CyberCertPrepOT Security FundamentalsOT Fundamentals: Safety Systems & Physical SecurityHARDFree question
A LOPA shows an initiating event at 0.1 per year with a BPCS control loop credit of 0.1. The tolerable mitigated frequency is 5e-5 per year. What must the added SIF achieve?
- A.A PFD of 0.5 or lower needing no SIL rating
- B.A PFD of 0.005 or lower placing it in SIL 2
- C.A PFD of 0.05 or lower placing it in SIL 1
- D.A PFD of 0.0005 or lower placing it in SIL 3
Why B is correct
Required PFD = tolerable frequency divided by initiating frequency times other credits = 5e-5 / (0.1 x 0.1) = 0.005, a risk reduction of 200, which falls in SIL 2. The other values mis-place the decimal or ignore the BPCS credit.
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