Brett Nelson
02-12-2010, 3:01 PM
There were many considerations, and I think it is going to end up costing me about $750.
I'll be using it mainly for finish carpentry, cabinets, and furniture. The products that I've used most are SW vinyl sealers, lacquers, and conversion varnishes. I prefer spraying dye stains instead of wiping pigment stains. I've heard a lot of you talk about switching over to targets WB finishes, but I just can't get myself to use them on anything that might be subject to more abuse, like cabinets and stairs.
It seems that most here have opted for a positive pressure booth under this circumstance, to avoid explosion proof equipment. In studying professional paint booth designs, modern technology indicates that a negative pressure is actually preferred. So here is what I ended up with, and the compromises made.
Negative pressure booth; 8'Wx8'Hx12'D...
Construction
Built in 4'x8' sections. Design allows for additional center sections to increase booth depth 4' at a time. Each section consists of two 4'x8' wall panels and one 4'x8' ceiling panel.
Frame
Was going to build the frame from T-slots aluminum, but that would've added another $300 to the project. I've built something like this from PVC before, but it was just too flimsy and I want something that will be easier to assemble and store in sections. So I settled on angle aluminum. Panel frames will be riveted, and quick release fasteners used to interconnect panels. Seal tape used between panels to ensure air-tightness.
Wall Material
6mil clear polyethylene. Wanted to use 1/8" polycarbonate, but gotta keep weight and cost down. Plastic cut to fit each panel and duct taped.
Ceiling Material
Also plastic sheeting with the exception of two additional aluminum cross members creating framed support for a 12"x48" strip of polycarbonate for a light window centered on the panel.
Intake
Intake will be passive and will happen at the front doors. Two 4'x8' panels will serve as doors and instead of plastic sheeting will be filled with tacky filter media. Filter surface area will be about 60sqft. Doors will be hinged at outer edges and will use seal strip and spring bolt latches to latch from the inside. I don't want someone walking in while I'm spraying.
Exhaust
Will happen at back wall. Unlike the intake where I'm trying for as much area as possible, the exhaust is designed to be approximately 40% of the intake area. This results in a 4'x6' vertical panel of paint filter centered at the base of the back wall. The rest will be plastic sheeting. The filter area will be framed in aluminum so that I can attach an exhaust box to the outside of the booth. This box will match the 4'x6' filter area and will be about 3' deep with a 16" hole out the back for exhaust fan attachment. The 3' depth will encourage a more even draw across the filter area. I found an explosion proof fan that had been used for a single auto restore for a couple hundred bucks. It is only 3200CFM, so it would not meet OSHA regs. Good thing I'm not a professional. I figure the cross sectional area of the booth when I am in it with my table is about 4500sqft. So working optimally, that fan only gives me about 71fpm of cross flow. Not up to the 100fpm OSHA standards, but should be fine for what I do.
Lights
Each 4' section will have one two-bulb 48" fluorescent light mounted outside the booth above the polycarbonate strip on the ceiling. Ambient lighting will also come through the walls from the shop.
Once built, I expect that assembly will take less than 20min each time I have a project. The negative pressure, cross-flow, modular setup has big advantages. The large intake surface and smaller exhaust surface provide for zero pressure at the intake and increasingly negative pressure as I move toward the back wall. This is close to ideal for spraying. There are no dead spots or vortexes as the air enters the booth very slowly and then speeds up as it passes the project to the exhaust. I can increase the length of the booth to provide room for drying racks without necessitating a larger fan or additional lighting. For small, less important projects, I'll be able to setup just the back section to use as an open face booth.
Any input is welcome from the more experienced members here. Questions are always a good thing too. Cheers. :)
I'll be using it mainly for finish carpentry, cabinets, and furniture. The products that I've used most are SW vinyl sealers, lacquers, and conversion varnishes. I prefer spraying dye stains instead of wiping pigment stains. I've heard a lot of you talk about switching over to targets WB finishes, but I just can't get myself to use them on anything that might be subject to more abuse, like cabinets and stairs.
It seems that most here have opted for a positive pressure booth under this circumstance, to avoid explosion proof equipment. In studying professional paint booth designs, modern technology indicates that a negative pressure is actually preferred. So here is what I ended up with, and the compromises made.
Negative pressure booth; 8'Wx8'Hx12'D...
Construction
Built in 4'x8' sections. Design allows for additional center sections to increase booth depth 4' at a time. Each section consists of two 4'x8' wall panels and one 4'x8' ceiling panel.
Frame
Was going to build the frame from T-slots aluminum, but that would've added another $300 to the project. I've built something like this from PVC before, but it was just too flimsy and I want something that will be easier to assemble and store in sections. So I settled on angle aluminum. Panel frames will be riveted, and quick release fasteners used to interconnect panels. Seal tape used between panels to ensure air-tightness.
Wall Material
6mil clear polyethylene. Wanted to use 1/8" polycarbonate, but gotta keep weight and cost down. Plastic cut to fit each panel and duct taped.
Ceiling Material
Also plastic sheeting with the exception of two additional aluminum cross members creating framed support for a 12"x48" strip of polycarbonate for a light window centered on the panel.
Intake
Intake will be passive and will happen at the front doors. Two 4'x8' panels will serve as doors and instead of plastic sheeting will be filled with tacky filter media. Filter surface area will be about 60sqft. Doors will be hinged at outer edges and will use seal strip and spring bolt latches to latch from the inside. I don't want someone walking in while I'm spraying.
Exhaust
Will happen at back wall. Unlike the intake where I'm trying for as much area as possible, the exhaust is designed to be approximately 40% of the intake area. This results in a 4'x6' vertical panel of paint filter centered at the base of the back wall. The rest will be plastic sheeting. The filter area will be framed in aluminum so that I can attach an exhaust box to the outside of the booth. This box will match the 4'x6' filter area and will be about 3' deep with a 16" hole out the back for exhaust fan attachment. The 3' depth will encourage a more even draw across the filter area. I found an explosion proof fan that had been used for a single auto restore for a couple hundred bucks. It is only 3200CFM, so it would not meet OSHA regs. Good thing I'm not a professional. I figure the cross sectional area of the booth when I am in it with my table is about 4500sqft. So working optimally, that fan only gives me about 71fpm of cross flow. Not up to the 100fpm OSHA standards, but should be fine for what I do.
Lights
Each 4' section will have one two-bulb 48" fluorescent light mounted outside the booth above the polycarbonate strip on the ceiling. Ambient lighting will also come through the walls from the shop.
Once built, I expect that assembly will take less than 20min each time I have a project. The negative pressure, cross-flow, modular setup has big advantages. The large intake surface and smaller exhaust surface provide for zero pressure at the intake and increasingly negative pressure as I move toward the back wall. This is close to ideal for spraying. There are no dead spots or vortexes as the air enters the booth very slowly and then speeds up as it passes the project to the exhaust. I can increase the length of the booth to provide room for drying racks without necessitating a larger fan or additional lighting. For small, less important projects, I'll be able to setup just the back section to use as an open face booth.
Any input is welcome from the more experienced members here. Questions are always a good thing too. Cheers. :)