User manual

Publication 1756-RM093F-EN-P - January 2010 47
Characteristics of Safety Tags, the Safety Task, and Safety Programs Chapter 5
SIL 2 Outputs
Follow these guidelines for SIL 2 outputs:
• Guard I/O output modules used for SIL 2 safety outputs must be
configured for dual-channel operation.
• All Guard I/O output modules are approved for use in SIL 2
applications.
– 1732DS-IB8XOBV4
– 1791DS-IB8XOBV4, 1791ES-IB8XOBV4
– 1791DS-IB4XOW4
– 1791DS-IB8XOB8
– 1734-OB8S
SIL3 Safety – the Safety
Task
Creation of a GuardLogix project automatically creates a single safety
task. The safety task has these additional characteristics:
• GuardLogix controllers are the only controllers that support the
safety task.
• The safety task cannot be deleted.
• GuardLogix controllers support a single safety task.
• Within the safety task, you can schedule multiple safety
programs composed of multiple safety routines.
• You cannot schedule or execute standard routines from within
the safety task.
The safety task is a periodic timed task with a user-selectable task
priority and watchdog. In most cases, it is the controller’s top priority
and the user-defined program watchdog must be set to accommodate
fluctuations in the execution of the safety task.
IMPORTANT
You cannot use Flex or 1756 output modules in EN 50156
SIL 2 applications.