ROTARY HULL SINGLE BUOY OFFSHORE LOADING TERMINAL
United States Patent 3735435
An outer buoyant rotary hull structure fixedly mounts an upper conduit system for rotation therewith. Flow communication is established between the lower end of the rotatable upper conduit system and the upper end of a stationary lower conduit system through a central swivel coupling. The upper end of the lower conduit system is supported within a moored lower base structure that is held stationary in a fixed position by an anchor system. A bearing assembly wholly enclosed within a watertight closure at the center of the buoyant rotary hull rotatably supports the lower base structure to maintain the upper and lower conduit systems rotatably aligned within the central swivel coupling.
US Patent References:
High speed turbo-electric generator bearing
Vigh - April 1967 - 3316038
BEARING
Miller - February 1969 - 3427656
Floating buoy for mooring of vessels and transfer of liquids from the land to the vessel and vice versa
Brackx - April 1965 - 3178737
STORAGE OR SIMILAR VESSEL
Beck - August 1970 - 3525312
Offshore floating terminal
Sutton - February 1968 - 3366982
High speed turbo-electric generator bearing
Vigh - April 1967 - 3316038
BEARING
Miller - February 1969 - 3427656
Floating buoy for mooring of vessels and transfer of liquids from the land to the vessel and vice versa
Brackx - April 1965 - 3178737
STORAGE OR SIMILAR VESSEL
Beck - August 1970 - 3525312
Offshore floating terminal
Sutton - February 1968 - 3366982
Inventors:
Mikulicic, Gunther M. (San Pedro, CA)
Katz, Yoram (San Pedro, CA)
Sada, Charles A. (North Hollywood, CA)
Katz, Yoram (San Pedro, CA)
Sada, Charles A. (North Hollywood, CA)
Application Number:
05/042802
Publication Date:
05/29/1973
Filing Date:
06/02/1970
View Patent Images:
Export Citation:
Primary Class:
International Classes:
B63B22/02; F16L39/04; B63B22/00; F16L39/00; B63B35/44; B63B21/52
Field of Search:
9/8P 115/134 308/203
US Patent References:
Primary Examiner:
Buchler, Milton
Assistant Examiner:
O'connor, Gregory W.
Claims:
What is claimed is
1. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility to an underwater pipeline comprising:
2. A floating offshore loading terminal as defined in claim 1 further comprising a pressurized annular fluid seal around the lower end of said hull structure to prevent entry of water between said hull and base structures into said chamber.
3. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility in an underwater pipeline comprising:
4. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility through an underwater pipeline comprising:
5. In a floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility through a swivel coupling between the terminal ends of a fixed lower conduit system coupled to an underwater pipeline and a rotatable upper conduit system coupled to the vessel, the improvement comprising:
6. The improvement of claim 5 wherein:
7. The improvement of claim 6, wherein:
8. The improvement of claim 5 further comprising:
9. The improvement of claim 6, further comprising:
10. The improvement of claim 5, wherein:
1. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility to an underwater pipeline comprising:
2. A floating offshore loading terminal as defined in claim 1 further comprising a pressurized annular fluid seal around the lower end of said hull structure to prevent entry of water between said hull and base structures into said chamber.
3. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility in an underwater pipeline comprising:
4. A floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility through an underwater pipeline comprising:
5. In a floating offshore loading terminal for transferring flowable materials between a vessel and a remote storage facility through a swivel coupling between the terminal ends of a fixed lower conduit system coupled to an underwater pipeline and a rotatable upper conduit system coupled to the vessel, the improvement comprising:
6. The improvement of claim 5 wherein:
7. The improvement of claim 6, wherein:
8. The improvement of claim 5 further comprising:
9. The improvement of claim 6, further comprising:
10. The improvement of claim 5, wherein:
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved single buoy off-shore loading terminal, and in particular, to a buoy terminal having an outer buoyant rotary hull structure fixedly mounting an upper conduit system that rotatably communicates with a stationary lower conduit system supported in an anchored lower base structure.
2. Review of the Prior Art
Considerable progress has been made in the development of offshore terminals for transferring fluid cargoes and supplies between ships, particularly large tankers and other seagoing vessels, and onshore storage facilities. Such offshore terminals provide a number of distinct advantages by eliminating the need for harbor and docking facilities for these vessels. In many instances, existing harbor and dock facilities are simply unable to accommodate the much larger tankers, now commonly known as super-tankers, that are presently in operation. Moreover, safety is another advantage of offshore terminals since the loading and discharging of petroleum fuels and certain liquid chemicals presents a distinct threat of fire and explosion that endangers nearby vessels and surrounding shore installations and facilities that tend to be concentrated in dock areas.
Most widely employed during recent years has been the single buoy floating terminals having a swivel assembly that permits the moored vessel to swing freely about the buoy in response to changes of tide and weather during transfer operations. Typically an underwater pipeline connects the onshore storage facilities to a junction structure set on the seabed bottom beneath the desired buoy location. Flexible hose coupled to the pipeline at the junction extends upwardly for connection to a lower conduit system on the floating buoy terminal. A spindle coupling arrangement rotatably connects the lower conduit system to an upper conduit system that is supported for rotational movement about the upper deck surface of the buoy, which is maintained in a fixed position by a bottom anchoring arrangement.
With such prior art buoy terminals, the upper conduit system had heavy pipe fittings extending rigidly outward over the upper deck surface to the edge of the circular buoy to be connected to the flexible floating hose leading to the transferring vessel. These pipe extensions with the floating hose attached have considerable weight, particularly when filled with fluid. With this heavy load on the long lever arm extending outward from the central swivel coupling, strong additional support near its outer end is needed. Typically, a heavy-duty roller bearing assembly provides support for these upper conduit pipe extensions near the outer ends for free-rolling movement around a circular track on the upper deck surface of the buoy at or near its edge. Pitching and rolling of the buoy in heavy seas places extremely heavy loads on these roller bearing support assemblies. Therefore, these bearing assemblies must not only withstand these loads, but be maintained in perfect operating condition.
However, in present installations, these roller bearing assemblies supporting the upper conduit extensions on the buoy are left exposed to a variety of potentially damaging and destructive conditions. Continuous exposure to sea water has potentially corrosive effects on metal bearings and such bearings can become clogged by salt deposits from evaporation. In cold weather environments, ice forming on the roller assembly elements can render the offshore terminal completely useless for long periods in winter unless the ice is constantly removed. Also the exposed roller bearing assemblies, particularly if located on the periphery of the buoy terminal as in some installations, are very vulnerable to damage even from minor collisions either with the large transferring vessels or, more frequently, with smaller service vessels used for maintenance and for mooring of the larger vessels to the buoy. Yet full protective shielding of the entire roller support assembly is impracticable, and only partial enclosure merely makes maintenance and repair more difficult.
Moreover, it is often necessary for maintenance and operating personnel to be on the buoy itself. With the heavy conduit pipes and roller supports moving over the top deck surface of the buoy, there is always considerable danger of serious injury to personnel and equipment on the buoy. To avoid this, an overlying platform can be provided to rotate on a roller assembly with the upper conduit extensions, but this substantially increases the load on the roller bearings and complicates required maintenance and repair.
SUMMARY OF THE INVENTION
The improved loading terminal buoy of this invention avoids the disadvantages of the prior art by eliminating the need for exposed heavy-duty roller bearing assemblies to support the outward extension of the upper conduit piping for rotational movement about the buoy. Instead the upper conduit system is held in a fixed mounting on a rotary buoyant hull structure. To accomplish this, the lower conduit system is mounted within a lower base structure held stationary by an anchoring system. The upper end of the lower conduit system rotatably communicates with the upper conduit system within a spindle coupling that extends upwardly into a central enclosure provided in the rotary buoyant hull structure supporting the upper conduit pipe extensions for connection to flexible floating hoses leading to the transferring vessel. The rotary buoyant hull structure is journaled for rotation about the lower base structure by central roller bearing assemblies surrounding the spindle coupling. These bearing assemblies are wholly contained within the central enclosure of the buoyant rotary hull structure with watertight seals preventing entry of water. All forces generated between the anchored lower base structure and the surrounding buoyant hull structure are borne by the roller bearing assemblies that closely surround the central vertical axis of rotation to reduce the lever arm for these forces.
In the preferred embodiment described herein, a tubular spindle casing extends upwardly from the lower base structure into the central enclosure within the buoyant hull structure. A secure watertight closure is maintained between the spindle casing and the surrounding bottom section of the buoyant hull to prevent water leakage into the central enclosure by means of a pressurized oil seal. An annular bearing cavity is formed between the outer surface of a stationary roller track on the tubular spindle casing and the inner surface of a circular roller housing assembly mounting individual rollers in contact with the track. Oil fed under a pressure head from a gravity tank located in the upper portion of the buoyant hull structure above the waterline fills the cavity to maintain a somewhat balanced watertight seal and at the same time lubricates the entire lower bearing assembly.
In this embodiment, the upper bearing assembly has individual self-lubricated roller cartridges mounted at spaced intervals in a circular housing to engage a roller track affixed to the upper end of the central spindle casing. Upper and lower roller bearing assemblies with roller and track surfaces beveled in opposite directions prevents relative motion from axial and radial forces between the upper and lower conduits at the rotary juncture within the spindle assembly. The upper conduits have outward pipe extensions rigidly supported on and within the buoyant hull structure and emerge from the outer periphery of the hull at the waterline to which are connected the floating cargo transfer hoses to the vessel loading or unloading.
With this arrangement, the entire upper deck surface of the buoy terminal consists of a unitary structure without relative movement between parts over the upper deck surfaces. Rather the entire buoyant hull rotates to follow the movement of the transferring vessel. Also, this simplified assembly with all moving parts enclosed within the center of the buoyant hull structure affords maximum protection from the adverse effects of marine environment and all but the most severe collisions. Maintenance and repairs are reduced to a minimum and it greatly simplifies both initial construction and later repairs.
FIG. 1 is a perspective view of one embodiment of an offshore loading terminal of this invention employed in an offshore loading system;
FIG. 2 is an elevational view of the offshore loading terminal of this invention shown in FIG. 1;
FIG. 3 is a plan view of the offshore loading terminal of this invention shown in FIGS. 1 and 2;
FIG. 4 is a cross sectional elevational view taken along the line 4--4 of FIG. 3;
FIG. 5 is a cross sectional elevational view taken along the line 5--5 of FIG. 3; and
FIG. 6 is an enlarged view of a portion of the structure shown in FIG. 5.
DESCRIPTION
Referring now to FIG. 1, an improved single buoy terminal 10 is shown in a remote offshore location connected by flexible underwater hoses 11 to a junction structure 12 set on the sea bottom below the desired location. An underwater pipeline 13 laid on the sea bottom connects onshore storage facilities 14 to the junction structure 12. The floating single buoy terminal 10 is maintained in a desired position on the surface of the water above the junction structure 12 by an appropriate multi-leg anchor mooring system. Typically bottom holding anchors 15 attached to anchor chains 16 are set in different radial directions around the desired float location with the upper ends of the anchor chains 16 being engaged by chain stopper mechanisms, as hereinafter described in more detail, to hold the floating buoy terminal 10 at a fixed position.
For purposes of this description, a double piping system is shown, which may for example be used to transfer different fluids, such as oil, fresh water, or even particulate slurries between an ocean going vessel 17 and the onshore storage facilities 14. Of course, it should be understood that this invention is applicable as well to single pipe systems or to systems involving three or more conduits. With the installation illustrated, the terminal ends of the two underwater pipes forming the pipeline 13 extend through the junction structure 12 to be coupled to the lower ends of the respective flexible underwater hose 11. Referring now also to FIGS. 2 and 3, the upper end of each flexible underwater hose 11 is secured by bolted flange couplings to the end of a separate lower conduit pipe 18 projecting downwardly from the bottom of the floating buoy terminal 10. The flexible underwater hose 11 may be provided with a number of flotation rings 19 distributed along its length to align the hose properly and provide sufficient buoyancy to prevent the weight of the hose in water, particularly when filled with a high specific gravity fluid, from exerting substantial downward force on the floating buoy terminal 10, such as might in heavy seas tend to pull the upper end of the hoses 11 loose from the couplings to the buoy at the ends of separate lower conduit pipes 18, and also to reduce the forces at the hose connections on the sealed junction structure 12.
Two upper conduit extension pipes 22 are fixedly mounted on and within the floating buoy terminal 10 to extend outwardly with the ends protruding beyond the buoy periphery to be attached to floating hoses 24. The floating hoses 24 are preferably of the self floating type but may be of the more conventional type with a number of flotation collars attached along it to provide the necessary buoyancy, with the outer end of each coupled as shown to a conduit or manifold piping system on the vessel 17. Mounted on the upper deck surface of the floating buoy terminal 10 is a roller fairlead structure 26 near the periphery adjacent the outer ends of the upper conduit pipes 22 with bollard 28 affixed at the center to receive mooring lines 30 from the vessel 17.
In a typical operation, a vessel 17 approaching the floating buoy terminal 10 extends a bow mooring line 30 to be inserted through the roller fairlead structure 26 to be secured over the bollard 28. The flexible floating hoses 24 are then retrieved by small boat or other appropriate hose handling means to be secured to the conduit or manifold piping system of the vessel 17. The mooring lines 30 are taken in to keep its length substantially shorter than the hoses 24 so that all mooring forces are transmitted along the mooring lines 30 to the bollard 28 to prevent strain on the flexible hoses and hose couplings. An appropriate navigational warning and locating system with a flashing light and foghorn is mounted in a mast assembly 32 extending upwardly from the deck surface of the floating buoy terminal 10.
Referring now to FIGS. 4 and 5, internal details of the unique construction of the floating buoy terminal 10 of the invention are shown in successive cross-sectional elevational views. The floating buoy terminal 10 consists of two major parts, an upper buoyant rotary hull structure 34 and a stationary moored lower base structure 36 coupled together to rotate relative to one another about a central spindle axis 37. The stationary lower base structure 36 has a cylindrical inner hull section 38 providing a cylindrical central conduit passage 40. The lower conduit pipes 18 extend upwardly through the central conduit passage 40 from the connection at their lower end to the flexible underwater hoses 11. The lower conduit pipes 18 extend through holes formed through the upper and lower circular hull plate sections 42 and 44, respectively, to which they are sealed, as by welding, to provide a watertight closure at either end of the cylindrical conduit passage 40. The hollow space within the cylindrical conduit passage 40 surrounding the lower conduit pipes 18 is preferably filled with polyurethane foam to form a water impermeable flotation chamber. Surrounding girder-like outer hull sections 45 are formed as separate elongated extensions to be attached along the periphery of the inner section as a symmetrical arrangement of equally spaced arms. Each outer hull section 45, typically four in number at right angles to one another, has an anchor chain receiving aperture 46 at its outer end. The inner ends of adjacent outer hull sections 45 fit together and are joined as by welding to the cylindrical inner hull section 38 to form a unitary watertight base structure and are secured together at the top by a heavy annular base ring 47.
The anchor chain receiving apertures 46 have a roughly rectangular cross-section with inwardly sloping side walls having a reinforcing thickness in the bottom area defining a wedge-shaped passage for receiving the upper end of one of the anchor chains 16. A chain stopper 48 which may be of conventional design, or preferably an improved type to be described and claimed in a later filed application, is held at the bottom of each anchor chain receiving aperture 46 to engage the upper end of the anchor chain 16. The vacant space within the apertures 46 above the stopper 48 serves as a hopper for additional links at the end of the anchor chain. Referring to FIG. 1, a bolted cover plate on the deck 50 covers a vertical hollow trunk (not shown) extending through the buoyant rotary structure 34 located the same radial distance from the central axis 37 as the anchor chain receiving apertures 46. Using index marks on the outer hulls, the rotary hull structure 34 may be turned to position the open trunk over each of the apertures 46 permitting use of a portable or permanent anchor chain tensioning hoist on the upper deck to be used in adjusting the chain lengths to achieve a desired mooring configuration.
Four radial supports 52 each attached to the outer end of one of the outer girder hull sections 45 of the stationary lower base structure 36 hold a steel peripheral fender ring 54 that surrounds the terminal 10 below the waterline. This protects the outer hull surfaces from minor collisions with larger vessels while permitting small boats to pass over to reach a boarding platform 55 at one edge of the buoyant rotary hull structure 34 to permit boarding by operating or service personnel. Rubber bumper rings 53 are attached to the periphery of the buoyant rotary hull structure just above the waterline and guard at deck level against minor damage from these small boats.
A tubular central spindle casing 56 is mounted at the top of the stationary moored lower base structure 36 on the base ring 47 to extend upwardly from the upper circular hull plate section 42 covering the cylindrical conduit passage 40 and into a central opening in the buoyant rotary hull structure 34. The spindle casing 56 consists of three axial sections rigidly joined end to end, to form an elongated tubular casing. The bottom section 58 is a short annular fitting with a regular cylindrical inner surface enclosing the upwardly extending lower conduit pipes 18. The outer surface of the lower section 58 has a smooth cylindrical lower portion abutting a lower sealing gland 60 and above that a frusto-conical roller bearing track surface 62 beveled inwardly to serve as part of a lower bearing assembly. An elongated central section 64 is essentially tubular in shape with a lower outwardly extending connecting flange abutting the upper end of the lower section 58. The lower and central sections 58 and 64 are rigidly attached to one another and to the base ring 47 by elongated high strength bolts 66 that extend completely through the lower section 58 to clamp it tightly between the outwardly extending bottom flange on the central section 64 and the mating upper surface of the lower base structure 38. A short distance above the flange a circumferential ridge 68 is formed on the outer surface of the tubular central section 64 and has a pair of grooves for containing O-ring seals 70. Above this, the elongated central section 64 has enlarged openings 72 in the casing walls to permit access to the lower conduit pipes 18 and gear-operated stop valves 74 for selectively closing off the flow of fluid in either pipe. A hand wheel 76 for manually operating each of the valves 74 extends through the opening 72 for ease of access by operating personnel.
A roughly cup-shaped upper section 78 of the spindle casing 56 has a bottom wall 80 with a conical central portion surrounded by a flat flange area that is rigidly clamped against a flat upper flange surface at the top of the central section 64. The lower conduit pipes 18 extend through separate holes formed in the conical portion of the bottom wall, to which they are sealed as by welding about their periphery to form a pressure tight closure. One of the lower conduit pipes 18 terminates just above the bottom wall opening in an outer fluid chamber defined by the inner walls of the cup-shaped upper section 78. The other lower conduit pipe 18 extends upwardly through this outer fluid chamber to connect with a cylindrical pipe section having its longitudinal central axis coincident with the central spindle axis 37, thus providing an inner fluid passage concentrically aligned with the outer fluid chamber at the upper section 78 of the tubular spindle casing 56. The cup-shaped upper section 78 has an outwardly extending portion or lip that is beveled down and inwardly on its outer surface to provide frustoconical roller bearing track surface 82 constituting the stationary portion of an upper bearing assembly. A succession of packing gland seals 84 are held in position by three metal follower rings 85 that fit the shoulders provided inside the lip.
A mating upper spindle assembly is mounted within the central opening of an annular deck connection flange 86 and has concentric inner and outer upper conduit passages extending downwardly to be rotatably engaged by the inner and outer concentric fluid passages of the stationary lower spindle assembly, thus forming a dual flow path swivel coupling between the upper and lower conduit systems. An annular supporting collar 88 affixed by bolts at the inner edge of the flange 86 has a downwardly extending tubular outer sleeve member 90 attached at its inner edge. The outer sleeve member 90 has a downwardly tapered inner wall defining the outer surface at the lower end of the outer conduit passage in the upper spindle assembly, and its outer cylindrical surface is held in fluid tight rotatable contact against the packing gland seals 84, which may preferably consist of a series of vane-type sealing rings, as shown, made of neoprene rubber or Teflon, capable of dropping the internal pressure by stages to prevent leakage.
An upper conduit housing 92 having an inverted cup shape is mounted on the annular deck connection flange 86 by peripheral bolts through an outwardly extending lip flange around its bottom edge to enclose a tubular upper conduit fitting 94 with inner and outer concentric cylindrical side walls that define both a cylindrical inner conduit passage 96 and an annular outer conduit passage 98. An upper conduit piping extension 100 extends through openings in the side wall of the housing 92 and in the outer side wall of the upper conduit fitting 94 to communicate through the inner side wall of the fitting 94 with the interior of the cylindrical inner conduit passage 96. Another upper conduit pipe extension 102 similarly extends through an opening in the housing side wall to communicate through the outer side wall of the fitting 94 with the annular outer fluid chamber 98. Of course the pipe extensions 100 and 102 are sealed as by welding to the surrounding side wall areas of upper conduit fitting 94 as by welding to form a pressure tight seal. The bollard 28 is affixed by bolts to the flat top surface of the upper conduit housing 92 to cover a central access aperture 104 through which may be reached a removable top closure plate 105 sealing the upper end of the cylindrical inner conduit passage 96.
The inner cylindrical side wall of the upper conduit fitting 94 surrounding the inner conduit passage 96 has a flanged lower portion to which an inner tubular sleeve member 107 is secured by bolts. The outer surface of the sleeve member 107 is tapered downwardly forming the inner surface at the lower end of the outer conduit passage in the upper spindle assembly. The inner surface of the sleeve member 107 encloses the centrally positioned upper extension of the lower conduit pipe 18 that forms the inner conduit passage in the lower spindle assembly. The sleeve member 107 has a lower inner surface portion in close diametric proximity with the outer surface of the enclosed pipe and has two upper steps forming shoulders for receiving two sets of vane-type packing gland seal rings 109 held in place by follower rings. The vanes of the two sets of packing gland seal rings 109 are oppositely oriented to form a pressure tight seal in both directions between the inner and outer conduits.
The mating ends of the upper and lower conduit assemblies forming the swivel coupling are maintained in sealed, freely rotatable engagement by upper and lower roller bearing assemblies surrounding the spindle casing 56 and enclosed within the central opening of the buoyant rotary hull structure 34. Referring now particularly to FIGS. 3 and 4, the buoyant rotary hull structure 34, which may be generally U-shaped in horizontal section, provides a round central enclosure space concentric with the radius of curvature of the curved portion of the U that surrounds the central spindle assembly and swivel coupling elements. Appropriately shaped flat plates preferably of steel are joined together as by welding to form the upper deck 106 and the hull bottom 108. Curved plates have their vertical adjacent edges welded together and their horizontal upper and lower edges welded to the upper deck plating 106 and the bottom plating 108 to form the outer and inner hull walls 110 and 112 of the buoyant rotary hull structure 34. Of course, the deck, bottom and side plating should be joined to and reinforced by conventional internal reinforcing structural frame members (not shown). Preferably, the enclosed space between the upper deck and bottom plating 106 and 108 and between the outer and inner hull walls 110 and 112 is filled with a highly buoyant substance 113, such as polyurethane foam, to provide non-floodable spaces in the event of collision damage by another vessel with the outer hull plating. The portions of the upper deck and bottom plating adjacent the inner hull walls 112 have a reinforced thickness and extends a short distance inwardly past the top and bottom edges of the inner hull walls 112 to provide circular mounting flanges at both ends of the central opening, as is shown in FIG. 5.
An annular support member 114 is bolted to the upper surface of the circular mounting flange provided by the inward extension of the bottom plating 108. The support member 114 has an irregular cross-section and an outer C-shape with upper and lower outwardly extending horizontal flanges joined by a vertical portion, the lower flange being affixed by bolts at the inner edges of the hull bottom plates 108. On the inner side of the vertical portion, another bottom flange extends inwardly to support a metal seal gland rotatable retainer ring 116 having a stepped cross-sectional configuration. An outer horizontal portion of retainer ring 116 is attached by bolts to the upper surfaces of the inner flange portion of the support member 114, and a vertical center portion extends downward over the edge to join an inwardly extending lower beveled portion of base ring 47 having an inner edge abutting the outer surface at the bottom of the annular member 58 that forms the lower section of the tubular central spindle casing 56. The space above the beveled extension and between the vertical faces of the rotatable retainer ring 116 and the stationary lower spindle casing member 58 has compressible seal gland rings 60 of a substance impermeable oil inserted therein. The seal gland rings 60 are compressed inwardly and downwardly by a guided metal follower ring 118 having a beveled lower end surface on a vertical inner edge portion that fits into the opening above the rings 60 to be forced downwardly by screw adjustment rods (not shown). Thus compressed seal gland rings 60 form a fluid impermeable seal between the rotating retainer ring 116 and the stationary spindle casing member 58. As shown, the upper surface of an outwardly extending horizontal portion of the follower ring 118 can receive a variable force to be applied to the seal gland rings 60 by peripherally spaced screw adjustments 121, each extending through a threaded hole in the top portion of the supporting structure for the lower roller bearing assembly between adjacent rollers.
Mating outer flanges on upper and lower roller bearing support members 120 and 122 are clamped together by bolts to the upper flange on the annular support member 114. Both roller bearing support members 120 and 122 have a thicker annular inner portions with vertically aligned holes extending through them at equally spaced points around their circumference for engaging individual low friction roller bearing units 124 of the beveled roller type. The internal details of these roller bearing units 124 for the lower bearing assembly are not shown or described herein in detail since various suitable units of this type could be readily constructed by those skilled in the art. Generally the roller bearing units 124 for the lower bearing assembly may employ a similar type of internal construction as that shown and described in connection with FIG. 6, which shows the roller bearing units for the upper bearing assembly, except that an enclosed oil filled cartridge is unnecessary, since as hereinafter described the entire lower bearing assembly is enclosed in an annular oil filled cavity. As shown, the bearing units 124 have upper and lower shaft support bearings 125, preferably of the double row X-roller type as shown in FIG. 6, held within the support member holes for rotatably engaging the shaft to resist axial and radial loads.
In the lower bearing assembly, each roller bearing unit 124 has a frusto-conical roller 126 with the beveled surface that matches the slope of the beveled track surface 62 around the exterior of the annular member 58 forming the lower section of the stationary spindle casing 56. The lower end of the roller unit is supported by a surrounding collar that bears against the horizontal under surface of the lower roller bearing support member 122. Each bearing unit 124 can be individually set with its roller 126 supporting an equal portion of the total downward axial forces by varying the position of a nut 128 that is received in an enlarged threaded section in the upper end of the hole through the upper bearing support member 120. The upper bearing support member 120 has a relatively narrow vertical section joining the thicker inner portion supporting the upper end of the bearing unit 124 with the outer flange portion clamped to the support members 114 and 122. A seal ring 130 having a cross-sectional inverted L-shape is held by bolts through its upper horizontal portion to the upper surface at the inner edge of the upper roller bearing support member 120 so that the vertical inner portion extends downwardly along the vertical inner surface of the member 120. The vertical inner surface seal ring 130 is located in close diametric proximity about the adjacent outer surface of the ridge 68 that protrudes from the outer wall of the elongated central spindle section 64 so that the O-rings 70 form a fluid tight seal between the abutting relatively movable surfaces. The upper and lower inward extensions of the support members 120 and 114 thus combine to form a circular partition with a roughly C-shaped cross-section around the bottom interior of the central opening in the buoyant rotary hull structure 34 with the open end facing inwardly to be sealed against the lower closed portion of the vertical spindle casing 56. This provides an annular fluid tight enclosure closely surrounding the spindle casing 56 which encloses the entire lower roller bearing assembly.
Regarding the upper bearing assembly, as illustrated in FIG. 5, the deck connection flange 86 has a downward extension with an outwardly extending horizontal supporting flange, to which outer support flanges on annular upper and lower roller bearing unit support members 132 and 134 are secured together by bolts. The upper bearing unit support member 132 has a thick inner portion vertically aligned with a thick inner portion on the lower bearing unit support member 134 that has a vertical intermediate portion joining the outer flange portion above. Vertically aligned holes formed through the thick central portions of the bearing support members 132 and 134 receive the individual upper roller bearing cartridge units 136. Each of the roller bearing units 136 has a frusto-conical roller 138 with a beveled angle matching the slope of an inwardly beveled frusto-conical track surface 140 that extends around the outer lip of the cup-shaped upper section 78 of the tubular lower spindle assembly 56.
Referring now particularly to FIG. 6, the cartridge type roller bearing units 136 for the upper bearing assembly each have a tubular cartridge casing 142 surrounding an elongated shaft 144 extending downward from the attached frusto-conical roller 138. An annular seal ring 146 has an outer threaded periphery for engaging interior threads formed at the top of the cartridge casing 142 and contains an O-ring seal 148 within a groove at its inner surface to form a fluid tight seal against the outer surface of the shaft 144 just below the roller head 138. An X-type double roller upper bearing 150 has an outer set of oppositely beveled races held against the interior of the cartridge 142 together with inner sets of oppositely beveled races affixed to the shaft 144 to engage the cylindrical rollers held between them. A similar X-type double roller bearing arrangement 152 is attached at the lower end of the shaft 144 and is separated from the upper bearing 150 by an interior tubular spacer 154. The lower bearing 152 is held in place against the lower end of the spacer 154 with its outer edge supported on the horizontal upper surface of an underlying spacer ring 156. The diameter of the shaft 144 is decreased in several downward steps to form successive shoulders bearing against the upper supporting surfaces of the attached inner bearing race rings. At the bottom of the shaft, a circular retainer plate having a diameter larger than the bottom end of the shaft 144 is affixed to it by cap screws to hold the shaft 144 at the bottom of the lower inner race ring against upward movement. A threaded adjusting nut 160 fits the interior threads formed at the bottom of the hole through the thick horizontal portion of the lower bearing support member 134. A flat end surface on the adjusting nut bears against the bottom of lower spacer ring 156 and the lower end surface of the tubular cartridge casing 142, with which a fluid tight seal is formed by an O-ring. By turning the adjusting nut 160, the vertical position of each cartridge type baring unit can be adjusted to bring the beveled surfaces of each roller 138 into precise load bearing contact with the track surface 140 so that each bears an approximately equal portion of the applied axial loads. In a like manner, the complete rotary hull structure 34 can be precisely aligned concentrically about the central spindle casing 56 by manipulating the adjusting nuts 160. This feature is also applicable to the lower bearing assembly by adjusting nut 128. After assembly, the entire remaining open space within the tubular cartridge casing 142 between the upper threaded seal ring and the interior upper surface of the adjusting nut 160 can be filled with a lubricating oil injected through an appropriately located check valve (not shown) so that the interior roller bearings 150 and 152 are constantly lubricated.
Parallel alignment of the upper and lower roller bearing assemblies and reinforcement of the entire central rotating structure may be provided by a number of peripherally spaced support stanchions 162, as shown in FIG. 5, that are rigidly attached between the upper surface of the upper bearing support member 120 for the lower bearing assembly and the bottom surface of the lower roller bearing support member 134 for the upper bearing assembly.
To prevent the possibility of corrosion damage or fouling due to the adverse effects of seawater on any of the working parts contained within the central opening in the buoyant rotary hull structure 34, the various fixedly attached elements enclosing this opening should be tightly sealed using gaskets or the like between the abutting surfaces. However, insuring against leakage through the bottom of this central opening, which being underwater is subjected to substantial water pressures, is most important, particularly at the junction between the bottom of the buoyant rotary hull structure 34 and the stationary spindle assembly extending upward from the underwater base structure 36. Such seawater leakage at the bottom is prevented most effectively by establishing a pressurized oil seal within the annular fluid tight enclosure, or cavity, formed at the bottom of the spindle casing 56, which at the same time provides generous lubrication for all of the moving elements in the lower bearing assembly. To accomplish this, a lubricating oil for forming the seal is introduced into this annular fluid tight enclosure surrounding the lower end of the spindle casing 56 through an open feed line 164 that is sealed in place to extend through the vertical wall portion of the upper bearing support member 120. The opposite end of the open feed line 164 communicates with the bottom of an oil reservoir tank 166 (FIG. 4) that is formed and supported in the upper portion of the buoyant rotary hull structure 34 within the outer enclosed space defined by the hull and deck plating and filled with a highly buoyant substance 113 such as polyurethane foam. Preferably the oil reservoir tank 166 is located as shown in FIG. 4 against the inner hull wall 112 immediately below the upper deck 106 so that this plating forms the top and one side of the tank, thus reducing the length of the open feed line 164 to a minimum. The oil reservoir tank 166 is filled and kept full by the introduction of the oil through a fill hole in the upper deck that is closed by a removable fill cap 168. The level of the oil in the reservoir tank 166 is substantially above the waterline on the buoyant rotary hull structure 34 so that a gravity head is produced for pressurizing the oil within the annular fluid tight enclosure. Accordingly, the oil pressure above the packing gland seal 60, which is between the bottom of the rotary hull structure 34 and the lower end of the spindle casing 56, is greater than the water pressure acting on the underside. Therefore, any leakage occurring through the seal 60 would result in the higher pressure oil being forced outwardly instead of the lower pressure water entering. It might be possible in a heaVy sea, or through failure to fill the oil reservoir tank 166, that this pressure differential across the seal 60 would be temporarily interrupted permitting some water to enter the annular oil seal enclosure. But, since the water is heavier than oil, it would tend to remain at the bottom of the enclosure to be forced out upon restoration of the proper pressure differential. In this regard, the entry of any significant amount of water into the annular oil seal enclosure due to loss of oil pressurization head would merely tend to force the lighter overlying oil back up through the small diameter open feed line 164, thus restoring the pressurization head at least to a condition of pressure equilibrium. This prevents any seawater from reaching the O-ring seal 70 at the top of the annular oil seal enclosure to insure against seawater leakage into the central opening space above, provided however that there are not serious breaches in both the upper and lower seals 60 and 70. Inspection of the oil reservoir tank level at regular intervals during routine maintenance should indicate the sealing efficiency of the packing gland seal 60 so that necessary sealing pressure adjustments might be made, such as by use of the adjusting screws 121. If a substantial quantity of oil is required during refills, this would indicate the pressure on the seal rings 60 should be increased to prevent excess oil leakage through it if there were no indications of substantial oil leakage through the upper O-ring seals 70.
1. Field of the Invention
This invention relates to an improved single buoy off-shore loading terminal, and in particular, to a buoy terminal having an outer buoyant rotary hull structure fixedly mounting an upper conduit system that rotatably communicates with a stationary lower conduit system supported in an anchored lower base structure.
2. Review of the Prior Art
Considerable progress has been made in the development of offshore terminals for transferring fluid cargoes and supplies between ships, particularly large tankers and other seagoing vessels, and onshore storage facilities. Such offshore terminals provide a number of distinct advantages by eliminating the need for harbor and docking facilities for these vessels. In many instances, existing harbor and dock facilities are simply unable to accommodate the much larger tankers, now commonly known as super-tankers, that are presently in operation. Moreover, safety is another advantage of offshore terminals since the loading and discharging of petroleum fuels and certain liquid chemicals presents a distinct threat of fire and explosion that endangers nearby vessels and surrounding shore installations and facilities that tend to be concentrated in dock areas.
Most widely employed during recent years has been the single buoy floating terminals having a swivel assembly that permits the moored vessel to swing freely about the buoy in response to changes of tide and weather during transfer operations. Typically an underwater pipeline connects the onshore storage facilities to a junction structure set on the seabed bottom beneath the desired buoy location. Flexible hose coupled to the pipeline at the junction extends upwardly for connection to a lower conduit system on the floating buoy terminal. A spindle coupling arrangement rotatably connects the lower conduit system to an upper conduit system that is supported for rotational movement about the upper deck surface of the buoy, which is maintained in a fixed position by a bottom anchoring arrangement.
With such prior art buoy terminals, the upper conduit system had heavy pipe fittings extending rigidly outward over the upper deck surface to the edge of the circular buoy to be connected to the flexible floating hose leading to the transferring vessel. These pipe extensions with the floating hose attached have considerable weight, particularly when filled with fluid. With this heavy load on the long lever arm extending outward from the central swivel coupling, strong additional support near its outer end is needed. Typically, a heavy-duty roller bearing assembly provides support for these upper conduit pipe extensions near the outer ends for free-rolling movement around a circular track on the upper deck surface of the buoy at or near its edge. Pitching and rolling of the buoy in heavy seas places extremely heavy loads on these roller bearing support assemblies. Therefore, these bearing assemblies must not only withstand these loads, but be maintained in perfect operating condition.
However, in present installations, these roller bearing assemblies supporting the upper conduit extensions on the buoy are left exposed to a variety of potentially damaging and destructive conditions. Continuous exposure to sea water has potentially corrosive effects on metal bearings and such bearings can become clogged by salt deposits from evaporation. In cold weather environments, ice forming on the roller assembly elements can render the offshore terminal completely useless for long periods in winter unless the ice is constantly removed. Also the exposed roller bearing assemblies, particularly if located on the periphery of the buoy terminal as in some installations, are very vulnerable to damage even from minor collisions either with the large transferring vessels or, more frequently, with smaller service vessels used for maintenance and for mooring of the larger vessels to the buoy. Yet full protective shielding of the entire roller support assembly is impracticable, and only partial enclosure merely makes maintenance and repair more difficult.
Moreover, it is often necessary for maintenance and operating personnel to be on the buoy itself. With the heavy conduit pipes and roller supports moving over the top deck surface of the buoy, there is always considerable danger of serious injury to personnel and equipment on the buoy. To avoid this, an overlying platform can be provided to rotate on a roller assembly with the upper conduit extensions, but this substantially increases the load on the roller bearings and complicates required maintenance and repair.
SUMMARY OF THE INVENTION
The improved loading terminal buoy of this invention avoids the disadvantages of the prior art by eliminating the need for exposed heavy-duty roller bearing assemblies to support the outward extension of the upper conduit piping for rotational movement about the buoy. Instead the upper conduit system is held in a fixed mounting on a rotary buoyant hull structure. To accomplish this, the lower conduit system is mounted within a lower base structure held stationary by an anchoring system. The upper end of the lower conduit system rotatably communicates with the upper conduit system within a spindle coupling that extends upwardly into a central enclosure provided in the rotary buoyant hull structure supporting the upper conduit pipe extensions for connection to flexible floating hoses leading to the transferring vessel. The rotary buoyant hull structure is journaled for rotation about the lower base structure by central roller bearing assemblies surrounding the spindle coupling. These bearing assemblies are wholly contained within the central enclosure of the buoyant rotary hull structure with watertight seals preventing entry of water. All forces generated between the anchored lower base structure and the surrounding buoyant hull structure are borne by the roller bearing assemblies that closely surround the central vertical axis of rotation to reduce the lever arm for these forces.
In the preferred embodiment described herein, a tubular spindle casing extends upwardly from the lower base structure into the central enclosure within the buoyant hull structure. A secure watertight closure is maintained between the spindle casing and the surrounding bottom section of the buoyant hull to prevent water leakage into the central enclosure by means of a pressurized oil seal. An annular bearing cavity is formed between the outer surface of a stationary roller track on the tubular spindle casing and the inner surface of a circular roller housing assembly mounting individual rollers in contact with the track. Oil fed under a pressure head from a gravity tank located in the upper portion of the buoyant hull structure above the waterline fills the cavity to maintain a somewhat balanced watertight seal and at the same time lubricates the entire lower bearing assembly.
In this embodiment, the upper bearing assembly has individual self-lubricated roller cartridges mounted at spaced intervals in a circular housing to engage a roller track affixed to the upper end of the central spindle casing. Upper and lower roller bearing assemblies with roller and track surfaces beveled in opposite directions prevents relative motion from axial and radial forces between the upper and lower conduits at the rotary juncture within the spindle assembly. The upper conduits have outward pipe extensions rigidly supported on and within the buoyant hull structure and emerge from the outer periphery of the hull at the waterline to which are connected the floating cargo transfer hoses to the vessel loading or unloading.
With this arrangement, the entire upper deck surface of the buoy terminal consists of a unitary structure without relative movement between parts over the upper deck surfaces. Rather the entire buoyant hull rotates to follow the movement of the transferring vessel. Also, this simplified assembly with all moving parts enclosed within the center of the buoyant hull structure affords maximum protection from the adverse effects of marine environment and all but the most severe collisions. Maintenance and repairs are reduced to a minimum and it greatly simplifies both initial construction and later repairs.
FIG. 1 is a perspective view of one embodiment of an offshore loading terminal of this invention employed in an offshore loading system;
FIG. 2 is an elevational view of the offshore loading terminal of this invention shown in FIG. 1;
FIG. 3 is a plan view of the offshore loading terminal of this invention shown in FIGS. 1 and 2;
FIG. 4 is a cross sectional elevational view taken along the line 4--4 of FIG. 3;
FIG. 5 is a cross sectional elevational view taken along the line 5--5 of FIG. 3; and
FIG. 6 is an enlarged view of a portion of the structure shown in FIG. 5.
DESCRIPTION
Referring now to FIG. 1, an improved single buoy terminal 10 is shown in a remote offshore location connected by flexible underwater hoses 11 to a junction structure 12 set on the sea bottom below the desired location. An underwater pipeline 13 laid on the sea bottom connects onshore storage facilities 14 to the junction structure 12. The floating single buoy terminal 10 is maintained in a desired position on the surface of the water above the junction structure 12 by an appropriate multi-leg anchor mooring system. Typically bottom holding anchors 15 attached to anchor chains 16 are set in different radial directions around the desired float location with the upper ends of the anchor chains 16 being engaged by chain stopper mechanisms, as hereinafter described in more detail, to hold the floating buoy terminal 10 at a fixed position.
For purposes of this description, a double piping system is shown, which may for example be used to transfer different fluids, such as oil, fresh water, or even particulate slurries between an ocean going vessel 17 and the onshore storage facilities 14. Of course, it should be understood that this invention is applicable as well to single pipe systems or to systems involving three or more conduits. With the installation illustrated, the terminal ends of the two underwater pipes forming the pipeline 13 extend through the junction structure 12 to be coupled to the lower ends of the respective flexible underwater hose 11. Referring now also to FIGS. 2 and 3, the upper end of each flexible underwater hose 11 is secured by bolted flange couplings to the end of a separate lower conduit pipe 18 projecting downwardly from the bottom of the floating buoy terminal 10. The flexible underwater hose 11 may be provided with a number of flotation rings 19 distributed along its length to align the hose properly and provide sufficient buoyancy to prevent the weight of the hose in water, particularly when filled with a high specific gravity fluid, from exerting substantial downward force on the floating buoy terminal 10, such as might in heavy seas tend to pull the upper end of the hoses 11 loose from the couplings to the buoy at the ends of separate lower conduit pipes 18, and also to reduce the forces at the hose connections on the sealed junction structure 12.
Two upper conduit extension pipes 22 are fixedly mounted on and within the floating buoy terminal 10 to extend outwardly with the ends protruding beyond the buoy periphery to be attached to floating hoses 24. The floating hoses 24 are preferably of the self floating type but may be of the more conventional type with a number of flotation collars attached along it to provide the necessary buoyancy, with the outer end of each coupled as shown to a conduit or manifold piping system on the vessel 17. Mounted on the upper deck surface of the floating buoy terminal 10 is a roller fairlead structure 26 near the periphery adjacent the outer ends of the upper conduit pipes 22 with bollard 28 affixed at the center to receive mooring lines 30 from the vessel 17.
In a typical operation, a vessel 17 approaching the floating buoy terminal 10 extends a bow mooring line 30 to be inserted through the roller fairlead structure 26 to be secured over the bollard 28. The flexible floating hoses 24 are then retrieved by small boat or other appropriate hose handling means to be secured to the conduit or manifold piping system of the vessel 17. The mooring lines 30 are taken in to keep its length substantially shorter than the hoses 24 so that all mooring forces are transmitted along the mooring lines 30 to the bollard 28 to prevent strain on the flexible hoses and hose couplings. An appropriate navigational warning and locating system with a flashing light and foghorn is mounted in a mast assembly 32 extending upwardly from the deck surface of the floating buoy terminal 10.
Referring now to FIGS. 4 and 5, internal details of the unique construction of the floating buoy terminal 10 of the invention are shown in successive cross-sectional elevational views. The floating buoy terminal 10 consists of two major parts, an upper buoyant rotary hull structure 34 and a stationary moored lower base structure 36 coupled together to rotate relative to one another about a central spindle axis 37. The stationary lower base structure 36 has a cylindrical inner hull section 38 providing a cylindrical central conduit passage 40. The lower conduit pipes 18 extend upwardly through the central conduit passage 40 from the connection at their lower end to the flexible underwater hoses 11. The lower conduit pipes 18 extend through holes formed through the upper and lower circular hull plate sections 42 and 44, respectively, to which they are sealed, as by welding, to provide a watertight closure at either end of the cylindrical conduit passage 40. The hollow space within the cylindrical conduit passage 40 surrounding the lower conduit pipes 18 is preferably filled with polyurethane foam to form a water impermeable flotation chamber. Surrounding girder-like outer hull sections 45 are formed as separate elongated extensions to be attached along the periphery of the inner section as a symmetrical arrangement of equally spaced arms. Each outer hull section 45, typically four in number at right angles to one another, has an anchor chain receiving aperture 46 at its outer end. The inner ends of adjacent outer hull sections 45 fit together and are joined as by welding to the cylindrical inner hull section 38 to form a unitary watertight base structure and are secured together at the top by a heavy annular base ring 47.
The anchor chain receiving apertures 46 have a roughly rectangular cross-section with inwardly sloping side walls having a reinforcing thickness in the bottom area defining a wedge-shaped passage for receiving the upper end of one of the anchor chains 16. A chain stopper 48 which may be of conventional design, or preferably an improved type to be described and claimed in a later filed application, is held at the bottom of each anchor chain receiving aperture 46 to engage the upper end of the anchor chain 16. The vacant space within the apertures 46 above the stopper 48 serves as a hopper for additional links at the end of the anchor chain. Referring to FIG. 1, a bolted cover plate on the deck 50 covers a vertical hollow trunk (not shown) extending through the buoyant rotary structure 34 located the same radial distance from the central axis 37 as the anchor chain receiving apertures 46. Using index marks on the outer hulls, the rotary hull structure 34 may be turned to position the open trunk over each of the apertures 46 permitting use of a portable or permanent anchor chain tensioning hoist on the upper deck to be used in adjusting the chain lengths to achieve a desired mooring configuration.
Four radial supports 52 each attached to the outer end of one of the outer girder hull sections 45 of the stationary lower base structure 36 hold a steel peripheral fender ring 54 that surrounds the terminal 10 below the waterline. This protects the outer hull surfaces from minor collisions with larger vessels while permitting small boats to pass over to reach a boarding platform 55 at one edge of the buoyant rotary hull structure 34 to permit boarding by operating or service personnel. Rubber bumper rings 53 are attached to the periphery of the buoyant rotary hull structure just above the waterline and guard at deck level against minor damage from these small boats.
A tubular central spindle casing 56 is mounted at the top of the stationary moored lower base structure 36 on the base ring 47 to extend upwardly from the upper circular hull plate section 42 covering the cylindrical conduit passage 40 and into a central opening in the buoyant rotary hull structure 34. The spindle casing 56 consists of three axial sections rigidly joined end to end, to form an elongated tubular casing. The bottom section 58 is a short annular fitting with a regular cylindrical inner surface enclosing the upwardly extending lower conduit pipes 18. The outer surface of the lower section 58 has a smooth cylindrical lower portion abutting a lower sealing gland 60 and above that a frusto-conical roller bearing track surface 62 beveled inwardly to serve as part of a lower bearing assembly. An elongated central section 64 is essentially tubular in shape with a lower outwardly extending connecting flange abutting the upper end of the lower section 58. The lower and central sections 58 and 64 are rigidly attached to one another and to the base ring 47 by elongated high strength bolts 66 that extend completely through the lower section 58 to clamp it tightly between the outwardly extending bottom flange on the central section 64 and the mating upper surface of the lower base structure 38. A short distance above the flange a circumferential ridge 68 is formed on the outer surface of the tubular central section 64 and has a pair of grooves for containing O-ring seals 70. Above this, the elongated central section 64 has enlarged openings 72 in the casing walls to permit access to the lower conduit pipes 18 and gear-operated stop valves 74 for selectively closing off the flow of fluid in either pipe. A hand wheel 76 for manually operating each of the valves 74 extends through the opening 72 for ease of access by operating personnel.
A roughly cup-shaped upper section 78 of the spindle casing 56 has a bottom wall 80 with a conical central portion surrounded by a flat flange area that is rigidly clamped against a flat upper flange surface at the top of the central section 64. The lower conduit pipes 18 extend through separate holes formed in the conical portion of the bottom wall, to which they are sealed as by welding about their periphery to form a pressure tight closure. One of the lower conduit pipes 18 terminates just above the bottom wall opening in an outer fluid chamber defined by the inner walls of the cup-shaped upper section 78. The other lower conduit pipe 18 extends upwardly through this outer fluid chamber to connect with a cylindrical pipe section having its longitudinal central axis coincident with the central spindle axis 37, thus providing an inner fluid passage concentrically aligned with the outer fluid chamber at the upper section 78 of the tubular spindle casing 56. The cup-shaped upper section 78 has an outwardly extending portion or lip that is beveled down and inwardly on its outer surface to provide frustoconical roller bearing track surface 82 constituting the stationary portion of an upper bearing assembly. A succession of packing gland seals 84 are held in position by three metal follower rings 85 that fit the shoulders provided inside the lip.
A mating upper spindle assembly is mounted within the central opening of an annular deck connection flange 86 and has concentric inner and outer upper conduit passages extending downwardly to be rotatably engaged by the inner and outer concentric fluid passages of the stationary lower spindle assembly, thus forming a dual flow path swivel coupling between the upper and lower conduit systems. An annular supporting collar 88 affixed by bolts at the inner edge of the flange 86 has a downwardly extending tubular outer sleeve member 90 attached at its inner edge. The outer sleeve member 90 has a downwardly tapered inner wall defining the outer surface at the lower end of the outer conduit passage in the upper spindle assembly, and its outer cylindrical surface is held in fluid tight rotatable contact against the packing gland seals 84, which may preferably consist of a series of vane-type sealing rings, as shown, made of neoprene rubber or Teflon, capable of dropping the internal pressure by stages to prevent leakage.
An upper conduit housing 92 having an inverted cup shape is mounted on the annular deck connection flange 86 by peripheral bolts through an outwardly extending lip flange around its bottom edge to enclose a tubular upper conduit fitting 94 with inner and outer concentric cylindrical side walls that define both a cylindrical inner conduit passage 96 and an annular outer conduit passage 98. An upper conduit piping extension 100 extends through openings in the side wall of the housing 92 and in the outer side wall of the upper conduit fitting 94 to communicate through the inner side wall of the fitting 94 with the interior of the cylindrical inner conduit passage 96. Another upper conduit pipe extension 102 similarly extends through an opening in the housing side wall to communicate through the outer side wall of the fitting 94 with the annular outer fluid chamber 98. Of course the pipe extensions 100 and 102 are sealed as by welding to the surrounding side wall areas of upper conduit fitting 94 as by welding to form a pressure tight seal. The bollard 28 is affixed by bolts to the flat top surface of the upper conduit housing 92 to cover a central access aperture 104 through which may be reached a removable top closure plate 105 sealing the upper end of the cylindrical inner conduit passage 96.
The inner cylindrical side wall of the upper conduit fitting 94 surrounding the inner conduit passage 96 has a flanged lower portion to which an inner tubular sleeve member 107 is secured by bolts. The outer surface of the sleeve member 107 is tapered downwardly forming the inner surface at the lower end of the outer conduit passage in the upper spindle assembly. The inner surface of the sleeve member 107 encloses the centrally positioned upper extension of the lower conduit pipe 18 that forms the inner conduit passage in the lower spindle assembly. The sleeve member 107 has a lower inner surface portion in close diametric proximity with the outer surface of the enclosed pipe and has two upper steps forming shoulders for receiving two sets of vane-type packing gland seal rings 109 held in place by follower rings. The vanes of the two sets of packing gland seal rings 109 are oppositely oriented to form a pressure tight seal in both directions between the inner and outer conduits.
The mating ends of the upper and lower conduit assemblies forming the swivel coupling are maintained in sealed, freely rotatable engagement by upper and lower roller bearing assemblies surrounding the spindle casing 56 and enclosed within the central opening of the buoyant rotary hull structure 34. Referring now particularly to FIGS. 3 and 4, the buoyant rotary hull structure 34, which may be generally U-shaped in horizontal section, provides a round central enclosure space concentric with the radius of curvature of the curved portion of the U that surrounds the central spindle assembly and swivel coupling elements. Appropriately shaped flat plates preferably of steel are joined together as by welding to form the upper deck 106 and the hull bottom 108. Curved plates have their vertical adjacent edges welded together and their horizontal upper and lower edges welded to the upper deck plating 106 and the bottom plating 108 to form the outer and inner hull walls 110 and 112 of the buoyant rotary hull structure 34. Of course, the deck, bottom and side plating should be joined to and reinforced by conventional internal reinforcing structural frame members (not shown). Preferably, the enclosed space between the upper deck and bottom plating 106 and 108 and between the outer and inner hull walls 110 and 112 is filled with a highly buoyant substance 113, such as polyurethane foam, to provide non-floodable spaces in the event of collision damage by another vessel with the outer hull plating. The portions of the upper deck and bottom plating adjacent the inner hull walls 112 have a reinforced thickness and extends a short distance inwardly past the top and bottom edges of the inner hull walls 112 to provide circular mounting flanges at both ends of the central opening, as is shown in FIG. 5.
An annular support member 114 is bolted to the upper surface of the circular mounting flange provided by the inward extension of the bottom plating 108. The support member 114 has an irregular cross-section and an outer C-shape with upper and lower outwardly extending horizontal flanges joined by a vertical portion, the lower flange being affixed by bolts at the inner edges of the hull bottom plates 108. On the inner side of the vertical portion, another bottom flange extends inwardly to support a metal seal gland rotatable retainer ring 116 having a stepped cross-sectional configuration. An outer horizontal portion of retainer ring 116 is attached by bolts to the upper surfaces of the inner flange portion of the support member 114, and a vertical center portion extends downward over the edge to join an inwardly extending lower beveled portion of base ring 47 having an inner edge abutting the outer surface at the bottom of the annular member 58 that forms the lower section of the tubular central spindle casing 56. The space above the beveled extension and between the vertical faces of the rotatable retainer ring 116 and the stationary lower spindle casing member 58 has compressible seal gland rings 60 of a substance impermeable oil inserted therein. The seal gland rings 60 are compressed inwardly and downwardly by a guided metal follower ring 118 having a beveled lower end surface on a vertical inner edge portion that fits into the opening above the rings 60 to be forced downwardly by screw adjustment rods (not shown). Thus compressed seal gland rings 60 form a fluid impermeable seal between the rotating retainer ring 116 and the stationary spindle casing member 58. As shown, the upper surface of an outwardly extending horizontal portion of the follower ring 118 can receive a variable force to be applied to the seal gland rings 60 by peripherally spaced screw adjustments 121, each extending through a threaded hole in the top portion of the supporting structure for the lower roller bearing assembly between adjacent rollers.
Mating outer flanges on upper and lower roller bearing support members 120 and 122 are clamped together by bolts to the upper flange on the annular support member 114. Both roller bearing support members 120 and 122 have a thicker annular inner portions with vertically aligned holes extending through them at equally spaced points around their circumference for engaging individual low friction roller bearing units 124 of the beveled roller type. The internal details of these roller bearing units 124 for the lower bearing assembly are not shown or described herein in detail since various suitable units of this type could be readily constructed by those skilled in the art. Generally the roller bearing units 124 for the lower bearing assembly may employ a similar type of internal construction as that shown and described in connection with FIG. 6, which shows the roller bearing units for the upper bearing assembly, except that an enclosed oil filled cartridge is unnecessary, since as hereinafter described the entire lower bearing assembly is enclosed in an annular oil filled cavity. As shown, the bearing units 124 have upper and lower shaft support bearings 125, preferably of the double row X-roller type as shown in FIG. 6, held within the support member holes for rotatably engaging the shaft to resist axial and radial loads.
In the lower bearing assembly, each roller bearing unit 124 has a frusto-conical roller 126 with the beveled surface that matches the slope of the beveled track surface 62 around the exterior of the annular member 58 forming the lower section of the stationary spindle casing 56. The lower end of the roller unit is supported by a surrounding collar that bears against the horizontal under surface of the lower roller bearing support member 122. Each bearing unit 124 can be individually set with its roller 126 supporting an equal portion of the total downward axial forces by varying the position of a nut 128 that is received in an enlarged threaded section in the upper end of the hole through the upper bearing support member 120. The upper bearing support member 120 has a relatively narrow vertical section joining the thicker inner portion supporting the upper end of the bearing unit 124 with the outer flange portion clamped to the support members 114 and 122. A seal ring 130 having a cross-sectional inverted L-shape is held by bolts through its upper horizontal portion to the upper surface at the inner edge of the upper roller bearing support member 120 so that the vertical inner portion extends downwardly along the vertical inner surface of the member 120. The vertical inner surface seal ring 130 is located in close diametric proximity about the adjacent outer surface of the ridge 68 that protrudes from the outer wall of the elongated central spindle section 64 so that the O-rings 70 form a fluid tight seal between the abutting relatively movable surfaces. The upper and lower inward extensions of the support members 120 and 114 thus combine to form a circular partition with a roughly C-shaped cross-section around the bottom interior of the central opening in the buoyant rotary hull structure 34 with the open end facing inwardly to be sealed against the lower closed portion of the vertical spindle casing 56. This provides an annular fluid tight enclosure closely surrounding the spindle casing 56 which encloses the entire lower roller bearing assembly.
Regarding the upper bearing assembly, as illustrated in FIG. 5, the deck connection flange 86 has a downward extension with an outwardly extending horizontal supporting flange, to which outer support flanges on annular upper and lower roller bearing unit support members 132 and 134 are secured together by bolts. The upper bearing unit support member 132 has a thick inner portion vertically aligned with a thick inner portion on the lower bearing unit support member 134 that has a vertical intermediate portion joining the outer flange portion above. Vertically aligned holes formed through the thick central portions of the bearing support members 132 and 134 receive the individual upper roller bearing cartridge units 136. Each of the roller bearing units 136 has a frusto-conical roller 138 with a beveled angle matching the slope of an inwardly beveled frusto-conical track surface 140 that extends around the outer lip of the cup-shaped upper section 78 of the tubular lower spindle assembly 56.
Referring now particularly to FIG. 6, the cartridge type roller bearing units 136 for the upper bearing assembly each have a tubular cartridge casing 142 surrounding an elongated shaft 144 extending downward from the attached frusto-conical roller 138. An annular seal ring 146 has an outer threaded periphery for engaging interior threads formed at the top of the cartridge casing 142 and contains an O-ring seal 148 within a groove at its inner surface to form a fluid tight seal against the outer surface of the shaft 144 just below the roller head 138. An X-type double roller upper bearing 150 has an outer set of oppositely beveled races held against the interior of the cartridge 142 together with inner sets of oppositely beveled races affixed to the shaft 144 to engage the cylindrical rollers held between them. A similar X-type double roller bearing arrangement 152 is attached at the lower end of the shaft 144 and is separated from the upper bearing 150 by an interior tubular spacer 154. The lower bearing 152 is held in place against the lower end of the spacer 154 with its outer edge supported on the horizontal upper surface of an underlying spacer ring 156. The diameter of the shaft 144 is decreased in several downward steps to form successive shoulders bearing against the upper supporting surfaces of the attached inner bearing race rings. At the bottom of the shaft, a circular retainer plate having a diameter larger than the bottom end of the shaft 144 is affixed to it by cap screws to hold the shaft 144 at the bottom of the lower inner race ring against upward movement. A threaded adjusting nut 160 fits the interior threads formed at the bottom of the hole through the thick horizontal portion of the lower bearing support member 134. A flat end surface on the adjusting nut bears against the bottom of lower spacer ring 156 and the lower end surface of the tubular cartridge casing 142, with which a fluid tight seal is formed by an O-ring. By turning the adjusting nut 160, the vertical position of each cartridge type baring unit can be adjusted to bring the beveled surfaces of each roller 138 into precise load bearing contact with the track surface 140 so that each bears an approximately equal portion of the applied axial loads. In a like manner, the complete rotary hull structure 34 can be precisely aligned concentrically about the central spindle casing 56 by manipulating the adjusting nuts 160. This feature is also applicable to the lower bearing assembly by adjusting nut 128. After assembly, the entire remaining open space within the tubular cartridge casing 142 between the upper threaded seal ring and the interior upper surface of the adjusting nut 160 can be filled with a lubricating oil injected through an appropriately located check valve (not shown) so that the interior roller bearings 150 and 152 are constantly lubricated.
Parallel alignment of the upper and lower roller bearing assemblies and reinforcement of the entire central rotating structure may be provided by a number of peripherally spaced support stanchions 162, as shown in FIG. 5, that are rigidly attached between the upper surface of the upper bearing support member 120 for the lower bearing assembly and the bottom surface of the lower roller bearing support member 134 for the upper bearing assembly.
To prevent the possibility of corrosion damage or fouling due to the adverse effects of seawater on any of the working parts contained within the central opening in the buoyant rotary hull structure 34, the various fixedly attached elements enclosing this opening should be tightly sealed using gaskets or the like between the abutting surfaces. However, insuring against leakage through the bottom of this central opening, which being underwater is subjected to substantial water pressures, is most important, particularly at the junction between the bottom of the buoyant rotary hull structure 34 and the stationary spindle assembly extending upward from the underwater base structure 36. Such seawater leakage at the bottom is prevented most effectively by establishing a pressurized oil seal within the annular fluid tight enclosure, or cavity, formed at the bottom of the spindle casing 56, which at the same time provides generous lubrication for all of the moving elements in the lower bearing assembly. To accomplish this, a lubricating oil for forming the seal is introduced into this annular fluid tight enclosure surrounding the lower end of the spindle casing 56 through an open feed line 164 that is sealed in place to extend through the vertical wall portion of the upper bearing support member 120. The opposite end of the open feed line 164 communicates with the bottom of an oil reservoir tank 166 (FIG. 4) that is formed and supported in the upper portion of the buoyant rotary hull structure 34 within the outer enclosed space defined by the hull and deck plating and filled with a highly buoyant substance 113 such as polyurethane foam. Preferably the oil reservoir tank 166 is located as shown in FIG. 4 against the inner hull wall 112 immediately below the upper deck 106 so that this plating forms the top and one side of the tank, thus reducing the length of the open feed line 164 to a minimum. The oil reservoir tank 166 is filled and kept full by the introduction of the oil through a fill hole in the upper deck that is closed by a removable fill cap 168. The level of the oil in the reservoir tank 166 is substantially above the waterline on the buoyant rotary hull structure 34 so that a gravity head is produced for pressurizing the oil within the annular fluid tight enclosure. Accordingly, the oil pressure above the packing gland seal 60, which is between the bottom of the rotary hull structure 34 and the lower end of the spindle casing 56, is greater than the water pressure acting on the underside. Therefore, any leakage occurring through the seal 60 would result in the higher pressure oil being forced outwardly instead of the lower pressure water entering. It might be possible in a heaVy sea, or through failure to fill the oil reservoir tank 166, that this pressure differential across the seal 60 would be temporarily interrupted permitting some water to enter the annular oil seal enclosure. But, since the water is heavier than oil, it would tend to remain at the bottom of the enclosure to be forced out upon restoration of the proper pressure differential. In this regard, the entry of any significant amount of water into the annular oil seal enclosure due to loss of oil pressurization head would merely tend to force the lighter overlying oil back up through the small diameter open feed line 164, thus restoring the pressurization head at least to a condition of pressure equilibrium. This prevents any seawater from reaching the O-ring seal 70 at the top of the annular oil seal enclosure to insure against seawater leakage into the central opening space above, provided however that there are not serious breaches in both the upper and lower seals 60 and 70. Inspection of the oil reservoir tank level at regular intervals during routine maintenance should indicate the sealing efficiency of the packing gland seal 60 so that necessary sealing pressure adjustments might be made, such as by use of the adjusting screws 121. If a substantial quantity of oil is required during refills, this would indicate the pressure on the seal rings 60 should be increased to prevent excess oil leakage through it if there were no indications of substantial oil leakage through the upper O-ring seals 70.