EN 13445-3: Support skirt (Shape B) - Middle line alignment

[FPPE]

Hi,

I have a doubt regarding design of support skirt connection (shape B).

eb=27 mm;
with ez=10 mm we are outside the limit of wall thickness ratio equation:

27/10=2.7

So (I think it is mandatory), it is necessary to increase skirt thickness to, at least, 12 mm:

27/12=2.25 (ok)

The doubt arises from the fact that our customer requires the external alignment of the skirt to the head, as follows:

Considering the dimension 'a', it is not clear in which direction it is taken. Considering the vertical alignment instead, aligning the skirt externally to the head we do not respect the tolerances provided by EN 13445:4 Table 6.2-1/2/3, because it would result in a offset equal to 7.5 mm. So we think it would be better to align skirt midline to head neck midline.

Can you advise me if there are more details in other parts of EN 13445?
Thanks

 

[r6155]

More info: diameter, wind, seismic, height, total weight, ......?

Regards

 

[FPPE]

External diameter of vessel 1850 mm,
wind and seismic according to italian NTC 2018 (wind zone 6, seismic zone 4),
skirt height: 1500 mm
total height: about 7000 mm,
weight: about 12 tons.

Why do you need these informations?
Thanks

 

[r6155]

This is minimal information to analyze. A diam 1500mm x 7000 mm or a diam 1000mm x 20000 mm is not the same. In this case there is no problem with a 10 mm skirt. But you have to accept what the owner says. The calculation defines.

Regards

 

[FPPE]

Sure, my doubt is about the accordance with the code, in this case EN 13445. Especially regarding the middle line alignment.

Thanks