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Storage Tank Pad Replacement Material

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Louisiana Inspector

Louisiana Inspector

Chemical
Jul 21, 2023
27
I have a 10ft Diameter sloped bottom Carbon Steel API 620 storage tank that rests on an elevated concrete foundation with leak detection grooves that was constructed in 1991. Between the tank bottom and the concrete foundation is a 1/2" Asphalt Impregnated board. Over time the Asphalt board has deteriorated and is absorbing moisture resulting in corrosion of the tank bottom and chime so the time has come to replace the pad.

My question is what is on the market that is used in place of the Asphalt Impregnated board? I know API recommends not using an impregnated board due to the issues I am experiencing now but it doesn't list other alternatives that would perform better. The tank operates at Ambient Temperatures and is located in South Louisiana.
 
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asphalt-impregnated board is used to avoid water infiltration underneath the tank bottom and to protect the tank bottom in direct contact with the concrete slab . In your case , apparently the board did not function its function.

In past , i specified mastic asphalt under the shell and asphaltic concrete t:50 mm thk or bitumen sprayed clean sand for the remaining tank bottom. In your case, concrete base with mastic sealant around the perimeter could be an option.

A foundation sketch showing the grooves, slopes , etc would be helpful to get better responds.

...


He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 
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Why bother with anything? Concrete to steel is not normally an issue. The foundation should be sloped down and away from the bottom. If the dike area floods nothing will help. The asphalt impregnated board is still available but as you have seen it is not great. Question: how do the grooves work if the fiberboard is between the tank and the foundation?
 
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