Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Cyclone Booth System A cyclone powder booth system, as pictured in Fig. 8, is made up of a spray booth, cyclone(s), a cartridge collector, and possibly ductwork. The spray booth can be made of metal, plastic, or composite sandwich de- signs. Metal booths provides strength and durability but attract more powder that will prolong color change time. Plastic will allow more light into the booth and will attract less powder, reducing color change time. Composite sandwich designs offer strength and attract the least power, significantly improving color change time. All powder booths should provide a smooth interior to facilitate easy and thorough cleaning. Ductwork connection(s) can be at one of several locations. The preferred method is to locate the ductwork connection in the base of the booth as this pro- vides a down-draft air flow inside the booth helping to keep it clean. The booth may have devices, such as baffles, to help control air flow within the booth, touch-up openings to provide access for manual spraying, and gun slots to provide access for automatic equipment. The cyclone is designed to separate most of the powder from the airflow be- fore entering the filtration section. This has several benefits. First, air entering the filter is "precleaned," which will lower the loading on the filter media. This translates to longer filter life. Second, the powder collected in the cyclone can be easily recycled. Since the cyclone is a cleanable device, color change is attainable without additional equipment. Multiple cyclones are used when air flow is so high that one cyclone isn't practical for a given plant ceiling height. Twin cyclones are used in parallel before the filtration section. Cyclone efficiency can vary by man- ufacturer and design with some systems delivering in excess of 90% of the pow- der into the reclaim device. The filtration section used with a cyclone booth is a cartridge collector, giv- en its name for the cartridges used to separate powder from the air flow. These paper cartridges are cleaned with a "back pulse" of compressed air to shock the powder from the cartridge surface. The cartridges will separate most of the pow- der out of the air flow from the booth (up to 99% efficiency). These are not cleanable devices for color change. The blower fan that produces the air flow in the booth typically is located on the clean air side of the filtration device. Final filters are used after the fan to remove powder particles, down to 0.3 micron in size, before the air is returned to the work environment. All of these devices—booth, cyclone, collector, fans, and absolute filters—can be connected by ductwork. The velocity of air within this ductwork usually is above 4,000 fpm and the ductwork is designed to promote laminar flow to assure "self- cleaning" during operation. Some powder booth manufacturers have taken the approach of reducing the ductwork in this type of booth. This design has numerous smaller cyclones at- tached directly to the powder booth wall. The booth airflow enters the cyclones directly and without ductwork. These cyclones are much smaller than those used in standard cyclone booths, allowing for simpler cleanup. The blower, fil- ter pack, and final filters are downstream from, and attached to, the cyclones, al- lowing the air to be returned directly to the plant. Cartridge Booth System The cartridge booth system (see Fig. 9) answers the same technical needs that all 166

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