Sciencemadness Discussion Board - fan selection for homemade fumehood - help

fan selection for homemade fumehood - help

EmmisonJ - 29-1-2009 at 07:21

as stated in a different post i've assembled a homemade fumehood built to handle acid vapors and flammable solvent fumes.

i've read some posts on here, very inspiring, by magpie which without those posts i'd have no idea what to even do. i downloaded some professional fumehood pdf's, without with i wouldn't even know what the components are.

i'm having a difficult time picking out a fan. i attached a picture showing the dimensions of the fumehood, 48" tall / 47" wide / 20" deep is the work area. i've read i can use a bilge fan or a squirrel cage fan and not have to spend over a couple hundred dollars which is why i'm aiming for.

any specific recommendations as to what i should get that is good for my work area?

i currently have no baffles or sash, just like a box with an open face, i can always add baffles (easy - thanks to magpie's assistance to others) and a sash (that one's going to be tricky) if need be. will not having those make my current fumehood completely inefficient? which is more important - a sash or baffles? i'm assuming the baffles only serve for low density vapors to be pulled behind them, out of the work area as opposed to being pulled straight up. and the sash is just to make the front opening smaller so the vacuum is more effective. the sash, if i build one, will never be closed entirely as everything i do requires my hands in the work area at the top of flasks (constantly adding, setting driprate, etc)

[Edited on 29-1-2009 by EmmisonJ]

fh_dimensions.jpg - 55kB

Contrabasso - 29-1-2009 at 11:58

Depends where you are! The cheapest fans come from surplus shops or demolition skips. The best fans cost a fortune. Consider also where you are going to send the fumes and how you will connect the ducting.

Maybe some speed control, maybe look for plastic fan blades to minimise corrosion. Good fans have a bifurcated trunking so that the motor is not in the (acid) gas flow.

The smaller the front opening the smaller the fan flow needed to keep the fumes inside.

EmmisonJ - 29-1-2009 at 12:19

the fumes will be going out the top of the fumehood to some ducting which will make a 90 degree curve so that it's horizontal and lead outside, it will be a very short distance, probably like 5 feet.

i never realized just how much of an artform fumehood building really is, it is not an easy thing by any means.

to be honest i'm hoping to just find an entire fan assembly i can slap in the box and go without spending more than a couple hundred dollars. the problem is, i only vaguely know what to look for so i'm having a hard time looking for a specific fan.

what do you guys here use? like a certain brand, model i can look at then figure out which model i'll need to move air properly in my work space

chemrox - 29-1-2009 at 19:42

Do not make any abrubt bends in ducting that eventually needs to turn 90*. The airflow will be seriously choked with turbulence and backflow. For example chimneys with 90* bends don't draw... at all. That out of the way, I've seen small DIY hoods that used computer fans. I'm skeptical. A bathroon exhaust fan, however, should meet your needs admirably and would be cheap enough. I just installed a 12" exhaust fan with louvers to move my lab air out of the building. I was looking for a complete change of air every ten minutes so I took the volume of the lab and the cfm rating of the available fans and specced the fan from there. Most industrial supply catalogs have the specs and from there you can figure out what to look for at the hardware or surplus bldg. material store. I suspect that Lowes and Home Depot or their equivalents post the fan specs somwhere on their web sites too.

Sauron - 29-1-2009 at 20:39

Do yourself a real favo and get a proper lab fume hood blower, which is driven by a separate motor so the motor never deals with the fumes. See Nalgene's site. If you work with HCl do not use PVC as it will catch fire with HCl gas.

Magpie - 29-1-2009 at 21:23

Quote:

If you work with HCl do not use PVC as it will catch fire with HCl gas.

Sauron, do you have a reference for that?

chemrox - 29-1-2009 at 21:50

@Sauron what concentration would do that? My partner was all worried about H2 and ether fumes until I sat down with him and worked through some scenarios from the real lab world. Sauron has a good point though; a hood is to protect your life, work space and equipment.. don't go cheap (unless you hold those things to be cheap too...)

Sedit - 29-1-2009 at 21:57

"PVC as it will catch fire with HCl gas."

Id like personaly to see one my self as I have worked with HCL around PVC alot and never had anysort of a problem..,and Im a Plumber by day

. Of couse I try not to get concentrations of anything to high around things that maybe reactive so I could see how a chlorinated vinyl could react under extream conditions.

Ok on topic, I have always found the fans from old heaters to be effective at moving the air out of a homemade fume hood. The motor is seperated from the blower so as long as precautions are taken one wouldnt have to worry about damage to the motor. These blowers can move ALOT of air, they are SPARKLESS and shaped in a nice way so that an air duct can be set up to divert the fumes outside.

I do forsee a problem here though with the acids even though alot of the fan constructions are stainless steel I wouldnt put to much faith in pumping concentrated acid vapors through them although since some air is drawn in from the side also they will dilute in the fan itself.

Possibly a spray coating of teflon would help ease any problems one has with acid damage. Iv always used mine for years now for smelly reactions and solvent vapors without incedent but Iv always strayed away from strong acids indoors.

Flammability of PVC in HCl

gsd - 29-1-2009 at 22:45

Quote:

Originally posted by Magpie

Quote:

If you work with HCl do not use PVC as it will catch fire with HCl gas.

Sauron, do you have a reference for that?

LOL

I have a reference to this, but unfortunately it says the chemical resistance of PVC to HCl upto 10 % concentration is excellent

further it says nothing about fire hazards of this pair.
It is a very credible reference: Perry 7th Ed. page 28-49
The entire chapter on MOC is attached herewith.

gsd

Attachment: CE_Handbook_Perry_7ed_Chap28.pdf (638kB)
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EmmisonJ - 9-2-2009 at 11:32

unfortunately a proper fume hood blower is out of my league ($1000+) and i don't think the bathroom exhaust fan would last very long would it even i'm able to find one that moves enough air?

i've been shopping online for bilge fans and they come quite cheap but would need a 12v to 120v adapter for them (no big deal) and squirrel cage fans but know too little about it to make a proper decision.

considering there is no sash, would 2 of these be suitable (2 x 240cfm = 480cfm)?

http://cgi.ebay.com/ebaymotors/BILGE-BLOWERS-EXHAUST-BLOWERS...

Magpie - 9-2-2009 at 11:55

using your data:

face velocity = (480ft3/min)(144in2/ft2)(1min/60sec)/[(47in)(48in)] = 0.51 ft/sec

You should have at least 1ft/sec face velocity.

A sash would cut down the face area thereby increasing your face velocity.

