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Author: Subject: LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS!
maleic
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[*] posted on 26-2-2015 at 00:06


Thanks for the funny video:D
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RogueRose
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[*] posted on 14-1-2016 at 05:47
Vacuum pumps from consumer products (compressor modifications)


I am in need of a vacuum that can pull a pretty high level of vacuum (ideally 24" Hg.) for an extended period of time (maybe 30 mins on - 10min off - repeat). I am capable of adding some kind of cooling to the compressor whether it is mearly a fan or enclosing the housing with a water jacket & running cold water through it - IDK what else may be possible.

I know fridges and freezers have compressors that will work for vacuums but are there other products that do as well? I would think maybe AC's and dehumidifiers may have something like this?

Anyone have any suggestion of other products?
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Bert
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14-1-2016 at 08:47
Macom24guitar0
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[*] posted on 13-3-2016 at 16:11


Many years ago when I didn't stick to the theoretical side of the equations. I had to solve the same problem concerning both vacuum & water for condensers, steam distillations, clean ups, etc. Since my "Shop" had neither running H2O or drains I had a number of issues to deal with. First I had to study & grasp the Bernoulli principle then I ordered a small submersible pump picked up some 1/2"pvc and glued up a little loop that led from my pump at the bottom of a 7gal. pail up thru my bench down to my aspiration and back into the pail. This device was not powerful enough, but was ideal for the condenser, so it wasn't wasted time, I found a 1hp submersible and used 3/4" copper pipe, and a 25-30gal. drum for my new aspirator and it worked great when the water was cold, so I kept. Half dozen plastic milk jugs in the freezer and it sucked solvents thru the Buchner in seconds and allowed me to distill at temperatures that indicated a vacuum of 14torr. With the addition of a cold finger trap it was ideal for my limited horizons. It's an inexpensive, inconspicuous, and easily built solution.
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XeonTheMGPony
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[*] posted on 6-9-2016 at 07:57


Quote: Originally posted by RogueRose  
I am in need of a vacuum that can pull a pretty high level of vacuum (ideally 24" Hg.) for an extended period of time (maybe 30 mins on - 10min off - repeat). I am capable of adding some kind of cooling to the compressor whether it is mearly a fan or enclosing the housing with a water jacket & running cold water through it - IDK what else may be possible.

I know fridges and freezers have compressors that will work for vacuums but are there other products that do as well? I would think maybe AC's and dehumidifiers may have something like this?

Anyone have any suggestion of other products?


Not sure if relevant for you, but I'll answer it for others who view it:

A reciprocating compressor commonly used in fridges will easily do 25" of mercury sustained as long as it is running

To use it as a vacuum pump one simply needs to remove the oil and replace with 200sus Mineral oil, and provide some form of cooling, if lucky to have a unit with an oil cooler in it you're set! Other wise sanding down the bottom and soldering on a coil of copper tubing to flow water through will suffice to cool it!

You must make a vacuum trap to prevent fluids or solids to get into the gas stream, and a chemical absorber to keep acid vapors out of it.

Window air conditioners and newer dehumidifiers use rotary vane compressors, they will pull a deeper vacuum, but they will run hotter and oiling is a bit trickier to keep it running long term.

Deep freezer compressors are the best for using as a vacuum pump as they are designed with the rarefied gas atmosphere taken to account for the piston displacement, Old R-12 ones are even better of a find due to them all ready using a mineral oil (All though I do recommend switching to the heavier grade as it will improve operational life time and vacuum achieved!)

All ways have the R-12 properly recovered as it is very detrimental to the environment!

Now the discharge! You need to make an oil capture jar, this can be as simple as a jar with the pipe sticking into the lid and a hole for the exit to capture any oil mist, to a nice coalescent unit!

There is allot you can do to make advanced systems or a simple crude system to give a very good vacuum system.

Attachment: Oil cooling diagram 2.pdf (65kB)
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