Optimum Design of Safety Systems

Abstract

This report treats the following three major problems concerning the optimum design of safety systems and their applications to the design of Direct Digital Control systems of a boiler where a high reliability must be assured. These three problems are how to calculate the reliability of systems easily, how to evaluate system elements from the viewpoint of reliability and what to be the most efficient way to improve the reliability of systems. The approaches to these problems are made using the network techniques as follows:
(1) The computer code of reliability calculation is developed by using the network techniques.
(2) The sensitivity and the effective sensitivity of the network relating to network elements are defined. The usefulness of the concept of sensitivity in the design of safety systems is discussed. Moreover, some useful formula to calculate the sensitivities are given.
(3) An optimum cost allocation problem is solved by Dynamic Programming when the systems' network and the total cost are given. The special feature of this method is the simplification of calculation by the introduction of the idea of sensitivity. As an example, the safety system of a once-through boiler operated by a DDC is designed and discussed.