LIFETIME PERFORMANCE OF ASME AG-1 SECTION FK RADIAL FLOW FILTERS

The American Society of Mechanical Engineers AG-1 Standard has added section FK for specialty HEPA filters. The Institute of Clean Energy Technology has performed as series of lifetime performance evaluations for a set of radial flow HEPA filters developed under guidelines of AG-1 Section FK. A series of 18 filters Section FK HEPA filters have been tested. This included testing two different configurations of 56.6 m/min (2000 cfm) filters, 12 remote change filters and 6 safe change filters. Testing consisted of lifetime performance evaluations using three different aerosol challenges and two different relative humidity/temperature conditions. Challenge aerosols ranged in mass median diameter (MMD) size from 500 nm (alumina) to 3000 nm (Arizona road dust). All testing was conducted consistent with NQA-1 standards. Test data were continuously collected for volumetric airflow, air temperature, relative humidity, up and downstream particle size distribution, up and downstream particle count, and filter differential pressure. Data provided in this paper include the mass versus differential pressure (dP) loading curves demonstrating loading capacity as a function of particle size. Results of mass loading are shown to follow current models for smaller aerosols, but large particle challenges demonstrated higher loading capacities than expected. Data will also be provided to demonstrate changes in the filter pack geometry during latter stages of loading (at differential pressures greater than 2986-3484 Pa (12-14 in. w.c.) dP). This change in pleat geometry (pleat collapse) leads to a threshold dP at which the differential pressure will continue to increase even if aerosols are no longer added to the air flow. Data will be presented to demonstrate that reducing the airflow by 25 percent will counteract this runaway increase in dP, even if reduction of airflow is done as late as 6221+ Pa (25+ in. w.c.). Filter failure for the units tested ranged from 7465 to 12442 Pa (30 to 50 in. w.c.). Video of filters collected inside the filter housing while loading indicated little flutter of pleats, however, ballooning of pleats was shown to occur during latter stages of the testing protocol. Photographs of the filter annulus prior to discontinuing airflow do not show evidence of bridging between pleats, even for very high filter loading. Additional photos of filters post-failure demonstrate the tendency of the filter pack to remain somewhat distorted with physical failure of the medium occurring at the medium-potting material interface.