Dear Sir,
I am working on a system which requires Code compliance of both B31.3 and EN 13480. My system comprises of a 4" line from the Xmas tree to the Production header.
When i compared the results for both B31.3 and EN 13480 there was vast difference in the SIF's applied at the weldolets and tees.

The formulas for calculating SIF's of weldolet as per
I) appendix D of B 31.3 are as follows
Branch Welded on fitting (Integrally Reinforced)
Flexibility factor - 1
Out of Plane SIF io - 0.9/(h^(2/3))
In Plane SIF i - 0.9/ (h^(2/3))
Flexibility Characteristics - 3.3 (T/r2) (where T-wall thickness & r2- mean radius of pipe)


II) EN 13480-3:2002 Table H3 Flexibility characteristics and SIF for In plane and out of plane Bending :
Out of Plane SIF io - 0.9/(h^(2/3))
In Plane SIF i - 0.75io +0.25
Flexibility Characteristics - 3.3 (en/r) (where en-wall thickness & r- mean radius of pipe)

From the above formulas its clear that B31.3 and EN 13480 has same Inplane SIF (for weldolets) and The Outplane SIF of EN 13480 Cannot exceed B31.3 outplane SIF on any account.

How ever my Caesar report shows a totally different sets of SIF applied in EN 13480 case. The values obtained for 4" and SCH 120 pipe are summarised .

B 31.3 - In plane SIF - 1.129
B 31.3 - Out plane SIF -1.129

EN 13480- In plane SIF - 2.502
EN 13480- Out plane SIF- 2.502

It shall also be noted that both Inplane and Out plane SIF's of En13480 is same in Caesar output .How ever the formulas are different .

Please Clarify this discrepency. Also confirm whether the formulas used above for weldolet is correct.

Thanks,

Anandathirthan R

Actually things are not the same.

First EN-13480 defaults (in CAESAR II) to using Appendix H.1, so the SIF is the same for both in-plane and out-of-plane. When using H.1, there are no weldolets, sweepolets or extruded welding tees recognized. If you select one of these fittings, CAESAR II changes them to an unreinforced tee. So the flexibility characteristic is "2 * en / dm". This is why you get different results.

If you want EN-13480 to use Appendx H.3, then you need to go to the Configuration Module, on the "SIF & Stress" tab, and check the checkbox to allow this code to use different in-plane and out-of-plane SIFs.

Additionally, for B31.3 weldolets, the in-plane and out-of-plane SIF equations are the same - hence B31.3 will yield the same SIFs while EN-13480 will yield different SIFs.

Anandathirthan,

You may find the SIF articles in the below link of interest.

http://paulin.com/TechnicalArticles.aspx

Hi,
Thanks for your replies. I have changed my CFG file and prompted the system to use table H3 . Now i am getting proper SIF's .

Thanks again for valuable guidance.

Regards,
Anandathirthan.R