Issues regarding pressure pipelines in the catalog of special equipment
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Pressure pipelines refer to tubular devices that use a certain pressure to transport gases or liquids. They are defined as pipelines with a maximum operating pressure of 0.1 MPa (gauge pressure) or more, carrying gases, liquefied gases, steam, or liquids that are flammable, explosive, toxic, corrosive, and have a maximum operating temperature equal to or higher than their standard boiling point, and with a nominal diameter of 50 mm or more. Question: 1. What is DN50? It is not specified either in GB∕T 1047-2019. According to Baidu, DN40 corresponds to φ45, and DN50 corresponds to φ57. If it is φ51, for example φ51*3, then is it DN40 or DN50? (Note: There is no DN45.) Question 2: Based on Baidu’s definition where DN40 is φ45 and DN50 is φ57, there are two possible interpretations. Does exceeding φ45 mean DN50? Is it still less than φ57, meaning DN40? First interpretation: For example, φ51, which is greater than φ45, corresponds to DN50 ； The second interpretation: for example, φ51, which is smaller than φ57, corresponds to DN40. The key lies in this catalog of special equipment; it would be good if it could be revised to read “pipes with an outer diameter of 50 mm or more”. ” The ultimate question is whether a steam pipeline with a pressure of 0.5 MPa and dimensions of φ51*3 counts as a special equipment ? ?
An outer diameter of φ51 is the standard for thin-walled sanitary pipes; it should be 2\" or DN50.
No! Check the pipe engineering specification sheet!
For pipes with a nominal diameter of 50 mm or more, I prefer 51*3; it does not fall into this category. .
DN50: Outer diameter of steel pipe Series A: 60.3 Series B: 57
DN50 refers to the nominal diameter, that is, the inner diameter through which fluid flows. The specific outer diameter values are specified in relevant standards, and these values must be looked up in the pipe size selection tables (SH3405-2012 or HGT20553-2011). For DN50, the available outer diameters according to the standards are 60.3 for Series I and 57 for Series II
Pipes are divided into two categories: Pipe and Tube. Pipes have their size series expressed in terms of nominal diameter, while Tubes generally have their size specifications indicated by outer diameter, without the concept of nominal diameter. For example: In ISO 2037, the outer diameter of a 2” pipe is 51 ； In ASME A270-3a, the outer diameter of a 2” pipe is 50.8. The Ф51 pipe mentioned in this article belongs to the Tube type; if applied to the catalog of special equipment, it can only be considered that Ф51 = 2” = DN50, and it falls under the category of pressure pipes.
All the points mentioned upstairs are correct; the problem lies in the standards