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.
Thanks, Roy.

In my opinion, there is no clear criteria as "out-of-roundness" for in-service tank.
However, according EEMUA 159, the differential settlement can be correlated with the degree of out-of-roundness, so I think a specialized inspection can answer also to this question.

To evaluate based on engineering basis whether the tank can still be used "as is", I think analyses based on API 579 should be performed.
It appears to be a complex non-linear model rather than simple criteria and I have to recognize I'm not familiar with such tank API 579 analysis.

Probably in practice are more simplified criteria used by specialized inspection companies, correlating directly the allowable differential settlement to shell out-of-roundness and tank plumbness.
I haven't such criteria, anyway.

Best regards.

Thanks for your input.
I've had a look API 579 and as the out-of-roundness is not constant along the axis a level 3 assessment is required. In reality that means FEA.

How can we check tank bulging effect in caeser-II
Can anybody explain?

Deepak,

Exactly what bulging effect?