Lugs in Heads of vertical vessels using line loads-EN 13445/COMPRESS

[dab2010]

Hello,

I have a question regarding the methodology for using line loads for calculating stresses in lifting lugs in the head of vertical pressure vessels. We recently have compared our methodology to EN-13445-3 (via COMPRESS). We found that the equivalent calculation diameter from EN-13445-3 16.6.3 to be equal to what in my mind should be the effective radius. We have not been able to resolve why this is, and I was wondering if anyone has any knowledge as to why the European code is using the effective diameter as the radius in the calculations?

Thanks

 

[ljans]

I am the other half of the "we" in the OP above.
Some further explanation:
Looking at calcs for lugs on a head, EN-13445 Section 16.6.3 defines equivalent diameter, D_eq as follows:
D_eq = R_i for spherical sections
and again
D_eq = D_i×SQRT(1-3((x/D_i)^2)) for 2:1 S.E. heads

these numbers seems to be short by a factor of two and I believe should read

D_eq = 2×Ri for spherical sections
and
D_eq = 2×D_i×SQRT(1-3((x/D_i)^2)) for 2:1 S.E. heads

I have sketched out the 2:1 head in CAD and checked the calculated D_eq against measuring the radius of the arc at varying offset distances, x
(I will try to post my sketches later)

The D_eq calcs match the CAD measurement of the radius

The only real concern we have is COMPRESS* uses this D_eq calculation for lugs on a head, and my personal calcs have suggested this may result in non-conservative line load stresses in the head

Thanks in advance if anyone can share comments or experience about this

*Build 7110