AU2014203356B2 - Pipe and Conduit Rehabilitation System - Google Patents

Abstract

A pipe and conduit rehabilitation system comprising a tubular, inflatable form supporting a settable resin-impregnated pre-form separated from said inflatable form by a replaceable separation sleeve, a hose attached to a first 5 closure fitting at one end of said inflatable form employed to supply flows of inflation air and heating steam to said inflatable form, a second closure fitting at the other end of said inflatable form having a fixed or adjustable outflow orifice, hauling lines attached to said hose and said second closure fitting employed to longitudinally displace said inflatable form, frangible 10 ties employed to maintain said inflatable form in collapsed condition and secure said preform, bridles attached to said first closure fitting and peelably bonded to said preform to retain it in position, a removable protective sleeve covering said preform during positioning of said inflatable form, and automated means employed to control inflation and 15 heating of said inflatable form. Sheet 1 of 4

Description

PIPE AND CONDUIT REHABILITATION SYSTEM

This invention relates generally to methods of rehabilitating pipes and conduits by the installation in them of structural liners. In particular, it relates to methods of rehabilitating pipes and conduits by the installation in them of soft liners - liners of a flexible, absorbent material which are impregnated with a settable resin, positioned within a pipe or conduit, inflated into intimate contact with the inner wall surfaces of the pipe or conduit, and maintained in an inflated condition until the settable resin has cured.

Buried pipes and conduits commonly fail in localised zones. Such failure may be the result of ground movement, causing a tributary connection to fracture close to its point of entry to a main; as the result of erosion caused by flow impingement at a point of water entry or directional change; or as the result of acid corrosion of concrete pipes. Localised failure of this type is normally repaired by installation in the damaged zone of soft liners. These comprise one or more layers of absorbent reinforcement material of woven, knitted, quilted or felted form or any combination of these, to the surfaces of which are optionally fixed one or more impervious outer layers. A soft liner is supported on an inflatable form, impregnated with a settable resin, winched or everted into place in a pipe or conduit and the form inflated with air to bring the liner into intimate contact with the inner wall surfaces of the pipe or conduit. Said settable resin is then allowed to cure at ambient temperature or, alternatively, curing is accelerated by the application of heat in the form of steam or hot water. Curing at ambient temperature is most common, particularly in pipes and conduits of smaller diameter. Accelerated curing methods are almost always employed in the installation of liners in pipes or conduits of larger diameter. Where hot water curing is employed in larger pipes or conduits, differences in level may result in the application of excessive hydrostatic pressures at lower zones with a consequent undesirable thinning of the liner in those zones. In main pipes or conduits, which will commonly have only small gradients, differences in hydrostatic pressure may not be significant. However, in branch pipes or conduits, significant depth differentials are common and may result in zones with unacceptably high hydrostatic pressures.

Where steam heating is employed, the inflatable form is provided at its distal end with a fixed calibrated orifice that permits a continuous outflow of suitable volume. The use of a fixed calibrated orifice is appropriate in most forms of the apparatus in which, in use, the distal end of the inflatable form is inaccessible. A flow of steam, which is normally more or less the full output of a small mobile boiler employed for the purpose, is mixed with a flow of air and maintained until curing of the resin is complete. A larger boiler having a modulatable burner is optionally employed at less than full output, but may result in lower efficiency of fuel use. Boiler operation and air pressure are monitored by an operator, air pressure being manually adjusted from time as required to provide the desired inflation pressure. The inflation pressure within the inflatable form at any time is principally the result of said air flow, with steam contributing in only a minor way due to condensation, the inflows being balanced against the outflow through said calibrated orifice. The air flow carries the steam through the inflatable form, acting to minimise the temperature differential along its length. The steam is delivered to the inflatable form effectively in a saturated state such that subsequent condensation within the inflatable form releases the latent heat of vaporisation. In this way, a relatively small volume of steam can be made to have a similar effect upon resin curing as a much greater volume of hot water, but with a significant improvement in simplicity and ease of handling.

Contracts for the repair of sewer pipe defects are commonly let for a number of connections in a specific area. Such contracts are veiy price-sensitive and, for their profitable completion, require a high degree of operational efficiency. To achieve this, labour and equipment must be efficiently deployed within a specified work zone and retained at each repair site for the minimum time possible. It is thus less practical for ambient curing of resin to be employed, a method which normally requires revisiting each repair site. Where steam curing is employed, manual coordination of air pressure and steam flow may require the constant attendance of an operator at a repair site, reducing the efficiency of labour deployment. Further, because only gross control is exercised over steam flow and air pressure, energy wastage may occur and, in some cases, unnecessarily long resin curing times may result.

Soft-liner repair methods are well known and many employ either heating of the settable resin during the impregnation process or heating of the liner post-installation to accelerate the curing process. An example is that taught by Imoto et al in JP4296531. This method employs compressed air for expanding the liner into place and, subsequently, a heating fluid, such as pressurized steam to accelerate curing of the resin. Another example is that taught by Abe in JP1200934. In this method, the curing agent for the resin is contained in microcapsules that are ruptured by heating using hot water or steam following installation of a liner. Another example is that taught by Uga et al in JP57041917 in which a reactive, thermosetting resin type lining material is applied to the internal surfaces of a pipe or conduit and a soft and elastic tube is expanded into place over the lining material by heated air and, subsequently, steam to cure and harden the lining material. Another example is that taught by Kamiyama in JP2000243609. In this method, a lining for a pipe is expanded into place using heated compressed air with the addition, subsequently, of steam heating to cure the thermosetting resin. Another example is that taught by Aiji in JP5084827. In this method, air pressure is employed to expand the liner into place and steam is subsequently introduced with pressure being kept constant. Another example is that taught by Otaki in JP8127068. In this method, air pressure is employed to expand the tube (liner) into place and steam is subsequently discharged to thermally cure the tube. Another example is that taught by Keyuan in CN102649317. In this method, to guarantee curing of the resin, it is heated immediately prior to the impregnation process, thereby eliminating the need for a pressurized steam boiler. Another example is that taught by Park in KR100888169. This method employs heated compressed air for expanding the liner into place and, subsequently, a heating fluid, such as warm water or steam vapour to accelerate curing of the resin. Another example is that taught by Choi in KR20020084669. In this method, hot water or steam is supplied to the entrance of the reinforcing tube for curing of the adhesive resin. Another example is that taught by Wood in GB1357355. In this method, a length of liner is inflated by an air pump. If the curing reaction is exothermic, an orifice may be opened to produce a through flow of air and prevent a build up of heat. To accelerate curing of the resin, the liner may be inflated with steam. Other examples are those taught by Driver in US 2003/0015247, US 2007/0031194, US 2007/0012373 and KR20080002740. In all of these methods, the liner is inflated with air and cured with steam. All of the prior art methods cited introduce the soft liner in a variation of one or other of the several methods commonly practised. All of the methods are directed at the installation of long (manhole-to-manhole) liners in pipes and conduits. Accelerated curing of the settable resin is obviously of advantage in the installation of long liners and liners of large diameter, as the process of installing these may, in some cases, require attendance of several days at a repair site. A further method now commonly practised is to use a soft liner impregnated with a radiation-curing resin. Following its introduction into a pipe or conduit, the soft liner is brought into intimate contact with the inner wall surfaces of the pipe or conduit by fluid pressure or other means and exposed to electromagnetic waves, ionising radiation, ultraviolet light or the like which rapidly catalyses the resin into a solid. Examples of this method are those taught by Hosao et al in JP2002219754 and Wood in WO 9508075. While this method offers advantages in some operational situations, it encounters difficulties in pipe or conduits of small diameter or with sharp bends or zones in which water is trapped. Additionally, where a greater mass of chemically catalysing resin accumulates in a zone of a liner, the exothermic release of heat during curing tends to cause a rapid and uneven curing of the resin in that zone. The use of a heated medium, either steam or water, to accelerate resin curing also acts to moderate heating of such localised hot spots. Where an excess of radiation-curing resin accumulates in a zone of a liner, creating a localised hot spot, no such moderation can occur. Such localised heating may involve temperatures high enough to cause breakdown of chemical components, thereby compromising the integrity of the liner and, in extreme cases, may result in charring of the resin.

