What standard does the nominal diameter DN indicated on ordinary valves and flanges follow?
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I would like to ask what standard the nominal diameter DN indicated on ordinary valves and flanges follows? For example, what standard does the nominal diameter DN15 of a ball valve correspond to? What is the typical inner diameter (bore size)? Is it the same as a flange?
For pipes with the same nominal diameter, the outer diameter remains constant; the inner diameter depends on the wall thickness. The same applies to flanges, but this is only true for WN types – SO and SW types are not affected by the inner diameter. As for what standard it refers to, it’s been in use all along; I really hadn’t thought about it. Same question.
The standards for valve flanges are generally determined by the owner or the designer; the manufacturer just needs to follow them.
What is the DN standard? I haven’t been there either; I guess it’s the US standard. In general pipe or fitting standards, two sizes are often specified: NPS and DN. If the standard for a piping system is established (such as HG, SH, ASME, DIN, JIS), then the corresponding outer diameter can be found. Its inner diameter can be found in the wall thickness table. {What is mentioned above generally refers to pipes; the thickness of the corresponding flanges and valves should be the same as that of the pipes, or it may be slightly thicker – it depends on the manufacturer.}
The nominal diameter DN of steel-reinforced plastic composite pipes refers to the inner diameter of the pipe; for example, if it is DN200, then the inner diameter is 200 mm.
It refers to the nominal diameter; in the water treatment industry, you will also see DN70
DN refers to the nominal diameter, also known as the named diameter