Evaluating hazard conflicts using inherently safer design concept

The application of Inherent Safety (IS) principles and Inherently Safer Design (ISD) concept has been proven to reduce the risk of accidents and economically attractive for process plants. However, there are always trade-offs and conflicts that arise from the suggested modifications. An inherently safer design from one perspective could possibly alter the hazards in other dimensions. Therefore, this limitation should be resolved before obtaining the best ISD alternatives. This paper presents a methodology for producing and evaluating Inherently Safer Design (ISD) alternatives using a risk-based approach at preliminary design stage. The proposed methodology is applied to nitration of toluene with the objective of preventing and minimizing runaway reaction. The results have shown that the new tool can capture the risk transferred due to the change of design proposed by the inherent safety principles at preliminary design stage in the form of new hazards and change of magnitude of existing hazards.