(82b) An Enhanced Process Inherent Safety Assessment Methodology

How to assess the inherent safety of a process is a critical step in process design. Aiming towards sustainability, the designers analyze various alternatives and select the one that can achieve maximal economic benefits with least safety and environmental impact. In 1999, Anna-Mari Heikkila developed an Inherent safety index to evaluate the safety level of a process. However, this methodology doesn't consider the number of equipments and the quantity of chemicals present in the process and only the worst case scenarios are considered for calculation. To overcome these limitations, the authors proposed an enhanced process inherent safety assessment methodology. In this new methodology, the potential hazard presented by all the equipments and chemicals in the process plant are taken into consideration. The number of equipments under different operating conditions and the quantity of chemicals are used in the calculation. Severity scores are given in two sub-categories: Total Chemical Inherent Safety Index and Total Process Inherent Safety Index. Addition of these two scores gives the Total Inherent Safety Score for the process. A lower score indicates an inherently safer process. The proposed methodology can be used at early stages of design to assess the alternatives and identify the inherently safest path. The efficacy of this methodology is demonstrated by a case study on different biodiesel production processes.