A kit and method for protecting pipework

Abstract

A method for protecting a section of pipework comprises (i) coating the section of pipework with a layer of viscoelastic material 215 to form a coated section of pipework; (ii) providing a substantial

Description

The present invention relates to a method for protecting a section of pipework, generally for protecting pipework from corrosion. In particular, the method comprises coating the section of pipework with one or more layers of a viscoelastic material followed by a jacket. The present invention also relates to a kit suitable for use in the method for protecting a section of pipework, the kit comprising a viscoelastic formulation for coating the section of pipework, and the jacket. Coated pipelines are well-known for the transmission and distribution of liquids and gases. Pipelines typically comprise metallic pipe elements. Pipe elements are typically cylindrical, several metres in length, and can be assembled contiguously, jointed, and welded to form a continuous pipeline. In buried situations, metallic pipe elements are vulnerable to corrosion. To mitigate metallic corrosion, a corrosion protection layer is commonly applied to the external surface of the pipe elements. The corrosion protection layer on the pipeline is known as the “mainline coating” or the “factory-applied coating” or the “parent coating”. To facilitate the jointing and welding of the pipe, and to avoid potential heat damage to the corrosion protection layer caused by heat from the welding process, the corrosion protection layer must be absent from the area of the weld and the area adjacent to the weld. The corrosion protection layer is either substantially removed from this area prior to jointing and welding, or else it is not applied to this area in the first place. This area is known as the “cutback” and typically extends around the full circumference of the pipe and typically at least 150 mm either side of the weld. The edge of the corrosion protection layer adjacent to the cutback may be chamfered or otherwise treated to facilitate subsequent coating processes. The contiguous pipe elements formed by the jointing and welding process are protected by a corrosion protection layer, along the major portion of the pipe element. However, in the area of the cutback, where the corrosion protection layer is not present, there is an absence of protection and, after completing the jointing and welding process, application of an additional corrosion protection layer to this area is required to effect corrosion protection to the entire length of the pipeline. In some cases, for example land-based pipeline construction, the jointing and welding of the pipe is typically carried out in-the-field. A joint formed in-the-field is known as a “field-joint”. The additional corrosion protection layer applied to the “cutback”, and the adjacent areas, is known as a “field-joint coating” (F-JC). To ensure continuity between the F-JC and the mainline coating, the F-JC is typically overlapped onto the mainline coating and extended onto the mainline coating about 50 mm to 100 mm either side of the cutback area. Pipework is understood to include pipe, pipe fittings (which includes irregular pipe sections, such as flanges, valves, elbows, tee-joints, etc.) and joins between pipe elements known in the art as fieldjoints. It is generally known in the art to use protective materials to protect pipework against corrosion, abrasion, and other potentially damaging actions. Such protective materials are known as coating systems and comprise for example liquid-applied coatings, heat shrinkable materials, tapes, and wraps. WO2019 / 229429 relates to an adhesive protective film for protecting pipework, the film comprising: a protection layer; a release layer; and an adhesive between the protection and release layer. Whilst such materials are effective, and well known in the art, they are all potentially vulnerable to mechanical damage which can be initiated by accidental impact with mechanical equipment used in pipelining, or by interaction with soil and rocks during construction and service. Such damage occurs commonly, and such coatings are typically employed in conjunction with a separate mechanically protective outer layer to reduce the risk and mitigate the harmful effects of damage from sharp stones and rocks and the like. Different types of mechanically protective outer layers can be used. Hot-applied “torch-on” products, often based on bitumen, were originally used. More recently, cold-applied filmic wraps, often based on polyethylene film or flexible PVC film, have been used. This latter type of wrap is typically stretched around the pipe helically and thereby exerts pressure, or so-called “hoop tension” on the protective coating. One advantage of this arrangement is that if the coating is mechanically punctured, there is a tendency for the underlying coating to flow into the area of damage and the system is, to some extent, self-healing. This cold flow self-healing effect is further enhanced by the inclusion of a semi-solid primer or paste applied to the pipe surface, which likewise flows into the area of damage. This combination of a primer, a tape, and a separate outer wrap is well known in the art and has been successfully employed for the protection of buried pipes in stable or normal soil conditions for many decades. By way of example, WO2005 / 005528 relates to a composition for the protection of a shaped article made from or consisting essentially of one or more metals, metal compositions or alloys against corrosion, said composition comprising a polyisobutene, a filler material and an anti-oxidant composition. WO2017 / 137769 relates to a corrosion-protection tape for wrapping a pipe joint, the tape comprising a shear-resistant layer for contacting the pipe joint and a self-healing layer, wherein the shear-resistant layer is separated from the self-healing layer by a barrier membrane. There is also disclosed a kit comprising the tape and a flexible wrapping tape comprising polyethylene or PVC. WO2020 / 229600 relates to an anti-corrosive wrapping suitable for wrapping metal pipes, metal pipe fittings and other metalwork and metal components. The disclosure provides an anti-corrosive wrapping in which the outerwrap is easily adhered to the innerwrap and which is easy to hand apply and so does not need the use of a wrapping machine also does not require application of a primer to the pipeline prior to wrapping. The glass fibre outerwrap is impregnated with and thereby carries an adhesive which penetrates the glass fibres of the innerwrap allowing the outerwrap to be adhered to the innerwrap. By “self-healing” it is meant that the protective material has rheological characteristics that allow it to flow under pressure to fill any points of damage in the coating and preferably amalgamate to re-form a continuous protective layer. At the same time the protective material must have sufficient resistance-to-flow to avoid leakage and uncontrolled flow of protective material. For best protective effect, the protective material must remain evenly distributed around the pipe surface. Although many types of coating can exhibit “self-healing” properties (for example petrolatum-based tapes), it is the class of coatings known as “viscoelastics" which are most noted in this regard. Viscoelastics are well known in the