Problem
A large storage tank in a refinery was experiencing corrosion under insulation with severe isolated pitting to which required a repair to continue operations without risk of failure or replacement.
Conditions
With the presence of localised corrosion and location of tank, which environment is highly corrosive due to gases, chemicals, and high humidity, a repair was required in order to sufficiently reinforce the thinned area to prevent failure and keep the tank in running condition. For additional safety, the repair was engineered for a through-wall situation. Due to location of the job, all work was completed on a specially built scaffold.
Solution
The surface shall be very clean and void of old paint/primer so that the new treatment can achieve optimum adhesion. The repair section was blasted and surface was prepared to specification to ensure that no residual oil, grease, contaminants and salts remains before treatment is applied. The high-compression filler was being applied to remove all stress concentrators, provide a smooth transition, and allow load transfer to the composite which provides the pressure retention and reinforcement. Thereafter, a novolac primer is being applied at 5 to 10 mil thickness. Custom-woven e-glass fibers are then saturated thoroughly to ensure full saturation and no dry spots. 12-inch width saturated engineered fiberglass with the correct layer count is being used for the patch repair to reduce the amount of work time required and get maximum coverage.
Result
Within only a few hours, our certified applicators were able to complete the application and achieve a full cure of the patch repair while the tank was still in service. Restoring the integrity to the tank and allowing the repaired section to withstand pressures higher than its original design specification. This allowed the asset owner to avoid costly downtime in replacement of the tank.