1. #1
    Hi,

    I've recently moved to smaller premise and i'm instantly noticing the plasma fumes, much more noticable that mig fumes, even though I have a water table on my cnc table.

    I'm wondering where is the best place to extract from, the width of hood and fan size. I can either add a hood at the cutter or make a larger hood to cover the whole 4x 4 table and extract from a single apex point. Currently have a lot of 6" 150mm hose should that be a good diameter.

    Any ideas or links welcome.

    Thanks
    Last edited by marbles; 19-09-2017 at 09:16 PM.

  2. #2
    Hi,

    I suggest the following

    Face area of table 2.5M x 1.25M x 0.75 = 2.34m3/s or 8437.5 m3/hr

    That would give a fan and ducting size of 630mm diameter.

    The 0.75 m/s comes from the HSE recommendation for venting of plasma tables.

    I went for something smaller as I did not want to cut that size hole in the wall, so I went for 500mm diameter and uprated the fan to move more pressure. It's louder but I can vary the speed as required.

    I vented from under the table, to prevent the finish face from discolouring etc.

  3. The Following User Says Thank You to philgrady For This Useful Post:


  4. #3
    How does your table work?
    Industrial tables usually have water baths which significantly reduce emissions to the workspace.
    You think that's too expensive? You're not a Model Engineer are you? :D

  5. #4
    That's great advice, thanks.

    I currently use a water table, which is a 100% necessity with plasma. TBH I use the plasma infrequently but when its on it runs on and off all day. i'll probably have to use a standard 300mm dia hose because thats the max exhaust size I can use to the outside. Will extend the hood and fan power accordingly.

  6. #5
    On my 4' x 2' table I boxed in 3 sides and created a duct for the 4th side fitted with a 6" flexible hose connected to a 1.5 HP 3000 rpm centrifugal fan exhausting outside the workshop. I drape fireproof blanket over the gap between the workpiece and the table edges so most of the smoke and fumes are extracted downwards.

  7. The Following User Says Thank You to Bladevane For This Useful Post:


  8. #6
    Quote Originally Posted by Bladevane View Post
    On my 4' x 2' table I boxed in 3 sides and created a duct for the 4th side fitted with a 6" flexible hose connected to a 1.5 HP 3000 rpm centrifugal fan exhausting outside the workshop. I drape fireproof blanket over the gap between the workpiece and the table edges so most of the smoke and fumes are extracted downwards.
    Nice 1, fire blankets a good way forward
    Last edited by marbles; 4 Weeks Ago at 08:53 PM.

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