The nominal diameter, also known as the mean outside diameter. Refers to the standardized diameter series of containers, pipes and their accessories. The use of the nominal diameter facilitates the standardization of parts and components, as well as the design, manufacture, repair and management, and reduces manufacturing costs. For containers, the nominal diameter is indicated by the inner diameter; for pipes, it is represented by a dimension smaller than the outer diameter and larger than the inner diameter. Corresponding to a nominal diameter of the pipe, the outer diameter is a certain value, and the inner diameter varies with the wall thickness.
The nominal diameter is indicated by the letter "DN" followed by a numeric sign. As the glyph, the symbol is indicated by the dimension in millimeters. The nominal diameter is the nominal of pipes such as cast iron pipes, seamed steel pipes, and concrete pipes, but seamless steel pipes are not used in this way. For example, DN50, a pipe with a nominal diameter of 50 mm. The relationship between inch NB (inch) and nominal diameter DN (mm) and outer diameter OD (mm) is as follows:
NB(inch)-----DN(mm)------OD(mm)
1/2--------------15 ----------21.3
3/4--------------20 ----------26.7
1-------------- 25 ------------33.4
1 1/4 ------------ 32---------42.2
1 1/2------------40 ----------48.3
2-------------- 50 ------------60.3
2 1/2--------- 65 ------------73.0
3-------------- 80 ------------88.9
4-------------100 ------------114.3
5-------------125 ------------139.8
6-------------150 ------------168.3
8-------------200-------------219.1
