Patent Description:
While the inventions has been devised particularly in relation to the construction of tubular structures in the form of pipes, it may also be applicable to the construction of other elongate hollow elements including tubular elements such as ducts and tubes, tubular structural elements such as shafts, beams and columns, and other tubular elements of composite construction.

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

It is known to construct pipes using fibre-reinforced plastic composites. Typically, such pipes are constructed by a process in which rovings of filaments of fibre material, (such as glass fibres) are impregnated with a thermosettable resin or thermoplastic composition and wound back and forth on a mandrel to form a pipe wall structure of composite construction.

Further, there have been attempts to produce a continuous pipe by pultrusion involving a wet body of reinforcement fibres being drawn through a heated mould to cure the pipe and the pipe then wound onto a spool. Pipes constructed in this way are typically limited to lengths of about <NUM> and diameters of about <NUM>.

Typically, such pipes are required to bear both hoop and axial stresses, and the construction can be a compromise between the hoop and axial stress bearing properties required for the pipe. Hoop strength can be optimised by winding the reinforcing filaments at an angle approaching <NUM>° to the pipe axis. Axial strength can be optimised by winding the reinforcing filaments at an angle approaching the pipe axis.

The length of pipe that can be constructed in such a way is dictated by the length of the mandrel or the roll of pipe that can be transported. Consequently, the construction process is not conducive to construction of long pipes to form a transportation network for liquids and gasses; that is, pipes which are much longer than available mandrels and also pipes which are of a length to constitute a pipeline extending continuously between two distant locations, perhaps hundreds to thousands of kilometres apart.

<CIT> discloses a method of lining a passageway with thermosetting resin. <CIT> discloses an elongate structural element with a tubular casing and a hollow interior filled with a polymer binding. <CIT> discloses a method of manufacturing a pipe using fibres and resin in a mold.

It would be advantageous for there to be a way in which a pipeline could be constructed using a pipe constructed on a continuous basis; that is, without having to be composed of a series of pipe sections joined one to another at junctions which are likely constituted areas of weakness in structural integrity of the pipeline.

It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed.

According to a first aspect of the invention there is provided a method of constructing an elongate hollow structure according to claim <NUM>. According to a second aspect of the invention there is provided a mobile installation plant according to claim <NUM>. Accordingly, there is provided a method of constructing an elongate hollow structure comprising a radially inner portion and a radially outer portion, with the two portions merging together to provide an integrated tubular wall structure, the method comprising: providing the radially inner portion: assembling the radially outer portion about the radially inner portion; and expanding the inner portion; wherein the outer portion comprises an outer tube of fibre reinforced composite construction surrounded by a flexible outer casing.

The outer tube of fibre reinforced composite construction comprises reinforcement and a binder.

The reinforcement may comprise one or more layers of reinforcing fabric. Preferably, each layer is configured as a tubular layer disposed about the radially inner portion. Typically, there is a plurality of tubular layers disposed one about another and hence also disposed about the inner tube.

The reinforcing fabric may comprise reinforcing fabric which incorporates reinforcement fibres featuring quadraxial fibre orientations. The reinforcement fibres may comprise glass fibres. The quadraxial fibre orientations offer the necessary hoop and axial stress bearing properties to the tubular structure.

Preferably, the binder comprises a settable plastic such as a resinous binder, which is commonly referred to as a resin. The binder sets to a resin matrix for binding the layers of reinforcing fabric together and to bind the reinforcement to the inner portion to provide the integrated tubular wall structure. The resin matrix may also bind the reinforcement to the outer casing.

Preferably, the inner portion comprises an inner tube comprising an inner liner with a fibrous layer bonded onto one face thereof, wherein the resinous binder impregnating the reinforcing fabric also impregnates the fibrous layer to integrate the outer portion with the inner portion.

Preferably, the outer casing comprises an outer layer and a fibrous layer bonded onto one face thereof, the arrangement being that the fibrous layer confronts the reinforcement. With this arrangement the fibrous layer of the outer casing may provide a breather layer through which air can move.

The flexible outer casing serves to resist radial expansion of the reinforcement, thereby causing it to be subjected to radial compression. With this arrangement, the reinforcement is confined in the space between the expanding inner portion and the flexible outer casing. The radially expanding inner portion operates in conjunction with the flexible outer casing to confine the reinforcement and also causes the volume of the space in which the reinforcement is confined to progressively decrease. This forces the binder within the reinforcement to fully impregnate the reinforcement; that is, the layers of reinforcing fabric become fully "wetted-out". In particular, it provides a compaction force to the reinforcement and effectively pumps the binder through the layers of reinforcing fabric to distribute the binder within the space in a controlled and constrained manner.

Further, the progressive decrease in volume of the space in which the reinforcement is confined may act to positively expel air from within the space which has the effect of enhancing impregnation of the binder within the reinforcement.

The outer casing and the various reinforcing fabric tubes may be adapted to facilitate the expulsion of the air. The outer casing and the various reinforcing fabric tubular layers may be configured to facilitate expulsion of air, for example, the outer casing and the various reinforcing fabric tubular layers may incorporate vents at intervals along their respective lengths to facilitate expulsion of the air. Additionally, or alternatively, the fibrous layer of the outer casing which provides the breather layer may facilitate displacement of air, typically upwardly and along the assembly to a release or venting point.

The flexible outer casing may have some resilience in order to yielding resist radial expansion of the reinforcing fabric tubes at least to some extent. However, the flexible outer casing typically has less resilience than the inner tube. In this way, the flexible outer casing can cushion the initial stage of the radial expansion of the reinforcing fabric tubular layers. In particular, it is desirable that the flexible outer casing have some elasticity. The flexible outer casing may have some elasticity for the purpose of enhancing control of the rate at which the binder progressively wets the reinforcement.

According to an example, there is provided a method of constructing an elongate hollow structure comprising a radially inner portion and a radially outer portion, with the two portions merging together to provide an integrated tubular wall structure, the method comprising: providing the radially inner portion comprising inner tube comprising an inner liner with a fibrous layer bonded onto one face thereof; assembling the radially outer portion about the radially inner portion; and expanding the inner portion; wherein the outer portion comprises an outer tube of fibre reinforced composite construction surrounded by a flexible outer casing and wherein the inner portion comprises an inner tube comprising an inner liner with a fibrous layer bonded onto one face thereof, whereby resinous binder impregnating the outer tube also impregnates the fibrous layer to integrate the outer portion with the inner portion.

According to a third aspect of the invention there is provided a method of constructing an elongate hollow structure comprising forming a flexible tubular wall structure about a central portion, expanding the central portion to cause the tubular wall structure to assume a prescribed cross-sectional profile, and hardening, curing or otherwise setting the tubular wall structure.

The central portion may comprise part of the wall structure.

The flexible wall structure may comprise a fibre-reinforced plastic composite.

The flexible wall structure may further comprise settable plastic such as a resinous binder. Typically, the settable plastic comprises a curable resin.

The fibre reinforced plastic composite may comprise reinforcement configured as a fabric incorporating reinforcement fibres.

Preferably, the reinforcing fabric has quadraxial fibre orientations. The quadraxial fibre orientations offer hoop and axial stress bearing properties.

The flexible tubular wall structure may further comprise a flexible outer casing surrounding the fibre-reinforced plastic composite.

The expandable central portion may comprise an inner tube which provides an inflatable bladder to expand the flexible tubular wall structure prior to hardening, curing or other setting thereof.

Preferably, the inner tube is integrated with and forms part of the tubular wall structure.

The continuous movement and then expansion of the flexible tubular wall structure serves to pre-stress and align fibres within the reinforcing fabric to enhance hoop stress bearing properties over the entire length of the elongate hollow structure under construction.

Preferably, the reinforcing fabric is also pre-stressed axially (linearly) to enhance tensile load bearing properties.

The central portion may be configured as a bladder.

The bladder may be inflated using a fluid medium such as air or water.

Preferably, the bladder is expandable elastically.

In one arrangement, the tubular structure may be of a specific length. The tubular structure may, for example, comprise a tubular element such as a pipe made to a specific length.

In another arrangement, the tubular structure may be formed progressively to any desired length. The tubular structure may, for example, comprise a tubular element such as a pipe formed continuously until the desired length is attained. In this regard, the pipe may be of a length to constitute a continuous pipe providing a pipeline extending between two distant locations.

In contrast to the prior art arrangement where a pipeline extending between two distant locations would typically comprise a plurality of pipe sections joined one to another, the pipe according to the first aspect of the invention can permit the pipeline to be formed as one continuous pipe.

