Champion Compressors Ltd. Manual No. 975203 Rev H
94
APPENDIX A DN - METRIC NOMINAL SIZES
DN - Nominal Size for Valves, Flanges and Fittings.
International Definition see ISO 6708-1980
Nominal size (DN): A numerical designation of size which is common to all
components in a piping system other than components designated by outside
diameters or by thread size.
It is a convenient round number for reference purposes and is only loosely
related to manufacturing dimensions.
The nominal size is designated by DN followed by a number, which shall be
shown without the addition of the unit of measure. Refer to DN equivalents
on the table shown below.
It should be noted that not all piping components are designated by nominal
size, for example steel tubes are designated and ordered by outside diameter
and thickness.
NOTE: The nominal size DN cannot be subject to measurement and shall
not be used for purposes of calculation.
Metric
DN
(Nominal Size)
A dimensionless
Designation.
Imperial
NS
(Nominal Size)
Designated in inches
sometimes as ND, NB or NPS
6 = 1/8”
8 = 1/4”
10 = 3/8”
15 = 1/2”
20 = 3/4”
25 = 1”
32 = 1.1/4”
40 = 1.1/2”
50 = 2”
65 = 2.1/2”
80 = 3”
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