spring

Abstract

A clamping spring (5; 105; 205; 305; 404; 505) suitable for attachment to a tubular member, the spring including an elastic body (6; 106; 206; 306; 406; 506) having first and second ends (8; 108; 208; 308; 408; 508), an inner surface (7; 107; 207; 307; 407; 507) adapted to seat within the clamping member, and an outer surface (9; 109; 209; 309; 409; 509) adapted to contact the outer surface of the tubular member, the inner and outer surfaces extending between the first and second ends, and the stiffness of the elastic body of the spring varying over the length of the elastic body between the first and second ends.

Description

[Technical Field]

[0001] The present invention relates to springs, and more particularly radial load springs, for use in clamping devices for securing submerged tubular members that are buoyant elements, particularly distributed buoyant elements such as flowlines, risers and umbilicals. [Background technology]

[0002] Oil and gas are typically transported from subsea reservoirs to the surface by rigid or flexible tubular members, such as pipes, known as risers. The outer diameter of a riser is subject to significant tolerances due to manufacturing specifications, tensions within the riser, internal pressure, hydrostatic pressure, and temperature of the fluid flowing within the riser. Thus, the outer diameter of a riser can vary along its length depending, among other things, on the hydrostatic pressure of the water surrounding the riser and the temperature and pressure of the recovered fluid flowing within the riser.

[0003] The weight of the risers and the hydrocarbons flowing within them can be supported from surface facilities in shallow water, but this requires strong risers and connections to maintain the integrity of long strings of risers that may extend over several hundred meters. It is therefore more economical to attach buoyancy elements to the risers to provide additional support.

[0004] Distributed buoyancy modules are provided on risers to isolate the subsea termination from the effects of vessel movement under weather and tidal conditions, or to maintain the riser in the position required for optimal use. For example, known configurations of risers between a floating production storage and offloading (FPSO) vessel and the seabed or floating subsea structure include configurations known as "Lazy S," "Lazy Wave," and "Lazy W," among others.

[0005] A clamp can be used to fit around the riser and attach the buoyancy module. Alternatively, the clamp may be an integral component of the buoyancy module. However, the attachment of the clamp to the riser must be done carefully to avoid any damage to the riser that could lead to failure of the flowline or failure to properly attach and position the buoyancy module.

[0006] These changes in internal and external pressure and temperature of the riser can significantly change the outer diameter of the riser, affecting the connection to the clamp. This can cause the clamp to slip along the outer surface of the riser. This can change the position of the buoyancy module, which can result in the riser configuration shifting away from its intended position. Additionally, the bending and tensile strains experienced by the riser during use further hinder proper sizing of the rigid clamp.

[0007] Known buoyancy modules include an arc- or C-shaped shell member having a semicircular channel extending the entire length of the shell member and disposed within an inner surface that dimensionally matches the outer surface of the riser. A number of such members are placed around the riser and secured in place with tensioning bands, such as titanium straps, or aramid fiber bands, such as KEVLAR® or TWARON®, to provide a clamp against which the buoyancy module can be secured.

[0008] An internal circumferential recess may be formed within the semicircular channel of the shell member within which the clamping component is mounted. The clamping component may be integral with the buoyant shell member or may be formed separately and seated within the recess.

[0009] For example, a bidirectionally loaded buoyancy module is shown in Figure 1. This module uses two semicircular shell members, each with an internal semicircular channel on the interior surface of the module, such that when the two modules are mated along their interior surfaces, they enclose a tubular member.

[0010] In this embodiment, the clamping component includes a spring mounted in the circumferential recess of the semicircular channel. In some known designs, a plurality of resilient springs, in the form of rectangular or cuboid blocks, are arranged in a centrally located array with two rows of three blocks around the circumferential recess of the semicircular channel. When the two buoyancy modules are brought together around the tubular member, the outer surfaces of the springs contact the tubular member at different points around the circumference of the tubular member, providing a resilient cushion between the buoyancy modules and the outer surface of the riser, distributing the load and subsequent contact pressure from the buoyancy modules around the tubular member.

