API 653. Tank shell deformation

[Bridgy]

What criteria do you use for assessment of deformations to the tank shell for in-service storage tanks? API 650 & 653 give construction tolerances for new build and reconstructed tanks. Is the same criteria applied to in-service tanks or are there other assessments that can be done.

 

[metengr]

I would use API 653 because this Standard concerns Tank Inspection, Repair and Alteration and Reconstruction. Also, review the Introduction of API 653. There is a section on Distortions. Unfortunately, it provides minimum guidance other than evaluate on a case-by-case basis. The good news is you have flexibility to evaluate using either new construction tolerances, FEA or API 579 as a last resort.

 

[Bridgy]

I have had a look at API579, the out of roundness is not constant along the axis and has to be classified as general distortion. This requires level 3 assessment which in reality will be FEA. I was just after some guidance as to what others in the industry were using. I will use the API 653 construction tolerances.
Thanks