AU652245B2 - Method for the repair of localised damaged portions of a cement sewer pipe laid beneath the surface of the ground - Google Patents

Description

AUSTRALIA

Patents Act 1990 652245

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: rr ar r o n u rr r r* c r* tu ~*sr a r rru r u*r* METHOD FOR THE REPAIR OF LOCALISED DAMAGED PORTIONS OF A CEMENT SEWER PIPE LAID BENEATH THE SURFACE OF THE GROUND.

The following statement is a full description of this invention, including the best method of performing it known to me:i F i i.

i I1 a 2 METHOD FOR THE REPAIR OF LOCALISED DAMAGED PORTIONS OF A CEMENT SEWER PIPE LAID BENEATH THE SURFACE OF THE GROUND The present invention relates to a method of patching up from within at least one selected portion of an at least partially buried conduit where the portion exhibits at I least one crack or analogous defective zone.

A method for the repair of localised damaged portions of a cement sewer pipe laid beneath the surface of the ground is known from the German Patent DE 39 22 351 Al, in which a single-layer, resin-impregnated fibrous composition mat, having overlapping ends, is utilised, which is wound-up on a hose-like carrier which is radially deformable by the application of internal pressure. In this method, there is overlapping over an angle of 90 degrees during the application to the inner surface of the cement pipe which is to be repaired.

During the expansion of the wound-up, hose-like, resinimpregnated lining until it attains the internal diameter of the cement pipe which is to be repaired, the hose-like carrier remains in a fixed location. In the region of the overlapping of the winding, there is friction between the two overlapping fibrous layers. The wound-up pipe lining also undergoes movement, during the increase of its 25 diameter, relative to the hose-like carrier, especially in the circumferential direction. On the way from the starting position of the hose-like, wound-up pipe lining until it makes contact with the inner surface of the pipe which is to be repaired, due to the internal pressure exerted by the hose-like carrier, there is no deformation of the mat layers, so that practically no resin is exuded at the ends or around the periphery. A pressing together of the mat layers only takes place after being pressed up against the inner surface of the cement pipe, so that the cement pipe actually provides the counter-thrust bearing i t

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i)i: i 3surface during this pressing operation.

During the use of the known localised damage repair method, the cement pipe which is to be repaired, because it has been weakened by cracks or has suffered any other sort of damage, has to act as the counter-thrust bearing surface for the new pipe lining and must be able to withstand the high pressure generated inside the hose-like carrier. This gives rise to the danger that the cement pipe could thereby suffer further damage.

It is an object of the present invention to improve the introduction of resin into cracks or other damaged sites of the conduit to be repaired.

Therefore in accordance with a broad aspect of the invention there is provided a method of patching up from 15 within at least one selected portion of an at least partially buried conduit wherein the at least one selected portion exhibits at least one crack or analogous defective zone, comprising the steps of impregnating a mat containing at least one layer of fibrous material with a hardenable plastic compound; convoluting the impregnated mat around a radially expandable and contractible carrier having an external surface, to form a tubular mat shell having overlapping portions, an internal surface and first and second axial ends and to permit frictional engagement between the external surface of the carrier and the j internal surface of the shell; establishing friction St: between the external surface of the carrier and the internal surface of the shell by introducing a polyethylene film therebetween before expansion of the carrier so that radial expansion of the carrier entails simultaneous radial expansion of the shell and slippage of the overlapping portions relative to each other; introducing the carrier, the polyethylene film and the shell into the at least one selected portion of the conduit; expanding the carrier, the -3A polyethylene film and the shell in and against the at least one selected portion of the conduit to cause flow of the hardenable plastic compound out of the mat into the at least one crack or analogous defective zone and (b) rotation of the carrier relative to the conduit due to the pronounced friction between the external surface of the carrier and an adjacent internal surface of the polyethylene film, which polyethylene film constitutes a coupling which prevents turning of the carrier relative to an adjacent turn of the shell; contracting the expanded carrier to cause separation of the contracted carrier from the expanded shell; withdrawing the contracted carrier and the polyethylene film from the shell; and causing or permitting the hardenable compound to set thus ensuring reliable sealing of the at least one crack or analogous defective zone and ensuring reliable adherence of the expanded mat against the at least one selected portion of rc the conduit.

