6-LOPA
Layer Of Protection Analysis (LOPA) quantifies the residual frequency of scenarios and checks the adequacy of independent protection layers (IPL), according to IEC 61511.
Toolbar
| Button / Control | Function |
|---|---|
| ⬆ Import PHA — Hazard study | Imports scenarios from the PHA — Hazard study as a LOPA starting point |
| ⬇ XLS | Exports to Excel |
| 👁 View / ✏ Edit | Read / edit mode |
| ＋ Add a scenario | Creates a new, empty LOPA scenario |
| ✦ AI | AI generation of LOPA scenarios with estimated IPLs |
Calculation principle
Current frequency = Initiating frequency × ∏ PFD(existing IPLs)
Target frequency = Current frequency × ∏ PFD(IPLs to add)If the target frequency remains above the acceptability criterion, additional IPLs are needed.
Structure of a LOPA scenario
Scenario header:
| Field | Description |
|---|---|
| Scenario | Description of the scenario (can be imported from the PHA — Hazard study) |
| Initiating event | Initial cause (e.g. Control valve failure) |
| Initiating frequency | Frequency of the initiating event without IPLs (events/year, scientific notation) |
| ERC | Central feared event |
| Consequence | Description of the effects |
| Severity | Severity level selected from the list |
Existing IPLs — barriers already in place:
| Field | Description |
|---|---|
| IPL label | Name of the barrier (e.g. SIS high-level emergency shutdown) |
| Type | SIS / Basic process control instrumentation / Passive barrier / Operator procedure / Relief valve… |
| PFD | Probability of Failure on Demand (e.g. 0.01 for SIL 2) |
The current residual frequency is displayed in real time under the existing IPL table.
IPLs to add — additional barriers required if the current frequency does not satisfy the criterion:
- ＋ IPL button — adds an IPL manually
- 📋 Library button — selects a standard IPL from the library (with a pre-filled PFD)
- ✦ AI button on the scenario — suggests IPLs suited to the scenario
The target residual frequency is calculated including these new IPLs.
LOPA Metrics tab
Configurable sub-tabs:
- 🎯 SIL targets — SIL thresholds according to IEC 61511, editable to fit the project (↺ Reset button)
- ⚠️ Severity — severity levels, with ＋ Add and ↺ Reset buttons
- 📊 Frequency — columns of the frequency matrix
- 🎨 Risk levels — ranges and colours
- 🟩 Risk matrix — click a cell to change its level
Quick link 🛡️ IPL types → to the Libraries/LOPA page to manage the IPL catalogue.
IPL list tab
Overall view of every IPL in the study, grouped by type. Useful for identifying barriers relied upon in several scenarios.