A method of lining a host pipe or conduit and a liner

Abstract: The invention provides a method of lining a host pipe or conduit (102) by eversion of a liner (104) within the host pipe or conduit (102); wherein the liner (104) is of a flattened or axially folded configuration and is carried on a tubular support (106), the liner (104) surrounding the tubular support (106), and the tubular support (106) being releasably bonded to the liner (104) by a peelable adhesive (110) at one or more circumferential locations on the inner surface of the liner (104) and not being bonded to the liner (104) either side of each said location, the liner (104) being arranged to peel away from the tubular support (106) and overt towards or into contact with the wall of the host pipe or conduit (102) as the tubular support (106) is towed through the host pipe or conduit (106). The invention also provides a method of forming a supported liner as well as liners supported on a tubular support.

Description: This invention relates to a method of lining a host pipe or conduit by an eversion method. Eversion methods of lining pipelines or conduits are well known and examples of such methods can be found in, for example, EP-A-0611914, GB-A-1025011, GB-A-2082285, GB-A-1559323, EP-A-0304914, GB-A-2042673, DE-A-2718877, EP-A-062100, EP-A-0620102, JP 60-7124, JP 64-182709 and JP 64-182710. Exemplary of conventional methods of eversion lining of pipes is the method disclosed in EP-A-0 301 895 (Angus Fire Armour Limited). This method is described in more detail below with reference to Figure 1 of the drawings appended hereto. One of the problems with the method of EP-A-0 301 895, and many other conventional methods of eversion lining, is that rather complex arrangements are usually required for applying fluid pressure or vacuum to the liner to force or draw the liner through the host pipe. Although generally workable, the need to use pressurised gases or water in a field situation can be inconvenient, and in certain circumstances may not be possible at all. It is an object of the present invention to provide a simplified method of eversion lining in which the liner can be introduced into the host pipe or conduit using standard winching equipment, and without the need for the aforementioned pressurising apparatus. Accordingly, in a first aspect, the invention provides a method of lining a host pipe or conduit by eversion of a liner within the host pipe or conduit; wherein the liner is of a flattened or axially folded configuration; characterised in that the liner is carried on and surrounds a tubular support, the tubular support being releasably bonded to the liner by a peelable adhesive at one or more circumferential locations on the inner surface of the liner and not being bonded to the liner either side of each said location, the liner being arranged to peel away from the tubular support and evert towards or into contact with the wall of the host pipe or conduit as the tubular support is towed through the host pipe or conduit. It is most preferred that the tubular support is moved through the host pipe or conduit solely by mechanical means, most preferably solely by towing, and without the use of fluid pressure from behind the everting liner, and without the application of vacuum in front of the everting liner. The liner can be selected such that after eversion, it is in tight contact with the wall of the host pipe or conduit, or it can be undersized with respect to the host pipe such that there is initially an annular gap between the host pipe wall and the liner. The undersized liner can then be caused or allowed to expand to tightness against the pipe wall. The expansion of the liner can be achieved by means of any of a number of well known processes, which can involve for example simple stretching and plastic deformation of the liner, or by building expansive stresses into the liner and releasing the expansive stresses through heat treatment of the liner after installation. According to the invention, the liner is adhered to the tubular support prior to eversion by means of a peelable adhesive. The advantage of using a peelable adhesive is that after the liner has everted, adhesive initially on the bore of the liner is presented on the outer surface of the liner and therefore serves at least partially to bond the liner to the wall of the host pipe when the liner is brought into contact with the wall. Alternatively, adhesive on the tubular support may be transferred to parts of the liner bore ultimately to help bond the liner to the host bore in like manner. The peelable adhesive is typically chosen such that the aforementioned bond to the wall of the host pipe is sufficiently strong to hold the liner against any residual contractive stresses. Such contractive stresses can arise after expansion of an initially undersized liner to tightness within the host pipe as part of the installation process, or after first recommissioning of the pipeline. in one embodiment, the invention provides a method of lining a host pipe or conduit by eversion of a liner within the host pipe or conduit as hereinbefore defined; wherein the liner is of a generally flattened or folded configuration and is carried on a tubular support, the liner being arranged to peel away from the tubular support and evert towards or into contact with the wall of the host pipe or conduit as the tubular support is towed through the host pipe or conduit, and wherein an adhesive-dispensing head is towed along the host pipe or conduit in front of the