Abstract:
A transporter system for handling heavy equipment, such as subsea blowout preventer stacks, on floating type drilling vessels. The transporter system includes rack and pinion mechanisms to move the transporter apparatus up and down and fore and aft on the drilling vessel.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns transporter apparatus for use on floating type drilling vessels and, particularly, transporter apparatus capable of moving heavy equipment up and down and fore and aft on the drilling vessel. More particularly, the invention concerns transporter apparatus for handling heavy blowout preventer (BOP) stacks on floating drilling vessels which is capable of moving a BOP stack into position over the well bay on the drilling vessel preparatory to lowering the BOP stack to the well located on the sea floor and of moving the BOP stack to and placing it on a test stump for repair maintenance and testing, and to provide a storage frame for the BOP stack during movements of the vessel from one location to another. 
     Heretofore, heavy equipment such as blowout preventer stacks were generally moved fore and aft on floating drilling vessels by bridge-type overhead cranes which suspended the blowout preventer stack from rails. Those overhead cranes had undesirable features which the present invention overcomes. For example, bridge cranes usually could not lift the entire stack necessitating partial dismantling of the stack; and wire lines used to support the stack permitted adverse motion due to pitch and roll of the vessel. The transporter system of this invention holds the stack rigidly with reference to the vessel. 
     SUMMARY OF THE INVENTION 
     An equipment handling system for moving equipment on floating drilling vessels on which two parallel beams or tracks are mounted. The tracks are located on each side of the spider deck opening and extend from underneath the drilling derrick substructure to a point beyond the substructure convenient for maintenance and testing of equipment being handled. The transporter apparatus consists of two individually powered mobile frame sides mounted on wheels which roll on the tracks as the tracking pinion gears are energized. Each frame side has a vertical mounted geared rack to which the equipment being handled is secured. The vertical racks overhang the spider deck opening so that the racks may travel vertically inside the spider deck opening. The racks are confined in a rack guide and are powered with individual motors driving a pinion gear which meshes with the rack gear. Lift lugs for engaging the equipment to be moved are connected to each rack for movement with it. Also, retainer latches are connected to each rack. A geared rack is arranged on each track to permit movement and control of the equipment along the track by means of a motor driven pinion gear mounted on each transporter frame side. Stabilizer rollers are also connected to each frame side for engaging flanges on the underside of each track to stabilize the fore and aft movement of each frame side and resist overturning. A power cable reel is mounted on each side of the frame and a power cable is wound on each reel and connected to a source of power for supplying power to the motor with which it is associated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a semisubmersible drilling vessel; 
     FIG. 2 is a plan view of the drilling vessel shown in FIG. 1 and including the transporter system of the invention positioned on the spider deck; 
     FIG. 3 is a view taken along lines 3--3 of FIG. 2 and illustrating also two other positions of the transporter frame; 
     FIG. 4 is a view taken along lines 4--4 of FIG. 3; 
     FIG. 5 is a front view of the transporter system; 
     FIG. 6 is a view taken along lines 6--6 of FIG. 5; 
     FIG. 7 is a view taken along lines 7--7 of FIG. 6; 
     FIG. 8 is a view taken along lines 8--8 of FIG. 6; 
     FIG. 9 is a side view of a modified transporter frame; and 
     FIG. 10 is a view taken along lines 10--10 of FIG. 9. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, and particularly FIGS. 1 and 2, there is shown a semisubmersible drilling vessel 10 comprising a pair of spaced apart pontoons or hulls 11 extending in parallel relation. Each pontoon supports a drilling platform, generally designated 12, on three vertical cylindrical caissons 13 and tubular trusses 14. The drilling platform 12 includes a rectangular working main deck 15, a spider deck 16 below the main deck and an upper deck 17. A crane 18 is mounted on the upper deck. A drilling derrick 19 having a substructure 20, including the derrick floor 21, is supported on main deck 15. 
     In FIG. 3, in which the transporter frame is shown in three positions A, B and C, the spider beams 25 and 26 form tracks which extend fore and aft on each side of the spider deck opening (Moon Pool) 5 in parallel relationship. They extend from underneath substructure 20 to a cross-structure 6 fastened to spider beams 25 and 26 and on which a test stump 31 is supported. Test stump 31 is used for storage, maintenance and testing of equipment being handled. Structure 6 is slotted, as indicated at 7, to allow full vertical movement of the racks in position A. The center line of the subsea well is indicated at 27. One side 28a of a transporter frame 28 is positioned on spider beam 25 and the other side 28b of frame 28 is positioned on spider beam 26. As will be seen the transporter frame is capable of moving the equipment it supports up and down as well as fore and aft of the drilling vessel. In position A a blowout preventer stack 30 supported on frame 28 has been lowered to test stump 31 and connected to it by connector 32. Position A is the storage position for blowout preventer stack 30. In moving the blowout preventer from position A to a position over the well the blowout preventer stack is first disconnected from stump 31 and raised to a height sufficient to free it therefrom. The frame and BOP stack is then moved to position C, shown in dotted lines, by the frame sides 28a and 28b driven along racks 33a and 33b arranged on each of the spider beams 25 and 26. Each transporter frame side is independently movable. When moving frame 28 and supported blowout preventer stack 30 to position C the blowout preventer stack 30 is lowered to clear obstacles such as cross beams 34 which support derrick floor 21. When frame sides 28a and 28b reach position C the center line of the well and stack 30 is in alignment with the derrick 19. The height of the BOP stack, H 1 , shown by dotted lines in position B, indicates the uppermost position of blowout preventer 30. This height allows clearance of test stump 31, but also indicates the upper limit of travel with the rack length illustrated. The distance D 1  represents the horizontal travel of the frame and BOP stack from position A to position B. The height of the BOP stack, H 2 , in position C, represents the lowermost position of stack 30 with the rack length illustrated. The distance D 2  represents the horizontal travel of the frame and BOP stack from position B to position C. 
     FIG. 4 shows the transporter frame and blowout preventer stack in position C in more detail. As shown in that Figure transporter frame sides 28a and 28b support blowout preventer stack 30. 
     In this position conventional guide cables 37 (four in number), connected to cable tensioners as indicated, are aligned in the guide tubes of BOP stack 30. 
     Referring to FIGS. 4 to 8, frame side 28b is provided with pinion gears 40b and 41b, driven by motors 42b and 43b through drive trains 44b and 45b. The gears 40b and 41b engage rack teeth 46b and 47b, respectively, of a vertical rack 48b. The rack is adapted to move vertically in rack guides 49b and 50b (FIG. 7). 
     The frame side 28b is adapted to be moved horizontally along spider beam 26 by a drive pinion gear 51b which is powered by a motor 52b. Rollers 53b, on frame side 28b, engage the top side of spider beam 26 while stabilizer rollers 54b, connected to frame side 28b, engage the underside of the top flange of spider beam 26. 
     A power cable 55b, having one end thereof wound on a spring reel 56b and its other end connected to a power junction box 57b, supplies power to operate the motors. Retractable-extendible lift lugs 58b mounted on pivot pins in slots 59b of rack 48b extend, as shown in FIGS. 6 and 8, to engage a portion of blowout preventer 30 to support the blowout preventer on the rack. The lugs are extended and retracted by means of a piston and cylinder assembly 60b. 
     The rack 48b is also provided with retainer latches 61b which are adapted to engage each side of a lower portion of BOP stack 30 and are operated in a manner similar to the operation of lugs 58b (not shown). Latches 61b prevent undesirable movement of the lower end of BOP stack 30 and steady it during vertical or horizontal movement during operation of the frame 28. An operator&#39;s recess 62b is provided on frame 28b with a control panel 63b by which an operator can control operation of the various motors and gears to move the frame sides 28a and 28b horizontally on spider beams 25 and 26 and move the racks 48a and 48b vertically. 
     Frame side 28a is provided with components identical to the aforementioned components on frame side 28b. The numbers of the corresponding components are provided with the suffix a. Thus, it is seen that frame side 28a is provided with an operators recess 62a and control panel 63a. A power cable similar to 55b is wound on a spring reel 56a and is connected to a junction box similar to 57b. The controls of the panels 63b and 63a may be synchronized, by means not shown, whereby a single operator, in either of the operators recesses, may operate both frame sides in unison or an operator may be positioned on both frame sides. 
     Vertical racks 48a and 48b overhang spider deck opening 5 to permit the racks to move vertically inside that opening. 
     OPERATION 
     In operation, to move the blowout preventer stack 30 from position A to position C (FIG. 3), the lift lugs 58b and 58a, of the racks 48b and 48a, are operated to engage each side of the upper portion of stack 30. The retainer latches 61b and 61a are also operated to engage each side of the lower portion of the stack 30. As shown in FIG. 5, W B  represents the maximum width of the blowout preventer which can be accommodated with the illustrated spider beam spacing. The connector 32 on the lower end of stack 30 is released from test stump 31 and the stack is raised clear of the test stump by actuation of motors 40b, 41b, 40a and 41a to cause racks 48b and 48a to move vertically upward. The stack is moved to approximately the height H 1 . The frame drive motors 52b and 52a are then energized to drive pinion gears 51b and 51a which engage the racks 33 b and 33a, respectively, on spider beams 26 and 25 and move frame 28 and BOP stack 30 are moved to any position on spider beams 26 and 25. 
     The racks 48b, 48a and blowout preventer stack 30 are then lowered by actuation of motors 40b, 41b, 40a and 41a to cause racks 48b and 48a to move vertically downward so that the top of the stack will clear overhead obstacles, such as cross beam 34 of the derrick substructure 20, during movement from position B to position C. When in position C the stack 30 may be moved to any desired vertical position, within the rack design limits. When in position C, guide cables are aligned through guide tubes on the stack 30 and conventional means are connected to the stack for lowering the stack for connection by connector 32, to the upper end of the well pipe adjacent the ocean floor. Once the lowering means is securely connected to the stack the operator can then operate the lift lugs 58a, 58b and retainer latches 61a and 61b to release them from engagement with the stack 30. The frame 28 is then operated to move on spider beams 25 and 26 and returns to the original position A. 
     Referring now to FIGS. 9 and 10, it may be desirable to connect frame sides 28a and 28b by a linking member such as 65 to ensure that the frame sides move together synchronously. The linking device may be adjustable as shown so as to accommodate the width of the stack 30 as shown. As shown in FIG. 3, a frame housing, indicated at 70, may be provided to protect frame 28 and stack 30 when in storage. 
     Changes and modifications may be made in the specific, illustrative, embodiments of the invention shown and/or described herein without departing from the scope of the invention as defined in the appended claims.