plc chemical reaction

Hello everyone. I have cqm1h cpu, 1 cq1h id213, 2 cq1h 0d213 and ad041. The cpu and modules are located in a control panel located near the waste water treatment facility. Eventually, the plc gives an i/o bus error and the operations turns into halt. Could the problem be a chemical reaction that resulted from chemical reaction? The modules are connected correctly.
Can anyone suggest any remedy because I will be replacing the cpu and modules with new model.

Thank you.

When it happens, how do you fix the problem? Do one of the components fail and you have to replace it, or do you just have to reset one of the I/O modules, or the PLC?

I have read the cq1h manual and it is indicated that I/O BUS ERROR results from incorrect connection of the modules but base on my observation modules are connected properly.
Is it internal circuit problem resulted from chemical reaction?
How can I protect my plc from chemical reaction?

I have read the cq1h manual and it is indicated that I/O BUS ERROR results from incorrect connection of the modules but base on my observation modules are connected properly.

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Dirty or corroded pins would be a safe bet. Remove it all from the DIN rail and push-pull the components a few times to 'clean up' the pins. It may work.

Is it internal circuit problem resulted from chemical reaction?

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Possibly but probably pins dirty/corroded.

How can I protect my plc from chemical reaction?

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Put the PLC in a different place. Chemical reaction will affect almost everything electrical even relays.
Not the fault of the product - the fault of the person who put the PLC where it is going to cop this sort of chemicals. A big NO NO!! I do not know of a PLC that is chemical resistant, or a VSD or anything else.
You could put in in a cabinet with positive pressure from a fan that draws air from somewhere where there are no chamicals in the air - that is about it - or move the control cabinet somewhere else where it is well and truly away from where there are chemicals in the air.

Thanks Bob!

I'll just update you if my problem has been solve by doing your suggestion.

With regards to the relocation of the panel I can not guarantee that because it cost much, perhaps I can do something about the fan.

BobB said:

Put the PLC in a different place. Chemical reaction will affect almost everything electrical even relays.
Not the fault of the product - the fault of the person who put the PLC where it is going to cop this sort of chemicals. A big NO NO!! I do not know of a PLC that is chemical resistant, or a VSD or anything else.
You could put in in a cabinet with positive pressure from a fan that draws air from somewhere where there are no chamicals in the air - that is about it - or move the control cabinet somewhere else where it is well and truly away from where there are chemicals in the air.

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I have seen this before in Waste Water Treatment Plants & Lift Stations specifically.
What Bob mentioned is absolutlely correct. The chemical reaction (Hydrogen Sulfide I think) effects relays, breakers, PLC's, radios, etc.
The best thing that we have ever done is to move the equipment away from the gases. I haven't tried the fan yet though.
PLC's, relays, etc. near Waste Water gases = BAD IDEA.

I am worried that the management would not approve the panel tranfer because it will consume long time. Long time for transfer means long time for line stop (no production). Is there any specific design for a chemical proof panel. If you are in my situation how would you protect your plc? How can you shield it from the chemicals in the air and avoid reaction?
Any suggestion for plc isolation and protection aside from control panel transfer?

I would try the fan idea that Bob mentioned if you can't move the panel. As for a chemical proof panel, I haven't had much luck with that.

Thank you for the suggestions. I'll try the fan as the initial solution.

You might try to attach a compressed air line to the cabinet as long as the air isn't to high in pressure & doesn't contain water or the gases. That would pressurize the cabinet to keep out the gases.

Actually I am conceptualizing the design for pressurize air in the panel.Any suggestion for the design?
Air flow in and out....

No suggestions, but I would like to know what you come up with.

Hydrogen Sulfide - nailed that in one. It is evil evil, and will dissolve traces on circuit boards very rapidly, even in low atmospheric concentrations.

For mitigating this (and I've had to in the past), there are a couple solutions, but they all involve some common steps.

1) Seal ALL conduits entering the cabinet. Completely.
2) Seal ALL mounting holes through the cabinet.

Now for specifics - Fresh Air
1) Close off any external vents on the cabinet, except for one smallish exhaust. Run a duct outside the building, with a blower, and positively pressurize the cabinet so there is always fresh outside air exiting through the exhaust vent.

Another option -
2) after completely sealing the cabinet, add an isolated barrier heat exchanger, either air to air or water to air, something like from http://www.norenproducts.com/

Yet another - AC Unit
3) Add a closed cycle AC unit to the cabinet.

Of the three options, #1 is the least expensive, and I've found to be the absolute best. Heat exchangers are the next best. I hate cabinet A/C units. #2 and #3 will only shift the problem, and delay it for a few years, as the copper in the heat exchanger and the A/C unit will also slowly disintegrate, and require replacement.

you may also consider changing the backplane. I've had similar problems due to a poor backplane this one however was in a non hostile environment

Duwop said:

You might try to attach a compressed air line to the cabinet as long as the air isn't to high in pressure & doesn't contain water or the gases. That would pressurize the cabinet to keep out the gases.

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If you use air off a compressor you will have to fight with the oil and water in it. We had EXP panels fixed up like that and they had oil dripping off them. The fan bringing air in sounds like a better idea.