Greetings,

I was wondering if anyone has gone through the calculations given for the integral attachments, I am trying at the moment and I have some sort of difficulty in understanding some of the issues as I tried to note in the attached file.

1. Notation "eord" is given in some pages of the code and description confuses the user. Fig 4.3-1 gives the definition of the wall thicknesses in a graph and explonation. This seems very clear. However, Table 11.3.2-1 has different definition for that. It calls it "nominal attachment wall thickness". I guess this should be called "nominal/order pipe wall thickness". The formula given by (11.3.3-7) is very common and "eord" is representing the nominal pipe wall thickness.

2.Formula (11.3.4-6) has one more wall thickness "eord,T". There is no definition for this anywhere in the code. Is it the hollow thickness attachment wall thickness?

3. There is a formula (11.3.4-9) for J for attachment. Other formulas (11.3.5-1), (11.3.5-2) and (11.3.5-4) are using Jbar. Are J and Jbar the same? If not how can we describe Jbar.

4. Formulas (11.3.7-7) is giben for hollow round cross section which includes rectangular attachment dimensions. I guess the formulas (11.3.7-7) and (11.3.7-7) should change the titles. Any ideas?

5. Figure 11.3.3-1 is given for circular attachments with keys a,b, and c. I could not find any use of this Figure in the code and causes confusion. Does anybody knows where to use this figure information in the code.

6. Formula (11.3.5-2) for "SigmaNT =..." second addition is given as "CN*W/ZN". I guess this should be replaced by "CN*MN/ZT". Any idea??

It became a bit long, but to be able to put the code formulation in the spreadsheet I gues we need to clarify all the questions above.

I was wondering if anyone has done integral attachment calculation for hollow and rectangular. I would like to receive a copy if available. But the clarification above still could be sufficient.

Kind regards,

Ibrahim Demir

Ibrahim,

I guess their intention was to follow N-391 cases, changing the notations to be more familiar to the EN readers.
You can see the result; it is full of mistakes- not only the notations, but also incorrect formulas.

I think you can clarify your remarks reading N-391 cases and comparing with EN.


Regards.

Hi Irahim,

As per Marigo reply, BS-EN followed the same procedure as in N-391 & N-392. In DNV-RP-D101 it is cleary mentioned that intergral attachment calculation mentioned in the BS-EN 13480 standard shall not be followed and it contain more errors in formula. Even if you have BS-806:1993 which is withdrawn but it is the earlier version of EN-13480 and u can find in that. Also in ASME B31.1-1992 edition also have a set of formula for designing the same...

The following are the reply for your query regarding hollow attachment,

1. Yes, it is nominal pipe wall thickness.
2. Not clear, but i suspect it is related to the creep temperature and is normally equall to "eord" if your case are free from creep range.
3. Same
4. Printing mistake, and 99.9% it has no effect, if the equations a,b,c,d,e are satisfied. Hence it can be neglected for non-critical piping.
5. The figure is used to show the weld arrangement for "Full penetration" and "Fillet weld" for understanding purpose.
6. Printing mistake. Your idea is correct.

Finally i conclude, please do not use the formulas given in EN-13480:2002 for intergral attachment design.

Hi Ibrahim,

Please correct my 2nd point reply. It is the ratio of nominal attachment wall thick to the nominal run pipe thick.

Mariog/Paldex,

Thanks for the references. I will go through those.
Thanks again.

Regards,

Ibrahim Demir

Greetings again,

I have found the original document in ASME Sec III, Div 1-2010 Appendix Y. It seems that N-391 and N-392 were replaced by the code under the Non-mandatory Appendix Y, and EN 13480 follows attachment calculation for Class 2 and Class 3 Piping of ASME.

By comparing these documents for hollow circular attachment calculation, I came across a big difference between ASME and EN in the pressure stress part of the equations for combinations. Assuming the original ASME is correct, there is a need for corrections in EN 13480 for these terms.

I attached an extraction from the New ASME III, Div 1-2010 Appendix Y and EN 13480 for the hollow circular section attachment. ASME is looking for hoop pressure stresses ad EN 13480 is looking for longitudinal pressure stresses in the combinations.

I do not mind using ASME III formulation for the calculations, however the there are some definitions that are not used by the B31.3 or EN 13480 applications, such as B1, B2.

Do you think, in EN13480, these values were included into calculation, and the final formulas look like the longitudinal stress effect instead of hoop stress? ASME is using B1=o.5 and B2=1 for straight pipe. I did not wanted to get this conclusion without getting a backup from you.


Thanks in advance and kind regards,

Ibrahim Demir

I think here you can find some "historical" considerations/ fundamentals on B1, B2 indices.

Regards

mariog,

Thanks for the link. Page 1 introduction is giving exactly the same EN formula for Class 2 piping. So I guessed correctly in the last paragraph of my previous reply.

Thanks and kind regards,

Ibrahim demir