1 - overview of safety controllers, Introduction, Safety concept – Rockwell Automation 1755-OF8 GuardPLC Controller Systems User Manual
Page 19: Chapter 1, Overview of safety controllers, Introduction safety concept, Chapter
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Publication 1753-UM001C-EN-P - March 2010
19
Chapter
1
Overview of Safety Controllers
Introduction
Safety Concept
GuardPLC controllers feature a fail-safe CPU according to IEC 61508
(SIL 3) and ISO 13849-1 (PLe/Cat. 4). Faults that cause loss of safety
function are detected within the safety time you specify. Faults that
cause loss of safety function only in combination with another fault,
are detected at least within the multiple error occurrence time (24
hours).
This results in these requirements for the safety concept:
•
You specify the safety time and the watchdog time. The multiple
error occurrence time is preset to 24 hours.
•
Even upon the detection of an error, the controller continues to
react in a safety-related way.
•
Faulty input signals (for example, incorrectly transmitted input
values) do not affect the safe function of the controller. Faulted
input signals have a 0 value.
•
An error in a non-safety-related module does not affect the
safety of the controller.
•
The failure of the controller has no effect on the safety of other
safety-related modules.
For more information on the safety concept, refer to the GuardPLC
Controllers Safety Reference Manual, publ
.
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