Need Help choosing a vacuum pump

[Teck]

Hello, i need to buy a vaccume pump for distilling nitric acid, I have unitedglass, glassware and I need to know if this pump will collaps my glassware cause it looks pretty powerful but if anyone knows please help out.

Gast DOA P115 AA air compressor vacuum pump
It is 115 volts, AC-DC,4.2 amps, and HZ 60
http://abacus.sj.ipixmedia.com/abc/M28/18d7768be856f1299325e3d596/i-1.JPG
http://www.gastmfg.com/vacuum.html


[This message has been edited by Teck (edited August 18, 2001).]

[10fingers]

My vacuum distillation setup is from united glass tech and I use a refrigeration type vacum pump. It will pump down to 30 in. of vacuum, which is near total evacuation. This glassware is designed for this and will not collapse.

[megalomania]

If you are using scientific glassware, especially the Standard Taper kind, it can sustain very low pressures. Check to make sure there are no cracks or chips whatsoever, the stresses at those points can be tremendous, and then it will implode. I recommend some sort of screen, like the plastic kind you can get from a hradware store for screen doors, metal would be better still. If you have the resources then use a full fleged screened and plastic plated vacuum safety shield, but noty many people have (or can afford) such a thing. Even a blanket between you and your glass can reduce the possibility of injury.

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For the most comprehensive and informative web site on explosives and related topics, go to Megalomania's Controversial Chem Lab at http://surf.to/megalomania

[Teck]

Thanks for info, so most glass will hold even with a big vacuum pump. Also another question vacuum presure pump is the same thing as a vacuume pump, and an aspirator is the same thing also?

[10fingers]

I have not heard the term vacuum pressure pump. An aspirator is a device that uses a stream of water to create a vacuum. You hook it to your water faucet. I have not tried one but I don't think they can pull as low a vacuum as a regular pump. One advantage to an aspirator would be that you would not any traps to keep acid vapor from getting into your pump. This can ruin a regular pump in short order.
There are two qualities in a pump, rate of flow, usually measured in cubic feet per minute or liters of air per minute. The other is maximum vacuum obtainable. The better the pump the higher vacuum it can reach. Usually you don't need a large pump for lab work.

[nbk2000]

In the Scientific American amatuer scientist articles, they use wood boxes to enclose vacuum equipment. Anyone should be able to manage a wood box.

Drill a small hole, covered with thick plexiglass, so you can see the flask. Include a small light so you can see inside.

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"The knowledge that they fear is a weapon to be used against them"

Go here (http://members.nbci.com/angelo_444/dload.html) to download the NBK2000 website PDF.

Go here (http://briefcase.yahoo.com/nbk2k) to download the NBK2000 videos.

[-A-]

Try to use flasks that are not big (<250 ml), bigger flasks can implode if they are not designed for powerful vacuum.

[EventHorizon]

<font face="Verdana, Arial" size="2">Originally posted by 10fingers:
I have not heard the term vacuum pressure pump. An aspirator is a device that uses a stream of water to create a vacuum. You hook it to your water faucet. I have not tried one but I don't think they can pull as low a vacuum as a regular pump. One advantage to an aspirator would be that you would not any traps to keep acid vapor from getting into your pump. This can ruin a regular pump in short order.
There are two qualities in a pump, rate of flow, usually measured in cubic feet per minute or liters of air per minute. The other is maximum vacuum obtainable. The better the pump the higher vacuum it can reach. Usually you don't need a large pump for lab work.</font>

A vacuum pressure pump usually is designed to pull a vacuum and to also have a high side for pressurizing. I have a smaller Gast that will pull ~25" vacuum and also pump up to 50 psi on the other side. However, some pumps are only vacuum, or pressure, but not both. I also have an airvac, it uses air pressure to pull a 28" vacuum and its only about the size of a matchbox.

[Teck]

EventHorizon: so your gast pump works perfect with your glass? Im planning in using 1 500ml RB flask and the other 1000ml RB flask. Also the spirator im asking about is this one.... http://www.industrialliquidators.com/photos/712i.jpg
This is a compressor made by Air Shields. Puts out 22 PSI and draws 17" of vacuum.
Will it work? It doesnt look like it runs on water.

Im calculating about 500 dollars in lab glass and a pump and I would not want it go all to ruin thats why I want to know, so I can get the right one.

[photonic]

I just found an old window air conditioner yesterday and I want to pull to air compressor off it to use as a vacuum pump. Is it alright to cut all the copper tubes? Also, I've been advised by the creator of powerlabs that if it has freon in it I shouldn't take it off. Is this true? It has four copper tubes(maybe 3, don't remembeR) coming off the compressor. The function of two is obvious. What are the other one/two for?

Edit: crappy ascii art

<small>[ July 10, 2002, 11:03 AM: Message edited by: photonic ]</small>

[Anthony]

I wouldn't worry about the freon unless you're an eco-freak, just don't breathe it :)

[Mick]

hold your breath, puncture one or more of the tubes, then get away from it.(obviously you would do this outside.)

my question is, how do you use an aircon compressor as a vacuum pump?

<small>[ July 10, 2002, 11:50 AM: Message edited by: Mick ]</small>

[10fingers]

*

<small>[ July 10, 2002, 05:47 PM: Message edited by: 10fingers ]</small>

[pyromaniac_guy]

mick,
any compressor has to suck from somewhere... it isnt just make up whatever it compresses out of nothingness...
to use a compressor as a vacuum pump you just hook up the suction port (normally the larger diameter tube) to whatever you want to form a vacuum on... the nice thing about compressors is that it's a totally sealed system, ie if you want to pull a vacuum on something AND recover the vapors that your pumped sucked up, all you need to do is connect a condensor to the output port on the compressor

[stanfield]

Do you have some good adresses where I can buy relatively cheap vacuum pump ? In €urope, these pump are pretty expensive... :(

thanx !

