Abstract:
A connection for sub-sea use employs locking dogs that are isolated from seawater and a backup system for operating the backup sleeve to the dogs. The normal actuation system for the backup sleeve is also isolated from seawater exposure. The set position of the backup sleeve is positively retained against the prospect of axial movement that could be triggered by transmitted vibration into the connection.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    In accordance with certain embodiments, the present invention relates to method and apparatus for lockable inserts for oilfield equipment and, more particularly, to equipment used subsea for choke applications among others. 
         [0004]    Offshore oilfield operation frequently requires making connections subsea, typically using Remotely Operated Vehicles (ROVs) or divers. Typically a connection between a male and female component completes the subsea connection. The connection can be a pipe coupling or the insertion of a valve interior component into a housing that is located subsea. Once the connection is brought together it is locked into that position, thus securing the connection. 
         [0005]    The subsea environment is hostile, and issues of attack on the components over a period of time are a concern in any such connection. Another general concern is debris that can get into the area where the locking is to take place. Over time some of these effects can operate in tandem to preclude a secure locking of the connection or to prevent unlocking when it is time to undo the connection. Exposure of the actuation assembly to seawater can also undermine its effective operation. Yet another issue affecting such connections is the long term effect of transmitted vibration to the connection, which can unintentionally move the actuation mechanism that locks the locking dogs into a surrounding recess or groove and potentially cause an inadvertent separation of the connected components. 
         [0006]    U.S. Pat. No. 6,237,964 is illustrative of the issues that are confronted in such subsea connections. With reference to the numerical reference numbers presented in this patent, Ostergaard shows a female component  14  that accepts a valve insert  4  and  6 . To connect these components, an actuating sleeve  20  is movable axially as the ring gear  28  that has threads  26  engages threads  24  on sleeve  20  to urge the sleeve down behind dogs  45 . The downward movement of the sleeve places dogs  45  into a locked position where surfaces  41  and  44  engage, thus locking the connection. In essence, the lower end of sleeve  20  cams the dogs  45  into locking engagement with the opposing recess in the female component  14 . A seal  18  is at the same time actuated to hold the pressure within the connection when the two components are locked together. 
         [0007]    A few features of this design are worth noting. The dogs  45  and their surrounding groove are exposed to seawater that enters between housing  11  and top face  22 . The operating mechanism that moves the sleeve  20  axially up or down is also exposed to seawater where the threads for driving engage one another. Additionally, there is no backup device to unlock the connection if the sleeve  20  fails to come up with the existing drive system. Finally, there is no device in this assembly to compensate for transmitted vibration which could result in inadvertent axial motion of sleeve  20  as vibration induces rotation back to input shaft  34 . In essence, the connection can inadvertently release because of vibration induced axial movement of the sleeve  20  that induce rotation at the threaded connection and back to input shaft  34 . 
         [0008]    A similar design is offered by Liaaen and shown in  FIG. 1 . It features a female component or valve body  10  that accepts a male component or insert  12 . When the two components are pushed together, a seal  14  retains pressure within the body  10 . In the split view of  FIG. 1  it can be seen that the insert  12  is secured to the body  10  by the urging of the dogs  18  into an opposing recess or slot  16 . An axially movable sleeve  20  then gets behind dogs  18  to prevent retraction of the dogs from recess  16 . An input shaft  22  rotates a mating thread  24  with the result being that the sleeve  20  can be moved axially in opposed directions. While a housing  26  keeps the driving components for the insert  12  isolated from seawater, it is clear that the rest of the components for locking the connection are exposed to seawater via fluid pathways represented by arrow system  30 . Seawater can have negative impacts on a threaded connection  24  by precluding makeup or release with no backup system available to raise sleeve  20  if rotation of shaft  22  does not get the job done, for instance. The dogs  18  are in seawater, and there is no anchoring mechanism to hold the position of sleeve  20  against vibratory forces. 
         [0009]    Those skilled in the art will appreciate the manner in which such problems are addressed from the description of the preferred embodiment, the drawings and from the full scope of the invention in the appended claims. 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with certain embodiments, the present invention provides a connection for subsea use that employs locking dogs that are isolated from seawater and includes a backup system for operating the sleeve that positions the dogs. The normal actuation system for the sleeve is also isolated from seawater exposure. The set position of the sleeve is positively retained against the prospect of axial movement that could be triggered by transmitted vibration into the connection. 
