spray booth:what cfm ventilation?

[daveg]

To those of you who have built your own spray booth, what cfm ventilation fan would you suggest, let's say for 3'x3'x4' ?

[Fireblade]

I believe the OSHA requirements are 100fpm (feet per minute) of airflow. You can actually buy a meter to meaasure airflow, for under $30, but it is not needed. I would say for the size booth you plan on building I would get a fan capable of pulling 1000cfm, it should be enough to take care of your needs.

[Hemi-T]

Wouldn't 1000 cubic feet of air flow per minute in a 3 foot square booth suck the powder right off the parts?

Hemi-T

[DALE]

I think 1000 cfm is way too much for that size booth.What type of fan mounting are you looking for? Box fan, squirel cage blower, wall mount? Also you can use a multispeed fan and then dial in the air flow to what you want.

[Fireblade]

Actually.......no. If you built a back wall with say 4 filters in the back panel then it would have a rather large surface area. The 1000cfm fan measures maybe 12" diameter, so the pull it would have would be great enough to pull the powder in towards the filters, but not great enough to have suck it completely by the part. You can use a dimmer switch to control the fan speed if need be, but it would be better to buy the larger fan and slow it down. You can't speed up a smaller fan.

[daveg]

I was thinking I could get by with something in the 100 to 200 cfm range using a squirrel cage setup and filtering it before the blower. Thanks for the replies on this guys, any more ideas are much appreciated.

[mildman61755]

how's about venting off each side thru filters & using in line duct blower assy.?

[Fireblade]

In my spray booth, mine is larger than the one we are talking about here, I originally had the filter and fan assembly on the side, but it caused problems. I had the filter and fan assembly on the right side of the booth, when I sprayed on the left side powder would escape out. I think the fan, or at least, the filter area should be at the back of the booth, so all the extra powder would be pulled into the booth, not across it. Maybe I am wrong on this kinda thing, but check this out first. Go to a Lowes or Home depot and check out and attic exhaust fan, they are cheap and I know they are not intrisically safe, but they will work for what you need. I now run a 14" squirrel cage with a 3/4hp motor, pulling it through 8 20"x25" filters, no powder comes out and it does not affect the powder adhering to the part. Like I said before, buy a fan larger than what you think and just slow it down with a dimmer switch. Don't go so large that the fan will have to turn REAL slow, fan blades are designed to operate at a certain speed.

[bzer1]

We built a 36"X36"X24" booth. Made the frame from 1/8" angle, and thin sheet walls. We picked up a duct box an cut a hole in it and mounted it to the bottom of the booth where we cut a matching hole and used a 14X20 duct filter. Out the side of the box an upspout to an 8" fan to the outside. We suspend the parts from the top and are able to spin them using a swivel. In the center of the filter sits a plastic tray with a piece of angle iron with a bolt welded to it. we attach a second ground strap to it so the excess powder is attracted to it and we can reclaim it or get rid of it and will have less filter clogging. Simple design...Less power needed in the motor, and you now have the ability reclaim powder. One thing I've learned in my years working in shops is to let your tools do the work. In this case we're letting the coating method do most of the work...The rest of the work was done by thinking it all out before building. You use grounding to make the powder stick to the parts...Why not use it to keep the booth clean too. We're currently using an 80cfm fan, which is not qiute enough. We'll be going to a 200cfm fan. Weather you're doing this as a hobby or as a business, you should always try to design your tools and workspace to allow you to work easier, and more efficiently.

[skiddz]

bzer1, can you post a picture of that setup? I'm about to embark on my next great finishing adventure and need to build a small booth and your ventilation setup sounds simple and effective.