Functional Safety HiD282*, HiD284*
Planning
20
21
-1
0
13
3.4
Characteristic Safety Values
HiD2822, HiD2824
Parameters
Characteristic values
Assessment type and
documentation
Full assessment
Device type
A
Mode of operation
Low demand mode or high demand mode
HFT
0
SIL
2
SC
3
Safety function
Output is de-energized.
1 output repeats the input signal.
2 outputs repeat the input signal
(HiD2822 only).
s
93 FIT
127 FIT
dd
19.5 FIT
16.5 FIT
du
43.4 FIT
18.9 FIT
total (safety function)
1
1
"No effect failures" are not influencing the safety function and are therefore not included in SFF and in the failure rates of the safety
function.
156 FIT
162 FIT
no part
34 FIT
34 FIT
SFF
1
72.2 %
88.4 %
MTBF
2
2
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 24 h. The value is calculated for one
safety function of the device.
310 years
237 years
PFH
4.34 x 10
-8
1/h
1.89 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
3
3
Since the current PTC value is < 100 % and therefore the probability of failure will increase, calculate the PFD value according to the
following formula:
PFD
avg
= (
du
/ 2) x (PTC x T
1
+ (1
–
PTC) x T
service
)
A service time T
service
of 20 years was assumed for the calculation of PFD
avg
.
2.26 x 10
-4
9.86 x 10
-5
PFD
avg
for T
1
= 2 years
3
4.15 x 10
-4
1.81 x 10
-4
PFD
avg
for T
1
= 5 years
3
9.79 x 10
-4
4.27 x 10
-4
PTC
99 %
Reaction time
4
4
Time between fault detection and fault reaction
< 20 ms
Table 3.2
