What is the difference between the tolerance diameter and diameter of a steel pipe?

Is there a saying for tolerance diameter? It should be the nominal diameter, and the nominal diameter is also called the nominal diameter or the average diameter.

The diameter of the tube can be divided into outer diameter, inner diameter, and nominal diameter. The outer diameter of the pipe is represented by the letter D, followed by the size and wall thickness of the outer diameter, for example, the outer diameter of the seamless steel pipe with an outer diameter of 108, the wall thickness is 5mm, represented by D108*5, the plastic pipe is also represented by the outer diameter, such as DE63, and others such as reinforced concrete pipes, cast iron pipes, galvanized steel pipes, etc. are represented by DN, and the nominal diameter is generally expressed in the design drawings, and the nominal diameter is a standard artificially specified for the convenience of design, manufacturing and maintenance, also called the nominal diameter, It is the specification name of the pipe (or pipe fitting). The nominal diameter of the tube is not equal to its inner diameter and outer diameter, for example:

There are several kinds of seamless steel pipes with a nominal diameter of 100mm, such as *5, 108 is the outer diameter of the pipe, and 5 represents the wall thickness of the pipe, therefore, the inner diameter of the steel pipe is (108-5-5) 98mm, but it is not completely equal to the difference between the outer diameter of the steel pipe minus twice the wall thickness, it can also be said that the nominal diameter is close to the inner diameter, but it is not equal to the inner diameter of a pipe diameter specification name, so the nominal diameter should be used in the design drawings, the purpose is to determine the pipe, pipe fittings, valves, Flange, gasket and other structural dimensions and connection dimensions, the nominal diameter is represented by the symbol DN, if the outer diameter is expressed in the design drawings, a pipe specification comparison table should also be made to indicate the nominal diameter and wall thickness of a certain pipeline.

The former has an inner diameter and the latter has an outer diameter.

The comparison table between the nominal diameter and the outer diameter of the seamless steel pipe is as follows:

The production process of general seamless steel pipe is divided into two types: cold-rolled and hot-rolled, and the appearance of cold-rolled seamless steel pipe is shorter than that of hot-rolled seamless steel pipe, and the wall thickness of cold-rolled seamless steel pipe is generally smaller than that of hot-rolled seamless steel pipe. But the surface looks brighter than the thick-walled seamless steel pipe headrock. There isn't too much roughness on the surface and not too many burrs on the caliber.

The maximum nominal diameter of cold-rolled pipes is 200 mm, and the maximum nominal diameter of hot-rolled pipes is 600 mm.

In fact, in the field of engineering, there is no complete comparison between the nominal diameter and the outer diameter of the pipeline, and the conversion of the outer diameter and the nominal diameter basically depends on experience.

Roughly the nominal diameter is approximately equal to the inner diameter (outer diameter minus two skin thicknesses).

But it's not exactly equal, it's about the same, just round it up. For example, the outer diameter of 108*7 is 108, and its nominal diameter is 100; Another example is 32*, the outer diameter is 32, and the nominal diameter should be 25. By analogy, we can get the correspondence between the outer diameter and the nominal diameter.

The nominal diameter of a steel pipe (DN) refers to the standard size of the pipe, which is usually measured in millimeters (mm). The nominal wall thickness (WT) of the tube corresponds to the nominal wall thickness (WT), which is also usually measured in millimeters.

The outside diameter (OD) of a steel pipe refers to the size of the outer diameter of the steel pipe, which is usually also measured in millimeters. The pre-trap corresponding to the outer diameter is the wall thickness (W) of the tube, which is also usually measured in millimeters.

In the standard specifications of steel pipes, the nominal diameter and outer diameter correspond to each other, and the comparison between them usually varies according to the material and use scenario of the steel pipe. For example, the nominal diameter and outer diameter comparison table of commonly used carbon steel pipe and stainless steel pipe are as follows:

Nominal diameter (dn) |Outer Diameter (OD) |

It should be noted that the nominal diameter and outer diameter of the steel pipe are only standard specifications, and there may be certain deviations in the actual production of the steel pipe, so it is necessary to make actual measurements and select the appropriate pipe according to the actual situation when selecting and using the steel pipe.

1. Water gas.

For conveying steel pipes (galvanized or non-galvanized), cast iron pipes and other pipes, the pipe diameter should be expressed by the nominal diameter DN;

2. Seamless steel pipe.

Welded steel pipes (straight or spiral seams), copper pipes, stainless steel pipes.

and other pipes, the diameter of the pipe should be expressed by the outer diameter and wall thickness;

3. Reinforced concrete.

or concrete) pipes, clay pipes, acid-resistant ceramic pipes, cylinder tile pipes and other pipes, the pipe diameter should be represented by the inner diameter d;

4. For plastic pipes, the diameter of the pipe should be expressed according to the method of product standards;

5. When the design is expressed by the nominal diameter DN, there should be a comparison table between the nominal diameter DN and the corresponding product specifications, and the specifications of the hard PVC pipe for building drainage are represented by DE (nominal outer diameter) E (nominal wall thickness).

In the specification table of the steel pipe, the outer diameter of the steel pipe + the thickness of the pipe wall + the theoretical weight per meter.

Dear, it's a pleasure to serve you, [smile] I'll answer for you below. The gauge diameter of the round steel pipe refers to the outer diameter. The most commonly used expression for pipes is the outer diameter and wall thickness.

For example: the outer diameter of 80mm, the wall thickness of the steel pipe, generally expressed as: 80, wherein, " represents the diameter, outer diameter; "t" indicates wall thickness.

The specification depends on the specific situation, if the pipe material is concrete and Kia prefabricated or on-site pouring materials, the pipe wall is thicker, at this time, the average of the outer diameter and the inner diameter can not be taken as the pipe diameter value, in this case, the inner diameter and outer diameter need to be indicated, and the pipe diameter of Chen Wei cannot be blurred.

I hope mine can help you and wish you a happy life [Sakura].