The choice of failure distribution for modelling the reliability and availability of a multi-component system

Reliability and availability modelling is often used to verify system performance for different configurations during the design phase of a system. Design changes can be implemented at this early stage to improve reliability, maintainability and availability to acceptable values. This paper discusses the results of a study to determine the availability of a multi-component system as a function of time to compare different failure distributions used for the components of the system. Discrete event simulation was used to determine the interval availability. It was found that the availability plots for the Weibull, gamma, triangular and Pearson input distributions for seven components did not differ significantly. The Weibull and gamma input distributions were also compared with a larger system comprising twenty components. Analysis of the availability data when steady state was reached indicated that there is no significant difference in the availability values when gamma input distributions were used compared with Weibull input distributions.