|DIN EN ISO 6708|
|title||Pipeline parts - definition and selection of DN (nominal diameter)|
The nominal diameter (abbreviation NW , or DN from French diamètre nominal ) is the inner diameter of a pipe or hose line or the size or connection dimension of a fitting ( valve , gate valve ). Together with the nominal pressure level and the material class, all dimensions of a pipeline , e.g. B. flange dimensions set. Steel is often not mentioned as a material, but it is assumed.
It should be noted that the actual inside diameter often deviates from the nominal width by several millimeters. In addition, it can only be assumed with certainty that pipes of different origins can be combined if the nominal width is specified with reference to the same DIN standard .
Deviations occur, among other things, since the outer diameter of the pipes used for plumbing match usually has to the pipes properly to each other connect to. If the wall thickness increases with increasing pressure level , the free cross section must be reduced.
The outer diameter is only increased in the case of very thick-walled pipes for very high pressures. The same applies to lines made of glass fiber reinforced plastic (mostly synthetic resin ): These are wrapped around a mandrel or a plastic pipe ("inliner"), which is why the wall thickness has to grow outwards.
The nominal width is specified in accordance with EN ISO 6708 using the designation DN, followed by a dimensionless number that roughly corresponds to the inner diameter in millimeters . For example, DN 50 according to EN 10255 (formerly DIN 2440; medium-heavy threaded pipes ) designates a pipe with an outside diameter of 60.3 mm and a wall thickness of 3.65 mm (inside diameter 53 mm).
As a rule, valves of a certain nominal size or size are manufactured in the respective connection size. In order to simplify the connection according to the installation situation, the manufacturers often offer valves of the same nominal size in the next larger connection size.
Threaded pipe EN 10255 (medium-heavy, steel)
|Pipe thread R,
|Wall thickness||Inner-ø||content||Cross sectional area|
|in inches||d a in mm||s in mm||d i in mm||in l / m||in m²|
|6th||1 ⁄ 8 ″||10.2||2.00||6.2||0.03||0.0000300|
|8th||1 ⁄ 4 ″||13.5||2.35||8.8||0.07||0.0000608|
|10||3 ⁄ 8 ″||17.2||2.35||12.5||0.12||0.0001227|
|15th||1 ⁄ 2 ″||21.3||2.65||16.0||0.20||0.0002011|
|20th||3 ⁄ 4 ″||26.9||2.65||21.6||0.37||0.0003664|
|32||1 1 ⁄ 4 ″||42.4||3.25||35.9||1.01||0.0010122|
|40||1 1 ⁄ 2 ″||48.3||3.25||41.8||1.37||0.0013723|
|65||2 1 ⁄ 2 ″||76.1||3.65||68.8||3.72||0.0037176|
In the case of threaded pipes, the nominal diameter is usually given in inches. For copper pipes, the outside diameter is usually given in mm (10; 12; 15; 18; 22; 28; 35; 42; 54; 64 etc.). The pipe wall thickness is 1 mm for 10–22 mm, 1.5 mm for 22–42 mm and 2 mm for 54–64 mm.
Threaded pipe EN 10255 (heavy, steel) (gas pipe)
|Pipe thread R||Outer-ø||Wall thickness||Inner-ø|
|in inches||d a in mm||s in mm||d i in mm|
|10||3 ⁄ 8 ″||17.2||2.9||11.4|
|15th||1 ⁄ 2 ″||21.3||3.25||14.8|
|20th||3 ⁄ 4 ″||26.9||3.25||20.4|
|32||1 1 ⁄ 4 ″||42.4||4.05||34.3|
|40||1 1 ⁄ 2 ″||48.3||4.05||40.2|
|65||2 1 ⁄ 2 ″||76.1||4.5||67.1|