Endress+Hauser RN221N Handbuch Seite 14

Table 1 Summary for RN 221N – IEC 61508 failure rates
Fail Safe Detected (λ λ λ λ
Fail Safe Undetected (λ λ λ λ
Fail Dangerous Detected (λ λ λ λ
Fail Dangerous Detected (λ
Fail High (λ
Fail Low (λ
Fail Dangerous Undetected (λ λ λ λ
No effect
No part
Total failure rate of the safety function (λ λ λ λ
Safe failure fraction (SFF)
DC
D
3
SIL AC
The failure rates are valid for the useful life of the Active Barrier preline RN 221N (see
Appendix 2).
2
The complete sensor element will need to be evaluated to determine the overall Safe Failure Fraction. The number
listed is for reference only.
3
SIL AC (architectural constraints) means that the calculated values are within the range for hardware architectural
constraints for the corresponding SIL but does not imply that all related IEC 61508 requirements are fulfilled.
H[LGDFRP
©
Stephan Aschenbrenner
14
Failure category
)
SD
)
SU
)
DD
)
dd
)
H
)
L
)
DU
2
GmbH
Siemens SN 29500 [FIT]
0
79
127
117
8
)
Total
E+H Wetzer 13-03-087 R012 V2R1.doc, July 15, 2013
RN221N
0
0
206
66
272
75%
75%
SIL 2
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