DN150 thread, outer diameter of steel pipe
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GB/T 20801-2020 states that for DN150 threaded flanges using 55° sealing pipe threads, an outer diameter of 165 mm is required. However, the standard GB/T 9114-2010 for threaded flanges specifies an outer diameter of 168 mm for steel pipes. I would appreciate some guidance on this matter. Thank you!
I’m not quite sure; it’s probably a matter of industry compatibility and interchangeability, right? In other words, all threaded fittings that match 165.1 are 55-degree threads, such as threaded flanges, pipe couplings, unions, threaded elbows, etc., and they are standard products ； It matches 168.3; it is the same as the American standard ASME, and it is also used for producing standard products ； If the thread type needs to be changed, it is equivalent to custom ordering.