NO344807B1

NO344807B1 - A bending restrictor module and system

Info

Publication number: NO344807B1
Application number: NO20181083A
Authority: NO
Inventors: Geir Huseby; Bjørn Guldbrandsen
Original assignee: Compocean As
Priority date: 2018-08-15
Filing date: 2018-08-15
Publication date: 2020-05-04
Also published as: NO20181083A1

Description

A bending restrictor module and system

FIELD OF THE INVENTION

The present invention relates to bending restrictors, and more specifically to a bending restrictor module connectable with mating bending restrictor modules into a bending restrictor string which in use is effective for restriction of bending in a flexible conduit or cable that is passed through a passage defined by the interconnected modules of the bending restrictor string. The invention also relates to a bending restrictor system.

BACKGROUND AND PRIOR ART

A typical use of bending restrictors (BR) is to support and prevent a cable or a flexible conduit from bending beyond a minimum allowed radius when subjected to external load. Examples of use can be found in both offshore and land-based industry, where electrical cables or flexible fluid pipes/conduits need protection against overbending of cable or conduit end sections upon termination in electrical, fluid transportation, hydraulic or other equipment or machinery such as transformers, cable or conduit joints, manifolds, pumps or compressors etc. In the following, the words “cable” and “conduit” shall be understood to cover both single and multichannel flexible structures for transfer of fluid or power or control signals, including but not limited to umbilicals, e.g.

BR components used in subsea installations must often be designed to accommodate substantial static and dynamic loads from heavy power cables and production fluid conduits, such as loads induced during pipe/conduit installation, static loading, at transient operation modes or caused by sea currents, waves, fishing equipment interaction etc.

It is known in the art to design BR components in steel for heavy duty applications, see for example NO 320897 B1. However, a steel structure is comparatively heavy which may complicate installation procedures, especially onboard sea vessels.

Typically, a lifting weight below 20-25 kg would be desired to significantly ease installation. In subsea applications, a BR component made in steel requires cathodic protection which will add to weight and increase installation costs. High submerged weight may also add significant permanent load to the termination system such that buoyancy aid may be required. Adding buoyancy will increase cost and increase space between terminations which may increase width of structure where terminations are fixed. There are often several terminations at the same place. Cost consequence of increased size of structure is large, especially for subsea structures. In some cases, non-magnetic materials are required in the BR string.

It is further known in the art to design BR components from plastic material such as polyurethane (PUR), which will overcome the drawbacks of corrosion associated with steel structures in subsea applications. Plastic material BR components will have reduced submerged weight compared to steel, however, plastic BR components typically have thick walls and large outer diameter such that the weight for handling is still high and usually above the weight limit for handling without crane. The diameter of a BR component made of PUR may require a larger distance between cables/conduits that are terminated at the same structure, and larger termination structure would lead to larger protection structures if that is required.

An illustrative example of a BR design suitable for manufacturing in PUR is disclosed in GB 2 428 760 A. In conventional way, the bending restrictor of GB 2 428 760 A is composed of a number of interconnected BR modules each comprising a male coupling end and a female coupling end. In connected mode, a radially projecting circular flange in the male end of one BR module is received in a radially recessed circular groove in the female end of an adjacent BR module.

US 5215338 A discloses a flexible supporting sheath for cables and the like, wherein bending radius is restricted by cooperating radial shoulders and projections or spacers that are formed or supported externally on mating male and female BR modules.

US 2010228295 A1 discloses a bend restrictor for a flexible conduit, wherein bending radius is restricted through a ring-shaped element which is supported externally between mutually opposing radial surfaces of the adjacent, interconnected male and female BR modules.

US 2005082824 A1 discloses a rotatable and pivotable connector comprising interconnecting male and female BR modules, wherein an exterior retention element, such as a fitting, is arranged about the female BR module so as to limit or prevent radial expansion and lockout of a female BR module end.

