API650 Center column internal floating roof 1

[Islem le baron]

Hi everyone. I'm a new joiner in this forum and I have a question. In our project we have a tank according to API650 with a floating roof and center column (it look weird I know). We erected the tank with Jacking method. And now we will start the IFR work. The first phase is the erection of this central column, and here the question the alignment of this column must be:
- must be vertical according to the roof center ring location regardless its projection to the bottom
- must be vertical according to the bottom center location regardless its projection to the roof
- or I need to take both center (most probably the column will not be perfectly vertical in this case)

I believe the last point is the correct one to avoid that the IFR stuck with the shell. Anyone can confirm.

Thank you in advance

 

[HTURKAK]

In our project we have a tank according to API650 with a floating roof and center column (it look weird I know). We erected the tank with Jacking method. And now we will start the IFR work.

I think (and must be) the roof is fixed roof with a central column and there is an internal floating roof..


API 650 limits plumbness to 1/200 . Check API 650 7.5.2 and Appendix H For tanks with internal floating roofs, apply the criteria of this section or Appendix H, whichever is more stringent.

 

[IFRs]

API 650 requires that the column be plumb within 1/200 of its height (7.5.2) or +/- 3 inches (H.4.5). API 650 Annex H requires that the well in the floating roof be 5" larger than the column, all around (H.4.5).

The most important thing is that the column be smooth (no thick splices), straight (without a bow or kink) and parallel to the tank shell. If the tank leans (which it should not) then the column should lean. If the tank is plumb then the column should be plumb. If there is a choice between being in the center of the tank or being parallel to the tank, the column should be parallel to the tank.

Some floating roofs would have the column well installed in the shop and others in the field. If yours is shop installed, make sure it has or will have the required clearance after the deck is complete. If it is field installed, center it on the column. Many floating roofs would be installed from the side to side rather than middle out but it should not really matter as long as the rim space is correct and consistent (for good sealing throughout the travel of the deck).

 

[Islem le baron]

thank you guys for your reply. I totally agree with you IFRs about what you said, this is why i preferred in my post to go with the center to center alignment and i will keep checking the distance from the column to the shell for each course before the final welding of the column.