DN or NB

[Pabster]

Good day all,

I'm having some contention over the use of DN or NB, now my understanding is that for metric units you state: DN 600 mm
or imperial units: 24" NB

Now due to possible ignorance NB has been used for both situations i.e. 600 mm NB or 24" NB

I cannot find anywhere that states explicitly what is correct i.e. code statement or dictionary. I feel that I may lose this battle due to the volume of rework but I'd at least like to know that I'm not being an expletive.

 

[MintJulep]

"When in doubt spell it out."

I have no idea what either DN or NB might possibly mean in the limited context of your post.

 

[Pabster]

My bad,

Diamètre Nominal or Nominal Bore for Pipe/Nozzle sizes

 

[ione]

The NPS (Nominal pipe size) is the standard used in North America to define a pipe size (inches). Nominal Bore (NB) is used interchangeably with NPS. The European standard equivalent to NPS is DN (diamètre nominal) and sizes are measured in millimetres.

 

[Pabster]

Yep this is all understood, so how do you tell someone that you can't use NB with a metric unit? ASME code reference for example.
I agree this is common knowledge and it 'just is right' but how do you argue the point more effectively?

 

[ione]

It depends under which code you are designing. European standards make use of DN designation (take a look at ISO 6708). American standards use NPS designation.

 

[Pabster]

Agreed, this is where the complication lies. Some projects are ASME codes but with metric pipe/nozzle sizes.

 

[ione]

IMO it is a false problem. Nominal Bore or better NPS is always expressed inches (imperial unit) and DN is always expressed in mm.