Abstract:
Controlled bending of a pipeline laying on the sea floor is achieved by attaching a bending sleeve assembly to a selected bending zone of the pipeline for limiting the controlled bending of the pipeline to a predetermined resulting bending configuration. External force is then applied on the bending sleeve assembly, bending the pipeline to the predetermined resulting bending configuration in cooperation with the bending sleeve assembly and the sea floor. External force can be exerted from one or more weights placed on top of the bending sleeve assembly. External force can be exerted from a winch attached to a wire, the wire passing through a pulley attached to a fixed structure, and the wire attached to the bending sleeve assembly. External force can be exerted through the bending sleeve assembly&#39;s contact reaction with an immobile object.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable. 
       INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0004]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    The invention generally relates to methods of controlled bending of a pipeline during the laying thereof in the sea. Specifically, the invented methods utilize external forces to produce controlled bending of a pipeline with aide of a bending sleeve attached to the pipeline. 
         [0007]    2. Background of the Invention 
         [0008]    Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. 
         [0009]    Steel pipelines to be laid on the bottom of the sea cannot be pre-formed or pre-adapted to the contour of the sea floor. This is because of the laying or installation procedure that must be used. 
         [0010]    There may be tolerated a certain degree of unevenness over which the pipeline is capable of spanning or bending, provided the specific load does not produce excessively high stresses in the pipeline steel. If stresses exceed allowable limits, the pipeline could be deformed permanently, either by buckling or cold bending, or both to an unacceptable configuration. Should cold bending occur through yielding of the steel in the pipeline, it could propagate uncontrollably. Requirements set by classification societies for construction and operation of offshore pipelines permit a certain degree of cold bending provided that it takes place under controlled conditions. Parameters for such controlled conditions entail that a pipeline may be cold bent to a minimum radius lesser than what is allowed for uncontrolled bending. 
         [0011]    Pipelines to be laid on an uneven sea floor are subjected to free spanning because of the rigidity of the pipeline. Specifications used for submarine pipeline installation permit plastic deformation as long as positive measures are taken to ensure that excessive bending is prevented. By allowing plastic deformation, it is possible to reduce to a considerable degree the occurrence of free spanning. Bending beyond elastic limits may be achieved by overloading the pipeline by increasing the weight. 
         [0012]    Submarine pipelines having a diameter of more than 12 inches usually require a weight coating to achieve negative buoyancy, which is necessary if the pipeline is to be submerged and also maintain a stable state with respect to the sea current. Plastic deformation of a pipeline having a weight coating of concrete will cause the concrete to crack and break loose. 
       PRIOR ART 
       [0013]    U.S. Pat. No. 5,192,166 describes a method for controlled bending of a pipeline during the laying thereof in the sea, utilizing bend controlling/stopping means which are mounted on the pipeline as a sleeve and interact with the pipeline. To achieve cold bending under controlled conditions, the pipeline is weight loaded internally at the selected bending zone. The weight loading may be achieved by means of a flexible string of weight elements and/or by introducing into the pipe a suitable heavy, readily flowable weight mass, for example, drilling fluid or water. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    Embodiments of the present invention include methods for controlled bending of a pipeline laying on the sea floor. The term “sea floor” used hereafter refers to the bottom of a body of water. For example, a sea floor can be the bottom of the sea, river, pond, or lake. 
         [0015]    In one embodiment of the present invention, a bending sleeve assembly is attached to a selected bending zone of the pipeline for limiting the controlled bending of the pipeline to a predetermined resulting bending configuration. An external force is then applied on the bending sleeve assembly attached to the pipeline. As a result, the external force causes the pipeline to be bent to the predetermined configuration in cooperation with the bending sleeve assembly and the sea floor. 
         [0016]    In another embodiment of the present invention, a bending sleeve assembly is attached to a selected bending zone of the pipeline for limiting the controlled bending of the pipeline to a predetermined resulting bending configuration. A pulley is attached to an anchoring point below the bending sleeve assembly. One end of an elongate flexible member is attached to the bending sleeve assembly. The elongate flexible member can be a wire, cable, belt, chain, rope, or strap. The elongate flexible member is passed through the pulley. The other end of the elongate flexible member is attached to a winch mounted on a structure above the bending sleeve assembly. The winch is operated to exert an external force to pull the bending sleeve assembly towards the pulley attached to the structure below the bending sleeve assembly. As a result, the external force bends the pipeline to the predetermined resulting bending configuration in cooperation with the bending sleeve assembly. 
