Siemens SIPART Series Operating Instructions Manual page 277

Abbreviation Full term in English
SIL Safety Integrity Level
SIS Safety Instrumented System
SIPART PS2 with and without HART
Operating Instructions, 10/2013, A5E00074631-11
Meaning
The international standard IEC 61508 defines four discrete
Safety Integrity Levels (SIL 1 to SIL 4). Each level corresponds
to a range of probability for failure of a safety function. The
higher the Safety Integrity Level of the safety-instrumented
system, the lower the probability that it will not execute the
required safety functions.
A safety-instrumented system (SIS) executes the safety
functions that are required to achieve or maintain a safe status
in a system. It consists of sensors, logic unit/control system and
final controlling elements.
Abbreviations
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