Abstract:
A high pressure swivel is disclosed which includes swivel modules each having a stationary inner structure and a rotatable outer structure that can rotate about the inner structure. The inner structure of each module has the same number of vertical passages as the others. The inner structure of each module has a circumferential flange on the top and on a bottom lip so that each swivel unit can be secured to another swivel in its top or bottom with clamps around the flanges. The inner structures are rotatably positioned with respect to each other when assembled so that a vertical passage from a stationary base manifold to an outlet on the rotatable outer structure is formed. Various combinations of standard swivel modules can be assembled to accommodate specific swivel stack requirements for flow capacity and separate or commingled flow paths.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates in general to swivel equipment for transferring fluids. In particular, the invention relates to a fluid swivel joint for a swivel stack assembly adapted for transferring fluids between tankers, storage vessels and the like and one or more conduits beneath the ocean surface. The fluid of the swivel may be product such as hydrocarbons to be transferred from the seabed to a vessel or may be water or gas to be transferred from the vessel to the seabed for well stimulation. 
         [0003]    Still more particularly, the invention relates to a novel fluid joint which can be stacked with one or more other fluid joints of like design so that a swivel stack can be assembled in a short time from an inventory of the fluid joints. 
         [0004]    2. Description of the Prior Art 
         [0005]    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 offshore loading terminals, which serve as centralized production sites for the entire field, have been developed. Flexible fluid lines, called risers, 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 from the vessel into subsea wells for purpose of control, well stimulation, or storage. 
         [0006]    Floating vessels can be moored to a single point mooring system, which permits the vessel to weathervane and rotate 360° about a single mooring point. To permit the vessel to rotate and move freely without causing twisting or entanglement of the various risers to which the vessel is attached, it is necessary to provide a fluid swivel assembly to connect the fluid lines to the mooring site. Furthermore, since a plurality of risers are involved, it is necessary that two or more swivel modules be stacked in order to have the capability of accommodating multiple fluid lines or risers. 
         [0007]    Separate swivel units or modules are stacked on top of each other with a swivel stack base fixed to a stationary frame which is anchored to the sea floor. 
         [0008]    Prior high pressure product swivels have provided an inner housing and an outer housing which is rotatively supported on the inner housing by a bearing so that the outer housing is free to rotate about the inner housing. A toroidally shaped conduit chamber is formed between the two housings when the two housings are placed in registration with each other. An inlet from the inner housing communicates with the chamber, and an outlet in the outer housing communicates with the chamber. Upper and lower dynamic seals in the form of face seals or radial seals are placed in grooves or gaps between axially opposed or radially opposed surfaces of the inner and outer housings to prevent fluid from leaking past the two facing surfaces while the high pressure fluid is present in the chamber. 
         [0009]    Prior swivel assemblies have required swivel units to be stacked on top of each other with each unit having its inner housing bolted to the inner housing of a unit stacked above or below. Furthermore, the entire stack of swivel units have been bolted to a base housing. Such an assembly functions properly as a swivel stack unit, but construction of the units and assembly requires that each stack be engineered for each requirement of an offshore application. Such prior assemblies have been costly to design, engineer, and build and have required a long lead time from contract signing to construction and delivery of the swivel stack. 
         [0010]    3. Identification of Objects of the Invention 
         [0011]    A primary object of the invention is to provide a high pressure fluid swivel arrangement constructed from swivel units or modules that can be stacked and secured to each other without securing the swivel units together with long bolts through their inner housing. 
         [0012]    Another object of the invention is to provide a pre-designed fluid swivel unit or module having vertical passages such that fluid swivel units can be pre-constructed and then stacked on top of each other and to a base housing so that fluid passages can be aligned from the base housing to desired outlets of the stacked fluid swivel units. 
       SUMMARY OF THE INVENTION 
       [0013]    The objects identified above, as well as other advantages and features of the invention are incorporated in a rotatable fluid swivel unit and an assembly of such units into a swivel stack onto a base housing. Each swivel unit has inner and outer housings with one or more fluid pressure carrying radial annular groove cavities in the annular outer housing. Each annular groove cavity has one or more outlets from the outer housing. Each swivel unit has at least one vertical passage in the inner housing that terminates at a radial groove, but has other swivel vertical passages spaced equally from each other around a circle of a horizontal cross section through the inner housing. 
         [0014]    An assembly of such swivel units is made from pre-constructed swivel units so as to achieve desired flow paths from the base housing to the radial outlets in the outer housings of the stacked modules. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The objects, advantages, and features of the invention will become more apparent by reference to the drawings which are appended hereto, wherein like reference numbers indicate like parts, and wherein an illustrative embodiment of the invention is shown, of which: 
           [0016]      FIG. 1  is a cross section view of a swivel module with a stationary inner annular structure and a rotatable outer housing with a plurality of vertical fluid passages spaced around a circle of the inner annular structure with one of the passages terminating at a fixed radial groove in the stationary inner structure, the groove communicating with a radial outlet of the rotatable outer housing; 
           [0017]      FIG. 2A  in a flat layout illustration showing the stationary inner structure of three identical swivel units stacked on top of each other and onto a base housing with certain vertical passages terminating at a lower swivel unit and other vertical passages communicating with vertical passages of units stacked above; 
           [0018]      FIG. 2B  is another flat layout illustration showing the stationary inner structure of three identical swivel units stacked on top of each other onto a base housing with a set of two vertical passages terminating at a lower swivel unit, with one passage blocked off and other vertical passages communicating with vertical passages of units stacked above; 
           [0019]      FIG. 3  is a top view of the swivel modules of  FIG. 2A  showing section lines  3 A- 3 A,  3 B- 3 B, and  3 C- 3 C of a swivel assembly that is illustrated in  FIGS. 3A, 3B, and 3C ; 
           [0020]      FIGS. 3A, 3B and 3C  are three separate section views (as indicated in  FIG. 3 ) of a stack of three identical swivel units each having a stationary inner annular structure with nine vertical passages as shown in  FIG. 2A ; 
           [0021]      FIG. 4  in an elevation view of the swivel stack of  FIGS. 3A, 3B, 3C  and with the vertical passages layout of  FIG. 2A ; and 
           [0022]      FIG. 5  is an elevation view of the stack of  FIG. 4  showing the lower swivel unit with the other swivel units removed to illustrate the stationary inner housing with vertical passages and the rotatable outer housing, all mounted on a base manifold. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0023]    The aspects, features, and advantages of the invention summarized above are described in more detail below by reference to the drawings where like reference numerals represent like elements. The following table provides a list of reference numbers used in this specification and the features that they represent: 
         [0000]    
       
         
               
               
             
               
               
             
           
               
                   
               
               
                 Reference Numeral 
                 Feature 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 3 
                 central passage 
               
               
                 5 
                 central longitudinal axis 
               
               
                 8 
                 upper flange 
               
               
                 9 
                 lower flange 
               
               
                 10 
                 swivel module - see FIGS. 2A, 2B 
               
               
                 11 
                 lower lip 
               
               
                 12 
                 segmented clamp - see FIGS. 3A, 3B, 3C 
               
               
                 13 
                 imaginary circle for vertical passages (FIG. 1) 
               
               
                 16 
                 swivel inner housing 
               
               
                 17 
                 seal plate 
               
               
                 20 
                 rotatable outer housing 
               
               
                 21 
                 lower axial swivel bearing 
               
               
                 22 
                 upper axial swivel bearing 
               
               
                 23 
                 lower radial bearing 
               
               
                 24 
                 upper radial bearing 
               
               
                 28 
                 fixed radial passage in inner housing 16 
               
               
                 29 
                 circular groove in outer housing 20 
               
               
                 30 
                 out passage 
               
               
                 40 
                 bolts 
               
               
                 41 
                 lower face seal 
               
               
                 42 
                 upper face seal 
               
               
                 50 
                 base manifold 
               
               
                 50-1-50-2, etc. 
                 radial inlets 
               
               
                 M1, M2 . . . , etc. 
                 vertical passages in base manifold 
               
               
                 A, U, V . . . , etc. 
                 vertical passages in swivel unit 
               
               
                 50-A, 50-B . . . 
                 liner conduit 
               
               
                 52 
                 stationary frame 
               
               
                 60 
                 swivel unit (MODULE 1) 
               
               
                 61 
                 outlet in swivel unit (MODULE -1) (FIG. 4) 
               
               
                 70 
                 swivel unit (MODULE 2) 
               
               
                 71 
                 outlet (MOD-2) 
               
               
                 80 
                 swivel unit (MODULE 3) 
               
               
                 81 
                 outlet (MOD-3) 
               
               
                 98 
                 static seal 
               
               
                 99 
                 static seal for conduits 50 
               
               
                   
               
             
          
         
       
     
         [0024]      FIG. 1  is a cross section elevation view of a swivel unit  10  according to the invention where this section view shows the inner annular stationary structure  16 ,  17  oriented about a central longitudinal axis  5  through a central passage  3 . The inner annular structure includes a swivel inner housing  16  and a seal plate  17  which are secured together by a plurality of bolts  40 . The rotatable outer housing  20  is rotatably mounted with respect to swivel inner housing  16  and seal plate  17  by axial lateral swivel bearings  21 ,  22 . Radial bearings  23 ,  24  provide radial support for outer housing  20  while rotating about stationary inner annular structure  16 ,  17 . 
         [0025]    The inner annular stationary structure  16 ,  17  includes an upper flange  8  formed about the outer periphery of seal plate  17 , and inner housing  16  includes a lower flange  9  formed on an outer periphery of a circumferential lower lip  11  which extends a short distance below the bottom of inner housing  16 . As illustrated below in  FIGS. 3A, 3B, 3C , the flanges  8  and  9  are used to couple swivel units stacked on top of each other. A plurality of clamps  12  (see  FIGS. 3A, 3B, 3C ) secure the flanges  8 ,  9  to vertically stacked swivel units. Such clamping enables a swivel unit to be removed and replaced much more easily and rapidly than in prior swivel assemblies where bolts extend through all swivels in a stack. 
         [0026]    The swivel unit  10  has plural vertical passages A, B . . . which have center points arranged on an imaginary circle  13  through the inner annular structure  16 ,  17 . A total of nine passages are shown in the drawings, but fewer or more passages could be provided for certain applications. All of the passages are of the same diameter.  FIG. 3  is a top view of a swivel unit like that of  FIG. 1 .  FIG. 3  shows, for an example configuration, that all seal plates  17  can be identical and have nine holes so they can be oriented in any angular position as needed for passage of liner conduits  50 . For the arrangement shown in  FIG. 2A , all passages below top seal plate  17  are used, and the holes in top seal plate  17  are unused. Usually in practice smaller utility swivels having small flow conduits passing through central passage  3  are attached on top of the stack of high pressure swivels. In this case the attachment covers the open holes in upper seal plate  17  and bolts  40  thereby protecting them from the elements. Swivel unit  10  of  FIG. 1  shows passage A which terminates and communicates with radial groove  28 , but passage A does not extend up to the hole through seal plate  17 . 
         [0027]    Outer housing  20  includes a circular groove  29  which communicates with radial passage  28  and has an outlet passage  30  which opens into groove  29 . This arrangement allows fluid flow through stationary housing  16  passage A to radial passage  28  into groove  29  and outlet  30  of rotatable housing  20 . 
         [0028]    Upper and lower face seal arrangements  42 ,  41  are described in a corresponding patent application by the same inventors of this application. Such application has Ser. No. 14/178,106 and was filed May 19, 2015. Such application is incorporated herein by reference into this specification. Such seal arrangements allow swivel operation at extremely high pressures. Static seals  98  provide static sealing between inner housing  16  and seal plate  17 . 
         [0029]      FIG. 2A  illustrates inner housings of a stack of swivel units like that of  FIG. 1 , where each unit  60 ,  70 ,  80  is like the others with each unit having nine vertical passages formed through the inner housing, with each passage starting in the bottom of the unit. The bottom unit  60  is illustrated as being stacked and clamped atop base manifold  50  which is secured on top of swivel stack support base  52  (see  FIG. 4 ). As illustrated in  FIGS. 3A, 3B, 3C  . . . , base manifold  50  has nine radial inlets,  50 - 1 ,  50 - 1 ,  50 - 3 ,  50 - 4 ,  50 - 5 ,  50 - 6 ,  50 - 7 ,  50 - 8 ,  50 - 9  equally angularly spaced from each other with each communicating with its assigned vertical passage, M 1 , M 2 , M 3 , M 4  . . . M 9 . 
         [0030]      FIG. 2A  illustrates that for an example swivel unit  60 , its vertical passages A, U, V, B, W, X, C, Y, Z, are spaced equally about its bottom surface and are aligned respectively with vertical passages M 1 , M 2 , M 3  . . . M 9  of base manifold  50 . For the example of  FIG. 2A , and of  FIGS. 3, 3A, 3B, 3C , each of the vertical passages in the swivel unit  60  and base manifold  50  are angularly spaced by 40 degrees (360°/9).  FIG. 2A  shows (see also  FIG. 5 ) that vertical passages A, B and C terminate in their respective radial passage  28  and communicate with circumferential groove  29  in the outer housing  20 , (see  FIGS. 1 and 5 ) so fluids input into passages M 1 , M 4  and M 7  of base manifold  50 , when aligned with vertical passages A, B and C of swivel unit  60  terminate via passages  28  to groove  29  and flow out via outlets  61  in swivel unit  60 . (See  FIG. 4 ) The other passages in swivel unit  60 , U, V, W, X, Y and Z traverse the entire height of internal structure  16 ,  17  of the swivel  60  as illustrated in  FIG. 2A .  FIG. 1  shows that passages X, C, Y, and Z traverse the entire height of internal structure  16 ,  17  and illustrates that several configurations of vertical path commingling are possible as illustrated in  FIG. 2A . 
         [0031]    As shown in  FIG. 2A , stacked swivel units  70  and  80  have the same vertical flow passages configuration as does swivel unit  60 . Swivel unit  70  is rotated by 40° (360°/9) with respect to the orientation of swivel unit  60 , so that the vertical passage A′ of unit  70  is aligned with through vertical passage U of unit  60 ; vertical passage B′ of unit  70  is aligned with through vertical passage W of unit  60 ; and vertical passage C′ of unit  70  is aligned with through passage Y of unit  60 . The fluid flow from vertical passages M 2 , M 5  and M 8  are commingled via radial passage  28 ′ to groove  29 ′ in unit  70 . Finally, for this example, the unit  80 , constructed like units  70 ,  60 , but stacked on top of unit  70  and rotated by 40° with respect to unit  70 , has it&#39;s A″ vertical passage aligned with through passages U′ of unit  70  and B″ aligned with W′ and C″ with Y′ of unit  70  so that fluid can flow from passage M 3  of base manifold  50  to outlet A″ of unit  80 . In the same way, fluid communication is established between outlet B″ and passage M 6  via B″ of unit  80 , W′ of unit  70  and X of unit  60 . Fluid communication is established between outlet C″ of unit  80  and M 9  of base manifold  50  via passages C″ of unit  80 , Y′ of unit  70  and Z of unit  60 . 
         [0032]      FIG. 2B  illustrates another configuration of the swivel units of the invention. The inner housing of the swivel units  60 ′,  70 ′,  80 ′ have nine vertical passages starting at the bottom of each unit.  FIG. 2B  illustrates that the vertical passages A, U, V, B, W, X, C, Y. Z of swivel unit  60 ′ are equally spaced about its bottom surface and each one is aligned respectively with one of the vertical passages M 1 , M 2 , M 3  . . . M 9  of base manifold  50 . Only two of the passages, A and B, terminate in a radial passage  28  and circular groove  29 . The swivel unit  70 ′ has its A′ and B′ passages aligned with M 2  and M 5  of base manifold  50  and have their circular grooves  29 ′ linked together. Swivel unit  80 ′ is similar, but has its vertical passage B″ blocked so that aligned passage W′ does not communicate with groove  29 ″. Many other configurations are possible.  FIG. 2B  shows that passages M 7  to W″, M 8  to X″, and M 9  to C″ remain open and available for additional single and two-path swivel modules mounted above swivel module  3  for more flow paths. 
         [0033]      FIGS. 3, 3A, 3B and 3C  illustrate the swivel stack of three units as indicated above for the arrangement of  FIG. 2A  and assembled atop of module  50 .  FIG. 3  is a top view of the stack of  FIG. 2A  with section lines  3 A- 3 A,  3 B- 3 B and  3 C- 3 C, each spaced 40° apart. The top view section  3 A- 3 A,  FIG. 3A , shows that the top of the unit  80  has a passage Y″ and Z′ that pierces the top of the unit, but other passages, such as Z″, U″, V″, W″ X″ cannot be seen because of the way the section A is positioned.  FIG. 3A  shows that a radial passage  50 - 1  from the exterior of manifold  50  communicates with vertical passage M 1  of base manifold  50 . Passage M 1  is aligned with vertical passage A of unit  60 . Passage A terminates and communicates with radial passage  28  of the swivel inner housing  16  which intersects with circular groove  29  and outlet  61  of rotatable outer housing  20 . 
         [0034]    Clamps  12  secure respective flanges  8  and  9  which face each other of the swivel units  60 ,  70  and  80 .  FIG. 3A  shows that passages Z′ and Y″ of units  70  and  80  are aligned and pierce the top of the stack as illustrated in  FIG. 3 . A liner conduit  50 A is placed in passages A and M 1  with static seals  99  to prevent leakage when fluid flows in those vertically aligned passages. 
         [0035]      FIG. 3B  shows the section view of the three swivel units  60 ,  70 ,  80  clamped together where the section view is drawn as in  FIG. 3  with section lines  3 B- 3 B.  FIG. 3  shows that passage Z″ of module  80  is visible from the top of the stack. Liner conduit  50 B with upper and lower static seals  99  is provided in the aligned passages of M 2  of base manifold  50  and U of module  60 , A′ of module  70  to insure leak-free passage of fluid from passage M 2  of base manifold  50  to the outlet  71  in module  70 . 
         [0036]      FIG. 3C  shows the section view of the swivel units  60 ,  70 ,  80  clamped together where the section view is drawn as in  FIG. 3  with section lines  3 C- 3 C. Liner conduit  50 C with static seals  99  is provided in the aligned passages of A″ of module  80 , U′ of module  70 , V of module  60  and M 3  of base manifold  50  to insure leak free passage of fluid from inlet  50 - 3  of base manifold  50  to the outlet  81  in module  80 . 
         [0037]      FIG. 4  is an elevation view of the stack of three swivel modules  60 ,  70 ,  80  stacked and secured to each other as illustrated in  FIGS. 2A, 3, 3A, 3B and 3C . The swivel modules are stacked atop base manifold  50  which is secured to support base  52 . Outlets  61 ,  71 ,  81  can be in any angular rotation position since outer housings  20  rotate. The illustration happens to have them aligned for convenience. 
         [0038]      FIG. 5  shows the swivel stack of  FIG. 4 , but with modules  70  and  80  removed and with a horizontal section view through module  60  presented. Vertical passages A, U, V, B, W, X, C, Y, Z are seen opening through inner housing  16  of module  60 . The horizontal circular groove  29  in outer housing  20  communicates respectively with passages A, B, C via radial passage  28 ,  28 ′ and  28 ″ which in turn communicate with outlets  30 A,  30 B and  30 C. The module  60  is illustrated as being secured to the top of base manifold  50 . Inlets  50 A,  50 U,  50 V communicate with vertical passages A, B, and C and with outlets  30 A,  30 B,  30 C. 
         [0039]    The orientation of modules  60 ,  70 , and  80  of  FIGS. 2, 3, 3A, 3B, 3C, 4, 5  is by way of example as to how swivel modules as illustrated in  FIG. 1  can be oriented. 
         [0040]    Of course the swivel stack base  50  is to be positioned on a stationary frame  52  anchored to the sea floor. Risers from the sea floor are connected to the inlets  50 - 1 ,  50 - 2 , . . . etc., of the manifold base  50 . Fluid lines to the vessel are connected to the outlets  61 ,  71 ,  81  . . . etc., and rotate, with the vessel, with respect to the base manifold  50 . Although  FIGS. 2A, 2B , through  5  illustrate coupling of multiple vertical passages, such as passages A, B and C coupled by groove  29  in module  60 , the swivel units can be configured so that one or more vertical passages can extend from the base module  50  to the top module of the module stack. Many different configurations can be formed while using identical components. 
         [0041]    The swivel module  10  of  FIG. 1 , with its modification as illustrated in  FIG. 2-5  have advantages of,
       (1) ease of assembly when stacking by connecting flanges of adjacent modules together rather than using bolts which extend the entire height of the stack;   (2) prefabrication of swivel units so that a stack can be assembled quickly when needed;   (3) relative ease of replacing a swivel unit in a stack if needed without disturbing swivel units below a unit which needs to be replaced. For example, when using a stack of three identical swivel modules,  10 A,  10 B,  10 C, an additional spare unit  10  can be stored on the vessel. If any module fails, the spare unit can be used as a replacement; and   (4) single swivel units can be independently assembled and tested at the factory for installation in any position in the stack. This advantage provides significant cost reduction and decreased delivery times.