centerline-stacked or flush-stacked, which one is better ? why? 1

[Roohol]

Dear All;
Centerline-stacked or Flush-stacked method, which one is better for storage tank installation? esspecially for ammonia tank and with air roof raising?
please clarify advantages and disadvantages of each method.
Regards;
Roohol

 

[Soln]

Flush inside is often specified for tanks with floating roofs, or in your case air raising roofs, so the seal is allowed to seat well. But, because the difference in shell thickness is usually no greater than 1/16", the offset of a center line stacked shell from course to course is only 1/32"- I don't think 1/32" is enough to make a difference. The weld profile if greater than 1/32", local shell deviations are commonly greater than 1/32". It's advantageous to use center line stacking during design/fabrication due to the common plate length for all shell courses rather than each course shell plate becoming successively smaller (by about a 1/16").