In practice with piping, issues arise with the DN65 and DN125 Series I
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Standard Number Standard Name Nominal Size of Steel Pipe Outer Diameter (Series I) Nominal Size of Steel Pipe Outer Diameter (Series I) GB/T 20808-2012 “Specifications for the Selection of Dimensions of Seamless and Welded Steel Pipes for Pipeline Engineering” DN 65 73 DN125 141.3 GB/T 12459-2017 Steel Butt-Welded Fittings Types and Parameters DN 65 73 DN125 141.3 GBT 9112-2010 Steel Pipe Flanges Types and Parameters (National Standard Flanges) DN65 76.1 DN125 139.7 HGT20592-2009 HGT 20592 Steel Pipe Flanges, Gaskets, and Fasteners DN65 76.1 DN125 139.7 HGT20553-2011 Series for the Selection of Dimensions of Seamless and Welded Steel Pipes for Chemical Plant Piping DN65 76.1 DN125 139.7 When GB/T 20808-2012 is used, there are no flanges that match the pipes; when HGT20553-2011 is used, there are no pipe fittings that match the flanges. I’m not sure how people handle this in actual projects. This issue already existed in the previous versions of HG/T 20553 and GB 12459, and it remains present in this version as well. Could no one have noticed such a simple question? The people in charge of formulating standards really don’t care; is changing standard numbers done just to make money? SHT3405-2012 forms an independent system; the flanges, fittings, and various specification options are all correspondingly matched.
Of course, use the actual flange. .
This post was last edited by nj_lijiaquan on 2017-6-13 at 11:02. The reason for this phenomenon is that the European piping system is divided into Series 1 and Series 2; Series 1 is roughly consistent with the American standard system. However, in European Series 1, DN65 equals 76.1 and DN125 equals 139.7, while under the American standard, these values are DN65=73 and DN125=141.3. Whenever European Series 1 flanges are used, the corresponding pipe sizes are 76.1 and 139.7, whereas with American standard flanges, the corresponding sizes are 73 and 141.3.
So, China’s standard plagiarism is done without any thought. . . The actual circumstances were not taken into account at all. They even blatantly changed the era name to scam people out of money. .