Sciencemadness Discussion Board - Outfitting a diaghphragm pump

Outfitting a diaghphragm pump

smaerd - 2-1-2013 at 08:34

Here's my experience with vacuum pumps. I had a fridge pump once, it gargled up the water in it's ice-water bath and died

. Though a few weeks ago I bought a rough vacuum diaphragm pump(~200mbar), previously I've relied solely on a water aspirator. I think it'll suit my needs for simple tasks such as vacuum filtration, and basic solvent removal. Won't be ripping any DMF or DMSO or anything, probably things like ethyl acetate, THF, dichloromethane (wouldn't want a fine vac for that anyways), etc. Not really lacking the theory on vacuums or anything not to say I'm an expert but the practical stuff is where I need some advice.

Anyways, I read the manual for it(provided by gast) to see what kind of in-let it uses as I am confused about the in-let that was provided. It's a 1/4 NPT thread but it's pretty peculiar I'm not sure what its function is. It had a two part red 'nozzle' thing that says 1/8 which I believe represents 1/8 inch for its outer diameter and it also says "SMC". Edit- it's actually a bit bigger then 1/8 inch so that theory is gone. On googling "SMC" or "1/8in SMC" shows pictures of cameras and dozens of other abbreviations.

Should I be trying to find a 1/4 NPT nipple connection to fit on some hose and replace this piece altogether, or should I be trying to fix hose to this weird red thing? A picture is provided. Any advice or guidance is much appreciated as always.

[Edited on 2-1-2013 by smaerd]

Mailinmypocket - 2-1-2013 at 11:07

Quote: Originally posted by smaerd

Here's my experience with vacuum pumps. I had a fridge pump once, it gargled up the water in it's ice-water bath and died

This won't be of much help... just my opinion, but I think a hose barb would be the easiest replacement. Actually what is that red thing anyways?

I recently bought a vacuum pump as well and had to hunt around for a hose barb adapter at Home Depot and found one in the plumbing section... Installed it on the pump and no problems so far. Could it be that the red bit is some sort of filter for particulates?

One thing I also found at the good old Home Depot in the air compressor accessories is an in-line filter to trap micro fine particles from entering your air tools, I bought it and it can hold a vacuum and works well. Not like I tried to vacuum shit up just for fun, just saying, it might be worthwhile if you need a filter of some sort.

[Edited on 2-1-2013 by Mailinmypocket]

Hexavalent - 2-1-2013 at 11:52

What are the innards of your pump made from, smaerd? Unless they are constructed from PTFE or another fluoropolymer, you'll probably want a trap for your pump to protect it. I started a thread about potential designs actually, as I've just acquired a nice Gast 68mbar pump and don't want to destroy it.

[Edited on 2-1-2013 by Hexavalent]

smaerd - 2-1-2013 at 13:08

Oh I will definitely be using a cold trap, it's bad practice not too. Even if the pump has protective material. Mine only pumps down to 200mbar so it won't be as hard to stop the solvents before going into the pump itself, especially with a nice friedrich condenser before a cold trap. This is partly why I chose it. Supposedly it is "corrosion resistant". For really volatile solvents I don't plan on using it, I figure the increasing of the surface area(rotary evaporation) as well as the heat from a warm water bath would easily do the trick of removing the solvent and quick enough at that.

Just unscrewed the pump-head, and did some cleaning all there is really that would be susceptible to solvent abuse would be the gaskets as its a diaphragm pump not a rotary vane. A repair kit costs 25 dollars if crap hit the fan, including a new gasket and o-rings, etc. I wonder how hard it would be to use an exact-o knife and cut out a new gasket out of a more resistant material anyways, this seems like EPDM. Probably wouldn't be bad at all. Could probably get a sheet to make 4 gaskets from of viton for 20 dollars.

I guess I'll have to check out the hard-ware store for the right sized nipple thing. Home-depots web-site didn't show too much promise.

[Edited on 2-1-2013 by smaerd]

Mailinmypocket - 2-1-2013 at 13:16

Quote: Originally posted by smaerd

Home-depots web-site didn't show too much promise.

Nope, the site is very poorly built :S Go to the section where clear plastic tubing is sold (near the toilet stuff in my local store) and you will find a huge variety of valves, adapters, hose barb adapters with threads inside and outside etc. Otherwise check the air compressor accessories and they have some, although not as many, types of hose barb adapters.

[Edited on 3-1-2013 by Mailinmypocket]

smaerd - 9-1-2013 at 08:59

Thanks mailinmypocket just went to the hard-ware store got the right sized fitting did a quick wrap with some teflon tape and screwed it in. Works a treat. Also scooped up some DCM

CaliusOptimus - 10-1-2013 at 18:05

That red fitting is called a push-to-connect fitting. You simply push in a hose of the correct diameter (1/8" OD for your fitting), and it is sealed by an o-ring and held in place by a (usually) stainless grasping ring. To remove the hose, you push down on the plastic ring, and pull out the hose. These fittings are common in compressed air systems, but leak like a sieve under vacuum.