U.S. patent application number 09/761825 was filed with the patent office on 2002-01-24 for method of repairing or reinforcing worn-out underground burried drainpipes by resin transfer molding process using both flexible tubes and bagging films.
This patent application is currently assigned to Korea Advanced Institute of Science and Technology. Invention is credited to Chin, Woo Seok, Kwon, Jae Wook, Lee, Dai Gil, Yoo, Ae Kwon.
Application Number | 20020009334 09/761825 |
Document ID | / |
Family ID | 19679435 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009334 |
Kind Code |
A1 |
Lee, Dai Gil ; et
al. |
January 24, 2002 |
Method of repairing or reinforcing worn-out underground burried
drainpipes by resin transfer molding process using both flexible
tubes and bagging films
Abstract
A method of repairing or reinforcing worn-out underground buried
drainpipes by a resin transfer molding process using both flexible
tubes and bagging films is disclosed. In the method of this
invention, a reinforcement is primarily inserted into a desired
position within a target worn-out drainpipe buried underground. The
reinforcement consists of a fiber preform internally having a
flexible tube, such as a silicon tube, axially extending along the
central axis of the preform and wrapped with an adhesive-coated
flexible film as a bagging film to provide protection from sewage
or underground water. The flexible tube is, thereafter, expanded to
bring the fiber preform into close contact with the interior
surface of the target drainpipe. The opposite ends of the
reinforcement are sealed with two lids. Thereafter, thermosetting
resin is transferred into the fiber preform, thus allowing the
fiber preform to be impregnated with the thermosetting resin. The
impregnated resin is, thereafter, cured to shape the fiber preform
as desired, thus repairing and reinforcing the target
drainpipe.
Inventors: |
Lee, Dai Gil; (Taejon,
KR) ; Kwon, Jae Wook; (Seoul, KR) ; Chin, Woo
Seok; (Suwon-si, KR) ; Yoo, Ae Kwon;
(Suwon-si, KR) |
Correspondence
Address: |
ROTHWELL, FIGG, ERNST & MANBECK, P.C.
555 13TH STREET, N.W.
SUITE 701, EAST TOWER
WASHINGTON
DC
20004
US
|
Assignee: |
Korea Advanced Institute of Science
and Technology
Taejon
KR
|
Family ID: |
19679435 |
Appl. No.: |
09/761825 |
Filed: |
January 18, 2001 |
Current U.S.
Class: |
405/184.1 |
Current CPC
Class: |
F16L 55/1654 20130101;
F16L 55/164 20130101 |
Class at
Publication: |
405/184.1 |
International
Class: |
F16L 055/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2000 |
KR |
2000-42253 |
Claims
What is claimed is:
1. A method of repairing or reinforcing worn-out underground buried
drainpipes by a resin transfer molding process using both flexible
tubes and bagging films, comprising the steps of: inserting a
reinforcement into a desired position within a target worn-out
drainpipe buried underground, said reinforcement consisting of a
fiber preform internally having a flexible tube axially extending
along a central axis of said preform and wrapped with a
adhesive-coated flexible film as a bagging film to provide
protection from sewage or underground water left within the target
drainpipe; expanding said flexible tube to bring the fiber preform
into close contact with an interior surface of said target
drainpipe; sealing each end of said reinforcement with a lid; and
transferring thermosetting resin into the fiber preform to
impregnate said preform with the thermosetting resin prior to
curing said thermosetting resin, thus repairing or reinforcing the
target drainpipe.
2. The method according to claim 1, wherein an viscosity
controllable adhesive agent is coated on an external surface of
said flexible film to allow said film to smoothly move within the
drainpipe without being damaged due to frictional contact with said
pipe.
3. The method according to claim 1, wherein each of said lids is
divided into two or more pieces when an inner diameter of the
target drainpipe is not smaller than a diameter of a manhole.
4. The method according to claim 3, wherein said pieces of each of
the lids are locked together into a single body using a dovetail
engaging structure at their locking surfaces, with a sealing
material applied to the locking surfaces of said pieces so as to
accomplish a desired sealing effect at said locking surfaces.
