6 safety manual – JUMO 701150 14597 safetyM STB/STW - Safety Temperature Limiter and Safety Temperature Monitor Operating Manual User Manual
Page 56
6 Safety Manual
56
6.12 Evaluating the achieved Performance Level PL and the relationship to the SIL
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 to perform a safety function under predictable ambient conditions
The following diagram depicts 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.