Comparison Table of Nominal Diameter (DN) And Pipe Size

For the first time contact with the nominal diameter of the pipe, the word is a bit unpredictable. In general, the diameter of the pipe can be divided into external diameter, internal diameter, nominal diameter.

The Meaning of De、DN、D、d、Φ
De (External Diameter) means pipe outside Diameter, PPR, pe pipe, polypropylene pipe, seamless steel pipe, welded steel pipe (straight or spiral seam) , copper pipe, stainless steel pipe and other pipe, Diameter should be outside Diameter wall thickness said (such as DE1084, de1594.5, etc.) ;

D generally refers to the inside diameter of the pipe.

d generally refers to the inner diameter of concrete pipe. Reinforced Concrete (or concrete) pipe, clay pipe, acid-resistant ceramic pipe, cylinder liner pipe and other pipe, pipe diameter d should be expressed (such as D230, D380, etc.) .

Φ represents the diameter of an ordinary circle or the outside diameter of a pipe, but this should be multiplied by the thickness of the wall. For example: 253, represents the outer diameter of 25 mm, wall thickness of 3mm pipe. For seamless steel or Non-ferrous metal pipes, “outer diameter wall thickness” shall be marked. For example, 1084 can be omitted. Some Chinese, ISO and Japanese Steel Pipe Standards Adopt The wall thickness dimension to express the steel pipe wall thickness series. The specification of this type of steel pipe is expressed as the outer diameter wall thickness of the pipe. For example, 60.53.8.

Outside Diameter of Pipe
At present, there are two series of steel tubes produced and used in our country: Series I and Series II, or series a and series B in the standard. Steel pipes of series I or a are “English pipes” , commonly known as “large outside diameter pipes” , while those of Series II or B are “metric pipes” , commonly known as “small outside diameter pipes” . The so-called “large diameter pipe and small diameter pipe” means: under the same nominal diameter of the pipe, pipe accessories (such as flanges, valves, pipe fittings and pipe filters, etc.) with steel pipe outside diameter size, the large size is called “big outside diameter” Tube; the small size is called “small outside diameter” tube. For example, the Flange with DN100 can choose the pipe with 114.3 mm outer diameter and the pipe with 108 mm outer diameter. The former is called “big outer diameter” pipe or “series I or series a” pipe The latter is called “small outside diameter” tube or “Series II or series B” Tube.

In the field of engineering, there is not a complete contrast between the nominal diameter and the external diameter of pipeline, and the conversion between the external diameter and the nominal diameter depends on experience. Roughly the nominal diameter is about equal to the inside diameter (outside diameter minus two skin thickness) but not exactly the same, roughly the same, take the whole line. For example, if 108 * 7 is 108, its nominal diameter is 100; if 32 * 4.5 is 32, its nominal diameter should be 25. By analogy, the relationship between the outer diameter and the nominal diameter can be obtained.

Pipe Size Inch-mm Reference Table

Comparison Table Of Pipe Diameter DN (nominal diameter) And Pipe External Diameter Ф(mm)

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