5. The method according to claim 3, wherein said pieces of each of
the lids are locked together into a single body using an
externally-threaded bolt and an internally-threaded hole at their
locking surfaces, with a snap ball formed on the locking surfaces
of said pieces to accomplish a precise alignment of the locking
surfaces and a sealing material applied to the locking surfaces so
as to accomplish a desired sealing effect at said locking
surfaces.
6. The method according to claim 1, wherein a wedge is installed
outside each of said lids so as to hold each of the lids in its
correct position during an injection of the thermosetting resin
under pressure into the fiber preform.
7. The method according to claim 1, wherein a steel wire extends
between said lids while passing through the flexible tube prior to
being tightened by nuts at its opposite ends outside of the lids,
thus holding the lids in their correct positions during an
injection of the thermosetting resin under pressure into the fiber
preform.
8. The method according to claim 1, wherein a groove is formed
along a circumferential surface of each of the lids, with an
annular tube fitted over the groove of each of the lids to seal a
gap between an internal surface of the drainpipe and an outside
edge of each of the lids.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of repairing or
reinforcing worn-out underground buried drainpipes through a
trenchless rejuvenation technology and, more particularly, to a
method of repairing or reinforcing such worn-out underground buried
drainpipes by RTM (resin transfer molding) process using both
flexible tubes and bagging films, the method being carried out by
primarily inserting a reinforcement into a desired position within
a target worn-out underground buried drainpipe, the reinforcement
consisting of a fiber preform internally having a flexible tube
axially extending along the central axis of the preform and
externally wrapped with an adhesive-coated flexible bagging film to
be protected from sewage or underground water left within the
drainpipe, and transferring thermosetting resin to the fiber
preform through the flexible tube to impregnate the preform with
the resin, and finally curing the impregnated resin in the fiber
preform, thus simply and easily repairing or reinforcing such
worn-out underground buried drainpipes while reducing the repairing
or reinforcing cost in comparison with conventional excavation and
trenchless rejuvenation technologies.
[0003] 2. Description of the Prior Art
[0004] As well known to those skilled in the art, at least
40.about.50% of pipes of drainage systems laid underground have
been reduced in their strength, and partially cracked, broken and
corroded before a lapse of their expected life span due to careless
management, and so they undesirably allow a leakage of sewage into
soil to finally contaminate soil and underground water in addition
to causing a ground subsidence.
[0005] The cracked or broken drainpipes also allow rainwater and
underground water to flow into drainpipes through cracks, thereby
undesirably increasing the sewage disposal cost. Another problem
experienced in the conventional drainage systems is that they force
users to pay excessive money and waste excessive labor and time
while managing, repairing or replacing the underground buried
drainpipes. That is, when it is desired to manage, repair or
replace drainpipes laid underground since the pipes are reduced in
their strength, partially cracked, broken or corroded before a
lapse of their expected life span, it is necessary to excavate
earth around target pipes, thus increasing the cost and being very
inconvenient to workers while managing, repairing or replacing the
pipes.
[0006] In many nations, most pipes for drainage systems had been
somewhat roughly designed, manufactured and buried underground
without carefully considering the dynamic relation between the
expected life span of the pipes, the depth of the pipes under the
ground surface, and surface load applied to the pipes laid
underground. Due to the above-mentioned problem experienced in the
design, manufacture and laying of the drainpipes in addition to
careless management of the pipes after laying the pipes
underground, most drainpipes are regrettably worn-out, reduced in
their strength, partially cracked, broken and corroded before a
lapse of their expected life span. Such cracked or broken
drainpipes undesirably allow a leakage of sewage into soil to
finally contaminate soil and underground water in addition to
causing a ground subsidence, and also allow underground water and
rainwater to flow into the drainpipes, thereby increasing the
quantity of sewage and increasing the sewage disposal cost.
