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Author: Subject: Fume Hood Construction
Texium (zts16)

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 Quote: Originally posted by Magpie I think the motor wouldn't last long in the corrosive exhaust stream. I wouldn't trust that sparkless claim, not with a duct full of ether fumes above the LEL.
Ok, thanks. I'll see how feasible it would be to change the configuration of that motor then.

Magpie
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 Quote: Originally posted by careysub Very interesting Magpie, thanks!

You are welcome.

 Quote: Originally posted by careysub But first I have to clean out the area of the garage where the fume hood would go. That is a bit of a project in itself!
Amen.

 Quote: Originally posted by careysub Plans of course will continue to be refined until it comes time to actually build, e.g., I am now considering the American Craftsman 37.75 in. x 56.75 in. 70 Series Double Hung window at Home Depot for a minor price increase (whole project cost considered), slightly larger, and gives me maximum flexibility with flow and shielding.
Good idea. I'm sure you will appreciate the extra space.

 Quote: Originally posted by careysub Looking at the Dayton blower you linked to, that is actually a direct drive - not a belt drive model. It appears that all of the belt drive units are larger than what I need. But I am considering the direct drive version, perhaps with the totally enclosed motor, as I don't really want to mess with the belt anyway. This also has the motor out of the air flow, and perhaps a metal screen - a la the Davy safety lamp - could be installed between the motor and the blower.

Totally enclosed fan cooled (TEFC) motors are the favorite of industry where there can be wet environments. Such as an outside area with no roof. Also picture an operator with a high pressure hose cleaning up a big spill of pulp slurry. These are not spark proof and IMO are a waste of money for our application. Instead I recommend a "drip-proof" motor - which is what I have.

While on the subject of motors I feel the "split-phase" is adequate, which is what I have. We don't have high starting torque or high cycling on and off which might require the more expensive motors like "capacitor start," etc. We also don't run continuous duty which could justify a more expensive motor that draws fewer amps.

Also the sleeve bearings that came with my motor seem to be adequate vs spending more money for ball bearings.

I'm certainly not an expert on the subject of motor selection, these are just my studied opinions. If anyone wants to add to this discussion I welcome that.

The single most important condition for a successful synthesis is good mixing - Nicodem
Texium (zts16)

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Well you probably know more about them than most people on here, so your studied opinions are greatly appreciated!

Magpie
lab constructor

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I'm still in the middle of fume hood maintenance. Here is a picture of the outlet louvre. It is discolored after 6 years of use (house was painted 6 years ago).

This morning I cleaned it with dish soap and hot water using a long-handled scrub brush. It looks like new now, almost. I will give it a coat of paint in a few days.

I'm anticipating that the blower wheel will be pulled today after I buy a hub puller.

The single most important condition for a successful synthesis is good mixing - Nicodem
Loptr
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Nice find with the 80/20 erector set!!!

This will be taking my fume hood construction in a new direction.

How expensive do you expect this to turn out with 80/20 pieces?
Magpie
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There is a pressure loss we have been forgetting, ie, that of the hood itself. Kewaunee shows that for a 100 fpm face velocity, 4' hood with 8.1ft^2 open area this pressure drop is 0.25" H2O. Be sure to take this into account.

Note that Kewaunee does not recommend a face velocity less than 100 fpm (1.67 fps)!

I am preparing a tutorial/instructable for calculating pressure drop for fume hood systems. I should have it ready in a day or two.

[Edited on 11-7-2016 by Magpie]

The single most important condition for a successful synthesis is good mixing - Nicodem
careysub
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 Quote: Originally posted by Loptr Nice find with the 80/20 erector set!!! This will be taking my fume hood construction in a new direction. How expensive do you expect this to turn out with 80/20 pieces?