art and are taught for example in US9133372. Advantageously formulating viscoelastics to provide the desired rheological characteristics for “self-healing” is well known in the art. Self-healing characteristics are defined for example under ISO 21809-3:2016 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems — Part 3: Field joint coatings. However, all such viscoelastic coatings have the disadvantage that it is necessary to control the pressure exerted on the viscoelastic material by application of an outer layer. In the absence of sufficient pressure, exerted by the outer layer, the viscoelastic material will not flow or will not flow to a sufficient extent. Such reduced flow or absence of flow negates the “self-healing” characteristic or renders the rate of self-healing too slow to be of practical use. Therefore, to achieve “self-healing” it is essential to have a protective material with suitable rheological characteristics combined with a means of exerting sufficient pressure. It will be readily appreciated that neither of these features in isolation is sufficient and that it is the combination of these features which is essential for the proper functioning of the system. To provide the necessary pressure an outer layer is used in conjunction with a viscoelastic coating. The outer layer is typically a self-adhesive polymer-based tape for example based on plasticised PVC or on polyethylene. Such tapes are typically wrapped under tension by hand or by using manually powered wrapping tools. Such tapes are capable of exerting sufficient pressure to affect the self-healing characteristic in the underlying viscoelastic coating. However, such systems have the disadvantage that the pressure is not readily measured, monitored, or controlled. A further disadvantage, in the case of manual application, is that the force exerted by the operator when wrapping the outer layer and hence the pressure exerted on the underlying viscoelastic coating is subject to variation based on the strength, skill and fatigue of the operator. A yet further disadvantage is that such systems, if mis-applied, are not readily amenable to correction or adjustment. A yet further disadvantage is that such systems are necessarily limited in their speed of application by the physical strength and endurance of the operator. A yet further disadvantage is that the outer wrap, when used on a pipe which is subjected to elevated temperatures, is liable to soften, melt, deform, and lose integrity which negates the intended function. Therefore, there is a need for an improved system which reduces or eliminates variability in pressure, tolerates high operational temperatures, ensures conditions for self-healing are achieved, conveniently allows correction or adjustment, can be rapidly applied, and provides measurable and objective confirmation that sufficient pressure has been applied. It is therefore an object of the present invention to provide a kit and method of use thereof which overcome, or substantially reduce, the aforementioned problems in the prior art and delivers one or more or all of these of these improvements, or at least provides a commercially useful alternative thereto. The present invention is defined in the claims appended hereto. Thus, in a first aspect of the present invention, there is provided a method for protecting a section of pipework, the method comprising: (i) coating the section of pipework with a layer of viscoelastic material to form a coated section of pipework; (ii) providing a substantially cylindrical jacket around the coated section of pipework; and (iii) mechanically tensioning the substantially cylindrical jacket to exert inward radial pressure on the layer of viscoelastic material. The present disclosure will now be described further. In the following passages, different aspects / embodiments of the disclosure are defined in more detail. Each aspect / embodiment so defined may be combined with any other aspect / embodiment or aspects / embodiments unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. A further aspect of the present invention provides a kit of parts suitable for use in the method, the kit comprising a viscoelastic composition formulated for coating the section of pipework, and a jacket sized to fit substantially once around the section of pipework once coated with the viscoelastic composition, and in some preferred embodiments, a tape (as described herein comprising a viscoelastic layer and an interleave layer) and a jacket. The kit and method may collectively be referred to herein as a system. The present invention may be applied to, but is not limited to, pipes, pipelines, field-joints between pipe elements, other joints between pipe elements, pipe barrels, pipe fittings and appurtenances. The system is particularly well suited to offshore laybarge application to pipes operated at elevated temperatures, for example from 80 °C to 120 °C. The pipe elements may be formed of, but are not limited to, carbon steel, metal alloy, stainless-steel, ductile iron, cast iron, and low alloy steel. The system may be employed in different situations including, but not limited to, buried situations, aboveground, within ducts and in aquatic environments. Aquatic environments include the oceanic, marine, coastal, littoral, benthic, estuarine, lacustrine, paludal and riverine environments. The system may be employed on pipework that is installed by any means including, but not limited to, entrenchment, lay-barge, s-laying, j-laying, tow-out, flotation, push-rack, thrust, bore and pipe-in-pipe. The present invention relates to a method for protecting a section of pipework, in particular for providing corrosion protection of metal pipework, such as an exposed metal pipe element or fieldjoint. Corrosion is a natural process which is the gradual destruction of metals to their oxides by chemical reaction with their environment. Thus, the method and use of the tape serves to reduce or avoid contact between the metal portions of joints or pipes and their environment. By substantially excluding moisture and air the longevity of the joint is prolonged. The method comprises coating the section of pipework with a layer of viscoelastic material to form a coated section of pipework. In some embodiments, the viscoelastic material may be applied to the section of pipework as a viscoelastic composition by means such as spraying or painting. In some preferred embodiments, a first step the method comprises providing a tape comprising a viscoelastic layer and an interleave layer and in a second step wrapping the section of pipework with the tape to form the coated (i.e. wrapped) section of pipework. By tape it is meant a strip of material in sheet form usable to cover a surface. The tape will typically be provided on a reel for ease of use. The likely dimensions of the tape for most applications will typically be 100 mm to 450 mm in width and 10 m to 30 m in length. The tape may be wrapped helically (whereby the tape partially overlaps itself and extends lengthwise down the pipework), or preferably circumferentially (whereby the tape is applied in a direction so as to completely overlap itself). In some embodiments, a single layer of tape may be wrapped circumferentially (i.e. to wrap a length of tape substantially equivalent to the circumference of the pipe or with a small degree of overlap of the end of the tape with itself to