Functional Safety KCD2-STC-(Ex)1(.SP)(-Y1), HiC2025(Y1)
Planning
201
8-08
13
3.4
Characteristic Safety Values
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
Characteristic values
Assessment type
Full assessment
Device type
A
Mode of operation
Low demand mode or high demand mode
HFT
0
SIL
2
Safety function
Signal transfer
s
122 FIT
dd
172 FIT
du
45 FIT
no effect
122 FIT
total (safety function)
338 FIT
not part
72 FIT
SFF
86.8 %
MTBF
1
1
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h.
278 years
PFH
4.45 x 10
-8
1/h
PFD
avg
for T
proof
= 1 year
1.95 x 10
-4
PFD
avg
for T
proof
= 2 years
3.90 x 10
-4
PFD
avg
for T
proof
= 5 years
9.74 x 10
-4
Reaction time
2
2
Time between fault detection and fault reaction
< 20 ms
Table 3.3
