The application of first and second orders of inherent safety in the chemical process industry

Abstract

The inherent safety (IS) concept has been introduced for more than 45 years, yet its adoption into process design is still very low. As a result, similar accidents keep on occurring worldwide since a majority of the risk reduction strategies used are based on the outer layers of protection such as active engineered and procedural. To enhance the uptake of inherent safety into chemical plant design, this paper aims to outline the common inherent safety strategies that have been used by the chemical process industry (CPI) to prevent accidents. 502 cases of inherently safer design (ISD) applications in the CPI have been collected and analysed. The process changes through plant modification are grouped based on the four main ISD strategies of minimisation, substitution, moderation, and simplification. The four main ISD keywords are then further classified into a hierarchy of inherent safety order. 58 cases (12 %) fall under first order IS which is from substitution keyword. For the 2nd order IS (magnitude), the keyword minimisation gives 242 cases (48 %) while moderation gives 151 (30 %). The simplification keyword which is under 2nd order IS (likelihood) gives 51 cases (10 %). The 2nd order IS (magnitude) seems to give the biggest numbers of design changes made by the CPI. Magnitude reduction strategy is the common choice by the CPI when designing safer equipment or process.