Operator workplace Freeze and loss or delay of data and alarm/events
We had an incident where the Operators noticed that a number of motors or valves stopped without any indication of a plant trip. They then tried to navigate through the system using the graphics, opened one of the overview graphics on a operator station but was unable to navigate any further. The operators at the other operator stations were also unable to navigate through the graphics as they were unresponsive for possibly up to less than a minute, operators then shut the plant down using a manual push button, soon after that the operator stations were normal, there was no red border indicating watchdog timeout or bad data indication, the screens just stopped for a certain duration and then started to work normally.
We checked the services on all servers, system alarm/event list and there were no service restarts and no system events reported, no indication of any system issues.
We reviewed the alarm and event log, there were some alarms and events related to intermediate trip tags but was no indication of a cause (input trip), it seems the safety system initiated a shutdown, but could not identify an input cause.
There are a few issues we are investigating
- Could a very short duration input change caused the plant to trip without the 800xa recording the event?
- What could have caused the slow response from the operator stations?
- There appears to be a delay between the events reported on the Alarm and event log and the sequence of the events seems to be not in order?
- A review of the event logs indicated that all equipment that should have tripped was already tripped prior to the operators initiated the trip using the push button, suggesting that the plant tripped as required but didn’t report the change of state on the displays and alarm/events.
The system is 5.1 FP4 Rev D RU2, with AC800M 5.0.2 and SG400 1.6/3, have anyone come across similar issues or any pointers on what could have gone wrong?
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