According to a fourth aspect of the invention there is provided a method of constructing an elongate hollow structure comprising forming a flexible tubular wall structure having an interior, inflating the interior of the flexible tubular wall structure to provide form and shape thereto; and hardening, curing, or otherwise setting the flexible wall structure to provide the tubular element.

The flexible wall structure may comprise a fibre-reinforced plastic composite which can cure to provide the tubular element.

The flexible wall structure may further comprise a flexible outer casing surrounding the fibre-reinforced plastic composite.

In certain applications the fibre-reinforced plastic composite cures to a rigid condition. In certain other applications the fibre-reinforced plastic composite cures to a more flexible condition.

The tubular wall structure may comprise a liner having a fluid impervious inner surface. The inner surface may be defined by a high gloss material such as a polyurethane liner.

According to a fifth aspect of the invention there is provided a method of constructing a pipe comprising forming a flexible tubular wall structure comprising a fibre-reinforced plastic composite, inflating the interior of the flexible tubular wall structure to provide form and shape thereto; and hardening, curing or otherwise setting the flexible wall structure to provide the pipe.

The pipe may be constructed on a continuous basis and progressively installed in position prior to curing of the flexible wall structure, whereby the flexible wall structure cures once in the installed position of the pipe.

According to a sixth aspect of the invention there is provided a method of constructing a pipe on a continuous basis, comprising forming a flexible tubular wall structure comprising a fibre-reinforced plastic composite, inflating the interior of the flexible tubular wall structure to provide form and shape thereto; and curing the flexible wall structure to provide the pipe.

In the method according to the sixth embodiment, the flexible wall structure may comprise inner and outer portions, wherein the method further comprises forming the inner portion to define an inner tube and forming an outer tube of fibre reinforced composite construction about the inner tube to define the outer portion.

The outer tube may be formed using one or more layers of reinforcing fabric, wherein the method further comprises configuring each layer as a tubular layer disposed about the inner tube, impregnating the tubular layers with a resinous binder, inflating the inner tube to provide form and shape to the tubular wall structure, and curing the resinous binder to harden the tubular wall structure.

The flexible outer casing is installed around the tubular layers of reinforcing fabric to contain the resinous binder.

The flexible outer casing may be formed of any appropriate material, including for example polyethylene.

More particularly, the outer casing comprises an outer layer of polyethylene and a fibrous layer bonded onto one face thereof, the arrangement being that the fibrous layer confronts the reinforcement, as described above.

The outer casing may remain in place and ultimately form an integral part of the tubular structure, or it may be subsequently removed after having served its purpose.

The exterior of the outer layer of the outer casing may be configured to adherence to a surrounding protective sheath, such as a concrete casing. This may comprise a surface roughness or formations such as tufts on the exterior of the outer layer of the outer casing.

The inner tube may comprise an inner liner with a fibrous layer bonded onto one face thereof, and the resinous binder impregnating the reinforcing fabric may also impregnate the fibrous layer to integrate the outer portion with the inner portion.

The pipe may be constructed in a mobile installation plant configured as a vehicle which can move in relation to an installation site such that the continuously formed pipe can be progressively delivered to the installation site.

According to a seventh aspect of the invention there is provided a method of constructing a pipe in a flexible condition, laying the pipe at an installation site, and allowing the flexible pipe to transform into a rigid condition at the installation site.

The installation site may comprise a trench into which the pipe is progressively laid in the flexible condition. The pipe may be laid directly into the trench or placed alongside the trench and subsequently installed in the trench. The trench may have a foundation of sand or other material shaped to provide a curved depression upon which the pipe is laid for support.

The pipe may be assembled in a mobile installation plant which can move with respect to the installation site, laying the pipe in the flexible condition.

According to an eighth aspect of the invention there is provided an elongate hollow structure constructed in accordance with the method according to the first, second, third or fourth aspect of the invention.

According to a ninth aspect of the invention there is provided a pipe constructed in accordance with the method according to third, sixth or seventh aspect of the invention.

According to a tenth aspect of the invention there is provided an elongate hollow structure of composite construction, comprising a radially inner portion and a radially outer portion, wherein the two portions merge together to provide an integrated tubular wall structure.

The outer portion may be configured as an outer tube of fibre reinforced composite construction. More particularly, the outer portion may comprise reinforcement impregnated in a resinous binder.

The outer portion may further comprise a flexible outer casing surrounding the outer tube.

The reinforcement may comprise one or more layers of reinforcing fabric, each configured as a tube disposed about the inner portion. The reinforcement may comprise a plurality of layers, each configured as a respective tube disposed one about another.

The inner portion may comprise an inner liner with a fibrous layer bonded onto one face thereof. The other face of the liner may define the interior surface of the tubular structure.

The resinous binder impregnating the reinforcing fabric may also impregnate the fibrous layer bonded on the inner liner to integrate the outer portion with the inner portion.

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:.

Referring to <FIG> of the drawings, the first embodiment of the invention is directed to an elongate hollow structure in the form of a tubular element configured as a pipe <NUM>, and to a method of construction of the pipe on a continuous basis.

The pipe <NUM> is of composite construction, comprising a radially inner portion <NUM> and a radially outer portion <NUM>, with the two portions <NUM>, <NUM> merging together to provide an integrated tubular wall structure. In the arrangement illustrated, the outer portion <NUM> is encased within a protective sheath <NUM> comprising a hardenable composition <NUM> such as cement or concrete contained by an outermost skin <NUM> of any suitable material; such as geotextile cloth. The protective sheath <NUM> is intended to afford protection to the pipe <NUM> against compression loading to which it might be exposed once in the installed condition.

The inner portion <NUM> comprises an inner liner <NUM> with a layer <NUM> of resin absorbent material bonded onto one face thereof. The other face of the liner <NUM> defines the interior surface <NUM> of the pipe <NUM>. Typically, the liner <NUM> presents a high gloss surface at the inner face <NUM>. The inner liner <NUM> may, for example, comprise polyurethane, polyethylene or any other resiliently flexible material which is preferably also impervious to air and also compatible to fluid to be conveyed within the pipe <NUM>. The resin absorbent layer <NUM> may, for example, comprise felt or flock.

As best seen in <FIG>, the inner portion <NUM> is configured as an inner tube <NUM> formed from a longitudinal strip <NUM> having longitudinal side edges <NUM>. The strip <NUM> is rolled longitudinally into a tubular configuration to provide the inner tube <NUM>, with the longitudinal edges <NUM> in abutting relationship to provide a butt joint <NUM>. An inner jointing strip <NUM> is applied to the inner side of the inner tube <NUM> and an outer jointing strip <NUM> is applied to the outer side of the inner tube <NUM>, with the two jointing strips <NUM>, <NUM> bridging the butt joint <NUM> and providing a continuous, fluid tight connection between the abutting longitudinal side edges <NUM>. In <FIG>, the jointing strips <NUM>, <NUM> are shown spaced from the butt joint <NUM> for the purposes of clarity, but in practice are actually in contact with the butt joint.

The inner tube <NUM> defines an inflatable bladder <NUM> having an inflation cavity <NUM>, the purpose of which will be explained later.

The outer portion <NUM> is configured as an outer tube <NUM> of fibre reinforced composite construction surrounded by a flexible outer casing <NUM>. More particularly, the outer tube <NUM> comprises reinforcement <NUM> impregnated in a resinous binder. The flexible outer casing <NUM> is installed around the tube <NUM> to contain the resinous binder, as will be described in more detail shortly. The flexible outer casing <NUM> may be formed of any appropriate material, including for example polyethylene. The outer casing <NUM> may remain in place and ultimately form an integral part of the pipe <NUM>, or it may be subsequently removed after having served its purpose.

The outer casing <NUM> comprises an outer layer of polyethylene and a fibrous layer bonded onto one face thereof, the arrangement being that the fibrous layer confronts the reinforcement <NUM>. The fibrous layer provides a breather layer and also is ultimately impregnated with the resinous binder for integration of the assembly.

The resinous material which provides the resinous binder may be of any appropriate type; a particularly suitable resinous materials comprise thermosetting resin such as epoxy vinyl ester or other suitable resin and thermoplastic resin systems.

The reinforcement <NUM> comprises one or more layers <NUM> of reinforcing fabric <NUM> (as shown in <FIG>), each layer being configured as a tubular layer <NUM> (as shown in <FIG>) disposed about the inner tube <NUM>. In this embodiment, there is a plurality of layers <NUM> configured as the respective tubular layers <NUM> disposed one about another (and hence also disposed about the inner tube <NUM> as previously mentioned). Adjacent fabric layers <NUM> may be bonded together in any suitable way such as by a hot welding chemical bonding, and/or mechanical fixing such as by stitching or stapling.

