Inliner Technologies files patent for steam-cure process with cured-in-place pipe

Dec. 17, 2003
Inliner Technologies LLC has filed a U.S. patent application for its particular method of using a combination of steam and compressed air to cure the resin in cured-in-place pipe.

PAOLI, Ind., Dec. 17, 2003 -- Inliner Technologies LLC has announced that it has filed a patent application with the United States Patent and Trademark Office for its particular method of using a combination of steam and compressed air to cure the resin in cured-in-place pipe (CIPP).

The filing is based on Inliner's method of calculating the cure time vs. liner temperature relationship, as applies to environmental factors including presence of groundwater, whether the groundwater is moving or static, and ground temperature.

While steam has been listed in the ASTM standards since the mid-1980s, its use has been limited because of insufficient knowledge about the process. "With styrenated-based resins, if the temperature rises too high, too quickly, the styrene can boil," said Ed Kampbell, PE, Inliner's vice president and general manager. "This would create voids in the CIPP wall structure, producing an unacceptable finished product."

Long-term benefits of using steam to cure CIPP include a higher quality finished product, as the higher temperatures achieved by using steam allow for a more thorough cross-linking of the resin. "Steam-cured CIPP shows typical gains of 20 to 25 percent in flexural modulus of elasticity," Kampbell said.

Among the short-term benefits include a faster processing time and less intrusion on sensitive landscaping.

"A project that would take two to three hours to cure with heated water, takes approximately 45 minutes with steam," said Kampbell. "And steam-curing is less intrusive because steam hoses are smaller and can be run through sensitive landscaping environments if the access points are remote from where the equipment is parked, such as a back yard, without removing fences or damaging groundcover," he added.

"For heated water cures, the pumping equipment has limits on the distance in which it can create enough suction lift to circulate the water," Kampbell explained. "Because steam doesn't create the weight that water does, it is an excellent choice for steeply sloped applications."

Inliner's research has shown that the steam-curing method is ideal for lines that are four inches to 24 inches in diameter, but has already used steam to successfully renew pipes up to 60 inches in diameter.

Inliner has also applied for a patent on its re-engineered fittings that seal the ends of the liner during curing. The fittings have an expanding taper on the barrel that tightens its hold on the tube as the tube wants to slip out - thus providing a stronger resistance to blowout, increasing the safety level for workers.

About CIPP

CIPP technology allows for the rehabilitation of damaged underground wastewater and storm sewer pipe without excavating. The process reduces noise, traffic disturbance, and road damage - and can be done in a shorter time frame and for less cost than replacing existing lines. With Inliner's method, a felt tube - saturated with resin and coated with a waterproof layer - is inserted into the pipe.

Hot water or steam is circulated through the tube, which hardens the resin. This material serves as a barrier between the damaged pipe and the wastewater that flows through it, or as a new stand-alone pipeline.

About Inliner Technologies

Inliner Technologies LLC is one of the largest CIPP companies in the U.S., with four licensees performing pipe renewal projects throughout the nation. Licensees include Kenny Construction Co., Reynolds Inc., Western Slope Utilities, and Lametti & Sons. Inliner Technologies maintains headquarters at 1468 West Hospital Road, Paoli, Ind. For more information, please visit