4567-1.doc Method and apparatus for lining of pipes Field of Invention This invention relates to internal in-situ repair of pipes and more particularly to repair up of small sections of relatively small sewage or drainage pipes. 5 However, the invention is not limited to the type or size of the pipe or the size of the repair. Background Pipes that convey fluids frequently pass through or under bodies, such as buildings and roads, which limit or prevent access to the pipe. It may be 10 impossible or not cost effective to replace a damaged pipe or damaged section of the pipe and one solution is an internal relining of the damaged section of the pipe. Repair systems exist in which a cylindrical liner for repair of the pipe is passed into the pipe and then expanded, using a bladder (also called a "packer") that 15 is expanded with air or water, to press the liner against the inner surface of the pipe. The liner typically has a two-pack or catalytically cured mixture that cures over a set period of minutes or hours to a relatively rigid form, sealing the damaged section. The curing times of such mixtures are usually dependent on their temperature, with higher temperatures reducing the curing time. 20 Curing at ambient temperature has the disadvantage that it can take many hours for all the material of the liner to cure sufficiently. It has been proposed to use hot water to reduce the curing time. Systems have been proposed in which a large reservoir of hot water is transported to the repair site and used to rapidly fill the bladder. However the transport of large amounts of hot 25 water it is not very practical. Further, it takes time to heat the water and the limit on the amount of water and/or the distance that it may be transported whilst remaining hot limits the size and location of repairs. Further, such systems rely on the water being retained in the bladder by a pressure sensitive valve. The water is released from the bladder by increasing the pressure in 30 the bladder above the threshold of the pressure sensitive valve. Once the pressure sensitive valve has been released, the water flows out of the bladder and the bladder deflates. At the elevated temperature the liner may be soft and so it is desirable to cool the liner before deflating the bladder, which such systems cannot achieve. Further, the hot water introduced into the bladder is 35 static and not replaced. Accordingly there is only a set amount of heat available to heat the bladder and liner. In an attempt to overcome at least some of the disadvantages of the prior art 4567-1.doc -2 the invention provides apparatus and methods to allow the use of hot water for reduced curing time without the need to transport preheated hot water. Embodiments of the invention allow the temperature of the bladder and the liner to be slowly increased and slowly decreased whilst the bladder is 5 inflated. Preferred forms are able to recirculate used water so reducing water and energy use. Preferred forms of the invention allow controlled inflation and deflation of the bladder and/or controlled heating and/or cooling of the bladder and liner. 10 Summary of the Invention In one broad form the invention provides apparatus for repair of pipes, the apparatus including: a bladder having an inlet and an outlet, whereby a fluid may be input and output from other bladder; 15 heating remains for heating the fluid; conduit means interconnecting the heating means and the fluid inlet, whereby repeated fluid may be introduced into the bladder, and valve mains up for controlling the ingress into and egress from the bladder of fluid, or both, whereby the volume of the bladder may be 20 controlled. In one broad form the invention provides an elongate inflatable bladder assembly for use in repair of pipes, the bladder assembly having: an inlet whereby fluid may be passed into the bladder, and an outlet whereby fluid may pass out of the bladder, 25 wherein said inlet and outlet are both located at one end of the bladder assembly. The inlet may include at least one conduit having at least one outlet adjacent the other end of the assembly. Preferably fluid introduced into the inlet passes into the bladder adjacent the 30 other end and flows toward the outlet at the first end.