The male and female couplings in the ends of the BR modules can be seen upon as circumferential flanges, one of which is facing radially outwards (male coupling flange) and the other one facing radially inwards (female coupling flange). In interlocked mode, a male coupling flange is hooked behind a female coupling flange to connect adjacent BR modules in longitudinal axial direction, while permitting restricted relative pivoting between connected BR modules in any arbitrary plane along and including the longitudinal axis.

To facilitate interconnection of BR modules, the BR modules are typically made as two separate cylinder halves which can be joined together by means of bolts or by means of surrounding clamps, e.g. Other embodiments include module halves which are hinged to each other in one longitudinal side and bolted together in the opposite side. In this connection it serves to mention, that prior art also finds examples of BR modules which are split longitudinally in three interconnectable parts which together form a passage for a cable or conduit, see for example GB 2 544 075 A.

Alternative designs comprise BR modules having male or female coupling means in both ends of a BR module, as well as BR strings essentially composed of male coupling modules whereas the intermediate female coupling modules are realized as short length clamps which do not substantially add to the overall length of the BR string.

In operation, i.e. bended under the load from a flexible cable or conduit passing through the BR string, the couplings between interconnected BR modules are subjected to various kinds of stresses:

i) in the radially inner curvature of the curved BR string, male coupling flanges will be subjected to axial compression from a radial shoulder that forms one side of a seat or groove that accommodates the male coupling flange in the female coupling end of the BR module, whereas the male and female coupling flanges in the radially outer curvature are subjected to tension in axial direction of the BR module, ii) in the curved BR string, bending load applied in radial direction will result in local concentration of stress at points of contact between BR modules in both the inner and outer curvatures of the BR string,

iii) the axial and radial loads in combination strive to expand the female coupling flange in circumferential direction, also referred to as hoop stress.

In order to accommodate the various kinds of loads and stresses that are applied to BR modules in use, polyurethane BR modules of prior art are typically rather massive components having comparatively thick walls resulting in large BR module diameter, as required in compensation for the lower strength and stiffness of polyurethane in contrast, e.g., to the strength and stiffness of metal such as steel.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a lightweight yet strong BR module.

It is an object of the present invention to counteract plastic deformation or failure in a polymer or composite BR module while avoiding oversizing of wall thickness and avoiding extensive use of material.

It is another object of the present invention to counteract crack formation in a composite BR module while avoiding oversizing of wall thickness and use of material.

It is an object of the present invention to reduce stress in coupling flanges of a BR module resulting from externally applied load.

It is an object of the present invention to provide load distribution in coupling flanges of a BR module

It is an object of the present invention to provide absorption of load applied to coupling flanges in a BR module.

It is another object of the present invention to provide a BR system that permits adaptation of bending radius in a BR string made up from BR modules of universal size.

One or more of these objects is met in a BR module as recited in appended claim 1, comprising a cylindrical or part-cylindrical body having an axial conduit or cable through passage which opens in a male end or in a female end of the body, wherein the male and female ends are mutually shaped for connection with mating female and male ends of adjacent BR modules in a BR string,

- coupling means comprising a circumferential coupling flange facing radially inwards in a female end of a BR module, and a circumferential coupling flange facing radially outwards in a male end of a BR module,

- the male and female coupling flanges in connected mode hooked behind each other to connect adjacent BR modules in longitudinal axial direction while permitting restricted relative pivoting between connected BR modules about an axis transversely to the longitudinal axis,

wherein the BR module is further specified through a circular or part-circular insert which is arranged coaxially with the BR module and secured in at least one of: a radially inwards facing region of a female coupling flange and/or a radially outwards facing region of a male coupling flange.

The said coupling flange insert is an element which by intrinsic properties and design is operative to reduce the effects of stress generated in structural components of a BR module under load from a cable or a flexible conduit, such as an umbilical e.g., passing through the BR module.

