Need to build a spray booth

[dave]

Hi all,

I want to build a small spray booth and I've found an explosion proof fan from Northern Tool for $600. I'd like some feeback on whether this should be adequate for a small booth.

http://www.northerntool.com/shop/tools/product_200460089_200460089

I am working with smaller parts for the foreseeable future so the booth won't be very large - maybe 2'x3'. And I don't do a heavy volume at any one time, so I am hoping I could filter the fumes/particles and then just put the air back in the shop (trying to avoid cutting any more holes in the walls of my garage).

Any problems with this plan??

 

[Bill Clemmons]

I can't comment on the explosion proof motor/fan, but I can tell you how I did my spray booth. I used a "positive pressure" approach rather than "negative pressure". It pushes air into the booth rather than pulling air out of the booth. That way I don't have to have explosion proof anything.

If you'd like to come see it, you're only about an hour from me. Let me know.

HTH

Bill

 

[dave]

Thanks Bill, that's interesting. I may take you up on your offer if that turns out to be a better option for me. I'll go do some reading on the pros/cons of negative versus positive pressure.

Dave

 

[ashley_phil]

are you building this for hobby use? or is it commercial?

either way these guys are in greensboro and have some of the best pricing for booths around:

http://www.toolsusa.com/paintbooth/

it is definitely worth talking to them before you drop $ 600 on equipment at northern tool and cobble something together.

also scour craigslist often land lords are practically giving these things away so someone will pay to dismantle it and remove it from their building. be learly of buying one already disassembled unless it's marked because even marked properly these things are an erector set to put together.

whatever you do, my recommendation is you go with bolt construction not welded or riveted. as much as you think you'll never take it down the reality is that in time you or someone else will likely need to move it.

 

[dave]

It's somewhere between hobby and commercial at this point, but it will never be a large amount of painting or large items that I'll be spraying. I've actually only been using aerosol spray paint for what I am doing and expect to continue with that. Problem is the fumes and also the over spray is settling on items around my work area.

Thanks for the link! I'll take a look at what they have.

 

[Glennbear]

IMHO $600 is a really large piece of change to be dropping for a fan in a 2' x 3' booth. I would look into a "push" type setup temporarily placed in front of a window. The other thing to be considered is that filters that will catch fumes in addition to overspray particles are going to be REALLY pricey containing a media such as activated carbon. :wsmile:

 

[dave]

Unfortunately, I don't have a window in my garage shop. :wsad:

If I could do the work outside, I would, but I am putting on multiple coats and it just would not be efficient to move everything in and out each time.

 

[Howard Acheson]

>>>> I used a "positive pressure" approach rather than "negative pressure". It pushes air into the booth rather than pulling air out of the booth. That way I don't have to have explosion proof anything.

Yup, that's the way to go if you can. Just need to be sure you are not blowing in any dust. But the OP's problem is that he wants to exhaust the air into the shop rather than outside. It's going to be difficult to get an air flow that will work with positive pressure.

 

[Howard Acheson]

>>>> I want to build a small spray booth

What type of finishes do you want to spray?

 

[bobby g]

I can't comment on the explosion proof motor/fan, but I can tell you how I did my spray booth. I used a "positive pressure" approach rather than "negative pressure". It pushes air into the booth rather than pulling air out of the booth. That way I don't have to have explosion proof anything.


Bill

Maybe the lights and switch?

bobby g

 

[dave]

>>>> I want to build a small spray booth

What type of finishes do you want to spray?

At present (and for about the next year) I am only using aerosol spray paint and stains on smaller pieces - nothing larger than around 12"x6" and some as small as 2"x6". I do want to work on several parts at a time though. My main desire is to eleminate over spray. The top of my workbench is no longer it's natural color, which is not big deal, but I know the overspray is falling on some of my tools as well. :wsmile:

 

[junquecol]

ShopNotes, issue #111 has a "Roll Around Spray Booth. It is ducted for exhaust though. I know a couple of people who have used grain dryer fans (about $120) from Agri-Supply in Garner for their booths. Main thing to prevent explosions is not to have sparks inside spray booth. Turn on electrical devices before using booth, and turn off after allowing booth to clear it's self. For an explosion to occur, you need two things, air fuel ratio in danger zone, and a spark. Eliminate either, and you can't have an explosion. But if you aren't venting outside, then the combustables will be in the air in the shop. Filters will get the solids, but not organic vapors.

 

[Vetteman9956]

Here is a picture of a lab fume hood that I turned into a small booth. It has an explosion proof motor and light in it. Pulls 750 cfm. they sold for over 5 grand new but I only gave $80 for it off of craigslist,so you might search for one since there are so many labs in this area I would think that they should be around

View image in gallery​

 

[Bill Clemmons]

Maybe the lights and switch?

bobby g

Good question Bob. I addressed this issue by putting the switches for both the blower and lights on an outside wall, rather than in the finish room itself. As for the lights, I use four, 4' florescent fixtures w/ electronic ballast. That's the only area I have any concern about: a spark when I turn the lights on. But after six years of use, I haven't had a problem so far. I'll keep my fingers crossed. :eusa_thin

The blower is housed outside the finish room at floor level in a sealed compartment. It pulls air from the general shop area through two filters before pushing it into the finish room. There is an 8" duct in the ceiling of the finish room for air to escape through. It is vented through the roof. When I close the doors to the finish room, it is sealed off (probably 95%+ air tight). I open a door at the far end of the shop to allow "make-up" air to enter. The blower is 300 CFM and the finish room is 1,440 cubic feet, which means I'm completely exchanging the air every five minutes. If I had it to do over, I would go w/ a stronger fan to replace the air quicker: maybe 500 or 600 CFM.

Bill

 

[dave]

Thanks for all the input everyone! I appreciate it!!