Need spark resistant/ “explosion proof” fan for spray booth- don’t have $1000

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11-03-2019, 6:53 AM
Malcolm Schweizer

Need spark resistant/ “explosion proof” fan for spray booth- don’t have $1000

Wow, these “explosion proof” fans don’t come cheap! I have a belt driven fan but the motor is mounted in the fan cage and is not explosion resistant. I thought I might mount it outside the fan cage with a longer belt and have the motor outside the booth. I figure, however, that the fan provides cooling for the motor, so that may not be ideal.

Has anyone here made their own on the cheap? The booth will be 10’x20’ with ceiling around 9’.

Also feel free to share any ideas on spray/finish rooms, as I’m starting with a clean slate here. Linin Gcm the walls with either PVC or Melamine so I can wash it down periodically. Lots of LED lighting. Enclosed cabinets in back for storage as this is really more a finish room than just specifically a spray booth.
11-03-2019, 7:50 AM
Edward Dyas

Yea, the prices of spray booth fans has gotten crazy. I bought two of them more than 30 years ago and they were only about double what the cost of a comfort fan. Before that I tried using a belt driven furnace blower. I thought the fumes would be drawn to the fan instead of the motor but after about a months use I noticed paint dust accumulating in the motor so I quit. I thought about just creating a spray booth where with duct work I could attach the furnace blower. I think that would have kept the motor out of the paint.
11-03-2019, 11:25 AM
Malcolm Schweizer

Quote:

Originally Posted by Edward Dyas

Yea, the prices of spray booth fans has gotten crazy. I bought two of them more than 30 years ago and they were only about double what the cost of a comfort fan. Before that I tried using a belt driven furnace blower. I thought the fumes would be drawn to the fan instead of the motor but after about a months use I noticed paint dust accumulating in the motor so I quit. I thought about just creating a spray booth where with duct work I could attach the furnace blower. I think that would have kept the motor out of the paint.

I had a similar thought. Even “regular” fans are pricey these days. A belt-driven fan with NO MOTOR, or pulley- just a fan and a metal box- is nearly $300 new. I had tossed the old belt drive fan and actually went back to the dumpster and pulled it out!!! There was a larger spray booth before I took over the space. This fan has a motor mounted in the fan box, and it is COVERED with overspray, so I’m thinking this whole exploding spray booth thing is rather rare, or surely this thing would have gone up like Hiroshima after many years getting pelted with volatile cabinet paint. I am usually “Mr. Safety, but I am about to clean up that fan and put it back where it was. The issue is I will be using automotive two-part finishes, and that stuff is pretty volatile. I may kick out $800 for a proper fan. Hoping someone has made a do-it-yourself solution.
11-03-2019, 11:47 AM
Bruce Page

There's someone here in Albuquerque selling one on CL for $250.
I don't know anything about it except what's in the ad.
https://albuquerque.craigslist.org/t...998232731.html
11-03-2019, 1:37 PM
Malcolm Schweizer

Quote:

Originally Posted by Bruce Page

There's someone here in Albuquerque selling one on CL for $250.
I don't know anything about it except what's in the ad.
https://albuquerque.craigslist.org/t...998232731.html

That’s what I need.
11-04-2019, 3:37 AM
Wayne Cannon

I modified a 24" belt-drive fan to put the fan in a cylindrical duct with a slot in the suction side for the belt to the externally-mounted motor. I figure air is being sucked INTO the slot, so vapors should not come out of the slot to the motor.

My spray 4' x 8' booth is made of 1" foil-faced foam insulation panels (incl top) held together with velcro straps. It fits inside my garage with the fan duct (and motor) outdoors. I've never experienced any problem with traditional lacquer or shellac, though most of my spraying is water-borne.

Am I being foolish?
11-04-2019, 4:50 AM
Malcolm Schweizer

Quote:

Originally Posted by Wayne Cannon

I modified a 24" belt-drive fan to put the fan in a cylindrical duct with a slot in the suction side for the belt to the externally-mounted motor. I figure air is being sucked INTO the slot, so vapors should not come out of the slot to the motor.

My spray 4' x 8' booth is made of 1" foil-faced foam insulation panels (incl top) held together with velcro straps. It fits inside my garage with the fan duct (and motor) outdoors. I've never experienced any problem with traditional lacquer or shellac, though most of my spraying is water-borne.

Am I being foolish?

That’s exactly what I had in mind. My only concern is will the motor get hot if outside the fan box? I guess there is only one way to find out.
11-04-2019, 8:26 AM
Rob Luter

Talk to someone about the actual classification of your booth. "explosion proof" covers quite a bit of territory. Once you know class and division, you may find some lower cost options. Many times a TEFC motor and sealed conduit are sufficient. Another option is a Push Through booth, but you need a dedicated enclosed space
11-04-2019, 9:48 AM
Jim Becker

Malcolm, one thing that's in your favor here based on the photos you provided of the new shared shop space is that it's "open air" already. That may help with lower concentration levels of volatiles and give you a little wiggle room. That said, if for some reason it becomes a commercial operation, you may then have to face the music because of regulation.
11-04-2019, 2:04 PM
Edward Dyas

Quote:

Originally Posted by Malcolm Schweizer

I had a similar thought. Even “regular” fans are pricey these days. A belt-driven fan with NO MOTOR, or pulley- just a fan and a metal box- is nearly $300 new. I had tossed the old belt drive fan and actually went back to the dumpster and pulled it out!!! There was a larger spray booth before I took over the space. This fan has a motor mounted in the fan box, and it is COVERED with overspray, so I’m thinking this whole exploding spray booth thing is rather rare, or surely this thing would have gone up like Hiroshima after many years getting pelted with volatile cabinet paint. I am usually “Mr. Safety, but I am about to clean up that fan and put it back where it was. The issue is I will be using automotive two-part finishes, and that stuff is pretty volatile. I may kick out $800 for a proper fan. Hoping someone has made a do-it-yourself solution.

