2
02
1-
07
12
Functional Safety KFD0-CS-(Ex)*.50(P), KFD0-CS-(Ex)*.51(P)
Planning
3.4
Characteristic Safety Values
The characteristic safety values like PFD, SFF, HFT and T
1
are taken from the
SIL report/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 and documentation
Full assessment
Device type
A
Mode of operation
Low Demand Mode or High Demand Mode
HFT
0
SIL
2
SC
3
Safety function
Current driver
Repeater
s
1
1
No effect failures" are not influencing the safety function and are therefore not included in SFF and in the failure rates
of the safety function.
57 FIT
0 FIT
dd
0 FIT
62 FIT
du
24.9 FIT
22.8 FIT
total (safety function)
1
82 FIT
85 FIT
not part
120 FIT
95 FIT
SFF
1
69 %
73 %
PTC
100 %
100 %
MTBF
2
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h.
438 years
438 years
PFH
2.49 x 10
-8
1/h
2.28 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
1.09 x 10
-4
1.00 x 10
-4
PFD
avg
for T
1
= 2 years
2.18 x 10
-4
2.00 x 10
-4
PFD
avg
for T
1
= 5 years
5.44 x 10
-4
5.00 x 10
-4
Reaction time
3
3
Time between fault detection and fault reaction
< 20 ms
Table 3.1