Remember, the primary reason for a sash is safety. If you are going to operate without one be sure to always have on eye, face and hand protection in case something blows up in your face.

From personal experience I can say that I feel much more confident doing unfamiliar reactions in my hood when I have a double pane of safety glass between my face and the reaction apparatus.

[Edited on 9-2-2009 by Magpie]

EmmisonJ - 9-2-2009 at 12:18

hm and for the price of ganging up bilge fans i really would be better off finding a sparkless centrifugal fan, plus i read in another thread on here about a concern with bilge fans not holding up long-term either, that they are meant to only run for a few minutes at a time.

magpie, i saw your fan in another post and am looking for a similar solution that will work with my setup. i like your idea of moving the motor outside the fume hood so you don't have to worry about it being explosion proof. how would you go about doing that exactly? remove the motor and mount it outside of the fume hood but have a small opening for the belt? wouldn't that pose as a risk for a leak? also since the motor would be a further distance away that means you'd have to get a longer belt, wouldn't that put a damper on performance of the fan as well since the belt's longer it wouldn't turn quite as quickly as a shorter distance belt? or is that performance hit minimal as long as its within a few feet and the motor's strong enough to begin with

being that my hotplate isn't explosion-proof (again, can't spend thousands) i definitely want to have safety in mind but can't spend more than a couple hundred dollars on the fan

[Edited on 9-2-2009 by EmmisonJ]

watson.fawkes - 9-2-2009 at 12:41

Quote:

Originally posted by EmmisonJ
unfortunately a proper fume hood blower is out of my league ($1000+)[...]

Nonsense. Here's a blower on eBay that took me just a couple of minutes to locate. (There's even points on fan curve in the description.) For about USD 100, you can have an adequate blower for a modest hood with short exhaust runs. That particular fan would need a plate adapter to seal it up, but if can build a hood, you can figure out how to get the fan mounted and sealed up.

Jor - 9-2-2009 at 12:45

When you do not have air-directing baffles, I think a sash is a must, or a lot of contaminants will be swept out of the hood at the upper half of the opening, where normally the sash would be.
I do not have baffles, but I do have a sash, wich can be opened to a maximum of halfway up. At this height, nothing will get out of the hood, at least when the motor is at 25% or 50% power. Higher, turbulence steps in, and small amounts leave the hood.

I think a sparkless motor is not an absolute necessary. Flammable vapours are diluted enough before they reach the motor. Ofcourse you should not boil ether away or something like that. However, you must put your blowers at the end of the duct, if you put it right above the hood, i can't guarantee vapours are not diluted. As far as I know, everyone on the german forum versuchschemie does not use sparkless blowers, including our member garage chemist.

A greater problem is corrosion. Make sure the coating of the area where the vapours go through is NOT metal, or HCl and such will make quick work of it. Mine is plastic coated, except a part in the back, but it doesn't seem like it would hurt much, as it looks to be some kind of armour protecting the motor.
I bought a blower for 120 EUR, and after months of passing through HNO3, HCl, halogens, solvents, etc, it still works just like when it was brandnew. And in case it will be destroyed by the vapours sometime, I will just buy a new one, take the destroyed blower out of the duct, and put the new one into the duct.

https://www.leafman.nl/ruck-rk160l-4standen-buisventilator-p...

This is the one I bought. It's a lot cheaper than those sparkless proof, corrosion proof ones, but may need replacement in a (few) year(s).

This is my hood design:
http://i405.photobucket.com/albums/pp133/Joris12345/P1090889...

Magpie - 9-2-2009 at 12:45

Have you read through the following thread? It seems that most of your questions have been addressed already:

http://www.sciencemadness.org/talk/viewthread.php?tid=11145&...

In that thread I show a manufacturer's picture of my fan. It cost around $260. You can mount this fan anywhere in the exhaust line. I chose to put it at the very end. This keeps my whole system under slight vacuum when the fan is operating. So small leak paths in the hood and ducting are inconsequential as air is just entering in very small amounts. No contaminants are escaping.

Jor - 9-2-2009 at 12:54

Magpie, I never seen your hood in real action

Can you make a small movie where you generate a large amount of NO2 or smoke, and see how the stuff is sucked at working height ?

EmmisonJ - 9-2-2009 at 13:55

Quote:

Originally posted by watson.fawkes
Nonsense. Here's a blower on eBay that took me just a couple of minutes to locate. (There's even points on fan curve in the description.) For about USD 100, you can have an adequate blower for a modest hood with short exhaust runs. That particular fan would need a plate adapter to seal it up, but if can build a hood, you can figure out how to get the fan mounted and sealed up.

thanks for the link! and i apologize for the confusion, i should have been more clear, by 'proper fume hood blower' i meant one with an explosion-proof motor. i'm assuming that the motor will need to be separated from the blower on all these Dayton and Grainger squirrel cage fans to keep them away from the fumes. i won't be working with ether, but distilling the likes of nitromethane, xylene, mek, are not out of the question. i'd hate to buy a fan off ebay to find out that removing the motor isn't going to work for that model, etc, as i have no knowledge on how these fans differ. perhaps i can get two of them or get by with one and put in a sash

since my hotplate isn't explosion-proof, i'll want to make sure this fan really sucks (can't help myself on that one). some baffles will be going in similar to magpie's (thanks), and if need be i'll put a sash in just to improve face velocity.

i have read that link you posted, magpie, in fact that's the first link i read when i started thinking about what needed to be done with the fume hood. i am currently in the process of re-reading it in hopes of picking up on things i may have missed out on the first time i read it since i've learned some since then (scary concept, but i do apologize for my ignorance on this topic as my knowledge and confidence regarding fans and air flow is zilch)

[Edited on 9-2-2009 by EmmisonJ]

Magpie - 9-2-2009 at 14:09

Jor, I would be glad to do that if I had the technology. I only have a digital camera.

I can say that based on visual flow paths of SO3, NO2, and smoke, and no smell of fugitive ammonia, that the efficiency and flow paths must be good. This performance does not seem to be affected by position of the sash (I have a constant flow design).

Jor - 9-2-2009 at 14:12

A moving sash (hard to make) is not necessary, but at least cover half of the opening of the box with a stationary sash.

Magpie - 9-2-2009 at 14:28

EmmisonJ says:

Quote:

i'm assuming that the motor will need to be separated from the blower on all these Dayton and Grainger squirrel cage fans to keep them away from the fumes.

The motor just needs to be out of the flow path. As you can see in the picture of the Grainger (Dayton) blower I posted the motor is out of the flow path as originally configured, ie, it's on top of the blower. To make my system a little more rugged I simply re-mounted the motor on the same piece of 3/4" plywood on which I mounted the blower, right next to the blower. I didn't change the spacing, just reused the existing belt. It's not rocket science.

edit: I'll take a picture and post it later - I have to charge camera battery now.

