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tnhrbtnhb
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cheap vacuum pump that can get down to 17 torr
How can I get or build a cheap vacuum pump that can get down to 17 torr (enough to boil water at 20 deg. C) ? I've searched this site and others,
the best I can find is venturi pumps that pump down to 42 torr or so (28.3 inches Hg below atmospheric) (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnu... .) I have a small air compressor with a resevoir, just for car tyres type thing.
I have asked on a hv/ac forum, and those guys say the vacuum pumps used in their industry only pull aka get below atmospheric by 29.9 "Hg, plus they
cost some serious $.
They also tell me using a fridge compressor will not get below 150 torr.
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Sauron
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Get on to labx and stalk your wily vacuum there, a second hand PTFE diaphragm pump is what you want.
I got a little KNF Neuberger on there that according to the stickers came out of an SKF lab (Smith Kline & French.
I think I paid $150 for it.
Later I bought a new Gast rotary vane pump that I paid $800 for locally, not worth a damn, the ultimate vacuum is not as good as my Eyela dual
asprator pump which pulls well under 20 torr.
[Edited on 13-1-2007 by Sauron]
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MargaretThatcher
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| Quote: | Originally posted by tnhrbtnhb
I have asked on a hv/ac forum, and those guys say the vacuum pumps used in their industry only pull aka get below atmospheric by 29.9 "Hg, plus they
cost some serious $.
They also tell me using a fridge compressor will not get below 150 torr. |
ac vacuum pumps are generally 2-stage rotary pumps. They will pump down to much less than 1 torr. You can pick up second hand ones fairly cheaply.
Change the oil if you need to get down to really low pressures.
It depends what sort of fridge compressor you have. You can still find some of the older rotary pumps that will get down to 1 torr or so in large
freezers and air conditioners.
http://www.belljar.net/refrig.htm
The reformative effect of punishment is a belief that dies hard, I think, because it is so satisfying to our sadistic impulses. - Bertrand Russell
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Magpie
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Checkout the specs for the Yellowjacket line:
http://www.yellowjacket.com/PDF/SuperEvac_Vacuum_Pumps.pdf
They claim an absolute pressure of 15 microns. I believe a micron is 10E-6 mHg or 10E-3mmHg. So 15 microns would be equal to 0.015 torr.
These Yellowjackets are frequently found on ebay.
The single most important condition for a successful synthesis is good mixing - Nicodem
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MargaretThatcher
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Those yellowjackets are much favoured by those over the pond. Can't see if it has got an oil mist filter - those are important if you don't want to
inhale the stuff (and you don't).
The reformative effect of punishment is a belief that dies hard, I think, because it is so satisfying to our sadistic impulses. - Bertrand Russell
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Sauron
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Vacuum pumps are not all created equal. Some pumps types that are perfectly fine for purging a Ac or fridge prior to putting in new refrigerant are
simply not at all a good idea for a lab.
The issues are not merely performance.
You have to consider exposure of pump materials to corrosive vapors, because you cannot count on your cold trap all the time.
You have to consider how different pump types handle flammable vapors.
Oil pumps are a pain.
And that is why I prefer to work with oil free PTFE diaphragm pumps. My fave is the Buchi V-500 series and esp the V1000 which is two V-500 set in
series for high capacity or parallel for low ultimate pressure. Not cheap new but sometimes turn up on LabX or eBay. I also have a V805 digital vacuum
controller which is very handy, sure beats a manometer and McLeod at least till you get down to very low pressures.
The KNF Neubergers are also very good.
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MargaretThatcher
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I think he is after something cheap that will pump down to 17 torr. To me, that gives 3 choices: 1. recirculating water-jet pump (US aspirator) with
cold water; 2. 2nd hand oil rotary pump (heating engineer pump etc.); 3. homebrew rotary pump from old freezer or a/c unit.
For many, a 2nd hand air rotary pump is the best combination of price/performance with minimal construction effort. Water-jet pumps are a cheap way to
put something together that is resistant to corrosive and high vapour pressure oil contaminants.
Yes, a PTFE diaphragm pump is great for certain jobs, just like a Bentley is for certain trips. If I had the spare cash to buy one, I'd spend it on
something else.
The reformative effect of punishment is a belief that dies hard, I think, because it is so satisfying to our sadistic impulses. - Bertrand Russell
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Sauron
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I got that KNF Neuberger PTFE diaphragm pump for $150
If you go see what the price is for a Nalgene aspirator (just a handful of plastic) it isn't that far off.
I used to use one of those. But Bangkok does not have cold water. My Eyela recirculating dual aspirator new cost me $800 plus another $400 or so for
gauge and chiller tube.
So all in all I hardly think $150 for a 2nd hand PTFE pump is splurging.
Cheap and dirty often does not get the job done. An unsuitable pump that results in an exlosion when you evacuate say, ether, or that gets corroded to
death when evacuating say, HCl gas, to cite two frequent applications, are not much of anyone's bargain.
