Taking galvanized welded steel pipe as an example, DN and De are marked as follows: DN 20 DE 25 X 2.5 MMDN 25 DE 32 X3 MDN 32 DE 40 X 4 MMDN 40 DE 50 X 4 mm, etc.
2, seamless steel pipe, welded steel pipe (straight seam or spiral seam), copper pipe, stainless steel pipe and other pipes, pipe diameter should be expressed by external diameter × wall thickness (such as de 108×4, de 159×4.5, etc. ); For seamless steel pipes or non-ferrous metal pipes, "outside diameter× wall thickness" shall be marked. For example, φ 108 x 4, φ can be omitted.
3, reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, cylinder tile pipes and other pipes, the pipe diameter should be expressed by the inner diameter d (such as d230, d380, etc.). ).
4, plastic pipes, pipe diameter should be expressed according to the product standard method; Generally, plastic pipes are expressed according to their outer diameters. In the actual construction process, we refer to pipes 20, 25 and 32 for short as De, not DN. There are differences in specifications here. Unclear can easily cause losses in the process of procurement and construction.
5. When the nominal diameter DN is used to represent the pipe diameter in the design, there should be a comparison table between the nominal diameter DN and the corresponding product specifications.
Extended data
1, DN refers to the nominal diameter of the pipeline, which is the average of the outer diameter and the inner diameter. DN value = DE value -0.5 * wall thickness. Note: This is neither the outside diameter nor the inside diameter. The nominal diameter "DN" (such as DN 15, DN50) shall be marked for water and gas transmission steel pipes (galvanized steel pipes or non-galvanized steel pipes), cast iron pipes, steel-plastic composite pipes and polyvinyl chloride (PVC) pipes.
2.De mainly refers to the outer diameter of pipes. Generally, the outer diameters of PPR, PE pipes and polypropylene pipes are marked with De, and they all need to be marked in the form of outer diameter x wall thickness, for example, De25 x 3.
3, d generally refers to the pipe diameter.
4. Inner diameter of concrete pipe. The pipe diameter of reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, cylindrical tile pipes, etc. shall be represented by the inner diameter D (such as d230, d380, etc.). );
5.φ represents the diameter of an ordinary circle; It can also represent the outside diameter of the pipeline, but it should be multiplied by the wall thickness afterwards. For example, φ25×3 indicates a pipe with an outer diameter of 25mm and a wall thickness of 3 mm. For seamless steel pipes or non-ferrous metal pipes, it should be marked with "outer diameter× wall thickness".
For example, φ 108 x 4, φ can be omitted. Some steel pipe standards in China, ISO and Japan indicate the series of steel pipe wall thickness by the wall thickness dimension. The specification of this steel pipe is expressed as pipe outer diameter x wall thickness. For example, φ60.5 x 3.8.
6.DN is the nominal diameter, that is, the nominal diameter.
7.De stands for outside diameter, which means outside diameter.
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