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Author: Subject: Fume Hood Construction
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[*] posted on 9-7-2016 at 17:48


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. :o
Ok, thanks. I'll see how feasible it would be to change the configuration of that motor then.



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[*] posted on 10-7-2016 at 12:24


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. ;)




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[*] posted on 10-7-2016 at 12:44


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



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[*] posted on 11-7-2016 at 08:44


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).

outlet louvre.jpg - 113kB

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.





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[*] posted on 11-7-2016 at 12:42


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?
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[*] posted on 11-7-2016 at 13:18


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.

http://kewaunee.com/uploadedFiles/Main/Home/Laboratory/Manua...

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]




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[*] posted on 12-7-2016 at 06:48


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]
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[*] posted on 12-7-2016 at 07:09


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.
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[*] posted on 12-7-2016 at 09:20


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.




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[*] posted on 12-7-2016 at 12:46
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 cleaned with water.jpg - 215kB
9 inch blower wheel washed with water


blower wheel outer edge.jpg - 205kB
blower wheel outer edge


blower shaft and inner bearing.jpg - 113kB
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]




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[*] posted on 13-7-2016 at 13:37


FYI I have posted a procedure for calculating the pressure drop in a fume hood system in Prepublication here





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[*] posted on 14-7-2016 at 10:47


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.
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[*] posted on 14-7-2016 at 11:23


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.


Books? I saw a bunch of PDF downloads, but what books?
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[*] posted on 20-7-2016 at 16:20


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.jpg - 179kB
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 removed.jpg - 120kB
upper baffle

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

ss hood floor pan.jpg - 110kB
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.

hood outlet (8 inch).jpg - 95kB
8" hood outlet

hood with upper baffle removed.jpg - 100kB
hood w/upper baffle removed





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[*] posted on 23-7-2016 at 10:08


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.

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[*] posted on 28-7-2016 at 08:43


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.



grass affected zone.jpg - 332kB




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[*] posted on 28-7-2016 at 12:31


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]
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[*] posted on 1-8-2016 at 10:40


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:



outlet plenum.jpg - 114kB




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[*] posted on 1-8-2016 at 10:53


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.


Books? I saw a bunch of PDF downloads, but what books?


I believe that I requested the books through this page.

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]
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[*] posted on 3-8-2016 at 09:42


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.

dangleometer at hood outlet.jpg - 100kB dangleometer at hood face.jpg - 127kB

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]




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[*] posted on 28-12-2016 at 02:29


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]




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[*] posted on 28-12-2016 at 09:37


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 just fast enough 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]




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[*] posted on 28-12-2016 at 10:39


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



Attachment: Chemical Fume Hood Guide 1.pdf (78kB)
This file has been downloaded 103 times

Attachment: Chemical Fume Hood Guide.pdf (772kB)
This file has been downloaded 1052 times

Attachment: Chemical Fume Hood Handbook.pdf (201kB)
This file has been downloaded 99 times

Attachment: Fume Hoods - Design, Construction, Maintenance and Use.pdf (298kB)
This file has been downloaded 105 times

Attachment: Fume Hoods - Ventilation.pdf (98kB)
This file has been downloaded 100 times

Attachment: How to Select the Right Laboratory Hood System.pdf (322kB)
This file has been downloaded 83 times

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


/CJ

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




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