Mean Flow Rating

Mean flow rating (MFR) defines the pore size at which 50 % of the total flow passes through larger pores and 50 % through smaller ones. It is derived from capillary-flow porometry and correlates directly with hydraulic behaviour, making it a more realistic indicator of retention than a nominal micron value. For woven or sintered media, MFR characterises both permeability and selectivity, bridging the gap between geometric and functional pore size. Engineers use MFR for filter design, quality control, and performance validation, linking it to pressure-drop curves and particle-retention tests. Stable MFR values across production lots ensure predictable flux and long-term consistency.