ASME B31.3 Appendix N

[cneumann]

Hello,

I'm new here, but already read some valueable information in this forum.
However, I'm working on a comparison of ASME B31.3 (2018) and european piping standards. So long the important standard, that came to my mind is the (DIN) EN 13480.
To be CE confirm it is necessary to fullfill the requirements of the PED 2014/68/EU, which states, that only european harmonised standards implicate confirmation.
Whilst reasearching in this forum I saw some references, that state, that the B31.3 can also fit under the PED, so I looked into the B31.3 and found the Appendix N.

Appendix N Application of ASME B31.3 Internattionally:
N100 refers to ISO 15649, thats from 2001 and has not many details about the desgin of process piping. Also the ISO 15649 refers back to ASME B31.3

N200 Compliance with the european pressure equipment directive (ped):
Here is the PED 97/23/EC refered, which is not in charge since 2016!
The new PED 2014/68/EU is not stated here and im wondering, if thats by mistake, or if im getting something wrong.
Also the ISO 15649 is not part of the list for harmonisated standards (

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52018XC0914(05)&rid=1)

I would be glad, if someone can help me on this topic.
Is the reference in the B31.3 (2018) a misstake, or am I understanding it wrong?

Thank you in advance

Christian

 

[DekDee]

XL83NL is very conversant with the PED and B31.3.
With a bit of luck he may see your post and respond.

 

[XL83NL]

Appendix N has been in B31.3 since the 2012 edt. Back then, 97/23/EC was current. No one ever took the effort to get the Code committee to revise it to 2014/68/EU. Most committee members don't deal with PED (a lot), not is this appendix something that sees a lot of 'work' in the code committee meetings, through ballots etc. Submit a formal inquiry to the Code committee for a change and Im sure they'll pick up it. See appendix Z.

Im not familiar with the background of app. N in B31.3, i.e. as to how it got in, and what its purpose was, but I think it was meant a simple guide for nen-EU users to get a bit more understanding when dealing with PED under B31.3.

In general, app. N doesn't provide a lot of directions to the how's etc. The reference to CEN/TR 14549 is useful, that TR (Technical Report) contains a good checklist to the differences between B31.3 and the PED.

ISO 15649 is not a harmonized standard indeed. For metallic industrial piping found in chemical, oil & gas applications, etc., EN 13480 is one of the few harmonized standards:

https://ec.europa.eu/docsroom/documents/40841

B31.3 has been and can be used in conjunction with the PED. You need to be careful though with the notified bodies. Some tend to take every Essential Safety Requirements very specific to the last dot or comma, others may be more flexible.

Is there something specific in B31.3 w/ PED you need help on?

Huub
- You never get what you expect, you only get what you inspect.

 

[cneumann]

Thanks for the fast reply.

That explains a lot. I will consider to submit a formal inquiry.

Is there something specific in B31.3 w/ PED you need help on?

Not directly, its more about curiosity. But as you also stated, the PED requires harmonised standards for presumtion of confirmity. (PED 2014/68, Art.12.1)
Furthermore the materials specification have to be one of the following forms:
— by using materials which comply with harmonised standards,
— by using materials covered by a European approval of pressure equipment materials in accordance with Article 15,
— by a particular material appraisal (PED 2014/68, Annex I.4.2.b)

As far as I can see ASME B31.3 can be used, but then it needs to be executed with a special treatment for confirmation, thus it's more time and money consuming, than using the En 13480.
Is this right? Or is it possible to use ASME standards in PED without additional costs?


For my workcase im researching the differences in the stress analyses for a pipe under sustained loads at cryogenic temperatures. The Material is austenitic (eg. A312 316/1.4401 or 316L/1.4404)
Im not into all details of both standards, but it seems like the equations for stress analyses of both are the same for the most cases. At least its the same for straight pipes. (Compare 13480-3 a2: chapter 7 with B31.3 para. 320.2)
So far I've heard and read, that the design with B31.3 is less restrictive, than with EN 13480.
But a comparisson in the given workcase leads me to the assumption, that working with EN-standards leads to higher allowable stresses.
Compare 13480-3: chapter 5.2.2.1 with B31.3 para. 302.3.2-d. Furthermore the base stresses in ASTM 312 are overall lower as in EN 10216-5.
Im wonder:
1. Are my assumptions right?
2.Do i need to calculate with tolerances in the stress analyses, in both ASME and EN?
Both write: "nominal thickness to be used", but B31.3 states, that allowances need to be considerd. EN 13480 states that tolerances need to be considered. This seems controversial to me.

 

[XL83NL]

Not directly, its more about curiosity. But as you also stated, the PED requires harmonised standards for presumtion of confirmity. (PED 2014/68, Art.12.1)
Furthermore the materials specification have to be one of the following forms:
— by using materials which comply with harmonised standards,
— by using materials covered by a European approval of pressure equipment materials in accordance with Article 15,
— by a particular material appraisal (PED 2014/68, Annex I.4.2.b)

As far as I can see ASME B31.3 can be used, but then it needs to be executed with a special treatment for confirmation, thus it's more time and money consuming, than using the En 13480.
Is this right? Or is it possible to use ASME standards in PED without additional costs?

You can use B31.3 w/ PED without additional costs, for sure. I can of course only tell from personal experience, which is piping systems, typically NPS 1/2" to NPS 8", SS316, SS304. Always cheaper in ASME/ASTM.

A full EN 13480 is not only more expensive, sometimes impossible. Weve had a lot of issues with piping systems to EN 13480, esp fittings and tube/pipe. We couldn't get a simple tee in 1.4404. If we did got one, it was machined from bar with a wall thickness of 13 mm instead of 2 mm. That wasn't a one-time incident. Flanges in 4404 are OK, but don't go beyond PN63, delivery time will go up.

There's one other to this approach, which is discussed below.

For my workcase im researching the differences in the stress analyses for a pipe under sustained loads at cryogenic temperatures. The Material is austenitic (eg. A312 316/1.4401 or 316L/1.4404)
Im not into all details of both standards, but it seems like the equations for stress analyses of both are the same for the most cases. At least its the same for straight pipes. (Compare 13480-3 a2: chapter 7 with B31.3 para. 320.2)

If I'm not mistaken, EN 13480 is the result of merging some national standards, and finishing it with a B31.3 sauce. In fact, for a lot of things, B31.3 seems to be the main ingredient. As for stress analysis, some sections in EN 13480 are just 1-to-1 copies of B31.3.

So far I've heard and read, that the design with B31.3 is less restrictive, than with EN 13480.

It depends on what you're focussing on. For a lot of stuff, yes, but there are some benefits of EN 13480. Its more prescriptive in a lot of details, where B31.3 would e.g. use 304.7.2 as the main 'escape'.

But a comparisson in the given workcase leads me to the assumption, that working with EN-standards leads to higher allowable stresses.
Compare 13480-3: chapter 5.2.2.1 with B31.3 para. 302.3.2-d. Furthermore the base stresses in ASTM 312 are overall lower as in EN 10216-5.

EN has higher allowbales, yes. And, whats mosot often forgotten, is that for B31.3, the allowable stresses from app A-1 need to be lowered for those cases where the piping systems is in cat I or higher (thus, when ESR's apply). This is esp. true for aust. stainless steels, with a relative low elongation.

Im wonder:
1. Are my assumptions right?

Some yes, some maybe not. Look at it case by case. Overall, I prefer B31.3 over EN 13480, even though the latter provides more methods and ways for a lot of details. The paperwork is a lot bigger in EN 13480 compared to B31.3 w/ PED. The bugs and errors in EN 13480 is an endless list. Symbolism isn't always correct, nomenclature isn't consistent, (which makes it easy to make a mistake, or have the user don't understand a method as background to symbols isn't provided). There's still too much work that needs to be done to EN 13480 to make it compatible and competitive to B31.3, imo.

2.Do i need to calculate with tolerances in the stress analyses, in both ASME and EN?
Both write: "nominal thickness to be used", but B31.3 states, that allowances need to be considerd. EN 13480 states that tolerances need to be considered. This seems controversial to me.

Depends on which equation you're looking at. In general, both follow the same approach afaik.

Huub
- You never get what you expect, you only get what you inspect.

 

[DekDee]

Just remember ASME IX does not have sufficient testing to comply with the requirements so additional tests are required.

 

[XL83NL]

@DD: your're correct, but i'd had to add "in some cases". It depends on the material and the NoBo. My personal experience with A106-B @ -29°C and (lots of) SS316 @ -47°C has been no complaints of the NoBo. In similar situations, our Canadian colleagues who did a PED-job, had a pain in the ass with their under the same or even milder conditions (SS @ -29°C).
Nowadays, most EU countries get their ASME IX PQR in conjunction with an equivalent EN ISO 15614 PQR. So as long as its a paper work trail/job, it can easily be managed.

Huub
- You never get what you expect, you only get what you inspect.

 

[cneumann]

Just remember ASME IX does not have sufficient testing to comply with the requirements so additional tests are required.

Thats the same thing I thought. The PED requires impact testing, that is not provided by ASTM standards and require additional tests.
I might confuse some things about the material standards, because im from europe and new to the american standards system, but Asme uses the ASTM standards for reference. right?
Additionaly a particular material appraisal is needed, when using non-harmonized material standards.

It depends on what you're focussing on. For a lot of stuff, yes, but there are some benefits of EN 13480. Its more prescriptive in a lot of details, where B31.3 would e.g. use 304.7.2 as the main 'escape'.

Would a 90° Piping bend be such a "escape"?
EN 13480 appendix b gives much detail about how to calculate stresses in piping bend, whereas I cant find equal details in B31.3.

EN has higher allowbales, yes. And, whats mosot often forgotten, is that for B31.3, the allowable stresses from app A-1 need to be lowered for those cases where the piping systems is in cat I or higher (thus, when ESR's apply). This is esp. true for aust. stainless steels, with a relative low elongation.

Can you provide a reference for the lowered allowable stress? I'd like to look that up. What means "relative low elongation" to you?

The bugs and errors in EN 13480 is an endless list. Symbolism isn't always correct, nomenclature isn't consistent, (which makes it easy to make a mistake, or have the user don't understand a method as background to symbols isn't provided). There's still too much work that needs to be done to EN 13480 to make it compatible and competitive to B31.3, imo.

I can relate to this. The nomencalture in EN 13480 is frustrating at least and quite hard to understand sometimes due to its inconsistancy.

Depends on which equation you're looking at. In general, both follow the same approach afaik.

For B31.3 i mean euqations 23a-d
For EN 13480-3/a2 i mean equation 12.3.2-2
in both cases the section modulus is key.
B31.3 319.3.5 speaks of nominal thickness, whilst 320.2 states, that allowances need to be used.

EN 13480-3/a2 4.3 defines the different wall thicknesses. thickness to be used in stress analyses is ec= e(calculated)+tolerance+allowance due to order.
But 4.4 states: nominal thickness to be used in calculations an thicknesstolerances to be considered.
Im sorry, if my translations are not as good, I only have the german version of EN13480.

My problem is the difference between theory and praxis.
I know from our qaulity assurance, that pipe manucfacturers always provide us the min-thickness given. The difference between stresses w/ and w/o tolerance however are massive (around 25%).
The question is: Can I calculate with the thicknesses given in the standard, even thou I know, that the thicknesses in reality are different? Is this difference considered?

 

[cneumann]

In edition to my original question:

today i got a reply from ASME:
"Thank you for your inquiry. We haven’t evaluated the accuracy of Appendix N for some time. Because of your note, we will open an agenda item (A-20-04) to update the text."

 

[XL83NL]

Sorry, haven’t had much time to respond. I’ll look into your questions asap.

Huub
- You never get what you expect, you only get what you inspect.

 

[XL83NL]

@OP: still interested in an ongoing discussion? Totally forgot about this and found this back

Huub
- You never get what you expect, you only get what you inspect.

 

[cneumann]

@OP: still interested in an ongoing discussion? Totally forgot about this and found this back

Thanks for coming back, but actualy I finished on that topic.
About the tolerances I came to the conclusion, that they need to be considered whilst calcultating allowable stresses.

If you dont have further interest in this thread it could be closed.