WO2015071684A2

WO2015071684A2 - Bend restrictor

Info

Publication number: WO2015071684A2
Application number: PCT/GB2014/053386
Authority: WO
Inventors: Gregory VAN HINSBERGH
Original assignee: Tekmar Energy Limited
Priority date: 2013-11-15
Filing date: 2014-11-14
Publication date: 2015-05-21
Also published as: WO2015071684A3; GB201320249D0

Abstract

A bend restrictor for longitudinally extensive protection apparatus configured to contain a longitudinally extensive service member, the bend restrictor comprising first and second end sections attachable in fixed relation to the longitudinally extensive protection apparatus, a plurality of intermediate sections arranged between the first and second end sections, a through longitudinal passage extending through the respective end sections and the intermediate sections in which the longitudinally extensive protection apparatus is accommodated;, one section of each adjacent pair of said sections including a male longitudinally directed projection which is received in a female recess of the adjacent section of said pair of sections; the male recess including a laterally outer wall which is always at least partially in juxtaposition with a corresponding laterally outer wall of the female recess, each respective outer wall consisting of a portion of the surface of a sphere such that a non-interlocking spherical joint is formed between the said adjacent sections.

Description

Bend Restrictor

[0001] This invention relates to a bend restrictor for use with an offshore longitudinally extensive protection apparatus. The longitudinally extensive protection apparatus is configured for protection of a longitudinally extensive service member. Examples of such longitudinally extensive service members include cables for the transmission of electricity, fibre optic cable and pipes for conveying fluid in connection with oil and gas extraction. The longitudinally extensive service member is arranged in use within the longitudinally extensive protection apparatus. The bend restrictor, through which the longitudinally extensive protection apparatus passes is arranged in use at least partially (and commonly wholly) in a sub-sea location. The bend restrictor is accordingly constructed and arranged to operate in, and to withstand, conditions prevailing in subsea environments.

[0002] The bend restrictor is particularly suitable for limiting the minimum bend radius of a longitudinally extensive protection apparatus arranged at or near to an offshore foundation, such as a foundation for constructions associated with offshore wind energy, including foundations for wind turbine generators and offshore substations. In such arrangements the longitudinally extensive service member contained within the longitudinally extensive protection apparatus can be a cable for the transmission of electricity, or a plurality of such cables.

[0003] The present invention relates in particular embodiments to a bend restrictor which is configured for use with a longitudinally extensive protection apparatus in the form of a flexible pipe or tube, especially a polymeric flexible pipe or tube.

BACKGROUND

[0004] Bend restrictors as such are well known in the art. However, conventional bend restrictors can have unpredictable behaviours at or towards the limit of their bend radius. For example, known bend restrictors in this condition can act as a spring. Embodiments of the present invention seek to provide a bend restrictor with more predictable bending behaviours at the limit. Embodiments of the invention further seek to provide a bend restrictor for which, in contrast to bend restrictors of the prior art, the minimum bend radius cannot normally be exceeded at typically available pulling forces applied to the

longitudinally extensive protection apparatus in an offshore use environment.

BRIEF SUM MARY OF THE DISCLOSURE

[0005] In accordance with a first aspect of the present invention there is provided a bend restrictor for a longitudinally extensive protection apparatus configured to contain a longitudinally extensive service member, the bend restrictor comprising first and second end sections attachable in fixed relation to the longitudinally extensive protection apparatus

a plurality of intermediate sections arranged between the first and second end sections

a through longitudinal passage extending through the respective end sections and the intermediate sections in which the longitudinally extensive protection apparatus is accommodated in use;

one section of each adjacent pair of said sections including a male longitudinally directed projection which is received in a female recess of the adjacent section of said pair of sections;

the male recess including a laterally outer wall which is always at least partially in juxtaposition with a corresponding laterally outer wall of the female recess, each respective outer wall consisting of a portion of the surface of a sphere such that a non-interlocking spherical joint is formed between the said adjacent sections.

[0006] In accordance with a second aspect of the present invention there is provided an assembly of a bend restrictor and a longitudinally extensive protection apparatus arranged within the bend restrictor and configured to contain a longitudinally extensive service member, the bend restrictor comprising:

first and second end sections attached in fixed relation to the longitudinally extensive protection apparatus;

a plurality of intermediate sections arranged between the first and second end sections;

a through longitudinal passage extending through the respective end sections and the intermediate sections and configured to accommodate the longitudinally extensive protection apparatus

[0007] In accordance with a third aspect of the invention there is provided an offshore installation comprising: an offshore structure having connected thereto a longitudinally extensive service member, the service member being disposed within a longitudinally extensive protection apparatus; and a bend restrictor arranged on the longitudinally extensive protection apparatus, the bend restrictor being as defined in the first aspect of the invention.