As a basic design, a hood made with four 7' tall pieces, four 30" deep side pieces, four 36" wide front/back pieces, the necessary connectors, and four economy leveling feet comes to $276. I intend to add a few more pieces though - two side pieces and a free side-to-side piece that can be attached to these two side pieces as a way of supporting frames and equipment. With proper planning using the perforated version of the square tube (pre-positioning threading inserts in the frame, etc.) you can easily think vertically - attaching things to the frame suspended above the work table surface (at extra cost). Other options that can increase price - the use of their flush mounting pins on the sides where sheet metal attaches. This is not essential though since you can simply drill holes in the sheet where bolt heads are. I intend to attach to galvanized steel sheet by simply drilling into the aluminum frame and using flange head screws with washers. [Edited on 12-7-2016 by careysub] MrHomeScientist International Hazard Posts: 1745 Registered: 24-10-2010 Location: Flerovium Member Is Offline Mood: No Mood  Quote: Originally posted by Magpie I am preparing a tutorial/instructable for calculating pressure drop for fume hood systems. I should have it ready in a day or two. That would be extremely valuable Magpie! I'm looking in to making a hood in the near future so this will be a great help. Definitely let us know when that's up. Worth a separate topic here IMO. Magpie lab constructor Posts: 5929 Registered: 1-11-2003 Location: USA Member Is Offline Mood: Chemistry: the subtle science.  Quote: Originally posted by MrHomeScientist That would be extremely valuable Magpie! I'm looking in to making a hood in the near future so this will be a great help. Definitely let us know when that's up. Worth a separate topic here IMO. Thanks. I'm planning on placing it in Prepublication. But I will place a link in this thread. The single most important condition for a successful synthesis is good mixing - Nicodem Magpie lab constructor Posts: 5929 Registered: 1-11-2003 Location: USA Member Is Offline Mood: Chemistry: the subtle science. blower maintenance continuation The blower wheel was removed this morning using a hub puller, a 12", and a 15" crescent wrench, and the help of my strong son. The following pictures show the results after 11 years of hobby use: 9 inch blower wheel washed with water blower wheel outer edge blower shaft and inner bearing My plan is to remove the rust on the blades and repaint with epoxy paint. [Edited on 12-7-2016 by Magpie] The single most important condition for a successful synthesis is good mixing - Nicodem Magpie lab constructor Posts: 5929 Registered: 1-11-2003 Location: USA Member Is Offline Mood: Chemistry: the subtle science. FYI I have posted a procedure for calculating the pressure drop in a fume hood system in Prepublication here The single most important condition for a successful synthesis is good mixing - Nicodem Loptr International Hazard Posts: 1240 Registered: 20-5-2014 Location: USA Member Is Offline Mood: Grateful Quote: Originally posted by careysub  Quote: Originally posted by Loptr Nice find with the 80/20 erector set!!! This will be taking my fume hood construction in a new direction. How expensive do you expect this to turn out with 80/20 pieces? As a basic design, a hood made with four 7' tall pieces, four 30" deep side pieces, four 36" wide front/back pieces, the necessary connectors, and four economy leveling feet comes to$276.

I intend to add a few more pieces though - two side pieces and a free side-to-side piece that can be attached to these two side pieces as a way of supporting frames and equipment. With proper planning using the perforated version of the square tube (pre-positioning threading inserts in the frame, etc.) you can easily think vertically - attaching things to the frame suspended above the work table surface (at extra cost).

Other options that can increase price - the use of their flush mounting pins on the sides where sheet metal attaches. This is not essential though since you can simply drill holes in the sheet where bolt heads are. I intend to attach to galvanized steel sheet by simply drilling into the aluminum frame and using flange head screws with washers.

[Edited on 12-7-2016 by careysub]

I went ahead and ordered the books they offer for free. They shipped out yesterday, so I should have them soon and have some idea of how all this fits together.

The books were free, so I figured why not.
careysub
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 Quote: Originally posted by Loptr I went ahead and ordered the books they offer for free. They shipped out yesterday, so I should have them soon and have some idea of how all this fits together. The books were free, so I figured why not.

Magpie
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My fume hood maintenance is still in progress and will be for another week or two.

The blower wheel was sand blasted to remove rust and then spray painted.

painted blower wheel

Today I removed the upper baffle and hosed it down in the backyard. Visibly there was only a layer of dust above the angled part.

upper baffle

The ss floor pan was removed for cleaning underneath where there was a surprising amount of loose dirt.

ss floor pan

With the pan in place I flushed the plastic duct from both ends with a garden hose/nozzle, catching the wash water in the pan.

Here's a couple pictures of the hood with the upper baffle and pan removed. You can see the slight yellowing of the epoxy painted walls. I believe this is due to exposure from my 400w UV light when making CCl4.

8" hood outlet

hood w/upper baffle removed

The single most important condition for a successful synthesis is good mixing - Nicodem
CaptainPike
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WOW – you guys are like – have your SHITE TOGETHER!!

I thought my idea of putting an old box fan in the upper part of the window at my table was my being really responsible and innovative.

Has anyone had any luck constructing an articulating duct with a funnel end which can be lowered and placed above and near the source of fumes? (like some college labs have)

There've only been a few times when I had to exit the building under duress because the ether fumes or the HCl gases were choking me.

Magpie
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This morning as I went out to weed my garden I noticed a band of dead grass about 4 feet long. I then remembered that it is in the spot where I washed off the angled part of my hood upper baffle. Hopefully it will grow back green.

The single most important condition for a successful synthesis is good mixing - Nicodem
careysub
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I hope you resisted the temptation to lick it!

(Probably just killed the foliage. I doubt it poisoned the earth.)

