Improvements in pipeline repair

Abstract

A tubular liner for a pipelines comprising a heating layer including electrically conductive non-woven fibres with a length less than or equal to 50 mm. the length may be less than 40 mm, preferably l

Description

Technical Field of the Invention The present invention relates to pipeline repair. In particular, the invention concerns a liner for a pipeline and a method of lining a pipeline using the liner. Background to the Invention In the field of pipeline repair, it is known to repair a pipeline using a liner which is run along the pipeline to cover over any cracks or unwanted holes formed in the pipeline. The so called “inversion technique” may be used to do this. The “inversion technique” involves inverting (or everting) the liner within the pipeline and securing the inverted (or everted) liner to the inner surface of the pipeline. The inverted (or everted) liner may be secured to the inner surface of the pipeline using a heat-curable resin with which the liner is impregnated. The liner may be provided with elongate conductors which extend longitudinally along the length of the liner. When a current is passed along those conductors, the conductors generate heat, which cures the heat-curable resin, thereby securing the liner to the inner surface of the pipeline. A disadvantage of the prior arrangements with the longitudinally extending conductors is that they do not provide even heating of the resin. This can lead to portions of the liner not being properly secured to the inner surface of the pipeline, meaning those portions migrate out of their intended position. Tears in the liner can also be formed as a result of these poorly attached portions of liner. In addition, the longitudinal conductors are also susceptible to chemical degradation. Further, the liners incorporating the longitudinal conductors are also susceptible to accumulating static electricity, potentially leading to damage of electrical components connected to the liner whilst the liner is applied to the pipeline. It is an object of the present invention to mitigate or obviate at least one problem with prior arrangements for lining a pipeline. Summary of the Invention According to a broad aspect of the present invention, there is provided a liner. The liner may be for a pipeline. The liner may comprise a resistive heating layer. The resistive heating layer may comprise non-woven fibres. The non-woven fibres may be electrically conductive. The non-woven fibres may have a fibre length that is less than or equal to 50mm. The liner may be tubular. The liner may further comprise a resin carrier layer. In one embodiment there is provided a tubular liner for a pipeline, comprising; a resistive heating layer including non-woven fibres that are electrically conductive, wherein the non-woven fibres have a fibre length that is less than or equal to 50mm. In another embodiment there is provided a liner for a pipeline, comprising; a resin carrier layer; and a resistive heating layer including non-woven fibres that are electrically conductive, wherein the non-woven fibres have a fibre length that is less than or equal to 50mm. According to a first aspect of the present invention, there is provided a tubular liner for a pipeline, comprising: a resistive heating layer including non-woven fibres that are electrically conductive, wherein the non-woven fibres have a fibre length that is less than or equal to 50mm. The resistive heating layer (with non-woven fibres that are electrically conductive) of the present invention ensures even heating of heat-curable resin (which in use is provided on the liner), meaning that there are no portions of liner that are poorly secured to the inner surface of the pipeline, meaning the liner does not migrate out of its intended position and tears in the liner do not develop. Further, the resistive heating layer exhibits exemplary chemical resistance, meaning that the liner is not vulnerable to degradation when it is stored before it is applied to a pipeline. In addition, the resistive heating layer also exhibits excellent static dissipation, meaning electrical components connected to the liner during a pipelining process are less vulnerable to damage The invention has environmental benefits in that it means pipelining operations are more effective and therefore less pipelining operations are required, saving carbon emissions associated with manufacturing liner materials and travel to site. The fibre length may be less than 40, 30, or 20 mm. Preferably, the fibre length is 15mm or less. The average fibre length may be in the range of 1 to 40 mm, 2 to 20mm, 2 to 15mm, 2 to 10mm, 2 to 9mm, 2 to 8mm, 3 to 8mm, 4 to 8mm, or 5 to 8mm. The size of the fibres may provide good conductivity / heating but also ensure the liner / resistive heating layer have good conformability. The non-woven fibres may be arranged irregularly. The non-woven fibres may be individual fibres. The non-woven fibres may be individually formed. A proportion of the non-woven fibres may be at least partially wound around other non-woven fibres of the resistive heating layer. At least a few of the non-woven fibres may comprise at least one twist. At least some of the non-woven fibres may be entangled with one another. Alternatively, all the non-woven fibres may be unentangled with one another. Each non-woven fibre may have a greatest transverse