self supported dome roof for above storage tank

[amine1340]

hello
currently , we are supervising construction of an above storage tank designed per API650
characteristics:
roof :

- dome self supported .
- D:29.03 m
- thickness =9mm .
- load from the roof = 2013404 N.
the roof was erected and welded on the ground , dimensional checking was done( it was ok) before welding but not after welding .
after the roof was erected;it was supposed to be seated on the top angle at a distance of 25 mm from the shell (refer refer to photo).
for some reason (maybe welding ) most of the roof now sits on the weld (joining the top angle and the shell) and the rest sits on the top angle properly .
my questions is:
1- contractor's proposal is to weld it as it's (which means there will be weld over a weld ), can this be done?.
2- 2nd proposal is to cut the roof's edges to make it all sit on the shell, is this feasible and are there any dimensional tolerances for the dome roof diameter and height .
thanks in advance.
3- is there any other propositions to fix it.

 

[Dhurjati Sen]

Dear amine1340,

Check the peeking and banding of the shell. You have to work on the top shell course instead of toying with the roof.

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[JStephen]

Tolerance at the top of the shell is a combination of out-of-roundness measured at the base of the shell and plumbness measured up the shell, and can easily be greater than 25mm.
I would be inclined to weld it where it is, I don't think you'd actually gain much by moving it around or trimming off here or there.

 

[amine1340]

thank you all for replying to my post
i went to check this morning and i found that the roof is seated on 3 different places : shell,the weld between the top angle and the shell , and few millimiters into the top angle , it's very uneven
you'll find in the attached photo the readings of roundness , plumbnes...etc.

Mr JStephen, the roundness is -35 mm meaning the shell is -15 mm from the toelrance which is 19mm.
this what strucks me odd , the roof should have had more than enough space to be seated on the top angle.
my concern is that the roof was not constructed properly. meaning diameter and curvature are not respected
is there any tolerance for that .
thank you in advance for your precious insight into this issue