NATURE OF DEFECT
The tank had suffered from corrosion under insulation (CUI) to the vertical tank shell. This resulted in corrosion patches and pitting of various sizes and depths. The client required composite patch repairs to prevent further external corrosion and restore the strength of the tank wall. Various defects were present on the tank shell with differing sizes and depths, and these were evaluated by the client against the requirements of EEMUA-159 above ground flat bottom storage tanks.
SOLUTION
Where this evaluation shows a repair is required, Metalyte Pipeworks produced a composite repair method using Herculyte epoxies to fair the defects with the specified number of layers of Dragon-Q-STD composite system.
REPAIR METHOD
The tank substrate was prepared using an MBX machine to gain a surface profile to SSP.SP11. All surface defects were repaired using Herculyte epoxies and 500 microns of Dragon resin were applied as a bonding coat to the entire repair area prior to application of the Dragon composite. The repair areas were patch wrapped in the required number of layers of engineered Dragon-Q-STD composite and cured until a minimum of 74.5 Shore D hardness was achieved.
