What is DN (Dimension Nominell) & Why Does DN32 Break the Trend?

[TSN79]

A lot of the time I see dimensions of pipes and fittings (mostly steel) written as "DNxx" where xx is a number I've seen from 15 to several hundered, but usually pretty round figures such as 20, 25, 40, 100, 150 and so on. Strangely, between 25 and 40 comes 32 which suddenly totally breaks with the trend.

I wonder what these dimensions are all about. Steel pipes don't usually have these dimensions, they are often much more spesific like 76.1, 114,3 mm etc.

Is DN an approximate dimension used for valves and such? Is it short for Dimension Nominell or something...? And what is up with that DN32 breaking with the "round figures" ??

 

[Q_Goest]

Is DN an approximate dimension used for valves and such? Is it short for Dimension Nominell or something...?

Yes, that's exactly right. Even in Europe, it seems the same pipe dimensions are used. It stands forhttp://www.engineeringtoolbox.com/nps-nominal-pipe-sizes-d_45.html"

And what is up with that DN32 breaking with the "round figures" ??

That's just inch and a quarter pipe in millimeters. Kinda weird I suppose, but it seems the world has standardized on this given set of dimensions for pipe.

Note that the dimension is strictly a nominal one. For example, there is nothing you can measure which is exactly 1" on a 1 inch (DN25) pipe. The OD is 1.315", and depending on the schedule wall thickness, the ID is not particularly close to 1" either.

 

[ravenprp]

DN stands for Dimension Nominell, which is a nominal size used to designate the size of pipes and fittings. This system is commonly used in Europe and is based on the internal diameter of the pipe in millimeters. So, for example, DN32 would have an internal diameter of 32 millimeters.

The reason why DN32 breaks the trend of round numbers is because it is based on the metric system, where measurements are more precise and exact. In the imperial system, measurements are often rounded to the nearest inch or foot, which may result in more "round" numbers. However, in the metric system, measurements are more precise and therefore, may not always result in a round number.

DN32 is not specific to valves, but is used for all types of pipes and fittings. It is a standard size used in the industry and is important for ensuring compatibility and consistency in plumbing and construction projects.

In summary, DN (Dimension Nominell) is a system used to designate the size of pipes and fittings based on their internal diameter in millimeters. DN32 breaks the trend of round numbers due to the precision of the metric system. It is an important standard size used in the industry for consistency and compatibility.