liner, the adhesive-dispensing head being arranged to apply adhesive to the front of the everting liner and/or to the host pipe wall, prior to the liner contacting the said wall. In this embodiment, the adhesive applied by the adhesive-dispensing head is additional to the peelable adhesive with which the tubular support has been releasably bonded to the liner. The tubular support typically is initially disposed within the liner so as to give an initial loose fit with an annular gap therebetween. The tubular support and liner can be formed separately and the support pulled through the bore of the liner. More usually however, the liner is extruded around the tubular support. This can be accomplished, for example, by extruding the tubular support at a first extrusion location and then extruding the liner around the tubular support at a second extrusion location downstream of the first. Adhesive can be applied to the inner surface of the liner and/or the outer surface of the tubular support between the first and second extrusion locations, or at one or both locations. Once the tubular support has been arranged within the liner, whether by pulling the support through the liner, or by extrusion of the liner about the support, or by any other means, the liner and tubular support are usually subjected to compression so as generally to flatten them, the flattening process serving to bond the liner to the tubular support. The ratio of the initial diameter (i.e. prior to compression) of the liner to the initial diameter of the tubular support is typically in the range from 2:1 to 5:1, more usually in the range 3:1 to 4:1. Following the compression step, the width of the flattened liner/tubular support combination typically is greater than the diameter of the host pipe into which the liner is to be installed (although it need not be), although the depth of the combination is significantly less than the diameter of the host pipe. The tubular support can be towed through the host pipe or conduit by means of a cable attached to a suitable mounting point at the leading end of the support. An adhesive-dispensing head, e.g. a dispensing lance, can be mounted so as to be movable along the host pipe in front (and preferably immediately in front) of the everting liner. For example, the lance can be mounted on a second cable, the dispensing head being connected to a supply line containing adhesive. The supply line can extend through the bore of the tubular support but more usually extends into the host pipe from the remote end thereof, i.e. the end at which the towing cable is connected to a winch or other towing means. The tubular support is usually formed from a plastics material such as a polyolefin e.g. polyethylene (high strength HDPE) or polypropylene. The liner is typically formed from a polymer such as a polyolefin homopolymer or a copolymer or mixture thereof. The liner can be unilaminar or have more than one layer. For example, the liner can have a main structural layer and a barrier layer formed from a polymer such as a polyamide. A reinforcing layer can also be present, for example a reinforcing layer containing a fibrous reinforcing material such as carbon fibres. The method of the present invention can be used for example to introduce into the bore of a host pipe or conduit liners having a wall thickness in the range from 0.1mm to 15mm, e.g. 0.5mm to 5mm. In another aspect, the invention provides a method of forming a supported liner suitable for use in the method as hereinbefore defined, the method comprising applying a peelable adhesive to the outer surface of a tubular support (e.g. by coating) and/or applying a peelable adhesive to the inner surface of the liner (e.g by coating), positioning the tubular support within the bore of a liner, and compressing the liner and tubular support so that the liner is urged into contact with the tubular support and is peelably bonded thereto over part, but not all, of its circumference. In one preferred embodiment, the method comprises extruding the tubular support at a first extrusion location; extruding the liner about the tubular support at a second extrusion location downstream of the first, such that the tubular support is initially loosely disposed within the liner; applying (e.g. by coating) a peelable adhesive to the outer surface of the tubular support and/or the inner surface of the liner; and then compressing the liner and tubular support to form a generally flattened composite assembly in which the liner is peelably bonded to the tubular support over part, but not all, of its circumference. In the aforementioned method of forming the supported liner, the peelable adhesive can be, for example, applied as a coating to the outer surface of the tubular support; or it can be applied as a coating to the inner surface of the liner. In a further alternative, the peelable adhesive can be applied in the form of one or more adhesive tapes, for example extending generally axially along the outer surface of the tubular support. The adhesive tape(s) can be double sided, the two sides of the tape having adhesives thereon of different peel strength, one side having a relatively high peel strength adhesive being bonded to the liner and the other side having a relatively low peel strength adhesive being bonded to the tubular support. In a still further aspect, the invention provides a liner supported on a tubular support as hereinbefore defined. The invention will now be illustrated, but not limited, by reference to the specific embodiments shown in