Assessing systems reliability: a Probabilistic Risk Assessment (PRA) approach

Assessing the reliability performance of complex system involves dealing with events whose occurrence cannot be predicted easily. Not only a good descriptive procedure of the system's components is required but the solution requires some means by which the likelihood of the events can be expressed in terms of quantitative methods. This can be done by adopting a probabilistic risk and reliability assessment method to assess system behaviour. This requires enhancing the reliability analysis with a probabilistic risk analysis technique. The procedure of integration suggested in this work is called Probabilistic Risk Analysis [PRA]. It involves: 1) Identification of the potential events of failures and their modes of failures. 2) Estimation of the consequences of these failures on the total system. 3) Estimation of the probability of occurrence of each event of failure. 4) Comparison of the results of the analysis against an acceptability criterion or criteria. The third step is the focus of this paper where the novelty of this work appears. Rather than drawing a deterministic FTD for identifying probability of occurrences of the failure events a probabilistic one is suggested to cater for any risks or uncertainties involved in the system. By allowing probabilistic input of basic events a probabilistic top event is produced giving managers more freedom to check among a range of failure probabilities that the system might fall in rather than one limited deterministic failure value. This gives more practicality to the assessment of the whole system resulting in better actions and higher reliable performance.