Conversion between DN and inches
Thread Content
DN is the nominal diameter; I’ve never understood the numbers that follow DN. Must the outer diameter of a DN50 pipe be 2"?
Is there a standard chart that correlates the numbers after DN with the actual dimensions? Or, for the same DN value, do different manufacturers have different actual dimensions? Thank you
Look at HG/T20592
Thank you. It is clearly specified in the HG/T 20592 Standard for Steel Pipe Flanges (PN series)
First, it is necessary to understand the difference between DN and other units: the DN designation system belongs to the European system, while the inch-based system is used in the American system. Although there are differences between them, there is also a certain connection. DN15 corresponds to 1/2”, DN50 corresponds to 2”, DN600 corresponds to 24”, and so on. However, in China, the outer diameters associated with DN fall into two series; the Series I values are roughly equivalent to those in inches, whereas the Series II values differ. For example, for DN50, the Series I value is Φ60.3, which is the same as the 2” outer diameter according to the American standard. But the Series II value is different – it is Φ57 according to the Chinese standard
It was explained in quite detail; I’ve learned it.
To be precise, it is a pipe with a nominal diameter of 50, that is, 2 inches. The nominal diameter is generally the inner diameter, but it is not necessarily exactly the same as the inner diameter size.
What do the domestic I and II series refer to? Are there relevant standards specifying this, or is it an industry-wide term? Thank you very much for your thoughtful reply.