Paint booth duct

I'm installing a used paint booth in my hangar. It came with some ductwork that went straight up and out the side of the building. My hangar is leased so I can't cut an opening in the wall. I rearranged the duct to what you see here. Now I need to connect the upper duct to the window exit. I've thought about just duct taping some insulation board together with 1x2 supports but am concerned about the volume of air I'm moving. The 24" tubeaxial fan is supposed to push 7900 CFM. The sheet metal duct is 22x22". Anyone have experience with something similar or HVAC folks want to comment. I'm open to suggestions. Thanks.

Easy!

Unscrew the window and store it carefully. Make the duct as large as needed, and replace the window when you move out.


It is likely you will need to filter the outflow so things around the exit duct don't get multi-color/non-removeable dust on 'em...

I've already got a plywood insert in the window with the exit 45deg elbow mounted. Just need to connect the upper duct to the window.

Pink foam and Gorrilla tape

Ducktape ( acrylic adhesive ) can lose adhesion. Gorrilla tape will not. Pay attention to an extension out the window ( mentioned above ) or you WILL get paint on the hanger wall. Also. Throttle your blower intake to just clear the booth of mist. The more air you move the more dirt you will get in the paint !

7900CFM!!!! That should suck the chrome off the bumper of a 55 Belair. Will definitely make a nice paint booth.

From the pic, it looks like an open front style with a rear filter wall. No worries about overspray getting into the ducting and out the window.
I have one of these, a 6’ x 8’ that I bought used and never set up. It’s for sale for anyone that can come pick it up.

This style of booth is great if you can control the environment in the room it is in for temperature, humidity, dust, and bugs. They draw room air, low flow high volume. So, typically no worries about having too much air flow.

I like this style of booth for many reasons - easy in/out, less chance of build up of explosive by-products like an enclosed booth, easy to light, easy to maneuver hoses, uniform airflow across work, etc...
You can add tenting onto the front and extend its capacity. I have a neighbor who converted a one bay garage using this type of a system. My plane was painted there along with many others on the field.

As far as ducting, you might consider having a HVAC contractor give you an estimate. It might not be as costly as you think. The steel ducting seams are connected with what is called “S’s and Drives”, an “S” shaped tie with another piece folded over on the edges that gets driven over the assembly to physically tie it together. They are pretty much air right but often duct taped over to elliminate any blow-by. I would tape the seam. You can see this on the 90 at the connection to the straight piece.
By the way, my first real job at age 15 was cleaning up a Sheet Metal Shop after school and bending S and Drives, hundreds of them, for the various duct sizes for the crew to have on their trucks.

Larry DeCamp said:

Ducktape ( acrylic adhesive ) can lose adhesion. Gorrilla tape will not. Pay attention to an extension out the window ( mentioned above ) or you WILL get paint on the hanger wall. Also. Throttle your blower intake to just clear the booth of mist. The more air you move the more dirt you will get in the paint !

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I was actually thinking of the metallic duct tape but I appreciate the insight about Gorrilla tape. I didn't realize the difference vs fabric "Duck" tape.

I can't throttle the fan, at least not without $$$ for a VSD. In theory, that 7900 CFM through a 22x22 duct will move at 27 mph. I don't really have a sense of how much pressure will be in the duct and whether pink foam or other insulation board can handle it.

Remember to have plenty of open space that is filtered for the intake. If it is moving air at 27 mph, that is the same speed air will be coming into the booth.

Before you spend a lot of time and cost building the ducts, I would run the fan just venting out the top and see ho windy it is in the booth. I used 2 - 20" box fans in my booth and it worked pretty well. I had one whole wall of (6) cheap 22" filters along the bottom. The air flow was ok for me. I did use a Hobby Air system. It is a pain and uncomfortable but with 40 years of construction breathing bad crapola, I felt I needed it.

Good luck. I think you will be happy with your system. I believe the foam will work fine. Just make sure the tape goes all the way around the duct and not just the joints.

JonJay said:

From the pic, it looks like an open front style with a rear filter wall. No worries about overspray getting into the ducting and out the window.
I have one of these, a 6? x 8? that I bought used and never set up. It?s for sale for anyone that can come pick it up.

This style of booth is great if you can control the environment in the room it is in for temperature, humidity, dust, and bugs. They draw room air, low flow high volume. So, typically no worries about having too much air flow.

Click to expand...

Mine is a 9'x8' cross section and 5' deep. I bought it from a friend who had it for maybe 10 years and never set it up and I've had it for at least 5 yrs before setting it up. It's in a 70x90 hangar so I hope that will serve as a stilling plenum. Just can't do anything about the temp and humidity.

JonJay said:

I like this style of booth for many reasons - easy in/out, less chance of build up of explosive by-products like an enclosed booth, easy to light, easy to maneuver hoses, uniform airflow across work, etc...
You can add tenting onto the front and extend its capacity. I have a neighbor who converted a one bay garage using this type of a system. My plane was painted there along with many others on the field.

Click to expand...

