Manual
<A1. SAFETY INSTRUMENTED SYSTEMS INSTALLATION>
A1-5
IM 01R01B30-00E-E 5th edition February 01, 2013 -00
All Rights Reserved. Copyright © 2003, Rota Yokogawa
A1.4 Assessment results
A1.4.1 Safety related parameters
The following results have been obtained from the assessment report Report No.: ROTA YOKOGAWA
08/07-23
R002
Version V2, Revision R1; August
2010 issued by exida.
Average PFD values have been calculated assuming a Diagnostic Coverage (DC) of 99%, a mission time
of 10 years and a Mean Time To Restoration of 24 hours.
Table 2: Summary for RAKD ([V1]) with fail-safe limit switches
3
– Failure rates
Prole 2 Prole 4
Fail Safe Detected (λSD) 0 FIT 0 FIT
Fail Safe Undetected (λSU) 132 FIT 174 FIT
Fail Dangerous Detected (λDD) 4 FIT 19 FIT
Fail Dangerous Undetected (λDU) 62 FIT 108 FIT
SFF
4
68.7% 64.1%
MTBF 486 years 310 years
SIL AC
5
SIL2 SIL2
Safety metrics according to ISO 13849-1
6
:
MTTF
d
(years) 1730 899
DC 6% 15%
Category (CAT) CAT 1 CAT 1
Performance Level (required) PL
r
= c PL
r
= c
Performance Level (calculated) 6.60E-08 1/h 1.27E-07 1/h
T[Proof] = 1 year T[Proof] = 5 years T[Proof] = 10 years
PFDAVG = 2.96E-04 PFDAVG = 1.37E-03 PFDAVG = 2.72E-03