Tube will be different nominal pressure according to different use of the environment and pressure , the same nominal diameter of the pipe may have a different diameter, would like to clarify the conditions of use and the nominal pressure PN, as well as temperature - pressure rating (Pressure / temperature Ratings) .Also, different materials at the same nominal pressure tube may also have a different diameter

 

Nominal diameter (nominal diameter), also known as the average diameter (mean outside diameter).

This is because of the thin metal tube wall, tube outer diameter and inner diameter are almost the same, so take average of the tube outer diameter and inner diameter as tube diameter call.

Because units are metric (mm) and imperial (inch) distinction, so there is the following method call.

 

1 in metric (mm) as a benchmark, known as DN (metric unit)

(2) to Imperial (inch) as the base, called NB (inch unit)

3. DN (nominal diameter)

NB (nominal bore)

OD (outside diameter)

4 [Example]

Galvanized steel pipe DN50, sch 20

Galvanized steel NB2 ", sch 20

5 diameter and DN, NB is as follows:

------ DN (mm) -------- NB (inch) ------- OD (mm)

15----------- --- 1/2--------------21.3

20----------- --- 3/4  --------------26.7

25----------- --- 1 ---------------- 33.4

32----------- --- 1 1/4 ----------- 42.2

40----------- --- 1 1/2  -----------48.3

50----------- --- 2 ---------------- 60.3

65----------- --- 2 1/2 ----------- 73.0

80----------- --- 3 ---------------- 88.9

100----------- --- 4 ------------ 114.3

125----------- --- 5 ------------ 139.8

150----------- --- 6 ------------ 168.3

200----------- ---- 8 ------------ 219.1