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  • Mini Fume Hood

    I don't do a lot of welding but when I do I hate the fumes and the way everything in my shop gets coated in grey dust so one of the things I have been hankering for is a welding fume hood.



    The fan is a 230 W 500 cfm squirrel cage fan that was used to drive air through a HEPA filter in an acid distillation lab at work. It was quite corroded and being thrown away but it came up alright with a bit of TLC.

    The light fitting came from a kerbside rubbish collection except for the top which is a clothes dryer door.

    I will be adding some sides and front doors so that I can also use it as mini spray painting booth

  • #2
    Looks good!!!! What did you use for your shop walls??

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    • #3
      Originally posted by Tamper84
      Looks good!!!! What did you use for your shop walls??
      My shop is about 32 x 15 ft. About one third of this is specifically dedicated to metal working and is lined it with mini orb corrugated Zincalum sheeting. I was a bit worried the mini orb would be noisy but is surprisingly not and backed with a fat layer of rock wool insulation helps reduce noise escaping to my 5 adjacent neighbours. Here is a picture of it last year when it was first built. The rest is sheeted in regular plasterboard with air cell (al foil covered bubble wrap) insulation. Heating is a non-issue where I live but in summer I'm using an air conditioner sometimes all day for many weeks on end.
      Last edited by BobL; 06-02-2012, 06:39 PM.

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      • #4
        Bob,

        Did you actually try welding there already?

        When I started converting my garage to a shop, I experimented quite a bit with different aproaches to DIY fume extraction. Finally, I went with an exhaust similar to yours (pyramide-shaped 4' x 4' hood at the ceiling level (10') with a powerful traditional exhast motor installed through the roof and connected to the hood with a 1' dia. flexible duct. It works very quetly, but I cannot say that it's very efficient in terms of quick evacuation of fumes. Ideally, the hood should stay very close above the table. At least, right above the head level. Then the quickly raising hot fumes don't have any chance to spread out and escape evacuation. I was thinking about making a hood that may move up and down, but mechanics of it was just too cumbersome to my taste, so I desided to trade efficiency for a convenience and put my hood at the ceiling level.

        However, despite its somewhat limited efficiency and wasteful loss of heated air, my hood allows me to do some welding in the winter when opening the garage door is not an option.

        As for having such reflective walls surrounding the area where you're going to weld, just make sure you realize that using an auto darkening helmet may become problematic. This and a massive UV reflection would cause me to think about painting the reflective walls over. Also, I find it uncomfortable to have any light source above or behind my head when I'm welding: too much light goes underneath the mask.
        Last edited by MichaelP; 06-06-2012, 03:16 PM.

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        • #5
          Originally posted by MichaelP
          Bob,

          Did you actually try welding there already?
          Not with the fan running

          When I started converting my garage to a shop, I experimented quite a bit with different aproaches to DIY fume extraction. Finally, I went with an exhaust similar to yours (pyramide-shaped 4' x 4' hood at the ceiling level (10') with a powerful traditional exhast motor installed through the roof and connected to the hood with a 1' dia. flexible duct. It works very quetly, but I cannot say that it's very efficient in terms of quick evacuation of fumes. Ideally, the hood should stay very close above the table. At least, right above the head level.
          My shop at that end is only 8'6 high and the hood is 16" high so the bottom of the hood is only 7'2" from the floor and 4'2" from the top of the table. I realise that this is too low for most people but most of the stuff I weld is small, that's one reason why I only have a 3 x 2 ' welding bench although the vice is on a 3 x 3" post and is easily removed.

          The other thing that I still have to add are a set of bi-folding doors which will completely surround the table and although one cannot obviously weld with them closed they can be partially closed (e.g. so all except the front is open which will help constrain the fumes. I also have a 3HP dust extractor in my shop which I have been using to evacuate the fumes but I don't want to use it continually as it clogs up my filter bags with welding dust and the only way to get them clean is to wash them. Also I plan to use the hood occasionally as a mini spray booth and paint is something one definitely does not want on filter bags (I've lost a set of bags doing this)

          However, despite its somewhat limited efficiency and wasteful loss of heated air, my hood allows me to do some welding in the winter when opening the garage door is not an option.
          My situation is reversed for me it's the summer that counts.

          As for having such reflective walls surrounding the area where you're going to weld, just make sure you realize that using an auto darkening helmet may become problematic. This and a massive UV reflection would cause me to think about painting the reflective walls over.
          If I was welding for long periods I would definitely take this into consideration but the amount of welding I do means the galv sheeting will probably loose it's shine very quickly especially when I start using it as a spray booth. The bifolding doors will be made from Dexion shelving and are already painted.

          Also, I find it uncomfortable to have any light source above or behind my head when I'm welding: too much light goes underneath the mask.
          I have actually found the reverse. my helmet curves right around my head and finally now I can better see what I'm doing.
          Last edited by BobL; 06-02-2012, 09:06 PM.

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          • #6
            Makes sense.

            And having a hood 4' above the table will, definitely, work quite well.

            Good luck to you with your shop. As far as I understand, the lonely towel is already a thing of the past.

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            • #7
              All of my welding and grinding is done out in the car-port with the roller door closed behind me. Sometimes the weather is a probelm - mainly with MIG gas stream - but I can wait.

              I'd much prefer to work in natural day-light.

              Warnings about "welding flash" are quite in order as if you ever get a "good" one you will never forget it. A series of them will not do your eyes any good either - same as inadequate shielding/hoods.

              A suspended "bath/shower screen" welding curtain will do a lot of good.

              Air extraction may be better if the nozzle is located closer to the welding pool.

              http://www.google.com.au/#hl=en&gs_n...w=1920&bih=818

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              • #8
                MichaelP brings up a really good point with the reflective surfaces. Like OT says, a welding curtain might be a good solution. I know one welder that got "arc flash" because there was a welding station directly behind him and no curtains. The UV from the welder behind him was being reflected inside his mask into his eyes.

                It'll sneak up on you. You'll wake up in the middle of the night and think you've got a bunch of sand in your eyes.

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                • #9
                  MichaelP brings up a really good point with the reflective surfaces. Like OT says, a welding curtain might be a good solution. I know one welder that got "arc flash" because there was a welding station directly behind him and no curtains. The UV from the welder behind him was being reflected inside his mask into his eyes.

                  I had a similar problem but, believe it or not, it was from wearing a white t-shirt. I was doing some long duration welding on a large piece of equipment. Consequently, it was mostly in the overhead position so I was looking up, which meant my mask was open at the bottom. The UV light was refelcting off of my white shirt and into the mask and then into my eyes. Since then, I'm very conscious about what happens INSIDE the mask. If notice any characteristic light creeping in, I stop and reposition or put on a different shirt! Alternatively, they make true welding hoods - I've heard them called "pancakes" with a cloth hood and a glass front to eliminate these reflection problems.

                  It'll sneak up on you. You'll wake up in the middle of the night and think you've got a bunch of sand in your eyes.

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                  • #10
                    Thanks for the info guys. FWIW my welding apron is mat black leather and the overalls I usual wear are dark blue. Like I said, I am more likely to use the fume hood as a spray booth than a welding hood so it won't be long before it is covered in a rainbow of matt paint. My BIL uses those welding hoods - I might ask him if he has a spare.
                    Last edited by BobL; 06-06-2012, 04:35 AM.

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