Multi-objective Offshore Safety System Design Optimization

The objective of this paper is to present a multi-objective approach to the design optimization process applied to systems that require a high likelihood of functioning on demand. In the real world it is common that there are several objectives to be met, not just maximising the system availability, and hence an approach is required to deal with these issues. A method is presented that integrates the latest advantages of the fault tree analysis technique and the binary decision diagram method to model the availability issue, along with a multi-objective optimization approach (the Improved Strength Pareto Evolutionary Approach) to cater for meeting the multiple criteria of assessment. The end product is a mechanism to yield the best design option. The paper presents the principles of the method and a case study to illustrate how the method is applied, along with the results produced. The case study relates to a high integrity protection system of an offshore platform. The optimization criteria involves unavailability, cost, spurious trip frequency and maintenance down time. Several enhancements to the optimization strategy to improve the efficiency of the approach are discussed.