CN112970158A

CN112970158A - Bending limiter

Info

Publication number: CN112970158A
Application number: CN201980072315.8A
Authority: CN
Inventors: 彼得.弗罗斯特; 朗.玛菲
Original assignee: Huawei Marine Networks Co Ltd
Current assignee: HMN Technologies Co Ltd
Priority date: 2019-01-30
Filing date: 2019-01-30
Publication date: 2021-06-15
Anticipated expiration: 2039-01-30
Also published as: EP3834261A1; CN112970158B; JP2022510006A; WO2020156661A1

Abstract

A bend limiter comprising a plurality of collars and a plurality of couplers, the plurality of collars being arranged in series, 5 wherein each collar is adjacent to two other collars in the series and is coupled to a first one of the collars by a first one of the couplers and is connected to a second one of the collars by a second one of the couplers, each collar being connected to a first one of the couplers by a rotational joint having a first axis, each collar being connected to a second one of the couplers by a rotational joint having a second axis that is non-parallel to the first axis, the bend limiter being configured to accommodate bending of a conduit passing through the bend limiter and to limit 10 the bending by abutment of adjacent collars upon rotation about the first and second rotational joints.

Description

Bending limiter

Technical Field

The present invention relates to a bend limiter for limiting bending of a conduit passing through the bend limiter, for example for use as a flexible mechanical coupling between a cable and subsea telecommunication equipment.

Background

At the interface between typical subsea wet equipment (e.g. subsea repeaters) and their connecting cables is a mechanical connection that allows articulation between the two components. The connection must withstand tensile loads during deployment and recovery operations. The conditions are particularly onerous when the component passes over the sheave of the cable-laying vessel, where both tensile and bending loads combine to stress the component in a complex manner.

The flexible mechanical coupling between the cable and the wet equipment, called the bending limiter, is required to withstand and exceed the cable breaking load of heavy armoured cables, and therefore the bending limiter is made of a high strength material, usually in most cases metal.

Fig. 1 shows an example of a subsea repeater 1, wherein

cables

3 and 13 are connected to the repeater 1. A metal bending limiter 2 is arranged at the interface between the repeater 1 and the cable 3. As shown in fig. 2(a) and 2(b), the bend limiter is formed by a series of outer yokes or collars 4 and inner rings 5 which are able to rotate relative to each other to accommodate but limit bending at the interface.

Of the total amount of cable used to interconnect wet equipment in recently deployed marine-spanning systems, only about 20% is of "armoured" construction, the remaining 80% being of "lightweight". Telecommunication subsea equipment manufacturers typically use a "one size fits all" high strength bend limiter design, such as the design shown in fig. 1 and 2, to connect different types of cables to the wet plant. This is the case for various reasons, mainly related to compatibility requirements and size limitations, such as minimum inner diameter limitations, minimum length limitations and fixed maximum bend angle limitations. The use of two (or more) different designs for different cable strengths has potential drawbacks because different interfaces and ancillary components will need to meet different requirements for each cable type.

However, in the case of deep water deployment, it is not generally necessary to use a bend limiter capable of withstanding the load of the armored cable. The high strength and often high cost bend limiters are oversized for most of the cables being laid. This approach limits deployment depth if the coupling accounts for a significant proportion of the total weight of the subsea equipment.

Significant weight and manufacturing cost savings can be achieved by connecting "lightweight" cables to the wet plant using lighter, lower strength bend limiters. The requirement for lighter components is increasingly important in the design of next generation subsea equipment. The continuing demand for higher fiber counts and larger capacities has driven a dramatic increase in volume and weight, both of which have adverse effects on deployment and retrieval depths.

It would be desirable to develop a bend limiter that can withstand the required loads and bend angles while also being adaptable to being made of different materials depending on the cable weight requirements of the application.

Disclosure of Invention

According to a first aspect, there is provided a bend limiter comprising a plurality of collars and a plurality of couplers, the plurality of collars being arranged in series, wherein each collar is adjacent to two other collars in the series and is coupled to a first one of the collars by a first one of the couplers and is connected to a second one of the collars by a second one of the couplers, each collar being connected to a first one of the couplers by a swivel joint having a first axis, each collar being connected to a second one of the couplers by a swivel joint having a second axis that is non-parallel to the first axis, the bend limiter being configured to accommodate bending of a conduit passing through the bend limiter and to limit the bending by abutment of adjacent collars upon rotation about the first and second swivel joints.

This may allow a versatile bend limiter design that can be applied to both metal and composite bend limiters and that can have a 25 year life under steady state operation.

