12 performance level, Performance level, 6 safety manual – JUMO 14597 safetyM STB/STW Ex - Safety Temperature Limiter and Safety Temperature Monitor Operating Manual User Manual
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6.12 Performance Level
For application in this part of DIN EN ISO 13849, the capability of safety-related parts to perform a safety function is expressed
through the determination of a Performance Level.
The PL must be assessed for each selected SRP/CS and/or SRP/CS combination that performs a safety function. The PL of
the SRP/CS must be determined by assessing the following aspects:
-
The MTTF
c
value of individual components (see Appendices C and D)
-
The DC (see Appendix E)
-
The CCF (see Appendix F)
-
The structure (see section 6)
-
The behavior of the safety function under failure conditions (see section 6)
-
Safety-related software (see 4.6 and Appendix J)
-
Systematic failures (see Appendix G)
-
The capability of performing a safety function under predictable ambient conditions
6.13 Relationship between the Performance Level (PL) and the Safety Integrity Level (SIL)
The following table shows the procedure for selecting the categories in combination with MTTF
d
for each channel and the
DC
avg
to achieve the required PL for each safety function.
PL
SIL (IEC 61508-1, for information) high/continual operating mode
a
No equivalent
b
1
c
1
d
2
e
3