[0008] In some preferred embodiments, the longitudinally extensive service member can comprise one or more pipes or cables. The pipe can be a pipe for the transmission of production fluids associated offshore fuel extraction, in particular oil or gas. The cable can be for the transmission of electricity associated with offshore energy production, in particular transmission from offshore wind turbines to offshore control or regulating apparatus and/or to shore.

[0009] In some preferred embodiments the longitudinally extensive protection apparatus can be a conduit such as a duct, pipe or tube within which the longitudinally extensive service member can be disposed. In some preferred embodiments, the longitudinally extensive protection apparatus can comprise a pipe or tube of a polymeric material such as high density polyethylene (HDPE).

[0010] In some preferred embodiments for each said pair of sections, a shoulder wall extends outwardly from a longitudinally inner limit of the outer wall of the male projection to an external wall of the section, and a corresponding shoulder wall extends outwardly from a longitudinally outer limit of the outer wall of the female recess to an external wall of the section, the respective shoulder walls being opposed and radially inner parts thereof adopting a contacting relation when the bend restrictor is at its minimum bend radius.

[0011] In some preferred embodiments surfaces of said through longitudinal passage of the bend restrictor are profiled so that, when the bend restrictor is at its minimum radius, radially inner surface portions of the passage form a smooth curve which conforms to the radially innermost part of the surface of the longitudinally extensive protection apparatus when contained within the passage.

[0012] The spherical joint formed between the said adjacent sections can be non- interlocking in the sense that (absent the constraint of the fixedly attached end sections) adjacent sections can be freely separated by moving axially apart without requiring any deformation, change in configuration or disassembly of said adjacent sections.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 shows a bend restrictor according to some embodiments of the invention at its minimum bend radius; Figure 2 shows a bend restrictor according to some embodiments of the invention in a substantially linear condition;

Figure 3 shows a simplified diagram of a female section of a bend restrictor according to some embodiments of the invention;

Figure 4 shows a simplified diagram of a male section of a bend restrictor according to some embodiments of the invention;

Figure 5 shows an alternative configuration of a bend restrictor according to some embodiments of the invention;

Figure 6 shows an assembly comprising a bend restrictor and a longitudinally extensive protection apparatus according to some embodiments of the invention with the bend restrictor at its minimum bend radius;

Figure 7 shows an assembly comprising a bend restrictor and a longitudinally extensive protection apparatus according to some embodiments of the invention in a substantially linear condition;

Figure 8 shows sections of a portion of the bend restrictor and the longitudinally extensive protection apparatus when in a bent condition;

Figure 9 shows sections of a portion of the bend restrictor and the longitudinally extensive protection apparatus when in a linear condition;

Figure 10A shows a bend restrictor according to some embodiments of the invention at its minimum bend radius;

Figure 10B is a section along A-A of Figure 10A;

Figure 10C shows in more detail the area marked "C" in Figure 10B;

Figure 10D shows in more detail the area marked "B" in Figure 10B;

Figure 11 A shows an assembly comprising a longitudinally extensive protection apparatus, a bend restrictor and some further apparatus or components which can advantageously be used with the bed restrictor;

Figure 11 B shows the assembly of Figure 11A when rotated 90° about its longitudinal axis;

Figure 11 C shows more detail of the use of a mounting apparatus shown in Figure 1 1A and 11 B;

Figure 12 shows an offshore installation according to some embodiments of the invention where the bend restrictor is arranged at an offshore structure of a first type; and Figure 13 shows an offshore installation according to some embodiments of the invention where the bend restrictor is arranged at an offshore structure of a second type

DETAILED DESCRIPTION

[0014] Referring now to the drawings, Figure 1 shows a bend restrictor 100A according to some embodiments of the invention at its minimum bend radius and Figure 2 shows a similar (though longer) bend restrictor 100B in a substantially linear condition. Figure 6 shows an assembly of the bend restrictor 100A and a longitudinally extensive protection apparatus 200 according to some embodiments of the invention with the bend restrictor 100A at its minimum bend radius. Figure 7 shows a similar assembly (though with a longer bend restrictor 100B) in a substantially linear condition. Figures 10A to 10D show a further example of a bed restrictor according to some embodiments of the invention. The bend restrictor includes a through bore, duct or passage 160 which in use can

accommodate the longitudinally extensive protection apparatus 200 which in some preferred embodiments of the invention is in the form of a flexible pipe or tube. In some preferred embodiments, the flexible pipe or tube 200 is formed from a polymeric material, in particular high density polyethylene (HDPE).