[Edited on 28-7-2016 by careysub]
Magpie
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It was a little cooler today so this morning I reinstalled my blower wheel. All that is left now is to connect the duct to the blower. By noon it was too hot in the attic so I quit for the day.

Below is a picture of the outlet plenum, something I really hadn't shown before:

The single most important condition for a successful synthesis is good mixing - Nicodem
Loptr
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Quote: Originally posted by careysub
 Quote: Originally posted by Loptr I went ahead and ordered the books they offer for free. They shipped out yesterday, so I should have them soon and have some idea of how all this fits together. The books were free, so I figured why not.

https://8020.net/requests

I didn't see the books were available as PDF at the time, but they sent me print outs of everything without costing me a penny. Besides, I prefer books to PDFs, anyway.

[Edited on 1-8-2016 by Loptr]
Magpie
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My hood maintenance was completed this morning. The first picture below shows airflow with the upper baffle still removed. The second picture is at the hood face with the baffle reinstalled. The paper is a strip of facial tissue paper (Kleenex).

Performance shows some improvement, IMO.

BTW, here's a very useful site that I stumbled upon:

http://www.centralblower.com/index.html

[Edited on 3-8-2016 by Magpie]

[Edited on 3-8-2016 by Magpie]

The single most important condition for a successful synthesis is good mixing - Nicodem
JJay
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I've been giving some thought to building a benchtop fume hood. I was thinking about constructing it out of drywall and sealing it together with plaster of Paris, making the floor a flat basin. That way, it could withstand some pretty large spills of nasty materials like concentrated sulfuric acid and could resist flames. Drywall is pretty brittle, though, and it's really not that lightweight... I wonder how hard it would be to work fiberglass into the construction....

There is a lot of appeal to using a small diameter exhaust, but with a 4 inch fan and a 4 foot wide fume hood, I'd only have 4.5 inches of working height at 60 fpm face velocity (assuming a 100 CFM fan). I haven't used a fume hood since high school and have never used one with complex apparatus... how much working height is really necessary?

[Edited on 28-12-2016 by JJay]

I'm no longer involved in this forum.
aga
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A decent fan/blower is certainly a hard-to-come-by item (here at least).

Mine ended up being a standard bathroom ventilator, which is pretty crap, but works.

It chugs away and removes nasties from the hood <i>just fast enough</i> when the sashes are closed.
Sash open = face full of honk.

So far it's handled NOx and Cl2 and is still chooching.

In the end, the capabilities of the extraction system have to be known, and the hood used within those known limitations.

i.e. there will definitely not be any bromine made in my 'hood until the fan system is upgraded.

[Edited on 28-12-2016 by aga]

Corrosive Joeseph
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Seeing as this is the sticky thread, I'll drop these here......................

Attachment: Chemical Fume Hood Guide 1.pdf (78kB)

Attachment: Chemical Fume Hood Guide.pdf (772kB)

Attachment: Chemical Fume Hood Handbook.pdf (201kB)

Attachment: Fume Hoods - Design, Construction, Maintenance and Use.pdf (298kB)

Attachment: Fume Hoods - Ventilation.pdf (98kB)

Attachment: How to Select the Right Laboratory Hood System.pdf (322kB)

Happy f%@king commercialized religious holiday................

/CJ

[Edited on 28-12-2016 by Corrosive Joeseph]

charley1957
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 Quote: Originally posted by Magpie Whatever fan you select it must be able to deliver enough flow to provide 1.0-1.5 fps face velocity at your hood opening. It also must be corrosion resistant and spark free in the exhausted air environment. If you don't have a constant flow design your face velocity is going to vary all over the place, depending on sash position. My squirrel cage fan blades are epoxy coated steel. I have never inspected my fan internals since installation (11 yrs ago). I just know that the fan still works well. 3/8" SP looks a little weak to me but I don't know the diameter, shape, and length of your ducting. My fan delivers 400-500 cfm at 3/4" SP. All of this guidance I have repeated several times in the hood threads to various posters. In the end I find that people just do whatever they had in mind in the first place. Everybody has their own space and money constraints. As garage chemist said: "any ventilation is better than none." [Edited on 6-7-2016 by Magpie]

That last line, any ventilation is better than none, is a good one. Years ago I was part of a forum of Robert Bruce Thompson's before he changed it all and it became a home schooling forum. There was a member there who called herself Xylene, and she often posted pics of her workups. Her fume hood was a piece of round rigid tin duct, about 3" diameter, with a computer fan taped to the end of it closest to the reaction, and the other end was poked out of the nearby open window. Seemed to work just fine for her.

...it has often proved true that the dream of yesterday is the hope of today and the reality of tomorrow.

Robert H. Goddard
Texium (zts16)

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