Technical Field

The present invention relates to underground pipe repair and more particularly, but not exclusively, to underground pipe repair in relation to sewerage networks.

Background .Art

It will be appreciated that underground pipework can be made of varying material types. For example, there are clay, steel, reinforced concrete, plastic and many other types of materials used to make underground pipes. Furthermore, these underground pipes are susceptible to wear and tear along with geological activity. Thus, it is necessary either to replace or repair such underground pipe networks as required.

Of particular concern are sewerage networks laid in the

Nineteenth Century and more recently. Typically, a sewerage pipe is designed to have a life in excess of fifty years but obviously environmental factors may alter life expectancy. If a sewerage pipe collapses it is impossible to repair other than by digging at the appropriate position within the pipe to replace the affected section. The present invention relates to so-called no-dig technology where worn out or potentially worn out sewerage pipe is lined with a reinforcing material.

It is known to provide tubes of non-woven material impregnated with a suitable curable impregnant for repair of worn out or damaged sewerage pipes. Generally, the non- woven fabric tube is made by folding over a flat piece of non-woven material and applying a stitch seam to create the tube. This tube may be inverted within the sewerage pipe

during installation and may have reinforcing tape applied to this stitch seam to provide additional resilience. The curable impregnant may be latex based and the non-woven material may have a polyurethane backer.

It is also known technology to survey sewerage pipeworks using visual cameras or ultrasonic or any other appropriate technique. Such surveying allows determination of the specific dimension which may have changed over time due to environmental conditions, wear and geological activity within the sewerage pipe and also location of those sections of pipe most in need of repair. Furthermore and obviously, surveying of a sewerage pipe network also allows determination of where there has been collapse and/or partial collapse of the sewerage pipework. No-dig technology cannot repair collapsed sections of sewerage pipework as the non-woven tube cannot be drawn or pushed through such collapse. In effect, the reinforced non-woven material tube extends the life of the existing clay or other material sewerage pipe.

A typical installation procedure for no-dig technology involves drawing or pushing the impregnated non-woven material tube through the sewerage pipe, one section at a time i.e. between manholes and then effectively inflating the tube of non-woven material normally with warm air or hot water in order to cure the impregnant and so rigidise the non-woven material tube in situ within the sewerage pipe.

It will be understood that a close fit between the non- woven reinforcing material tube and the existing sewerage pipe provides the best performance. In use, the pipe should have a close fit as variation from such a close concentric fit between the non-woven material tube and sewerage pipe can lead to problems for example with abrasive wearing between the tube and the sewerage pipe, imperfect reinforcement of the existing sewerage pipe, unacceptable

pressure upon the non-woven tube material seam and wear of any polyurethane backing film applied to provide an additional barrier. Furthermore, surface features within the existing pipe may cause wrinkling within the reinforcing non-woven tube which can diminish performance. Such surface features may be typically over-flange couplings between existing sections of sewerage pipe. Finally, of course it is desirable to insert as long a section of non-woven tube as possible in one operation i.e. preferably beyond merely the distance between two manhole covers or other entry points. Thus, it is necessary to cut into the non-woven tube to accommodate these intermediate manhole entries and side pipe access points to the reinforced, in use, non-woven tube.

Unfortunately existing non-woven tube material is supplied in a regulation size i.e. it is consistently 4 inch, 8 inch or 10 inch along its length and so structural features and variations in existing sewerage pipe are not accommodated.

Technical Improvements and Advantages

It is an objective of the present invention to provide a so>lluuttiioonn wwiitthhiinn tthhee aarreeaa ooff nnoo--ddiigg pp.ipe reinforcement techniques to the above mentioned problems.