The object of the present invention is to provide an efficient and economical system for the making of short-length, soft-liner, structural repairs of defects in sewer pipes and conduits; in which a repair is easily and reliably located in a repair zone; in which the repair is easily and reliably inflated into position; in which the repair is rapidly cured using steam in an automatically controlled process; and in which ancillary equipment employed in the installation process is easily and reliably withdrawn from a sewer pipe or the like after curing of a repair. Most importantly, the system must require only a single visit to each repair site, with a minimum time spent at each site.

According to the present invention, a soft-liner structural repair of a defect in a sewer pipe or the like is made by impregnating a tubular preform comprising one or more layers of resin-absorbent reinforcement material with a settable resin, positioning said preform over an inflatable tubular form of soft, flexible, reinforced, sheet polymer material, positioning said settable resin-impregnated preform in the desired repair zone, inflating said tubular form to bring said preform into intimate contact with said repair zone and maintaining inflation of said inflatable form to keep said preform in intimate contact with said repair zone until said settable resin is properly cured. A suitable hose connected to a first closure fitting at one end of said inflatable form is employed to inflate and deflate said inflatable form and, in conjunction with a hauling line, to draw said inflatable form carrying said preform into position in a repair zone in said sewer pipe or conduit. The other end of said inflatable form is closed with a second closure fitting having a calibrated orifice permitting a predetermined outflow volume of air or steam at a predetermined pressure. Said second closure fitting is adapted to have fixed to it a hauling line employed to tow a closed-circuit television camera behind said inflatable form and, following completion of a repair, to draw said inflatable form from said sewer pipe or conduit. A replaceable separation sleeve of a suitable thin, flexible sheet polymer material is positioned between said inflatable form and said preform covering more or less all of said inflatable form, one end of said sleeve being fixed to said first closure fitting, the other being allowed to trail freely. Said separation sleeve protects said inflatable form from said settable resin and acts to ensure detachment of said inflatable form from said preform following curing of said settable resin. It is common practice in the industry for pre-forms for the making of soft-liner repairs to be secured to inflatable forms using adhesives, frangible ties, adhesive tapes (masking tape) or elastic ties. It is well known for these securing means to be broken or disrupted while a liner assembly is being drawn into place in a pipe or conduit, resulting in a liner moving on an inflatable form and, as a result, being installed in an incorrect position. To retain said resin-impregnated preform on said inflatable form during its positioning within a sewer pipe or conduit, a plurality of suitable bridles fixed to said first closure fitting are peelably bonded to the inside edges of said preform prior to its impregnation. Prior to introduction of said assembly of inflatable form, separation sleeve, preform and bridles into a sewer pipe or conduit, a protective sleeve of a suitable thin, durable, flexible sheet polymer material is placed over said assembly, said protective sleeve acting to protect said preform during the process of positioning it within a sewer pipe or conduit. One end of said protective sleeve is removably attached to said first closure fitting with the other extending beyond the end of said inflatable form and allowed to trail freely. A retrieval line attached to said trailing end of said protective sleeve is employed to detach said protective sleeve from said assembly before its final positioning within a sewer pipe or conduit. Following the installation of said protective sleeve on said inflatable form, said preform is impregnated with said settable resin by depositing a measured quantity of mixed resin and catalyst between said separation sleeve and said protective sleeve and then passing said inflatable form, said preform and said separation and protective sleeves between rollers to work said resin into said preform. Said assembly, including said settable resin-impregnated preform, is then drawn into the sewer pipe or conduit to be repaired by means of a hauling line attached to said hose and positioned with said settable resin-impregnated preform at the repair zone. Correct positioning of said preform is verified, where necessary, with the use of a closed-circuit television camera and said hose is led up to the surface, where it is connected to supplies of compressed air and steam. Prior to final positioning of said settable resin-impregnated preform, said protective sleeve is displaced and drawn away from said inflatable form by tension applied to said retrieval line, exposing the outer surface of said preform. Said inflatable form is then finally positioned and inflated into intimate contact with the inner wall surfaces of said sewer pipe or conduit by a flow of compressed air supplied through said hose, a continuous flow of air escaping via said calibrated orifice of said second closure fitting. Suitably-spaced, frangible ties placed over said inflatable form and said settable resin-impregnated preform ensure that said inflatable form expands in a way that prevents the trapping of lying water during said inflation process. A flow of steam from a small, portable boiler is then introduced via said hose to accelerate curing of said settable resin, said flow of air being reduced to maintain the required inflation pressure, the outflow of air and steam via said calibrated orifice of said second closure fitting acting to ensure a continuous inflow of heating steam to said inflatable form. Automatic control means are optionally employed to control said air and steam flows to maintain the required inflation pressure and to achieve the desired heating of said settable resin. Following curing of said settable resin, a depression is applied to said inflatable form to collapse it, said hose is disconnected from said compressed air and steam supplies and withdrawal of said inflatable form is commenced by the application of tension to said hauling line fixed to said second closure fitting. As said inflatable form is displaced longitudinally in this manner, said separation sleeve is everted and continued displacement causes it to peel away from said cured repair. Similarly, said bridles are drawn back through said cured repair, continued displacement causing their ends to peel away from said cured repair. Said assembly of inflatable form, hose, everted separation sleeve and detached bridles is drawn out of said sewer pipe or conduit and prepared for re-use.

The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is a partial, diagrammatic, longitudinal cross-sectional view of apparatus employed in the installation of a soft-liner repair in accordance with the present invention;

Figure 2 is a detailed, partial, diagrammatic, longitudinal cross-sectional view of a first end of apparatus employed in the installation of said soft-liner repair prior to introduction into a sewer pipe or conduit, the components depicted inflated for clarity of illustration;

Figure 3 is a more general, partial, diagrammatic, longitudinal cross-sectional view of the apparatus first end depicted in Figure 2, the components depicted in their inflated form within a sewer pipe or conduit;

Figure 4 is a detailed, partial, diagrammatic, longitudinal cross-sectional view of a second end of the apparatus employed in the installation of said soft-liner repair;

Figure 5a is a diagrammatic, transverse cross-sectional view of a first mode of collapsing an inflatable form of the present invention;

Figure 5b is a diagrammatic, transverse cross-sectional view of a second mode of collapsing said inflatable form of the present invention;

Figure 6 is a medial transverse cross-sectional view of the apparatus and soft-liner preform of Figure 1, said components being depicted in more or less flat form ready for rolling to distribute settable resin in said preform;

Figure 7 is longitudinal cross-sectional view of a fitting employed to fix a hauling line to the end fitting of Figure 4;

Figure 8 is longitudinal cross-sectional view of the fitting of Figure 7 along a plane rotated 90° to that of Figure 7;

No meaning should be inferred from the fact that the various figures are drawn to different scales. For the purpose of providing clarity of exposition, normally abutting components are depicted slightly separated.

With reference to Figures 1 and 6, a soft-liner structural repair of a defect in a sewer pipe or conduit is made by impregnating with a settable resin a tubular preform 1 comprising one or more layers 2, 3 of resin-absorbent reinforcement material in wrapped sheet or closed tubular form, positioning said preform over an inflatable tubular form 4 of soft, flexible, reinforced, sheet polymer material, positioning said settable resin-impregnated preform in the desired repair zone, inflating said tubular form to bring said preform into intimate contact with said repair zone and maintaining inflation of said inflatable form to keep said preform in intimate contact with said repair zone until said settable resin is properly cured. A replaceable separation sleeve 5 of a suitable thin, flexible sheet polymer material is positioned between said inflatable form and said preform covering more or less all of said inflatable form. In the preferred embodiment, said separation sleeve is made from a polymer material, such as polyethylene, to which said settable resin adheres poorly. In an alternative embodiment, said separation sleeve is treated with talcum, a silicone coating or the like to minimise its adhesion to said resin of said settable resin-impregnated preform. Said separation sleeve protects said inflatable form from said settable resin and acts to ensure detachment of said inflatable form from said preform following curing of said settable resin. Said inflatable form is made from a material which is essentially inelastic and it and said separation sleeve are made with diameters in the range 150% to 200% of the internal diameter of the sewer pipe or conduit in which said soft-liner repair is to be made. In the preferred embodiment, said inflatable form and said separation sleeve are made with diameters 150% of the internal diameter of the sewer pipe or conduit. Said preform is made elastic or otherwise expandable with a relaxed diameter in the range 50% to 100% of the internal diameter of the sewer pipe or conduit in which said soft-liner repair is to be made. In the preferred embodiment, said preform is made with a relaxed diameter in the range 75% to 85% of the internal diameter of the sewer pipe or conduit in which said soft-liner repair is to be made. Said preform is made with an uncompressed thickness to suit the nature of the repair to be made and, in the preferred embodiment, this falls in the range 2 to 15 millimetres. In the preferred embodiment, said preform comprises two discrete layers, a first layer which provides resin carrying capacity and a second, reinforced, layer which provides strength. Said first layer is normally of a felted material and said second layer is normally of a woven, quilted or knitted material. i Said preform is optionally made with a durable and impervious inner surface layer which protects said cured soft-liner repair.

With additional reference to Figures 2 and 3, one end of said inflatable form is closed by means of first closure fitting 8, to which is connected suitable hose 7, said hose being employed to inflate and delate said inflatable form and, in conjunction with a hauling line (not shown), to draw said inflatable form carrying said preform into position within a repair zone in a sewer pipe 29 or conduit. Said first closure fitting is provided with flow-through duct 9 and the diameter of said duct and the internal diameter of said hose and its associated fittings is made sufficient to carry the volume flows required for the proper installation of said soft-liner repair. In order to minimise the possibility of penetration damage to said inflatable form, said first closure fitting is made with a rounded internal surface 10. In a first alternative embodiment, said closure fitting is made in a single piece, including plain or barbed spigot 15. In a second alternative embodiment, said plain or barbed spigot is made separately with a threaded male end 16 and a hexagonal collar 19, said threaded end being sealingly screwed into threaded bore 18 of said closure fitting and said hexagonal collar being accommodated within suitable recess 17 formed in said closure fitting. Said spigot is optionally made longer or shorter. Where said spigot is made shorter, said hose end is pressed over it, the end of said inflatable form is positioned over said hose end and the two are fixed to said spigot by means of whipping 12 with a suitable material. In the preferred embodiment, said whipping material is a braided polymer material having a high tensile strength and a small degree of elasticity permitting an elastic extension of up to 5%. Said whipping material is stretched during the whipping process, the elastic contraction so generated acting to ensure maintenance of a good seal between said hose end, said inflatable form end and said spigot during thermal expansion and contraction. In alternative embodiments, said whipping is replaced by suitable clamping means, a layer of suitable heat-resistant elastomer being optionally provided between said clamping means and said hose end and the end of said inflatable form. The end of separation sleeve 5 is fixed over said end of said inflatable form by means of removable clamp 20. Where said spigot is made longer (as depicted in Figure 3), the end of said hose is sealingly clamped to the outer part of said spigot by clamping means 14 and the ends of said inflatable form and said separation sleeve are clamped to the inner part of said spigot by means of clamping means 13. In an alternative embodiment, separate clamping means are provided to secure the ends of said inflatable form and said separation sleeve to permit the ready removal and replacement of said separation sleeve.

With additional reference to Figure 4, the other end of said inflatable form is closed by means of a second closure fitting 22 having a calibrated orifice 21 permitting a predetermined outflow volume of air or steam at a predetermined pressure. In order to minimise the possibility of penetration damage to said inflatable form, said second closure fitting is made with a rounded internal surface 23. Depending upon the size of the soft-liner repair to be made, the diameter of said calibrated orifice falls typically in the range 4 to 10 millimetres. In the preferred embodiment, the diameter of said calibrated orifice falls in the range 5.5 to 8 millimetres. In the preferred embodiment, the end of said inflatable form is sealingly fixed to spigot 24 of said second closure fitting in the manner described in relation to said first closure fitting. The end 26 of separation sleeve 5 is unattached and, in the preferred embodiment, extends beyond the end of inflatable form 4. Boss 27 formed on the outer end of spigot 24 is provided with one or more opposed pairs of threaded recesses 28 for attachment of a hauling line (not shown). Said hauling line is employed to tow a closed-circuit television camera (not shown) behind said inflatable form and, following completion of a said soft-liner repair, to draw said inflatable form from said sewer pipe or conduit. To retain said settable resin-impregnated preform on said inflatable form during its positioning within a sewer pipe or conduit, a plurality of suitable bridles 30 fixed to said first closure fitting are peelably bonded at points 31 to the inside edges of said preform prior to its impregnation. In a first alternative embodiment, the outer ends of said bridles are fixed with the end of said separation sleeve over spigot 11 of first closure fitting 8 by means of clamping means 20. In a second alternative embodiment, the outer ends of said bridles are fixed to said spigot by means of separate clamping means.

With additional reference to Figures 7 and 8, yoke 41 comprises parallel side panels 33 joined by end panel 35 and pierced towards their free ends by attachment apertures 34. Hauling line 37 is fixed to terminal fitting 38 which passes through aperture 36 in said end panel, the enlarged head 39 of said terminal fitting being captured within said yoke. In the preferred embodiment, said hauling line takes the form of a braided steel cable swaged into said terminal fitting. Said yoke is fixed to boss 27 of said second closure fitting by means of attachment bolts 40 being passed through attachment apertures 34 and threaded and tightened into threaded recesses 28.

To prevent the entrapment of standing water during inflation of said inflatable form with said settable resin-impregnated preform, said inflatable form and said preform are restrained against expansion by means of a plurality of frangible ties (not shown). Typically, said ties are made of a vegetable fibre, woollen yam or the like and are provided at a spacing in the range 3 to 5 times the internal diameter of the sewer pipe or conduit to be repaired over said preform and 1.5 to 2.5 times said internal diameter over said exposed inflatable form. In the preferred embodiment, said tie spacing is in the range 4 times the internal diameter of the sewer pipe or conduit to be repaired over said preform and 2 times said internal diameter over said exposed inflatable form. The earlier rupturing of said ties over said preform and the later rupturing of said ties over said inflatable form acts to positively displace outwardly any standing water in and adjacent to the repair zone.

With reference to Figures 5a and 5b, where difficulty of access requires a more compact form, said inflatable form is optionally collapsed in any suitable mode before tying of said frangible ties. In the preferred embodiment, said inflatable form is collapsed in the modes depicted before tying of said frangible ties. Figure 5a depicts a method of collapsing involving simple folding. Figure 5b depicts a method of collapsing involving the creating of a plurality of parallel pleats.

Prior to introduction of said assembly of inflatable form, separation sleeve, preform and bridles into a sewer pipe or conduit, a protective sleeve 6 of a suitable thin, durable, flexible sheet polymer material in wrapped or closed tubular form is placed over said assembly, said protective sleeve acting to protect said preform during the process of positioning it within a sewer pipe or conduit. Said protective sleeve is made with a diameter in the range 100% to 200% of the internal diameter of the sewer pipe or conduit in which said soft-liner repair is to be made. In the preferred embodiment, said protective sleeve is made with a diameter of 150% of the internal diameter of the sewer pipe or conduit in which said soft-liner repair is to be made and extends beyond the trailing end (that is, the end trailing during the introduction of said assembly of inflatable form, settable resin-impregnated preform, separation sleeve and protective sleeve into a sewer pipe or conduit) by a minimum of four diameters. One end of said protective sleeve is removably attached to said first closure fitting by means of a suitable elastic retaining ring 32 or the like. A retrieval line attached to said trailing end of said protective sleeve is employed to detach the leading end of said protective sleeve from said retaining ring and to draw said protective sleeve away from said assembly of inflatable form, separation sleeve, settable resin-impregnated preform and bridles before its final positioning within a sewer pipe or conduit. Following installation of said protective sleeve over said assembly of inflatable form, separation sleeve, preform and bridles, said preform is impregnated with said settable resin by depositing a measured quantity of mixed resin and catalyst between said separation sleeve and said protective sleeve and then passing said assembly, including said protective sleeve, in flat form between opposed cylindrical rollers to work said resin into said preform. Said assembly, including said protective sleeve, is then drawn into the sewer pipe or conduit to be repaired by means of a hauling line attached to said hose and positioned with said settable resin-impregnated preform at the repair zone. Prior to final positioning of said settable resin-impregnated preform, said protective sleeve is displaced and drawn away from said assembly by means of tension applied to said retrieval line, thereby exposing the outer surface of said settable resin-impregnated preform. Final positioning of said preform is verified, where necessary, with the use of a closed-circuit television camera and said hose is led up to the surface, where it is connected to supplies of compressed air and steam.

With said settable resin-impregnated preform accurately located in said repair zone, said inflatable form is inflated by a flow of pressurised air supplied through said hose, a continuous flow of air escaping via said fixed calibrated orifice of said second closure fitting. Inflation of said inflatable form brings said preform into intimate contact with the inner wall surfaces of said sewer pipe or conduit, said frangible ties progressively rupturing during said inflation process. The use of said fixed calibrated orifice is appropriate in most forms of said apparatus in which, in use, the distal end of said inflatable form is inaccessible. In an alternative embodiment (not shown), where the distal end of said inflatable form is accessible in operation, said orifice of said second closure fitting is optionally made manually adjustable. In this embodiment, the cross-sectional area of said orifice is adjusted by screwably adjusting the depth of engagement of a conical valving element with a circular valve aperture. A flow of steam, which is normally more or less the full output of a small mobile boiler employed for the purpose, is mixed with the flow of air and introduced to said inflatable form via said hose to heat and accelerate curing of said settable resin, said combined flow of air and steam being maintained until curing of said resin is complete. A larger boiler having a modulatable burner is optionally employed at less than full output, but may result in lower efficiency of fuel use. Boiler operation and air pressure are monitored by an operator, said air flow being manually adjusted from time to time as required to provide the desired inflation pressure and rate of flow through said inflatable form, said steam flow being adjusted to maintain the desired temperature. Said steam flow is reduced by venting to atmosphere or, if appropriate, by boiler burner modulation. The inflation pressure within said inflatable form at any time is principally the result of said air flow, with steam contributing in only a minor way due to condensation, the input flows being continuously balanced against the outflow through said calibrated orifice. Said air flow carries said steam through said inflatable form, acting to minimise the temperature differential along its length, the outflow of air and steam via said fixed calibrated orifice of said second closure fitting acting to ensure a continuous inflow of heating steam to said inflatable form. Said flow of steam is delivered to said inflatable form effectively in a saturated state such that subsequent condensation within said inflatable form releases the latent heat of vaporisation. The temperature of said steam delivered to said hose is normally in the range 105° C to 110° C, but is dependent upon the length of the hose, the i objective being for said steam to enter said inflatable form at a temperature just above 100° C. Release of the latent heat of vaporisation allows a relatively small volume of steam to have a similar effect upon curing of said resin as a much greater volume of hot water, but with a significant improvement in simplicity and ease of handling. In an alternative ) embodiment (not shown), said air and steam flows are combined in a small mixing chamber before being delivered to said hose. Said mixing chamber takes the form of a simple T junction with arms having diameters more or less that of said hose or, in a more complex form, a cylindrical canister having a diameter in the range 2 to 5 times the diameter of said j hose and a length in the range 2 to 5 times the diameter of said canister, said air and steam delivery lines entering said canister tangentially.

Automatic control means are optionally employed to control said air and steam flows to maintain the required inflation pressure and to achieve the desired heating of said settable resin. Said inflatable form is ) inflated by the application of pressures in the range 50 to 250 kPa. Said settable resin-impregnated preform is maintained at a temperature in the range 50° to 95° C. In the preferred embodiment, where said repair is made in a straight section of said sewer pipe or conduit, said inflatable form is inflated by the application of a pressure of 100 kPa and heated to a temperature of 70° C to 100° C. Where said repair is made in a curved section of said sewer pipe or conduit, any of said preform, said inflatable form, said separation sleeve and said protective sleeve are made up to 50% larger in diameter and said inflatable form is inflated by the application of a pressure of 85 tol 50 kPa. Where said preform is made larger, stretching to accommodate a bend acts to take up almost all excess material.

In an alternative embodiment (not shown), with said settable resin-impregnated preform accurately positioned in the repair zone of a sewer pipe or conduit in the manner described, said hose is led out to the surface and connected to sources of compressed air and steam (not shown). Said inflatable form is inflated by means of a flow of compressed air supplied via said pipe, bringing said preform into intimate contact with the inner wall surfaces of said sewer pipe or conduit. Said frangible ties progressively rupture during said process of inflation. The inflation pressure within said inflatable form is maintained by balancing the inflow volume of air with the escape flow via said calibrated orifice in said second closure fitting. In the preferred embodiment, said source of compressed air takes the form of an air receiver of suitable capacity charged by an air compressor, the driving motor of said air compressor being provided with automatic cut-off means which reference pressure in said receiver. Said receiver supplies air via a pressure reducing valve reducing pressure to a predetermined value and a manually-operated cutoff valve. A pressure sensing line (not shown) extends from a location at approximately mid length of said inflatable form to the diaphragm of an air flow regulating valve. A pressure indicating instrument indicating the pressure in said sensing line is mounted at said air flow regulating valve for reference by an operator. One or more thermistors are embedded in said settable resin-impregnated preform and connected by suitable leads to an electrically-operated steam flow control unit. Said leads pass between the outer surface of said inflatable form and the inner surface of said separation sleeve and are taped to the external surface of said separation sleeve where they pass through it. Said leads are connected to said thermistors by means of plugs that are easily separated by tension applied to said leads. Following inflation of said inflatable form by means of air flow, a flow of steam is admitted to said hose. In the preferred embodiment, said source of steam takes the form of a small, portable, self-contained boiler fuelled by oil or liquid petroleum gas, in normal operation, the full steam output of said boiler being applied to said hose. Said boiler is provided with all normal safeguards, including automatic shutdown in the case of loss of water supply, over-temperature, etc and supplies said steam flow via said steam flow regulating valve and a manually-operated shut-off valve. A larger boiler having a modulatable burner is optionally employed at less than full output, but may result in lower efficiency of fuel use. As a pressure rise in said inflatable form caused by said steam flow is sensed via said pressure sensing line, said air flow regulating valve adjusts air flow to keep the total inflation pressure applied to said inflatable form at a pre-set level. At the same time, the temperature within the mass of said preform is sensed via said thermistors, the signal being processed in a suitable microprocessor-based control unit to generate control signals to said steam flow regulating valve. When the sensed temperature within the mass of said settable resin-impregnated preform rises to a predetermined value, the steam flow through said steam flow regulating valve is reduced in steps to maintain the desired temperature. Said steam flow is reduced by venting to atmosphere or, if appropriate, by boiler burner modulation. Where said steam flow is reduced, said air flow regulating valve automatically provides a compensating increased flow. The flow characteristics of said steam flow regulating valve are mapped and a suitable algorithm is employed to process said signals from said thermistors and generate said control signals. The inflation pressure within said inflatable form at any time is principally the result of said air flow, with steam contributing in only a minor way due to condensation, the input flows being continuously balanced against the outflow through said calibrated orifice. In the event of power failure, said steam flow regulating valve closes and initiates shutdown of said boiler. In an alternative embodiment (not shown), a steam discharge line extends from the inner end of said first closure fitting substantially along the inner length of said inflatable form, steam discharge orifices being provided at a number of points along said steam discharge line. In an alternative embodiment (not shown), condensation occurring within said inflatable form is sucked away via a suitable drain line, suction being generated by small ejector powered by a flow of compressed air or steam. During removal of said inflatable form from said sewer pipe or conduit, said leads are detached from said thermistors by separation of said plugs. In an alternative embodiment (not shown), said leads are made with weakened points near said thermistors which rupture under tension.

In an alternative embodiment (not shown), said calibrated orifice in said second closure fitting is replaced with a controllable outflow valve. In this embodiment, said outflow valve is optionally a two-position valve, closed or opened by air pressure applied to a piston in a cylinder, or by a solenoid or the like. Said outflow valve is also optionally a flow modulating valve in which a tapered valving element is progressively entered into or withdrawn from a circular seat, said valve being electrically-operated, by means of a suitable electric motor driving screw means, or manually-operated, by means of motion transmitted by a Bowden cable. Said controllable outflow valve permits said inflatable form to be maintained in an inflated state with no outflow, or permits a greater or lesser outflow of air and/or steam from said inflatable form, to suit the heating requirements of a particular said soft liner repair.

Where a said hauling line is fixed to said second closure fitting in the manner described, in an alternative embodiment, said protective sleeve is made in the form of a rectangular sheet wrapped around said assembly of said inflatable form, separation sleeve, settable resin-impregnated preform and bridles and secured by said elastic retaining ring at said first closure fitting. The said embodiment permits said protective sleeve to be drawn away from said assembly without interference from said hauling line.

Following curing of said settable resin, said hose is disconnected from said compressed air and steam supplies and a depression applied to said inflatable form to collapse it. In the preferred embodiment, said depression is generated by means of a suitable ejector powered by a flow of compressed air or steam. Withdrawal of said collapsed inflatable form from said sewer pipe or conduit is then initiated by the application of tension to said hauling line fixed to said second closure fitting. As said inflatable form is displaced longitudinally in this manner, said separation sleeve is everted and continued displacement of said inflatable form causes said separation sleeve to progressively peel away from said cured repair. Similarly, said bridles are drawn back through said cured repair, continued displacement of said inflatable form causing their ends to peel away from said cured repair. Said assembly of inflatable form, hose, everted separation sleeve and detached bridles is drawn out of said sewer pipe or conduit and prepared for re-use.

The settable resins employed with the described system provide good pot life at ambient temperatures while the curing temperatures cited are able to provide reliable curing in under 60 minutes. The ease of installation provided by the system, the rapid and reliable curing and the ease of removal combine to provide minimal times on site and the need for only a single attendance at each repair site. It therefore provides maximum efficiency in the use of all principal contractor inputs.

Claims (47)

1. A pipe and conduit rehabilitation system comprising a tubular, inflatable form; a pre-form of one or more layers of resin-absorbent reinforcement material positioned over and supported upon said inflatable form; a settable resin with which said preform is impregnated; a replaceable separation sleeve of a suitable thin, flexible sheet polymer material positioned between said inflatable form and said preform covering more or less all of said inflatable form; a first closure fitting closing a first end of said inflatable form; a second closure fitting closing a second end of said inflatable form, said closure fitting being provided with a fixed or adjustable outflow orifice; a hose sealingly attached to said first closure fitting; a first hauling line attached to the outer end of said hose; a second hauling line attached the outer end of said second closure fitting; a closed-circuit television camera attached to said second hauling line; a plurality of bridles fixed to said first closure fitting and peelably bonded to the inside edges of said preform; frangible ties to retain said inflatable form in its collapsed condition and to retain said preform in position on said inflatable form; a protective sleeve of a suitable thin, durable, flexible sheet polymer material covering said assembly of inflatable form, separation sleeve and settable resin-impregnated preform; an air receiver of suitable capacity charged and maintained at a predetermined pressure by an air compressor to supply a flow of compressed air to said inflatable form via said hose, a pressure reducing valve, a flow regulating valve and a manually-operated cut-off valve; a pressure sensing line extending from a location at approximately mid length of said inflatable form to said air flow regulating valve, an instrument indicating the pressure in said sensing line mounted at said air flow regulating valve for reference by an operator; a boiler having a fixed or modulatable output supplying a flow of steam to said inflatable form via said hose; electrically-operated steam flow regulating means; an optional mixing chamber in which said flows of air and steam are combined before delivery to said hose; thermistors embedded in said settable resin-impregnated preform to detect the temperature within its mass; and a microprocessor-based control unit receiving signals from said thermistors and generating signals to activate said steam flow regulating means.

2. The rehabilitation system of Claim 1 in which said inflatable form, together with said settable resin-impregnated preform, is positioned within a zone of a sewer pipe or conduit to be repaired, said positioning being confirmed by observation via said closed-circuit television camera; inflating said inflatable form by a flow of compressed air, thereby rupturing said ties and bringing said preform into intimate contact with the surfaces of said repair zone; maintaining inflation of said inflatable form to keep said preform in intimate contact with said repair zone; heating said inflatable form and, thereby, said preform by a flow of steam until said settable resin is properly cured; evacuating said inflatable form to collapsed it into compact form; and withdrawing said inflatable form from said sewer pipe or conduit by tension applied to said second hauling line, leaving said cured soft liner in place.

3. The rehabilitation system of Claim 1 in which discrete zones of pipes and conduits are repaired using soft liners of short length.

4. The rehabilitation system of Claim 1 in which said pre-form is made in the form of a wrapped sheet or a closed, tubular form.

5. The rehabilitation system of Claim 1 in which said tubular inflatable form is made from a soft, flexible, reinforced and essentially inelastic sheet polymer material.

6. The rehabilitation system of Claim 1 in which said separation sleeve separates said inflatable form from said settable resin and acts to ensure detachment of said inflatable form from said preform following curing of said settable resin, said separation sleeve being attached at one end to said first closure fitting, its other end being unattached and extending beyond said second end of said inflatable form.

7. The rehabilitation system of Claim 1 in which said separation sleeve is made from a polymer material, such as polyethylene, to which said settable resin adheres poorly, said sleeve optionally being treated with talcum, a silicone coating or the like to minimise adhesion of it to said settable resin.

8. The rehabilitation system of Claim 1 in which said inflatable form and said separation sleeve are made with diameters equal to 150% of the internal diameter of the sewer pipe or conduit to be repaired.

9. The rehabilitation system of Claim 1 in which said inflatable form and said separation sleeve are made with diameters in the range 150% to 200% of the internal diameter of the sewer pipe or conduit to be repaired.

10. The rehabilitation system of Claim 1 in which said preform comprises a first layer of felted material providing resin carrying capacity and a second layer of woven, quilted or knitted material providing strength; said pre-form being made elastic or otherwise expandable with a relaxed diameter in the range 50% to 100% of the internal diameter of the sewer pipe or conduit to be repaired and with an uncompressed thickness falling in the range 2 to 15 millimetres; said preform optionally being made with a durable and impervious inner surface layer which acts to protect said repair following its installation.

11. The rehabilitation system of Claim 1 in which said preform is made with a relaxed diameter in the range 75% to 85% of the internal diameter of the sewer pipe or conduit to be repaired.

12. The rehabilitation system of Claim 1 in which said protective sleeve is made of a suitable thin, durable, flexible sheet polymer material in a wrapped or closed tubular form covering said assembly of inflatable form, separation sleeve and settable resin-impregnated preform, said protective sleeve acting to protect said preform during the process of positioning said assembly within a sewer pipe or conduit; said protective sleeve being made with a diameter in the range 100% to 200% of the internal diameter of the sewer pipe or conduit to be repaired and of a length such that one end extends beyond said second end of said inflatable form by a minimum of four diameters and is unattached, the other end of said protective sleeve being removably attached to said first closure fitting by means of a suitable elastic retaining ring or the like; a retrieval line attached to said free end of said protective sleeve being employed to detach the leading end of said protective sleeve from said retaining ring and to draw said protective sleeve away from said assembly of inflatable form, separation sleeve and settable resin-impregnated preform before its final positioning within a sewer pipe or conduit.

13. The rehabilitation system of Claim 12 in which said protective sleeve is made with a diameter equal to 150% of the internal diameter of the sewer pipe or conduit to be repaired.

14. The rehabilitation system of Claim 1 in which said first closure fitting is sealingly connected to a hose employed to supply flows of air and steam to inflate, heat and deflate said inflatable form, a first hauling line employed to draw said inflatable form carrying said settable resin-impregnated preform into position within a repair zone in a sewer pipe or conduit being attached to the distal end of said hose; said closure fitting being provided with a flowthrough duct, the diameter of said duct and internal diameter of said hose and its associated fittings being sufficient to carry the volume flows required for the proper installation of said soft-liner repairs; said closure fitting being made in a single piece, including an integral, plain or barbed spigot, or with said spigot made removable and screwably and sealingly attached to said closure fitting, and with a rounded internal surface in order to minimise the possibility of penetration damage to said inflatable form.

15. The rehabilitation system of Claims 1 and 14 in which said spigot is optionally made longer or shorter; where said spigot is made shorter, the end of said hose end being pressed over it, the end of said inflatable form being gathered and positioned over said hose end and the two fixed to said spigot by means of whipping with a suitable material or by suitable clamping means, a layer of a suitable heat-resistant elastomeric material being optionally provided between said clamping means and said hose end and the end of said inflatable form, the end of said separation sleeve being gathered and fixed over said whipped end of said inflatable form by removable clamping means; where said spigot is made longer, the end of said hose being sealingly clamped to the outer part of said spigot by removable clamping means, the ends of said inflatable form and said separation sleeve being clamped to the inner part of said spigot by separate removable clamping means.

16. The rehabilitation system of Claim 15 in which separate clamping means are provided to secure the ends of each of said inflatable form and said separation sleeve, thereby permitting the ready removal and replacement of said separation sleeve.

17. The rehabilitation system of Claim 1 in which said second closure fitting is made with a fixed calibrated orifice permitting a predetermined outflow volume of air or steam at a predetermined pressure, the use of said fixed calibrated orifice being appropriate in most forms of said apparatus in which, in use, the distal end of said inflatable form is inaccessible, the diameter of said calibrated orifice being dependent upon the size of the soft-liner repair to be made and falling typically in the range 4 to 10 millimetres; the end of said inflatable form being sealingly fixed to a spigot of said second closure fitting by whipping with a suitable material or by suitable clamping means; a boss formed on the outer end of said spigot being provided with one or more opposed pairs of threaded recesses accepting fastenings for fixing of the attachment fitting of said second hauling line, said hauling line being employed to tow a closed-circuit television camera behind said inflatable form and, following completion of a said soft-liner repair, to draw said inflatable form from said sewer pipe or conduit; said second closure fitting being made with a rounded internal surface in order to minimise the possibility of penetration damage to said inflatable form.

18. The rehabilitation system of Claim 17 in which the diameter of said calibrated orifice falls in the range 5.5 to 8 millimetres.

19. The rehabilitation system of Claim 17 in which said calibrated orifice is replaced with a controllable outflow valve, said outflow valve optionally being simple and manually controllable, or being a two-position valve, closed or opened by air pressure applied to a piston in a cylinder or by a solenoid or the like, or being a flow modulating valve in which a tapered valving element is progressively entered into or withdrawn from a circular seat, said valve being electrically-operated, by means of a suitable electric motor driving screw means, or being manually-operated by means of motion transmitted by a Bowden cable, said controllable outflow valve permitting said inflatable form to be maintained in an inflated state with no outflow, or permitting a greater or lesser outflow of air and/or steam from said inflatable form to suit the heating requirements of a particular said soft liner repair.

20. The rehabilitation system of Claims 15 and 17 in which said whipping material is a braided polymer material having a small degree of elasticity permitting an elastic extension of up to 5%, said whipping material being stretched during the whipping process, the elastic contraction so generated acting to ensure maintenance of a good seal between said hose end, said inflatable form end and said spigot during thermal expansion and contraction incurred during said repair process; a layer of a suitable heat-resistant elastomeric material being optionally provided between said clamping means and said hose end and the end of said inflatable form.

21. The rehabilitation system of Claims 1 and 10 in which, to retain said settable resin-impregnated preform on said inflatable form during its positioning in a repair zone within a sewer pipe or conduit, a plurality of suitable bridles attached to said first closure fitting are peelably bonded to the inside edges of said preform prior to its impregnation, the outer ends of said bridles, together with the end of said separation sleeve, being optionally fixed by said clamping means, to said spigot of said first closure fitting.

22. The rehabilitation system of Claims 1 and 17 in which said attachment fitting of said second hauling line takes the form of a U-shaped yoke comprising parallel side panels joined by an end panel; said hauling line taking the form of a braided steel cable having a terminal fitting with an enlarged head swaged to it; said hauling line passing through an aperture in said yoke end panel such that said enlarged head is captured within said yoke; said side panels being pierced towards their free ends by attachment apertures and fixed to said boss of said second closure fitting by means of attachment bolts passed through said attachment apertures and threaded and tightened into said threaded recesses in said boss.

23. The rehabilitation system of Claims 1 and 2 in which, to prevent the entrapment of standing water during inflation of said inflatable form together with said settable resin-impregnated preform, said inflatable form is maintained in a collapsed state and said preform is retained on said inflatable form by means of a plurality of frangible ties; said ties being typically made from a vegetable fibre, woollen yam or the like and provided over said preform at spacings in the range 3 to 5 times the internal diameter of the sewer pipe or conduit to be repaired and, over said inflatable form, 1.5 to 2.5 times said internal diameter; the earlier rupturing of said ties over said preform and the later rapturing of said ties over said inflatable form acting to positively displace outwardly any standing water in and adjacent to the repair zone.

24. The rehabilitation system of Claim 23 in which said tie spacing over said preform is 4 times the internal diameter of the sewer pipe or conduit to be repaired and, over said inflatable form, is 2 times said internal diameter.

25. The rehabilitation system of Claims 1 and 23 in which, prior to the tying of said frangible ties, said inflatable form is collapsed into compact form by laying it flat and folding approximately one quarter of its width on either side inwardly to meet at its centreline.

26. The rehabilitation system of Claims 1 and 23 in which, prior to the tying of said frangible ties, said inflatable form is collapsed into compact form by folding the parts to either side of its centreline to form a plurality of parallel pleats of more or less equal length and which extend more or less in to the centreline.

27. The rehabilitation system of Claim 1 in which, following installation of said protective sleeve over said assembly of inflatable form, separation sleeve and preform, said preform is impregnated with said settable resin by depositing a measured quantity of mixed resin and catalyst between said separation sleeve and said protective sleeve and then passing said assembly, including said protective sleeve, in flat form between opposed cylindrical rollers to work said resin into said preform; said assembly, including said settable resin-impregnated preform, then being drawn into the sewer pipe or conduit to be repaired by means of said first hauling line attached to said hose and positioned with said preform at the repair zone; prior to final positioning of said preform, said protective sleeve being displaced and drawn away from said assembly by means of tension applied to said retrieval line, thereby exposing the outer surface of said settable resin-impregnated preform, final positioning of said preform being verified, where necessary, through the use of said closed-circuit television camera; said hose being led out to the surface, where it is connected to said sources of compressed air and steam.