4567-1.doc -3 The bladder assembly may include rigid members at each end thereof and a flexible membrane extending between the two rigid members. The fluid inlet may be a conduit that extends from the first rigid member toward the second rigid member. 5 The conduit may be attached to the second member. The conduit may be connected to the second member on or adjacent the centre line of the assembly. Preferably the conduit is flexible. Preferably the conduit has one or more openings located adjacent the other 10 end. In another broad form the invention provides a method for the internal repair of pipes, the method including: placing an inflatable bladder and a curable repair liner that has a curing period within a pipe having a damaged section adjacent damage 15 section with the repair liner surrounding the bladder and extending over the damaged section, expanding the bladder to press the liner against the inner surface of the pipe, after expanding the bladder and whilst the bladder is expanded, 20 heating the liner to above ambient temperature; maintaining the liner at above ambient temperature for a period of time, cooling the liner and then, collapsing the bladder to leave the cured liner against the inner surface 25 of the pipe. Expanding the bladder may include introducing an unheated fluid into the bladder. Preferably the unheated fluid is air or water. If the unheated fluid is air, after expanding the bladder with air and before 30 heating the liner, the air is preferably replaced with unheated water.
4567-1.doc -4 Preferably heating the liner includes introducing a heating fluid into the bladder. Preferably maintaining the liner at above ambient temperature includes passing a heating fluid through the bladder. 5 The heating fluid may be supplied at a substantially constant flow rate. The heating fluid may be supplied at a substantially constant temperature. Preferably the heating fluid is supplied to the bladder at about 65 degrees centigrade. During the step of maintaining of the liner at above ambient temperature the 10 fluid in the bladder may be maintained at a substantially constant pressure. Maintaining of the liner at above ambient temperature may include maintaining the liner at a substantially constant temperature for at least part of the period. Preferably the heating fluid is water. 15 The step of cooling the liner may include introducing a fluid into the bladder that is cooler than the bladder at that time. The step of cooling the liner may include passing a cooling fluid through the bladder, the cooling fluid being supplied at a substantially constant flow rate. The step of cooling the liner may include cooling the liner until it is below a 20 predetermined temperature, until it has a predetermined strength, or for a predetermined time. In another broad form the invention provides a system for the internal repair of pipes, the system including: an inflatable bladder adapted to be placed in a pipe to be repaired 25 with a curable repair liner, that has a curing period, surrounding the bladder, the bladder having an inlet for the introduction of fluid into the bladder and outlet for the removal of fluid from the bladder; a supply of at least one pressurised fluid, whereby the bladder may be expanded to press the liner against the inner surface of a pipe; 30 heating means for heating the liner to above ambient temperature; cooling means for cooling the liner from above ambient temperature; 4567-1.doc -5 valve means in fluid communication with the inlet and outlet and operable to selectively control the supply of fluid to and from the bladder, and control means operative to control the heating and cooling of the liner, 5 whereby the liner may be heated and then cooled in situ whilst the bladder is inflated. The heating means may include heating fluid at above ambient temperature. The system may include a heater for heating the heating fluid on demand. The heating fluid may be water. 10 The cooling means may include cooling fluid at or near ambient temperature. The cooling fluid may be water. The system may include a first conduit for connection to a source of cooling fluid at or near ambient temperature and a second conduit for connection to a source of heating fluid at above ambient temperature, said first and second 15 conduits supplying said first and second fluids to a common supply conduit. The valve means may include valves in the first and second conduits for selectively controlling the supply of respective cooling or heating fluid to the common supply conduit. The system may include a third conduit connected to a source of a third fluid 20 and a valve for controlling supply of said third fluid. The system may use gas as the third fluid and may include a supply of compressed gas for expanding the bladder. The valve means may include a valve on or downstream of the outlet. The system may include a connector for connection to a supply of pressurised 25 water. The system may include a supply of pressurised water. Brief Description of the Drawings Figure 1 is a cross section though a damaged pipe schematically showing the apparatus of the invention installed but before commencement of repair.