[0011] The number of shell members and corresponding clamp components of a buoyancy module may typically be two to four, although the buoyancy module and clamp may be formed of more members if desired.

[0012] The demand for clamps to handle higher buoyancy loads and deployment in rougher sea conditions, and to accommodate higher riser strains and tighter riser bend radii, as well as high rates of change of these radii as the riser or other tubular member expands and contracts under operating conditions, has continually challenged the limits of performance.

[0013] Typically, reducing the number of clamping components changes the distribution of radial loads around the riser's exterior surface. Reducing the number of clamping components means that the springs in each clamping component extend a greater distance around the riser's outer curved surface, which can result in uneven force and pressure distribution around the tubular member. In extreme cases, particularly when two-component buoyancy modules and clamps are deployed, greater force can be exerted toward the center of the buoyancy module's clamping component than at its outer ends. This could theoretically cause the pipe to crush in the center of the clamping segment and bulge at its outer ends, potentially leading to a riser collapse.

[0014] While known clamps offer significant advantages over previously known tools in terms of reducing the capstan effect and equalizing the loads applied and received by the individual components of the clamp, applicant has developed a modified clamp which further mitigates the aforementioned effects. Summary of the Invention [Problem to be solved by the invention]

[0015] It is therefore an object of the present invention to provide an improved spring for a clamping component of a buoyancy module that overcomes or at least mitigates the above-mentioned problems.

[0016] SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a clamp for attaching a buoyancy module to a tubular member that overcomes, or at least mitigates, the above-mentioned problems.

[0017] It is a further object of the present invention to provide a buoyancy module that can be formed from multiple circumferentially offset members clamped around a tubular member, such as a riser, to provide the buoyancy necessary to maintain a given riser configuration. [Means for solving the problem]

[0018] According to a first aspect of the present invention, there is provided a spring for a clamp suitable for attachment to a tubular member, the spring comprising an elastic body having first and second ends, an inner surface adapted to seat within the clamp member, and an outer surface adapted to contact the outer surface of the tubular member, the inner and outer surfaces extending between the first and second ends, and the stiffness of the elastic body of the spring varying over the length of the elastic body between the first and second ends.

[0019] Optionally, the elastic body of the spring is arc-shaped.

[0020] Optionally, the stiffness is greater towards the first and second ends of the elastic body than towards the centre of the elastic body.

[0021] Optionally, the stiffness of the elastic body also varies gradually from the first and second ends towards the centre of the elastic body.

[0022] Optionally, the outer surface of the elastic body has a corrugated shape.

[0023] Optionally, this can take the form of a plurality of protrusions or undulations having peaks or hills and valleys along the outer surface of the spring.

[0024] Conveniently, each peak on the outer surface of the spring may be the same height as the adjacent valley.

[0025] Alternatively, the height of a peak on the outer surface of the spring relative to an adjacent valley may be different.

[0026] In one embodiment, the height of the peaks on the outer surface of the spring closest to the center of the spring relative to the adjacent valleys may be greater than the height of the peaks closer to the first and second ends of the spring relative to the adjacent valleys.

[0027] Alternatively, the height of the outer surface peaks closest to the center of the spring relative to the adjacent valleys may be less than the height of the peaks closer to the first and second ends of the spring relative to the adjacent valleys.

[0028] Alternatively, cavities are formed in the elastic body to vary the stiffness of the elastic body along its length.

[0029] Conveniently, the cavity may have different volumes and / or shapes over the length of the spring between the first and second ends.

[0030] Conveniently, the cavities adjacent the first and second ends of the spring may be smaller in volume and / or size than cavities closer to the centre of the spring.

[0031] Optionally, the elastomer comprises rubber, which in some embodiments may be nitrile rubber.

[0032] Optionally or alternatively, the elastomer comprises polyurethane.

[0033] Optionally or alternatively, the elastic body comprises a fiber reinforced plastic.

[0034] According to a second aspect of the present invention, there is provided a clamping component for attachment to a tubular member, the clamping component including a housing and a spring according to the first aspect of the present invention mounted in a seat on an inner surface of the housing.

