FEA of Rectangular Tank

[rashidmaqbool]

Dear All,

Due to a human error, one of the rectangular diesel tank was exposed to significantly higher pressure than its design conditions. As a result, bulging in tank was observed. The maximum deviation from the true vertical plane is 83 mm. Certain internal welds were also cracked which shall be repaired in any case. The tank is on an offshore platform and while a replacement tank is being fabricated, we intend to use the current tank for on going operations.

After deformation, the tank was filled with water to establish any leakage, and we did not encounter any leakage in it. However, to ensure that it is safe for a certain period, we are considering an option to carry out FEA of the tank. In my opinion:

1: The tank should be modeled in its current condition, i.e. with deflected plates and members.
2: Once modeled, it should be filled with liquid (diesel in this case) and checked for induced stresses against residual stresses left in the deformed structure.
3: The residual stresses of deformed members can be established either using some software (which i am unaware of) or through a reasonable estimate.
4: I believe software such as "STAAD Pro" does take into account deformed condition of members.

I expect the results would be approximate in the range of 70~80%

Please suggest your experiences or thoughts.

Regards

 

[amos4]

Beside filling with water to check for leakage, did you test it to operating pressure after proper repair procedures? what "if" another human error occurs? any mitigating plans or design review conducted?