4567-1.doc -6 Figure 2 is a view of the inlet control unit of the apparatus shown in figure 1. Figure 3 is a view of the outlet control unit of the apparatus shown in figure 1. Figure 4 is a cross section though the damaged pipe at a first stage of the repair. 5 Figure 5 is a cross section though the damaged pipe at a second stage of the repair. Figure 6 is a cross section though the damaged pipe at a third stage of the repair. Figure 7 is a cross section though the damaged pipe at a fourth stage of the 10 repair. Figure 8 is a cross section though the damaged pipe at a fifth stage of the repair. Figure 9 is a cross section though a bladder according to another form of the invention. 15 Detailed Description of Preferred and other Embodiments Referring to figures 1 to 8 there is shown a pipe 10 that requires repair of a damaged section 12. The damaged section 12 lies between two access points 14 and 16. A repair bladder 18 and a repair liner 20 are positioned within the damaged 20 pipe 10 to extend along and over the damaged section 12. The bladder 18 has an inlet at 22 and an outlet at 24, to which are connected inlet and outlet hoses 26 and 28, respectively. The liner 20 is a conventional two-pack or catalytically cured mixture. The hoses 26, 28, may be attached to rope, wire, cable or the like, whereby 25 the bladder 18 and the liner 20 may be moved along the pipe into position. The bladder 18 is initially deflated and the liner 20 is folded and taped about the bladder 18 so the package has reduced size. This is to ease introduction through the access points 14 or 16 and to ease movement along the pipe 10. The inlet hose 26 is connected to an inlet control unit 30, shown in more 30 detail in figure 2. The outlet hose 28 is connected to an outlet control unit 32, shown in more detail in figure 3.
4567-1.doc -7 The inlet control unit 30 has a regulated air outlet 34 and a regulated water outlet 36. The inlet hose 26 may be connected to either of these outlets 34, 36, preferably via quick release fittings. Alternatively, a single outlet may be provided with a valve controlling whether air or water is supplied to the 5 outlet. A source of compressed air 38 supplies compressed air to the air outlet 34 via a supply valve 40 and a regulator 42. The source of compressed air may be a compressor or a bottle of compressed air. A pressure gauge 44 enables the operator to set a desired pressure at the outlet 34 using the regulator 42. 10 The control unit 30 has a source of water 46, typically a mains water supply. The water is usually at or near ambient ground temperature typically about centigrade, which varies throughout the year. The water supply 46 is connected to a cold water supply pipe 48 and also a hot water heater 50 that supplies hot water to a hot water supply pipe 52. The hot and cold water 15 supply pipes 48, 52 are joined together at 54 to a common delivery line 60. Each pipe, 48, 52 has a control/isolation valve, 56 and 58, respectively, upstream of the junction 54. The isolation valves 56, 58 allow the operator to selectively supply hot or cold water to the common supply line 60. A pressure regulator 62 is located downstream of the junction 54 and upstream of the 20 water outlet 36. Pressure gauges 64, 66 are located upstream and downstream, respectively, of the regulator 62. These enable the operator to set a desired pressure at the outlet 36 using the regulator 62. The regulator 62 preferably maintains a substantially constant pressure at the outlet 36 independent of the inlet pressure and the flow rate. However, this is not 25 critical and, if desired, a simple adjustable valve may be used instead. Suitable back flow prevention valves (not shown) are preferably provided to prevent back flow of water in the system. The heater 50 is preferably the type that heats water on demand and so has no storage tank. As such it is not necessary to transport any water and it is not 30 necessary to wait whilst a tank of water is heated to the desired temperature. The temperature of the hot water supplied is preferably set using the temperature control 68 and the heater automatically adjusts the heat input according to the flow rate of water through the heater to maintain a substantially constant outlet temperature as set by the temperature control 35 68. The heater 50 is preferably a gas heater, supplied by a portable gas bottle or tank, such as an LPG bottle. An electric heater maybe used, but a source of electricity is required. Other sources of heat may be used for heating the water. For example, if the heater is located permanently on a vehicle then the vehicle's engine cooling system may be used to heat the water.
