GB2555776A

GB2555776A - Tubular structure repair

Info

Publication number: GB2555776A
Application number: GB1615024.5A
Authority: GB
Inventors: Syme Allan; John Kennedy Stephen
Original assignee: Intelligent Engineering Bahamas Ltd
Current assignee: Intelligent Engineering Bahamas Ltd
Priority date: 2016-09-05
Filing date: 2016-09-05
Publication date: 2018-05-16
Also published as: GB201615024D0; WO2018042205A1

Abstract

Repairing a tubular structure comprises positioning a plurality of shell sections 3 around the tubular structure 1 in spaced apart relation. The shell sections are then sealed to the tubular structure so as to form a cavity and an uncured plastics material is injected into the cavity. It is cured so that it adheres to inner surfaces of the shell sections and the outer surface of the tubular structure to form an intermediate layer 2 with sufficient strength to transfer shear forces between the tubular structure and the shell sections. Sealing the shell sections to the tubular structure comprises providing a resilient seal member 40 between the shell sections and the tubular structure and bolting the shell sections together so as to compress the resilient seal member. The resilient sealing member can be an elongate member in a closed loop around the tubular structure, which can be positioned between the shell and the tubular structure. The seal can be tapered, projecting into a gap between an edge of a shell section and the tubular structure. Each shell section can be substantially half-cylindrical.

Description

(54) Title of the Invention: Tubular structure repair

Abstract Title: Repairing a tubular structure with a curable material (57) Repairing a tubular structure comprises positioning a plurality of shell sections 3 around the tubular structure 1 in spaced apart relation. The shell sections are then sealed to the tubular structure so as to form a cavity and an uncured plastics material is injected into the cavity. It is cured so that it adheres to inner surfaces of the shell sections and the outer surface of the tubular structure to form an intermediate layer 2 with sufficient strength to transfer shear forces between the tubular structure and the shell sections. Sealing the shell sections to the tubular structure comprises providing a resilient seal member 40 between the shell sections and the tubular structure and bolting the shell sections together so as to compress the resilient seal member. The resilient sealing member can be an elongate member in a closed loop around the tubular structure, which can be positioned between the shell and the tubular structure. The seal can be tapered, projecting into a gap between an edge of a shell section and the tubular structure. Each shell section can be substantially half-cylindrical.

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TUBULAR STRUCTURE REPAIR [0001 ] The present invention relates to methods of and apparatus for repairing tubular structures, for example oil pipes in off-shore structures.

[0002 ] Large pipelines, for example pipelines conducting hydrocarbon products, are often located in hostile environments such as off-shore structures. Pipelines may therefore be subjected to corrosion and/or damage from collisions or even deliberate attacks, e.g. to steal fuel. Frequent replacement and/or repair of pipelines may therefore be necessary. As well as the expense of the replacement or repair, it may be necessary to shut down equipment to which the pipeline is connected whilst the replacement or repair is carried out.

[0003] WO/2002/020341 discloses amethod of repairing or reinforcing apipe which involves welding a reinforcing layer to the pipe so as to form a cavity into which an uncured elastomer is injected and allowed to cure. This method reduces but does not completely eliminate the need to weld to or in the vicinity of the pipeline. Therefore it may still be necessary to shutdown associated equipment and/or flush the pipeline before the repair can be effected.

[ 0004 ] There is therefore a need for improved approach to repair of tubular structures, such as caissons, pipes and pipelines.

[ 0005 ] According to an aspect of the invention, there is provided a method of repairing a tubular structure comprising: positioning a plurality of shell sections around the tubular structure in spaced apart relation thereto; sealing the shell sections to the tubular structure so as to form a cavity; injecting an uncured plastics material into the cavity; and curing the plastics material so that it adheres to inner surfaces of the shell sections and the outer surface of the tubular structure to form an intermediate layer with sufficient strength to transfer shear forces between the tubular structure and the shell sections; wherein sealing the shell sections to the tubular structure comprises: providing a resilient seal member between the shell sections and the tubular structure; and bolting the shell sections together so as to compress the resilient seal member.

