Sciencemadness Discussion Board

Stupid little nalgene aspirators...

evil_lurker - 14-3-2008 at 16:32

I finally broke down and bought one, paid about $25 after shipping, and I must say this is the best aspirator I have found yet.

Why anyone would want to take the time to build one after using one of their aspirators is beyond me.

No pumping out the side arm due to the internal check valve and my cheap $35 1/2HP harbor freight sump pump easily keeps up with it @ 55PSI due to the smaller orifice. Most importantly it has a LOT of vacuum capacity.

The only catch is now I'm going to have to have rig my sump setup with an overflow drain so I an add a constant flow of cooling water. This is due to the pump causing considerable warming of the water.

It should be ready to go as soon I get some 1/4" tygon vacuum tubing. Its true, just like the aspirator, the stuff is expensive but it works better than anything I have tried thus far.

bio2 - 14-3-2008 at 17:32

Yep, I've been promoting these for some time. Look at the spec and you will see they are designed for relatively low pressure and flow.

Mine will pull 10mm with ice water using only about 25PSI @ 1.5 GPM. I use a 260 watt pump (1/4-1/3 HP). Much better than the water hogs designed for 60- 80PSI or so.

Even an external pump heats the water quickly making the cooling feed necessary
but it doesn't need much flow maybe 1/3 GPM with an external pump to keep the water temperature below 30-35 degrees. I have the pump under the house about
5 feet away to abate the noise almost completely.

I recommend removing the silicone check valve as it WILL eventually fail when you least expect it.

Don't rely on the check valve, always valve it off and vent before stopping the pump
and don't forget the trap. The first time the whole rig fills with water you will install a permanent trap. Make it at least a liter capacity. I learned this the hard way, lol.

evil_lurker - 14-3-2008 at 17:59

Oh yeah, I know all about those traps and check valves.. I've been flooded once before and those aromatic hydrocarbons have a nasty tendency to make the check valves swell up completely shut.

chemrox - 14-3-2008 at 19:28

Send me a PM of where you got it will you? I wanted one and ended up with a metal one by default. The metal one works OK.. better than OK pulling theoretical vacuum with somewhat constricted flow. But those little Nalgenes revel in constricted flow situations. You could just about gravity feed one. I have a Cole-Palmer aspirator pump that uses two aspirators. I think I can improve it by replacing the aspirators with Nalgene ones.

evil_lurker - 15-3-2008 at 00:47

www.vwrlabshop.com is where I got the aspirator. I like to deal with them. Their website lets you know up front if an item is in stock, the sell to private individuals, and they have a fast out-the-door time.

If you buy a case of 24 aspirators, you can get them for $11 each... several times I have considered getting a case of them and selling them on Ebay.

I'm not for sure if VWR has a minimum order, so I added some cork flask support rings as a bonus. This is about the only place I have seen them that sells to individuals.

Prices range from about $20-30 for a set of thee depending on size. A bit pricey IMO, but sure beats having your flasks roll off the shelves or wherever and break.

[Edited on 15-3-2008 by evil_lurker]

garage chemist - 15-3-2008 at 06:07

Tell me, why don't you just get an aspirator made of glass?
I once got such an aspirator from ebay and it is simply perfect for the chemist. It can handle any vapor that the glass distillation apparatus itself can handle.
No swelling of valves, no attack on the material. Can be cleaned with acids, bases or solvents accoring to need.

Klute - 15-3-2008 at 08:12

I'm very satisfied with my recircualting setup, suing one of those nalgen aspirators and good external water pump (3,5 bar pressure max). I don't haev any means of introducing cold water, except changing buckets every 10 min when it's used for long periods, and that's is a slave work! I'm surely going to build an overflow also, consatntly introducing a small flow of cold water.
One problem I have is rusting of the pump: the water colors itself into orange after a few days, and a rust deposit appears. I guess the initial attack was du to traces of acid vapors, as I never cared of using a kin do trap, just changing the water regularily. Now that the surface is attacked, the rusting just slowly continues. I paid only 20E for the pump, and in any case in over 3years of use, it still works perfect.

Here it is:



GC, I also have a glass aspirator, but it is much larger than the nalgene one. I couldn't use it with the first, immersed, pump I had, as it didn't have enough power to give a good vacuum. I will try it on this setup, now that you have reminded me about it :)


[Edited on 15-3-2008 by Klute]

evil_lurker - 15-3-2008 at 11:49

Quote:
Originally posted by garage chemist
Tell me, why don't you just get an aspirator made of glass?
I once got such an aspirator from ebay and it is simply perfect for the chemist. It can handle any vapor that the glass distillation apparatus itself can handle.
No swelling of valves, no attack on the material. Can be cleaned with acids, bases or solvents accoring to need.