Preferably, said expanding a method as claimed in claim 1, wherein said expanding step further includes pressing the overlapping portions against each other and expelling hardenable compound beyond at least one axial end of the expanded shell.

Preferably further, when the conduit has a predetermined inner diameter, the convoluting step includes winding the impregnated mat around a tubular carrier having prior to said expanding step an outer diameter considerably less than said inner diameter, said expanding step including expanding the tubular carrier from within with a 30 pressurized fluid.

Preferably also, said convoluting step includes converting the impregnated mat into a shell having an axial length such that the carrier extends beyond the axial ends of the shell.

i; i Prfe ab y sai e a t X 0 weensi xadn te ute nldspesn h 3B During the inflation of the deformable hose-like carrier, it has been found that the friction between the polyethylene sheet and the hose-like carrier is greater than the friction between the resin-impregnated fibre-glass mat and the polyethylene sheet plus the friction between the fibre-glass mats themselves. The extra length of the polyethylene sheet and fibre-glass mat required for the enlargement of the deformable hose-like carrier is supplied by displacement of the currently involved external layers (decrease of the overlapping at the current involved external circumference). The start of the polyethylene sheet remains in its original position on the deformable carrier. Determined by this, C tC

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4; -4the deformable carrier turns through an angle during inflation which is analogous to the lengthening of the circumference.

This rotary motion is advantageous because, owing to the inflation process and the displacement of the resin-impregnated fibre-glass mats in relation to each other, this results in a compression of these fibre-glass mats and resin exudes onto the outside periphery of the mat layers and said resin is spread around the inside of the cement pipe to be repaired during this rotary motion.

The wall thickness of the new localised pipe lining can be determined by the double or multiple winding of the single-layer fibre mat, or of a multi-layered fibre mat around the deformable carrier.

With the use of the method in accordance with the present invention, it is possible, depending upon the internal diameter of the cement pipe to be .i *repaired, to prescribe the internal pressure in the deformable carrier required for the displacement of the resin-impregnated fibre mat layers in the coil, and to I 15 specify the material used for the fibre mats and the number of layers of the fibre mats before positioning in the cement pipe and also the pressure to be applied against the inside surface of the wall of the pipe to be repaired.

Depending upon the extent of damage to the existing pipe, a conservative application pressure can be achieved, because the extrusion of the resin around the periphery and at the ends of the coil is effected during the time the diameter of the coil is being increased owing to the inflation of the carrier.

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Additional implementations of the invention are set out in the dependent Patent Claims and are dealt with in the following description of examples of preferredet ooM# 4medienti4A with reference to the accompanying drawings, in which is depicted: *9 0 0 4 4 t41:4 g I C 4 4 Fig. lA-lE Fig. 2A-2E Fig. 3A Fig. 3B Fig. 3C Fig. 4A Fig. 4B Fig. 5 B Fig. 6 impregnation of the fibre-glass mat at the work-site and the winding of the resin-impregnated fibre mat onto a packer, a variation of Fig. 1A 1E, a packer in longitudinal section during positioning, a packer in transverse section during positioning, a packer with inflated carrier, which has a double winding of a triple-layer fibre mat, in cross-section, a front view of a packer subjected to pressure, a cross-section of a packer subjected to pressure, longitudinal section of a localised repair in accordance with the present invention, a diagrammatic representation of quadruplicate localised repairs during one operation cycle.

0* b *0*0 Impregnation of the fibre mat A flat working support 3 of height H, width B and length L is placed in the immediate vicinity of a work-site for the localised repair of a cement pipe. These measurements of the working support are determined by the particular work to be carried out. The width B corresponds to approximately half that of the fibreglass mat being used. The length L corresponds to approximately twice the internal circumference of the pipe undergoing repair and the height H is a dimension which allows for the free unrolling of the packer (Fig. 1E).

