Funnel vs. Fume Hood
 

I am installing a new vent system and am considering using a funnel positioned with the torch blowing straight into it instead of installing a full fume hood. I saw this at Lucio's studio in Italy and thought that it made sense.

I have had a look thought the ventillation threads, but most are geared towards the fume hood set up.

Does anyone use a funnel set up? Is this as effective as a full fume hood? Does the same surface area formula for fan sizing apply to the funnel set up? For those of you who have full fume hoods, did you consider using a funnel? Why did you choose the vent hood instead?

Thanks muchly.

A "funnel" can certainly be effective. There has been little published formation on how to calculate CFM needed to have a acceptable air flow to ensure lampworkers safety. Most applications for funnel system I have seem are usually applied to welding industry. Usually in welding application there is visible evidence (smoke) of how effective ventilation is performing. Unfortunately in out endeavors there is little smoke or evidence of if ventilation is effective. When pictures show up in lampwork studios there is usually not and documentation to determine its effectiveness. At this time I can only suggest that you use funnel opening as big as practical, use at least 6 inch ducting (smooth wall) maybe larger and at least 350-500 cfm blower and extensively test system with torch "on" and lots of "smoke" (either real or synthetic) to test effectivenesses of system....

Positioning of funnel will probably be critical as to how effective you can capture combustion plume. Torch "size" may also play a part in effectiveness...

IF you try this system I would like to know your results and also what are the specifications of your system. Maybe with some documentation we can establish parameters for this technique for ventilation.

Dale

get ya some sage, fire up your whole system, light up the sage, and wander around with the sage, to see how the smoke moves...
i have an inclosure right now, but think i might shift over to 8 inch funnel... and my fan is 1350cfm

I am going to give this a try. I have a 600 cfm fan and will try to get it setup.

I have run some tests on this fan (away from my lampwork bench)with a 6-8" reducer as the funnel and the thing has crazy suction when testing with a string.

My lampwork bench is right in front of a window so once I figure out how and where to mount the fan, it will only have about 6' max of ducting to go through to get to the outlet. I think that the 600 cfm may actually be too much suction for this setup.

You have to consider the further away from funnel opening the less the air flow (cfm) so if your funnel is 18-24 inches away from torch, flow (velocity of air) is going to be reduced....

Dale

I use a funnel system for my soft-glass work. It works really well for me.

I have a question about the funnel. I move the position of my torch up or down depending on the application. Wouldn't you need a large opening to accomodate the torch range?

Am I the only one who changes torch positions? I am seriously looking into better ventilation myself.

It depends on how you work, the funnel is going to only be about 12" from the end of my torch, so even if I adjust the angle, it will still likely hit the inside of the funnel, if not I will add a 8" to 10" adapter onto the end of my 6-8" adaptor ("funnel"). I intend to make my system completely mobile as I move alot, currently live in a rented apartment and cannot put in a fixed system. I am waiting for an adapter to arrive in the mail to get my setup installed, but should be able to post a photo next week.

Lucio has his on flexible alluminum ducting, and uses square funnels which are stood up on an easle (or music stand) kinda thing so that the students can adjust the funnel on the bench as they like. I am thinking that a galvanized square planter box from Ikea may make a nice funnel intake if one feels like getting industrious by cutting holes in metal.

I wonder how a galvanized "pail" from the hardware store woud work :)

I have a funnel type system. I used an old gas lamp for the funnel section. My fan sucks so well that if a dot flys off from not being kept heated it sucks them right up and I can hear it run clear through the whole system.

Here is a photo.



I didn't do the whole hood thing with the sides because it made me feel to confined. This passes the insense test with flying colors. I will soon be running this with all hard line once we get moved. The soft line was just a temp fix.

I don't see any reason why it wouldn't work.

That looks great. How big is your blower, and what are your ducting dimensions?

I really like this set up - including the glass rod placement. You have given me a great idea :)

OMG Tracy - that vent funnel looks awesome! Would you mind sharing your set up information? Would love to do something like that for my work area.

I have mine set up like this. I used one of the big oversized stainless steel salad bowls for the funnel. Just cut an opening in the bottom with the dremel tool for the collar to fit into. Works great.
Alan

If you want to see a very interesting Plume Extraction Hood, you should check out the Summer 2007 issue of the Annealer Magazine. There are parts of the article that I can't quite agree with, they state much lower cfm requirements than I think are adequate, but that Plume hood looks great. Also they have special photo's of the thermal plume created by a torch that are interesting.

The article is written by Bill Harrison and is very informative. I have conversed with Bill quite a bit via e-mail and I can vouch for his numbers and theories.

I was privileged to see article before publishing and had time to review it and can honestly say it is pretty much in line with most of the theories put forward today for studio ventilation.

If someone is interested maybe they should contact Bill directly and ask if he is wiling to supply copy of article or ask if he is willing to act as consultant to a system design.

