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Tank shell dent - repair or not?

Tank shell dent - repair or not?

Tank shell dent - repair or not?

(OP)
We recently noticed a dent in the 2nd to top shell course of one of our tanks. The 6" gooseneck screen was plugged so I assume the tank was exposed to vacuum recently. The question is, is there anything required to do to this tank now that the shell has a dent in it? I cannot find anything in API653 about repairing a "dented" or "deformed" shell plate. I realize there will be a slight loss of volume, but the tank is not normally filled to full capacity. Do the welds around the deformation need any type of inspection? Please see the attached photo.

RE: Tank shell dent - repair or not?

I see this mentioned in 4.3.5.
I'm wondering to what extent the dent would pop back out if the tank were filled full.

RE: Tank shell dent - repair or not?

(OP)
It is possible, the contents of this tank have a S.G. of 1.4. The operating level of this tank typically is around 35 ft (40ft tall tank). I am not sure if anything actually needs to be done. I believe I will MT the weld seam at the top of the dent and let the tank continue operation. I am fairly new to tank inspections so am seeking additional guidance on my thoughts.

RE: Tank shell dent - repair or not?

You have damage (dent) to a tank. Determining whether or not you can continue to operate is a fitness-for-service question. Perform a Level 1 or Level 2 assessment per API-579-1. Or have someone perform it for you.

There are going to be concerns about the transition point between the undented and dented tank wall. As a minimum, I would be looking to MP the edge of the dent.

I've done this type of evaluation before. For a single dent, it's pretty straight forward. I've also evaluated tanks where 75% of the upper 3 courses had dents/wrinkles due to pulling a vacuum. That required a Level 3 assessment...

RE: Tank shell dent - repair or not?

Check that the depth of the dent (Normal outside radius minus the radius at the dent) is less than 0.07xDiameter. If so, then I would suggest a Level 1 assessment (API 579-1) for your records. That is a pretty nasty dent and quite visible from a distance, and people may query it.

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