Issues regarding the welding of pipes and flanges in different outer diameter series
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For pipes and flanges in the large outer diameter and small outer diameter series, as I understand it: it’s no problem to weld pipes with large outer diameters to flanges with large outer diameters, and flanges with large outer diameters can also be paired with flanges with small outer diameters. It’s simply not possible to weld directly between tubes with a large outer diameter and those with a small outer diameter. I’m not sure if this understanding is correct
There is some truth to what was said; it’s better if the outer diameter of the flanged connections belongs to the same series. For example, for DN100 flanges, the outer diameter of the connections should either be 108 or 114. It wouldn’t look good if 108 and 114 were welded together – one being thicker and the other thinner It affects the appearance; it is recommended to replace one of the flanges.