For each collar, the respective first and second couplers may be offset along a longitudinal direction of the bend limiter, and the respective collar may extend between the first and second couplers along the longitudinal direction. For each collar through which it is connected to an adjacent coupling, the axis of the swivel joint may be offset along the longitudinal direction of the bending limiter. This may allow the bend limiter to accommodate bending of a conduit passing through the bend limiter.

Each coupling may be connected to an adjacent collar by a respective rotational joint, and the axes of the joints may lie in a common plane perpendicular to the longitudinal direction of the bending limiter.

Each collar may define a bearing surface configured to: when those collars are tilted relative to each other by rotating about their joints, which are connected to the couplings extending between those collars, the bearing surface abuts against the bearing surface of the adjacent collar. Each collar may define two such bearing surfaces facing in opposite directions along the longitudinal direction of the bend limiter. This may allow the bend limiter to limit bending of the conduit and to withstand tensile loads.

The bearing surface may be defined such that: the bearing surfaces of the collars abut each other at a linear or two-dimensional contact surface, regardless of the direction of inclination between two adjacent collars. The geometry of the adjacent bearing surfaces of the collars may ensure contact between adjacent collars while in full flexion and along all axes of flexion. This may allow for excellent bend control, optimized contact stresses and reduced wear.

The bearing surface may be configured for limiting a maximum bending angle of the bending limiter to less than 70 degrees. The bearing surfaces may be configured such that the maximum angle of inclination between adjacent collars is less than 20 degrees. This may provide a degree of flexibility to the movement of cables coupled to the bend limiters while preventing damage.

The collar and/or the coupler may be annular and define a passage for the conduit to pass therethrough. This may allow the bend limiter to limit bending of the conduit.

Each collar may be attached to its respective first and second couplers by connector pins that extend parallel to the respective first and second axes. The connector pin may conveniently allow the components of the bend limiter to be assembled and disassembled as required.

The bend limiter may further comprise two ends, each end being adjacent to the collar at respective first and second ends of the bend limiter and being connected to one of the couplers connected to the collar by a swivel joint. The ends of the bend limiters may be connected to other parts of the system. The product has wide application and is suitable for various sea diameters. The design is compatible with existing and new generation wet plant products using specially configured adapters that connect to the inside and/or outside diameter of the sea state outer collar.

The collar and the coupler may be configured to bear a tensile load applied between the ends. This contributes to the life of the subsea equipment reaching 25 years at steady state operation.

The collar and/or the coupling may be rigid. This may allow the components of the bend limiter to carry tensile loads.

For each collar, the respective first and second couplings may be positioned inside the collar about a longitudinal axis of the bend limiter. This may make the design more compact.

Drawings

The invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

fig. 1 shows a known bending limiter coupled to a subsea repeater.

Fig. 2(a) and 2(b) show a close-up view and an exploded view, respectively, of the known bending limiter shown in fig. 1.

Figure 3 shows an example of a bending limiter coupled to a subsea repeater according to the present invention.

Fig. 4(a) and 4(b) show a close-up view and an exploded view, respectively, of the bend limiter shown in fig. 3.

Fig. 5 illustrates the relative positions of the components of the bend limiter at the maximum bend angle of the bend limiter.

Fig. 6 illustrates how the contact surface of each collar segment is defined.

Figure 7 illustrates a collar and ring connected using a pin.

FIG. 8 illustrates the retention of a pin connecting the collar and the ring of the bend limiter.

FIG. 9 illustrates the collar of the bend limiter machined from a single tube.

Detailed Description

Fig. 3 shows an example of a bending limiter 6 according to the invention. The bending limiter 6 comprises a plurality of

collars

7, 8, 9, two of which are indicated with 10 and 11, and a plurality of couplings arranged in series. The collar and the coupling are rigid and annular and define a passage for the cable 3 to pass through. The coupler is positioned inside the collar about a longitudinal axis of the bend limiter such that the coupler fits inside the collar when the collars are connected in series. Each collar 7 is adjacent to the other two collars 8, 9 in series and is coupled to a first one of the collars 8 by a first one of the couplings 10, the collar being coupled to the first one of the couplings 10 by a rotary joint having a first axis 20. Each collar 7 is also coupled to a second one of the collars 9 by a second one of the couplings 11, the collar being coupled to the second one of the couplings 11 by a swivel having a second axis 21 that is non-parallel to the first axis 20. When the bending limiter is in its straight configuration, the axes are orthogonal when projected onto a plane perpendicular to the longitudinal axis of the bending limiter. Each collar is attached to its respective first and second couplers by connector pins 30 that extend parallel to the respective first and second axes. The bend limiter further comprises two ends 15, 16, each end being adjacent to the collar at respective first and second ends of the bend limiter. The ends 15, 16 are connected by means of a swivel joint to a coupling which is connected to the adjacent collar. The collar and coupling of the bend limiter 6 are configured to take tensile loads applied between the

ends

15, 16.

