What is the primary purpose of Layers of Protection Analysis (LOPA) in process safety?

The primary purpose of Layers of Protection Analysis (LOPA) in process safety is to evaluate the adequacy of independent protection layers (IPLs) in mitigating the risks associated with hazardous events, and to determine the required Safety Integrity Level (SIL) for Safety Instrumented Functions (SIFs). LOPA is a semi-quantitative risk assessment technique that simplifies the risk analysis process by focusing on the independent protection layers that are in place to prevent or mitigate hazardous events. Independent protection layers are safeguards that can prevent a hazardous event from occurring or can mitigate the consequences of the event, and they must be independent of each other, meaning that the failure of one layer does not affect the performance of the other layers. The goal of LOPA is to determine whether the existing IPLs are sufficient to reduce the risk to an acceptable level. If the risk is not acceptable, LOPA is used to identify the need for additional IPLs or improvements to existing IPLs. A key outcome of LOPA is determining the Safety Integrity Level (SIL) required for Safety Instrumented Functions (SIFs). SIFs are specific safety functions that are implemented using Safety Instrumented Systems (SIS) to prevent or mitigate hazardous events. LOPA helps determine the required SIL by quantifying the risk reduction needed from the SIF, taking into account the frequency of the initiating event, the severity of the consequences, and the effectiveness of the other IPLs. For example, if a LOPA study determines that a high-pressure scenario poses an unacceptable risk despite existing relief valves and operator interventions, it may recommend a Safety Instrumented System with a specific SIL rating to automatically shut down the process and prevent a rupture.