Allen-Bradley 1756-L6 Series, Reference Manual, Page: 21 / 134

Rockwell Automation Publication 1756-RM001I-EN-P - May 2012 21
SIL Policy Chapter 1
• Test all digital input or output channels to verify that they are not stuck in
the ON or OFF state.
– Manually cycle inputs to make sure that all inputs are operational and
not stuck in the ON state.
– Manually test outputs which do not support runtime pulse testing. The
relays in the redundant power supplies must be tested to make sure
they are not stuck in the closed state.
Users can automatically perform proof tests by switching ground open
on input modules and checking to make sure all input points go to zero
(turn OFF.).
• Calibrate analog input and output modules to verify that accurate data is
obtained from and used on the modules.
Proof Testing with Redundancy Systems
A ControlLogix redundancy system uses an identical pair of ControlLogix
chassis to keep your process running if a problem occurs with one of those chassis.
When a failure occurs in the primary chassis, control switches to the
secondary controller.
The switchover can be monitored so that the system notifies the user when it has
occurred. In this case (that is, when a switchover takes place), we recommend that
you replace the failed controller within the mean time to restoration (MTTR)
for your application.
If you are using controller redundancy in a SIL 2 application, you must perform
half the proof test on the primary controller and half the proof test on the
secondary controller.
For more information on switchovers in ControlLogix redundancy systems and
ControlLogix redundancy systems in general, see these redundancy system
manuals:
• ControlLogix Standard Redundancy System User Manual, publication
1756-UM523
• ControlLogix Enhanced Redundancy System User Manual, publication
1756-UM535
IMPORTANT
Each specific application will have its own time frame for the proof test
interval.
TIP
If you are concerned about the availability of the secondary controller if the
primary controller fails, it is good engineering practice to implement a
switchover periodically (for example, once per proof test interval).
Allen-Bradley Motors