In one embodiment, the insert is arranged to reduce the effects of external load by distribution of load over a larger area and portion of a coupling flange in the BR module. In this embodiment the insert is realized as a ductile and elastic element which accommodates load under elastic deformation at loads below the ultimate load limit of the coupling flange, this way reducing peak stress levels in local areas of the flange. In other words, “distribution” of load as used herein refers to an ability of the insert to receive a concentrated load applied to the insert and transform it into a distributed load applied to the coupling flange.

In another embodiment, the insert is arranged to reduce the effects of external load by absorption of load applied to a coupling flange under load. In this embodiment the insert is realized in the form of an element which is dimensionally stable and significantly stiffer than the surrounding material also at loads above the ultimate load limit of the coupling flange, thus effectively counteracting plastic deformation, creep and rupture of the coupling flange. In other words, as used herein “absorption of load” refers to an ability of the insert to take up load applied to the coupling flange without large deformations in neither the insert nor the coupling flange.

In other words, the present invention provides stress relief to coupling flanges in a BR module under external load by means of an insert element inserted in the coupling flange, wherein the insert element is chosen to provide either distribution of load or absorption of load. Within these two embodiments, an insert can be realized in various embodiments with respect to material and design.

The load applied to a BR module from a conduit or cable passing through it will follow the stiffest element of the BR module, i.e. the coupling flange. In the following examples of embodiments, the designs provide geometries which add stiffness to several modes of deformation.

In one embodiment the insert has the shape of a band or flat strip of material forming a short cylinder or part-cylinder that has an axial orientation in coaxial relation with the BR module. This embodiment provides simplicity of manufacture since the insert can be designed as a ring of metal or as a fibre-reinforced plastic ring. Accordingly, the insert comprises a cylindrical or part-cylindrical insert portion coaxial with the BR module and seated in at least one of: the region of an inwards facing periphery of the female coupling flange and/or the region of an outwards facing periphery of the male coupling flange.

In one embodiment, a rim portion is attached to the cylinder portion of the insert.

This rim portion can be joined to any lateral edge of the cylinder portion or it can be arranged rising from any location between the lateral edges of the cylinder portion. The rim portion may adjoin the cylinder portion at any angle, including a slanting orientation wherein a face on the rim portion extends in a radial plane that intersects with the longitudinal axis at an angle of between 30° and 150°. This embodiment adds rigidity to the insert and preserves its circular/part-circular shape.

In one embodiment, a radially projecting rim portion respectively adjoins each lateral edge of the cylinder portion in a cross-sectional u- or n-profile. Beside adding rigidity to the insert, this embodiment also provides better anchoring of the insert in the coupling flange.

In one embodiment, radial faces on rim portions define the width of a gap which is dimensioned to receive a male coupling flange under a play that determines the range of pivoting movement for the male coupling flange engaging the gap.

In one embodiment, the insert is a closed sectional profile having three or more sides and a hollow interior. In addition to the aforesaid technical effects and advantages, this embodiment provides higher shear strength both to insert and coupling flange. The closed section will increase torsional stiffness of the flange.

In still another embodiment, the insert is a solid body with three or more sides and a non-hollow interior. The solid embodiment provides high shear strength, high form stability/arcuate shape, and a simplified mould design.

In a BR system according to the present invention, exchangeable inserts are made with various gap widths and insertable in a female coupling flange of the BR module by means of a common coupling interface with the coupling flange. This embodiment reduces the required number of differently sized BR modules to meet various needs, since a BR module of universal size can be adapted for various specifications in regard to maximum load and maximum/minimum bending radius.

The subject insert can be secured to the BR module by any suitable method, including but not limited to one of gluing, melting, mechanical fastening, form fitting engagement or embedment.

Regardless of method, it is essential that the insert is placed in close contact with the BR module and without play between the insert and the BR module, so that load and mechanical stress is transferred directly between the BR module and the insert.

