Abstract:  

The complexity of systems in the current process industry is conducive to the concerns of industrialists about the risks that may be inherent in these systems. Risk reduction measures should be considered and implemented to reduce the initial risk to an acceptable level. This is usually achieved by using a combination of systems that provide security, inter alia, Safety Instrumented Systems (SIS). The implementation of a SIS requires the determination of its Safety Integrity Level (SIL) which it must have in order to attain the tolerable risk. The standards IEC 61508 and 61511 provide a framework for the determination of SIL and propose different methods.

               The objective of this work consists in proposing an approach of allocation and optimization of the security barriers, using the methods of risk graph and LOPA (Layer Of Protection Analysis) In order to evaluate the performance of the safety measures put in place for the control of risks in a hydrocarbon storage station. A cost benefit analysis (CBA), as a decision support tool, is carried out to improve the safety level of the process studied.

Keywords: Safety Instrumented System, safety integrity level, SIL Allocation, Risk Graph, LOPA, CBA.