Abstract:
A tendon or riser connector has a separate lock-down device that overrides the connector&#39;s ability to unlock if the riser or tendon goes slack. The connector has a lock ring that engages a groove profile on a receptacle and is prevented from accidentally unlocking with a cam ring and set of blocks. The blocks are movably positioned between engaged and disengaged positions that correspond to the locked and unlocked positions of the lock ring.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates in general to tendon or riser mooring connectors and, in particular, to an improved system, method, and apparatus for enhancing the retention of tendon or riser moorings. 
         [0003]    2. Description of the Related Art 
         [0004]    In the prior art, one type of tendon or riser mooring connector for platforms typically operates with vertical motion only. At the sea floor, the connector is lowered a short distance into a receptacle mounted to the sea floor, lifted vertically, and locks into a profile in the receptacle. If lowered a longer distance into the receptacle, such as when the riser or tendon goes slack, an unlocking mechanism allows the connector to release from the receptacle. Under extreme environmental operating conditions, such as hurricanes, the connector can be accidentally unlocked due to motion of the platform at the surface and severely jeopardize the safety of personnel and equipment. Thus, an improved solution for enhancing a secure connection between tendon or riser moorings and receptacles would be desirable. 
       SUMMARY OF THE INVENTION 
       [0005]    One embodiment of a system, method, and apparatus for locking down a tendon or riser mooring incorporates a separate lock-down device that overrides the connector&#39;s ability to unlock if the riser or tendon goes slack. The locking device engages a groove profile on a receptacle and is prevented from accidentally unlocking with securing means located between the locking device and the connector. The securing means is movably positioned (e.g., rotationally or axially) between engaged and disengaged positions that correspond to the locked and unlocked positions of the lock device. 
         [0006]    In one embodiment, the lock device is a lock ring that is biased radially outward into engagement with the groove profile. The securing means may utilize a cam ring that is actuated by a diver, a remotely-operated vehicle (ROV), or a hydraulic or mechanical drive mechanism. The cam ring moves a set of blocks to selectively engage the lock ring with slots, weldments, levers, and the like. 
         [0007]    The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0009]      FIG. 1  is a sectional side view of one embodiment of a bottom mooring constructed in accordance with the present invention; 
           [0010]      FIG. 2  is a sectional top view of a connector in the bottom mooring of  FIG. 1  in a locked position, taken along the line  2 - 2  of  FIG. 1  and is constructed in accordance with the present invention; 
           [0011]      FIG. 3  is an enlarged sectional side view of the connector of  FIG. 2  taken along the line  3 - 3  of  FIG. 2  and is constructed in accordance with the present invention; 
           [0012]      FIG. 4  is a sectional top view of the connector of  FIG. 2  in an unlocked position and is constructed in accordance with the present invention; 
           [0013]      FIG. 5  is an enlarged sectional side view of the connector of  FIG. 4  taken along the line  5 - 5  of  FIG. 4  and is constructed in accordance with the present invention; 
           [0014]      FIG. 6  is a sectional side view of a second embodiment of a bottom mooring connector constructed in accordance with the present invention; 
           [0015]      FIG. 7  is a sectional side view of a third embodiment of a bottom mooring connector constructed in accordance with the present invention; 
           [0016]      FIG. 8  is a front view of a portion of a securing mechanism of the connector of  FIG. 7  constructed in accordance with the present invention; 
           [0017]      FIG. 9  is a sectional side view of a fourth embodiment of a bottom mooring connector constructed in accordance with the present invention; and 
           [0018]      FIG. 10  is a front view of a portion of a securing mechanism of the connector of  FIG. 9  constructed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to  FIGS. 1-5 , one embodiment of a system, method, and apparatus for securing a mooring connection is disclosed. One skilled in the art will recognize that the invention also is suitable for other applications including squnch connectors, handling tools, etc. A mooring receptacle  11  is located on the sea floor  13 . 
         [0020]    A bottom connector  17  has a tubular member  18  (e.g., a tendon or riser) extending therefrom to a platform at a sea surface (not shown). Alternatively, the bottom connector  17  may comprise a squnch connector, a handling tool, etc. The bottom connector  17  is secured to an interior groove profile  15  in the receptacle  11  with a lock device  19  (e.g., lock ring, lock dogs, etc.) that is horizontally movable relative to the groove profile  15 . The lock device  19  may be biased radially outward into engagement with the groove profile  15 , or it may be neutrally biased or biased radially inward. 
         [0021]    In the embodiment shown, the bottom connector  17  may be connected to and disconnected from the receptacle  11  strictly via vertical motion. In this way, the bottom connector  17  locks into the receptacle  11  by being lowered into the receptacle for a limited distance, past a locked position, but not enough to engage an unlocked position, and then raised back up to the locked position. The bottom connector  17  is unlocked from the receptacle  11  by being lowered beyond the locked position to the unlocked position, after which the bottom connector  17  may be removed from the receptacle  11  by upward vertical motion. An optional sleeve (e.g., anode sleeve) may be lowered onto and secured to an exterior of the receptacle  11  to provide cathodic protection for the installation. 
         [0022]    The invention also comprises securing means  21  for preventing the lock ring  19  from disengaging the groove profile  15  so that the bottom connector  17  cannot be further lowered to the unlocked position and, thus, accidentally unlocked from the receptacle  11 . In one embodiment, the securing means  21  is integrated with the bottom connector  17  and is adjacent the lock device  19 . 
         [0023]    In one embodiment, a lockdown mechanism or the securing means  21  (see, e.g.,  FIG. 5 ) has an engaged position that restrains the lock device  19  from disengaging the groove profile  15  via horizontal motion relative to the receptacle  11 , and a disengaged position that permits the lock device  19  to disengage the groove profile  15  via horizontal motion of the lock device  19  relative to the receptacle  11 . As will be recognized by those skilled in the art, the securing means  21  may be actuated by a diver, a remotely-operated vehicle (ROV), and a hydraulic drive mechanism. 
         [0024]    In some of the embodiments of the present invention, the connector  17  and securing means  21  utilize an upper body  31  ( FIG. 3 ). The upper body  31  may comprise a cavity  33  that contains the lock device  19 . A cam ring  35  is located in the upper body  31  adjacent the cavity  33 . The cam ring  35  is movable (e.g., rotatable about a central axis or axially movable) relative to the lock device  19  between a locked position ( FIGS. 1-3 ) and an unlocked position ( FIGS. 4 and 5 ). 
         [0025]    The securing means  21  also comprises a set of blocks  41  (e.g.,  6  to  8 ) located in the upper body cavity  33  between the cam ring  35  and the lock device  19 . The blocks  41  have an engaged position ( FIGS. 1-3 ) that prevents the lock device  19  from disengaging the groove profile  15 . The blocks  41  also have a disengaged position ( FIGS. 4 and 5 ) that permits the lock device  19  to disengage the groove profile  15 . The blocks  41  are movable (e.g., radially or axially) between the engaged and disengaged positions as the cam ring  35  is moved between the locked and unlocked positions, respectively, such that the cam ring  35  moves relative to the blocks  41  and the lock device  19 . 
         [0026]    In the embodiment of  FIGS. 1-5 , the cam ring  35  has a perimeter  43  and slots  45  formed in the perimeter  43 . The blocks  41  move between the engaged and disengaged positions by movement out of and into the cam ring slots  45  as the cam ring  35  is rotated between the locked and unlocked positions, respectively. The cam ring  35  and the blocks  41  have a loose fit with radial gaps therebetween in the locked and engaged positions, respectively. Alternatively, the cam ring  35  and blocks  41  may remain in contact with no gaps therebetween such that forces are immediately transmitted. The blocks  41  may be secured to the lock device  19  such that the lock device  19  is required to move with the blocks  41  as the blocks  41  are moved between the engaged and disengaged positions. 
         [0027]    As illustrated in  FIGS. 1-5 , the connector  17  and securing means  21  may utilize a lower body  47  that is located below the upper body  31 , both of which have a sloped surface  49 . The lock device  19  and the blocks  41  have lower ends that are mutually supported on the sloped surface  49 . The cam ring slots  45  are rectangular with inclined surfaces  46  ( FIG. 2 ) for facilitating radially outward motion of the blocks  41  from the disengaged position to the engaged position. 
         [0028]    In some embodiments, the cam ring  35  is retained in the upper body  31  with a restraining ring  51 . In addition, the cam ring  35  has a key or lug  53  formed on a lower portion thereof that moves in a slot  55  formed in the upper body  31  for limiting rotational motion of the cam ring  35  between the locked and unlocked positions. Furthermore, in one embodiment the cam ring  35  has crenelations  57  formed on an upper portion thereof for facilitating rotational motion of the cam ring  35  via an external influence (e.g., diver, a remotely-operated vehicle (ROV), a hydraulic or mechanical drive mechanism, etc.), such as those known in the art. 
         [0029]    Referring now to  FIG. 6 , another embodiment of the securing means is shown. In this embodiment, the cam ring comprises a cam weldment  61  having a set of weld blocks  63  on a lower portion thereof. The weld blocks  63  are complementary to the blocks  41  for retaining the blocks  41  in the engaged position when the cam weldment  61  is in the locked position, and for allowing the blocks  41  to move to the disengaged position when the cam weldment  61  is in the unlocked position. Other features of this embodiment of the invention are similar or identical to those described above. 
         [0030]    The cam weldment  61  is retained in the upper body  31  with a restraining ring  65 . The cam weldment  61  has a key or lug  67  formed on a lower portion thereof that moves in a slot  69  formed in the upper body  31  for limiting rotational motion of the cam weldment  61  between the locked and unlocked positions. In one embodiment, the cam weldment  61  has pad eyes  62  formed on an upper portion thereof for facilitating rotational motion of the cam weldment  61  via an external influence. 
         [0031]    Referring now to  FIGS. 7 and 8 , another embodiment of the cam ring  71  has drive slots  73 . In this version, each block comprises a block body  75 , an arm  77  extending from the block body  75  through a respective one of the drive slots  73 , and a pin  79  extending from the arm  77  located opposite the block body  75  for retaining the block on the cam ring  71 . The block body  75  is located between the lock device  19  and the upper body  31  in the locked position (i.e., solid lines in  FIGS. 7 and 8 ), and the block body  75  is removed from between the lock device  19  and the upper body  31  in the unlocked position (see dashed lines in  FIGS. 7 and 8 ) to permit the lock device  19  to move from the engaged position to the disengaged position, respectively. 
         [0032]      FIGS. 9 and 10  depict an alternate embodiment wherein the blocks comprise lever arms  81  mounted to the lower body  47 . The lever arms  81  are pivotably movable between engaged (see dashed lines) and disengaged positions as the cam ring  83  is moved between the locked and unlocked positions, respectively. The cam ring  81  may moved between the locked and unlocked positions via rotational movement ( FIG. 10 ) where an end  87  of lever arms  81  move in a slot  85 , and vertical axial motion ( FIG. 9 ). In the engaged positions, the lever arms  81  abut the lock device  19  to prevent the lock device  19  from unlocking and, in the disengaged positions, the lever arms  81  are pivoted away from the lock device  19  to permit the lock device  19  to unlock. 
         [0033]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.