Sciencemadness Discussion Board

compressor safety

resveratrol - 21-2-2012 at 09:16

I have an old compressor/aspirator, this model actually:

http://www.ebay.com/itm/Air-shields-Dia-Pump-Vac-Aspirator-C...

it says explicitly not to use in the presence of flammable anesthetics, which tells me that one of its intended purposes was not for removal of organic solvents. So I am also assuming it is not immune to chemical attack. However....i know many use refrigerator compressors as an improvised vacuum pump, and I assume my pump operates similarly.

Maybe if I ran the gas through a condenser and a chamber of activated carbon before it reached the pump this would help ease my concern?

bahamuth - 21-2-2012 at 10:37

That pump is a diaphragm pump and works nothing like a refrigirator compressor except that both compresses gas.

The diaphragma or membrane is made of either rubber or teflon(FEP most likely), if teflon you are good but most rubbers are attacked by solvents and thus will kill your pump.

The special thing about that pump you got there is that it does not contaminate the air passed through with oil as it is a respiration pump, even the water saturator is depicted on that ebay listing.


The
Quote: Originally posted by resveratrol  
not to use in the presence of flammable anesthetics
means it does not have a spark safe motor, thus making it a potential firestarter.

Pick it apart, care to not destroy any gaskets, and see what the diaphragm is made of. Only this would give you a good idea if it is usable for organic vapors.
Quote: Originally posted by resveratrol  
Maybe if I ran the gas through a condenser and a chamber of activated carbon before it reached the pump this would help ease my concern?

A condenser is always a good thing (a must really, big no-no not to use one. I myself might be sloppy in that regard..), as solvents tend to condense in those pumps and make them sputter solvent through the exhaust port, but you will need a mighty long activated carbon column to get rid of all the organic vapors, plus it will get saturated at one point anyways.


Edit: This is not supposed to be in the organic chemistry section...

[Edited on 21-2-2012 by bahamuth]

resveratrol - 21-2-2012 at 11:27

Thank you, bahamuth. Would you consider this carburetor example to be a reasonable depiction of the pump I have?

http://www.cdxetextbook.com/fuelSys/gasoline/carbsysComp/fue...

If so, I have a better understanding as to how it works now. I understand why there is potential flammability. But just to be clear, the electromagnet, and 'sparks' (if present), are clear of the path of solvent vapors, correct? So long as the thing isn't sucking up solvent I should be good (with regards to potential fire hazards). But as far as maintenance of the diaphragm I should probably take it apart to see what it's made of so I'm not dissolving it.

bahamuth - 21-2-2012 at 12:22

That fuel pump gives the basic idea.

Concerning the path of the solvent vapor, if there is vapor at the exhaust port it will be evenly distributed in all three dimensions if not directed through tubing and so on.

If the pump manufacturer explicitly says it not should be in an area with flammable it probably produces sparks, though you can easily check this by looking if the motor is brushless or not (brushless equals no sparks). Either way you might get a leak and (example follows..) set aflame the 10s of grams of diethyl ether you just passed through your pump and blow the walls of the room a meter wider apart in the process.

One additional note, those pumps usually don't pull low enough vacuum to be used for anything other than vacuum filtrations IMO as in my experience one needs sub 1 mbar pressures to really affect distillations, and I would guess thet pump can't "suck" harder than down to 20-200 mbar.

Hexavalent - 21-2-2012 at 14:04

This should be in Reagents and Apparatus Acquisition, no?

ScienceSquirrel - 21-2-2012 at 14:35

Yes, moved

resveratrol - 21-2-2012 at 16:13

Quote: Originally posted by bahamuth  

Concerning the path of the solvent vapor, if there is vapor at the exhaust port it will be evenly distributed in all three dimensions if not directed through tubing and so on.


Of course.
Quote: Originally posted by bahamuth  
If the pump manufacturer explicitly says it not should be in an area with flammable it probably produces sparks, though you can easily check this by looking if the motor is brushless or not (brushless equals no sparks). Either way you might get a leak and (example follows..) set aflame the 10s of grams of diethyl ether you just passed through your pump and blow the walls of the room a meter wider apart in the process.


