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Dent in tank shell

Dent in tank shell

Dent in tank shell

(OP)
I have a 35 ft atmospheric tank which shows some dent (inward deformation). Bulge would be a better word but bulge is for outward deformation.

How can I evaluate them for integrity and return in service ? API 579 don't include cylindrical with more than 42 inches diameter...(section 12). Can you help me to find some acceptance criteria ?

Does the fact that dent are inward and tank is only atmospheric pressure (under 16 psi at the bottom)help to not being a big issue here ?

Please discuss
Cedric

RE: Dent in tank shell

Can it have hot water or steam introduced?  If so the vessel vent is undersized for the MAV (maximum allowable vacuum). Vacuum created by condensate/cooling.

RE: Dent in tank shell

(OP)
That seems a possible cause of the problem.

Now, what code or calculation guide can I use to evaluate the damage I have.

Dents are not deep, maybe 1 to 2 inches maximum.

RE: Dent in tank shell

I've performed a number of evaluations to API 579 for this exact type of damage.  The restriction that you state is for a Level 1 or Level 2 assessment.  We've done the Level 3.  It's reasonably straight forward to perform, if you know what you're doing with Level 3...

RE: Dent in tank shell

(OP)
Level 3 is a FEA and before going there, I want to know for other criteria available.

If I have no choice, the FEA will be the solution.
Thanks

RE: Dent in tank shell

As described, it's hard for me to imagine that such a dent would be an issue.  If this is a million barrel tank, maybe I'd be concerned.

Has the tank had product or water in it since the dent's been there?

 

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