Nominal diameter size:

DN20 HDPE Pipe: The outer diameter is 20mm

DN25 HDPE Pipe: The outer diameter is 25mm

DN32 HDPE Pipe: The outer diameter is 32mm

DN40 HDPE Pipe: The outer diameter is 40mm

DN50 HDPE Pipe: The outer diameter is 50mm

... (By analogy, there are DN63, DN75, DN90, DN110, DN125, DN140, DN160, DN180, DN200, DN225, DN250, DN315, DN355, DN400, DN450, DN500, DN630, etc., with the outer diameter gradually increasing).

Donghong Pipe industry's HDPE pipe, nominal diameter range is PN20-1200mm.
What is diameter size?

The nominal outside diameter of the pipe is generally expressed by dn, which refers to the specified value of the outside diameter of the pipe or pipe fitting socket, such as the nominal outside diameter of the dn315mm pipe is 315mm.

We use a "π" ruler to measure the average outer diameter dem of the pipe, and the average outer diameter has the allowable deviation. For example, the allowable average outer diameter deviation of dn315mm pipe in GB/T13663.2-2018 is 315-316.9mm. Then the minimum average outer diameter dem, min, and maximum average inner diameter dem measured by us are obtained. max in this range is qualified for average outside diameter.

The average outside diameter is often confused with the outside diameter at any point, as illustrated by the legend :(A is the smallest outside diameter at any point, B is the average outside diameter measured using the "π" ruler).

The minimum outer diameter A point value at any point may be less than the nominal outer diameter, because the ellipticity of the pipe is caused, but it does not mean that the pipe is unqualified.

The difference between the maximum outside diameter C at any point and the minimum outside diameter A at any point is the non-roundness (also known as ellipticity, max-min), and the non-roundness should be measured at the production site (as described in the standard). The non-roundness is still due to the cause of gravity, regardless of any thickness and any material of the pipe will occur elliptic trend, but in the plastic pipe performance is more prominent, but does not mean that the product is unqualified.

Occasionally, the pipe often appears in the end of the "shrinkage" phenomenon, especially in the thin wall and large diameter thick wall is obvious, shrinkage in the standard is clearly stated, that is, the average outer diameter of the pipe should be measured at least 1.5dn or 300mm away from the pipe end (take a small value), but the most shrinkage D can not be less than 98.5% of the measurement point.

For example, for dn1000mm PE pipe, the measured average outer diameter should be set as position B 300mm (1.5*1000=1500mm > 300mm) from the end of the pipe, assuming that the measured average outer diameter of position B is 1003.0mm (1000-1009.0mm qualified). The average outer diameter of the "shrink" position D of the tube end can not be less than 1003*0.985=987.955mm.

Application size:

DN20: Suitable for small water supply systems, irrigation systems and industrial pipelines.

DN50: Suitable for small and medium-sized water supply systems, petrochemical pipelines and heating pipelines.

DN110: Suitable for medium water supply system, chemical pipeline and gas pipeline.

DN250: Suitable for large water supply systems, sewage treatment and industrial transmission pipelines.

DN500: Suitable for very large water supply systems, drainage systems and submarine pipelines.

In addition, I will introduce the knowledge of nominal wall thickness and SDR, so that you can better estimate the size of the Hdpe pipe.

The nominal wall thickness of the pipe is generally expressed by en, which refers to the specified value of the wall thickness of the pipe, equal to the minimum allowable wall thickness ey, min, there is no average wall thickness of this concept, and this concept is nonsense (the design pressure of the plastic pipe is the minimum point wall thickness ,and the thickest point has no positive impact on the pipe pressure).

The SDR value of the pipe is also called the standard size ratio, the SDR value is the division of the outer diameter of the pipe and the wall thickness, round to an integer, this value is often used in the gas PE pipe (the gas standard has no nominal pressure), that is

SDR= Nominal outside diameter dn/ nominal wall thickness en

Sometimes the material grade and SDR value of the pipe are commonly used to indicate the selection of the pipe.

PE100 grade, dn110mm, SDR11 pipe is dn110*10.0mm*1.6MPa PE100 grade pipe.