plc chemical reaction

[lostsomemore]

You could nitrogen purge it too.

 

[Andybr]

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.

I am generally in agreement on this however from personal experience I would recommend the fresh air option every time. Copper tubing in an Air Conditioning unit will fail even quicker than your electronic equipment as it only needs one microscopic hole to render it useless. I would also advise you to be careful about the source of your fresh air as it is all too easy to pull in air which is already contaminated in a waste water treatment plant.

 

[Duwop]

I like the fresh air option, as long as it keeps out the contamination.
I work more with Water Treatment & we'v had AC units on enclosures before, but that was another problem in itself. The compressed air was an idea that could work, but I agree about fighting dirt & water. Fresh air is a better way to go & cheaper.

 

[Bobbias]

There are Nema rated enclosures designed for environments with hydrogen sulphide. Specifically, they are under Enclosures for Hazardous Locations (Division 1 or 2), group C, NEC Class 1.

Found that on: http://www.ab.com/en/epub/catalogs/3377539/5866177/5635113/5641752/

In any environment where hydrogen sulphide is present, you should be using enclosures designed specifically for that environment, otherwise you will find out very quickly, how damaging that gas can be.

 

[jetru.llave]

Thank you rdrast.
I agree that option number one would be the best option and it fits my budget. I am going to propose that on our management meeting.

Let us see the result.

thank you so much guys!

 

[jetru.llave]

Thank you Bobbias.

Your suggestion is highly considered.

 

[Bobbias]

Your welcome. I just thought it would be good to point that out, since even if it doesn't end up helping you out directly, maybe someone else will see it and save themselves the trouble of dealing with enclosures that aren't designed with the environment in mind, like you have to.

 

[Tom Jenkins]

A a quick (and perhaps temporary) solution, I have had some success with those little corrosion inhibiting cartridges that Hoffman and others sell.

The problem with a fan is that the H2S is pretty well distributed in many wastewater locations. You would almost have to duct the air from a "clean" location. Otherwise the fan may just replenish the supply of corrosives!

 

[Gil47]

I see this type of corrosion in certain areas where I work and my observations are that it is always worse if there is a moist atmosphere or humid.

I have often thought that a household type of dehumidifier would go a long way to reduce the thick, heavy corrosion that appears, and only leave you with a low level of corrosion that would always be present unless the panel is fully sealed.

 

[rdrast]

A a quick (and perhaps temporary) solution, I have had some success with those little corrosion inhibiting cartridges that Hoffman and others sell.

The problem with a fan is that the H2S is pretty well distributed in many wastewater locations. You would almost have to duct the air from a "clean" location. Otherwise the fan may just replenish the supply of corrosives!

True, which is why I always ducted it in from literally outside the building, with a 2 or 3 foot intake vent stack. The concentration of the gas inside every building I was ever in was 200-300 times that which was measurable outside on the roof or at least 8 feet above ground level.

Also, when working in an environment like that, tis obviously best to air out the area thoroughly before entering, or use approved breathing equipment.

 

[Bobbias]

Well, part of the problem with Hydrogen Sulphide is that even though it's toxic to us, we can survive lower concentrations with little reprocussions, but those same levels are very damaging to electronics. If it had been more dangerous, the buildings would be more adequitely designed to get rid of it, and we'd have less of a problem with the electronics, lol.