28. The rehabilitation system of Claim 1 in which, with said settable resin-impregnated preform accurately located in said repair zone, said inflatable form is inflated by a flow of pressurised air supplied through said hose, a continuous flow of air escaping via said fixed calibrated orifice of said second closure fitting, inflation of said inflatable form bringing said preform into intimate contact with the inner wall surfaces of said sewer pipe or conduit, said frangible ties progressively rupturing during said inflation process; a flow of steam being more or less the full output of a small mobile boiler or the partial output of a modulatable larger boiler then being mixed with said flow of air and introduced to said inflatable form via said hose to heat and accelerate curing of said settable resin, said combined flow of air and steam being maintained until curing of said resin is complete; operation of said boiler and pressure of said air pressure being monitored by an operator, said flow of air being manually adjusted from time to time as required to provide the desired inflation pressure in said inflatable form; said flow of steam being adjusted from time to time to maintain the desired temperature within said inflatable form, adjustment of said steam flow being effected by venting to atmosphere or, if appropriate, by boiler burner modulation, the inflation pressure within said inflatable form at any time being principally the result of said air flow, with steam contributing in only a minor way due to condensation, said input flows being continuously balanced against the outflow through said calibrated or adjustable orifice ensuring a continuous inflow of heating steam to said inflatable form, said air flow carrying said steam through said inflatable form and acting to minimise the temperature differential along its length.

29. The rehabilitation system of Claim 28 in which said boiler is provided with all normal safeguards, including automatic shutdown in the case of loss of water supply, over-temperature and the like.

30. The rehabilitation system of Claim 28 in which said flow of steam is delivered to said inflatable form effectively in a saturated state such that subsequent condensation within said inflatable form releases the latent heat of vaporisation, the temperature of said steam delivered to said hose being normally in the range 105° C to 110° C, but dependent upon the length of the hose, the objective being for said flow of steam to enter said inflatable form at a temperature just above 100° C, release of the latent heat of vaporisation allowing a relatively small volume of condensing steam to have a similar effect upon curing of said settable resin as a much greater volume of hot water, but with a significant improvement in simplicity and ease of handling.

31. The rehabilitation system of Claim 28 in which said air and steam flows are combined in a small mixing chamber before being delivered to said hose, said mixing chamber taking the form of a simple T junction with arms having diameters more or less equal to that of said hose.

32. The rehabilitation system of Claim 28 in which said air and steam flows are combined in a mixing chamber in the form of a cylindrical canister having a diameter in the range 2 to 5 times the diameter of said hose and a length in the range 2 to 5 times the diameter of said canister, said air and steam delivery lines entering said canister tangentially.

33. The rehabilitation system of Claims 1 and 28 in which automatic control means are employed to control said air and steam flows to maintain the required inflation pressure and to achieve the desired heating of said settable resin-impregnated preform.

34. The rehabilitation system of Claims 1 and 28 in which said inflatable form is inflated by the application of pressures in the range 50 to 250 kPa, said settable resin-impregnated preform being maintained at a temperature in the range 50° to 95° C.

35. The rehabilitation system of Claim 34 in which, where said repair is made in a straight section of said sewer pipe or conduit, said inflatable form is inflated by the application of a pressure of 100 kPa and heated to a temperature of 70° C to 100° C.

36. The rehabilitation system of Claim 34 in which, where said repair is made in a curved section of said sewer pipe or conduit, any of said preform, said inflatable form, said separation sleeve and said protective sleeve are made up to 50% larger in diameter and said inflatable form is inflated by the application of a pressure of 85 tol50 kPa, stretching of said preform to accommodate said curve acting to take up almost all excess material.

37. The rehabilitation system of Claim 1 in which one or more thermistors are embedded in said settable resin-impregnated preform and connected by suitable leads to a microprocessor-based control unit controlling electrically-operated steam flow regulating means, said leads passing between the outer surface of said inflatable form and the inner surface of said separation sleeve and being taped to the external surface of said separation sleeve where they pass through it, said leads being connected to said thermistors by means of plugs or weakened connections that are easily separated by tension applied to said leads.

38. The rehabilitation system of Claims 33 and 38 in which, as a pressure rise in said inflatable form caused by said steam flow is sensed via said pressure sensing line, said air flow regulating valve automatically adjusts air flow to keep the total inflation pressure applied to said inflatable form at a pre-set value, at the same time, temperature within the mass of said preform is sensed via said thermistors, the signal being processed in said microprocessor-based control unit to generate signals to control said steam flow regulating means; rising of the sensed temperature within the mass of said settable resin-impregnated preform to a predetermined value causing the flow through said steam flow regulating means to be progressively reduced to maintain the desired temperature, said air flow regulating valve automatically providing a compensating increased in air flow; the flow characteristics of said steam flow regulating means being mapped and a suitable algorithm employed to process said signals from said thermistors and to generate said control signals.

39. The rehabilitation system of Claim 38 in which, in the event of power failure, said steam flow regulating means interrupt said flow of steam and initiate shutdown of said boiler.

40. The rehabilitation system of Claim 28 in which a steam discharge line extends from the inner end of said first closure fitting substantially along the inner length of said inflatable form, steam discharge orifices being provided at a number of points along said steam discharge line, said steam discharge line acting to provide a more uniform distribution of steam along the length of said inflatable form.

41. The rehabilitation system of Claim 28 in which condensation occurring within said inflatable form is sucked away via a suitable drain line, suction being generated by small ejector powered by a flow of compressed air or steam.

42. The rehabilitation system of Claims 37 and 44 in which, during removal of said inflatable form from said sewer pipe or conduit, tension applied to said leads causes them to be detached from said thermistors by separation of said plugs or by rupturing of said weakened connections.

43. The rehabilitation system of Claims 12 and 22 and in which said protective sleeve is made in the form of a rectangular sheet wrapped around said assembly of said inflatable form, separation sleeve and settable resin-impregnated preform and secured by said elastic retaining ring at said first closure fitting such that said protective sleeve is able to be drawn away from said assembly without interference from said second hauling line.

44. The rehabilitation system of Claims 1 and 28 in which, following curing of said settable resin, said hose is disconnected from said compressed air and steam supplies and a depression applied to said inflatable form to collapse it, withdrawal of said collapsed inflatable form from said sewer pipe or conduit then being initiated by the application of tension to said second hauling line, longitudinal displacement so generated causing said separation sleeve to become everted and, with continued displacement of said inflatable form, to progressively peel away from said cured repair; the drawing back of said bridles through said cured repair causing their ends to peel away from said cured repair; said assembly of inflatable form, hose, everted separation sleeve and detached bridles finally being drawn out of said sewer pipe or conduit and prepared for re-use.

45. The rehabilitation system of Claim 44 in which said depression is generated by means of a suitable ejector powered by a flow of compressed air or steam.

46. The rehabilitation system of Claims 1 and 27 in which the settable resins employed have an extended pot life at ambient temperatures but, at the curing temperatures cited, are able to provide reliable curing in under 60 minutes.

47. The rehabilitation system of any of Claims 1 to 46 in which automated control of the curing process, rapid and reliable curing and ease and reliability of removal of the apparatus combine to require minimal time and only a single attendance at each repair site.