[0015] In typical arrangements the longitudinally extensive protection apparatus 200 (in particular in the form of a flexible pipe or tube) can have an internal diameter in the range of from about 50mm to about 1000mm, such as from about 50mm or 100mm to about 750mm, in particular from about 150mm, to about 500mm.

[0016] Also in typical arrangements the longitudinally extensive protection apparatus 200 (in particular in the form of a flexible pipe or tube) can have a wall thickness which is determined in accordance with operating conditions and demands such as axial load, bending moment and shear force loads. Typically these parameters are in the ranges of: axial load, 0 to 150kN; bending moment 0 to 400kNm; shear load 0 to 400kN. Thus the longitudinally extensive protection apparatus 200 can typically be designed and configured to withstand in service at least the upper values of the preceding three ranges. The axial load, bending moment and shear load may not be continuous and will depend on factors such as the installation method and equipment and prevailing environmental conditions (e.g. currents etc) during the working lifetime of the longitudinally extensive protection apparatus. Typically the said wall thickness can be in the range of from about 3mm to 75mm.

[0017] Further in typical arrangements the length of the longitudinally extensive protection apparatus 200 (in particular in the form of a flexible pipe or tube) is determined by its particular application or use, for example by the distance between offshore installations between which the longitudinally extensive protection apparatus extends. Typically the longitudinally extensive protection apparatus (in particular in the form of a flexible pipe or tube) can have a length of at least 1m such as at least 5m. The maximum length of the longitudinally extensive protection apparatus 200 can be 1km or more (e.g. up to 5km), but about 100 - 150m is a typical maximum length.

[0018] The length of the bend restrictor 100 can be determined in accordance with circumstances and design requirements of its intended use. In some preferred embodiments the bed restrictor can have a length of from about 1 m to about 20m, such as from about 1m to about 10m.

[0019] The bend restrictor 100 can comprise a plurality of cooperating sections. Each bend restrictor can include two end sections 110, that is, one at each end of the bend restrictor. The end sections 110 can be secured so that they do not move relative to the longitudinally extensive protection apparatus. In particular, the respective end sections 110 can be fixedly secured to the longitudinally extensive protection apparatus 200 such as to provide at least 30kN of axial restraint before any slippage occurs between a given end section 110 and the longitudinally extensive protection apparatus 200.

[0020] The bend restrictor 100 can further comprise a plurality of intermediate sections. In the illustrated embodiments of Figures 1 , 2, 6, 7 and 10A to 10D the bend restrictor 100 includes alternate male sections 120 and female sections 130. As illustrated in Figures 3 and 4, each male section 120 can have two opposed longitudinally directed projections 122. Each female section 130 can have two opposed female recesses 132.

[0021] In other configurations, as shown for example in Figure 5, most intermediate sections can have one male projection and one female recess. In the example of Figure 5 one male section 120 is provided to cooperate with one of the end sections 110.

[0022] When assembled into a bend restrictor 100, the male projection 122 of a given section 120, 140 can be received into the female recess 132 of an adjacent section 130, 140.

[0023] The external surface of the bend restrictor as a whole can be defined by the consecutive external surfaces 114, 124, 134 (or 144 in Fig 5) respectively of the end sections and intermediate sections. In some preferred embodiments, the major part of the external profile of the bend restrictor 100 can be cylindrical (with the bend restrictor 100 in a linear conformation). Thus in some preferred embodiments the external surface of each intermediate section 120, 130, 140 is at least approximately cylindrical.

[0024] The internal surface of the bend restrictor as a whole, forming the surface of the passage 160 can be defined by consecutive internal surfaces 116, 126, 136 (146, Fig 5) respectively of the end sections and the intermediate sections. The respective internal surfaces can be cylindrical or near cylindrical and can be sized to conform to the external profile of the longitudinally extensive protection apparatus which is received in the passage 160 (which is also typically cylindrical).

