Issues with seamless steel pipes DN?
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Issues related to the DN of seamless steel pipes: 1. It is said that the nominal diameter DN refers to the inner diameter of the pipe ； It is also said that the nominal diameter DN is a certain value between the inner and outer diameters of the pipe. Which one is correct, and what standards should be followed? 2. For this table, first look at the outer diameter of the DN15 A series and the outer diameter of the B series. If the outer diameter remains constant while the wall thickness varies according to the different grades specified, then the inner diameter will also change. Is this still the same issue mentioned earlier? Solve?
The nominal diameter mentioned by DN is neither the outer diameter nor the inner diameter; it is simply a general term used for simplifying calculations in engineering. The detailed outer and inner diameters need to be looked up based on the specific pipeline series, and nominal diameter DN cannot be used for the detailed calculations.
Nominal diameter, also known as mean outside diameter. It refers to the standard diameter after standardization, denoted by DN, in millimeters. \"Definition and Selection of Pipe Fittings DN (Nominal Size)\” GB/T 1047-2005 defines DN as a size designation in the form of a combination of letters and numbers used for pipe system fittings. It consists of the letters DN followed by a dimensionless integer, which is directly related to characteristic dimensions such as the bore or outer diameter of the end fitting (expressed in mm). Note 1: Unless otherwise specified in the relevant standards, the digits following the letter DN do not represent measurement values and cannot be used for calculation purposes. Note 2: For those standards that use the DN designation system, the relationship between DN and the dimensions of the pipe component should be specified, such as DN/OD or DN/ID.
The 3rd floor is the correct answer. It’s admirable that you’ve been figuring things out step by step since the start of school
DN has no direct relationship with the outer and inner diameters of the pipe, but generally speaking, DN is related to the outer diameter. The DN size of a certain series determines its outer diameter; even if the PN rating increases, the outer diameter remains unchanged. From this perspective, chemical and petrochemical pipes are outer-diameter pipes. The high-parameter tubes for electricity are related to the inner diameter; as the PN rating increases, the inner diameter changes little while the outer diameter increases. So the boiler drawings will show that the main feedwater connection of DN250 is D273, while the main steam connection of DN250 is D325. I once tried to have a valve with a power rating of DN250 designed by a design institute while working in a chemical plant; when it arrived, I found it to be too small – for chemical applications, DN300 should have been the appropriate size. When dealing with pipelines related to electricity generation, one needs to be careful; electricity does not follow the same rules as those applied in the petrochemical industry. Instead, the dimensions for electricity-related pipelines are determined according to GD2000 or GD2016.
What was said on the third floor is right – the experts are among the common people
Why bother over it, the owner? It’s enough to know the nominal diameter