Risk Assessment & Hazard Analysis Flashcards
7 cards from real SIL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Risk Assessment & Hazard Analysis flashcards as text
Which method is most appropriate for identifying common-cause failures in redundant safety systems?
Answer: Beta-factor model analysis
The beta-factor model quantifies common-cause failure probability in redundant architectures by estimating the fraction of failures that affect multiple channels simultaneously.
When applying LOPA, the Initiating Event Likelihood (IEL) represents:
Answer: The frequency per year at which the initiating cause occurs without any protection
IEL is the unmitigated frequency of the initiating event per year, before credit is taken for any independent protection layers.
A 'Tolerable Risk' criterion of 1×10⁻⁵ per year for a fatal event means:
Answer: The probability of a specific individual being fatally harmed does not exceed one in 100,000 per year
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.
In FMEA, 'criticality' combines which two factors?
Answer: Severity of failure effect and probability of occurrence
Criticality in FMEA is determined by the combination of the severity of the failure effect and the probability (rate) of the failure occurring.
Which hazard analysis technique maps causes and consequences on either side of a central event using bow-tie diagrams?
Answer: Bow-tie analysis combining FTA and ETA
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.
What is the significance of the 'Safe Failure Fraction (SFF)' in IEC 61508?
Answer: It influences the hardware safety integrity level that can be claimed for a given architecture
SFF, combined with hardware fault tolerance, determines the maximum SIL that can be claimed for a subsystem according to IEC 61508 Route 1H architectural constraints.
During a What-If analysis, the review team asks 'What if the cooling water supply fails?' This is an example of:
Answer: A structured brainstorming question to identify hazard scenarios
What-If analysis uses structured open-ended questions to systematically explore potential failure scenarios and their consequences.