[0035] Advantageously, the clamp body includes a plurality of clamp components, each component having a housing and a spring member mounted on the housing.

[0036] Optionally, the clamp can have two, three, four or other numbers of clamp components.

[0037] According to a third aspect of the present invention, there is provided a clamp comprising a plurality of clamp components according to the second aspect of the present invention and tensioning means for securing the components about a tubular member.

[0038] Preferably, the tensioning means comprises a band which surrounds the clamp.

[0039] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 is a perspective view of a buoyancy module incorporating a known bidirectional loading spring. [Figure 2a] 2 is a schematic diagram of a clamp spring of the first embodiment of the present invention when the spring is brought into contact with a tubular member. FIG. [Figure 2b] FIG. 1 illustrates the deformation of a spring when a load is applied. [Figure 3a] FIG. 2 is a schematic diagram of a further embodiment of the present invention. [Figure 3b] 10 is a schematic diagram of a further embodiment of the present invention in which the spring is deformed when a load is applied; [Figure 4a] FIG. 10 is a schematic diagram of yet another embodiment of the present invention. [Figure 4b] 10 is a schematic diagram of yet another embodiment of the present invention in which the spring is deformed when a load is applied. [Figure 5a] FIG. 10 is a schematic diagram of a further alternative embodiment of the present invention. [Figure 5b] 10 is a schematic diagram of a further alternative embodiment of the present invention in which the spring is deformed when a load is applied; [Figure 6a] FIG. 10 is a schematic diagram of yet another alternative embodiment of the present invention. [Figure 6b] 10 is a schematic diagram of yet another alternative embodiment of the present invention in which the spring is deformed when a load is applied. [Figure 7a] FIG. 10 is a schematic diagram of yet another alternative embodiment of the present invention. [Figure 7b] FIG. 7b is an enlarged detail of a portion of the spring of FIG. 7a. DETAILED DESCRIPTION OF THE INVENTION

[0041] Referring now to the drawings, a first embodiment of the present invention is shown in Figure 2a, which shows a cross-sectional view of a segment of a component of a clamp for attaching a buoyancy module around the circumference of a tubular member such as a riser, pipe, umbilical, etc.

[0042] The clamp component 1 comprises a housing 2 adapted to fit around the outer surface of a tubular member. In the illustrated embodiment, the clamp has a second similarly shaped component, each having a semicircular channel 3 extending along its inner surface from the top surface of the component to the bottom surface of the component.

[0043] When the two clamp components come together around the tubular member, the clamp will enclose the tubular member held within the channel through the clamp.

[0044] The surface of the semicircular channel 3 in the housing serves as a seat 4 for a spring 5 to absorb forces when the clamp is secured around the outer surface of the tubular member.

[0045] The spring includes an elastic body 6 that has an arcuate shape when mounted on the clamp housing. The elastic body 6 is preferably formed from a material such as rubber, nitrile rubber, polyurethane, fiber-reinforced plastic, or a combination thereof, which allows the elastic body to absorb forces as the clamp component presses against the outer surface of the tubular member and the elastic body is crushed between the clamp housing and the outer surface of the tubular member.

[0046] The inner surface 7 of the spring 6 is adapted to be mounted within the seat 4 of the housing. In the illustrated embodiment, the seat 4 is provided by the arcuate surface of a semicircular channel. The spring can be mounted equidistant between the top and bottom ends of the housing, although in some embodiments the spring may extend completely between the top and bottom surfaces of the housing. Alternatively, in some embodiments the position of the spring between the top and bottom ends of the housing can be varied as desired.

[0047] The spring extends from adjacent one end of the semicircular channel 3 to adjacent the other end of the semicircular channel. As can be seen in Figure 2a, the spring is mounted adjacent to but spaced from the beginning of the semicircular channel. Thus, the spring has a length that is slightly less than the length of the concave arcuate surface of the semicircular channel 3 in the housing 4.

[0048] The outer ends 8 of the elastic bodies 6 (only one of which is shown) in the illustrated embodiment taper inward toward the center of the semicircular channel 3, with the length of the outer surface of the elastic body 6 being shorter than the length of the inner surface of the elastic body. The performance of the spring can be adjusted by changing the taper angle of the ends of the spring.

