Characteristic Safety Values - Pepperl+Fuchs KFD2-UT2 Series Manual

Functional Safety KFD2-UT2-(Ex)*(-1)
Planning
3.4

Characteristic Safety Values

The following tables contains no SFF data, since this value has to be calculated
with consideration of the connected field device.
KFD2-UT2-(Ex)*
Parameters
Assessment type
Device type
Mode of operation
Safety function
HFT
SIL
SC

s
2

dd
3

du
4

no effect

total (safety function)

no part
SFF
5
MTBF
6
PFD for T = 1 year
avg 1
PFD for T = 2 years
avg proof
PFD for T = 5 years
avg proof
PTC
7
Reaction time
Table 3.1
1
For the proven-in-use demonstration, sales figures, customer returns and questionnaires filled out by customers were used
which show that no unknown systematic faults are expected. The device is based on a former device that was evaluated
for a proven-in-use statement by exida.com GmbH.
2
"Fail high" and "Fail low" failures are considered as dangerous detected failures 
3
"Annunciation failures" that only influence the diagnostic function were marginal and added to the 
4
"No effect failures" are not influencing the safety function and are therefore added to the 
5
acc. to SN29500. This value includes failures which are not part of the safety function/MTTR = 8 h.
6
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 = ( / 2) x (PTC x T
avg du
A service time T of 10 years was assumed for the calculation of PFD
service
7
Step response time
The characteristic safety values like PFD, PFH, SFF, HFT and T
the FMEDA report. Observe that PFD and T
The function of the devices has to be checked within the proof test interval (T
12
6
6
+ (1 – PTC) x T )
1 service
Characteristic values
FMEDA report with proven-in-use assessment
B
Low demand mode
Transfer of analog value
0 (acc. to IEC/EN 61511)
2
2
0 FIT
333 FIT
79.2 FIT
295 FIT
706 FIT
33.4 FIT
81 %
154 years
-4
8.33 x 10
-3
1.14 x 10
-3
2.08 x 10
90 %
• for temperature input: < 1.5 s
• for potentiometer input: < 3 s
.
dd
.
s
.
avg
are taken from
1
are related to each other.
1
1
.
du
).
1