Issues regarding the temperature and pressure rating values of flanges per GB/T 9124.1-2019 standard
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In the national standard flanges specified in GB/T 9124.1-2019, a comparison of the temperature and pressure ratings of 304 and 316L shows that, at the same pressure level and temperature, the rated pressure of 304 is lower than that of 316L. However, in the standard for forged flanges NB/T 47010-2017, the strength of 304 is higher than that of 316L. How can this be explained? In the industry flange standards HG/T 20592-2009 and SH/T 3406-2013, the rated pressure for 304 is higher than that for 316L.
The temperature and pressure rating values for flanges according to the GB/T 9124.12-2019 standard are the same as well.
GB/T 9124.1 is based on ISO 7005-1:2011, and ISO 7005-1 in turn refers to EN 1092-1 for matters such as materials and temperature/pressure ratings. In EN 1092-1, the material standard specified is EN 10222-5; according to this standard, the strength of 304 material is lower than that of 316L material. Therefore, it is acceptable for the rated pressure of 304 material to be lower than that of 316L material in either ISO 7005 or EN 1092-1. The problem is that GB/T 9124.1 adopts the temperature and pressure ratings specified for other materials; since no such standards exist for these materials, NB/T 47010 was used instead. However, it turned out that the strength of 304 material as specified in NB/T 47010 is higher than that of 316L material, which creates this contradiction. Version HG/T 20592-97 also had this issue, but it was corrected in the 2009 version. Actually, there’s no problem using it; just consider more margin.
The localization work wasn’t done well:lol