Pepperl+Fuchs KFD2-SH-Ex1 - Page 14

2017-04
14
Functional Safety KFD2-SH-Ex1(.T)(.OP), KHA6-SH-Ex1
Planning
KFD2-SH-Ex1
Parameters acc. to IEC 61508 Characteristic values
Assessment type and
documentation
FMEDA, proven-in-use assessment, certificate
Device type A
Mode of operation Low Demand Mode or High Demand Mode
HFT 0
1
1
The redundant relays can be considered as elements with hardware fault tolerance. For this calculation the
redundant relays were considered as "diagnostics" for the relay with a DC value of 99 % to take care of a
possible common cause failure.
0
SIL 3 (proven-in-use) 2 (proven-in-use)
Safety function Output I is de-energized when
input in low state
Output II is de-energized when
input in low state

s
237 FIT 203 FIT

du
0.6 FIT 51.9 FIT

dd
50.5 FIT 36.6 FIT

no effect
2
2
"Annunciation failures" are not directly influencing the safety functions and are therefore added to the 

no effect
value.
215 FIT 156 FIT

total (safety function)
288 FIT 291 FIT
SFF 99.8 % 82 %
MTBF
3
3
acc. to SN29500. This value is calculated with the failure rates of the device components which are part of the
safety function of the device.
204 years 254 years
MTTF
d
2240 years –
DC
d
98.7 % (medium) –
B10
d
250000 –
Category (ISO 13849-1) 3 –
PL d –
PFH 6.47 x 10
-10
1/h 5.19 x 10
-8
1/h
PFD
avg
for T
1
= 1 year 2.83 x 10
-6
2.27 x 10
-4
PFD
avg
for T
1
= 2 years 5.67 x 10
-6
4.55 x 10
-4
PFD
avg
for T
1
= 5 years 1.42 x 10
-5
1.14 x 10
-3
Reaction time
4
4
Time between fault detection and fault reaction.
< 30 ms < 30 ms
Table 3.2