Optimization of performance and costs in safety instrumented system design

Costs as well as safety performance are usually taken into account in safety instrumented system design. Modeling a SIS is time consuming and fallible and altering a SIS design may lead to recreating the model, so it´s difficult to compare one design with others effectively and quickly. Markov model and its automatic creation for SIS are described in this paper, followed by the analysis of SIS life cycle cost related to SIS design process. Then, optimization problem between safety performance and costs is established and how to solve it is discussed. By automatic Markov model creation and solving algorithm, average probability of failure on demand and costs can be calculated quickly and accurately, which enlightens a numerical way in achieving the optimal solution for the optimization problem. Optimization of performance and costs help not only getting an optimal design but also realizing the correct coupling relation between performance and costs.