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Author Topic: How can I create a vacuum?  (Read 9034 times)

Offline The Scientist

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How can I create a vacuum?
« on: 01/07/2010 15:10:41 »
How complicated is it to create a vacuum and how to create it? Is it even possible to create a 'perfect' vacuum? Thanks!


 

Offline Bored chemist

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How can I create a vacuum?
« Reply #1 on: 01/07/2010 19:18:29 »
It's impossible to create a perfect vacuum.
How complicated the equipment is varies depending on how good a vacuum you want.
The simplest vacuum pumps commonly in use are water pumps which will remove about 97% of the air from a vessel. The most expensive complex vacuum systems will remove something like all but a thousandth of a millionth of a millionth of the air, but there's still some left.
 

Offline tommya300

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How can I create a vacuum?
« Reply #2 on: 02/07/2010 04:30:50 »
How complicated is it to create a vacuum and how to create it? Is it even possible to create a 'perfect' vacuum? Thanks!


Big expense if you wish to pump down to an Ultra High Vacuum.
Ideally, start with a stainless Steel hull or titanium reinforced ribbed spherical chamber.
Ultra cleaned and baked to remove any debris in the micron range of measurement.
A displacement or diffusion pump is used for a rough pump down, to approx 1e-6 torr. Then a Mercury Ion pump can be used to attempt maximum negative pressures below 1e-6 torr to remove the gas atoms remaining. I think 1e-9 torr is in the region of UHV. Every part inside the chamber and these flow areas need to be ultra clean and dry. The diffusion pump works with the exhaust portion in atmospheric pressure. The exhaust portion of the ion pump needs to be in a particle to low vacuum to operate.
I think the term, Angstroms of Mercury, has been replace but I am not sure.
Even outer space is the closest entity to a perfect vacuum known to man and that is also not an absolute.
 
« Last Edit: 02/07/2010 04:45:28 by tommya300 »
 

Offline Murchie85

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How can I create a vacuum?
« Reply #3 on: 02/07/2010 13:38:09 »
If your wanting to do a few fart about experiments at home then you could get a clean container with an opening that fits the nozzle of your hoover (vacuum cleaner) attach the nozzle and suck the air out. The trick would be getting the cap on without letting any air back in.
 

Offline tommya300

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How can I create a vacuum?
« Reply #4 on: 02/07/2010 17:06:43 »
You can go a little bit farther and wait to do some seasonal canning, vacuum packing in Mason, Kerr or Ball jars, a USA product.
A little machanical manipulation on an air compressor, to reverse its operation, might work too.
you might get a pump down to about -25 lbs per square inch.
 

Offline SeanB

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How can I create a vacuum?
« Reply #5 on: 02/07/2010 20:23:24 »
Using an old refrigeration compressor you can at least get down to 30mmHg, and if you place 2 in series you can get down low enough to make neon signage, around 2mmHg. A better vacuum gets more costly very rapidly, as you start adding extra pumps in series, each providing a small improvement in the vacuum you create.
 

Offline syhprum

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How can I create a vacuum?
« Reply #6 on: 02/07/2010 20:49:21 »
There used to be quite a cottage industry re-gunning TV CRT,s some of the now redundent equipment may be available on EBay or  dumped at the back of factories.
 

Offline tommya300

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How can I create a vacuum?
« Reply #7 on: 02/07/2010 21:33:01 »
If you can find a dollar store that sells odds and ends there is a 12 volt electric tire pump, all you need is to flip the pistons ring upside down and epoxy a small metal tube to its intake and use that as a suction that will get you to at a little more than a negative 1 atmosphere I never tried 2 in cascade that sounds like a good idea. The refrigeration compressor and the oils that may be emitted might be dangerous as it atomizes in the exhaust but that would certainly work the best.
 

