2. Maintenance & Repair

3. Renovation

4. Replacement & New Installation

Renovation

Renovation of pipelines is performed to improve the condition of the sewer or
watermain, which will increase its life expectancy or efficiency. The application of a
protective liner on the interior surface is one of the more common and effective methods
used. Liners are classified according to the materials used and the way they are applied.
They can be classified into three categories:

1. Sliplining

2. Inverted lining

3. Sprayed coatings

3.1 Sliplining

Sliplining of old or deteriorated pipes involves the insertion of a rigid preformed
liner pipe within the existing pipe. Depending on the design parameters, the new liner
will act as either a waterproof or structural membrane, or both. There are many variations
of this basic approach; the following specialized methods are included in this report:

1) Swaging

2) Roll-down

3) Thread-jointed pipe

4) Romo-line

5) Interline

6) "U" Liner

7) Spiral liner


Before any sliplining can commence, the existing pipe must be cleaned, obstructions
removed and a survey performed to determined the size and type of liner required. It is
also necessary to record the position and diameter of all laterals so that they can be
reconnected once the liner is in place. Cutting and reaming of the laterals is done by a
robot and controlled by a technician who, with the aid of in-pipe CCTV, views the
operation on a video screen from ground level.


When using long lengths of butt-fusion welded polyethylene pipe for sliplining, an
entrance pipe has to be excavated to accommodate the liner as it is bent down from the surface to enter the existing pipe. These pits are not needed with mechanically jointed liner pipes since they are normally manufactured in lengths that can be fed into the host pipe from existing manholes or small diameter excavations or caissons.


Typical diameters for liners range from 75 to 1600 mm, with the installation lengths
depending upon the conditions and the system used.

3.1.1 Swaging

Medium or high density polyethylene pipe is generally butt-fusion welded together at
ground level and laid out in its full length ready to be winched through the existing
pipe. The liner pipe is slightly larger than the host pipe, so that it will fit tightly
against the existing wall, thus eliminating the need for grouting. The diameter of the
liner is reduced for insertion by heating the pipe on site using a special process and by
maintaining the pipe in tension during the insertion process. The liner pipe reverts to
its original diameter once the tension is released and the pipe has cooled.

3.1.2 Roll-down

This method is similar to swaging, except that the liner diameter is reduced for
insertion by running the liner pipe through a cold rolling machine. This rearranges the
long chain structure of the plastic to produce a smaller diameter pipe with thicker walls
and minimal elongation. Once the polyethylene liner has been pulled through, reversion is achieved by hydraulically pressurizing the line (see Figure 11 for details). Presently
liners are available in several diameters from 75 to 500 mm.


Roll-down has the advantage over swaging in that the treated liner pipe will remain at
the reduced diameter for a considerably longer period of time. The Roll-down system also does not rely on tension or mechanical means to prevent the liner from reverting to its original size prior to insertion.

3.1.3 Thread-jointed pipe

This form of sliplining is one of the simplest and quickest rehabilitation systems
available. As with all sliplining techniques, the existing sewer must be surveyed and
cleaned and the position of the laterals recorded. Short lengths of slightly undersized
polyethylene pipe are inserted into the existing pipeline at a manhole or small access pit and literally screwed together to form a continuous liner, as seen in Figure 12. As each piece is added, the total length is either pushed or winched towards the next manhole or pit. Upon completion the annular space between the liner pipe and the existing pipeline is grouted.


The patented "in-wall" thread design ensures smooth interior and exterior
pipe surfaces. Although the original cross- sectional area will be reduced, the liner pipe
compensates by providing an improved pipe surface finish, thus increasing flow velocity.


The major advantage of this system is that specialized equipment or skilled labour is not required. The pipe is available in diameters ranging from 75 to 1600 mm and in various lengths, which allow any length of pipe to be lined using multiple pieces.

3.1.4 Romo-line

This system is used for the rehabilitation of non-circular sewers using moulded
polyethylene profiled pipes. Once the existing sewer has been surveyed, the liner profile
is designed such that it will slip through the narrowest section of the sewer but still
maintain the flow characteristics of the original sewer. As with the thread-jointed pipe
described above, the cross-sectional area will be reduced. However, the liner compensates by providing a smoother pipe surface, thus increasing flow velocity.


The liner pipes are manufactured by rotational moulding in lengths that allow
installation from existing manholes and small diameter access shafts. The pipes are
butt-fusion welded in the manhole or shaft, and winched through from manhole to manhole. Once the liner is in place, the annular space between the liner and the existing pipe is filled with a low density foam grout, specific gravity of 1.1. Prior to grouting, the
liner pipe is filled with water and the ends sealed. This reduces deformation and
flotation during the grouting process.

3.1.5 Interline

Interline is a renovation technique intended to separate the waterproofing and the
structural functions of sewer repair. The concept of interline is to waterproof the
existing sewer by means of a flexible sheath through which a structural lining is
installed. The annular space between the waterproofing and the structural lining is then
filled with grout (see Figure 13).


The waterproof sheath is manufactured from PVC coated fabric. The structural liner can
be made from various materials, but generally plastic pipes are used in lengths that will
fit down the existing manholes. Since a separate outer waterproof membrane is used in
conjunction with the pipes, the pipe joints can be the simple open "ogee" type. Prior to grouting, a bag is pulled through the structural liner pipes and inflated with
water. This aligns the pipes, prevents the ingress of grout at the pipe joints and
overcomes the flotation problems associated with grouting.

3.1.6 "U" Liner

This high strength polyethylene liner is used for the rehabilitation of gas and water
mains and sewers. The liner is deformed at the factory to a folded "U" shape under pressure and high temperature. The "U" profile is then fixed by cooling. The deformed liner is available in all shapes and sizes from 100 to 450 mm, with the lengths depending on the shipping capabilities. Once winched into position in the existing pipeline, it is reverted to its original shape using pressurized steam and hot water. Since the liner is manufactured slightly larger than the internal diameter of the carrier pipe, the "U" liner fits tightly against the wall, leaving no annular space. Service connections for sewer lines are reconnected using internal cutters, while external excavation is required for each individual service for watermains and gas lines (see Figures 14a and 14b for details).

3.1.7 Spiral liner

Spiral winding renovation systems create a PVC liner from a continuous PVC profile
strip on site. The strip is fed through a helical winding machine in the bottom of the
existing manhole and fed directly into the sewer or pipeline. The seams in the
spirally-wound liner are mechanically sealed using patented joints specific to each
manufacturer. The diameter of the formed liner is usually slightly less than the existing
pipe. It is therefore necessary to grout the annular space between the two pipes in this
type of installation. However, at least one manufacturer has developed a process whereby the spiral liner is expanded inside the original pipe until it is flush with the pipe wall (see Figure 15).


As with other sliplining techniques, the laterals are reconnected after the grouting
operation. Hydro-jet high water pressure cutting is generally used with this type of
lining installation to open the side wall at each lateral.

3.2 Inverted Lining

This system is used to renovate existing watermains and sewers by lining the walls of
the existing pipe with a hardened synthetic fibre tube. This system differs from
sliplining in that the lining is introduced into the existing pipeline in a soft,
flexible, collapsed condition and then inverted by either water or air pressure, as seen
in Figure 16. Hardening of the resin soaked fibre tube is achieved using steam, hot water or ultra-violet light, depending on the specific manufacturer's process.


The inversion process forces the lining against the existing pipe walls, thus
eliminating the need for annular space grouting. As with sliplining, the cleaning and
clearing of the existing pipeline has to be completed prior to surveying the laterals. The
survey should also record the variations in pipe diameter in order that the fibre tube can
be manufactured to the exact dimensions for a perfect fit.


Once the liner is completely cured, the laterals are relocated and reconnected by
cutting and reaming the liner. Robotic devices guided by a technician at ground level are used for non-man-entry systems. The operator is able to view the operation with the aid of an in-pipe CCTV camera and remote monitor. For man-entry systems, the laterals are reconnected using hand held cutters.


Inverted lining can be used for all pipe shapes, with diameters ranging from 100 to
2700 mm.

3.3 Sprayed Coatings

Sprayed lining systems use either epoxy resins or cement mortar to form a continuous
lining within the existing pipe. These systems result in improved corrosion resistance and additional hydraulic capacity.

3.3.1 Sprayed epoxy resin lining

Sprayed epoxy resin has been used for some time to repair short lengths of damaged and cracked pipe but now attempts are being made to develop this technique into an economical lining system. The system consists of a lining machine which is winched through the pipeline while straddling two profiled and static hoses, which it splits open to draw supplies of resin and hardener. The coating or resin sticks to wet surfaces because it is hydrophobic and applied with a high impact force. At laterals, the spray forms small blobs scattered harmlessly along the pipe.

3.3.2 Sprayed cement mortar lining

Sprayed cement mortar lining is a proven economical technique for the renovation of
deteriorated cast iron, ductile iron and steel pipelines. As with other liners, the pipes
must first be thoroughly cleaned and dried. For diameters between 100 and 600 mm, the cement mortar is applied by a robot. The mortar is pumped to a head which rotates at high speed using centrifugal force to place the mortar on the walls (see Figure 17). A
conical-shaped trowel attached to the end of the machine is used to smooth the walls. For larger diameter pipes, 600 to 3600 mm, the cement is carried to the lining machine by carts. The length is limited by the length of hose available and the distance between
valves, bends, tees, etc.

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