ensure a complete layer is applied). In some other embodiments, multiple sections of tape are wrapped circumferentially to partially overlap each another, preferably around the entire circumference (particularly where the pipework is a field-joint and two (or more) layers of tape are wrapped to overlap across at least the width of the weld). The interleave layer may be removable or non-removable as described in further detail herein (and may be referred to as a carrier layer as is conventional for tapes). The interleave layer may have a thickness of from 40 to 200 microns. The tape is wrapped so as to contact the viscoelastic layer with an outer surface of the pipework, preferably to provide a substantially continuous viscoelastic layer surrounding the full circumference in the section of the pipework. Preferably, the total thickness of the layer of viscoelastic material coated on the section of pipework is 1.0 mm to 8 mm. Where a tape is used, individual viscoelastic layers may have a thickness of from 1.0 to 4 mm and multiple layers may be coated on the section of pipework as described herein. The thickness of the viscoelastic layer remans substantially the same under application of the inward radial pressure from tensioning the jacket (i.e. there is no change in volume of the viscoelastic layer in response to the compression). A small quantity of viscoelastic may however extrude at the axial ends of the wrapped jacket around the circumference of the pipework to form a bead at the edges. Preferably, the viscoelastic material is one as described in US9133372. In a particularly preferred embodiment of the present invention, the viscoelastic layer comprises one or more of polyisobutene, polybutene, butyl rubber, polyisoprene, atactic polypropylene or amorphous poly alpha olefin (APOA). Preferably, the viscoelastic material used in the present invention exhibits a phase angle between stress and strain in an oscillatory mode rheology measurement of from 20 to 70 degrees, more preferably from 30 to 55 degrees, when measured at a temperature of 23 °C, with a strain sweep range of from 0.01% to 10% and an angular frequency of 10 radians per second. Such measurement may be performed using a TA Instruments AR 1000 rheometer using 8 mm diameter parallel plates (TA Instruments is a brand of the Waters Corporation). As described above, the viscoelastic coating is applied to the outer surface of the pipe element. Optionally the viscoelastic coating is positioned in a substantially circumferential manner and optionally overlapping onto adjacent coating if present. Optionally additional layers of viscoelastic coating may be deployed to provide additional protection to the typically vulnerable weld area and / or to the typically vulnerable transition between the steel surface and pre-existing adjacent coating. The continuity of the viscoelastic coating may be determined at this stage by means known in the art, for example visual inspection or electrical inspection by so-called “holiday detection”. Following wrapping of the pipework with one or more layers of the tape, and optionally removing the interleave so as to leave behind the viscoelastic layer, the method further comprises a step of providing a substantially cylindrical jacket around the wrapped section of pipework followed by a step of mechanically tensioning the substantially cylindrical jacket to exert inward radial pressure on the viscoelastic layer. The cylindrical jacket can provide a uniform application of pressure around the full circumference of the pipe, as well as along the whole axial length. The pre-determined pressure achieved by the jacket may be in the range of from 0.1 MPa to 4 MPa. Advantageously, the present invention allows for the jacket to be optimised to exert a pre-determined pressure (for example, inward radial pressure) on the layer of viscoelastic material upon mechanical tensioning. Such a controlled application of pressure may be achieved by selecting one or more, and preferably all, of the jacket material, the jacket thickness, and the jacket length relative to the circumference of the coated section of pipework. The jacket may comprise a substantially rectangular jacket sheet comprising first and second opposite surfaces which is sized to fit substantially once around the wrapped section of pipework. The jacket may be shaped prior to installation and / or may assume the substantially cylindrical shape by conforming to the wrapped section of pipework. The jacket is comprised of a plastic sheet such as a sheet of polyethylene or polypropylene, preferably polypropylene. Furthermore, the plastic jacket sheet exhibits at least some elasticity when strained to the extent necessary to apply the inward radial pressure on the viscoelastic layer. For example, the elongation at yield of the material may be at least 5%, preferably at least 10% though provided that the elongation used to apply inward radial pressure does not exceed the elongation at break, the jacket will function to exert an inward radial pressure. The direction of strain being oriented parallel with the circumference of the cylindrical object (e.g. the pipe element). The jacket is positioned onto and around the pipework and has sufficient flexibility to be applied around the circumference of the pipework affording its substantially cylindrical shape. As will be appreciated, pipework is generally cylindrical though may have additional surface features such as weld beads or corrugation, or other irregular fittings or appurtenances. Equally, the jacket may be applied over a section of a pipe element including a pipe joint for example and preferably also on adjacent portions of the factory-applied coating which are typically chamfered. In a particularly preferred embodiment of the present invention, the plastic sheet is a heat shrinkable layer. Heat shrinkable materials per se are known in the art and are taught in for example US3144398. Preferably, the jacket sheet is formed of heat shrinkable polyethylene or heat shrinkable polypropylene. That is, preferably the sheet is formed from radiation cross-linked polyethylene or radiation cross-linked polypropylene. Simple non-radiation crosslinked polyethylene is not preferred because the melting point is too low for high temperature use such that non-radiation crosslinked polypropylene is preferred after radiation cross-linked plastic. In such embodiments, inward radial pressure on the viscoelastic layer may be created by the combination of stretching the plastic jacket sheet during the positioning of the jacket onto and around the pipework and then subsequently shrinking the plastic jacket sheet by the application of heat. The jacket may be in any form including but not limited to a single layer, a plurality of layers, a composite comprising one or more lamina layers, a composite comprising one or more lamina layers and one or more elements disposed to provide mechanical reinforcement, such reinforcement being known in the art and including but not limited to strands, fibres, rovings, filaments, fabrics, meshes, and nets. Preferably, the jacket does not comprise an adhesive. Preferably, the total thickness of the jacket sheet is from 0.5 mm to 4.0 mm. As described herein, the thickness of the jacket and its material composition are preferably selected to provide the desired pressure in relation to the pipework size. The jacket is brought