A Flexible PVC Pipe Lining System Conforms to Any Host Pipe Shape

Irregular-shaped or badly damaged pipes are no problem for this pliable, steam-heated liner.

A Flexible PVC Pipe Lining System Conforms to Any Host Pipe Shape

A crew from Clearwater Structures uses a Thermoform pipe lining system to rehab a culvert that runs under a highway near Belleville, Ontario.

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A pipe lining system that conforms to any host pipe shape — square, round, ovate and anything in between — might sound highly implausible. But it’s a reality at Clearwater Structures, a civil construction firm in Ontario that has embraced Thermoform pipe lining technology from Warrior Trenchless Solutions.

The company, based in Ajax, just east of Toronto, saw that Thermoform’s shape-shifting capabilities would be an invaluable asset on projects where more conventional pipe rehab technologies can’t be used. Furthermore, Thermoform is a chemically inert PVC product, which makes it more eco-friendly, says Mark Philpott, who co-owns Clearwater Structures with Mike Ciceri.

Founded in 2005, Clearwater Structures employs about 200 people and mainly serves customers throughout the province of Ontario. Its core markets are municipal sewer rehab, bridge construction and steel fabrication.

The company used to primarily rely on cured-in-place felt liners and HDPE lining, where a rigid pipe is pulled into a leaking host pipe. Any annular space between the replacement pipe and the host pipe is filled with grout. But sometimes these rigid pipes can’t pass through a deformed culvert, for example, Philpott explains.

“Thermoform can be used even if a pipe has deformities and deflections. It conforms to the exact shape of the host pipe.

“We’ve used it in projects where pipes were bent or deformed, which would prevent a rigid round pipe from ever getting through. It’s a very good product for damaged pipes located in places where you can’t excavate to make repairs.”

Flexible but strong

Thermoform pipe is made the same way as conventional PVC pipe, except that while it’s still hot during the extrusion process, it’s folded into a C or H shape and then coiled onto reels in whatever lengths are required. It’s available in diameters ranging from 4 to 36 inches, and the wall thickness is variable, depending on the application.

To install Thermoform pipe, it’s first heated with steam to make it flexible and pliable. To do this, Clearwater Structures fabricated a system that’s affixed to a 24-foot-long flatbed trailer; it includes a powerful hydraulic system to turn the large reels that hold the pipe and an enclosure into which the steam is pumped until it reaches about 200 degrees F, Philpott says.

After the pipe is pliable enough, it’s hooked to a cable that’s attached to a winch located downstream. Clearwater Structures uses a winch made by HammerHead Trenchless and boilers made by Sioux and Easy-Kleen Pressure Systems. The winch then pulls the pipe through the host pipe at a speed of about 100 feet per minute.

The pipe cools down in about five minutes, which reduces its pliability. So workers then install steel caps on each end of the liner and pump in steam to make it pliable enough to inflate. Typically, the installation process requires three to four such heating-cooling cycles until the pipe inflates enough to fit tightly against the host pipe, creating a watertight seal; this process could take three to four hours, depending on the ambient temperature outside, Philpott notes.

“The pipe shrinks a bit as it changes shape, which is why you have to repeat those cycles,” he says. “If you don’t do enough cycles, the pipe could eventually crack and fail.

“We monitor the amount of shrinkage after each cycle. When the shrinkage is negligible between cycles, you know you can stop and run a camera through it.” Clearwater Structures relies on an Aries Industries Pathfinder System for pipe inspection.

 Not perfect? No problem

Thermoform offers another key benefit: If the installation isn’t quite right, a crew can reheat the liner, then fix an error while the liner is pliable, Philpott says.

That capability came in handy during Clearwater Structures’ first Thermoform installation, where the liner twisted a bit and left a wrinkle. Workers merely reheated the liner and rotated it slightly by hand, eliminating the wrinkle. “We’ve never had that particular problem again.”

The largest and longest lining project Clearwater Structures has tackled so far involved a 450-foot-long, 24-inch-diameter storm sewer culvert. Buried in the middle of a freeway median, the culvert was accessible only via two manholes, which required the liner to make a sharp, 90-degree bend inside each manhole in order to enter the host pipe.

The company had just 10 hours to do the job before a closed lane of traffic was scheduled to reopen. When the crew couldn’t get through the required heating cycles, Thermoform’s flexibility came into play once again.

“After we ran out of time, we just let the liner collapse inside the host pipe,” Philpott says. “Then we went back the following night and finished the job. You can’t do that with a felt liner. When you run out of time with a felt liner, you’ve got a problem.”

Speed versus value

Philpott says that sometimes Thermoform lining projects can take longer compared to using conventional liners. They also take more care and skill to install; as such, the company relies heavily on Ryan Hack, a lining superintendent who’s “one of the best,” Philpott says.

“It can be tricky to work with. But the true value of this particular technology is that you can use it in so many different pipe conditions. Plus, there’s no release of any harmful chemicals during the installation process.”

So far, Clearwater Structures has installed more than 8,000 feet of Thermoform — primarily inside culvert pipes that run under highways — since it first invested in the technology in 2018. But Philpott says the company is also trying to use it in municipal markets.

“We’ve already used Thermoform to line smaller, 10-inch-diameter sanitary sewer pipes for the city of Toronto. Because it’s a relatively new product, a lot of municipalities haven’t used it yet. It costs a little more than felt liners. But Thermoform also has a longer life span.

“It’s hard to convince municipalities to spend more money upfront on capital costs in exchange for lower life-cycle costs. But it’s emerging technology and a very good product. I believe it’s the product of the future.” 


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