Decommissioning and withdrawal from service
© exida.com GmbH TURCK 04-07-14 R001 V2R0.doc; February 8, 2013
Stephan Aschenbrenner Page 21 of 25
Appendix 1: Possibilities to reveal dangerous undetected faults during the
proof test
According to section 7.4.3.2.2 f) of IEC 61508-2 proof tests shall be undertaken to reveal
dangerous faults which are undetected by diagnostic tests.
This means that it is necessary to specify how dangerous undetected faults which have been
noted during the FMEDA can be detected during proof testing.
Table 7 and Table 8 show a sensitivity analysis of the ten most critical dangerous undetected
faults and indicate how these faults can be detected during proof testing.
Appendix 1 shall be considered when writing the safety manual as it contains important safety
related information.
Table 7: Sensitivity Analysis of dangerous undetected faults of IM33-**(Ex)-Hi/24VDC
Component
% of total λ
λλ
λ
du
Detection through
T8 24,11%
100% functional test with monitoring of the
expected output signal
IC6 8,44%
100% functional test with monitoring of the
expected output signal
IC3 4,82%
100% functional test with monitoring of the
expected output signal
IC4 4,82%
100% functional test with monitoring of the
expected output signal
IC8 4,82%
100% functional test with monitoring of the
expected output signal
IC13 4,82%
100% functional test with monitoring of the
expected output signal
IC2 4,34%
100% functional test with monitoring of the
expected output signal
IC9 2,89%
100% functional test with monitoring of the
expected output signal
IC7 2,89%
100% functional test with monitoring of the
expected output signal
C23 2,41%
100% functional test with monitoring of the
expected output signal
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