[Edited on 9-2-2009 by Magpie]

Magpie - 9-2-2009 at 21:36

Here's a picture of my blower as installed. As you can see I moved the motor from the top of the blower as supplied by the manufacturer and remounted it on the same base as the blower. I didn't see why the blower housing should have to support the motor.

blower motor.jpg - 114kB

EmmisonJ - 10-2-2009 at 06:07

thanks for the picture! now it's beginning to make a lot more sense. so with your particular model, it wasn't necessary to move the motor as it appears from the original stock picture ( http://www.grainger.com/Grainger/items/7C651 ) like it's already out of the way of the fumes, you just did so to take that additional weight off the blower's housing by mounting it the same distance away just on wood instead of the housing.

would the following attached picture be correct? if so then i wouldn't need any bends on the ducting because the blower takes care of the change in direction itself or at least it appears to be in the manufacturer's stock picture. the picture below isn't completely lined up but hopefully it's decent enough to show what i'm trying to do. i seriously had no idea what the difference was between centrifugal, inline, or any other design for that matter. now i'm beginning to understand the differences or at least what to look for. Centrifugal designs are going to change the direction of airflow which in my case means i won't need any actual bends in the ducting, inline would require for me to put bends eventually equaling 90 degrees (or a slant of some type so it's more gradual) which is going to decrease airflow considerably as well as the fact that inline fans are going to have the motor inline with the fumes as well (unless otherwise stated), whereas centrifugal fans i'm looking at have the motor mounted externally, out of the path of the fumes it seems, and i'd only need to move the motor if i want the weight off the blower itself or if the motor is simply in the way of how i want to ducting to connect to the blower, etc, then that may be another reason to move it as well.

but getting back to the pre-school style picture i attached, the ducting from the blower to the fume hood would only be about a vertical 1-3' run then the immediate horizontal outside run of 1-2'. i see the "special plenum to adapt my fan rectangular outlet to the louvred and screened outlet in the wall of my garage" per http://www.sciencemadness.org/talk/viewthread.php?tid=11145&... and since i don't have a pre-existing outlet in the wall for this i won't need to get anything special made, i'll just make the hole in the garage's wall to accommodate the blower and put a little outside vent which is what the little upside-down triangle in the picture is supposed to be. from the outside of the house it will just look like a 2nd dryer vent as it will be only a few feet away from the actual dryer vent as it will be exiting the side of the house, not the roof.

[Edited on 10-2-2009 by EmmisonJ]

Untitled-1.jpg - 81kB

Magpie - 10-2-2009 at 09:36

As you say, my blower configuration does introduce a 90 degree turn in the flowpath.

To do what you propose you would have to mount the blower base in a vertical plane, which is not standard. This would introduce axial stress on the fan and motor bearings.

I wouldn't do this without consulting with the manufacturer (Dayton) first.

[Edited on 10-2-2009 by Magpie]

EmmisonJ - 10-2-2009 at 11:34

wow very good point, so if i were to use the example that watson.fawkes provided ( http://cgi.ebay.com/NEW-Dayton-1TDR9-Psc-Blower-463CFM-115V-... ) and it says "Mounting: All Position" would that include a vertical mount like my picture shows or is what i'm trying to do considered non-standard?

also i see in that ebay example above that it's direct drive unlike magpie's which is belt driven. is that what the "plate adapter" is for, to separate the blower from the direct drive motor which i guess is something you don't worry about on the belt driven models?

[Edited on 10-2-2009 by EmmisonJ]

Magpie - 10-2-2009 at 12:17

Quote:

wow very good point, so if i were to use the example that watson.fawkes provided ( http://cgi.ebay.com/NEW-Dayton-1TDR9-Psc-Blower-463CFM-115V-... DVWQQrdZ1QQcmdZViewItem ) and it says "Mounting: All Position" would that include a vertical mount like my picture shows or is what i'm trying to do considered non-standard?

also i see in that ebay example above that it's direct drive unlike magpie's which is belt driven. is that what the "plate adapter" is for, to separate the blower from the direct drive motor which i guess is something you don't worry about on the belt driven models?

I'm not sure that "Mounting: All Position" would include a mounting that places axial stress on the fan bearings. Although I have seen motors mounted that way. Perhaps someone else on the forum can comment on that.

In answer to your second question: yes.

EmmisonJ - 11-2-2009 at 08:33

hm and i definitely can't do a 90 degree to simply mount the blower horizontally on top of the fume hood as the picture attached shows which would be a very short run with a total of only 3' altogether. any ideas on how i can pull this off? can i perhaps elevate it a little bit more, above the fume hood to allow the ducting to turn more gradually. would 2 x 45 degree angles separated by 1' of ducting be better than 1 x 90 angle which, from what i read, would kill the blower's vacuum within the fume hood

Untitled-2.jpg - 80kB

EmmisonJ - 11-2-2009 at 08:46

maybe mount it up further to allow the ducting to be as straight as possible and angle it, mount the blower directly up against the wall. it would probably still need a small angle or two of some sort, perhaps a 45 degree angle at the bottom connecting to the fume hood and another 45 degree angle connecting to the blower.

Untitled-1.jpg - 104kB

EmmisonJ - 12-2-2009 at 10:46

this is just for those tuning in who are as knowledgeable on this as i am. i found this piece of information regarding blowers that states why you need an adapter plate for direct-drive blowers.
taken from http://www.alpinehomeair.com/viewcategory.cfm?categoryID=86

Quote:

Blower housings and blower wheels come it two types: direct drive and belt drive. Direct drive means the motor is mounted inside the blower housing and the motor shaft connects directly into the center of the blower wheel. Belt drive means the motor mounts on the outside of the blower housing, has a pulley on the motor shaft and a pulley on the blower wheel, and a belt to connect the two pulleys together.

so i'm down to 2 final issues i'm working out, one having to do with plate adapters for direct-drive blowers and the other regarding my ducting/air flow/mounting problem so i was wondering

1) does anyone have a link pointing to adapter plates for direct-drive blowers, where i can buy them? or can i just basically call up grainger/dayton directly and ask? tried googling quite a bit and found a lot of webpages for parts from distributors but none of them appeared to be what i would be looking for if i go with a direct-drive model.

