Abstract:
This invention is directed to a system and method which uses hydrostatic pressure to lock two plates together subsea. It also allows for remotely disconnecting the two plates. A common application of this invention is for the hydraulic junction plates.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Provisional Application Ser. No. 60/847,533, filed on Sep. 27, 2006. 
     
     FIELD OF THE INVENTION 
       [0002]    This invention is directed to a system and method which uses hydrostatic pressure to lock two plates together subsea. It also allows for remotely disconnecting the two plates. A common application of this invention is for the hydraulic junction plates. 
     
     
       DESCRIPTION OF THE DRAWINGS 
         [0003]      FIG. 1  is a side view of an apparatus embodiment of the invention with the plates uncoupled. 
           [0004]      FIG. 2  is a block diagram of a method embodiment of the invention. 
           [0005]      FIG. 3  is a block diagram of another method embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0006]    A first preferred apparatus embodiment of the invention is directed to a system for securing two structures subsea and is shown in  FIG. 1 . This preferred embodiment comprises a fixed structure located subsea  10 . In another preferred embodiment, the fixed structure is a plate. This preferred embodiment further comprises at least one rod  12  attached to the fixed structure, and at least one first hydraulic coupler component  14  attached to the fixed structure. In a preferred embodiment, the invention further comprises a first guide member, such as at least one guide pin  16  attached to the fixed structure. In a preferred embodiment, as shown in  FIG. 1 , the invention comprises first and second rods  12 . 
         [0007]    The first hydraulic coupler component has a first gender, either male or female. In another preferred embodiment, the invention further comprises a first latching element, such as a latch receiver  18 , attached to the fixed structure. In a preferred embodiment, the latch receiver is adapted to receive a detent mechanism, as shown in  FIG. 1 . 
         [0008]    This preferred apparatus embodiment further comprises a removable structure  20 , at least one rod housing  22  attached to the removable structure and adapted to snugly engage a rod, at least one second hydraulic coupler component  24  attached to the removable structure, the second hydraulic coupler adapted to engage the first hydraulic coupler component, as shown in  FIG. 1  In one preferred embodiment, the rod housing is a cylinder. In a preferred embodiment, the cylindrical rod housing diameter may be configured as a function of water depth such that a required locking force is obtained. 
         [0009]    The second hydraulic coupler component has a gender opposite to the gender of the first hydraulic coupler component. In another preferred embodiment, the removable structure is a plate, as shown in  FIG. 1 . In a preferred embodiment, as shown in  FIG. 1 , the invention comprises first and second rod housings  22  adapted to snugly receive the first and second rods, respectively. 
         [0010]    In a preferred embodiment, the invention further comprises a second latching element, such as a latch  26 , attached to the removable structure and adapted to be received by the fixed structure. In another preferred embodiment, the latch comprises a detent mechanism, as shown in  FIG. 1 . In a preferred embodiment, the invention may use the Junction Plate latching mechanism available from Oceaneering International Inc. of Houston, Tex., as a latch mechanism. 
         [0011]    In another preferred apparatus embodiment, the invention comprises the features and components described above for the first preferred embodiment as well as a guide funnel; an ROV bucket  28  connected to the latch and a valve  29  installed in a line connecting each rod housing, as shown in  FIG. 1 . In one preferred embodiment, the valve is a pilot operated check valve. In another preferred embodiment, the valve is a check valve in parallel with a ball valve or a needle valve. The valve is open when the rod is being inserted into the rod housing. Once the rod is fully inserted into the rod housing, the valve is closed, thereby producing a vacuum locking effect between the fixed plate and the removable plate. 
         [0012]    In a preferred embodiment, the fixed subsea plate has a closely toleranced rod attached, along with hydraulic couplers and guide pins. In one preferred embodiment, the removable plate comprises a mating guide member adapted to mate with the first guide member. In another preferred embodiment, the mating guide member is a guide funnel  27 , as shown in  FIG. 1 . In a preferred embodiment, the removable plate has a close toleranced rod housing in the form of a cylinder along with a guide funnel  27  positioned and sized to receive each guide pin. In another preferred embodiment the fixed plate comprises first and second guide pins, and the removable plate comprises first and second guide funnels positioned and sized to receive the first and second guide pins, respectively, as shown in  FIG. 1 . 
         [0013]    Other embodiments of the invention are directed toward methods of securing a first structure to a second structure, as shown in  FIGS. 2 and 3 . A first preferred method embodiment comprises the steps of landing a removable structure on a fixed structure subsea  30 , drawing the structures together  35 , and inserting a rod on the fixed structure into a rod housing on the removable structure  40 , as shown in  FIG. 2 . 
         [0014]    Additionally, as the rod is inserted, a check valve is used to allow water to exit the rod housing  45 . During the inserting, a check valve is used to prevent water from reentering the rod housing  50 , as shown in  FIG. 2 . In a preferred embodiment, steps  35 ,  40 ,  45 , and  50  are performed simultaneously, as shown in  FIG. 2 . In a preferred embodiment, the check valve is pilot operated. In another preferred embodiment, a latching mechanism may be used to draw the structures together. 
         [0015]    A second preferred method embodiment comprises the steps of the first preferred method embodiment as well as opening the check valve  60 ; equalizing the pressure inside the rod housing with ambient pressure  65 ; and separating the two structures  70 , as shown in  FIG. 3 . 
         [0016]    In a preferred embodiment, the removable plate is landed on the fixed plate and the latching mechanism is used to draw the plates together. This inserts rod/piston on the fixed plate into the rod housing on the removable plate. As the rod is inserted a pilot operated check valve allows the water to exit the rod housing. Since the check valve prevents water from reentering the rod housing as do the seals between the rod and the cylinder, the removable plate is locked to the fixed plate, by the surrounding hydrostatic pressure. 
         [0017]    This locking force depends on the water depth and the cylinder diameter. Since the water depth is fixed the rod housing can be sized such that the required locking force is obtained. The mechanical latching device that draws the two plates together can now be unlatched. 
         [0018]    To disconnect the plates in one embodiment, a pilot signal opens the check valve equalizing the pressure inside the rod housing with the ambient. In one preferred embodiment, the pilot signal comes from the surface. The two plates are free to separate after the pilot valve is opened. 
         [0019]    Inherent fail safe capabilities of one or more embodiments include the operational attribute that if the hydraulic lock does not release, the plates can still be separated if sufficient external force is applied without damaging any of the components. 
         [0020]    It will be understood that various changes in detail, parameters, and arrangements of the steps which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention.