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Functional Safety HiC2871A
Planning
3.4
Characteristic Safety Values
Parameters
Assessment type
Device type
Mode of operation
HFT
SIL (SC)
Safety function
1
s
dd
du
1
total (safety function)
no part
1
SFF
2
MTBF
3
PFH
3
PFD
for T
= 1 year
avg
1
4
Reaction time
Table 3.1
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.
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 24 h.
3
As the
failure rate is 0 FIT, the PFD calculation yields a PFD of zero, independent from the proof test
d
interval.
4
Time between fault detection and fault reaction
Note!
The characteristic values apply to all modes of operation that can be set on the
device.
The characteristic safety values like PFD, PFH, SFF, HFT and T
the FMEDA report. Observe that PFD and T
The function of the devices has to be checked within the proof test interval (T
Characteristic values
Full assessment
A
Low demand mode, high demand mode or
continuous mode
0
3
The output is de-energized if the input is in low
condition
76 FIT
0 FIT
0 FIT
76 FIT
197 FIT
100 %
262 years
0 1/h
0
< 1 s
are related to each other.
1
are taken from
1
).
1
11
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