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The annular plate can be replaced by slotting the tank shell, when replacing an annular plate check weld spacing at the vertical seams and allow a large enough replacement to stay out of the critical weld zone of the tank shell.

tank is empty or below the critical level right ?

The first shell course is welded ( Corner weld,Both sides) to the annular plate. Then to replace the annular plate is a major repair. Try to repair the craks drilling (3mm) the ends of the crakcs grinding between the holes and reweld with the same original WPS and Pt or MT over the new weld.

• The bottom plates of oil storage tanks sometimes need to be replaced due to corrosion or riveted joint leakage. This replacement work usually involves lifting the tank with hydraulic jacks, a costly and time-consuming exercise.

• In 1980, Nippon Petroleum Refining Co. and Niigata Construction Co. have jointly developed a new non-jacking method that allows the tank bottom plates to be replaced by supporting the tank with simple jigs.

• Engineering analysis and strain gauge measurements prove that the method does not generate unacceptable stress levels in the tank, even from earthquake and wind loads, during the work.

• The method has been successfully applied to bottom plate replacement of more than 260 tanks, and it has demonstrated remarkable cost and time savings when compared with the conventional Jack-up Method.

• Free download the following file for details of Support Piece Method for replacing bottom & annular plates for oil storage tanks: Replacing_Bottom_Plates_of_Oil_Storage_Tanks