Need advice on ventilation system for stick welding inside shed

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Hi Guys,I have been welding outside the last 4 months, now with the rain, need to move my practice sessions insude shed. Here is what I am working with. Lean -to shed -10' wide by 14' deep with welding table by one window on higher side, which is about 10' inside, with all walls covered with 1/4" cement board and alum flashing covering other interior spaces. Only the ceiling is not covered. Harbor freight ventilator:3300 rpm, 1590 cfm hi, 1380 cfm low  1.4 amps8 " but with flange is 9.75". We have 8" alum flex pipe , and another window open, with window fan blowing in, across from window with vent pipe going out. Two 10' tall doors , each 3' wide, usually closed or one door opened, depending on direction and intensity of rain. I need some advice as to where to buy some adapters out of tin or ss, to connect the 8" flex alum pipe to the 8.25" neck just past the 9.75 flange on the exhaust port of the ventillator.  Same is neede for the inflow side of the 8" to ventilator( both sides the same measurements)And a sizeable hood (12" by 8") to pick up over my table when welding. All with the 8" flex alum pipe. We set up a mock prototype with duct tape as joinery. Worked ok, but some smoke escaped the 8" pipe hanging 12" over weld area. What would work to be able to use clamps so is more permanent, but can be broken down easy if needed?Where can I get these, or have them made. I do not have the experience to even try to fabricate them. Here is a pic, Thank you in advance for any advice , Raf
Reply:Is the shed closed up when welding? I Imagine that will not give you as much flow as you want and it also depends on where it come in from. I bet a little hood on the intake would help out and I would not expect all the fumes to get taken up either it would be very difficult as would be with mig. 8" pipe seems a little large too.
Reply:Try inexpensive 10" flex-coil A/C ducting from A/C supply house, and good ole duck tape like you already use.That 8" hose you got stuck in the window for intake is your real problem. It's a restriction and causes a negative pressure when fan is energized..I know you thinkin 8" out equals 8" in, but in practice that don't work....However I believe you said the shed had 2 3ftX10 ft doors where usually one remained open depending on rain, where if so, you have plenty of unrestricted intake.As a boiler inspector, one of the things I always had to look for was adequate intake air for the combustion process, where I first determined the CFM of boiler blowers, then calculated the area of boiler room building intake louvers. You would be surprised to discover how much larger the intake louvers needed to be compared to the blower duct diameter to prevent negative pressure in the boiler house and ensure safe evacuation of leaking fuel gases and fumes.
Reply:Thank guys, and to wornoutwelder,That picture is of the outflow sticking out the window, not the inflow,Sorry for the confusion, my bad. Thanks for the advice. Raf
Reply:Originally Posted by wornoutoldwelderTry inexpensive 10" flex-coil A/C ducting from A/C supply house, and good ole duck tape like you already use.That 8" hose you got stuck in the window for intake is your real problem. It's a restriction and causes a negative pressure when fan is energized..I know you thinkin 8" out equals 8" in, but in practice that don't work....However I believe you said the shed had 2 3ftX10 ft doors where usually one remained open depending on rain, where if so, you have plenty of unrestricted intake.As a boiler inspector, one of the things I always had to look for was adequate intake air for the combustion process, where I first determined the CFM of boiler blowers, then calculated the area of boiler room building intake louvers. You would be surprised to discover how much larger the intake louvers needed to be compared to the blower duct diameter to prevent negative pressure in the boiler house and ensure safe evacuation of leaking fuel gases and fumes.
Reply:A range hood from off an old stove top, positioned over your welding table would help capture and vent some more of the fumes/smoke out of the area for you. Try to find one to mount over your table to direct more smoke into the ventilator. I would also look into building a shelf and cover on the outside wall to mount the vent motor on. That will cut down on some of the noise in the shop when it is running.
Reply:Originally Posted by mikecwikI figured a smaller (to some extent, I know there is a limit to it) would create a more powerful draw rather.
Reply:Might be a good reason t get a mig.
Reply:I also suggested a hood and I understood what I suggested. I am having problems with the  tube size though. Research must follow!