2) regarding the airflow problem (just bumping my 2 above posts) are 2 x 45 degree turns like in the bottom pic better than the 1 x 90 degree turn like in the top pic? i know you guys say that a 90 degree turn in ducting is going to kill air flow but if it's such a short run like in the top pic would it really hurt it? better to do a long run at a slant like the bottom pic?

i suppose putting it at the top of the back of the fume hood like this guy did with his paint spray booth is going to kill the dynamic of the fume hood's air flow with the baffles huh? because if not then it would be much better than me introducting any ducting curves in front of the blower (but i guess a curve after the blower like in this link is ok because that's the pressurized side?)
http://sluggyjunx.com/workshop/carpentry/2005_01_23-spray_bo...

otherwise i think i'm stuck needing a 90 degree elbow and adopt a "remote blower" setup like in page 12 of the labconco attached pdf. these guys say what magpie's theory was which is to keep the ducting under vacuum, although my run is such a short one that i don't think it'd matter much in my case. they show under "integral motor/blowers" on page 13-14 the setup i was thinking of originally but i don't want to risk misaligning the bearings or anything because who knows what type of blower labconco is using, i'm sure they have ones that are meant to be mounted like that and not just some oddball blower like i'm going to have. so is the remote blower setup with the 90 degree elbow really so bad, it appears my options are limited.

thanks again guys, all of you are great. i'm really a lot further along at understanding this than i was just a week ago.

[Edited on 12-2-2009 by EmmisonJ]

Attachment: fhpdf.pdf (322kB)
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watson.fawkes - 12-2-2009 at 11:23

Quote:

Originally posted by EmmisonJ
1) does anyone have a link pointing to adapter plates for direct-drive blowers [...]
2) regarding the airflow problem (just bumping my 2 above posts) are 2 x 45 degree turns like in the bottom pic better than the 1 x 90 degree turn like in the top pic?

1) When I initially used the term "adapter plate", I was talking about a way of sealing a duct onto the input side of the particular fan I posted. That fan had no stub for affixing an input duct, and so one would have to be fashioned. I envisioned a plate with a hole in it, sealed with silicone caulk.

As for a motor mounting plate, the easiest thing is a hinge and a piece of plywood. Orient the motor so that its own weight tensions the belt. You might need a spring, in addition, for adequate tension.

2) There are tables available of the static pressure drop for different duct sizes and shapes. There are two rules of thumb, though, that is most of what you need. (a) The larger the cross section, the lower the loss. (b) The slower the turning of the bend, the lower the loss. Using wide-sweep fittings is always preferable.

EmmisonJ - 16-2-2009 at 06:47

Quote:

Originally posted by watson.fawkes
1) When I initially used the term "adapter plate", I was talking about a way of sealing a duct onto the input side of the particular fan I posted. That fan had no stub for affixing an input duct, and so one would have to be fashioned. I envisioned a plate with a hole in it, sealed with silicone caulk.

As for a motor mounting plate, the easiest thing is a hinge and a piece of plywood. Orient the motor so that its own weight tensions the belt. You might need a spring, in addition, for adequate tension.

2) There are tables available of the static pressure drop for different duct sizes and shapes. There are two rules of thumb, though, that is most of what you need. (a) The larger the cross section, the lower the loss. (b) The slower the turning of the bend, the lower the loss. Using wide-sweep fittings is always preferable.

ah, thanks that clears up a lot and, i believe, only leaves me with one more question:

so i'm wondering, do these dayton direct-drive blowers need their motor relocated? the direct-drive models that use a rod to turn the fan like the one in the ebay link watson_fawkes provided and the pic attached (some random dayton model i found that had a good side view) as opposed to a belt-driven model like magpie's where the motor is typically on the side? i just can't tell if the motor on these direct-drive models are open to fumes or not. i imagine there must be at least a small hole where the rod would be located and connect between the motor and fan but am not sure if that would present a problem or not as i am unfamiliar with blowers.

i'd really like to get a direct-drive blower to save about $200, but will just continue saving money for a belt-drive model if there's no way to separate the motor entirely from the fume path on direct-driven models.

[Edited on 16-2-2009 by EmmisonJ]

57ab_1.JPG - 20kB

Phosphor-ing - 16-2-2009 at 06:53

Pretty much any direct drive motor will be exposed to the fumes. Belt drives are preferable. Unless you can afford a new blower every so often.

EmmisonJ - 16-2-2009 at 07:02

oh ok thanks, i'll just have to save up for a bit longer and get a belt-driven

Magpie - 16-2-2009 at 08:51

Although I have not examined a direct drive centrifugal blower like you show in your picture I suspect that there is just a small hole in the housing sufficient to permit the shaft to connect to the fan wheel. Also, when this fan is in operation that area will be under vacuum (it's in the center of a centriguge) and so the motor will not be exposed to corrosive fumes/gases. In my opinion that cheaper blower should work OK in reference to motor corrosion resistance.

Now whether or not you have it properly sized for your application is another question.

EmmisonJ - 4-3-2009 at 11:38

not much of an update yet. i put on a couple coats of epoxy paint as recommended in my other fumehood related thread and ordered a belt-driven blower and am waiting for it to come in which gives me time to put in my baffles and sash.

Magpie,

in this thread (http://www.sciencemadness.org/talk/viewthread.php?tid=11145) you gave the measurements of the gaps between your baffles. i was wondering how tall your bottom baffle is (the actual bottom baffle itself)?

[Edited on 4-3-2009 by EmmisonJ]

Magpie - 4-3-2009 at 12:55

Quote:

i was wondering how tall your bottom baffle is (the actual bottom baffle itself)?

It's 13 inches.

Aristocles - 6-3-2009 at 10:47

I purchased this from ebay, and await its delivery:

http://i5.ebayimg.com/06/i/001/35/27/ffdb_1.JPG

http://i20.ebayimg.com/02/i/001/35/28/0219_1.JPG

I got it for 20 USD, so it's not the end of the world if I have to toss it... the guy guarantees it to run well, etc. but I'll do some cleaning, oiling, and slap some paint on.

I have bought it rather in the dark and await its arrival to send some specs to Magpie for his opinion, re: viability. I fear that although belt driven and motor qua motor is out of the way of noxious fumes, the bearings/shaft are not... I hope it's not a throw away...

Good and informative thread, thanks to all!
KentuckyPWRLFTR... yeah, self signed

volfrahm - 8-3-2009 at 08:25

Great thread, really cleared up a few lingering questions I had about blowers.

It sounds like the case, but I'd really like to put a fine point on it: in the case of the belt-driven squirrel cage blowers, are these effectively "explosionproof" with regard to vapors coming from within the fumehood? What if I'm evapping diethyl ether all day (for example, of course)?

Does anyone have a good (non-ebay) source for a truly explosionproof blower?