         [0017]    In yet another embodiment of the present invention, a bending sleeve assembly is attached to a selected bending zone of the pipeline for limiting the controlled bending of the pipeline to a predetermined resulting bending configuration. The pipeline is installed from a vessel which holds one end of the pipeline. The bending sleeve assembly attached to the pipeline is positioned next to an immobile object. The pipeline is then deviated horizontally around the immobile object. As a result, the bending sleeve assembly makes contact with the immobile object and the reaction from the immobile object exerts an external force that causes the pipeline to bend to the predetermined angular configuration in cooperation with the bending sleeve assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0018]      FIG. 1A  illustrates a bending sleeve assembly attached at one end to a pipeline in one embodiment of the present invention. 
           [0019]      FIG. 1B  shows a cross-sectional view of the bending sleeve assembly attached at one end to the pipeline in  FIG. 1A  in one embodiment of the present invention. 
           [0020]      FIG. 2  shows a semi-section view of a coupling connection in one embodiment of the present invention. 
           [0021]      FIG. 3  shows the use of a weight as an external force to induce bending of a pipeline at the location where a bending sleeve assembly is attached in one embodiment of the present invention. 
           [0022]      FIGS. 4A-C  show a method of using a weight as an external force to induce bending of a pipeline at a location where a bending sleeve assembly is attached in different directions in one embodiment of the present invention. 
           [0023]      FIG. 5  shows the method in  FIG. 4  where the wires are attached to winches mounted on a vessel in one embodiment of the present invention. 
           [0024]      FIG. 6  shows a method of using a winch mounted on a vessel, a wire, and a pulley to exert an external force to bend a pipeline attached to a bending sleeve assembly in one embodiment of the present invention. 
           [0025]      FIG. 7  shows a method of using permanent weights to exert an external force to a bending sleeve assembly attached to a pipeline which induces bending of the pipeline in one embodiment of the present invention. 
           [0026]      FIGS. 8A and 8B  show a plan view of a method using a vessel and an anchor to bend a pipeline at a section where a bending sleeve assembly is attached to the pipeline in one embodiment of the present invention. 
           [0027]      FIGS. 9A and 9B  show a plan view of a method using a vessel to install a pipeline around an immobile object where a bending sleeve assembly is attached to the pipeline in one embodiment of the present invention. 
       
    
    
       [0028]    Like elements in the various figures are denoted by like reference numerals for consistency. 
       DETAILED DESCRIPTION OF THE INVENTION 
     Bending Sleeve Assembly 
       [0029]      FIG. 1A  illustrates a bending sleeve assembly  100  attached at one end to a pipeline  105  in one embodiment of the present invention. As further described below, the other end of the bending sleeve assembly  100  is free to move along the longitudinal axis of pipeline  105  which is required when bending takes place.  FIG. 1B  shows a cross-sectional view of the bending sleeve assembly  100  attached at one end to the pipeline  105  in  FIG. 1A .  FIG. 1B  shows four coupling connection as an example. Each coupling connection is comprised of a male and a female coupling part, which are locked together in grooves by a steel ring, as further detailed in  FIG. 2 . The number of coupling connections can be increased to as many as is required by the design for a specific location. Typically, steel pipelines are encased with an external concrete coating when laid on the sea floor. The external concrete coating has been removed from a section of the pipeline  105  where the bending sleeve assembly  100  is positioned. The example bending sleeve assembly  100  is comprised of five pieces coupled together by four couplings connections: a tube sleeve piece welded to a male coupling part  110 ; three interconnecting pieces with female and male coupling parts  115 ,  120 , and  125 ; and a tube sleeve welded to a female coupling part  130 . Only one of the tube sleeves is attached to the pipeline. In this example, the tube sleeve with the male coupling part  110  is attached by welding to the pipeline  105 . The tube sleeve with the female coupling part  130  is free to move along the longitudinal axis of pipeline  105 , which is required when bending takes place. The interconnecting pieces  115 ,  120 , and  125  each comprise of a female coupling part welded to a male coupling part. Alternative embodiments of the interconnecting piece can include a tube (also called an “interconnecting tube”) welded between the female and male coupling part—the female coupling part is welded to one end of the tube and the male coupling part is welded to the other end of the tube. The interconnecting tube extends the distance between the female and male coupling part as required to achieve a predetermined resulting bending configuration. A bending sleeve assembly comprises at least one interconnecting piece, and can comprise as many interconnecting pieces as required to achieve the predetermined resulting bending configuration. 
