Workflow

This workflow describes the process of performing a Layer of Protection Analysis (LOPA) by defining the initiating event, frequency of event, consequence, enabling events, safeguards, and conditional modifiers.

In the following workflow diagram, the blue text in a shape indicates that a corresponding description has been provided in the sections that follow the diagram. For more information, refer to the topic Interpreting the Workflow Diagrams.

Persona: Analyst

Create a LOPA by defining the consequence, initiating event, initiating event frequency, and required mitigated consequence frequency. To define these values, you can refer to the plant history, trip event reports, or the expected frequency provided by the manufacturer. When you create a LOPA, you can also define the Risk Severity and Risk Category of the consequence. When you use the LOPA for SIL Assessment in a SIL Analysis, the severity and category of the risk defined in the LOPA is used to map the unmitigated risk of the scenario on a Risk Matrix.

Persona: Analyst

For each enabling event, provide the details of the event and the probability of its occurrence. This value should be based on industry-accepted failure data for each device or system.

Persona: Analyst

Determine if there are factors that can decrease the probability of the event. For example, if the event is releasing flammable gas into an explosive atmosphere, then the presence of an operator for only 12 hours a day can decrease the risk of injury.

Persona: Analyst

For each conditional modifier, create a Conditional Modifier record to define the probability.

Persona: Analyst

Determine the Independent Protection Layers (IPLs) that have been set up to prevent a hazardous event from occurring or to reduce the severity of the event. These protective layers must meet the independence, specificity, dependability, and auditability requirements specified in IEC 61511. Link the IPL to an Equipment and a Functional Location that correspond to the asset that acts as an independent protection layer.

Persona: Analyst

Review the Safety Integrity Level (SIL), Probability of Failure on Demand (PFD), and Risk Reduction Factor (RRF) values based on the guidelines specified in IEC 61511.

Persona: Analyst

Go to the SIL Assessment workflow.

Persona: Analyst

Go to the HAZOP Analysis workflow.

Persona: Analyst

Go to the What-If Analysis workflow.