WO1995033953A2

WO1995033953A2 - Improvements relating to pipeline insulation and anticorrosion protection

Info

Publication number: WO1995033953A2
Application number: PCT/GB1995/001291
Authority: WO
Inventors: Thomas Christopher Arnott
Original assignee: Thomas Christopher Arnott
Priority date: 1994-06-04
Filing date: 1995-06-05
Publication date: 1995-12-14
Also published as: WO1995033953A3; GB9411218D0

Abstract

Improved pipe-coating materials (10) and methods, and improved coated pipes (30) formed thereby, in which a thermally insulating coating is formed from a strip of striated insulating material (10), such that individual bars (16) of said insulating material are isolated from one another and encapsulated by water-impermeable barriers in the finished coating, whereby water ingress into any one bar of said material will be restricted thereto, thereby allowing the use of materials, including open-celled foams, which would otherwise be vulnerable to water penetration. Also disclosed are means for improving impact resistance, improved methods of forming striated insulating materials and improved means for tensioning strip-like insulating materials as they are helically wrapped upon a pipe or the like.

Description

"Improvements Relating to Pipeline Insulation and Anti- corrosion Protection"

This invention relates to the coating of pipelines and the like, particularly subsea pipelines and risers, but also other forms of ducting and piping, for the purpose of providing relatively high level thermal insulation and anti-corrosion protection. The invention provides an improved coating method and an improved coated pipeline formed thereby.

Oil and gas are transported by steel pipes from subsea wells to fixed platforms or moored floating platforms. The oil and gas temperature at the wellhead is in the range of temperatures between 70°C and 130°C. The sea temperature at seabed level of the North Sea is in the range of temperatures of between 4°C and 8°C. Over a relatively short distance the oil and gas temperature is reduced to the surrounding sea temperature. This in turn increases oil viscosity and solidifies any waxes present, and in the case of gas will produce hydrate formation, drastically reducing flow and possibly causing blockage of the line.

Methods of overcoming these problems in the past have included:

a The injection of chemicals at the wellhead to prevent waxes forming. This method is expensive and not always effective, and is environmentally unacceptable as chemicals are entrained in the water which is present in oil wells and which is separated and dumped into the sea.

b The "pipe in a pipe" method consists of placing the oil pipe into a larger diameter pipe concentrically. The annulus formed is filled with a polyurethane foam. Polyurethane foam produces good insulating values but is low in mechanical strength and unable to resist seawater, therefore an outer steel pipe is required to provide resistance to hydrostatic forces and produce a waterproof barrier. This method of construction restricts the way a pipeline can be installed and is most suited to shallow water and short lengths of lines.

c Syntactic insulation is achieved by dispersing microspheres or insulating material particles into a matrix of elastomer plastic or epoxy. The introduction of microspheres or insulation particles into such a matrix greatly reduces the physical properties of the matrix material. The maximum amount normally considered acceptable is approximately 40% which improves the thermal insulation property of the matrix but in many instances not significantly enough to meet common insulation requirements.

d Laminated systems consist of a first layer of elastomer, normally extruded onto the pipe, a layer of insulation material, such as PVC foam or a similar closed cell foam able to resist hydrostatic pressures, followed by a further coat of elastomer. PVC foam has been applied in the past in the form of pre-formed, part-cylindrical shells and as helically wound strip of relatively thin material. The latter requires multiple layers to be applied. The assembled system is placed into an autoclave and cured under temperature and pressure to crosslink the elastomer and form a bond between the insulation material and the pipe. The laminated system produces a thermally efficient coating but has disadvantages. Spaces exist at the joints of the insulation material which are not filled by the elastomer. During the autoclaving, entrapped air can cause blistering of the outer cover of elastomer. If the outer coating, which is generally of low mechanical property, is breached during installation or on the sea bed, water floods the helical or circumferential joints and penetrates any striations in the insulation destroying thermal efficiency of the system.

A further proposal for applying PVC foam to form a laminated coating as discussed above is disclosed in FR-A-2538077 and O/89/12199> wherein a relatively thick, elongate strip of PVC foam is formed with transverse V-shaped grooves (or striations), allowing a sufficient thickness of material to be wrapped around the pipe in a single layer. The grooved surface of the strip faces the pipe, and the grooves close up as the strip is wrapped around the circumference of the pipe. The grooves may be formed at an angle to the lateral edges of the strip allowing continuous helical winding. This approach simplifies the application of the PVC foam to the pipe, but the need for autoclaving remains, as do the associated problems caused by air trapped in voids in the wrapped PVC. Grooved foam of this type will be referred to hereinafter as "striated foam".

WO-A-93/12370 provides an improvement of this last approach, with the object of providing a thermally efficient insulation system with good mechanical strength, and which obviates or mitigates the above mentioned disadvantages of prior methods and materials.

WO-A-93/12370 discloses a method of applying a thermally insulating anti-corrosion coating to a pipe, comprising the steps of: applying a first, inner elastomeric, anti-corrosion layer to the pipe; applying a layer of thermally insulating material over said first elastomeric layer in the form of striated, rigid, closed-cell, foamed material wrapped around said pipe; and applying a second, outer elastomeric, protective layer over said insulating layer; wherein a predetermined gap is formed between sections of said wrapped insulating material sufficient to ensure penetration by said second layer of elastomeric material into said gaps so as to encapsulate said insulating material.

As disclosed in WO-A-93/12370, this method is described as being intended primarily for use with closed cell foams, preferably PVC. This is because the individual bars of the striated foam remain connected at the bottoms of the striations. Accordingly, if an open cell foam were used, any water penetration into one bar under hydrostatic pressure would be able to spread to adjacent bars, ultimately flooding all of the bars of any continuous strip of striated foam. Accordingly, the method as disclosed therein would not generally be suitable for foamed materials which are not closed cell. Similar disadvantages may apply to foams which are nominally closed cell, but which cannot resist water penetration under hydrostatic pressures, such as polyurethane foam.

Owing to the high cost of PVC and similar closed cell foams having high resistance to water ingress, it would be desirable to employ less expensive foamed materials in a pipeline coating system having the same advantages as the method of WO-A-93/12370. It is an object of the present invention to provide an improved coating method, and improved coated products formed thereby, whereby the methods of WO-A-93/12370 may be applied to open cell foamed material without the risk of flooding of the insulation due to water ingress. This improvement is also applicable to closed cell materials, particularly those with poor resistance to hydrostatic pressures. The same approach may also be employed advantageously in producing pipe coatings having resistance to high temperatures. This involves the use of more expensive materials, but provides an improved high-temperature coating. The invention may likewise be employed to enable the use of other materials having properties which are desirable in a particular coating application but which are vulnerable to water ingress.

It is a further object of the present invention to provide additional improvements in the manufacture of striated insulating materials for pipeline coating. These improvements are equally applicable to closed and open cell foam materials, and to applicable non-foam materials .

In accordance with a first aspect of the present invention there is provided a method of applying a thermally insulating anti-corrosion coating to a pipe, comprising the steps of: applying a first, inner, substantially water-impermeable anti-corrosion layer to the pipe; applying a layer of thermally insulating material over said first water-impermeable layer in the form of striated, thermally insulating material wrapped around said pipe with a predetermined gap being formed between sections of said wrapped insulating material; and injecting substantially water-impermeable material into said gaps; said striated insulating material comprising a plurality of bars of thermally insulating material connected together in a continuous strip with grooves formed between adjacent bars; wherein the bars of said striated insulating material are substantially isolated from one another in said strip and substantially encapsulated by substantially water- impermeable material.