[0025] The internal diameter of the bend restrictor 100 and the external diameter of the longitudinally extensive protection apparatus can be sized such that the longitudinally extensive protection apparatus is a relatively tight fit in the bend restrictor 100, that is, such that the clearance between the internal surface of the bend restrictor and the external surface of the longitudinally extensive protection apparatus is small. In some preferred embodiments, such clearance can be about 10mm or less, in particular about 5mm or less. Such limited clearance between the longitudinally extensive protection apparatus 200 and the bend restrictor 100 can be advantageous in reacting bending moment load as tension (at the radially outer portion of the longitudinally extensive protection apparatus 200) and compression (at the radially inner portion of the longitudinally extensive protection apparatus 200) since the longitudinally extensive protection apparatus 200 is prevented by the tight fit of the bend restrictor from ovalising.

[0026] The presence or absence of such ovalising of the longitudinally extensive protection apparatus 200 is schematically illustrated in Figure 8 which shows a portion of the bend restrictor 100 and the longitudinally extensive protection apparatus 200 when in a bent condition. Part (c) of Figure 8 shows a longitudinal section through a portion of an assembly of the bend restrictor 100 and longitudinally extensive protection apparatus 200. The assembly is in a bent condition with surface 100' being radially outermost and surface 100" being radially innermost. Arrows 170 indicate that the radially innermost portion of the longitudinally extensive protection apparatus 200 is in compression and arrows 172 indicate that the radially outermost portion of the longitudinally extensive protection apparatus 200 is in tension. Parts (a) and (a') of Figure 8 are lateral cross sections which illustrate the configuration of the longitudinally extensive protection apparatus 200 when constrained by the bend restrictor 100 according to the invention. It can be noted that the longitudinally extensive protection apparatus 200 is maintained in a circular shape in cross section. Parts (b) and (b') of Figure 8 are lateral cross sections which illustrate the configuration of the longitudinally extensive protection apparatus 200 when not adequately constrained by a bend restrictor. It can be noted that the longitudinally extensive protection apparatus 200 adopts an oval or elliptical shape in cross section.

[0027] Figure 9 shows a portion of the bend restrictor 100 and the longitudinally extensive protection apparatus 200 when in a linear condition. Part (b) of Figure 9 shows a longitudinal section through a portion of an assembly of the bend restrictor 100 and longitudinally extensive protection apparatus 200. Arrows 174 illustrate that the longitudinally extensive protection apparatus 200 is maintained in tension (as discussed further below). Parts (a) and (a') of Figure 9 indicate that the longitudinally extensive protection apparatus 200 maintains a circular shape in cross section.

[0028] In some preferred embodiments the internal surfaces 116, 126, 136, 1 6 of the bend restrictor can be profiled so that when the bend restrictor is at its minimum radius (100A, Figures 1 and 6) the radially inner surface portions (with respect to the bend radius) of the passage 160 form a smooth curve which conforms to the radially innermost part of the surface of the longitudinally extensive protection apparatus contained within the passage 160, as can be seen in particular in Figure 6. Thus, each of the sections , 120, 130, 140 can have an inner surface which provides a segment of said smooth curve. It follows in these embodiments that the internal surfaces 116, 126, 136 and 146 are not perfectly cylindrical. However the internal surfaces 160h of the end sections 110 are preferably substantially cylindrical.

[0029] Each male section projection 122 can project longitudinally, that is in a direction generally parallel to the longitudinal axis 150 of the bend restrictor 100 when the bend restrictor is in its linear condition (Figures 2 and 7, 100B). As can be seen in particular in Figures 3 and 4 each male projection 122 can be defined by a forward face 123 which can extend substantially along a radius of axis 150 and a laterally outer neck wall 125 which extends from a radially outer circumferential edge of the forward face 123. From a longitudinally inner boundary of the neck wall 125 a shoulder wall 127 can extend to the external surface 124 of the section 120.

[0030] Each female section recess 132 can be recessed longitudinally, that is in a direction generally parallel to the longitudinal axis 150 of the bend restrictor 100 when the bend restrictor is in its linear condition (Figures 2 and 7, 100B). As can be seen in particular in Figures 3 and 4, each female recess 132 can be defined by an inner face 133 which can extend substantially along a radius of axis 150 and a laterally outer neck wall 135 which extends from a radially outer circumferential limit of the inner face 133. From a longitudinally outer boundary of the neck wall 135 a shoulder wall 137 can extend to the external surface 134 of the section 130.

