LOPAanalyysien

LOPA stands for Layer of Protection Analysis. It is a semi-quantitative risk assessment technique used to evaluate the adequacy of existing safeguards, or to determine the required safeguards, to prevent or mitigate hazardous events. LOPA is often employed in industries where safety is critical, such as chemical processing, oil and gas, and nuclear power. The core concept of LOPA is that a hazardous scenario can be made acceptably safe if there are sufficient independent layers of protection that can prevent or mitigate the event.

The LOPA process typically begins with identifying a specific hazardous scenario. This scenario describes a sequence of events that could lead to a major accident. Once the scenario is defined, the likelihood of the initiating event occurring and the likelihood of the scenario proceeding to a consequence without intervention are estimated. This is where the "layers of protection" come into play. Each layer is considered an independent safeguard designed to prevent or mitigate the hazardous event. Examples of independent protection layers include basic process controls, alarms, operator actions, safety instrumented systems, and physical protection measures like dikes or relief valves.

For each layer, LOPA assesses its independence and its effectiveness. Independence means that one layer's failure does not cause another layer to fail. Effectiveness relates to the probability that the layer will perform its intended function when called upon. The analysis then determines the probability of the hazardous event occurring given the presence and effectiveness of the independent protection layers. If this residual risk is deemed too high according to the organization's risk tolerance, additional layers of protection may be required. LOPA provides a structured way to justify the presence and integrity of safety systems, ensuring that risks are managed to an acceptable level.