Method for solving logical loops in system reliability analysis

The procedure for solving Boolean equations with unknown element(s) is presented. Discussions are made for operation of typical engineering systems with loop structure. It is revealed that components are necessary to be classified into three types. Time-dependent expression of a component's state is given and operating states of loop structures are identified by Boolean algebraic procedure. The procedure proposed in this paper is applicable to the condition that components can start at any time in system operational sequence, and each component has multiple chances to be started. A sample system was analyzed and the result was confirmed by a step by step analysis. The procedure shown in this paper is very useful in evaluating engineering systems which have logical loop structure(s), and also useful in effectively designing high reliable systems. Keyword: system reliability; availability analysis; loop structure; boolean equation