[0031] In some preferred embodiments, the neck wall 125 of projection 122 can be formed as portion of a sphere. In particular the neck wall 125 can be the spherical component of a spherical segment (a spherical segment being the solid defined by cutting a sphere with a pair of parallel planes). In some preferred embodiments neck wall 135 of recess 132 can likewise be formed as portion of a sphere. Figures 3 and 4 include construction lines 138A.B and 128A.B to indicate the respective spheres from which the neck walls 125, 135 are derived. [0032] The respective shapes and sizes of the projection 122 and recess 132 of the sections can be such that the projection 122 of one section can be received in the recess of an adjacent section. A non-interlocking spherical joint is thereby formed. When so received, the forward face 123 of the projection 122 can be juxtaposed to, and in close proximity to, the inner face 133 of the recess 132 and the neck wall 125 of the projection 122 can be juxtaposed to, and in close proximity to, the neck wall 135 of the recess 132. Also the shoulder wall 127 of the section 120 can be juxtaposed to, and in close proximity to, the shoulder wall 137 of the section 130.

[0033] For forming a non-interlocking spherical joint, the respective sections can be configured such that, for adjacent sections, the maximum radial length extending from the centreline or axis of the section to the neck wall 135 of the female recess 132 is never less than the maximum radial length extending from the centreline or axis of the section to the neck wall 125 of the male projection 122.

[0034] The bend restrictor can be configured such that, when the bend restrictor 100 is in its linear condition (Figures 2 and 7, 100B) juxtaposed forward face 123 and inner wall 133 respectively of the projection 122 and recess 132 are in close but non-contacting relation.

That is, the forward face 123 and inner wall 133 can be spaced apart by a relatively small distance. Similarly, when the bend restrictor 100 is in its linear condition (Figure 2, 100B) juxtaposed shoulder walls 127, 137 respectively of the projection 122 and recess 132 can be in close but non-contacting relation. That is, the shoulder walls 127, 137 can be spaced apart by a relatively small distance. However, neck wall 125 of projection 122 can be in contacting relation with neck wall 135 of recess 132.

[0035]

[0036] With particular reference to Figures 1 6 and 10B, when the bend restrictor adopts its minimum bend radius (100A) at the radially inner side (with respect to the bend radius) for adjacent sections 120, 130 (or 110, 120) the forward face 123 can be (but is not necessarily) in full contacting relation with the inner face 133, the neck wall 125 of the projection 122 can be in full contacting relation with the neck wall 135 of the recess 132 and the respective shoulder walls 127, 137 of the projection 122 and recess 132 can be in full contacting relation.

[0037] Also, when the bend restrictor adopts its minimum bend radius (100A) at the radially outer side (with respect to the bend radius) for adjacent sections 120, 130 (or 110, 120) the forward face 123 can be spaced apart from the inner face 133, the neck wall 125 of the projection 122 can be in partial contacting relation with the neck wall 135 of the recess 132 and the respective shoulder walls 127, 137 of the projection 122 and recess 132 can be spaced apart. However the construction of the forward face 123, inner face 133, neck walls 125, 135 and shoulder walls 127, 137 can be such that, at the radially outer side (with respect to the bend radius), the spacing of the shoulder walls 127, 137 cannot be further increased. Specifically, the spacing of the shoulder walls 127, 137 cannot be further increased to the extent that the neck walls 125, 135 are no longer in at least partial juxtaposition. In this way, further bending of the bend restrictor 100 to further reduce the bend radius is prevented. In a strict absolute sense, further bending of the bend restrictor is not prevented in as much as with sufficient applied force the material of the bend restrictor itself could be compressed. However, the applied force required for such compression would be several orders of magnitude greater than would be experienced in normal working conditions when pulling the longitudinally extensive protection apparatus with, say, a conventional winch.

[0038] In some preferred embodiments, as illustrated in Figures 6 and 7 a spacer such as an "0" ring 180 can be arranged between the respective sections (110, 120, 130, 140) to maintain a minimum spacing between the forward face 123 of a male projection and the inner face 133 of a female recess. Spacers such as Ό" rings 180 can have the further advantage of "biting" into the longitudinally extensive protection apparatus 200 to provide additional bending resistance.

[0039] In some preferred embodiments, the sections 110, 120, 130 can be formed from a polymeric (plastic) material such as polyurethane, PVC or polyethylene (in particular HDPE). In other preferred embodiments, the sections 1 10, 120, 130 can be formed from a metal such as cast iron. In some preferred embodiments, said polymeric material is a polyurethane. The particular grade of polyurethane can be selected by the skilled person in accordance with design requirements such as environmental conditions over the working life of the bend restrictor 100.

