fume extractor hood over welding table

[rodwerkz]

i've found myself being alot more sensitive the last few years to welding fumes. I've was originally thinking about mounting a cheapo ducted kitchen hood over my bench to help get the **** out of my shop, quick and easy.. however first off i'd probably like to fab something so it's a little bigger, roughtly the surface are of my table.. secondly, i have no idea if those wimpy 180cfm units woudl do a thing..

so, needless to say i'm thinking about just making somethng.. Anybody made something like this? Say i made a hood 30x48, what kind cmf's should i be looking for in a fan?

Any advice would be appreciated...

 

[shopforeman]

I am thinking about doing the same sort of thing when I build my new shop. Right now I am putting up with the fumes.
One of the things I have wondered about is the issue of the exhaust fan drawing flue gases into the shop from the shop heaters exhaust. Those fumes are potentially more harmful than the welding fumes. I assume one would want to have some sort of fresh air inlet to avoid negative draft issues with the furnace. I think that with a hood over the welding area that you would not need too many cfm to vent the fumes. The fumes are hot so they are already inclined to rise. A little air movement would probably whisk them away nicely. Without a hood, ie: just a louvered fan in a wall nearby, I think a higher volume fan would be required. I would be interested as well in hearing from somebody who is in the know on this subject.

 

[brownbagg]

go find you a HVAC dealer installer, they throw away old furance squirrel cages daily. there is usually a couple out by the trash pile. it will move a lot more air

 

[kbs2244]

Shopforman has a very good point. Too much air removed can be a bad thing.
I would go with the stove hood for starters. 180 CFM may not sound like much, but it is a lot more than you are getting now.
If it isn't enough, I would enlarge the hood before enlarging the fan. Just catch more fumes.
If you do go with a old furnace fan, for sure you want a way to make up the air removed. Maybe a vent from the outside to the underside of your table?

 

[5wndwcpe]

Check the auctions for used restaurant equipment. You'll find your hood already pre-fabbed and in stainless to boot.

 

[Stuart in MN]

The commercial welding fume exhaust systems I've seen use a flexible hose that you locate close to where you're welding. Here's one example:
http://www.ventafume.com/content/pages/place-a-vent-cr.php I see the smallest version is 165cfm. It seems like it would be pretty simple to build something similar with parts from Home Depot.

 

[mhoffm911]

Yep, I've sold items like this at auction. Check www.auctionzip.com or www.auctioneers.org for auctions in your area.

 

[Franz©]

WHAT DO YOU INTEND OT DO FOR MAKEUP AIR???

Doesn't matter one bit how many CFM the fan is capable of if you don't have replacememnt air coming into the room. Makeup air must equal exhaust air or no air leaves the room.

 

[Roospike]

WHAT DO YOU INTEND OT DO FOR MAKEUP AIR???

Doesn't matter one bit how many CFM the fan is capable of if you don't have replacememnt air coming into the room. Makeup air must equal exhaust air or no air leaves the room.

Now that would be one tight a$$ shop with no "makeup air" for an exhaust

How do you think people have run gas / oil /wood / coal ect heaters in there home with a chimney / exhaust for all these years ? ..... ....... .... HELLO!?

 

[rodwerkz]

trust me i have plenty of leaks .. There is plenty of make up air..

Right now i just have electric heat which doesn't do a thing, but i will be putting a hot dawg in within the next month or so. since it's a heat exchanger style i don't think i'd have to worry about pulling in fumes.. that is a very good point though...

aside from the make up air too much air flow would screw with my shielding gas anyway (alot of my work is mig)..at max i was thinking about doing something in the 300 cfm range and putting a dampner on it..