[0007] When drainpipes are worn-out, reduced in their strength,
partially cracked, broken and corroded as described above, earth
has to be excavated in a large area around the target pipes using
power excavators to allow replacement of the existing pipes with
new pipes, while closing a road and regulating the traffic for a
lengthy period of time. Furthermore, such a conventional method
undesirably results in a breakage of pavements before a lapse of
expected life span of the pavements, social and financial burden on
the community due to the closing of the road and the regulating of
the traffic for a lengthy period of time, and consumption of
excessive labor and time for management of drainpipes.
[0008] In an effort to overcome such problems experienced due to
the excavation of earth while managing or repairing drainage
systems, a variety of trenchless rejuvenation technologies have
been proposed and preferably used. Such trenchless rejuvenation
technologies are particularly advantageous in that it is possible
to remarkably save time, labor and money while managing or
repairing the drainpipes buried underground. The trenchless
rejuvenation technologies are also preferably usable for the
management or repair of the pipes of waterworks in addition to the
pipes of drainage systems.
[0009] Well-known trenchless rejuvenation technologies for
underground buried pipes are classified into several types: reverse
lining processes, slip lining processes, cured-in-place lining
processes (CIPL), close-fit lining processes, spirally wound pipes
lining processes and etc. Of such well-known trenchless
rejuvenation technologies, a reverse lining process using unwoven
fabric tubes impregnated with proper resin, such as polyester, and
a spirally wound pipes lining process using thermoplastic resin
have been most preferably and widely used.
[0010] In the conventional reverse lining process, it is necessary
to keep the unwoven fabric tubes impregnated with polyester within
a refrigerated container so as to prevent the polyester of the
tubes from being cured before a practical use of the tubes at a
construction field. Therefore, this process is problematic in that
it is necessary to always use refrigerated transport vehicles for
the unwoven fabric tubes impregnated with polyester and to use the
tubes within a short period of time after the resin impregnation,
thus being very inconvenient to workers and increasing the cost of
repairing or reinforcing the drainpipes.
[0011] On the other hand, the conventional spirally wound pipes
lining process using thermoplastic resin is problematic in that it
is necessary to use large-sized heaters for melting the
thermoplastic resin and additional power devices for forcibly
transferring the highly viscous molten resin to a desired position
within drainpipes laid underground.
[0012] In addition, a resin transfer molding process (RTM) for
repairing or reinforcing the pipes without excavating earth has
been proposed and used. However, the conventional RTM process is
problematic in that underground water or sewage left within
existing pipes is naturally and undesirably impregnated into fabric
preforms, thus reducing the resin impregnation capability of the
preforms and deteriorating the processing effect, and failing to
accomplish a desired strength of the repaired or reinforced
pipes.
[0013] Since the conventional spirally wound pipes lining processes
use thermoplastic resin, it is necessary to inject an adhesive
agent under pressure into the gap between a target drainpipe and an
extruded resin tube or to forcibly expand the extruded resin tube
so as to bring the resin tube into close contact with the internal
surface of the target drainpipe. However, it is very difficult to
perform such a process of bringing the resin tube into close
contact with the drainpipe, and so the conventional spirally wound
pipes lining processes fail to accomplish desired processing effect
or desired strength of repaired or reinforced pipes.
SUMMARY OF THE INVENTION
[0014] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and an object
of the present invention is to provide a method of repairing or
reinforcing worn-out drainpipes by a resin transfer molding process
using both flexible tubes and bagging films, which uses
thermosetting resin capable of improving the adhesiveness between
reinforcements and worn-out drainpipes without any separate
adhesive agent, and which is thus free from any separate process of
forcing the resin tubes to come into close contact with the
drainpipes, different from the conventional spirally wound pipes
lining process and thereby saving time while repairing or
reinforcing the worn-out drainpipes, and which does not require any
consideration of prevention of resin curing during the process,
different from the conventional reverse lining process, thus being
free from use of refrigerated transport vehicles and being very
convenient to workers, and reducing the cost of repairing or
reinforcing the worn-out drainpipes.
