A. Different marking methods for various pipes

For water gas transmission steel pipes (galvanized or non-galvanized), cast iron pipes and other pipes, the pipe diameter should be indicated by the nominal diameter DN (such as DN15, DN50);

For seamless steel pipe, welded steel pipe (straight seam or spiral seam), copper pipe, stainless steel pipe and other pipes, the pipe diameter should be expressed as outer diameter D × wall thickness (such as D108 × 4, D159 × 4.5, etc.);

3 For pipes such as reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, and cylinder tile pipes, the pipe diameter should be indicated by the inner diameter d (such as d230, d380, etc.);

For plastic pipes, the pipe diameter should be expressed according to the product standard method;

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.

Relationship between B, DN, De, Dg

De is the diameter of the outer wall of the pipe

DN is the number obtained by subtracting half the thickness of the pipe wall from De. Dg is generally not used.

The pipe diameter should be in mm.

The expression of the pipe diameter should meet the following requirements:

For water gas transmission steel pipes (galvanized or non-galvanized), cast iron pipes and other pipes, the pipe diameter should be indicated by the nominal diameter DN;

For seamless steel pipe, welded steel pipe (straight seam or spiral seam), copper pipe, stainless steel pipe and other pipes, the pipe diameter should be expressed as outer diameter × wall thickness;

For pipes such as reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, and cylinder tile pipes, the pipe diameter should be indicated by the inner diameter d;

For plastic pipes, the pipe diameter should be expressed according to the product standard method;

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

The specifications of rigid PVC pipes for building drainage are expressed by de (nominal outer diameter) × e (nominal wall thickness) (GB 5836.1-92).

The specifications of polypropylene (PP) pipes for water supply are represented by de×e (nominal outer diameter×wall thickness) The marking of plastic pipes on engineering drawings

metric designation ( metric dimension size )

Expressed in DN, it is generally called "nominal size", which is neither the outer diameter of the pipe nor the inner diameter of the pipe. Is the average of the outer diameter and the inner diameter, we call the average inner diameter.

For example: Metric designation (mm dimension size) DN50 for a plastic pipe with an outer diameter of 63mm

ISO metric designation ( ISO metric dimension size )

The outer diameter of PVC pipe, ABS pipe is expressed in Da

Denote the outer diameter of the PP pipe and the PE pipe

For example: the metric designation of a plastic pipe with an outer diameter of 63mm ( mm dimension size )

Da63 for PVC pipe, ABS pipe.