The cured-in-place-pipe, also known as CIPP, is a soft lining layer impregnated with liquid thermosetting resin on the inner wall of the existing old pipe. It is cured by heating (using hot water, hot steam or ultraviolet rays, etc.) or solidifying at normal temperature to form a thin tube closely matching the old pipeline. There is almost no loss in the section of the pipeline, but its flow performance is greatly improved. There are two construction methods for the soft lining method, namely, the reverse impregnation resin hose lining method and the CIPP pull-in resin lining method.
1. Inversion lining of impregnated resin
In this technology, fiber reinforced hose or braided hose with impermeable film soaked in thermosetting resin is used as lining material. One end of the hose soaked with resin is turned over and fixed at the inlet of the pipeline to be repaired. Next, the inner layer of the soft liner immersed in resin is turned over to the outside by using water pressure or air pressure, and then it is bonded with the inner wall of the old pipe. When the soft liner reaches the end point, hot water or steam is injected into the pipe immediately to solidify the resin, forming a layer of anti-corrosion and anti-seepage hard lining close to the inner wall of the old pipe. The flexibility and internal pressure of the resin tube before curing can make it fill cracks, span gaps, and bypass bending sections. After the resin is cured, the soft liner tube forms a new tube with the same shape as the original tube and a slightly smaller inner diameter than the original tube.
2. CIPP pull-in method lining
CIPP pull-in method lining is to use the non-woven felt hose with anti-seepage film. After being fully impregnated with resin, it is pulled into the pipeline to be repaired from the inspection well. The hose is rounded by water pressure or air pressure, and a solid and smooth new pipe is formed after solidification, so as to achieve the purpose of rehabilitation. According to the repair of old pipes abroad, due to the strong adaptability and reliable quality of this technology, a shovel of soil doesn't need to be moved by using inspection well operation. It is trenchless rehabilitation in true sense and has been widely used in sewage pipeline rehabilitation.
The loss of the over-flow section of the pipeline repaired by CIPP is basically negligible, but its flow performance is greatly improved. This kind of repair technology can be used to repair cast iron pipe, steel pipe, concrete and other underground pipelines. It can be used not only for the rehabilitation of water supply, sewage and gas pipelines, but also for the chemical industry and other industrial pipelines. It is especially suitable for the pipelines in the city where the traffic is congested, the ground facilities are concentrated or occupied seriously, and the conventional excavation method that cannot be used to repair and update the pipelines. This repair technology has the advantages of all-weather construction, no joints, good fluidity, and adaptability to non-circular cross-sections as well as curved pipe sections. It can be applied to repair various pipelines with a diameter of 50～2000mm. Its limitations are high requirements for pipeline cleaning, high cost, long resin curing time (generally more than 5h) and each section of construction braided pipe needs to be customized separately.