Home / Flange / What is the difference between the diameter DN and De?
Stainless Steel Flanges

What is the difference between the diameter DN and De?



DN refers to the nominal diameter of the pipe. Note: This is neither the outer diameter nor the inner diameter; it should be related to the imperial unit in the initial development of the pipeline engineering; it is usually used to describe the galvanized steel pipe. Its correspondence with the imperial units is as follows: 

  • 1 1/4 inch tube: 1 1/4 inch: DN32;
  • 1/2 Inch tube: 1 1/2 inch: DN40; 
  • 2 inch tube: 2 inches: DN50;
  • 3 inch tube: 3 inches: DN80 (also marked DN75 in many places);
  • 4 inch tube: 4 inches: DN100;


De mainly refers to the outer diameter of the pipe, generally marked with De, and needs to be marked as the outer diameter X wall thickness; mainly used for description: seamless steel pipe, PVC and other plastic pipes, and other pipes requiring a 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
  • DN32 De40×4mm
  • DN40 De50×4mm

We are accustomed to using DN to label welded steel pipes. It is rarely used to mark pipes without involving wall thickness; however, labeling plastic pipes is another matter; it is related to industry habits, during actual construction. The pipes we call 20, 25, and 32, etc., refer to De, not to DN. There is a difference between them. 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 are separated by a gasket to avoid contact.
The respective ranges of De, DN, d, and ф! De– PPR, PE pipe, polypropylene pipe Outer diameter DN– Polyethylene (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe nominal diameter a
D– Nominal diameter of concrete pipe ф– Nominal diameter of seamless steel pipe, its specification is, for example, ф100:108 × 4

  • DN15-ф22mm, DN20-ф27mm,
  • DN25-ф34mm, DN32-ф42mm,
  • DN40-ф48mm, DN50-ф60mm,
  • DN65-ф76 (73) mm, DN80-ф89mm,
  • DN100-ф114mm, DN125-ф140mm,
  • DN150-ф168mm, DN200-ф219mm,
  • DN250-ф273mm, DN300-ф324mm,
  • DN350-ф360mm, DN400-ф406mm,
  • DN450-ф457mm, DN500-ф508mm,
  • DN600-ф610mm, DN15-ф18mm,
  • DN20-ф25mm, DN25-ф32mm,
  • DN32-ф38mm, DN40-ф45mm,
  • DN50-ф57mm, DN65-ф73mm,
  • DN80-ф89mm, DN100-ф108mm,
  • DN125-ф133mm, DN150-ф159mm,
  • DN200-ф219mm, DN250-ф273mm,
  • DN300-ф325mm, DN350-ф377mm,
  • DN400-ф426mm, DN450-ф480mm,
  • DN500-ф530mm, DN600-ф630mm.

Source: China Stainless Steel Pipelines Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

About www.nctv.net

www.yaang.com provide a wide range of steel products as Steel pipe, Steel pipes and seamless pipes, Alloy pipes, Pipe fittings, Composite steel pipe used in the industry, construction etc.

Leave a Reply

Your email address will not be published. Required fields are marked *