A Heuristic Algorithm for System Failure Frequency

For reliability analysis, the choice between tie-sets and cut-sets is not a matter of convenience but depends on assessment of computational effort. The system configuration alone determines the preference of the approach. The present paper offers a faster algorithm for evaluating system failure frequency using both approaches. An expression for system failure frequency between two specified nodes is derived using either tie-sets or cut-sets. The expression is in terms of failure frequency, availability, and unavailability of the system elements. A heuristic algorithm to obtain the expression can be programmed for a computer. The algorithm is illustrated through an example. The manner in which Abraham's algorithm can be used to determine system probability of failure using cut-sets is suggested. The algorithms are also useful for evaluating sensitivity coefficients.