20
16-
06
12
Functional Safety HiD2035, HiD2036
Planning
3.4
Characteristic Safety Values
HiD2035, HiD2036, 1oo1 Structure
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 acc. to IEC 61508
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
Safety function
Current transfer from the field side to the control
side
sd
+
su
1
1
"Not considered" failures are considered 50 % as dangerous undetected and 50 % as "No effect". "No effect"
failures are not influencing the safety functions and are therefore not included in the calculation of the SFF.
0 FIT
dd
124 FIT
du
1
71 FIT
total (safety function)
194 FIT
not part
0 FIT
SFF
63 %
PTC
100 %
MTBF
2
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h. This value
is calculated for one safety function of a device.
298 years
PFH
7.06 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
3.09 x 10
-4
PFD
avg
for T
1
= 2 years
6.18 x 10
-4
PFD
avg
for T
1
= 5 years
1.54 x 10
-3
Reaction time
< 100 ms
Table 3.1
