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maleic
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Thanks for the funny video
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RogueRose
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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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Threads Merged
14-1-2016 at 08:47 |
Macom24guitar0
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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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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)
This file has been downloaded 1203 times
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dicyanin
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Water cooling is overkill, I used a ventilator on my fridge compressor, continuously blowing air on the top of the compressor. I have been able to
perform a 12 hour vacuum distillation that way without triggering the overheating sensor.
Recently I've read somewhere that the max. strength of a fridge vacuum pump/compressor could be increased by adding the right kind of hard start
capacitor.
https://www.aliexpress.com/i/32965670749.html?spm=2114.12057...
sic transit gloria mundi
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wg48temp9
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| Quote: Originally posted by dicyanin | Water cooling is overkill, I used a ventilator on my fridge compressor, continuously blowing air on the top of the compressor. I have been able to
perform a 12 hour vacuum distillation that way without triggering the overheating sensor.
Recently I've read somewhere that the max. strength of a fridge vacuum pump/compressor could be increased by adding the right kind of hard start
capacitor.
https://www.aliexpress.com/i/32965670749.html?spm=2114.12057... |
That's probably BS.
Most fridge compressor motors are induction motors.
The motor start capacitor is only used during start so once the pump is running the start cap can not effect the strength of the pump.
I also doubt it can have much of a beneficial during start up any different than a regular start cap.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
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earpain
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| 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? |
My first pump was ripped out of a fridge, and then all A/C or dehumidifier pumps since then. I built a frame on wheels mostly from the parts of an
Air Conditioner on wheels, with the vibration/noise dampeners and all. And I was just throw caution to the wind. Every so often an A/C pump would
get destroyed, and I would already have another old A/C ready to be cannibalized.
Now I bought a very high end HVAC rotary vane pump, 7CFM 2 stage:
http://www.jbind.com/products/product-search-detail.aspx?SKU...
In complete honesty, the A/C vacuum pumps were better. Each had its pros and cons, but what stands out the most is that the A/C pumps hardly made a
sound. I'm talking about prolonged distillations as well. So long as there was no leak, there was hardly any audible sound.
I also experimented with the outlet side as air compressors. Also, blows my mind, how quiet these things are, pushing such high pressure and pulling
such deep vacuum, when compared to their properly labeled and purposed equivalents.
Some advantages to the HVAC pump:
Obviously no special creativity is needed to connect lines to it. THey usually have a T with 3 standard NPT(just like plumbing pipes) thread brass
pipe connectors. And you can choose which ones to block off and which to use.
I have to this day never bought a single ml of vacuum pump oil!
I have used: non-detergent mineral oil, compressor oil, power steering fluid., baby oil
Both types of pumps will take most abuse to their oil. I usually destroyed my A/C pumps with a peroxy-compound and/or acid.
Granted, the HVAC pump can be very easily disassembled, and it's like a little child's puzzle, one can figure out everything without a manual more or
less.
With the freshest oil, on the newest system, with the simplest line/valve/gauge lines that were the least collapsible, with a vacuum still head, both
types of systems have brought me down to sub torr vacuum. I -had- a digital gauge(identical components to a k type thermocouple), and tested against
solvent BP such as propylene glycol.
Why can't the fancy companies, for both air compressors and vacuum pumps, make them silent?
OR do they 'choose' not to? Perhaps because consumers equate loudness with power?
Lastly, granted, the HVAC pump never gets hotter than 50C
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Texium
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Thread Untopped
14-9-2023 at 08:15 |
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