
Rockwell Automation Publication 1756-RM001I-EN-P - May 2012
23
SIL Policy
Chapter 1
•
The switchover between controllers slows system response. The
switchover time of a redundancy system depends on the network update
time (NUT) of the ControlNet network.
For more information about switchover times in redundancy systems, see
one of these ControlLogix redundancy system user manuals:
–
ControlLogix Standard Redundancy System User Manual,
publication
–
ControlLogix Enhanced Redundancy System User Manual,
publication
Safety Watchdog
Configure the properties of the task used for safety correctly for your application.
•
Priority: must be the highest-priority task in the application (lowest
number)
•
Watchdog: the value entered must be large enough for all logic in the task
to be scanned, and it must be less than the task period
If the task execution time exceeds the watchdog time, a major fault occurs on the
controller. Users must monitor the watchdog and program the system outputs to
transition to the safe state (typically the OFF state) in the event of a major fault
occurring on the controller. For more information on faults, see
Faults in the ControlLogix System
.
The task watchdog time must be < 50% of the expected safety demand rate for
each application.
See the ControlLogix System User Manual, publication
, for more
information about setting the watchdog.
Safety Certifications and
Compliances
Diagnostic hardware and firmware functions, as well as how you apply
ControlLogix components, enable the system to achieve CL SIL 2 compliance.
ControlLogix products referenced in this manual may have safety certifications
in addition to the SIL certification. If a product has achieved agency certification,
it is marked on the product label. To view additional safety certifications for
products, go to
and click the Product Certifications link.
IMPORTANT
To avoid nuisance trips, you must account for the additional cross checking
time of a duplex system when setting the watchdog time.
IMPORTANT
You must implement these requirements or at minimum the intent of the
requirements defined in this manual to achieve CL SIL 2.
Summary of Contents for 1756-L6 Series
Page 24: ...24 Rockwell Automation Publication 1756 RM001I EN P May 2012 Chapter 1 SIL Policy Notes ...
Page 76: ...76 Rockwell Automation Publication 1756 RM001I EN P May 2012 Chapter 6 FLEX I O Modules Notes ...
Page 126: ...126 Rockwell Automation Publication 1756 RM001I EN P May 2012 Appendix D Checklists Notes ...
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