Refrigerant recovery unit -- vacuum pump?

I won a Sun "refrigerant recovery unit" in a military auction for $55. I have not picked it up yet, but it looks to have been used very
lightly, if at all (I'll see, it is rated A4). As I learned after I won it, it is for "old style R12" systems, whatever that is. So it is not that valuable.
My issue is that I need a vacuum pump. Are vacuum pumps in these machines any good and can they be ripped out and outfitted with regular 1/4" NPT fittings.
Thanks
i
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R12 is a refrigerant that is/was commonly used. It is gawd awful expensive these days. Small amounts can be recovered from refrigerator freezers and old working auto air conditioning units. But it will have contaminants in it, and the processing equipment to clean it up can be costly. Also, you will need a tester to identify the refrigerant you are working with to keep from mixing them, which makes them nearly worthless. The fractional distiller to separate mixes is very expensive. Also, you will need licensing and accreditation to legally be messing with this stuff. I know you need a license to buy it, but am not sure what you will need to sell it. Perhaps you will just keep it back for your own use. Not a bad idea if you have been to a car shop lately and priced AC work. Other common refrigerants are less expensive, but you would have to read the manual, or find out if you can do various refrigerants in YOUR apparatus.
HTH, and good luck.
Steve
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Yes, you do need a license to buy the stuff, but that's a relatively moot point. You can get a certificate for about $20. There is an online test that you take to get the cert. I don't have the link off hand, but it's a pretty basic test. If you can't answer the questions, you shouldn't be messing with A/C anyways.
It isn't that big of deal to convert most R-12 systems to R-134. And R-134 is off the shelf. At least in Minnesota. Biggest thing is flushing the system of the old oil and using R134 compatible ester oil.
JW
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for the $20 certificate, see http://www.macsw.org/imaca.php

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"Steve B" wrote: (clip) you would have to read the manual, or find out if you can do various refrigerants in YOUR apparatus. ^^^^^^^^^^^^^ I got the impression from what the OP wrote that he wants to use this thing as a vacuum pump, not as a part of a refrigeration system. Lots of my friends use the pumps out of refrigerators and ice machines for pulling a vacuum--specifically, vacuum chucking on wood lathes. They work fine.
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wrote:

Yes, I am not really looking to get into the "refrigerant recovery" business. I was thinking about ripping out a vacuum pump from that unit and using it as a vacuum pump for general purposes.
i
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That's why its hard to answer your question. I have a couple of lab vacuum pumps that pull a much better vacuum than a refrigerator type compressor used as a vacuum pump. But yours might be suitable for what you want to do.
Ignoramus13653 wrote:

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Thanks Steve. What you wrote was very educational. I think that I would not want to go into refrigerant recovery, as such. I was just hoping that I could rip out a vacuum pump from that unit and use it for general purpose projects.
i
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On Fri, 27 Jan 2006 17:30:16 GMT, Ignoramus13653

Depends on why you want a vacuum. Such a pump should pull at least 28" of Hg, which is useful for some purposes but not for others. It's fine for degassing molding materials, not nearly enough vacuum for sputtering mirrors or metallization.
What would you use it for?
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wrote:

My first use would be desoldering. I am not sure about future uses and whether I would need "deep vacuum". Good question though. In terms of percentage of air that such pumps remove, would you know how good are these refrigerant removal pumps?
Thank you
i
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On Fri, 27 Jan 2006 19:51:53 GMT, Ignoramus13653

If it pulls 28 in of Hg, and atmospheric pressure is 29.9 in Hg.......do the math!
It would work fine for desoldering if you have a vacuum reservoir. The pumps are low volume pumps but a reservoir could provide a pulse of vacuum when you open a valve. A suitable valve might be the little pushbutton valve in a cheap blowgun, as: http://tinyurl.com/cweo9
I've seen these at HF for about $2.
A suitable vacuum reservoir might be an old 16.4 oz propane bottle.
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wrote:

Thanks Don. I will see what kind of pump is in that unit, and will try to decide, but your information is very helpful. As far as "do the math" is concerned, you are right, but the answer depends on just exactly how much "above 28" the vacuum is.
i
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On Fri, 27 Jan 2006 22:10:26 GMT, Ignoramus13653

It does indeed! Some pumps in good condition will go down to microns of Hg. That would make no noticable difference for degassing or soldersucking.
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Thanks, Don and others. I picked up the recovery unit today and will check into it. A lot of good advice was given.
i
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A recovery unit has a lot of extra stuff in it because it has to cool the compressed refrigerant before it goes into the cylinder. You can probably strip out the pump but the other parts fall into that permanent junk box classification of "useless but to valuable to throw away". :-)
If it is in good condition the pump should pull down into the mili-torr range. My cheapo little RobinAir will easily peg a normal vacuum gauge. It can't keep up with my Sargent-Welch but then you can't pick up the S-W and haul it around the shop.
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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Milli-torr is certainly very encouraging.
I think that if I cannot sell the unit for much more than a comparable pump is worth, I would just disassemble the unit and keep the pump.
Thanks Glenn.
i
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I wonder if some people responding are confused with the type of "pump" you have. I do HVAC work and we have three or four recovery pumps around. None of them will pump much more than 10" of HG. We have several vacuum pumps to "vac" the system down when doing repairs that will do much lower vacuum, down in the 100-200 micron range. Recovery pumps are painfully slow at pulling a vacuum, their job is to remove refrigerant. Depending on what you plan on doing with it, it may be enough, or not! Greg
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Thanks for pointing that out. Unless it is a recovery/recharging station I certainly wouldn't expect that much out of it either. The recovery unit I used years ago for automotive systems shut the system off at about 17 inches Hg. It also had a scale and a circulating pump and filter for cleaning the reclaimed refrigerant. It was essentially a refrigerator compressor with some valving.
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Ignoramus13653 wrote:

For what you want it for, desoldering, and maybe some future vacuum clamping, it should work for you but with one, in my opinon hassle. Some vac pumps made specifically for pulling down A/C systems are piston driven and have a lubricant in their crankcase. Some, actually allow the Freon to go thru the crankcase not much unlike a two stroke engine. This is the case with your rotary automobile pumps and Refrigerator pumps.
What this might mean for you is oil mist in the exhaust side of your pump, and you need to catch it. If it is USED to lubricate the pump, you need to replace the lost oil somehow. Additionally, that oil mist is not beneficial in certain shops (like a body shop).
For what you want, and if this one does not work out, watch ebay for a Gast or Thomas oiless rotary vane pump like this: http://cgi.ebay.com/1-3-HP-Gast-Vacuum-Pump-compressor-0523-101Q-G582DX_W0QQitemZ7584558664QQcategoryZ109622QQrdZ1QQcmdZViewItem
These will run clean and relatively quiet, pull 26 to 28 inches, often plenty for clamping with a good seal. They can be put on a tank as long as you put a checkvalve in it so it does not run backwards when you shut it down.
Even though these are always rated as continuous duty, you can throw a swtich in line to cycle it on and off once the tank is full.
If your going to desolder, be sure to locate a tank or cleanable vessel between you or the pump... the solder has to go somewhere !
Grummy
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Glenn Ashmore wrote:

I have a medical vacuum pump. Would it be suitable for A/C system evacuation? Any idea if medical pumps have to meet a lesser spec in terms of in/Hg?
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