Definition:
An Independent Protection Layer (IPL) is a device, system, or action that can lower the risk (probability or severity) of a hazardous event independently from the initiating event. Technically a SIF is an IPL, but not every IPL is a SIF.
An IPL must have four things (classic test question!): independent, specific, dependable, and auditable.
Key Points:
- Must be independent, auditable, and dependable.
- Key building block in Layer of Protection Analysis (LOPA).
Example:
A PSV (pressure relief valve) relieving excess pressure is an IPL independent of the BPCS. It is an IPL as it is fully mechanical and does not rely on anything else.
Cited Source:
- CCPS Guidelines for Initiating Events and IPLs.