Exhaust hood/vent fan?

All topics related to smoke evacuation, ventilation, and water tables.
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gamble
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Exhaust hood/vent fan?

Post by gamble » Tue May 16, 2017 2:29 pm

I do have a water table but always leave it a little low due to my heavy aluminum cutting. I have a small fume extractor plumbed into the side of the table but it's a little under powered even for a 2' table. I want to build a hood with exhaust fan to blow all the fumes outside.

What kind of fan do you guys recommend? I want to keep as much of the smoke and dust out of the shop as possible.

Also totally on a side bar. Who sells those yellow see through curtains that some people weld behind? I want to put one between the laptop and the plasma table to keep all the stuff off the laptop
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fireside
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Re: Exhaust hood/vent fan?

Post by fireside » Tue May 16, 2017 9:51 pm

You can do a welding curtain search on amazon and you will get a bunch that come up.

https://www.amazon.com/s/ref=nb_sb_noss ... g+curtains
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jimcolt
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Re: Exhaust hood/vent fan?

Post by jimcolt » Wed May 17, 2017 7:51 am

It is not advisable to build a hood....as this implies that you are allowing the smoke/fume to rise out of the table and get pulled through the precision moving parts of your cnc cutting table. Plasma fumes/dust are small, hard, sharp pieces of the material you are cutting and will affect performance, wear and life on the cnc table.

Downdraft is a better way to pull the dust and fumes from a plasma cutting operation. Fan sizing will be determined by 1. what you are cutting, 2. What is the area of your table that you are pulling from, 3. at what power (amperage) level are you cutting.

A typical small shop table with 4 x 4 dimensions cutting 10 gauge steel will typically need about 3200 cfm air flow for best results in removing fumes. Industrial plasma tables may need a thousand times that flow rate!

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gamble
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Re: Exhaust hood/vent fan?

Post by gamble » Wed May 17, 2017 8:10 am

Thanks Jim, but I'm not interested in building a downdraft.
What fan would you recommend? Instead of an overhead vent I may do one at the end of the table.
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Silicone&paint
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Re: Exhaust hood/vent fan?

Post by Silicone&paint » Sun Apr 07, 2019 8:13 am

Old thread I know but I have a water table that I keep like a 1/4 inch from the bottom of the sheetmetal and I am in the process of putting a hood with fan on top just for the smoke. My logic is the water is still catching the slag and the smoke still rises up from table, across those parts without the hood/fan.

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Re: Exhaust hood/vent fan?

Post by 2015cmax » Sun Apr 07, 2019 12:49 pm

There is a line of fans that are intrinsically safe. Their motors and bearing are sealed to prevent the dust from contaminating the components. They are available in many sizes and CFM ratings. Most often the fans are used in industrial applications. I did a quick web search and here is a link to use as reference to give you an idea of a few options.

https://www.industrialfansdirect.com/co ... lator-fans

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Re: Exhaust hood/vent fan?

Post by Bladevane » Sun Apr 07, 2019 1:26 pm

I lashed up a 1/2 HP centrifugal fan with a 4" flexible hose secured close to the torch using an old coffee tin. See photo. This, combined with a water table, keeps a lot of the smoke out of the workshop.

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SeanP
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Re: Exhaust hood/vent fan?

Post by SeanP » Sun Apr 07, 2019 6:04 pm

I've gone in another direction and it's working fine for me, I built a enclosure round the table and added a fan to remove smoke and dust, water table doesn't stop it all by any means in some cases, likes of base plates there is still a lot of crap shoots straight up from the plate at the pierce, galvanised is another nasty one, but using this method really does keep the area outside the table clear.

https://photos.app.goo.gl/1K1cbLMnNAjjco4GA

I got a 18'' fan same as this, seems to have plenty pull.
Fan.png

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Silicone&paint
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Re: Exhaust hood/vent fan?

Post by Silicone&paint » Sun Apr 07, 2019 8:07 pm

We have a piranah 4 x 8 table. We got the water table thinking we wont have to vent it because it was a kind of a long run, but it became evident that we needed to.

It still came with the downdraft fan, so I'm going to try to use that fan for the hood. Its 16" and the manual says 1200 cfm at 3" sp but I cant find any other info on this fan. Not even on the fan itself

If its insufficient we'll upgrade the fan

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