I Ia-rn -6- A transparent polyethylene sheet 2, which is approximately twice as wide as the width B and somewhat longer than the length L of the working support, is laid flat over the working support. The fibre-glass mat 1 to be impregnated is placed on this polyethylene sheet in such a manner that the entire working support is covered and the mat extends out to the right-hand side. A layer 14 of readymixed resin is manually spread, as uniformly as possible, over the upper surface of the fibre-glass mat lying on top of the working support. Then the extra length of the fibre-glass mat is folded back over the resin-coated mat on the working support to form a double layer. The remainder of the resin mixture 14 is then spread over the upper surface of double layer of the mat (Fig. 1B). The polyethylene sheet 2 is then folded back over the top of the fibre-glass mat so that the mat is enclosed on all sides by the transparent polyethylene sheet. The C repoxide resin is then manually worked into the fibre-glass mat by using the hand-held roller 4 (Fig. 1C). The transparent polyethylene sheet makes it possible to see any occluded air, any incompletely impregnated pockets and any other inadequate conditions and thus to take action to eliminate them. By using at a the roller in the sideways direction of the width B, any occluded air is forced out into the lateral regions 5 (Fig. 1C). After completion of the pore-free impregnation of the fibre-glass mat (Fig. 1D), the upper layer of the polyethylene sheet is pulled back to expose the mat which can then be wound around the packer (Fig. 1E).

A variant of the impregnation of the fibre-glass mat is depicted in Fig. 2a to Fig.

2E. For this variant, single layers of the fibre-glass mat are impregnated with a hardening (curing) synthetic resin.

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-7- Positioning of the fibre-glass mat on a packer The packer is provided with a carrier 6 which is prefezably fabricated from a length of robust, deformable, rubber hose which forms a sleeve on a metal tube to which it is attached at both ends 16 in a gas-tight or water-tight manner.

Inside the metal tube 15 there is a connection 17 provided for the supply of a pressure medium to the annular space between metal tube and rubber hose. The carrier 6 is inflatable so that it applies pressure to the resin-impregnated fibre mat and forces it up against the internal surface of the cement pipe at the site where it is damaged.

10 Preferably, a glass roving fabric is used as the fibre mat, onto which a binderfree fibre-glass mat is sewn with the use of a polyester thread. Especially suitable is a fibre mat consisting of 550 g/m 2 glass roving fabric, combined with 450 g/m 2 fibre-glass mat. This type of mat has a thickness of approximately one 4a.

millimetre. For the prevention of corrosion, the utilisation of E-CR-Glass types is recommended.

4* .Epoxide resins are especially suitable as hardening synthetic resins, which ~harden either at normal environmental temperatures or under the influence of applied heat. Preferably, a coupling agent is added to the resin mixture, because, in the repair of cement pipes, the work is predominantly carried out on wet surfaces. It is also recommended that a deaerator should bc incorporated in small amounts in order to avoid the occlusion of air. Both these additives are available in the relevant trade circles.

Fibre-reinforced synthetic plastics materials possess a mechanical strength which is higher when they contain a greater proportion of orientated fibres. This i applies for glass fibres, for carbon fibres, Kevlar and so forth. The higher the 'I -8mechanical strength of a localised repair to a damaged cement pipe which can be guaranteed, the smaller will be the required wall thickness of such a repair.

Every measure employed for pipe repair must be regarded as a reduction of the flow cross-section through the pipe.

After the determination of the site and the dimensions of the damaged zone, an appropriately wide resin-impregnated fibre-glass mat, which can be either singlelayered or multi-layered, is wound two or more times around a packer of appropriate diameter and then this packer, under observation from a camera, is Spulled into position in the cement pipe to be repaired by means of a cable 10 winch, or else pushed into position in the cement pipe to be repaired with the aid of a self-propelled TV-camera 18. In both cases, the packer is coupled with a supply hose for the pressure medium. The carrier 6 of the packer is expanded by means of compressed air or pressurised fluid, up to the stage where the multilayered resin-impregnated fibre mat is pressed against the internal surface of the 15 wall of the cement pipe. Because the hardening time of the epoxide resin is adjustable, the packer may be deflated after a short period of time and withdrawn from the cement pipe. The localised repair has then been completed.

S. .A packer which is suitable for the method under discussion is enclosed within two layers of a polyethylene sheet 7. The ends of the sheet are secured against slippage/unwinding with the use of adhesive strips. The polyethylene sheet 7 extends beyond the ends of the packer (Fig. 1E). The first layer of the sheet, in i! the region of the ends of the packer, is affixed firmly to the mountings of the four wheels on the packer by means of plastic bands (straps).

