Insituform Sets New Record for Large-Diameter Sewer Rehab in the Netherlands

It’s not every day that you get the opportunity to repair a sewer big enough for a professional basketball player to stand up inside. But Insituform Rioolrenovatietechieken bv, Insituform’s Netherland subsidiary, accepted the challenge and, in doing so, completed its largest pipe rehab project ever. The largest diameter sewer ever rehabilitated in the Netherlands using the Insituform® process was a 5.9-foot (1,800 mm) diameter sewer in Amsterdam that the company repaired in 1996.

The Tilburg sewer, which is 6.5-feet in diameter and more than three foot ball fields long, is located beneath a busy street in an industrial section of Tilburg, a city of 200,000 in the Netherlands.

Tilburg city officials first became concerned about the concrete pipe when they noticed several gaps in the road above it. Further inspection found several leaking joints, which were made worse by rising groundwater.

After considering several alternatives, including sliplining and completely replacing the 43-year-old sewer, the City opted for the Insituform ® cured-in-place pipe (CIPP) rehabilitation method. On a typical project, a crew works from a manhole, using water pressure to insert a flexible liner inside the sewers. Once in place, the liner is then heated and cured into a structurally sound pipe-within-a-pipe with a life span comparable to that to a new sewer. Given the Tilburg sewer’s size, however, this project wasn’t exactly typical.

After the liner’s thickness had been calculated to withstand the area’s groundwater pressure, a custom-made felt tube was ordered from Insituform® Linings PLC, the U.K. manufacturer of Insituform materials. Normally, the felt tube would then be shipped to the Insituform facility in Delft, The Netherlands, to be impregnated with thermosetting resin.

Because of the tube’s large size, however, it was shipped instead to Insituform France, which had the facilities needed for the special large-diameter vacuum impregnation process. There, over the course of three days, workers injected more than 70 tons of thermosetting resin into the 941-foot-long (289-meter-long) tube. To make the trip to Tilburg, the “super-sized” impregnated tube required special transportation. The resin-filled tube, plus the trailer produced a combined total load of approximately 110 tons (100,000 Kg). Because of load restrictions on some roadways, alternate routes added an additional 186 miles (300 km) to the trip. On a Monday morning, February 10, workers closed incoming sewers and dismantled a manhole in the vicinity of the sewer line. The dismantling was necessary because the impregnated tube couldn’t fit through the existing 20 _-inch-diameter manhole.

By the time the tube arrived at the site at the end of February, Insituform and Tilburg officials had already made preparations for handling traffic and ensuring the safety of the workers and passersby.

“There are a lot of issues to be aware of, so good preparation was essential,” says E. Uppelschoten, account manager at Insituform Rioolrenovatietechieken bv. “The biggest difference between a small-diameter and a large-diameter sewer like this is know-how.”

On February 21, workers used hydrostatic pressure to invert (turn inside out) the massive tube in the sewer through the dismantled manhole. The water pressure forced the tube through the pipe while pressing it tightly against the inside of the existing pipe.

Once the tube reached the termination point, the inversion water – all 1,240 cubic yards (950 cubic meters) of it -- was circulated through four heat exchangers to reach a temperature of approximately 176° F (80ºC). The heat cured the resin, forming the tube into a hard, jointless and corrosion-resistant pipe-within-a pipe. After the water cooled down and was removed, workers went on to open and renovate the 19 lateral sewers connected to the main line.

Tilburg city employees walked through the renovated sewer to see the results for themselves, before reopening the sewer on February 28.

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