The insert may, e.g., be secured by embedment upon moulding a BR module in polymer material or in rubber.

The insert may, e.g., alternatively be secured by embedment or lamination into the body-shell of a BR module made in composite and/or having a laminate structure. A BR module made in composite material can be designed with comparatively thinner wall and less radius than a corresponding PUR component, the composite alternative leading to less weight, less volume and less use of material. By implementation of a load distributing or absorbing insert as disclosed, a composite design can be realized without the expense of strength.

The conventional practice of forming BR modules in two halves which are separated by longitudinal parting lines usually raises an issue of shear in the assembled BR module. In one embodiment, the insert is arranged rotated in circumferential direction into overlapping relation with a parting line between coupled BR module halves. In other words, the same insert will be seated in both BR module halves when assembled, this way counteracting the effects of shear in longitudinal directions.

In other words, the insert provides stress relief by distribution of stress in the BR module coupling flanges, or in a material which provides stress relief by absorption of stress, generating in coupling flanges under external load.

An insert capable of providing stress relief is a component which can be made from a range of materials, including but not limited to one of polymers, co-polymers, composites and metal.

In one embodiment, the insert is a ductile and elastic element having a tensile strength below the ultimate load limit of the BR module. In one embodiment the insert is a dimensionally stable element having a tensile strength above the ultimate load limit of the BR module.

In one embodiment, the insert is a dimensionally stable element which is stiff relative to the material into which it is embedded or attached to. The stiffness is obtained by a higher E-modulus of the insert material, and by the shape and sectional profile of the insert. The E-modulus of the insert material is advantageously at least about three times higher than the E-modulus of the surrounding material in the coupling flange.

In another embodiment, the insert is a ductile and elastic element such that it will not crack from high contact forces generated between connected BR elements, such as at geometrical sharp corners where stress concentrations occur. The insert material can range from a typical rubber, to a typical metal like construction steel. The main issue is that it shall not form unacceptable damage like significant permanent damage, cracking or permanent creep. Typically, the purpose is to prevent high local stresses in the main load bearing material when this material is a brittle material where cracks may be formed.

In a second aspect of the present invention, a bending restrictor system comprises BR modules connectable with mating BR modules into a BR string which in use is effective for restriction of bending in a flexible conduit, cable or umbilical that is passed through a passage defined by the interconnected BR modules of the BR string, wherein the connection between interconnected BR modules includes a male coupling flange engaging a female coupling flange under a play that permits a restricted relative bending movement determined by the width of a circumferential internal gap provided in the female coupling flange. According to the present invention, gaps of various widths are formed in a set of interchangeable inserts with identical coupling interfaces for insertion in a BR module of universal size.

By changing to an insert of other gap width, the angle between adjacent BR modules can be changed, and the minimum/maximum bending radius can in this way be changed accordingly. This can also be combined with changing the length of BR modules. Length can be changed by having a modular mould wherein a straight pipe section between coupling flanges is exchangeable, e.g. Changing the length of the BR modules will also change the allowable bending radius. By having both length and angle to play with for a BR system design, the system can be optimized with respect to weight, cost and performance.

SHORT DESCRIPTION OF THE DRAWINGS

Embodiments of the bending restrictor module will be disclosed below with reference made to the accompanying drawings. In the drawings:

Fig. 1 shows a BR module of prior art in 3-dimensional view,

Fig. 2 shows a couple of interconnected BR modules of prior art in sectional view, forming a cut out portion of a BR string under bending load,

Fig. 3 shows a first embodiment of a BR module and insert according to the present invention, in 3-dimensional view,

Fig. 4 is a sectional view through the insert included in Fig. 3,

Fig. 5 is a broken away sectional view showing a second embodiment,

Fig. 6 is a broken away sectional view showing a third embodiment;

Fig. 7 is a broken away sectional view showing a fourth embodiment,

Fig. 8 is a broken away sectional view showing a fifth embodiment.

