Maximum test pressure for pipe.

[hfpolo]

Which is the formula to calculate the maximum pressure to which they may submit a carbon steel pipe?

that standard is?

Thanks for you help.

Good day.

hfpolo

 

[brimmer]

So many things I could say here, but the simple answer would be:

To 100% SMYS of the pipe. Use Barlows Formula P=2St/D.

The code governing your pipelines (in the country/area(s)) you are in may state a specific maximum test pressure, some codes do not, but typically you would not test past a hoop stress of 100% SMYS.

 

[zdas04]

I rarely approach half of SMYS during tests. Test pressure is a multiple of MAWP in most of the codes, and you really have to pick a code, do the math to define an MAWP, and then use the appropriate multiple. Without even knowing if we're talking about HVAC piping, field oil piping, field gas piping, distribution piping, transmission piping, etc. it is really hard to give meaningful advice.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[XL83NL]

Depends on the Code and the load case.
Ultra max is as brimmer wrote.

For B31.3 piping, the hydrostatic or pneumatic leak test would either restrict you to 100% resp. 90% SMYS.

 

[BigInch]

There is no prescribed maximum test pressure given in 31.4/8
The limit is described as a maximum 2% strain.

Independent events are seldomly independent.

 

[SNORGY]

You are so often limited by flanges and fittings that the actual stress you can impart to the pipe wall becomes irrelevant.

So, if you were to follow ANSI / ASME B16.5 or B31.4/8 (here in Canada, CSA Z662 & Z245.11/12) limits for fittings/flange ratings, you'd probably be set.

 

[BigInch]

It would not be uncommon for flange ratings and their test pressures to be considerably higher than those of both pipe and fittings used in a pipeline assembly.

Independent events are seldomly independent.

 

[SNORGY]

BigInch,

I'll concede to you on that one...the pipe sizes I deal with are more in the small range by comparison, I suspect.

If I ever found myself in a situation where the flange rating exceeded the pipe rating, I'd look to find either lower rated flanges or thicker wall pipe. To me, that would just feel odd.

 

[BigInch]

If we only need 65 Barg for a 100 km pipeline, its hard to justify buying 100 Barg pipe just to equal the rating for what might be only the inlet and outlet flanges.

Independent events are seldomly independent.

 

[LittleInch]

Hfpolo,

The fact you are asking this sort of very basic question troubles me. The answer to you question will vary widely depending on which code you are designing to - if you don't know ask you boss / client - where you are (plant, countryside, town), what your deign factor is (important for B31.8), what your design pressure is etc etc.

Given the complete lack of info on any of these items I am not willing to give you potentially critically incorrect information which you then use in a test of unknown size pipe which could easily seriously injure someone if it all goes wrong.

Always look at the weakest point (lowest point) and lowest rated pipe / equipment.



My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[zdas04]

BigInch,
Last time we had this discussion I had the same opinion that SNORGY has, it just felt wrong to have an ANSI 300 system that wasn't rated to 600 psig. You convinced me that what you were saying was correct and I've taken off the "flange defines the system" blinders. It is a hard step for people never do big inch pipelines.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[LittleInch]

That's why pipeline design codes (31.4, 31.8, ISO 13623 etc) and pipeline design methods are different from piping codes because the cost of excess metal in the pipe to meet flange pressure ratings which it will never see becomes very signficant - I'm sure you know that, but just for general readers....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

For a minute I thought it was deja vu all over again then I remembered it was you that drifted over to my corner last time. Now we're 3 ... or 4, counting LittleInch. Great minds think alike ... eventually.

Independent events are seldomly independent.

 

[SNORGY]

I wish I had a great mind. Oh well. I can dream.

Actually, BigInch, your post sent me away to bed with my iPad, trying to imagine what it would be like to have a 24" OD pipeline using 3/8" wall thickness and PN-100 flanges with an MOP of 9930 kPag. I came to the conclusion that you had a valid point.

 

[racookpe1978]

Yeah. I'm looking at a pipe now that burst through its wall (like a balloon blowing up) inside a turbine - not the welds or fittings attaching it to the casing...

But "they" want to replace it with the same pipe and pipe wall thickness. Sometimes its hard to convince people that "more steel is good" .... even on a 8 foot length.

 

[BigInch]

That's the other end of the extreme.
Worse in the face of prior trouble.
Not learning from experience is a very serious mistake.
That's what destroys my faith in the self-policing theory.
The accountants, shareholders and engineers with bonus $$ in their eyes, that seem to make up 102% of the police force.

Independent events are seldomly independent.

 

[BigInch]

PS. Snorgy... you're #4... I think.

Independent events are seldomly independent.