Sciencemadness Discussion Board - Another DIY Fume Hood Topic

Another DIY Fume Hood Topic

KingBoo - 11-5-2013 at 23:41

I want to make a fume hood for my garage and needed more information than what was available from a search on this site.

Essentially all I will be doing is natural extraction, and maybe simple reactions such as soap making and esterfication. So I will just be working with some acids/bases and organic solvents.

There are a few problems I need the answers for, then I can make a proper tutorial rather than what is available on you tube and this site.

1.) I want it to be portable, around 2 1/2 feet width, 2 feet high, 2 feet depth. So I figured I would use 1/4" plastic sheets and put them together with the appropriate glue. I need a plastic that is cheap, but also not soluble in organic solvents such as methlyene chloride, ethyl acetate, hexanes, etc. I saw acryllic but it looks like the fusing glue is just methylene chloride, which I would assume would not suffice since the vapors would just dissolve the plastic eventually.

2.) There is always a risk of fire, if a fire occurs in the hood the plastic will melt/burn. How should I prevent this long enough so I can put on the flame with a fire extinguisher and not damage the plastic?

3.) What fan should I use? I know the copper coils need to be away from any air source to prevent organic vapors from catching on fire, but I didn't see any names of these types of fans anywhere. Would they sell them at home depot?

4.) I need to choose the outlet. Worse comes to worse i use pvc, but I would rather have those flexible stretching tubes, would something like this do? It is made out of HDPE which I think would be safe. http://thd.co/17gw7kj

Thanks for the help, I am hoping I will be able to post a topic and video about it ACTUALLY documenting the steps instead of showing off the final product with no specs...

blogfast25 - 12-5-2013 at 05:52

You're aware that there is a thread on this already? Do use the search facility to find and consult it first.

bob800 - 12-5-2013 at 14:12

Quote: Originally posted by KingBoo

3.) What fan should I use? I know the copper coils need to be away from any air source to prevent organic vapors from catching on fire, but I didn't see any names of these types of fans anywhere. Would they sell them at home depot?

Here's what I used: http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT2?cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1 At the time I found this model for $100 on ebay, so don't think you have to pay Grainger's price.

The other (and slightly better) option is to buy a seperate motor and fan, connected by a pulley. This is much more expensive and harder to implement, however. With enough airflow, you shouldn't have to worry about vapors igniting.

Regardless of what blower you buy, make sure it has a good "fan curve". The CFM ratings usually listed refer the the blower's capacity without airflow resistance taken into account. The actual CFM rating on many cheap blowers often drops sharply as resistance is introduced.

Keep in mind that any length of ducting, sash closure, etc. will introduce airflow resistance. There are many formulas for calculating these things if you search for other threads.

KingBoo - 12-5-2013 at 17:15

Quote: Originally posted by bob800

What specifically made you choose this model? What keywords should I look up to make sure this is what I want? All I see is "Motor Enclosure - Open" which I would assume is the motor would be in contact with the flammable vapor? I do not see any keywords indicating that is it chemically resistant.

Thanks for the post!

hyfalcon - 12-5-2013 at 17:48

Go to ebay and type in "PSC Blower". That should take care of you.

KingBoo - 12-5-2013 at 18:42

Quote: Originally posted by hyfalcon

Go to ebay and type in "PSC Blower". That should take care of you.

Thank you for the response. Can you give a basic explanation why a Permanent Split Capacitor would be safe to use with solvent fumes?

KingBoo - 12-5-2013 at 21:07

Decided on polypropylene, but I need a transparent material in the front so I can view what I am doing.

This is a problem because all of the transparent plastics I found (Acrylic (polymethlamethacrylate), Butyrate (cellulose acetate butyrate), Lexan (polycarbonate), and PETG (glycol modified polyethylene terphthalate) do horrible with acetone/ethyl acetate/etc.

Is there any transparent alternative other than glass?

Thanks!

bob800 - 13-5-2013 at 14:51

Quote: Originally posted by KingBoo

--It has a good fan curve (see the @0.000... inches SP table in the specs page)

--The motor's internal workings are separated from the metal piece that spins around (the little cylinder in the back is the motor). The only exposed piece is the shaft.

--Chemical-resistant blowers cost thousands of dollars and are completely unnecessary for a home lab. I simply took out the metal blower (which is mild steel BTW) and sprayed it with protective enamel. After a few years of use it is slightly rusted but still in good shape, and I expect it to last for several more years.

The ONLY disadvantage to this blower, IMO, is that the outlet is square-shaped so it might be hard to attach ducting. My setup didn't require any ducting so I just built a little wooden box protruding to the window.

EDIT: In terms of sash material, I used a piece of plexiglass. However, I rarely work with significant quantities of solvents, so I don't know if fogging will present an issue... Keep in mind, though, that with enough airflow, you needn't worry to much about these things. I would just buy some plexiglass and see how long it lasts.

[Edited on 13-5-2013 by bob800]