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Dust collector as spray booth?

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Forum topic by Gary Fixler posted 02-26-2009 12:38 PM 8935 views 0 times favorited 10 replies Add to Favorites Watch
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Gary Fixler

1000 posts in 2843 days


02-26-2009 12:38 PM

Topic tags/keywords: dust collector spray booth fumes spraying aerosol air control air cleaning filter filtering filtration health

This is something that’s popped in and out of mind over the last couple of years. Has anyone heard of, or had an experience with building a little spray booth/box hooked to a dust collector to draw in the fumes? Of course, I don’t want all of that going into my pipes and hoses, and don’t want flammables flying past the motor, or gumming up the impeller, but with the right filter, or filter combo, perhaps there’s a way to entirely cleanse the air of things like aerosol spar urethanes, or HVLP varnish coats.

I have a woefully small shop. I’ll post about it here someday with pictures, and it’s smallness will fill you with woe. I have to double-up on things, and one problem I have, encountered again just this afternoon on my lunch break while coating a lazy susan with spray-on spar urethane outside, is wind. It is always windy midday here. It quite literally never hasn’t been. It’s something about neighborhood life in west LA. There are just always whirling breezes making good spray coats in my back yard mostly impossible. I can’t spray in the garage, because it’s so tiny. I tried it once, and the fume-fogged garage was too noxious to enter for a whole day, and the film of the spray settled on everything. I had to do a lot of wiping down of things.

My DC pulls in a good amount of air, though, and spraying smaller things up on a workbench with something like 2’x2’ hood leaned over the area, with some side walls to channel the airflow over the piece would catch everything. I’ve taken to setting up a hood in this fashion when random-orbital sanding a piece, taking off the collection bag and just keeping the vent pointed toward the hood. The shop air stays quite clear.

I’m curious to know if something like this has been done to create spray booths, if there are standard drawbacks to be aware of, and if any standard [Home Depot?] filter or combos thereof can really catch it all without killing the airflow too much. Thanks!

Edit: I just did some deeper digging after posting this, and stumbled onto airbrush spray booths for hobbyists, and at the bottom of e.g. this model's page are replaceable filters in the $30-$60USD range. Seems a good place to start, though the booths are a bit pricey. I feel I could rig something myself that’s more suited to my space, and probably even collapsible/winchable into the rafters. The models seem designed to blow the air right back into the room with you, so perhaps the filters do completely clean the air.

-- Gary, Los Angeles, video game animator


10 replies so far

View Tim Pursell's profile

Tim Pursell

499 posts in 3244 days


#1 posted 02-26-2009 02:11 PM

No reasonably priced filter I know of will stop the solvent content of the finish and alow enough air flow to be an efective spray booth. I do have a type of “spray booth” set up in my shop. I already had a cage blower from an old furnace. It has a belt drive, external motor, so while not trully explosion proof, it’s pretty darn close. I built two cabinets that are mounted in a corner of the shop, hung the doors so that they are hinged away of each other, so when the doors are open they form “wings” that help control the air flow. Inside of the 2 cabinets have no bottom & a regular (read cheap) furnace filters mounted in channels on an angle so the bottom is up against the back of the cabinet & the top is out near front edge. I cut a 12” round hole in the top of each cabinet & ran flex duct up thur the ceiling into a homemade manifold that connects to the blower. from there I ran more duct work out thru a louvered vent in the side wall of the second floor of my shop. The system sucks so much air out of the shop you HAVE to open a door or window or you can feel you ears pop! LOL
It’s worked quite well for a number of years. I have even sprayed for several hours in below freezing temps due to the radiant heated floor in my shop. I just prop a scrap of 2×4 under the overhead door and the cold incoming air warms up quickly while flowing in over the warm floor. I can hold the temps near 70.

-- http://www.etsy.com/shop/tpursell?ref=si_shop

View Moron's profile

Moron

5032 posts in 3355 days


#2 posted 02-26-2009 02:48 PM

I use my spray booth on occasion to act as a dust collecter but have yet to use my dust collector as a spray booth

-- "Good artists borrow, great artists steal”…..Picasso

View Douglas Bordner's profile

Douglas Bordner

4012 posts in 3526 days


#3 posted 02-26-2009 04:16 PM

Sounds like a fuel-air bomb ready to happen. I am a great proponent of water-borne finishes, which have come a long, long way in the last few years. Check out Target Coatings or Jeff Jewitt’s http://www.homesteadfinishing.com/.

-- "Bordnerizing" perfectly good lumber for over a decade.

View Hacksaw's profile

Hacksaw

185 posts in 2838 days


#4 posted 02-26-2009 06:27 PM

Just an Idea (based on a commercial spray booth) if you were to build a small frame(box) to hold furnace filters and then cover said filters with tyvek installed backwards (printing on the inside) and hook that up to your dust collector that may work.Keep in mind you would need to replace the tyvek fairly often as it will plug with the material.I also like the solution offered using a furnace blower motor.Add the tyvek and I think it would work quite well.I may have to give it a go myself..

-- Nothing's impossible...it just gets expensive

View Bob #2's profile

Bob #2

3809 posts in 3483 days


#5 posted 02-26-2009 07:31 PM

There is ystem that circulates water down a glass plane to trap the VOC’s as they head to a filtering system.
Don’t know how well it works but it might be something to google.