<small>[ July 10, 2002, 04:51 PM: Message edited by: stanfield ]</small>

[megalomania]

They are expensive everywhere. Your best bet for a good deal is to find a used lab equipment dealer or auction website. You may also get lucky at flea markets and garage sales, but you need to know what to look for. I got a crappy one that way (it's ugly, but it works).

Try <a href="http://www.labx.com" target="_blank">www.labx.com</a> for laboratory equipment auctions. Check out <a href="http://www.labx.com/v2/adsearch/detail3banners.cfm?adnumb=125980" target="_blank">http://www.labx.com/v2/adsearch/detail3banners.cfm?adnumb=125980</a> This pump is $16 as of this posting!

[rikkitikkitavi]

why pay for a vaccum pump when a water aspirator is good enough for distilling HNO3? much cheaper and also HNO3-resistant , which the vacuum pump most likely isnt.
A water aspiratior pulls vacuum down to the vapour pressure of the
water , somewhere around 15 torr@20C.

If you are using a vacuum pump a cold trap is essential so the HNO3 vapours condenses out. And for that you need LN2.

/rickard

[ALENGOSVIG1]

Aspirators are good but if you live in an area with low water pressure its not going to do you much good. You can still use an aspirator in low water pressure ares, but you will have to build a recirculating pumping station for it to work well.

stanfield you should look into finding an old refirgerator compressor. Theres info on using them as vacum pump on the forum.

[stanfield]

ok, thanx but a "compressor" isn't an "aspirator" ? no ?

[rikkitikkitavi]

yes , you need some water pressure to get the aspirator running, or acutally pull vacuum, but I thought it would be cheaper to hook up a extra pressure-booster pump after the tap feeding the aspirator than than purchasing a designated vacuum pump, however this takes some skills.

A compressor is not a aspirator.
Different name for aspirator= water ejector . Extensivly used in industry as a cheap and reliable source of vacuum. Also driven by high pressure steam... Basically a device where pressure (J/m3)is transformed into kinetic energy .

A compressor is a pump working with gases instead of a liquid.
It compresses the gas(duh :) so the gas leaves at higher pressure than it enters. By its design it can be used as a source of vacuum-se previous posts.

/rickard

[stanfield]

ok, that's interresting...
I just found a pump in a catalog : you add it to a drill, it give you 1500 Liter by hour and it cost 45€ (about 45$) ! impresive, no?
The only major problem is that the body is ONLY in brass ! That's not good for nitric acid vapors but, at this price, it doesn't matter !

see ya !

[xoo1246]

Remove

<small>[ December 11, 2002, 01:34 PM: Message edited by: xoo1246 ]</small>

[rikkitikkitavi]

stanfield, I know what kind of water pump you are refering to, and they give quite a output...
anyway, the HNO3 vapour is only a problem if you build a closed system, where the same water is recirculated over and over again.
But a small addition of NaOH into the water effiently neutralizes
acid.

xoo1246, go ICQ...

/rickard

[10fingers]

A vacuum pump costs $100.00 or more. Requires a trap to catch acid vapors. Pumps overheat with prolonged use and require expensive vacuum pump oil.
An aspirator costs $10.00 and requires no trap.
The one I have is made of Nalgene, an acid resistant plastic. It will work fine on as little as 20 psi of water pressure. If you have fluctuating water pressure such as a well with a pump that switches on and off then you will require a check valve between the aspirator and your glassware to prevent water from getting sucked in to your apparatus. These only cost a couple of dollars and I think some aspirators have them built in.

[PYRO500]

You all reminded me that I hgave yet to take pics of my recirculating aspirator station. I will say this about them, the more water in the system the better not only will the acid vapors get reduced but the water will stay much cooler. If I paid full price for the spa pump and everything though I would have paid somewhare around 130$.

[pyromaniac_guy]

if anyone is useing a mechanical vacuum pump in a corrosive environment, and is worried about causing damage to your pump, i strongly recomend a product by the kurt lesker corporation. (www.lesker.com) Thor-oil (page 15-15 of their current catalog) is the best non pfpe based oil i have ever hurd of for corrosive or agressive atomospheres. the stuff is fairly expensive, but then again, proper vacuum pumps are expensive as well. a gallon goes for 218$, and would be more than enough for a lifetime of operation on any small vacuum pumps... The stuff is compatable with halogen gases and acid vapors....
a less expensive pump oil is tko-300 and runs 65$ a gallon. either of these oils will ellimate the need for a cold trap, although i personally recomend the thor oil myself... either way it sure as hell beats the 1400$ a gallon for pfpe based vacuum pump oils!!!!

[Rat Bastard]

Nice work your HN03 pdf file, PYRO500. When you get those pics of your aspirator station, are you going to include them in a new pdf file?, or just show them here.

P.S: Is this the kind of aspirator you are using?
<a href="http://www.indigo.com/glass/gphglass/vacuum-aspirator.html" target="_blank">http://www.indigo.com/glass/gphglass/vacuum-aspirator.html</a>

<small>[ July 28, 2002, 03:13 AM: Message edited by: Rat Bastard ]</small>

[vulture]

To everyone who's intending to buy a vacuum aspirator, please purchase one with a kick back valve. This prevents water from being sucked into the setup and can lower water usage significantly.

[PYRO500]

I would say that in my experiences with my aspirator a long length of hose between the aspirator and the glassware is more effective than the kick back valve witch actually allows a slow flow of water back into the aparatus if the water pressure ever slightly lowers