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Functional safety
8.1
General safety notes
8.1.1
Safety-instrumented system
Definition: Safety-instrumented system
A safety-instrumented system executes the safety functions that are required to achieve or
maintain a safe status in a system. It consists of a sensor, logic unit/control system and final
controlling element.
Example:
A safety-instrumented system is made up of a pressure transmitter, a limit signal sensor and
a control valve.
Definition: Safety function
A defined function executed by a safety-instrumented system with the objective of achieving
or maintaining a safe system status taking into account a defined dangerous occurrence.
Example:
Limit pressure monitoring
Definition: Dangerous failure
Failure with the potential to bring the safety-instrumented system into a dangerous or non-
functional status.
Description
The sensor, logic unit/control system and final controlling element combine to form a safety-
instrumented system, which executes a safety function.
Note
This document deals with the SIPART PS2 positioner exclusively as part of a safety function.
SIPART PS2 with PROFIBUS communication
Operating Instructions, 09/2007, A5E00127926-07
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