[0015] In order to accomplish the above object, the present
invention provides a method of repairing or reinforcing such
worn-out drainpipes by a resin transfer molding process using both
flexible tubes and bagging films, which comprises the steps of:
inserting a reinforcement into a desired position within a target
worn-out drainpipe buried underground, the reinforcement consisting
of a fiber preform internally having a flexible tube, such as a
silicon tube, axially extending along the central axis of the
preform and wrapped with an adhesive-coated flexible film as a
bagging film to provide protection from sewage or underground
water; expanding the flexible tube to bring the fiber preform into
close contact with the interior surface of the target drainpipe;
sealing opposite ends of the reinforcement with lids; and
transferring thermosetting resin into the fiber preform to
impregnate the preform with the thermosetting resin, and finally
curing the impregnated resin in the fiber preform.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0017] FIGS. 1 to 5 are views, showing the process of repairing or
reinforcing worn-out drainpipe in accordance with the preferred
embodiment of this invention;
[0018] FIG. 6 is a sectional view, showing the construction of a
reinforcement used in the process of this invention;
[0019] FIGS. 7 to 9 are views, showing the construction of lids
having different structures according to different embodiments of
this invention and used for closing opposite ends of a
reinforcement having a flexible tube in the process of this
invention;
[0020] FIGS. 10 and 11 are views, showing lid clamping structures
in accordance with different embodiments of the present invention,
the structures being used for holding the lids in their correct
positions in the case of an injection of highly pressurized
thermosetting resin into the fiber preform; and
[0021] FIG. 12 is a sectional view, showing a lid sealing structure
in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The process of repairing or reinforcing worn-out underground
buried drainpipe in accordance with the preferred embodiment of
this invention comprises the first to fourth steps as follows:
[0023] Step 1:
[0024] As shown in FIG. 1, the interior of a target drainpipe 5 is
cleaned using a mobile robot 3. After the robot 3 is recovered from
the cleaning process, a rope 4 having a predetermined length is
connected to the robot 3 prior to inserting the robot 3 into the
pipe 5 through one manhole 1. The robot 3 moves along the pipe 5
while dragging the rope 4 prior to being recovered from the pipe 5
through another manhole 2, and so it is possible to array the rope
4 along the pipe 5 with both ends of the rope 4 being positioned
outside of the two manholes 1 and 2.
[0025] Thereafter, a flexible tube 7 wrapped with a fiber preform 6
is connected to one end of the rope 4 as shown in FIG. 2. In such a
case, the fiber preform 6 is wrapped with a flexible film 19 as a
bagging film as shown in FIG. 6, with an adhesive agent 20 coated
on the surface of the flexible film 19 at which the film 19 comes
into contact with the drainpipe 5.
[0026] Thereafter, the flexible tube 7 is pulled using a winding
machine 8, and so the tube 7 is arrayed within the pipe 5. In such
a case, the flexible film 19 prevents the fiber preform 6 from
being scratched or damaged by the internal surface of the pipe 5
when the flexible tube 7 together with the preform 6 is dragged
within the pipe 5. Therefore, the fiber preform 6 is prevented from
being undesirably impregnated with underground water or sewage left
within the pipe 5, and so the preform 6 is free from an undesired
reduction in its resin impregnation capability during the process.
In addition, when the adhesive agent 20 coated on the flexible film
19 is properly controlled in its viscosity, it is possible to
collaterally use the adhesive agent 20 as a lubricant for allowing
the film 19 to smoothly move within the pipe 5 without being
damaged due to frictional contact with the pipe 5.
[0027] Step .sub.2:
[0028] One end 9 of the flexible tube 7 is closed, while the other
end 10 is connected to a heater compressor or a heater pump 11 as
shown in FIG. 3. Thereafter, hot air or hot water under pressure is
supplied from the compressor or the pump 11 into the tube 7, thus
expanding the tube 7. Due to the supply of hot air or hot water
into the flexible tube 7, the binder within the fiber preform 6 is
melted by applying heat and hardened by cooling, thus forming a
desired shape of the preform 6 corresponding to that of the pipe 5.