into close contact with and conforms to the substantially cylindrical shape of the pipe and viscoelastic assembly. Stress is applied to the jacket such that strain in the circumferential direction is induced (i.e. the jacket is mechanically tensioned). The terminal ends are joined such that tension is maintained in the jacket sheet. The so-called hoop tension in the jacket resolves to exert a radial compression on the pipe and the viscoelastic layer. The pressure exerted thereby in combination with the rheological properties of the viscoelastic material combine to ensure that the material exhibits self-healing behaviour. The dimensions, amount of contraction and mechanical properties of the jacket are selected to ensure that the minimum requirement for pressure to ensure self-healing is satisfied. The jacket remains in-situ whereby it exerts continuous radial pressure and also provides mechanical protection to the underlying viscoelastic coating. The essential feature of the jacket is that stress may be controlled by ensuring that a controlled amount of strain is applied during and / or after installation, the stress produced being sufficient to achieve the require radial pressure to ensure “self-healing” of the viscoelastic coating, wetting of the viscoelastic coating onto the pipework surface and consequently rapid bonding of the viscoelastic coating onto the surface. Preferably, the self-healing feature is confirmed with reference to the method described in ISO 21809-3:2016 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems — Part 3: Field joint coatings, as measured at 23 °C. The strain can be controlled by ensuring that the amount of extension in the circumferential direction is controlled within limits. Extension can be conveniently controlled by ensuring that the layer is sized (relative to the circumference described by the outer surface of the applied viscoelastic coating) to ensure that the stretching imparted in the act of installation provides the required extension. The substantially uniform extension of the jacket by mechanical tensioning ensures that the resultant radial pressure is likewise substantially uniform and therefore an advantageous consistent and repeatable outcome is achieved that eliminates operator-based variability. It is generally preferred that the jacket comprises one sheet with two terminal ends which are brought together to induce tension for simplicity and ease of installation and the following description generally refers to use of such a jacket. However, it will be readily apparent that the jacket may comprise two (or, less preferably, more than two) sections or sheets secured to one another (such as via flanges as described herein) to mechanically apply tension around the circumference of the pipe. In some preferred embodiments, the length of the substantially cylindrical jacket as provided before being applied to the pipework is from 90% to 99% of the circumference of the wrapped section of pipework, preferably from 95% to 98%, more preferably from 97% to 98%. Preferably, the length of the jacket relative to the circumference of pipework is selected such that mechanical tensioning induces a strain (i.e. an increase in length) of from 1% to 5%, preferably from 2% to 3%. In other embodiments, these percentages may be that of the unwrapped pipework (the thickness of the tape provides a marginal increase in the total circumference which in turn only increases the pressure applied after tensioning). As will be appreciated, such a length is that measured between the two points of the jacket which are to be secured together after application to the pipework (for example, the abutment faces of two elongate bars attached to distal ends of the jacket sheet). After applying the mechanical tension to stretch the jacket, the length will equal that of the wrapped section of pipework (i.e. 100%). A cylindrical pipe of diameter X will have a circumference of about 3.14X. For example, the circumference of the pipework may be in the range of from 500 mm to 5,000 mm, such as from 750 mm to 2,500 mm. For example, a pipe element may have cylindrical diameter of about 324 mm providing a circumference of about 1,018 mm. A 5 mm thick viscoelastic layer without an interleave would increase the effective diameter by 10 mm to about 334 mm providing a circumference of about 1,049 mm. The inventors have found that the gap between the terminal ends of the jacket prior to mechanical tensioning and stretching may preferably be about 10 mm to 60 mm, preferably from 30 mm to 50 mm, particularly for pipework having a circumference of about 1 m. Preferably, the jacket has first and second flanges which, in use, are drawn together to provide the mechanical tensioning of the substantially cylindrical jacket. Such flanges are typically elongate, and may be arranged parallel to each other at distal ends of the jacket sheet (so that the jacket may be provided around the circumference of the pipe bringing the flanges into close proximity to one another and brought into contact with the step of mechanical tensioning). Each flange may be attached to the first surface of the jacket sheet. In some embodiments, the flanges may be an integral part of the jacket, extending from the first surface. In some embodiments, one or both flanges are located at the sheet at the terminal edge such that a face of the flange is coincident with the edge of the sheet. In some embodiments as described in further detail herein, the sheet may extend beyond the outer edge or face of the flange, said face being the outer face with respect to the opposite flange. As will be appreciated, the outer faces of each flange are the faces which face one another. The outer faces may be urged towards one another to create mechanical tension, and preferably are brought into abutment with one another once the jacket is wrapped around the pipework (in which case they may be referred to as abutment faces). The second surface of the jacket sheet (i.e. the opposite surface to that attached to the flanges) is that contacted with an outer surface of the wrapped section of pipe. That is, the jacket sheet is contacted with the pipework wrapped with the tape which may have optionally had the interleave layer removed (if removable). Each flange may be joined to the jacket sheet by a weld material or an adhesive. The weld material or adhesive may fill or substantially fill a slot in the jacket flange and extend from the slot to engage the first surface of the jacket sheet. The slot may have a cross-section taken perpendicular to the longitudinal axis of the jacket flange which may be rectangular, trapezoid, circular or T-shaped, for example. The opposing flanges are arranged parallel such that the abutment faces of the flanges may be brought into contact across their entire length upon wrapping the jacket around the pipework. The inventors have found that a jacket as described in GB2597256, which is concerned with the protection of piles of jetties and the protection of sheet pile walls from corrosion, may be used in the present invention. Securing the pair of jacket flanges together maintains the inward radial pressure on the viscoelastic layer. Stretching the layer around the circumference of the pipework (such as a cylindrical pipe element) and abutting the terminal ends of the layer via the flanges provides one means of controlling the extension. The