[0049] In the illustrated embodiment, the stiffness of the spring's elastic body 6 varies along its length from one end of the body to the other. In this embodiment, the outer surface 9 of the elastic body has a wavy shape with rounded peaks 10 separated by valleys 11. The thickness of the elastic body 6 from the inner surface 7 to the outer surface 9 at the peaks 10 is greater than the thickness from the inner surface 7 to the outer surface 9 at the spring's valleys 11. Furthermore, the width of the individual peaks increases from the central peaks at the ends of the spring to the outer peaks. Because the stiffness of the spring in the peak regions is greater than the stiffness of the spring in the valley regions, the stiffness of the spring is higher at the ends of the spring than in the center.

[0050] In the illustrated embodiment, the depth of the first valleys 11 closest to the outer ends 8 of the elastic is shallower than the depth of the valleys 11' at the center of the elastic. The depth of the valleys 11 in this embodiment gradually increases between the outermost valleys and the central valley. In alternative embodiments, the valley depths may be equal along the length of the elastic.

[0051] As shown, by forming the elastic body to have a corrugated outer surface, fingers are formed on the elastic body 6, which provide the elastic body with more flexibility than a solid block of elastic material as described in prior art clamps.

[0052] As shown in FIG. 2b, when the clamp component 1 is initially fitted around the outer surface of the tubular member, the peaks 10 on the outer surface 9 of the spring's resilient body contact the outer circumference of the tubular member. As the clamp component is pressed against the outer surface of the tubular member, the resilient body 6 is compressed between the clamp component housing 2 and the outer surface of the tubular member. The spring fingers are compressed and tensioned around the outer surface of the tubular member. As shown in FIG. 2, the rounded peaks 10 on the outer surface flare outward toward the valleys 11, essentially closing them. This increases the circumferential length of the interface between the clamp spring and the outer surface of the tubular member beyond that currently available in prior art springs and also provides a uniform distribution of pressure within the spring from the center to the outer edge 8, thereby preventing abnormal deformation of the tubular member when the clamp component is tightened.

[0053] Thus, the clamping component spring 5 shown in Figures 2a and 2b provides superior performance over currently known springs. In the described embodiment, the clamping component is intended to be attached to the exterior surface of a tubular member to provide an anchor point for the buoyancy module around the tubular member. Alternatively, the clamping component may be integrally formed within the buoyancy module, and the clamping component housing 2 may be, for example, a C-shaped buoyant shell member in a bidirectionally loaded module, or an arc-shaped shell segment intended to form part of a multi-segment buoyancy module, as is known in the art.

[0054] While the above-described embodiments of the present invention are believed to offer significant advantages over known spring and clamp components, alternative embodiments are also envisioned that offer similar or even improved operating characteristics over known designs.

[0055] A further embodiment of the present invention is shown in Figures 3a and 3b. In this embodiment, reference numbers have been increased by 100 for ease of reference. In this embodiment, the housing 102 of the clamping component is as described in the previous embodiment.

[0056] The outer surface 109 of this embodiment is modified so that, rather than gradually increasing in valley depth, the depth of the valleys 111 increases from relatively shallow outer valleys to a significantly deeper central valley 111'. Thus, the thickness of the elastic 106 toward the ends 108 of the elastic is greater than the thickness at the center of the elastic, and as a result, the stiffness of the elastic 106 varies along the length of the elastic between the outer ends 108 such that the stiffness is greater toward the ends of the elastic than at the center of the elastic.

[0057] Additionally, in this embodiment, the outer end 108 of the elastic body 106 is modified so that, while the outer end still tapers toward the center of the clamp component, in this embodiment the outer end of the elastic body extends beyond the end of the semicircular channel 103 in a plane parallel to the outer end of the clamp housing 102.

[0058] As shown in FIG. 3b, when the clamping component 101 is pressed against the outer surface of the tubular member, the fingers of the spring 105 are pressed together and the inner surface 107 of the elastic body 106 is drawn around the outer circumference of the tubular member, thereby distributing the load within the elastic body 106 along the length of the elastic body.

[0059] The angle at which the end of the elastomer tapers can be varied to tune the performance of the spring. Varying the taper angle controls the angular position of the shoulder 112 when the spring is at rest, i.e., before the outer surface 109 contacts the outer surface of the tubular member, and the subsequent angular position of the shoulder (relative to the center of the tubular member) when the spring is under load, i.e., when the spring is compressed between the housing and the tubular member.

[0060] Yet another embodiment of the present invention is shown in Figures 4a and 4b. In this embodiment, the reference numbers have been increased by 200 for ease of reference. In this embodiment, the housing 202 of the clamping component 201 is as described in the previous embodiment.

[0061] In this embodiment, the outer end 208 of the elastic is approximately perpendicular to the end of the inner surface 207, and the outermost peaks of the outer surface 209 are replaced by flat shoulders 212. Rounded peaks 210 separated by valleys 211 are formed on the outer surface between the two flat shoulders 212 at either end of the elastic 206. In this embodiment, valleys are formed between the inner ends of the flat shoulders 212 and the relatively shallow outermost peaks 210, with the valleys increasing in depth between the outermost valleys and the center of the elastic.

[0062] As shown in Figure 4b, when the spring is compressed between the housing 202 and the outer surface of the tubular member, a flat shoulder 212 at the end of the outer surface 209 of the elastic body contacts the outer surface of the tubular member, providing an area of ​​increased friction between the elastic body and the outer surface of the tubular member. The variation in stiffness of the elastic body caused by the variation in depth of the elastic body at different points along its length improves the distribution of load and pressure from the center of the elastic body toward the outer end 208 over prior art springs.

[0063] A further embodiment of the present invention is shown in Figures 5a and 5b of the drawings. In this embodiment, reference numerals have been increased by 300 for ease of reference. In this embodiment, the housing 302 of the clamp component 301 is modified so that the outer ends of the surfaces of the semicircular channel 303 terminate in straight portions 313 that extend perpendicular to the outer end of the clamp housing. The inner surfaces 307 of the resilient bodies 306 are modified to meet at each outer end 308 so that a right-angled inner shoulder is formed between the straight portions of the housing 313 and the ends of the resilient bodies. Thus, in this embodiment, the outer ends 308 of the resilient bodies extend in the same plane as the outer end of the housing and form an extension of the outer end of the housing.

[0064] In this embodiment, spring 305 is further modified in that the contours of outer surface 309 are replaced by cavities 314 enclosed within the elastic body 306 of the spring. In the embodiment shown, the cavities are generally circular and extend through the elastic body from top to bottom. In some embodiments not shown, the cavities may have a different shape or may not extend through the elastic body from top to bottom, but may be completely enclosed within the elastic body. The volume of the cavities gradually increases along the length of the elastic body, from the outermost cavities in the ends of the elastic body to the cavities at the center of the elastic body.

[0065] 5b, when the clamping component 301 is compressed between the housing 302 and the outer surface of the tubular member, cavities 314 within the elastomeric body of the spring 305 cause the spring to deform in a controlled manner, distributing the load and pressure over the length of the spring better than prior art springs. This embodiment provides a further improvement in that the contact interface between the spring 305 and the outer surface of the tubular member extends over the entire outer surface 309 of the elastomeric body.

[0066] The diameter and spacing of the cavities 314 located within the spring can be modified to match or tune the stiffness of the spring to ensure that natural peak loads and pressures at the center of the spring are reduced by regions of high compression that correspond to larger cavities upon compression. Towards the ends of the spring, the diameter of the cavities gradually decreases, or in some embodiments, they may be eliminated entirely to create regions of low compression that correspond to smaller diameters or no cavities at all (when compared to regions of the spring with larger diameter cavities).

[0067] A further embodiment is depicted in Figures 6a and 6b. In this embodiment, the reference numbers have been increased by 400 for ease of reference. In this embodiment, the housing 402 of the clamp component 401 is modified similarly to the embodiment shown in Figures 5a and 5b above. Thus, the outer end of the surface of the semicircular channel 403 terminates in a straight portion 413 that extends perpendicular to the outer end of the clamp housing.

[0068] In this embodiment, the inner surface 407 of the elastic body 406 is modified to conform at each outer end 408 to follow the change in direction from the arcuate portion to the straight portion of the semicircular channel 403. However, in this embodiment, the ends of the elastic body 406 are truncated so that they do not extend completely along the straight portion 413 of the sheet 404, but rather terminate before the point where the straight portion 413 meets the outer end of the housing 402.

[0069] The outer end 408 of the elastic 406 in this embodiment is further modified to provide a flat shoulder 412 at the end of the outer surface 409. However, unlike the previously described embodiment in which the flat shoulder directly connects to a first valley in the outer surface, in this embodiment the outer surface of the elastic extends along the flat shoulder 412 but then turns downward at a nearly 90-degree angle toward the inner surface 407 of the elastic before returning toward the outer end of the elastic, thereby forming an undercut 415 below the flat shoulder 412. From the open end of the undercut, the outer surface 409 is undulated by a series of rounded protrusions 416 separated by rounded grooves 417. In the illustrated embodiment, each protrusion has a similar height from the inner surface 407 of the elastic, although it is contemplated that in some embodiments the height of the protrusions may vary. The height of each protrusion is less than the height of the end 408 of the elastic. Thus, in this embodiment, when the clamping component contacts the outer surface of the tubular member, the flat shoulder 412 on the end of the elastomer first contacts the outer surface of the tubular member.

[0070] When the clamping component 401 is pressed against the outer surface of the tubular member, the flat shoulders on the ends of the elastic body are compressed between the ends of the elastic body and the outer surface of the tubular member, expanding around the tubular member toward the center of the elastic body. Further compression of the spring causes the rounded projections 416 to contact the outer surface of the tubular member and extrude such that the projections deform within grooves 417. This embodiment provides a significantly improved spring that distributes the load and pressure around the tubular member to which the clamping component 401 is attached from the center of the component toward the outer ends, thus reducing the risk of the tubular member collapsing or buckling under the load and pressure of the spring, which may concentrate forces toward the center of the spring.

[0071] A further embodiment is shown in Figures 7a and 7b. In this embodiment, the reference numbers have been increased by 500 for ease of reference. In this embodiment, the housing 502 of the clamp component 501 is modified similarly to the embodiment shown in Figures 6a and 6b above. Thus, the outer end of the surface of the semicircular channel 503 terminates in a straight portion 513 that extends perpendicular to the outer end of the clamp housing.

[0072] The outer end 508 of the elastic body 506 in this embodiment is similarly modified to provide a flat shoulder 512 at the end of the outer surface 509 and an undercut 515 below the flat shoulder 512 .

[0073] In this embodiment, the outer surface 509 is formed with a series of frustoconical projections 516 separated by deep rounded grooves 517. The height of the projections varies along the length of the elastic. In the embodiment shown, the height of the projections at the center of the elastic is less than the height of the projections at the ends of the elastic. In other embodiments, all of the projections can have the same height from the inner surface 507 of the elastic.

[0074] The height of each protrusion is less than the height of the end 508 of the elastic body. Thus, in this embodiment, when the clamping component contacts the outer surface of the tubular member, the flat shoulder 512 on the end of the elastic body first contacts the outer surface of the tubular member.

[0075] When the clamping component 501 is pressed against the outer surface of the tubular member, the flat shoulders on the ends of the elastic body are compressed between the ends of the elastic body and the outer surface of the tubular member, expanding around the tubular member toward the center of the elastic body. Further compression of the spring causes the frustoconical projections 516 to contact the outer surface of the tubular member, pushing the projections out so that they deform into the grooves 517.

[0076] Similar to the embodiment shown in Figures 6a and 6b, this embodiment provides a significantly improved spring that distributes the load and pressure around the tubular member to which the clamping component 501 is attached from the center of the component towards the outer ends, thus reducing the risk of the tubular member collapsing or buckling under the load and pressure of the spring, which may concentrate forces towards the center of the spring.

[0077] Variations of the above embodiments are also envisaged in which features that affect the stiffness of the spring are combined, for example by incorporating the cavities of Figures 5a and 5b into the spring, by modifying the embodiment shown in Figures 2a and 2b, or by modifying the ends of the spring of any example with the ends described in any other example.

[0078] As noted above, in each embodiment the clamp component has been described as having a housing and a spring member mounted within a seat in the housing. Of course, it will be apparent to those skilled in the art that any of the described embodiments may be incorporated into the clamp to which the buoyancy module is attached, or alternatively may be integrally formed within the buoyancy module such that the housing of the clamp component may be replaced by an appropriately shaped portion of the buoyancy module itself.

[0079] The springs described in connection with any of the above embodiments can be retrofitted to current buoyancy modules by replacing the original springs described in connection with prior art devices with modified springs in accordance with the present invention, providing a cost-effective way of providing the benefits of the present invention to an existing stock of buoyancy modules.

[0080] Each of the above embodiments can be mechanically secured to the clamping component via a set screw or washer. Openings and / or cavities can be provided through the ends of the resilient body and / or along its length. Alternatively, the spring can be directly bonded to the clamping component, for example, using an adhesive. In this case, openings and / or cavities would not be necessary.

[0081] The above embodiments can be modified by changing the outer diameter of the tubular member, increasing or decreasing the number of lugs based on the required circumference of the spring. Additionally, the overall thickness, width and length of the spring can be modified.

[0082] Those skilled in the art will appreciate that the present invention provides an improved solution for the distribution of contact pressure between segments of a multibody clamp and a tubular member such as a riser, umbilical, pipe, etc. This mitigates collapse of the tubular member due to uneven pressure distribution, which can result in pressure concentrations leading to crushing of the tubular member.

[0083] The present invention provides a cost-effective solution in which contact pressure is more evenly distributed around the outer surface of the tubular member.

[0084] By reducing the peak pressure, the size, ie, weight and lift force, of the offshore clamping device can be increased beyond conventional values.

Claims

1. 1. A clamp spring for distributing a load from a clamp attached around a tubular member, the spring including a resilient body having first and second ends, an inner surface adapted to seat within a clamp member, and an outer surface adapted to contact an outer surface of the tubular member, the inner and outer surfaces of the resilient body of the spring extending between the first and second ends, the outer surface of the resilient body being undulating in shape, the outer surface of the resilient body including a plurality of peaks and valleys along the outer surface of the spring, the height of a peak on the outer surface of the spring relative to an adjacent valley varies along the length of the spring, and the stiffness of the resilient body of the spring varies over the length of the body between the first and second ends, the stiffness being higher towards the first and second ends of the resilient body than at a center of the resilient body.

2. The spring of claim 1 , wherein the spring's elastic body is arcuate.

3. 3. The spring of claim 1, wherein the stiffness of the elastic body gradually changes from the first and second ends toward the center of the elastic body.

4. 4. The spring of claim 1, wherein a height of a peak on the outer surface of the spring closest to a center of the spring relative to the adjacent valley is greater than a height of an apex closer to the first and second ends of the spring relative to the adjacent valley.

5. The spring according to any one of claims 1 to 4, wherein the elastic body comprises rubber.

6. The spring of claim 5 , wherein the resilient body comprises nitrile rubber.

7. The spring according to any one of claims 1 to 6, wherein the elastic body comprises polyurethane.

8. The spring of any one of claims 1 to 7, wherein the elastic body comprises fiber-reinforced plastic.

9. A clamping component for attachment to a tubular member, comprising a housing and a spring according to any one of claims 1 to 8 mounted in a seat on an inner surface of the housing.

10. A clamp comprising a plurality of clamp components as described in claim 9.

11. The clamp of claim 10 , wherein the clamp has two, three, or four clamp components.

12. A clamp as described in claim 10 or 11, including tensioning means for securing the clamp component around a tubular member.

13. 13. The clamp of claim 12, wherein the tensioning means comprises a band surrounding the clamp.

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