turck IM12-CD, Safety Manual, Page: 14 / 22

14
Safety Planning
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5.4.2 Average probability of dangerous failure on demand (Low Demand mode)
With the FMEDA results and the values specified in the following table the average frequency of
dangerous failure can be calculated exemplarily:
T1
8760 h
MTTR
24 h
IMX12-CD01-2R-2U - safety functions PFDavg
SIL2 – [E1]

[A1] or [E2]

[A2] 7.96E-05
SIL3 – [E1+E2]  [A1+A2]
7.97E-06
SIL3 – [E3]  [A1+A2]
7.97E-06
IMX12-CD01-2R-2U - safety functions PFDavg
SIL2 - [E1]  [A1]
7.96E-05
SIL3 - [E1]

[A1+A2] 8.64E-06