Page 332 - Trenchless Technology Piping Installation and Inspection

Construction and Inspection for Cur ed-in-Place Pipe 291

FIGURE 7.5 Inversion technique of CIPP installation. (Source: Insituform
Technologies.)

The manufacturer should be consulted for a recommended use of
thermocouples applicable to their liner system. The thermocouple
wires can be used for both pull-in and inverted techniques, and are
critical for monitoring the curing of the resin/catalyst system. These
sensors must be installed before the tube is in place or before the
tube is pressurized.

7.4.3 Preliner Options
In some cases it may be necessary to install a preliner into the existing
pipeline to prevent washout or contamination of the resin, or to
reduce friction during liner installation. A preliner may be required
for heavily leaking pipelines, existing pipes located under ground-
water, in contaminated soils, and existing pipes containing coatings
that are not compatible with the liner and resin being installed. Pre-
liners will remain in place and become part of the liner pipe installa-
tion. Depending on the nature of the leakage or friction, two other
options are available: grouting of the existing pipeline to eliminate all
infiltrating water, or installing a foil along the invert of the existing
pipe to reduce friction during pull-in of the CIPP liner.

7.4.4 CIPP Liner Curing
As said earlier, there are three methods of resin curing. The most com-
mon method is curing by hot water. In this method, cure temperatures
are monitored at access points and at each end of the installation.
Figure 7.6 illustrates hot water curing. The second method is curing
with hot air or steam. In this method, once the liner is in place and