2
02
1-
12
14
Functional Safety HiC283*
Planning
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 and
documentation
Full assessment
Device type
A
Mode of operation
Low demand mode, high demand mode or continuous mode
HFT
0
SIL
2
SC
3
MTBF
1
(HiC2831*)
1
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 24 h.
154 years
MTBF
1
(HiC2832*)
120 years
PTC
99 %
Safety function
Inverse mode of operation
2
2
The device can be used in two modes of operation, inverse of mode operation and normal mode of operation.
Normal mode of operation
2
safe
106 FIT
106 FIT
dd
3.3 FIT
3.3 FIT
du
26.8 FIT
22.8 FIT
total (safety function)
136 FIT
132 FIT
SFF
3
3
"Annunciation failures" and "No effect failures" are not influencing the safety function and are therefor not included in the calculation
of the SFF.
80 %
82 %
PFH
2.68 x 10
-8
1/h
2.28 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
1.28 x 10
-4
1.09 x 10
-4
PFD
avg
for T
1
= 2 years
2.56 x 10
-4
2.18 x 10
-4
PFD
avg
for T
1
= 5 years
6.40 x 10
-4
5.44 x 10
-4
Fault reaction time
4
4
The combined fault detection and fault reaction time is the time in which the device reacts to an occurred fault.
< 100 ms
Table 3.3