Fig. 9 is a broken away sectional view showing a sixth embodiment, and

Fig. 10 is a broken away sectional view showing an eighth embodiment, of an insert according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 illustrates a part-cylindrical bending restrictor (BR) module element or BR module half. This particular BR module is a prior art design (GB 2428 760 A) and represents the typical build-up of BR-modules made in polyurethane (PUR). More precisely, the BR module 1 made of PUR extends axially between a male end 2 and a female end 3, a cylinder wall 4 defining a lumen for passage of a flexible cable or conduit through the BR module. In the male end, a male coupling flange 5 is facing radially outwards from the longitudinal axis X in the centre of the BR module. In the female end, a female coupling flange 6 is facing radially inwards, towards the centre of the BR module. The female coupling flange defines a circumferential internal groove 7 which opens towards the centre of the BR module. A radial shoulder 8 forms an inner side of the groove 7. The groove 7 and the male coupling flange 5 are dimensioned, with respect to radius and width, to permit engagement with a male coupling flange or a groove respectively of an adjacent BR module in a string of interconnected BR modules, forming a flexible BR string. Reference numbers 9 refer to a set of holes in the wall of the BR module, intended for passage of bolts upon assembly.

In interconnected mode, the male and female coupling flanges are hooked behind each other to connect BR modules in longitudinal axial direction (X), while permitting restricted relative pivoting between interconnected BR modules (see Fig. 2) about a transverse axis I intersecting the longitudinal axis X.

In a highly schematic way, the arrows in Fig. 2 indicate the application points of various kinds of load that is transferred to the BR module 1 of prior design from externally applied bending moment and shear load. In a curved string of BR modules 1, compressive load Fx is applied to coupling flanges in the inner and outer curvatures of the BR string. This load couple balances the bending moment Mz acting in transverse direction, C, compression load Fy will act locally at points of connection between coupling flanges in both the outer and the inner curvatures. Fy will balance the applied shear load Ty.

The applied load will result in hoop tensile stress in the female end of the BR module, and compression hoop stress in the male end. As the assembled BR module consists of two or more parts, the connections between them must be able to transfer these stresses. This load transfer capacity is usually obtained by a bolted connection (compression load will be transferred by contact only). Also shear stress needs to be transferred between the elements. This is usually done by a bolted connection.

Please observe that in practise the actual positions of load application points will be related to the subject BR module design, and the locations shown in Fig. 2 are thus merely indicative.

In other BR module designs, load may be transferred differently between interconnected BR modules. In Fig. 2the arrows show approximately where the applied loads are transferred to the adjacent BR module. Internally, within each module, the applied load will follow a load path to the next BR module. The loads may give rise to local stress concentrations and deflections. The method of assembling a two-piece or three-piece BR module will also decide load path and local stress levels as well as deformations.

In BR modules made in polymer, such as PUR e.g., elastic deformation of coupling flanges and cylinder portions of the BR module can to some extent be accepted. However, long-term loading at high stress level may cause creep in the material that results in deflection of the BR module wall and coupling flanges if loading is maintained. In order to preserve integrity in the shape of the BR module made in PUR, wall thickness is usually big to provide sufficient low stress level in the BR module.

Figs. 3 and 4 illustrate one embodiment of a BR module 10 of new design. BR module 10 comprises a body or a body shell 11. An elongate body portion 12 is in one end formed with a female coupling flange 13, whereas the other end of the elongate body portion is in this case formed with a male coupling flange 14. As previously explained, other designs (not shown in the drawings) may include BR modules having male or female coupling flanges in both ends of the BR module, as well as BR modules composed of three interconnectable parts, or BR modules forming an integer cylindrical body. For simplicity of disclosure, the term “partcylindrical” and “part-circular” as used herein shall be understood to include, twopiece modules or inserts, three-piece modules or inserts etc.