Bob

-- A mind, like a home, is furnished by its owner

View Chris Wright's profile

Chris Wright

540 posts in 2943 days


#6 posted 02-26-2009 08:18 PM

It’s my understanding that most dust collectors house the motor outside of the impellor chamber so as not to seize up from dust getting inside, that on top of the simple fact that light dust and lots of sparks equal a fireball. If the motor doesn’t happen to be housed outside the impellor chamber then I’d hope that it would be sealed for that very reason. Either way I’d think there would be little more risk of any fumes reaching a spark in the DC then from any other spark source in your shop. Now I understand that if you do this there will be a higher concentration of fumes getting near your motor then if you didn’t. But from all the spray booths I’ve used and worked with, they’ve all had what looks to be a simple filter to trap the solids and a fan behind it. You’ll never be able to trap the VOCs, they should be vented outside, but what you can trap is the solids in the overspray. You could also look into getting a simple squirrel cage blower and use that as your extractor fan, it would take some rigging to get it to hook up, but I think it might be better, then you’re not blowing fumes into your dust bag. Just a thought.

-- "At its best, life is completely unpredictable." - Christopher Walken

View dennis mitchell's profile

dennis mitchell

3994 posts in 3776 days


#7 posted 02-26-2009 10:00 PM

A $19.95 box fan in not an approved method…

View pickles's profile

pickles

68 posts in 2875 days


#8 posted 02-27-2009 05:17 AM

This is a very dangerous proposition. For starters, dust collector motors are not explosion proof (with a few industrial exceptions).

The following is from Leeson:
Totally enclosed machines — Most totally enclosed machines are fan-cooled, Figure 16. However, some models in fhp ratings are totally enclosed and nonventilated. Totally enclosed motors are more expensive, but offer better protection. Outside ventilating air and contaminants are excluded from interior parts of a totally enclosed motor. The motor is not airtight, but usual entrances to the interior, such as the conduit box, are gasketed. Clearances like those around shafts are kept as small as possible.

Explosion-proof machines — Hazardous atmospheres require special totally enclosed motors. Motors for these atmospheres are designed to standards established by Underwriters Laboratories (UL). Only after a motor has been examined and approved by UL can it be sold as an explosion- proof motor.

If they are not are tight, and you are not removing 100% of the solvent (VOC) you stand a chance of making a nice bomb that has a 14” propeller as shrapnel.

Remember safety shouldn’t stop at the tablesaw.

View Gary Fixler's profile

Gary Fixler

1000 posts in 2843 days


#9 posted 02-27-2009 05:56 AM

Thanks for all the great responses, folks. I’m going to go with the wisdom of the group and say “Okay, bad idea.” I’ve thought about it a bit more, and realized I have a 2’x2’ square window I’m not using (even papered over it for privacy from a neighbor who has about 5 windows that look down into it.

It got me thinking about putting a fan in it, but with the motor well off to the side, belted to the fan from 3 or 4 feet away. Still explosive? I’d have some kind of 3-sided box in the room I could spray into with a hose running from there to a shroud around the window fan. This way the motor is in a separate space. I’d be say, 6’ away from the motor with the spray being ducted up the hose and out the window.

-- Gary, Los Angeles, video game animator

View Toddler's profile

Toddler

2 posts in 2820 days


#10 posted 03-16-2009 07:23 PM

This is an interesting thread. I’ve browsed here before, but never signed in to comment. I’m actually planning to build a dust collector vented spray booth. I’ve drawn up plans for a small 6’x6’x7’ tall modular booth to spray project in my garage, and a dust collector seems like an ideal venting fan. So I am curious why you guys think it wouldn’t be safe.

For me, the booth is both to vent the fumes and to provide a dust free place to finish projects. My dust collector is just a small 1.5HP job. It’s so small that I simply vent it into the bushes outside my garage to maximize airflow. No filters or bag to limit airflow, just a 30gallon pail with a Thein baffle in it to catch most of the larger chips.

Delta would say the DC pulls over 500 CFM, but I assume that’s with no lines or filters. I figure I get more like 250-300cfm since there’s usually 15-20’ of 4” piping, and consider it barely adequate for what I am doing.

My booth plans have 3 24” square ac filters in the back to let air in, and 2 24” filters for the exhaust. Plain old MERV 6 or 7 filters will catch more than 30% of 3-10 micron particles at around 400 CFM, and I suspect with all these filters I’ll have less than that. I think 200 CFM is a fair guess, no?

There will be a total of 6’ of 4” PVC pipe. My gun is a mini HVLP that’ll use 4-5CFM. That’s if I run it full time. I won’t, so guess 3.5CFM spray per minute.

If 1/3 or more of the spray stays on the object, there’s a max 2.5cfm of spray going into the air and in theory, exiting the booth. Lets say all of that gets past my filters, so 2.5 CFM of spray MAX in 200CFM of air going past the impellor and out the window. The motor is to the side, so any fumes that get to the motor would have even less than that 2.5cf of spray in 200cf of air.

Since the spray has to go a foot past the object I’m spraying even before it hits the filter, it seems like most of what will hit the impellor will be dry spray. I simply can’t see any ignition risk. The booth’s air will get cycled about 1x per minute, which isn’t great, but it’s not bad even with my cheap DC. If someone were to do this with a real DC, and move 600 or more CFM, the ignition risk just doesn’t seem like a real issue even with a big gun.

So what am I missing?

Thanks,
Todd

PS) http://www.kushaludhyog.com/spray-booths.htm

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