(It is noted here that no elastomeric or polymeric material is 100% water-impermeable. As used herein, "substantially water-impermeable" is intended to mean resistant to water ingress at typical hydrostatic pressures. )

In one embodiment of the invention, said bars are encapsulated by said injected water-impermeable material penetrating between adjacent bars to form a substantially water-impermeable barrier therebetween.

In an alternative embodiment of the invention, said bars are encapsulated at least partially by means of water-impermeable material applied to at least those surfaces of the bars which form the faces of the striations of the ^hermally insulating material, prior to the striated material being applied to the pipe.

Preferably, the outer surface of the striated material is covered by a second layer of substantially water- impermeable material. In one embodiment, said outer layer of water-impermeable material is applied after the insulating material has been applied to the pipe, most preferably at the same time. In an alternative embodiment, said striated insulating material is applied to a strip of substantially water-impermeable material prior to being applied to said pipe, said strip of water-impermeable material forming said second, outer layer.

Preferably, the bars of said striated insulating material are secured to a substrate so as to form a continuous strip prior to application to the pipe, said bars being substantially isolated from one another on said substrate. In one particularly preferred embodiment, said striated material comprises striated foam and said substrate is formed from a substantially water-impermeable material, which may provide an outer water-impermeable coating for the coated pipe.

Preferably also, said thermally insulating material is applied to said substrate in a solid layer of the required thickness, said striations being formed by cutting said solid layer, and said striations extending through said layer into said substrate so as to divide said layer into a plurality of mutually separate bars. Alternatively, the bars of said striated material are spaced apart from one another on the surface of said substrate.

Preferably, said substrate is formed from elastomer material or from chlorinated PVC foam.

Preferably, said striated foamed material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate material.

Preferably also, said first and second water- impermeable layers are formed from polyurethane or epoxy.

Preferably also, said first water-impermeable layer is formed from a thermally insulating material resistant to temperatures exceeding 95°C, suitably a syntactic material formed from polyurethane, vinyl esters or polyester resins, epoxy or polypropylene.

Preferably also, said insulating material is applied before cross-linking of said first water-impermeable layer is complete.

Preferably also, said injected elastomer or polymer material is applied by pouring or spraying, so as to fill said gaps and seal the ends of said striations.

Where required, a thin adhesive anti-corrosion layer is applied to said pipe prior to the application of said first water-impermeable layer.

Preferably also, said adhesive layer is epoxy or polyurethane adhesive.

Preferably also, said adhesive layer extends to within a first predetermined distance of the ends of said pipe and said water-impermeable layers extend to within a second predetermined distance of the ends of said pipe, said second distance being greater than said first distance.

Preferably also, an aggregate material is applied to the outer surface of said second water-impermeable layer prior to curing thereof.

Preferably also, said striated insulation is applied as a continuous, helically wound strip, said gap being formed at the helical interface between successive turns thereof.

Alternatively, said striated insulation is applied in discrete, annular sections, said gaps being formed between adjacent sections.

Preferably also, said first and (where applicable) second water-impermeable layers and said injected water-impermeable material are applied whilst the pipe is being rotated, by a traversing pour or traversing spray method in one or more passes.

Preferably also, said first water-impermeable layer is a composite layer comprising a first, innermost layer of water-impermeable material having a first tensile strength; a second, middle layer of water-impermeable material having a second tensile strength less than that of said innermost layer; and a third, outermost layer of water-impermeable material having a third tensile strength greater than that of said middle layer.

Alternatively, said first water-impermeable layer comprises a layer of material applied to the pipe in which, prior to the curing of said material, a continuous strip of open mesh or woven material is wound about the pipe or the like at a pitch angle such that successive turns of the fabric overlap one another, whereby a plurality of layers of the mesh or woven material are embedded in said water-impermeable layer.

The reinforced layer may be part of an inner anti- corrosion layer, in which case a first water- impermeable layer is preferably applied to the pipe or the like prior to said layer in which said open mesh or woven material is embedded.

Alternatively or additionally, open mesh or fabric material may similarly be incorporated in the outer water-impermeable layer, in which case a second water- impermeable layer is preferably applied on top of said layer in which the open mesh or woven material is embedded.

Preferably, said pitch angle and the width of the open mesh or woven material are selected such that the number of layers of fabric is in the range 2 to 10.

Preferably, said open mesh or woven material may be formed from glass fibre, metal or polymeric materials.

In accordance with a second aspect of the invention, there is provided a thermally insulated and corrosion protected pipe, said insulation and corrosion protection being provided by a coating applied in accordance with the above defined methods, said coating comprising a thermally insulating layer of at least semi-rigid, thermally insulating material encapsulated in substantially water-impermeable material, providing anti-corrosion and mechanical protection; said striated insulating material comprising a plurality of bars of thermally insulating material connected together in a continuous strip with grooves formed between adjacent bars; wherein the bars of said striated material are substantially isolated from one another in said strip and substantially encapsulated by water-impermeable material.

Preferably, said insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam or phenolic foam, or a high temperature thermally insulating material such as P.I.R. foam or a calcium silicate material, and said elastomeric or polymeric material is polyurethane or epoxy.

Preferably also, said first water-impermeable layer is formed from a thermally insulating material resistant to temperatures exceeding 95°C, suitably syntactic polyurethane or epoxy.

Preferably also, said pipe is further provided with an innermost, thin, anti-corrosion layer of adhesive intermediate the outer pipe surface and the inner surface of said first layer of water-impermeable material.

Preferably also said adhesive is epoxy or polyurethane adhesive. Preferably also, said adhesive layer terminates at a first distance from each end of each length of pipe, and said water-impermeable material terminates at a second distance from each end of each length of pipe, said second distance being greater than said first distance.

Preferably also, said first water-impermeable layer is a composite layer comprising a first, innermost layer of material having a first tensile strength; a second, middle layer of material having a second tensile strength less than that of said innermost layer; and a third, outermost layer of material having a third tensile strength greater than that of said middle layer.

Alternatively, said first water-impermeable layer comprises a layer of material applied to the pipe in which, prior to the curing of said water-impermeable material, a continuous strip of open mesh or woven material is wound about the pipe or the like at a pitch angle such that successive turns of the fabric overlap one another, whereby a plurality of layers of the mesh or woven material are embedded in said water- impermeable layer.

Alternatively or additionally, open mesh or fabric material may similarly be incorporated in the outer water-impermeable layer, in which case a second layer of water-impermeable material is preferably applied on top of said layer in which the open mesh or woven material is embedded.

Preferably also, said pipe is further provided with aggregate material embedded in the outer surface of said water-impermeable material.

In accordance with a third aspect of the invention there is provided a method of forming a strip of striated insulating material in which said insulating material is moulded directly onto the surface of a continuous elongate strip of substrate material to form a slab of material having a predetermined thickness.

Preferably, said substrate is fed piecewise through a mould, said strip of insulating material being formed in a plurality of sections.

In one embodiment, said insulating material is moulded as a solid, generally planar slab and said striations are formed by cutting means subsequent to the moulding of the slab.

Most preferably, said substrate is formed from an elastomer material.

Preferably also, said striations penetrate through said insulating material into said substrate such that individual bars of said striated material are isolated from one another on said substrate. Alternatively, said cutting means may be arranged such that the bars of the striated material are separated from one another on the surface of the substrate.

In an alternative embodiment, said striations are formed by said mould.

Again, said substrate preferably formed from an elastomer material.

Preferably, said mould is configured such that the bars of said insulating material are separated from one another on the surface of said substrate.

In each of the foregoing embodiments, the method may further include the step of applying a coating of water-impermeable material to at least one face of each of said striations.

Preferably also, said substrate is formed from an elastomer or from chlorinated PVC foam.

Preferably also, said insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate material.

In accordance with a fourth aspect of the invention, there is provided a striated foam insulating material for application to a pipeline, comprising an elongate substrate having a predetermined thickness of insulating material applied thereto, said insulating material being divided into a plurality of bars by a plurality of transverse grooves formed therein, wherein said bars are separated from one another by said grooves .

In one embodiment, said grooves penetrate through said insulating material into said substrate.

In an alternative embodiment, said grooves are configured such that said bars are separated from one another on the surface of the substrate.

Preferably, said substrate is formed from an elastomer material or from chlorinated PVC foam.

In accordance with a fifth aspect of the invention there is provided a method of applying an insulating material to a pipe in which said insulating material is formed as a continuous elongate strip and is wound onto said pipe in a helical manner, wherein an elongate tensioning tape is secured to said pipe and wound thereon along with and overlying said strip, tension being applied to said tape by tensioning means.

Preferably, said applied tension is variable.

Preferably also, said tensioning means comprises a reel from which said tape is unspooled as the strip and tape are wound about said pipe. Preferably also, said variable tension is provided by a variable braking force applied to said reel.

In accordance with a sixth aspect of the invention there is provided a thermally insulated pipe comprising at least a first pipe having a thermally insulating coating applied thereto enclosed within a second carrier pipe, wherein said thermally insulating coating comprises striated insulating material wrapped around said first pipe.

The carrier pipe may enclose a plurality of pipes having said striated insulating material applied thereto.

Preferably, said striated insulating material is applied with predetermined gaps between adjacent sections, and water-impermeable material is injected into said gaps.

Preferably also, a layer of adhesive, such as fusion bonded epoxy, is applied to said at least one pipe prior to the application of said striated insulating material.

In accordance with a seventh aspect of the present invention, there is provided a method of reinforcing a coated pipe or the like against impact, wherein a layer of water-impermeable material is applied to the pipe or the like and, prior to the curing of said water- impermeable material, a continuous strip of open mesh or woven metal or polymeric material is wound about the pipe or the like at a pitch angle such that successive turns of the open mesh or woven material overlap one another, whereby a plurality of layers of the open mesh or woven material are embedded in said water- impermeable material .

Alternatively or additionally, the reinforced layer may be part of an outer protective layer, in which case a second water-impermeable layer is preferably applied on top of said layer in which the open mesh or woven material is embedded.

In accordance with an eighth aspect of the invention, there is provided a coated pipe or the like having at least one reinforced layer applied thereto in accordance with the seventh aspect of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of strips of striated foam insulation material prepared for wrapping around a pipe; Fig. 1(a) is an enlarged detail of a portion of the strip of Fig.l; Fig. 2 is a perspective view of the reverse side of the strips of Fig.l, connected in a continuous strip by a backing material; Fig. 3 is a perspective view of a length of pipe in the process of being coated, showing the application of various coating layers; Fig. 4 is a sectional side view of a coated pipe in accordance with the invention; Fig. 4(a) is an enlarged, sectional detail of the pipe of Fig.4; Fig. 5 (A) is a schematic cross-section through a first embodiment of a pipe having a coating formed thereon in accordance with the invention; Fig. 5 (B) is a schematic cross-section through a second embodiment of a pipe having a coating formed thereon in accordance with the invention; Figs. 6(A) and 6(B) are, respectively, schematic plan and side views illustrating a method of forming striated insulating foam in accordance with a first embodiment of a third aspect of the invention, and Fig. 6(C) is a schematic side view of a portion of striated foam produced thereby; Figs. 7(A) and 7(B) are, respectively, schematic plan and side views illustrating a method of producing striated insulating foam in accordance with a second embodiment of the third aspect of the invention; Fig. 8 is a schematic side view of a preferred embodiment of a portion of striated foam produced in accordance with the method shown in Fig. 6; Fig. 9 is a schematic side view of a preferred embodiment of a portion of striated foam produced in accordance with the method shown in fig. 7; Fig. 10 is a schematic end view of a pipe a d a mandrel illustrating a method of applying an elastomer coating to the striations of a strip of striated foam as it is wound onto the pipe from the mandrel; Fig. 11 is a schematic plan view illustrating a method of applying foam insulating material to a pipe in accordance with a fourth aspect of the invention; Figs. 12(A) and 12(B) are schematic cross- sections through pipes enclosed within carrier pipes and having insulating coatings formed thereon in accordance with still a further aspect of the invention; Fig. 13 is a perspective view of an alternative embodiment of strips of striated insulation material prepared for wrapping around a pipe; Fig. 13(a) is an enlarged detail of a portion of the strip of Fig.13; and Fig. 14 is a partial schematic, cross- sectional view of a pipe coated with the material of Fig. 13.

Referring now to the drawings, Figs. 1 and 2 show the general configuration of striated thermally insulating material prepared for application to a pipe. In prior art pipe coating systems employing striated material of this general type, the material has been rigid, foamed PVC. The present invention provides improvements of such striated foam, its method of production and its method of application to a pipe. Certain of these improvements are applicable particularly to the use of other foamed materials, especially open cell foams or nominally closed cell foams with limited resistance to water penetration (most preferably high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam or phenolic foam.), and also to non-foamed insulating materials, which would otherwise be vulnerable to flooding in the event of damage to the protective, substantially water-impermeable, outer elastomer coating of the pipe.

The following discussion will refer primarily to foam insulating materials. However, it will be appreciated that the encapsulation of the insulating material, which is the basis of the main aspects of the invention, is also applicable to non-foam types of insulating materials which may be employed in pipe coatings in certain circumstances. Also, where reference is made to the use of elastomer materials for anti-corrosion layers, for encapsulation of the insulating material for outer, water-impermeable layers, and for impact-resistance layers, it will be understood that other suitable materials, including polymer materials, might be employed in place of or in addition to elastomer materials. Such alternatives are within the scope of the invention, and examples of embodiments employing such alternative materials are described herein with reference to Figs 13 and 14.

As seen in Figs 1 and 2, the insulation material comprises a plurality of flat blocks or sheets 10 having a plurality of parallel, V-shaped grooves or striations 14 formed in one major face thereof. The striations 14 form a series of spaced bars 16, such that the material can be wrapped around a pipe with the striated surface facing the surface of the pipe. In prior art coating systems employing striated foam, the bars 16 are interconnected at their bases by flexible webs 18 of the foam material.

Insulating material of this general type is disclosed in FR-A-2538077, WO/89/12199 and WO93/12370, and can be applied to pipes either in separate, annular sections extending around the circumference of the pipe (in which case the striations 14 extend at right angles to the lateral edges of the strips), or, preferably and as illustrated herein, as a continuous, helically wound strip (in which case the grooves 14 are disposed at an angle to the lateral edges corresponding to the helical pitch angle, such that the grooves 14 extend parallel to the long axis of the pipe when the material is wound thereon) . In the latter case a plurality of relatively short strips 10 of striated insulating material are connected end to end to form a continuous strip 20 by means of a continuous substrate 22 affixed to the other major face of the short strips 10 by any suitable means, such as a suitable adhesive (preferably epoxy or polyurethane based), as seen in Fig. 2. The present invention includes improved methods of forming continuous strips of striated insulating material, as will be described in greater detail below.

The continuous strip can be temporarily wound onto a cardboard mandrel (not shown) of the same diameter as the pipe, and dispensed directly onto the pipe therefrom. Alternatively, the strip might be reverse-wound onto a large diameter reel, with the striated surface facing outwards.

In the case of the discrete, annular sections, the bars 16 might be formed individually and connected by a substrate, as with the sections of the continuous strip.

The spacing of the striations 14, the angle of the V-section and (where applicable) the pitch angle are determined by the diameter and circumference of the pipe, and the width and thickness of the insulation material. Typically, the blocks 10 of material might be 200 mm to 1100 mm in width, 10 mm to 50 mm thick, and about 1000 mm in length (when applied in discrete, annular sections the length will obviously be determined by the circumference of the pipe such that the ends of each section can be mated) . The spacing of the striations 14 might suitably be l/36th of the pipe circumference, and the angle of the V-section is determined such that the striations will close upon wrapping of the material around the pipe.

Herein, the grooved material is referred to as "striated insulation", which in the examples given is applied as a continuous, helically wound strip. It will be appreciated, however, that the method and materials described are also applicable if the insulation is applied as discrete, annular sections.

The use of striated material allows an adequate thickness of insulation to be applied in a single layer. Multiple layers can still be applied if necessary or desirable; eg two 25 mm layers might be applied to give a total thickness of 50 mm. Where multiple layers are helically wrapped, it is preferred that alternate layers are wrapped in opposite directions. Where multiple layers are formed from discrete, annular sections, it is preferred that the sections of successive layers are displaced longitudinally, such that the sections of one layer bridge the junction between adjacent sections of the preceding layer.

Referring now to Figs 3 and 4, a composite thermal insulation and anti-corrosion coat is applied to a pipe 30 as follows: The pipe 30 is first coated with a thin layer of fusion bonded epoxy coating 32 and a first elastomeric anti- corrosion coating 34, after which the strip 20 of insulation material is helically wound onto the pipe. As the strip 20 winds around the pipe, the bars 16 locate longitudinally of the pipe and the gaps between the bars close providing a single layer of insulation of the desired thickness. The insulation is applied in such a manner that a space of between 5 and 8 mm is formed at the interface 38 between successive turns of the strip 20.

A second coating of elastomer 40 is applied by the pressure pour ("ribbon pour" or "rotational cast") method or by spraying, filling the helical interface 38 and sealing the ends of the grooves 14 and applying a protective coating of a minimum of 5 mm thickness, covering the outer surface of the wound strip 20. In an improvement described in greater detail below, the substrate 22 of the strip 20 may be formed from an elastomer of suitable thickness, which itself provides the protective outer layer. In this case it is only necessary for the elastomer applied following wrapping of the strip 20 to fill the gaps between successive turns of the strip.

The elastomeric material of the layers 34 and 40 is preferably polyurethane or epoxy.

Finally, an adhesive carrier tape 42 carrying aggregate 44 is spirally wound on the uncured outer protective coating 40 before cross linking is completed. The adhesive tape 42 is removed from the coating after the elastomer has fully cured, leaving the aggregate 44 embedded on the surface of the outer protective coating 40 .

As an alternative to forced pouring, the first and second elastomer (polyurethane) coats 34 and 40 may be applied by spraying. In either case, the coats are applied at first and second traversing pouring/spraying stations 46 and 48 as the pipe is rotated, in one or more passes.

Prior art coating methods typically use EPDM rubber for elastomeric layers, which requires vulcanisation in an autoclave. Such materials do not fill gaps adequately, and may require manual filling and/or gaps to be left as voids. Bond quality may also be poor.

Polyurethane, on the other hand, cures without heat, and the gel time can be controlled between about five and twenty minutes. The first layer 34 of polyurethane might suitably be 5 mm to 10 mm thick, the striated insulation being applied before gelling is complete to ensure good bedding in the inner elastomeric layers 40. Where the inner layer 40 is to be relatively thick, it might be applied in two or more coats, the first coat(s) having a short gel time and the final coat(s) having a longer gel time.

The gap formed at the helical interface 38 of the wound strip 20 allows complete penetration by the poured/sprayed polyurethane of the second layer 40, which can be directed into the gaps, to ensure complete encapsulation and sealing of the insulation material. The initial 400 to 500 micron coat of fusion bonded epoxy 32 (or, alternatively, polyurethane adhesive) extends to within 50 mm of the pipe ends, and the composite elastomeric coating encapsulating the insulation material extends to within 100 mm of the pipe ends. The extension of the epoxy coat 32, which provides a first anti-corrosion coat, beyond the other layers simplifies the completion of field joints whilst ensuring the continuity of anti-corrosion protection. Autoclaving and subsequent trimming of the elastomers would damage such a coating and would compromise the integrity of the anti-corrosion protection.

Where the pipe in use will not be subject to normal impact or loading forces (eg. where the coated pipe is enclosed by a carrier pipe), a single 3 or 4 mm layer of polyurethane adhesive may be applied serving both as the adhesive layer 32 and the first elastomeric layer 34.

The application of the aggregate 44 increases the coefficient of friction of the outer surface, which is desirable for allowing tension to be applied to the pipe during pipelaying operations and for providing a key for concrete or other weight-coatings which may be required.

The performance of the foamed thermal insulation material may be degraded by relatively high pipeline temperatures, particularly' with regard to compressive strength and creep resistance. In such cases the pipeline coating may be modified by applying a first coat of syntactic material, such as polyurethane, vinyl esters or polyester resins, epoxy or polypropylene, to a thickness of approximately 6 mm to 20 mm (preferably 6 mm to 15 mm, most preferably about 10 mm) , suitably by the ribbon pour (or "rotational cast") method, prior to the application of the adhesive coat and PVC foam. The syntactic material, providing a high temperature resistance matrix, serves as a preliminary insulation layer which reduces the approach temperature to the foam material to an acceptable level so as to avoid degradation thereof. The syntactic material also serves as an anti-corrosion layer, replacing the anti- corrosion layer previously referred to as being applied on top of the adhesive layer. Other examples of coatings having high temperature resistance will be described later with reference to Figs. 13 and 14.

Dependent upon the pipe diameter, wall thickness and the amount of insulation coating applied, the specific gravity of the pipe may be reduced to the point where the seabed stability of the pipeline is adversely affected. This situation may be remedied by the application of a conventional concrete coating over the insulation. However, the use of an inflexible concrete weight coating has well known disadvantages. The use of a flexible (eg. polyurethane-based) weight coating is preferable. Such coatings have been proposed in the past, but have not been widely used on the grounds of cost. In the context of the integrated coating system provided by the present invention, a polyurethane based weight coating applied as part of the complete coating process is more attractive economically.

As discussed above, prior proposals for the use of striated foam in pipe coatings have been primarily directed towards PVC foam, which is a closed cell material having high resistance to water penetration under hydrostatic pressure. Accordingly, any water ingress into PVC foam will remain localised and will have minimal adverse effect on the insulating properties of the coating. However, with other foam materials which are either open cell or which are nominally closed cell but which have poor resistance to water penetration under hydrostatic pressure, any water ingress is liable to spread throughout the foam, unless checked by a water-impermeable barrier. Where a pipe is coated using continuous, helically wound material, this may result in a serious reduction of the insulating properties of the foam over a complete pipe joint (typically 12 metres in length) .

The present invention provides improvements in striated foam materials which allow water ingress to be localised in foam materials of types which are liable to flooding in this manner, obviating or mitigating the abovementioned disadvantages. The invention also provides improved methods of forming strips of striated foam per se, which are also applicable to striated foam materials of existing types.

Figs. 6 and 7 illustrate two embodiments of improved methods of forming striated foam strips for wrapping around a pipeline.

Figs. 6(A) and 6(B) show a method in which a continuous slab 100 of foam insulation material is moulded directly onto a substrate 102. A continuous strip of the substrate 102 is fed from a roll 104, under guide/tension rollers 106 and through an elongate, hinged mould 108. The substrate 102 is fed piecewise through the mould 108, where the foam material is cast in sections directly on the substrate to form a continuous slab 100 on the substrate 102. The mould 108 is hinged and is opened to allow the substrate to be advanced after each section of the slab is cast.

In this embodiment, the foam is cast as a generally planar slab of the required thickness, and the slab is subsequently striated by any suitable means such as saws 110 located at any convenient position downstream of the mould 108. Fig. 6(C) is a side view of a portion of the slab showing a first unstriated section 112 and a second striated section 114. As is also shown, the adjacent sections of the moulded slab may be connected by a layer of elastomer 116. Alternatively, the adjacent sections may be connected to one another by means of a suitable adhesive, such as a fast cure cyanoacrylate adhesive. The use of such elastomer 116 or adhesives is also applicable when the strip is fabricated by assembling preformed slabs of foam onto a substrate (as in prior art systems). In either case, the elastomer/adhesive prevents spacing of the slab sections due to elongation of the substrate during wrapping of the material around a pipe.

Figs. 7(A) and 7(B) show an alternative embodiment similar to Fig. 6 except that the striations 117 in the foam slab 118 are formed by the mould 119 as the foam is moulded on the substrate 120. The substrate 120 is again fed piecewise through the mould 119 from a roll 122, via a tension/guide roller 124.

In both the embodiments of Figs. 6 and 7, moulding the foam directly onto the substrates obviates the need to assemble pre-moulded blocks of foam on a substrate as in previous striated foam systems.

In accordance with a further improvement, the substrate of the strip of striated foam may be formed from an elastomer material of suitable thickness, which forms the outer elastomer coat of the pipe when the striated foam is wrapped thereon. Accordingly, subsequent to wrapping the striated foam it is only necessary to apply elastomer to fill the gaps between wraps, rather than applying a complete outer coating as in previous systems, as described above. It is again preferred that the elastomer of the substrate is polyurethane, as is the elastomer 116 interposed between sections of the slab in Fig. 6(C) .

In order to limit the penetration of water into striated foam materials which are either open-celled or which are nominally closed-cell but which have poor resistance to water penetration, it is necessary firstly to isolate portions of the foam from one another a d secondly to form a water impermeable barrier between the isolated portions . Figs . 8 and 9 show two embodiments of striated foam materials which are suitable for this purpose.

In Fig. 8, the foam 130 is applied to a substrate 132, preferably of elastomer material, and the striations 134 are formed so as to penetrate through the foam 130 into the substrate 132. Accordingly, the individual bars of foam 130 defined by the striations are isolated from one another. In Fig. 9, the foam 140 is applied to the substrate 142, again preferably of elastomer, and the striations 144 formed such that the bars of foam 140 are separated from one another on the top surface of the substrate 142 and are thus isolated from one another.

The embodiment of Fig. 8 may be formed by cutting the striations using saws or the like as in the method of Fig. 6, or after assembly of slabs of foam onto the substrate as in prior systems. The embodiment of Fig. 9 may be formed by either of the methods of Figs. 6 and 7, or by the pre-moulding and subsequent assembly of individual bars onto the substrate.

The necessary substantially water-impermeable barrier may be formed between adjacent, isolated bars of the striated foam in a number of ways . A coating of elastomer 136, 146 may be applied to the faces of the striations as shown in Figs . 8 and 9 either as an additional process step during the production of the striated strip or subsequently. In Figs. 8 and 9 the elastomer coatings 136, 146 are shown as being applied to both of the opposed faces of each striation. However, it will be appreciated that the required barrier may be formed by applying the elastomer to only one face of each striation. The top surfaces of the bars of foam are sealed by the top surfaces being bedded in the initial elastomer coating applied to the pipe prior to wrapping of the striated foam, whilst the end surfaces of the bars are sealed by the elastomer introduced into the gaps between the wrapped foam after wrapping, so that the individual bars are completely encapsulated in isolation from one another by substantially water-impermeable elastomer. These surfaces could also be coated in the same way as the faces of the striations, if desired.

Accordingly, any water penetration into an individual bar will be contained within that bar.

Fig. 10 shows a method of applying the elastomer coating to the faces of the striations as the foam strip 150 is being wrapped onto a pipe 152 from a mandrel 154 (or reel) . The strip 150 is helically wrapped about the mandrel 154 and is transferred from the bottom thereof to the bottom of the pipe 152 by rotating the mandrel 154 and pipe 152 in the direction indicated. Elastomer may be applied to the surfaces of the striations 156 of the strip between the mandrel 154 and the pipe 152 by any suitable pouring or spraying means 158. The pouring/spraying means 158 would be mounted for movement relative to the length of the pipe and the width of the strip 150 in synchronism with the wrapping of the strip 150.

Fig. 11 illustrates a further improvement in the method of applying the strip of striated insulating material to a pipe by helical wrapping. This improvement is applicable to all types of striated insulating material.

As seen in Fig. 11, a strip 160 of striated foam material is being transferred from a mandrel 162 to a pipe 164, both of which are mounted for rotation about their longitudinal axes upon a traversing support carriage 165. It has been found in the past that it is difficult to maintain and control a sufficiently high degree of tension on the strip of striated foam during wrapping.

In accordance with the present improvement, a tensioning tape 166, suitably of synthetic fabric, is fed from a tensioning reel 168 located on the opposite side of the mandrel 162 from the pipe 164, over the top of the strip 160 and has its end secured to the pipe 164. The reel 168 remains stationary relative to the traversing carriage 164, and the tape 166 extends from the reel 168 at an angle to the mandrel 162 and pipe 164 equal to the helical pitch angle of the strip 160. Accordingly, the tape 166 overlies the strip 160 as it is transferred from the mandrel 162 and wrapped around the pipe 164, and any tension applied to the tape 166 by the braking force of the tensioning reel 168 is transferred to the strip 160 as it is wrapped.

This allows a higher tension to be applied than could normally be applied directly to the strip 160, and the tension can be controlled simply by means of varying the braking force applied to the tape 166 by the reel 168. This has been found to be a far superior method of applying and controlling tension on the foam strip than the previous practice of braking the mandrel 162.

Fig. 5(A) shows a sectional view of a completed pipe 60 coated in accordance with the present invention so as to limit water penetration, including a number of optional coating features. The pipe 60 has formed thereon a first thin layer of fusion bonded epoxy (FBE) 62, a first anti-corrosion layer of elastomeric material 64, a thermally insulating layer 66 formed of striated foam 66 as described above, and an outer protective layer of elastomeric material 68. The elastomeric layers 64 and 68 are preferably of polyurethane, and the whole is preferably formed in accordance with the methods previously described.

Optionally, the first elastomeric layer 64 may be a composite layer having inner, middle and outer layers 70, 72 and 74 respectively, in which the inner and outer layers 70, 74 are formed from a first elastomeric material having a first tensile strength and the middle layer 72 is formed from a second elastomeric material having a tensile strength less than that of the inner and outer layers 70, 74. Preferably, the inner and outer layers 70, 74 are formed from high performance polyurethane, typically having a tensile strength of 38 MPa, and the middle layer 72 is formed from standard polyurethane, typically having a tensile strength of approximately 16 MPa. Each of the layers 70, 72, 74 is suitably about 2 mm thick, giving a total thickness of 6 mm for the composite layer 64. The three layers 70, 72, 74 can be formed simultaneously in a single pass by a three-head applicator device.

The composite layer 64 significantly enhances the impact absorption characteristics of the coated pipe.

The sectional view shown in the drawing is of a schematic nature and it will be understood that the diameter of the pipe and relative proportions of the various layers have been altered for the sake of clarity.

Impact resistance may be further enhanced, particularly at elevated temperatures, by incorporating a layer 76 of relatively rigid mesh material (such as fibre glass or metal) in the central layer 72 of the first elastomeric layer 64.

It will be seen that the individual bars of the foam 166 are isolated from one another and completely encapsulated by the elastomer of the inner coating 64, the outer coating 68 (which may comprise the substrate of the wrapped strip as described above) and by elastomer 78 applied to the faces of the striations prior to or during wrapping of the strip. Similarly, adjacent wraps or turns of the strip are isolated from one another by the elastomer introduced into the predetermined gaps therebetween during or after wrapping. Fig. 5(B) shows a cross section through an alternative embodiment of a coated pipe 90, incorporating an alternative type of impact resistant coating. Again, the pipe incorporates a first anti-corrosion coating 91, typically 2mm to 4mm thick, of solid or syntactic elastomer (preferably applied by ribbon pouring), a second coating 92 of similar material, also typically 2mm to 4mm thick and preferably also applied by ribbon pour. The second coating 92 is followed immediately by a continuous helical wrap of open mesh or woven material, suitably of glass fibre, metal or polymeric material 94 which embeds itself in the uncured elastomer 92. The material 94 may be between 100mm and 500mm in width and is wrapped at a pitch angle such that successive turns of the material overlap one another.

Depending on the pitch and the width of the material 94, multiple successive turns may overlap to provide between two or more (preferably from 2 to 10) layers of material embedded in the elastomer of the second coating layer 92. These multiple layers are indicated schematically by a single dashed line 94 in Fig. 6. The embedded material 94 reinforces the elastomer to provide enhanced impact resistance.

A thermal insulation coating 93 of striated foam is applied on top of the reinforced inner elastomer layer 92. If required, an outer, protective elastomer coating can also be applied. As illustrated, this outer elastomer coating can be formed as a first layer 95, in which helically wrapped glass fibre, metal or polymeric open mesh or woven material 97 is embedded as described above, and a second layer 96. The provision of a reinforced outer coating 95, 96, 97 can be in addition to or instead of the reinforced inner coating 91, 92, 94. Polyurethane, epoxy and polyester materials, or the like, may be employed for such reinforced coatings . The use of metal or polymeric reinforcement materials as described can be incorporated in elastomeric coatings in a variety of coating schemes, including insulating materials other than striated foam and is not limited to the particular examples described herein.

The use of striated foam has hitherto been proposed as an alternative to conventional insulation/protection systems such as the "pipe-in-a-pipe" approach, using an outer elastomer coating to provide the outer protection afforded by the carrier pipe of pipe-in-a-pipe systems. However, the efficiency of application of striated foams means that their use may also be advantageous where operational considerations require the use of a carrier pipe.

In this case, where the striated foam would be enclosed by the outer pipe, the outer elastomer coating may be dispensed with. Where the striated material is applied with predetermined gaps, elastomer need only be injected into the gaps and smoothed off flush with the outer surface of the foam. The inner anti-corrosion coat of elastomer may also be dispensed with, the foam being bonded directly to the innermost adhesive layer using fusion bonded epoxy or the like. Such use of striated foam material is applicable to pipe-in-a-pipe systems whether the carrier pipe encloses a single pipe or a bundle of pipes, as shown schematically in Figs 12(A) and 12(B). In Fig 12(A), a carrier pipe 170 encloses a single inner pipe 172 coated with adhesive 176 and striated foam 174. In Fig 12(B), a carrier pipe 180 encloses a plurality of inner pipes 182, 188, 194 each coated with adhesive 1186, 192, 198 and striated foam 184, 190, 196.

Figs. 13 and 14 illustrate a further embodiment of striated insulating material and a pipe coating incorporating such material, which is particularly applicable where the coating is required to be resistant to high temperatures within the pipe.

Fig. 13 and 13(a) is similar to Fig. 1 and 1(a), and shows a strip 200 of insulating material in which bars 202 of a first insulating material having high temperature-resistance are laminated to a substrate 204, preferably formed from a second insulating material. In this example, the first insulating material is a semi-rigid calcium silicate material providing good insulating properties and high compressive strength, and the substrate is formed from chlorinated PVC (CPVC) foam. The first insulating material is water-permeable, while the substrate material is water-impermeable. As seen in Fig. 13(a), the striations 206 penetrate through the first insulating material and into the substrate 204, isolating the bars 202 from one another, as in previous embodiments using foamed insulating materials and elastomer substrates.

The calcium silicate material can withstand temperatures up to or exceeding 850°C and, in use, serves to reduce the interface temperature to the substrate material to less than 100°C. CPVC foam itself can withstand temperatures up to about 110°C, and is resistant to water ingress at depths up to 500 meters. The substrate 202 is formed by bonding slabs of CPVC foam end to end, and slabs of the calcium silicate material are laminated to the substrate 202 using a temperature resistant elastomer. The striations 206 are then cut through the first insulating material and into the surface of the substrate 204, as described in relation to previous embodiments .

Fig. 14 illustrates the use of the insulating strip 200 of Fig. 13 in coating a pipe 208.

A temperature-resistant anti-corrosion coating 210 is first applied to the outer surface of the pipe, having a typical thickness of 0.5 mm to 2 mm. This coating is suitably a two-component, solvent-free, modified synthetic polymer, which develops a good bond to a clean, prepared steel surface without the need for primers or bonding agents. The chemical cured polymer develops good physical properties, is highly resistant to water permeation and ingress, and produces no chemical reaction harmful to carbon or stainless steel.

The strip 200 is applied in substantially the same way as described in relation to previous embodiments, suitably at he same time as the polymer coating 210 is applied by rotational pouring. The top surfaces of the bars 202 are bedded in and bonded to the polymer coating 210, and the polymer material 212 is also forced into the striations and the gaps between adjacent helical wraps of the strip, so as to encapsulate the individual bars 202 of insulating material, as before. An outer coating 214 of high performance PU elastomer, or other suitable external coating material, is finally applied by rotational pouring or other suitable method to the external surface of the CPVC substrate 204. The encapsulating material 212 within the striations might alternatively be applied by any of the methods previously described in relation to other embodiments .

A coating of this type is intended for high temperature operation up to a continuous temperature of 160°C, which is able to accept thermal shock and which can operate without deterioration at temperatures below 20°C.

It will be understood that other materials having the required properties for any particular application may be substituted for those described. Other types of high temperature insulting materials may include, for example, PIR foams or syntactic materials. The polymer encapsulating material may also be a syntactic material. It will also be seen that the use of striated materials in such a manner that the individual bars of the material are isolated from one another and individually encapsulated by water-impermeable material may be employed to enable the use of a range of insulating materials which may otherwise be unsuitable owing to their vulnerability to water ingress.

As can be seen from the foregoing, the invention provides improved methods of forming and applying thermal insulation/anti-corrosion materials to a pipe, whereby the efficiency of production and application may be enhanced and a wider variety of materials may be employed; and improved, coated pipes formed by such methods.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims

1. A method of applying a thermally insulating anti- corrosion coating to a pipe, comprising the steps of: applying a first, inner, substantially water- impermeable anti-corrosion layer to the pipe; applying a layer of thermally insulating material over said first water-impermeable layer in the form of striated, thermally insulating material wrapped around said pipe with a predetermined gap being formed between sections of said wrapped insulating material; and injecting substantially water-impermeable material into said gaps; said striated insulating material comprising a plurality of bars of insulating material connected together in a continuous strip with grooves formed between adjacent bars; wherein the bars of said striated insulating material are substantially isolated from one another in said strip and substantially encapsulated by a substantially water-impermeable material.

2. A method as claimed in Claim 1, wherein said bars are encapsulated by said injected water-impermeable material penetrating between adjacent bars to form a substantially water-impermeable barrier therebetween.

3. A method as claimed in Claim 1, wherein said bars are encapsulated at least partially by means of water- impermeable material applied to at least those surfaces of the bars which form the faces of the striations of the insulating material, prior to the striated insulating material being applied to the pipe.

4. A method as claimed in Claim 1, wherein the outer surface of the striated insulating material is covered by a second layer of substantially water-impermeable material .

5. A method as claimed in Claim 4, wherein said second layer of substantially water-impermeable material is applied after the insulating material has been applied to the pipe.

6. A method as claimed in Claim 4, wherein said second layer of water-impermeable material is applied at the same time as said insulating material is applied to the pipe.

7. A method as claimed in Claim 4, wherein said striated insulating material is applied to a strip of substantially water-impermeable material prior to being applied to said pipe, said strip of water-impermeable material forming said second, outer layer.

8. A method as claimed in Claim 1, wherein the bars of said striated insulating material are secured to a substrate so as to form a continuous strip prior to application to the pipe, said bars being substantially isolated from one another on said substrate.

9. A method as claimed in Claim 8, wherein said substrate is formed from a substantially water- impermeable material, which may provide an outer water- impermeable coating for the coated pipe.

10. A method as claimed in Claim 8, wherein said insulating material is applied to said substrate in a solid layer of the required thickness, said striations being formed by cutting said solid layer, and said striations extending through said layer into said substrate so as to divide said layer into a plurality of mutually separate bars.

11. A method as claimed in Claim 8, wherein the bars of said striated insulating material are spaced apart from one another on the surface of said substrate.

12. A method as claimed in any one of Claims 8 to 11, wherein said substrate is formed from elastomer material.

13. A method as claimed in any one of Claims 8 to 11, wherein said substrate is formed from chlorinated PVC foam.

14. A method as claimed in any preceding Claim, wherein said striated insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate.

15. A method as claimed in any preceding Claim, wherein said first and second water-impermeable layers are formed from elastomeric or polymeric materials, including polyurethane or epoxy.

16. A method as claimed in any preceding Claim, wherein said first water-impermeable layer is formed from a thermally insulating material resistant to temperatures exceeding 95°C.

17. A method as claimed in Claim 16, wherein said first water-impermeable layer comprises a syntactic material formed from polyurethane, vinyl esters or polyester resins, epoxy or polypropylene.

18. A method as claimed in any preceding Claim, wherein said first water-impermeable layer comprises elastomeric material and said insulating material is applied before cross-linking of said elastomeric material is complete.

19. A method as claimed in any preceding Claim, wherein said injected water-impermeable material is applied by pouring or spraying, so as to fill said gaps and seal the ends of said striations.

20. A method as claimed in any preceding Claim, wherein a thin adhesive anti-corrosion layer is applied to said pipe prior to the application of said first water-impermeable layer.

21. A method as claimed in Claim 20, wherein said adhesive layer is epoxy or polyurethane adhesive.

22. A method as claimed in Claim 20 or Claim 21, wherein said adhesive layer extends to within a first predetermined distance of the ends of said pipe and said water-impermeable layers extend to within a second predetermined distance of the ends of said pipe, said second distance being greater than said first distance.

23. A method as claimed in any preceding Claim, wherein an aggregate material is applied to the outer surface of said second water-impermeable layer prior to curing thereof.

24. A method as claimed in any preceding Claim, wherein said striated insulation is applied as a continuous, helically wound strip, said gap being formed at the helical interface between successive turns thereof .

25. A method as claimed in any of Claims 1 to 23, wherein said striated insulation is applied in discrete, annular sections, said gaps being formed between adjacent sections.

26. A method as claimed in any preceding Claim, wherein said first and (where applicable) second water- impermeable layers and said injected water-impermeable material are applied whilst the pipe is being rotated, by a traversing pour or traversing spray method in one or more passes.

27. A method as claimed in any preceding Claim, wherein said first water-impermeable layer is a composite reinforced layer comprising a first, innermost layer of material having a first tensile strength; a second, middle layer of material having a second tensile strength less than that of said innermost layer; and a third, outermost layer of material having a third tensile strength greater than that of said middle layer.

28. A method as claimed in any one of Claims 1 to 26, wherein said first water-impermeable layer is a reinforced layer comprising a layer of material applied to the pipe in which, prior to the curing of said material, a continuous strip of open mesh or woven material is wound about the pipe or the like at a pitch angle such that successive turns of the fabric overlap one another, whereby a plurality of layers of the mesh or woven material are embedded in said water- impermeable layer.

29. A method as claimed in Claim 27 or Claim 28, wherein said reinforced layer comprises part of an inner anti-corrosion layer.

30. A method as claimed in Claim 29, wherein a first water-impermeable layer is applied to the pipe or the like prior to said reinforced layer.

31. A method as claimed in any preceding Claim, wherein open mesh or fabric material is incorporated in the outer water-impermeable layer.

32. A method as claimed in Claim 31, wherein a further layer of substantially water-impermeable material is applied on top of said layer in which the open mesh or woven material is embedded.

33. A method as claimed in any one of Claims 28 to 32, wherein said pitch angle and the width of the open mesh or woven material are selected such that the number of layers of fabric is in the range 2 to 10.

34. A method as claimed in any one of Claims 28 to 33, wherein said open mesh or woven material is formed from glass fibre, metal or polymeric materials.

35. A thermally insulated and corrosion protected pipe, said insulation and corrosion protection being provided by a coating applied in accordance with the method of any one of Claims 1 to 34, said coating comprising a thermally insulating layer of at least semi-rigid, thermally insulating material encapsulated in substantially water-impermeable material, providing anti-corrosion and mechanical protection; said striated insulating material comprising a plurality of bars of insulating material connected togeti. r in a continuous strip with grooves formed between adjacent bars; wherein the bars of said striated insulating material are substantially isolated from one another in said strip and substantially encapsulated by water- impermeable material.

36. A thermally insulated and corrosion protected pipe as claimed in Claim 35, wherein said insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate material.

37. A thermally insulated and corrosion protected pipe as claimed in Claim 35 or Claim 36, wherein said water- impermeable material is an elastomeric or polymeric material, including polyurethane or epoxy.

38. A thermally insulated and corrosion protected pipe as claimed in Claim 35 or 36, wherein said first water- impermeable layer is formed from a thermally insulating material resistant to temperatures exceeding 95°C,

39. A method as claimed in Claim 38, wherein said first water-impermeable layer comprises a syntactic material formed from polyurethane, vinyl esters or polyester resins, epoxy or polypropylene.

40. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 35 to 38, wherein said pipe is further provided with an innermost, thin, anti- corrosion layer of adhesive intermediate the outer pipe surface and the inner surface of said first water- impermeable layer.

41. A thermally insulated and corrosion protected pipe as claimed in Claim 40, wherein said adhesive is epoxy or polyurethane adhesive.

42. A thermally insulated and corrosion protected pipe as claimed in Claim 40 or 41, wherein said adhesive layer terminates at a first distance from each end of each length of pipe, and said water-impermeable material terminates at a second distance from each end of each length of pipe, said second distance being greater than said first distance.

43. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 35 to 42, wherein said first water-impermeable layer is a composite layer comprising a first, innermost layer of material having a first tensile strength; a second, middle layer of material having a second tensile strength less than that of said innermost layer; and a third, outermost layer of material having a third tensile strength greater than that of said middle layer.

44. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 35 to 42, wherein said first water-impermeable layer comprises a reinforced layer of material applied to the pipe in which, prior to the curing of said water-impermeable layer, a continuous strip of open mesh or woven material is wound about the pipe or the like at a pitch angle such that successive turns of the fabric overlap one another, whereby a plurality of layers of the mesh or woven material are embedded in said water-impermeable layer.

45. A thermally insulated and corrosion protected pipe as claimed in Claim 44, wherein said reinforced layer is part of an inner anti-corrosion layer.

46. A thermally insulated and corrosion protected pipe as claimed in Claim 45, wherein a first water- impermeable layer is applied to the pipe or the like prior to said layer in which said open mesh or woven material is embedded.

47. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 35 to 46, wherein open mesh or fabric material is incorporated in the outer water-impermeable layer.

48. A thermally insulated and corrosion protected pipe as claimed in Claim 47, wherein a further layer of water-impermeable material is applied on top of said layer in which the open mesh or woven material is embedded.

49. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 44 to 48, wherein said pitch angle and the width of the open mesh or woven material are selected such that the number of layers of fabric is in the range 2 to 10.

50. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 44 to 49, wherein said open mesh or woven material is formed from glass fibre, metal or polymeric materials.

51. A thermally insulated and corrosion protected pipe as claimed in any one of Claims 35 to 50, wherein said pipe is further provided with aggregate material embedded in the outer surface of said water-impermeable material .

52. A method of forming a strip of striated foam insulating material in which said thermally insulating material is moulded directly onto the surface of a continuous elongate strip of substrate material to form a slab having a predetermined thickness.

53. A method as claimed in Claim 52, wherein said substrate is fed piecewise through a mould, said strip of insulating material being formed in a plurality of sections .

54. A method as claimed in Claim 52 or Claim 53, wherein said insulating-material is moulded as a solid, generally planar slab and said striations are formed by cutting means subsequent to the moulding of the slab.

55. A method as claimed in any one of Claims 52 to 54, wherein said substrate is formed from an elastomer material.

56. A method as claimed in any one of Claims 52 to 55, wherein said striations penetrate through said insulating material into said substrate such that individual bars of said striated material are isolated from one another on said substrate.

57. A method as claimed in any one of Claims 52 to 55, wherein said cutting means is arranged such that the bars of the striated material are separated from one another on the surface of the substrate.

58. A method as claimed in Claim 52 or 53, wherein said striations are formed by said mould.

59. A method as claimed in Claim 58, wherein said mould is configured such that the bars of said insulating material are separated from one another on the surface of said substrate.

60. A method as claimed in any one of Claims 52 to 59, wherein the method further includes the step of applying a coating of water-impermeable material to at least one face of each of said striations.

61. A method as claimed in any one of Claims 52 to 60, wherein said substrate is formed from an elastomer.

62. A method as claimed in any one of Claims 52 to 60, wherein said substrate is formed from chlorinated PVC foam.

63. A method as claimed in any one of Claims 52 to 60, wherein said insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate material.

64. A striated insulating material for application to a pipeline, comprising an elongate substrate having a predetermined thickness of insulating material applied thereto, said insulating material being divided into a plurality of bars by a plurality of transverse grooves formed therein, and wherein said bars are separated from one another by said grooves.

65. A striated insulating material as claimed in Claim 64, wherein said grooves penetrate through said foam material into said substrate.

66. A striated insulating material as claimed in Claim 64, wherein said grooves are configured such that said bars are separated from one another on the surface of the substrate.

67. A striated insulating material as claimed in any one of Claims 64 to 66, wherein said substrate is formed from an elastomer material.

68. A striate insulating material as claimed in any one of Claims 64 to 66, wherein said substrate is formed from chlorinated PVC foam.

69. A striated foam insulating material as claimed in any one of Claims 64 to 68, wherein said insulating material is high density polyurethane (P.U.) foam, polyisocyanurate (P.I.R.) foam, phenolic foam or calcium silicate material.

70. A method of applying an insulating material to a pipe in which said insulating material is formed as a continuous elongate strip and is wound onto said pipe in a helical manner, wherein an elongate tensioning tape is secured to said pipe and wound thereon along with and overlying said strip, tension being applied to said tape by tensioning means.

71. A method as claimed in Claim 70, wherein said applied tension is variable.

72. A method as claimed in Claim 71, wherein said tensioning means comprises a reel from which said tape is unspooled as the strip and tape are wound about said pipe.

73. A method as claimed in Claim 72, wherein Preferably also, said variable tension is provided by a variable braking force applied to said reel.

74. A thermally insulated pipe comprising at least a first pipe having a thermally insulating coating applied thereto enclosed within a second carrier pipe, wherein said thermally insulating coating comprises striated insulating material wrapped around said first pipe.

75. A thermally insulated pipe as claimed in Claim 74, wherein the carrier pipe encloses a plurality of pipes having said striated insulating material applied thereto.

76. A thermally insulated pipe as claimed in Claim 74 or Claim 75, wherein said striated insulating material is applied with predetermined gaps between adjacent sections, and water-impermeable material is injected into said gaps.

77. A thermally insulated pipe as claimed in Claim 74, Claim 75 or Claim 76, wherein a layer of adhesive, such as fusion bonded epoxy, is applied to said at least one pipe prior to the application of said striated insulating material.

78. A method of reinforcing a coated pipe or the like against impact, wherein a layer of water-impermeable material is applied to the pipe or the like and, prior to the curing of said water-impermeable material, a continuous strip of open mesh or woven metal or polymeric material is wound about the pipe or the like at a pitch angle such that successive turns of the open mesh or woven material overlap one another, whereby a plurality of layers of the open mesh or woven material are embedded in said water-impermeable material.

79. A method as claimed in Claim 78, wherein said reinforced layer is be part of an inner anti-corrosion layer.

80. A method as claimed in Claim 79, wherein a first water-impermeable layer is applied to the pipe or the like prior to said layer in which said open mesh or woven material is embedded.

81. A method as claimed in any one of Claims 78 to 80, wherein, alternatively or additionally, the reinforced layer is part of an outer protective layer.

82. A method as claimed in Claim 81, wherein a second layer of water-impermeable material is applied on top of said layer in which the open mesh or woven material is embedded.

83. A method as claimed in any one of Claims 78 to 82, wherein said pitch angle and the width of the open mesh or woven material are selected such that the number of layers of fabric is in the range 2 to 10.

84. A coated pipe or the like having at least one reinforced layer applied thereto in accordance with the method of any one of Claims 78 to 83.