What causes the depression on the upper part of the tank?
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We currently have a floating roof crude oil storage tank and a dome-shaped fire water tank, both of which exhibit dents in the upper part of their tanks; this is likely to occur in areas where the liquid level has not reached those areas. Currently, during the summer, the highest temperature at noon is around 50 degrees, while it’s in the 30s at night. This depression was there before as well, but it seems to be larger recently. Please help analyze and judge it; thank you very much!
Is there a problem with the breathing valve? Negative pressure may occur at the top of the tank when the medium is discharged
It is clearly caused by negative pressure; check the breathing valve and related connections.
Perhaps defects remaining from the design and manufacturing process: the wind-resistant ring is not properly designed, failing to provide sufficient support for the wall panels; stress causes the thinner upper wall panels to be more prone to buckling； It is not ruled out that multiple repairs may be required during installation, causing the area around the welds to be heated repeatedly, which leads to a decrease in strength and the formation of local depressions.
This post was last edited by ftxswb on 2021-6-29 07:47. These two storage tanks do not have wind turbulence dampeners installed, and the material used for the tank bodies has not suffered any loss in strength； Such a large-scale depression is caused by negative pressure instability.
It is likely due to a small diameter of the breather valve or poor airflow, as well as large temperature differences or a drop in the floating disk, which results in negative pressure inside the tank.
The breathing valve was opened for inspection and disassembly. It was found that the valve had good air permeability and no issues; there was no floating plate inside, it was straight-through, with no abnormalities, and the cavity was fine as well. The filter screen had a layer of dust on it, so it was cleaned.