[0006] According to an embodiment, providing a resilient seal member comprises adhering an elongate resilient member in a closed loop around the tubular structure.

[0007 ] According to an embodiment, the resilient seal member fits between the tubular structure and the shell sections.

[0008 ] According to an embodiment, providing a resilient seal comprises providing a tapered seal member projecting into a gap between an edge of a shell section and the tubular structure.

[0009] According to an embodiment, providing a resilient seal member comprises adhering a resilient seal member to an inner surface of a shell section.

[0010 ] According to an embodiment, an elongate edge member is fixed to the inner surface of a shell section and providing a resilient seal member comprises adhering the resilient seal member to a distal surface of the edge member.

[0011 ] According to an embodiment, the resilient seal member comprises a plurality of fins.

[0012 ] According to an embodiment, the resilient seal member is formed of an ethylene propylene diene monomer (M-class) rubber.

[0013] According to an embodiment, the shell sections have an outwardly projecting flange along an edge thereof and bolting the shell sections together comprises bolting the flanges of adjacent shell sections together.

[0014] According to an embodiment, a gasket is provided between flanges of adjacent shell sections.

[0015] According to an embodiment, each shell section is substantially half-cylindrical.

[0016] According to an embodiment, a pair of adjacent shell sections has cut-outs in adjacent edges to accommodate a projecting fitting of the tubular structure.

[0017 ] According to an embodiment, each shell section has an axial length in the range of from 0.5 m to 10 m.

[0018] According to an embodiment, the shell sections are made of metal and have a thickness in the range of from 0.5 mm to 20 mm, desirably 2 to 20 mm.

[0019] According to an embodiment, the cavity has a thickness in the range of from 5 to 200 mm, desirably 10 to 100 mm.

[ 0020 ] According to an embodiment, the tubular structure is a pipe.

[0021 ] According to an embodiment, the tubular structure is a caisson.

[ 0022 ] According to an aspect of the invention, there is provided apparatus for repairing a tubular structure, the apparatus comprising: a plurality of shell sections configured to fit around the tubular structure in spaced apart relation thereto; and a resilient seal member configured to seal between the shell sections and the tubular structure; wherein the shell sections are configured to be bolted together so as to compress the resilient seal member against the tubular structure.

[ 0023 ] According to an aspect of the invention, there is provided a repaired tubular structure comprising: a plurality of shell sections around the tubular structure in spaced apart relation thereto so as to form a cavity; an intermediate layer filling the cavity and adhered to the shell sections and the tubular structure with sufficient strength to transfer shear forces between the tubular structure and the shell sections; and a resilient seal member compressed between the shell sections and the tubular structure to seal the cavity; wherein the shell sections are bolted together so as to compress the resilient seal member.

[0024 ] With the present invention, a robust and effective repair and/or reinforcement of a tubular structure, such as a pipeline can be effected quickly and without necessitating the shutdown of equipment to which the pipeline is connected and/or without halting flow of a conveyed fluid through the pipeline. With the present invention, hotwork, such as welding, can be avoided so that the invention is especially applicable for pipelines carrying hydrocarbon products.

[ 0025 ] Embodiments of the invention will be described below with reference to the accompanying drawings, in which:

[0026] Figure 1 depicts in partial cutaway a pipe repair according to an embodiment of the invention;

[0027] Figure 2 is longitudinal cross-section of the pipe repair of Figure 1;

[0028] Figure 3 is atransverse cross-section of the pipe repair of Figure 1;

[0029] Figure 4 is a longitudinal cross-section of an arrangement for accommodating a flanged joint in a pipe;

[ 0030 ] Figure 5 is an enlarged cross-section of an access port in a the pipe repair of Figure 1;

[ 0031 ] Figure 6 is an enlarged view showing the joint of a resilient seal member;

[ 0032 ] Figure 7 is a perspective view of a pipe repair according to another embodiment of the invention;

[ 0033 ] Figure 8 is a cross-sectional view of a part of the pipe repair of Figure 7;

[ 0034 ] Figure 9 is a perspective view of a pipe repair according to another embodiment of the invention;

[ 0035 ] Figure 10 is a cross-sectional view of a part of the pipe repair of Figure 9;

