INOR IPAQ C520, Дополнительное руководство по инструкции

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SAFETY-RELATED CHARACTERISTICS
7
15
IPAQ C520/R520
www.inor.com 02/2019 - 86B520S001 - AD 520 SIL R1.4 en
7.2 Specific safety-related characteristics
According to table 2 of IEC 61508-1 the average PFD for systems operating in low demand mode
has to be
≥
10
-3
to
≤
10
-2
for SIL 2 Safety Instrumented Functions (SIFs). For systems operating in
high demand mode of operation the PFH value has to be
≥
10
-7
to
≤
10
-6
for SIL 2 SIFs according to
table 3 of IEC 61508-1. A generally accepted distribution of PFD
avg
and PFH values of a SIF over
the sensor part, logic solver part, and final element part assumes that 35% of the total SIF
PFD
avg
value is caused by the sensor part (including the transmitter).
For a SIL 2 application operating in low demand
low demand low demand
low demand mode the total PFD
avg
value of the SIF should be
smaller than 1.00E-02, hence the maximum allowable PFD
avg
value for the sensor part would
then be 3.50E-03.
For a SIL 2 application operating in high demand
high demand high demand
high demand mode the total PFH value for the SIF should be
smaller than 1.00E-06 1/h, hence the maximum allowable PFH value for the sensor part would
be 3.50E-07 1/h.
For type B components with a hardware fault tolerance of 0 the SFF shall be > 90% for SIL 2 SIFs
according to table 3 of IEC 61508-2.
Under the assumptions described in the chapter before and the definitions given in chapter
"Desription of the failure categories" the following table show the failure rates according to
IEC 61508.
λ
SD
: Fail safe detected
λ
SU
: Fail safe undetected
λ
DD
: Fail dangerous detected
λ
DU
: Fail dangerous undetected
FIT: Failure rate [1/h]
SFF: The number listed is for reference only. The SFF, PFD
avg
and PFH must be determined for
the complete Safety Instrumented Function (SIF) Safety Instrumented Function (SIF) Safety Instrumented Function (SIF) Safety Instrumented Function (SIF).
PFD
avg
: The PFD
avg
was calculated for profile 2 using Markov modeling. The results must be
considered in combination with PFD
avg
values of other devices of the Safety Instrumented
Function (SIF) in order to determine suitability for a specific Safety Integrity Level (SIL)
For SIL 1 applications, the PFD
avg
value needs to be < 10
-1
for the SIF.
For SIL 2 applications, the PFD
avg
value needs to be < 10
-2
for the SIF.
T[Proof]: It is assumed that proof testing is performed with a proof test coverage of 99%.
PFH: =
λ
DU
(Fail dangerous undetected)
SIL AC: SIL AC (architectural constraints) means that the calculated values are within the range for
hardware architectural constraints for the corresponding SIL level
Table 7-1: Explanation of table headers for the tables showing failure rates on upcoming pages.