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Author: Subject: Is it safe using a diaphragm pump for vacuum distillations
proxymethoxy
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[*] posted on 7-7-2015 at 09:56
Is it safe using a diaphragm pump for vacuum distillations


Hi,
I have an old German diaphragm pump that I want to use for vacuum filtration and distillations and I wonder if the design of the motor makes it safe for work with highly flammable organic solvent fumes.

It seems like it wasn't intended to be opened by untrained personnel so I haven't actually checked the design of the motor to see if it includes brushes that could give off a spark.

If I had to make a guess I'd imagine its safe since the pump is for lab use (but of course I could be horribly wrong).

Any advice would be appreciated.
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battoussai114
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[*] posted on 7-7-2015 at 17:36


Really can't say... IF it uses a brushless motor AND is teflon coated it should be safe.... now brushed motors may create sparks and fires, and without teflon most diaphragm materials I know wouldn't stand much before the solvent attacks it.
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proxymethoxy
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[*] posted on 7-7-2015 at 21:28


In that case I'd buy liquid nitrogen and build a vapour trap to lower the risk.
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Zombie
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[*] posted on 8-7-2015 at 04:02


Any brushed motor can be made ignition safe with a fine stainless mesh added at all the air vents of openings in the case. I convert alternators / starters for marine use, and they must be ignition proofed for gasoline powered boats.



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MrHomeScientist
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[*] posted on 8-7-2015 at 05:29


That's pretty brilliant, actually. It's the Davy Lamp principle!
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proxymethoxy
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[*] posted on 8-7-2015 at 10:23


I knew I've come to the right place.

I'd love to just go ahead and see if warm ether vapours would cause the apparatus to explode but even though its interesting its also dangerous and I don't want to bring harm to local residents nor get arrested for it.

Are laboratory diaphragm pumps used for this sort of thing in general? I agree certain solvents might easily damage an unprotected membrane which prompted to think of ways to limit the solvent flow rate without compromising the pressure. A really cold vapour trap is what I imagine would help.
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Zombie
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[*] posted on 8-7-2015 at 16:36


The trap will condense, and collect any vapors as a liquid before it reaches the pump mechanism.
Then you only have to deal with the collected liquid.

You can buy #10-20 stainless mesh from Ebay, and actually enclose the motor in a mesh box if you are not comfortable opening it up to modify it. The idea works, and if you look it up for Marine electrical components they are thoroughly tested in explosion proof chambers where they use Propane/oxygen mixtures. The cool part is they always use a secondary Ign source to verify the gas mixture. They blow it on purpose.

I'd like that job.

I never heard of Davy Lamps so thanks for the link. That was cool to read.

[Edited on 7-9-2015 by Zombie]




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