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within the spray booth and separation of this particulate from the airstream by using filters for reuse or disposal. Some spray booth designs, which use contained and separate collection sys- tems, require that enough air be intro- duced into the spray area to ensure a safe condition. Furthermore, all pow- der booths that return the booth air back to the plant airspace must use final filters capable of removing par- ticulate down to 0.3 micron. This fine filtration will ensure that all safety codes for personnel areas are enforced, while the returned air will eliminate any air make-up requirements. Powder booths come in three configu- rations: cartridge (Figure 7), cyclone (Figure 8), and filter belt. Cartridge booths use paper or fabric cartridges in a collection system to separate the powder particles from the contain- ment airstream. Cyclone booths use cyclone(s) to remove most of the pow- der particulate before it's further cleaned by a cartridge collector. Filter- belt booths use a rotating internal fab- ric belt to separate the particulate from the airstream while a separate collection device vacuums the belt clean. Selecting which booth is best- suited to your particular application is accomplished after careful considera- tion of many factors: • Colors to be sprayed or collected • Color change time requirements • Floor space available • Additional safety devices needed (segregation dampers, explosion vents, and explosion ductwork) Because the filtration techniques used in powder coating are so efficient, col- lection of the overspray powder mate- rial for reuse is a definite advantage to this process. Sometimes the amount, and subsequent value, of the over- spray powder material is so small that collection for reuse isn't prudent. In these cases, powder coatings can be disposed of, in most cases, as non-haz- ardous materials. Systems that reuse overspray powder material incorpo- rate sieves and fresh powder replen- ishment devices to ensure properly conditioned powder material neces- sary for consistent product quality. (See Figure 9.) Powder booths come in all shapes and sizes. Batch-type booths, in which products are manually transported into and out of the booth, can be small bench-top designs or large walk-in booths capable of containing 20-foot, or larger, parts. Conveyorized booths, in which products are automatically transported through the booth, are available in standard sizes or custom designs. These booths can be designed to be compatible with chain-on-edge (Figure 10), powered-overhead (Figure 11), or power-and-free-overhead con- veyor systems. Equipment suppliers offer limitless booth designs that can accommodate high- or low-volume pro- duction requirements for just about any size product. Lean manufacturing systems have gained great popularity in re cent years with powder coating systems that use spray-to-waste booths in con- junction with quick color change appli- cation equipment. These systems (Fig- ure 12) depend upon the high transfer efficiency of the application gun to apply most of the powder onto the part, reducing the amount (and value) of the overspray powder coating. Color Figure 9 A powder coating spray booth sieve and hopper system Photo courtesy Deimco Finishing Equipment. Figure 8 Cyclone spray booth system Photo courtesy Gema USA. Figure 10 A chain-on-edge conveyorized powder coating system Photo courtesy Deimco Finishing Equipment. Figure 7 Cartridge spray booth system Photo courtesy Gema USA. 28 POWDER COATING, December 2018