Abstract:
A mechanical joint assembly for a steel catenary riser (SCR) is disclosed. The lower section of the mechanical joint assembly is comprised of steel or alternate high strength components, rather than elastomers to absorb the high loads and increase life of the unit. The lower mechanical joint assembly provides for reduction of bending moments and resulting fatigue stresses at the SCR top by removing resistance to movement in all angular directions, providing increased lateral and in-plane angles to provide increased construction tolerances for the pipeline approach corridor. Pipeline approach angle increase is accommodated by providing dual orthogonal trunnions in addition to an axial swivel. The upper mechanical joint assembly, acting without riser tension loads, allows for the use of either flexible high-pressure pipe or swivel arrangements to accommodate angular flexure before the rigid deck piping. As a system, the mechanical joint assembly provides for upstream and downstream valving for safety and maintenance without decreasing the fatigue life of SCR&#39;s.

Description:
The present application is a § 371 of PCT/US00/10938 filed Apr. 20, 2000, which claims the benefit of U.S. Provisional Patent Application Serial No. 60/130,579 filed Apr. 21, 1999. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an SCR Top Connector Assembly for the articulating connection of a conduit, such as an offshore flowline or pipeline used in the petroleum industry, to a foundation subjected to differential motions of the conduit and structure. More particularly, this invention relates to a subsea pipeline with significant unsupported length, termed a “steel catenary riser” (SCR), which would utilize the SCR Top Connector Assembly to connect the SCR to a fixed or floating structure, including several parts that work together to provide fluid communication from the SCR to the platform piping system, to allow dynamic and relative motions of the SCR and the structure. 
     BACKGROUND 
     In the offshore oil and gas sector, recent developments in deeper water depths have demonstrated the need for improved solutions for the economic attachment of a flowline, or pipeline, to a structure, whether fixed or floating. Initial development utilized flexible pipe from the seabed to the floating platform; however, many operators have begun to favor the potential safety and savings offered by the use of steel catenary riser (SCR) configurations, wherein the pipeline is suspended for some distance off the seabed and connected to the structure, or floating platform. 
     The prior art assembly of SCR flexible joints greatly limit the approach corridors of flowlines due to the degree of dynamic angular movement that can be accommodated. Manufacturing and installation tolerances offshore in deep water leave little dynamic allowance in the prior art once the static offset of floating vessels are included. The angular limits of the prior art assembly pose difficulties for the design and construction engineers of offshore pipelines to ensure that the installation tolerances, fabrication tolerances, and operational conditions will not exceed the limits of the flexible joint and potentially lead to failure of the SCR. If the limits of the flexible joint are exceeded, all flexibility is lost and the SCR is exposed to very large bending moments resulting in dramatically and unpredictably shortened fatigue life, thereby leading to possible failure of the SCR below the flexible joint near the platform. Failure of an SCR in petroleum gas service or an SCR connector component without a viable safety shutdown valve would pose a very high risk of fire and loss of life as the gas in the pipeline (extending frequently 60 miles from the host platform) would be released at the base of the manned structure which contains sources of ignition. Although a gas leak may be more hazardous, failure of a SCR in petroleum liquid service would lead to a fairly large oil spill in open water since much of the oil in the pipeline would be siphoned out of the pipeline by the low pressure wake of the SCR falling to the seabed. Additionally, the oil would be expelled by expanding gases within the oil, as well as normal molecular diffusion. 
     It is an object of this invention to have features which greatly increase safety over present art by eliminating a risk of gas leakage at an offshore platform by allowing the use of normal and proven safety valves. This reduces the potential for fire, and eliminates potential oil leakage into seawater when used with oil lines. Current SCR flexible joints utilize elastomeric and metal laminations, which provide pressure containment. The same elastomeric materials serving as seals must absorb the full SCR vertical reactions while repeatedly being deflected under high vertical loads. The vertical loads can reach 100 tons due to the suspended riser weight, motions of the SCR subjected to continual environmental loading, and relative platform movements. Under cyclic loading, the elastomeric elements containing the fluids, under various conditions of temperature and pressure, may likely become a path for gas or oil leakage which would result in oil contamination of the surrounding seawater or leakage of gas at the base of the offshore platform. This would cause a gas plume and a risk of sinking the floating vessel or risk of fire to the structure overhead. If a semi-submersible were to sink at a corner, it would likely lose tendons and capsize. The industry considers systems with moving elastomeric parts to have maintenance or replacement requirements at some point in time and therefore leakage considerations are valid considerations with elastomers subjected to high cyclic compressive and shear loads acting as the sole safety barrier under pressure. Although platform piping valves can be closed on the platform side in the present art flexible joint, it is presently not considered possible to provide a safety block valve below the prior art flexible connector due to the high axial loads and high bending moments at the top of the SCR. These loads would be extremely taxing to the integrity of the valve and would not be a reliable safety feature. 
