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Cured in Place Pipe

During the cured-in-place pipe (CIPP) renewal process, a flexible fabric liner, coated with a thermosetting resin, is inserted into the existing pipeline and cured to form a new liner. The liner is typically inserted into the existing pipe through the manhole. The fabric tube holds the resin in place until the tube is inserted in the pipe and ready to be cured. Commonly manufactured resins include unsaturated polyester, vinyl ester, and epoxy, with each having distinct chemical resistance to domestic wastewater.

The CIPP method can be applied to rehabilitate pipelines with defects such as cracks, offset joints, and structurally deficient segments. The thermosetting resin material bonds with the existing pipe material to form a tighter seal than most other trenchless techniques.

The two primary methods of installing CIPP are winch-in-place and invert-in-place. These methods are used during installation to feed the tube throughout the pipe. The winch-in-place method uses a winch to pull the tube through the existing pipeline. After being pulled through the pipeline, the tube is inflated to push the liner against the existing walls. The more typically applied inversion-in-place method uses gravity and either water or air pressure to force the tube through the pipe and invert it, or turn the tube inside out. This process of inversion presses the resin-coated tube against the walls of the existing pipe. During both the winch-in-place and inversion-in-place methods, heat is then circulated throughout the tube to cure the resin to form a strong bond between the tube and the existing pipe.

With either CIPP method, as the liner expands to fit the new pipe, dimples occur in the line where the lateral exists. Dimples in the line can be found by video inspection or robotic equipment. In some applications, a tee is placed at the junction before rehab begins. The tee enables junctions to be easily identified and modified after the pipeline has been re-lined. Laterals are typically reinstated with robotic cutting devices (Reinstatement Cutters) or, for large-diameter pipe, by manually cutting the liner.




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