IMPORTANCE computer code. [For computing various measures of probabilistic importance of basic events and cut sets to a fault tree]
Howard E. Lambert, F.M. Gilman · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 1977
The IMPORTANCE computer code computes various measures of probabilistic importance of basic events and cut sets to a fault tree. The availability of such a code contributes to making fault tree analysis a design tool. The code requires as input the minimal cut sets, the failure rates, and the fault duration times (i.e., the repair times) of all basic events contained in the min cut sets. The failure and repair distributions are assumed to be exponential. The code can compute seven measures of basic event importance and two measures of cut set importance. All measures are computed under the assumption of the statistical independence of basic events. For systems where repair is not allowed, the code accepts proportional hazards as input data. In another option, where repair is permitted, failure rate data can also be expressed in relative terms by representing the failure rate and repair rate data for the basic events in terms of a reference time unit. The use of the code is illustrated by examples. In addition, a survey of some of the existing fault-tree computer codes is presented. 38 figures, 3 tables.