In addition, the flexible film 19 wrapping the fiber preform 6 is
heated and expands to be brought into close contact with the
internal surface of the pipe 5. The adhesive agent 20 in such a
case fixes the flexible film 19 to the internal surface of the pipe
5.
[0029] When the fiber preform 6 is made of a material capable of
allowing the preform 6 to maintain its desired shape and to come
into close contact with the pipe 5 without being undesirably
changed in its shape due to resin pressure during the process, it
is possible to produce the fiber preform 6 without adding a
binder.
[0030] Step 3:
[0031] After the step 2, opposite ends of the flexible tube 7
wrapped with the fiber preform 6 are closed by two lids 14 and 15.
In such a case, the first lid 14 is provided with a gate 12, while
the second lid 15 is provided with an air vent 13.
[0032] When the inner diameter of the target drainpipe 5 is smaller
than the diameter of the manholes 1 and 2, it is possible to
produce each of the two lids 14 and 15 as a single body. However,
when the inner diameter of the target drainpipe 5 is not smaller
than the diameter of the manholes 1 and 2, it is necessary to
produce each of the two lids 14 and 15 as divided pieces to allow
the lids 14 and 15 to be inserted into the pipe 5 through the
manholes 1 and 2.
[0033] FIGS. 7 to 9 are views, showing the lids 14 and 15 having
different structures according to different embodiments of this
invention.
[0034] In the embodiment of FIG. 7, each of the disc-shaped lids
14a and 15a is divided into two semicircular pieces, with a
dovetail rail formed along the central axis of the linear locking
surface of one of the two pieces and a dovetail groove 20 formed
along the central axis of the linear locking surface of the other
piece. When it is desired to assemble the two pieces into a single
lid 14a or 15a, the dovetail rail is fitted into the dovetail
groove 20. Before assembling these two pieces, a conventional
O-ring (sealing material) 21 is applied to the junction of the two
pieces so as to accomplish a desired sealing effect at the
junction. When the size of the lids 14a and 15a is substantially
larger than that of the manholes 1 and 2, each of the lids 14a and
15a may be divided into three or more pieces.
[0035] In the embodiment of FIG. 8, each of the disc-shaped lids
14b and 15b is divided into two semicircular pieces, with an
externally-threaded bolt 22 provided at the center of the linear
locking surface of one of the two pieces and an internally-threaded
hole formed at the center of the linear locking surface of the
other piece. When it is desired to assemble the two pieces into a
single lid 14b or 15b, the bolt 22 is tightened to the
internally-threaded hole. Before the assembly, a rubber coated film
(sealing material) 23 is applied to the junction of the two pieces
so as to accomplish a desired sealing effect at the junction. In
such a case, two snap balls 24 are preferably formed on the locking
surface of one of the two pieces, while two rounded depressions are
formed on the locking surface of the other piece at positions
corresponding to the two snap balls 24, thus accomplishing a
precise alignment of the two locking surfaces. In this embodiment,
each of the lids 14b and 15b may be divided into three or more
pieces when the size of the lids 14b and 15b is substantially
larger than that of the manholes 1 and 2 in the same manner as that
described for the embodiment of FIG. 7.
[0036] In the embodiment of FIG. 9, each of the disc-shaped lids
14c and 15c is divided into four pieces, with a snap fastener 25
provided at the locking surface of each of the four pieces. When it
is desired to assemble the four pieces into a single lid 14c or
15c, the four pieces are locked to each other by the snap fasteners
25. Before the assembly, a conventional O-ring (sealing material )
21 is applied to the junction of the four pieces so as to
accomplish a desired sealing effect at the junction.
[0037] Step 4:
[0038] As shown in FIG. 5, a resin supply device 17 is connected to
the gate 12 of the first lid 14 through a resin-feeding pipe 16,
and feeds thermosetting resin 18 to the fiber preform 6.
