The Proper Use of 47-mm Flat Disc Filters in Filter Sizing Studies

Small flat-disc filters, typically 47 mm in diameter, are often used as models in filter sizing exercises to quantify the effective filter area (EFA) needed to filter an entire batch. The proper implementation of the flow decline method of assessing EFA requirements, however, necessitates knowing the precise EFA of the model filter, which should be measured using staining techniques. Furthermore, such indicator studies should be followed by verification trials using pleated filters, to ensure greater accuracy.