width dimension (W) that is less than 20 micrometres (pm). Preferably, W is 3 to 10 pm, and most preferably 5 to 9 pm. W may be a fibre diameter of each fibre. The non-woven fibres may make up at least 10% of an entire mass of the resistive heating layer. The non-woven fibres may make up at least 20% of the entire mass of the resistive heating layer. The non-woven fibres may make up at least 30% of the entire mass of the resistive heating layer. The non-woven fibres may make up at least 40% of the entire mass of the resistive heating layer. The non-woven fibres may make up at least 50% of the entire mass of the resistive heating layer. The resistive heating layer may comprise at least 100 non-woven fibres. The resistive heating layer may comprise at least 1000 non-woven fibres. The resistive heating layer may comprise at least 10000 non-woven fibres. The resistive heating layer may comprise at least 100000 non-woven fibres. The resistive heating layer may have a basis weight of 4 to 400 grams per square metre. The resistive heating layer may have a basis weight of 4 to 200 grams per square metre. The non-woven fibres may be formed from chopped material. The non-woven fibres may comprise carbon. The carbon may be graphite or graphene. Alternatively or additionally, the non-woven fibres may comprise metal. The non-woven fibres may therefore comprise a mix of the carbon and the metal. The metal may comprise copper, steel or nickel. The metal may comprise one or more precious metals. The metal may be an alloy. The alloy may comprise the copper, steel, nickel, or one or more precious metals. Each non-woven fibre may comprise a coating. The coating may be electrically conductive. The coating may be metallic. The metallic coating may comprise nickel, copper, steel or one or more precious metals. Each non-woven fibre may comprise a core. The coating may be provided on the core. The core may be non-conductive (non-electrically conductive). The core may be electrically conductive. The core may comprise carbon. The carbon may be graphite or graphene. The resistive heating layer may comprise additional non-woven fibres that are electrically conductive and have a fibre length in excess of 50mm. Most of the non-woven fibres (that are electrically conductive) present in the resistive heating layer may have a fibre length less than or equal to 50 mm. The resistive heating layer may have a tubular form. The resistive heating layer may further comprise a binder. The binder may comprise binder fibres. The binder fibres may be non-conductive (in other words not able to conduct electricity). The binder fibres may be non-woven (or not woven). The binder fibres may comprise plastic. The plastic may be polyester or Polyvinyl acetate (PVA). The resistive heating layer may comprise a blend of binder fibres and the nonwoven fibres. The fibre length of the non-woven fibres may be a first fibre length. The binder fibres may have a second fibre length. The second fibre length may be the same as or greater than the first fibre length. The non-woven fibres may make up at least 10% of the blend. The binder fibres may make up 50% or more of the blend. In one preferred embodiment, the binder fibres make up 70% of the blend and the non-woven fibres make up 30% of the blend. The blend provides a robust resistive heating layer whilst providing good resistive heating / conduction. The resistive heating layer may be substantially sheet like. The resistive heating layer may be formed from compacted material. The resistive heating layer may be formed entirely from the compacted material. The resistive heating layer may be a mat. The resistive heating layer may be nonwoven (or not woven). The resistive heating layer may be wet laid or encased in a waterproof membrane. The liner may have at least one elongate conducting element extending along a liner length (the length of the liner) of the liner. The at least one elongate conducting element may be in electrical contact with the resistive heating layer. The at least one elongate conducting element may be in direct physical contact with the resistive heating layer. The at least one elongate conductive element may be electrically conductive. The liner may extend between first and second ends thereof. The at least one elongate conductive element may extend from the first end to the second end. The liner may have a longitudinal axis. The elongate conductive element may extend between the first and second ends of the liner in a direction that is parallel to the longitudinal axis of the liner. The at least one elongate conductive element may be at least one strip of conductive material. Alternatively, the at least one elongate conductive element may be at least one conductive wire. The at least one elongate conductive element may be at least partially embedded in the resistive heating layer. Preferably, the at least one elongate conductive element comprises first and second elongate conductive elements. When the liner comprises the at least one elongate conductive element, the entire mass of the resistive heating layer may exclude an elongate conductive element mass (the mass of the at least one elongate conductive element) of the at least one elongate conductive element. The liner may comprise heat curable resin. The heat curable resin may be located within the liner. The heat curable resin may be located between layers of the liner. The liner may comprise a resin carrier layer. The resin carrier layer may be impregnated with a heat-curable resin. Alternatively, the resin carrier layer may be capable of absorbing the heat-curable resin. In particular, the resin carrier layer may be produced without the heat-curable resin and may be impregnated with the heat-curable resin just before a pipelining operation. Alternatively, the resin carrier layer may be non-absorbent to the heat curable resin and the heat-curable resin may be applied to a surface of the resin carrier layer. Any suitable heat-curable resin may be employed such as epoxy, silicate, polyester and vinylester. The resin carrier layer may comprise an absorbent material which is impregnated with the resin. The absorbent material may comprise glass fibres or any other suitable material. The absorbent material may be a glass fibre and non-crimp fabric. The liner may comprise a first protective layer. The resistive heating layer may be located between the resin carrier layer and the first protective layer. The resistive heating layer may be radially nestled between the first protective layer and the resin carrier layer. The first protective layer may be waterproof. The first protective layer may be transparent. Optionally, the first protective layer comprises one or more of polyvinyl chloride, polythene, polyurethane and silicone. The first protective layer may comprise foil. The resin carrier layer may be an innermost layer of the liner. The resin carrier layer may be the innermost layer of the liner as supplied. The resin carrier layer may be the outermost layer as installed. The first protective layer may be an outermost layer of the liner. The first protective layer may be the outermost layer of the liner as supplied. The first protective layer may be the innermost layer as installed. This means that, in some embodiments, in practice when the liner is inverted (or everted) into a pipeline, the resin carrier layer is in contact with the inner surface of the pipeline. The liner may comprise a second protective layer. The resin carrier layer (when comprising heat curable resin) may be located between the resistive heating layer and the second protective layer. This means that, in some embodiments, there is heat curable resin within the liner and in practice when the heat curable resin is cured the liner stiffens such that it is retained within the pipeline, but no heat curable resin is actually in contact with the inner surface of the pipeline. Optionally, the second protective layer comprises one or more of polyvinyl chloride, polythene, polyurethane and silicone. The second protective layer may comprise foil. The tubular liner may be formed from a rolled sheet. The rolled sheet may have opposing edges which are connected to each other. The rolled sheet may comprise the resistive heating layer. The rolled sheet may further comprise the resin carrier layer. The rolled sheet may further comprise the first protective layer. The rolled sheet may further comprise the second protective layer. Preferably, the opposing edges may be connected by at least one non-conductive thread. Alternatively, staples, adhesive or tape may be used to connect the opposing edges. The first and second elongate conductive elements may be provided adjacent the connected opposing edges. Here “provided adjacent the connected opposing edges” means the first and second elongate conductive elements run alongside the connected opposing edges. In practice, the first and second elongate conductive elements are supplied with current and have different polarities. The construction of the liner of the present invention ensures that current flows longitudinally along the elongate conductive elements but also circumferentially via the resistive heating layer from the first electrically conductive element to the second elongate conductive element when the first elongate conductive element has a negative polarity and the second elongate conductive element has a positive polarity. This means the resistive heating layer is well supplied with current and leads to efficient heating / curing of the heat-curable resin. The resistive heating layer may have a tubular form. The resin carrier layer may have a tubular form. The first protective layer may have a tubular form. The second protective layer may have a tubular form. The liner may be flexible. The liner may be invertable (or evertable). The liner may be stiffenable. The resistive heating layer may extend circumferentially around the longitudinal axis of the liner. The resistive heating layer may extend longitudinally from the first end of the liner to the second end of the liner. The liner may further comprise at least one near field communication device. The near field communication device may be operable to communicate with an external device via any suitable communication protocol, including but not limited to FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and finger protocol. The near field communication device may comprise a data store. This means data pertaining to the liner can be stored. The information stored could, for example, be: the date of installation, individual installer details, company installer details, materials supplier details, job number, customer details, resin type, resin batch number, liner batch number, the liner type and length, installation company contact details