The embodiment of a BR module 10 shown in Fig. 3 can be built in fibre-reinforced plastic. The composite structure allows the design of a shell-formed, thin-walled and light-weight component with high strength.

The female coupling flange 13 has a cup-shaped sectional profile which faces inwards, towards the longitudinal centre of the body 11. The male coupling flange 14 faces radially outwards, at a radius which permits engagement with a mating female coupling flange of an adjacent BR module.

In accordance with the teachings of the present invention, an insert 15 is fitted to the inwardly facing side 16 of the female coupling flange. The insert 15 is a ringshaped, circular or part-circular element which can be rotationally symmetric. A radially inner side of the insert 15 comprises a groove 17 which is defined between an outer shoulder face 18 closer to the end of the BR module, and an inner shoulder face 19 as seen with respect to the axial extension of the BR module. The bottom of the groove 17 is formed by a cylindrical portion 20 of the insert 15, whereas the shoulder faces 18 and 19 are formed on radially projecting rim portions 21 and 22 adjoining the lateral edges 23 and 24, respectively, of the cylinder portion 20.

As appropriate, separate, supporting ring 21’, preferably of a stiffer, may be arranged on a radially inwards facing periphery of therim portion 21.

A radially outer side 25 of the insert 15 is shaped to provide a form-fitting engagement between the insert 15 and the inner side 16 of the female coupling flange 13.

A tight engagement between the insert 15 and the BR module 10 allows the insert to accommodate load or stress resulting from externally applied load to the BR module. In other words, applied load will be substantially absorbed in a rigid insert 15 of high E-modulus and transferred further to the female coupling 13 as a unitary structure, thereby providing stress relief to the coupling 13. In alternative embodiment, a ductile insert 15 of lower E-modulus will counteract local concentration of stress and provide distribution of load to a larger portion of the coupling flange 13, in axial, radial and circumferential directions. Embodiments of the insert 15 can be realized in the form of a polymer, a co-polymer, a composite or a metal element.

It should be noted that an insert 15’, as illustrated in dash-dot lines in Fig. 3, may alternatively be supported on the male coupling flange 14 so as to be seated in the female coupling flange, together with the male coupling flange, upon assembly of BR modules.

In the BR module 10, the female coupling flange 13 adjoins the cylindrical portion 12 via a wall segment which forms a radial step 26 bridging the difference in radial width between the cylindrical portion 12 and the coupling flange 13. This transition region can be a critical region in terms of ability to withstand bending stress. In one embodiment of the BR module 10, the transition region is supported by a second wall segment 27 of conical shape that forms part of the exterior of the BR module, the wall segment 27 acting like a beam effective for absorbing tensile stress in the body-shell as the BR module is subjected to bending load.

If appropriate, an inlay 28 can be embedded between laminating layers of wall segments 26 and 27 in the wall of the BR module 10.

In longitudinal direction of the BR module, the groove 17 provides a gap 17 having a width w which is dimensioned to provide a male coupling flange a play between the shoulder faces 18 and 19 when the male coupling flange is seated in the groove or gap 17. The size of this play, i.e. the width w, is one design parameter which can be used to define the allowed (minimum/maximum) bending radius in a BR string.

The BR module of Fig. 3 provides, through interchangeable inserts 15 with gaps 17 of different widths w, a modular BR system wherein BR modules of universal size can be customized to specifications by choice of an appropriately sized insert 15. Interchangeability is provided through a coupling interface by which the insert is seated securely in the female coupling flange, firmly and free of play.

Additional design freedom can be incorporated at low cost if the mould, in which the BR-elements are produced, is made modular such that the length of a straight section of the BR element can be changed, such as by exchangeable mould inserts of various lengths e.g.

In Fig. 3, a semi-circular insert 15 is shown in somewhat rotated position with respect to a semi-cylindrical BR module, this way in one side of the BR module projecting outside the parting line 29 and in the opposite side of the BR module retracted inside the parting line 30. When joined with mating BR module and insert halves, the projecting portions of the inserts overlap the parting lines, respectively, this way providing an interlocking of the BR module halves and adding shear transfer capability to the assembled BR module.

