Optimal safety system performance

This paper investigates the efficiency of a design optimization scheme which is appropriate for systems which require a high likelihood of functioning on demand. Traditional approaches to the design of safety critical systems follows the preliminary design, analysis, appraisal and redesign stages until what is regarded as an acceptable design is achieved. For safety systems whose failure could result in loss of life it is imperative that the best use of the available resources is made and a system which is optimal not just adequate is produced. The methodology presented in the paper retains the commonly used fault tree method to analyse the individual system designs. By the use of house events a single fault tree is constructed to represent the failure causes of each potential design to overcome the time consuming task of constructing a fault tree for each design investigated during the optimization procedure. The final design specification is acheved using a genetic algorithm to perform the optimization with the constraints incorporated by penalising the fitness of infeasible designs. To demonstrate the practicality of the method developed it has been applied to a High Integrity Protection System (HIPS).