Page 93 - Trenchless Technology Piping Installation and Inspection

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FIGURE 2.9 A resin lining process. (Source: Raven Lining Systems.)

2.3.5 Close-Fit Pipe
This type of trenchless pipeline renewal temporarily reduces the
cross-sectional area of the new pipe before it is installed. After place-
ment, liner expands to its original size and shape at the jobsite, just
to provide a close fit with the existing pipe and for pressure (more
common) and gravity applications. This method can be used for both
structural and nonstructural purposes. Lining pipe can be reduced
on-site and reformed by heat and/or pressure or in case of thin poly-
ethylene pipe. There are two versions of this approach: structural and
semi-structural. Figure 2.10 presents a semi-structural close-fit pipe
(CFP) process.

2.3.6 Thermoformed Pipe
Thermoformed is a terminology in North America for pipes that are
reduced in cross-section in factory, by folding. After insertion, the
liner is heated (thermoform) to conform to the existing pipe dimen-
sions with a close fit. Both PVC and PE can be used for this method,
but PVC is more common. A sample thermoformed pipe (THP) is
illustrated in Fig. 2.11.