You can drop a nalgene aspirator and it won't break.

They are also pre-threaded so they are easier to mount.

If something does happen to it, it cost about $20 to replace.

Pulls a darn good vacuum, and fairly quickly.

Low water consumption.

bio2 - 26-3-2008 at 14:23

...... One problem I have is rusting of the pump: the water colors itself into orange after a few days, and a rust deposit appears. I guess the initial attack was du to traces of acid vapors, as I never cared of using a kin do trap, just changing the water regularily. Now that the surface is attacked, the rusting just slowly continues. .............

Try adding some of that car radiator treatment to the tank. It lasts a while and lubricates the pump. It's severely hydro-treated mineral oil, whatever that is. Mineral oil miscible with water, what a concept.

Otherwise just throw some Na Carbonate or other base in now and then to keep the pH around 10. Acidic conditions will damage the pump, slowly dissolving the impeller and/or
housing.

evil_lurker - 26-3-2008 at 15:35

Well its almost up and running.

Got the parts in for my trap, got the manifold put together, and the manometer is here.

All I need now is the mercury and to install the intercooler lines on the sump and I should be in business.

Have a couple more questions though...

Is it acceptable to put a hair bit of grease on the glass and metal tubing connectors to facilitate removal of the hoses?

And, is it acceptable for the aspirator discharge tubing to be below the surface of the water in the sump?

bio2 - 26-3-2008 at 16:14

Silicone grease will help the glass to metal seal but I have found that it makes
it so slippery that the integrity of the connection is compromised even using hose clamps.

Best is to NOT lubricate and apply a film of red silicone with enough to form a bead
wiped with the finger, Then clamp and don't take it apart. If you do eventually have to take it apart then it will release easier than the dry rubber or PVC alone which tends to take a set and can be a bitch to remove.

The aspirator discharge tube length is critical and submerging it will degrade the vacuum somewhat depending on the depth. Keep it about a half inch or so above the water level. Placing in the corner with a baffle will keep the bubbles from entering the pump suction which should be at the opposite corner.

evil_lurker - 26-3-2008 at 23:35

OK I may have gone a bit overboard with this setup.



Yeah its got more connections, hook ups, and joints than a Willie Nelson concert. But I can shut off the aspirator vacuum before going into the trap thus being able to do leak testing of the entire system. And I can isolate the manometer two ways. Finally, I can bleed the vacuum to the system without ever powering off the water pump.

[Edited on 27-3-2008 by evil_lurker]

S.C. Wack - 27-3-2008 at 01:12

On recirculating dual-jet pumps sold for big wads of cash, the aspirators are at an angle closer to horizontal than vertical, pointed to discharge against the lower back edge of the tank some distance away. I haven't noticed any drop except in decibels on submersion of the outlets, but then I haven't looked for one...the bottom of the aspirators is only 1" above the top of the impeller.

Klute - 27-3-2008 at 13:50

Thanks for the advice Bio, i will try them when i will change the water.. but that is going to be in a few months, when i can use my hand again.

Once, i distilled off some aq. NH3 from a acetamide synth, and the water quickly turned black! I finally distilled the nh3 off at atm with a hcl wash bottle, and the acetamide under vac and the color didn't reappear. Must have attacked some plastic, the tubes perhaps.

bio2 - 27-3-2008 at 16:24

Well Evil Lurker, I must say that's the fanciest trap I ever saw.

Sheesh, I use a 1L filter flask.

For a portable setup think refrigeration service manifold. 3 ports
2 or 3 valves 2 gauges and the small hoses can be replaced with
1/2" PVC if desired. The high pressure gauge can be replaced with
a 0-30 inch bourdon or just buy the manifold alone.

evil_lurker - 27-3-2008 at 18:25

Ok so I got the mercury in this afternoon... I was supposed to have gotten a pound, but turns out they sent me 500g... most interestingly it came ORM-D in a paint can shipper.

I can't hardly believe how dense mercury is. Its quite amazing stuff.

Anyways, when I filled the manometer, I took a 18 gauge needle and syringe and sucked the mercury out of the bottle and filled it up to the manometer's 5mm mark. Then I laid the manometer on its side and hooked it up to my refrigeration pump and let it run for about 5 mins... overkill probably, but the end result was there was no visible air above the mercury in the center tube.

Testing of the vacuum system indicated a stready 35mm @ 15ºC and 50PSI or thereabouts. Adding adding a small quantity of ice resulted in the pressure dropping to around 29mm.

I think it could be hair better, but I think its good enough for most purposes... I dunno, might change up the trap later to something a bit simpler but I ain't got enough cash at the moment for much more.