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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 50

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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 50 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | 4.3 Analytic Development of Availability and Maintainability in Engineering Design 473 Table 4.5 Process capacities per subgroup Sub-system group No. of subgroups Capacity per subgroup A 1 100 B 2 75 C 3 50 Process limitations Quality limitations etc. Each state in the simple power plant example has only one subgroup that is the limiting factor or bottleneck for the plant s power output capability in that state. This constraint is illustrated in Fig. 4.35 where the example plant is represented as a set of pipes and valves of varying capacities. Each section of pipe and valve corresponds to a subgroup in which the subgroup s unavailability is analogous to a valve being closed The single A subgroup consisting of two coal bin sub-systems is wide enough to handle 100 of the flow Each of the two B subgroups consisting of the two slurry mill sub-systems is wide enough to handle 75 of the flow Each of the three C subgroups consisting of three gas turbines and three generators is wide enough to handle 50 of the flow. For example if two C subgroups are unavailable and one B subgroup is unavailable the C subgroup is the limiting factor because its remaining capacity is only 50 whereas the remaining capacity in any one of the B subgroups is 75 . Furthermore when two C subgroups are unavailable there could be either no unavailable B subgroups or one unavailable B subgroup without further reducing the process flow from the resulting 50 output brought about by the one available C subgroup. f Defining Different States 1 Table 4.5 shows the percentage of the plant s process flow capability that each type of subgroup could support. 2 Table 4.6 shows the reduction in plant flow capacity as the number of unavailable subgroups in each sub-system group increases given that all other subgroups are available. Where excess capacity beyond 100 exists in a subgroup 100 is given as the throughput capacity. 3 Table 4.7 shows the flow capacities and state definitions. The flow capacities are .