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VACUUM CHAMBER for DRYING ELECTRONICS

Some time back, it occurred to me that a sufficiently strong vacuum would be useful for drying wet electronics.

After all, water boils at lower temps at higher elevations, and in space, water will even boil at 33F ( 1 C)

Freeze-drying coffee is another example of using high vacuum to desicate stuff.

I hooked up a vacuum pump which had been marketed for bleeding hydraulic brakes and clutches to a pressure chamber for extending the life of tennis balls.  It did not seem to work when I tried rapid drying a damp paper towel. Indeed, my control, another paper towel left out at room temps dried before the one in the vacuum chamber.

I think I've heard of repurposing a refrigeration pump to act as a vac-pump. Someday, I may try that, but would prefer not to have to deal with the freon. Besides that, if someone is scrapping a fridge, and I can pick it up free, will the pump be any good?

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I do some insultating of HV coils with resin in a vaccum.

For that purpose I first used a fridge compressor but upgradednow to a proper 2 stage vac pump used for aircon filling/cleaning.

When using an old fridge compressor I see one massive problem:
Water contamination of the oil!
For small jobs it might be ok, but for ongoing use you will have not much fun.

As an example:

My pump holds about 400ml of oil, using it to dry stuff that is really wet won't work as the oil saturates with water too fast.

To do it properly I can give you these tipps:
Use a good vacuum pump and a gauge - the gauge is needed to monitor the pressure as only when all is dry you can pull a full vacuum.

You can use a fridge pump but it won't pull as vacuum as strong as a pump designed for the job.

To get proper drying without the need of constantly replacing the oil you need a setup that allows for the collection of the water.

Most simple design could be like this:
Pump connects to a suitable container filled with rice, inlet on the top over the rice, outlet (to the next stage) on the bottom.
This container should be frozen over night before use.
Connect the second container with the stuff you want to dry to the first and connect the gauge on it as well.

The container holding the stuff to dry should be pre-heated to about 40° celsius - go higher if no harm is done for the electroniks or whatever you dry. This will speed up the process massively.

When you now turn on the pump the moisture will travel into the cooled container before reaching the pump, in there the water condenses on the cold rice.

It is like a destillation process in reverse.

Once done or the rice is saturated you simply put the container in the oven at 100° until the rice is dry again and ready to be re-used.

Most wreckers and scrap metal collectors can supply a fridge compressor for a few bucks or even free, for more power seek a compressor from an old aircon - the bigger the better.

You might find a pipe that is clamped shut and sealed - this was to fill the system.

To replace the oil you open this pipe and add a valve or in the most simple form a screw to close it.

The same on the bottom of the pump - you need a hole and plug/valve/screw to release to old oil when necessary.

After using expensive vacuum pump oil for a long time I now only use synthetic engine oil with a low viscosity - works as good for my jobs.

I hope this will help you to solve your drying problem for good and cheap.

Toga_Dan (author) 2 years ago

Thanks for the advice everyone. Keep pump runnin, cryotrap to freeze h2o out, fridge compressor.

I suppose that if I acquire a fridge, I'll have to have someone pump out the freon. Any suggestions on how to get this done free/cheap?

Toga_Dan (author) 2 years ago

Thanks for the advice everyone. Keep pump runnin, cryotrap to freeze h2o out, fridge compressor.

I suppose that if I acquire a fridge, I'll have to have someone pump out the freon. Any suggestions on how to get this done free/cheap?

caitlinsdad3 years ago

You have to keep the pump continuously running until the item is dried. You have to evacuate the moisture that is floating around in the vacuum as it dries or it will probably just condense back on your item when the chamber is opened.

Toga_Dan (author)  caitlinsdad3 years ago

I guess I had forgotten about the fact that h2o becomes "the atmosphere" even if a strong vacuum has been produced in the 1st place.

That's why you need a cryotrap for the water. You freeze it out on the chamber once its boiled out of the sample

hazzalandy2 years ago

I have used a couple of fridge compressors as both vacuum pumps and compressors, ( not at the same time, that would be counterproductive!). They move a very small volume of air but can operate at massively high pressures, 600 psi if your plumbing is up to it.