Metal Finishing Guide Book


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The filtration section used with a cyclone booth is a cartridge collector, given 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 powder 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 ���selfcleaning��� 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 attached 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, filter pack, and final filters are downstream from, and attached to, the cyclones, allowing 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 powder recovery systems must address: safe containment and separation of powder coating overspray. In a cartridge booth system, this is accomplished by filtration of powder from the containment air using a cartridge collector attached to the booth. There are no external filtration devices (or ductwork to connect them) with this system. The cartridge collector is usually located in the wall of the booth (side draft) or in the base of the booth (down draft). The powder-laden air flow enters the collector. The air passes through the cartridge filter and the powder is deposited on the filter surface. Periodically, cartridges are back-pulsed with compressed air to shock the powder from their surface and deposit it in the collector base. Powder in the base is pumped to a reclaim stand for reuse or to a container for disposal. The cartridge filter pack can be removed from the blower pack for color change. A separate cartridge pack is required for each recoverable color. Cartridges are made of a paper filter media. The blower pack houses the blower fan and filter assembly. The blower is on the clean-air side of the cartridges. Air from this powder booth system is returned to the plant. The booth may have touch-up openings and/or gun slots depending upon the application for which it is used. The booth is typically of metal construction, though some manufacturers prefer plastic. This type of powder booth system is known for its compactness. Safety is another important benefit to this design. Since there are no ���enclosed��� devices the need for explosion venting is eliminated. 252

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