[ 0036 ] Figure 11 is a perspective view of a pipe requiring repair;

[0037] Figure 12 is an end view of the pipe of Figure 11;

[0038 ] Figure 13 is a perspective view depicting the attachments of shell sections to the pipe of Figure 11;

[0039] Figure 14 is an end view depicting the attachments of shell sections to the pipe of Figure 11; [0040 ] Figure 15 depicts a shell section in place on the pipe of Figure 11;

[0041] Figure 16 is an enlargement of part of Figure 15;

[0042 ] Figure 17 depicts two shell sections in place on the pipe of Figure 11; and [0043] Figure 18 is an enlargement of part of Figure 17.

[0044 ] In the Figures, like parts are indicated by like references.

[ 0045 ] An embodiment of the present invention provides method of repairing a tubular structure comprising: positioning a plurality of shell sections around the tubular structure in spaced apart relation theerto; sealing the shell sections to the tubular structure so as to form a cavity; injecting an uncured plastics material into the cavity; and curing the plastics material so that it adheres to inner surfaces of the shell sections and the outer surface of the tubular structure to form an intermediate layer with sufficient strength to transfer shear forces between the tubular structure and the shell sections; wherein sealing the shell sections to the tubular structure comprises: providing a resilient seal member between the shell sections and the tubular structure; and bolting the shell sections together so as to compress the resilient seal member.

[0046] Embodiments of the present invention can therefore enable a pipe repair to be carried out with no on-site hotwork. The shell sections and resilient member can be fabricated off-site, e.g. in factory conditions for reliability. On-site, all connections between shell sections are performed by bolted connections which compresses the resilient seal member sufficiently to seal the cavity against injection of the plastics material to form the core. Adhesives may be used in addition, e.g. to fix the resilient seal member to either the tubular structure or the shell sections.

[0047] Preparation of the tubular structure for the application of a repair according to the invention need not involve more than cleaning, e.g. sand blasting, of the outer surface of the tubular structure and there often need be no interruption to the flow of fluid through a pipe. Downtime of the pipeline or associated plant is avoided or minimised.

[ 0048 ] Preferably the plastics material is injected as a two component mixture that reacts to form the intermediate layer without requiring additional action. Curing the plastics material may therefore amount to allowing the plastics material to cure itself. Generally, the process of curing is exothermic. Fluid flowing through the pipe may affect the curing process, either by conducting away heat if the fluid is cold or supplying additional heat if the fluid is hot. It may be necessary to include additives in the plastics material to control the rate of the curing to compensate for the effect of the fluid in the pipe. If necessary additional heating or cooling can be provided during the curing process.

[0049] Once the plastics material is cured, a structural sandwich member is formed, as shown for example in Figure 1. The existing pipe wall 1 forms a first outer layer of the structural sandwich member. The cured plastic material forms an intermediate, or core, layer 2 and the shell sections form a second outer layer 3. The intermediate layer 2 is bonded to each of the first and second outer layers 1, 3 with sufficient strength to transfer shear loads between the outer layers so as to form a composite structural member capable of bearing loads significantly greater than self-weight.

[0050 ] The first and second outer layers 1, 3 are made of metal and the intermediate layer 2 is made of a plastic or elastomeric material. The absolute and relative dimensions of the structural sandwich member and the precise materials employed will depend on the application to which the member is to be put (e.g. the size of the pipe, the internal pressure thereof and the external environment) and in general may be as described in US-5,778,813 and US-6,050,208. Steel or stainless steel may be used in thicknesses of 0.5 to 20 mm. Similarly, the plastics or polymer core may be any suitable material, for example an elastomer such as polyurethane, as described in US-5,778,813 and US-6,050,208 and is preferably compact, i.e. not a foam. The core is preferably a thermosetting material rather than thermoplastic. The intermediate layer may have a thickness of 5 mm to 200 mm, desirably 10 to 100 mm.

[0051 ] Desirably, the intermediate layer has a modulus of elasticity, E, of at least 250 MPa, preferably 275 MPa, at the maximum expected temperature in the environment in which the member is to be used. In maritime applications this may be 100 °C. Desirably, the elastomer is not too stiff so that E should be less than 2,500 MPa at the lowest expected temperature, -40 or -45 °C in maritime applications.