The polyethylene sheet is marked on the outside to indicate the centre point of the width of the resin-impregnated fibre-glass mat. The packer is now placed centrally on the resin-impregnated fibre-glass mat at one end of the working i S 41 I -9support, and by rolling the packer along, the fibre-glass mat is wound tightly around the packer (Fig. 1E). The wheels projecting from the packer at both ends are located outside the range of working support.

A packer which is suitable for the method under discussion is provided with four wheels 9 (Fig. IE), which are attached in such a manner that it is not possible for the rolled-up fibre-glass mat to come into contact with the base of the cement pipe when the packer is being introduced into the pipe to be repaired, that is to say, there is a permanent separation distance D between them (Fig. 1E).

a 10 The packer is now prepared and ready to be introduced into and positioned correctly in the cement pipe to be repaired by way of an inspection shaft with the use of a cable winch or a self-propelled TV-camera.

The polyethylene sheet which is used as an impregnation-aid/protective-cover, after the lifting-off from the packer, is folded together in such a manner that the S: 15 resin-coated surface comes to lie on the inside. The polyethylene sheet which has been folded up into a compact package is laid aside for future disposal. Any fluid resin residue dinging to the sheet will harden automatically within a period of two to three hours.

Carrying out the localised repair t The packer which has been positioned in the cement pipe to be repaired is j inflated with the use of compressed air or pressurised fluid. This procedure enlarges the external diameter of packer "The resin-impregnated multi-layer fibre-glass mat which is wound around the packer adapts itself to this diameter enlargement by displacement of the individual layers. For example, a packer for 10 d tightly the repair of a cement pipe DN 400 has a diameter of 250 millimetres. In the case fibr othof a two-layer fibre-glass mat, this would have a length of 2 x t x 350 millimetres of 2200 millimetres. For a diameter of 400 millimetres (circumference 1266 app millimetres) this length still gives a 1.75-fold (2200 (440 x 7t)) over-layering of in fl Jed with ded with 5 the fibre-glass mat. In actual practice, the length of the fibre-glass mat to be used 5 wir it is not is calculated from the internal diameter of the cement pipe to be repaired. wit e base of Slayi pe to be An additional example of^embodiment is depicted in Fig. 3C, in which the lining hea between of the cement pipe 12 is effected with a triple-layer resin-impregnated fibre mat S19, which was laid around the carrier 6 with two winding layers. To this must be Th 10 added an overlapping on the side facing towards the carrier and on the side 10 oft ositioned osone facing towards the wall of the cement pipe 12 over an angle of a degrees. len haft with dis] SEqual cement pipe diameters may be provided with linings of different me thicknesses in one operating cycle, where the carrier required for this is oft ive-cover, subjected in each case to the same working pressure. That is to say, the resin- r that the 15 impregnated complete layer (same thickness of the lining) may consist of 1, 2, 3 15 Th t w or 4 layers, or of individual layers which each have a length of twice the internal resi osal. Any circumference of the pipe to e lined, plus an overlap length of approximately .plu Sa period 100 millimetres, and thes e are always simultaneously wound onto the carrier as wal i f depicted in Fig. 3C. Du This application is conceived for the localised repair of damaged cement pipes 20 lay< and it will be clear to the technical expert that such locally damaged cement diai epaired is pipes can withstand only specified internal pressures during the repair operation pip procedure I pr dto avoid total destruction of the pipe. am nulti-layer she Sdiameter For the method as described in the foregoing, the mutual frictional forces 25 layi pcer r 25 between layers during the displacement of the wound-up resin-impregnated Th 11 fibre-glass mat layers are known, it being assumed that the recommended length of the mat 2 x the circumference of the cement pipe to be lined plus approximately 100 millimetres length of overlap) is adhered to. During the inflation of the carrier of the packer there is an inevitable displacement of the winding layers in relation to each other. The displacement takes place, even with multi-layer fibre-glass mats over a displacement surface 20 between the layers, indicated by the reference number 20 in Fig. 3C and represented by heavy lines.

