ISA CAP Risk Management & Mitigation 2

Question 1

In a Safety Instrumented System (SIS), what does the term 'spurious trip rate' measure?

Accepted Answer

The rate of false shutdowns not caused by actual process hazards

Answer

Spurious trip rate measures how often a SIS trips (shuts down) when no actual hazard exists, causing unnecessary downtime.

Question 2

Which IEC 61511 concept refers to the fraction of time a safety function is unavailable due to failure?

Accepted Answer

Probability of Failure on Demand Average (PFDavg)

Answer

PFDavg quantifies the average probability that a safety function will fail to operate when a demand occurs over a defined interval.

Question 3

A HAZOP study uses guide words to identify deviations. Which guide word specifically addresses the situation where a process variable is absent?

Accepted Answer

No/None

Answer

The guide word 'No/None' identifies the complete absence of the intended condition, such as no flow or no temperature.

Question 4

In risk matrix methodology, what happens to the residual risk after applying safeguards?

Accepted Answer

It is reduced but must still be compared to the tolerable risk criterion

Answer

After applying safeguards, residual risk is reduced but must be evaluated against the organization's tolerable risk criterion to determine if further action is needed.

Question 5

What is the primary purpose of a 'proof test' in a safety instrumented system?

Accepted Answer

To detect latent dangerous failures that do not reveal themselves during normal operation

Answer

Proof tests are performed to reveal dangerous undetected (latent) failures that cannot be identified through self-diagnostics during normal operation.

(ISA CAP) ISA Certified Automation Professional Practice Test

(ISA CAP) ISA Certified Automation Professional Practice Test

ISA CAP Risk Management & Mitigation 2