[ 0052 ] The tear, compression and tensile strengths as well as the elongation are desirably maximised to enable the structural sandwich plate member to absorb energy in unusual load events, such as impacts. In particular, the compressive and tensile strengths of the elastomer should be at least

20, and preferably 40, MPa. The compressive strengths can, of course, be considerably greater than these minima.

[0053] The metal layers are preferably structural steel though may also be aluminium, stainless steel or other structural alloys in speciality applications where lightness, corrosion resistance or other specific properties are essential. The metal should preferably have a minimum yield strength of 240 MPa and an elongation of at least 20%.

[ 0054 ] The ductility of the elastomer at the lowest operating temperature is desirably greater than that of the metal layers, which is about 20%. A preferred value for the ductility of the elastomer at lowest operating temperature is 50%. The thermal coefficient of the elastomer is desirably sufficiently close to that of the steel so that temperature variation across the expected operating range, and during welding, does not cause delamination. The extent by which the thermal coefficients of the two materials can differ will depend in part on the elasticity of the elastomer but it is believed that the thermal expansion coefficient of the elastomer may be about 10 times that of the metal layers. The coefficient of thermal expansion may be controlled by the addition of fillers to the elastomer.

[ 0055 ] The bond strength between the elastomer and metal layers is desirably at least 3, preferably 6, MPa over the entire operating range. This is preferably achieved by the inherent adhesiveness of the elastomer to steel but additional adhesives may be provided.

[ 0056 ] In an embodiment, the elastomer essentially comprises a polyol (e.g. polyester or polyether) together with an isocyanate or a di-isocyanate, a chain extender and a filler. The filler is provided, as necessary, to reduce the thermal coefficient of the intermediate layer, reduce its cost and otherwise control the physical properties of the elastomer. Further additives, e.g. to control hydrophobicity or adhesion, and fire retardants may also be included.

[ 0057 ] The ratio of the total thickness of the outer layers to the thickness of the elastomer, (Tl + T3) / T2, is in the range of from 0.1 to 2.5.

[ 0058 ] Coatings, e.g. for cosmetic or corrosion resistance reasons, may be applied to the outer surfaces of the metal layers either before or after fabrication of the laminate.

[ 0059 ] The intermediate layer 2 may also include a plurality of hollow box-shaped forms enclosing voids. The size and material of the forms are chosen so that the overall density of the forms is lower than the density of the material of the intermediate layer 2, preferably less than 50% of the density of the material of the intermediate layer 2, or preferably less than 25% and most preferably less than 10%. The purpose of the forms is essentially to take up space within the intermediate layer 2 and thus reduce the amount of the main core material required whilst maintaining or even increasing the desired spacing between first and second outer layers 1,3. This reduces cost both directly as the forms arc less expensive by volume than the main core material and secondly because the weight of the panels is reduced.

[0060] The forms do not need to contribute to the overall structural strength of the structural sandwich member but must have physical properties sufficient to withstand pressures and temperatures arising during casting and curing of the intermediate layer 2. The size, shape and distribution of forms within the intermediate layer 2 is chosen so that a sufficient number of ribs and/or columns of main core layer material extend between and bond to first and second outer layers 1, 3 at regular intervals across the length and width of the structural sandwich member. The forms do not have to be hollow, e.g. if made of a suitable lightweight material such as a foam, or may be filled with lightweight material, which may be insulating and/or fire resistant. A particularly useful material for the forms is expanded polystyrene, having a density of 20 to 40 kg/m³, which may be provided, e.g., either as spheres or ribs.

[0061] The structural sandwich member is substantially stronger and stiffer than a member of the same thickness of metal but no intermediate layer. This is because the member acts in an analogous manner to a box girder or I-beam with the intermediate layer performing the function of the web(s).

To so function, the intermediate layer itself and the bonds to the outer layers must be sufficiently strong to transfer the forces that will arise in use of the member.

