Questions regarding the selection of pipe size series for chemical process piping
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The standard HG/T-20553-2011 – Series for the Selection of Dimensions of Seamless and Welded Steel Tubes for Chemical Engineering Piping – specifies three dimension series: Ia, Ib, and II. It states that Ia is the preferred series, while II is a series that is still in use; some sources indicate that series II will gradually be phased out； Almost all sources recommend against using pipes with diameters of DN32, DN65, and DN125. But the fact is that all design institutes I’ve seen default to using the Series II, and they almost always use pipes with diameters of DN32, DN65, and DN125. Dear sea friends, why?
Since it’s all based on existing templates, it saves effort – there’s no need to recalculate and redesign everything
Every industry has its own conventions; it seems that the petrochemical industry uses DN32, DN65, and DN125 less often
Yes, driven by the two major oil companies, the petrochemical industry generally uses standards equivalent to the American standard SH3405, that is, Series I of HG20553. In the chemical industry, however, the national standards based on the European standard system are used, that is, Series II of HG20553. As for DN32, 65, and 125, design firms following the American standard system recommend against their use. Yet those who have experience in designing or installing fire protection pipelines know that DN65 is the most common specification~~~~
Every pipe diameter has its own uses; there’s no reason to pick out a few that are not recommended for use
It can be used, but it is not recommended. Since it is rarely used in the market, there are few manufacturers, and stock levels are low; as a result, it is difficult to obtain, which poses challenges for procurement and affects the progress of projects
There is another reason why it is not recommended; just compare these specifications in 20553 and GB12459 and you will understand