CyberCertPrepOT Security FundamentalsOT Fundamentals: Safety Systems & Physical SecurityMEDIUMFree question
A low demand safety function is verified at an average PFD of 0.004. Which SIL band does IEC 61508 place it in?
- A.SIL 3 with a PFDavg band of 0.0001 to 0.001
- B.SIL 1 with a PFDavg band of 0.01 to 0.1
- C.SIL 4 with a PFDavg band of 0.00001 to 0.0001
- D.SIL 2 with a PFDavg band of 0.001 to 0.01
Why D is correct
For low demand mode SIL 2 spans PFDavg from 0.001 up to 0.01. A value of 0.004 lies inside that range. SIL 3 needs a PFD below 0.001 and SIL 1 allows values from 0.01 to 0.1.
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