What is described as a ‘single point of failure’ in LOPA?

In Layer of Protection Analysis (LOPA), a ‘single point of failure’ refers specifically to the failure of a single Independent Protection Layer (IPL) that can directly result in a hazardous event occurring. This concept emphasizes the importance of each IPL, as it serves as a critical barrier against risks; if this barrier fails, the risk that was being mitigated potentially becomes realized.

For instance, if a safety interlock system fails, it can lead directly to an unsafe condition, illustrating the consequences of relying on one layer of protection without having sufficient redundancy or alternative layers in place. This highlights the need for robust risk management measures where the failure of any one IPL is well understood and accounted for within the overall safety system designed to protect against hazardous events.

The other options reflect scenarios that do not constitute a ‘single point of failure’ as clearly:

• The failure of multiple IPLs due to an external event suggests interconnected failures but does not isolate the specific concern regarding a single point of vulnerability.

• A general failure due to system overload applies to broader system failures rather than pinpointing an individual layer.

• The correct execution of safety measures indicates successful operation rather than a failure scenario.

Focusing on the IPL, option B provides clarity on the singular dependency