[0040] In some preferred arrangements, the end sections 1 10 can be bonded to the longitudinally extensive protection apparatus, so that the end sections 1 10 are maintained in fixed relation to the longitudinally extensive protection apparatus. Such bonding can be especially convenient where the longitudinally extensive protection apparatus is in the form of a flexible pipe or tube, such as a polymeric pipe or tube.

[0041] In other preferred arrangements, the respective end sections 110 can be secured to the longitudinally extensive protection apparatus by a clamping arrangement. Such a clamping arrangement can also be particularly suitable where the longitudinally extensive protection apparatus is in the form of a flexible pipe or tube, such as a polymeric pipe or tube. One suitable clamping arrangement is illustrated in Figures 10A, 10B and 10C. In the illustrated embodiment, each end section 110 can be formed as two half sections 110f, 110g which can preferably be symmetrical about a plane including the longitudinal axis or centreline 150. The half sections can be secured together by complementary threaded nuts and bolts 110a, 110b so that faces 110c of the half sections 110f, 110g are maintained in contacting confronting relation and half surfaces 160h are in confronting, and optionally contacting, relation with the longitudinally extensive protection apparatus 200. In some preferred arrangements an insert layer can be provided between the half surfaces 160h and the longitudinally extensive protection apparatus 200 to further maximise securing of the end section 110 to the longitudinally extensive protection apparatus 200. Such insert layer can for example be a relatively softer material as compared with the material from which the half sections 110f, 110g are formed. Half sections 110f, 110g can, for example be formed from a relatively hard polyurethane material and the insert layer can be formed from a relatively softer polypropylene material. Alternatively or additionally a layer of adhesive or other bonding agent can be provided between the longitudinally extensive protection apparatus 200 and the half section 110f, 110g.

[0042] In some preferred arrangements the respective end sections can be fixedly secured to the longitudinally extensive protection apparatus such as to provide at least 30kN of axial restraint before any slippage occurs between a given end section and the longitudinally extensive protection apparatus.

[0043] In some configurations the longitudinally extensive protection apparatus can be placed under tension prior to fixing in place on the longitudinally extensive protection apparatus of the end sections 110, this being done with the bend restrictor in a linear condition. In these configurations when the bend restrictor articulates to conform to bending of the longitudinally extensive protection apparatus the neutral axis length varies only by a small amount, not affecting the pre-tensioning. This has the advantage of avoiding breaking of the bond between the end sections and the longitudinally extensive protection apparatus and/or of causing a stretching or the like which reduces the tension obtained from the pre-tensioning.

[0044] In some preferred arrangements the sections 1 10, 120, 130 can be formed as unitary components and the longitudinally extensive protection apparatus can be inserted through the respective components before installation of the longitudinally extensive protection apparatus, such as at the time of on-shore manufacture. In other arrangements, which can be suitable for retro-fitting of the bend restrictor to an existing longitudinally extensive protection apparatus, the respective sections 110, 120, 130 can be formed as conjoinable components allowing fitting on site around the existing longitudinally extensive protection apparatus.