So if it's brushless, I'm probably fine - but either way there's a potential for ignition of solvent vapors. I don't like the sound of that, and that was my initial concern.
Quote: Originally posted by bahamuth  
One additional note, those pumps usually don't pull low enough vacuum to be used for anything other than vacuum filtrations IMO as in my experience one needs sub 1 mbar pressures to really affect distillations, and I would guess thet pump can't "suck" harder than down to 20-200 mbar.


it's sucking power isn't really an issue. I know it's powerful enough to boil off volatile solvents. It pulls to around 600 mm Hg (at least), so that's around 800 mbar

Perhaps I should look into buying a better pump.

bahamuth - 21-2-2012 at 17:06

Quote: Originally posted by resveratrol  
Perhaps I should look into buying a better pump.


May I suggest one of these:

Vacuubrand MZ 2C
Ilmvac MPC 101 Z (I have this one and I love it for rotavapor and filtering jobs, pulls ~13mbar)

But if you want to vacuum distill some high boiling stuff you should just buy a small cheap rotary vane pump used by those refrigeration guys. Or read the thread on fridge compressors, LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS! though I myself actually have no idea how low the fridge pumps can pull a vacuum.

Edit: Actually today I was with some friends working at the University today, dismanteling an old SEM to trash it, leaving behind two oil diffusion pumps and a giant high flow vacuum pump. Some inhouse guys wanted the Edwards 18 rotary vanes. Neither did I take anything else as I did not have proper transportation or storage in the apartment.... Was a Jeol 840 Scanning Electron Microscope.

[Edited on 22-2-2012 by bahamuth]

resveratrol - 21-2-2012 at 18:16

hm. i do have a mini fridge i could take apart and hijack its compressor. Seems like it might be a lot of work though.

too bad none of those videos work in peach's thread.

i hope nothing went to waste with the SEM

resveratrol - 21-2-2012 at 18:46

sifting through all of the penis pumps on eBay, i found this:

http://www.ebay.com/itm/ELECTRIC-VACUUM-PRESSURE-DIAPHRAGM-P...

i do not think 16 in Hg is sufficient though, to boil RT solvents.


what if I was to employ TWO condensers (Allihn --> Grahams), which terminate into a large column filled with activated carbon....which then leads to my current vacuum pump. This would be very easy to set up....i just don't know if the vacuum would pull hard enough through all that activated carbon.

bahamuth - 21-2-2012 at 23:27

That's actually another thing, if you have to narrow tubing, and to long a path very low pressures will take a long time.

Anyways, that last pump looks like crap to me, and 16 in. Hg. is very very poor, know a couple of girls that can suck harder than that....

Think your best bet is to check the pump you have and get a set of wash bottles (after the cryo-condenser and filled with e.g. activated charcoal) and a in-line cryo-condenser which you can fill with e.g. one of these freezing mixtures. -70 degrees C. is good enough for most jobs if you periodically remove the condensed solvent and don't plan for sub mbar pressures, though any drop in temperature will greatly reduce the amount of vapor you pull into your pump..
Quote: Originally posted by resveratrol  
sifting through all of the penis pumps on eBay, i found this:
You know you can sort by category, like business and industrial...:P

resveratrol - 22-2-2012 at 08:31

It would be nice to have a Dewar style condenser for this job, that way i could just throw in some dry ice/acetone and be done with it. I could even recollect my solvent. Hmmmm.....

resveratrol - 22-2-2012 at 08:44

Fuck it. I'm buying one.

GreenD - 22-2-2012 at 09:00

does anyone want my alcatel 2002bb? I've been trying to sell it on here for a year!!

100$ including shipping - fresh oil, refurbished by me (motor had a chunk of metal in there that kept it from circulating - no real damage though)

resveratrol - 22-2-2012 at 09:39

Hmm. I might actually be interested in that.

resveratrol - 22-2-2012 at 09:48

How strong of a vacuum does it pull, and how loud is it?

GreenD - 23-2-2012 at 10:52

never tested, never verified the vacuum, I put my finger on the inlet - that brought the heart rate up.

It is loud enough to keep you awake. If you attach it to a bench top that will help considerably since most of the noise I experienced was from it wanting to bounce up and down off the floor.

I don't know what I would equate the sound to...