The reinforcing fabric <NUM> comprises reinforcing fabric which incorporates reinforcement fibres featuring quadraxial fibre orientations, as shown in <FIG>. The reinforcement fibres comprise axial fibres36a (at an angle approaching the pipe axis, which is depicted by line <NUM> in <FIG>), transverse fibres 36b (at an angle approaching <NUM> degrees to the pipe axis) and angular fibres 36c (at an angle approaching <NUM> degrees to the pipe axis). The reinforcement fibres may comprise glass fibres. The quadraxial fibre orientations offer the necessary hoop and axial stress bearing properties to the pipe.

Each reinforcing fabric tubular layer <NUM> is assembled from a strip <NUM> of reinforcing fabric material having longitudinal edges <NUM> which are brought together in overlapping relationship at joint <NUM> to form the tubular layer <NUM>. The overlapping edges <NUM> are secured together in any appropriate way to maintain the tubular formation. In this embodiment, the overlapping edges <NUM> are secured together by hot melt welding using a hot melt adhesive. In <FIG>, the overlapping edges <NUM> are shown spaced apart for the purposes of clarity, but in practice are actually in contact with each other to provide the joint <NUM>, as shown in <FIG>. The structural integrity of the joint <NUM> is subsequently established by the impregnation of resinous binder into the reinforcing fabric <NUM> from which the respective tubular layer <NUM> is formed. Specifically, the resinous binder impregnates the overlapping edges <NUM> and bonds them together to supplement and supplant the initial bond established by the hot melt adhesive.

The various tubular layers <NUM> are oriented such that the respective joints <NUM> are offset with respect to each other, as shown in <FIG>. In the arrangement shown in the drawings, the tubular layers <NUM> are oriented such that the respective joints <NUM> are disposed towards the underside <NUM> of the pipe <NUM> under construction. This may be advantageous as the underside <NUM> is the area in which resinous binder is likely to be plentiful to enhance the bond between the overlapping edges <NUM> at each joint <NUM>.

The resinous binder impregnating the reinforcing fabric <NUM> also impregnates the layer of felt <NUM> on the inner liner <NUM> to integrate the outer portion <NUM> with the inner portion <NUM>.

The reinforcing fabric tubular layers <NUM> are impregnated with the resinous binder after the tubular layers have been disposed one about another and hence also about the inner tube <NUM> as previously described. In an alternative arrangement, the reinforcing fabric tubular layers <NUM> may be impregnated with resinous binder after each tubular layer has been assembled. Each assembled reinforcing fabric tubular layer may be attached to the preceding inner reinforcing fabric tubular layer, such as by hot melt welding. However, it may be preferable to not so attach adjacent reinforcing fabric tubular layers so that each can move freely relative to the others for transfer of loads and stress whereby each layer can accept its share of the load.

Typically, air is removed from the reinforcing fabric tubular layers <NUM> prior to impregnation with the resinous binder.

After the reinforcing fabric tubular layers <NUM> have been impregnated with the resinous binder, but prior to curing thereof, the inflatable bladder <NUM> defined by the inner tube <NUM> is inflated by introduction of an inflation fluid such as air into the inflation cavity <NUM>. This causes the inflatable bladder <NUM> to expand radially towards the flexible outer casing <NUM>, providing form and shape to the surrounding outer portion <NUM> In particular, the outer portion <NUM> assumes a circular profile in cross-section.

The continuous expansion of the inflatable bladder <NUM> as it moves through the compression device <NUM> stretches the reinforcing fabric tubular layers <NUM> in all directions, serving to enhance hoop stress and axial stress bearing properties of the pipe <NUM>. In particular, the expansion serves to pre-stress fibres within the reinforcing fabric tubular layers <NUM> to enhance hoop stress bearing properties and also axially tensions the reinforcing fabric tubular layers to pre-stress fibres therein axially to enhance tensile load bearing properties of the pipe <NUM>.

The flexible outer casing <NUM> serves to resist radial expansion of the reinforcing fabric tubular layers <NUM>, thereby causing the reinforcement <NUM> to be subjected to radial compression. With this arrangement, the reinforcement <NUM> is confined in the space <NUM> between the expanding inner tube <NUM> and the flexible outer casing <NUM>. The radially expanding inner tube <NUM> operates in conjunction with the flexible outer casing <NUM> to confine the reinforcement <NUM> and also causes the volume of the space <NUM> in which the reinforcement <NUM> is confined to progressively decrease. This forces the resinous binder within the reinforcement <NUM> to fully impregnate the reinforcement <NUM>; that is, the layers <NUM> of reinforcing fabric <NUM> configured as the tubular layer <NUM> become fully "wetted-out". In particular, it provides a compaction force to the reinforcement <NUM> and effectively pumps the resinous binder through the layers <NUM> of reinforcing fabric <NUM> to distribute the resinous binder within the space <NUM> in a controlled and constrained manner. It is a particular feature of the embodiment that the step of delivering resinous binder to the reinforcement and the step of fully wetting out the reinforcement <NUM> with the resinous binder are separate and distinct actions.

Further, the progressive decrease in volume of the space <NUM> in which the reinforcement <NUM> is confined acts to positively expel air from within the space <NUM> which has the effect of enhancing impregnation of the resinous binder within the reinforcement <NUM>. The outer casing <NUM> and the various reinforcing fabric tubular layers <NUM> may be adapted to facilitate the expulsion of the air. The breather layer defined by the fibrous inner layer of the outer casing <NUM> facilitates this expulsion of air. Further, the outer casing <NUM> and the various reinforcing fabric tubular layers <NUM> may, for example, incorporate vents at intervals along their respective lengths to facilitate expulsion of the air, as shown in <FIG>. In one arrangement, the vents <NUM> may comprise perforations, such as puncture holes, formed in the outer casing <NUM> and the various reinforcing fabric tubular layers <NUM>. With such an arrangement, the perforations are ultimately sealed by the resinous binder to ensure the sealed integrity of the pipe <NUM>. In another arrangement, the vents may comprise ports inserted in the outer casing <NUM> and the various reinforcing fabric tubular layers <NUM>. The ports may, for example, comprise tubular inserts formed of a material which dissolves or otherwise degrades upon exposure to the resinous binder. With such an arrangement, the apertures in which the ports were accommodated are ultimately sealed by the resinous binder to ensure the sealed integrity of the pipe <NUM>.

The flexible outer casing <NUM> may have some resilience in order to yielding resist radial expansion of the reinforcing fabric tubular layers <NUM> at least to some extent. In this way, the flexible outer casing <NUM> can cushion the initial stage of the radial expansion of the reinforcing fabric tubular layers <NUM>. In particular, it is desirable that the flexible outer casing <NUM> have some elasticity. The flexible outer casing <NUM> may have some elasticity elastic for the purpose of enhancing control of the rate at which the progressively rising pool of resinous binder progressively wets the reinforcement <NUM>. If, on the one hand, the resinous binder rises within the space <NUM> too rapidly, it may be that full wet-out of fibres in the reinforcement <NUM> is not achieved. If, on the other hand, the resinous binder rises within the space <NUM> too slowly, it may be that the resinous binder could commence to cure before full wet-out of fibres in the reinforcement <NUM> is achieved.

The elastic nature of the flexible outer casing <NUM> installed around the assembled around the reinforcement <NUM> functions somewhat as a girdle for controlling external pressure exerted on the rising pool of resinous binder. The elastic characteristic of the flexible outer casing <NUM> is selected to achieve the desired rate of wet-out. The elastic force exerted by the outer casing <NUM> provides some counterbalancing of the tension exerted by the inflating bladder <NUM> defined by the inner tube <NUM>.

The inflatable bladder <NUM> is maintained in the inflated condition until such time as the resinous binder has hardened sufficiently to maintain the form and shape of the pipe, after which the inflation fluid can be released from the inflation cavity <NUM>. The pipe <NUM> thus is formed, with the inner liner <NUM> defining the central flow passage within the pipe.

The inner tube <NUM> may be preformed, or may be assembled on site as part of the construction process for the pipe <NUM>.

