Functional Safety M-LB-(Ex-)2000-System
Planning
201
9-02
13
3.4
Characteristic Safety Values
1oo1 Structure
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
Full assessment
Device type
A
Mode of operation
Low demand mode or high demand mode
Safety function
1
1
The safe state of the surge protection barrier depend on the application.
Pass through the signal
HFT
0
SIL
2
2
The maximum safety integrity level of the safety loop in which the device might be used depends on the performance values
of the whole safety loop or the elements of the safety loop. See chapter 7.
3
Devices
AI, AO, BI, BO, RTD
TC
s
17.2 FIT
0 FIT
du
1.1 FIT
18.2 FIT
dd
0 FIT
0 FIT
total (safety function)
18.3 FIT
18.2 FIT
no part
0.3 FIT
0.3 FIT
MTBF
3
3
acc. to SN 29500. This value includes failures which are not part of the safety function/MTTR = 8 h.
The value is calculated for one safety function of the device.
3163 years
3171 years
PFH
1.05 x 10
-9
1/h
1.82 x 10
-8
1/h
PFD
avg
for T
1
= 1 year
4.60 x 10
-6
7.97 x 10
-5
PFD
avg
for T
1
= 2 years
9.20 x 10
-6
1.59 x 10
-4
PFD
avg
for T
1
= 3 years
1.38 x 10
-5
2.39 x 10
-4
PTC
100 %
100 %
Reaction time
4
4
Since the disturbance cannot be distinguished from the signal under EMC conditions according to EN/IEC 61326-3-1,
the reaction time increases to 100 ms.
< 1 ms
Table 3.2
