Sciencemadness Discussion Board - Vacuum pump HELP

Vacuum pump HELP

RonPaul2012 - 16-3-2012 at 04:58

I am looking for a cheap vacuum pump for my buchner funnel / glassware.

I have wasted my money one three different hand pumps over the course of a year ; hand pumps DON'T WORK :mad:

I want a foot pump that I can use with my table , by using a long hose ; something like this

They used to make bicycle pumps that could be inverted to be used as a vacuum but I can't find one.

I either want a "how to" on how to convert a foot pump into a good vacuum pump or I want a link to a vacuum pump.

I would really like the forum members advice/experience on this.

Is this a good idea or do you have a better solution ?

Thank you.

[Edited on 16-3-2012 by RonPaul2012]

neptunium - 16-3-2012 at 05:57

i did see a thread on this and i`ll try to forward you the link when i find it.
However i think you are wasting your time.
I have been using refrigerator compressor for years with very little set up and great result.

i am sure there is a junk yard where you can go and salvage 4 or 5 compressors from .or a neighbor who wants to replace his...

I measure the vacuum produced by the average compressor at about 100mmHg (sometimes 50mmHg and lower!) wich is more than enough for filtration.

hook it up ,turn it on. done

oh here it is

http://www.sciencemadness.org/talk/viewthread.php?tid=16047#...

[Edited on 16-3-2012 by neptunium]

RonPaul2012 - 16-3-2012 at 06:29

the vacuum pumps I used could get 760mmhg but I only could get to 500mmhg with a 500ml filter flask .

I am not well versed in pumps so I can see this will take some time.

Well I'm here to learn so I don't mind

Maybe I would just be better off getting my hands on an electric pump since I don't want to have to pump everytime pressure drops.

I just don't want to spend much on a pump is all , so I'm going to have to jerry rig something I guess.

I'm also a little concerned about corrosion (that's what got my pumps) , is there any way to deal with corrosive gases ?

[Edited on 16-3-2012 by RonPaul2012]

[Edited on 16-3-2012 by RonPaul2012]

[Edited on 16-3-2012 by RonPaul2012]

neptunium - 16-3-2012 at 08:15

a cold trap or a bubbler or both

DJF90 - 16-3-2012 at 13:00

Get a water aspirator pump. A glass one will take you down to about 60mbar, a plastic one can sometimes do better (15mbar). No need to worry about corrosive gases for the first one, and no need to have to pump anything by hand. If you're worried about wasting water, then set up a recirculating system. This has been mentioned before here I believe

zoombafu - 16-3-2012 at 13:19

Get this vacuum aspirator. I have it and HIGHLY recommend it.
<a href="http://www.amazon.com/gp/product/B002VBW41E/ref=as_li_ss_tl?ie=UTF8&tag=thehomche0e-20&linkCode=as2&camp=1789&creative=390957&am p;creativeASIN=B002VBW41E">Bel-Art Vacuum Water Aspirator </a><img src="http://www.assoc-amazon.com/e/ir?t=thehomche0e-20&l=as2&o=1&a=B002VBW41E" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />

RonPaul2012 - 17-3-2012 at 01:04

I am not close enough to a tap to make that practical.

This doesn't mean that I play around with acid without taking safety precautions and it is close enough that I can walk across the room and reach it.

I am pretty much just interested in a pump.

ripple - 22-3-2012 at 16:22

Are you close enough to an electrical outlet?

There are plans around for hooking up 1 or 2 aspirators (in parallel) to a water pump in a closed loop with a reservoir. Used water pumps can often be found at garage sales for cheap, surplus stores are also a good bet.

Buchi and others (Whatman?) even manufacture aspirator/pump systems for lab use. The main benefit is that no mechanical parts are exposed to vapours, and that water soluble vapours can also be harmlessly absorbed/removed.

I dont have much experience with hand-pumps, but they might be worth another try since they vary in quality. If you're only filtering, you should be able to find one at a decent price that does the job. Check Cole-Parmer or similar, just dont buy the cheapest one you can find.