Offline LeeE

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How can I create a vacuum?
« Reply #8 on: 03/07/2010 08:01:02 »
The easiest way to create a partial/near vacuum is to get a long tube that has an airtight seal at one end, fully immerse it in water and let all of the air escape, then raise the sealed end of the tube out of the water, tilting it until it's upright.  As the water drops down the tube, due to gravity, it will leave a near vacuum in the space at the top of the tube, apart from some water vapour.  This is known as a Torricellian vacuum (Torricelli is credited with first performing this experiment, although he used mercury instead of water, which being heavier created a larger vacuum - I wouldn't reccommend you messing about with mercury though, and in any case, you'd need quite a lot of it).
 

Offline syhprum

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How can I create a vacuum?
« Reply #9 on: 03/07/2010 08:42:33 »
The problem with the water tube is that you need at least 10 meters if you live in a second floor apartment you can setup your tube outside with a tap at the bottom and your vacuum chamber at the top with means to fill it with water.
If you refrigerate the chamber you could freeze out the water vapour but I don't know what the ultimate vacuum you could achieve this way.
The water will contain quite an amount of dissolved gas it would be a good idea to boil it before use
 

Offline Bored chemist

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How can I create a vacuum?
« Reply #10 on: 03/07/2010 16:57:56 »
Vacuum cleaners hardly produce a vacuum at all; they move air.

"you might get a pump down to about -25 lbs per square inch."
Oh no you won't.
 

Offline LeeE

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How can I create a vacuum?
« Reply #11 on: 03/07/2010 18:30:11 »
The problem with the water tube is that you need at least 10 meters...

Oops! yes, you're absolutely correct.
 

Offline SeanB

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How can I create a vacuum?
« Reply #12 on: 03/07/2010 20:30:56 »
I have a vacuum that will generate around 0.5 bar of suction with zero flow. It will collapse the canister slightly at that level, although it will not be very good for the motor to run at that level for long, as it is cooled by the outlet air from the impeller system. I have replaced the motor once, and used a pattern part that cost around 10 pounds, as opposed to the original part that they wanted close to 90 for the same item ( though theirs came with a 1 year warranty whereas the second source did not although it is made in the same factory on the same line). Not bad for a unit that has been used for 10 years plus every day to clean offices.
 

Offline Geezer

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How can I create a vacuum?
« Reply #13 on: 04/07/2010 01:35:37 »
I have a vacuum that will generate around 0.5 bar of suction with zero flow.

That really sucks!  ;D

OK! OK! I can leave under my own steam, thank you very much. I'll have you know I've been thrown out of far better forums than this.
 

Offline SeanB

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How can I create a vacuum?
« Reply #14 on: 04/07/2010 11:41:10 »
I did use that to temporarily replace a vacuum pump used for production machinery. It had barely adequate specs to do in the pinch while the replacement pump was being airfreighted in and assembled. It ran for around 50 hours there, I bought a new motor assembly just in case it was needed, but no smoke came out, though I did take a big slice of the motor life off there.
 

Offline syhprum

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How can I create a vacuum?
« Reply #15 on: 04/07/2010 13:31:57 »
The HELL scanner/recorders that I used to work with had a heavy duty vacuum pump to hold the film and a screen onto the recording end of the machine.
Most of the later machines had laser generated screening and required much less vacuum to hold only the film on and when the vacuum pump failed a decent vacuum cleaner would serve as a temporary substitute until the correct replacement could be obtained.
 

Offline Bored chemist

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How can I create a vacuum?
« Reply #16 on: 04/07/2010 13:36:31 »
I can do better than 0.5 bar with a drinking straw.
 

Offline SeanB

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How can I create a vacuum?
« Reply #17 on: 04/07/2010 14:28:39 »
Can you do 100 litres per minute at that suction without exploding?


 

Offline Bored chemist

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How can I create a vacuum?
« Reply #18 on: 04/07/2010 16:47:08 »
Not for long, but that wasn't the question.
Vacuum cleaners move lots of air (as I said) they don't produce much of a vacuum.
 

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How can I create a vacuum?
« Reply #18 on: 04/07/2010 16:47:08 »

 

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