Sewer system: Corrosion protection for buried odor-control ductwork

The city of Austin, Texas, undertook a complex wastewater project that included a new 3.9-mile/6.3-km wastewater tunnel. Because the project was designed to increase wastewater capacity in the downtown district and facilitate residential and business growth in the area, city officials knew that it would be important to control odor in and around the tunnel. ECS Environmental Solutions (Belton, Texas) was contracted to provide odor control equipment and relied on Vipel vinyl ester resin from AOC Resins (Collierville, Tenn.) for more than 1,000 ft/305m of fiberglass ductwork and accessories. The ductwork would range in diameter from 12 to 72 inches (305 to 1,829 mm). Approximately half of it would be buried below grade and would have to withstand thousands of pounds of high-density loads from vehicle traffic. Additional project elements would include field joint kits, flexible connectors, control and back-draft dampers, bolt gaskets and two 40,000 cfm fiberglass exhaust fans.

ECS manufactured the ductwork using a state-of-the-art computerized filament winder. The fiber was impregnated with AOC’s Vipel K022 corrosion-resistant vinyl ester resin. “The K022 resin was the best choice for this project,” says ECS president Jeff Jones. “Some of the gases in the air stream are corrosive — including hydrogen sulfide and ammonia. There’s also sulfuric acid. Pipes built with this resin are very resistant to what goes in them and they won’t easily corrode.”

To ease installation, ECS prefabricated and assembled duct subsections at its facility before shipping them and a field crew of five to handle field layup, to the construction site in Austin. “We work in a controlled environment in the shop, but in the field you are open to the elements,” adds Jones. “Some of the days we were in Austin were cold and others were really hot. We had to adjust promotion levels and add inhibitors to work with the resin long enough to do a quality job under tough conditions.”

"

 

A key factor in the project’s success was that AOC’s Scott Lane, product leader, and Eric Stuck, sales representative, offered technical assistance as ECS reformulated the resin to meet changing conditions in the field. Jones adds, “With the long runs and thick pipes, we went through material much faster than normal, and AOC was very good at meeting this fluctuation in demand.”