Dale

thanks for the info, I just ordered a copy of the magazine.

How hot would it get? My understanding is galvanized metals let of fumes that are very bad for you if heated too much. something about zinc. I can not say for sure, but I think I'd check this out very well before I used galvanized. just in case ya know.

Rob.

The zink coating will put off fumes if you get it to red heat.... Anything less and its pretty inert. Besides you are sucking out fumes more dangerous than what the zink may produce with with system so whats to worry about? Galvanized steel ducting is material of choice on many heating and A/C applications.

Dale

Ok, here goes, this is the first time I will have uploaded anything on this forum so hope this works.

She ain't pretty but she works. I cut a 1.5" piece of foam insulation to use as a window insert. When I am done torching, I pull the whole thing back inside and shut the window (don't need the neighbours thinking I've got a grow op. in my house). I am using a 600 cfm squirrel cage fan with 6 inch ducting (2 x 90 degree elbows), funnel is just an 8-6" reducer. The nice thing about this setup is it is completely mobile and will easily move with me, I will just have to replace the foam an maybe extend the ducting as the situation requires. Makeup air is coming from an open window in the next room, seems to work alright, but I will probably get a little cold.



This side view shows how I have the fan sitting in a metal box, I was stumped on how to easily secure the unit without actually having to do any constuction (very heavy and tippy) for a while until I came up with this idea. The box is sitting on a cheap Ikea shelf unit which is just about the perfect height for my Ikea work bench.



Torch on and smoke test looks good to me! (Ignore all the smears you see on the left of the papertowel, they are just marks on the bench and backsplash, not smoke. The smoke is heading straight into the funnel.)

Right now I have a cast iron fan that was my brothers leaf blower. It is very strong but I have no idea how strong. I just know that if a dot flys off my bead it is sucked up and I can hear it go. It also sucks so well that if I don't have my sons window in his room wide open it sucks all the smoke from the wood stove and fills the house. It may be a bit of overkill but the fan was free! I have also done the smoke test from many places on my bench and it works just great. This is a temp setup since I will be moving soon. Right now it is just the flexible duct work but once We move this spring it will be the regular hard line. It is 6" going to 8" after the fan and out the window.

You can get old parking lot lamps from the salvage place that are more domed than this but I got this one free and it works fine.

Here is information on the ventilation that Andrea Guarino's husband designed that is a funnel system.
http://www.southernflames.org/Tips%2...entilation.htm

Kristi

Is the smoke test really accurate? Isn't the plume coming off the torch a lot hotter, and wouldn't that mean it might behave completely different from incense or other types of smoke? (I'm just asking because I don't know, and I would like to!)

It is actually a really good way to see how the air is moving because the smoke particles are so small and light they go where the air is going making invisible air currents visible! If the air is hot and moving, the smoke goes with it.

I did the smoke test all around the torch while the torch was lit, including holding it at the base of the torch and it goes straight into the funnel. I showed this picture so that you can get an idea of what size the funnel catchment area actually is with this blower and duct configuration.

Most of the combustion gas is propelled off the end of the flame due to the velocity of the gas/flame coming out of the torch. The idea is that funnel catches the fumes and sucks them away before they bloom out and disperse into the space, eliminating the need for a full enclosure or baffles, unlike when the intake is positioned above the torch in a fume hood.

Very good setup for claustrophobic me. Some may not like having the fan intake right in front of them on their bench though but it doesn't seem to affect my work style at all.

Do smoke test with torch lit....

Smoke test indicates air flow, not total effectiveness..

Dale

That's what I was thinking. So how do we really know if our exhaust is effective?

Cracking open those 2nd year engineering fluid and thermodynamics textbooks would be a start :) I'm a manager now so I don't have to actually do any math these days :mrgreen:

The fact that the fan can pull the smoke along the top or along side the flame into the funnel while the torch is on is a pretty good visual clue to me that the fumes are being taken out as well. If they weren't and going say perpendicular to the flame (if we imagine them to be rising) that would block or deflect the smoke, causing it to curl back and waft all over the place. Remember that smoke is made up of small particles of solid matter, and is probably heavier that the gas molecules coming off the torch, so I would guess that if the airflow is moving the smoke, it is moving the gas. Or I could be completely off base on this, I do think I am getting less smart as I age.

I had hoped that my smoke test was a good way to tell. Thanks for the info. I just went into the studio again and did the test and found out I needed to tweek the location of my hood a for the best results. I hadn't done this since we moved and never thought that maybe the hood wasn't in exactly the same location once it was hooked back up.

I am also claustrophobic and could never work in a box of any kind. I know they are safer and contain the glass but they arn't for me.

hi- i found your picture of your ventilation system and i wondered what size duct you are using for the opening and for the duct going back to the fan? thanks Margaret