or the temperature used to cure the liner. This ensures that a subsequent relining job is carried out as quickly, efficiently and effectively as possible, and that there are measurable statistics and contacts in the event of any future repair works or issues with the installation. The near field communication device may be attached to the liner during installation or during its manufacture. The liner may further comprise at least one temperature sensor. The at least one temperature sensor may comprise a plurality of temperature sensors spaced apart along the length of the liner. The at least one temperature sensor may be embedded in the liner. The at least one temperature sensor enables accurate recording of the temperature of the liner at points along its length. If the reading indicates that one part of the liner is too hot, the supply of current to the lattice can be adjusted. This results in even heating of the liner / heat-curable resin. The at least one temperature sensor may have a temperature communication unit and a temperature data store. The temperature communication unit may be operable to communicate with an external device via any suitable communication protocol, including but not limited to FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and finger protocol. According to a second aspect of the present invention, there is provided a method of lining a pipeline, comprising the steps of: providing the liner of the first aspect with heat curable resin; positioning the liner within the pipeline; and then passing an electrical current through the resistive heating layer to cure the heat-curable resin. The resistive heating layer (with non-woven fibres that are electrically conductive) of the present invention ensures even heating of heat-curable resin (which in use is provided on the liner), meaning that there are no portions of liner that are poorly secured to the inner surface of the pipeline, meaning the liner does not migrate out of its intended position and tears in the liner do not develop. Further, the resistive heating layer exhibits exemplary chemical resistance, meaning that the liner is not vulnerable to degradation when it is stored before it is applied to a pipeline. In addition, the resistive heating layer also exhibits excellent static dissipation, meaning electrical components connected to the liner during a pipelining process are less vulnerable to damage. The invention has environmental benefits in that it means pipelining operations are more effective and therefore less pipelining operations are required, saving carbon emissions associated with manufacturing liner materials and travel to site. The providing step may comprise applying the heat-curable resin to a surface of the liner or impregnating the liner with the heat-curable resin. In practice, this step could be performed on site. Alternatively, the heat curable resin may be added to the liner during manufacture of the liner. It can be beneficial to supply a liner with resin already applied as this can save time on site. Positioning the liner in the pipeline may comprise inverting (or everting) the liner into the pipeline. Inverting the liner into the pipeline may involve inverting the liner into the pipeline such that the heat curable resin is in contact with the inner surface of the pipeline. The cured heat curable resin may secure the liner to the inner surface of the pipeline. Alternatively, positioning the liner within the pipeline may comprise pulling the liner into the pipeline. When the liner is pulled into the pipeline the heat curable resin may be provided internally within the liner, and the cured heat curable resin may stiffen the liner such that the liner is retained within the pipeline. The method of the second aspect of the present invention may incorporate any or all features of the liner of the first aspect of the present invention as desired or as appropriate. According to a third aspect of the present invention, there is provided a system for lining a pipeline, comprising: a liner for the pipeline in accordance with the first aspect; and a controller operable to control a supply of current to the resistive heating layer. The system of the third aspect of the present invention may incorporate any or all features of the liner of the first aspect of the present invention or the method of the second aspect of the present invention as desired or as appropriate. The system may further comprise a near field communication device reader in communication with the controller. The controller may be connected to or connectable to a display and / or data store and the controller is arranged to communicate a first signal from the near field communication device reader to the display and / or data store. This allows the user to be provided with information relating to the liner. This ensures the lining operation is efficient as possible because, for example, it allows the operator to select the correct liner for the operation and to ensure that the correct heating of the liner is performed. The system may further comprise a machine operable to load data onto a near field communication device. This means data pertaining to the liner can be stored. This ensures that a subsequent relining operation is carried out as quickly, efficiently and effectively as possible. The controller may be arranged to not supply current to the resistive heating