In circumstances where the inner tube <NUM> is preformed, it may be delivered to site in a collapsed condition. The inner tube <NUM> may be collapsed in any appropriate way. Typically, the inner tube <NUM> can assume a collapsed condition by being folded in a folding pattern to provide a compact arrangement in cross-sectional profile. In the arrangement shown in <FIG>, the inner tube <NUM> is collapsed into a flattened condition in cross-sectional profile using a folding pattern which defines two longitudinal side portions <NUM> and fold portions <NUM> therebetween. With this arrangement, the longitudinal side portions <NUM> can be in abutting contact with each other to provide a compact formation. In the arrangement shown in <FIG>, the inner tube <NUM> is collapsed into a flattened condition in cross-sectional profile using a folding pattern which defines two longitudinal side portions <NUM> and re-entrant fold portions <NUM> therebetween. With this arrangement, the re-entrant fold portions <NUM> each extend inwardly from one longitudinal side of the collapsed inner tube <NUM>. <FIG> is a schematic cross-sectional view of the inner tube <NUM> shown in a folded condition. In <FIG>, the inner tube <NUM> is shown in a partly flattened condition. In <FIG>, the inner tube is shown in a fully flattened condition. The inner tube <NUM> assumes the various conditions at various stages during fabrication of the pipe <NUM>.

The reinforcement <NUM> is assembled about the inner tube <NUM>. In particular, the reinforcing fabric tubular layers <NUM> are assembled sequentially about the inner tube <NUM>. As described above, each reinforcing fabric tubular layers <NUM> is assembled from a respective strip <NUM> of reinforcing fabric material having longitudinal edges <NUM> which are brought together in overlapping relationship at joint <NUM> to form the tube structure.

The various tubular layers <NUM> are arranged in a series <NUM> comprising an innermost tubular layer 35a, an outermost tubular layer 35b, and one or more intervening tubular layers 35c disposed between the innermost tubular layer 35a and the outermost tubular layer 35b. The tubular layers <NUM> in the series are of progressively increasing diameters in order to provide a good fit and alignment one with respect to another and thereby afford some precision in the construction of the pipe <NUM>. In order to accommodate the progressively increasing diameters between the tubular layers <NUM>, the respective strips <NUM> of reinforcing fabric material need to be of different widths, with the widths progressively increasing from the innermost tubular layer 35a to the outermost tubular layer 35b. Each tubular layer <NUM> is designed to be inflated, unfolded or unfurled to its maximum diameter by the inflation force of the fluid pressing against the inner tube <NUM> to provide the full expansion of the assembly and the fibres within it to hold the loads of the pipe <NUM> in operation.

As described above, the various tubular layers <NUM> in the series <NUM> are oriented such that the respective joints <NUM> are offset with respect to each other, as best seen in <FIG>.

Each tubular layer <NUM> is assembled from its respective strip <NUM> by progressively moving the strip through a transition from a first condition in which the strip is flat to a second condition in which the strip is in a tubular configuration with the edges <NUM> in overlapping relation. In <FIG> of the drawings, the strip <NUM> is depicted with a section 41a thereof in the first (flat) condition and a further section 41b thereof in the second (tubular) condition. In the first condition, the strip <NUM> can be stored in roll form <NUM> on a reel <NUM>, as shown in <FIG>.

An assembly system <NUM> is provided for progressively moving the respective strip <NUM> through the transition from the first (flat) condition to the second (tubular) condition and for securing the overlapping edges <NUM> together to establish the joint <NUM> and thus form the tubular layer <NUM>. As the strip <NUM> moves through the transition from the first (flat) condition to the second (tubular) condition it progressively envelopes the inner tube <NUM>.

The assembly system <NUM> comprises a guide system <NUM> for progressively moving the respective strip <NUM> through the transition from the first (flat) condition to the second (tubular) condition. The guide system <NUM>, which is best seen in <FIG>, comprises a guide <NUM> comprising a body <NUM> defining an entry end <NUM>, an exit end <NUM> and a guide path <NUM> extending between the entry end and the exit end. The body <NUM> is configured as a tubular structure <NUM> having longitudinal marginal edge portions <NUM> which are disposed in overlapping relation and spaced apart to define a longitudinal gap <NUM> therebetween. The tubular structure <NUM> is configured such that the guide path <NUM> tapers inwardly from the entry end <NUM> to the exit end <NUM>. With this arrangement, the tubular structure <NUM> provides a tapering guide surface 67a which is presented to the respective strip <NUM> as it advances along the guide path <NUM> from the entry end <NUM> to the exit end <NUM> and which progressively moves the strip <NUM> through the transition from the first (flat) condition at the entry end <NUM> to the second (tubular) condition at the exit end. As the strip <NUM> advances along the guide surface 67a, the longitudinal marginal edges <NUM> of the strip are progressively turned inwardly by the tapering profile, with one of the longitudinal marginal edges <NUM> of the strip <NUM> partially entering the longitudinal gap <NUM> in the tubular structure <NUM> and the other of the longitudinal marginal edges <NUM> overhanging the inner marginal edge 68a. With this arrangement, the longitudinal edges <NUM> are progressively brought together in overlapping relationship in readiness to be secured together to establish the joint <NUM> and complete formation of the tubular layer <NUM>.

As the strip <NUM> is being assembled into the tubular configuration to form the tubular layer <NUM>, the inner tube <NUM> is also moving along the guide path <NUM> from the entry end <NUM> and the exit end <NUM>. In this way, the tubular layer <NUM> can be assembled about the inner tube <NUM> and thereby envelopes it.

Similarly, the innermost intervening tubular layer 35c can be assembled about tubular layer 35a and the inner tube <NUM> about which the latter is formed, and then any other intervening tubular layers 35c and ultimately the outermost tubular layer 35b can be assembled about the preceding tubular layers <NUM>.

The tubular structure <NUM> may incorporate means for attracting and holding the strip <NUM> against the guide surface 67a. Such means may comprise a suction system incorporating a plurality of holes in the guide surface 67a to which suction is applied to draw the strip <NUM> into contact with the guide surface as the strip moves along the guide path <NUM>.

The assembly system <NUM> further comprises a guide roller <NUM> about which the respective strip <NUM> turns in its path from the reel <NUM> to the entry end <NUM> of the tubular structure <NUM> in order to align the strip <NUM> correctly for entry into the tubular structure <NUM>.

The assembly system <NUM> further comprises a bonding system <NUM> for securing the overlapping edges <NUM> together to establish the joint <NUM> and thus complete formation of the tubular layer <NUM>. The bonding system <NUM>, which is shown in <FIG>, comprises means <NUM> for applying hot melt adhesive between the overlapping edges <NUM> and then bringing the edges together to establish the joint <NUM>. In the arrangement shown, such means <NUM> comprises a delivery head <NUM> for delivering one or more bands <NUM> of hot melt adhesive between the overlapping edges <NUM>. The delivery head <NUM> is adapted to receive a supply of hot melt adhesive from a source <NUM> by way of a delivery line.

The bonding system <NUM> further comprises means <NUM> for bringing the overlapping edges <NUM> together with the hot melt adhesive therebetween to establish the joint <NUM>. In the arrangement shown, such means <NUM> comprises a press <NUM> for pressing the overlapping edges <NUM> together. The press <NUM> comprises two cooperating press rollers <NUM> between which the overlapping edges <NUM> pass to be pressed together to establish the joint <NUM> by way of the hot melt adhesive. While not shown in the drawings, the assembly system <NUM> may further comprise means for facilitating rapid setting of the holt melt adhesives Such means may comprise an arrangement to deliver a cooling agent, such as cold air, to the area at and around the joint <NUM>.

The construction process of the pipe <NUM> according to the embodiment will now be described in more detail. In this embodiment, the pipe <NUM> is constructed on a continuous basis and progressively laid into a trench <NUM> which has been dug to receive the pipe. The pipe <NUM> is laid in the trench79 prior to curing of the resinous binder which impregnates the reinforcing fabric <NUM> and also the layer of felt <NUM> on the inner liner <NUM>. The curing occurs after laying of the pipe <NUM> within the trench <NUM>. In this way, the pipe <NUM> is in a flexible condition to facilitate it being guided into the trench and laid into position, and hardens once in position.

Referring in particular to <FIG>, the pipe <NUM> is assembled in a mobile installation plant <NUM> configured as a vehicle which can travel alongside the trench <NUM> such that the continuously formed pipe <NUM> can "snake" from the mobile installation plant <NUM> into the trench <NUM>. The pipe <NUM> may be cured within the trench <NUM> in any appropriate way. In the arrangement illustrated, a curing unit <NUM> is provided to progressively move along the trench <NUM> to expose the recently laid section of the pipe to a curing action. The curing unit <NUM> may, for example, apply heat or other radiation such as UV radiation or light (according to the nature of the resinous binder) to the pipe <NUM> to facilitate the curing process. In an alternative arrangement, the resinous binder may incorporate an appropriate catalyst to cure the pipe in ambient conditions.

The mobile installation plant <NUM> comprises a pipe assembly line <NUM>, as shown in <FIG> (which is presented in two parts, <FIG>).

Referring to <FIG>, the assembly line <NUM> comprises a supply of material <NUM> in strip form and stored on a roll <NUM>. The material <NUM> provides the inner liner <NUM> with the layer of resin absorbent material <NUM> bonded thereto. The material <NUM> is progressively unwound from the roll <NUM> and conveyed as a strip <NUM> to a first assembly station <NUM> at which it is formed into the inner tube <NUM>. As described previously, the strip <NUM> is rolled longitudinally into a tubular configuration to provide the inner tube <NUM>, with the longitudinal edges <NUM> in abutting relationship to provide the butt joint <NUM>, and the jointing strip <NUM> applied to the inner side of the inner tube <NUM> to bridge the butt joint <NUM> and provide a continuous, fluid tight connection.

The assembly line <NUM> further comprises one or more supplies of material <NUM>, each in strip form and stored in roll form <NUM> on respective reels <NUM>. In the arrangement shown in <FIG> there are two reels <NUM>, but other numbers are possible. The material <NUM> provides the reinforcing fabric <NUM> incorporating reinforcement fibres featuring quadraxial fibre orientations. The material <NUM> is progressively unwound from the respective reel <NUM> and conveyed as strip <NUM> to a second assembly station <NUM> at which it is formed into the respective reinforcing fabric tubular layer <NUM> about the inner tube <NUM>. As described previously, each reinforcing fabric tubular layer <NUM> is assembled from the strip <NUM> of reinforcing fabric material having longitudinal edges <NUM> which are brought together in overlapping relationship to form the tubular layer. The overlapping edges <NUM> are secured together in to maintain the tubular formation. In this embodiment, the overlapping edges <NUM> are secured together by hot melt welding. The respective tubular layers <NUM> are disposed one about another and also disposed about the inner tube <NUM> as previously mentioned. Adjacent fabric layers <NUM> may be bonded together by a hot welding or chemical bonding process. The layers may comprise a bonding or forming material to more effectively hold the layers together. This may for example comprise chop strand mat, felt or veil to enhance the laminar shear between the layers of high strength quadraxial fabric and allow for easier release of air from the laminate.

The reinforcing fabric tubular layers <NUM> and the inner tube <NUM> provide a tube structure <NUM>. The tube structure <NUM> is conveyed to a third station <NUM> at which it is compressed between compression rollers <NUM> to extract air therefrom and force the resinous binder into direct contact with the reinforcement <NUM> and the adjacent layer <NUM> of resin absorbent material.

The tube structure <NUM> is then conveyed to a fourth station <NUM> at which it is impregnated with the resinous binder. In the illustrated arrangement, the tube structure <NUM> is passed through a resin bath <NUM>, circulating between rollers <NUM> to work the resinous binder into the felt <NUM> and the reinforcing baric <NUM>. At least some of the rollers <NUM> are driven to assist movement of the tube structure <NUM>.

The tube structure <NUM> is then conveyed to a fifth station <NUM> at which is engaged by doctor rollers <NUM> to remove excess resinous binder which can be collected in a catchment zone <NUM>.

The tube structure <NUM>, which is now impregnated with resinous binder, is then conveyed to a sixth station <NUM> at which the flexible outer casing <NUM> is installed to complete assembly of the tube structure <NUM>. Referring now to <FIG>, the assembled tube structure <NUM> is then conveyed to a seventh station <NUM> at which there is provided a compression device <NUM> comprising two endless drives <NUM> defining a passage <NUM> through which the tube structure <NUM> can pass. The assembled tube structure <NUM> is compressed in the passage <NUM> to define a choked zone <NUM> blocking the passage of air along the interior of the assembled tube structure. The two endless drives <NUM> incorporate opposing elements <NUM> such as cleats which cooperate to pinch the tube structure <NUM> at intervals and close it against the passage of air while allowing the impregnated resinous binder within the tube structure to pass through the choke passage <NUM>.

The compression device <NUM> also functions to apply traction to the assembled tube structure <NUM> to convey it along its path.

The section 100a of the assembled tube structure <NUM> beyond the device <NUM> is expanded by introduction of inflation fluid such as air into the interior thereof which defines the inflation cavity <NUM>. This causes the assembled tube structure <NUM> to expand both radially and axially, providing form and shape thereto. The expansion of the assembled tube structure <NUM> stretches the reinforcing fabric tubes <NUM> in all directions, serving to enhance hoop stress and axial stress bearing properties of the pipe <NUM>. In particular, the expansion serves to pre-stress fibres within the reinforcing fabric tubular layers <NUM> to enhance hoop stress bearing properties and also axially tensions the reinforcing fabric tubular layers to pre-stress fibres therein axially to enhance tensile load bearing properties of the pipe <NUM>.

The inflation fluid cannot escape from the inflation cavity <NUM> because the end is closed by the chocked zone <NUM> of the assembled tube structure <NUM> as previously explained. In other words, the compression device <NUM> functions as a valve to close the interior of the tubular structure <NUM> to prevent the escape of inflation fluid from the inflation cavity <NUM>. Further, the compression device <NUM> acts as a brake to hold the expansion loads imposed by the inflation of the inner tube <NUM> with an inflation fluid. Still further, the compression device <NUM> acts as a drive to start the process before the inflation begins.

As described previously, the flexible outer casing <NUM> serves to resist radial expansion of the reinforcing fabric tubular layers <NUM>, thereby causing the reinforcement <NUM> to be subjected to radial compression. The reinforcement <NUM> is confined in the space <NUM> between the expanding inner tube <NUM> and the flexible outer casing <NUM>. The radially expanding inner tube <NUM> operates in conjunction with the flexible outer casing <NUM> to cause the volume of the space <NUM> in which the reinforcement <NUM> is confined to progressively decrease. This forces the resinous binder within the reinforcement <NUM> to progressively rise within the space <NUM> displacing the air and ultimately fully impregnate the reinforcement <NUM>; that is, the layers <NUM> of reinforcing fabric <NUM> configured as the tubular layer <NUM> become fully "wetted-out". In this way, the resinous binder is forced through the layers <NUM> of reinforcing fabric <NUM> to distribute the resinous binder within the space <NUM> in a controlled and constrained manner.

It is a particular feature of the embodiment that the step of delivering resinous binder to the reinforcement <NUM>, and the step of fully wetting out the reinforcement <NUM> with the resinous binder, are separate and distinct actions. Specifically, resinous binder is introduced into the tubular structure <NUM> before the latter passes through the compression device <NUM>, and the resinous binder is caused to fully wet-out the reinforcement <NUM> following the introduction of inflation fluid into the inflation cavity <NUM> after the tubular structure <NUM> has passed through the compression device <NUM>.

Further, the progressive decrease in volume of the space <NUM> in which the reinforcement <NUM> is confined acts to positively expel air from within the space <NUM> which has the effect of enhancing impregnation of the resinous binder within the reinforcement <NUM>, as previously described.

At this stage the resinous binder has not cured and so the section 10a of the pipe <NUM> assembled in a mobile installation plant <NUM> is in a flexible condition. The uncured section 10a of the pipe <NUM> leaves the mobile installation plant <NUM> and is guided into the trench <NUM>, as previously mentioned. The pipe <NUM> may be cured within the trench <NUM> is any appropriate way. In the arrangement illustrated, the curing unit <NUM> progressively moves along the trench <NUM> to expose the recently laid section of the pipe to a curing action.

The assembled tube structure <NUM> is maintained in the inflated condition until such time as the resinous binder has hardened sufficiently to maintain the form and shape of the pipe <NUM>, after which the inflation fluid can be released from the inflation cavity <NUM>. The pipe <NUM> thus is formed, with the inner liner <NUM> defining the central flow passage within the pipe.

Because the tubular structure <NUM> is assembled progressively as described, it can be considered to have a commencement end <NUM> and a terminal end <NUM>. Typically, the inflation fluid such as air for the inner tube <NUM> is introduced through the commencement end <NUM> of the tubular structure <NUM>.

The commencement end <NUM> is shown in <FIG>. In the arrangement shown, the commencement end <NUM> is fitted with an end fitting <NUM> which comprises an end flange portion <NUM> and a spigot portion <NUM>. The end fitting <NUM> is installed onto the commencement end <NUM> immediately after it has emerged from the compression device <NUM>. The installation procedure involves insertion of the spigot portion <NUM> into the end of the tubular structure <NUM> and then clamping the commencement end <NUM> of to the spigot portion, typically by clamping means <NUM> such as straps or clamping rings. A collar (not shown) may be installed onto the commencement end <NUM> to give it form and shape to receive the spigot portion <NUM> of the end fitting <NUM>.

The flange portion <NUM> has provision <NUM> for communication with a fluid line for delivery of inflation fluid into the inner tube <NUM>. In the arrangement shown, the provision <NUM> includes a port <NUM> through which the delivery end section of the fluid line extends.

The terminal end <NUM> is shown in <FIG>. In the arrangement shown, the terminal end <NUM> is fitted with an end fitting <NUM> which closes the end. The end fitting <NUM> comprises a clamp <NUM> adapted to clampingly engage the tubular structure to sealingly close the terminal end <NUM>. The clamp <NUM> is adapted to be fitted onto the tubular structure <NUM> after the latter has been assembled but prior to it passing through the compression device <NUM>. The clamp <NUM> is adapted to pass along the passage <NUM> between the two endless drives <NUM> without interfering with the operation of the opposing elements <NUM> which cooperate to pinch the tube structure <NUM> at intervals along the passage <NUM>. The arrangement is such that the clamp <NUM> moves in timed relation with the two endless drives <NUM> so that the position of the clamp <NUM> along the passageway does not at any stage coincide with a point at which the tubular structure <NUM> is being pinched closed by cooperating opposing elements <NUM> of the two endless drives <NUM>. In this way, the clamp <NUM> can pass along the passage <NUM> while attached to the tubular structure <NUM> without interfering with the operation of the opposing elements <NUM>.

In circumstances there may be a requirement for the end section of the tubular structure <NUM> adjacent to the terminal end <NUM> to be of a specific cross-sectional profile. In such circumstances, a profile forming system <NUM> may be utilised, as shown in <FIG>. The profile forming system <NUM> comprises an external die <NUM> corresponding to the desired profile, the arrangement being that the end section of the tubular structure <NUM> adjacent to the terminal end <NUM> passes through the die <NUM> after having exited the compression device <NUM>. Internal pressure may be applied to the end section of the tubular structure <NUM> adjacent to the terminal end <NUM> in order to urge the end section outwardly into contact with the die <NUM> so that the desired profile can be applied to the end section. In the arrangement shown, the internal pressure is applied by way of an inflation assembly comprising inflatable bladder <NUM> and an associated flexible fluid delivery line <NUM> along which an inflation fluid can be delivered to inflate the bladder <NUM>. The inflatable bladder <NUM> is adapted to be inserted into the end section of the tubular structure <NUM> adjacent to the terminal end <NUM> prior to attachment of the clamp <NUM> to the terminal end <NUM>. The fluid delivery line <NUM> extends to the exterior of the tubular structure <NUM>, passing through a hole formed for the purpose in the tubular structure <NUM>. The inflatable bladder <NUM> is inserted into the end section of the tubular structure <NUM> in a deflated condition and passed through the compression device <NUM> in the deflated condition along with the flexible fluid delivery line <NUM>. The bladder <NUM> is inflated once the terminal end <NUM> has exited the compression device <NUM> but prior to the end section of the tubular structure <NUM> adjacent to the terminal end <NUM> being engaged by the die <NUM>. Inflation of the bladder <NUM> applies internal pressure to the end section of the tubular structure <NUM> adjacent to the terminal end <NUM>, thereby urging the end section outwardly into contact with the die <NUM> so that the desired profile can be applied to the end section.

It is a particular feature of the embodiment that the step of delivering resinous binder to the reinforcement <NUM> and the step of fully wetting out the reinforcement <NUM> with the resinous binder are separate and distinct actions. Specifically, the resinous binder is delivered to the reinforcement prior to passage of the tubular structure <NUM> through the compression device <NUM>. The inner tube <NUM> is inflated after the tubular structure <NUM> has passed through the compression device <NUM>. The inflation of the inner tube.

Referring now to <FIG> (which is presented in two parts, <FIG>), there is shown a pipe assembly line <NUM> for a pipe according to a second embodiment. The pipe assembly line <NUM> is similar in some respects to the pipe assembly line <NUM> used for the first embodiment and corresponding reference numerals are used to identify corresponding parts.

The second embodiment does not use a resin bath (as was the case in the first embodiment) for impregnating the tube structure <NUM> with the resinous binder. Rather, resinous binder is delivered to the assembled tube structure <NUM>.

Referring to <FIG>, a flexible outer casing <NUM> is installed around the assembled portion of the outer tube structure <NUM> to contain the resin binder, as will be described in more detail shortly. The outer casing <NUM> may be formed of any appropriate material, including for example polyethylene. The outer casing <NUM> may remain in place and ultimately form an integral part of the pipe, or it may be subsequently removed after having served its purpose. The material <NUM> from which the outer casing <NUM> is assembled is in strip form and stored on roll <NUM>. The material <NUM> is progressively unwound from the roll <NUM> and conveyed as a strip <NUM> to station <NUM> at which it is assembled into a tube <NUM> which provides the outer casing <NUM>. The tube <NUM> is assembled from the strip <NUM> by bring the longitudinal edges of the strip together in overlapping relationship to form the tube. The overlapping edges are secured together to maintain the tubular formation by any appropriate means such as stitching, welding or stapling.

Resinous binder is delivered into the flexible outer casing <NUM> through open end <NUM> thereof. The resinous binder is delivered along delivery line <NUM> which extends into the flexible outer casing <NUM> through the open end <NUM> and has an outlet end <NUM> disposed inwardly of the open end <NUM>. The delivery line <NUM> receives the resin from a reservoir <NUM> such as a supply tank. A pump <NUM> is provided for pumping the resin along the delivery line <NUM> from the reservoirs <NUM> to the outlet end <NUM>. Resinous binder is delivered into the flexible outer casing <NUM> tends to a pool <NUM> at the bottom of the tube <NUM> which provides the outer casing <NUM>.

The assembled tube structure <NUM> is compressed to define the choked zone <NUM> by the compression device <NUM> comprising the two endless drives <NUM>. The opposing elements <NUM> (such as cleats) on the two endless drives <NUM> cooperate to pinch the tube structure <NUM> and close it against the passage of air while allowing the impregnated resinous binder confined within the flexible outer casing <NUM> to pass through the choke passage <NUM>. The action of the cooperating elements <NUM> serves to pinch the assembled tube structure <NUM>, together with the outer casing <NUM>, at intervals. This causes the resinous binder, which is contained in the outer casing <NUM> and which is pooling at the bottom thereof, to collect in "puddles" in the sections of the outer casing <NUM> between each set of cooperating elements <NUM>, as shown in <FIG>.

As the assembled tube structure <NUM> progressively moves beyond the compression passage <NUM> defined by the device <NUM>, the pool <NUM> of resinous binder progressively rises in the annular space <NUM> between the inner liner <NUM> and the surrounding flexible outer casing <NUM>. This occurs because the expanding inner tube <NUM> progressively reduces the cross-sectional size of the annular space <NUM>, thereby causing the level of the pool <NUM> of resinous binder to progressively rise. This is depicted schematically in Figure 8B and <FIG> in which the surface of the pool <NUM> is identified by reference numeral <NUM>. The rising pool <NUM> of resinous binder within the annular space <NUM> progressively displaces air within the annular space. The outer casing <NUM> is constructed to facilitate the displacement of the air. This may involve provision of slow release air valves within the outer casing <NUM> at intervals along its length and non woven breather materials as part of the outer casing to facilitate air release from the pipe and along the length of the pipe. Additionally, or alternatively, vacuum points may be provided along the length of the tubular structure <NUM>.

The surface <NUM> of the progressively rising pool <NUM> forms a wave profile as depicted by line <NUM> in <FIG>.

The progressively rising pool <NUM> of resinous binder progressively wets the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>. Ultimately, the assembled tube structure <NUM> is fully impregnated with resinous binder.

Referring now to <FIG> there is shown part of a pipe assembly line <NUM> for a pipe according to a third embodiment. The pipe assembly line <NUM> is similar in some respects to the pipe assembly line <NUM> used for the second embodiment and corresponding reference numerals are used to identify corresponding parts.

The pipe assembly line <NUM> used for the second embodiment employed a flexible outer casing <NUM> installed around the assembled outer tube structure <NUM> to contain the resin binder and establish the progressively rising pool <NUM> of resinous binder for progressively wetting the assembled tube structure <NUM>.

The pipe assembly line <NUM> used for the third embodiment also employs an flexible outer casing <NUM> to contain the resin binder within the assembled outer tube structure <NUM> and establish the progressively rising pool <NUM> of resinous binder.

In this third embodiment, the flexible outer casing <NUM> is elastic for the purpose of enhancing control of the rate at which the progressively rising pool <NUM> of resinous binder progressively wets the assembled tube structure <NUM>. If, on the one hand, the pool <NUM> of resinous binder rises within the annular space <NUM> too rapidly, it may be that full wet-out of fibres in the assembled tube structure <NUM> is not achieved. If, on the other hand, the pool <NUM> of resinous binder rises within the annular space <NUM> too slowly, it may be that the resinous binder could commence to cure before full wet-out of fibres in the assembled tube structure <NUM> is achieved.

The elastic nature of the flexible outer casing <NUM> functions somewhat as a girdle for controlling external pressure exerted on the rising pool <NUM> of resinous binder. The elastic characteristic of the flexible outer casing <NUM> is selected to achieve the desired rate of wet-out. The elastic force exerted by the outer casing <NUM> provides some counterbalancing of the tension exerted by the inflating inner tube <NUM>.

In this embodiment, the tube structure <NUM> is compressed prior to installation of the elastically flexible outer casing <NUM> to complete assembly of the tube structure. In the arrangement shown, the compression of the tube structure <NUM> is achieved by passing it through a constriction <NUM> which is configured as a funnel.

Referring now to <FIG>, there is shown part of a pipe assembly line <NUM> for a pipe according to a fourth embodiment. The pipe assembly line <NUM> is similar in some respects to the pipe assembly line <NUM> used for the first embodiment and corresponding reference numerals are used to identify corresponding parts.

In this fourth embodiment, resinous binder is delivered to the various tubular layers <NUM> forming the reinforcement <NUM> during assembly of the tube structure <NUM>, rather than using a resin bath as was the case in the first embodiment. The tube structure <NUM> is progressively assembled by forming the reinforcing fabric tubular layers <NUM> about the inner tube <NUM>, with each tubular layer <NUM> being formed from respective strip <NUM> within the respective assembly system <NUM>, as shown in <FIG>. As each reinforcing fabric tubular layers <NUM> is assembled, a quantity of resinous binder is deposited into the interior of the tubular layer. Further, resinous binder may be sprayed, rolled or otherwise deposited onto the exterior of each tubular layer <NUM> after assembly thereof. In the arrangement shown in <FIG>, there is provided a delivery system <NUM> for depositing a slug of resinous binder into the interior of each tubular layer <NUM> as the respective strip <NUM> from which the tubular layers is formed moves through the transition from the first (flat) condition to the second (tubular) condition. In the arrangement shown in <FIG>, there is further provided a spray roller or other system <NUM> for spraying resinous binder onto the exterior of each tubular layer <NUM> after assembly thereof and prior to installation of the next tubular layer <NUM> therearound. With this arrangement, resinous binder is applied to the reinforcement <NUM> to fill most of the available volume while still allowing for movement of the resinous binder through the various tubular layers <NUM> to displace air from the lower region of the space <NUM> between the expanding inner tube <NUM> and the flexible outer casing <NUM> to the upper region of the space for subsequent venting.

In certain applications, there may be a need to facilitate a relatively rapid wet-out of the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>, rather than relying solely on progressively rising pool of resinous binder as described in previous embodiments. Such an application may, for example, relate to a pipeline installation in which the tubular structure <NUM> has an inclined section in which the resinous binder would migrate downwardly under the influence of gravity and not achieve a satisfactory wet-out the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>.

Referring now to <FIG>, <FIG> and <FIG>, there is shown part of a pipe assembly line <NUM> for a pipe according to a fifth embodiment. The pipe assembly line <NUM> is similar in some respects to the pipe assembly line <NUM> used for the first embodiment and corresponding reference numerals are used to identify corresponding parts.

In the arrangement shown the tubular structure <NUM> has a section <NUM> thereof which is steeply inclined to an extent that the resinous binder would migrate downwardly under the influence of gravity and not achieve a satisfactory wet-out of the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>.

The pipe assembly line <NUM> incorporates apparatus <NUM> to facilitate a relatively rapid wet-out of the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>.

The apparatus <NUM> comprises a plurality of roller arrays <NUM> disposed in spaced apart relation. Each roller array <NUM> comprises a plurality of rollers <NUM> arranged in an annular formation <NUM> defining a central circular space <NUM> through which the assembled tubular structure <NUM> can pass in a constricted condition.

Each roller array <NUM> comprises a central axle <NUM> configured as a ring upon which the respective rollers <NUM> are rotatably mounted. The rollers <NUM> are disposed angularly one with respect to another because of the ring configuration of the central axle <NUM>. The rollers <NUM> are also located close together. Because of the angular disposition and close positioning of the rollers <NUM>, the cylindrical rolling surfaces <NUM> of the rollers <NUM> cooperate at the inner side <NUM> of the annular array <NUM> to present a rolling contact surface <NUM>. Additionally, gaps <NUM> are formed between adjacent rollers <NUM> at the outer side <NUM> of the annular array <NUM>.

The roller arrays <NUM> are spaced axially one with respect to another, with spaces <NUM> defined between each two adjacent roller arrays.

The rings <NUM> are connected one to another to maintain the roller arrays <NUM> in position. In the arrangement shown, the axles <NUM> are connected together by connecting rods <NUM>. The presence of the gaps <NUM> between adjacent rollers <NUM> at the outer side <NUM> of the annular array <NUM> provides access for attachment of the connecting rods <NUM> to the axles <NUM>.

The apparatus <NUM> is adapted to be progressively moved along the assembled tubular structure <NUM> once the inner tube <NUM> has been inflated. In the arrangement shown in <FIG>, the apparatus <NUM> is positioned closely behind the device <NUM>.

Typically, the apparatus <NUM> is pulled along the assembling tubular structure <NUM> closely behind the compression device <NUM>.

The apparatus <NUM> may also be adapted to impart vibration to the tubular structure <NUM> to excite the resinous binder and enhance the wetting process.

With this arrangement, the tubular structure <NUM> is subjected to manipulation akin to a peristaltic pressing action when passing through the apparatus <NUM>, as depicted schematically in <FIG>. Specifically, the tubular structure <NUM> is constricted when passing through each central circular space <NUM> and then expands into the intervening spaces <NUM> under the influence of the inflation pressure within the inner tube <NUM>. This successive constriction and expansion manipulates the assembled tubular structure <NUM> to distribute the resinous binder and facilitate relatively rapid wet-out of the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>.

The preceding embodiments have been described with reference to construction of the pipe <NUM> which is progressively laid into a trench dug to receive the pipe.

The invention, including the pipe according to various embodiments which have been described and illustrated, is not limited a pipe which is and progressively laid into a trench dug to receive the pipe.

The pipe may be adapted to be laid on the ground, either directly or indirectly in a support arrangement such as suspension cradles disposed along its length. The pipe may also be supported in an elevated condition, such as for example in an installation in an industrial or chemical plant.

It is a particular feature of the pipe constructed in accordance with the invention that it can be constructed and then installed in position prior to curing of the resinous binder. In this way, the pipe may be in a flexible condition to facilitate it being guided into an installation position, with the pipe subsequently becoming rigid once in position upon curing of the resinous binder. With this arrangement, the pipe while in the flexible condition can be carried or otherwise conveyed into intended position and then installed prior to curing of the resinous binder.

Such an arrangement may be particularly advantageous in circumstances where a pipe in required to follow a path weaving around one or more obstructions or to otherwise follow a tortuous path. This can be a common occurrence for pipelines in industrial or chemical plant.

Referring now to <FIG>, there are shown sections of a pipe <NUM> according to a sixth embodiment. The pipe <NUM> according to the sixth embodiment incorporates one or more straight sections, one of which is depicted in <FIG> and identified by reference numeral <NUM>. The pipe <NUM> also incorporates one or more bend sections, one possible form of which is depicted in <FIG> and identified by reference numeral <NUM>, and another possible form of which is depicted in <FIG> and identified by reference numeral <NUM>.

The bend section <NUM> is configured as a gentle curve having an outer side <NUM> and an inner side <NUM>. The flexible outer casing <NUM> stretches on the outer side <NUM>, and contracts on the inner side <NUM>, to accommodate the curvature. The fibres within the reinforcement <NUM> are able to slip to also accommodate the curvature and spread the load.

The bend section <NUM> is configured as a tight curve having an outer side <NUM> and an inner side <NUM>. The bend section <NUM> is formed by removing sections of the assembled tubular structure <NUM> adjacent the inner side <NUM>, as shown in <FIG>, to create recessed formations <NUM> along the inner side to facilitate folding of the tubular structure to form the assembled tube structure <NUM>. In the arrangement shown, the removed sections are of a v-configuration such that each recessed formation <NUM> has two opposed inclined side edges <NUM> which abut in overlapping relation upon formation of the bend section <NUM>, as shown in <FIG>. The abutting edges <NUM> are sealing bonded together.

In certain applications there may be a need for the pipe <NUM>, or at least a section of the length thereof, to be flexible after construction of the pipe and curing of the resinous binder. Such an application may involve a pipe <NUM> which provides a flexible pipeline extending between an underwater location and a facility at the water surface.

A pipe <NUM> according to a seventh embodiment, which is shown in <FIG>, is constructed for use in such an application. The pipe <NUM> may, for example, provide a flexible riser between a subsea location and an offshore production rig. In this embodiment, the pipe <NUM> is assembled at an installation plant <NUM> aboard a marine vessel such as a ship or a barge and is laid into a body of water <NUM>, the surface of which is identified by reference numeral <NUM>.

The installation plant <NUM> assembles the tubular structure <NUM> is a manner similar to the previous embodiments. In this embodiment, the installation plant <NUM> employs apparatus <NUM> to facilitate a relatively rapid wet-out of the reinforcement <NUM> and the adjacent resin absorbent layer <NUM> of the inner liner <NUM>, as described previously in relation to the fifth embodiment. Additionally, the installation plant <NUM> has a support structure <NUM> to support the assembled tubular structure <NUM> as it is laid into the water <NUM>.

In this embodiment, the resinous binder used in the construction of the pipe <NUM> hardens but to a more flexible state (as opposed to hardening to a rigid state as was typically the case with previous embodiments). Specifically, the resinous binder remains flexible after curing in order to provide the pipe <NUM> with the required flexibility. Resinous binders and other binding agents suitable for such purpose are well known in composite construction techniques and examples of which include rubber modified polyester, rubber modified vinyl ester, rubber modified epoxy and polyurethane. In this embodiment, rubber modified vinyl ester is preferred as the resinous binder, as it has high shear strength and good interlaminar bonding but also affords the structure some ability to yield to accommodate movement.

Because of the need for the assembled tubular structure to descend in the water as the pipe <NUM> is laid, it may not be appropriate to use air as the inflation fluid for the inner liner <NUM> as air may provide undesirable buoyancy to the assembled tubular structure. In this embodiment, water is used as the inflation fluid. The water acting as the inflation fluid is sourced from the surrounding body of water <NUM>. In the arrangement shown, the bottom of the descending tubular structure (being its commencement end <NUM>) has a fitting <NUM> through which water can be pumped into the tubular structure <NUM> to inflate the inner liner <NUM>. The inflation fluid is introduced to establish and maintain a level above the water surface <NUM> in order to establish a pressure head for pressurising the water sufficiently to inflate the liner <NUM> as necessary. The level of the water within the tubular structure <NUM> above the water surface <NUM> is identified by reference numeral <NUM>.

In this embodiment, the compression apparatus <NUM> functions as a brake system to control the descent of the assembled tube structure <NUM> rather than applying traction for movement relative to the tubular structure as was the case with preceding embodiments.

The preceding embodiments have related to construction of pipes of a length to constitute a pipeline extending continuously between two distant locations. The invention need not, however, be limited to construction of such long pipes. Indeed the invention may have application in the production of other pipes, such as for example production of pipes which are adapted to be connected one to another to form a pipeline and as such are typically of shorter length for handling and installation as individual units. The production of such pipes may be accommodated within a production facility such as a factory.

The next embodiment, which is not shown in the drawings, is directed to such a pipe. The embodiment is similar in some respects to previous embodiments and corresponding terminology is thus adopted in the description of the embodiment.

In this embodiment, the inner portion is placed on a core (such as a mandrel) adapted for axial and radial expansion, and the outer portion is positioned about the inner portion to provide an assembled tube structure. The outer portion may be positioned about the inner portion before, during, or after placement of the inner portion on the core. The resinous binder impregnating the reinforcing fabric of the outer portion also impregnates the layer of felt on the inner liner to integrate the outer portion with the inner portion, as was the case with earlier embodiments. Prior to curing of the resinous binder, the core is expanded, thereby causing the assembled tube structure to expand both radially and axially, providing form and shape thereto. The expansion of the assembled tube structure stretches the reinforcement in the outer portion in all directions, serving to enhance hoop stress and axial stress bearing properties of the pipe <NUM>, as was the case with previous embodiments. The assembled tube structure <NUM> can then be removed from the core once the resinous binder has cured sufficiently, thereby providing the pipe.

In this embodiment, the core is used to expand the assembled tube structure both radially and axially, rather than an inflation fluid as was the case with the earlier embodiments.

In another arrangement, a relatively short pipe can be produced by producing a pipe in accordance with any one of the first, second or third embodiments and then cutting the pipe into sections each constituting a short pipe.

A pipe in accordance with any of the preceding embodiments may require a coupling at one or both of its ends. The coupling may be required to couple the pipe to other pipe in a pipeline, or to connect the pipe to another component (such as a filters, pump and valve). Further, it may be necessary to fit a coupling to a pipe at the start and end of a construction run in which the pipe is produced.

The couplings may be fitted to the pipe ends in any appropriate way. One way may involve a coupling device having an anchoring portion and a coupling portion, the anchoring portion being configured for attachment to the pipe and the coupling portion presenting a coupling part (such as a coupling flange) for attachment to a corresponding coupling part on another other pipe or component to which the pipe is to be coupled.

The anchoring portion may be adapted to be embedded in the adjacent end of the pipe <NUM>. The anchoring portion may be configured to key with the pipe. The keying may be achieved in any suitable way, such as by provision of formation which keys with the outer portion <NUM> of the pipe <NUM>. The formation may comprise lateral protrusions such as pins which key with the reinforcement <NUM> and the resinous binder impregnated therein. Alternatively, or additionally, the formation may comprise holes into which the reinforcement <NUM> and the resinous binder impregnated therein can locate to effect the keying action. Further, fibres in the reinforcement <NUM> can be wound about, inserted through, or otherwise attached to the formation to assist in securing the anchoring portion in position.

The preceding embodiments have related to construction of composite tubular structures configured as pipes.

The invention may have application to construction of any appropriate tubular structure, including for example, various tubular objects, elements, parts or other formations. The tubular structures may include structural elements such as shafts, beams and columns. The tubular structures may also include hollow structural sections of composite construction and also tubing.

Such tubular structures may be constructed in any appropriate way. A particularly convenient way of constructing such tubular structures may be similar to the process described in relation to an earlier embodiment involving a core (such as a mandrel) adapted for axial and radial expansion, and the outer portion is positioned about the inner portion to provide an assembled tube structure which constitutes the tubular structure.

The feature of applying vibration to the assembled tubular structure <NUM> to excite the resinous binder and enhance the wetting process may be used in relation to the construction of any of the elongate hollow structures according to the invention.

From the foregoing it is apparent that it is a particular feature of the embodiments described that the step of delivering resinous binder to the reinforcement <NUM>, and the step of fully wetting out the reinforcement <NUM> with the resinous binder, are separate and distinct actions. Specifically, resinous binder is introduced into the tubular structure <NUM> before the latter passes through the compression device <NUM>, and the resinous binder is caused to fully wet-out the reinforcement <NUM> following the introduction of inflation fluid into the inflation cavity <NUM> after the tubular structure <NUM> has passed through the compression device <NUM>.

It should be appreciated that the scope of the invention is not limited to the scope of the embodiments described.

Claim 1:
A method of constructing an elongate hollow structure (<NUM>) comprising a radially inner portion (<NUM>) and a radially outer portion (<NUM>), with the two portions merging together to provide an integrated tubular wall structure, the method comprising: providing the radially inner portion; assembling the radially outer portion about the radially inner portion; and radially expanding the inner portion; wherein the outer portion comprises an outer layer of fibre reinforced composite construction surrounded by a flexible outer casing (<NUM>), wherein the inner portion (<NUM>) is configured as an inner tube (<NUM>) that expands;
wherein there is a space between the inner tube (<NUM>) and the flexible outer casing (<NUM>);
wherein the outer layer of fibre reinforced composite construction comprises reinforcement and a binder;
wherein the flexible outer casing (<NUM>) serves to resist radial expansion of the reinforcement, thereby causing it to be subjected to radial compression; and
wherein the inner tube (<NUM>) operates in conjunction with the flexible outer casing (<NUM>) to cause the volume of the space between the inner tube and the flexible outer casing (<NUM>) to progressively decrease thereby causing the binder within the reinforcement (<NUM>) to be distributed through the space between the inner tube (<NUM>) and the flexible outer casing (<NUM>).