Applying LOPA and fuzzy logic to identify SIL requirement for safety critical functions in a direct reduction iron industry

Abstract LOPA 1 (Layer of Protection Analysis), is a semi-quantitative hazard analysis technique that can be used after a Qualitative Hazard Analysis Techniques such as HAZOP (Hazard and Operability Analysis) technique, and before a QRA (Quantitative Risk Analysis). LOPA can be used to identify the rate of the SIL (Safety Integrity Level), which specifies the level of safety protection and consequently identifies if the safety system is reliable or requires extra protection layers. LOPA has been used in many industrial processes such as LNG (Liquefied Natural Gas), petroleum and petrochemical industries. This study aims at performing the HAZOP technique on a specific node of a DRI (Direct Reduction Iron) industry, followed by LOPA to have quantified results and to determine whether the available independent protection layers (IPLs) in the system are sufficient. Moreover, it identifies the outcome required by the SIL target. Finally, fuzzy logic method for risk assessment is used as an efficient way to estimate the severity and determine the SIL rate to be compared with the one obtained by LOPA study.