Page 331 - Trenchless Technology Piping Installation and Inspection

290 Cha pte r Se v e n

The wet-out equipment is generally fixed in place and can be main-
tained on as needed basis. Tubes can be wet-out using a static mixing
system that regulates and combines the correct amounts of resin and
catalyst for a proper wet-out of the tube. Once the tube is wetted-out,
it can be placed, on ice, into a refrigerated unit and delivered to the
job site. The majority of CIPP tube wet-out is performed in a factory
setting. Specially designed truck trailers make it possible to haul large
diameter and long length tubes.

7.4 CIPP Installation Methods
As mentioned earlier, there are two basic methods of CIPP installa-
tion: the pulled-in-place process and the inversion process. Different
manufacturers provide specific variations of these techniques. This
section provides more details for each method.

7.4.1 Pulled-in-Place Process
Using a power winch, the impregnated tube is typically pulled
through an existing manhole or other approved access point, fully
extending the tube to the next designated manhole or termination
point. Water and/or air are used to inflate the liner after it is pulled in
the existing pipe. Care needs to be exercised not to overstress and
damage the tube during pull-in as a result of increased friction, espe-
cially where curve alignments, offsets, protruding services, and other
friction-producing existing pipe conditions are present. The pulling
force induced on the tube, as it is being pulled into the existing pipe,
should be monitored and should not exceed the recommended maxi-
mum allowable pulling force for the size and thickness of tube being
installed.

7.4.2 Inversion Process
In the inversion method, the resin saturated tube is inserted through
an existing manhole or other approved access point and then installed
into the existing pipe by means of a pressurized (water or air) head,
with a volume sufficient to fully extend the tube to the next desig-
nated manhole or termination point. The speed of inversion typically
should not exceed 30 ft per minute for small diameter tubes. Larger
diameter tubes are installed significantly slower as recommended by
the manufacturer. Figure 7.5 illustrates inversion technique of CIPP
installation.
In order to monitor the curing temperature, a thermocouple or
temperature measuring device is installed at access points between
the existing pipe and the CIPP liner at the pipe invert or 6 o’clock
position. These devices can be placed at each end and at all inter-
mediate manhole access points along the length of the installation.