Dent in tank shell

[cedeng]

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

 

[psafety]

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.

 

[cedeng]

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.

 

[TGS4]

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...

 

[cedeng]

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

 

[JStephen]

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?