I like that too. It should allow a lot of capability with minimal permanent footprint in the hangar. Like you say, I can extend it for a fuselage or wings. I can even close the end if needed.

JonJay said:

As far as ducting, you might consider having a HVAC contractor give you an estimate. It might not be as costly as you think. The steel ducting seams are connected with what is called ?S?s and Drives?, an ?S? shaped tie with another piece folded over on the edges that gets driven over the assembly to physically tie it together. They are pretty much air right but often duct taped over to elliminate any blow-by. I would tape the seam. You can see this on the 90 at the connection to the straight piece.

Click to expand...

I should probably get a quote. I tend to assume worst case when maybe I shouldn't. I did decode the S's and drives connections. I moved the 90 from the end to the transition. There's probably a special tool for it but a big screwdriver and BMFH got it done.

Thanks for the input.

Board and flow rate

Pinkboard will be fine. You are not making pressure, because, you will throttle the intake until it just cleats the mist consistently. No Variaible frequency drive , just tape pink foam over the fan intake and cut the hole bigger ubtil a spray can in the air wil go out the fan

rockwoodrv9 said:

Remember to have plenty of open space that is filtered for the intake. If it is moving air at 27 mph, that is the same speed air will be coming into the booth.

Before you spend a lot of time and cost building the ducts, I would run the fan just venting out the top and see ho windy it is in the booth. I used 2 - 20" box fans in my booth and it worked pretty well. I had one whole wall of (6) cheap 22" filters along the bottom. The air flow was ok for me. I did use a Hobby Air system. It is a pain and uncomfortable but with 40 years of construction breathing bad crapola, I felt I needed it.

Good luck. I think you will be happy with your system. I believe the foam will work fine. Just make sure the tape goes all the way around the duct and not just the joints.

Click to expand...

The booth has an exit plenum that the fan draws from that has a wall of filter elements. You can see some of the 20"x20" grid behind the ladders in the picture. It should have a flow of ~100 lineal FPM across the booth cross section. That fits with OSHA guidelines to which I assume it was engineered.

Larry DeCamp said:

Pinkboard will be fine. You are not making pressure, because, you will throttle the intake until it just cleats the mist consistently. No Variaible frequency drive , just tape pink foam over the fan intake and cut the hole bigger ubtil a spray can in the air wil go out the fan

Click to expand...

Not with this style of booth. The ?intake? is the entire front of the booth. The fan is sized appropriately to work with the intake area, or at least it is supposed to be.
The fan ?intake? is behind the filter wall, in a plenum. If you try taping off the actual fan intake, good luck, it is a big sucka, and you risk loading the motor past spec and burining it up. You don?t want to reduce the filter wall either.
If indeed this was a Home spun booth, some ?intake? adjustment may be necessary, but you would do it at the front of the booth by changing the shape or size of the intake area.
If it is designed properly to start with, no adjustment should be needed.

JonJay said:

Not with this style of booth. The ?intake? is the entire front of the booth. The fan is sized appropriately to work with the intake area, or at least it is supposed to be.
The fan ?intake? is behind the filter wall, in a plenum. If you try taping off the actual fan intake, good luck, it is a big sucka, and you risk loading the motor past spec and burining it up. You don?t want to reduce the filter wall either.
If indeed this was a Home spun booth, some ?intake? adjustment may be necessary, but you would do it at the front of the booth by changing the shape or size of the intake area.
If it is designed properly to start with, no adjustment should be needed.

Click to expand...

It's not home grown. This booth was from Grainger. I had to get a new motor and pulley and they dug out the specs and got me set up. For those not familiar, I got the booth in pieces and used this picture to help me put it back together.

Sorry, I misread. Yours looks like my Global Refinishing Systems booth and may be what Grainger supplied(s). They still make the same one today, and you can order filter media from them too, although I haven’t compared prices.
They also have assembly manuals, etc... although you already figured it out from the picture, even though I don’t think the pic is a Global booth. Doesn’t matter.

You might consider adding a manometer. You can get them for under $50. Very handy instrument to let you know when your filter media is getting loaded and needs changing. It’s a lot of media material so good to use it as long as you can and a manometer takes the guess work out.

Good luck and let us know how it works for you.

Mine came with a manometer too. The hoses are dry rotted so I've got to get new ones to hook it up. Also bought the filter elements from Grainger. They are different from the pic and are standard 20x20.

gyoung said:

Mine came with a manometer too. The hoses are dry rotted so I've got to get new ones to hook it up. Also bought the filter elements from Grainger. They are different from the pic and are standard 20x20.

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You are dialed in!
Show us your in operation pics when you get going with it. It will work great.

JonJay said:

...I have one of these, a 6? x 8? that I bought used and never set up. It?s for sale for anyone that can come pick it up....

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I have property in Camas. Next time I'm going to be there with my pick-up, I may come get it if it is still available.

Dantilla said:

I have property in Camas. Next time I'm going to be there with my pick-up, I may come get it if it is still available.

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PM me if interested. I?ll make a smokin good deal for any RV enthusiast. It?s going back on CL soon.

JonJay said:

PM me if interested.

Click to expand...

PM sent...