API 650 tank internal pressure

[lps123]

Hi Can any one let me know if the tank over turning moment due to tank internal pressure on cone roof (uplift force on roof) needs to be considered as part of seismic overturning moment calculation for self-anchored tanks?

 

[JStephen]

In the current API-650, Equation E.6.2.1.1.1-1 includes a term for 0.4W-int in the evaluation of J, which is the effect of pressure uplift.
This has been changed in more recent editions, and older editions didn't include this term, so an existing tank may not have included this interaction. Or, if you're using an outdated edition, it may not be there.
Logically, the seismic uplift would be included in the maximum pressure equations in Appendix F as well, but currently isn't.

 

[lps123]

Thanks JStephen. Agree to your comments and thanks.