terminal flanges may be adapted to facilitate stretching the layer. The adaptation may include means of locating on and engaging with equipment used to apply strain. The flanges may be bars or rods attached to the jacket sheet, the major axes or the rods or bars being oriented parallel to the major axis of the pipework. The rods or bars may be adapted to accommodate bolts, nuts, set screws, threaded connectors, or other mechanical closure devices. The bars may be adapted to include threaded inserts, said inserts forming a threaded receiver into which threaded bar may be screwed. The flanges may be formed of a plastic such as HDPE. In all cases the jacket is disposed in such a manner so as to ensure that on completion of installation a mechanically continuous hoop is formed circumferentially around the pipework. This can be conveniently achieved by use of jointing methods and materials well known in the art for example, welding, gluing, stitching, welting, bolted assemblies, staples, pins, pot rivets, clamps, crimps and screws. The free ends of the jacket are brought into proximity to facilitate jointing as described above. The positioning of the free ends and the tension thereby applied may be facilitated by using a clamping device. The clamping device may be electrically actuated, hydraulically actuated, hand powered, or actuated via threaded components such as those disclosed in US2726694A or WO2018 / 220351. The jacket may include elements to facilitate engagement with the clamping device. And the clamping device may be adapted to facilitate engagement with and alignment of the jacket. In some preferred embodiments, the pair of flanges are secured together using glass reinforced plastic bolts and nuts. Preferably, the plastic nuts are countersunk into the flanges. The jacket may include an integral or additional slip layer extending beyond the outer surface of one or more of the flanges. The slip layer may be integral being the terminal end of the jacket sheet or may be provided by a separate sheet, optionally attached to a flange. WO2018 / 220352 relates to a protective cover for an underwater beam which the inventors have found is suitable for use in the present invention. The protective cover of WO2018 / 220352 comprises a slip layer referred therein as an overlapping segment of the body. Such an element being in the form of a layer provides a slip plane to reduce friction and facilitate the smooth movement of the flange(s) under extension and during installation. The slip plane prevents the leading edge of the flange(s) from gouging the viscoelastic coating during installation. The slip layer may extend to substantially the same width as the jacket sheet and extend in the circumferential direction around the pipe element. The slip layer extends to just a portion of the circumference and is sized to ensure that one terminal end of the jacket rides over it during installation. The slip layer may conveniently have the same composition and construction as the jacket but may differ in composition and construction. Such an element is optional and the need for it depends on the method of installation and design of the jointing system. Optionally, the slip layer may be surface treated with a lubricating agent to provide lubricity. Such agents include, but are not limited to, mineral oil, grease, surfactants, and formulated lubricants. Such agents may be applied by spray application, brush application, or other means of deposition. Such agents may be applied immediately prior to installation. The tape may comprise removable interleaves. During and after installation of the viscoelastic the removable interleaves are removed to expose a surface of viscoelastic layer which the inner (second) surface of the jacket can be disposed against. Such an arrangement causes the viscoelastic to adhere to the inner surface of the jacket causing the jacket and the viscoelastic layer to combine to form a single assembly. Conversely, the tape may include a non-removable interleave on the outer surface which prevents bonding between the viscoelastic layer and the jacket. Such an arrangement causes the jacket and the viscoelastic layer to remain as separate entities. Thus the system can be configured as two separate entities or as a single assembly. It is common industry practise for systems wherein the outer layer is bonded to the inner layer to be treated as an integral system and conversely for systems wherein the outer layer is not bonded to the inner layer to be treated as separate items. The distinction between an integral system and separate items is important for the purposes of specification, testing and procurement. The invention can thus be configured to meet either requirement. Thus, in some embodiments the interleave layer is removable and the method comprises removing the interleave layer after wrapping the tape to expose the viscoelastic layer before wrapping with the jacket. Preferably, the interleave layer is a substantially continuous or partially continuous nonremovable interleave layer. A non-removeable layer may be a film or fabric forming a substantially continuous layer, or the layer may be a fabric, net or mesh forming a partially continuous layer. More preferably, the interleave layer is formed of: (1) polypropylene, preferably in the form of a plain-woven fabric or a mesh, or (2) glass fabric, preferably in the form of a plain-woven or knitted fabric or a mesh. For example, the inventors have found that a tape comprising a polypropylene mesh backing can also withstand higher operating temperatures when compared to polythene backed tapes. In the case of a partially continuous layer, the rate and extent of bond strength development is reduced by virtue of the reduced interfacial area and or reduced contact area. A reduced rate and extent of bond strength development allows for removal, re-alignment, and repositioning of the jacket as may be required if it is inadvertently mis-aligned during application. It also allows for unimpeded movement of the jacket across the surface of the viscoelastic layer during installation. A heat shrinkable layer is particularly well adapted for the jacket to high service temperatures and by virtue of being cross-linked exhibits better heat resistance than conventional non-cross-linked polymers such that these are preferred for the jacket as described above. Moreover, conventional polymers tend to expand when subject to heat with the undesirable consequence that the systems tends to become loose when heated whereas a heat shrinkable layer will shrink when exposed to heat and self-tighten securely around the pipework. The source of such heat may be external or may be the endogenous heat from the media transported within the pipe for example hot oil or hot gas. Heat may be applied to the heat shrinkable material causing contraction of the heat shrinkable layer and thereby application of further radial pressure. The heat may be from any source and may be radiative, hot air, convective, or direct flame impingement. This process being useful to correct any area of mis-application that are not under adequate strain though it is an advantage of the present invention that external heating is not required. For similar reasons, the present invention is particularly suitable for high temperature pipework applications in which the protected pipework is subsequently used to convey fluid at a