Results Of The Assessment - turck IM35-11Ex-Hi/24VDC Bedienungsanleitung

Sicherheitshandbuch – Signaltrenner

5 Results of the assessment

exida.com did the FMEDAs together with Werner Turck GmbH & Co. KG.
For the calculation of the Safe Failure Fraction (SFF) the following has to be noted:
λ consists of the sum of all component failure rates. This means:
total
λ = λ + λ
total safe
SFF = 1 – λ
du
For the FMEDAs failure modes and distributions were used based on information gained from
[N3] to [N5].
For the calculation of the PFD
were used. As after a complete proof test all states are going back to the OK state no proof test
rate is shown in the Markov models but included in the calculation.
The proof test time was changed using the Microsoft® Excel 2000 based FMEDA tool of
exida.com as a simulation tool. The results are documented in the following sections.
λ λ λ λ
du
du
Figure 3: Markov model for a 1oo1D structure
λ λ λ λ
d
d
Figure 4: Markov model for a 1oo1 structure
exida.com
© GmbH
Stephan Aschenbrenner
28
+ λ .
dangerous no effect
/ λ
total
the following Markov models for a 1oo1D and a 1oo1 system
AVG
ok
λ λ λ λ
λ λ λ λ s
dd
dd
τ τ τ τ
Test
ok
τ τ τ τ
λ λ λ λ
s
Abbreviations:
du
undetected
dd
τ τ τ τ
s
Repair
λ
du
failures
λ
dd
λ
s
T
Test
τ
Test
s
T
Repair
τ
Repair
Abbreviations:
d
s
Repair
λ
d
λ
s
T
Repair
τ
Repair
s
TURCK 04-07-14 R001 V2R0.doc; February 8, 2013
Hans Turck GmbH & Co. KG • Tel. +49 208/4952-0 • Fax +49 208/4952-264
The system has failed dangerous
The system has failed dangerous detected
The system has failed safe
Failure rate of dangerous undetected
Failure rate of dangerous detected failures
Failure rate of safe failures
Test time
Test rate (1 / T )
Test
Repair time
Repair rate (1 / T )
Repair
The system has failed dangerous
The system has failed safe
Failure rate of dangerous failures
Failure rate of safe failures
Repair time
Repair rate (1 / T )
Repair
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