[0062] Another advantageous property of such a structural sandwich member, is that the intermediate layer acts to prevent crack propagation between the inner and outer layer. The elasticity of the intermediate layer prevents the stress concentration at the tip of a crack in one outer layer being transmitted to the other as a rigid connection would, instead the load is spread out.

[0063] A first embodiment of the invention is shown in Figures 1 to 6. Figure 1 is a perspective view in partial cutaway; Figure 2 is a longitudinal cross-section and Figure 3 an end view. Figures 4 to 6 illustrate various details.

[0064 ] As can be seen in Figure 1, pipe repair 10 is made by two semi-cylindrical shell sections 30 which are positioned around the existing pipe 1 with a clearance C. Shell sections 30 have longitudinal flanges 31 projecting perpendicularly outwardly from their longitudinal edges and arcuate end flanges 32 projecting perpendicularly from their end edges. Longitudinal flanges 31 and arcuate end flanges 32 are provided with bolt-holes 34 at positions to match with corresponding bolt-holes 34 on another shell section. When the shell sections are bolted together by bolts 36 via the longitudinal flanges 31a shell unit surrounding the pipe 1 is formed. Gaskets 41 made of resilient material are provided between the longitudinal flanges 31 and edge flanges 31 help to seal the shell sections together.

[0065] A shell sections 30 may have a length in the range of from 0.5 to 10 m. Shorter shell sections 30 are easier to handle and can better accommodate distortions of the existing pipe. Longer shell sections may enable quicker repairs with fewer joints.

[0066] Shell sections 30 can be manufactured by cutting sections of steel pipe of a suitable diameter and welding on the necessary flanges.

[0067] Shell sections 30 can be manufactured to subtend less than 180° at the centre of the pipe 1 so that more than two shell sections are required to enclose a pipe. Two 180° shell sections is often advantageous in minimising the labour required to perform a pipe repair and the number of seals. However for larger pipes, smaller shell sections may be desirable to ensure that each shell section can be manually manoeuvred and so the need for lifting equipment can be avoided. The shell sections need not be identical although this is desirable from the point of view of manufacturing and interchangeability of parts can make on-site work easier. Handles 35 are provided at convenient locations on the outer surfaces of shell sections 30 to assist in handling of the shell sections during the repair process. Handles 35 can be left in place or cut-off after the repair is complete.

[0068] End flanges 32 can sometimes be omitted for a short repair requiring only one shell unit or at the ends of a multi-unit repair.

[0069] Seal members 40 are fixed to the existing pipe, e.g. using adhesive or adhesive tape. Alternatively or in addition, seal members 40 can be attached to the inner surfaces of shell sections 30. Seal members 30 are formed of a resilient material, e.g. an ethylene propylene diene monomer (Mclass) rubber. Seal members 30 have a thickness somewhat greater than the difference between the outer radius of the pipe 1 and the inner radius of shell sections 30 so that when the shell sections 30 are bolted together, the seal members 30 are compressed between the shell sections and the pipe 1.

The width of seal members 40 is selected, together with the amount of compression and any adhesives used, to be sufficient to resist pressures exerted by the plastics material when curing to form the intermediate layer 2.

[0070 ] In an embodiment, seal members 40 are straight lengths of resilient material that are cut to length. As shown in Figure 6, one end of seal member 40 is cut to have a protruding tongue 40a and the other end is cut to have a matching groove 40b. Adhesive can be applied to fix the ends of the seal member together. Other means of joining the ends of the seal member together can be employed. If the ends of the seal members are joined under tension, then the resulting force against the pipe can assist in holding the seal member in place when the shell sections are fitted.

