Metal Finishing Guide Book


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Page 816 of 903

There are a wide range of powder cartridge filter products available today���different media, various treatments, as well as customized manufacturing technologies (i.e., special gasketing, variation in pleat count, design, depth and spacing, etc.). To ensure optimum performance and value, one must consider the design capabilities and limitations of the filter, in addition to the application factors that might have an impact on a filter���s performance. There are three media styles typically used in powder cartridges: cellulose, spun bond polyester and expanded polytetraflouroethylene (ePTFE) membrane; 100% cellulose and 80/20 blend (80% cellulose ��� 20% polyester) are ���depth-loading��� media constructed with tightly packed pleats and an outer wire mesh screen for support. This is the least expensive media style available, offers only moderate efficiency, and is best suited for low- to mid-volume, spray-to- waste powder operations. Pulse cleaning cellulose cartridges can be difficult at times because the powder has a tendency to become trapped between the pleats, resulting in very high powder retention within the filter (20���45 lbs.) and more rapid pressure drop. Cellulose-style cartridges would not be appropriate for high-moisture conditions or high-volume reclaim operations, as they tend to plug up much quicker. One-hundred percent spun bond polyester is a continuous strand, ���surfaceloading��� media that is tougher and slicker than cellulose and does not require outer screen support to maintain pleat rigidity and strength. Spun bond polyester cartridges also require 50���70% less surface area than cellulose filters to handle a given air volume. This allows for a wider pleat spacing and fuller utilization of filter media, and together with the higher efficiency that polyester provides, results in the following benefits in relation to cellulose: ��� Lower pressure drop and longer service life ��� Higher recovery rate of reclaim powder ��� Less powder retention within cartridge (80���90% less) ��� Less compressed air needed to pulse clean filters (40���60psi) ��� Less downstream contamination of system and plant air ��� No linting contamination of reclaimed powder or paint finish Better resistance to aggressive and abrasive powder (i.e., frit or porcelain) ��� Superior moisture resistance ��� Ability to wash and reuse filters Spunbond polyester media also offers several specialty treatments and membrane selections to enhance filter performance in more challenging conditions: Aluminized polyester (anti-static). This treatment coats the face of the media with a thin layer of aluminum, which dissipates the electrical charge of the filtered powder. This makes it an ideal filter for effective pulse cleaning when static electricity buildup is a concern. Hydro-oleophobic polyester (moisture-resistant). This type of cartridge is treated with a fluorocarbon or teflon bath that provides an oil and water repel803

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