What do the various sets of data in the specification table for DN seamless steel pipes mean, and under what conditions should each type be chosen?
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Look at the following passage: Additionally, there is the SH_T 3405-2017 standard for the size series of steel pipes used in the petrochemical industry. How should one choose the appropriate pipe? I’ve seen that in many cases, pipe outer diameters such as 57, 89, and 108 are used. I hope experts can provide an answer. The nominal diameter of a pipe is denoted by the symbol DN. If the outer diameter is used in the design drawings, a table indicating the specifications of each type of pipe should also be provided, showing its nominal diameter and wall thickness. The meaning of DN: it represents the nominal diameter of the pipe. The symbol Ф denotes the outer diameter of the pipe. For example, DN15-ф22mm, DN20-ф27mm, DN25-ф34mm, DN32-ф42mm, DN40-ф48mm, DN50-ф60mm, DN65-ф76(73)mm, DN80-ф89mm, DN100-ф114mm, DN125-ф140mm, DN150-ф168mm, DN200-ф219mm, DN250-ф273mm, DN300-ф324mm, DN350-ф360mm, DN400-ф406mm, DN450-ф457mm, DN500-ф508mm, DN600-ф610mm. There are also cases like DN15-ф18mm, DN20-ф25mm, DN25-ф32mm, DN32-ф38mm, DN40-ф45mm, DN50-ф57mm, DN65-ф73mm, DN80-ф89mm, DN100-ф108mm, DN125-ф133mm, DN150-ф159mm, DN200-ф219mm, DN250-ф273mm, DN300-ф325mm, DN350-ф377mm, DN400-ф426mm, DN450-ф480mm, DN500-ф530mm, DN600-ф630mm. For seamless steel pipes, the outer diameter is indicated by the letter D, followed by the actual outer diameter value and the wall thickness. For example, a seamless steel pipe with an outer diameter of 108 mm and a wall thickness of 5 mm is denoted as D108*5. Plastic pipes are also specified using their outer diameter, such as De63. Pipes made of reinforced concrete, cast iron, or galvanized steel, among others, are designated using DN. In design drawings, the nominal diameter is generally used for representation. It is a standard established artificially for the convenience of design, manufacturing, and maintenance. It differs from the nominal bore and serves as the specification name for pipes (or pipe fittings). The nominal diameter of a pipe is not equal to its inner or outer diameter. For example, for a seamless steel pipe with a nominal diameter of 100 MM, there are several variations such as 102*5 and 108*5. Here, 108 represents the outer diameter of the pipe, while 5 indicates the wall thickness. Thus, the inner diameter of this pipe is (108*5 – 5) = 98 MM. This value is not exactly equal to the outer diameter minus twice the wall thickness. In other words, the nominal diameter is a specification name for the pipe diameter that is close to, but not exactly equal to, the inner diameter. The nominal diameter is used in design drawings so that the structural and connection dimensions of pipes, fittings, valves, flanges, gaskets, etc., can be determined based on it. The nominal diameter is denoted by the symbol DN. If the outer diameter is used in the design drawings, a table showing the specifications of the pipes, including their nominal diameter and wall thickness, should also be provided.
DN refers to the nominal diameter, which is a commonly used term for ease of communication; Ф denotes the outer diameter of the pipe. Currently, the European and American standards are in use, and pipes with the same nominal diameter can have two different outer diameter specifications. For example, the outer diameter of a DN100 pipe is Ф108 according to European standards, while it is Ф114 according to American standards. The series of larger outer diameters under European standards corresponds to those under American standards. As for which one to choose, it depends on the pipe standard being used, and it has little impact on the design; it’s sufficient to specify this in the initial regulations
Thank you for your guidance; I think I understand now
DN is the nominal diameter – it’s just a name; there are various corresponding outer diameters and wall thicknesses. For example, metal pipes are usually denoted as φ108×4, φ114×5, φ114×2, all of which refer to the DN100 category, with different pressures associated with each. Additionally, metal pipes are indicated as outer diameter × wall thickness, while pipes made of other non-metallic materials are indicated as DN100, PN10/DN50, PN16.
We rarely use the outer diameters of 57, 89, and 108 these days; instead, we use 60, 89, 114 and similar values. The standards are different, right?