Rockwell Automation AADvance Controller PFH avg and PFD avg Data - Manual (Page 15)

Document: 553847
(ICSTT-RM449_EN_P) Issue 04:
1-9
System Configurations System Configurations System Configurations System Configurations
The PFH and PFD calculations are derived from IEC 61508 Section 6 and the examples
below show how the calculations are used to define the probability of failure for a SIF.
Example 1 Example 1 Example 1 Example 1
This illustrates a SIL3 SIF with one signal input and one signal output; it has a MTI of 1
year and a MTTR of 8 hours, it is configured as a de-energized to trip arrangement.
Refer to the Table 3
Exa Exa Exa Example 2 mple 2 mple 2 mple 2
This illustrates a SIL 3 SIF with 2 inputs on dual input modules and 1 output with an
MTI of 1 year and MTTR = 8 hours, configured as 1oo2 de-energize to trip.
Refer to Table 3