The ultimate goal of the filter sizing exercise is to quantify the effective filter area (EFA) needed to filter an entire
production batch over a set time frame. Such testing typically is done using a flat disc with a diameter of 47-mm. The proper
implementation of the flow decline method of assessing EFA requirements necessitates knowing the precise EFA of the model
filter, which can be measured using staining techniques.
A filter-sizing study using a 47-mm flat disc is intended as indicator trial, which is preliminary to a more meaningful verification
trial, or even to a more cogent assurance trial. The latter will require filter models characterized by a pleated membrane
design. The EFA assessment of the pleated filter models can be performed with confidence. This will result in dependable projections
of the EFA required for the batch processing filters.
Maik W. Jornitz is the group vice president of marketing & product management, filtration and fermentation technologies, and Wayne Garafola is an application specialist, both at Sartorius Stedim Biotech, Bohemia, NY, 631.870.8463, firstname.lastname@example.org
Theodore H. Meltzer is the principal at Capitola Consulting Co., Bethesda, MD.
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