EmmisonJ - 11-3-2009 at 15:36

got the same blower as magpie, did a lot of looking around and it seemed to be the best bang for the buck as far as belt-driven blowers. the manual that came with it is a safety manual and doesn't have any instructions regarding installation. i spent the past hour searching online for some type of manual or documentation to help me out and the best thing i could find is this:
http://www.lauparts.com/catalog/servefile.aspx?id=2015

where did you guys get your materials to install your blowers? i can't even figure out how to get a power source to it. i'm definitely no tim taylor, in fact assembling a grill usually entails me swearing for an hour, throwing something, then finishing it the next day. my wife thinks it's a riot but, me, not so much

Magpie - 11-3-2009 at 17:14

Since you say you know nothing about how I will give some very basic direction:

1. I used 8" irrigation PVC pipe for ducting. The outside diameter (OD) of this pipe is less than 9". The inlet of the blower is 9". To make a seal here I bought a 2" strip of rubber (probably EPDM) of an appropriate thickness and placed around the pipe end. Probably glued it to the PVC pipe with silicone. This closed the gap between the inlet of the fan and the OD of the pipe. I just shoved the pipe into the inlet. My pipe and blower are well supported so they don't move out of position.

2. The outlet of the fan, which is rectangular, is shoved into my custom made outlet plenum (sheet metal box) that adapts the blower to the outlet grate built into my garage wall. Again, everything is well supported so nothing moves out of position. The plenum is mounted to the garage wall with screws.

3. The motor comes mounted on the blower. I took it off and mounted it on the same piece of 3/4" plywood that I mounted the blower on. Everything on the plywood is mounted with 1/4" bolts, locked by double nuts or lock nuts.

You have several options for positioning the blower with respect to its mounting base. Choose the one that is appropriate to your configuration. Be sure the motor is properly aligned with the blower (pulleys in the same plane). Tension the belt so that it deflects about 1/2" when you press on it.

4. Bring a #14, 3-wire insulated cable to the motor box and attached the white and black wires as indicated. Also attach the green (or bare) wire as indicated. This is the ground wire.

The wire can come directly from a 120VAC, 15-amp circuit breaker in your service entrance. Or you can tee into an existing wire of the same type, if there is adequate excess amp capacity to do so. Add up your existing amp loading and the motor amp load and see if it is within your circuit breaker's capacity.

You will need to install a switch (like a light switch) in the cable also.

If you feel that this electrical work is beyond your capabilities by all means get qualified help. Nothing here is worth burning your house down or killing someone by electrical shock.

[Edited on 11-3-2009 by Magpie]

[Edited on 11-3-2009 by Magpie]

EmmisonJ - 12-3-2009 at 05:46

thanks magpie, you've really gone above and beyond!

mine actually came with the blower and motor shipped separately, looks like it's in need of a spacer between the blower motor and its pulley. i'm going to call grainger when i get home and work all that out minor assembly stuff out with them.

but as far as the electrical side goes, it sounds like you install it just like you would a ceiling fan and make sure it's 15 amp? i'll ask grainger about that too because i don't see any wires or anything coming outside the housing. i'll give grainger a ring later today and post back what they say.

EmmisonJ - 13-3-2009 at 05:23

have the assembly figured out thanks to grainger and he explained the power to me:

terminal 4 (where blue is - bring in common white)
terminal 1 (where line 2 is - bring in power)

unfortunately i have no idea how to do this but wanted to research what was involved before deciding if i can do it myself or not. i know so little about this that i'm not sure how to ask a question about what it is i'm trying to pull off. i was thinking it was just going to be a standard interface to go into an ac outlet. is there some type of brief overview or 'how to' that somebody might be able to link over that would help me get an idea of how to get this blower motor hooked up to standard ac? excuse my ignorance, first time home owner here and a very unhandy one at that. but with some proper reading i'm sure i can pull it off.

watson.fawkes - 13-3-2009 at 06:03

Quote:

Originally posted by EmmisonJ
have the assembly figured out thanks to grainger and he explained the power to me:

terminal 4 (where blue is - bring in common white)
terminal 1 (where line 2 is - bring in power)

If it's the same as motor's I've powered, there are screw terminals underneath a removable plate. Just screw the wires down. Generally there's also a hole to affix flexible conduit onto. Use it; it will make your life better later.

EmmisonJ - 13-3-2009 at 06:36

Quote:

Originally posted by watson.fawkes
If it's the same as motor's I've powered, there are screw terminals underneath a removable plate. Just screw the wires down. Generally there's also a hole to affix flexible conduit onto. Use it; it will make your life better later.

yeah i was able to find that and mine will need a connector crimped onto the wires as opposed to having a screw. but what i was curious about was the electrical part of it, is there any easy way to run those 2 wires i need for power? what in my house am i going to need to tap into, to run those 2 wires the blower motor will need? i used to do car stereo way back in my younger years but have never done anything in a house aside from the 2 ceiling fans i mounted which already had the wires run, so i never had to run wires in a house before.

watson.fawkes - 13-3-2009 at 09:12

Quote:

Originally posted by EmmisonJ
yeah i was able to find that and mine will need a connector crimped onto the wires as opposed to having a screw. but what i was curious about was the electrical part of it, is there any easy way to run those 2 wires i need for power?

For the motor side, install a standard 3-prong plug. Near the motor (<= 6ft), install an branch circuit. Put this branch circuit on an ordinary light switch. With this advice, I'm assuming you have a fairly small motor (<= 2 HP). You have find instructions for running branch circuits in any of the electrical books at your local big box home store.

You could direct-wire it in, but this solution is a more conservative answer to the problem. You can install the outlet first, and test it, and make sure it's safe, all before plugging in the fan. Later, if you get more ambitious, you could also use a separate contactor (i.e. motor relay), industrial start and stop switches, dedicated low-amperage circuit breakers, an operating lamp and a whole lot else. Start with a simple switched outlet, though; it should get you started just fine.

Magpie - 13-3-2009 at 09:58

Since you want to do this the easiet way possible I second watson's recommendation. I will amplify abit:

1. If you have a standard 120VAC wall outlet (a "duplex") replace that with a switched single 120VAC outlet.

2. Get a flexible 3-wire cord, #14, and attach it to a 3-pronged plug. This cord can be bought by the foot. Get the minimum length needed.

3. Attach the other end of the cord to the terminals in the motor box per Grainger.

Home Depot will have all the parts you need.

