Where do NPS or DN stand for?
It is common to identify pipes by inches using NPS or “Nominal Pipe Size”. NPS is often incorrectly called National Pipe Size, due to confusion with national pipe thread (NPT). The metric equivalent is called DN or “diametre nominel”.
ISO
The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous piping used in buildings.
NPS
The use of NPS does not conform to American Standard pipe designations where the term NPS means “National Pipe Thread Straight”.
Based on the NPS and schedule of a pipe, the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M.
Process connections for the digital mass flow meter the MASS-VIEW and MASS-STREAM are: G 1/4" BSPP female and G 1/2" BSPP female, depending on model. We have adapter-sets for different tubing sizes: 3mm, 6mm, 8mm, 12mm and 1/2'', 1/4'', 1/8'' available.
The magnetic flow meter the MAG-VIEW has an inner tube with the following nominal diameters: DN 2, 3, 6, 7, 8, 10, 20, 25
| Diameter Nominal DN (mm) | Nominal Pipe Size (inches) | Outside diameter (OD) |
|---|---|---|
| 6 | 1/8 | 0.405 in (10.29 mm) |
| 8 | 1/4 | 0.540 in (13.72 mm) |
| 10 | 3/8 | 0.675 in (17.15 mm) |
| 15 | 1/2 | 0.840 in (21.34 mm) |
| 20 | 3/4 | 1.050 in (26.67 mm) |
| 25 | 1 | 1.315 in (33.40 mm) |
| 32 | 1 1⁄4 | 1.660 in (42.16 mm) |
| 40 | 1 ½ | 1.900 in (48.26 mm) |
| 50 | 2 | 2.375 in (60.33 mm) |
| 65 | 2 ½ | 2.875 in (73.02 mm) |
| 80 | 3 | 3.500 in (88.90 mm) |
| 100 | 4 | 4.500 in (114.30 mm) |
| 150 | 6 | 6.625 in (168.27 mm) |
| 200 | 8 | 8.625 in (219.08 mm) |
| 250 | 10 | 10.75 in (273.05 mm) |
DN and NPS in flow meter selection
Knowing the difference between DN and NPS helps to select a flow meter with the correct process connection. However, connection size is only one part of selecting the right flow measurement solution.
Engineers typically also consider:
- Gas or liquid medium
- Flow range
- Operating pressure and temperature
- Required accuracy
- Digital communication options
- Connection type and tubing size
Selecting the right flow meter for your DN or NPS connection
Knowing the correct DN or NPS size is an important first step when selecting a flow meter. However, choosing the right flow meter also depends on the medium, flow range, pressure, temperature and required measurement accuracy.
Mass Flow Online offers digital gas flow meters, liquid flow meters and flow controllers for laboratory, industrial and OEM applications with a wide range of connection options.
Explore suitable flow measurement solutions:
Not sure which flow meter best fits your application? Our flow specialists can help you select the correct flow measurement technology, connection size and flow range.