API 650 Tank, Plumbness on Tank shell

[MOHAMMED89]

Dear All,

For a tank designed as per API 650, Tank dimension is 30m Dia and 25m height. After hydro-testing the tank the settlement reading is quiet confusing.
Due to the differential settlement the plumbness on the shell is 115mm.
When i go through API 650, As per clause 7.5.2 the maximum allowable plumbness is H/200, So in our case H/200 = 125mm.
Since Plumbness on the shell is 115 and this is lower than 125mm hence this plumbness is acceptable as per code.
But my concerns are:-

1.​

As a design point of view what are all the other factors to be considered in this case.

2.​

Is this 115mm is acceptable ??? If so, How we can justify on this.

3.​

Any other analysis required to check the integrity of the tank?

4.​

Please shared some reference on this subject.


Thanks in Advance.

 

[JStephen]

The plumbness is supposed to be measured prior to hydrotest. It is a measure of how vertical the shell is relative to the foundation (which has its own tolerances for levelness), and is not intended to measure foundation tilt.
For foundation tilt, refer to the requirements in the hydrotest section about settlement monitoring and acceptable limits.