4567-1.doc -8 The outlet control unit 32 (see figure 3) in this embodiment comprises a bleed valve 70 and a pressure gauge 72 connected to the end of the outlet hose, preferably via a quick release fitting. As will be explained later, the bleed valve 70 is used to allow fluid flow through the bladder 18 whilst selectively 5 maintaining an above ambient pressure in the bladder 18. After the bladder 18 and the liner 20 have been moved into position the initial step is to inflate the bladder 18, break any tapes holding the liner in a compact position and expand/unfold the liner 20 so that the liner 20 is pressed firmly against the inside of the pipe 10. The bleed valve 70 is fully 10 closed and the inlet hose 26 connected to the air outlet 34. At this stage the air isolation valve 40 and/or the regulator are fully closed. The air isolation valve 40 is opened, so allowing air 35 to flow into and expand the bladder 18. The regulator 42 is adjusted to slowly increase the pressure in the hose, as indicated by the pressure gauge 44, to usually lie in the range of about 18 to 15 20 psi with the preferred bladder and liner. Depending on the bladder and the strength of the tape this may be anywhere between 10 and 30 psi. The liner 20 is usually attached to the bladder 18 by tape that is designed to easily break at or below this pressure as the bladder 18 expands and allows the bladder 18 to expand, pressing the liner 20 against the inner surface of the pipe and any 20 defects in the pipe. This pressure range is required to firmly press the liner 20 against the surface of the pipe. Depending on the nature of the pipe, the nature of the fluid carried and/or the liner itself, other pressures or ranges of pressures may be required and this pressure range in itself is not critical to the working of the invention. It is merely necessary that the bladder be 25 expanded to a pressure sufficient to ensure a good bonding of the liner to the surface of the pipe at the completion of the repair and in particular the breaking of the tapes. Once the bladder 18 has fully expanded the pressure indicated by the pressure valve 42 will stabilise and at this point one may assume that the bladder 18 30 and liner 20 are fully expanded. After expansion by air the regulator 42 and/or the air isolation valve 40 are closed to cut off supply of pressurised air to the inlet hose 26. The bleed valve 70 is opened and the excess air released to reduce the pressure in the bladder. When the pressure has reduced to or near atmospheric, as indicated 35 by the pressure gauge 44, the inlet hose 26 may be removed from the air supply outlet 34 and connected to the water outlet 36. Whilst this pressure reduction is not essential, the relaxing of the bladder at this point allows a second chance for all tapes to break and for the liner to form out into position. The use of air allows for this relaxing effect.
4567-1.doc -9 Whilst not desirable, if quick-release fittings are used the inlet hose 26 may be removed from the air outlet 34 while still pressurized and the excess air released via the inlet hose 26. After connecting the inlet hose 26 to the water outlet 36 the bleed valve 70 is 5 left opened. The bleed valve 70 may need adjusting but this is not critical at this point. At this point both the water isolation valves 56, 58 and the water regulator 62 are all preferably closed. The hot water isolation valve 58 remains closed and the cold water isolation valve 56 is opened. The regulator 62 is slowly opened and this delivers cold 10 water 37 to the water outlet 36 and slowly fills the bladder with cold water, expelling air in the hoses and the bladder via the bleed valve 70, as shown in figure 5. With a typical installation a pressure at the water outlet 36 in the range of about 25 to 30 psi is preferred whilst filling the bladder. Higher pressures may 15 be used, so long as they do not damage the bladder. Initially just air 35 will flow out of the bleed valve 70, then a mixture of air 35 and water 37 and finally just water 37. Once water (i.e. a mixture of water and air) starts flowing out of the bleed valve 70, the water supply pressure is preferably dropped to be in the range of about 16 to 18 psi. The higher pressures used 20 when filling with water are not essential but provide for faster filling of the bladder whilst not translating into higher pressure in the bladder until the air has been expelled from the system. Finally, once the bladder 18 is full of water, as indicated by only water 37 flowing out of the bleed valve 70, the bleed valve 70 is partially closed to restrict the flow of water to about 2.4 25 t/min. This has the effect of causing the bladder to expand under the resultant back pressure. This back pressure is measured at gauge 72. The pressure indicated by the gauge 72 is then dropped to be in the range of about 9 to 12 psi. Because of pressure losses the pressure at the gauge 66 will be higher. The bleed valve 70 and the regulator 62 are adjusted so the flow rate 30 is about 2.4 litres per minute. The flow rate and the pressure used will vary depending on the size and nature of the pipe. By using the bleed valve 70 with the regulator 62, the pressure and flow rate may be easily controlled. If desired, expansion of the bladder with air may be omitted and the bladder expanded using cold water. 