Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR LINTNG A PIPE OR MAIN
The present invention relates to a method for lining a pipe
or main and is particularly directed to the lining of
underground gas or water mains or sewer pipes.
A method for lining a pipe or main is known comprising
providing a length of synthetic-resin liner pipe of external
diameter substantially equal to or greater than the internal
diameter of the pipe or main to be lined. The liner pipe is
mechanically deformed to reduce its external diameter to less
than the. internal diameter of the pipe or main to be lined,
generally by pulling the liner pipe through a die. The liner
pipe of reduced diameter is then caused to enter the pipe or
main to be lined. This method is known by the registered
trade mark 'swagelining'. Examples of this method are
described in GB 2186340, GB 2218370, GB 2218484, GB 2218485,
GB 2218486, GB 2218487, GB 2218488, GB 2218489, GB 2221741,
GB 2242850, GB 2257767, GB 2257768 and GB 2288216.
However, the liner pipe may become at least slightly porous,
especially when the lined pipe or main conveys high pressure
fluid. Some conveyed fluid may pass through the wall of the
liner to between the liner and the pipe or main. When the
flow of fluid through the lined pipe is stopped or
interrupted reducing the pressure within the liner, the
CONFIRMATION COPY
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pressure of the fluid between the liner and the pipe or main
may cause the liner pipe to collapse.
According to the present invention the liner pipe is provided
with means to convey fluid along the length of its outside
surface and a vent is provided in fluid communication with
the means to convey fluid along the outside surface of the
liner pipe.
The present invention enables fluid trapped between the liner
and the pipe or main to be expelled through the vent
preventing collapse of the liner when fluid flow is stopped
or interrupted. The vent may be provided with a one way
valve. The means to convey fluid along the outside surface
of the liner pipe may comprise one or more grooves along the
length of the liner pipe. The grooves or ridges may form one
or more longitudinal passages along the length. of the outside
surface of the liner pipe. If there are more than one
longitudinal passages along the length of the liner pipe they
may be interconnected at one or more points along their
length. The groove may be arranged spirally around the
liner pipe or a plurality of passages may be provided in an
array around the liner pipe. The means for conveying fluid
along the outside surface of the liner pipe may comprise one
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or more conduits provided with means for fluid to enter or
leave the conduits.
Before causing the liner to enter the pipe or main the liner
may be heated to assist the reduction of its diameter.
However, the liner need not be heated and may be used to line
the pipe or main in normal atmospheric or 'cold' conditions.
An example of the present invention will now be particularly
described with reference to the drawings in which:
Figure 1 is a plan view of a rig suitable to preheat and
reduce the external diameter of a length of liner pipe,
Figure 2 is a more detailed cross-section of the front end of
the rig in use,
Figures 3 to 9 show in schematic form a typical sequence of
operations in the lining of a section of an existing main and
Figures 10 and 11 are longitudinal sections through one form
of device for closing the ends of the liner pipe so that it
can be expanded by pressurisation, Figure 10 showing the
situation before expansion and Figure 11 the situation after
expansion.
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Referring to Figure 1 the rig 1 comprises a heater tube 2
which in use is supported above ground on a support frame 3
(see also Figures 5 and 6). The tube 2 has a rear end 4 to
receive a liner pipe for preheating on passage through the
tube 2 and a front end 5 adapted to reduce the external
diameter of the preheated liner pipe.
Extending parallel to the heater tube 2 is a smaller diameter
tube 6 serving to provide hot gas for preheating a liner pipe
within the heater tube 2.
The tube 6 is closed at a rear end 7 by an apertured plate ~8
through the aperture of which extends a gas supply pipe 9 for
supplying gas to a gas fired burner 10 located within the
tube 6. The tube 6 is provided with an air-take 11 at a
point adjacent to the plate 8 to supply air for combustion of
the gas within the burner 10.
Hot gas supplied by the burner 10 travels forwardly in the
direction of the arrows to. an elongated chamber 12 forming
the front end of the tube 8. The chamber 12 terminates in a
distributor 13 which has a rectangular outlet 14
communicating with a similar shaped rectangular slot in the
wall of the heater tube 2. In this way the hot gas is
caused to renter the heater tube 2 from the chamber 12
radially at a point adjacent to its front end 5 taking the
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direction of the arrows. Once inside the tube 2, the gas
travels rearwardly in the direction of the arrows.
Some of the hot gas then leaves the tube 2 by way of an
exhaust pipe 15 located adjacent to the rear end 4 of the
tube 2. The remaining majority of the hot gas re-enters the
tube 6 by way of a radial tube 16 connecting the tubes 2 and
6 at a point adjacent to their rear ends.
The chamber l2 is provided with a circulating fan 17 to cause
the circulation of the gas within the assembly to be
accelerated.
Referring to Figures 1 and 2 the front end of~the tube 2 is
formed by two swaging dies 18 and 19 serving in use to reduce
the external diameter of the liner pipe 20 being drawn
therethrough.
A first die 18 is located within the tube 2 and is held
within a die holder 21 secured to the internal wall of the
tube 2. The first die 18 has a forwardly tapering entry
section 22 leading to a circular exit section 23. The
tapering entry section 22 serves to provide the initial and
major proportion of the reduction in the external diameter of
the preheated liner pipe 20 as shown in Figure 2.
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The second die 19 is located beyond the end of the tube 2 and
is bolted to a circular flange 24 welded to the outer surface
of the tube 2. The second die has a forwardly tapering
aperture 25 serving to provide a final and minor proportion
of the reduction in the external diameter of the preheated
liner pipe 20.
In use, the preheated liner pipe 20 is drawn sequentially
through the dies 18 and 19 by means of the cable 26 of the
winch (shown in Figure 4). To achieve this the leading end
of the liner pipe 20 is formed in the shape of a cone 28 by
cutting the end of the liner pipe 20 into suitably triangular
portions 29, folding the portions 29 to form the cone 28 and
then welding adjacent portions 29 together. These portions
29 are formed with holes to receive the ends of bolts 30 and
gaps 31 are Left between the portions 29 so that when the
cone 28 has been formed the inside of the cone 28 can be
accessed manually to place nuts 32 on the ends of the bolts
30. Next a steel cone 33 matching the tip of the pipe cone
28 is placed over the tip as shown in Figure 2, the steel
cone 33 having holes to correspond with those in the pipe
cone 28, and the cones 28 and 33 are bolted together by the
nuts and bolts 30 and 32.
The steel cane 33 has an eye 34 which is in use as shown in
Figure 2 connected to the cable 26 of the winch.
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The internal diameter of the wall of tube 2 is greater than
the external diameter of the liner pipe 20 so that an annular
space 35 is formed between the outer wall of the liner pipe
20 and the inner wall of the tube 2. In use, this space 35
when the liner pipe 20 is within the tube 2 is enclosed at
one end by the internal die 18 and at the other end by an
apertured plate 36 attached to the rear end 4 of the tube 2,
the wall of the aperture 37 in the plate 36 forming a close
fit with the external wall of the liner pipe 20. Thus, the
hot gas entering the tube 2 from the distributor 13 is caused
to flow within the enclosed annular space 35 to heat the
external wall of the liner pipe 20.
Referring to Figures 3 to 9, in the first stage of the lining
process (Figure 3) the section 40 of the main 41 to be lined
has ends 42, 43 isolated from adjacent portions 44, 45 ~of the
main 41. This is done by digging excavations 46, 47 at two
distant points in the main 41 and then removing pieces from
the main 41 to expose the ends 42, 43 of the section 40,
In the next stage of the process (Figure 4) a motorised winch
48 is mounted at ground level adj acent to the end 42 of the
main section 40. A stiff rod 49 is then pushed along the
main section 40 from the end 42 to the end 43. That end 50
of the rod 49 nearest the winch 48 is connected to the winch
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cable 26 after the cable 26 has been fed through guide rolls
51 mounted on the floor of the excavation 46. The rod 49 is
then pushed completely through the main section 40 so that
the cable 26 eventually emerges from the end 43 of the
section 40. The cable 26 is then detached from the rod 49
and is fed through the reducing rig 1 as shown in Figure 5.
The cable 26 is then attached to the leading end of the pipe
liner 20 in the manner previously described with reference to
Figure 2. Sections of the pipe liner 20 are fed
successively to a butt-welding machine 60 located upstream of
the reducing rig 1. The machine 60 enables adj oining ends
of the pipe liner sections 20 to be butt welded together to
form a continuous length. The machine 60 may have
facilities for removing both internal and external weld beads
from the pipe liner which ideally is of polyethylene. The
outside surface of the pipe liner 20 is provided with grooves
along its length to enable fluid to pass along the length of
the pipe liner 20 between the pipe liner 20 and the main
section 40 when fitted.
The motor of the winch 48 is then actuated to draw the cable
26 towards the end 43 of the main section 40 as shown in
Figure 6. This causes the liner pipe 20 to enter the
heater 2 through which hot gas is circulating. The liner
pipe 20 is then preheated by the gas in the manner previously
described to a temperature of about 100°C and the preheated
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pipe 20 is then drawn through the dies to effect a reduction
in the external diameter of the pipe 20 to an extent
permitting the reduced diameter pipe 61 to enter the end 43
of the main section 40 by way of guide rolls 62 mounted on
the floor of the excavation 47.
The reduced diameter pipe 61 is then drawn as a continuous
length along the main section 40 to and out of the far end 42
as shown in figure 7. The reduction in diameter of the
liner pipe 20 may be of the order of 30 or more.
Once the liner pipe 20 has reached and extended beyond the
far end 42 of the main section 40, the winch cable 26 is
disconnected from the eye 34 on the steel cone 33. ~ The
steel cone 33 is then removed from the pipe cone 38 thus
leaving the liner pipe 20 with ends 62 and 63 lying exposed
beyond the ends 42, 43 of the main section 40.
The liner pipe 20 may be left to expand into contact with the
internal wall of the main section 40.
However, in this example both ends of the pipe 20 are closed
by closures 64 and air is injected into one end of the pipe
20 by mews of a compressor 65 mounted at ground level
adjacent to the end 63 of the main section 40 as shown in
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Figure 8. The air is injected at super atmospheric pressure
e.g. 2 to 67 bar for an extended period say 24 hours. This
causes the liner pipe 20 to expand into contact with the
internal wall of the main section 40 as shown in Figure 9.
A suitable closure 64 for the liner pipe 20 is shown in
Figures 10 and 11. The closure 64 comprises a tubular
sleeve 66 for receiving one end of the liner pipe 20 and a
cap 67 for attachment to the sleeve 66.
The cap 67 has a cylindrical portion 68 having an outwardly
flanged open end 69 for connection to a similar outwardly
flanged end 70 on the sleeve 66 by means of several nut and
bolt assemblies 72 (only two shown). The cap 67 has one end
closed by a plate 72 which has a valve 73 which is adapted
when open to connect the interior of the closure 64 to a
compressor or like device for supplying air under pressure to
the closure 64. Alternatively the valve 73 can be closed
when the closure 64 is serving as a seal for preventing the
escape of air from one end of the liner pipe 20 when air is
being injected at the other end.
Located in two circumferential grooves 74 on the inner
surface 75 of the sleeve 66 are two O-ring seals 76 which are
arranged tc~ engage the outer surface 77 of the liner pipe 20
when an end of the pipe is located within the sleeve 66.
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These seals 76 form a seal outer surface 77
between of
the
the liner pipe 20 and the inner surface 75 the sleeve
of 66
and permit movement of the liner pipe withinthe sleeve
20 65
since the liner pipe 20 expands radially and contracts
longitudinally as pressure is applied the
to interior
of
the
liner pipe 20.
In use, both the exposed ends of the liner pipe 20 are closed
with a closure device 64. The sleeve 66 may have a recessed
end portion 78 to fit over the spigot end of the main section
40 as shown in Figures 10 and 11. Each closure 64 is
supported against the internal walls of the excavation by
means of struts 79 extending outwardly from the cap 67 to
prevent its being blown off during pressurisation of the
closure 64. One of the closure devices 64 is connected to
the compressor 65 by means of the valve 73 which is opened..
The valve 73 of the other closure device is closed. Air is
then supplied by the compressor to pressusrise the liner pipe
20. After use, the closure devices 64 are removed and the
ends of the liner pipe 20 are connected up to the adjacent
portions 44 and 45 of the main 41 by conventional means.
The pressurisation of the liner pipe may form part of a
standard pressure test to test the soundness of the liner
pipe.
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A vent 80 is provided in the wall of the main section 40 as
shown in Figures 10 and 11. In this example the vent 80 also
passes through the end position 78 of sleeve 66, but the vent
80 could be positioned at a portion of the main section 40
which is clear, of the sleeve 66 to avoid having to pass
through sleeve 66. Grooves 81 are are provided in the
outside wall of liner pipeline 20 such that when the main
section 40 is lined with the liner pipe 20, the vent 80 is in
fluid communication with grooves 81 to enable gas which may
for example have passed through the slightly porous liner 20
to escape from the region between the liner pipe 20 and the
main section 40. The vent 80 is provided with a valve 82 to
enable fluid to escape. The longitudinal grooves 81 are
provided with one or more transverse grooves 84 to
interconnect them and enable trapped fluid to reach the vent
80.
This means to convey fluid along the outside surface of the
liner pipe 20 may not necessarily be as described above. For
example there may be provided one or more grooves arranged
spirally around the outside surface of the liner pipe 20 or
an array of grooves arranged around the outside surface of
the liner pipe 20, with the grooves in fluid communication
with the vent 80. Alternatively, instead of grooves there
may be pro~rided one or more conduits arranged between the
outside surface of the liner pipe 20 and the inside surface
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of main section 40 with means for fluid to enter or leave the
conduits such as a number of holes, with the conduits being
in fluid communication with the vent 80.
Many alterations may be made to the example described above
whilst still falling within the scope of the invention. For
example the liner pipe 20 need not be heated before~being
passed through the dies but could simply be pulled through at
its normal or ambient temperature.
