HexJam - 10-11-2014 at 16:11
Hi all,
I've been thinking of getting a proper vacuum pump (I'd previously just been using a airbrush compressor to do quick vacuum filtrations), one that
could hold and sustain a decent vacuum for an extended period of time so I can have a go at vacuum distillation.
I was considering one of these two:
http://www.hvacstore.co.uk/acatalog/3cfm_Vacuum_Pump.html
http://www.hvacstore.co.uk/acatalog/VPump_4_CFM_Vacuum_Pump....
I'm something of a noob (read: I'm a noob!) regarding vacuum pumps, I'm guessing either of these two would be able to do the trick? Is there much/any
advantage of getting the more expensive 4 CFM one?
I don't think either comes with a gauge, any recommendations of which of these I'd need:
http://www.hvacstore.co.uk/acatalog/Vacuum_Gauges.html
As I understand it, if I get one with a manifold setup, I'd be able to control the level of vacuum rather than it being an all or nothing vacuum,
right? Last noob question, the hose that comes from the pump has 'a 1/4" Flare SAE threaded fitting with a hose barb with 1/8" BSP thread' I take it I
can get some kind of adapter to attach that to my scrubber / quick fit set up?
Thanks in advance for your advice! 
Apologies for asking any questions that have
(no doubt) been asked a million times already.
[Edited on 11-11-2014 by HexJam]
jamit - 10-11-2014 at 16:54
[Edited on 11-11-2014 by jamit]
JAVA - 16-11-2014 at 07:38
1) price/quality ratio
2) How much mBar is needed (only filtration?)
3) oil: low vacuum compared to water because of the higher vapor pressure from water.
4) Diaphragm pumps are another option, but this pumps don't run on oil and no need to refresh the oil from corrosive chemicals. Can run automatical
but finding special wires, electronics to repair the controller is a expensive and tuff job.
greenlight - 17-11-2014 at 03:24
Isn't CFM a different rating altogether for vacuum pump performance.
I read that there is the vacuum rating which measures the largest amount of vacuum the pump can generate measured in "Hg (millimeters of mercury), and
the CFM (cubic feet per minute) which measures how many cubic feet of air the pump is able to move.
Doesn't the CFM just mean how fast you can get your vessel to full vacuum, so it shouldn't make much difference in performance and the real rating to
look at is the "Hg.
While on the subject of vacuum pumps, I want to start vacuum distilling my Nitric acid for a cleaner and more concentrated acid. How important is it
to have a cold trap (water trap) between the vacuum receiver joint and the pump to catch the acid vapours. Will my pump completely corrode and die if
I do not use one or should i go straight out and buy one.
[Edited on 17-11-2014 by greenlight]
Lambda-Eyde - 19-11-2014 at 14:25
If you an use oil pump for vacuum distillations without a cold trap, it's just a matter of time before it dies. If you intend to expose it to
corrosive vapors (really, any vapor - water in the pump oil isn't good either), use a cold trap. Or keep your eyes peeled for a good deal on a
diaphragm pump.
greenlight - 19-11-2014 at 21:33
Would one of these be fine to buy and use to protect the vacuum pump if it is filled with sodium hydroxide solution or sodium bicarbonate solution?
http://sciencesupply.com.au/shop/dreschel-gas-wash-bottles/2...
[Edited on 20-11-2014 by greenlight]
chemrox - 20-11-2014 at 01:50
If you have lots of money buy a new two stage oil pump. If not keep your eye out for a deal. I got a Welch for $20 that achieves 1-2 mm. It had been
abused; probably used for distillation without a trap. But Welch is a great pump and after flushing with cleaning oil several times it works just
fine. I got a corrosive vapor Welch as part of a vacuum station that included a manifold, gauge and cart. That I got for shipping costs.