I used to go by a heating and air conditioning place and they would let me remove blowers from furnaces. They would otherwise just take the old furnaces they were removing from peoples houses to the scrap yard. In recent years though the furnace blowers tended to have self contained motors but I think some brands are still belt driven.

It does take a pretty good concentration of paint fumes to ignite but there isn't a way to measure it so it's risky to spray paint. I sometimes refinish a customers cabinets inside their house. I normally open the doors and windows near where I'm working and put one of my spray booth fans in the door blowing out. I then make sure there is no open flame in the house and in the room where I'm working turn on the lights and put tape over the switch to make sure they stay on. Even the action of turning a light on or off is enough to create a spark.
11-04-2019, 5:39 PM
Steve Fish

If you have some spare materials around you might try something similar to what’s in this link using your reclaimed fan.
https://extremediy.org/paint-booth-e...ation-venturi/ I have no idea how effective this approach would be but it keeps the fan in “clean” air
11-04-2019, 10:04 PM
Malcolm Schweizer

Quote:

Originally Posted by Rob Luter

Talk to someone about the actual classification of your booth. "explosion proof" covers quite a bit of territory. Once you know class and division, you may find some lower cost options. Many times a TEFC motor and sealed conduit are sufficient. Another option is a Push Through booth, but you need a dedicated enclosed space

This really helped, thank you. I found a TEFC motor on the cheap on eBay and did some reading up. Apparently it still needs to be mounted outside the fan box, so I may do this and just use a longer pulley and mount it outside the fan box. If not, I can always find use for another motor.

Quote:

Originally Posted by Jim Becker

Malcolm, one thing that's in your favor here based on the photos you provided of the new shared shop space is that it's "open air" already. That may help with lower concentration levels of volatiles and give you a little wiggle room. That said, if for some reason it becomes a commercial operation, you may then have to face the music because of regulation.

Yes, it is very open air. The windows don’t even have the glass in them. The problem is the new booth will be sealed air tight with only the exhaust fan for a vent, and filtered ports on the opposite wall for intake. The rest of the shop I’m not too worried about, but am concerned with the booth itself since I spray surfboards sometimes with automotive clear coat.

Regulation? We don’t really have that here. I mean... technically we do, but nothing is enforced. Oh the things I have seen.

Quote:

Originally Posted by Edward Dyas

I used to go by a heating and air conditioning place and they would let me remove blowers from furnaces. They would otherwise just take the old furnaces they were removing from peoples houses to the scrap yard. In recent years though the furnace blowers tended to have self contained motors but I think some brands are still belt driven.

It does take a pretty good concentration of paint fumes to ignite but there isn't a way to measure it so it's risky to spray paint. I sometimes refinish a customers cabinets inside their house. I normally open the doors and windows near where I'm working and put one of my spray booth fans in the door blowing out. I then make sure there is no open flame in the house and in the room where I'm working turn on the lights and put tape over the switch to make sure they stay on. Even the action of turning a light on or off is enough to create a spark.

I considered a squirrel cage fan, but we don’t have heaters here. I am sure I can find one in some discarded something somewhere. I also thought about using a dust collector somehow as a remote fan since the motor mounts on the outside.

Quote:

Originally Posted by Steve Fish

If you have some spare materials around you might try something similar to what’s in this link using your reclaimed fan.
https://extremediy.org/paint-booth-e...ation-venturi/ I have no idea how effective this approach would be but it keeps the fan in “clean” air

I have looked into a Venturi system. My main concern is efficiency. How much power would it take to generate the CFM’s I need versus a fan? We pay a lot for electricity here.
11-05-2019, 9:09 AM
Edward Dyas

I think the dust collector might work if you didn't have a huge amount of fumes and you ran duct work to the spray booth rather than having it close by. I've seen people use window fans and get away with it but I sure wouldn't recommend it. I saw a lacquer spray booth catch fire once and flames where coming out and going up to a 14' ceiling. About six of us put the fire out with fire extinguishers but was pretty scary. I think one person alone wouldn't have a chance.
11-09-2019, 4:30 PM
Malcolm Schweizer

1 Attachment(s)

Update: Found an explosion proof Baldor 1/2 hp 3500 rpm motor on feeBay for a decent price and will upgrade the old belt driven fan with it. Not sure if it is going to give me the 8,000 cfm that I’m looking for. I may go with a positive flow and have an equalizer fan blowing into the booth if this does not work. Pics of booth posted in the workshop page, but here is the progress so far. The window will be covered except the fan.

Attachment 419256