Cured-in-place pipe project tests composites capabilities

Insituform Technologies' iPlus Composite cured-in-place pipe (CIPP) technology helped reduced the time and cost of expanding San Diego International Airport (San Diego, Calif., USA). Insituform (St. Louis, Mo., USA) completed the work using Vipel resin from AOC Resins (Colliersville, Tenn., USA).

Expansion plans by the San Diego Airport Authority put a new terminal over a 96-inch/2,438-mm diameter concrete sewer pipeline. The pipe was 25 ft/7.6m underground and not designed for the structural loads the new project would add. Because pipe excavation and replacement was deemed unfeasible, engineers explored trenchless technologies.

Keeping the wall thickness of the new liner at less than 1.26 inches/32mm became a critical design factor to ensure that the upgraded pipe’s flow rate could handle current and projected volumes. To make the liner strong enough, slip-lining would have added approximately 12 inches/305 mm of wall thickness; conventional CIPP would have added 2.07 inches/51 mm.

For a solution, general contractor Charles King Co. asked Insituform Technologies to install a custom 1,700-ft/518m-long fiber-reinforced iPlus Composite liner. Carbon fibers in the iPlus Composite for the airport project resulted in a pipe strong enough to withstand the new structural loads at a wall thickness that is 40 percent less than conventional CIPP.

The Vipel 102NA resin is specially designed to efficiently wet out the reinforced liner,” says Bill Moore, AOC product leader for CIPP. “The resin technology optimizes the performance and superior mechanical properties of the carbon fiber-reinforced composite structure.”

With no appropriate manhole available for the installation, site workers created a single access point for two inversions in opposite directions. The job established a new benchmark for iPlus Composite technology, which to date had not been used for a water inversion greater than 200 ft nor in a host pipe larger than 60 inches in diameter.