Reply:Originally Posted by wornoutoldwelderAnd yeah, Bistineau, I just call you a Coonazz, but with the greatest respect
Reply:Originally Posted by mikecwikI figured a smaller (to some extent, I know there is a limit to it) would create a more powerful draw rather.
Reply:Originally Posted by BistineauIn the case of ventilation/smoke removal, volume not velocity is what is needed A larger diameter can naturally flow MORE volume for a given pressure differential. Smaller diameter hose causes more restriction to flow than does a larger one, given the 1380 CFM of the ventilator blower.
Reply:how about going old school and placing an old (or new) box fan at your back blowing toward the window and placing one of those dual window sash fans that we used before air conditioners pulling out?i.u.o.e. # 15queens, ny and sunny fla
Reply:Neighbor gave old barbecue. Mod with hf blower.Have used those aluminum wound 8 " like used here, but abandoned because, tend to unwind,when hung vertical.Rectangle bar tilts vertical, fume hood can be positioned up/down, tilted forward/back.Cheap solution, works okay. Charl
Reply:Originally Posted by xmancharlNeighbor gave old barbecue. Mod with hf blower.Have used those aluminum wound 8 " like used here, but abandoned because, tend to unwind,when hung vertical.Rectangle bar tilts vertical, fume hood can be positioned up/down, tilted forward/back.Cheap solution, works okay. Charl
Reply:Originally Posted by BistineauIn the case of ventilation/smoke removal, volume not velocity is what is needed A larger diameter can naturally flow MORE volume for a given pressure differential. Smaller diameter hose causes more restriction to flow than does a larger one, given the 1380 CFM of the ventilator blower.
Reply:Originally Posted by docwelderhow about going old school and placing an old (or new) box fan at your back blowing toward the window and placing one of those dual window sash fans that we used before air conditioners pulling out?
Reply:One thing I mentioned was to make a shelf outside for the blower with a cover over it to deflect the rain. That way there would be less noise inside the shop from the blower motor.
Reply:Neighbor gave old bbq?Or hadn't he looked on his back porch before this was posted!HAHAHA!Anyways, its a brilliant repurposing of something that would have ended up on the curb on trash day.Nice job!
Reply:Originally Posted by BistineauOne thing I mentioned was to make a shelf outside for the blower with a cover over it to deflect the rain. That way there would be less noise inside the shop from the blower motor.
Reply:Originally Posted by docwelderhow about going old school and placing an old (or new) box fan at your back blowing toward the window and placing one of those dual window sash fans that we used before air conditioners pulling out?
Reply:Originally Posted by BistineauNo offense taken you ole fossil. I see in your signature line you list USS Hunley. Shouldn't that be CSS Hunley?
Reply:I have found that it was easier to just change all the air in the shop, rather than trying to just get all the smoke out. Two windows, one at either end of the shop, one with box fan blowing in and the other with box fan blowing out, which was in and which was out depended on the wind.Ian TannerKawasaki KX450 and many other fine tools
Reply:Thank You, fortyonethirty,I appreciate the post,Raf
Reply:I have the same problem on a smaller scale.  I use  a Mig welder with gas shielding, so the fumes are not nearly as strong as with stick welding.  That being said, there should be some combination of fans and cross ventilation that can create a workable solution for you.  In my case I robbed the squirrel cage motor out of an old electric dryer and mounted it on the wall above the work bench.  It only has a 4 inch dryer hose, but it does ventilate the shop fumes fairly well.  In your case, though, you need something about 100 times more powerful.  I am thinking something like they use for drying carpet in a room that has had flooding.  These fans are about 36" across and sit on the floor or any horizontal surface.  I think something like that that was mounted in a hole in the outside wall near your work bench might do the trick.  Another possibility is an attic fan.  These have louvers that automatically close when the fan is turned off, and they are pretty quiet since the blades do not turn real fast.You would have to make a large hole in the roof or the upper wall to make this work, but an attic fan would move enough air fast enough to do the job for sure.  As far a sources you might try the RESTORE or goodwill.    Also Home depot did have some large belt driven shop fans during the summer. These are about 48" in diameter, and might also have enough capacity, but I would shoot for the attic fan first if you have any choice.Another option is to use a welding hood with forced air from a clean source outside the shop.  I have been watching You Tube vids on the pipeline welders using this method.  I think they use a belt mounted air pump with a filter on it, but you are not limited to this design limitation.Originally Posted by fortyonethirtyI have found that it was easier to just change all the air in the shop, rather than trying to just get all the smoke out. Two windows, one at either end of the shop, one with box fan blowing in and the other with box fan blowing out, which was in and which was out depended on the wind.