In accordance with the present invention there is provided a method of reinforcing or repairing an existing pipe, the method including the steps of:

a) surveying a subject section of pipe using surveying means in order to create a digital representation of that section of pipe in terms of cross sectional shape and/or damage and/or variation and/or localised surface variation; b) considering said digital representation in order to

1 determine a stitch path to recreate said variation along the length of pipe in a fabric tube, said stitch path determining the seam of the tube created by folding a sheet of non-woven material i.e. the stitch

5 path being the equivalent of an offset from the folded edge of the non-woven material; c) stitching said folded sheet of non-woven material to create a non-woven material tube consistent with variation in said section of pipe;

^0d) inserting said tube of non-woven material into said section of said pipe; and, e) rigidising said tube of non-woven material within that section of pipe.

^J -5 The material may be impregnated with a curable impregnant to rigidise in use the tube.

Preferably, the survey means may also identify location of side pipes to the pipe section and said side pipes may be

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* ^v accommodated within the stitch path either by a break in the stitch seam during forming of the non-woven material tube or by provision of a double stitch in these regions to allow reinforced cuts in the non-woven material tube for such side tubes. 25

The stitch path may include areas of specific stitching type i.e. spring stitching to allow expansion where necessary, double stitching for reinforcement about a surface feature or other localised variation in the stitch 30 path to accommodate presented localised features in the pipe.

Typically, the pipe will be a section of sewerage pipe.

35

Preferably, the survey means is a camera capable of presenting visual images to an image frame grabber in order that digital cross sections of the section of pipe may be

determined at appropriate spacings within the pipe. For example, an acceptable spacing may be every 10 centimetres or whatever is necessary in terms of tolerance for expected variations i.e. pipes made from brick sets may require spacing slightly less than the dimension of each brick set in order to determine when one brick set has been displaced.

It may be understood that the fabric tube could be non- woven or woven fibre textile material and may be reinforced using a curable .impregnant or any other appropriate means including thermoformable fibres within the material.

Brief Explanation of Drawings

An embodai ent of the present invention will now be described by way of example only with reference to the accompanying drawing in which:

Figure 1 is a schematic cross section illustrating surveying of a pipe section;

Figure 2 is a schematic cross section of a stage in material type manufacture for the pipe section of Figure 1; and,

Figure 3 is a schematic plan view of a stitched material tube in accordance with the present invention.

Mode of Carrying Out the Invention Including Working Examples and Industrial Application

In Figure 1 there is a schematic representation of the present invention. A section of pipe 1 is illustrated with a surveying device generally denoted 2 located within it. The pipe 1 will normally be located in an inaccessible location such as underground or possibly behind a wall or in a ceiling or a building. Thus, access to the pipe 1 is

2 difficult if replacement or repair is necessary.

The surveying device 2 can take many forms provided the essential features of the pipe 1 can be determined. These

5 features for the purposes of the present invention are its cross-sectional shape, identification of localised surface variations and determination of cross-sectional dimensions. Thus, a visual camera 3 with illumination element 4 can be used. Alternatively, ultrasonic, mechanical feeler or other

10 techniques can be used to determine the necessary pipe 1 parameters. It will be understood that highly accurate determination of the pipe 1 parameters is not important provided sufficient detail is achieved for subsequent material tube formation. Thus, determination at for example

1 15" separation in the circumference about the tube 1 cross section may be sufficient detail to provide an accurate digital representation of the pipe 1 for tube formation as indicated later. Furthermore, several determination techniques could be used in combination. For example, in ^r -- ⁰ the illustrated embodiment of the invention shown in Figure 1, the surveying device 2 includes rotating wheels 5 in order to move the device 2 along the pipe 1, it may be these wheels 5 are mounted such that they can be displaced relative to the notional centre X-X of the pipe 1 and this

25 displacement recorded as indication of variation in pipe 1 parameters i .e . diameter . However, in the embodiment of Figure 1 the principle surveying technique is the use of camera 3 in association with illumination element 4 .

30

The illumination element 4 can simply provide a sufficiently bright beam to illuminate the pipe 1 for visual inspection by the camera 3. However, this may create data acquisition problems in a frame grabber data acquisition element (not shown) thus, it is envisaged that the

35 illumination element 4 will present a laser beam to the inner surface of pipe 1 in order to create a discreet and well defined illuminated ring 6. This ring 6 will be easier

to identify by the frame grabber element in order to determine variations in the pipe 1 as the device 2 travels along it.