layer until the nearfield communication device has been loaded with the data. This ensures that the loading of information onto the near field communication device is always carried out, meaning it is always possible in a subsequent lining operation to obtain data from the previous lining operation. The liner may further comprise at least one temperature sensor. The controller may be in communication with the at least one temperature sensor. The controller may be arranged to adjust the supply of current to the resistive heating layer in response to a second signal from the at least one temperature sensor. This results in even heating of the liner / heat-curable resin. The system may further comprise an alarm in communication with the controller. The controller may be arranged to activate the alarm if the controller receives a third signal from the at least one temperature sensor that a sensed temperature has exceeded a pre-determined threshold. This ensures that the liner / heat-curable resin is not overheated. Detailed Description of the Invention In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 shows a liner for a pipeline; Figure 2 shows a resin carrier layer of the liner; Figure 3 shows a resistive heating layer of the liner with elongate conductive elements applied thereto; Figure 4 shows a first protective layer of the liner; Figure 5 shows a longitudinal cross-section of a sheet for forming the liner of Figure 1; Figure 6 shows a transverse cross-section of the sheet of Figure 5; and Figure 7 is a schematic diagram showing a system for lining a pipeline. With reference to Figure 1 there is shown a liner 10 in accordance with the present invention. In particular, a cross-sectional view of the liner 10 is shown in Figure 1. As shown, the liner 10 is a tubular liner and in the depicted example is made up of a resin carrier layer 12, a first protective layer 14 and a resistive heating layer 16. Each of these layers will be described in greater detail below. As shown, each of the layers 12, 14, 16 has a tubular form. The resin carrier layer 12 may be the radially innermost layer, and the resistive heating layer 16 may be provided between the resin carrier layer 12 and the first protective layer 14. The first protective layer 14 is therefore the radially outermost layer. The liner 10 may be intended for inversion (or eversion) into a pipeline, so that following inversion the resin carrier layer 12 is the outermost layer and abutting the inner surface of the pipeline. Alternatively, the liner 10 may be formed with an internal resin carrier layer and formed to be pulled into the pipeline. In such embodiments, curing of the heat curable resin may stiffen the liner to retain the liner within the pipeline. As shown the liner 10 may comprise first and second longitudinally extending elongate conducting elements 20, 22, which are applied to the resistive heating layer 16. As shown, the liner 10 is preferably formed from a rolled sheet (formed from the layers 12, 14,16) with connected opposing edges 30. The opposing edges 30 are preferably connected by a thread 35 which comprises a non-conductive material. However, other means could be employed, such as adhesive or tape. With reference to Figures 2 to 4, the various layers 12, 14, 16 of the liner 10 will now be explained in detail. Each of the layers 12, 14, 16 are shown in a planar form preassembly. Once the liner 10 is assembled they are each provided in a tubular form as shown in Figure 1. The resin carrier layer 12 is shown in greater detail in Figure 2. The resin carrier layer is formed to carry a heat-curable resin (i.e. a resin that cures when heated). This is known in the art as “hot cure resin”. The resin carrier layer 12 may be provided with or without the heat-curable resin. In particular, the resin carrier layer 12 may be impregnated with the heat-curable resin as part of the manufacturing process of the liner. Alternatively, the resin carrier layer 12 may be impregnated at the point of use. In particular, the resin carrier layer may comprise an absorbent material which is impregnated with the heat-curable resin. The absorbent material may comprise glass fibre, polyester or any other suitable carrier material, and the heat curable resin may comprise epoxy, silicate, polyester or vinylester. With reference to Figure 3, the resistive heating layer 16 is shown in detail. The resistive heating layer 16 is essentially a non-woven mat (or veil) comprising non-woven fibres, which are electrically conductive. The resistive heating layer 16 is formed to provide heat when supplied with current. This heat in use is used to cure the heat curable resin carried by the resin carrier layer 12. The specific heating layer 16 of the present invention is particularly beneficial because it provides even heating of the resin as well as among other advantages exemplary chemical resistance and static dissipation. The non-woven fibres are individual fibres and relatively small. In more technically definitive terms, they have a fibre length that is less than or equal to 50mm, and a greatest transverse width dimension (W) of the non-woven fibres is less than 20 micrometres (pm). In one preferred embodiment, the fibre length is 15mm or less, and W is in the range of 5 to 9 pm. The non-woven fibres may be formed from chopped material and the non-woven fibres may make up at least 10% (preferably 30%) of