API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
(OP)
Hi everyone,
regarding Appendix F, F.5.1 "Required Compression Area at the Roof-to-Shell Junction", I'd like to clarify what DLR does it mean.
As per code description, it should be the "nominal weight of roof plate plus any attached structural", please find below my doubts:
- corroded weight?
- in case of supported roof, the structure weight (usually not welded to the roof plates) should be considered or not?
Thank you.
regarding Appendix F, F.5.1 "Required Compression Area at the Roof-to-Shell Junction", I'd like to clarify what DLR does it mean.
As per code description, it should be the "nominal weight of roof plate plus any attached structural", please find below my doubts:
- corroded weight?
- in case of supported roof, the structure weight (usually not welded to the roof plates) should be considered or not?
Thank you.





RE: API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
"nominal" means as-built, not corroded.
"attached structural" means rafters that are under the roof plate and welded to it, or rafters that are on top of the roof plates. Standard structural that is not attached to the roof plate would not be considered.
RE: API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
RE: API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
I think API has flipflopped on some of this. If the corrosion in your case is normally uniform corrosion over the entire surface, then you would more appropriately consider the corroded weight. If corrosion is somewhat localized, then it would make sense to neglect the loss of weight in the structure. And in some cases, the corroded weight could actually increase- the iron oxide is heavier than the iron, so until they get separated, the tank is getting heavier.
RE: API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction
I recommend sticking to JStephens interpretation as being the conservative approach.
Cheers,
gr2vessels
RE: API 650 12th - F.5 - Required Compression Area at the Roof-to-Shell Junction