Safety Manual SIL KCD2-STC-(Ex)1.HC(.SP), HiC2025HC
Planning
2
012-
07
9
2.4
Characteristic Safety Values
The characteristic safety values like PFD, SFF, HFT and T
proof
are taken from the
SIL report/FMEDA report. Please note, PFD and T
proof
are related to each other.
The function of the devices has to be checked within the proof test interval
(T
proof
).
Parameters acc. to IEC 61508
Values
Assessment type and documentation
FMEDA report
Device type
A
Mode of operation
Low Demand Mode or High Demand Mode
HFT
0
SIL
2
Safety function
Signal transfer
λ
s
126.3 FIT
λ
dd
0 FIT
λ
du
50.3 FIT
λ
no effect
228.3 FIT
λ
total (safety function)
405 FIT
λ
not part
32.2 FIT
SFF
87.58 %
MTBF
1
261 years
PFH
5.03 x 10
-8
1/h
PFD
avg
for T
proof
= 1 year
2.20 x 10
-4
PFD
avg
for T
proof
= 2 years
4.41 x 10
-4
PFD
avg
for T
proof
= 5 years
1.10 x 10
-3
Reaction time
2
< 20 ms
1
acc. to SN29500. This value includes failures which are not part of the safety function.
2
Time between fault detection and fault reaction.
Table 2.3
