Health, Safety and Environment (HSE) is the important aspect in the chemical process industries in order to ensure smooth operation without interruption. Companies have made an effort to reduce the risk due to the major loss in chemical process industries which related to human life, assets, company reputation, etc. through process risk management. In the current practice, risk reduction strategies can be divided into four categories i) inherent ii) passive iii) active iv) procedural. These strategies are the part of a conventional safety layer of protection (LOPA) where multiple devices, systems or actions are provided to reduce the likelihood of an undesirable event. However, these approaches did not eliminate the hazards, the hazard remains in the system and combination of failures may lead to an accident .
The lack of the above techniques to proactively reduce or eliminate the source of risk bring a new approach in safety analysis known as inherently safer design (ISD). This concept has been introduce by Trevor Kletz nearly thirty years ago as a proactive approach for hazard management by eliminate the root causes of the hazards and reduce the reliance on ‘add-on’ engineered safety system. The principle of ISD can be divided into four main categories; i) intensification ii) substitution iii) attenuation iv) limitation of effects/simplification. Detailed explanation related to the strategies given in Table 1. Previous major industrial accident such as Flixborough in 1974 and Bhopal accident in 1984 show the importance of inherently safer design. In Bhopal case, improper functions of active risk reduction strategies lead to a major disaster. In both cases, the impact of this accident can be reduce through inherently safer design practice if less hazardous materials was stored on-site.
Table 1: Inherent safety principles (adapted from )
Inherent safety principle Definition
Intensification Reduction in quantity of hazardous materials
Substitution Use of safer materials
Attenuation Operation at comparably safer operating conditions such as room temperature and pressure and liquid phase
Limitation of effects Changing the design and operation for less severe effects
Simplification Avoidance of complexities such as multi-product or multi-unit operations, or congested pipe or unit settings
The main objective of ISD concept is to avoid or eliminate inherent hazards from the source, rather than accepting their existence and designing control systems to manage them. It was believed by implementing this concept, the technical and management cost can be reduce for a lifetime of the process . Although consideration for ISD can be done at every stage of process design, this strategy is highly effective when it can be considered during the early stages of process development and it can offer a great potential cost reduction. As can be seen in Figure 1, conceptual design take only 2% of the total project cost and it can contributes...