2
018-
06
12
Functional Safety KFD0-CS-(Ex)*.54*, KFD0-CS-(Ex)*.56*
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
FMEDA report
Device type
A
Mode of operation
Low Demand Mode or High Demand Mode
HFT
0
SIL (SC)
2
1
Safety function
Safety-relevant communication
Analog current signal transfer
s
60 FIT
0 FIT
dd
0 FIT
34.0 FIT
du
5.7 FIT
34.2 FIT
total (safety function)
132 FIT
68 FIT
no effect
66 FIT
58 FIT
not part
16.0 FIT
22.2 FIT
SFF
95.6 %
49 %
PTC
100 %
100 %
MTBF
1
1
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h. The value is calculated for
one safety function of the device.
770 years
770 years
PFH
5.74 x 10
-9
1/h
3.40 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
2.50 x 10
-5
1.49 x 10
-4
PFD
avg
for T
1
= 2 years
5.02 x 10
-5
2.98 x 10
-4
PFD
avg
for T
1
= 5 years
1.26 x 10
-4
7.49 x 10
-4
Reaction time
2
2
Time between fault detection and fault reaction
• 50
s for .54 versions
• 250
s for .56 versions
Table 3.1
