LAYER OF PROTECTION ANALYSIS (LOPA)

LOPA provides a method for evaluating the risk of hazard scenarios and comparing it with risk tolerance criteria to decide if existing safeguards are adequate, and whether additional safeguards are needed. It is a method for evaluating the effectiveness of independent protection layers in reducing the frequency and/or consequence severity of hazardous events. LOPA is used to determine:

A) Safety Integrity Level (SIL) required for a Safety Instrumented Function

B)·Need for further risk reduction by adding further layers of protection to reduce the risk to meet risk acceptance criteria.

Sigma-HSE uses a PHA study report for identification of Hazardous Event, causes of the hazardous event or the Initiating Events and consequences of the hazardous event. During LOPA study, our team then assesses.

a) Frequency of all initiating events and probability of enabling conditions.

b) Probability of failure on demand (PFD) for all conditional modifiers and of independent protection layers (IPL) providing risk reduction for each initiating event.

c) Calculate the mitigated event frequency and compare this to the acceptance frequency to determine if further risk reduction is required.

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