filtration rating
The particle size a filter is rated at, as a length — 21 microns on the WIX 51521, 32 on the 57035, 10 on the 33390, 4 on the Baldwin BF7633. It is never a bare number: it is quoted AT an efficiency, ON a basis and UNDER a test method, so it carries three qualifiers (`filtration_efficiency`, `filtration_basis`, `filtration_standard`) exactly as `list_price` carries `price_basis`. Without them a comparison strips the meaning and returns a wrong answer on real parts — 4 microns absolute is not 2.5 times finer than 10 microns nominal. Distinct from Strainer's `mesh_grade`: that is the coarse qualitative grade of a straining VESSEL that holds liquid transiently; this is the measured rating of a consumable ELEMENT with no holding volume, and the two families are disjoint.
Filtration rating is a measured figure, given in millimeters or inches.
It belongs to measurement — its measurable, physical facts.
the bundle what travels with each filtration rating
A filtration rating is not a lone value — each statement is a self-correlating bundle, carrying its own:
asked by the kinds that answer it
2 kinds answer it, each for a single value. The same question can be reused by unrelated kinds — one meaning, many homes.
asked by kinds that answer it
The same question can be reused by unrelated kinds — one meaning, many homes.
| kind | how many |
|---|---|
| filter | one |