OFISI, a novel optimizable inherent safety index based on fuzzy logic

We develop a novel inherent safety index, OFISI (Optimizable Fuzzy Inherent Safety Index). The index, based on fuzzy logic, assesses the inherent safety of a piece of equipment or process, and ranks different alternatives. Another intention of this index is to provide a systematic methodology to optimize the safety level. The index is divided into three different sub-indices, accounting for different inherent safety design principles, and allows the designer to consider inherent safety at the same level as the other main objectives (economic and environmental) during the early design of a process. The sub-indices are based on logic relationships that can be easily modified. This allows the decision maker to consider various scenarios and assign different levels of importance to the diverse aspects of a plant. Once the index is presented, a case study highlights its usefulness, proving that the safety objective is at the same level as other criteria.