Page 83 - Trenchless Technology Piping Installation and Inspection

Existing Pipeline Renewal and Replacement Methods 53

• Productivity and schedule
• Quality of installation
• Project cost-effectiveness
• Applicability and constructability

Table 2.4 present specific applications of renewal and replacement
methods for common pipeline problems. Table 2.5 presents the main
characteristics of specific renewal and replacement methods. More
information on the main methods of lining and replacement systems
are provided in the following sections with additional installation con-
siderations for pipe replacement and CIPP are presented in Chap. 6 and
Chap. 7 respectively. Figure 2.4 illustrates a guide to select a trenchless
renewal, replacement or repair method. Due to the importance of coat-
ings and linings (CL) in potable water pipe applications, Chap. 3 is
dedicated to these methods.

2.3.1 Cured-in-Place Pipe
The cured-in-place pipe (CIPP) process involves the insertion of a
resin-impregnated fabric tube into an existing pipe by use of water or
air inversion or winching. Usually the fabric is a polyester material,
reinforced fiberglass, or similar. Usually water or air is used for inver-
sion process. The pliable nature of the resin-saturated fabric prior to
curing allows installation around curves, filling of cracks, bridging of
gaps, and maneuvering through pipe defects. CIPP can be applied for
structural or nonstructural purposes. Figure 2.5 shows a CIPP instal-
lation process.

2.3.2 Sliplining
Sliplining (SL) is mainly used for structural applications when the
existing pipe does not have joint settlements or misalignments. In this
method, a new pipeline of smaller diameter is inserted into the existing
pipe and usually the annular space between the existing pipe and new
pipe is grouted. This installation method has the merit of simplicity
and is relatively inexpensive. However, there can be a loss of hydrau-
lic capacity.
Sliplining can be categorized into two main categories: continuous
and segmental. The continuous sliplining method involves accessing
the deteriorated pipe at strategic points and inserting high-density
polyethylene (HDPE) or polyvinyl chloride (PVC) pipe, joined into a
continuous pipe string. The segmental sliplining method involves
the use of short sections of pipe that incorporate a flush sleeve joint
commonly used in microtunneling and pipe-jacking processes.
Figure 2.6 illustrates a schematic diagram for the conventional sliplin-
ing process.