The meaning and difference of pipe diameters Dn, De, D, d, and Φ

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 early development of pipeline engineering and the imperial units; it is usually used to describe galvanized steel pipes, and its corresponding relationship with the imperial units is as follows:

4-inch pipe: 4/8 inch: DN15;

6-inch pipe: 6/8 inch: DN20;

1-inch pipe: 1 inch: DN25;

2-inch pipe: 1 and 1/4 inch: DN32;

1/2-inch pipe: 1 and 1/2 inch: DN40;

2-inch pipe: 2 inch: DN50;

3-inch pipe: 3 inch: DN80 (also marked as DN75 in many places);

4-inch pipe: 4 inch: DN100;

De mainly refers to the outer diameter of the pipe

Generally, those marked with De need to be marked in the form of outer diameter x wall thickness;

Mainly used to describe: seamless steel pipes, plastic pipes such as PVC, and other pipes that require clear wall thickness.

Take galvanized welded steel pipe as an example, the two marking methods of DN and De are as follows:

DN20 De25×2.5mm

DN25 De32×3mm

DN32 De40×4mm

DN40 De50×4mm

And so on… We are used to using DN to mark welded steel pipes, and rarely use De to mark pipes without involving wall thickness; But marking plastic pipes is another matter; it is still related to industry habits. In the actual construction process, the pipes we simply call 20, 25, 32, etc. all refer to De, not DN, which is a difference in specifications. If you don’t understand it, it is easy to cause losses during procurement and construction.

The connection methods of the two pipe materials are nothing more than: threaded connection and flange connection. Other connection methods are rarely used.

Galvanized steel pipes and PPR pipes can use the above two connections, but it is more convenient to use threads for pipes less than 50, and it is more reliable to use flanges for pipes greater than 50.

Note: If two metal pipes of different materials are connected, it is necessary to consider whether a galvanic reaction will occur, otherwise it will accelerate the corrosion rate of the active metal material pipe. It is best to use flange connection and use insulating materials such as rubber gaskets to separate the two metals, including bolts, to avoid contact.

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

De– Outer diameter of PPR, PE pipe, polypropylene pipe

DN– Nominal diameter of polyethylene (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe

d– Nominal diameter of concrete pipe

ф– Nominal diameter of seamless steel pipe, its specifications are, such as 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.