Regarding the outer diameter of steel pipes according to national and chemical industry standards
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We will only discuss Series 2; the figures shown refer to the outer diameter of seamless steel pipes as specified in GB 17395, and the outer diameter of steel pipes used for chemical piping as specified in HG 20553. Why is there only one specified outer diameter for steel pipes in the chemical industry standards, while there are multiple specifications for outer diameters in national standards?
With a larger outer diameter, it’s easier for fittings and flanges to get mixed up, right?
Generally, the outer diameter of series 2 comes from the old Soviet system, which was adopted by us decades ago; it allows for significant cost reduction in applications that require large sizes. Series 1, on the other hand, originates from Europe and the United States. Now that the Soviet system no longer exists, the systems of Europe and the United States are gradually becoming international standards
HG 20553 also comes in tubes with large outer diameters and small outer diameters, thank you!