subversive cooling issues

[wildrabbitt]

Hi,

my latest idea for my submersive cooling system is to paint the capacitors on


the PCB in the PSU with gloss paint so that no chemicals leak from them

because I came to the possibly erroneous conclusion that chemical leaks from

the caps is the reason that the transformer oil in the tank is getting

contaminated.

Three questions:

1) Could my conclusion be correct?

2) Is there something better I can do?

3) If I painted the whole of the PCB except the heatsinks in gloss paint, would it work still?

[VBCurtis]

What does gloss have to do with it? Does your paint conduct electricity? Are you sure?

How would you get paint under the caps?

[wildrabbitt]

My reasoning was that since emulsion dissolves in water, it might dissolve

in transformer oil whereas gloss paint being waterproof wouldn't allow the oil to get into contact with the insides of a capacitor.

The idea was to paint the outside of each capacitor thereby creating an impenetrable film to keep the inside and outside apart.

I've found excretions on the metal part which shows on the tops of capacitors.

I'm not certain gloss paint doesn't conduct but I'd put a bet on it.

[CRGreathouse]

Maybe something like this?
http://www.aremco.com/electrical-coatings/

[retina]

You'd probably only need to paint the tops, and put a ring around the bottom to stop the oil from getting underneath the cap. As whether you use paint or a proper sealant it up to you, but I would choose silicon RTV (or equivalent), it is designed to seal and is oil resistant. The extreme heat resistance is not important because everything is never going above 100C.

ETA: The caps have been designed for outgassing to prevent <something, not sure what>, so you might want to look into that scenario also.

[Xyzzy]

Originally Posted by retina

Reason: Maybe they explode if sealed?

They sometimes explode during ordinary usage, so sealing them seems to be an interesting gamble.

[Madpoo]

Originally Posted by retina

You'd probably only need to paint the tops, and put a ring around the bottom to stop the oil from getting underneath the cap. As whether you use paint or a proper sealant it up to you, but I would choose silicon RTV (or equivalent), it is designed to seal and is oil resistant. The extreme heat resistance is not important because everything is never going above 100C.

ETA: The caps have been designed for outgassing to prevent <something, not sure what>, so you might want to look into that scenario also.

Electrolytic caps have a fun "feature" that will vent outwards if there's an internal short or overvoltage. Otherwise you'd have a pressure vessel explosion (on a small scale of course). I can't count how many caps were exploded in my various electronics labs by myself or others... drove our professors nuts when you'd hear the telltale pop and a whiff of smoky oil.

Anyway, electrolytic caps could, I guess, have some leakage in/out of the device itself, thanks to the required venting. If you coated it in something and there was an internal short and the thing just had to go "pop", I suppose what happens next depends on the size of the cap and the thickness of whatever you coated it with. It may still vent out the proper hole, or you may get something more dramatic.

For example, I wouldn't want to totally seal a large capacitor and then have it arc inside and explode, having sealed the vent on it. Just google "capacitor explosion" and you'll get an idea of what happens even when it's allowed to vent.

In regards to non-oil filled caps (ceramic, etc) they don't do anything too spectacular when they fail except make a funny sort of crinkling noise and a slight whiff of ozone-ish smell. If you even notice at all.

[bgbeuning]

Originally Posted by wildrabbitt

reason that the transformer oil in the tank is getting

Some capacitors have lines etched in the top so when the cap needs to vent
the lines will give first and it can vent in one direction instead of all directions.
If the lines are in tack, it has not vented.

Your PC has 100's of parts made by many different vendors following different
standards. How do you know some part is not soluble in oil?

[kladner]

Originally Posted by Xyzzy

They sometimes explode during ordinary usage, so sealing them seems to be an interesting gamble.

I was once sitting at my desk when I heard a soft "poof" sound, and the screen went blank. A cap had blown on the graphics card.Fortunately, I had a backup, and the blown one was under warranty.