EmmisonJ - 13-3-2009 at 10:15

...and you guys even broke it down into terms i can understand, thanks guys! i will post back the results

EmmisonJ - 19-3-2009 at 14:52

one more question about the wiring of the blower motor:

the blower motor came with a green/yellow wire grounded to the chassis of the blower motor. the #14-3 cable has a white, black, and green. i know what terminals the white/black go to but was wondering if i should disregard the green on the #14-3 or should i ground it to the same exact place the blower motor's ground is?

Magpie - 19-3-2009 at 15:40

Ground the green wire to the same place as the motor ground.

Grounding is an important safety feature, never ignore it. This is how it works: If your hot wire (the black one) should accidentaly come in contact with the metal case of the motor it will short to ground and pop open the circuit breaker in your service entrance. This prevents you from an accidental shock when touching the motor casing.

[Edited on 19-3-2009 by Magpie]

EmmisonJ - 4-5-2009 at 06:45

Magpie, did you put any type of spacer between the belt pulley on your blower and the housing? likewise for the blower motor, any spacer between the pulley and the actual blower motor itself?

p.s. i called grainger and they said to just leave a little space between the pulley and the housing when you tighten it down, that you don't really need any type of spacer, just leave an open space there if necessary. i guess i'm concerned with it sliding back up against the housing but if you tighten it down tight enough then that's really a non-issue per grainer. i trust grainger's tech support but i don't trust my ability to adequately describe the question to them because i'm such a newbie with this i don't know the terminology to correctly describe the situation, so i'm curious what somebody else with the same model ended up doing.

thanks as always you guys are a great help.

[Edited on 4-5-2009 by EmmisonJ]

Magpie - 4-5-2009 at 07:57

I don't see where this matters. My pulleys are 1/4"-1/2" from the blower or motor, respectively. Just make sure the pulleys are aligned with each other and the belt is properly tensioned. The rule-of-thumb on tensioning is 1/2" of deflection using moderate finger pressure. Actually, the way mine is set up the weight of the motor automatically tensions the belt. I assume yours will be the same.

watson.fawkes - 4-5-2009 at 11:26

Quote: Originally posted by EmmisonJ

[...] they said to just leave a little space between the pulley and the housing when you tighten it down, that you don't really need any type of spacer, just leave an open space there if necessary.

While you don't need a spacer, I might recommend a bit of thread-locking compound on the setscrew for the pulley, since there's often enough vibration in a fan system to loosen screws.

DJF90 - 4-5-2009 at 13:05

You could also use a "sprung washer". It exerts axial force on the bolt, preventing it from undoing.

Magpie - 4-5-2009 at 13:44

I like sprung washers and lock nuts also but they are really not appropriate for this application. The pulleys are affixed to the shaft using an internal hex head set screw.

EmmisonJ - 5-5-2009 at 04:28

thanks watson, i think a thread-locking compound as you recommended is just what i need, if nothing else to help me sleep better at night knowing the pulley's not going to fly off during operation and hit me in the head

DJF90 - 5-5-2009 at 04:57

Didnt realise it was a grub screw, sorry. For anything where the bolt head resides above the surface then a sprung washer is perfect. If the threaded end is above the surface than use a locking nut. Alternatively, I believe you could use a sprung washer that end also

watson.fawkes - 5-5-2009 at 05:16

As long as we're talking about motor-sheave-belt-fan systems, I should mention the merits of link belt. It's a substitute for ordinary V-belts made up of a number of interlocked links. The links and the way they interlock fit right in the groove profile of a standard sheave.

The advantages for me are principally reduced noise and vibration. They are also more energy-efficient. All these are related. Because the links are connected non-rigidly, they're free to move and rotate with respect to each other. That means that, unlike a V-belt, it doesn't transmit torque along the axis of the belt, decoupling oscillation modes on the two ends of the belt system. The links also move with respect to each other when the belt passes over a sheave. A V-belt will develop internal strain, part of which is dissipated as heat.

A completely practical advantage is that you can adjust the belt length to match the dimensions of your tensioning system, rather than find the right belt to match your dimensions.

Magpie - 5-5-2009 at 07:05

Quote:

The advantages for me are principally reduced noise and vibration

This is always of interest, even if you don't have close neighbors. I do hear a little "belt slap" with my system.

EmmisonJ - 10-5-2009 at 09:46

here's an update:

so the blower is installed and seems to be running fine, i still need to put in baffles and a sash. when i closed one of the doors to the fumehood i noticed the suction got much much stronger so that just enforces the fact that i need to put in a sash and then the vacuum will be very satisfactory. i just generated some smoke to test this out.

EmmisonJ - 11-5-2009 at 10:28

i found a great supplier who is willing to fabricate some steel for my ducting at a great price, the problem is that its galvanized and not stainless steel.

the fumes that will be pushed through this ducting are all solvent fumes for the most part: dcm, toluene, different alcohols, except there will also be some hcl. of course my only concern (and major concern) is the hcl, would i be able to coat the galvanized steel with anything (ptfe spray, epoxy paint, etc) to protect it from any hcl? or is there no question that i just need to find somewhere else and get the stainless steel?

[Edited on 11-5-2009 by EmmisonJ]

DJF90 - 11-5-2009 at 12:01

Epoxy is pretty much resistant to most things. Stainless isn't perfect (its only stain-less) so I would probably opt for a coating of epoxy in either case.

zed - 22-5-2009 at 13:26

Stainless steel usually costs a bundle. Too much! Hastalloy would be dandy....Costs even more. Galvanized is cheap, but reactive. An appropriate paint, with primer, will generally protect it. But, very few coatings can stand up to massive amounts of either acetone or dcm.......Paint removers!

For really grueling, long term exposure to high concentrations of chemicals, the generally recommended material used to be.........wood! Probably still is. But, wood has its limitations too.

Nothing is perfect.....Well, maybe teflon, but short of that, there is always some sort of compromise.

smaerd - 11-1-2011 at 20:25

I didn't want to start a new thread for this.

Would a fan like this suffice for 'general' purposes?
http://www.homedepot.com/Building-Materials/h_d1/N-5yc1vZ1xh...

I don't ever plan on making ether or chloroform, and even if so it would be in small amounts and in theory the air would dilute it before it hit the fan. Would a fan like this pose a serious fire threat for dealing solvents like acetone? I know lexan is a polycarbonate plastic of some kind and polycarbonate has decent resistance to most common things.

I really would appreciate a nice fan with a belt driven motor but have kind of a 50 dollar budget on this for right now. I just want something to make sure volatile aldehydes, some light/acid/base exposure don't end up in my lungs or on basement plumbing, and rather outside.

