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## adamjin

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See More: : Repair of cone roof tank

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## ramaseshans

Hi,
Good morning.
If you are removing the top shell course, the rafter resting on the top shell with clips should remain and ofcourse with curb angle and roof. Once you erect the top three shell courses with new curb angle, then you can design the pad and clips for the rafters (similar to existing), then hopefully you can place the rafters back along with roof. Only you need to remove the fillet welds from the existing roof to curb angle portion and redo the same with NDE.
Hope this clarifies at top level.
Thanks
Ram

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## npsrinivasarao

Dear Ram,
 The questen raised by "adamjin" is still unanswered by you. For your better under standing below is his question

_I have a scenario where there is diesel tank of 24m dia and 12.8m height. The inspection report recommends renewal of the top 3 courses of shell. the tank roof is ok. Can someone advise if it can be done without removal of the roof? or do i have to remove it?
how to remove it? the roof plates are just laid onto the rafters. Any one with solution please provide an answer_

Regards

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## npsrinivasarao

Dear adamjin,

It is understood from your question, the subject Tank is a self supporting / shell supported Tank. Your scope is to replace the top 3 shell courses. You have the following options
1. Lift the roof, remove it and replace the shell courses.
2. -	Provide a temporary column support (multi column) from the inside of the tank. Ensure the columns are sufficiently brazed between each other to secure them from falling apart. 
-	Separate the tank roof weld on the curb angle portion.
-	Lift the tank roof to a sufficient height with the help of the temp column supports provided on the internal side. 
-	Secure the roof with the help of gay wires externally to secure the roof from lift off due to high wind.

Assuming you might have provided scaffolding on the external side for performing the shell replacement work.
-	Now you can start shell replacement accordance to API 653 and perform the required tests put the tank into service again.  

Hope the above clarifies to you the process. The process mentioned is not the only option there might be other options also but I have personally followed this process and executed the overhaul of some tanks. Belive some other from thsi forum may provide you with other options. 

Cheers and best of luck. 

Regards.

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