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The difference between the diameter Dn, De, D, d, Φ

Views:13     Author:Site Editor     Publish Time: 2019-08-29      Origin:Site

The diameter of the tube can be divided into outer diameter (De), inner diameter (D), and nominal diameter (DN).

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DN is the nominal diameter of the pipe

Note: This is neither the outer diameter nor the inner diameter, but the average of the outer diameter and the inner diameter, called the average inner diameter.

When the design uses the nominal diameter DN to indicate the pipe diameter, there should be a comparison of the nominal diameter DN and the corresponding product specifications.

Pipes such as 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 shall be marked with the nominal diameter "DN" (eg DN15.DN20).


De mainly refers to the outer diameter of the pipe

Generally marked with De, all need to be marked as the outer diameter X wall thickness;

Mainly used for description: seamless steel pipes, PVC and other plastic pipes, and other pipes that require clear wall thickness.

Take galvanized welded steel pipe as an example. The two methods of marking with DN and De are as follows:

DN20 De25×2.5mm

DN25 De32×3mm

We are accustomed to using DN to label welded steel pipes. It is rarely used to label pipes without involving wall thickness; however, labeling plastic pipes is another matter; it is related to industry habits, during actual construction. The 20, 25, 32 and other pipes that we simply call refer to De, not to DN. Here is a difference. It is easy to cause losses in the procurement and construction process without knowing it.

The connection of the two pipe materials is nothing more than: threaded connection and flange connection. Other connections are used sparingly.

Both the galvanized steel pipe and the PPR pipe can be connected by the above two types, but the pipe thread of less than 50 is more convenient, and the flange of more than 50 is relatively reliable.

Note: If the metal pipes of two different materials are connected, it is necessary to consider whether the primary battery reaction will occur, otherwise the corrosion speed of the active metal material pipe will be accelerated. It is best to use flange connection and use rubber gasket type insulation material to The metal is separated, including the bolts, which are separated by gaskets to avoid contact.


D generally refers to the inner diameter of the pipe

d indicates the inner diameter of the concrete pipe

Φ represents the diameter of a common circle

Φ can also indicate the outer diameter of the pipe, but at this time it should be multiplied by the wall thickness.

For example: Φ25×3, which means 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” shall be marked.

Such as: Φ107 × 4, where Φ can be omitted.

Some steel pipes in China, ISO and Japan are marked with wall thickness to indicate the wall thickness of the steel pipe. For such steel pipes, the method is expressed as pipe outer diameter x wall thickness.

Such as: Φ60.5×3.8


The respective ranges of De, DN, d, and ф

De--PPR, PE pipe, polypropylene pipe

DN--polyethylene (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe nominal diameter

d--the nominal diameter of the concrete pipe

ф--Seamless pipe or non-ferrous metal pipe should be marked "outer diameter × wall thickness"


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