values in the set U is to be estimated. Suppose also that the distribution of u depends on an unknown parameter F , with values in the parameter space F. F ) be the probability distribution of the variable u,...
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Thus, in the case of expert judgment, new estimate values in the form of a like- lihood function are incorporated into a Bayesian reliability model in a conventional way, representing updated information in the form of a posterior (a posteriori) prob- ability distribution that depends upon a prior (a priori) probability distribution that, in turn, is subject to the estimated...
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In any complex process plant, there are literally thousands of different systems, sub-systems, assemblies and components, which are all subject to failure and, there- fore, require specific attention with respect to the integrity of their design, design configuration as well as integration. Cost critical items are the relatively few systems items of which the engineer- ing costs (development, operational, maintenance...
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3.4 Application Modelling of Reliability and Performance in Engineering Design 253. equipment physical data such as type, make, size, mass, volume, number of parts;. equipment rating data such as performance, capacity, power (rating and factor), efficiency and output;. equipment measure data such as rotation, speed, acceleration, governing, fre- quency and flow in volume and/or rate;. equipment operating data such as...
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3.4 Application Modelling of Reliability and Performance in Engineering Design 263. 3.67 Hazards criticality analysis assembly condition. portion of the FMEA results are very similar at both levels. Thus, in a hazards criti- cality analysis of the condition of selected components for inclusion in a design, the following component condition data illustrated in Fig. Figure 3.68 illustrates a hazards criticality...
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3.4 Application Modelling of Reliability and Performance in Engineering Design 273. 274 3 Reliability and Performance in Engineering Design. to the DCS or PLC. For ex- ample, a PLC may control the flow of cooling water through part of a process, such as the reverse jet scrubber, but the SCADA system allows operators to change the set points for the...
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The Kolmogorov–Smirnov goodness-of-fit test The Kolmogorov–Smirnov (K–S) test is used to decide if a sample comes from a population with a specific distribu- tion. The K–S test is based on the empirical distribution function (e.c.d.f.) whereby, given N ordered data points Y 1 , Y 2. An attractive feature of this test is that the distribution of the K–S test...
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Nuclear Eng Design revised from Sandia Natl Lab Rep SAND88-2253C, and Nuclear Regulatory Commission Rep NUREG/CP-0097 5, pp 1–25 Pahl G, Beitz W (1996) Engineering design. Elsevier, New York Simon HA (1981) The sciences of the artificial. 294 3 Reliability and Performance in Engineering Design Steele AD, Leitch RR (1996) A strategy for qualitative model-based diagnosis. Zadeh LA (1973) Outline...
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Inherent availability can be defined as “the prediction of expected system per- formance or system operability over a period which includes the predicted system operating time and the predicted corrective maintenance down time”.. Achieved availability can be defined as “the assessment of system operability or equipment usage in a simulated environment, over a period which includes its predicted operating time...
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What is the economic loss of production in the event of systems A1 and A2 being down for 5 days as a result of downtime?. Relative lost time cost = 5 days day × 10%. Relative lost time cost = 5 days day × 60%. $60 , 000 Relative lost time cost. Would there be a difference in the calculations...
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In applying NPV, the net cash flows are usually available as input data, which are assumed to occur instantaneously at the ends of the periods t. Also usually known is an estimate of the discounting rate, i, to be used. While the point estimate of NPV is informative, in that one can determine if it is positive, negative, zero or...
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To obtain a reasonable measure of the process capability, the length of the time frame should be chosen such that it is long enough to reflect all the substantial sources of variation in the process. The pilot process output should be sampled in such a way that a ‘fair’. representation is obtained of the process over the chosen time frame....
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The effective capacities of multiple system operations or processes within the same engineering design installation are usually different. A bottleneck is a process that has the lowest effective capacity of any process in the designed installation and, thus, limits total output. Also, the focus on bottlenecks is the means to increasing throughput and, consequently, the mass-flow rate of product and...
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As with the two-state Markov model, the mathematical expressions for the multi- state Markov model, including supplementary variables indicating partial operation or a reduced efficiency of the system, are given in the following Markov multi-state model equations, according to Fig. 1 − μ f ( x )Δ t ] (4.72) λ j is the jth constant failure rate of the...
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Routine maintenance is the preventive action in maintenance that cares for the operational condition of equipment through inspection, adjustment, recording, monitoring, servicing and lubrication, to ensure that the equipment’s operational functions conform to the required limits of performance.. Evidently, this type of preventive action can only be directed towards the operational condition of equipment.. Thus, the way in which corrective...