ABB S800 I/O - Page 74

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The safety switch should be arranged to shut down the power of not only the
electronics system but also transmitters, transducers and other process devices. In
other words, a total power shut down for the plant section controlled.
Regardless of the way, the results and consequences of a shut down will be:
– Zero output to the process devices (S800 I/O).
– De-energized output relays (S800 I/O). Not for normally closed contacts.
– The system is ready for a restart. Restart can be performed when the
reason for the shut down is cleared away.
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Beyond the most drastic way of shut down, by disconnecting power, there is an
other way to “stop” the S800 I/O:
• Stop program execution in the controller
• Disconnect the I/O station from the fieldbus.
The results of the manual stop method:
• Output modules goes to the OSP state.
• The system is ready for a restart. Restart can be performed by starting the
execution in the controller or connecting the fieldbus.
After necessary measures, a restart can take place.
Since the safety switch is a plant component this document can not stipulate and describe the
design exactly. Please check the plant documentation in this respect carefully. Instructions,
as to the extent of the power shut down, should preferably be attached to the safety switch.