Patent Application
20110008099
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.
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.
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.
Referring to
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
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
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 (
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.
