<A2. SAFETY INSTRUMENTED SYSTEMS INSTALLATION>
A2-6
IM 01R01B02-00E-E 12th edition October 01, 2014 -00
All Rights Reserved. Copyright © 2003, Rota Yokogawa
Table A2.24: Summary for RAMC ([V2]) with 4-20mA output – Failure rates
Prole 2 Prole 4
Fail Safe Detected (λSD) 0 FIT 0 FIT
Fail Safe Undetected (λSU) 60 FIT 60 FIT
Fail Dangerous Detected (λDD) 260 FIT 344 FIT
Fail Dangerous Undetected (λDU) 193 FIT 200 FIT
SFF
4
62.3% 66.8%
DC
D
57% 63%
MTBF 191 years 166 years
SIL AC
5
SIL1 SIL1
Safety metrics according to ISO 13849-1
6
:
MTTF
d
(years) 252 210
DC 57% 63%
Category (CAT) CAT 1 CAT 2
Performance Level (required) PL
r
= c PL
r
= c
Performance Level (calculated) 4.53E-07 1/h 5.44E-07 1/h
T[Proof] = 1 year T[Proof] = 5 years T[Proof] = 10 years
PFDAVG = 9.28E-04 PFDAVG = 4.28E-03 PFDAVG = 8.46E-03
3
The switching contact output is connected to a fail-safe NAMUR amplier (e.g. Pepperl+Fuchs KF**-SH-Ex1). The failure rates of the
amplier are not included in the listed failure rates
4
The complete sensor subsystem will need to be evaluated to determine the overall Safe Failure Fraction. The number listed is for
reference only.
5
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 all related IEC 61508 requirements are fullled.
6
Depending on the application and possible external diagnostics a higher DCD and therefore also a higher category might be possible
to achieve.
7
The switching contact output is connected to a standard switching amplier (e.g. Pepperl+Fuchs KF**-SR2-Ex*.W). The failure rates of
the amplier are not included in the listed failure rates.
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