[0071] In an embodiment of the invention, a pipe repair can accommodate a flanged j oint between sections of the pipe 1. In such a joint, flanges 11 provided on the ends of the pipe sections are bolted together to join two sections of the pipe 1. It is generally undesirable to make the shell sections large enough to accommodate the flanged joint as that would make the intermediate layer 2 too thick, adding excessive weight. In an embodiment of the invention, two shell sections are positioned either side of the flanged joint with a gap sufficient to accommodate the flanged joint. As shown in Figure 4, bridging unit 50 fills the gap between the two shell sections. Bridging unit comprises two short semicylindrical sections of pipe 51, having a diameter larger than the outer diameter of flanges 11, with bridging end flanges 52 projecting outwardly from both ends. Bridging end flanges 52 are bolted to end flanges 32 of the shell sections either side of the flanged joint. Thus a bridging cavity 53 accommodating the flanged joint is formed. The bridging cavity 53 may be contiguous with the cavity of one of the adjacent shell sections so that a continuous intermediate layer is formed. Alternatively bridging cavity may be isolated from the shell sections either side of it by additional seal members and separately injected with plastics material.

[0072 ] In an embodiment, an inspection port 60 is provided to allow access to the outer surface of pipe 1 through the pipe repair. Port 60 is shown enlarged in Figure 5. Port cylinder 61 is welded into port aperture 62 in the shell section wall 3, projecting toward pipe 1. Port gasket 63, formed of a resilient material, seals between the inner end of port cylinder 61 and the outer surface of pipe 1. Port seal 64 seals the outer end of port cylinder 61. Port seal 64 can be threaded and engage with a complementary thread on the internal surface of port cylinder 61.

[0073] The process for repairing a pipe according to an embodiment of the invention can be summarised as:

• prepare the outer surface of the pipe 1 to promote adhesion to the intermediate layer 2, e.g. by sand blasting to remove dirt, rust, paint, etc.

• select and customise (if necessary) shell sections 30 • fix seal members 40 to the outer surface of pipe 1 (or inner surface of shell sections 30) • fix gaskets 41, 42 to flanges 31,32 • position shell sections 30 around pipe 1 • bolt shell sections together to create cavity sealed by the compressed seal members 40 • inject uncured plastics material to fill cavity • allow plastics material to cure (applying heating or cooling as necessary) • grind off and/or fill injection ports and vents as necessary.

[0074 ] These steps are repeated as necessary to establish a series of shell units to repair the desired length of pipe. After the first shell unit is assembled, filled and cured, subsequent shell sections are bolted to the already completed repair sections via the end flanges. In subsequent repair sections, it is possible to use only one seal member 40, so that the cavity is bounded at the other end by the seal member of a previous repair section and the intermediate layer 3 bridges between repair sections. Conversely, it is possible to use multiple seal members within one repair section so that the cavity is divided into multiple parts which can be separately injected. This requires additional injection ports and vent holes but can be helpful in reducing injection volumes on large repairs.

[0075] Another embodiment of the invention is shown in Figures 7 and 8. Figure 7 is aperspective view of a complete repair section and Figure 8 is an enlarged cross-sectional view of the seal arrangements. The embodiment of Figures 7 and 8 is the same as the embodiment of Figures 1 to 6 save as described below. The embodiment of Figures 7 and 8 is installed by essentially the same process as described above.

[0076] The main difference between the embodiment of Figures 7 and 8 and that of Figures 1 to 6 is in the seal arrangement. Rather than fixing a seal member to the pipe 1, arcuate seal member 43 is generally L-shaped in cross-section, with a foot portion 43a that is placed against the pipe 1 and has an inclined upper surface 43b. The foot portion tapers from an outer side (away from cavity) to an inner side (toward the cavity). The leg portion 43c extends away from the pipe 1 at the outer, thicker side of the foot portion. Arcuate seal member 43 is desirably semi-circular so that two are required for a complete seal. An arcuate seal plate 44 is fixed to the outer side of the leg portion and has bolt-holes corresponding to the bolt-holes in the edge flange 32 of the shell section. To seal the cavity when the shell sections are bolted together around the pipes, bolts 36 through the bolt holes in the seal plate 44 and edge flange 36 are tightened to urge the tapered foot portion 43a into the gap between pipe 1 and shell section 32.

[0077 ] As described above, seal member 43 may be made of rubber, e.g. EPDM rubber. The dimensions of the seal member and clamping force applied can be varied as required to resist pressures occurring in the cavity during curing of the intermediate layer. The seams between arcuate seal members 32 need not be aligned with the joins between shell sections 32. This embodiment is advantageous for effecting relatively long single-section repairs since the clamped seal can resist large internal pressures arising during the injection and curing of a large cavity.

[0078 ] Also depicted in Figures 7 and 8 are hexagonal head screws 37 which seal apertures 38. Apertures 38 may function as vents or injection ports. Ribs 3 la extend perpendicularly to longitudinal flanges 31 to the outer surface of shell section 31 in order to support longitudinal flanges 31.

[0079] Another embodiment of the invention is shown in Figures 9 and 10. Figure 9 is a perspective view of a complete repair section and Figure 10 is an enlarged cross-sectional view of the seal arrangements. The embodiment of Figures 9 and 10 is the same as the embodiment of Figures 7 and 8 save as described below. The embodiment of Figures 9 and 10 is installed by essentially the same process as described above.

[ 0080 ] The embodiment of Figures 9 and 10 differs from that of Figure 7 and 8 in the form of the seal. Seal 45 comprises a wide band having a plurality, e.g. 6, of tapered ribs 45a projecting from one surface thereof. Seals 45 are fixed to the inner surface of shell sections 30 at the longitudinal ends thereof with the ribs 45a facing inwardly. Seal 45 may be adhered to the inner surface of the shell sections 30. Seals 45 may be restrained against longitudinal movement by a lip 32a formed by a part of end flange 32 that extends inwardly and a ring 46 welded to the inner surface of shell section 30. [0081 ] When the shell sections 30 are bolted in place about pipe 1, the ribs 45a are compressed against the pipe 1 to form a seal. Figures 9 and 10 show the ribs 45a in their uncompressed state. Compared to the embodiment of Figures 7 and 8, the embodiment of Figures 9 and 10 is advantageous in having fewer parts and in forming a good seal to the pipe even in the event of deformation of the pipe in the seal area.

[ 0082 ] An embodiment of the invention which is applied to the repair of a caisson is shown in Figures llto 18. Figures 11 and 12 depict the caisson in perspective and plan views prior to repair. The caisson comprises two cylindrical steel members la, lb welded end to end along seam 12. Steel straps 14 arc welded across the scam 12 to provide additional reinforcements. Fittings 13, in the form of short cylindrical members terminated by flanges, project from various locations of the caisson. Corrosion and/or damage may occur in the vicinity of the seam and the fittings.

[ 0083 ] Figures 13 and 14 depict custom shell sections 30 that fit around the caisson, accommodating both the fittings 13 and straps 14. The custom shell sections may be constructed off-site. Shell sections 30 are arranged so that their joins line up with fittings 13 and flanged cut-outs 310 are provided to accommodate the fittings. Where the fittings 13 are aligned or nearly diametrically opposed, just two shell sections can be used. However, if there are more fittings or the fittings are differently spaced around the caisson, it may be necessary to use more than two shell sections. Lifting points (not shown) can be added to facilitate the installation process. The shell sections 30 form a steel jacket that completely encapsulates the corroded or damaged region and extends above and below sufficient to transfer a force equal to the full yield capacity of the existing caisson from one side of the corroded region to the other.

[0084 ] Figures 15 and 16 show one shell section fitted to the caisson ready to receive the second shell section. As can be seen most clearly in Figure 16, a perimeter bar 47 is provided on the inner surface of shell section 30 adjacent the axial edge thereof. A resilient seal or gasket, e.g. formed of EPDM rubber, is provided between the inner side of the perimeter bar 47 and the caisson 1 in order to seal the cavity between the shell sections and the caisson. The perimeter bar is sized to ensure that the shell sections are spaced sufficiently far from the caisson to provide clearance for straps 14 and to provide a core thickness with optimum curing temperatures for an operational caisson. Seals or gaskets, e.g. or EPDM rubber, are also provided between the longitudinal flanges 31 and between the flanged cut-outs 310 and fittings 13. The seals also provide some tolerance between the existing and new construction as they are compressible.

[0085] Figures 17 and 18 show the completed repair. Longitudinal flanges 31 are bolted together to seal the shell unit comprising the shell sections around the caisson using bolts 36. The installation process is described below:

• the external surface of the caisson is be blasted to remove any surface corrosion and provides the correct surface preparation for bonding • the shell sections are secured over the caisson and around any penetrations, to form a jacket defining a cavity against the existing caisson. The seals and gaskets provide a tight cavity into which the elastomer can be injected.

• The elastomer is injected into the bottom and the air vented from the top. This arrangement allows complete filling of the cavity. Injection ports and vent holes are simply closed out with a threaded plug.

[0086] Having described exemplary embodiments of the invention, it will be appreciated that modifications and variations of the described embodiments can be made. In particular, although described in relation to repair of structures that are generally cylindrical, it is also possible to apply the method to structures having different cross-sections. The invention is not to be limited by the foregoing description but only by the appended claims.

Claims

1. A method of repairing a tubular structure comprising:

positioning a plurality of shell sections around the tubular structure in spaced apart relation thereto;

sealing the shell sections to the tubular structure so as to form a cavity; injecting an uncured plastics material into the cavity; and curing the plastics material so that it adheres to inner surfaces of the shell sections and the outer surface of the tubular structure to form an intermediate layer with sufficient strength to transfer shear forces between the tubular structure and the shell sections;

wherein sealing the shell sections to the tubular structure comprises:

providing a resilient seal member between the shell sections and the tubular structure; and bolting the shell sections together so as to compress the resilient seal member.

2. A method according to claim 1 wherein providing a resilient seal member comprises adhering an elongate resilient member in a closed loop around the tubular structure.

3. A method according to claim 2 wherein the resilient seal member fits between the tubular structure and the shell sections.

4. A method according to claim 1, 2 or 3 wherein providing a resilient seal comprises providing a tapered seal member projecting into a gap between an edge of a shell section and the tubular structure.

5. A method according to any one of the preceding claims wherein providing a resilient seal member comprises adhering a resilient seal member to an inner surface of a shell section.

6. A method according to any one of the preceding claims wherein an elongate edge member is fixed to the inner surface of a shell section and providing a resilient seal member comprises adhering the resilient seal member to a distal surface of the edge member.

7. A method according to any one of the preceding claims wherein the resilient seal member comprises a plurality of fins.

8. A method according to any one of the preceding claims wherein the resilient seal member is fonned of an ethylene propylene diene monomer (M-class) rubber.

9. A method according to any one of the preceding claims wherein the shell sections have an outwardly projecting flange along an edge thereof and bolting the shell sections together comprises bolting the flanges of adjacent shell sections together.

10. A method according to claim 9 further comprising providing a gasket between flanges of adjacent shell sections.

11. A method according to any one of the preceding claims wherein each shell section is substantially half-cylindrical.

12. A method according to any one of the preceding claims wherein a pair of adjacent shell sections has cut-outs in adjacent edges to accommodate a projecting fitting of the tubular structure.

13. A method according to any one of the preceding claims wherein each shell section has an axial length in the range of from 0.5 m to 10 m.

14. A method according to claim 14 wherein the shell sections are made of metal and have a thickness in the range of from 0.5 mm to 20 mm, desirably 2 to 20 mm.

15. A method according to claim 14 or 15 wherein the cavity has a thickness in the range of from 5 to 200 mm, desirably 10 to 100 mm.

16. A method according to any one of the preceding claims wherein the tubular structure is a Pipe.

17. A method according to any one of the preceding claims wherein the tubular structure is a caisson.

18. Apparatus for repairing a tubular structure, the apparatus comprising:

a plurality of shell sections configured to fit around the tubular structure in spaced apart relation thereto; and a resilient seal member configured to seal between the shell sections and the tubular structure;

wherein the shell sections are configured to be bolted together so as to compress the resilient seal member against the tubular structure.

19. A repaired tubular structure comprising:

a plurality of shell sections around the tubular structure in spaced apart relation thereto so as to form a cavity;

an intermediate layer filling the cavity and adhered to the shell sections and the tubular structure with sufficient strength to transfer shear forces between the tubular structure and the shell sections; and a resilient seal member compressed between the shell sections and the tubular structure to seal the cavity; wherein the shell sections are bolted together so as to compress the resilient seal member.

Intellectual

Property

Office

Application No: Claims searched: