Abstract:
A bend restrictor for a flexible conduit includes at least two adjacent vertebrae. Each vertebra includes a central passage for the flexible conduit, a ball portion, and a receiver portion configured to receive the ball portion. The ball portion of one adjacent vertebra is disposed within the receiver portion of the other adjacent vertebra. The bend restrictor further includes a vertebra insert disposed between the at least two adjacent vertebrae. The vertebra insert prevents a lock out position between the ball portion and the receiver portion.

Description:
BACKGROUND 
       [0001]    Bend restrictors are used to prevent overbending of flexible flow lines, cables, umbilicals, and other conduits that may be damaged if bent beyond a certain radius. One type of bend restrictor used for larger flexible conduits is a vertebra bend restrictor (VBR), which is shown in  FIGS. 1A and 1B .  FIG. 1A  shows a half section of an individual vertebra  101 . The vertebra  101  includes a ball portion  10  and a receiver portion  105  at opposing ends. The ball portion  110  is adapted to fit into the receiver portion  105  of an adjacent vertebra. Multiple vertebrae  101  are interlocked end-to-end with their respective ball portions  110  and receiver portions  105  to create a VBR, as shown in  FIG. 1B . Assembly of the VBR is performed by clamping the receiver portion  105  of two half sections of each vertebra  101  onto the ball portion  110  of another vertebra  101 . The half sections of each vertebra  101  are bolted together or otherwise fastened to form a continuous structure around the flexible conduit  131 , which is protected within a central passage  120 . The vertebra may be made from various materials depending on the operating conditions. Suitable materials include metals, rubber, and polyurethane. 
         [0002]    To limit bending, the ball portion  110  includes a flange  111  that fits within a groove  106  inside the receiver portion  105 . The flange  111  has two opposing angled surfaces  112  and  113 , which respectively contact surfaces  108  and  107  in groove  106  when at the minimum bend radius (R) or lock out position illustrated in  FIG. 1B . In the VBR shown in  FIGS. 1A and 1B , surfaces  108  and  107  are perpendicular to the axis of the vertebra i  01 . When the respective angled surfaces come into contact, the VBR is locked out and begins to absorb bending loads to protect the flexible conduit inside VBR. 
         [0003]    Various dimensions of the vertebra  101  may be adjusted to provide a desired minimum bend radius for a selected size of flexible conduit. One variable is a chord length of each vertebra  101 , which is defined by the distance between centers of rotation  130 A and  130 B. Lengthening the chord increases the minimum bend radius. The relative angle allowed between two adjacent vertebrae  101  is another variable for the minimum bend radius. Increasing the relative angle decreases the minimum bend radius. The relative angle can be adjusted by varying distances and angles between respective surfaces of the ball portion  110  and the receiver portion  105  of the vertebra. Once designed, manufactured, and assembled as a VBR surrounding a flexible conduit, the minimum bend radius is fixed. 
       SUMMARY OF INVENTION 
       [0004]    In one aspect, the present disclosure relates to a bend restrictor for a flexible conduit. The bend restrictor includes at least two adjacent vertebrae. Each vertebra includes a central passage for the flexible conduit, a ball portion, and a receiver portion configured to receive the ball portion. The ball portion of one adjacent vertebra is disposed within the receiver portion of the other adjacent vertebra. The bend restrictor further includes a vertebra insert disposed between the at least two adjacent vertebrae. The vertebra insert prevents a lock out position between the ball portion and the receiver portion. 
         [0005]    In another aspect, the present disclosure relates to a method of varying a minimum bend radius of a vertebra bend restrictor. The method includes disposing a ball portion of a first vertebra in a receiver portion of a second vertebra. The ball portion of the first vertebra and the receiver portion of the second vertebra lock out at a first relative angle between chords of the first vertebra and second vertebra. The method further includes passing a flexible conduit through a central passage of the vertebrae and disposing a vertebra insert between the first vertebra and the second vertebra. The vertebra insert restricts the relative angle between the first vertebra and the second vertebra to a second relative angle smaller than the first relative angle between chords of the first vertebra and second vertebra. 
         [0006]    In another aspect, the present disclosure relates to a method of deploying a flexible conduit to an offshore location. The method includes assembling a vertebra bend restrictor around a portion of the flexible conduit. The vertebra bend restrictor comprises at least two adjacent vertebrae and provides a first minimum bend radius. The method further includes spooling the flexible conduit, transporting the spooled flexible conduit to the offshore location, and unspooling the flexible conduit, assembling a vertebra insert between the at least two adjacent vertebrae to increase the minimum bend radius. The vertebra insert reduces a maximum relative angle between chords of the at least two adjacent vertebrae. The method further includes deploying the flexible conduit. 
         [0007]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1A  is a half of a vertebra for a vertebra bend restrictor. 
           [0009]      FIG. 1B  is an assembled vertebra bend restrictor including the vertebra shown in  FIG. 1A . 
           [0010]      FIG. 2  is a vertebra insert for a vertebra bend restrictor in accordance with one embodiment. 
           [0011]      FIG. 3  is a vertebra adapted for use with the insert in  FIG. 2  in accordance with one embodiment. 
