Siemens SIPART PS2 Sicherheitshandbuch Seite 20

Anhang
A.2 Prüfbericht (Auszug)
Management summary
This report summarizes the results of the hardware assessment with proven-in-use
consideration according to IEC 61508 / IEC 61511 carried out on the Electro-pneumatic
Positioner SIPART PS2 with software version C4 and C5. Table 1 gives an overview of the
different configurations that belong to the considered Electro-pneumatic Positioner SIPART
PS2.
The hardware assessment consists of a Failure Modes, Effects and Diagnostics Analysis
(FMEDA). A FMEDA is one of the steps taken to achieve functional safety assessment of a
device per IEC 61508. From the FMEDA, failure rates are determined and consequently the
Safe Failure Fraction (SFF) is calculated for the device. For full assessment purposes all
requirements of IEC 61508 must be considered.
Table 1: Configuration ov
[Conf 1] 6DR501*_*E***_****
[Conf 2]
[Conf 3] 6DR521*_*****_****
[Conf 4] 6DR531*_*****_****
For safety applications only the 4..20 mA control input with the corresponding pressure output
was considered to work as a single-acting shut-down module ("tight closing bottom"). All other
possible input and output variants or electronics are not covered by this report.
The failure rates of the electronic components used in this analysis are the basic failure rates
from the Siemens standard SN 29500.
SIEMENS AG, A&D PI TQ2 and exida.com
mechanical parts of the Electro-pneumatic Positioner SIPART PS2 to calculate the mechanical
failure rates using different failure rate databases ([N6], [N7], [N8] and exid a 's experienced-
based data compilation) for the different mechanical components (see [D32] and [R6]). The
results of the quantitative analysis are included in the calculations described in sections 5.2 to
5.5.
According to table 2 of IEC 61508-1 the average PFD for systems operating in low demand
mode has to be 10
PFD
that 50% of the total SIF PFD
pneumatic Positioner SIPART PS2 is only one part of the final element it should not claim more
than 20% of the range. For a SIL 2 application the total PFD
smaller than 1,00E-02, hence the maximum allowable PFD
then be 2,00E-03.
The Electro-pneumatic Positioner SIPART PS2 is considered to be a Type B
hardware fault tolerance of 0.
Type B components with a SFF of 60% to < 90% must have a hardware fault tolerance of 1
according to table 3 of IEC 61508-2 for SIL 2 (sub-) systems.
1
Type B component:
© exida.com GmbH
Stephan Aschenbrenner
A-4
erv iew
6DR501*_*N***_****
6DR511*_*****_****
-3 -2
to < 10
values of a SIF over the sensor part, logic solver part, and final element part assumes
AVG
AVG
"Complex" component (using micro controllers or programmable logic); for details
see 7.4.3.1.3 of IEC 61508-2.
2-wire Ex (L250) without HART; single-acting
2-wire standard (L350) without HART; single-acting
2-wire standard (L300) with HART; single-acting
2-, 3-, 4-wire Ex (L200) with HART; single-acting
2-, 3-, 4-wire standard (L220) without HART; single-acting
together did a quantitative analysis of the
for SIL 2 safety functions. A generally accepted distribution of
value is caused by the final element. However, as the Electro-
siemens 04-12-06 r004 v1 r1.0.doc, April 11, 2005
value of the SIF should be
AVG
value for the positioner would
AVG
1
component with a
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SIL-Sicherheitshandbuch
Betriebsanleitung, 06/2005, A5E00442120-01