cheap acrylic fume hood

[kronix]

hey everyone, hows it going?

i was at my local recycling yard today cherry picking circuits when i realized that he most likely had acrylic and plexiglass waste kicking around from the company that makes light up signs. he pointed me to a few bins full. i pulled out some good sheets, and he charged me 28 cents a lb for 37 lbs, just over 10 dollars.

the sides will be white acrylic, and the window will be clear plexiglass.

from what i have read it will hold up to most chemicals used for refining other than nitric acid over 10%, but nox fumes are OK.
http://www.acuitybrandslighting.com/library/ll/documents/otherdocuments/acrylic-polycarbonate-compatibility.pdf


if i have a HDPE catch bin in the bottom it should be fine for 50/50 nitric and aqua regia, as long as i don't spill any on the sides.

i will be attempting to make something similar to this, i got a quote from them for around $750 but it was the ducted model. thats also not including shipping to canada.
http://www.sentryair.com/specs/Ductless-Fume-Hood-Spec-218-DCH.htm


for venting i was kind of hoping for some input from some members here as to the best bang for my buck.
one idea i had was a 3 bucket scrubber system with a wet/dry vac at the end pulling air through, although im not sure if that would be a good idea or not.

any input would be greatly appreciated, and considered for the final build, once all the kinks are worked out.

also, the sheets are 1/4 inch thick, and a pain in the arse to cut.. does anyone have any better methods than a dremel to score and a fine toothed hand saw to cut? is there a recommended adhesive for acrylic, and does anyone know of any type of sealant like caulking for the inside edges that will stand up to the fumes?

i have a copy of cad 3d, i was going to play around and make a model in there first to get all the measurements worked out.

once i get around to cutting and building ill take pictures and upload them as i go.

cheers - Ian

 

[glondor]

The second one shown in the video ( where they are doing drugs) is a better size. I would have it MUCH taller and deeper. The best and easiest and cheapest heat is an electric skillet or if larger is needed an electric breakfast griddle. Plan your base size accordingly. I have 2 griddles and a 5 gallon waste pail that live in mine. Plus you need room for a couple of 4 liter pails and some beakers. You can run out of room fast.

An idea I may implement on mine is a side box vented into the main hood for a couple of 5 gal pails for A/P processing. Still needs venting, just not so much. You can check a furnace repair shop for furnace blowers. I get mine for $50 bucks and they last about 2 years and will run on 110 v non stop.

Good lighting is a must

Forget the flippy door config shown in the videos. Use a slide up style. Easy to do with plastic channels and a couple of screws.

For what it is worth, I threw a box of baking soda down on the base of mine and placed a steel server cabinet panel that fit almost perfectly on the soda, then I threw another box of soda on the steel, pans and buckets live in a little soda sandbox. Not too attractive but any drips and slops are zero'd out instantly.

I found if the blower draws from the back wall it worked better than out the top. Maybe just a design quirk. Make the doorway as close to full width as you can and have a 2 inch lip across the opening as a heavy vapor stop.

Make the minimum draw space at least 4 inches high. (opening) but have a fully closed stop for shut down or emergency.

Have at least 10 outlets available for pans, heat guns, crock pots, blower, lights, pumps and compressors. I use little peristaltic pumps and nebulizer compressors for most needs. Figure your current draw and add necessary breakers. Build in an emergency light that comes on if the power goes off. Have your chem cabs close and your water supply as well.

Just my .10 cents

 

[glondor]

Deleted double post... RE: cutting.. A skill saw with a fine tooth panel blade installed backwards should do the trick. Try a test cut. Better yet a table saw will give a better cut. The blade is backwards to prevent chipping, shards and tearout.

Drawing through a scrubber system will take some strong vac system. They are loud and will not survive long.

 

[kronix]

hey everyone!

so i started cutting my acrylic sheets today, i found it was best to score it multiple times and then break on the edge of a table, and in a door for smaller pieces.

it makes fairly straight breaks with the odd sharp tooth here and there.

also i was looking around for a suitable fan for handling acid fumes, and i think i may have found a cheap solution. its Christmas and everyone has the inflatable yard decorations, which come with a plastic fan that's waterproof. it may not last forever but it should work fine.

ill post some pics of the build once i have all my ducks in a row, I'm going to need to go to industrial plastics and paints soon and pick up some more acrylic and a few things before i can start building.

-Ian

 

[kronix]

I have also decided to go with your advice about the sliding door and I was wondering if I should use some sort of weather stripping to keep most of the assembly airtight except the opening?

What size lip do you have as a heavy vapour stop?

Do you use a lubricant on the sliding door?

Thanks! -Ian

 

[nickvc]

For lighting try clear acrylic tubes with strips of LEDs running inside, little heat but decent light, they do need the protection from the heat and acids, very simple to install and not too pricey.

 

[scrappile]

I bought some of the 36lumen ones to check out, they work on a plugin wall trans former(not included of course) and provide good light
http://www.mpja.com/36-Lumen-LED-Modules-White-12VDC/productinfo/19444+OP/

they have the 72 lumin module also $4.95

 

[kronix]

yeah i still have to figure out the lighting. LED's are a good idea, although i may just rip apart a few scanners and wire up a few cold cathode fluorescent tubes instead, i mean if they're free why not? plus they're bright as hell, combined with the gloss white interior i should have good light quality.

i was looking at designs online, and came across this one:



i was planning to incorporate the pieces in the back to direct the air currents but without the sliders, as my hood will only be about 28 x 20 x 20 with a sash opening of 18".I will also be using ABS pipe as my exhaust vent, out of the window (with a piece of wood cut to fit and sealed with weather stripping.) and possibly a scrubber if i ever process large amounts but hopefully at that point i can afford a real one.

I'm only planning to use HCL-CL, HCL, sulfuric inside it, not nitric, unless im precipitating gold, although there shouldn't be any nitric at that point anyways.

well i am going to go do some more work on it hopefully get some pieces glued and clamped today!

-Ian

 

[scrappile]

Berkley has a hood that pushes air in, I know you have a fan, just found their design interesting, link to site and a picture from there


http://ateam.lbl.gov/hightech/fumehood/fhood.html

 

[kronix]

interesting, that's actually a good idea.

i havn't gotten the fan yet, i was waiting to see if one came up for free online after Christmas, or if anyone i know has a ripped inflatable.

i could probably rig something up with computer fans, using ABS pipe to channel the air through 2 pipes (top and bottom of sash) with holes drilled to direct air directly into the sash opening.

is there closed systems, that operate with the sash airtight, introducing air via ducts internally? in the future i may experiment more once i get this one built, i have access to lots of really cheap acrylic at the recycling yard that i have a deal with.

either way i will most likely have to wait until after Christmas to complete this project, as funds are a little tight. i think ill still need at least 3-4 more lengths of .5"x.5" by 6 feet clear acrylic, I'm using this to beef up inside corners and some outside joints, and a few other things.

I just have to run to my father in law's to grab some clamps so i can start gluing the base pieces together. then i will upload a few pictures with my materials i have and the base.

 

[scrappile]

just found this,
Small fans are located at the top and bottom of the hood's face, pushing some air into the hood, and some into the user's face," said Bell. "This creates an 'air divider' zone, separating the user from the interior. Since there is a barrier preventing inside air from escaping into the room, the exhaust fan can be run at a much lower velocity."

looks like it still needs exhaust fan, just slower speed,

on the air tight, they have an inlet at top of the sash that looks open all time

 

[butcher]

The baffle in the back of the fume hood with the opening at the bottom of the hood is important, as many of these fumes are heavier than air, and will fall to the floor of the fume hood, the opening at the floor will suck out these fumes from the draft behind the baffle.

 

[scrappile]

The baffle in the back of the fume hood with the opening at the bottom of the hood is important, as many of these fumes are heavier than air, and will fall to the floor of the fume hood, the opening at the floor will suck out these fumes from the draft behind the baffle.

I was wondering about the hood Noxx had plans for because It doesn't have baffles shown, or at least I didn't see them on the pdf ,..

 

[kronix]

i finished gluing the pieces to the base, and surprisingly it made quite a difference in the sturdiness of the base.

i have started to figure out the measurements for the baffle system, and i was wondering if i should have the vent in the middle on the back portion. i was thinking that it might be better suited to leave it out so there is more suction to remove the heavy vapors from below.

here's some pics:





all of the white acrylic i have has a layer on the other side that looks like it came from a sign. it doesn't peel easily though i was hoping someone had a suggestion on a way to remove it a little easier. i have lots of smaller pieces to experiment with so any ideas are welcome


well that's all for today but i hope to work on it a little more tomorrow.

- Ian

 

[glondor]

Hey K Sorry I did not get back to you. The channel for the sliding door can be a bit loose for easy operation. I would recommend the door be on the out side not the inside. I lube the tracks with fluid film. I use a 1/4 by 2 inch aluminum bar as a threshold for fume retention. So it is 2 inches high. Which makes a perfect hanger for spray bottles.

RE airtight. Mine is not, as it is always under negative pressure, I just never turn it off. However it is tight enough hold any fumes during a power outage.

 

[butcher]

The base of floor I would consider making it like a tray to catch spills, possibly at a slight angle so the spill drain to one area and could be siphoned up, or better with a drain to a bucket, or use a catch tray that can be removed from the hood.

No need for the fume hood to be sealed for air leaks.

Most fume hoods baffles I have seen only had opening slot at base and top (no vent in middle), fumes normally rise or fall, and with draft are pulled up and out.

Fume hood door or window opening, can also have a bearing on CFM of air flow, you can only suck out the amount of air you let in, if door opening is too large or fan or exhaust duct too small or too many restrictions in ductwork elbows and so on air changes could be less, or may not work as well.

Another thing to consider when running a fume hood in a building, the building or lab would need just as much outside or fresh air supply to be able to enter the room, as the fume hood was trying to pull out, if room could not get this air the fume hood would not work properly, you can only suck out the amount of air you let in, (in cold weather this air would need heating to keep lab warm), one way to help with this is to let most of air into lab close to door of the fume hood, so this cooler air for the fume hood with a small portion of air supplied across the lab opposite of fume hood, vents dampers windows and so on can be adjustable, but you should also provide a minimum opening for air flow that cannot be closed, and would provide minimum air flow for the hood.

Maybe just a little heat from a heat gun will help to remove paper from plexiglass, plexiglass can also be bent into shapes with a heat gun or electric heating pad.

 

[kronix]

i will have a hdpe catch basin inside once it is all finished, to catch any spills. i figured this would be the safest, and easiest route rather than trying to build it in.
also, i have a side room attached to my lab room that i will open the window to vent air in to the room. i was planning to light a bunch of incense at different places in my area to see how the air flows once the hood is built and installed.

the door is designed to slide inside, but the top piece will end right at where it slides up, with a lip extending down about an inch or 2 with some weather stripping for a seal.

this is my first time building anything out of acrylic. i hope it all goes well, it might look a little funny with the red and gold stickers on the other side, but as long as i can make it functional that's all that really matters. all i can say is this stuff can be a pain in the arse to work with, and it can be as sharp as glass as well, i ran my hand along a scoring line and got an invisible splinter, im pretty sure i removed more skin than actual sliver trying to get it out. now i wear gloves, of course lol.

- Ian