Chemical Processing - September 2007 - (Page 53)

Dirt-holding-capacity ratings aren’t particularly valuable. The contaminant particles used in the multipass test are lightweight, consistent in size and, therefore, don’t represent field conditions. The ratings can give a sense of relative service life among elements with the same micron ratings but actual field conditions may produce different results because of the random size and weights of the trapped particles. The best practice is to use rated elements that have been tested with a widely accepted method. Avoid elements that aren’t rated to any test or standard. 11. Choice of cartridge or bag filter. There’s no definitive basis on whether it’s better to specify a cartridge filter or a bag filter. Cartridge filters typically cost two-to-four times more than bag filters but their larger surface area yields a longer service life. A pleated cartridge filter is strongly recommended if the majority of the particulate contamination in the fluid is smaller than 10 micron. Pleated cartridge filters also offer higher efficiencies and are available with the micron ratings required to maintain a high degree of fluid purity. Not surprisingly, flow rate and viscosity also can affect your selection decision. Cartridge filters, especially high porosity ones that use micro-fiberglass or polyester material, better suit fluids with higher viscosities. Bag filters are good choices for applications with low viscosity fluids like water, low filtration requirements and larger particulates (40 micron and larger). Bag filters also may be easier to specify for materials compatibility. Bag filters require a larger housing to match the clean (initial) differential pressure of a pleated cartridge. 12. Filter vessel sizing. A common error is to specify a filter vessel with too few filter elements. Such undersizing often stems from a desire to keep initial costs down. However, it’s actually advantageous to specify a filter vessel that can contain a few elements more than the minimum. Oversizing will add some initial cost but the long-term savings will pay for the up front investment. A filter is essentially a restriction in the flow line. The flow line is less likely to experience interruption or pressure drop when its restrictive qualities are minimized; a larger filter vessel reduces the strain on the system. In addition, it will offer better filtration performance because the fluid’s velocity as it travels through the system is reduced, allowing the filter to capture more particles — even if the filters are specified to a lower micron rating. Therefore, a larger filter vessel with additional elements can improve performance and reduce long-term maintenance costs. CP Tim Mills is an applications engineer for Kaydon Custom Filtration Corp., LaGrange, Ga. E-mail him at TMills@kaydon.com.PO;; www.chemicalprocessing.com MONITOR VISCOSITY SIMPLY Sense Motor Horsepower with Universal Power Cell EASY INSTALLATION • No holes in tanks or pipes • Away from sensitive processes VERSATILE • One size adjusts for motors, from small up to 150 HP • Works on 3 phase, fixed or variable frequency, DC and single phase power SENSITIVE • 10 times more sensitive than just sensing amps CONVENIENT OUTPUTS • For meters, controllers, computers 4-20 milliamps, 0-10 volts CALL NOW FOR YOUR FREE 30-DAY TRIAL 888-600-3247 WWW.LOADCONTROLS.COM http://www.koboldusa.com http://www.koboldusa.com http://WWW.LOADCONTROLS.COM http://www.chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing - September 2007

Contents From the Editor Field Notes In Process Energy Saver Compliance Advisor Succeed at Simulation Rethink Your Approach to Process Safety Avoid Blending Blunders Get the Right Cartridge or Bag Filter Wireless Proponents Take HART Membrane Boasts Material Benefits Process Puzzler Plant InSites Chem Show Product Preview ISA Product Preview Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - September 2007

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