Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 16 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. . | Analytic Development of Reliability and Performance in Engineering Design 133 The overall performance index OPI can be calculated as OPI PPI SPI mn 1 1J 1 J where m is the number of performance parameters and n is the number of systems. Computation propagation rule 1 only X and only Y and G only Range G X Y OPI corners PPI SPI 1 12 x 1 .2 x 1 .6 1 .2 x 1 .7 1 .2 x x x 1 . 6 x 1 . 7 x 1 . 7 x x x x x 1 12 x x x x x x x x x x x x x OPI range PPI SPI 1 12 x 1 12 x and OPI all-parts only Description The overall performance index OPI is a combination of the parameter performance index PPI and the system performance index SPI and indicates the overall performance of the operational parameters PPI and the overall contribution of the system s items on the system SPI itself. The numerical value of OPI lies in the range 0-100 and can thus be indicated as a percentage value which is a useful measure for conceptual design optimisation. The reverse jet scrubber system has an overall performance in the range of to 54 which is not optimal. The critical minimum performance level of as well as the upper performance level of 54 indicate design review. Analytic Development of Reliability Assessment in Preliminary Design The most applicable techniques selected as tools for reliability assessment in intelligent computer automated methodology for determining the integrity of engineering 134 3 Reliability and Performance in Engineering Design design during the preliminary or schematic design phase are failure modes and effects analysis FMEA failure modes and effects criticality analysis FMECA and fault-tree analysis. However as the main use of fault-tree analysis is perceived to be in designing for safety whereby fault trees provide a useful representation of the different failure paths .