RonPaul2012 - 22-3-2012 at 16:28

Quote: Originally posted by neptunium

i did see a thread on this and i`ll try to forward you the link when i find it.
However i think you are wasting your time.
I have been using refrigerator compressor for years with very little set up and great result.

i am sure there is a junk yard where you can go and salvage 4 or 5 compressors from .or a neighbor who wants to replace his...

I measure the vacuum produced by the average compressor at about 100mmHg (sometimes 50mmHg and lower!) wich is more than enough for filtration.

hook it up ,turn it on. done

oh here it is

http://www.sciencemadness.org/talk/viewthread.php?tid=16047#...

[Edited on 16-3-2012 by neptunium]

Ok my captain.
I have acquired 2 yes 2 compressors.

One is from a fridge and the other is from an AC.

I'm sure I could figure it out but it always helps if you have a little understanding of what you're doing , so could you link/explain what to do next.

If not I will see what I can do with the search button

[Edited on 23-3-2012 by RonPaul2012]

Bot0nist - 22-3-2012 at 20:18

<a href="http://www.sciencemadness.org/talk/viewthread.php?tid=14435&goto=search&pid=186901">LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS!

No need to UTFSE</a>

[Edited on 23-3-2012 by Bot0nist]

magnus454 - 22-3-2012 at 21:29

Harbor Freight (www.harborfreight.com) sells a good vacuum pump for around 87$ and a really good 25 micron vacuum pump for about $150. I have the 25micron unit, have used it to run a babson/surge milking machine, and repair the A/C in my truck, You can always get yourself a neutralizing filter for your vacuum pump system, I'd buy one for an HVAC from an online supplier or Grainger, the local shops are always a b!t@h about over charging people who do not have an HVAC/EPA license even for non licensed parts. They have a molecular sieve that will prevent particles and debris from entering your pump, also absorb moisture and neutralize acids. Also if your pump oil is cloudy after use, drain and refill with fresh, especially if your running with caustic vapors.

RonPaul2012 - 25-3-2012 at 13:36

I am going to use this guys tutorial.

http://www.paragoncode.com/shop/vacuum_pump/

It seems like a good one

watson.fawkes - 25-3-2012 at 15:26

Quote: Originally posted by RonPaul2012

I am going to use this guys tutorial.

You'll be able to do vacuum filtration with this rig. According to his own report, it gets rid of about 90% of the atmosphere pressure. That means it gets 90% of the force that "total" vacuum would provide, and that's plenty.

For corrosive gases, beware. Because these are sealed compressors, you'll have a hard time changing out the oil completely. The innards are not serviceable should you have a trap failure.

It will get you started, at least.

Chordate - 25-3-2012 at 15:40

Quote: Originally posted by ripple

There are plans around for hooking up 1 or 2 aspirators (in parallel) to a water pump in a closed loop with a reservoir. Used water pumps can often be found at garage sales for cheap, surplus stores are also a good bet.

Wait, I thought the lower limit of aspirators was a function of the vapor pressure of the cold water. Why would hooking up two in parallel give you any kind of improvements?

watson.fawkes - 25-3-2012 at 15:47

Quote: Originally posted by Chordate

Wait, I thought the lower limit of aspirators was a function of the vapor pressure of the cold water. Why would hooking up two in parallel give you any kind of improvements?

Two aspirators in parallel yields higher pumping rates, which is useful if you are trying not just to evacuate a chamber faster, but also to get rid of vapors that might be produced by a reaction.

arsphenamine - 25-3-2012 at 20:55

Quote: Originally posted by magnus454

Harbor Freight (www.harborfreight.com) sells a good vacuum pump for around 87$ and a really good 25 micron vacuum pump for about $150.

YES! It's like a Welch 1402-lite except you can move it around without a dolly.

Add a gas trap with calcium carbonate chunks and you have a winner.

Usage tip: straight 30W or 20W50 automotive oil will do fine if you run out of expensive uber-oil for vacuum pumps.

magnus454 - 25-3-2012 at 21:15

Hey thanks for the tip on the oil, I have a US general 3cfm 25 micron vacuum pump I use for some of my physics work, I did rig up a neutralizing/moisture trap for an ac unit to protect it, but it required some odd oil that I haven't been able to locate. When I looked at all the charts what you stated was very similar to the ISO ratings on the pump oil they list, I'd probably use fully synthetic 20w50.