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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 60

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Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 60 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. . | 574 5 Safety and Risk in Engineering Design The cause-consequence diagram is reduced to a minimal form by firstly removing any redundant decision boxes and secondly manipulating any common failure events that exist on the same path. The common failure events can be extracted as common sub-modules or individual events. This process is equivalent to constructing the fault tree converting it to a BDD and identifying and extracting independent sub-modules. 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 trigger event. This is achieved without having to construct the fault tree of the system and retains the documented failure logic of the system Ridley et al. 1996 The minimised cause-consequence diagram is then analysed using a BDD analysis procedure. Thus exact rather than approximate calculations are performed. The advantages of the cause-consequence diagram are The diagram can be constructed directly from system description. Dependencies in the system can be incorporated in the analysis. The system is modularised to increase efficiency. Exact calculation procedures are adopted. Repeated events The four-stage procedure developed to construct and analyse a cause-consequence diagram is capable of dealing with the events that occur in more than one fault-tree structure attached to the decision boxes in any sequence path. The CCD method can deal with repeated events in a more efficient way to that used for FTA Ridley et al. 1996 . Using the CCD method there is no need to obtain the Boolean expression of the top event and then manipulate it to produce a minimal form prior to analysis. The converse approach of the cause-consequence method deals with sequences of events that either occur fail or do not occur work . The probability of a particular outcome is obtained by summation of the probabilities of all paths that .