IDEC FS1A Controller - Manual (Page 15)

2-6
Safety performance
SafetyOne can be used in a system for control category B to 4.
Average probability of failure on demand （PFD） and Probability of a dangerous failure
per hour（PFH）
The following table describes PFD and PFH. They are needed for calculation of safety integrity
level (SIL) which is applied to a system with SafetyOne. SafetyOne can be used in a system for
SIL 1 to 3.
Proof test interval Note1
Average Probability of Failure
on Demand （PFD） Probability of a dangerous Failure per
Hour（PFH）
6 months < 1.8 x 10 -5
1 year < 3.1 x 10 -5
2 years < 5.7 x 10 -5
5 years < 13.4 x 10 -5
< 1.2 x 10 -8
Note1: Refer to Maintenance and Inspection in “Chapter 7 APPENDIX” for proof test procedure.
Mean Time To dangerous Failure (MTTF
d
) and diagnostic coverage (DC)
The following table describes MTTF
d
and DC. They are needed for the calculation of
Performance Level (PL) which is applied to a system with SafetyOne. SafetyOne can be used
in a system for PL a to e.
Mean time to dangerous failure (MTTF
d
) Average Diagnostic Coverage (DC)
100 years 99% or more