Thanks for any help.

grndpndr - 12-1-2011 at 23:49

That looked like some nice sheetmetal fabrication magpie.Im assuming you had no sheet metal brakes etc. Nice work.
Ive also been wondering why occaisonal use with acids would nescessarily trash a squirrel cage fan motor if it were direct drive given the small hole for the impeller.I wonder if there wasnt some way to dissasemble the squirrel cage to install a kind of rubber/etc washer over the motors shaft to help prevent any incursion of gases particularly if as you say a vacum would be created away from the area of the motor shaft.Still i would be very hesitant with flammable gases.Lacking flammable gasses in the hood, sciplus often has an nice selection of squirrel cage blowers at a replaceable price.

@smaerd,looks nice easy to install but awfully exposed.I dont have much experience with attempting to keep moving parts moving in a acidic envoroment but I was very suprised how little actual acidic fumes it took to gum up the works on a rel. HD drill chuck I was forced to use with a stirrer even though the chuck itself had a very vigorous air flow keeping acid fumes away from the drill or so I thought. The tough mech. chuck required serious lubrication and work to get it functional again despite the fact I saw No fumes. Im actually suprised the drill motor itself wasnt trashed from 2 minutes of stirring.

[Edited on 13-1-2011 by grndpndr]

[Edited on 13-1-2011 by grndpndr]

peach - 13-1-2011 at 02:42

It's interesting, to me, to note that a number of inline, direct drive, hydroponics fans are now external rotor, induction motors.

What that means is, the coils carrying the electricity from the mains are stationary and sat behind the fan blades - they don't move or make any connections inside the fan.

The motor spins because there are some coils inside the the rotor head sat over those mains powered coils - being magnetised and moved by the one that sits still, via induction.

For an even more simple explanation, there are NO brushes involved in the design. And it is the brushes that create the showers of sparks from other motors (look into the cooling holes on a desktop fan, a hand drill or another similar tool at night with the lights off, and you will likely see blue flashes from the contacts).

An indirect drive would be great, but the lack of these contacts would make the fans considerably safer than the others for things like fume hoods.

You can take some of these fans to bits to get access to the rotor and motor as well, allowing you to paint the insides with something like epoxy. Be sure to check the fan over yourself if doing this, as stoner's tend not to be all that interested in how it works, only that it does.

I also see a complete lack of interest in scrubbers in all of these fume hood threads. If you blow a highly flammable mixture out the side of the house, something out there could also ignite that, or if it's toxic, it could be blowing in some kids face - I believe government funded labs (like universities) tend to duct the exhaust up to the roof to keep it away from the pockets of undisturbed air, and people, near ground level.

That aside, placing a scrubber of some form before the fan would help prevent the corrosive materials getting to the fan in the first place.

Dealing with acids, flammable and toxic things, you should always make an attempt to neutralise, minimise or entirely avoid the thing getting airborne to start with; ideally.

This is not a guide, argument starter or recommendation, it's some ideas.

[Edited on 13-1-2011 by peach]

grndpndr - 13-1-2011 at 06:51

In a perfect world you bethca it would solve alotta problems
not to mention immediate safety but long term safety via less toxins in the air.Naturally no worries about the fan/explosions-corrosion, use of specialized materials-processes.
Problem being how to accomplish?Activated Charcoal filter?water bath sorta arrangement? I have no clue what the cost would be for a filter capable of handling the variety of nastys in the volume w/o inhibiting air flow and killing the operator
in the process.maybe a very large air/water bubbler?No Im not trying to be funny, purposely stupid just imagining the difficultys.Realistically though not that any amount of pollutions acceptable Id Imagine what every hobbyist generates in the way of pollutants is miniscule in comparison with almost any large plateshop,paint booth, small coal fired
electrical plant. Or even wood stoves from Gillette WYO on a cold day.
Really not making light of the situation it would save a fortune in components for the hobbyist if it could be made practical.

peach - 13-1-2011 at 07:40

In terms of the environment (having hugged a tree myself) at home chemistry is not an issue.

But it would be nice if it helps with it, the safety and protects your fan.

For example, chlorine can be absorbed onto activated carbon - there is a long list of others a.Carbon actually and it is ubiquitously found around gas filters (half a kilo of air float activated carbon costs a few pounds).

Using a bubbler won't work due to the massive pressure difference required to blow bubbles through it whilst maintaining that volume of flow.

Respirators use scrubbers, and there are not that many different cartridges to deal with a wide spread of gases - it's usually along the lines of, organics (solvents), acid gases, base gases, ammonia, halogens. Googling for cartridge composition will likely yield what is being used for each stage, and it's likely the same thing for all the manufacturers (as this is an industry where standards MUST be maintained).

Again, by far the best option is to avoid it getting into the air in the first place.

As I just replied to magpie, chlorine, for example, can be scrubbed out of the exhaust of the glass by bubbling it through 10% NaOH - which avoids it getting airborne in the first place. The same applies for many other gases. The more reactive, the better it works.

This is how industrial chemists deal with it when they have tanker truck quantities of harmful things trying to escape. They can't use fume hoods, have all their staff in HazMat suits in board meetings or simply blow it out the chimneys, it needs to be dealt with as it tries to leave the sealed process - the respirators go on if something goes wrong.

[Edited on 13-1-2011 by peach]

smaerd - 13-1-2011 at 09:24

@grndpndr - thanks for saving me the trouble. I'll look for a more 'real' fan. Yea I liked it because I am not so good with electronics and it seemed a simple set up. Though yea your right, it'd only take a little HCL before that thing met it's fate even if it was epoxy coated.

Hmm I have a couple pounds of activated carbon for fishes(cheaply acquired).

I was actually intending to make a thread about scrubbers. I can't seem to think of a way to effectively build one. The only thing I could find was some pot growers lining little mesh garbage cans/pencil holders with panty-hose and stuffing them with activated carbon. Obviously this is not suitable due to the chemical resistance of panty-hose lol.

Looks like they sell them pre-made upon simple googling.
http://www.google.com/products/catalog?hl=en&q=ducting+f...

How effective these kitchen ones would be for HCL though seems like an entirely different story. It could prolong a bad fan though.

edit - I'm still having a hard-time finding an affordable fan. Induction fans running 2,000? belt driven fans $400(used)?

edit again - squrrel cage fans look affordable, but does brushless mean sparkless?

Would something like this not be ideal?
http://www.horticulturesource.com/hydrofarm-active-air-blowe...
I can't tell but it looks like the motor is directly connected to the fan. Maybe leading to sparky sparky? It appears to be metal and of a decent quality. I doubt there would be much exposure of fumes to the motor? Blade replacement doesn't look expensive or hard.