         [0030]      FIG. 2  shows a semi-section view of a coupling connection  200  in one embodiment of the present invention. A male coupling part  205  and a female coupling part  210  are assembled on one section of a pipeline  215 . The male coupling part  205  is engaged to a female coupling part  210  in an overlapping relationship. The male and female coupling parts  205 ,  210  have two mutually aligned annular grooves  220 ,  225  into which a locking ring  230  is inserted. The tolerance between the annular grooves  220 ,  225  and the locking ring  230  will be a determining factor for the degree of angular deviation that may be accepted by the coupling connection. These angular deviations will also determine the maximal bending to the pipeline  215  extending through the bending sleeve assembly. 
       Controlled Bending by External Force 
       [0031]      FIG. 3  shows a method of using a weight  300  as an external force to induce bending of a pipeline  305  where a bending sleeve assembly  310  is attached to the pipeline  305  in one embodiment of the present invention. The pipeline  305  is free spanning over the sea floor  315 . The weight  300  is placed on top of the bending sleeve assembly  310 . The weight  300  is suspended from one or more elongate flexible members such as a wire  320 , where one end of the elongate flexible member  320  is attached to the weight  300 . Different elongate flexible members, in addition to wires can be used to serve the same purpose. For example, a cable, belt, chain, rope, strap or the like can be used instead of a wire. The weight  300  is positioned on top of the pipeline  305  where the bending sleeve assembly  310  is attached. The weight  300  provides an external force on the bending sleeve assembly  310  and pipeline  305 , permanently bending the pipeline  305  to a curvature predefined by the bending sleeve assembly  310 . The bending sleeve assembly  310  is designed to absorb the point load forces from the weight  300  and restrict the increase in diameter or flattening as a result of the bending of the pipeline  305 . 
         [0032]      FIGS. 4A-C  show a method of using a weight  400  as an external force to induce bending of a pipeline  405  where a bending sleeve assembly is attached (not shown in detail) in different directions in one embodiment of the present invention. The pipeline  405  is free spanning over the sea floor  410 . The elongated-shaped weight  400  is held by two (or more) elongate flexible members such as wires  415  attached to opposite ends of the weight  400 . Different elongate flexible members, other than wires, can be used to serve the same purpose. For example, cables, belts, chains, ropes, straps or the like can be used instead of wires. The angle of the external force exerted by the weight  400  can be altered by adjusting the length of the wires  415 . 
         [0033]    The weight  400  can exert an external force on the pipeline  405  in different directions, depending on the bending requirement.  FIG. 4A  shows the weight  400  exerting an external force in a vertical direction on the bending sleeve assembly attached to the pipeline  405 .  FIGS. 4B and 4C  show one end of the weight  400  resting on the sea floor  410  with the weight  405  exerting an external force in a diagonal direction on the bending sleeve assembly attached to the pipeline  405 . 
         [0034]      FIG. 5  shows the method in  FIG. 4  where the wires  415  are attached to winches  505  mounted on a vessel  500  in one embodiment of the invention. The winches  505  are operated to control the angle of the external force exerted by the weight  400  on the bending sleeve assembly attached to the pipeline  405  by adjusting the lengths of the wires  415 . Remotely operated underwater vehicles (ROVs) with video cameras and other subsea surveying equipment commonly known in the industry may be used to guide the position of the weight  400  at the desired location. 
         [0035]      FIG. 6  shows a method of using a winch  600  mounted on a vessel  605 , a wire  610 , and a pulley  615  to exert an external force to bend a pipeline  620  attached to a bending sleeve assembly (not shown) in one embodiment of the present invention. One end of the wire  610  is attached to the winch  600  mounted on the vessel  605  positioned above the bending sleeve assembly. The wire  610  runs from the winch  600  through the pulley  615  secured to the sea floor  625  below the bending sleeve assembly. The other end of the wire  610  is attached to the pipeline  620  where the bending sleeve assembly (not shown) is attached. A different elongate flexible member, other than a wire, can be used to serve the same purpose. For example, a cable belt, chain, rope, strap or the like can be used instead of a wire. When the winch  600  is activated to pull the wire  610 , the pulley  615  directs the wire  610  to exert an external force on the pipeline  620 , bending the pipeline  620  towards the pulley  615 . 
         [0036]      FIG. 7  shows a method of using permanent weights  700  to exert an external force to a bending sleeve assembly (not shown) attached to a pipeline  705  which induces bending of the pipeline in one embodiment of the present invention. Weights  700  are placed on top of and around the pipeline  705  at a section of the pipeline  705  where the bending sleeve assembly (not shown) is attached. The bending sleeve assembly is designed to be sufficiently strong to accept permanent external forces exerted by the weights  700  and possible forces from ice and actions from the sea. The weights  700  can be made of natural material such as large rocks or of manufactured components (man-made material). The weights  700  are permanently placed at specific locations to bend the pipeline  705  to an acceptable bending radius to conform to the seabed. This approach also provides physical protection for the pipeline  705  from other external forces such as ice, wave actions and sea currents. This embodiment is particularly useful at locations where pipelines are laid on sea floor where rock formations are present. 
         [0037]      FIGS. 8A and 8B  show a plan view of a method using a vessel  800  and an anchor  805  to bend a pipeline  810  at a section where a bending sleeve assembly  815  is attached to the pipeline  810  in one embodiment of the present invention. The vessel  800  installs the pipeline  810  on the sea floor. The bending sleeve assembly  815  attached to the pipeline  810  is positioned on the pipeline  810  at a section where bending is desired. One end of a wire  820  is attached to the pipeline  810  where the bending sleeve assembly  815  is attached. The other end of the wire  820  is attached to an anchor  805  resting on the sea floor. Alternatively, the other end of the wire  820  can be attached to an immobile object, a vessel, or the sea floor itself. A different elongate flexible member, other than a wire, can be used to serve the same purpose. For example, a cable belt, chain, rope, strap or the like can be used instead of a wire. The vessel  800 , holding one end of the pipeline  810 , turns in a direction deviating horizontally away from the anchor  805 . As a result, the anchor  805  exerts an external force on the bending sleeve assembly  815  attached to the pipeline  810 , bending the pipeline  810  in the direction of the vessel  800 .  FIG. 8A  shows the pipeline  810  before controlled bending.  FIG. 8B  shows the pipeline  810  after controlled bending. 
         [0038]      FIGS. 9A and 9B  show a plan view of a method using a vessel  900  to install a pipeline  905  around an immobile object  910  where a bending sleeve assembly  915  is attached to the pipeline  905  in one embodiment of the present invention. The vessel  900  lays down the pipeline  905  around the immobile object  910 . The bending sleeve assembly  915  attached to the pipeline  905  is positioned next to the immobile object  910 . The vessel  900 , holding one end of the pipeline  905 , turns in a direction deviating horizontally around the immobile object  910 . As a result, the bending sleeve assembly  915  makes contact with the immobile object  910  and the reaction from the immobile object  910  exerts an external force on the bending sleeve assembly  915  attached to the pipeline  905 , bending the pipeline  905  around the immobile object  910 .  FIG. 9A  shows the pipeline  905  before controlled bending.  FIG. 9B  shows the pipeline  905  after controlled bending. 
         [0000]    Controlled Bending by External Force in Combination with Internally Loaded Weight 
         [0039]    Alternative embodiments of the present invention can include using the invented methods for controlled bending by external force in combination with prior art methods for controlled bending; for example, internally loading weights in the pipeline to exert a force on the selected bending zone of the pipeline. 
         [0040]    The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention. Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims.