SIL Risk Assessment & Hazard Analysis 3

Question 1

Which method is most appropriate for identifying common-cause failures in redundant safety systems?

Accepted Answer

Beta-factor model analysis

Answer

The beta-factor model quantifies common-cause failure probability in redundant architectures by estimating the fraction of failures that affect multiple channels simultaneously.

Question 2

When applying LOPA, the Initiating Event Likelihood (IEL) represents:

Accepted Answer

The frequency per year at which the initiating cause occurs without any protection

Answer

IEL is the unmitigated frequency of the initiating event per year, before credit is taken for any independent protection layers.

Question 3

A 'Tolerable Risk' criterion of 1×10⁻⁵ per year for a fatal event means:

Accepted Answer

The probability of a specific individual being fatally harmed does not exceed one in 100,000 per year

Answer

A tolerable individual risk of 1×10⁻⁵/yr means no more than a 1-in-100,000 annual probability of a fatal outcome for any specific exposed individual.

Question 4

In FMEA, 'criticality' combines which two factors?

Accepted Answer

Severity of failure effect and probability of occurrence

Answer

Criticality in FMEA is determined by the combination of the severity of the failure effect and the probability (rate) of the failure occurring.

Question 5

Which hazard analysis technique maps causes and consequences on either side of a central event using bow-tie diagrams?

Accepted Answer

Bow-tie analysis combining FTA and ETA

Answer

Bow-tie analysis integrates FTA on the threat/cause side with ETA on the consequence side, centered on the top event, providing a complete risk picture.

(SIL) Safety Integrity Level Certified Practice Test

(SIL) Safety Integrity Level Certified Practice Test

SIL Risk Assessment & Hazard Analysis 3