HIGH PRESSURE PRODUCT SWIVEL

Abstract: A rotatable swivel and swivel assembly (5) by which one or more conduits are rotatably (7) connected. The swivel is especially adapted for rotatable connection of conduits carrying fluids under high pressure. Inner and outer concentric ring structures (10, 20) are provided which upon registration define a fluid conduit chamber (30) and a bearing raceway chamber (40). Bearing balls (41) are placed in the bearing raceway chamber (40). Face seals (15, 16) are provided in annular upwardly and downwardly facing grooves (17, 18) in one of the ring structures above and below the fluid conduit chamber and sealingly engage annular surfaces (116, 117) of the other of the ring structures. A second embodiment of the rotatable swivel includes a swivel body, a ball bearing assembly, and a primary upper seal (270) axially offset from a primary lower seal (274) for sealing a conduit chamber (216) is disclosed. Pressurization of the conduit chamber (216) of the swivel in cooperation with the differential axial offset of the primary seals creates axial pre-loading of the swivel operably aiding in the sealing of the conduit chamber and maintaining the concentricity of the bearing assembly between a rotable outer ring (248) and a stationary inner ring (222) and providing wear compensation for the swivel. Secondary upper (280) and lower seals (286) are disclosed whereby if the primary seals fail to retain pressure in the conduit chamber, the respective secondary seal maintains the initial axial loading of the failed primary seal.

Description: HIGH PRESSURE PRODUCT SWIVEL BACKGROUND OF THE INVENTION Field of the Invention This invention relates in general to equipment for transferring fluids. In particular, the invention relates to a product swivel and a swivel assembly adapted for transferring fluids between tankers, storage vessels and the like and one or more conduits beneath the ocean surface. Description of the Prior Art The offshore search for oil and gas has greatly expanded in recent years and progressed into deep rough waters such as the North Sea. To facilitate production of oil and gas from remotely located offshore fields, complex mooring systems for floating vessels which serve as centralized production sites for the entire field have been developed. Flexible fluid lines extend from a subsea location to the mooring site to permit the transfer of fluids between a moored vessel and a subsea location. For example, certain fluid lines may be used to convey oil and gas into the floating vessel while other fluid lines may be used to inject liquids or gases back into the field for purpose of field stimulation or storage. Floating vessels can be moored to a single point mooring system, which permits the vessel to weather vane and rotate 360 degrees about a single mooring point. To permit the vessel to rotate and move freely without causing twisting or entanglement of the various fluid lines to which the vessel is attached, it is necessary to provide a swϋvel mechanism to connect the fluid lines to the mooring site. Furthermore, since a plurality of fluid lines are involved, it is necessary that such a swivel have the capability of accommodating multiple lines. Multiple line swivels for offshore use are known in the prior art. For example, U.S. Patent No. 4,306,741 issued to Foolen describes a swivel assembly where a plurality of swivels are mounted coaxially and have an axial radial bearing structure with axial rollers and radial rollers bearingly supporting the inner and outer rings of each swivel as well as supporting one swivel with respect to each other on top of another. The seals of the Foolen patent are radial seals which seal against the outer wall of the inner ring. The seals are disposed in radial grooves in the inner wall of the outer ring making it practically impossible to assemble the swivel unit with seals of adequate rigidity to withstand the required pressure without being extruded into the seal gap between the inner and outer swivel rings. Seal material of adequate rigidity cannot be stretched enough for the seal ring and be inserted in a radial groove in the inner ring or compressed enough for insertion into radial grooves in the outer ring. U.S. Patent 3,698,433 to Dobler et al illustrates a fluid swivel in which an outer ring is supported by means of ball bearings with respect to a cylindrical band secured to a drum like structure. Other U.S. patents illustrating rotatable swivels include, U.S. Patent 2,293,585 Bard U.S. Patent 3,237,220 Bengt-Ake Brandt U.S. Patent 3,462,176 Goodrum U.S. Patent 3,466,061 Fonda-Bonardi U.S. Patent 3,966,249 Lindquist U.S. Patent 4,065,159 Leroy U.S. Patent 4,111,467 de Fremery U.S. Patent 4,126,336 Ortloff et al U.S. Patents showing swivel assemblies for carrying oil or other cargo between a ship and subsea installations include. U.S. Patent 3,074,082 Griebe U.S. Patent 3,366,982 Sutton U.S. Patent 4,142,767 Karl U.S. Patent 4,254,523 Kentosh Dutch patent application 73,10795 illustrates a stacked swivel. The radial seals of the prior art do not operate efficiently under high pressure because high pressure product in the conduit between the outer ring and the inner ring tends to separate the rings. In other words, the inner ring deflects inwardly and the outer ring deflects outwardly, thereby forcing the radial seals out of sealing engagement of one ring from the other ring. The radial seals of the Foolen patent, as referenced above are in axial alignment above and below the conduit chamber thereby resulting in balanced axial loading between the inner and outer rings. The prior art bearing assemblies, though designed to transfer large radial and thrust loads, lose their concentricity as the inner and outer rings deflect away from each other upon pressurization of the conduit chamber, as discussed above, thereby creating looseness in the bearing assembly. Also, as the bearing assembly wears, additional looseness results in the bearing assembly. Such problems are compounded when the swivels are exposed to extremely high pressures. Identification of Objects of the Invention It is an object of this invention to provide a high pressure product swivel which effectively functions to rotatably connect an inlet with an outlet during conduction of high pressure product fluid through a conduit chamber. It is another object of the invention to provide a high pressure product swivel in which inner and outer rings defining a conduit chamber are bearingly supported by means of a bearing ball filled toroidal raceway chamber formed integral with the inner and outer rings. It is another object of the invention to provide a sealing means between inner and outer rings of a high pressure swivel structure especially adapted to maintain sealing of the rings when high pressure product in the conduit chamber is distorting the inner and outer swivel rings. It is another object of the invention to provide a high pressure product swivel with seal arrangements which allow convenient installation and replacement of rigid seal rings as required to resist leakage of product under very high pressure in the conduit chamber. It is another object of the invention to provide means for detecting leaks across the sealing means between upper and lower seals above and below a toroidally shaped conduit chamber. It is another object of the invention to provide a high pressure product swivel in which the pressurization of a conduit chamber in cooperation with radial offsetting of seals creates an axial loading which will tend to force the sealing surfaces together rather than causing separation of the seal surfaces, as is common in swivel existing designs. It is another object of the invention to provide a high pressure product swivel in which pressurization of the conduit chamber in cooperation with offsetting of primary seals creates axial loading of the swivel to provide a uni-directional loading on a plurality of bearing balls to assure that the bearing balls will support and guide the rotating swivel rings firmly without separating movements of the seal surfaces even when the bearing balls and races have sustained substantial wear after prolonged service. It is another object of the invention to provide a high pressure product swivel having a four point contact ball bearing assembly for transferring uni-directional loading between inner and outer rings of a swivel and between upper and lower stacked swivels. It is another object of the invention to provide a high pressure product swivel with secondary seals to retain the pressure in the conduit chamber upon failure of primary seals for maintaining the sealing and the axial loading of the inner ring and the outer ring of the swivel. SUMMARY OF THE INVENTION The objects identified above as well as other advantages and features of the invention are incorporated in the embodiments of the invention. In its broadest sense, the invention in for a product swivel adapted for rotating about a substantially vertical axis. The swivel includes a swivel body having an inner ring having a substantially vertical axis, and includes a swivel body having an inner ring having a substantially outwardly facing surface and an outer ring having a substantially inwardly facing surface. These surfaces, when the inner ring is in registration with the outer ring, form a torodially shaped conduit chamber. One ring is stationary. Means are provided for rotatingly supporting one ring with respect to the other ring. The swivel body has an inlet and an outlet communicating with the conduit chamber. A primary upper face seal is disposed above the conduit chamber in a first annular groove in one ring for sealingly engaging a sealing surface of the other ring and a primary lower face seal is disposed below the conduit chamber in a second annular groove in one ring for sealingly engaging a sealing surface of the other ring. According to a first embodiment of the invention, a rotatable swivel is provided which comprises an inner ring structure having an outwardly facing concave inner conduit surface and an outwardly facing concave bearing raceway and an outer ring structure having an inwardly facing concave conduit surface and inwardly facing concave bearing raceway. When the outer and inner ring structures are assembled with their respective conduit surfaces in registration and their respective bearing surfaces in registration, a toroidally shaped conduit chamber and toroidally shaped bearing raceway chamber are created. A plurality of bearing balls are disposed in the bearing chamber rotatingly supporting one ring structure with respect to the other. An upper and a lower face seal are disposed in an upper and a lower annular groove in one of the ring structures disposed above and below its conduit surface sealingly engaging respective downwardly and upwardly facing annular surfaces above and below the conduit surface of the other ring structure. Means are provided for connecting a tubular conduit to the toroidally shaped conduit chamber from the interior of the structure and means are provided for connecting a tubular conduit to the toroidally shaped chamber from the exterior of the structure. The swivel, according to the invention, " is advantageous over prior marine product swivels in the use of face seals between the inner and outer rings in that even if the inner and outer rings are not assembled precisely coaxially with one another, sealing of the conduit chamber is accomplished. Such sealing overcomes one of the disadvantages of the before mentioned prior swivel structure where seals are used to seal radially between inner and outer rings, because if the prior inner and outer rings are not machined and assembled exactly coaxially, proper sealing of the rigid seals required for high pressures may not be effected when the swivel is being rotated. Another advantage of the structure described above according to the invention over that of the prior marine swivels is the machining of the sealing surfaces at the same time as the ball bearing races are created. According to the invention, a structure is provided whereby accuracy of the sealing and bearing surfaces is assured at the time of manufacture and is not dependent upon accuracy of the assembly as is required in the prior apparatus described for example in the Foolen patent where radial sealing surfaces -are disclosed. According to the invention, the swivel structure described above may have its inner ring structure stationary with the outer ring rotatable about the inner ring structure or the outer ring structure may be stationary with the inner ring structure rotatable within the outer ring According to a second embodiment of the invention, a rotatable product swivel is provided comprising a swivel body, a ball bearing assembly, and a primary upper seal offset a greater distance from the vertical rotation axis of the swivel than a primary lower seal. Pressurization of the conduit chamber of the swivel in cooperation with the differential offset of the upper and lower primary seals creates axial preloading on the support bearing of the swivel. The pressurization of the conduit chamber urges the rotatable outer ring downwardly with respect to the stationary inner ring and decreases the vertical distance between the outer and inner rings operably aiding in the sealing of the conduit chamber of the swivel. Secondary upper and lower seals are for retaining pressure in the conduit chamber upon failure of a respective primary seal. The secondary seals are positioned so as to maintain the thrust or axial preloading of the primary seals even if one of the primary seals were to fail. The swivel, according to the invention, includes a ball bearing assembly where pressurization of the conduit chamber in cooperation with the offset of the primary seals creates axial pre-loading on the bearing assembly. The axial pre-loading provides uni-directional loading on the plurality of bearing balls within the bearing assembly to prevent separation of seal surfaces due to loose bearing fits and further to provide automatic wear compensation for the bearing assembly. According to the second embodiment" of the invention, the bearing assembly comprises a four point contact ball bearing assembly positioned between a stationary inner ring and a rotatable outer ring. The bearing assembly comprises either two or three annular bearing race elements forming a toroidally shaped bearing chamber or race having four annular inwardly facing contacts. The swivel provides a uni-directional thrust or axial loading on the bearing assembly capable of tolerating radial deflections which occur upon pressurization of the conduit chamber. BRIEF DESCRIPTION OF THE DRAWINGS The objects, advantages and features of the invention will become more apparent by reference to the drawings which are appended hereto and wherein like numerals indicate like parts and wherein illustrative embodiments of the invention are shown. Figures 1-6 illustrate a first embodiment of the invention, and Figures 7-11 illustrate a second embodiment of the invention of which: Figure 1 illustrates in a plan view a swivel assembly for three separate products according to the invention in which three swivels are stacked coaxially together for connecting three conduits from beneath and interior to the swivel assembly to three conduits exterior to the assembly; Figure 2 shows a side view of the swivel assembly of Figure 1 partially in cross-section; Figure 3 illustrates a cross-section through a wall of the swivel and further illustrates the embodiment of the invention where the inner rings are stationary and secured to stacked top and bottom swivels; Figure 4 illustrates a ball bearing loading port and plug by which ball bearings are loaded into a toroidally shaped raceway chamber of the swivel; Figure 5 illustrates a lateral cross-section through the raceway chamber illustrating the raceway chamber being loaded with bearing balls and spacers; Figure 6 illustrates an alternative embodiment of the invention where the outer rings are bolted one to another in a swivel assembly and are stationary and where the inner rings are individually rotatable with respect thereto; Figure 7 illustrates in a plan view a swivel assembly in which three swivels are stacked coaxially together for connecting three conduits from beneath and interior to the swivel assembly to three conduits exterior to the assembly; Figure 8 shows a side view of the swivel assembly of Figure 7 partially in cross-section; Figure 9 illustrates a cross-section through a swivel . of the invention and further illustrates the preferred embodiment of the invention where the inner rings are stationary and the outer rings are independently rotatable; Figure 10, which shows a section through lines 4-4 of Figure 9, illustrates a raceway chamber of a bearing assembly being loaded with bearing balls and spacers; and Figure 11 illustrates an alternative embodiment of the invention where the outer rings are stationary and the inner rings are individually rotatable with respect thereto. DESCRIPTION OF THE INVENTION Description of a first embodiment of the invention (Figures 1-6) Figures 1 and 2 illustrate a swivel assembly 5 comprising three coaxially stacked swivels which are essentially identical to one another except as to their size. Figure 1 shows in a plan view the swivel assembly 5 and the conduit connectors 8, and 8B (connector 8A not visible) which connect vertically disposed conduits 7, 7A and 7B to swivel conduit chambers 30, 30A and 30B. In Figure 1, the external connectors 9, 9A, and 9B connecting to chambers 30, 30A and 30B are illustrated. Figure 2 illustrates in a side view the three external connectors 9, 9A and 9B which may be connected to external conduits for connecting to the conduit chambers 30, 30A and 30B respectively of the stacked swivel structures. Although three swivels are illustrated in an assembly, more or less swivels may of course be stacked. Figure 3 is an axial cross-section through a portion of one of the swivels, specifically the middle swivel illustrated in Figure 2. Figure 3 will be discussed immediately below describing the swivel structure where its inner ring is stationary and adapted for being bolted to stacked below and above swivel structures while Figure 6, to be discussed below, illustrates the embodiment of the swivel where the outer portion of the swivel ring is secured to outer rings of stacked above and below swivels. Turning now to Figure 3, an inner ring structure 10 includes a primary inner ring 11 and an inner ring annular plate 44 secured to the primary inner ring 11 by means of one or more bolts 100. The primary inner ring 11 has an outwardly facing conduit surface 12 and an outwardly facing raceway surface 14. The swivel construction further includes an outer ring structure 20 including a primary outer ring 21 and an outer ring annular plate 42 secured to the primary outer ring 21 by means of one or more bolts 102. The primary outer ring 21 includes an inwardly facing concave conduit surface 22 and an inwardly facing concave raceway surface 24. When the outer ring structure 20 is assembled concentrically about the inner ring structure 10, the inwardly facing concave conduit surface 22 comes into registration with the outwardly facing conduit surface 12 defining a toroidally shaped conduit chamber 30. In like manner, the inwardly facing concave raceway surface 24 comes into registration with the outwardly facing raceway surface 14 defining a toroidally shaped raceway chamber 40. A plurality of bearing balls 41 are disposed within the toroidally shaped raceway chamber 40 providing a means by which the inner ring structure 10 and the outer ring structure 20 are axially and radially supported with respect to one another. Figure 5 illustrates that the bearing balls 41 are preferably spaced from one another by means of spacers 43. Figure 4 illustrates that in another longitudinal cross-section of the wall of the swivel, that the bearing balls 41 may be loaded within the toroidally shaped raceway chamber 40 by means of a ball loading port 104. Port 104 may be closed by a plug 106 in conventional fashion. The primary inner ring 11 includes an upper flange 108 and a lower flange 110. Outer ring annular plate 42 includes an overlapping annular region 112 which overlaps flange 108. The primary outer ring 21 also includes a lower flange portion 114 which overlaps flange 110 of the primary inner ring 11. Disposed in the upper part of flange 108 of primary inner ring 11 are grooves 17 and 18 in which are placed upper face seals 15 and 16. Upper face seals 15 and 16 sealingly engage the downwardly facing annular surface 116 of flange 112 of outer ring annular plate 42. Similarly, grooves 28 and 29 are disposed in the lower portion of flange 110 of the primary inner ring 11. Lower face seals 26 and 27 are placed in grooves 28 and 29 and sealingly engage the upwardly facing annular surface 117 of flange 114 of the primary outer ring 21. The placement of the upper face seals 15 and 16 and the lower face seals 26 and 27 for sealingly engaging lateral annular surfaces 116 and 117 cooperate with the entire swivel structure in order to enable the toroidally shaped conduit chamber 30 to effectively carry high pressure fluid therein. High pressure fluid is designated by the letter P within toroidally shaped conduit chamber 30 and illustrates that pressure P acts on the inner ring structure 10 and the outer ring structure 20 tending to force them apart. In so doing, the face seals continue to provide sealing engagement about the lateral surfaces 116 with respect to the upper flange 108 of the primary inner ring 11 and the annular surface 117 with respect to the lower flange portion 110 of the primary inner ring 11. Such face seals effectively overcome the disadvantages of the use of seals in radial.grooves in the mating surfaces of an inner ring structure and an outer ring structure which are known in the prior art. The prior art orientation of seals makes it difficult or impossible to install seals that are sufficiently rigid to withstand the high pressures required (up to 6000 psi) . Use of face seals as illustrated offers significant advantages especially where the swivel is used to carry very high pressure fluids. Of special importance is the ease with which seals made of rigid material may be installed or replaced without need for stretching and damaging the very rigid materials required for high pressure service (up to 6000 psi) . Another advantage of the placement of the upper face seals 15 and 16 and the lower face seals 26 and 27 about lateral sealing surfaces is that the machining of such surfaces occurs at the same time as the machining of the outwardly facing bearing surface 14 and the inwardly facing concave bearing surface 24. Thus, sealing accuracy is assured for the sealing surfaces where sealing is achieved even though the outer ring structure 20 may not be precisely coaxial with respect to the inner ring structure 10. Thus, the outer ring structure 20 may be slightly displaced radially yet sealing is achieved between the lateral face seals 15 and 16 and the annular surface 116 of the outer ring annular plate 42 and likewise sealing is achieved by the lower face seals 26 and 27 against the annular surface 117 of the outer ring flange 114. The upper face seals 15 and 16 and the lower face seals 26 and 27 are continuous without splices and may be each machined from a single slab of seal material. As illustrated, the face seals have spring fingers 16A and 16B for example, of face seal 16. Such face seals are known generally in the art for applications other than for high pressure product swivels. Preferably the face seals are fabricated of synthetic fluorine containing resins known by the trademark Teflon. A leak detection channel 50 is provided extending laterally through the outer ring annular plate 42 to a position 120 between upper face seals 15 and 16. Likewise, a leak detection channel 52 is provided in the wall of primary outer ring 21 and extends to a position 122 between the lower face seals 26 and 27. A leak detection valve 51 is connected to the leak detection channel 50. Similarly, leak detection valve 53 is connected to leak detection channel 52. The leak detection channel 50 in corporation with leak detection valve 51 provides a means to determine externally from the swivel whether or not leakage is occurring past the upper face seal 15. Likewise, leak detection channel 52 in corporation with leak detection valve 53 provides a means to determine if pressurized fluid is leaking past lower face seal 26. The swivel further includes downwardly facing annular grooves 124 and 126 in the bottom of the flange 114 of the primary outer ring 21. Face seals 55 and 54 sealingly engage an upwardly facing surface of inner ring annular plate 44. Face seal 124 serves to prevent debris and dirt from entering the toroidally shaped raceway chamber 40. Face seal 126 serves as a grease retaining seal maintaining lubrication within the ball bearing raceway chamber 40. Figure 3 illustrates the embodiment of the swivel in which the inner ring structure 10 is held stationary with respect to the rotatable outer ring structure 20. In this regard, stacked swivels are shown in dashed outline stacked above and below the swivel cross-section shown in detail in Figure 3. Threaded studs and nuts shown generally at 60 secure lower and upper flanges of stacked swivels so that the inner ring structures 10 are held together and are stationary with respect to each other. The outer ring structures 20 may be individually rotated with respect to the stationary inner ring structures. Auxiliary lower plates 44A and upper plate 44B fastened to ring 20 and ring 10 respectively provide means for stacking the swivels on one another. Auxiliary lower plate 44A rotates about plate 42 of the swivel below. Auxiliary plate 44B is secured to the inner ring of the swivel above. Figure 6 shows an alternative embodiment of the swivel structure and assembly from that of Figure 3 and illustrates the embodiment of the invention where the outer ring structures 20' are stationary with respect to the rotatable inner ring structure 10'. In this instance in a similar fashion, when the outer ring structure 20' is assembled about the inner ring structure 10' a toroidally shaped conduit chamber 30' is defined as well as a toroidally shaped bearing raceway 40* in which bearing balls are disposed for axially and radially supporting the outer and inner ring structures with respect to one another. In a similar fashion illustrated in Figure 3, upper face seals 15' and 16' sealingly engage inner ring annular plate 13 while face seals 26' and 27' sealingly engage an upwardly facing annular surface of a lower flange 114' of the primary inner ring 11'. An outer ring annular plate 6 is disposed beneath the primary outer ring 20' and serves to engage face seals 124' and 126'. Face seal 126' serves a debris excluding seal while face seal 124' serves as a grease retaining seal. The outer rings 21' are connected to outer rings of stacked swivels above and below it by means of threaded studs and bolts 60'. Description of a second embodiment of the invention (Figures 7-11) A swivel assembly S embodying the present invention is shown in detail in Figures 7 - 11. An alternative embodiment, swivel assembly S* , is shown in Figure 11.. The swivel assembly S is adapted for rotating about a vertical axis 210 as shown in Figures 7 and 8. The swivel assembly S comprises two or more coaxially stacked swivels which are essentially identical to one another in structure but are of different sizes. Figure 7 shows in a plan view of coaxially stacked swivels 212, 212A and 212B and respective external connectors 214, 214A and 214B which may be connected to external conduits for connecting to conduit chambers 216, 216A and 216B, respectively, of the stacked swivels, as shown in Figure 8. As shown in Figure 8, internal conduit connectors 218, 218A and 218B connected to vertically disposed conduits 220, 220A and 220B, respectively, and conduit chambers 216, 216A and 216B, respectively. Although three swivels are illustrated in the preferred embodiment of the assembly, more or less swivels may of course be stacked in alternative embodiments. As shown in Figure 9, an inner ring 222 includes an annular primary inner ring 224, a first annular lower sealing portion 226, a second annular lower sealing portion 228, a bottom flange portion 230 and a first upper sealing portion 232. The first lower sealing portion 226 and the second lower sealing portion 228 are secured below the primary inner ring 224 by one or more bolts 234 threadedly received into threaded bores in the primary inner ring 224. The bottom flange portion 230 overlapping portion 228, is secured below the primary inner ring 224 by means of one or more bolts 236 threadedly received into a threaded bore in the primary inner ring 224. The first upper sealing portion 232 is secured above the primary inner ring 224 by means of one or more bolts 238 threadedly received into a threaded bore of the primary inner ring 224. As shown in Figures 8 and 9, the first upper sealing portion 232B of the inner ring 222B is secured to the bottom flange portion 230 of inner ring 222 by one or more bolts 240. As shown in Figure 8, inner ring 222A is bolted to inner ring 222 by bolts 240A similar to the connection as described between inner ring 222 and inner ring 222B. Inner ring 222B is bolted to stationary base 242, as shown in Figure 8, by bolts 240B securing the inner rings 222, 222A and 222B together in a stationary fashion. Turning once again to Figure 9, static high pressure 0-rings 244 are provided in annular grooves of the inner ring 222 in order to provide sealing between surfaces opposing the inner ring 222. In the same fashion, static high pressure O-rings are provided in an inner ring 222A and inner ring 222B. The inner ring 222 has a substantially outwardly facing surface 246 comprising the surfaces of the primary inner ring 224, the first upper sealing portion 232, the first lower sealing portion 226 and the second lower sealing portion 228. The swivel body further includes an outer ring 248 comprising an annular primary outer ring 250, an annular lower sealing portion 5 252, an annular bottom flange portion 254, an annular first upper sealing portion 256 and an annular second upper sealing portion 258. In the preferred embodiment, the first upper sealing portion 256 and the second upper sealing portion 258 are secured above the primary outer ring 250 by means of one or more bolts 260 threadedly received into one or more threaded bores of the primary outer ring 250. The lower sealing portion 252 is secured below the primary outer ring 250 by means of one or more bolts 262 threadedly received into a threaded bore of primary outer ring 250. The bottom flange portion 254 is secured below the lower sealing portion 252 by means of one or more bolts 264 threadedly received into a threaded bore in the portion 252. Static high pressure O-rings 244 are disposed in annular grooves in the outer ring 248 for providing sealing between opposing surfaces in the outer ring 248 similarly to the sealing of the O-rings 244 in the inner ring 222. The outer ring 248 has a substantially inwardly facing surface 266 comprising the surfaces of the primary outer ring 250, the first upper sealing portion 256, the second upper sealing portion 258 and the lower sealing portion 252. When the outer ring 248 is assemblied concentrically about the inner ring 222, the inwardly facing concave conduit surface 266 of the primary outer ring 250 comes into registration with the outwardly facing concave conduit surface 246 of the primary inner ring 224 defining a toroidally shaped conduit chamber 216 and forms a gap above and below the conduit chamber 216. The gap is defined by the substantially outwardly facing surface 246 of the inner ring 222 and the substantially inwardly facing surface 266 of the outer ring 248. Disposed above the conduit chamber 216 in a first annular groove 268 of the primary inner ring 224, a primary upper face seal 270 is disposed for sealingly engaging a downwardly facing sealing surface 272 of the first upper sealing portion 256 of the outer ring 248. A primary lower face seal 274 is disposed below the conduit chamber 216 in a second annular groove 276 in the primary outer ring 250 for sealingly engaging an upwardly facing sealing surface 278 of the first lower sealing portion 226 of the inner ring 222. The primary upper seal 270 is offset a greater radial distance Δ from the vertical axis 210, as shown in Figure 8, than the primary lower seal 274. Pressurization of the conduit chamber 216 in cooperation with the offset of the primary seals 270 and 274 creates axial loading of the swivel S to urge the rotatable outer ring 248 downwardly with respect to the stationary inner ring 222. Such downward urging of the outer ring 248 tends to decrease the vertical distance between the sealing surface 272 and annular groove 268 for seal 270 and the vertical distance between sealing surface 278 and annular groove 276 for seal 274 operably aiding the sealing of the conduit chamber 216. The offset of primary seals 270 and 276 provides a resultant force of such magnitude to create a uni-directional force on the swivel S operably aiding continuously in the sealing of the conduit chamber 216. In other words, the uni-directional downward force on the outer ring 250 with respect to inner ring 224 of the preferred embodiment is of a magnitude such that when upward external forces act on the swivel, the resultant force is uni-directionally downwardly. The swivel S further comprises a secondary upper face seal 280 disposed above the conduit chamber 216 in vertical alignment with the primary upper face seal 270 in a third annular groove 282 of upper sealing portion 232 of the inner ring 222 for sealingly engaging a sealing surface 284 on the second upper sealing portion 258 of the rotatable outer ring 248. The secondary upper seal 280 is in communication with the primary upper seal 270 by the gap defined by the substantially outwardly facing surface 246 of the inner ring 222 and the substantially inwardly facing surface 266 of the outer ring 248. Also a secondary lower face seal 286 is disposed below the conduit chamber 216 in vertical alignment with the primary lower face seal 274 in a fourth annular groove 288 in the lower sealing portion 252 of the outer ring 248 for sealingly engaging a sealing surface 290 of the second lower sealing portion 228 of the inner ring 222. The secondary lower face seal 286 is in communication with the primary lower face seal 274 through the gap defined by the substantially outwardly facing surface 246 of the inner ring 222 and the substantially inwardly facing surface 266 of the outer ring 248. if the primary upper seal 270 fails to retain pressure in the conduit chamber 216, the secondary upper seal 280 maintains the pressure which results in the thrust or axial loading of the inner and outer rings, as if the primary seal 270 were still in sealing engagement. This is achieved by the vertical alignment of the secondary upper seal 280 relative to the primary upper seal 270. Because the thrust loading has been maintained, the vertical distance between the surfaces 246 and 266 does not change, therefore providing another advantageous feature of the invention. Similarly upon a failure of the primary lower seal 274, the vertically aligned secondary lower seal 286 maintains the axial loading of the swivel S thereby maintaining the vertical distance between the surfaces 246 and 266. A ball bearing assembly generally designated as 292, is disposed between the inner ring 222 and the outer ring 248 and having a plurality of identical bearing balls 294. As shown in Figures 9 and 10, the assembly 292 rotatingly supports the inner ring 222 axially and radially with respect to the outer ring 248. Figures 9 and 10 illustrate the plurality of bearing balls 294 in a toroidally shaped raceway chamber 296 preferably spaced from one another by means of spacers 298. The bearing assembly 292 further comprises a first annular bearing race element 2100 secured to the inner ring 222 between the second lower sealing portion 228 and the bottom flange portion 230. The bearing race element 2100 has an outwardly facing concave bearing surface 296 and two outwardly facing annular contacts 2102 and 2106. A second annular bearing race element 2108 is positioned adjacent the lower sealing portion " 252 of the outer ring 248. A third annular bearing race element 2114 is positioned below the second annular bearing race element 2108 and adjacent the lower sealing portion 252 of the outer ring 248. The second race element 2108 and the third race element 2114 may be formed of one integral race element similar to element 2100. The second element 2108 and the third element 2114 present an inwardly facing concave bearing surface 2110. The surface 2110 of element 2114 has an annular inwardly facing contact 2116 thereon and the surface 2110 of the second element 2108 has an annular inwardly facing contact 2112 thereon. The second element 2108 and the third element 2114 are secured below and adjacent lower sealing portion 252 by bolt 2118 threadedly received in a threaded bore in portion 252. When the outer ring 248 and inner ring 222 are assembled together with the first element 2100, the second element 2108 and the third element 2114 assembled therebetween, the bearing surfaces 2110 and 296 form a toroidally shaped raceway chamber 297, as discussed above, having four contacts 2102, 2106, 2112 and 2116 thereon. The four point contact ball bearing assembly 292 aids in transferring the uni-directional axial loading created upon pressurization of the conduit chamber 216 in cooperation with the offset of the primary seal means 270 and 274 while tolerating radial forces and deflections. The radial deflections include deflections resulting from the pressurization of the conduit chamber 216. The thrust or axial loading of the swivel S urges the rotatable outer ring 248 toward the stationary inner ring 222 for uni-directional loading on the bearing balls 294 to assure concentricity of the bearing balls 294 between the bearing race elements 2100, 2108, and 2114 and therefore, between the inner ring 222 and the outer ring 248. Additionally, the axial loading provides wear compensation for the bearing assembly means 292. The axial loading created by the offset of the seals is of such a magnitude that the force resisted by the bearing balls 294 is uni-directional, therefore producing more favorable loading for the bearing assembly 292. In other words, the rotatable outer ring 248, of the preferred embodiment, will exert a downward load on the elements 2108 and 2114 and in turn on balls 294. Such downward load is greater than expected external upward loads of the ring 248 with respect to outer ring 222. Element 2100 and inner ring 222 are stationary in the preferred embodiment. The bearing balls 294 provide an equal and opposite uni-directional force in reaction to the downward force or load of the rotatable outer ring 248. This upwardly directed force of the bearing balls is uni-directional in that it is in reaction to the sum of downward forces of ring 248 with respect to ring 222 due to pressurization and possible external upward forces on ring 248 with respect to ring 222. A leak detection channel 2120 is provided extending laterally through the first upper sealing portion 256 of the outer ring 248 to an opening between the primary upper seal 270 and the secondary upper seal 280. Likewise, a leak detection channel 2122 is provided in the primary outer ring 250 and extends to an opening between the primary lower seal 274 and the secondary lower seal 286. A leak detection valve 2124 is connected to the leak detection channel 2120. Similarly, leak detection valve 2126 is connected to leak detection channel 2122. The leak detection channel 2120 in cooperation with leak detection valve 2124 provides a means to determine externally from the swivel S whether or not leakage is occurring past the primary upper seal 270. Likewise, leak detection channel 2122 in cooperation with leak detection valve 2126 provides a means to determine if pressurized fluid is leaking past primary lower seal 274. It is to be understood that in the preferred embodiment face or lip seals are used for seals 270, 274, 280, and 286 but that other types of seals may be used advantageously in this invention. Each swivel section (except the lower most section as illustrated in Figure 8) further includes two downwardly facing annular grooves 2128 and 2130 in the bottom flange portion 254 of the outer ring 248. Flange 254 is secured to lower sealing portion 252 by means of bolt 264. Excluder seals 2132 and 2134 sealingly engage an upwardly facing surface 2136 of the swivel section adjacent below (see Figure 1) . Excluder seals 2128 and 2134 prevent debris and dirt from entering the toroidally shaped bearing raceway chamber. Excluder seal 2128 also serves as a grease retainer maintaining lubrication within the ball bearing raceway chamber 296. Figure 7 also illustrates the lower most swivel section has an "L" shaped bottom flange portion 254* which has two excluder seals for sealingly engaging a downwardly facing surface of the bottom flange portion 230'. Closing ring 213 bolted to the topmost swivel section has two seals 255 for sealing the top outer rotatable ring with respect to the top inner stationary ring. Figure 11 shows an alternative embodiment of a swivel assembly S' from that of Figures 8 and 9, where an outer ring 248' is fixed to a stationary pedestal 242' while the inner ring 222' is rotatable. When the outer ring 248' is assembled with the inner ring 222' a toroidally shaped conduit chamber 216' is defined. A toroidal bearing raceway chamber 296*, in which bearing balls 294' are disposed for axially and radially supporting the outer and inner rings with respect to one another. The chamber 296' is formed by elements 2108', 2100' and 2114'. In similar fashion to that illustrated in Figure 9, primary upper seal 270* sealingly engages stationary outer ring 248' rotatable inner with rotatable inner ring 222' and primary lower seal 274* sealingly engages the inner ring 222' with the outer ring 248' providing sealing of conduit chamber 216' . Secondary upper seal 284' vertically aligned above and in communication with primary upper seal 270' and secondary lower seal 286' vertically aligned below and in communication with the primary lower seal 274' are positioned so that upon failure of the respective primary seal, the respective secondary seal will maintain the axial loading initially created by the radial offset of primary upper seal 270* with primary lower seal 274'. In the alternative embodiment, inner ring 222' provides a thrust load upwardly to decrease the vertical distance between the sealing surfaces operably aiding in the sealing of the conduit 216'. Simultaneously, the upward movement of the inner ring 222' provides a uni-directional thrust load on the bearing assembly means 292' upon pressurization of the conduit chamber 216' to assure concentricity of the bearing balls 294' between the inner ring 222' and the outer ring 248' and to provide wear compensation for the bearing assembly means 292'. Outer ring 248' may be connected to outer rings stacked above and below it by means of threaded bores and bolts. Various modifications and alterations in the described structures will be apparent to those skilled in the art of the foregoing description which does not depart from the spirit of the invention. For this reason, these changes are desired to be included in the appended claims. The appended claims recite only the limitation to the present invention in the descriptive manner which is employed for setting forth the embodiments and is to be interpreted as illustrative and not limitative.

Claims: WHAT IS CLAIMED IS: 1. A product swivel adapted for rotating about a substantially vertical axis, and including: a swivel body having, an inner ring having a substantially outwardly facing surface; an outer ring having a substantially inwardly facing surface; said surfaces, when said inner ring is in registration with said outer ring, forming a toroidally shaped conduit chamber; one ring being stationary and the other ring rotatable about the stationary ring; and means for rotatingly supporting one ring with respect to the other ring; characterized in that, a primary upper face seal is disposed above the conduit chamber in a first annular groove in one ring for sealingly engaging a sealing surface of the other ring; and a primary lower face seal is disposed below the conduit chamber in a second annular groove in one ring for sealingly engaging a sealing surface of the other ring. 2. A product swivel adapted for rotating about a substantially vertical axis, including: a swivel body having, an inner ring having a substantially outwardly facing surface; an outer ring having a substantially inwardly facing surface; said surfaces, when said inner ring is in registration with said outer ring, forming a toroidally shaped conduit chamber; one ring being stationary and the other ring rotatable about the stationary ring; means for rotatingly supporting one ring with respect to the other ring; characterized in that, a primary upper seal means is disposed above the conduit chamber in a first annular groove in one ring for sealingly engaging a sealing surface of the other ring; a primary lower seal means is disposed below the conduit chamber in a second annular groove in one ring for sealingly engaging a sealing surface of the other ring; and one primary seal means is offset a greater distance from the vertical axis of the swivel than the other primary seal means; whereby pressurization of the conduit chamber in cooperation with the offset of the primary seal means creates axial loading of said rings to urge the rotatable ring toward the stationary ring for decreasing vertical distance between the sealing surfaces operably aiding in the sealing of the conduit chamber. 3. The swivel of claim 2 wherein said inner ring is stationary and said outer ring is rotatable about said inner ring. 4. The swivel of claim 2 wherein said supporting means comprises a four point contact ball bearing assembly positioned between a stationary inner ring and a rotatable outer ring, said ball bearing assembly including a plurality of bearing balls. 5. The swivel of claim 2 further comprising a secondary upper seal means disposed above the conduit chamber in vertical alignment with said primary upper seals means in a third annular groove in one ring for sealingly engaging a sealing surface of the other ring, said secondary upper seal means being in communication with said primary upper seal means; a secondary lower seal means disposed below the conduit chamber in vertical alignment with said primary lower seal means in a fourth annular groove in one ring for sealingly engaging a sealing surface of the other ring, said secondary lower seal means being in communication with said primary lower seal means; whereby if said primary upper or lower seal means were to fail to retain pressure in the conduit chamber, said respective secondary seal means would maintain the axial loading of the inner and outer rings thereby maintaining the tendency to decrease the vertical distance between the sealing surfaces. 6. The swivel of claim 5 wherein said primary and secondary seal means are face seals. 7. The swivel of claim 5 wherein said first and third annular grooves are disposed in a stationary inner ring, and said second and fourth annular grooves are disposed in a rotatable outer ring. 1 8. The swivel of claim 2 wherein said rotating 2 means is a ball bearing assembly positioned between said 3 inner ring and said outer ring having a plurality of 4 bearing balls for rotatingly supporting one ring with 5 respect to the other ring. 1 9. The swivel of claim 4 wherein said bearing 2 assembly further comprises 3 a first annular bearing race element secured to 4 said inner ring having an outwardly facing concave bearing 5 surface, said bearing surface having two annular outwardly 6 facing annular contacts thereon, 7 a second annular bearing race element secured to 8 said outer ring having an inwardly facing concave bearing 9 surface, said bearing surface having an annular inwardly 0 facing contact thereon, 1 a third annular bearing race element secured to 12 said outer ring, said third bearing race element 13 presenting an inwardly facing concave bearing surface, 14 said third bearing surface having an annular inwardly 15 facing contact thereon, 1.6 a plurality of bearing balls disposed in said 17 bearing chamber rotatingly supporting one ring with 18 respect to the other ring, whereby 19 when said outer and inner rings are assembled 20 with said first, second and third elements, said bearing 21 surfaces form a toroidally shaped bearing chamber having 22 four contacts, and 23 said four point contact ball bearing assembly 24 operably maintains uni-directional axial loading under 25 conditions of external axial loading while simultaneously 26 while tolerating radial deflections that occur as a result 27 of the pressurization of the conduit chamber. 10. .A rotatable swivel comprising an inner ring structure having an outwardly facing concave conduit surface and an outwardly facing concave bearing raceway, an outer ring structure having an inwardly facing concave conduit surface and an inwardly facing concave bearing raceway, said outer and inner ring structures assembled with their respective conduit surfaces in registration and with their respective bearing raceways in registration forming a toroidally shaped conduit chamber and a toroidally shaped bearing raceway chamber, a plurality of bearing balls disposed in said bearing raceway chamber rotatingly supporting one ring structure with respect to the other, an upper and a lower face seal disposed in an upper and a lower annular groove in one of the ring structures disposed above and below its conduit surface sealingly engaging upward and downwardly facing annular surfaces above and below the conduit surface of the other of the ring structures, means for connecting a tubular conduit to said toroidally shaped conduit chamber from the interior of said inner ring structure, and means for connecting a tubular conduit to said toroidally shaped conduit chamber from the exterior of said outer ring structure. 11. The swivel of claim 10 wherein said inner ring structure is stationary and said outer ring structure is rotatable about said inner ring structure. 12. The swivel of claim 10 wherein said outer ring structure is stationary and said inner ring is rotatable within said outer ring structure. 13. The swivel of claim 10 further comprising a second upper and a second lower face seal disposed in a second upper and a second lower annular groove in one of said ring structures, said second upper and said second lower annular grooves being coaxial with each other, said second upper and said second lower face seals also sealingly engaging said upper and lower annular surfaces above and below the conduit surface of the other of the ring structures, an upper leak detection channel extending through said outer ring structure to a position through the annular surface of the outer ring facing said first and second upper face seals and between said first and second upper face seals, an upper leak detection valve connected exterior of said outer ring structure to said upper leak detection channel, a lower leak detection channel extending through said outer ring structure to a position through the annular surface of the outer ring structure facing said first and second lower face seals and between said first and second lower face seal, and a lower leak detection valve connected exterior of said outer ring structure to said lower leak detection channel. 14. The swivel of claim 11 wherein said inner ring structure comprises a primary inner ring in which said outwardly facing concave inner conduit surface and said outwardly facing concave bearing surface are formed, and an inner ring annular plate secured to the bottom of said primary inner ring, said inner ring annular plate overlapping a portion of said outer ring structure. 15. The swivel of claim 14 wherein said outer ring structure comprises a primary outer ring in which said inwardly facing concave outer conduit surface and said inwardly facing concave bearing surface are formed, and an outer ring annular plate secured to the top of said primary outer ring, said outer ring annular plate overlapping a portion of said primary inner ring. 16. The swivel of claim 15 further comprising seal means disposed in a downwardly facing annular groove means in said primary outer ring for sealingly engaging said inner ring annular plate. 17. The swivel of claim 12 wherein said groove means comprises first and second grooves, and said seal means includes a debris excluding face seal and a grease retaining face seal disposed in said first and second grooves. 18. The swivel of claim 12 wherein said outer ring structure comprises a primary outer ring in which said inwardly facing concave inner conduit surface and said inwardly facing concave bearing surface are formed, and an outer ring annular plate secured to the bottom of said primary outer ring, said outer ring annular plate overlapping a portion of said inner ring structure. 19. - The swivel of claim 18 wherein said inner ring structure comprises a primary inner ring in which said outwardly facing concave outer conduit surface and said outwardly facing concave bearing surface are formed, and an inner ring annular plate secured to the top of said primary inner ring, said inner ring annular plate overlapping a portion of said primary outer ring. 20. The swivel of claim 19 further comprising seal means disposed in a downwardly facing annular groove means in said primary inner ring for sealingly engaging said outer ring annular plate. 21. The swivel of claim 20 wherein said groove means comprises first and second grooves, and said seal means includes a debris excluding face seal and a grease retaining face seal disposed in said first and second grooves. 22. A rotatable swivel assembly for a plurality of conduits comprising, a rotatable swivel associated with each conduit having an inner ring structure having an outwardly facing concave conduit surface and an outwardly facing concave bearing raceway, an outer ring structure having an inwardly facing concave conduit surface and an inwardly facing concave bearing raceway, said outer and inner ring structures assembled with their respective conduit surfaces in registration and with their respective bearing raceways in registration forming a toroidally shaped conduit chamber and a toroidally shaped "bearing raceway chamber, " a plurality of bearing balls disposed in said bearing raceway chamber rotatingly supporting one ring structure with respect to the other, an upper and a lower face seal disposed in an upper and a lower annular groove in one of the ring structures disposed above and below its conduit surface sealingly engaging upward and downwardly facing annular surfaces above and below the conduit surface of the other ring structures, means for connecting a tubular conduit to said toroidally shaped conduit chamber from the interior of said inner ring structure, means for connecting a tubular conduit to said toroidally shaped conduit chamber from the exterior of said outer ring structure, said rotatable swivels being mounted coaxially together. 23. The swivel assembly of claim 22 wherein said inner rings of each rotatable swivel are secured together and are stationary and the outer ring of each rotatable swivel is independently rotatable with respect to the stationary inner rings. 24. The swivel assembly of claim 22 wherein said outer rings of each rotatable swivel are secured together and are stationary and the inner ring of each rotatable swivel is independently rotatable with respect to the stationary outer rings. 25. The swivel assembly of claim 22 wherein each of said swivels further comprises a second upper and a second lower face seal disposed in a second upper and a second lower annular groove in one of said ring structures, said second upper and said second lower annular grooves being concentric with each other, said second upper and said second lower face seals also sealingly engaging said upper and lower annular surfaces above and below the conduit surface of the other of the ring structures, an upper leak detection channel extending through said outer ring structure to a position through the annular surface of the outer ring facing said first and second upper face seals and between said first and second upper face seals, an upper leak detection valve connected exterior of said outer ring structure to said upper leak detection channel, a lower leak detection channel extending through said outer ring structure to a position through the annular surface of the outer ring structure facing said first and second lower face seals and between said first and second lower face seal, and a lower leak detection valve connected exterior of said outer ring structure to said lower leak detection channel.

Inventors: ETHERIDGE CHARLES O, PEDERSEN KRISTEN I, ETHERIDGE, CHARLES, O., PEDERSEN, KRISTEN, I.
Applicants: SOFEC LTD, SOFEC, LTD.
Application year: 1985
Main classification: F16L39
IPC codes: F16L39