Problem
A large 32-inch OD high pressure column with multiple nozzles on the problem section in a refinery was experiencing isolated wall thinning due to internal erosion and corrosion.
Conditions
With the presence of the many obstructions and limited access around the area of concern, a niche repair method with the ability to conform with complex geometry was required in order to sufficiently reinforce and/or prevent a through-wall defect on the thinned area. In addition, a composite with a high service temperature was required and external heating is to be conducted to cure the epoxy as operating temperature of the colum is below the curing temperature. A couple of seneraios were generated and crossed checked using equations from ASME PCC-2 and ISO TS24817 and discussed with the client to have the best solution implemented on the balance life expectancy, budget and safety considerations.
Solution
To design an engineered wrap solution. The wrap selected must be able to restore the section of the column back to its intended pressure ratings and restore structural integrity. The selected composite will also withstand the elevated temperature of the column. Obstructions to the repaired section was cold-cut and filler was used to provide a smooth transitioning for the wrap. An additional compensation plate was also installed and cured in place to ensure proper bonding on the area of concern where erosion is most prominent. Thereafter, the engineered composite was installed following the layercount and L-over required to fully reinforce the section.
Result
The client was alble to repair and restore the section of column to a higher than original design pressure. The addition of the compensation plate and composite wrap provided additional safety in event of possible breach in containment. The column could remain in service without the need for a shutdown, until the next available replacement opportunity.