35 The bladder 18 is now ready to have hot water introduced. The water supply 46 supplies the hot and cold water sub-systems. Thus, when the water isolation valves 56, 58 are fully open, the water pressure upstream of the regulator 62 is substantially the same whether water is supplied via the hot or cold water supply sub-system. It will be appreciated that there is a slight 4567-1.doc - 10 pressure drop across the water heater 50 when hot water is flowing. Thus the change to hot water can be made by merely opening the hot water isolation valve 56 and then closing the cold water isolation valve 58. As the cold water isolation valve 58 is closed the hot water flow will increase proportionally 5 until all water is passing through the hot water heater 50. A slight adjustment of the regulator 62 may be required to maintain the outlet pressure substantially constant. In the preferred embodiment the temperature controller 68 is set so that the hot water heater provides water at approximately 65 degrees centigrade. 10 Since the water outlet 36 is near the hot water heater 50 hot water 39 will leave the water outlet 36 at substantially this temperature. The water flows through the inlet hose 26, pushing the cold water 37 in the inlet pipe 26, bladder 18 and outlet hose 28 ahead of itself, as shown in figure 6. The temperature of the water expelled from the outlet bleed valve 70 is 15 monitored until hot water flows out of the bleed valve. This monitoring maybe by merely checking the temperature of the water against the operator's skin or a temperature gauge may be provided as part of the outlet control unit 32 to give a more accurate reading. The amount of water contained in the bladder is not sufficient to heat the 20 liner and maintain the liner at an elevated temperature throughout the curing process. Accordingly, hot water needs to be passed through the bladder to heat the liner during the curing process. Once hot water 39 is flowing out of the bleed valve 70 this flow is continued so the bladder 18 and liner 20 continue to be heated with "fresh" hot water 25 rather than relying on the heat of a static body of water to heat the liner 20. The hot water 39 passing through the bladder 18 heats the bladder, which in turn heats the liner 20. The rate of heating depends on the temperature and flow rate of the water passing into the bladder, the nature and thickness of the material of the bladder, the nature and thickness of the material of the 30 liner 20 and the temperature of the pipe 10 and the material (such as concrete or earth) surrounding the pipe 10. The liner 20 has a curing time or period, which depends on its temperature. In the preferred method the start of the curing time commences when the water flowing out of the bleed valve has a substantially constant, hot, temperature. 35 A flow rate of about 2.4 litres/min provides sufficient heating for most pipes of about 10 cm diameter. Lower flow rates may be used, but heating of the liner takes longer. In the preferred embodiment the heater is an instantaneous heater that requires a minimum flow rate when heating, which in this instance is 2.4 litres/min. This specific flow rate is not critical. Higher 40 flow rates may be used as needed (for larger pipes) or as appropriate but 4567-1.doc - 11 there is a point at which higher flow rates do not significantly decrease heating time and merely use more hot water. The curing period depends on the material of the liner and whether it provides a fast, medium or slow cure time. Curing times typically range from 5 about 20 minutes to over 60 minutes when using hot water at about 65 degrees centigrade, depending on the material of the liner and the pipe. Pipes made of plastics such as PVC have a much lower heat capacity than those made of concrete, terracotta or the like and so the liner will heat up more rapidly in a PVC pipe than in a concrete pipe. 10 During the curing period the flow and supply temperature of the hot water is preferably maintained substantially constant. If needed, the bleed valve 70 and/or the regulator 62 may be adjusted to maintain substantially constant flow rates and temperature. Temperature gauges