temperature of from 80 °C to 130 °C, preferably from 100 °C to 120 °C. The system may include a force or pressure sensor. In some embodiments, the method further comprises positioning a force or pressure sensor between the jacket sheet and the viscoelastic layer, between successive layers of the viscoelastic layer, and / or between the viscoelastic layer and the surface of the pipework. The sensor may also be placed between the layer forming a slip plane and the jacket sheet. The measurement obtained can be advantageously used to confirm that uniform and repeatable pressure has been achieved. Typically, the pressure sensor is a suitably calibrated thin-film force sensing resistor. As described herein, a further aspect of the present invention provides a kit of parts for use in the method described herein to protect a section of pipework, the kit comprising: (I) a viscoelastic composition formulated for coating the section of pipework; and (II) a jacket sized to fit substantially once around the section of pipework once coated with the viscoelastic composition. In some embodiments, the kit comprises: (I) a tape comprising a viscoelastic layer and an interleave layer (for example, as a roll or a reel from which the tape may be cut to size / length); and (II) a jacket sized to fit substantially once around the section of pipework once the pipework is wrapped with the tape. The inventors have found that the kit may be applied to pipework of about 1 m diameter in less than half the time than would be required for a conventional heat shrink sleeve applied with a gas torch, and may be applied in less than four minutes. In addition, the cold applied kit provided far greater hoop tension compression on the inner viscoelastic layer. In a further aspect, the kit further comprises the section of pipework to be protected by the viscoelastic composition and the jacket, the jacket sized accordingly to the pipework supplied as part of the kit. Preferably, the jacket is optimised to exert a pre-determined inward radial pressure on the viscoelastic composition upon mechanical tensioning, preferably by selecting one or more of a jacket material, jacket thickness, and jacket length relative to a circumference of the coated section of pipework. For example, it is preferred that the jacket length is selected to be from 1% to 5% shorter than a circumference of the coated section of pipework (such that a strain of from 1% to % is imparted upon mechanical tensioning). A further aspect of the present invention provides a pipe formed using the kit described herein or obtained by the method described herein, the pipe comprising a wrapping of a viscoelastic layer and a jacket secured thereto exerting inward radial pressure on the viscoelastic layer. Advantageously, the jackets exerts sufficient pressure so as to be able to render the viscoelastic material self-healing in accordance with ISO 21809-3:2016 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems — Part 3: Field joint coatings, as measured at 23 °C. A further aspect provides the use of a pipe described herein protected with the kit described herein to convey fluid at a temperature of from 80 °C to 130 °C, preferably from 100 °C to 120 °C. Advantageously, the system can withstand elevated operating temperatures greater than 115 °C (or 240 °F) to the ISO standard requirement. Figures The present invention will now be described further with reference to the following non-limiting Figures, in which: Figure 1A shows a schematic view of a pipe joint, in a cross-section comprising the major axis of the pipe, wrapped with a first layer of tape comprising a viscoelastic layer applied over the weld bead. Figure 1B shows a schematic view of the pipe joint shown in Figure 1 A, further with a second layer of a tape comprising a viscoelastic layer applied over the weld bead and a portion of the first layer of tape. Figure 1C shows a schematic view of the pipe joint shown in Figure 1B, further with a jacket applied over the weld bead and the first and second layers of tape. Figure 2 shows a schematic view of a pipe joint, in a cross-section comprising the major axis of the pipe, protected with a kit as described herein. Figure 3 shows a perspective view of a jacket suitable for use in the present invention. Figure 4 shows a part of a protected pipe, in a cross-section in a plane perpendicular to the major axis of the pipe. Figure 1A illustrates a metal pipe joint comprising a cutback area formed from two pipe elements (100a, 100b) having a central welded joint with a weld bead (110) and an adjacent chamfered factory applied coating (105a, 105b) on either side of the cutback is provided. A section of tape (115) as described herein is positioned to overlap onto the adjacent factory applied coating (105a) and to overlap onto the weld bead (110) and to extend beyond the weld bead (110) a distance of some 50 mm, said distance measured parallel to the major axis of the pipe (100a, 100b). The tape (115) is applied around the full circumference of the pipe (100a, 100b) and overlaps onto itself in the circumferential direction some 100 mm. A separate section of tape (120) is positioned over the remaining, substantially uncoated portion as illustrated in Figure 1B, the tape (120) positioned to overlap onto the proximal adjacent chamfered factory applied coating (105b) and to overlap onto the weld bead (110) of the pipe and similarly extend beyond the weld bead (110) a distance of some 50 mm, said distance measured in the antiparallel sense to the major axis of the pipe (100a, 100b). The further tape (120) is applied around the full circumference of the pipe (100a, 100b) and overlaps onto itself in the circumferential direction some 100 mm. Thus a continuous layer is formed in the entire cutback area by the application of two pieces of tape (115, 120), and a double viscoelastic layer is provided over the weld bead (110) and some 50 mm either side of the weld. A jacket (125) formed of a sheet of radiation cross-linked heat shrinkable plastic is applied around the entire wrapped section of pipework as illustrated in Figure 1C. The terminal ends, not shown in the cross-section illustrated, are mechanically brought together to stretch the jacket around the circumference of the pipe and secured in place thereby exerting inward radial pressure on the viscoelastic layer. Figure 2 illustrates a pipe joint between two metal pipes (200a, 200b) and weld bead (210) protected with a tape (215) and jacket (225), equivalent to that shown in Figure 1C, with the exception that a single layer of tape (215) is applied around the full circumference of the pipe (200a, 200b) overlapping both sides of the chamfered factory applied coating (205a, 205b) and to overlap onto the weld bead (210) of the pipe, the tape having been applied to overlap onto itself in the circumferential direction some 100 mm. Figure 3 illustrates a substantially cylindrical jacket (300) that is formed from a heat shrinkable plastic sheet (305) having a first surface (305a) to which a first flange (310a) and a second flange (310b) are adhered at distal terminal ends. In use, as illustrated by the configuration of the jacket in Figure 3, the jacket sheet is substantially cylindrical taking the form of the pipework to which it is applied, the second surface (305b) of the jacket sheet (305) serving to contact the wrapped pipework once the pipework is wrapped with the tape as described herein. The sheet (305) has been mechanically tensioned by stretching around the pipework in a circumferential manner in order to bring two abutment faces of the flanges (310a, 310b) into contact with each other. The flanges (310a, 310b) are secured together by glass reinforced plastic nuts and bolts (315). The jacket further comprises an additional slip layer (320) formed from the same material as the sheet (305) and is also attached to a first flange (310a). The slip layer (320) may be lubricated and, during mechanical tensioning, the second flange (310b) will ride over the slip layer (320) to minimise damage to the viscoelastic layer by the leading abutment face of the flange (310b). Figure 4 illustrates a close-up cross-section of a protected pipe comprising a pipe wall (400). The protected pipe further comprises a layer of viscoelastic material (405) wrapped around its entire circumference and a jacket secured thereto and under tension exerting an inward radial pressure. The jacket comprises a plastic sheet (410) which is wrapped and stretched around the entire circumference of the pipe wall (400) and viscoelastic layer (405). At two terminal ends (410a, 410b) of the jacket sheet are attached two flanges (415a, 415b) in the form of elongate bars having holes oriented in the circumferential direction passing through the full depth of the bar. The flanges (415a, 415b) are aligned and positioned such that the bolt holes on each bar are in common alignment and secured together using a nut and bolt (420) whereby the nut is countersunk into one of the bars (415b). Examples Example 1 A 324 mm diameter steel pipe was helically wrapped with a mesh-backed viscoelastic tape having a total thickness of 1.5 mm. The tape was overlapped onto itself to the extent that a double layer of tape was formed on the outer surface of the pipe giving a total thickness of 3.0 mm. A jacket was placed around the pipe and positioned over the tape whereby the terminal ends of the jacket were adjacent on the crown of the pipe. The jacket comprised a rectangular sheet of radiation cross-linked heat shrinkable polyethylene 1.5 mm thick, 400 mm wide and 1,023 mm long. The jacket further comprised two rigid polythene bars each secured to the terminal ends of the sheet. The bars were 400 mm long, 40 mm high and 25 mm wide and featured 4 bolt holes drilled to equal centre spacing. Said bolt holes were oriented in the circumferential direction passing through the full depth of the bar and positioned such that the bolt holes on each bar were in common alignment pairwise to the bolt holes on the adjacent bar. A clamp was positioned over the two bars and engaged with the two centremost sets of bolt holes by means of the locating pins on the surface of the face of the clamp. The clamp was clamped shut drawing the bolt holes into alignment and the bars together into contact on their vertical proximal faces. The strain value attained was 1.03. The bars were bolted together using stainless-steel nuts and stainless-steel bolts positioned to the outermost bolt holes. The clamp was removed revealing the centremost bolt holes. The bars were further secured using stainless-steel nuts and stainless-steel bolts position to the centre-most boltholes. To confirm the self-healing properties, a 6 mm hole through the jacket sheet and tape was obtained by using a 6 mm hollow hammer punch, and the surface was cleaned to base steel. The whole pipe assembly was maintained at 23 °C for 24 hours and self-healing characteristics were confirmed with reference to the method described in ISO 21809-3:2016 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems — Part 3: Field joint coatings. Example 2 Tape was applied in the manner shown in Figures 1 A, 1B, and 1C, said tape having a total thickness of 2 mm and comprising a layer of viscoelastic material laminated to a non-removable polythene film. The strain value was 1.04 and the other parameters were as per Example 1 saving that glass reinforced plastic bolts and polypropylene bolts were used in place of stainless-steel nuts and stainless-steel bolts. To confirm the self-healing properties, a 6 mm hole through the jacket sheet and tape was obtained by using a 6 mm hollow hammer punch, and the surface was cleaned to base steel. The whole assembly was maintained at 23 °C for 24 hours and self-healing characteristics were confirmed with reference to the method described in ISO 21809-3:2016 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems — Part 3: Field joint coatings. Example 3 In a particularly preferred example, tape was applied in the manner shown in Figures 1 A, 1B, and 1C, said tape having a total thickness of 2 mm and comprising a layer of viscoelastic material laminated to a non-removable polythene film. The strain value was 1.05 and the other parameters were as per Example 1 saving that glass reinforced plastic bolts and polypropylene bolts were used in place of stainless-steel nuts and stainless-steel bolts and that the jacket comprised a 2.0 mm thick polyethylene film jacket sheet and, in addition, a thin-film force sensing resistor was inserted in the space between the layer of viscoelastic material and the jacket sheet prior to installation of the jacket. The pressure sensor was connected to a laptop computer and after installation the pressure was measured and recorded as being 0.27 MPa. As used herein, the singular form of “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. The use of the term “comprising” is intended to be interpreted as including such features but not excluding other features and is also intended to include the option of the features necessarily being limited to those described. In other words, the term also includes the limitations of “consisting essentially of” (intended to mean that specific further components can be present provided they do not materially affect the essential characteristic of the described feature) and “consisting of” (intended to mean that no other feature may be included such that if the components were expressed as percentages by their proportions, these would add up to 100%, whilst accounting for any unavoidable impurities), unless the context clearly dictates otherwise. It will be understood that, although the terms "first", "second", etc. may be used herein to describe, for example, various elements, layers and / or portions, the elements, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, layer or portion from another, or a further, element, layer or portion. Spatially relative terms, such as “under”, "below", "beneath", "lower", “over”, "above", "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) and generally with respect to the major central axis of the pipework 5 where relevant. It will be understood that the spatially relative terms are intended to encompass different orientations of the kit and / or pipework in use or operation in addition to the orientation depicted in the figures. Numerical lower and upper limits of features described herein may preferably be combined to provide 10 a closed range. The foregoing detailed description has been provided byway of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within 15 the scope of the appended claims and their equivalents. For the avoidance of doubt, the entire contents of all documents acknowledged herein are incorporated herein by reference. 21 05 24

