Tank shell dent - repair or not?

[waltzt]

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.

 

[JStephen]

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.

 

[waltzt]

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.

 

[TGS4]

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...

 

[bernoullies123]

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.