Novel Methodology for Inherent Safety Assessment in the Process Design Stage

Various physical and chemical hazards are intrinsic to the material itself or its manner of storage and use. Inherently safer design of the chemical process and equipment has been increasingly used by the design engineers to minimize or eliminate these hazards. This approach aims to mitigate hazards by design instead of add-on measures. This presentation describes a new design approach, introducing comprehensive inherent safety index (CISI), for use in the early stages of process development. Chemical, process and connectivity scores are calculated for individual units in the process, based on which the CISI assigns safety scores for the equipment. Each chemical in the unit has a weighted severity score. Reactivity score is calculated for mixture of chemicals in that unit. Connectivity score in introduced because the units can be highly interconnected, leading to compounding of hazards. Biodiesel and methyl methacrylate processes were studied to demonstrate the new safety assessment methodology. The results of the assessment are used to clearly identify key areas for improvement in a root-cause analysis.