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Magpie
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I bought a single stage, rotary vane, vacuum pump rated at 2.5cfm from Harbor Freight for $100.
It works fine for vacuum distillations pulling down to 1-2mmHg. So why would I need a 2-stage?
During a vacuum distillation all you need capacity for is for leaks in your system. If you seal your system right there will be very little leakage.
So why would you need anything more than 2.5cfm? Probably could use a lot less.
I bought this one because it was cheap. I've had this pump for several years and have only had to change the oil twice. If I'm distilling something
that is compatible with oil I don't change the oil.
Edit: I wanted to add that when distilling something really nasty, like nitric acid, I will by all means use my aspirator if at all possible.
[Edited on 1-12-2016 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Db33
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Quote: Originally posted by Magpie  | I bought a single stage, rotary vane, vacuum pump rated at 2.5cfm from Harbor Freight for $100.
It works fine for vacuum distillations pulling down to 1-2mmHg. So why would I need a 2-stage?
During a vacuum distillation all you need capacity for is for leaks in your system. If you seal your system right there will be very little leakage.
So why would you need anything more than 2.5cfm? Probably could use a lot less.
I bought this one because it was cheap. I've had this pump for several years and have only had to change the oil twice. If I'm distilling something
that is compatible with oil I don't change the oil.
Edit: I wanted to add that when distilling something really nasty, like nitric acid, I will by all means use my aspirator if at all possible.
[Edited on 1-12-2016 by Magpie] |
if distilling something like that, could i just use a vacuum pump and fresh oil and then afterwards change the oil without worrying about to much
damage?
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Magpie
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I would guess that would be OK as long as this is a small quantity like 500mL.
Why can't you use a $20 aspirator. Calculate your water costs. I'm guessing it won't be that much.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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I got a cheap single-stage vac pump from Italy off ebay.
After a Lot of abuse it stopped working.
All it needed was taking apart and the rust cleaning off, then it worked fine again for simple vac needs (which is all i have).
http://www.sciencemadness.org/talk/viewthread.php?tid=66097
Still working fine today, although it did work better with just baby oil.
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Db33
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| Quote: Originally posted by Magpie | I would guess that would be OK as long as this is a small quantity like 500mL.
Why can't you use a $20 aspirator. Calculate your water costs. I'm guessing it won't be that much. |
i have an aspirator but i dont have a faucet to use it on, and making a recirculating station seems like it would take be too much of a pain.
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zed
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Good enough. But, an aspirator is extremely useful. Quiet, and extremely adjustable. And, it can, of course, be used without the presence of
electricity. Uses up a lot of water that way, but perhaps the water can be diverted to your garden. There are times when electricity and
chemistry, aren't friends.
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wg48
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Don't forget the ballast.
If you have regular rotary vane pump it frequently has a ballast. The ballast lets a controlled amount of air in to the pump that helps to stop
condensable gases from condensing in the pump or the oil.
The procedure for pumping gases that may condense in the pump is to run the pump with the ballast open and at the conclusion of pumping run the
isolated pump for say an hour with the ballast open to flush out volatile contaminates left in the pump.
So if you must pump gases like chlorine or nitric acid vapours with out a trap the above procedure should help.
Here is some info on ballasts:
https://avs.org/AVS/files/06/0613373e-c93e-4bc6-8b79-38a1e19...
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XeonTheMGPony
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And pre-heating the pump goes a looong way.
I use my vacuum pump for dehydrating hvac systems that I flushed with isopropyle alcohol.
That can destroy your pump easy if not care full, I pre heat the pump by running it blanked off till hot to the touch and as said above I ballast the
pump as I start till bulk of it is removed then seal the air bleed for ultimate vac.
Cold trap is your best defense to help protect the pump.
I am building a deep vacuum chamber, So I am building a refrigerated cold trap (2 stage, first stage 134a second stage will be R-507 or R-410a at
-50c)
Normal is Acetone and dry ice for small batch run set ups (-80c) that is the future target of building an auto cascade
But most runs I just ordered a Water aspirator as water pumps are cheap and so are 55g barrels! ( http://www.ebay.ca/itm/262437828357 ) As they are by far the best thing for simple distilations, no issues with worrying about the far more
expensive and complicated vacuum pumps that you need when you need a real vacuum like H2SO4 distillation or Mercury distillation.
http://www.ebay.ca/itm/DC12V-45W-Diaphragm-Water-Pump-With-P...