           [0012]      FIG. 4A  is an assembled vertebra bend restrictor including the vertebra shown in  FIG. 3  in accordance with one embodiment. 
           [0013]      FIG. 4B  is an assembled vertebra bend restrictor including the vertebra insert shown in  FIG. 2  and the vertebra shown in  FIG. 3  in accordance with one embodiment. 
           [0014]      FIG. 5A  is an assembled vertebra bend restrictor including a vertebra insert in accordance with one embodiment. 
           [0015]      FIG. 5B  is an isometric external view of the assembled vertebra bend restrictor shown in  FIG. 5A . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present disclosure relates to apparatus and methods for varying the minimum bend radius of a VBR. 
         [0017]    In  FIG. 2 , a vertebra insert  201  for varying the minimum bend radius of a VBR is shown in accordance with one embodiment. The vertebra insert  201  is adapted to fit between adjacent vertebrae in a VBR to increase the minimum bend radius. The vertebra insert  201  may be formed from two half sections to aid assembly. The material for the vertebra insert  201  may be, for example, metal, plastic, rubber, or polyurethane. A vertebra  301  for use with the vertebra insert  201  is shown in  FIG. 3 . Like the vertebra  101  shown in  FIG. 1A , vertebra  301  includes the ball portion  110  and the receiver portion  105 . The vertebra  301  may include an exterior flange  305 . The vertebra insert  201  fits between the neck  308  of the ball portion  110  and the exterior flange  305 . To improve fit, the vertebra insert  201  and the vertebra  301  may include complimentary surfaces and features. For example, the angle of surface  206  on the vertebra insert may be about the same as the angle of surface  306  on the exterior flange of the vertebra  301 . Matching angles between the two complimentary surfaces helps to transfer bending loads between adjacent vertebrae in the VBR. The angle of surface  306  may be negative (less than 90 degrees) to trap the vertebra insert  201  during loading. The vertebra insert  201  may further include an inner flange  207 , which fits in insert groove  307  on the vertebra  30 l. The complimentary inner flange  207  and insert groove  307  help to keep the vertebra insert  201  in place as the VBR bends and straightens. 
         [0018]      FIGS. 4A and 4B  show an assembled VBR using the vertebra shown in  FIG. 3 .  FIG. 4A  does not include the vertebra insert  201 , which provides a minimum bend radius R 1 .  FIG. 4B  includes vertebra inserts  201  between adjacent vertebrae  301 , which provides an increased minimum bend radius R 2 . Without the vertebra insert  201 , the ball portions  110  and receiver portions  105  interact like the VBR shown in  FIG. 1B . Specifically, the angle of the adjacent vertebrae  301  relative to each other is restricted by flange  111  contained inside groove  106 . The vertebrae  301  are able to flex until the lock out position is reached between the ball portions  110  and the receiver portions  105 , which occurs at minimum bend radius R 1  shown in  FIG. 4A . In one embodiment, the lock out position maybe at about 9 degrees between chord lines of adjacent vertebrae  301  to provide a minimum bend radius R 1  of about 96 inches (2.44 meters) with a chord length of about 12.6 inches (32.0 cm). With 9 degrees bending between each adjacent vertebrae pair, eleven vertebrae  301  (ten adjacent vertebrae pairs) would provide about 90 degrees of bending coverage. Those having ordinary skill in the art will appreciate that chord lengths and relative angles between adjacent vertebrae may be altered according to the design and utilization of any particular flexible conduit. 
         [0019]    When an increased minimum bend radius R 2  is desired, vertebra inserts  201  are assembled onto each vertebra  301 , as shown in  FIG. 4B . The vertebra inserts  201  can be added to the VBR without disassembly of any portion of the VBR. Instead, two half sections of the vertebra inserts  201  can be placed around the corresponding exterior portion of each vertebra  301  and secured. In one embodiment, a band  401  is strapped around the vertebra insert  201  to secure the two half sections around the vertebra  301 . The vertebra insert  201  may include an exterior groove  210  to aid with placement of the band  401 . The band  401  may be metal, such as bands used to secure cargo to pallets. The band  401  allows for quick assembly of the vertebra inserts  201  into the VBR. 
         [0020]    The addition of the vertebra inserts  201  changes the loading arrangement of the VBR by shortening the distance between end  310  and exterior flange  305  of adjacent vertebrae  301 . As a result, the filly angled lock out position of the ball portions  110  and the receiver portions  105  does not occur because the vertebra insert  201  is compressed between end  310  and exterior flange  305  at a shallower angle between adjacent vertebrae  301 . Thus, the vertebra insert  201  effectively reduces the maximum relative angle between adjacent vertebrae  301 , which increases the minimum bend radius of the VBR. Continuing with the 96 inches (2.44 meters) minimum bend radius R 1  example in  FIG. 4A , the minimum bend radius R 2  may be increased to about 144 inches (3.66 meters) with the addition of the vertebra inserts  201  between each adjacent vertebrae pair. The increased minimum bend radius R 2  is achieved by reducing the maximum relative angle between chords of each adjacent vertebrae pair by about 2.5 degrees. The addition of the vertebra inserts  201  does not affect the chord length of the vertebrae  301 . 
         [0021]    In  FIGS. 5A and 5B , an assembled VBR in accordance with another embodiment is shown. As with the vertebra insert  201  in  FIG. 2 , the addition of a vertebra insert  510  reduces the maximum relative angle between adjacent vertebrae  501 , which results in a larger minimum bend radius. Absent the vertebra insert  510 , the relative angle between adjacent vertebrae  501  is limited by the lock out position of the ball portion  110  and the receiver portion  105 . In this embodiment, the end of the vertebra  501  with the receiver portion  105  includes an exterior ball portion  530 . The vertebra insert  510  includes a receiver portion  531 , which is adapted to receive the exterior ball portion  530  of the vertebra  501 . When the vertebra insert  510  is assembled between adjacent vertebrae  501 , the exterior ball portion  530  is received into the receiver portion  531  of the vertebra insert  510 . As a result, the maximum relative angle between adjacent vertebrae  501  is restricted by the lock out position of the exterior ball portion  530  and the receiver portion  531 , which is at a smaller relative angle than the lock out position between the ball portion  110  and the receiver portion  105 . 
         [0022]    The vertebra insert  510  and the vertebra  501  may include additional features to improve assembly and aid with force distribution. In one embodiment, the vertebra  501  includes an exterior flange  520 , which is adapted to fit in a groove  521  on the vertebra insert  510 . The mating flange  520  and groove  521  help to hold the vertebra insert  510  in position during bending, and, at the minimum bend radius, distribute the bending loads between the vertebra insert  510  and adjacent vertebrae  501 . The flange  520  may be dovetailed to resist separation during bending. If the flange  520  is dovetailed, assembly of half sections of the vertebra insert  510  may require the use of a mallet or other tool to provide sufficient force to snap the flange  520  into the groove  52   1 . For use with a strap or band, the vertebra insert  510  may further include an external groove  511 . 
         [0023]    The vertebra  501  may be comprised of two half sections  501   a  and  501   b , as shown in  FIG. 5B . To aid alignment during assembly, each half section may include alignment pins  502  and/or corresponding holes to receive the alignment pins, as shown in  FIG. 5A . The half sections  501  a and  501   b  may be held together using bolts (not shown) inserted through holes  503  distributed at various locations on the vertebra  501 . When a greater minimum bend radius is desired, the vertebra insert  510  is assembled between adjacent vertebrae  501 . The vertebra insert  510  may also comprise two half sections  510   a  and  510   b , which may be held together with a band or strap (not shown) in groove  511 . When a smaller minimum bend radius is desired, the vertebra insert  510  may be removed by cutting or otherwise removing the band or strap. 
         [0024]    The ability to vary the minimum bend radius is useful for VBRs for umbilicals, flying leads, and flexible pipe (collectively referred to as “flexible conduit”) for oilfield applications, especially offshore applications. For transport from a supplier to a service location, flexible conduit is wrapped around a spool. Because of restrictions on the size of the spool for transport on roads, railways, and ships, the smallest minimum bend radius for the flexible conduit is desired. Without additional loading, such as tension, the flexible conduit can withstand a smaller minimum bend radius. Accordingly, the VBR as shown in  FIG. 4A  may be used. At the point of use for the flexible conduit, other forces may be applied to the flexible conduit as it removed from the spool. For example, in offshore applications, the flexible conduit is exposed to tension from its own weight and any attached equipment, in addition to shear forces from ocean currents and loading from wave action. The additional complex loads cause the flexible conduit to have a greater minimum bend radius to avoid damage. To avoid that damage, the minimum bend radius provided by the VBR can be increased as the flexible conduit is removed from the spool by assembling the vertebra insert, as shown in  FIG. 4B . The vertebra inserts may be quickly banded between adjacent vertebrae as the VBR is straightened out while being removed from the spool. The addition of the vertebra inserts requires no disassembly of the VBR already in place. Accordingly, the need to disassemble one VBR to replace it with another VBR with a greater minimum bend radius is avoided. The time savings is particularly valuable in offshore applications in which daily operation costs may be well over a $100,000 per day. 
         [0025]    If the flexible conduit is later recovered, the process may be reversed to allow spooling of the flexible conduit. The vertebra inserts may be removed, for example, by cutting off the band. This allows the minimum bend radius of the VBR to be decreased to allow reeling of the flexible conduit onto the spool for transport. As with the original deployment, significant time savings are achieved by avoiding the replacement of one VBR for another VBR to change the minimum bend radius. 
         [0026]    Although this detailed description has shown and described illustrative embodiments of the invention, this description contemplates a wide range of modifications, changes, and substitutions. Those having ordinary skill in the art will appreciate that many of the design features shown and described in the above embodiments may be changed or eliminated without departing from the scope of the present disclosure. For example, the vertebra inserts and vertebrae include various complimentary surfaces for improving the fit between each other and for distributing bending loads. Many of the advantages of the present disclosure may be achieved without such features, or with different angles and curves for complimentary surfaces. Accordingly, it is appropriate that readers should construe the appended claims broadly, and in a manner consistent with the scope of the invention.