Abstract:
A connector assembly for connecting two members that allows manual lockdown to prevent accidental disengagement. The connector assembly can be used to connect a tension ring to a housing on a riser by using a lower set of hydraulically actuated dogs. A set of upper hydraulically actuated dogs on the connector assembly can be used to connect the tension ring to a diverter housing mounted on a rig. The connector assembly also has position indicators that ride along with the dogs to indicate whether the dogs are in the engaged or disengaged position.

Description:
FIELD OF INVENTION 
     This invention relates in general to tension rings and in particular to a dog-type lockout assembly for a tension ring that has a manual lockdown feature and indicates the dog position. 
     BACKGROUND OF THE INVENTION 
     Locking mechanisms for oilfield equipment often include a cylindrical locking mechanism called a dog. The dog is put into a locking position between two components, such as a tension ring and a housing, to hold a position or take a load. For example, the dog can be part of a tension ring that can maintain a riser in stable tension when offshore platforms heave. When the riser is retrieved, the dog can be locked to a housing located on the riser to prevent it from falling and injuring personnel. An additional dog can lock onto another component for storage. 
     To prevent the accidental unlocking of the dogs, a manual lockout can be employed to secure the dog in a locked position. When the lockout is engaged, the dog is locked in an engaged position. When the lockout is disengaged, the dog is free to move between an engaged and a disengaged position. However, the actual position of the dog is unknown. For example, when a lockout is disengaged, the dog may still be in the engaged position. This may cause problems for the operators. 
     A need exists for a technique to manually lockdown dogs and indicate whether a dog is in a locked or unlocked position. The following technique may solve these problems. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present technique, a dog-type lockout assembly is provided that integrates a position indicator that can provide visual confirmation as to whether the dog is in the engaged or disengaged position. The dogs can be manually locked down in the engaged position to prevent the dog from being accidentally disengaged. The dog-type lockout assembly allows two components, such as a tension ring and a housing, to be locked together to thereby hold a position or take a load. 
     In the illustrated embodiment, the dog-type lockout assembly has a tension ring. The tension ring can have eyelets disposed circumferentially around its exterior and adapted to receive wires that attach to the structure of a rig. The ring can be adapted to maintain tension on a drilling riser comprised of several thousand feet of pipe and extends from a rig down to the seafloor. The tension is applied to the riser via the wires attached to the ring to thereby prevent the riser from collapsing. The tension ring can apply tension to the riser through a housing connected to a slip joint. 
     When retrieving the drilling riser, in this example, the reaction point between the housing and the tension ring is removed and the tension wires go slack, allowing the tension ring to fall. This can be very dangerous to personnel working on platforms below the tension ring. To prevent the tension ring from falling during retrieval of the riser, a dog is used with the tension ring to lock into a mating passage on the housing. This prevents the tension ring from falling and allows the ring to be carried upwards to where another component can be mounted. The component can be, for example, a diverter support housing mounted on the rig. Another set of dogs on the tension ring can engage with the diverter support housing when the tension ring contacts the diverter support from below. The tension ring can be stored in this position. 
     A hazard can arise if the dogs are accidentally disengaged by actuating the dogs hydraulically. To prevent this hazard, a manual lockdown can be used to ensure the dog remains in the engaged position. The lockdown can be a mechanically driven screw located behind the engaged dog. When the lockdown is retracted the dog can float into both engaged and disengaged positions. When the lockdown is extended, the dog is only permitted to be in an engaged position. The solution adds a floating ring and position indicator rod to the dog that rides along with the dog to show the position of the dog. The position indicator will visually appear recessed within the ring body when the dog is in the engaged position and will appear retracted from the ring body when the dog is in the disengaged position. The floating ring can easily be radially positioned to make it easier to manufacture an assembly. 
     The dog-type lockout thus integrates position indication in one assembly. The combination of features allowing manual lockdown of the dogs into an engaged position and providing visual confirmation as to whether the dogs are in an engaged or disengaged position, advantageously increase safety by preventing accidental disengagement of the dogs and providing a simple way to ascertain the position of the dogs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a tension ring in contact with a housing and lower dogs in the engaged position, in accordance with an embodiment of the invention; 
         FIG. 2  is an enlarged sectional view of the dog and position indicator within a tensioner ring, in accordance with an embodiment of the invention; 
         FIG. 3  is an enlarged sectional view of the dog and position indicator within a tensioner ring with the lockdown member retracted, in accordance with an embodiment of the invention; 
         FIG. 4  is a sectional view of a tension ring in contact with a diverter housing and upper dogs in the locked position, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an embodiment of the invention shows a tensioner ring or connector assembly  10  for connecting two members. One member can be, for example, an outer member such as the riser tensioner ring  10  itself and the other member can be, for example, an inner member such as a housing  11  on a slip joint  12  connected to a riser  14 . 
     In this example, the connector assembly  10  can have eyelets  15  disposed circumferentially around its exterior and adapted to receive wires  16  that attach to a tension system that maintains constant tension. The tensioner ring  10  can be adapted to maintain tension on a drilling riser  14  comprised of several thousand feet of pipe that extends from a rig down to the seafloor. The tension is applied to the riser  14  via the wires attached to the ring  10  to thereby prevent the riser  14  from collapsing. The tensioner ring  10  can apply tension to the riser  14  through a housing  11  connected to a slip joint  12 . 
     Referring to  FIG. 2 , the tensioner ring  10  can comprise a frame or body  18  having at least one fluid cylinder or opening  19 . An actuator comprising a lower dog  20  that is movable between an engaged position and a disengaged position in a lower fluid cylinder  21  in response to fluid pressure. Lower dog  20  has a piston  21  that sealingly engages opening  19 . Hydraulic lines  22  can provide the fluid pressure to be exerted on piston  21 . The lower dog  20  has an interior end  24  that extends through an interior opening  26  on the interior of the frame  18  when the lower dog  20  is in the engaged position. In the engaged position the lower dog  20  engages a mating hole or groove formed on the housing  11 . To indicate the position of the lower dog  20  a collar or floating ring  28  connected to the lower dog  20 , carries a lower position indicator  30 . In the illustrated embodiment, the lower position indicator  30  is recessed within an aperture or opening  32  on the frame  18  when the lower dog  20  is in the engaged position, thus providing a visual confirmation of dog&#39;s position. When the lower dog  20  is in the disengaged position, the lower position indicator  30  will extend out from the aperture  32  in the illustrated embodiment. Position indicator  30  is a rod that is parallel to an offset from an axis of opening  19 . However, devices other than a rod may be used as a position indicator for the lower dog  20 . 
     The openings  19  on the frame  18  can be covered by lower and upper caps  56 ,  58 . The lower cap  56  has a threaded opening  36 . The aperture  32  for the lower position indicator  30  can similarly be formed on the lower cap  56 . The upper cap  58  can likewise have a threaded opening  54  that allows the upper locking member  52  to pass through it. The aperture  50  for the upper position indicator  48  can similarly be formed on the upper cap  58 . 
     A lower lockdown member or screw  34  extends through threaded opening  36  of cap  56 . In the illustrated embodiment, the lockdown member  34  is threaded to enable it to move between retracted and extended positions relative to the cap  56 . Screw  34  has a base that abuts the head of a screw  37  attached to and forming part of lower dog  20 . Extending the lower lockdown member  34  when the lower dog  20  is in the engaged position causes the lockdown member  34  to lock the lower dog  20  in the engaged position to prevent the dog  20  from moving to the disengaged position. The lower lockdown member  34  thus assures that the lower dog  20  will remain engaged to the housing  11  as the riser  14  is retrieved. Conversely, the lower dog  20  is free to move between the engaged and disengaged positions when the lower lockdown member  34  is in the retracted position. 
     Continuing to refer to  FIG. 2 , a similar locking mechanism can be used to store the housing  11  after the riser  14  is retrieved. An upper dog  38  can be located above the lower dog  20  and within the frame  18 . The upper dog  38  has a piston  39  and slidingly moves between engaged and disengaged positions in an upper fluid cylinder  39  in response to fluid pressure. Hydraulic lines  40  can provide the fluid pressure. The upper dog  38  has an interior end  42  that can extend through an interior opening  44  on the interior of the frame  18  when the upper dog  38 , is in the engaged position. In the engaged position the upper dog  38  engages a mating hole or groove formed on a member such as a diverter housing  70  ( FIG. 3 ). To indicate the position of the upper dog  38  a collar or floating ring  46  connected to the upper dog  38  carries an upper position indicator  48 . In the illustrated embodiment, the upper position indicator  48  is recessed within an aperture or opening  50  on the frame  18  when the upper dog  38  is in the locked position, thus providing visual confirmation of the dog&#39;s position. When the upper dog  38  is in the disengaged position, the upper position indicator  48  will extend out from the aperture  50  in this embodiment. 
     An upper lockdown member or screw  52  extends through a threaded opening  54  in cap  58 . Threads on rotary screw  52  enable it to move between retracted and extended positions relative to cap  58 . Screw  52  has a base that abuts the head of a screw  55  attached to and forming part of upper dog  38 . Extending the upper lockdown member  52  when the upper dog  38  is in the engaged position causes the base of the lockdown member  52  to engage the upper dog  38  and prevents the dog from moving to the disengaged position. The upper lockdown member  52  thus assures that the upper dog  38  will remain engaged to the diverter housing  70  ( FIG. 3 ) to allow storage of the housing  11  within the diverter housing  70 . The upper dog  38  is free to move between the engaged and disengaged positions when the upper lockdown member  52  is in the retracted position as shown in  FIG. 2 . 
     The portion of the frame  18  that houses the upper dog  38  can be radially offset outward farther than lower dog  20 . This offset creates an incrementally larger inner diameter at the upper dog  38  portion of the frame  18  that facilitates engagement with the diverter housing  70 . 
     While the invention has been shown in only one 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.