Metal Finishing Guide Book


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finishing equipment & plant engineering SELECTING CARTRIDGE FILTERS FOR POWDER COATING OPERATIONS BY JOHN WALZ, CHEMCO MANUFACTURING CO., NORTHBROOK, ILL. As air emission standards have become more and more stringent over the last 20 years, the trend toward powder coating���which typically eliminates the VOCs and hazardous waste generated by more traditional painting methods���continues to grow as we move forward into the 21st century. Contributing greatly to this growth was the early 1980���s advent of the cartridge filter recovery system, which enabled metal finishers to utilize as much as 99% of the powder paint purchased. This advancement in powder recovery technology dramatically enhanced powder coating productivity and allowed finishers to realize significant cost savings by switching from liquid to powder. Today, the cartridge filter collector is the most popular type of powder separation and recovery system in the marketplace. The focus of this article will be on the most critical aspect of this system���the cartridge filter. We will discuss the range of products available, the effect different conditions and circumstances can have on filter performance, and what types of cartridges should be selected for these various situations. In doing so, we hope to show why cartridge filters used in powder coating equipment should be viewed as something more than just a commodity. Cartridge filter replacement can be one of the larger operating expenses in a powder booth system. So to adopt an ���I���ll buy what came with the system��� mentality, or to choose a filter solely based on price, can be a costly mistake. Buying the lowest priced option can actually be more expensive in the long run, since there are usually some undesirable reasons why it is the cheapest item. While the service life and price of the filter determine the cartridge replacement cost, improved filter performance (i.e., higher efficiency, lower pressure drop, reduced downtime for maintenance, better quality reclaim, etc.) can have an even larger impact on the total cost of operating a powder system. Consistent airflow, for instance, is a critical factor necessary for efficient booth operation. Air velocity through the application booth should be between 100���120 fpm to ensure good transfer efficiency and to contain the powder overspray from drifting outside the booth. Selecting the wrong cartridge filter is one way to compromise consistent air flow Figure 1: Various types of cartridge filters. through a system. 801

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