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Issue link: https://ct.epubxp.com/i/178128
Applications Applications Te 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 ofcials 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 f/305m of fberglass ductwork and accessories. Te 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 trafc. Additional project elements would include feld joint kits, fexible connectors, control and back-draf dampers, bolt gaskets and two 40,000 cfm fberglass exhaust fans. ECS manufactured the ductwork using a state-of-the-art computerized flament winder. Te fber was impregnated with AOC's Vipel K022 corrosion-resistant vinyl ester resin. "Te K022 resin was the best choice for this project," says ECS president Jef Jones. "Some of the gases in the air stream are corrosive — including hydrogen sulfde and ammonia. Tere'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 feld crew of fve MANHOLE COVERS to handle feld layup, to the construction site in Austin. "We work in a controlled environment in the shop, but in the feld 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, ofered technical assistance as ECS reformulated the resin to meet changing conditions in the feld. 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 fuctuation in demand." Composites replace cast iron on university campus Ductile cast iron (cast iron with added magnesium) has been used for manhole covers and frames since the mid-20th Century due to its durability and high compressive strength. Engineers who design underground infrastructure have rarely considered the use of alternative materials. However, operators of localized multibuilding heating systems, such as those on college campuses, have become increasingly aware of the dangers posed by cast-iron manhole covers. Cast iron becomes very hot when exposed to internal steam and external sunshine, and it also conducts electricity — a concern when manhole covers are located in walkways where students wear sandals or go barefoot in warm weather. In addition, although cast iron stands up to heavy loads and severe impacts, it is very heavy — the density of a cast-iron manhole cover can be as high as 450 lb/f3 (7,208 kg/m3). A small 32-inch/813-mm diameter cover can weigh as much as 250 lb/113.4 kg, which can lead to injuries to workers who have to move them. Source | Fibrelite Source | AOC Corrosion protection for buried odor-control ductwork Tese factors led the utilities department of a leading engineering university based in Cambridge, Mass., to replace traditional manhole covers with composite versions manufactured by Fibrelite Composites (Skipton, North Yorkshire, U.K., and Pawcatuck, Conn.). Many other universities in both the U.S. and Canada have since followed suit, says the company. Fibrelite uses multiaxial and woven glass reinforcements to make a preform with a fber architecture that maximizes bending stifness and strength-to-weight ratio. Te preform is then infused with polyester in a resin transfer molding process; for higher-temperature or highly corrosive applications, vinyl ester resin is used. Te thermal gradient properties of Fibrelite's composite covers signifcantly reduce heat transfer from the steam vault below — the surface temperature of the cover is typically only slightly higher than the ambient temperature. Extensive testing has shown that composite covers stay cool to the touch and support the same wheel loads as 32-inch cast-iron manhole covers, yet they weigh nearly 70 percent less. Fibrelite emphasizes that its cover eliminates the possibility of electrical shock and resists corrosion caused by salts, oils, water and steam and avoids thef of cast-iron covers, which have value as scrap metal. As an added incentive, Fibrelite can permanently mold into the cover's top surface any style of school logo or other marking in single or multiple colors. CT oCTober 2013 SEWER SYSTEM 41