Ultra Solution

A thermoforming PVC alloy pipe enables a Florida utility to reline a culvert scheduled for open-cut repair, save money and reduce disruption.

Point repair crews from the Atlantic Beach (Fla.) Public Works Department had made several repairs to the road and inlets at either end of a 50-foot-long elliptical culvert in a residential area. The department was concerned that the culvert could collapse with the next big rainstorm.

The city had obtained a quote from its point repair contractor for replacing the 45-year-old, 18- by 29-inch elliptical metal pipe culvert by open-cutting the road, but public works director Rick Carper wanted to test a trenchless solution.

Steve Bagby of S Bagby and Company in Jacksonville Beach put Carper in touch with Gary Pender, vice president of Engineered Lining Systems Inc. (ELS) in Jacksonville. Bagby had seen the results ELS achieved relining storm drains using a custom PVC alloy fold- and-form piping system manufactured by Ultraliner Inc. in Oxford, Ala. Carper invited Pender to demonstrate the process on the damaged culvert.

Master mold

A public works crew cleaned the line, and the ELS team inspected it. “The culvert was heavily corroded with breached joints,” says Pender. “There were several places three to four feet long and inches wide where corrugated pipe was missing.”

ELS engineers determined that a 24-inch Ultraliner with a standard 3/4-inch thick wall would work. The factory-produced liner arrived folded like an “H” lying on its side and wrapped around a wooden spool. A boom lifted the spool into a hotbox where steam from a boiler truck at 280 degrees heated the material until it was pliable enough to be pulled.

The head of the liner was tapered, and two opposing holes were then drilled 12 inches in from the edge. “We fed a chain through the holes, hooked it to a 3/8-inch cable, and inserted the liner through a brick catch basin,” says Pender. The 30-ton hydraulic winch across the street pulled the liner through the culvert in less than 90 seconds.

A flow-through sewer plug from Plug-It Products sealed the upstream end, allowing a hose to introduce steam that heated the alloy and prevented post-installation longitudinal shrinkage. Once the downstream end was plugged, the team increased the boiler pressure to 18 psi to inflate the liner.

Letting off steam

Once the liner formed to the pipe, the pressure was reduced to 12 psi to hold it in place as an after-cooler blew in 80-degree air. “We monitor the temperature at the exhaust end,” says Pender. “Once it drops below 100 degrees, we turn off the pressure because the liner is hard enough not to collapse. The process is very fast.”

Depending on the diameter and length of the pipe, liners cure in one to two-and-a-half hours. If a mistake occurs, the liner can be reheated, extracted, and reinserted.

Engineers, project managers, and designers from Atlantic Beach and Jacksonville Beach public works departments observed the demonstration. “Ultraliner lined the complete culvert and made a substantial improvement,” says Carper. “Before the repair, I had a skeleton of a corrugated metal pipe that was showing me ribs. The demo proved the product’s worth to our department.”



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