All Member Open Forum

Hello all,

I am a Support Supervisor in high speed conveyor for processing bulk parcels and and I noticed yesterday that one of our PLC started generating fire alarms every 5mins and blocking the SCADA. 

NB: Something we should note is that, we switch our main power source in the same day from the grid to generator. Do you think this may have some form of effect on the PLC?

I am posting this here to figure out the root cause from other experienced experts here, because we cycled power to the PLC and the alarm went away and I do not feel satisfied since that is not the root cause but just a band aid fix. All suggestions and opinions are welcomed.
Thanks in advance.

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Ikechukwu Ofeweke BSc
Maintenance Supervisor
Stellantis
Etobicoke ON
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This will depend on your generator, or why you switched from grid to generator.  Did the grid power go down?  If so, I have seen brownouts and power spikes cause weird issues with several brands of PLC.  This could happen when switching from grid to generator.  There may be improvements that can be made to your power system and generator to help prevent this.  As to root cause of the weird PLC behavior, very hard to prove but I would say a spike caused a RAM memory corruption in the PLC.  Hence resetting power cured the issue.  I have seen all kinds of weird behaviors after power spikes/brownouts.  Most often the cure is resetting power.  Hope this helps.

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Gerald Sapp II
Reliability Engineer
SKF USA Inc.
West Valley City UT
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