What is the difference between standard flanges for valves in the chemical industry and mechanical flanges?
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The flanges specified by the Ministry of Chemical Industry and those specified by the Ministry of Machinery are the same for DN15-DN25; for flanges above DN25, the outer diameter needs to be 5 units larger. Is there another issue? Are the lengths of the check valves (rising stem and swing type) that comply with national standards the same as those of the national standard gate valves? It would be best to explain it, so it’s easier to understand. Thank you!
HG was developed with reference to foreign standards; I don’t know how JB came about
That’s right; valve flanges generally follow the JB standard, but users can request that valve manufacturers use the HG standard
The data for Series I of JB flanges and Series A of HG20592 flanges are quite similar; they are basically derived from international standards； Both the II series of JB flanges and the fittings of the B series of HG20592 are designed for metric pipes (i.e., pipes with a small outer diameter). The difference lies in the fact that the dimensions of the JB II series flanges have been adjusted in detail according to domestic mechanical standards, such as the width of the flange’s outer edge and the size of the bolt holes. Meanwhile, the HG20592B series only involves changes to the outer diameter of the fittings compared to the A series ； The A series of HG20592 clearly refers to the international standard EN1092, while it is not clear whether the I series of JB refers to an earlier version of EN1092; no explicit information on this is available. By comparing the two standards, it can be inferred that the I series of JB and the A series of HG20592 should be based on the same standard.