contributing area of roof plates - Annex F

[oolivares]

Hello All
In Api 650 tanks, compression ring must be designed according to figures F-2. Details 'i' and 'j' clearly states that pieces conforming the compression bar has to be joined with butt welds; details 'a' through 'h' and 'k' in change do not indicate the same. It is supposed to be that lap welded plates of roof plates in the compression area contributes to resist compression stresses as well?? According to other standard (API 620) in 5.12.2 roof plates joints with lap welded joints in the compression ring cannot be considered as contributive to the total area for resisting compression stresses. Should I consider the same in API 650 tanks???

Thanks in advance for you replies. Sorry about my English, if you cannot understand me I will improve the construction of my question.

 

[IFRs]

The lap welds only ocurr irregularly and once in a while and as such I'd not consider them in area calculations.

 

[JStephen]

In API-650, there's a 0.3 factor for wh, and the comparable equation in API-620 uses 0.6 as for the shell. I assumed this was to allow for the possibility of lap welds, etc.