an entire mass of the resistive heating layer. There are a relatively large number of non-woven fibres in the resistive heating layer (at least 100). The resistive heating layer 16 is formed of compacted material meaning that at least some of the non-woven fibres may comprise at least one twist and at least a few of the fibres may be entangled with each other. However, it is foreseen that the mat or veil could be provided with unentangled non-woven fibres. The compaction of the compacted material means that the non-woven fibres are arranged irregularly. In one preferred embodiment, the resistive heating layer is formed of a blend of the non-woven fibres (which are electrically conductive) and binder fibres. These binder fibres are non-conductive and preferably comprise plastic (such as polyester or Polyvinyl acetate (PVA)). The blend is such that non-woven fibres may make up at least 10% of the blend. The binder fibres may make up 50% or more of the blend. In one preferred embodiment, the binder fibres make up 70% of the blend and the non-woven fibres make up 30% of the blend. The specific blend of non-woven and binder fibres is advantageous because it provides a robust resistive heating layer 16 whilst providing good resistive heating / conduction. It also means the liner exhibits good conformity. In some embodiments, the fibre length of the non-woven fibres is a first fibre length and the binder fibres have a second fibre length. In such embodiments, the second fibre length is at least the same or greater than the first fibre length. This can also provide a robust resistive heating layer 16 whilst providing good resistive heating / conduction. In some embodiments, the resistive heating layer 16 may comprise a core and a coating. The coating is preferably metallic (and may comprise nickel) and the core may be carbon. As shown in Figure 3, the elongate conducting elements 20, 22 are arranged such that they are in physical and electrical contact with the resistive heating layer 16 along the length of the resistive heating layer 16. The elongate conducting elements 20, 22 are arranged to be connected to a source of electrical current and to pass that current to the resistive heating layer 16. Optionally, the elongate conducting elements 20, 22 are at least partially embedded in the resistive heating layer 16. With reference to Figure 4, the first protective layer 14 is shown in detail. The first protective layer 14 serves to provide an outer skin for the liner. Preferably, the first protective layer 14 is waterproof and most preferably the first protective layer comprises one or more of polyvinyl chloride, polythene, polyurethane and silicone. In one preferred embodiment, the first protective layer is transparent. To form the liner 10, first of all, a sheet is formed as shown in Figures 5 and 6. In the sheet, the resin carrier layer 12, resistive heating layer 16 and first protective layer 14 are stacked with the resistive heating layer 16 between the resin carrier layer 12 and the first protective layer 14. The sheet is then rolled and the opposing edges 30 of the sheet are connected (as shown in Figure 1), optionally by stitching the opposing edges together with the non-conductive thread, as illustrated in figure 1. Other connection methods such as staples or tape may alternatively be employed. Once connected, the tubular form of the liner 10 is achieved. As best shown in Figure 1, the elongate conducting elements 20, 22 are provided adjacent (i.e. run alongside) the connected edges 30. In use, the first elongate conducting element 20 has a negative polarity and the second elongate conducting element 22 has a positive polarity. The particular construction with the elongate conducting elements 20, 22 adjacent to opposing edges 30 is robust but also ensures that current flows longitudinally along the elongate conductive elements but also circumferentially, leading to even heating of the heat curable resin in use. In some embodiments, the liner 10 may be provided with at least one temperature sensor and at least one near field communication device (both of these features are not depicted in Figures 1 to 6 but the at least one temperature sensor and the at least one near field communication device are depicted in Figure 7 below). Figure 7 shows a system 100 for lining a pipeline. As shown, the system 100 comprises the liner 10 described above, and a controller 102 arranged to control a supply of current to the resistive heating layer 16 of the liner 10. In particular, the controller 102 may be in communication with a power supply 103 which supplies current to the resistive heating layer 16, as shown. The system may further comprise a display 104 arranged to display data provided to it via the controller. A user input control may be associated with the display 104. The system may further comprise a near field communication device reader 110, and the controller 102 may be in communication with the near field communication device reader 110. The controller 102 may be arranged to communicate a first signal from the near field communication device reader 110 to the display 104, or to a data store that may be connected to the controller 102. As depicted the controller 102 is also in communication with a machine 108 operable to load data onto a near field communication device 28. This allows the liner to be electronically tagged before it is