Innovative Composite Tank Repair

Coatings/Corrosion Prevention

USS BOXER experienced recurring corrosion pinhole leaks in the steel hot water accumulator tank’s watertight boundary. Previous attempts using external epoxy-based patches were applied with poor results due to pressurization and thermal expansion of the hot water system. Based on excessive interior pitting from previous surface preparation issues, a welding alternative was desired. Replacement of the accumulator tank presented major obstacles:

• Lead time for new tank
• Extensive interference removal and access cuts
• Significant shipyard resources and planning time
• Compressed availability constraints

When an emergent condition is assessed, composite repairs offer a convenient alternative. Internal composite repairs were determined to be an appropriate repair method based on previous success from the use of composite repairs on commercial accumulator tanks. Many tank lining companies had concerns with existing internal pitting surface; therefore, Southwest Regional Maintenance Center chose SUNREZ’s unique fiberglass and resin system that offers a Vinyl-Ester, pre-impregnated, fiberglass fabric (already saturated with resin) that utilizes an Ultraviolet (UV)-Cure process. Key advantages included:

• Rapid application: full cure within 60 seconds
• Simplified process: pre-saturated fiberglass reduced handling complexity
• Durability: reinforced, corrosion-resistant liner capable of withstanding high-pressure hot water

The USS BOXER repair request combined a large volume repair with interior ship challenges. Working pressures and temperatures of this accumulator were within the SUNREZ composite design capability for a successful repair, and the repair was completed in one day. This repair not only restored watertight integrity to the steel accumulator tank for unrestricted operations but also provided a reinforced fiberglass composite liner. This repair method allowed the USS BOXER to meet operational commitments with minimal downtime. Even though water from this system was determined to be isolated from the ship’s potable water system, SUNREZ did have their composite repairs materials submitted for National Sanitation Foundation 61 certification. The repair was also completed pier-side without requiring hot work repair or tank replacement. This repair technology saved a significant amount of time, labor, and financial investment for the navy. This opportunity will allow NAVSEA to continue evaluation of this technology’s value and establish limited approvals for unrestricted use. Not only did this innovation option allow USS BOXER to maintain their operational commitment, but it also prevented unscheduled deployment extensions of other naval assets. Recently published NAVSEA Drawing 630-9014545 provides installation details of this product for smaller scale patches in limited areas. NAVSEA is also working on additional testing which will mitigate challenges of larger patch repairs and additional interior use.