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We have a bank of 12 blowers in our industrial wastewater treatment plant and they have all been shutting down Tuesday mornings. Looking back it happened last year where they shut down at about 7:45 AM give or take about 5 minutes 8 times over about 6 months (with one time at 6AM) always on Tuesday morning. Then the problem went away and didn't happen for about 9 months. Now it is happening again only every other Tuesday morning at about 7AM since mid-June. As soon as the operators notice they are down they can re-start them from the HMI without having to clear any alarms or reset them in the field.
Control wise there is no common interlock to shut down all the blowers each shut down is per blower. I have added extra points to our historian to try to see if it is the PLC shutting it down but haven't found anything. All I have found is that we lose the run command and the run status at the same time so I am going to try to see if I can add traps to the logic to find which happens first because either will trigger the other.
Incoming power wise they added some relays to the incoming power (2 separate transformers each feeding half the blowers) and when the shutdown happened the relays were still energized meaning they didn't lose power.
I have sent an e-mail request to the facility to see if anybody does work in that area on Tuesday mornings or does anything routinely on Tuesday mornings and nobody could think of anything.
We are starting to look at signal power inside the PLC cabinet but the fact that it is so routinely on Tuesday mornings make me think it is something that is programmed instead of just an equipment glitch.
The blowers are not on a VFD it is a simple starter in the MCC for each.
Anybody experience something like this before and can guide me on where to look or what to do next? I would greatly appreciate any help.
Control wise there is no common interlock to shut down all the blowers each shut down is per blower. I have added extra points to our historian to try to see if it is the PLC shutting it down but haven't found anything. All I have found is that we lose the run command and the run status at the same time so I am going to try to see if I can add traps to the logic to find which happens first because either will trigger the other.
Incoming power wise they added some relays to the incoming power (2 separate transformers each feeding half the blowers) and when the shutdown happened the relays were still energized meaning they didn't lose power.
I have sent an e-mail request to the facility to see if anybody does work in that area on Tuesday mornings or does anything routinely on Tuesday mornings and nobody could think of anything.
We are starting to look at signal power inside the PLC cabinet but the fact that it is so routinely on Tuesday mornings make me think it is something that is programmed instead of just an equipment glitch.
The blowers are not on a VFD it is a simple starter in the MCC for each.
Anybody experience something like this before and can guide me on where to look or what to do next? I would greatly appreciate any help.