     
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0012]      FIG. 1  is a prior art design shown in section; 
           [0013]      FIG. 2  is a section view showing various aspects of the present invention in accordance with certain exemplary embodiments; and 
           [0014]      FIG. 3  is a different section than  FIG. 2  showing the position lock feature when the insert is installed in the body, in accordance with certain exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 2  illustrates an exemplary choke  31  where the body  32  has an inlet  34  and an outlet  36 . This exemplary choke  31  includes an insert assembly  38  that features an exterior stationary cage  40  and a movable plug  42  that is operated within so that ports  44  and  46  can be brought into or out of alignment. Body  32  has a top flange  48  secured to it through bolt holes  50  with fasteners (not shown). Seal  52  seals between the body  32  and the flange  48 . Flange  48  has a recess or circular groove or grooves or some other surface irregularity  54  that preferably has a conforming shape to dog or dogs or equivalent locking members  56 . Locking members  56  can be short segments that are individually actuated as well as a split ring whose diameter grows as the split is opened when it is urged out radially. A sliding sleeve  58  can be forced behind dogs  56  to force them into conforming grooves  54  after the insert assembly  38  is fully advanced into the body  32 . The insert assembly  38  has a lower support plate  60  that is supported by hub  62 . A seal  64  seals out sea water from below dogs  56  in its position between plate  60  and flange  48 . Housing  66  in conjunction with plate  60  define an opening through which the dogs  56  can be cammed radially for a lock into recess  54  of flange  48 . Housing  66  has a seal  68  that is above dogs  56  to keep seawater away from dogs  56  from above by sealing against flange  48 . 
         [0016]    Sliding sleeve  58  has inner seal  70  and outer seal  72  to define cavity  74  that is connected to a hydraulic pressure source  76  through lines  78 . By providing pressurized hydraulic fluid into cavity  74 , the increase in pressure raises sleeve  58  as a backup way to retract the dogs  56  for release of the insert assembly  38  from the body  32 . The normal way that the dogs  56  are cammed radially outward is by applying axial force on rod  80  in a direction toward body  32 . Rod  80 , and there could be one or more than one, extends through a sealed housing  82  that is filled with a lubricant and is sealed to exclude seawater as rod  80  is moved in opposed directions by an ROV (not shown). Plate  86  moves in tandem with rod  80 . Rod  88  is connected to plate  86  at its upper end and sleeve  58  at the lower end. As a result, when the ROV moves rod  80  down, sleeve  58  moves down and dogs  56  get cammed into recess  54 . To release the insert assembly  38  from body  32 , the rod  80  is raised and the insert assembly  38  will come out in response to an upward pull, since the dogs  56  are now unsupported after the retraction of sleeve  58 . Again, sometimes the sleeve  58  will not budge under a force applied to rod  80 . If that happens, there is a backup way to get the sleeve  58  to come up by applying hydraulic pressure to cavity  74 . The insert assembly  38  is normally operated using components in housing  82  using an ROV to manipulated shaft  102  in a manner known in the art. 
         [0017]    It can be seen that seals  64  and  68  that surround dogs  56  keep circulating seawater away from the dogs  56 , thus keeping debris out and the corrosive effects of such exposure to a minimum. While some small quantity of seawater is present at makeup, the amount is very small and continuous exposure thereafter is no longer an issue. The moving parts that operate the sleeve  58  are disposed within housing  82  that excludes seawater and preferably has lubricating oil within. By placing these components in a lubricating bath, design life can be improved, seawater corrosion can be prevented, algae growth can be limited, and the ingress of debris can be retarded. Additionally, it is only the portion of the rod  80  that extends from housing  82  that sees seawater. A seal, not shown, surrounds rod  80  as it slides through plate  90  of housing  82 . 
         [0018]    The position lock feature of sleeve  58  can be better understood by noting the relative positions of upper plate  92  and lower plate  94  in  FIG. 2 , before looking at  FIG. 3 .  FIG. 3  is a section at a different orientation than the  FIG. 2  section to show this additional feature.  FIG. 3  shows a rod  96  that extends through upper plate  92  in a threaded relationship. The rod  96  bears on lower plate  94  when properly rotated by an ROV or otherwise to advance against plate  94 . Because of the threaded connection at plate  92  rod  96  is tightly forced against plate  94  thus holding sleeve  58  tightly in the  FIG. 2  position where it holds dogs  56  locked to recess  54  in flange  48  despite transmitted vibration. While one type of position lock against vibration has been illustrated those skilled in the art will recognize that different locking designs can be used. One distinct advantage of the locking feature is that it too is within the housing  82  and is therefore protected from the adverse effects of prolonged exposure to seawater. 
         [0019]    Those skilled in the art will appreciate that dogs  56  can be held retracted for run in with a band spring or equivalent  100 . 
         [0020]    The described design keeps the locking dogs  56  isolated from seawater as well as the entire drive mechanism for locking sleeve  58  except for a portion of rod  80  that extends above plate  90  in housing  82 . The locking mechanism described in  FIG. 3  is also isolated from seawater in housing  82 . Additionally, a backup way of retracting the sleeve  58  exists if pulling on rod  80  fails to raise the sleeve  58 . 
         [0021]    The above description is illustrative of the exemplary embodiments of the present invention, and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: