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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 10

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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 10 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. . | 3.2 Theoretical Overview of Reliability and Performance in Engineering Design 73 the reliability of relatively simple systems with series and parallel assemblies to estimations of the reliability of multi-state systems with random failure occurrences and repair times i.e. constant failure and repair rates of inherent independent assemblies. Reliability assessment in this context is considered during the preliminary or schematic design phase of the engineering design process with an estimation of the probability that items of equipment will perform their intended function for specified intervals under stated conditions. The most applicable methods for reliability assessment in the preliminary design phase include concepts of mathematical modelling such as Markov modelling To estimate the reliability of multi-state systems with constant failure and repair rates of inherent independent assemblies. The binomial method To assess the reliability of simple systems of series and parallel assemblies. Equipment aging models To assess the aging of equipment at varying rates of degradation in engineered installations. Failure modes and effects analysis criticality analysis A step-by-step procedure for the assessment of failure effects and criticality in equipment design. Fault-tree analysis To analyse the causal relationships between equipment failures and system failure leading to the identification of specific critical system failure modes. 3.2.2.1 Markov Modelling Continuous Time and Discrete States This method can be used in more cases than any other technique Dhillon 1999a . Markov modelling is applicable when modelling assemblies with dependent failure and repair modes and can be used for modelling multi-state systems and commoncause failures without any conceptual difficulty. The method is more appropriate when system failure and repair rates are constant as problems may arise when solving a set of linear algebraic equations for large systems where system failure and .