[0045] Figures 11A and 1 1 B show an assembly 500 including a bend restrictor 100 of the invention, illustrating the bend restrictor 100 in the context of a typical use arrangement. The assembly 500 comprises a longitudinally extensive protection apparatus 200 which can in preferred embodiments comprise a pipe or tube of polymeric material such as HDPE. A bend restrictor 100 is mounted to the longitudinally extensive protection apparatus 200 such that the longitudinally extensive protection apparatus 200 passes through the through longitudinal passage of the bend restrictor. In this arrangement, the bend restrictor 100 is conveniently arranged towards the middle of the longitudinally extensive protection apparatus 200 (with respect to the length thereof), but other location can be convenient depending on the particular circumstances of use. The assembly 500 can further comprises a progressive bend stiffener 560 at one end thereof. Progressive bend stiffeners are known in the art. The assembly 500 can also comprise one or more clump or stability weights which can be effective in holding a portion of the assembly 500 on the seabed for example. Still further the assembly 500 can include at a leading end thereof a pulling (or pull-in) head 550 to which a line or cable can be attached for pulling the assembly to a position of use. In some arrangements the assembly 500 can further comprise a mounting clamp 530 configured to hold a bend restrictor end section 110 and one or more second mounting clamps 540 configured to hold the longitudinally extensive protection apparatus 200. The mounting clamps 530, 540 can be of similar construction with appropriate variations to account for, for example, the differences in size of the longitudinally extensive protection apparatus 200 and the bend restrictor end section 110. The mounting clamps 530, 540 are configured for attaching the longitudinally extensive protection apparatus 200 and the bend restrictor end section 110 to an offshore foundation, in particular an offshore foundation having a suitably placed structural member or spar 570 (Fig 11 C). The mounting clamps 530, 540 can include a main body portion defining first and second half shells. The first half shell can be configured to accommodate the said structural member or spar and the second half shell can be configured respectively to accommodate the end section 110 (clamp 530) of the longitudinally extensive protection apparatus 200 (clamp 540). The respective clamps 530, 540 further comprise a first complementary half shell section and a second complementary half shell section. The first complementary half shell section is securable to the main body portion (such as by complementarily threaded nuts and bolts) thereby to define a through passage or bore surrounding the structural member or spar 570 and clamping thereto. Similarly the second complementary half shell section is securable to the main body portion (such as by complementarily threaded nuts and bolts) thereby to define a through passage or bore surrounding respectively the end section 110 or the longitudinally extensive protection apparatus 200 and clamping thereto. The longitudinally extensive protection apparatus 200 and the bend restrictor end section 110 can thereby be fixedly attached to the offshore structure. [0046] Figure 12 shows an offshore installation 600 comprising: an offshore structure 610 having connected thereto a longitudinally extensive service member, the service member being disposed within a longitudinally extensive protection apparatus 200; and a bend restrictor 100 according to embodiments of the invention arranged on the longitudinally extensive protection apparatus 200. The longitudinally extensive protection apparatus extends from the seabed 614 to an upper part of the offshore structure 610 where the leading end of the longitudinally extensive protection apparatus 200 is suspended from a hang off apparatus 618.

[0047] The portion of the longitudinally extensive protection apparatus 200 extending along the seabed 614 can have arranged thereon one or more clump or stability weights 510 effective to hold the longitudinally extensive protection apparatus 200 on the seabed 614 and a progressive bend stiffener 560. Arrow 616 is indicative of a longitudinally extensive service member extending from the longitudinally extensive protection apparatus 200. The longitudinally extensive service member could conveniently be buried under the seabed 614 for its protection or a further length of the longitudinally extensive protection apparatus 200 containing the longitudinally extensive service member could extend from the progressive bend stiffener 560. Other arrangements are possible depending on the particular circumstances.

[0048] The longitudinally extensive protection apparatus 200 is secured to the offshore structure at one or more locations between the hang off apparatus 618 and the seabed 614. In the embodiment illustrated the offshore structure is a foundation, in particular a jacket which could, for example, be suitable for mounting thereto of a wind turbine generator or associated equipment. The jacket 610 includes a plurality (e.g. three or four) of upright member 612 and a plurality of connecting lattice spars 613. In the embodiment of Figure 12 the longitudinally extensive protection apparatus 200 is secured to the jacket 610 by one or more mounting clamps 540 similar to, or the same as, those of Figures 11A- C. In this embodiment, the mounting clamp(s) 540 is (are) secured to an upright member 612.

[0049] In the embodiment of the assembly as illustrated in Figure 12 the bend restrictor 100 extends from the seabed 614 to the offshore jacket 610 and limits the minimum radius of curvature of the longitudinally extensive protection apparatus 200 as it transitions from a nominally horizontal condition on the seabed 614 to a nominally vertical condition as attached to the jacket 610. The end section 110 at the upper end of the bed restrictor 100 can be secured to the jacket 610 by suitable means, in particular a mounting clamp 530. Said end section thus can be fixed in position on the jacket 610. [0050] Figure 13 shows an offshore installation 700 comprising: an offshore structure 710 having connected thereto a longitudinally extensive service member, the service member being disposed within a longitudinally extensive protection apparatus 200; and a bend restrictor 100 according to embodiments of the invention arranged on the longitudinally extensive protection apparatus 200. The longitudinally extensive protection apparatus extends from the seabed 614 to an upper part of the offshore structure 710. The full upward extent of the longitudinally extensive protection apparatus 200 is not illustrated in this embodiment.

[0051] The portion of the longitudinally extensive protection apparatus 200 extending along the seabed 614 can have arranged thereon one or more clump or stability weights 510 effective to hold the longitudinally extensive protection apparatus 200 on the seabed 614 and a progressive bend stiffener 560. Arrow 716 is indicative of a longitudinally extensive service member extending from the longitudinally extensive protection apparatus 200. The longitudinally extensive service member could conveniently be buried under the seabed 614 for its protection or a further length of the longitudinally extensive protection apparatus 200 containing the longitudinally extensive service member could extend from the progressive bend stiffener 560. Other arrangements are possible depending on the particular circumstances.

