Page 314 - Trenchless Technology Piping Installation and Inspection

278 Cha pte r Se v e n

7.1.2 Method Description
Cured-in-place pipe (CIPP) is a thermoset resin system (polyester, vinyl
ester, or epoxy) that is delivered via a felt, fiberglass, or carbon fiber
tube of the design thickness specified. After cleaning and inspection,
the existing pipe is used as a mold. The soft, resin impregnated and
saturated, tube is inserted by inverting the tube into position using
water or air. Another method is to first pulling the tube into place by a
winch and then inflating it with air or water. Once in place and properly
inflated, the resin is cured using hot water, steam, or ultraviolet light,
resulting in a new pipe within a pipe. See Sec. 7.4 for more information.
Although originally developed for sanitary sewer applications,
CIPP may be manufactured to suit many pipeline shapes, and can
accommodate deformations and changes in direction of the pipe.
Using this technology, pipe lengths up to half mile have been installed
successfully in one single operation.

7.2 Site Compatibility and Applications
Cured-in-place pipe (CIPP) can be used effectively for a wide range
of applications that include sanitary and storm sewers, gas pipelines,
potable water pipelines, chemical and industrial pipelines, and pres-
sure pipelines. There are a variety of tube materials and configura-
tions, including reinforced or nonreinforced, that can be used with a
variety of liquid resin systems, to address structural and corrosion
resistance requirements. The physical properties of CIPP make it
especially suitable for different types of pipe geometries including
straight pipes, pipes with bends, pipes with different cross-sectional
geometries, pipes with varying cross-sections, pipes with lateral con-
nections, and deformed and misaligned pipelines. However, several
factors must be evaluated before choosing CIPP as the method of
renewal for an individual project. Factors such as space availability,
chemical composition of the fluid carried by the pipeline, the number
of laterals, the number of manholes, installation distance, renewal
objectives, structural capabilities of the existing pipe, and the like,
must be assessed before making a choice on the renewal system. CIPP
is also used for localized repairs in a wide range of pipe applications.
The possibility of negotiating bends depends on the installation
and curing process of the various systems. Pipe liners that are inverted
during insertion can often negotiate bends up to 90°. There are, how-
ever, limitations to the degree of bending that ultraviolet (UV) cured
liners can manage. Bends can also present problems for liners that are
pulled into place, because the liner must remain on the underlying
protective foil and must under no circumstance become twisted. It is
important to be aware that vertical folds and wrinkles may occur in
the liner when negotiating sharp bends. Table 7.1 presents an over-
view of CIPP applications and possible limitations.