The nominal diameter (DN) of a pipe is a numerical designation of size, which is common to all components in a piping system other than components described by outside diameter or by thread size. It is a convenient round number for reference purposes and is only loosely related to manufacturing dimensions.
Understanding Nominal Diameter (DN)
- Definition: The nominal diameter, designated by the abbreviation "DN" followed by a number, roughly represents the inside diameter of a pipe in millimeters. It's a simplified size designation.
- Metric System: DN is a metric measurement.
- Not Exact: The DN value isn't always the exact inner diameter but serves as a standardized identification. Actual inner diameter will vary based on the pipe schedule (wall thickness).
- Standardization: Nominal pipe size helps ensure that fittings and pipes of the same DN will fit together, regardless of the manufacturer.
Example
A pipe designated as DN 50 roughly corresponds to a pipe with an inner diameter of approximately 50 mm. However, the actual inside diameter could be slightly different depending on the material, manufacturing tolerances, and pipe schedule.
Key Takeaways
- Nominal diameter (DN) is a size designation.
- It's expressed in millimeters.
- It's an approximate value, not an exact measurement of the inner diameter.
- It's used for standardization across different manufacturers.