It will be appreciated that the more cross sections taken of the pipe 1 using the surveying device 2 the more accurate the survey and subsequent material tube formation will be. However, it will also be understood there must be a balance between the quantity of data acquired and that necessary for processing with the necessary accuracy for determining the formed tube. In the present invention it is therefore envisaged that the spacing of acquired cross- sectional parameters of the pipe 1 will be determined by expected variations. Thus, if the pipe 1 is made of a mosaic of discreet brick elements it will be expected that the spacing of cross sectional slices acquired by the survey device will be roughly equivalent to the presented dimensional width of the brick element i.e. to ensure that if one brick is displaced then the surveying device will be able to identify this displacement. Alternatively if the pipe 1 is of a more unitary nature i.e. a clay or reinforced concrete pipe, a spacing of up to /2 metre may be acceptable.

A further consideration is the likelihood of missing pipe 1 variations i.e. side pipes 7 or pipe junctions 8. These variations 7, 8 in the pipe 1 may be missed if the spacing of the acquired cross sections of the pipe 1 were too great. Thus, if there are side pipes having a notional cross section of 10 cm it may be advisable to have a digital cross section acquiring gap of less than this 10 cm dimension to ensure that proper acquisition i.e. location of the side pipe 7 is achieved. Similarly, the survey device 2 could be psuedo-intelligent in that if the pipe 1 was known to be presented in lengths of 50 metres it could note such expected spacing in junctions 8 and so if a new junction was not met within this noted length the device 2 could hunt

— b —

where expected for such connectors 8. Furthermore, with displaceable wheels 5 such traumatic variations as would be presented by a side pipe 7 or a junction 8 could be noted and a device stimulated to make a more accurate survey of these features of the pipe 1. Similarly, the device 2 could be intelligent about a notional spacing of the acquired cross sections of the pipe 1 if it noted a variation in the pipe 1 i.e. more cross sections could be taken to ensure a more accurate survey in these regions of the pipe 1.

10

The device 2 could be independent i.e. battery driven and simply allowed to creep along the pipe 1 from an entry point to a subsequent exit point from the pipe 1. Furthermore, the device 2 could be arranged in such ^{•■ •} * independent operation to either store the digital data representative of the pipe 1 in an internal memory device or transmit such information to an external recipient device. Usually the device 2 will be remote controlled to allow manual override for further inspection as necessary of the

20pipe 1 and to terminate surveying if adverse conditions i.e. pipe 1 collapses, are noted. As an alternative to battery operated remote control the device 2 could be coupled through an umbilical power/control cable to a remote location. 25

The objective of the device 2 is to present a numerically readable digital data set which defines the geometrical variation of the pipe in the surveyed section 1. As indicated above this will generally be achieved taking cross sectional determinations of the pipe 1 at various spacings along its length. These cross sectional determinations will be consolidated in a memory device and when read sequentially it will be understood, define the necessary digital data to determine the profile of the pipe 1. This digital data is processed in order to achieve a stitch or cut path for the manufacture of a material tube 13. It is known to project longitudinal contour lines, at

I notional angular spacings about each cross sectional profile circumference acquired by the device. These longitudinal contour lines reflect the lateral dimensional variations in the pipe 1 along its length. These variations in effect

5 create an offset spacing variation from a folded edge 11 of material which is the stitch or cut path necessary to create the material tube 13.

Figure 2 illustrates in schematic cross section a 10 folded sheet of material 10. Generally, the sheet 10 will be compressed by some means to ensure good definition of the fold edge 11. Normally the folded sheet of material 10 will be laid upon a support bed (not shown) with a stitch or cutter device 12 located above it. The material 10 will 15 generally be a non-woven felt of sufficient density and absorbency for impregnation of a curable reinforcing compound. However the material 10 may be alternatively reinforceable by some other means.

