Case History

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

Account:
Manufacture of diesel engines

Paint Type:
Water base paint using water miscible solvents

Paint Load:
Spraying 100-gallons of paint per day

Transfer Efficiency:
50%

Design

Very old recovered downdraft paint booth built by George Koch & Sons. Manifold pipes delivered water spray to the eliminators using fan spray jet style nozzles. The sump is located directly below the floor grates and has a rectangular shape with side extensions and a flat bottom. A vertical re-circulating pump is installed in a pump well box attached to the side corner of the sump tank. The water draw to this pump came from the area near this corner. No other sump agitation was present and most of the water in this sump was “quiet.”l The system lacked any paint recovery system. They started with a manual spray operation painting 230 engines per day and later invested in robots that helped increase production to 300 engines per day.

Problems

• Water-based paint saturating the booth water.
• Manifolds constantly plugging up with paint solids.
• Heavy paint sludge build-up in the booth sump pan.
• Exhaust stacks and fans blocked up with paint solids. It was so severe that they had to cut bypasses in the roof exhaust stack before the fans to relieve the overload.
• High production levels limited the maintenance time on the booth, however the stacks and fans were being cleaned once per week, and the sump was being manually shoveled out every three to four weeks.

Once the original retrofit designs were in-place an automatic centrifuge system was installed, but a competitor implemented the wrong paint kill program and no paint solids were being removed.

Solutions

• Modified the booth pans to eliminate "dead areas" of booth water agitation.
• Mass water flow system was designed below water surface in sump pan to "drive" the suspended paint particles to the centrifuge pick-up point.
• High efficiency manifolds with less clogging spray nozzles installed.
• Main booth exhaust fans were upgraded.
• A larger more efficient automatic centrifuge was installed when increased engine production added excess solids to the system.
• Replaced our competitor's polymers with our paint kill polymer program and immediately started to remove paint solids from the booth water. Utilized the proper polymer for charge neutralization, which broke the paint molecule from the water and coagulated it into the proper micron size for improved centrifugal separation.

Results

Sump clean outs scheduled only once per year now. Exhaust fans, stacks, and booth manifolds are remaining sludge free. Successfully removing paint solids, generating one drum of dry land fill able solid waste every day and a half. Very little maintenance time (clean-ups) devoted to downdraft paint booth. Only maintenance is floor grate, robot and good quality preventative maintenance.

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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