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Denton Turns to Composite Technology

04 September 2009

Denton, Texas, recently completed its installation of a 4,700 feet sewer line based upon composite pipe technology. The line, which was made from 48-inch underground piping, was designed and processed using Flowtite technology along with Vipel unsaturated polyester resin.

The Flowtite process manufactures pipe on a continuous advancing mandrel, which aims to increase production efficiency rate for fast and just-in-time delivery. The composite wall of the pipe is reinforced with a combination of continuous and chopped glass fibre to achieve the optimum balance of cost and performance.

The resin for the Denton pipeline was a Vipel unsaturated polyester formulated to proprietary Flowtite specifications. Garrett J. Doucet, PhD, Quality Assurance/Quality Control Manager for U.S. Composite Pipe South said Flowtite formulation is said to have smooth processing characteristics for high finished quality, as well as ensuring high resistance to the corrosive effects of wastewater and sewer gases.

The pipe was installed by Texas United Excavators under the direction of Project Manager Rocky Hill. “This was first time we used composite pipe,” said Hill, “and my foremen really like it. Compared to the alternative, which was PVC (polyvinyl chloride), the composite showed no deflection and installed in less time. The ‘Flowtite’ composite coupling system with gasket snapped right into place. And with composite pipe lengths of 28 feet (8.5 meters) versus 21 feet (6.4 meters) in PVC, there were 25 percent fewer joints.”

Curtis Donovan, a certified independent inspector, tested the pipe’s integrity before the line was put into operation. “The pipes were joint-tested according to the Public Works Standards published by the North Central Texas Council of Governments,” he said. “The protocol calls for holding at a steady internal pressure of 3.5 pounds per square inch (0.24 bar) for 2 minutes. Then the compressor is detached, and the pressure is observed for a period of 10 seconds. A drop of greater than one PSI during the final 10 seconds results in a failed test. For this project, every FRP-to-FRP joint passed on the first attempt.”

Commenting on the pipe’s dimension stability, Donovan said he walked the entire length of the installation at least two times and found every section of pipe to be “perfectly round.”