Definition:
Layer of Protection Analysis (LOPA) is a semi-quantitative method to evaluate risk reduction and assign Safety Integrity Levels (SIL). This has become more common over time. It is often done with the HAZOP in one large/long meeting and in a single tool.
Key Points:
- Focuses on initiating event frequencies and IPL performance.
- Commonly used for SIL determination.
- Often managed via a software package or an Excel spreadsheet.
- Not technically part of the H&RA, but could be done with the HAZOP.
Example:
A LOPA study determines that an independent high-pressure trip is required to achieve SIL 2 for a reactor system. Thus it is the LOPA that determines the SIF is needed to be SIL 2.
See also: HAZOP, H&RA, semi quantitative
Cited Source:
- CCPS Guidelines for LOPA.