Proceedings of the Eighth International Conference on Probabilistic Safety Assessment & Management (PSAM)
170 Reliability Analyses of a Self-Holding Type Relay System by a Dynamical Event Tree and the GO-FLOW Methodology (PSAM-0214)
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The authors have developed a system reliability analysis methodology GO-FLOW, which is a success oriented system reliability analysis method. A modeling technique produces a GO-FLOW chart, which represents system configuration, engineering function and system failure phenomena. The GO-FLOW can analyze dynamic systems, and it has been already applied to a hold-up tank problem. In the present paper, a self-holding type relay system is taken up as an example of a dynamic system, and analyses are performed by the GO-FLOW methodology and by a dynamical event tree which has been developed for the analysis of dynamical system behavior and presented at PSAM4.
Self-holding type relay systems are widely used for switching on/off of an engineering system and secures to prevent the unintentional restart of an engineering system after the recovery of electrical power source. If failure occurs for each component, the intended function will not be satisfied with a certain probability. The purpose of the present analysis is to quantify the time series of mission success probability.
It is shown that the dynamical event tree can treat a self-holding type relay system. But, for the modeling of this relay system, we have to make two event trees. The first one is for the actuation by the first switch and following event sequence, and the second one is for self-holding sequence by the second relay.
Analysis by the GO-FLOW is also performed. A self-holding type relay system is easily modeled into a GO-FLOW chart. The GO-FLOW automatically identifies all the possible combinations of component failures, that is, all the possible system states or all the possible sequences with component actions and failures.
Comparison of the analysis procedures shows us the advantages of the GO-FLOW. Modeling of the GO-FLOW is straightforward and well corresponds to the layout of the relay system.