New studio vent hood questions

[CO_Phantom]

Ok.
After much searching and reading (as much as my Blackberry will allow since I don't have internet otherwise!)...I have a vague idea what I need for a vent hood but need some help with final calculations and with the Grainger catalog.

I've done the math using the calculations posted by Mike A. but my blackberry won't allow me to see "table 1" in a decent format, so I can't calculate the static pressure to find the blower I need from Grainger.

My workbench is 41" deep and 93" long. I have 2 ways I can do this--one large hood to vent the whole bench (I'm afraid might be not ideal since one torch would be running with 2 set up under the hood so it might create flame disturbances). Or, I can split the bench in half and switch out torches depending on what I'm using, so the torch sits centered under the smaller vent hood.

The torches: a japanese B8, a MiniCC, and a Barracuda. Only one will be running at any given time.

If creating a vent hood for half the workbench (and just setting up the torch I'm using at the time):
Square ft= 12.8
CFM (for ceiling mounted)=1600

We have 6" duct from other HVAC projects that I'd like to use if possible, but I could use 8" duct if that proves to be more efficient.

Velocity (for 6")=8163
(for 8")=4585

Velocity Pressure (for 6")=4.2
(for 8")=1.3

Bend loss (thinking just one 90 degree bend to vent from wall)
(For 6")=0.5
(For 8")=0.16

Total run of duct approx 6'

Static Pressure (for 6")= (4.2)(6)(_____)+0.5
(For 8")=(1.3)(6)(_____)+0.16

I need help finding the loss factor from "table 1" posted by Mike A. And then I need help to determine which Grainger part # would work best for me. Also someone to check my math would be great! I want to get this right the first time!

Keep in mind the calculations were done based on the size of workbench, not size of hood, but should be close in size to the actual hood.

Am I on the right track? Anything I'm missing?

Thanks!!

-Amy

[Otter's Flame]

Amy,
I will leave the calculations to the experts but I just thought I would throw a monkey in the wrench for you. In my personal studio at home, I have an excellent ventilation set up for running one torch at a time. If I had it to do all over again.... and as a matter of fact I am going to do it over again, I am going to set my work station up to be able to run multiple torches at one time. I get tired of changing out my torches for different glasses and different things I am doing. It is also a pain when I want to teach here at my home studio.

Since you are using a B8, a Mini CC and a Cuda.... , I am assuming you may be working more than one COE. If I had the luxury of setting up multiple stations for my multiple COE's and for teaching, I would have initially. Since I know you... I feel safe to say if you are not exploring multiple COEs right now you will be. I would also imagine you may want other people to torch with you at times and I could easily foresee you teaching.

If I were you and I would sure consider setting up multiple torch stations at the same work bench.

And by the way....... ((((((((((((((( AMY ))))))))))) Hugs to you It is good to see you around.

Otter

[NMLinda]

Amy - I've seen pics every once in a while here on LE on how folks have put dividers in their hoods so that they can run multiple torches on one long workbench, like you're describing. Mike A. might have pics posted on his site:

http://mikeaurelius.wordpress.com/

Been a while since I looked at them, so I don't remember where on his site they are.

You might also search

www.ArtGlassAnswers.com

There might be some pics there, too.

Running the vent ducting may be a bit tricky, so that you get a balanced and sufficient draw for each station, and you'll likely need a rather large fan (such that you really won't want to use 6" ducting - too lossy for what it sounds like you want to do), but you'd have a marvelous work area.

You might consider re-posting and ask specifically if anyone has set up multiple work-stations under one hood and if they have specific guidance for you.

Linda

[Dale M.]

If you use larger duct work than 6 inch you can almost forget static pressure issues with the smaller duct..... Reducing hood area to smaller sections and using dampers and such to create separate areas for fan to draw from allows you to reduce the duct size and fan size, the negative is you have to use dampers in ducting, you have to be sure the one is open for section you are using and the "others" are closed..... Also if you choose to separate sections of hood into separate "station" you probably need to bring dividers down from hood to bench top.... The can be anything, plastics or glass will give you a more open feeling....

Keep in mind while doing calculations that for every inch in diameter you increase in duct size it almost double the area of duct in square inches... So larger ducting decrease static pressure dramatically....

Dale

[CO_Phantom]

Linda-- those were the sites I was reading and couldn't find quite what I was looking for, which is why I posted my question here.

Dale--i had a feeling I'd want to use larger duct than 6". You can see by the calculations I was able to do that the larger duct is just more efficient and would decrease the fan size needed.

Otter-- HEY!!!! I originally thought of setting up more than one torch and vent the entire workbench, but I got a little worried about balancing the air flow and wasn't sure how that should be done. I have many COEs in my world at the moment. While I don't forsee myself teaching anytime soon, I did consider it would be a PITA to change out torches every time I wanted to jump to a different one. The only reason I'd considered splitting the workbench down to a smaller section is the cost of the blowers necessary to vent the bench.

Needing some guidance 'cause I'm confused as all get out and want to get this figured out!

-Amy