Underground Infrastructure - April 2023 - 37

Close-Fit Liners
Sectional pipe sizes range from 12 to 120 inches (or larger)
with panel systems for larger sizes. This process is generally
accomplished by inserting short lengths of PVC or GRP pipe
or panels through existing manhole openings. The panel systems
typically have two or more pieces making up a " ring " that
is assembled inside the pipeline. After these systems are put
into place, a non-shrink grout is pumped into the annulus.
These systems are applicable to round, rectangular, egg,
arch and elliptical shaped host piping. Bends and transitions
in size can also be accommodated by the panel systems. Service
re-connections are typically accomplished by excavation.
Spiral-wound pipe is manufactured in narrow continuous
strips of PVC with an interlocking edge that, when installed,
locks the strips together as they are machine wound into the
host pipe. The material has a ribbed structure and can be
reinforced with steel rings for greater strength. PVC spiralwound-in-place
systems can be installed in sizes starting as
small as 8 inches.
A grout-in-place lining system (GPLS) is typically composed
of a thin sheet of plastic, either PVC or HDPE, bonded
to a structural grout layer. The GIPLS is a composite
structure with the original pipeline. Owing to its method
of installation (forms are typically constructed to support
the grouting operation), GPLS is typically limited to worker-entry
size piping. The exception to this is the PVC spiral-wound-in-place
system, which can be installed in sizes
starting as small as 8 inches.
Spiral wound trenchless pipeline renewal is designed for
and used primarily in large-diameter pipelines, typically worker
entry. This process is unique as it can provide a customized
structural solution to aging pipelines.
Segmental panel systems are a series of molded or translucent
PVC panels that, when assembled, form a new pipe or
culvert within the existing damaged structure. A structural
grout may be used to fill the annular space between the new
segmental panel pipe and its host. This restores the structural
strength of the original pipe, as well. The unique see-through
walls allow visual monitoring of the grouting process.
Water Main Lining
Most water main lining technologies require that the existing
pipe be thoroughly cleaned and prepared for application of the
coating. Some cleaning techniques include hydraulic, mechanical,
chemical, swabbing, scraping, pigging and air scouring.
Cured-in-place liner systems are typically installed in pipe
sizes of 6 to 24 inches. These liners span and seal leaking
joints, pinholes and minor cracks. Services/laterals are reinstated
from inside the pipe, with no excavation typically required,
except for access pits. Resins used with potable water
are typically NSF 61 approved. Installation lengths of up to
1,000 feet are not unusual and liners can negotiate bends in
the existing main.
UndergroundInfrastructure.com | APRIL 2023 37
Modified sliplining systems use PE or PVC material that
is either site- or factory-folded or radially reduced prior
to insertion into the host pipe. With the pipe liner profile
reduced in size, allowing for easier installation, it is inserted
utilizing techniques similar to those used in traditional
sliplining applications.
Air or water pressure and/or steam are used to revert the
liner back to its original round shape, thereby forming a close
fit with the host pipe. The new liner isolates the flow stream
from the host pipe wall, eliminating internal corrosion and
typically providing a full structural renovation solution. In
addition, the new liner allows for service connections to be
reinstated either externally to the new liner, or internally with
newly developed robotic technologies.
The sliplining method incorporates the installation of a
smaller or reduced size steel, ductile iron, polyethylene, PVC
or other pipe material inside the existing pipeline. Pressure-rated
pipe capabilities can be selected for most main applications.
In some cases, grouting is required to fill the gap between
the host pipe and the new PE pipe. Very long lengths can
be installed using this method. Service taps are typically excavated
and directly reconnected. Sliplining can be applied
in transmission and distribution mains of 6 to 60 inches in
diameter. UI
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Underground Infrastructure - April 2023

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