PirateDocBrown
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Thoughts on a cheap vacuum pump?
Been looking at this:
https://www.amazon.com/Super-Deal-Single-Stage-3-5CFM-Refrig...
Anyone try one like this for filtration or vacuum distillation?
Or can offer a better choice?
$50 shipped is hard to beat.
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Ursa
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I mean, If you're making small amounts of any product, an aspirator can work. That is, only if you have an adequate water supply. Also, you could also
make your own pump out of the fridge pump megathread....
[Edited on 10-3-2017 by Ursa]
Vivo!
Ens causa sui
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PirateDocBrown
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Modding a fridge pump seems silly vs. spending 50 bucks.
[Edited on 3/11/17 by PirateDocBrown]
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AvBaeyer
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Go for it! I have one just like this which will pull 0.3 - 0.5 mm Hg on a well set up vac distillation system. These pumps are so cheap they are
almost disposable should they gum up. I change the oil frequently and it just keeps going.
AvB
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Ursa
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Yeah, you're right for cost efficiency, mea culpa, but for efficacy of the pump, the fridge would be markedly better. That's the main reason why it
came to my head.
Vivo!
Ens causa sui
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ElizabethGreene
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Unless you will be doing vacuum distillations that require extremely low pressures, I'd suggest an aspirator too. Every time I do a vacuum filtration
with my AC pump I'm pulling solvents into the pump's oil. With an aspirator that isn't a concern.
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RogueRose
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I found this pump while comparing items from the auction I was bidding on. They are $450-600 new but can be had on ebay for a good price.
I have a pump similar to the one you posted, it's 1/3 HP rated at 2.5CFM and 110PSI (I highly doubt it) by harbor freight. It was meant for air
brushing. It gets SUPER hot after 20 mins running under NO load, just blowing air into about 8" deep water (so some load). These things are not
worth the $$ IMHO.
NOTE: HEAT is not always the enemy when dealing with pumps, especially on the vacuum side. As the head heats up any moisture in the air will be
vaporised (if sufficient heat is available) allowing it to be expelled. If moisture collects in the pump head (where bearing grease or oils are often
present) the oils and grease can be degraded drastically shortening the life of the unit. So if the unit gets hot, that isn't an issue unless it is
hot like a stove top. I really don't know a temp which is over the recommended level but I know people who deal with vacuum forming stuff (car parts,
boat hulls, kayaks, etc) all use pumps that get hot and stay that way for 3-24 hours at a time.
The name of the item is: THERMO SCIENTIFIC 420-1901 VACUUM PRESSURE PUMP and I've attached the manual to see if it might be what you need.
Here is the unit for $39.99 + $7 shipping - Ebay listing
Listing on Ebay $49.99 Shipping is a little though.
Here it is for $480
For $435
A compressor/vacuum from a AC unit (or fridge/freezer) would blow the socks off these pumps anyday. you could find a unit free on craigslist or maybe
buy a beat up unit for $10-40, pull the compressor and take it to the scrap yard (or curb pickup in some areas).
I also have some compressors from old air conditioner units as well as dehumidifiers. The unit from a 5600BTU AC is about 4x the HP of the
dehumidifier (which wasn't a small unit). The thing is that they are SUPER quiet and they can be used for compressors as well, easily generating over
300PSI of compressed air (a propane tank can hold this pressure if it is still certified) so that is a benefit of the. They may require oil to be
added to the intake line ever X hours of operation (depends on what it is drawing as vacuum - like solvents or moist air). It can be a little
daunting to set them up as there are 4-7 wires that can be confusing and you NEED the starting capacitor. I've figured this out and can help if you
decide to go this route. If you find a motor that doesn't start at all, the chances are it is just a bad capacitor as from what I have heard the
motors very rarely go bad unless the unit was in a fire or something 
Attachment: THERMO SCIENTIFIC 420-1901 VACUUM PRESSURE PUMP Manual.pdf (116kB)
This file has been downloaded 226 times
[Edited on 10-3-2017 by RogueRose]
[Edited on 10-3-2017 by RogueRose]
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Liamatpm
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I am also thinking about get a vacuum pump
I am also thinking about get a vacuum pump .
This is the one I think I am going to get:
https://www.amazon.com/dp/B012CFTYX4/ref=wl_it_dp_o_pC_nS_tt...
I think it's a bit higher quality but I'm not sure.
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PirateDocBrown
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Pulled the trigger. Delivery expected within a week. Will report on arrival.
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PirateDocBrown
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Okie dokie! Arrived today! Filled it with oil, and am looking for a barb nipple to fit it to some hose. Turns when plugged in and switched on, though!
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Corrosive Joeseph
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Oooohh. Waiting patiently................... 
/CJ
Being well adjusted to a sick society is no measure of one's mental health
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PirateDocBrown
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Set up and running.
I got a 350 mL 9cm #3 frit with a 24/40 joint and vacuum connection.
I just set it up on a flask with a ring stand clamp and hooked it up to the pump, and it works.
Water will stand on top of the frit when the pump is off, but will be rapidly pulled through with it running.
Rigged a 250 mL sidearm Erlenmeyer with a one-hole stopper and some bent glass tubing to serve as a suckback trap. Guess I could put in some
neutralizer solution as needed, as well. (Thiosulfate, hydroxide, bicarbonate, etc.)
I'm in business (for filtration, anyway)! Need to get some paper to sit on top of the frit and keep it clean.
It's really quite wonderful to have one's own lab, and not merely some employer's or university's! I haven't felt like this since I was a kid with my
Skilcraft set!
[Edited on 3/28/17 by PirateDocBrown]
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