Tank Bottom Flatness and Foundation Tolerances 1

[KnaT]

Hey Guyz!

I have a few queries regarding Storage Tank Bottom Flatness and Foundation Inspection. I hope you'll be able to guide me.

1. Looking at Inspection methods and tolerances for tank dimensions in API 650, there is no direct tolerances defined for bottom flatness. There is a reference for tolerances in Waviness and flatness in API 650 7.5.2 but its for tank plumbness.
Can it be used for bottom flatness as well?
If yes, what is the cross reference?
If no, what reference should be used?

2. Tolerances for Tank foundations are defined in 7.5.5 with reference to the Tank concrete ring wall. I have a case where the ring wall is well within the tolerances but the central part of the foundation is approx -+22mm from average values. I can find no reference to reject the foundation except simple logic that this uneven foundation will effect the tank bottom flatness and slope of the tank bottom.
Can anyone give me a better reason?

Thanks in advance guyz!

 

[JStephen]

I've never seen a tolerance for bottom flatness. I recall a line, possibly in AWWA D100, saying that out-of-plane distortion of 1% of diameter was not out of the ordinary.

On the 22mm difference- if it's a large tank, I'd say that was a neglible difference. If it's a small tank, it'd be more noticeable, but also easy to correct.

 

[compit]

Take a look in API 653, there are tolerances for tank bottom flatness, bulges and depressions.