Help needed~ Issues with piping using US standard DN65 flanges
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It has been found that for SH/T 3406 and ASME B16.5, the outer diameter of the welded end of the DN65 flanged weld joint is 73, while for HG/T 20615, it is 76.1. Should steel pipes with a diameter of 73 be used for the former case, and those with a diameter of 76.1 for the latter? Logically, all three of these standards are part of the American system. However, it turns out that for this DN65 flange, whether welding is done by butt welding or socket welding, the dimensions specified in the Ministry of Chemicals’ standards differ from those in the other two standards. I hope the expert can give some guidance
Logically, it should be the same; the latest national standard 9124.1-2019 has changed the series from 1 to 73. Perhaps the standards set by the Ministry of Chemicals will be revised in the next update, but the exact reason is unclear. Just mention the specific standard number when installing the pipes.
When placing an order, if SH/T 3406 is specified, the flanges used are compatible with pipes of size 73; if HG/T 20615 is specified, the flanges used are compatible with pipes of size 76. . It’s pretty awkward. .
Normally, materials are purchased according to the design drawings, which specify the outer diameter and thickness of the pipes, the flange standards, and the interface standards for valve equipment. The newly built systems should not encounter issues related to material mismatches. Such problems usually arise during renovations, for example when domestic valve equipment is replaced with imported one, or vice versa; in such cases, it is necessary to customize non-standard components for conversion.
If ASME flanges are to be used, the outer diameter of the piping will be 73； If HG flanges are used, the outer diameter of the piping will be 76.1.
Nonsense, where would the design drawings for standard flanges come from?
That’s indeed the case; the SH standard is the closest to the American standard, but it’s not exactly the same. So even though it’s all part of the American system, it’s necessary to verify the data; one can’t assume that everything is exactly the same.