You can get cheaper ones!
[Edited on 3-12-2016 by XeonTheMGPony]
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Db33
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| Quote: Originally posted by XeonTheMGPony | And pre-heating the pump goes a looong way.
I use my vacuum pump for dehydrating hvac systems that I flushed with isopropyle alcohol.
That can destroy your pump easy if not care full, I pre heat the pump by running it blanked off till hot to the touch and as said above I ballast the
pump as I start till bulk of it is removed then seal the air bleed for ultimate vac.
Cold trap is your best defense to help protect the pump.
I am building a deep vacuum chamber, So I am building a refrigerated cold trap (2 stage, first stage 134a second stage will be R-507 or R-410a at
-50c)
Normal is Acetone and dry ice for small batch run set ups (-80c) that is the future target of building an auto cascade
But most runs I just ordered a Water aspirator as water pumps are cheap and so are 55g barrels! ( http://www.ebay.ca/itm/262437828357 ) As they are by far the best thing for simple distilations, no issues with worrying about the far more
expensive and complicated vacuum pumps that you need when you need a real vacuum like H2SO4 distillation or Mercury distillation.
http://www.ebay.ca/itm/DC12V-45W-Diaphragm-Water-Pump-With-P...
You can get cheaper ones!
[Edited on 3-12-2016 by XeonTheMGPony] |
i thought someone said that a pump like that wasnt enough to make a good enough vacuum?
also would this aspirator work cuz this si the one i have.
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zed
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Looks OK to me.
A side note though....An aspirator can pull enough vacuum to collapse a 55 gallon drum. That drum has a lot of surface area, the metal isn't usually
very thick, and an imperfect vacuum, is still vastly less than normal atmospheric pressure. Jewelers used to use an aspirator with a 55 gallon drum
in line, to store vacuum. Good way to boil investment, in route to lost wax casting. Turn the valve, and instant decompression! Except, sometimes
the drum would collapse, at a bad time, and screw up the process.
https://www.youtube.com/watch?v=zdoWE_Vr8b8
Now, I have a stainless steel beer keg, that I figure to be a lot sturdier than your average 55 gallon drum. I plan to put it to the test.
[Edited on 4-12-2016 by zed]
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NedsHead
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While we're on the subject of vacuum pumps I found that (iso 32 hydraulic oil and hydraulic jack oil) are a cheap source of bulk vacuum pump oil, I
use this product on my machinery http://www.penriteoil.com.au/products.php?id_categ=5&id_... and discovered it's also suitable for vac pumps
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XeonTheMGPony
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Beer kegs are amazing I speak from a ton of experience on that! they will hold all the vac you can throw at em!
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NeonPulse
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I actually built a vacuum aspirator pump exactly like Nurdrages unit and it actually performs quite well. It works just as well as he shows in his
video. The whole thing cost around 50$ to construct and I must say it was $ well spent for a cheap reliable vacuum source. I was able to distill
acetone with only it's evaporation cooling effect at around 18c.
The only problem is the one way valve in the aspirator is shit. It hardly stops the water from being sucked back when you kill the vacuum but for this
reason it is advisable to add a quality check valve to the vacuum line. Also as Nurdrage suggested you can enhance the vacuum by using a fluid like
ethylene glycol. You can buy premixed 5l bottles at most car products stores which are 50% and if used ice cold you should get a substantial increase
in vacuum power. A medium esky cooler shoul work as a reservoir to keep the working fluid cold enough along with some gel filed freezer bricks.
[Edited on 10-12-2016 by NeonPulse]
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Sulaiman
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for vacuum filtration and reduced pressure distillation I have been sucessfully using one of these
http://www.ebay.co.uk/itm/DC12V-DC-Micro-Piston-Vacuum-Pump-...
materials exposed to the gas flow are POM and silicone rubber - so far no problem.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Magpie
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| Quote: Originally posted by NeonPulse |
The only problem is the one way valve in the aspirator is shit. It hardly stops the water from being sucked back when you kill the vacuum but for this
reason it is advisable to add a quality check valve to the vacuum line.
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You can install a tee with a valve opening to the atmosphere. This valve is normally closed. Before turning off the water open this valve slowly.
This will gently bring the system to atmospheric pressure. Then turn off the water.
edit: see the brass valve/tee combo in the picture:
[Edited on 10-12-2016 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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