The insert 15 is a representative of ductile and elastic embodiments of the invention which provide stress relief by distribution of load.

Dimensionally stable embodiments of the insert which provide stress relief by absorption of load shall now be briefly discussed with reference to Figs. 5 to 10, wherein the male and female coupling flanges are, for reasons of simplicity, illustrated schematically as heels that are hooked behind each other in connected mode.

In Fig. 5, an insert 50 is formed as a flat ring or part of a ring secured in a radially inner (ri) region or circumference of a female coupling flange 13. A ring-shaped insert 50 may in a corresponding way be secured in a radially outer (rout) region or circumference of a male coupling flange 14, if appropriate. In the embodiment of Fig. 5, the inserts 50 are recessed into the surface of the coupling flanges.

Fig. 6 illustrates an alternative arrangement according to which inserts 50 of the previous flat design are secured by being embedded in the material of the coupling flanges 13 and 14.

The flat, band-shaped inserts 50 of Figs. 5 and 6 can be seen as 2-dimensional elements having a width dimension d extending in coaxial relation with the BR module and a length in the circumferential direction of the BR module, however lacking any substantial radial dimension.

Inserts of more distinctive 3-dimensional design are shown in Figs. 7-9. More precisely, in Fig. 7 an insert 51 of L-shaped cross-sectional profile comprises a radially projecting rim portion 52 which extends mainly in radial direction from a flat, axially oriented and cylindrical portion 53 of the insert 51. The radially projecting rim portion 52 may be arranged at a slanting angle, oriented in a radial plane rP which intersects the longitudinal axis X at an angle α of from 30° to 150°. Inserts with a cross-sectional T-profile (not shown) can be formed in a corresponding way.

With further reference to Fig. 7, an insert 51 of cross-sectional u- or n-profile comprises radially projecting rim portions 52 and 54 respectively, separately attached to each lateral edge region 55, 56 of the cylinder portion 53 of the insert 51.

It will be understood that such insert geometries, including even cup-shaped sectional profiles provide stiffness against bending around both main axis in the sectional plane, as well as tension and compression stiffness in all main directions.

Fig. 8 illustrates inserts 57 comprising a closed sectional profile enclosing a hollow interior, whereas Fig. 9 illustrates solid inserts 58 with a non-hollow interior.

Fig. 10 shows an insert 50 of flat design attached in the radially outer and inner peripheries respectively of the female and male coupling flanges 13 and 14 of a thin-walled, composite BR module of laminate structure.

It should be noted that by introducing stiffening elements 50-57 as shown below in a softer material like for instance PUR, stress level at contact area may increase, however, the “beam-like” structure of the inserts will distribute the load along the flange circumference and reduce stress for instance in the inner corner of the flange and reduce global deformations and creep issues.

In the present disclosure of embodiments of the invention, details in the BR module design which are not necessary for understanding and working the invention have been omitted from the drawings for the sake of clarity. One such detail is means for joining the BR module parts together in a BR module assembly, such as clamps, threaded bolts, bolt holes, nuts, nut seats, ears and lugs etc., all of which a skilled person can apply to the illustrated embodiments from numerous examples found in the literature and in open use.

Also omitted from disclosure are specialized BR modules designed for anchoring a BR string to the equipment in which a protected cable, conduit or umbilical is to be connected. Even if an end module in a BR string is often in one end designed with a special coupling interface adapted for connection with the equipment, it will be understood that the insert of the invention may still be applied as disclosed in the other end of an end BR module.

