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Composites Play Critical Role in Water Plant

11 April 2011

A new water filtration plant under construction in The Bronx is the centrepiece of the largest single construction project in the history of New York City.

The filtration plant is designed to ensure that water from the Croton System watershed is aesthetically pleasing and meets or exceeds all drink water quality standards. When completed in 2012, the plant will provide roughly 10 percent of New York City's 1.4 billion gallon average daily demand for water. During drought or other conditions affecting other watersheds servicing New York, the new plant can deliver up to 30 percent of in-City water needs.

To achieve a design capacity of 320 million gallons (1.2 million cubic meters) per day, each link in the filtration process chain has been engineered for the optimum in reliability and performance. An-Cor Industrial Plastics made 38 fibreglass-reinforced polymer (FRP) composite tanks for the filtration plant to standards set by the American Society of Mechanical Engineers (ASME) and the Fiberglass Reinforced Plastics Institute (FRPI).

How the tanks were made

To achieve performance requirements, An-Cor used Vipel vinyl ester resins from AOC. The inner corrosion barriers of each vessel were made with Vipel F010 bisphenol-A epoxy vinyl ester because of its corrosion resistance and U.S. Food and Drug Administration (FDA) compliant properties. The barrier liners were formed using hand lay-up of the resin with veils and fibreglass mats. In addition to the standard barrier, each tank designed to hold sodium hypochlorite added a 116 mil (2.95 millimeter) thick corrosion allowance for extending the equipment life.

Structural laminates were manufactured with Vipel K022 bisphenol-A epoxy vinyl ester. The high performance resin meets project specifications for high strength, excellent chemical resistance and, with synergist addition, Class I fire-retardant properties per ASTM E84.

""The Vipel resins were selected for their ability to meet critical end-use performance specifications,"" said Rob Merrill, An-Cor (Vice President-Operations). ""The technical support that AOC provided with the resins was excellent. AOC Corrosion Specialist Bill Holtzclaw's knowledge of FRP processing and quality standards was very helpful. Both Bill and AOC Product Leader Scott Lane were quick to respond when we needed to optimize processing.""

The corrosion barriers of the cylinders were made using the hand lay-up method utilizing fibreglass taped goods. Depending upon the diameter of the tank, the structural portion of the cylinders were built using mechanical applications of chop strand mat, woven roving, and/or winding glass.

The top and bottom heads of the 10- and 12 -foot (3- and 3.7-meter) tanks were resin-infused using Vipel K022EBB resin. Balsa wood cores were encapsulated into the glass fibre-reinforced laminate to achieve higher stiffness. The heads of the smaller tanks were made by hand lay-up of fibreglass and resin. All tanks were post-cured in a convection oven prior to shipment.

The project sponsor was the New York City Department of Environmental Protection, who will ultimately be responsible for running the plant. The main contractor is a Skanska/Tully Construction joint venture. Haley & Aldrich was geo-technical consultants, digital automation architecture was provided by Emerson, and a Hazen & Sawyer/Metcalf & Eddy joint venture acted as client consultant. URS provided support in construction management, cost estimating plus resident engineering, geotechnical engineering and tunnelling inspection.






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