Why Use a System with Redundant Software Backup?
Production Down Times Cost Time and Money
The increasing level of automation of industrial plants in order to increase productivity and quality Also increases dependence on the availability of the automation systems. The failure of an automation system (e.g. due to CPU failure) can be extremely expensive due to the loss of production and plant idle time.
In many areas of application, the demands placed on redundant backup quality or the size of the installations that require automation systems with redundant backup are not such that the use of a special system offering very high levels of availability is not absolutely necessary.
In many cases, straightforward software mechanisms that enable a failed control sequence to be taken over by a backup system are sufficient.
Such requirements are fully satisfied by the use of redundant software backup.
Redundant Software Backup Means Greater Availability
The redundant-backup software can run on standard S7-300 and S7-400 automation systems. Greater availability can be provided for single-channel local peripherals on an ET 200M with redundant-backup slave interface (redundant IM 153-3 or IM 152-2). The DP slave interfaces havettwo DP interfaces one of which is connected to the DP master system on station A and one to the DP master system on station B.
In order that control tasks subject to high availability requirements can be continued in the event of failures, both automation systems have redundant software backup.
“Control tasks subject to high availability requirements” refer to that part of the application program for which it is absolutely essential that they are taken over by the reserve station if the master station fails. This may be the complete application program or only a certain part of it.
Redundant software backup can be used to manage the following types of failure:
· Failure of CPU components (power supply unit, rear-panel bus, DP master)
· CPU failure due to hardware or software faults
· Breaks in the bus cable for the redundant-backup link or the redundant-backup DP slave
interface
· Faults on a PROFIBUS module in the redundant-backup slave interface (e.g. IM 153-3)
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