Amir Farzad Farokhzad - Nargam, Engineers & Constructors, Tehran, Iran
Ramin Bozorgmehry - Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran
Mahmoud Reza Pishvaie - Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran

The term ‘inherently safer’ implies that the process is safe by its very nature and not externally constrained to be safe by the use of add-on systems and devices, hence making it a proactive approach to process safety. It is very effective if applied at the beginning stages of design, leading to cost effective and timely solutions and modifications. In this paper, after elements of risk and its management strategies are briefly discussed, Inherently Safer Design (ISD) - as well as its quantification by indices developed specifically for ISD - is elaborated, in order to rank alternative processes based on their inherent safety adaptability. Considering the advantages and the shortcomings of ISD quantification indices in the literature, a new modified ISD index is proposed, covering ISD aspects of a process at both route selection and flowsheeting stage, which leads to better ranking in comparison with its predecessor.