Help: Why are there both A-series and B-series pipes recommended in GB T17395-2008 \"Dimensions and Shapes of Seamless Steel Tubes\"?
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Dear experts, when choosing DN350 pipes, I referred to the dimensions recommended in \"GB T17395-2008 Seamless Steel Pipe Dimensions\"; the size specified for Series 1 is φ356, which corresponds to Class A pipes. However, in practice, it seems that everyone chooses pipes with a diameter of φ377, which is a size not recommended by the standards. What is the reason for this discrepancy? . Please help resolve my sister’s confusion. .
Personal opinion: Series A (imperial) is an internationally standard series that was introduced to China only in recent decades, while Series B (metric) follows the domestic standard series. Domestic companies* usually use the B series, as it is also cheaper.
It’s just a difference between domestic and international standards
Standardization of caliber for market release: It’s just a difference between domestic and international standards； In reality, it’s a matter of *habit in use. Regarding the current market inventory, all are in stock. But if all of them can be used, 377 will save a lot of money····
356 is a British standard pipe, while 377 is a metric standard pipe. It seems that the domestic petrochemical industry uses imperial-sized pipes, so imported equipment must be equipped with such pipes as well. The light industry has always used metric pipes; I’m not sure if the chemical industry does the same, but I guess it does, as alcohol factories used metric pipes in the past. Actually, there is logic to the standard that recommends using imperial pipes first; after all, to integrate into the global market, if foreign projects use metric pipes, it will be very troublesome to replace them and have to import them from within the country
Since it is not recommended, it seems that they will move closer to international standards in the future; however, the pipes in the old plants are still of type 377, so we have no choice but to make do with them.