Endress+Hauser Proline Promag 50, Proline Promag 53 Handbuch Seite 14

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Table 3: Summary for the worst case version – IEC 61508 Failure rates
O
SD
0 FIT
Table 4: Summary for the worst case version – PFD
The boxes marked in yellow (
allowed range for SIL 2 according to table 2 of IEC 61508-1 but do not fulfill the requirement to
not claim more than 35% of this range, i.e. to be better than or equal to 3,50E-03. The boxes
marked in green (
SIL 2 according to table 2 of IEC 61508-1 and do fulfill the requirement to not claim more than
35% of this range, i.e. to be better than or equal to 3,50E-03. The boxes marked in red (
mean that the calculated PFD
table 2 of IEC 61508-1.
The failure rates listed above do not include failures resulting from incorrect use of the
electromagnetic flow measuring system PROMAG 50/53, in particular humidity entering through
incompletely closed housings or inadequate cable feeding through the inlets.
The listed failure rates are valid for operating stress conditions typical of an industrial field
environment similar to IEC 60654-1 class C (sheltered location) with an average temperature
over a long period of time of 40ºC. For a higher average temperature of 60°C, the failure rates
should be multiplied with an experience based factor of 2,5. A similar multiplier should be used
if frequent temperature fluctuation must be assumed.
A user of the electromagnetic flow measuring system PROMAG 50/53 can utilize these failure
rates in a probabilistic model of a safety instrumented function (SIF) to determine suitability in
part for safety instrumented system (SIS) usage in a particular safety integrity level (SIL). A full
table of failure rates is presented in sections 5.1 to 5.6. along with all assumptions.
It is important to realize that the “no effect” failures are included in the “safe undetected” failure
category according to IEC 61508. Note that these failures on its own will not affect system
reliability or safety, and should not be included in spurious trip calculations.
The failure rates are valid for the useful life of the electromagnetic flow measuring system
PROMAG 50/53 (see Appendix 3).
4
Note that the SU category includes failures that do not cause a spurious trip
5
DC means the diagnostic coverage (safe or dangerous).
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Stephan Aschenbrenner
14
O O
4
SU DD
265 FIT 756 FIT
T[Proof] = 1 year
PFD = 1,29E-03
AVG
) mean that the calculated PFD
AVG
GmbH
O
SFF
DU
295 FIT 77%
values
AVG
T[Proof] = 5 years
PFD = 6,43E-03
AVG
) mean that the calculated PFD
values are within the allowed range for
AVG
values do not fulfill the requirements for SIL 2 according to
e+h 06-02-03 r039 v1 r1.doc, October 4, 2006
Proline Promag 50, 53
5 3
DC DC
S D
0% 71%
T[Proof] = 10 years
PFD = 1,28E-02
AVG
values are within the
AVG
)
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