Siemens SIPART PS2 PA Handbuch Seite 22

Anhang
A.2 Prüfbericht (Auszug)
The assessment has shown that the Electro-pneumatic Positioner SIPART PS2 PA / FF
when used as a single-acting shut-down module ("tight closing") has a PFD
allowed range for SIL 2 according to table 2 of IEC 61508-1 and table 3.1 of ANSI/ISA–
84.01–1996 and a Safe Failure Fraction (SFF) of more than 86% when using the shut-
down input (terminal 81/82) for the safety function.
The Electro-pneumatic Positioner SIPART PS2 PA / FF has been developed without
considering IEC 61508, however, and so IEC 61511-1 First Edition 2003-01 section 11.4.4 is
used as a basis for arguing that proven-in-use shows the unlikelihood of systematic failures for
the mechanical / pneumatic components.
The failure rates listed above do not include failures resulting from incorrect use of the Electro-
pneumatic Positioner SIPART PS2 PA / FF, 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 Dx (outdoor 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 Electro-pneumatic Positioner SIPART PS2 PA / FF 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 5.2 and 5.3 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 Electro-pneumatic Positioner SIPART PS2
PA / FF, which is estimated to be 10 years (see Appendix 3).
exida.com
©
Stephan Aschenbrenner
A-6
GmbH siemens 05-01-04 r014 v1 r1.0.doc, August 16, 2005
Ergänzungen zum Gerätehandbuch, 09/2005, A5E00489774-01
within the
AVG
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SIL-Sicherheitshandbuch (PA/FF)