 

[Vicegrip]

I too have noticed that metal fumes and even grinder dust is bothering me more and have to wear a mask all the time when preping, welding and finishing metal. I have have a shop vac mounted in another space that was originaly set up for dust and chip removal. There is a pipe system that lets me use it from almost anywhere in the shop. I mucked up a cheapo ceiling fan control with an added relay to use as a remote on/off. I now use this system for dust and fume control and as the air sucked from the shop is ejected outside it has 100% removal. All I did for the fume hood is cut some cardboard into a 3 foot square inverted funnel and ether hang from a tripod or set it up somehow above the work at hand. If the work is not portable I tape it up to something if it is I use the rolling hood. The shop vac intake is far enough away that it does not move so much air that the shielding gas is disturbed but the fumes being hotter than the surrounding air and rise up and into the hood. When not in use I pop one seam and fold it up. If working in tight spaces line under a dash welding in roll bar tubing I just put the vac hose about a foot above the work and most of the fumes rise up and get sucked up. At some point I will make a better one from foil covered ridged foam insulation but for now it works good enough to not mess with it. I have no problems with makeup air, it pulls in around the roll door.

This setup might not be as nice as a pro fume system but it is double duty from equipment that does other tasks.

You could make one easy by using a bottom of the line cheap shop vac and a long hose. Put the shop vac outside and run the hose through a window or door. With the vac outside there is no worries about filtration any that passes the filter is dumped outside anyway.

 

[shopforeman]

Most shops, mine included will have plenty of "make up air" for a range hood fan I'm sure! I was thinking about using a squirrel cage fan etc. with a louvered wall vent near the welding area to get the fumes and generally provide shop ventilation, in a future new, insulated, wrapped, lined & painted shop, so I would be moving a higher volume of air and perhaps have less naturally occurring "make up air". I have seen "make up air" vents in new homes where the vent is brought in high on the wall, dropping down to the floor then looping back up the wall about halfway using a 5"-6" flexible plastic insulated duct. Something like this could work I imagine. Since I just thought of this now...is anyone using a carbon monoxide detector in their shop?
I like the idea with the dust collector...I have a similar idea for using a dust collector to ventilate a small blasting booth I've been thinking about for the shop. Of course I'll still need breathing air to be in the booth but my aim is too take as much dust as I can to the dust collector in a shed outside the shop...theres probably a way that I could use just the dust collector for both the booth and the shop ventilation but I think it will be better to have separate dust/ventilation systems.

 

[Franz©]

I just hope all you guys installing dust collectors and fume exhausters are also installing proper incipient fire warning systems and safety interlocks.

 

[russlaferrera]

My take on this. Is the heated fumes rise. The bigger the collection area (hood) would be the most beneficial . The hood must be tapered to allow the fumes to travel up to the fan. A small fan 100 cmf at the top would remove the fumes to the outside.

As mentioned. You don't want a draft to remove the shielding gas. Depending on air movement the fumes should go straight up.

 

[AGBill]

Just another opinion on welding fumes, sparks and molten metal inside a shop...

Because of the fire hazard, the nasty fumes and molten metal burning holes in an epoxy floor coating, I have decided to do my welding outside only.

This will require a welding table on wheels, (a fun welding project), an electrical outlet for the welder near the roll-up door and a 20-30 foot extension cord for the welder.

Welding outside solves a lot of the problems of inside welding, including eliminating the need for a fume extraction system, with only minor disadvantages. Some people might consider moving welding projects in/out of the garage a pain, and weather might interfere with your welding plans..

 

[rodwerkz]

ok guys.. i got myself a 140 cfm squirrel cage. I"m now going to attempt to build a fume hood into the mezanine above my welding table. I'll be sure to do a post with plenty of pics.. Thanks guys for the input...

 

[sethbriancollins]

check out the jalopy journal tech post i did - it covered this.
http://www.jalopyjournal.com/forum/showthread.php?t=225989

i used a HF dust collector with semi rigid dryervent to pull the fumes away,

eventually i also want to fab up an overhead collector as well, the problem with an overhead collector is the fumes have to go past you to get removed, so you tend to breathe them.

my next project is a down draft table like the one here
http://www.dualdraw.com/dual_draw_products_detail.asp?CO=DD&CMD=RET&AINID=TT500

my s list included the mig gun with a vac attachment to remove the smoke.
http://weldingdirect.stores.yahoo.net/srsmremiggun.html


the overhead units done't need a lot of cfm because they have a laminar flow over the boundry layer that hugs the sides of the hood. this bacically makes it easy for the smoke to rise towards the vent,

also i would NEVER combine a wood and metal shop dust collection system. you are asking for trouble.