Claims

1. A method for protecting a section of pipework, the method comprising:(i) coating the section of pipework with a layer of viscoelastic material to form a coated section 5 of pipework;(ii) providing a substantially cylindrical jacket around the coated section of pipework; and(iii) mechanically tensioning the substantially cylindrical jacket to exert inward radial pressure on the layer of viscoelastic material;wherein the jacket is sized to fit substantially once around the coated section of pipework and10 wherein the jacket has first and second flanges which, in use, are drawn together to provide the mechanical tensioning of the substantially cylindrical jacket.

2. The method according to claim 1, wherein the jacket is optimised to exert a pre-determined inward radial pressure on the layer of viscoelastic material upon mechanical tensioning.

153. The method according to claim 2, wherein the jacket is optimised by selecting one or more of a jacket material, jacket thickness, and jacket length relative to a circumference of the coated section of pipework.20 4. The method according to any of the preceding claims, wherein the length of the substantiallycylindrical jacket provided in step (iii) is from 90% to 99% of the circumference of the coated section of pipework, preferably from 95% to 98%.

5. The method according to any of the preceding claims, wherein mechanical tensioning induces 25 a strain in the jacket of from 1 % to 5%, preferably from 2% to 3%.

6. The method according to any of the preceding claims, wherein coating the section of pipework with a layer of viscoelastic material comprises wrapping the section of pipework with a tape, wherein the tape comprises a viscoelastic layer and an interleave layer.

307. The method according to claim 6, wherein the interleave layer is removable and the method comprises removing the interleave layer wrapping with the tape in order to expose the viscoelastic layer before step (ii) of providing the substantially cylindrical jacket.35 8. The method according to claim 6, wherein the interleave layer is a substantially continuous orpartially continuous non-removable interleave layer.21 05 249. The method according to claim 8, wherein the interleave layer is formed of: (1) polypropylene, preferably in the form of a plain-woven fabric, or a mesh, or (2) glass fabric, preferably in the form of a plain-woven or knitted fabric, or a mesh.5 10. The method according to any of the preceding claims, wherein the layer of viscoelasticmaterial has a total thickness of from 1.0 mm to 8 mm.

11. The method according to any of the preceding claims, wherein the viscoelastic material comprises one or more of polyisobutene, polybutene, butyl rubber, polyisoprene, atactic10 polypropylene or amorphous poly alpha olefin (APOA).

12. The method according to any of the preceding claims, wherein the jacket comprises a jacket sheet having a thickness of from 0.5 mm to 4.0 mm.15 13. The method according to any of the preceding claims, wherein the jacket is formed ofpolypropylene, or heat shrinkable polyethylene or polypropylene.

14. The method according to any of the preceding claims, further comprising positioning a force or pressure sensor between the jacket and the layer of viscoelastic material, between successive20 layers of the viscoelastic material, and / or between the layer of viscoelastic material and the surface of the pipework.

15. A kit of parts for use in the method according to any of the preceding claims to protect a section of pipework, the kit comprising:25 (I) a viscoelastic composition formulated for coating the section of pipework; and(II) a jacket sized to fit substantially once around the section of pipework once coated with the viscoelastic composition;wherein the jacket has first and second flanges which, in use, are drawn together to provide the mechanical tensioning of the substantially cylindrical jacket.3016. The kit according to claim 15, wherein the jacket sheet is formed of polypropylene, or heat shrinkable polyethylene or polypropylene.

17. The kit according to claim 15 or claim 16, further comprising the section of pipework to be35 protected.

18. The kit according to claim 17, wherein the jacket is optimised to exert a pre-determined inward radial pressure on the viscoelastic composition upon mechanical tensioning.

19. The kit according to claim 18, wherein the jacket is optimised by selecting one or more of a jacket material, jacket thickness, and jacket length relative to a circumference of the coated section of pipework.5 20. The kit according to according to any of claims 15 to 19, wherein the jacket length is selectedto be from 1% to 5% shorter than a circumference of the coated section of pipework.

21. A pipe formed using the kit according to any of claims 15 to 20, the pipe comprising a wrapping of a viscoelastic layer and a jacket secured thereto exerting inward radial pressure.

022. Use of the pipe according to claim 21 to convey fluid at a temperature of from 80 °C to130 °C, preferably from 100 °C to 120 °C.21 05 24

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