Patent Application
20070290503
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:
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.
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.
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
Those skilled in the art will appreciate that dogs 56 can be held retracted for run in with a band spring or equivalent 100.
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
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:
