Process Safety
LOPA
LOPA (Layer of Protection Analysis) is a semi-quantitative methodology used to assess the adequacy of safeguards, ( i.e. have you done enough to address the hazard?).
LOPA is particularly useful for analysis of scenarios of concern identified in the HAZOP.
SIL (Safety Integrity Level) is the degree of confidence in a given safeguard. This applies only to Safety Instrumented Functions (SIFs) and a SIL allocation for SIFs is a requirement of EN 61511.
Per EN 61511, a SIL assessment should be carried out for all Safety Instrumented Functions, i.e. instrumented loops called up as safeguards or as recommendations in the HAZOP or similar exercise.
LOPA is just one way of carrying out a SIL assessment.
