ISO 6708:1995 pdf download – Pipework components – Definition and selection of DN(nominal size).
ISO 6708 gives the definition of DNinoninal size) when applied to components of apipework system. as specified in those standardswhich use the DN designation system.
NOTE 1 Other methods of size designation are also used,e.g.products having threaded, cormpression,solder orwellded end connections or products designated by NPS(nominal pipe size).OD loutside diameter).iD oinside diam-eteri. but these are not defined in this lnternational Stan-dard.
This lnternational Standard gives a list of preferred DNvalues.
2 Definition
2.1DN: An alphanumeric designation of size forcomponents of a pipework system, which is used forreference purposes. it comprises the letters DN fol-lowed by a dimensionless whole number which is in-directly related to the physical size,in millimetres,ofthe bore or outside diameter of the end connections.
2 The number following the letters DN does not representa measurable value and should not be used for calculationpurposes except where specified in the relevant standard.
3 ln those standards which use the DN designation sys-term, any relationship between DN and component dimen-sions should be given, e.g. DNIOD or DN/ID.