Localized area of concern on shell 2

[Cristian N]

So one of our maintanance personnel noticed coating failure in a straight localized vertical line initiating from the top shell course down to the second(shell course above the bottom one. We decided to further investigate and realized the ID of the tank displayed an affected area, but we don't know what it is.

The tank is a 120' Diameter external double deck floating roof tank. Not sure on what the product is.
The affected area is not near or adjacent to a seam weld. There is no cracking, distortion, or anything of that nature.
The seal is comprised of a mechanical shoe primary and a wiper secondary, not sure who is the manufacturer.

I was thinking maybe a damaged mechanical shoe is rubbing up against the shell, but I find it unlikely to cause the localized coating failure on the OD.
The pictures are attached below.

 

[JStephen]

It's possible that the ID problem and OD problem are unrelated.
On the OD, one possibility is that after the surface was abrasive blasted, a stream of water or other contaminant ran down the shell there and wasn't properly removed.
It's possible that something was welded on the inside and removed, or that a vertical line was heated for flame-straightening after the exterior coating was in place.
It's hard to tell from the photos, but looks like the inside line is vertical and the outside line slants to one side, so I'm not sure they're actually in the same place.

 

[MJCronin]

Consider re-posting on the "Storage Tank Engineering" forum .... you will get more eyeballs there ...

MJCronin
Sr. Process Engineer

 

[HTURKAK]

Dear Cristian N (Petroleum),

Will you pls provide more high definition fotos from outside above the wind girder and from inside around top angle ??
Will you pls check from interior above the FR max. level for the scratches?..

Apparently the interior vertical line exrtends above the max operation level of EFR..

I guess some hot work and grinding performed from the interior after the exterior coating completed.. Could be for removal of some temporary attachments for access scaffold ,ladder etc..

I just want to remind also,provide more detail to get better responds..

 

[IFRs]

Was the seal replaced recently?
If so was there an anti-rotation bar welded to the tank shell that was removed?

 

[Cristian N]

HT and IFR


Thanks for the replies as well as everyone else. After doing some research, I am almost positive it had an anti-rotation angle iron removed at some point. The picture from the inside was taken from the opposite side of the tank on the gouger's platform.