Operation and Maintenance
Fail-Safe Systems
6-4 A5E00085588-03
See Also
You can find additional information on modifying the Safety Program in the
following sections:
• Deactivating Safety Mode
• Changes to the Safety Program in RUN
• Downloading Changes
• Changing Fail-Safe Constants in CFC Test Mode
6.5 Replacing Software and Hardware Components
Replacing Software Components
When you replace software components on your programming device/ES, for
example in new PCS 7 or STEP 7 versions, you must comply with the guidelines
on upward and downward compatibility contained in the documentation and in the
readme files of these products.
Installing New Versions of the Software Packages
After you have installed a new version of STEP 7 or add-on packages such as
CFC or SCL, proceed as follows:
1. Compile the Safety Program in the new environment (new compiler or new
libraries).
Compare the overall signature of the newly compiled Safety Program with the
overall signature of the accepted Safety Program (see "Checking the Overall
Signatures" in the section entitled "Initial Acceptance of a Safety Program").
2. If the overall signatures are identical, the programs are the same.
3. If the overall signatures are not identical, the program has been changed.
Proceed in the same way as when there is a change to the Safety Program.
Replacing Hardware Components
The replacement of hardware components for the S7-400 FH (modules, cards,
batteries, etc.) is carried out in the usual way. You can find descriptions in manuals
/1/, /2/, /5/ and /7/. (Please refer to the references in Appendix B.)
Duration of the Repair with the S7 FH Systems
For redundant components in S7 FH Systems, repairs should be organized in
such a way that, in the event of a failure, repairs do not take longer than 24 hours,
if possible. On weekends, repairs can last up to 72 hours for unattended systems.
As a general principle, availability increases as the duration of the repair is
reduced.
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