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Tablets & Capsules March 2017 37 differential pressure reaches the specified maximum, usually 10 inches water gauge. At that point, the dust feed stops. Stage 6 mimics a post-upset scenario. Air flow is reduced to 25 percent of the specified value, and continu- ous pulse cleaning runs for 10 cycles. The system is then returned to the specified air flow, and the differential pressure is measured. Next, the dust feed is restarted and final measurements are taken. This stage replicates a process commonly known as "downtime cleaning." As the filters are cleaned, emission levels will fluctuate because the shock of compressed air that cleans them also allows some dust to pass through the filter media. The pressure drop will increase when cleaning is paused and decrease when it restarts. The frequency of cleaning affects the pressure drop in the system, and the com- pressed air used for cleaning is the main driver of energy consumption. Filters with inherently greater pressure drop consume more energy because they require more pulsing/compressed air and thus more electricity is needed for the fan's motor to overcome the higher static pressure in the system. The tests use calcium carbonate dust, and section 6.1 of the Standard specifies its properties, including particle size, bulk density, and moisture content. By using a standardized material, the test results are applicable across all industries. Measuring performance parameters Emissions. The tests used in Standard 199 measure not only the initial emissions, but emissions over the duration of testing, an approach that is more meaningful to manu- facturers than others. Emissions are measured in mil- ligrams per cubic meter of air. Pressure drop. The more dust a filter can hold and the better it can release the dust, the less frequently it will need cleaning. That, in turn, helps the system maintain a low pressure drop throughout the filter's service life. Compressed air usage. How much air the system con- sumes varies according to how self-cleaning the filter is. The better the cleaning characteristics, the less com- pressed air the system needs. Energy consumption. Pressure drop and compressed air usage largely determine how much you spend running the system. A filter with a low pressure drop—in con- junction with a variable-frequency drive, as is specified for the test rig in Standard 199—will reduce electricity usage and extend the filter's service life. Pulsing less fre- quently also cuts energy consumption because it con- serves compressed air. Emission reading. It's important to know how much dust penetrates the filters and reaches the outlet. The emissions undergo photometric measurement in accor- dance with 40 CFR Part 50 and are categorized by partic- ulate mass (PM): • PM1: Particles less than 1 micron, • PM2.5: Particles less than 2.5 microns, and • PM10: particles less than 10 microns. All testing is performed on standard dust collection units. Even so, the results can also apply to containment techceuticals.com echnical Services Director/CEO Technical Services Director/CEO ousey Michael T Tousey "The best training I've - Nik Steinert had in twenty years." equipment." proactive on actual and put them to take lessons learned "Great to be able to Zoetis im Kingsley, - T Tim Kingsley,