The frictional forces which must be overcome for the displacement of the layers 10 of the winding of the fibre-glass mat, are equal for equal diameters and standard lengths of the fibre mats. The analogous pressures which bring about the ,displacement can be determined very precisely. In this way, in the present method, it is also possible to predetermine a definite pressure for the application of the lining to the inside surface of the cement pipe to be repaired.

:15 The total pressure in the packer equals the pressure required to enlarge the resin-impregnated fibre mat to the internal diameter of the existing cement pipe plus the pressure needed to force the lining into intimate contact with the pipe wall.

During the inflation of the packer and the associated displacement of the mat layers, the packer rotates through the distance equal to the enlargement of the i diameter; the packer appears to screw itself, to a limited extent, into bore of the I pipe to be repaired. The rotary movement arises because of the very substantial amount of friction between the packer and the first layer 7 of the polyethylene i sheet; it acts like a fixed clamp (Fig. 4B). Because of the displacement of the mat layers in relation to each other, these layers experience a mutual compression.

The forcing-out of the resin which is associated with this results in the resin i ii IL 2 i L r L -a i L i *ii I_ I- I t 1 1-: ii i: ii -12exuding into regions outside the fibre-glass mat. The exuded resin thus creates an uninterrupted transition zone to match the inside surface of the existing pipe and it flows on to fill any cracks or damaged areas 10 of the pipe (Fig. 2E).

The packer remains in the inflated condition until the hardening of the resin is ensured. The hardening time of the resin may be varied by having different proportions of its components or by the application of heat.

o o 0 o.4. 10 r t C~ C After completed hardening of the resin, the packer is deflated and the packer returns to its original diameter. The polyethylene sheet wrapped around the packer easily separates from the hardened epoxide resin (no adhesion) and, because of the quadruplicated fastening 8 to the wheel mountings on the packer, it is withdrawn from the pipe along with the packer. When the localised repair of the pipe is completed, the product is a thin-walled mechanically very strong segment of pipe which provides uninterrupted transition to the existing pipe.

General features of the method S> 15 It is recommended that, during the short period of time of the introduction and positioning of the packers, the flow of water through the cement pipe should be stopped. After the packer has been positioned correctly, the flow of water will no longer interfere with the localised repair operation; the packers used in the method are hollow and thus they do not hinder the flow (Fig. 4A).

The use of polyethylene sheet as the separating means and as the means for contact-free impregnation of the fibre-glass mat allows for absolutely-safe use of epoxide resins, which are physiologically harmful, and for exemplary manipulation and disposal of any epoxide resin residues. At no time during the work does liquid epoxide resin come into contact with personnel and environment.

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i I 13 The positioning of several packers in one stretch of Dipeline By "stretch of pipeline" is meant the distance between two inspection shafts. It happens frequently in actual practice that a stretch of pipeline may exhibit a plurality of localised damage sites. The method in accordance with the present invention is suitable for the positioning of a number of packers, one after the other, in such a stretch of pipeline Fig. 6).

To effect the successive pulling-in, positioning and inflation of several packers, it is essential to insert the hose for the pressure medium through each of the successive packers while they are still above ground. The TV-camera 18 which monitors the positioning of the individual packers is returned to its starting position after each positioning ,has been successfully completed. In actual practice, this signifies that a plurality of successive operations of pulling-in, positioning and inflation in one stretch of pipeline will result in a substantial reduction of the waiting time (for resin hardening) and make it possible to carry out the work continuously.

Modifications may be made to the invention as would be apparent to a person skilled in the art of pipe repair.

These and other modifications may be made without departing 25 from the ambit of the invention, the nature of which is to s be determined from the foregoing description, the drawings i .tv and the claims. i C I

Claims (13)

