01
ANR: definition and engineering context
Atmosphère Normale de Référence. Reference-air condition used by some pneumatic catalogs for normalized flow.
The term belongs to the flow & valves context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.
02
Why ANR affects pneumatic selection
Keep ANR values tied to the catalog's stated reference definition.
- Qn: Compare only when pressure conditions and measurement conventions match.
- ΔP: Available valve and line flow changes with pressure drop.
- Cv: Do not compare it directly with nominal NL/min without the fluid state and test conditions.
- Kv: Cv and Kv are related conventions but are not numerically identical.
03
How to evaluate ANR in a catalog or replacement project
Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.
For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.
- Nominal or normalized flow rate: Catalog flow value defined under a stated test condition.
- Pressure drop: Difference between upstream and downstream pressure.
- U.S. flow coefficient: A conventional coefficient describing flow capacity under a defined test basis.
- Metric flow coefficient: Metric coefficient convention commonly used for valve flow capacity.
Selection checklist
What to verify before selection
- 01
Keep ANR values tied to the catalog's stated reference definition.
- 02
Compare only when pressure conditions and measurement conventions match.
- 03
Available valve and line flow changes with pressure drop.
- 04
Do not compare it directly with nominal NL/min without the fluid state and test conditions.
Application caution
Common mistakes
- Treating ANR as a universal definition without checking the manufacturer or standard context
- Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
- Selecting a component from the term or nominal value alone without checking the complete operating point and drawing
FAQ