the accompanying drawings of which: Figure 1 is a sectional elevation illustrating a known method of eversion lining of a host pipe; Figure 2 is a schematic side sectional elevation illustrating one embodiment of the invention; Figure 3 is a sectional elevation along line I-I in Figure 2; Figure 4 is a sectional elevation along line III-III in Figure 3; Figure 5 is a sectional elevation through a liner having a tubular support loosely disposed therein prior to bonding together; Figure 6 is a schematic sectional elevation illustrating a tubular support and liner pipe after compression to bond the two together; and Figure 7 is a schematic sectional elevation showing the support and liner pipe of Figure 6 after removal of the compressive force. Referring now to the drawings, Figure 1 illustrates a known method of eversion lining of a pipe or conduit as described in European Patent Application EP-A-0 301 895. In the method of EP-A-0 301 895, a host pipe 2 is lined with a flexible liner 4 which is fed into the bore of the host pipe from a reel 6. One end 4a of the liner is secured about the mouth 2a of the host pipe , and the liner is then forced into the host pipe by the pressure of a compressed fluid (indicated schematically by the letter P) such as compressed air or water. As the liner 4 is forced along the host pipe, so it gradually everts or turns inside out as shown by the arrows O in the drawing. As an alternative to using fluid pressure to evert the liner, the liner can instead be drawn through the host pipe by the application of vacuum to the leading surface of the liner. A major disadvantage of the arrangement shown in Figure 1 is that it requires the use of a source of fluid pressure or vacuum, which in turn requires the components of the lining system to be fitted together in a fluid tight condition. A further disadvantage is that for relatively small bore pipes, very large pressures tend to be required in order to bring about eversion. The present invention provides a means of avoiding the use of fluid pressure, the liner being capable of being everted simply by towing it through the host pipe using a suitable winch or other towing device. As shown in Figure 2, according to the invention, a host pipe 102 is lined with a liner 104 which can be formed from, for example, a polyolefin mixture of 2mm thickness. The liner 104 is carried on a tubular support 106, which can be formed from a high density polyethylene (HDPE). To the leading end of the tubular support 106 is attached an end of a towing cable 108, the other end of which is attached to a winch at the remote end of the host pipe. The tubular support and liner, are initially both formed in a circular cross section, the tubular support being extruded through a suitable die of a conventional extruder at a first extrusion location and the liner being extruded around the tubular support at a second extrusion location downstream of the first. Between the first and second extrusion locations, or at one of the locations, a layer 110 of a tacky peelable adhesive is coated onto the outer surface of the tubular support and/or the inner surface of the liner. As shown in Figure 5, immediately after extrusion of the liner around the tubular support, the tubular support is loosely arranged within the liner. Before it can be used in the eversion process, the tubular support/liner combination shown in Figure 5 is compressed, for example between rollers, to give a profile as shown in Figure 6. During this compression step, the liner is bonded to the tubular support by the peelable adhesive. Once the compressive force is released, the resilience of the material causes it to resile to a limited extent towards a more circular "eye" shape as shown in Figure 7, before the combination is wound on to a drum as shown in Figure 8. In use, as shown in Figure 2, an end 104a of the liner 104 is stretched over the mouth 102a of the host pipe by means of a suitable expanding tool optionally provided with thermal softening capability, and the cable 108 is used to draw the tubular support and liner into the bore of the host pipe 102. As can be seen from Figures 2 and 4, before insertion into the host pipe the flattened form of the liner/support combination means that the width W of the liner is typically greater than the diameter of the host pipe. As the tubular support is towed along the bore, the liner 104 is progressively peeled away from the support and turned inside out (everted) such that the surface 104b formerly facing radially inwardly, now faces radially outwardly and is in contact with or near to the wall 112 of the host pipe. As will be apparent from the drawings, part of the surface of the liner will have been in contact with the tubular support and will therefore have picked up a layer of peelable adhesive from the support. Alternatively, substantially all of the surface of the liner can be provided with a coating of peelable adhesive, the adhesive having been applied to the inner surface of the liner during the extrusion step. Following eversion, the peelable adhesive on the liner helps to secure the liner in place against the host pipe and prevent inadvertent axial displacement along the host pipe. A major advantage of the method of the invention is that it avoids the need for the complex equipment and fluid-tight conditions typically required for everting liners using fluid pressure or vacuum. Instead, the liner can be introduced into the host pipe simply by towing the tubular support through the host pipe with a conventional winch.

Claims: A method of lining a host pipe or conduit (102) by eversion of a liner (104) within the host pipe or conduit (102); wherein the liner (104) is of a flattened or axially folded configuration; characterised in that the liner (104) is carried on and surrounds a tubular support (106), the tubular support (106) being releasably bonded to the liner (104) by a peelable adhesive (110) at one or more circumferential locations on the inner surface of the liner (104) and not being bonded to the liner (104) either side of each said location, the liner (104) being arranged to peel away from the tubular support (106) and evert towards or into contact with the wall (112) of the host pipe or conduit (102) as the tubular support (106) is towed through the host pipe or conduit (102). A method according to claim 1 wherein the tubular support (106) is moved through the host pipe or conduit (102) solely by towing and without the use of fluid pressure from behind the everting liner (104). A method according to claim 1 or claim 2 wherein the tubular support (106) is releasably bonded to the liner (104) at at least two circumferentially spaced apart locations on the inner surface of the liner (104b). A method according to any one of claims 1 to 3 wherein the liner (104) is of flattened circular cross section. A method according to any one of the preceding claims wherein the tubular support (106) is of flattened circular cross section. A method according to any one of the preceding claims wherein the tubular support (106) is towed through the host pipe or conduit (102) by means of a cable (108) secured to a leading end of the support (106). A method according to any one of the preceding claims wherein the liner (104) has a wall thickness in the range from 0.1mm to 15mm, for example in the range 0.5mm to 5mm. A method according to any one of the preceding claims wherein the ratio of the diameter of the liner (104) to the diameter of the tubular support (106), prior to any flattening of the liner (104) and tubular support (106), is in the range from 2:1 to 5:1, for example in the range 3:1 to 4:1. A method according to any one of the preceding claims wherein the peelable adhesive (110) takes the form of: (i) a coating of adhesive applied to the outer surface of the tubular support (106) and/or the inner surface (104b) of the liner (104) prior to eversion; or (ii) one or more adhesive tapes extending generally axially along the outer surface of the tubular support (106), and optionally wherein for example the adhesive tape(s) is or are double sided, the two sides of the tape having adhesives thereon of different peel strength, one side having a relatively high peel strength adhesive being bonded to the liner (104) and the other side having a relatively low peel strength adhesive being bonded to the tubular support (106). A method according to any one of the preceding claims wherein the liner (104) is formed from an extruded polymeric material. A method according to claim 10 wherein the extruded polymeric material is a polyolefin. A method of forming a supported liner (104) suitable for use in the method as defined in any one of the preceding claims, the method comprising coating a tubular support (106) on its outer surface and/or coating a liner (104) on its inner surface (104b) with a peelable adhesive (110), positioning the tubular support (106) within the bore of a liner (104), and compressing the liner (104) and tubular support (106) so that the liner (104) is urged into contact with the tubular support (106) and is peelably bonded thereto over part, but not all, of its circumference. A method of forming a supported liner (104) suitable for use in the method as defined in any one of claims 1 to 11, the method comprising extruding the tubular support (106) at a first extrusion location; extruding the liner (104) about the tubular support (106) at a second extrusion location downstream of the first, such that the tubular support (106) is initially loosely disposed within the liner (104); applying, e.g. by coating, a peelable adhesive (110) to the outer surface of the tubular support (106) and/or the inner surface (104b) of the liner (104); and then compressing the liner (104) and tubular support (106) to form a generally flattened composite assembly in which the liner (104) is peelably bonded to the tubular support (106) over part, but not all, of its circumference. A method according to claim 12 or claim 13 wherein: (i) the peelable adhesive (110) is applied as a coating to the outer surface of the tubular support (106) and/or the peelable adhesive (110) is applied as a coating to the inner surface (104b) of the liner (104); or (ii) the peelable adhesive (110) is applied in the form of one or more adhesive tapes, for example extending generally axially along the outer surface of the tubular support (106), and wherein optionally for example the adhesive tape(s) is or are double sided, the two sides of the tape having adhesives thereon of different peel strength, one side having a relatively high peel strength adhesive being bonded to the liner (104) and the other side having a relatively low peel strength adhesive being bonded to the tubular support (106). A method of lining a host pipe or conduit (102) according to claim 1 wherein an adhesive-dispensing head is towed along the host pipe or conduit in front of the liner, the adhesive-dispensing head being arranged to apply adhesive to the front of the everting liner and/or to the host pipe wall, prior to the liner contacting the said wall. A liner (104) suitable for use in a method as defined in any one of claims 1 to 11, the liner (104) being of a flattened or axially folded configuration and being characterised in that it is carried on and surrounds a tubular support (106), the tubular support (106) being releasably bonded to the liner (104) by a peelable adhesive (110) at one or more circumferential locations on the inner surface of the liner (104) and not being bonded to the liner (104) either side of each said location, the liner (104) in use being capable of peeling away from the tubular support (106) and everting towards or into contact with the wall (112) of a host pipe or conduit (102) as the tubular support (106) is towed through the host pipe or conduit (102).

Inventors: LIPPIATT RAYMOND, LIPPIATT, RAYMOND
Applicants: EVOLVED PROCESSES LTD, EVOLVED PROCESSES LIMITED
Application year: 1998
Main classification: F16L55
IPC codes: F16L55