[Edited on 13-1-2011 by smaerd]

peach - 14-1-2011 at 03:42

Brushless SHOULD mean sparkless yes. As there are no electrical contacts involved, just coils of wire and magnetic fields.

The US guys seem to have tons of squirrel cage fans lying around, but they're not so abundant in the junk of the UK. I'm not sure how many of them are inductive and so on, but I think quite a few of them are brushed.

The cannabis farm fans use inductive, brushless motors a lot, and they're way cheaper than $2k, they're more like $50-100 and will do thousands of CFM.

The easiest method I came up with for adding a scrubber would be to buy a sewer pipe fitting called an 'access bend' or 'access joint'. These are lengths of pipe with a big port on the side that screws open and shut - it's big enough to get a hand in and they're used to provide inspection and jetting points. There's a picture of one at the end.

You could easily cap off a section of this with mesh on each end and then fill the inside with your media. You can also get it back out easily enough with a hoover. The fittings feature air tight seals and are supported by a range of couplings to fit them onto other pipes of more random size (e.g. the inlet on a blower).

You need to be careful with the word HCl, as hydrochloric acid (HCl[aq]) and hydrogen chloride (HCl([g]) are significantly different in terms of their ability to corrode things. Hydrogen chloride will corrode stainless steel and attack chrome. The only truly resistant materials against that level of attack are Monel and PTFE (or one of it's sisters). You won't find or be able to afford either of those. So it's a question of making the best of the rest. For example, these fittings are big enough to paint the inside.

You can also scrub gases by having a section of duct with water jets in it - e.g. those little garden misters you can get for automatically watering the garden would seem like a possibility. Something like hydrogen chloride has a huge solubility in water. You then need to consider that mist getting into the motor if it's happening upstream of it and it's inline.

A good tool for considering these things is Cole Parmers chemical resistance guide. Which rates epoxy A - Excellent for hydrochloric at 20 and 37%, as well as the dry gas.

[Edited on 14-1-2011 by peach]

smaerd - 14-1-2011 at 09:18

Thanks a bunch as always peach. Your always willing to help spell things out and share worthy ideas. Misting is a great idea, I never even thought of that.

Regolith - 7-2-2011 at 02:24

I hate to Necro this thread but a cheap junk source of direct drive squirrel cage fans are readily available.

The type of large microwave that mounts above a stove. The ventilation fans are quite powerful. They are meant to be the vent fans for the stove they are above, as such the motor is somewhat out of the air stream and its not too difficult to seal the motor away from fumes. All the models I've come across are double sided there is no reason you can't take one of the cages off (slight extra bearing load tho) to give the extra power to the other or dual your air stream and/or have dual intakes for wider larger vent hoods.

The motor is a synchronous AC that has no brushes. It can be easily controlled with a simple scr based fan controller available at almost all hardware stores, next to the light dimmers, don't use a regular dimmer on a motor of this type you will cause overheating and blow the motor, that is IF you don't want the thing at full blast all the time, they can be quite loud! Many of the models have plastic fan blades (some are metal pick your preference). Simply looking inside the bottom will show you the fans blades. here are pictures of a unit that is awaiting installation as the blower for my oil fuelled metalworking furnace and a plastic version I just froze my ass off and tore out of a scrap micro in the garage, for pictures sake.

Both of these had a HEAFTY price tag of me being cold and patient to get (cold based on season) and a giant 0 dollars and 0 cents. When, or if(depends on how well you seal it) they die replacements are as above not hard to get. The white between the 2 fans is a pack of coffee filters shows for a sense of scale.

sdodgen62 - 12-1-2012 at 17:48

why not build a hood on the same principle as an asperator works? nothing in the stream, im pondering how to build one myself and this is what im thinking

sdodgen62 - 12-1-2012 at 17:49

i'll post pics when complete

sdodgen62 - 12-1-2012 at 17:52

being a carpenter by trade in thinking of using a tempered glass window unit for the sash, which is somewhat how most hood are made. pls post with input

Magpie - 12-1-2012 at 20:11

Quote: Originally posted by sdodgen62

why not build a hood on the same principle as an asperator works? nothing in the stream, im pondering how to build one myself and this is what im thinking

I hope you have better luck than I:

http://www.sciencemadness.org/talk/viewthread.php?tid=3625#p...

Building contractors sometimes use air jet ejectors to move a lot of air at a job site. They commonly use air at about 100 psi, and I believe they are noisy as hell.

They are commonly known as Coppus blowers, but there are other manufacturers as well. I had quite a time finding them as I wasn't using the right keyword, which is venturi. To find them use "venturi air blower." Here's an example:

http://www.airblast.com/Airblast%20Venturi%20Air%20Blowers.p...

[Edited on 13-1-2012 by Magpie]

[Edited on 13-1-2012 by Magpie]

sdodgen62 - 13-1-2012 at 04:41

yeah i see magpie,
but im thinkin more 600cfm 20" attic fan as my jet of air, i see no reason it shouldn't draw more air than i want but i guess i ccould be wrong i have been before lmao

AirCowPeaCock - 13-1-2012 at 12:04

Probably irrelevant by now, but for anyone else viewing this thread for the same question, I went to my local surplus store, bought the biggest baddest fan they have there for just 27$, It works like a charm, and 1/4 sash I must have at-least 120 lfm, at its full sash a little gets out, but I rarely need it that high.

[Edited on 1-13-2012 by AirCowPeaCock]

RonPaul2012 - 6-3-2012 at 06:55

I am helping my friend make a fume hood and we are running into some problems.
I might post pics if I can't figure it out.

Just bumping incase I need it.

tastyphenome - 6-3-2012 at 15:58

I know this is a crappy post, but has anyone ever seen an air powered fan? This, while perhaps totally impracticable and expensive, would provide you an indirect motor or sorts.

I am thinking like the small air powered mag stirrers. A low friction bearing, a wheel, and an in/out line for pressurized air to be blown thru.

It seems like loads of pointless work(coal>heat>steam flow>electric>compressor>air flow>fan=airflow) but could be done super cheap if you have an air sources already, and totally sparkless.

http://www.jitlab.com/MAGNETIC-STIRRER-AIR-OPERATED-TURBINE-...

watson.fawkes - 7-3-2012 at 04:31

Quote: Originally posted by tastyphenome

I know this is a crappy post, but has anyone ever seen an air powered fan?

Not so much a fan itself, but pneumatic motors (or air motors) were invented exactly for spark-free operation in hazardous atmospheres. They're rather common; Grainger carries them, for example.

tastyphenome - 7-3-2012 at 19:39

i love rediscovering fire... makes me feel so content. no thats not it, dumb. thats it.

=]