De, DN, D, d, pipe diameter designation

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This post was last edited by “Hasty Passerby” on December 20, 2018, at 16:15. The meanings of the notations De, DN, D, d, and Φ for pipe diameters: 1. DN (Nominal Diameter) refers to the nominal diameter of a pipe; it is the average value of the outer and inner diameters. The value of DN = the value of De – 0.5 * wall thickness. Note: This is neither the outer diameter nor the inner diameter. Pipes such as water and gas transmission pipes (galvanized or ungalvanized steel pipes), cast iron pipes, steel-plastic composite pipes, and polyvinyl chloride (PVC) pipes should be marked with the nominal diameter “DN” (such as DN15, DN50). 2. De (External Diameter) refers to the outer diameter of a pipe. For PPR, PE, and polypropylene pipes, which are generally indicated using “De”, it is necessary to specify their dimensions in the format of outer diameter * wall thickness; for example, De25×3. 3. D generally refers to the inner diameter of the pipe. 4. d generally refers to the inner diameter of a concrete pipe. For pipes such as reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, and cylinder tile pipes, the pipe diameter should be indicated by the inner diameter d (e.g., d230, d380, etc.). 5. Φ represents the diameter of a ordinary circle ； It can also indicate the outer diameter of the pipe, but in that case the wall thickness should be multiplied by it. For example: Φ25×3 indicates a pipe with an outer diameter of 25 mm and a wall thickness of 3 mm. For seamless steel pipes or non-ferrous metal pipes, “outer diameter × wall thickness” should be indicated. For example, Φ108×4; the Φ can be omitted. Some steel pipe standards in China, ISO, and Japan use wall thickness dimensions to denote the steel pipe wall thickness series. The notation for the specifications of this type of steel pipe is outer diameter × wall thickness. For example, Φ60.5×3.8. Methods of expressing pipe diameter: 1. For pipes such as steel pipes for water and gas transmission (galvanized or ungalvanized), cast iron pipes, and plastic pipes, the nominal diameter “DN” should be indicated (e.g., DN15, DN50). 2. For pipes such as seamless steel pipes, welded steel pipes (with straight or spiral seams), copper pipes, and stainless steel pipes, the diameter should be indicated as outer diameter × wall thickness (e.g., De108×4, De159×4.5, etc.) ； For seamless steel pipes or non-ferrous metal pipes, “outer diameter × wall thickness” should be indicated. For example, Φ108×4; the “ф” can be omitted. 3. For pipes made of reinforced concrete (or concrete), clay pipes, acid-resistant ceramic pipes, earthenware pipes, etc., the pipe diameter should be expressed as the inner diameter d (e.g., d230, d380, etc.). 4. For plastic pipes, the pipe diameter should be indicated in accordance with the methods specified in the product standards. 5. When the pipe diameter is specified using the nominal diameter DN in the design, there should be a table linking the nominal diameter DN to the corresponding product specifications.