in the bladder or liner may be used to provide a reading 15 of the temperature of the liner and/or bladder and adjustments made in response to those readings. The end of the curing period may be when a predetermined temperature is reached. At the end of the curing period it is preferable that the liner be allowed to coot to allow the resin of the liner 20 to harden and become stiffer and 20 stronger before the bladder 18 is deflated. Although the resin of the liner will have cured, at the elevated temperature used, the resin may be soft and lack the desired strength and/or stiffness. Deflating the bladder 18 whilst the liner 20 is still hot and soft may result in the liner 20 putting away from the surface of the pipe 10 under its own weight or through adhesion to the bladder 18, 25 with a resulting failure of the repair. Accordingly, the liner 20 is preferably cooled by passing cold water 37 into and through the bladder 18. This is achieved by opening the cold water isolation valve 58 and then closing the hot water isolation valve 56. Cold water 37 then flows into and through the hoses 26, 28 and the bladder 18, expelling the hot water 39. Again the temperature 30 of the water exiting the bleed valve 70 is monitored and, once the temperature has stabilised at a cold temperature, the cooling period commences. With the PVC or other plastics pipes a cooling time of at least 30 minutes is typically required to coot the liner to a low enough temperature for the liner to be stiff enough for the bladder to be deflated. The temperature to 35 which the liner needs to be cooled depends on the resins used and the size of the pipe. The time depends on factors such as the ground and cold water temperature. With clay, terracotta, concrete or other similar types of pipes 40 minutes or more is required, due to the need to remove more heat energy from the pipe. It is not essential that the liner be cooled to ambient 40 temperature, just below a set value for the particular repair.
4567-1.doc - 12 As an alternative the hot water in the bladder may be replaced by cold water and the cold water "locked off" at the desired pressure using the valve 70 and regulator 62. The cold water then slowly cools the bladder 18 and liner 20 without a continuous flow, thus reducing water usage. 5 Once the cooling period has expired the bladder 18 may be emptied and deflated. The 62 regulator and/or the cold water isolation valve 58 are closed and the inlet hose is connected to the air outlet 34. The bleed valve 70 is fully opened and the regulator slowly opened to feed air 35 into the bladder 18. Typically this will be a pressure of approximately 5-7 psi, but this is not 10 critical. The air is fed into the bladder until substantially all of the water 37 has been expelled via the bleed valve 70. At this point there will be just air expelled from the bleed valve 70. Passing of air is usually required because the bleed valve 70 is usually at approximately the same level as the opening of the inlet hose 26 and more 15 importantly is above the level of the bladder, so no drainage will naturally occur. If one end is lower than the other some drainage may naturally occur, but passing of air through the system is quicker and ensures most or substantially all of the water in the bladder is expelled. The air regulator 42 and/or the isolation valve 40 are then closed and the inlet 20 hose 26 is disconnected from the air outlet 34. The bladder 18, now being only filled with air, will tend to collapse under its own weight, leaving the now rigid liner firmly against the pie and sealing the damaged section 12. The bladder 18 may now be withdrawn by merely pulling it out through one of the access points 14, 16. If necessary the bladder 18 maybe actively collapsed by 25 closing the bleed valve 70 and applying a vacuum to the inlet hose 26. In the embodiments described above the water supply is mains water and the water is passed through the bladder 18 once and then discharged via the bleed valve 70, with no recycling. If desired, the outlet hose 28 may be connected to the control unit 30 so water may be selectively re-used, particularly the hot 30 water. In this case a pump may be needed or provided to raise the pressure of the recycled water. Recycling of cold water during the cooling stage is not desirable as the aim is to cool the liner 20, unless a heat exchanger is provided to cool the water before re introduction into the bladder 18. The temperature of the water in the bladder may be controlled more 35 accurately by providing one will more temperature sensors, preferably in or on the bladder and more preferably near the outlet of the bladder. These may be located on the external surface of the bladder, within the wall of the bladder