Issues with the dimensioning of pipeline valves
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Connection sizes are used when selecting piping instruments such as valves and flow meters, but some use DN25, some use 1\", and some use φ25.4. Could someone please explain under what circumstances each of these should be used? Is it related to the connection method?
Any of them will work; it depends on your choice
The standard should be the outer diameter plus wall thickness, but I usually use the inner diameter as well
These three sizes are the same; DN denotes the nominal diameter, 1 inch is the international notation, and φ represents the outer diameter of the pipe. It doesn’t have any special meaning; there’s no need to overthink it
The DN25 size is available in two variants: the larger one has an outer diameter of 34 mm, while the smaller one has an outer diameter of 32 mm. φ25.4, as it should be a DN20 pipe, not a DN25 one.
DN stands for nominal diameter. Due to the special circumstances in China, there are two standards for the outer diameter of steel pipes: the European standard (German standard) and the American standard. To standardize the way pipe dimensions are referred to, the term nominal diameter DN was introduced. DN comes in two series: Series A and Series B; Series A corresponds to the American standard, while Series B corresponds to the German standard. For example, for DN50, the outer diameter of a pipe from Series A is 60.3 mm, whereas that of a pipe from Series B is 57 mm. Therefore, when using DN to refer to a pipe’s size, it’s important to specify whether it’s Series A or Series B. The American standard uses inches for measurement, so when someone mentions a 2-inch pipe, its outer diameter is clearly 60.3 mm, with no possibility of confusion regarding 57 mm. When using φ to indicate the diameter, it directly represents the outer diameter of the pipe. It’s particularly important to note that when DN is used, it’s essential to specify whether it’s Series A or Series B; otherwise, the flanges might not fit properly with the pipes. For some diameters, the difference isn’t significant; for example, for DN80, the outer diameter is 88.9 mm for Series A and 89 mm for the German standard series.
I checked HG20592-2009, and the dimensions specified there do not correspond to those used in biological fermentation; the values indicated on the drawings are Φ25.4, Φ38.1, etc., which are also outer diameter values. I couldn’t find these numbers in the chemical industry standards
The nominal diameter corresponds to different outer diameters due to varying pipe wall thicknesses, right? I’ve always been confused by this.
The outer diameter remains the same; what changes is the inner diameter...
I’m not quite sure about this; I’ll wait for answers from other sea travelers