tank bottom repair 3

[mectarek]

Hello All,

Looking at the method of using patch repair plates on the tank Bottom in accordance with API653

does API 653 states any maximum size of patch plates?

what to do if you find several adjacent damaged plates on the bottom of the tank?

Can you cover a whole part of the bottom with new plates welded above the old plates?

if yes, how to know the limit where it is better to replace the whole bottom?

 

[LittleInch]

I'm not hugely familiar with 653, but you're normally limited by how big a hole you've cut into the side of the tank.

You repair them all

Yes

When the cost of patches exceeds the cost of a total floor.

If it's that bad why dont you coat the whole floor in GRE or some other coating?

Suggest you contact an experienced repair contractor to provide specific advise.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IFRs]

For repairs in the critical zone, see 9.11.1.2, there are some size limitations.
There is no maximum size limitation for bottom patch plates away from the critical zone, but as you get close to or overlap existing seams or 3-way joints you may need a larger repair plate that exceeds what you can purchase or handle.

 

[HTURKAK]

Dear mectarek ,

When you say , patch repair, you should look ( 9.10 Repair of Tank Bottoms ) and the reference figure (Figure 9.13—Typical Welded-on Patch Plates on Tank Bottom ) which specifies the minimum sizes of patches, minium distances etc.


If you say this is replacement of some or all of the plates rather than patch repair .

The following excerpts are copy and paste from API 653 ( 5th ed.)

-12.3.3.3 Bottom Repair or Replacement Outside the Critical Zone
Portions of new bottoms (any or all rectangular plates or large segments of plates) in tanks may be replaced without a
hydrotest when the subgrade under the new plates is found to be in a condition acceptable to the authorized inspector
or is restored to such condition and either of the following conditions is met....

You may replace several bottom plates as long as conforming the code.
But , my gut feeling says, if you need to replace several of the bottom plates, the remaining plates could have critical thk.
I would suggest you , conduct tank bottom evaluation study and check for the minimum Thickness for tank Bottom Plates.

Consider the full Replacement of Tank Bottom Plates ( 9.10.2 )

 

[mectarek]

thank you all, your comments were very helpful