or on the internal surface of the bladder. A location between the bladder and the liner is preferable. It will be appreciated that when passing hot water 4567-1.doc - 13 through the bladder the coldest part of the liner will be that the nearest to the outlet, since the hot water will have been cooled as it passes through the bladder. Similarly, when cooling the liner that part of the liner will be cooled last. 5 The temperature of the liner 20, the water flow rate and/or the water temperature at the control unit water outlet 34 may be controlled to adjust for heat losses due to the length of the inlet hose, the ground temperature and/or the type of pipe being repaired. This adjustment may be manual in response to a temperature display or an 10 automatic feedback system may be provided that uses the sensed temperatures to adjust one or both of the water flow rate and the water temperature at outlet 34. Whilst a mains water supply is the preferred source of water, this is not essential. A static body of water may be used, with a pump to provide 15 appropriate pressure and water flow. This is a source of water is not available the invention may include transport of a static body of cold water to the repair site and for on site heating. The embodiment shown in figures of 1 to 8 uses a conventional elongate bladder in which there is an inlet 22 at one end and an outlet 24 at the other 20 end. A problem with this arrangement is the need to have hoses extending from both ends of the bladder. The downstream outlet hose 24, because it extends from the front of the bladder 18 as it is pulled into position or to withdraw the bladder, can cause jamming in the pipe or tangling with the hauling cable. 25 Figure 9 shows a bladder 100 according to the invention. The bladder 100 has a downstream end 110 and an upstream end 112. The downstream end at 110 has a plug 114 to which a hauling cable 116 is attached. There is no outlet from the bladder at the downstream and the end 110. A flexible and expandable membrane 108 extends between the ends 110 and 112. 30 The upstream end 112 has a plug at 118 having inlet and outlet connectors 120, 122 respectively, for connection to inlet and outlet hoses 124 and 126, respectively. Plug 118 has a first inlet passageway 128 that connects to an internal hose 130. The hose 130 extends toward the downstream plug 114 and is preferably secured to the downstream plug 114. The internal hose 130 has 35 one or more outlets 132, preferably at or adjacent downstream plug 114. These outlets 132 are preferably located on or near the centre line of the bladder, but this is not essential.
4567-1.doc - 14 The internal hose 130 is preferably flexible so as to enable the bladder to be more easily drawn around tight bends. The internal hose preferably does not transfer load from the downstream plug 114 to the upstream plug 118, but may do so if desired. 5 The bladder 100 may be used with the method and apparatus as described with figures 1 to 8. The inlet and outlet hoses 126, 128 are connected to the inlet 120 and outlet 122 of the bladder 100 and the bladder and a liner moved into position using the cable 116. Because both hoses 124, 126 are pulled behind the bladder there is no problem with tangling with the hauling cable 10 116. When fluid flows through the bladder, it enters the inlet 120 and flows along the internal hose 130. The fluid then exits the internal outlets 132 adjacent the downstream plug 114 and flows backwards to the outlet 122 and then into the outlet hose 128 for discharge. Accordingly, substantially the entire 15 bladder and liner is subjected to a fluid flow and will be heated or cooled substantially as before, albeit with a reverse flow of fluid. When the time comes to withdraw the bladder the cable 116 is merely drawn out of the pipe, drawing the bladder 118 and the hoses 126, 128 behind. Because there is no hose connection at the forward end 110 of the bladder 20 100, withdrawal is easier and less likely to result in jamming, tangling or like. Whilst the fluid flow has been described as from inlet 120, through the bladder and out via outlet 122, it is not essential that the flow be in this direction. Fluid flow may be reversed, from outlet 122, through the bladder and out via outlet 120. The flow direction depends on whether the forward 25 end 110 is above or below the upstream end 112, as it is important that all air be substantially vented during filling. Whilst the bladder of figure 9 is preferably used with the method of the invention previously described it is not limited to use with this method and other methods of use may be used. 30 It will be apparent to those skilled in the art that many obvious modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.