20 The stitch or cutter device 12 is located above the folded sheet 10 to allow A-A movement as indicated by the arrowheads. The folded sheet 10 will be fed in a direction perpendicular to the plane of the drawing and the device 12 moved in the A-A plane in order to give the necessary offset

^• 25variation from the folded edge 11. It will be appreciated by such offset variation the potential cross sectional dimension of the tube once manufactured is varied and will subsequently be consistent with the variations in the daimensions of the pipe 1. 30

The device 12 as indicated can be a stitcher or a cutter. A stitch device 12 obviously creates a stitch line at the variable offset from the edge 11 in order to define the material tube 13 for insertion into the pipe 1. The

35 stitch line may be a single row of stitches or may include breaks to accommodate side pipes 7 or may include reinforcing i.e. double or speciality stitch formations to

further strengthen or define the material tube created as necessary. A cutter device 12 would simply cut the folded material 10 to define the necessary material tube dimensions however, it will be appreciated that it may be more appropriate with a cutter device 12 not to present the material in a folded form but to arrange for the cutter 12 to cut respective sides of the material in order to define abutment edges for creation of the material tube in such case the edge 11 will be a centre line of the material. The edges are created after cutting with a cutting device 12 could be butt welded together by known techniques. Irrespective of whether the edges of the material are secured together by stitches or butt welding it will generally be appropriate to apply a reinforcing tape to the material tube in order to provide resistance within the pipe 1 during the draw or push through stage of installation of the material tube in the pipe 1.

Figure 3 illustrates an example (severe) example of a variation in a stitch line 14 compared to the edge. It can be seen that the offsets a, b from the edge 11 to the stitch line 14 vary slightly about a notional tube d.imension which is roughly equivalent to the expected diameter of the pipe 1 surveyed in accordance with the description above. With the stitch line 14 in place the excess material 15 can be removed or trimmed as required. Typically, this excess material 15 may be reprocessed into further non-woven material felts. If a hot knife cutting technique is used to trim the material 15 it would be appreciated that a further sealing effect may be achieved behind the stitch line 14 to the benefit of the eventual reinforcing tube 13 inserted into the pipe 1. In use the tube 13 created by the material 10 and stitch line has a stitch and/or butt weld seam and may be inverted such that the tails on the excess material side of the stitch line 14 will be on the inside away from the surface of the pipe 1 in use.

I Typically the formed tube 13 will now be impregnated with a suitably curable reinforcing compound. The material is not impregnated until this stage to allow for recycling of excess material 15 as required and also as it will be

5 appreciated that the curable reinforcing compound may cure before required within the pipe 1 i.e. before insertion.

It will be understood it is at the core of the present invention that the formed tube 13 is bespoke for a

10 particular section of pipe 1 thus the tube 13 can be printed with an appropriate designation which associates it with its pipe 1 and also may have features such as side pipes 7 and connections 8 marked in order to allow an installer to understand the position of various features within the pipe 5 l.

As the present invention uses a fabric in its preferred embodiment it will be understood that the pull and push technique of locating the formed tube 13 in the pipe 1 may 0 create various stretch and squeeze distortions in the tube 13. It is thus normal for the process of converting the data set acquired by the survey device 13 into a digital representation of the pipe 1 will incorporate the necessary ability to appreciate the stretch/squash effects of

25 presenting the formed tube 13 in the pipe 1.

It will also be appreciated that reinforcing patches could be applied where deemed necessary to the tube 13 in accordance with the survey conducted by the device 2 i.e.

30 where the pipe 1 is particularly worn or heavily distorted.

An example of a suitable surveying arrangement is the PIRAT robot devleoped by the Australian Natinal Science Agency, CSIRO and Melbourne Water. The PIRAT (Pipe

35 Inspection Real-time Assessment Technique evaluates the soundness of sewers. Alternatively, there is a similar system called KARO which is designed to inspect sewerage

pipes and has been developed by Fraunhofer USA, Inc. The inspection project named LAOKOON in Germany also has evaluated suitable sewer inspection robots for the present invention.