Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Vacuum pump recommendations/considerations
HexJam
Harmless
*




Posts: 25
Registered: 29-9-2008
Member Is Offline

Mood: Steady

[*] posted on 10-11-2014 at 16:11
Vacuum pump recommendations/considerations


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.

:D

[Edited on 11-11-2014 by HexJam]
View user's profile View All Posts By User
jamit
National Hazard
****




Posts: 372
Registered: 18-6-2010
Location: Midwest USA
Member Is Offline

Mood: No Mood

[*] posted on 10-11-2014 at 16:54




[Edited on 11-11-2014 by jamit]
View user's profile View All Posts By User
JAVA
Hazard to Self
**




Posts: 71
Registered: 9-1-2014
Member Is Offline

Mood: No Mood

[*] posted on 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.




www.versuchschemie.de

"Keep sportive it's like Soccer: play on the ball, not on the players"
View user's profile View All Posts By User
greenlight
International Hazard
*****




Posts: 689
Registered: 3-11-2014
Member Is Offline

Mood: Energetic

[*] posted on 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]
View user's profile View All Posts By User
Lambda-Eyde
International Hazard
*****




Posts: 856
Registered: 20-11-2008
Location: Norway
Member Is Offline

Mood: Cleaved

[*] posted on 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.



This just in: 95,5 % of the world population lives outside the USA
You should really listen to ABBA
Please drop by our IRC channel: #sciencemadness @ irc.efnet.org
View user's profile View All Posts By User
greenlight
International Hazard
*****




Posts: 689
Registered: 3-11-2014
Member Is Offline

Mood: Energetic

[*] posted on 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]
View user's profile View All Posts By User
chemrox
International Hazard
*****




Posts: 2953
Registered: 18-1-2007
Location: UTM
Member Is Offline

Mood: LaGrangian

[*] posted on 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.



"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
View user's profile View All Posts By User

  Go To Top