Tank Bottom Corrosion and Edge Settlement 1

[Inchtain]

We have a Fire Fighting Water Storage Tank (Fixed Roof) with the following data:

Diameter: 15240 mm, Total height: 10265 mm, Capacity: 2000 m3, Material: Bottom plate: A 283 Gr C
Construction Mode: Welded / Lap weld, Built in 1972.

During our preliminary visual inspection, noticeable damage
discerned on the bottom:
✓ Presence of many Holes in some Plates
✓ Presence of Uniform internal Edge Settlement around the Tank. (Acceptable according to API)
✓ The Majority of plates was found bulged

- MFL analysis showed general corroded locations with variable depth
from 20% to 100% on practically all bottom

What do you think shall be the proposed repair Method:

1. Replace bottom and new foundation.
2. Replace bottom and realign exiting foundation
3. To repair the Bottom plate by patch plates according in
Figure 9.13 API 653 Last edition other wise to replace the
full plates.
4. Establish new bottom “Double” using” envelope” method
with respect the additional technical requirements
described in § 10.3.3.1 (C) API 653 & in §9.10.2. API 653

My second query is that, how to patch or replace that tank bottom (all lapped joints even under the tank shell), without lifting the tank?

Thank you for your feedback

 

[MJCronin]

You got nearly 50 years out of a carbon steel tank, ....... Sooooooooo

My vote is for Option 5.

5. Replace old tank with a brand new coated API-650 tank that meets all Fire Protection requirements
and a matching, non-settling concrete pad foundation

.... and enjoy another 50 years of service ....

MJCronin
Sr. Process Engineer

 

[bimr]

Agree with MJCronin, the tank is not that large and should be replaced. If you are in Turkey, you also should review the tank's seismic design.