Pepperl+Fuchs HiC2871A, Manual, Page: 11 / 20

Functional Safety HiC2871A
Planning
20
17-
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3.4 Characteristic Safety Values
The characteristic safety values like PFD, PFH, SFF, HFT and T
1
are taken from
the FMEDA report. Observe that PFD and T
1
are related to each other.
The function of the devices has to be checked within the proof test interval (T
1
).
Parameters Characteristic values
Assessment type Full assessment
Device type A
Mode of operation Low demand mode, high demand mode or
continuous mode
HFT 0
SIL (SC) 3
Safety function The output is de-energized if the input is in low
condition

s
1
76 FIT

dd
0 FIT

du
0 FIT

total (safety function)
1
76 FIT

no part
197 FIT
SFF
1
1
"No effect failures" and "Annunciation failures" are not influencing the safety function and are therefore not
included in SFF and in the failure rates of the safety function.
100 %
MTBF
2
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 24 h.
262 years
PFH
3
3
As the

d
failure rate is 0 FIT, the PFD calculation yields a PFD of zero, independent from the proof test
interval.
0 1/h
PFD
avg
for T
1
= 1 year
3
0
Reaction time
4
4
Time between fault detection and fault reaction
< 1 s
Table 3.1
Note!
The characteristic values apply to all modes of operation that can be set on the
device.