Risk Mitigation in Major Hazard Scenarios Through Process Safety Management and Barrier Analysis

Abstract

Process safety emphases on preventing fires, explosions and accidental chemical releases in chemical process facilities using hazardous materials such as refineries, steel industries and oil and gas installations. Many techniques can be used for process safety management. LOPA (Layers of Protection Analysis) or QRA (Quantified Risk Assessment) are some techniques used for improving process safety performance. DuPont’s safety management system provides a 14 element structure for managing process safety. Out of these elements, process hazard analysis forms the backbone for managing the risk associated with the processes. As hazard can never be eliminated, emphasis is laid on mitigating the risk associated with the hazard.
This work focusses on qualitative risk assessment which discusses about the process hazard review process by utilising the bowtie methodology. Bowtie analysis and barrier management technique is based on Swiss cheese model. Swiss cheese model is an approach which relates a hazard and the threats wherein number of barriers are kept between hazard and a top event. In this model, barriers that prevent, detect, control and mitigate a major accident are represented as slices, each having a number of holes. The holes represent imperfections in the barrier, which can be defined as specific performance standards. Hole size is proportional to the ineffectiveness of barrier management. Accident occurs when all the holes get matched. Bowtie analysis is a new tool used in the steel industries in India. Credible scenarios are analysed based on the past accident data and consequence modelling. For the selected scenarios, hazard and top event is defined for which bowtie is developed using the software BowTie XP.
Bowtie diagrams are essentially a combination of fault tree analysis and event tree analysis. These diagrams are attached in as figures in this work. Apart from these diagrams, barrier management sheet is also discussed with each barrier identified and categorised. Barriers can be active, passive, mixed or procedural. Critical equipments for managing process safety risks are also identified through this sheet which enables review of the same. Process safety critical tasks too are identified during the development of this sheet.