Rockwell Automation 1791ES-IB16 Guard I/O EtherNet/IP Safety Modules - Manual (Page 92)

92 Rockwell Automation Publication 1791ES-UM001D-EN-P - May 2013
Appendix B Safety Data
Figure 24 - PFD versus Proof Test Interval 1791ES-IB16
Table 27 - Calculated Values for Probability of Failure on Demand (PFD), Probability of Failure per
Hour (PFH), and Mean Time To Failure (MTTF)
Figure 25 - PFD versus Proof Test Interval 1791ES-IB8XOBV4
Cat. No. Proof Test Interval PFD
(1/hour) PFH
(1/hour) Spurious
Trip Rate
(STR) MTTF (years)
Year Hour
1791ES-IB16 1 8760 2.06E-06 4.98E-10 3.309E-06 34.48
2 17520 4.13E-06
5 43800 1.03E-05
10 87600 2.06E-05
1791ES-IB8XOBV4 1 8760 2.09E-06 5.04E-10 5.612E-06 20.33
2 17520 4.17E-06
5 43800 1.04E-05
10 87600 2.09E-05