Cascading Alarms

How have others dealt with cascading alarms or, in some cases, avalanches of alarms? For instance, we have a pump station controlled by a PLC, with the PLC and comms radio on a UPS. On a power failure, I want to return an alarm for station power fail, but not every float switch, VFD, and security limit switch alarm that gets de-energized on loss of power. Obviously I could place these devices all on the battery backup, but we’d rather just filter the other alarms so the operator gets a clear picture of what just happened.

Also, will the new alert system accommodate this type of problem?

You could do a CASE…WHEN in your query on the alarm table to show either the power failure alarm or the general alarms.

You could also latch a bit on the the PLC on the first scan to keep all the other alarms from firing on a power-up.

Use the Severity to group your alarms. You might make the power failure High severity, pump failure Medium-High severity. Then you can use a query to display only the highest severity alarms.


The new system will have some better facilities for this, such as the ability to bind whether an alarm is evaluated to a condition, and a lot more potential for logic in how alarms are processed. However, I think that until we have specific support for this in some way, you’re still going to have to use other mechanisms like the suggested use of severity to really get anywhere. There is also the ability to define arbitrary data on alarms in the new system (which can also be bound), so maybe there’s more potential than what’s currently coming to mind…