Question about type of fan i've been using

Cornbread · #1 2011-08-31, 10:44am

Hi folks. Well, I've made it to the big time and have a designated area for my studio.

Here is a link: http://www.facebook.com/media/set/?s...3972901&type=1

My question is about my fan. I turned my torch on for the first time last night since moving to the new space and I decided I'd let the torch run and the ventilation run for about 10 minutes. (I was watching from outside, keeping an eye on it).

Upon reentry i could tell the exhaust of my torch was not out of the room. I think my fan is not suitable for my hood and ducting setup. If it is my set-up, please let me know. What kind of fans could i replace without putting my whole setup in to file 13?

The fan i have is purposed to push air (which may be the key) down in to man holes so the workers have fresh air. Its rated for about 1200 cfm on the high setting (which i always use), but something is flawed and I need some advice.

I'll be around all day to answer any other questions. so PM me if you don't get an immediate response.

Thanks folks,
justin

edit: my makeup air is an open door to my storage room, which has an open door to the outside.

Edit: a video of a smoke test. noticed the ACpushed the smoke in to the room so it has to be off for now http://www.youtube.com/watch?v=UDE8l...el_video_title

LarryC · #2 2011-08-31, 10:50am

Not sure I can see the hood or inlet for ventilation nor where the makeup air is coming from in any of these pictures. Hard to judge from this.

Baywinger · #3 2011-08-31, 10:55am

Justin
the fan is probably fine, from the pics though there is very little to trap gases and direct them into the exhaust duct
ways to correct this are make or install an actual hood above your work station, try adding more baffles above your workstation or run the ducting to just in front of your torch.

Baywinger · #4 2011-08-31, 10:56am

also the air conditioner will blow the gasses away from the vent so running the duct to your torch might be the ideal solution if you have enough distance on the bench in front of the flame from that awesome torch that is

Cornbread · #5 2011-08-31, 10:57am

Well i don't have any pictures of the makeup air. I can go re-take some photos if that would make it easier. but the whol building is divided in half. the glass door between the storage half and the studio half is open...and the door do the storage half opens to the outside..so the air passes through the storage area to the studio. studio space is 12 by 11

Cornbread · #6 2011-08-31, 10:57am

and the inlet could use a better photo...i'll work on that right now

JoeDeM · #7 2011-08-31, 11:01am

There are 3 problems, first your hood is not really a hood, you need to make it smaller and lower it closer to the torch, and add sides to it to increase the capture zone. The second is the fan, it may be rated at 1200cfm, but at what static pressure, most propeller fans have low max static pressure, a squirrel cage type fan is the best and are rated for 6"wc or higher at the rated CFM, 3rd I don't see a fresh air return, unless you are using the door. Dale has a few sketches that illustrate good set-ups with a hood and fresh air return, if you do a search I'm sure you will find them.

Cornbread · #8 2011-08-31, 11:05am

Here are the photos...it is a wide angle fisheye lense so everything looks farther away and larger than it is. but here are the updated photos

Cornbread · #9 2011-08-31, 11:06am

whoops

Cornbread · #10 2011-08-31, 11:09am

Hey joe, thanks for the reply. I am aware of Dale's sketches and i do have a basic understanding of air flow. I could lower the hood (would just extending down be okay?). I dont feel like it is too high above the torch though...because it's almost at my head. I'll go get a measurement and edit this post with the distance between the table top and bottom of hood.

Hood is 50" deep by 65" wide and 18" tall. The table distance from bottom of hood is 40" and the torch is 16 inches inward under the hood.

fan does not have a static pressure rating on it...just the cfm 1590 high 1350 low

Cornbread · #11 2011-08-31, 11:26am

Quote:

Originally Posted by Baywinger

also the air conditioner will blow the gasses away from the vent so running the duct to your torch might be the ideal solution if you have enough distance on the bench in front of the flame from that awesome torch that is

just noticed these posts. thanks! yes i did a smoke test with a bunch of taped together matches and noticed right off the AC has to be off. it WAS blowing the smoke back in to the room.

JoeDeM · #12 2011-08-31, 11:31am

Quote:

Originally Posted by Cornbread

Hey joe, thanks for the reply. I am aware of Dale's sketches and i do have a basic understanding of air flow. I could lower the hood (would just extending down be okay?). I dont feel like it is too high above the torch though...because it's almost at my head. I'll go get a measurement and edit this post with the distance between the table top and bottom of hood.

Hood is 50" deep by 65" wide and 18" tall. The table distance from bottom of hood is 40" and the torch is 16 inches inward under the hood.

fan does not have a static pressure rating on it...just the cfm 1590 high 1350 low

The easiest fix would be to bring the duct down to where the torch is, and add a 12" cone in front of the torch. The hood is way to large, you have spread your capture zone too thin and away from the torch, the products of combustion are not being captured properly. Because of the way you have your duct, your "hood" is not acting like a hood, the only thing it's capturing is heat.

edit:
face capture is ~30cfm effective

Cornbread · #13 2011-08-31, 11:36am

Quote:

Originally Posted by JoeDeM

The easiest fix would be to bring the duct down to where the torch is, and add a 12" cone in front of the torch. The hood is way to large, you have spread your capture zone too thin and away from the torch, the products of combustion are not being captured properly. Because of the way you have your duct, your "hood" is not acting like a hood, the only thing it's capturing is heat.

Thanks. So should i still get another fan because of the static pressure? If I add any more elbows or bends to get a funnel in front of the torch i feel like it will make it worse. I'm getting to the point where time is money and I'm ready to spend a little extra to get torching again. I have 150 Christmas gifts to make already.