1. 2. A method as claimed in claim i, wherein said i expanding step further includes pressing the overlapping portions against each other and expelling hardenable compound beyond at least one axial end of the expanded shell.
2. 3. A method as claimed in claim 1 of patching up at least one selected portion of an at least partially buried conduit having a predetermined inner diameter, wherein said convoluting step includes winding the impregnated mat around a tubular carrier having prior to said expanding step an outer diameter considerably less than said inner diameter, said expanding step including expanding the r Itubular carrier from within with a pressurized fluid. C I
3. 4. A method as claimed in claim 3, wherein said I convoluting step includes converting the impregnated mat into a shell having an axial length such that the carrier S extends beyond the axial ends of the shell. 'o5. A method as claimed in any one of claims 1 to 4, wherein said step of establishing friction comprises introducing a polyethylene film between the mat and the carrier. S S25 6. A method as claimed in claim 5, wherein said introducing of said polyethylene film is carried out subsequent to said impregnating step and prior to said convoluting step.
4. 7. A method as claimed in claim 5, wherein said convoluting step further includes converting the film into a tubular body which surrounds and extends axially beyond 16 the carrier.
5. 8. A method as claimed in any one of claims 1 to 4, wherein said step of establishing friction comprises introducing a multilayer polyethylene film between the mat and the carrier.
6. 9. A method as claimed in claim 8, wherein said convoluting step further comprises converting the multilayer film into a tubular body having axial ends extending beyond the shell and surrounding the carrier, and affixing the ends of the tubular body to the carrier to prevent unwinding of the tubular body during radial expansion of the carrier. A method as claimed in any one of claims 1 to 9, wherein said convoluting step further comprises converting I 15 the mat into a spiral having a plurality of turns.
7. 11. A method as claimed in claim 10, wherein the 0 spiral has a plurality of full turns plus a portion of a turn.
8. 12. A method as claimed in any one of claims 1 to 9, I 20 wherein the mat contains a plurality of overlapping layers of fibrous material and said convoluting step further comprises converting the mat into a spiral having a plurality of turns. t 13. A method as claimed in any one of claims 1 to 12, wherein said expanding step includes introducing into the carrier a fluid having a pressure which is a function of a plurality of parameters including the extent of required expansion of the carrier to bias the shell against the conduit with a predetermined force and the nature of i fibrous material in the mat. i -17-
9. 14. A method as claimed in claim 13, wherein another of said parameters includes the circumferential length of the convoluted mat. A method as claimed in any one of claims 1 to 14, 2 wherein the fibrous material of the mat is selected from the group consisting of glass fibers, carbon filaments and KEVLAR (Trade mark) fibers.
10. 16. A method as claimed in any one of claims 1 to wherein said impregnating step comprises applying hardenable plastic compound over a plurality of layers of fibrous material, superimposing the layers upon each other, confining the superimposed layers and the applied plastic compound in an envelope of polyethylene film, and applying I to the envelope external forces in directions to effect penetration of plastic compound into the layers.
11. 17. A method as claimed in cla4im 16, wherein the film of the envelope transmits light.
12. 18. A method as claimed in claim 16, wherein said step of applying forces comprises manually spreading the plastic compound within the envelope with a rolling pin.
13. 19. A method .af patching up from within at least one selected portion of an at least partially buried conduit *wo substantially as herein described with reference to the accompanying drawings. DATED THIS 1ST DAY OF JUNE 1994 HANS MULLER By Its Patent Attorneys GRIFFITH HACK CO Fellows institute of Patent Attorneys of Australia 1 41 Ab :i-i ABSTRACT OF THE DISCLOSURE Method for the repair of localised damaged portions of a cement sewer pipe laid beneath the surface of the ground. In the method for the repair of localised damaged portions of a cement sewer pipe (12) laid beneath the surface of the ground, for covering a damaged site in the cement pipe, a fibre mat impregnated with a hardening resin, is wound around a hose-like carrier which is deformable by pressure applied internally. e The external diameter of the carrier is considerably smaller than the internal diameter of the cement pipe to be repaired. The length of the carrier is greater than the width of the wound-on fibre mat. The resin-impregnated fibre mat, S" with its side facing towards the hose-like carrier is held firmly in position by increased friction against the hose-like carrier During enlargement of i diameter of the wound-on fibre mat due to inflation of the hose-like carrier, said l 0 carrier is rotated with the fibre mat and, during the enlargement of the diameter .15 of the wound-on fibre mat, the layers of the fibre mat are forced together. The resin which is forced out by this compression flows into the cracks (10) and other damaged sites of the cement pipe to be repaired. A fibre-free ring of resin is formed at each end of the mat (Fig. 3C). 0tb* yp i'' ;1 ii"