Wind turbine towers can be found all over the globe. As withall steel structures exposed to the elements, corrosion willeventually take over and degrade the structural integrity of thetower if no protective coatings are applied to form a barrierbetween the steel structure and moisture. Aegion’s CorrosionProtection platform’s coatings inspection group was onsite toinspect the complete removal of existing coatings on the exteriorof a 178-foot-tall turbine tower and perform spot repairs onthe inside of the tower. The tower is owned by a wastewatertreatment plant that uses the generated electricity to help powerthe facility. The owner of the tower realized the added benefit ofhaving an Aegion NACE certified coatings inspector onsite eachday to ensure all aspects of the project were carried out by thecontractor according to the specification. The added cost of anonsite NACE certified coatings inspector was minimal.
The tower consists of a concrete foundation with three separatesections that were hoisted by crane and bolted together on theinside of the structure. The structure has a tapered shape, with a13-foot inside diameter at the base and an 8-foot inside diameterat the top. To access the entire exterior, scaffolding was installedfrom the ground to the top of the tower. A containment systemwas then installed around the scaffolding, forming a sealed workarea to prevent any paint chips and other debris from escapingthe work area during abrasive blasting. This process alsoremoved the old coatings and rust. The scaffold and containmentstructure was engineered and designed with specific wind loadratings to both ensure the safety of the workers and preventmore stress on the tower than it was designed to tolerate.
The scope of work consisted of the following:
- Blast clean the outer surface according toSSPC-SP10/NACE No. 2
- Near white blast cleaning followed by a zinc-rich epoxy primer
- Epoxy stripe coat to all welds and connection seams
- Full epoxy intermediate coat
- Full polyurethane topcoat
The interior of the structure also needed repairs in many locations.The interior of the structure had multiple cables and an array ofelectronic equipment inside. This required using vacuum-shroudedpower tool cleaning to repair this area. Wrapping of all electroniccomponents in plastic was also needed to protect the equipmentfrom paint chips and other debris prior to cleaning and painting.Two coats of the same epoxy used on the exterior were appliedto the interior. The blasting work prior to applying this coatingstarted at the top of the tower. At the end of each blasting day,the primer was spray applied to all cleaned surfaces to ensureno flash rusting occurred overnight. It took several days tocomplete the blasting and priming work. The stripe coat wasthen completed by brush and roller, ensuring the product wasworked into the segment seams as well as on the weld seams.Finally, the full epoxy and polyurethane coats were spray applied,resulting in a smooth and shiny appearance.
Every step of the process was documented by Aegion’s NACEcertified inspector. This includes measuring the thickness of eachcoat applied and making sure any rework was completed priorto the next step. All inspection reports, as well as photographstaken, were included in a project binder and given to the ownerat the end of the project. It is expected that this coatings rehabproject will extend the life of this tower for at least 30 years.