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S.C. Wack
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| Quote: | Originally posted by Sauron
I got that KNF Neuberger PTFE diaphragm pump for $150
If you go see what the price is for a Nalgene aspirator (just a handful of plastic) it isn't that far off. |
OK...*goes to www.nalgenelabware.com*...they're $11.27 each, in a case of 24. Cole-Parmer sells them for $12.40 for a single one.
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MadHatter
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Vacuum Gear
A picture of my vacuum gear is in this thread:
(4th post in thread)
http://www.sciencemadness.org/talk/viewthread.php?tid=1649#p...
IMHO, for most applications in chemistry, the hydroaspirator is still the best vacuum source.
Pulls a decent vacuum, cost effective, and washes many nasty fumes down the drain.
If mine goes up I'll pay the $12 for another one !
An example of water vapor pressures at given temperatures:
SELECT VAPOR PRESSURES OF WATER:
UNDERLINES USED TO MAINTAIN SPACING
KPA VALUES FROM CRC 85TH PAGE 6-8
_C__/_____F__/______KPA__/____TORR__/__HG(INCHES)
_0__/__32.0__/____.61129__/___4.585__/__29.74
_1__/__33.8__/____.65716__/___4.929__/__29.727
_2__/__35.6__/____.70605__/___5.295__/__29.712
_3__/__37.4__/____.75813__/___5.686__/__29.697
_4__/__39.2__/____.81359__/___6.102__/__29.681
_5__/__41.0__/____.87260__/___6.545__/__29.663
10__/__50.0__/___1.22810__/___9.211__/__29.558
15__/__59.0__/___1.70560__/__12.793__/__29.417
20__/__68.0__/___2.33880__/__17.542__/__29.23
25__/__77.0__/___3.16900__/__23.769__/__28.985
30__/__86.0__/___4.24550__/__31.843__/__28.667
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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Sauron
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And in Thailand where I am the Nalgene agent gets about $40 as they want to make a profit and the import duty on plastic products is high for
protectionist reasons.
I have used a Nalgene aspirator before here, with municipal water supply which is rather warm and indifferent results but adequate to evacuate a three
liter rotavap.
Also used a pricier Nalgene hand vacuum pump with a gauge, local agent did not stock the gaugeless version, that one DID cost me about as much as the
KNF Neuberger, of course I got a lot of useful hand exercise out of it.
I still liked the KNF better, although it was US voltage and I had to run it off of a stepdown transformer.
I seem to recall plans for building your own Siibata or Eyela style recirculating aspirator, single or dual, on Rhodium. That would be a simple
project for the non-craft challenged (craft nonchallenged I mean) requiring a plastic tank with a lid, a sump, two asprators, and some tubing. Add
icewater and away you go. That will get you <17 torr for cheap. You might want to throw in some ice once in a while, provide for overflow, and
change the water every few days before it starts to stink or before accumulated acids can corrode anything.
I elected to throw money at the problem just because I have more of that than time and patience for DIY projects.
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Sauron
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If anyone is interested I can scan and put up the illustrated manual for my Eyela dual recirculating aspirator with accessories.
Much better illustrations than the DIY piece on Rhodium. The Eyela asprators are plated steel but no reason why the Nalgene jobs would not do.
Costliest component will be finding a sump (submersible electric pump) with right capacity. Hit eBay.
Let me know if anyone wants this.
[Edited on 15-1-2007 by Sauron]
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Sauron
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I am not suggesting that anyone do what I did but rather than you build your own for a small fraction of the selling price of the commercial one.'
The pump on this A1000S has 150W output power and it has more than enough displacement to keep two aspirators happy.
If the water is cold (5 C) this unit will achieve 13 torr. By my own experience its displacement is quite good. It is oretty much a copt of the
Siibata model which Buchi used to sell under their own name.
Note that the two independent asprator ports can be joined with a simple Y-adapter to make a single vacuum line, or you can evacuate two systems at
same time.
There's an overflow valve so you can just keep chucking in ice to maintain low water temperature. Or if you have a recirculating chiller to cool your
condenser, you insert an optional cooling coil and plunb it inline. As my local mains water is warm, I use a chiller for this purpose.
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Sauron
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@S.C.Wack, this is OT but you mentioned Cole Parmer. I have their full catalog as well as their Encyclopedia Microflex.
I have bought from their local agent for years.
Recently I imported a Labconco glove box with gloves from USA second hand. It was properly declared and it included a pair of neoprene glove box
gloves/gauntlets. US Customs did not require any special paperwork at all and neither did Customs here.
The gloves were old and needed to be replaced so I looked them up in Cole Parmer, expensive but what the hell. I got a bargain on the box and it is
useless without gloves.
I ordered them. Three months later I was still waiting. After a number of outright lies the agent finally told me Cole Parmer was waiting for an
EXPORT LICENSE approval from the US Government.
