14 Rockwell Automation Publication 1756-RM012B-EN-P - April 2018
Chapter 1 Safety Integrity Level (SIL) Concept
Safety Task Period and Safety Task Watchdog
The safety task period is the interval at which the safety task executes.
The safety task watchdog time is the maximum permissible time for safety task
processing. If the time to process a safety task exceeds the safety task watchdog
time, a nonrecoverable safety fault occurs in the controller, which results in a
transition to the safe state (off).
You define the safety task watchdog time, which must be less than or equal to
the safety task period.
The safety task watchdog time is set in the task properties window of the
Studio 5000 Logix Designer application. This value can be modified online,
regardless of controller mode, but it cannot be changed when the controller is
safety-locked or once a safety signature is created.
Contact Information If Device
Failure Occurs
If you experience a failure with any safety device, contact your local
Rockwell Automation sales office or Allen-Bradley distributor to initiate the
following actions:
• Return the device to Rockwell Automation so the failure is logged for
the catalog number that is affected, and a record is made of the failure.
• Request a failure analysis (if necessary) to try to determine the cause of
the failure.
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