Generic rules to evaluate system-failure frequency

Frequency of failure of a system with s-independent components can be obtained from the system availability (unavailability) expression and failure and repair rates of the components. Although, Grouped Variable Inversion is an efficient technique to find the system availability, there is no convenient method to convert the “availability expression obtained by this technique” into an “expression for system-failure frequency.” This paper present generic rules to find system-failure frequency, particularly, when the availability or unavailability expression of a system is obtained using this technique. The rules are straightforward, and produce appreciably shorter expressions for system-failure frequency. Examples illustrate the simplicity and efficiency of the proposed rules