DN and φ indicate the differences between pipes
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DN and φ are used to denote the differences between pipes. Having seen many people discussing the issue of DN, I would like to share my insights based on my work experience; I hope everyone can offer their corrections. Generally speaking, pipes are divided into two main categories: welded steel pipes and seamless steel pipes. 1. Welded steel pipes are denoted by DN or inches, and this value represents the nominal diameter (it is neither the outer diameter nor the inner diameter; it is a conceptual nominal value, with different inner and outer diameters depending on the wall thickness). Depending on their intended use, such pipes can be classified as structural pipes or pipes for transporting fluids. When purchasing welded steel pipes in practice, attention should be paid to the pipe connection method you choose (welding or threaded connection). For welded steel pipes of DN150 and below, for pipes of the same specification, there are generally two outer diameters: one larger (for imperial pipes, such as an outer diameter of 114) and one smaller (for metric pipes, such as an outer diameter of 108). Welding allows the use of metric pipes (such as those with an outer diameter of 108), but when using threaded connections (which require threaded fittings), metric pipes must be used (such as those with an outer diameter of 114). For seamless steel pipes of DN200 and above, there is only one specification for the outer diameter in the commonly used series. Ordinary galvanized steel pipes use threaded connections, so their outer diameters correspond to the larger type of pipes (imperial pipes). Once the pipeline is determined, when selecting flanges, in addition to specifying the pressure rating, it is also necessary to specify the requirements for the inner diameter of the flange. 2. For seamless steel tubes, the outer diameter is denoted by φ. Of course, depending on their intended use, there are also structural tubes (such as 8162) and fluid-handling tubes (such as 8163\3087). When you choose a seamless steel pipe of a certain specification, its outer diameter remains constant regardless of the wall thickness.
I feel that for seamless steel pipes here, it seems like they also use DN as a parameter, considering it to be the inner diameter. I’m not sure why…… Could someone with more knowledge please explain?
Nominal diameter (DN, also known as nominal bore) is the standard diameter for various pipes and piping fittings. Pipes and piping fittings of the same nominal diameter can be connected to each other, offering interchangeability. It is not the actual outer or inner diameter of the pipe, although its value is relatively close to or equal to the pipe’s inner diameter ； To standardize the connection dimensions of pipes and fittings, nominal diameter (also known as nominal bore or nominal size) is used. For example, welded steel pipes can be classified by thickness into thin-walled pipes, ordinary pipes, and thick-walled pipes. Its nominal diameter is not the outer diameter nor the inner diameter, but rather a nominal size that is close to the inner diameter of ordinary steel pipes. For each nominal diameter, there is a corresponding outer diameter, while the inner diameter value varies depending on the thickness. The nominal diameter can be expressed in metric millimeters or imperial inches. φ is used to denote the outer diameter of steel pipes; some domestic steel pipe manufacturers use φ multiplied by the wall thickness to indicate it
Could some expert please explain what DG means? Thank you
DN is the nominal diameter, also known as the mean outside diameter. DN stands for nominal diameter, and its unit is millimeters; however, the nominal diameter is a nominal value, not an absolute actual size. For example, the actual inner diameter of DN200 is not necessarily exactly 200. But the outer diameter is generally the same, at 219. DN50 corresponds to 57. However, the inner diameter varies depending on the thickness of the pipe.] Φ refers to the outer diameter of the pipe; generally, DN200 should be written as Φ219x7 (8, etc.), with the wall thickness also specified. For more detailed information, please refer to the mechanical design manual.
DG is the same as DN; it was an usage from a few years ago. DN denotes the nominal diameter, while φ represents the outer diameter of the steel pipe. Steel pipes in China come in different outer diameters, and it is essential to specify both the outer diameter and wall thickness when placing an order
Usually, DN denotes the nominal diameter, while Φ refers to the outer diameter of the pipe.
Thank you all for your explanations; they helped me resolve my doubts regarding material procurement.
Φ refers to the outer diameter of the pipe; steel mills use this value to indicate the specifications of the pipe. The outer diameter of the pipe multiplied by its wall thickness gives an indication that facilitates the selection of materials for piping systems.
DN=Dg, PN=10Pg; for example, the valve DN150PN10 is equivalent to the valve Dg150Pg100.
For pipes smaller than DN15, the specification is given as outer diameter X wall thickness
Generally, DN stands for nominal diameter, which is a value close to the inner diameter of the pipe; it is an approximate figure. The standard sizes are usually fixed at 10, 15, 20, 25, 40, 50, 80, 100, 150, 200, and 250. . . . . Φ refers to the outer diameter of the tube. It is an exact value. For example, for a DN100 pipe, the actual outer diameter is 110 mm, and there are various wall thicknesses, but they are all considered DN100 pipes. When denoted by Φ, it is always ΦXXX*yy; here, XXX represents the outer diameter and yy represents the wall thickness, both being exact values.
Piping discipline: dg=DN; dg is the original notation method, while DN is the current notation method. Equipment parameters: Dg = the nominal diameter of the equipment, Vg = the nominal volume of the equipment. :)
In fields such as water supply and drainage, the symbol Φ is often used; whereas in industries like petrochemicals, pipes are generally indicated using DN or inches
Generally, DN denotes the nominal diameter, while Φ refers to the outer diameter of the pipe.!!!
What are the standards for purchasing pipes in China?
Simply put, DN represents the nominal diameter, while Φ refers to the outer diameter of the pipe!
DN is the nominal diameter; I know that. The other one is the outer diameter of the pipe – thanks for explaining
As I understand it, whether it’s welded steel pipes or seamless steel pipes, within the same system, as long as the nominal diameter is fixed, their outer diameter remains the same. When making purchases, you must determine whether you need pipes with a larger outer diameter or a smaller one, so that the fittings you buy will be compatible with them; it’s important to specify the standard clearly. Also, when purchasing, choose reputable manufacturers of pipe fittings – if you tell them the standard, the products they send you will generally be fine. If you opt for small, unestablished manufacturers in order to save money, sometimes even after explaining things to them for a long time they still won’t understand what you need. Hehe
DN refers to the nominal diameter, while Φ denotes the outer diameter of the pipe; the nominal diameter was previously denoted as DG.
Who knows which pipe diameters are included in a DN series? For example, how many pipe diameters are included in DN50?