Safety in F-Systems
4.8 Safety Requirements
Safety Engineering in SIMATIC S7
4-12
System Manual, 04/2006, A5E00109529-05
4.8
4.8
Safety Requirements
Standardized Safety Requirements
The following safety requirements can be met with S7 Distributed Safety and
S7 F/FH Systems F-systems:
•
Safety class (Safety Integrity Level) SIL1 to SIL3 in accordance with IEC 61508
•
Category 2 to Category 4 in accordance with EN 954-1
Determining the Safety Integrity Level in Accordance with IEC 61508-5
The qualitative methods of the risk graphs enable the safety integrity level for a safety-
related system to be determined based on knowledge of the risk factors involved:
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Figure 4-1
Risk Graphs in Accordance with IEC 61508-5
S
Starting point of the analysis for risk reduction
C
Risk parameter for the effect
F
Risk parameter for the frequency and exposure time
P
Risk parameter for possibility of avoiding dangerous occurrence
W
Probability of occurrence of undesirable event
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No safety requirements
a
No special safety requirements
b
A single electrical/electronic/programmable electronic
system is not sufficient.
1, 2, 3, 4
Safety integrity level
