
Rockwell Automation Publication 1756-UM013B-EN-P - October 2019
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Appendix
D
Safety Data for Safety Modules
This appendix lists calculated values for probability of a dangerous failure on
demand (PFD), average frequency of a dangerous failure per hour (PFH), and
mean time to failure (MTTF). PFD and PFH calculations comply with
IEC61508, edition 2, 2010.
• For the 1756-IB16S, calculated values of PFD and PFH appear in
• For the 1756-OBV8S, calculated values of PFD and PFH appear in
.
PFD and PFH must be calculated for the devices within the system to comply
with the SIL level that is required for application.
You are responsible for following the requirements of ISO 13849-1:2008, to
assess Performance Levels in your safety system.
You must functionally test every I/O module by individually toggling each input
point and also verify that the controller detects it within the safety reaction time
(SRT). Additionally, you must individually toggle each output point by the
controller and user-verified that the output point changes state.
For more information, see the GuardLogix® 5580 and CompactGuardLogix 5380
Controller Systems Safety Reference Manual, publication