LarryC · #14 2011-08-31, 12:05pm

Ahhh. Now I see the inlet. As others have already stated, you need a better hood closer to the torch or a funnel at the back. How are you supplying make up air? I see the open doors but you really need to have a fan pulling fresh air in at your back into the hood when you are torching.

Dale M. · #15 2011-08-31, 12:09pm

After looking at picture at the above website (facebook), and if you are still using same fan, dump it...........

Get squirrel cage fan calculated to size of hood.... By other post you state a 50x65 inch face opening for hood.... The math tells me you need a 2200 to 2800 cfm to be at lease effective in moving enough air to maintain minimal ventilation... Also your make up air capability needs to match fan capacity...

Other solution would be more "traditional" hood, smaller and lower with more defined capture zone over torch....

Dale

JoeDeM · #16 2011-08-31, 12:20pm

you want something like this, with a better fan.

Cornbread · #17 2011-08-31, 12:25pm

wow...yall rock!! thank you so much and WOW what and awesome picture joe! I'm weighing out a couple different options right now and I'll post what i get!

One being a vent a fume system, now that smaller box hood, removing the AC and putting in an attic fan with a little duct and a funnel. Or just adding an attic fan right in front of me and leaving the other system in place.

Cornbread · #18 2011-08-31, 1:46pm

not sure why i didn't share this sooner. here is a crude smoke test. this was the first time i tried out the hood. discovered the AC being on pushed some smoke in to the room instead of letting it rise up to the hood.http://www.youtube.com/watch?v=UDE8l...el_video_title

Dale M. · #19 2011-08-31, 3:36pm

Quote:

Originally Posted by JoeDeM

you want something like this, with a better fan.

Go with this concept.... Its a proven system....

Dale

Jazarra · #20 2011-08-31, 5:41pm

My fam is 650 or 450 cfm I forget which is that good for use with a minor torch ?

Cornbread · #21 2011-08-31, 7:43pm

well...long story short. i have a 1600 +/- attic fan in front of me. because of where the studs in the wall to the outside fall out, i had to scrap the current system. I'm almost done mounting it so once i finish ill post some pictures and try to do another smoke test video for you guys. thanks for all the help!

Dale M. · #22 2011-08-31, 7:44pm

Quote:

Originally Posted by Jazarra

My fam is 650 or 450 cfm I forget which is that good for use with a minor torch ?

Its not the type of torch that determines what the fan size is its the shape of the "capture area" (hood) the determines fan size...

Dale

Cornbread · #23 2011-08-31, 9:12pm

K, did a smoke test and it passed just not with flying colors.... I forgot to pick up a box fan to push fresh makeup air in to the room, but i think as it, it will be safe. I ran the torch for about 5 minutes (mirage outer flame on) and stepped back in to the room and did not smell or feel like there was any lack of oxygen or any unvented torch fumes. I'm too tired to upload a picture so I'll have to do it tomorrow. Thank a million for your help everyone!!!

BAGGEDCHEVYS · #24 2011-08-31, 9:34pm

im just curious what the overall size of your room is?

Cornbread · #25 2011-09-01, 7:05am

it is a 10 by 12 and ceilings are about 7 foot on one part then 8-9 feet on the other part (where the hood is)

Cornbread · #26 2011-09-01, 7:12am

here is the new ventilation system along with my sad faced old ducting and fan. putting in the new system was WAY quicker and easier. but it's a 1630 (or maybe 1690?) cfm attic fan.

Dale M. · #27 2011-09-01, 7:31am

Quote:

Originally Posted by Cornbread

K, did a smoke test and it passed just not with flying colors.... I forgot to pick up a box fan to push fresh makeup air in to the room, but i think as it, it will be safe. I ran the torch for about 5 minutes (mirage outer flame on) and stepped back in to the room and did not smell or feel like there was any lack of oxygen or any unvented torch fumes. I'm too tired to upload a picture so I'll have to do it tomorrow. Thank a million for your help everyone!!!

If ventilation is working properly you should NOT need a fan to push air into room, it just means you do not have the "evacuation" (hood/fan) correct....

IF one thinks about it the "studio space" is just open part of a long large "duct" beginning at fresh air intake (makeup air) and ending on outside of building as point exhaust exits with work space in the middle. A fan pushing air into studio will cause more air turbulence in studio and possible disrupt flame.

Also the air conditioner is going to probably blow directly into area of torch flame and caue it to dance and weave around, you may need to place baffle in front of it to redirect air so its not going directly at flame...

Dale

Cornbread · #28 2011-09-01, 8:07am

i agree...it IS trying to slam my two doors shut. but i'd like to try and close my studio door since it has a screen on it (the opening is just smaller than having it open) so if i mount a fan on the screen maybe i could get more make-up air if i helped to push it in instead of drawing it in.

bugs are terrible in louisiana so I'd like to keep em out if i can. And if this fan in the window doesn't work, i won't use it. I certainly value my life and health and don't want to compromise it.

Thanks everyone a million for the help!

Dale M. · #29 2011-09-01, 10:22am

Larger screen door...... A screen door should not be problem, It may just be you need more area....

Dale

Cornbread · #30 2011-09-01, 10:46am

Quote:

Originally Posted by Dale M.

Larger screen door...... A screen door should not be problem, It may just be you need more area....

Dale

yeah the screen door has a sliding window in it. it's about 24x24 in. when open. I'm hoping a boxfan will help, if not, ill just leave the door open.