Pepperl+Fuchs KFD2-VR4-Ex1.26 - Characteristic Safety Values

Functional Safety KFD2-VR4-Ex1.26
Planning
2018-03
11
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 FMEDA report
Device type A (only hardware)
Mode of protection Low demand mode or high demand mode
HFT 0
SIL (hardware) 2

sd
+ 
su
1
1
Failures in components that are part of the safety function but do not influence the safety function are regarded as safe undetected.
338 FIT

dd
0 FIT

du
103 FIT

total (safety function)
477 FIT

not part
35.1 FIT
SFF 76 %
PTC 100 %
MTBF
2
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h.
239 years
PFH 1.03 x 10
-7
1/h
PFD
avg
for T
1
= 1 year 4.52 x 10
-4
PFD
avg
for T
1
= 3 years 9.03 x 10
-3
PFD
avg
for T
1
= 5 years 2.26 x 10
-3
Reaction time
3
3
The time that is needed to transfer a signal from the input of the device to the output according to the safety function.
12.5 µs
Table 3.1