Nominal Filtration
Definition
A filtration rating indicating an approximate particle-removal efficiency — commonly 50–90 % — at the stated micron size, without a guaranteed single-pass value.
Nominal ratings describe typical rather than guaranteed performance and are not standardized between manufacturers. A "10 µm nominal" element may remove roughly 60–90 % of 10 µm particles depending on flow, viscosity and loading.
Nominal media are cost-effective for bulk clarification, pre-filtration and applications where a precise cut-off is not required. Where reproducible quality matters, an absolute rating should be specified instead.
Relevance for high-flow filtration
R+F polypropylene high-flow media cover nominal grades across 1–100 µm for economical pre-filtration and general liquid clarification.
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Related terms
A filtration rating stating that a defined percentage — typically 99.9 % (beta 1000) — of particles at or above the rated micron size is removed in a single pass.
Beta Ratio (β)A dimensionless number expressing filtration efficiency: the ratio of particles of a given size upstream to those downstream of the filter.
Micron RatingThe nominal particle size, in micrometers (µm), that a filter is designed to remove — stated as either an absolute or a nominal value.
Polypropylene (PP) Filter MediaA thermoplastic filter medium prized for broad chemical compatibility, low cost and freedom from binders or additives.
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