ISO 6708:1995 pdf free download.Pipework components – Definition and selection of DN nominal size ).
1 Scope
ISO 6708 gives the definition of DN (nominal size) when applied to components of a pipework system, as specified in those standards which use the DN designation system.
NOTE 1 Other methods of size designation are also used, e.g. products having threaded, compression, solder or welded end connections or products designated by NPS (nominal pipe size). OD (outside diameter). ID (inside diarneter). but these are not defined in ISO 6708. ISO 6708 gives a list of preferred DN values.
2 Definition
2.1 DN: An alphanumeric designation of size for components of a pipework system, which is used for reference purposes. It comprises the letters UN followed by a dimensionless whole number which is indirectly related to the physical size, in millimetres, of the bore or outside diameter of the end connections.
NOTES
2 The number following the letters DN does not represent
a measurable value and should not be used for calculation
purposes except where specified in the relevant standard.
3 In those standards which use the DN designation system, any relationship between DN and component dimensions should be given. e.g. DN!OD or DN/ID.
3 DN Series
The preferred DN values are as follows:
DN1O DN250 DN1500
DN15 DN300 DN1600
DN2O DN350 DN1800
DN25 DN400 DN2000
DN32 DN450 0N2200
DN4O DN500 DN2400
DN5O DNSOO DN2600
DNSO DN700 DN2800
DN65 DN800 DN3000
DN8O DN900 DN3200
DN100 DN1000 DN3400
DN 125 DN 1100 DN 3 600
DN15O DM1200 DN3BOO
DN200 DN1400 DN4000