Case History

Paint de-tack program using centrifuge as the solids control and removal system.

Account:
Manufacture of metal roasting pans.

Paint Type:
High solids baking enamel mostly black with white and other colors. Black is an acrylic/melamine resin and all others are polyester/melamine resins.

Paint Load:
Spraying 20-gallons of paint per day

Transfer Efficiency:
40%

Design

Initial operation was a standard “E” Style water wash spray booth with a manual centrifuge. A Company in Milwaukee, Wisconsin did original modifications to the spray booth. These modifications involved trying to efficiently remove the paint particles. However, they fell short of properly retrofitting the sump pan and directing the water flow for optimum paint particle suspension and centrifuge removal. Basically they placed a pump at the backside of the booth with a bottom center paint booth pick-up point, which fed the manually cleaned centrifuge located in a remote location approximately 15 feet from the booth. Three automatic paint spray guns are operating in a fixed position spraying the product (pans). These guns are scheduled to "fire" well in front of the pan and continue spraying paint until the pan clearly passes through the spray pattern. The pans are mounted on a pedestal on top of a conveyor chain. As the pans entered the spray booth the pedestal's rotated for total paint coverage of each pan and accompanying lid.

Problems

Half of the paint over-spray was building up well short of the water on an extended pan located directly in front and below the chain conveyor line. The operator was flushing off this mass of “live” paint with a hose directly into the booth sump at the end of his shift. Plugging of the upper water spray manifold occurred since it was impossible for the polymer to de-tackify these "globs" of paint, thereby releasing live paint solids up the stack and onto the roof and surrounding neighborhood. Partially dead paint made the manual centrifuge hard to clean resulting in operators letting the unit fill-up and not cleaning it until end of day. Excess paint solids accumulated in paint booth falling into bottom areas of the pan, eventually filling booth up with “sticky” paint sludge. The centrifuge was drastically under-sized for this operation and filled up within two hours, making proper clean-outs impossible. Large amounts of foam being generated from the high paint solids content in the booth water required large amounts of de-foamer to control this situation. The booth had to be entirely cleaned-out every four weeks resulting in 4 operators working costly non-production 10-hour days consuming 40-man hours. 18 drums of "live" paint sludge were generated at a sludge disposal cost of $400.00 per drum.

Solutions

• Added a short water flood sheet to the front of the booth directly below the conveyor chain in order to catch all of the over-spray as an atomized paint particle.
• Replaced the upper standard metal pipe manifold with a new high efficiency PVC unit.
• Replaced the manual centrifuge with an automatic centrifuge.
• Set-up automated chemical feed with in-line draw down tube installed.

• All paint over spray entering booth water as an atomized spray paint particle.
• No more "live" clumps of paint solids.
• No "live" paint particles up the stack.
• Quick and thorough de-tackification of all paint solids from improved manifold.
• Quick efficient removal of paint solids handled by automatic centrifuge.
• The only manual labor requirement is changing the sludge drum when filled.
• Sludge is relatively dry, compact and with no solvent content.
• The sludge is now landfill disposable at a much lower cost.
• Booth is now cleaned-out once per year, yielding no drums of "live" paint sludge.

Benefits

• Less Booth Maintenance
• Dryer Sludge Cake
• Reduced Sludge Volume
• More Production
• Cleaner Emissions
• Reduced Operating Costs

Paint De-Tack Program Case Study (PDF - 425K)

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