Safety
Fail-Safe Systems
A5E00085588-03
7-7
Example:
A safety function is implemented with an S7 FH System. The CPUs and F-SMs
involved in the safety function are listed in the table below. These CPUs and F-
SMs are used in a redundant configuration. Their proof test interval is 10 years.
The F-SMs are in safety mode for SIL 3. Operation is in high demand mode:
CPUs, F SMs and Safety-
Related Communication
Equipment Involved in the
Safety Function.
Number Redundancy Probability of a
Hazardous Failure
per Hour
F-capable CPU 1 Yes 1,42E-09
SM 326; DO 10 x DC 24V/2A;
with diagnostic interrupt
6ES7 326-2BF00-0AB0
1 Yes 1,59E-10
SM 326; DI 24 x DC 24V; with
diagnostic interrupt
6ES7 326-1BK00-0AB0
2 Yes 2,28E-12
Safety-related communication 1,00E-09
Total 2,58E-09
7.3 System Configuration
The limits for the system configuration of the S7 F/FH System are set mainly by the
CPU used. You can find the relevant values in the technical specifications of the
CPU in /3/, Chapter 5.
You will find any restrictions that apply to the S7 FH System in the readme file in
the "S7 H Systems" optional package.
In Appendix A you will find the certified hardware and software components of an
F-system in the form of check lists.
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