Reply:Thanks Tillerman6,Thanks for the ideas, alot of food for thought. Raf
Reply:Thanks Norite,Yes, our winter last year was terrible. That is a good point, the heat in the shed would get sucked out. Raf
Reply:Originally Posted by rafThanks Norite,Yes, our winter last year was terrible. That is a good point, the heat in the shed would get sucked out. Raf
Reply:Originally Posted by BistineauYour not worried about keeping the heat in, just getting the smoke OUT. Remember? So mount two attic fans in the shed and be done with it, no more smoke problems when welding in the shed.
Reply:You say you have 10' doors, what's the ceiling height? Maybe you could make a hole at the top of a door and mount the blower in it. Then open a window on the opposite wall an inch or so. The smoke will rise to the ceiling and be pulled to the blower by the cross ventilation, and on out to the outside. If the ceiling height is close to the top of the door, this would work, and it wouldn't matter where in the shop you were working. If the ceiling is a couple of feet higher than the doors, then a hole through the wall at ceiling height to do the same thing. The opening would be right below the soffit and be protected from the weather there.Last edited by Bistineau; 10-07-2015 at 08:09 PM.
Reply:Even at my age I can hold my breath long nuff to burn a stick to a stub, then take a cigarette break outside while the shed airs out...but that's just me
Reply:hey Jon, just cut a nice size hole in the roof and put in an attic fan with lots of cfms, connected to a switch, turn on when welding and off when setting up, the smoke rises to the ceiling and then it will be pulled right out of the shed, you can open the windows on each side for fresh air in....any kind of ventilation will pull the heat out in the winter, but at least this way you can keep some in with control of the fan with the switch..Of all the things I lost I miss my mind the most...I know just enough about everything to be dangerous......You cant cure stupid..only kill it...
Reply:Originally Posted by wornoutoldwelderEven at my age I can hold my breath long nuff to burn a stick to a stub, then take a cigarette break outside while the shed airs out...but that's just me
Reply:Originally Posted by BistineauYou say you have 10' doors, what's the ceiling height? Maybe you could make a hole at the top of a door and mount the blower in it. Then open a window on the opposite wall an inch or so. The smoke will rise to the ceiling and be pulled to the blower by the cross ventilation, and on out to the outside. If the ceiling height is close to the top of the door, this would work, and it wouldn't matter where in the shop you were working. If the ceiling is a couple of feet higher than the doors, then a hole through the wall at ceiling height to do the same thing. The opening would be right below the soffit and be protected from the weather there.
Reply:Originally Posted by roadkillbobbhey Jon, just cut a nice size hole in the roof and put in an attic fan with lots of cfms, connected to a switch, turn on when welding and off when setting up, the smoke rises to the ceiling and then it will be pulled right out of the shed, you can open the windows on each side for fresh air in....any kind of ventilation will pull the heat out in the winter, but at least this way you can keep some in with control of the fan with the switch..
Reply:Sorry I missed this earlier. I've seen guys take an old range hood and set it up over their weld table. Then they will pipe the output of the fan to a window with some of that flexible metal ducting. AT the window, they'll take a piece of plywood and cut a hole in it the duct will fit thru. On the opposite side, open the window some.Similar idea uses an inline vent fan, and round duct on each side. You position the input duct near your work to suck up the fumes, and exhaust out the window as mentioned before.The higher CFM on the fan you can get the better. This coupled with 6" or 8" duct should work.Last option is to get one of those round kitchen wall fans and see if it will fit in the open window. Build a "box" to hold the fan and stick that in the open window like a window Ac unit..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:mabe you can retrofit one of these for fresh air to breath...Of all the things I lost I miss my mind the most...I know just enough about everything to be dangerous......You cant cure stupid..only kill it...