Skript vom Sommersemester 2012 - Institut für Automatisierungs ...

§ 15 Sicherheitsnachweis (SN)
ZSA
Design features (zu TS2)
Technique/ Measures
1. Protection against operating errors
Plausibility checks
2. Protection against single fault for discrete
components
All hazardous failure modes to be either detected
and negated or demonstrated to be inherently safe
3. Protection against single fault for integrated circuits
stuck-at fault model (SIL1), or DC-fault model (SIL2),
or permanent and transient malfunction model on
item level (SIL3/4)
4. Physical independence
Insulation distances should be dimensioned to the
reinforced value according to EN 50124-1
5. Detection of single and multiple faults
Dependent on the safety target. The time for
detection-plus-negation should be within the safety
target
SIL1 SIL2 SIL3/4
R R HR
R R HR
R R HR
R R HR
R R HR
© 2012 IAS, Universität Stuttgart
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