used to line a pipeline, meaning subsequent lining operations can be carried out more effectively. Preferably, the controller 102 is arranged to not supply current to the resistive heating layer 16 until the near field communication device has been loaded with the data. The controller 102 is preferably in communication with the at least one temperature sensor 24 of the liner 10 and is arranged to control the supply of current to the resistive heating layer 16 of the liner 10 in response to a second signal from the at least one temperature sensor 24. In this way, the temperature of the resistive heating layer 16 can be controlled and overheating of the liner can be prevented. Preferably and as depicted there are a plurality of temperature sensors 24 spaced apart along the length of the liner 10. The controller 102 may be in communication with an alarm which the controller 102 is arranged to activate if the controller receives a third signal from the at least one temperature sensor 24 that a sensed temperature has exceeded a pre-determined alarm threshold. In this way, overheating can be prevented. Preferably, the alarm may be a visual alarm provided on the display 104. However, an audio alarm may also be provided. With reference to Figure 7, in use, when the liner is to be used to line a pipeline, if the resin carrier layer of the liner 10 does not already carry a heat-curable resin as it has been supplied “dry”, the heat-curable resin is added to the resin carrier layer as a first step. The liner 10 is then positioned within the pipeline. When the liner has an external resin carrier layer, the liner 10 is positioned in the pipeline by inverting the liner into the pipeline. In particular, the liner 10 is secured to an inversion drum or other suitable means, and then inverted into the pipeline such that the resin carrier layer abuts the inner surface of the pipeline. The controller 102 can then cause the power supply 103 to then supply current to the resistive heating layer 16. This has the effect of heating the heat-curable resin carried by the resin carrier layer, thereby curing the resin and securing the liner 10 to the inner surface of the pipeline. When the liner has an internal resin carrier layer, the liner is positioned in the pipeline by pulling the liner into the pipeline. The controller 102 can then cause the power supply 103 to then supply current to the resistive heating layer 16. This has the effect of heating the heat-curable resin carried by the resin carrier layer, thereby curing the resin and stiffening the liner to retain the liner within the pipeline. The controller 102 may not allow the supply of current to the resistive heating layer 16 until it has received a notification from the machine 108 operable to load data onto the near field communication device 28 that the data has indeed been loaded onto the near field communication device 28. This ensures that the liner 10 is always tagged with a near field communication device 28 loaded with relevant data (such as construction data) ensuring that subsequent lining operations are efficiently and effectively carried out. Once the near field communication device 28 has been loaded with the data it may be attached to the liner, preferably with adhesive. If the pipeline has been lined previously with an old liner and the old liner was tagged with an old near field communication device, the operator can obtain information relating to the old liner by scanning the old near field communication device with the near field communication device reader 110. This information may be communicated to the user by the controller 102 via the display 104. During the heating of the liner 10 the at least one temperature sensor 24 feeds back temperature data to the controller 102. If the at least one temperature sensor indicates to the controller 102 that the sensed temperature has exceeded a pre-determined threshold the controller 102 can adjust the supply of current to the resistive heating layer 16 to prevent overheating of the liner. If the controller 102 receives notification from the at least one temperature sensor 24 that the temperature exceeds a pre-determined alarm threshold, the controller 102 activates the alarm, thereby indicating to the operator that the liner is overheating, meaning they can cease the operation and prevent damage to the liner 10. The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims. It should be noted that the heat resistive layer could be formed to include additional non-woven fibres that are electrically conductive. Although the vast majority of the nonwoven fibres would be less than 50mm there could be a small number of non-woven conductive fibres that are longer than 50mm due to a slight imperfection in a manufacturing 5 process of the resistive heating layer. It should also be noted that the resin carrier layer may be provided internally within the liner in the context of a so called “GRP liner”. In such a construction, the resin carrier layer impregnated with the heat-curable resin is provided between two protective layers. The heating of the heat-curable resin by the resistive heating layer may stiffen the liner 10 such that the liner is retained within the pipeline. It should be noted that the tubular liner may be provided with only the resistive heating layer and the resistive heating layer could have the heat-curable resin applied thereto.

Claims

1. A tubular liner for a pipeline, comprising:a resistive heating layer including non-woven fibres that are electrically conductive,wherein the non-woven fibres have a fibre length that is less than or equal to 50mm.

2. The liner of claim 1, wherein the fibre length is less than 40mm.

3. The liner of any preceding claim, wherein the non-woven fibres are arrangedirregularly.

4. The liner of any preceding claim, wherein the non-woven fibres are individual fibres.

5. The liner of any preceding claim, wherein each non-woven fibre has a greatest transverse width dimension (W) that is less than 20 micrometres (pm).

6. The liner of any preceding claim, wherein the non-woven fibres make up at least 10% of an entire mass of the resistive heating layer.

7. The liner of any preceding claim, wherein the resistive heating layer comprises at least 100 non-woven fibres.

8. The liner of any preceding claim, wherein the non-woven fibres are formed from chopped material.

9. The liner of any preceding claim, wherein the resistive heating layer comprises a blend of binder fibres and the non-woven fibres.

10. The liner of claim 9, wherein the fibre length of the non-woven fibres is a first fibre length, wherein the binder fibres have a second fibre length, wherein the second fibre length is the same as or greater than the first fibre length.

11. The liner of claim 9 or 10, wherein the non-woven fibres make up at least 10% of the blend and the binder fibres make up 50% or more of the blend.

12. The liner of any preceding claim, further comprising at least one elongate conducting element extending along a liner length of the liner, wherein the at least one elongate conducting element is in electrical contact with the resistive heating layer.

13. The liner of any preceding claim, wherein the liner extends between first and second ends thereof, wherein the at least one elongate conductive element extends from the first end to the second end.

14. The liner of claim 13, wherein the at least one elongate conductive element comprises first and second elongate conductive elements.

15. The liner of any preceding claim, wherein the tubular liner is formed from a rolled sheet.

16. The liner of claim 15 when claim 15 is dependent on claim 14, wherein the rolled sheet has opposing edges which are connected to each other, wherein the first and second elongate conductive elements are provided adjacent the connected opposing edges.

17. The liner of any preceding claim, further comprising a resin carrier layer.

18. The liner of any preceding claim, further comprising a first protective layer.

19. The liner of claim 18 when claim 18 is dependent on claim 17, wherein the resistive heating layer is located between the resin carrier layer and the first protective layer.

20. A method of lining a pipeline, comprising the steps of:providing the liner of any preceding claim with heat curable resin;positioning the liner within the pipeline; and thenpassing an electrical current through the resistive heating layer to cure the heat-curable resin.

21. A system for lining a pipeline, comprising:a liner for the pipeline in accordance with any of claims 1 to 19; anda controller operable to control a supply of current to the resistive heating layer.

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