Piping classes origin

[Melimelo]

Hello everybody!
First, I introduce myself: I'm a novice process engineer working on a gas company since soon 3 months...
I used to ask my questions on chemical process engineering forum.
I would like to ask a new question about "piping classes origin", I have found an interesting discussion here about this topic...(thread378-123846 )
I would like to know why they have choose exactly these numbers: 150, 300, 400...etc...and not 200, 350... for example?
Someone spoke about the pressures in psig at the corresponding saturated steam temperature, do you know more??
(I apologize for my bad English, I am French...)
Thanks a lot!
Méli )

 

[C2it]

I bet your next question will be 'why is an 8" pipe not 8" OD when a 16" pipe is 16" OD ?'

Like the ASME flange classes which is what you are quoting, there was good reason a long time back, and why change it now. I suspect that the classes resulted from developing work in the American steam locomotive or stationary boiler industry. It's not UK based ... not our fault !!

You might note that EN pressure standards follow pretty much the same categories with PN 50, PN 250, PN 420 etc.

 

[Melimelo]

Well, I have found that for pipes, the DN numbers are a "progression géométrique" (I don't know how to say that in English...) where the "raison" is "10square10". It is called "Les séries de Renard" where Charles Renard is a French military engineer who decided to normalize le DN...
I though there is a same nice story for classes pinping...
(Sorry again for my English ))
Méli

 

[BigInch]

Surprized that it wasn't something to do with the Romans.

(BTW, just turn it around, EN: Geometric progression" and again, ES: progresión geometrica)

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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http://virtualpipeline.spaces.live.com/

 

[pennpiper]

Melimelo's next question is going to be:
"Why do they call it a Flange?"

Flange
(From Wikipedia, the free encyclopedia)
A flange is an external or internal rib, or rim (lip), for strength, as the flange of an iron beam or I-beam (or a T-beam); or for a guide, as the flange of a train wheel; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc, or on the lens mount of a camera. Thus a flanged rail is a rail with a flange on one side to keep wheels, etc., from running off. The term "flange" is also used for a kind of tool used to form flanges.

 

[BigInch]

Well then they also keep the pipe from sliding off the piperacks. Isn't that interesting? Never thought about that one before.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[Melimelo]

OK, sorry for my questions...
I just like to understand the origin of things.
Méli

 

[BigInch]

No worries. That's just our fun way of saying we don't have a clue.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[Melimelo]

Ah OK, I thought you were making fun of me...(

 

[BigInch]

Non mon ami. Jamais dan ma vie.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[moltenmetal]

Meli: just be thankful that there IS a standard. Just about any standard is better than NO standard, ie. three or five or ten competing standards depending on where you go in the world!

As to the origins of the NPS pipe sizes and selected ANSI flange classes, I have no idea. It's really a good question in the Engineering History thread- bet there's somebody out there who knows!

 

[moltenmetal]

Origin of Nominal Pipe Sizes (NPS):

http://en.wikipedia.org/wiki/Nominal_Pipe_Size

It appears that it was a standardization approach that started out with good intentions, but went awry in an attempt to keep consistent with pre-existing iron pipe sizes and wall thicknesses currently in use at the time the standard was being developed. The standard-writers' attempt to provide backward compatibility is the reason we've ended up with a system which appears to have no consistent basis- until you're at 14" at which point at least all schedules have the same OD.

Analogous to the old gem about the gauge of the railway tracks being based on the width of two horses' @sses!

 

[JLSeagull]

http://en.wikipedia.org/wiki/Rail_gauge

Perhaps the individual gauge selection depended upon the breed of the horses. ;-)

As with B16.5 for flange classes, the forward of ASME B36.10 provides some insight. The pipe schedule numbers related to ratios associated with Barlow formula for pipe thickness.

 

[BigInch]

moltenmetal

All schedules have the same OD, no matter what diameter they are for.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[moltenmetal]

D'oh! Fingers faster than brain, again! Yes, every schedule has the same OD...

What I MEANT to say was 14" plus has an OD equal to the nominal size...

 

[JLSeagull]

- in inches.

 

[dcasto]

as for the reason for class, like 150, 300, 600, The only trend I see is that those rateings are close th typical superheated steam tables at elevated temperature. Ie a class 600 will hold 600 psis steam with some superheat. the same for 300, 400.

I'm not saying thats the basis, but its an interest trend.