Clarifier Tank Agitation Wing Repair
Addressing Severe Corrosion in Critical Infrastructure
Constellation Nine Mile Nuclear Station faced a severe issue with the agitation wing inside a clarifier tank. Corrosion had caused the loss of 15-20% of the wing’s surface, leading to structural instability. Initially, the plant planned to completely replace the agitation section of the clarifier. However, do to time constraints with the outage window Carbon Fiber Engineering Solutions (CFES) introduced the idea of rebuilding the wing using a corrosion-resistant carbon fiber composite, offering a cost-effective alternative.
Experience always overcomes challenges
The proposed solution presented unique challenges, including:
How can a structure with 20% material loss be rebuilt to provide the necessary strength and durability?
What materials and techniques can ensure long-term resistance to corrosion and erosion in such a demanding environment?
Inspection and Preparation
CFES conducted detailed inspections and prepared the surface for repair:
Surface Preparation:
Removed the failed coating system from the entire agitation section.
Grit blasted the substrate (steel and concrete) to an SSPC SP-10 Near White Metal finish with a 3+ mil angular profile.
Material Selection:
A 19.5 oz bi-directional carbon fiber was selected for its exceptional strength and stiffness, capable of replacing over ¼ inch of steel.
Innovative Repair Methods
The repair process involved several critical steps:
Carbon Fiber Application:
Multiple layers of saturated carbon fiber were applied, creating a 160-mil-thick composite.
The carbon fiber was adhered to the tack coat and folded to recreate the blade’s point.
Epoxy Coating:
Two coats of a corrosion-resistant epoxy liner were applied over the entire agitation section to provide long-term protection against corrosion and erosion.
Key Outcomes
Rebuilding Structural Integrity: The carbon fiber composite effectively restored the structural integrity of the clarifier wing, providing strength equivalent to the missing steel.
Preventing Future Corrosion: The epoxy liner created a durable barrier, preventing future corrosion and extending the life of the agitation section.
Cost Savings and Efficiency: Rebuilding the wing with composite materials offered significant cost savings compared to full replacement, minimizing downtime while delivering a robust solution.
