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Functional Safety HiC2883
Planning
3.4
Characteristic Safety Values
Parameters acc. to IEC 61508
Assessment type
Device type
Mode of operation
HFT
SIL (SC)
Safety function
s
dd
du
total (safety function)
1
SFF
PTC
2
MTBF
PFH
PFD
for T
= 1 year
avg
1
PFD
for T
= 2 years
avg
1
PFD
for T
= 5 years
avg
1
PFD
for T
= 10 years
avg
1
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.
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
12
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
130 FIT
0 FIT
0.02 FIT
130 FIT
99.9 %
100 %
129 years
-11
2.00 x 10
1/h
-8
8.76 x 10
-7
1.75 x 10
-7
4.38 x 10
-7
8.76 x 10
< 1 s
are taken from
1
are related to each other.
1
).
1
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