Testing PLC equipment that got wet

if it hasn't burned up disconnect the power and dry it out
i actually had a micro logix get wet while it was running ( Panel Leaked)
I opened it up, used a hair dryer to dry it out , washed everything with electrical cleaner
redryed it, after reassembly it ran for many years before it was upgraded because it aged out.

Pure water has a pretty low conductivity. It's the dissolved ions that determine its conductivity. It's also this soluble matter that causes problems later once the water has evaporated.

So depending on the source of the water, if there's a lot of deposited minerals you're more likely to have issues later down the track with corrosion etc.

Use a cleaner like Gary did. Then dry it out, check for any deposits. Reassemble test

I've cleaned salt water-damaged equipment by removing modules and washing them with distilled water, then alcohol, then dry warm air. I've successfully done that with 1771 I/O that was submerged in cement slurry.

Anything else is taking a substantial risk of premature failure.

Rockwell hardened their warranty and rebuild policies after the Katrina and Sandy storms. Anything flooded with salt water is scrap, and they don't attempt to recondition it.

The thing that keeps me up at night is network address DIP switches. A tiny bit of deposited salt and a humid day and the door left open and a power cycle and some bad luck and you've got the wrong I/O drop turning on its outputs, and you're an expert witness facing a Kentucky jury.

My nightmares are remarkably specific.

Ken Roach said:

My nightmares are remarkably specific.

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That nightmare sounds only slightly better than being the defendant in said nightmare.

One of my senior electricians told me about a large urban pump station in a "big" city here in the 80s that had the switchroom completely flooded during a storm event. They used to build the whole station below ground. He turned up after a high level alarm was received by the autodialer system and after opening the switchroom hatch found water lapping at his boots. All pumps still running, you could see the panel lamps glowing on the MCC (fully submerged!). Eventually the water level returned to normal and they isolated and cleaned out the switchboard as best as possible... but over the next few weeks contactors, relays etc all started failing. Full switchboard replacement required, all the copper bars etc had started to tarnish.

We've had similar, power-washing panels with the doors not latched shut.

Our Client took the decision to replace as the wet components could not be relied upon. But kept them as a "Testbed" for the development of other systems.

On a side note, a lot of industrial components are conformally coated to protect from moisture and to give it longevity.

mad4x4 said:

On a side note, a lot of industrial components are conformally coated to protect from moisture and to give it longevity.

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Considering WHO will be in the plants with their equipment I presume all manufacturers figure at one time or another their component will be submerged or full of coffee, and design for such.

I_Automation said:

I presume all manufacturers figure at one time or another their component will be submerged or full of coffee, and design for such.

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Not a Logitech Wireless mouse !!!!!!!

jimtech67 said:

Not a Logitech Wireless mouse !!!!!!!

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I have tested their keyboards more than once and they hold up nice

jimtech67 said:

Not a Logitech Wireless mouse !!!!!!!

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Change that to "Industrial controls component manufacturers"


Plus, my Logitech wireless mouse, and 2 wireless trackballs have endured quite a lot of mis-use and fluids.

Used to have a technician that washed the PC keyboards in the shower and hung them up to dry...most were fine..we manufactured organic pigment, and this was one way to deal with the colour.
PCs would be stacked high of pigment as it got in the PC vents. This was blown out by cans of compressed air - they were usually Hewlett Packard PCs (90s vintage..) and they worked well with non-conductive pigment.

But, we had a warehouse with a Klockner Moeller MCC, plastic covers, and it was in the "services" corner of the warehouse..
Late one night, the adjacent water main blew, spraying water over the MCC, which had some open gland holes on top...We had a major fire that night, and lost most of the warehouse due to water and electricity not mixing too well...

The problem is you don't know what was in the water. If it was a wet sprinkler system (which about 95% of indoor sprinkler systems are) then there is water sitting in the pipes for literally years and that water can be some pretty nasty stuff. A dry system uses air pressure to keep the water out of the pipes so the water is has a lot less contamination but you still don't know what's in it. The water itself isn't a problem, the "stuff" in the water is what can cause damage over time. With that, Ken makes an excellent point. What's going to happen if the system fails? Will an output go high when it shouldn't and what (more importantly) or who is going to get damaged? I'd replace the system. Look at it this way, you have an opportunity to have insurance help pay for a system upgrade. Take advantage of it.

Back in the old DOS days we connected an IBM 8088 to a tape machine tool. The old 10 pound keyboard would fill with coolant and chips so it went home to the dishwasher.