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Hi,
We all are aware that for Pipe we usually use NPS are NB to identify a pipe.
I have gone through the articles in "Training" and I had bit clearer picture but still then could anyone please clarify for me how do we differentiate NB from NPS.
One more thing, 1" should be 25.4 mm but pipe OD is 33.4 mm but when we see 14" pipe its OD is 14" (355.6)mm.
Why does the OD after 14" remain same & OD 12" and below varies?
Its a basic question but I had some doubt .
Karthik,
#1
You and any others who still are not clear about Pipe, Pipe sizes, Pipe outside diameters, Pipe Inside Diameters, pipe wall thicknesses, Pipe Schedule nomenclature/NPT to DN Cross Refference, etc should look at this web site. You should copy (Print out) the chart and study it in detail.
http://www.maselmon.com/Content.aspx?ContentID=24
#2
NPS = Nominal Pipe Size (US) For metric the term is "DN" = Diameter Nominal
#3
You used the initials "NB". I can only assume that you mean "Nominal Bore". If I am correct in this assumption, then you should understand this. There is no such thing as a nominal bore. The "Bore" of all pipe for a specific pipe size (NPS or DN) changes with the Schedule change or wall thickness change. So there is really no such thing as Nominal (Normal) Bore.
#4
The person responsible for setting (selecting) the pipe wall schedule is the Piping Material Engineer. The Schedule (or wall thickness) is determined by the system Design Pressure/Design Temperature/Commodity/Corrosion Allowance/Plant Life and other mitigating factors. Look at the chart. There are seven (7) listings for 4" (DN 100) pipe commercially produced and available. Each has a different wall thickness and multiple schedule listings. Some of the listings (5S, 10S, 40S, etc.) are for Stainless Steel pipe. The others are for Carbon Steel and Alloy Steels.
#5
As for why do we have one method for 12" (DN 300)and under sizes and a different method 14" (DN 350) and larger sizes. I do not know the answer to that. I do not think anyone else knows the real reason either. I have seen some peoples thoughts on it but I suspect they are just guessing. It is like Gravity, we do not fully understand everything about it but we just learn to accept it.
JOP is correct.
Also, there is a pipe chart here:
http://pipingdesigners.com/wp//downloads/pipechart.htm
Take a look through the "Training" "Tip" "Tools" and "Standards" tabs above .............. there is a lot of good information to be had there!
Dear Jop & Anton,
Thank you very much for ur reply ? Yup 'NB' i mentioned was Nominal bore.
I was really not aware of 'DN" = Diameter Nominal I have been working in piping for all most 4 yrs but every one uses NB(nominal bore).
do i have any doc which specifies this so that i can educate my colluges with some proof because every one uses trem NB (nominal bore). to specifey a pipe in MM for ex --25NB, 50NB
thank u very much for educating us reg the assumption of NB and DN .
Hi shrivallabha,
Thank you very much for ur reply, the question i arised seems to be simple .
But many of us really dont know why the dimension varries . this would really educate all of us who are all not aware of this .
once again thank u very much to all of you .
Have a Nice day
shrivallabha, KARTHIK
I am going to try again. Some of the piping nomenclature (terminology) is not logical, most pipers accept that and go on with the job. As I said above, "NPS" and the related "DN" designations are like Gravity. We do not really understand gravity. You cannot see gravity. You cannot taste gravity. You cannot feel gravity itself you can only feel the effect of gravity. We just accept gravity and move on with our lives.
It is very important to understand only one thing about this subject. "Nominal" is defined as: being such in name only; so-called; putative: a nominal treaty; the nominal head of the country. Therefore the nominal pipe size in name only.
You do not need to understand "NPS" or "DN" or the obvious incorrect pure mathematical relationship between the two. It is not even important to the day to day activities of a piper no matter where you live or work.
The calculations that "shrivallabha" is trying to promote (above) is not valid and could lead other novice pipers to go down a wrong path.
This is not a false calculation I was promoting. I never intended to mislead someone. If I've done that then I apologize. Being a chemical engineer, I thought on these lines.
Its not that I want to pick up gauntlet for the guess I made. There's a rational reason for things around us. There's someone else who thought in much the same way as I did. Google helps you in many ways.
Please check the link
http://www.engineeringtoolbox.com/pipes-tubes-d_347.html
Regards,