I'm a US citizen in a country that's a US major non-NATO ally (MNNA). It's a pair of ordinary neoprene gloves. I got mad and cancelled the order.
And now am looking for a vendor that is in a country that does not have its head up its ass.
The obstructing agency is the Commerce Department, the State and Defense Depts do not care.
What BS!
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quicksilver
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I know this is a bit OT but does Thailand import from mainland China? There must be a boatload of labware concerns made in China....
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MargaretThatcher
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I would have thought that Thailand itself would have some pretty good on-going concerns, especially for a resident Yank.
The reformative effect of punishment is a belief that dies hard, I think, because it is so satisfying to our sadistic impulses. - Bertrand Russell
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Sauron
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@Maggie, please explain what you mean by your comment.
Do you mean that I should be worried about Thailand or vice versa?
Actually the answer is neither.
What are your concerns about Thailand? A very safe place for Thais and expats alike.
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MargaretThatcher
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I don't mean dangerous, I mean readily available lab. equipment and for a good price. I found a good outlet a while back in Bangkok.
I agree that it is a very safe and nice country.
(Edit: concern = business)
[Edited on 18-1-2007 by MargaretThatcher]
The reformative effect of punishment is a belief that dies hard, I think, because it is so satisfying to our sadistic impulses. - Bertrand Russell
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Sauron
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@Mrs. T., sorry, I misunderstood.
Lab equipment companies in Bangkok are usually happy to do business with anyone with a local corporation or other form of business entity and not too
happy about individuals. I do have a corporation, and am thinking about setting up a not for profit foundation for chemical research and education. It
takes a million Thai baht ($20,000 US and change) cash or equivalent in goos, I have a lot more than that worth of lab equipment and chemicals. It
takes ten people to form such a foundation and it has to be vetted by the National Culture Ministry and the Special Branch of the National Police but
that is not a big problem. I've got appropriate people for that including a recent Thai chemist retiree from the National Research Council.
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MadHatter
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Vacuum Gauge
Sauron, that's cool if you can get a non-profit group setup. If it means easier access to
what you need it's well worth it IMHO. It sounds like, that beyond the initial vetting,
you'll have few, if any, problems with the authorities.
Back on topic. I just ordered a laboratory grade vacuum gauge from eBay. It goes from
0 to 750 mm(Torr) Hg. The only other gauge I have is on an automotive vacuum pump.
It reads in inches Hg and kPa. I don't have faith in the accuracy of this device.
When connected to the hydroaspirator the gauge shows over 29 inches Hg being
pulled but I want a more accurate device, and in Torr.
The biggest problem I had with the hydroaspirator was setting up the combination
of adapters to run it off the kitchen faucet. There was no convenient faucet-to-1/4" barbed
adapter in the hardware store. I already had the faucet-to-garden hose(3/4") adapter.
Got that one to run my still !  So the combination of faucet-to-3/4",
3/4"-to-1/2",
1/2"-to1/4" barbed, all wrapped with teflon tape was the only OTC method available.
The cost was low even for brass fittings and less then the hydroaspirator.
The nosy cashier at Lowes asked me what all that was for. I told her I needed it for a chemistry
application that requires vacuum. She got a dumbfounded look on her face at that point
which I interpreted as "What a fucking geek !". Better than "terrorist" or "meth-cook" !
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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Sauron
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@MadHatter, I suppose so! Actually I had the same problem (adapting aspirator to faucet). Fortunately here the machine shops work cheap so I just had
an adapter made up out of brass hex stock. Still had trouble because water temp was never cold and in daytime was downright hot.
And that's why I went to other systems.
What brand is the vacuum gauge?
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Maya
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the automotive vacuum , or ac/ refrigeration pump gauges are really bad for accuracy
Best for me was the digital kind, SUPCO VG64 DIGITAL VACUUM GAUGE
0-12,000 microns claimed
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
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Sauron
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@Maya, sounds nice. I have a digital Buchi V805 purchased new for godawful price, it's not just a gauge but a controller with a microprocessor to run
a valve. Intended primarily for rotavaps. The display is in torr or mPa or psi at your selection, Variable hysteresis, programmable controls. I
hardly ever used the control aspects and didn't much care for the "automatic distillation" stuff, but as a gauge it is good but overpriced. This one
is nomainally 220V but runs perfectly on 110 anyway. However it does not have a bottom end as low as the one you describe.
What sort of $$ is the Supco?
[Edited on 19-1-2007 by Sauron]
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Maya
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I picked it up new for $80 or so at a well known place that sells these things. but they usually retail double that
The J-Kem controllers looked nice to me for programmable solutions until I saw their prices, tho still reasonable for academic purposes
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
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MadHatter
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Bourdon
Here's a picture of it. It's analog but it has to be better than that automotive vacuum pump
gauge.
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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