Claims

1. A bending restrictor (BR) module for restriction of bending in a flexible conduit or cable, the BR module comprising:

- a cylindrical or part-cylindrical body having an axial through passage which opens in a male end or in a female end of the body, wherein the male and female ends are mutually shaped for coupling with mating female and male ends of adjacent BR modules to form a BR string,

- wherein coupling means comprises a circumferential coupling flange (13) facing radially inwards (rin) in a female end of a BR module, and a circumferential coupling flange (14) facing radially outwards (rout) in a male end of a BR module,

- the male and female coupling flanges in connected mode hooked behind each other to connect adjacent BR modules in longitudinal axial direction while permitting restricted relative pivoting between connected BR modules about an axis (I) transversely to the longitudinal axis (X),

the BR module further comprising:

- a circular or part-circular insert (15; 50; 51; 57; 58) is arranged coaxially with the BR module and secured in at least one of: a radially inwards facing region of a female coupling flange (13) and/or a radially outwards facing region of a male coupling flange (14), characterized in that the insert (15; 50; 51) comprises a cylindrical or part-cylindrical insert portion (20; 50; 53) coaxial with the BR module and seated in at least one of: the region of an inwards facing periphery of the female coupling flange (13) and/or the region of an outwards facing periphery of the male coupling flange (14).

2. The bending restrictor module of claim 1, wherein the insert (15; 51) comprises a rim portion (21; 22; 52; 54) projecting from the cylinder portion (20; 50; 53) at an angle.

3. The bending restrictor of claim 2, wherein the rim portion (21; 22; 53) carries a face (18; 19; 52’) in a radial plane (rP) that intersects with the longitudinal axis (X) at an angle (α) of from 30° to 150°, in cross-sectional L- or T-profile.

4. The bending restrictor module of claim 3, wherein a rim portion (21, 22; 52, 54) respectively adjoins each lateral edge (23, 24; 55, 56) of the cylinder portion (20; 53) in cross-sectional u- or n-profile.

5. The bending restrictor module of claim 4, wherein radial faces (18; 19) on rim portions (21; 22) define the width (w) of a gap (17) which is dimensioned to receive a male coupling flange (14) under a play that determines the range of movement for the male coupling flange (14) engaging the gap (17).

6. The bending restrictor module of claim 4, wherein the insert (57) is a closed sectional profile having three or more sides enclosing a hollow interior.

7. The bending restrictor module of claim 4, wherein the insert (58) is a closed sectional profile having three or more sides enclosing a solid, non-hollow interior.

8. The bending restrictor module of any previous claim, wherein the insert (15;

50; 51; 57; 58) is secured to the BR module by any suitable method including but not limited to one of gluing, melting, mechanical fastening, form fitting engagement, or embedment.

9. The bending restrictor module of claim 8, wherein the insert (50; 51; 57; 58) is secured to the BR module by embedment upon moulding a BR module in polymer material or rubber.

10. The bending restrictor module of claim 9, wherein the insert (50) is secured by embedment or lamination into the body-shell of a BR module made in composite and/or having a laminate structure.

11. The bending restrictor module of any previous claim, wherein the insert (15;

50; 51; 57; 58) is arranged rotated in circumferential direction into overlapping relation with a parting line (29; 30) between coupled BR module parts.

12. The bending restrictor module of claim 1 to 5, wherein the insert (15) is one of: a ductile and elastic element or a dimensionally stable element above the ultimate load limit of the BR module.

13. The bending restrictor module of claim 12, wherein the insert is a component made of one of polymers, co-polymers, composites and metal.

14. A bending restrictor (BR) system comprising BR modules connectable with mating BR modules into a BR string which in use is effective for restriction of bending in a flexible conduit or cable that is passed through a passage defined by the interconnected BR modules of the BR string, wherein the connection between interconnected BR modules includes a male coupling flange (14) engaging a female coupling flange (13) under a play that permits a restricted relative bending movement determined by the width of a gap (17) provided to the female coupling flange, characterized in that gaps (17) of various widths (w) are formed in a set of interchangeable inserts (15) with identical coupling interfaces for insertion in a BR module (10) of universal size.