Fig. 4(a) and 4(b) show a close-up view and an exploded view, respectively, of the bend limiter of fig. 3. For each collar 7, the respective first and

second couplings

10, 11 are offset along the longitudinal direction of the bend limiter 6, and the respective collar 7 extends along the longitudinal direction between those first and

second couplings

10, 11. For each collar, the axis of its rotary joint connected to the adjacent coupling is offset along the longitudinal direction of the bending limiter. The bend limiter accommodates bending of the cable 3 and limits this bending by abutment of adjacent collars when rotating about the first and second rotary joints.

Each

collar

7, 8, 9 defines two bearing surfaces configured to: when those two collars are tilted relative to each other by rotating about their joints, which are connected to the coupling extending between those two collars, they abut against the bearing surfaces of the adjacent collars. The two bearing surfaces are facing in opposite directions in the longitudinal direction of the bending limiter. The bearing surface is defined such that: the bearing surfaces of the collars abut each other at a linear or two-dimensional contact surface, regardless of the direction of inclination between two adjacent collars.

Figure 5 shows the components of the bend limiter when it is at its maximum bend angle. The bearing surface is configured to limit a maximum bending angle of the bending limiter. In one example, the maximum bend angle of the bend limiter is limited to less than 70 degrees. In this example, the bearing surfaces are configured such that the maximum angle of inclination between adjacent collars is less than 20 degrees. Other values of maximum bend angle are also possible. One way to vary the maximum bend angle of the bend limiter is by repositioning a pin that connects the collar and the coupler and defines an axis of rotation.

The geometry of the adjacent contact surfaces of the collar ensures that: continuous contact between any two adjacent collars while the bend limiter is at its maximum bend angle along all axes. Thus, the design of the present invention maximizes the contact area at full bending, resulting in excellent bend control and contact stress optimization.

Fig. 6 shows the definition of one of the contact surfaces in more detail. Each collar has a contact surface directed towards the first end of the bend limiter and a contact surface directed towards the second end of the bend limiter. Preferably, the contact surfaces of all collars pointing towards the first end of the bending limiter describe the same surface. Preferably, the contact surfaces of all collars pointing towards the second end of the bending limiter describe the same surface. Preferably, the two contact faces of each collar describe the same surface, although facing in opposite directions. The contact faces of adjacent collars are cooperatively configured such that: when the collars are maximally tilted relative to each other about any tilt axis, their contact surfaces make contact over an area larger than one point, preferably a straight line. The line may lie on a plane passing through the central axis of one or both of the collars, and thus the line may be a substantially radially oriented line. Since the collar extends longitudinally relative to the bend limiter, longitudinal deflection of each contact surface is facilitated. Each contact surface may have 180 degrees of rotational symmetry about the central axis of its collar. Each contact surface may be a mirror image of itself rotated 90 degrees. Each contact surface may have an extent in a radial direction relative to a central axis of its collar. Within this range, the surface may be inclined in a plurality of positions with respect to the central axis of the collar. Conveniently, the portions of the surface that are offset 180 degrees relative to each other about the central axis may be inclined in one sense (e.g., their radially outer edges are closer to the ends of the bend limiters than their radially inner edges), and the portions of the surface that are offset 90 degrees relative to the preceding portions may be inclined in the opposite sense (e.g., their radially inner edges are closer to the ends of the bend limiters than their radially outer edges). The contact surface of the collar may have a generally sinusoidal form when rotated about the central axis of the collar. A collar having this feature may conveniently allow line contact between adjacent collars when it is fully flexed.

In the example of fig. 6, the geometry of the contact surface comprises two convex regions or "lobes" and two concave regions or "valleys". This design feature allows contact between any two adjacent collars while the bend limiter is at its maximum bend angle because the geometry of one "valley" matches the geometry of one "peak" of an adjacent collar. Along the length of the bend limiter, the male portion of each collar nests in the female portion of an adjacent collar.

