Forum 
Buried annluar plate - Sunday, January 31, 2010 - Dursosono [667]
The annular plate that extended to outer shell plate may to burying with asphalt?
If yes/no what the reason to allowed/not this condition?
Re: Buried annluar plate - Monday, February 01, 2010 - JDM [672]
You post is kind of difficult to understand .
But if you are saying you think that the chime of your tank bottom is buried under asphalt. Then you should verify.
You should list your postings a little better to help the forum give better answers.
Re: Buried annluar plate - Monday, February 01, 2010 - karsadi [652]
No, for corrosions inspection/control and maintenance purpose.
Re: Buried annluar plate - Monday, February 01, 2010 - dursosono [667]many thanks for all advices, Karsadi: I agree with you but is there any statement in API 650 regarding your opinion?
Re: Buried annluar plate - Monday, February 01, 2010 - BABRTs [53]
What you are asking is so specific as not to be addressed by 650,
And trying to determine just what your are wanting, you can put a cove of asphalt on top of the chime to shed water away from the corner. There is a product called NATASCO Tank Cement that is used for this purpose. It is available from Sherwin Williams.
The tank cement can be used to seal the space between the plates and the ring wall to prevent water from getting under the floor.
The chime and up the shell needs to be coated and free of holidays before you apply the material. One problem using Asphault is it shrinks as it dries and allows moisture to get behind it causing corrosion. The NATASCO tank cement dries out a lot slower. I have seen some tanks that it has been applied over 15 years and still in good shape.
This will become a maintenance issue over time as it needs to be inspected annually to be sure it has not began seperating from the shell.
Do not know if this is what you wanted.
Re: Buried annluar plate - Tuesday, February 02, 2010 - CNT [492]I think you are asking if it is allowable to have the floor extension covered with asphalt.
Ive seen it, even with tanks that are not on ringwalls. I think it was applied to keep water off of the floor extension, but as stated above, it cracks and will end up trapping moisture and causing corrosion. It also makes it really difficult to shoot the settlement elevation of the tank because the asphalt is not very even in thickness. It also masks corrosion, so you cant see problems even if they are there.
It is just a coating, and it is allowable to coat the floor extension, so I dont think it is exactly against code, but I have recommended that the asphalt be removed because it hinders the proper visual inspection of the floor extension during routine external and formal external inspections, which are required inspections. The purpose of a routine external inspection is to look for signs of corrosion of obvious changes in the condition of the tank. If the asphalt coating is not in excellent condition and is hindering those inspections, then I say it needs to be properly repaired, or removed and replaced with a more suitable coating.
