Cured-in-place pipe

A cured-in-place pipe (CIPP) is one of several trenchless rehabilitation methods used to repair existing pipelines. CIPP is a jointless, seamless, pipe-within-a-pipe with the capability to rehabilitate pipes ranging in diameter from 0.1–2.8 meter (4"–110"). As one of the most widely used rehabilitation methods CIPP has application in water, sewer, gas, and chemical pipelines.

A resin-saturated felt tube made of polyester, fibreglass cloth or a number of other materials suitable for resin impregnation, is inverted or pulled into a damaged pipe. It is usually done from the upstream access point (manhole or excavation). It is possible to invert the liner upstream (e.g. from the downstream access point) but this carries greater risk. It is possible to install a liner from the downstream access point, upstream to a blind end however this carries the highest risk of all the CIPP installation methods. Little to no digging is involved in this trenchless process, making for a potentially more cost-effective and less disruptive method than traditional "dig and replace" pipe repair methods. The liner can be inverted using water or air pressure. The pressure required for inversion can be generated using pressure vessels, scaffolds or a "Chip unit". Hot water, UV light, ambient cured or steam is used to cure the resin and form a tight-fitting, jointless and corrosion-resistant replacement pipe. Service laterals are restored internally with robotically controlled cutting devices in the larger diameter pipe. Smaller diameters (100mm) can be opened remotely however they are often reinstated by excavation. The service lateral connection can be sealed with specially designed CIPP materials. The resin used is typically polyester for mainline lining and epoxy for lateral lines. Since all resins shrink (epoxy resins shrink far less than poly and vinyl ester versions) and it is impossible to bond to a sewer that has fats, oils, and grease an annular space exists between the new CIPP liner and the host pipe. The annular space exists in all installations just some are larger than others and depending on the severity may need additional rehabiliation. There are multiple ways to prevent water from tracking in the annular space and entering back into the waste stream including: water swelling material (hydrophilic), lining of the entire connection and host pipe with a continous repair (YT repari) gaskets, and point repairs placed at the ends of the host pipe and at the lateral connections. The rehabilitated pipe is then inspected by closed-circuit television (CCTV). CIPP is considered a trenchless technology.

...
Wikipedia