     A lower block valve, though not practical with present (prior art) equipment, would prevent elastomer leakage from causing the entire pipeline or SCR from back-flowing gas into the platform creating an uncontrollable hazard to life of platform personnel. In fact, the bending moments and related stresses are so high in the top section of the SCR, below the flexible connector, that specially fabricated tapered ‘stress’ joints are required to minimize the stress concentration factors in these installations. The stress intensification values are primarily due to the high bending moments resulting from the flexural high stiffness of the prior art SCR Top Connector to which the SCR is connected. The high bending moments are primarily a result of the high rotational stiffness of the laminated elastomeric elements being deflected laterally in shear while under high compression loads. 
     The replacement, or leakage failure correction, of the elastomers within the prior art assemblies is essentially impossible by the platform crew or by means that can be flown offshore to the site, or otherwise be effected in a short duration to reduce a prolonged platform hazard. It is a further object of this invention to eliminate elastomers from the multiple role duties of high load absorption, flexural cycling, and high-pressure containment of petroleum liquids and gases. 
     To correct fluid leakage of the prior art assemblies, it is necessary to remove the SCR and its associated pipeline from service by shutting in the platform and purging the section in order to provide a safe repair environment. It is also necessary to employ the use of costly offshore deepwater service equipment with sufficient lifting capacity to remove and re-attach a new assembly since the elements are not able to be replaced by the platform crew in a timely fashion in the prior art assemblies. 
     Prior art is described in part by the following patents: 
     U.S. Pat. No. 3,692,337 Flexible Coupling, Mischel; Howard T., San Diego, Calif. Sep. 19, 1972. 
     U.S. Pat. No. 3,952,526 Flexible Supportive Joint for Subsea Riser Flotation, Watkins; Bruce J., Rancho Palos Verdes, Calif. Apr. 27, 1976. 
     U.S. Pat. No. 5,791,695 Flexible Joint for Facilitating Bending of Tubular, Snider; David A., Hurst, Tex. Aug. 11, 1998. 
     U.S. Pat. No. 5,615,977 Flexible/Rigid Riser System, Moses; Charles J., Alvarado, Tex. Apr. 1, 1997. 
     U.S. Pat. No. 5,628,586 Elastomeric Riser Tensioner System, Arlt, III; Edward J., Arlington, Tex. May 13, 1997. 
     U.S. Pat. No. 4,105,266 Laminated Bearing with Plural Modulus Layer, Finney August 1978. 
     U.S. Pat. No. 4,759,662 TLP Marine Riser Tensioner, Peppel July 1988 
     It is a further object of the present invention to minimize the potential for fire risk and loss of life; oil spills, uncontrolled and extended leakage, high maintenance costs and pipeline/platform downtime duration. 
     It is another object of the present invention to provide a system with automatic shut-in safety block valve capability on each side of any non-metallic elements which may be subject to leakage. 
     It is a further object of the present invention to increase the allowable dynamic displacement angles to reduce the chance of bottoming out and causing premature SCR fatigue failure. 
     It is an additional object of the present invention to minimize the high stress levels which occur at the base of the prior art flex joint to eliminate the needs for specially fabricated tapered stress joints and provide extended fatigue service life of the SCR by reducing the top section fatigue moments. 
     It is yet another object of this invention to isolate the high loads due to the suspended risers from acting on flexible or elastomeric elements. 
     It is also an object of this invention to use load isolated swivels which convert pendular motions to rotary motion and allow system use when pressure and diameter restrictions prevent the safe use of flexible pipe. 
     It is also an object of the present invention to provide external means of dynamic high-frequency damping. 
     It is also an additional object of the present invention to allow essentially unlimited pipeline approach angle to the pre-installed attachment of steel catenary risers on platforms. 
     SUMMARY OF THE INVENTION 
     The present invention includes a mechanical joint assembly in which the load-absorbing base is composed of steel or alternate high strength components, providing a higher level of safety and spill prevention than is offered by prior art. The present invention further provides for the use of valving upstream and downstream of the only non-metallic maintenance item(s) without decreasing fatigue life. The present invention also reduces bending moments and resulting fatigue stresses at the SCR top by removing resistance to movement in all angular directions, with increased lateral angles to provide increased construction tolerances for the pipeline approach corridor. The present invention allows the use of increased angles of in-plane dynamic motion with elimination of large vertical SCR supported weight reactions from acting on elastomeric components. 
     The safety requirement, of preventing uncontrolled back feeding of the pipeline or SCR and thus averting fire and loss of life, is achieved by absorbing all reactions of the SCR prior to subjecting elastomers to pressure containment requirements. By isolating the high loads, downstream and upstream, remote or manual-operated, shut-off valves can be provided to fully isolate any leak within a short section without sacrifice of the system fatigue life. Preventing any block valve from absorbing the high SCR environmental reactions minimizes the chance of valve leakage or malfunction. 
     The long service outage and high maintenance costs are eliminated by providing the above noted block valves, limiting possible maintenance items to simple diver replacement components without the need for any offshore service vessels. 
     The present invention therefore separates the design requirements of high load control and that of allowable motion and flexure. The separation point may involve several means, which are described herein along with more specific details of the preferred embodiments. 
     In the preferred embodiment, increasing the allowance for the pipeline approach angles is accommodated in the lower base by providing dual orthogonal trunnions in addition to an axial swivel to compensate for installation rotational misalignment. A comparison can be made between the present invention and that of the prior art: when the normal construction tolerances are subtracted from the systems three to four times greater allowable dynamic angles are achieved by the proposed system than when compared to the prior art. This increase greatly reduces the chance of exceeding the flexure rates associates with high stress levels when pressure limits are exceeded. 
     Doubling the load carrying capacity is achieved in the present invention by providing a robust design with heavy cross sections and gradual section transitions in the base to minimize stress levels and, stress intensification factors, thereby providing improved fatigue resistance and load handling. 
     Elimination of specially prepared tapered stress joints is achieved by the omission of elements which resist the angular motion of the SCR by high-bending moments, as is in the case of the prior art assembly, and the substitution of either low friction, higher-paired pivot systems, bearings, bushings, low-friction coatings, or ultra smooth surfaces. Systems above the base are provided to absorb the angular rotation without tensile loading and with low rotational stiffness. 
     The Top Connector Assembly may include an optional damping system to curtail high frequency motion. The damping system is subjected to the high SCR reactions and may be maintained, or replaced, without shut-in of the system by a diver and small platform-mounted equipment. Because the fluid medium for damping may be seawater, or other benign fluids, failure of the system in any way does not constitute an emergency. The maintenance could include only the installation of a new damper. 
     The benefits afforded by the objects of this invention, as defined, clearly address safety concerns of the prior art devices and increase the operational limits and reliability by allowing greater SCR motions with less constraint while eliminating present concerns of installation tolerances. These features in turn allow for measurably larger SCR storm-induced dynamic movement angles with safety. 
     The assembly of the preferred embodiment of the present invention is composed of several principal parts which make up the load absorbing base and the flexible assembly: 
     (A) A pressure carrying body which is attached to the uppermost portion of the SCR riser. This component incorporates a pair of male trunnions, which are structurally connected to the pressure containment body and located at opposite sides of the pressure-carrying body, which is an extension of the SCR pipe. The trunnions include features of higher paired rolling motion that provide essentially frictionless motion. Alternate arrangements when friction is less significant due to light SCR reactions include bearings, or lubricated bushings for the trunnions. Rotary motion of the pressure containment body is provided by interior coatings or other means to prevent locked-in torsional stresses during installation; 
     (B) A trunnion adapter, which consists of a female trunnion on the interior surface, which mates with the pressure containment body and additionally contains a second “outer” male trunnion pair, as described above, located on the outer surface and on an orthogonal plane (a perpendicular plane) to the interior trunnions; 
     (C) A foundation receptacle that is attached to a foundation of the structure and accepts the outer surface trunnion pair of the second part. The trunnions act in the principle of a universal joint and allows movement in any angle; 
     (D) Rounded-knife edge pivot, bearings, or bushings may be utilized to provide for rotation of the trunnions to reduce the friction to the degree required for the application; 
     (E) An optional damper, which can be utilized to absorb high frequency motions and prevent resonance of an undesirable mode due to dynamic excitation of the environment may be included in the assembly as a system approach solution; 
     (F) A series of swivels converting pendular to rotational motion, flexible pipe, or other means of the prior art, is incorporated into the assembly above the load absorbing base to provide flexure. The load requirements for the swivels and/or flexible pipe are significantly lower because the external loads have been absorbed by the trunnion assembly and associated components; 
     (G) The swivel or flexible pipe assembly may be preferentially protected at each end with automatic or manual valving at the upstream and downstream ends for automatic and manual shut-in safety without compromising the fatigue life of the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be made to the detailed description of the preferred embodiment which references the following drawings of which like parts are given like reference numerals and wherein: 
     FIG. 1 depicts a typical SCR application showing the major elements of the present invention with use of a flexible pipe as the flexible assembly; 
     FIG. 1 a  depicts a typical SCR application showing the major elements of the present invention with use of a rotary swivel system as the flexible assembly; 
     FIG. 2 depicts a cut away view of the SCR Top Connector Load Absorbing Base of the preferred embodiment of the present invention, denoting the principle components and indicating the magnitude of allowable motions; 
     FIG. 3A depicts the SCR pressure carrying extension with the inner trunnions of the preferred embodiment of the present invention; 
     FIG. 3B is an end view of the carrying extension shown in FIG. 3A; 
     FIG. 3C depicts an alternate embodiment of the SCR pressure carrying extension; 
     FIG. 3D is an end view of the carrying extension shown in FIG. 3C; 
     FIG. 4A depicts the top view of the outer trunnion adapter of the preferred embodiment of the present invention; 
     FIG. 4B depicts the side view of the outer trunnion adapter of the preferred embodiment of the present invention; 
     FIG. 5A depicts the plan view of the foundation receptacle of the preferred embodiment of the present invention with installation of SCR attached top connector components partly in phantom line; 
     FIG. 5B depicts the front view of the foundation receptacle of the preferred embodiment of the present invention; 
     FIG. 5C depicts the side view of the foundation receptacle of the preferred embodiment of the present invention; 
     FIG. 6 depicts alternate trunnions or bearings, a higher pairing extra low friction trunnion, a bearing and a bushing subassemblies (FIGS. 6A,  6 B, and  6 C, respectively) for the pressure-carrying body and the trunnion adapter of the preferred embodiment of the present invention are determined; 
     FIG. 7 depicts the manner of assembly in which the reliefs of the outer trunnion adapter  630  of the preferred embodiment of the present invention are determined; 
     FIG. 8 depicts an optional damper assembly of the preferred embodiment of the present invention having three views: FIG. 8A, a top view; FIG. 8B, a front view; and FIG. 8C, a side view; 
     FIG. 9A depicts damper details of the preferred embodiment of the present invention; 
     FIG. 9B depicts a detail of the preferred embodiment of the present invention; 
     FIG. 10 depicts the Flexible Assembly incorporating a rotary swivel system arrangement of the preferred embodiment of the present invention; and 
     FIG. 11 a  depicts the side exterior of a single-seal, high-pressure rotary seal option typifying the rotary swivel system. 
     FIG. 11 b  is an end view of the rotary seal shown in FIG. 11 a;    
     FIG. 11 c  is a cross-sectional cutaway taken along lines A—A in FIG. 11 a;    
     FIG. 11 d  is a detail of a portion of the rotary seal cross-section of FIG. 11 c.   
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The SCR application is depicted in FIG. 1 wherein the water surface  100  supports the floating structure  300  above the seabed  200 . The floating structure  300  is connected to the seabed pipeline by the steel catenary riser (SCR)  400  connected to deck piping  500  by the Top Connector Assembly  600 . The Top Connector Assembly  600  connects the SCR  400  to the deck piping  500  via the lower valve  800  which is connected to one end of a Flexible Assembly  700 . In FIG. 1, the Flexible Assembly is composed as a flexible pipe. The other end of Flexible Assembly  700  is connected to a topsides closure valve  900 . FIG. 1A depicts the Flexible Assembly to be composed of a rotary swivel system configured to absorb the translation and pendular motions of the lower valve  800  as in the case of large diameter and high-pressure risers. 
     The preferred embodiments of the present invention, as shown in FIG. 2, use a universal type joint SCR Top Connector Assembly  600  Load Absorbing Base, which is attached to the floating structure  300  via the foundation support  610 . Top Connector Assembly  600  includes a pressure containing SCR extension  620 , which connects the SCR riser  400  for fluid connection to the deck piping  500 . SCR riser  400  is connected to the pressure containing SCR extension  620  by welding  621  or other appropriate mechanism. A trunnion adapter  630  or outer trunnion forms an intermediate structure between an inner trunnion  625  of the SCR Top Connector Assembly  600  and the foundation support  610 . A bearing assembly  640  is mounted to the orthogonal trunnions of the outer trunnion assembly  630 . The pressure containing SCR extension  620  trunnions are depicted with a bearing assembly  641  option covered by a cover plate  650 . 
     A remote operated vehicle, or ROV, or other diver-friendly retainer  660  is shown in the closed position. The retainer  660  retains the trunnion bearing assembly  640  in the foundation support  610 . The retainer  660  prevents the trunnion adapter or outer trunnion assembly  630 , and hence the SCR Top Connector or swivel assembly  600 , from being moved out of the foundation support  610 . 
     FIG. 3A details a portion of the embodiment shown in FIG.  2 . Three pieces, SCR extension assembly  620 , inner trunnion housing  680  and collar  690 , are shown in FIG.  3 A. For assembly, inner trunnion housing  680  slides over the outer surface  671  of SCR extension assembly  620  and is held in place by collar  690 , also surrounding surface  671  and bolted by bolts  691  to SCR extension assembly  620 . 
     FIG. 3B illustrates a variation of the SCR extension assembly  620 . In FIG. 3A, the upper flange  670  is shown connected to a SCR extension assembly  620  with a trunnion  681  extending from an inner trunnion housing  680 , such as by casting, thereby allowing axial rotation in one plane. The inner trunnion housing  680  is free to rotate around the axis of SCR extension  620  because pressure containing SCR extension assembly  620  is not welded or otherwise connected directly to inner trunnion assembly  680  but is merely juxtaposed to it freely permitting the rotation of inner assembly  680  around the axis of SCR extension  620  (FIG.  3 A). The vertical movement of the SCR extension assembly  620  is restricted by the collar  690  (FIG.  3 A), which is attached to SCR extension  620  by bolting  691  or other appropriate means. Alternatively (FIG.  3 B), the upper flange  670  may be connected to a sufficiently thick pressure retaining segment  620 ′ which incorporates the inner trunnion  681  as an integral component without a separate trunnion assembly  680  or collar  690 , although rotation is thus eliminated in this case for the SCR extension relative to the inner trunnion  680 , as in FIG.  3 A. 
     FIGS. 4A and 4B show the details of the trunnion adapter or assembly  630 , which transmits forces to the foundation support  610  from the SCR riser extension assembly  620 . Trunnion adapter  630  comprises external support or outer structural envelope  631  having reliefs  632  cast or otherwise machined therein. Reliefs  632  are sized to receive trunnion  681  (FIGS. 3A and 3B) to be received in reliefs  632 . External support  631  further includes clearance relief surfaces  636 , permitting rotation on the opposite axis. In addition, external support  631  includes trunnion  635  having an inner threaded bore  633  partly formed therein. In addition, flange bolt holes  637  are also formed in  631  to receive flange  650  (not shown in FIG. 4, but see FIG. 2) held in place by bolts  651  (FIG. 2) threaded into opening  637 . To accommodate trunnions  681 , openings  634  are formed in external support  631  as shown in FIG. 4B for the insertion of trunnion  681  into openings  634  to be held in place by bearings  641  (FIG.  2 ). 
     Details of the foundation support  610  are shown in FIGS. 5A-C. Foundation support  610  accepts the outer trunnion adapter  630  and thereby restrains the SCR extension  620  to the floating or fixed structure  300  (FIG.  1 ). Foundation support  610  is generally horseshoe or foundation-friendly shaped, having back support  611  and two parallel extensions or lateral supports  612  farthest from support  612  extending orthogonally from back support  611 . The ends of lateral supports  612  farthest from support  611  include recesses  613  sized to receive bearing support  640  therein (FIG.  2 ), as well as recesses  614  to receive retainer  660  therein as shown in FIG.  5 . In addition, foundation support  610  includes openings  615  sized to receive in each opening a ROV-friendly pin  665  locking the retainer  660  in position and foundation support  610  also includes a relief surface  616  to allow for movement of SCR extension  620  and its attached parts during rotation. Detent  617  is formed in order to control the amount of material needed for the foundation by diminishing some of the material. In assembly, outer bearing assembly  640  is received in openings  613  and is then slid over its outer surface bearings  1000 , which are held in place by an outer bearing retainer  1110  which is secured by bolts  1115 . The foundation support  610  may also be configured to adapt to existing receptacles in lieu of attaching directly by welding or other means to the structure  300 . 
     FIG. 6 depicts the various methods in which the motions of the outer trunnion adapter  630  may be accommodated. FIG. 6A is that of a higher paired, knife-edged alternative embodiment of trunnion  635 ′ of trunnion  635  wherein the radius and contact surfaces are composed of high strength metallurgy to allow for high loads. Methods as described can provide low rotational friction values. FIG. 6B illustrates the option of a higher paired roller or low friction bearing assembly  1000 . FIG. 6C illustrates the option of a standard bushing  1000 ′ instead of bearing  1000 . Further, the bearing  1000  and bushing  1000 ′ incorporate the use of concentric and hardened segments which make the metallurgical requirements of the forging or casting less critical regarding metallurgy and hardness. 
     FIG. 7 shows the method of assembly of the SCR extension  620  with the outer trunnion assembly  630 . The illustration depicts the manner in which the relief was determined to allow for the inner trunnion  681  to be passed into the outer trunnion  630  by providing relief in lieu of external bolted connections. FIG. 7 shows the sequence of that connection, the sequence moving from left to right as one faces the page. 
     FIG. 8 illustrates an alternative damper assembly  1200  attached above the SCR Top Connector Assembly  600  at the upper flange  670 , utilizing a spacer  1210  to accommodate the thickness of the damper assembly  1200  and support  1201  which may be anchored to foundation  610  or directly to the structure  300 . The top view, FIG. 8A, illustrates the support system  1201 , which allows a high degree of angular movement. FIG. 8A also illustrates the top view of the damper  1200 , with cover removed, identifying the outer housing  1250 , the outer housing support padeyes  1260 , and the spacers  1210  (FIGS.  8 A and  8 C), which accommodate the required diameter of the fluid swivel flange. In this case, the valve  800  would connect above the damper assembly  1200 . 
     FIG. 9 shows the top cover  1270  of outer housing  1250  removed and shows the hydraulic damper working parts without structural components for clarity. Within the annular space  1252  (FIG. 9B) formed inside outer housing  1250 , seawater is admitted via ball check, or similar parts,  1255 . As the central section  1290  is moved radially off center, fluid contained in the annular sections  1252  is restricted from motion due to spring  1292 . The tolerance and configuration of the damping system assembly provide limited flow paths, hence differential pressure of the sides of the central section to provide a damping force to external motions. 
     FIG. 10 shows the Flexible Assembly  700  being comprised of a rotary swivel system arrangement. The configuration, as shown, allows the upper valve  900  to remain stationary and be rigidly mounted while the lower valve  800  moves in 3D pendular manners about the orthogonal trunnions of the SCR Top Connector Assembly  600 , FIG.  2 . As the lower valve  800  moves during pivot motion about the outer trunnion, adapter trunnions  635  FIG.  2  and FIG. 4A, rotation is allowed in swivels  750   a ,  750   b , and  750   c . No rotation occurs in  750   d ,  750   e , and  750   f . Swivel  750   c  remains at the same global coordinates as prior to lower valve  800  motion but allows rotation. Swivel  750   a  moves as a rigid object with the lower valve  800  motion but allows rotation. The linkage formed by the two pipe segments between the swivels causes swivel  750   b  to move both vertically, laterally, and rotate due to the fixed lengths of the linkages made up by the pipe bends  799  and the inactive swivels  750 d,  750   e , and  750   f.    
     With motion caused by the SCR extension assembly trunnions  681 , FIG. 2, FIG.  3 A and FIG. 3B, swivels  750   a ,  750   b , and  750   c  do not rotate but act as rigid segments along with the pipe bends  799  which make up the linkages. Swivel  750   f  remains stationary vertically and laterally but allows rotation. Swivel  750   d  moves as a rigid body with the upper valve  800  while allowing rotation. The differential distances are accommodated by displacement and rotation of swivel  750   e.    
     For combined motions, the system functions in the same manner. The configuration and use are unique to this invention and application. 
     FIG. 11 depicts a swivel assembly which may occupy any position in the swivel arrangement described above. Any capable swivel will suffice in a satisfactory configuration. The unique feature of this swivel is the use of only one rotary seal  784 . A seal backing ring  785  is provided for assembly ease. Minor bending moments caused by pressure thrust loads on the bends  799 , FIG. 10, are absorbed by the sleeve bushings  790  which extend along the outside diameter of the internal swivel body  780 . The longitudinal pressure thrust loads caused by the bends  799 , FIG. 10, are absorbed by the radial thrust load bushings  786 ,  787 . The external swivel body  760  serves as one end of the attachment to the piping system at end  763  while the inner swivel body  780  attaches to the piping system at  781 . The addition of added seals for testing or seals to provide assurance against seawater ingress do not compromise the features or lend claim to benefits unaware to this application. 
     Retainer  770  is attached to the external swivel body  760  with fasteners  761 ,  762 , or other means to contain the Rotary Swivel Components. 
     Hardened systems at points of high contact stress to minimize size requirements, reduce friction, and prevent surface galling, fretting and associated surface failures may be used. Further, SCR Top Connector Assembly incorporates copper alloy components or surfaces applied by cladding, and/or electrically, mechanically, or thermal applied, for applications of seawater exposure and areas such as pivot points which must be free of crustacean and other sea growths. Further, SCR Top Connector utilizes a thick walled fluid conduit section with wall thickness transition to accommodate a wide variation of SCR or similar conduit wall and grade. Also, SCR Top Connector Assembly utilizes a conduit section which may incorporate either an integral or attached trunnion assembly to provide for variation of material properties and thickness. 
     SCR Top Connector Assembly utilizes a fluid containment section which incorporates a surface of low friction materials to allow rotational motion preventing alignment difficulties during installation and minimizing rotational torque of the SCR during installation thereby improving the fatigue life. 
     A higher paired trunnion may be used which incorporates a rocking motion with primarily rolling motion due to the utilization of essentially identical radii of the fulcrum and beam section; the components may be arranged in any manner to achieve the desired action and the materials of the trunnion may utilize coatings or cladding such as iron carbide or ceramic or non-ferrous materials to provide high wear resistance without susceptibility to corrosion. 
     Thus, the SCR Top Connector Swivel System transforms the pendular motions of an SCR Top Connector Load Base to three or more rotary motions allowing the distant ends of the swivel system to be fixed or sliding for thermal expansion of the attached piping system. 
     Other applications associated with the object of the invention includes: electrical conduit, or an umbilical attached in the manner of an SCR. These applications would utilize the object, of this invention; however, the pressure-containing component would be substitutes for a segment to accommodate the umbilical or conduit and limit the minimum radius while allowing greater installation tolerances and dynamic motions. 
     While the best mode and preferred embodiments of the invention have been described, it is to be understood that the invention is not limited, thereto, but rather is to be measured by the scope and spirit of the appended claims.