Thread: Looking for extraction hood spec
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19-09-2017 #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.
ThanksLast edited by marbles; 19-09-2017 at 10:16 PM.
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21-01-2018 #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.
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The Following User Says Thank You to philgrady For This Useful Post:
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22-01-2018 #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
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22-01-2018 #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.
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19-07-2019 #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.
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The Following User Says Thank You to Bladevane For This Useful Post:
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19-07-2019 #6
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