[0052] . In the embodiment illustrated in Figure 13 the offshore structure 710 is a monopile which could, for example, be suitable for mounting thereto of a wind turbine generator or associated equipment. Monopile constructions as such are well known in the art. The longitudinally extensive protection apparatus 200 extends from the seabed 614 through an aperture (at 722) of the monopile into the interior or the monopile 710. The aperture is located in the wall of the monopile 710 at a height above the seabed 614. A centraliser 720 can protectively surround the longitudinally extensive protection apparatus 200 as it passes through the aperture 722 to prevent damage to the longitudinally extensive protection apparatus 200 from the edge of the aperture and to assist in maintaining the assembly including the longitudinally extensive protection apparatus 200 in its intended position. Bend restrictor 100 can extend from the seabed 614 to the aperture 722 and limits the minimum radius of curvature of the longitudinally extensive protection apparatus 200 as it transitions from a nominally horizontal condition on the seabed 614 to an inclined configuration as it approaches the aperture 722.

[0053] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0054] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0055] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1. A bend restrictor for a longitudinally extensive protection apparatus configured to contain a longitudinally extensive service member, the bend restrictor comprising:

first and second end sections attachable in fixed relation to the longitudinally extensive protection apparatus;

a plurality of intermediate sections arranged between the first and second end sections; a through longitudinal passage extending through the respective end sections and the intermediate sections for accommodating the longitudinally extensive protection apparatus; one section of each adjacent pair of said sections including a male longitudinally directed projection which is received in a female recess of the adjacent section of said pair of sections;

2. An assembly of a bend restrictor and a longitudinally extensive protection apparatus arranged within the bend restrictor and configured to contain a longitudinally extensive service member, the bend restrictor comprising:

a plurality of intermediate sections arranged between the first and second end sections; a through longitudinal passage extending through the respective end sections and the intermediate sections and configured to accommodate the longitudinally extensive protection apparatus

the male recess including a laterally outer wall which is always at least partially in juxtaposition with a corresponding laterally outer wall of the female recess, each respective outer wall consisting of a portion of the outer surface of a sphere such that a non- interlocking spherical joint is formed between the said adjacent sections.

3. An offshore installation comprising: an offshore structure having connected thereto a longitudinally extensive service member, the service member being disposed within a longitudinally extensive protection apparatus; and a bend restrictor arranged on the longitudinally extensive protection apparatus, wherein the bend restrictor is as claimed in claim 1.

4. A bend restrictor as claimed in claim 1 or an assembly as claimed in claim 2 or an installation as claimed in claim 3 wherein the longitudinally extensive service member comprises one or more pipes or cables.

5. A bend restrictor or an assembly or an installation as claimed in claim 4 wherein the pipe is a pipe for the transmission of production fluids associated offshore fuel extraction.

6. A bend restrictor or an assembly or an installation as claimed in claim 4 wherein the cable is for the transmission of electricity associated with offshore energy production.

7. An assembly as claimed in claim 2, 4, 5 or 6 or an installation as claimed in any of claims 3 to 6 wherein the longitudinally extensive protection apparatus is a conduit such as a pipe or tube.

8. A bend restrictor as claimed in claim 1 , or any of claims 4 to 6 or an assembly as claimed in claim 2 or any of claims 4 to 7 or any installation as claimed in any of claims 3 to 7 wherein for each said pair of sections, a shoulder wall extends outwardly from a longitudinally inner limit of the outer wall of the male projection to an external wall of the section, and a corresponding shoulder wall extends outwardly from a longitudinally outer limit of the outer wall of the female recess to an external wall of the section, the respective shoulder walls being opposed and radially inner parts thereof adopting a contacting relation when the bend restrictor is at its minimum bend radius.

9. A bend restrictor as claimed in claim 1 , or any of claims 4 to 6 or 8 or an assembly as claimed in claim 2 or any of claims 4 to 8 or an installation as claimed in any of claims 3 to 8 wherein surfaces of said through longitudinal passage of the bend restrictor are profiled so that, when the bend restrictor is at its minimum radius, radially inner surface portions of the passage form a smooth curve which conforms to the radially innermost part of the surface of the longitudinally extensive protection apparatus when contained within the passage.

10. A bend restrictor substantially as hereinbefore described with reference to any of Figures 1 to 9.

11. An assembly substantially as hereinbefore described with reference to Figures 6 or 7.