EN 13480 and Weld Strength Reduction Factor

[DSB123]

Hi,
We know that high temperatures cause reduction in Strength of Welds compared to the Pipe Material hence the ASME B31.3 Code applying a W Weld strength Reduction factor. However if you look into the EN 13480 Code there is no explicit mention of an equivalent Weld Strength Reduction Factor. So the question is do we apply a Weld Strength Reduction Factor or not ? (I beleive we should) I beleive this has been missed in the EN 13480 Code.

Just wanted to see the communities thoughts on this.

 

[gerhardl]

Seems that EN1348 (if I found the right one, and last issue/paper) have been under some discussion. I recommend you to take a search, and also double check that you have been given the last updated version with all amandments.

See article

http://www.piping.bilfinger.com/fileadmin/power_piping/Mediathek/BHR_Prospekte/1337_BHR_3R_e.pdf

 

[XL83NL]

That billfinger paper is old, and some things have changed over the years. Its useful for background, but other than that Im not sure how up2date it is.

Recently we had a job that required alloy 800H piping acc EN 13480 @ 700+ C. At some point I noticed EN 13480 could not be used for creep design, as it only specifies creep rupture stresses for that material, and no tensile and yield stress values. Applying the formula for time-dependent stresses, requires one to have this data. Since only the creep rupture stress was present I was getting ridiculously high allowable stresses in the creep range. The question form I submitted to the EN 13480 committee acknowledged this, and EN 10216-5 will be adjusted to incorporate the yield strength at temperature.

To answer your question; I believe it is not required. The code itself requires caution for use in the creep regime (say anything > 600 C), so just stay away from it and switch to B31.3 when you go high temp. Thats what we did, and we had good success with it.

 

[denstan]

XL83NL,
I think you are mistaken. If you look at para 5.3.1 it basically says where you do not have creep properties for the weld metal that you should reduce the base metal creep strength by 20%.

My concern is that by just reducing the creep strength by just 20% is un- conservative for high temperatures. It can be as much as 50% for some materials.

Also if you look at the complementary vessel standard EN 13445 it clearly says that for the creep range the joint factor z should be multiplied by zc. The equations for cylinder thickness and the allowable stress basis in the creep range are the same for EN 13480 and EN 13445.

 

[XL83NL]

denstan, in that you're correct. I believe it may be as much as 50%, at certain temperatures ...
second, where does creep begin in EN 13480 (see attachment for a POV of the EN committee on this)

http://files.engineering.com/getfil...P_EN_13480-3_Clause_4.5_Question_ZETON_BV.pdf

however, if there are no published material properties for the creep regime in the relevant component standard, like EN 10216-5 (other than creep rupture strength values in appendix A of EN 10216-5), how do you want to apply EN 13480 to the creep? I think that at that point it doesnt matter what 5.3.1 says - you cant seem to use it.

see attached an interpretation I proposed to the EN 13480 committee. their answer seems to be in line with my POV.

http://files.engineering.com/getfil...P_EN_13480-3_Clause_4.5_Question_ZETON_BV.pdf

 

[denstan]

XL83NL,
Wonder if you can advise on the procedure to submit a query tothe EN about EN 13480? What is the protocol?

 

[XL83NL]

Go here. Then at the bottom, see 'Submission of questions'. Download the Word file, and [link mailto:en13480@unm.fr]send[/url] it to the committee.

 

[denstan]

XL83NL,
Many thanks for the info.