As shown in FIG. 6, two spline curves may be used to construct each contact surface. Spline curve a is located on the outer diameter of the tube forming the collar, while spline curve B is located on the inner diameter of the tube of the collar. The contact surface smoothly connects the two spline curves. The splines may be conveniently defined using predetermined points. The points are positioned equidistantly around the outer collar circumference. Each point of the spline curve a has a corresponding point on the spline curve B that is located at the same angular position about the central axis of the collar. All the points of the spline curve B are radially offset by the same distance with respect to the points of the spline curve a. This distance sets the maximum bending angle. Preferably, this is the same for all collars within the bend limiter.

To define the axial offset of the point, a parallel plane is defined that is perpendicular to the axis of rotation of the collar. The two pairs of planes define an effective contact surface. The distance between two planes in a pair is the bend angle distance. The first plane (labeled "length plane") in the pair controls the length or depth of the "valley"/"peak" geometry. The second plane (labeled "angle plane") in the pair controls the angle.

By modifying the location of the spline curve defining points, the length and maximum bend angle can be adjusted, allowing design flexibility. As a result of the parametric design, the bending characteristics can be easily adjusted by modifying the design input parameters.

Fig. 7(a) - (c) illustrate how the collar and coupler are connected together by connector pin 30. The connector pins extend parallel to the respective first and second axes of rotation to allow the

components

7 and 10 to rotate relative to each other about the rotational joint.

As shown in the drawings, the swivel pins 30 that connect the outer collars 7 to the inner collar couplings 10 and allow them to rotate during articulation can be held at both ends against loosening using two different holding methods, as follows:

-hold inward: the tapered geometry at the top of the pin (as shown at 17) matches a complementary groove on the outside of the collar 7 and limits the movement of the pin 30 to prevent it from moving below the outer surface of the collar 7. The stop position of the pin is calculated so that the tapered front surface of the pin is flush with the outside diameter chamfer of the collar 7.

-holding outwards: the pin is retained using a ring 18, a groove 19 at the bottom of the pin 30 and a corresponding groove at the bottom of the bore of the inner coupling 10. The ring is mounted on the pin and the outer collar is aligned with the inner coupling, concentric with the pin bore. Then, the user can use the device to perform the operation,

the chamfer of the inward retaining groove is used to insert the pin 30 into the bore of the outer collar to compress the ring. Once the pin is in place, the front face of the ring groove of the pin becomes aligned with the front face of the groove of the inner coupling, allowing the ring to be in its "at rest" position. The vertical front face of the groove of the inner ring acts as a stop on the ring, preventing the pin from coming out under normal operating conditions.

Therefore, the rotation holding pin can be installed without requiring a special tool, thereby improving convenience in assembling and disassembling the bending restrictor.

The present configuration proposes the use of a single design of bend limiter that can utilize high strength to weight ratio composite for 80% of the cases where lightweight cable equipment is used, and metal solutions for the remaining 20% of the cases where armor equipment is used.

The metal bending limiter may be made of a corrosion resistant high strength metal compound such as steel, beryllium copper or a high strength titanium alloy. The material may be selected according to the specific requirements of the application, but preferably should be able to withstand the cable breaking load of the heaviest armoured cable to which the wet equipment product is connected, currently in the range of 550 KN.

Bend limiters for lightweight cables may be made of carbon fiber reinforced resin composite material and may only need to be able to withstand the cable breaking load of the heaviest lightweight cable, currently in the range of 115 KN. In terms of size, carbon composites offer high strength and light weight, which are two key parameters required for this application. The carbon fiber composite provides the highest specific modulus in any commercial yarn, with a tensile modulus of 230-400GPa and an ultimate tensile strength of about 3.5-5.0 GPa. In addition, the carbon fiber composite material also exhibits excellent interlaminar shear strength, fatigue resistance, and a low coefficient of thermal expansion.

The key attributes in the choice of resin system are good mechanical properties, low degradation rate, good resistance to thermal stress, excellent corrosion resistance and low water absorption. The use of a matt impregnation method has shown that: optimum composite properties can be obtained by full saturation of pre-impregnated carbon fibers with resin matting and good fiber wettability specific to the carbon fiber tow size.

As a result of the superior strength to weight ratio achievable when using carbon fiber composites, the components can be lightweight, reduced in size, and provide higher performance relative to other composites and a true replacement for metals for similar applications.

The bend limiters described herein may also allow for more streamlined machining. As shown in fig. 9, the collar 7 and the

ends

15, 16 may be machined from the same material tube by a tool 40. The outer collar and the inner coupling may thus be manufactured from two tubes of predetermined dimensions. This may result in less manufacturing waste. The same geometry of the active bearing surfaces of the collars allows the collars to be machined by removing a small amount of material from a single prefabricated tube between adjacent active surfaces of two consecutive collars.

Thus, the bending limiter described herein is a versatile design that can be applied to both metal and composite bending limiters and can have a 25 year life under steady state operation.

The two embodiments of the bending limiter may share the same dimensions (inner and outer diameter, total length, maximum full bending angle) and geometry and may be connected to the wet plant using similar solutions. The product has wide application and is suitable for various sea state diameters. The design is compatible with existing and new generation wet plant products using specially configured adapters that connect to the inside and/or outside diameter of the sea state outer collar.

The invention may allow for improved maximum deployment depth of subsea equipment by using components that are lighter in weight than can be achieved with metal equivalents having similar strength and corrosion resistance. This reduces the overall weight of the deep water submarine cable system, which is typically limited by metal components. It also improves deployment and recovery restrictions and increases the installability of wet plant products. Furthermore, the lower cost and mass per unit volume of the composite bend limiter compared to metal solutions (e.g. when using titanium grade 5) allows significant cost savings with lightweight solutions.

Although the invention has been described above with respect to an example of a bending limiter for use with subsea repeaters, the invention is also applicable to other subsea telecommunication devices, such as amplifiers, switches, multiplexers and demultiplexers. Such as branching units and reconfigurable optical add-drop multiplexers (ROADMs).

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that the feature or combination is capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether the feature or combination of features solves any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. A bend limiter (6) comprising a plurality of collars (7, 8, 9) arranged in series and a plurality of couplers (10, 11), wherein each collar is adjacent two other collars in series and is coupled to a first one of the collars by a first one of the couplers and to a second one of the collars by a second one of the couplers, each collar being connected to a first one of the couplers by a swivel joint having a first axis (20), each collar being connected to a second one of the couplers by a swivel joint having a second axis (21) which is non-parallel to the first axis, wherein the bend limiter is configured to accommodate bending of a conduit passing through the bend limiter, and limiting the bending by abutment of adjacent collars upon rotation about the first and second rotary joints.

2. The bend limiter of claim 1, wherein, for each collar, the respective first and second couplers are offset along a longitudinal direction of the bend limiter, and the respective collar extends between the first and second couplers along the longitudinal direction.

3. The bend limiter of claim 2, wherein, for each collar, the axis of the swivel is offset along the longitudinal direction of the bend limiter, the each collar being connected to an adjacent coupler by the swivel.

4. The bend limiter of claim 2 or 3, wherein each coupler is connected to an adjacent collar by a respective rotational joint, and the axes of the joints lie in a common plane perpendicular to the longitudinal direction of the bend limiter.

5. The bend limiter of any preceding claim, wherein each collar has a bearing surface that abuts against a bearing surface of an adjacent collar when the two collars are tilted relative to each other by rotation about their joint to a coupling extending between the two collars.

6. The bend limiter of claim 5, wherein each collar has two such bearing surfaces facing in opposite directions along the longitudinal direction of the bend limiter.

7. The bend limiter of claim 5 or 6 wherein the bearing surface is shaped such that: the bearing surfaces of the collars abut each other at a linear or two-dimensional contact surface regardless of the direction of inclination between two adjacent collars.

8. The bend limiter of any one of claims 5 to 7 wherein the shape of the bearing surface is designed so as to limit the maximum bend angle of the bend limiter to less than 70 degrees.

9. The bend limiter of any one of claims 5 to 8 wherein the bearing surfaces are shaped such that the maximum angle of inclination between adjacent collars is less than 20 degrees.

10. The bend limiter of any preceding claim, wherein the collar and/or the coupler is annular and defines a passage for the conduit to pass therethrough.

11. The bend limiter of any preceding claim, wherein each collar is attached to its respective first and second couplers by a connector pin extending parallel to the respective first and second axes.

12. The bend limiter of any preceding claim, wherein the bend limiter further comprises two ends, each end being adjacent to a collar at respective first and second ends of the bend limiter and being connected to one of the couplers connected to the collar by a swivel joint.

13. The bend limiter of claim 12, wherein the collar and the coupler are configured to withstand a tensile load applied between the ends.

14. The bend limiter of any preceding claim, wherein the collar and/or the coupling are rigid.

15. The bend limiter of any preceding claim, wherein for each collar, the respective first and second couplings are positioned inside the collar about a longitudinal axis of the bend limiter.