[0039] In such a case, the thermosetting resin 18 is a monomer
having a low viscosity, and so it is possible to smoothly feed the
resin 18 to the preform 6 with less power. The thermosetting resin
18 is impregnated into the fiber preform 6, thus repairing and
reinforcing the cracked or damaged portion of the pipe 5. In such a
case, air existed in the void of the fiber perform is expelled to
the atmosphere through the air vent 13 of the second lid 15.
[0040] After the thermosetting resin 18 impregnated in the fiber
preform 6 is completely cured, the flexible tube 7 is removed from
the fiber preform 6 to complete the process.
[0041] In the present invention, the flexible tube 7 is covered
with Teflon or a release agent, and so it is possible to easily
remove the tube 7 from the fiber preform 6 after the process. It is
also possible to leave the flexible tube 7 within the preform 6
after the process. In such a case, the flexible tube 7 accomplishes
a coating effect of the internal surface of the preform 6.
[0042] When it is desired to repair or reinforce a long drainpipe
5, it is necessary to use a long tube 7. In such a case, the
flexible tube 7 is heavy, and so it is somewhat difficult to set
the tube 7 within the fiber preform 6 or to remove the tube 7 from
the preform 6 after the process. In such a case, it is preferred to
use a thin and flexible plastic film, such as a polyethylene film,
in place of the flexible tube 7 so as to overcome the
above-mentioned problem experienced in using the long tube 7.
[0043] It is also necessary to design the lids 14 and 15 to
effectively resist a high pressure of about 1.0 MPa during an
injection of the highly pressurized thermosetting resin 18 into the
fiber preform 6.
[0044] In order to accomplish the above object, a lid clamping
structure is used for holding the lids 14 and 15 in their correct
positions in the case of an injection of the highly pressurized
thermosetting resin 18 into the fiber preform 6 as shown in FIGS.
10 and 11. In the embodiment of FIG. 10, a wedge 26 is used for
holding each of the lids 14 and 15 in its correct position. In the
embodiment of FIG. 11, a steel wire 27 extends between the two lids
14 and 15 while passing through the flexible tube 7 prior to being
fully tightened by nuts 28 at its opposite ends outside the lids 14
and 15, thus holding the positions of the two lids 14 and 15.
[0045] In addition, it is necessary to seal the gap between the
internal surface of the drainpipe 5 and the outside edges of the
lids 14 and 15 so as to prevent an undesired leakage of air or
resin through the gap. In the preferred embodiment of the present
invention, a groove 29 is formed along the circumferential surface
of each lid 14 or 15, with an annular expansible tube 30 fitted
over the circumferential groove 29 of each lid 14 or 15. In such a
case, the tube 30 is made of a flexible material and can be
inflated with air or liquid to seal the gap between the pipe 5 and
each lid 14 or 15. Of course, it should be understood that a
conventional O-ring may be used in place of the annular tube 30
without affecting the function of this invention.
[0046] After the injection of the thermosetting resin 18 into the
fiber preform 6, the step 2 is performed again to expand the
flexible tube 7 to pressurize the impregnated resin within the
preform 6. In such a case, it is possible to increase the fiber
volume fraction of the resin impregnated fiber perform and to
remove air bubbles from the resin impregnated fiber preform.
[0047] As described above, the present invention provides a method
of repairing or reinforcing worn-out underground buried drainpipes
by a resin transfer molding process using both flexible tubes and
bagging films. This method uses thermosetting resin capable of
improving the adhesiveness between reinforcements and worn-out
drainpipes without requiring an application of any separate
adhesive agent. The method thus saves time while repairing or
reinforcing worn-out underground buried drainpipes. This method is
also very convenient to workers, and reduces the cost of repairing
or reinforcing worn-out underground buried drainpipes in comparison
with conventional excavation and trenchless rejuvenation
technologies. It is also possible to use the method of this
invention for repairing or reinforcing worn-out pipes of waterworks
when harmless resin is used as the thermosetting resin during the
process.
[0048] Although a preferred embodiment of the present invention has
been described for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *