Turret support system and bearing unit

Information

  • Patent Grant
  • 6502524
  • Patent Number
    6,502,524
  • Date Filed
    Tuesday, October 10, 2000
    24 years ago
  • Date Issued
    Tuesday, January 7, 2003
    22 years ago
  • CPC
  • US Classifications
    Field of Search
    • US
    • 114 2301
    • 114 23012
    • 114 293
    • 384 12
    • 384 99
    • 384 100
    • 384 105
    • 384 107
    • 384 111
    • 384 121
    • 384 161
  • International Classifications
    • B63B2100
    • Term Extension
      32
Abstract
The invention is a bearing unit and bearing system for supporting a large rotatable element, such as a mooring turret. The bearing unit includes a hydrostatic suspension system which enables the bearing unit to accommodate fabrication tolerances and also enables the bearing unit to conform to relative movements between the ship and the turret, thereby providing a compliant bearing system. The system includes multiple bearing units of the invention which serve as thrust and/or radial bearings for supporting the turret. By manifolding a plurality of bearing units together in a fluidly-isolated group, the pressure applied to the bearing units in that group is self-equalizing so that all the bearing units act in unison to equally support the load, while also allowing some degree of self-alignment and tilting of the load. As a result, the bearing system emulates a self-aligning bearing system and is able to compensate for axial and angular misalignment. The system allows for monitoring of each bearing unit, automatic lubrication of the bearing surfaces, and in situ replacement of bearing liners should wear or damage occur while the system is in operation.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention generally relates to offshore vessel mooring systems that include a turret rotatably mounted within an opening or well within a vessel and connectable to a seabed mooring. More particularly, the invention relates to a method and apparatus for rotatably supporting a mooring turret within a vessel hull.




2. Description of the Prior Art




In recent years, the offshore oil and gas drilling industry has gravitated away from fixed platforms and toward floating storage and production vessels. Under this arrangement, a ship, such as a retired tanker, is moored to a mooring buoy, spider, or similar device connected to the seabed at the location of an undersea well. A riser is connected from the undersea well to the ship for delivering the oil or gas product. In this manner, the ship receives the oil or gas product from the undersea well and acts as a temporary storage facility for the product.




It is desirable in open or unprotected waters to moor the ship to the mooring buoy in such a manner that the ship is free to rotate or swivel about the mooring in a practice known as weathervaning. By this method, the ship is free to move in accordance with the prevailing currents and winds, while still remaining moored to the seabed. This freedom to swivel is commonly accomplished by mounting a cylindrical mooring turret vertically within the ship in such a manner that the turret is able to rotate or swivel about a vertical axis relative to the ship. The turret is commonly moored by one or more mooring lines know as catenaries which extend to the seabed. A mooring buoy, spider, or other connection joint or platform may be used to interface between the catenaries and the bottom of the turret. In addition, one or more oil production risers extend from a wellhead on the seabed into the turret, and the output from the risers is fed into the tanks in the ship for temporary storage.




To enable rotation of the turret relative to the ship, the turret is supported within the turret enclosure by a bearing system. These bearing systems usually include at least one thrust or axial bearing system for supporting axial loads, and at least one radial bearing system for supporting radial loads. Under one conventional arrangement, a thrust bearing system and a first radial bearing system are located near the upper end of the turret, such as on the forecastle of the ship, and a second radial bearing system is located near the bottom of the turret within the turret well. However, it is also known in the art to eliminate the lower radial bearing system to reduce maintenance and alignment problems with the turret, but such an arrangement greatly increases the load and wear on the upper bearing systems. Accordingly, such single-radial-bearing arrangements require an upper bearing system that is durable and compliant.




Also, in the case of smaller ships, turrets having rigid bearing systems have been used successfully to enable the turret to rotate relative to the ship. However, in the case of large turrets, and particularly in heavy seas conditions whereby heaving of the ship may cause vessel hull deflections and substantial loads between the turret and the hull, there is a need for some bearing compliance between the turret and the vessel. Compliant bearing systems used in the past for forming an interface between the turret and the ship include spherical self-aligning bearings, compliant plane bearing systems, and crane-wheel-type bearing systems mounted on springs or rubber pads. However, there is a continuing need for improvement over the conventional turret support systems to achieve a less complex, more efficient, and more reliable support system that maintains compliancy between the turret and the ship.




SUMMARY OF THE INVENTION




Under one aspect, the present invention sets forth a novel bearing pad unit for use in the turret support system of the invention. The bearing unit includes a hydrostatic suspension system which enables the bearing unit to accommodate turret fabrication tolerances and also enables the bearing unit to conform to relative movements between the ship and the turret, thereby providing a compliant bearing system. The bearing unit includes one or more bearing plates supported by a hydrostatic load element. The turret includes a stainless steel liner or race which runs directly against the bearing plates of a plurality bearing units. One or more grease ports are provided in each bearing plate to enable the periodic application of lubricant to the interface between the bearing plates and the stainless steel bearing liner of the turret.




In each bearing unit, the hydrostatic load element supports the bearing plate or plates and allows minor realignments of the bearing plates to be made while the bearing plates are under load. The hydrostatic load element includes a bearing pad block upon which the bearing plate or plates are mounted. A cylindrical pedestal engages with a cylindrical cavity located in the bearing block for supporting the bearing block. A pressurized hydraulic fluid is disposed within the cylindrical cavity between the pedestal and the bearing block so that the block is hydrostatically supported. A primary fluid seal and a secondary fluid seal are included at the interface between the pedestal and the bearing unit to prevent leakage of the hydraulic fluid. The primary seal is the main load-bearing seal, and is essentially static in service. The secondary seal is included as a backup should the primary seal fail. Also included in the interface between the pedestal and the bearing block is an annular ring bearing which transmits side loads from the block to the pedestal so as to prevent damage to the seals and to prevent direct contact between the block and the pedestal. In addition, if hydraulic pressure is lost in a bearing unit, the bearing block will be supported by a polymer cushion located on top of the pedestal. The cushion protects the pedestal and the block from high contact stresses by preventing direct metal-to-metal contact between the block and the top of the pedestal if hydraulic pressure is lost.




Pressurized hydraulic fluid may be pumped into the cylindrical cavity to support the bearing block and to put the bearing plates in contact with the turret bearing race surface. A bleed line is included in the bearing block to enable air in the cylindrical cavity to escape when fluid is pumped into the cylindrical cavity. A fluid supply line runs through the pedestal body and the cushion so that the fluid supply line outlet opening is located on the upper end of the pedestal. The fluid supply line is connectable to the pressurized hydraulic fluid circuit, and a plurality of bearing units may be manifolded together by being placed in isolated fluid communication with each other for equalizing the pressure on each bearing unit, thereby providing a self-adjusting feature among a plurality of bearing units.




Accordingly, under an additional aspect, the invention is directed to a system for supporting a turret within a turret well or enclosure. The system includes multiple bearing pad units which serve as thrust and/or radial bearings for supporting the turret. The bearing contact elements are supported hydrostatically so as to compensate for deformations due to fabrication tolerances and vessel hull deflections under load. As a result, the bearing system emulates self-aligning bearings and is able to compensate for axial and angular misalignment. The system allows for monitoring of each bearing unit, automatic lubrication of the bearing surfaces, and in situ replacement of bearing liners should wear or damage occur while the system is in operation.




Under another aspect, the invention sets forth a novel method and apparatus for mounting and operating bearing units for supporting a turret within a turret well in a ship's hull. Under one embodiment, the thrust and radial bearings are mounted in an equally-spaced manner about the perimeter of the turret bearing surface. The thrust bearing units are all manifolded together so that hydraulic fluid is able to flow between the individual thrust bearing units, but the fluid system is otherwise isolated. Similarly, the radial bearing units are manifolded to other radial bearing units, but otherwise isolated from the fluid circuit so that fluid is able to flow between the radial bearing units, but not to the rest of the fluid circuit. By manifolding a plurality of bearing units together, the pressure applied by the bearing units is self-equalizing so that all the bearing units act in unison to equally support the load, while also allowing some degree of self-alignment and tilting of the load.




In addition, according to another embodiment, the bearing units are mounted in two or more distinct groups, and preferably three groups, with each group being centered 120 degrees apart from adjacent groups of bearing units. The bearing units in each group are manifolded together, so as to act as a single bearing support, but are not manifolded to either of the other two groups of bearing units. This results in the three distinct groups of bearing units behaving as three single bearing pads, thereby providing a self-aligning compliant support, but allowing no tilting of the load. The arrangement of this second embodiment is particularly advantageous in the case of large diameter turrets of, for example, 10 meters diameter and larger.











BRIEF DESCRIPTION OF THE DRAWINGS




The foregoing and additional objects, features, and advantages of the present invention will become apparent to those of skill in the art from a consideration of the following detailed description of the preferred embodiments of the invention, taken in conjunction with the accompanying drawings.





FIG. 1

illustrates a plan view of a first embodiment of a bearing unit of the invention.




FlG


2




a


illustrates an elevation view of the bearing unit of

FIG. 1

, with a sectional view taken along line


2




a





2




a


of FIG.


1


.




FlG.


2




b


illustrates a second embodiment of the bearing unit of

FIG. 2



a.







FIG. 3



a


illustrates an elevation view of a pedestal of the invention.





FIG. 3



b


illustrates a top view of the pedestal of

FIG. 3



a.







FIG. 3



c


illustrates a cross section view taken along line


3




c





3




c


in

FIG. 3



b.







FIG. 3



d


illustrates a cross section view taken along line


3




d





3




d


in

FIG. 3



b.







FIG. 4



a


illustrates a first embodiment of a bearing plate for use with the bearing unit of the invention illustrated in

FIGS. 1 and 2



a.







FIG. 4



b


illustrates a cross section view taken along line


4




b





4




b


in

FIG. 4



a.







FIG. 4



c


illustrates a cross section view taken along line


4




c





4




c


in

FIG. 4



a.






FlG.


5




a


illustrates a second embodiment of a bearing plate for use with the bearing unit of the invention illustrated in

FIG. 2



b.







FIG. 5



b


illustrates a cross section view taken along line


5




b





5




b


in

FIG. 5



a.







FIG. 5



c


illustrates a cross section view taken along line


5




c





5




c


in

FIG. 5



a.







FIG. 6

illustrates a partial cross sectional elevation view of a radial bearing unit of the invention.





FIG. 7



a


illustrates an elevation view of a turret supported by a first embodiment of an arrangement of the bearing system of the invention.





FIG. 7



b


illustrates a view taken along line


7




b





7




b


in

FIG. 7



a.







FIG. 8

illustrates a plan view of a second embodiment of an arrangement of the bearing system of the invention.





FIG. 9

illustrates a hydraulic fluid circuit for use with the bearing system of the invention.











DETAILED DESCRIPTION




The present invention sets forth a bearing system for use in supporting a large rotatable element, such as for supporting a turret within a turret well enclosure of a ship, or the like. The system includes a plurality of bearing pad units for supporting the turret. In

FIGS. 1 and 2



a


there is illustrated a first preferred embodiment of a bearing pad unit


10


of the invention. In its broadest aspect, bearing unit


10


includes an outer member


12


movable relative to an inner member


14


for hydraulically supporting at least one bearing element


16


in contact with the large rotatable element (not shown in

FIGS. 1 and 2



a


). Thus, the preferred embodiment of bearing unit


10


includes a bearing block


20


as part of outer member


12


having a bearing plate


22


as bearing element


16


mounted on an upper bearing-element-support surface


24


of block


20


. Bearing block


20


includes a cylindrical cavity


26


for moveable engagement with inner member


14


, which is in the form of a cylindrical pedestal


28


in the preferred embodiment. Thus, bearing block


20


is axially moveable relative to pedestal


28


along the major axis of pedestal


28


. By the introduction of hydraulic fluid into cylindrical cavity


26


, bearing block


20


can be hydraulically supported on pedestal


28


so that bearing unit


10


is able to act essentially as a hydrostatic load element. However, as will be described in greater detail below, the fluid in bearing units


10


is not entirely static, since fluid is able to flow between two or more fluidly-connected bearing units


10


to enable bearing units


10


to adjust for load variations.




As illustrated in

FIG. 2



a


, a block collar


30


is connected to the lower portion of bearing block


20


. Block collar


30


includes an annular collar shoulder


32


which projects inward toward pedestal


28


, and which will engage with the lower edge of an outwardly-projecting annular pedestal shoulder


34


on pedestal


28


, as also illustrated in

FIGS. 3



a


-


3




b


. The engagement of collar shoulder


32


with pedestal shoulder


34


limits the upward movement of block


20


relative to pedestal


28


when pressurized fluid is introduced into cavity


26


. Thereby, collar


30


is able to retain block


20


on pedestal


28


. However, it is desirable that bearing plate


22


engage with a surface to be supported prior to the contact of collar shoulder


32


with pedestal shoulder


34


. Collar


30


is secured to bearing block


20


by collar machine screws


36


, or other suitable means. Collar


30


, pedestal


28


, block


20


, and the other structural components of the invention may be constructed from stainless steel, carbon steel, cast iron, or any other suitable materials or combinations thereof, taking into account the loads to be supported and the corrosiveness of the environment of use. Furthermore, a dust seal


38


may be included in a cutout


40


located on the inner periphery of collar shoulder


32


for preventing contamination of the fluid seals and cavity


26


.




Bearing unit


10


includes two fluid seals for increased reliability. A primary fluid seal


42


is located at a peripheral annular undercut


44


on pedestal


14


, immediately adjacent to a lip


46


on the upper end


48


of pedestal


28


. Thus, primary fluid seal


42


is retained between lip


46


and an undercut shoulder


50


formed by undercut


44


. Primary fluid seal


42


is preferably a circular polymer seal having a generally V-shaped cross section, and may further include a securing O-ring


52


for added assurance. Primary seal


42


bears the full hydraulic load when bearing unit


10


is under pressure. A secondary fluid seal


54


is located in a peripheral annular recess


56


in block


20


at the interface between block


20


and block collar


30


. Secondary fluid seal


54


may be of the same type and material as primary fluid seal


42


, but of a slightly larger diameter. Secondary fluid seal


54


provides retention of any fluid leakage past primary fluid seal


42


, and thereby contributes to the reliability of bearing unit


10


.




Immediately below primary fluid seal


42


there is located a radially-acting ring bearing


58


. Ring bearing


58


is located on the opposite side of pedestal shoulder


34


from block collar


30


, and is constructed as a circular ring of bearing bronze, nickel-bronze alloy, or other relatively lubricious high-bearing-strength material. Ring bearing


58


is of a slightly greater diameter than pedestal shoulder


34


, and absorbs and transmits lateral forces imposed on bearing block


20


, thereby protecting primary fluid seal


42


and secondary fluid seal


54


from excessive wear due to side loading. Thus, side loads imposed on bearing plate


22


due to friction, or the like, are transmitted by ring bearing


58


to pedestal


28


. Ring bearing


58


also prevents direct metal-to-metal contact between pedestal


28


and bearing block


20


, while the relative lubricity of ring bearing


58


allows low friction axial movement of bearing block


20


relative to pedestal


28


even during side loading. In addition, block


20


and block collar


30


include lubrication ports


59


for enabling lubrication of the interface between block


20


and pedestal


28


. Furthermore, it should be noted that other materials may be substituted for bronze for forming ring bearing


58


, including synthetic materials. One preferred alternative material is a synthetic polymer tape of sold under the brand name Thoratape™, available from Thordon Bearings, Inc. of Canada, which may be wrapped around pedestal


28


below primary seal


42


to serve as ring bearing


58


in place of the bronze ring.




Bearing plate


22


is retained on bearing block


20


by recessed machine screws


60


, as illustrated in FIG.


1


. Furthermore, a circular projection


62


is centrally located on upper surface


24


of block


20


for engaging with a circular recess


64


which is centrally located in the underside of bearing plate


22


. This arrangement acts to transfer lateral forces from bearing plate


22


to block


20


, rather than having to rely solely on the shear strength of machine screws


60


. As also illustrated in

FIGS. 4



a


-


4




c


, bearing plate


22


is preferably a rectangular bronze plate having a synthetic lining of low friction TRAXL bonded to its surface. TRAXL is a brand name used by Thordon Bearings, Inc. of Canada, and is a synthetic bearing lining typically applied to a bronze or stainless steel backing. Of course, the invention is not limited to a particular material or lining for the bearing plates, and any suitable material may be used for forming the bearing plates of the invention. Lubrication ports


66


are provided in bearing plate


22


to enable the periodic application of lubricant to the surface of the plate through lubrication channels


68


. Application of lubricant such as grease may be accomplished manually or automatically using known systems.




Under a second embodiment, as illustrated in

FIG. 2



b


, a pair of smaller bearing plates


70


may be located on upper surface


24


of block


20


instead of single bearing plate


22


. As also illustrated in

FIGS. 5



a


-


5




c


, bearing plates


70


include a downwardly projecting key member


72


which is used to secure bearing plates


70


to upper surface


24


of block


20


. This key member


72


fits within a key slot


74


formed on upper block surface


24


and enables bearing plates


70


to be removed from bearing unit


10


for repair or replacement without necessitating access to the upper or bearing surface


75


of bearing plates


70


. Accordingly, bearing plates


70


may be removed from a bearing unit


10


during use of adjacent bearing units


10


, without requiring dismantling of the entire bearing unit


10


. In addition, key members


72


also serve the same shear-transferring purpose as circular projection


62


and circular recess


64


in the first embodiment, and, accordingly, circular projection


62


and circular recess


64


are not required for the second embodiment. As with the first embodiment


22


of the bearing plate, bearing plates


70


may include lubrication ports


66


and channels


68


, and are constructed of similar materials. In addition, lubrication ports


66


may be formed on both sides of plate


70


so that plate


70


may be interchangeably used on either end of block


20


.




Referring back to

FIGS. 1 and 2



a


, Pedestal


28


may be secured to a suitable support surface (not shown) by using a two-piece clamp plate


76


. Clamp plate


76


annularly engages an annular groove


78


formed in the lower end of pedestal


28


. Thus, clamp plate


76


encircles pedestal


28


in a collar-like manner for securely retaining pedestal


28


. Clamp plate


76


may then be bolted or otherwise secured to the surface such as with bolts


80


. In addition, clamp plate


76


includes a brace assembly


82


which projects upward adjacent to block


20


. Brace assembly


82


is positioned so as to prevent rotation of the generally rectangular block


20


. This serves to keep bearing plates


22


,


70


, properly oriented with respect to the bearing race of the element being supported (not shown).




While the foregoing embodiments of the invention are primarily intended for use in supporting an axial load, the bearing unit of the invention may also be used as a radial bearing. Thus, in a third embodiment, as illustrated in

FIG. 6

, a radial bearing unit


11


includes swivelable bearing plates


84


mounted on upper surface


24


of block


20


. Radial bearing unit


11


is essentially the same as bearing unit


10


, with the exception of the arrangement of bearing plates


84


. Swivel bearing plates


84


are able to pivot about a pivot axis


86


, which enables bearing plates


84


to conform to a cylindrical (curved) bearing race (not shown) rather than a flat bearing race. This enables a plurality of radial bearing units


11


to be arranged circumferentially around the cylindrical periphery of a large rotatable element for supporting radial loads imposed on and by the rotatable element. Swivel bearing plates


84


also include lubrication ports and channels, as with the bearing plates


22


,


70


of the first two embodiments, and may be similarly constructed.




As illustrated in

FIGS. 3



a


-


3




c


, pedestal


28


includes a main fluid port


88


for connection to a source of pressurized hydraulic fluid (not shown in

FIGS. 3



a


-


3




c


). Fluid port


88


runs in the direction of the primary axis of pedestal


28


, and has an opening in a cylindrical depression


90


formed on the upper surface of pedestal


28


. As illustrated in

FIGS. 2



a


and


6


, a bleed port


92


is provided in block


12


for enabling air in cylindrical cavity


26


to exit when cavity


26


is being filled with hydraulic fluid. Accordingly, pressurized hydraulic fluid may be pumped into cylindrical cavity


26


through main fluid port


88


, thereby displacing air in cylindrical cavity


26


through bleed port


92


. In addition, pedestal


28


may include a cushion


94


located in depression


90


on top of pedestal


28


. Cushion


94


may be formed of a suitable synthetic material compatible with hydraulic fluid, such as Thorflex™, a material sold by Thordon Bearings, Inc. of Canada. Cushion


94


serves to protect pedestal


28


and block


20


from high contact stresses by preventing direct metal to metal contact between block


20


and the top


48


of pedestal


28


if hydraulic pressure is lost. Cushion


94


is mounted in depression


90


using machine screws (not shown) and screw holes


96


, as illustrated in

FIGS. 2



b


and


2




e


. In addition, cushion


94


includes a through-hole (not shown) which aligns with main fluid port


88


for permitting fluid to pass from main fluid port


88


into cavity


26


.





FIGS. 7



a


-


7




b


illustrate a first arrangement for mounting and operating a plurality of bearing units


10


,


11


for supporting a large rotatable element, such as a mooring turret


98


mounted in the hull of a ship


99


. A first set of a plurality of bearing units


10


are arranged in a radially symmetrical, equally spaced pattern for acting as thrust bearings for axially supporting turret


98


. A second set of a plurality of bearing units


11


are symmetrically arranged within a turret well enclosure


100


for acting as radial bearings. Thus, the thrust bearing units


10


are in sliding contact with a first bearing race


102


located on a downward-facing flat surface located near the upper end of turret


98


. A second bearing race


104


having a cylindrical configuration is provided on the outer periphery of the cylindrical surface of turret


98


for engagement with radial bearing units


11


. First and second bearing races


102


,


104


are preferably formed of stainless steel, although other suitable materials may also be used. It will be apparent that as turret


98


rotates about a vertical axis relative to ship


99


, bearing races


102


,


104


slide across bearing plates


22


,


70


,


84


, while bearing units


10


,


11


serve to maintain the spatial position of turret


98


relative to ship


99


and turret enclosure


100


, and thereby prevent binding, contact, and the like.




In the embodiment illustrated in

FIGS. 7



a


-


7




b


, once thrust bearing units


10


are pressurized, the fluid circuit is isolated from the fluid pumping unit (not shown in

FIGS. 7



a


-


7




b


) and thrust bearing units


10


are all manifolded together in fluid communication so that hydraulic fluid is able to flow between the individual bearing units


10


, but not back to the rest of the fluid circuit. Thus, the pressure applied by bearing units


10


is self-equalizing so that all bearing units


10


act in unison to equally support the load, while also allowing some degree of self-alignment and tilting of the load. For example, if a greater load is applied to one side of the bearing arrangement, say, due to deflections on turret


98


, the bearing units


10


on the side under greater load will tend to depress under the greater pressure, and the fluid in those bearing units


10


will circulate out of those bearing units


10


and toward the bearing units


10


on the opposite side of turret


98


. As the unequal load is relieved, the pressure applied to each bearing unit


10


will equalize, and, accordingly, the fluid will return to the bearing units


10


that were formerly depressed. This enables the bearing arrangement of

FIGS. 7



a


-


7




b


to act as a compliant, self-adjusting bearing system. Radial bearing units


11


may be similarly manifolded together in a group so that they also are compliant and self-adjusting.




In a second embodiment, as illustrated in

FIG. 8

, a plurality of thrust bearing units


10


are mounted in three distinct pad groups


110




a


,


110




b


, and


110




c


, with each pad group being centered 120 degrees apart from adjacent pad groups


110




a


,


110




b


, and


110




c


. The bearing units


10


in each individual pad group


110




a-c


are manifolded together, so that the distinct pad group acts as a single bearing support, but are not manifolded to the bearing units


10


in either of the other two pad groups


110




a-c


. This results in the three groups of bearing units


10


behaving as three single bearing pads, thereby providing a self-aligning support within each pad group, but allowing no tilting of the load (in this case, turret


98


). The arrangement of this second embodiment is particularly advantageous in the case of large diameter turrets of, for example, 10 meters diameter and larger.





FIG. 9

illustrates a portion of an exemplary fluid circuit of the invention that may be used with the bearing arrangement of FIG.


8


. The fluid circuit of the invention includes a number of conventional components, such as a fluid sump, main pump, purge pump, accumulators, and the like, which are well known in the art, and which are illustrated schematically as pump unit


112


.

FIG. 9

further illustrates the fluid circuit schematic for pad groups


110




a


,


110




b


, and


110




c


. Each pad group


110




a-c


is connected to a main fluid line


114


and a purge/flush line


116


. A main line valve


118


and a purge/flush line valve


120


are included for each bearing unit


10


, so that each bearing unit


10


may be isolated, such as in the case of a bearing unit


10


requiring repair, replacement, deactivation due to fluid seal leakage, or the like. A bleed/purge fluid line


122


is also provided, and a bleed valve


124


is provided for each bearing unit


10


to enable bleeding/purging of individual bearing units


10


. In addition, each pad group


110




a-c


includes a main line isolation valve


126


. Isolation valves


126


enable each pad group


110




a-c


to be isolated from the pump unit


112


. However, by positioning main line valves


118


in the open position and purge line valves


120


and bleed valves


124


in the closed position, each bearing unit


10


in a particular pad group


110




a-c


remains in fluid communication with only the other bearing units


10


in that particular pad group


110




a-c


, and thus, the bearing units


10


in each pad group


110




a-c


are manifolded to each other, but not to bearing units


10


in other pad groups


110




a-c


. The fluid pressure in each pad group


110




a-c


may be monitored by pressure gauges


128


, or the like to determine that each pad group


110




a-c


remains properly pressurized.




In initial operation, bleed valves


124


, main line valves


118


, and isolation valves


126


are opened, while purge line valves


120


remain closed. Pump unit


112


is used to supply pressurized hydraulic fluid to bearing units


10


. Upon bleeding of all air from bearing units


10


, bleed valves


124


are closed. Bearing units


10


are then pressurized to a desired pressure so as to bring bearing plates


22


,


70


into contact with first bearing race


102


and to thereby support turret


98


. Isolation valves


126


are then closed so that each pad group


110




a-c


is isolated from the other pad groups


110




a-c


. However, each bearing unit


10


in a particular pad group


110




a-c


remains in fluid communication with the other bearing units


10


in that particular group


110




a-c


. Thus, each pad group


110




a-c


acts as a single bearing unit, while the individual bearing units


10


in the pad group


110




a-c


are able to compensate among themselves for misalignments, irregularities in the bearing race


102


, or the like, by fluid flow between the bearing units


10


in that group. In addition, the number of bearing units


10


in each pad group


110




a-c


do not have to be uniform. For example, pad group


110




a


might consist of eight bearing units while pad groups


110




b


and


110




c


might only consist of six bearing units. This may be advantageous if pad group


110




a


is in line with the major axis of the ship and is subject to greater loads than pad groups


110




b


and


110




c.






The radial bearing units


11


may also be arranged in distinct pad groups in the manner described above. In addition, it is not necessary that the pad groups be distinctly spaced from each other. For example, bearing units


10


,


11


shown in the arrangement of

FIGS. 8



a


-


8




b


may also be manifolded into pad groups if so desired. Under one such preferred arrangement, the thrust bearing units


10


may all be manifolded together, while the radial bearing units


11


may be manifolded into groups of three or four separate pad groups. Other such manifolding combinations will also be apparent to those skilled in the art, and it is to be understood that the embodiments shown are merely exemplary.




Should it be necessary to repair or replace a bearing unit


10


, (or a radial bearing unit


11


) while the bearing system is in use, main line valve


118


is first closed to isolate the bearing unit


10


to be replaced from the other bearing units


10


in that group. Purge line valve


120


is then opened and purge line


116


is used to remove the fluid from that bearing unit


10


, while not affecting the operation of the remaining bearing units


10


. Following repair or replacement, purge line


116


is used to repressurize the repaired bearing unit


10


and the repaired bearing unit


10


is put back into fluid communication with the other bearing units


10


in its pad group


110




a-c


by closing purge line valve


120


and opening main line valve


118


. In addition, it should be apparent that the schematic for a single pad group, for example, pad group


110




a


, represents the operation schematic for the first embodiment described above with reference to

FIGS. 7



a


-


7




b


in which all the bearing units


10


are manifolded together, and, accordingly, further description of the fluid circuit operation of that embodiment is not believed to be necessary.




Thus, the present invention sets forth a novel bearing unit and bearing operation system for use in supporting a large rotatable object. While the best mode of the invention has been set forth in a manner applied to a support system for a turret in an offshore mooring system, it will be apparent to those skilled in the art that other applications for the invention may also be advantageous. In addition, variations in the specific structure of the invention will also be apparent. For example, the positions of the block and the pedestal may be reversed so that the pedestal acts as a ram for supporting the bearing element. Also, other types of bearing elements might be substituted for bearing plates


22


,


70


,


84


. For example, rollers might be mounted on top of block


20


for use as the bearing elements for contacting bearing races


102


,


104


. Other structural variations will also be apparent and are believed to be within the scope of the invention. Accordingly, while the foregoing disclosure sets forth exemplary embodiments of the present invention, it is to be understood that the invention is not limited to the particulars of the foregoing embodiments, but is limited in scope only as set forth in the following claims.



Claims
  • 1. An apparatus for supporting a mooring turret for rotatable movement within a turret well enclosure on a ship, said apparatus comprising:a plurality of bearing units positioned for supporting the turret, said bearing units including an outer member having a cavity, an inner member extending into the cavity, a hydraulic fluid located within said cavity for supporting the outer member relative to the inner member, a bearing element mounted on one of said outer member or said inner member for contacting a bearing race on the turret, wherein said inner member is a fixed pedestal and said outer member is a movable block which supports said bearing element.
  • 2. The apparatus of claim 1 in which some of said bearing units are axially oriented relative to the turret for acting as thrust bearings, while others of said bearing units are radially oriented relative to the turret for acting as radial bearings.
  • 3. The apparatus of claim 1 further including a ring bearing mounted on said pedestal for transferring lateral loads from said block to said pedestal.
  • 4. The apparatus of claim 1 further including a primary fluid seal and a secondary fluid seal located between said block and said pedestal for retaining the fluid within said cavity.
  • 5. The apparatus of claim 1 wherein said bearing element comprises at least one bearing plate located on said block opposite to said pedestal for contacting a bearing race on the turret.
  • 6. The apparatus of claim 5 wherein there are two said bearing plates and said bearing plates are pivotally mounted on said block for contacting a curved bearing race.
  • 7. The apparatus of claim 1 further including a cushion located on the top of said pedestal for contacting said block should hydraulic pressure be lost in said cavity.
  • 8. The apparatus of claim 1 further including a first set of fluid lines and a second set of fluid lines, said first set of fluid lines enabling fluid communication between the cavities of a first group of a plurality of said bearing units, and said second set of fluid lines enabling fluid communication between the cavities a second group of a plurality of said bearing units, whereby fluid is able to flow among the bearing units of said first group for equalizing a load, but not among the bearing units of said second group, and whereby fluid is able to flow among the bearing units of said second group for equalizing a load, but not among the bearing units of said first group.
  • 9. An apparatus for supporting a mooring turret for rotatable movement within a turret well enclosure on a ship, said apparatus comprising:a plurality of bearing units positioned for supporting the turret, said bearing units including; a fixed pedestal having a major axis; a block mounted on said pedestal for movement in a direction along the major axis of said pedestal, said block having a cavity for receiving said pedestal and a hydraulic fluid, whereby the hydraulic fluid supports said block in relation to said pedestal; and a bearing element mounted on said block opposite to said cavity for contacting a bearing race on the turret.
  • 10. The apparatus of claim 9 in which some of said bearing units are axially oriented relative to the turret for acting as thrust bearings, while others of said bearing units are radially oriented relative to the turret for acting as radial bearings.
  • 11. The apparatus of claim 9 further including a ring bearing mounted on said pedestal for transferring lateral loads from said block to said pedestal.
  • 12. The apparatus of claim 9 further including a primary fluid seal and a secondary fluid seal located between said block and said pedestal for retaining the fluid within said cavity.
  • 13. The apparatus of claim 9 wherein said bearing element comprises at least one bearing plate located on said block opposite to said pedestal for contacting a bearing race on the turret.
  • 14. The apparatus of claim 13 wherein there are two said bearing plates and said bearing plates are pivotally mounted on said block for contacting a curved bearing race.
  • 15. The apparatus of claim 9 further including a cushion located on the top of said pedestal for contacting said block should hydraulic pressure be lost in said cavity.
  • 16. The apparatus of claim 9 further including a first set of fluid lines and a second set of fluid lines, said first set of fluid lines enabling fluid communication between the cavities of a first group of a plurality of said bearing units, and said second set of fluid lines enabling fluid communication between the cavities a second group of a plurality of said bearing units, whereby fluid is able to flow among the bearing units of said first group for equalizing a load, but not among the bearing units of said second group, and whereby fluid is able to flow among the bearing units of said second group for equalizing a load, but not among the bearing units of said first group.
  • 17. An apparatus for supporting a mooring turret for rotatable movement within a turret well enclosure on a ship, said apparatus comprising:a plurality of self-equalizing bearing units positioned for supporting the turret, said bearing units including a fixed pedestal having a major axis, a block mounted on said pedestal for movement in a direction along the major axis of said pedestal, said block having a cavity for receiving said pedestal and a hydraulic fluid, and a bearing element mounted on said block opposite to said cavity for contacting a bearing race on the turret, whereby the hydraulic fluid supports said block in relation to said pedestal, and whereby the fluid is able to flow between said bearing units for self-equalizing said bearing units.
  • 18. The apparatus of claim 17 further including a ring bearing mounted on said pedestal for transferring lateral loads from said block to said pedestal.
  • 19. The apparatus of claims 17 further including a primary fluid seal and a secondary fluid seal located between said block and said pedestal for retaining the fluid within said cavity.
  • 20. The apparatus of claim 17 further including a cushion located on the top of said pedestal for contacting said block should hydraulic pressure be lost in said cavity.
US Referenced Citations (34)
Number Name Date Kind
3598369 Yielding Aug 1971 A
3782789 Koester et al. Jan 1974 A
3799628 Van Gaasbeek et al. Mar 1974 A
3806975 Fyfe Apr 1974 A
3934295 Koster et al. Jan 1976 A
3971598 Rudge Jul 1976 A
3994540 Petersen Nov 1976 A
3995915 Koster et al. Dec 1976 A
4006505 Koster et al. Feb 1977 A
4099802 Heinemenn et al. Jul 1978 A
4200341 Kauschke Apr 1980 A
4544285 Shapiro et al. Oct 1985 A
4601252 Wuttudal Jul 1986 A
4610431 Andrae et al. Sep 1986 A
4610486 Baigent Sep 1986 A
4647253 Jacobson et al. Mar 1987 A
4749282 Spargo et al. Jun 1988 A
4753553 Carlsen et al. Jun 1988 A
4892417 Spargo et al. Jan 1990 A
4928339 Klawe May 1990 A
5051035 Glorstad Sep 1991 A
5071261 Stuve Dec 1991 A
5228378 Bathory Jul 1993 A
5356321 Boatman et al. Oct 1994 A
5466068 Andra Nov 1995 A
5515804 Pollack May 1996 A
5597240 Fyfe Jan 1997 A
5762017 Groves Jun 1998 A
5782197 Pollack Jul 1998 A
5913279 Braud Jun 1999 A
5957076 Pollock Sep 1999 A
6014939 Gusmeri et al. Jan 2000 A
6017168 Fraser, Jr. et al. Jan 2000 A
6164233 Pollack et al. Dec 2000 A