Toroidal fluid swivel for transfer of fluid across a rotary interface

Abstract

A swivel for transfer of fluid across a rotary interface around a swivel rotation axis between an incoming fluid line and an outgoing product piping includes a fixed annular element and a rotating annular element, each arranged around a common rotation axis and having a substantially equal diameter. One selected element from the fixed annular and rotating annular elements includes an annular disk provided with a toroidal cavity in a first of its circular end surfaces, and the other selected element is arranged with a flat circular end surface adjacent to and in close proximity above the first circular end surface to close the toroidal cavity and form a toroidal chamber with the annular disk. The rotary interface is perpendicular to the rotation axis, and is formed by the flat circular end surface of the other selected element and the adjacent first circular surface of the one selected element.

The invention claimed is: 
     
       1. A swivel for transfer of pressure flows of oil and/or gas across a rotary interface formed around a swivel rotation axis between an incoming fluid line and an outgoing product piping, the swivel comprising:
 a fixed annular element; and 
 a rotating annular element, 
 each of the fixed annular element and the rotating annular element arranged around a common rotation axis, 
 the fixed annular element comprising an annular disk provided with circular end surfaces and a toroidal cavity inside a first of said circular end surfaces, and 
 the rotating annular element having a flat circular end surface that is adjacent to and located in proximity above said first circular end surface of said annular disk of the fixed annular element so as to close the toroidal cavity of the fixed annular element and thereby form a toroidal chamber within said annular disk, 
 the rotary interface being formed by the flat circular end surface of the rotating annular element and the first circular surface of the fixed annular element located adjacent thereto, the rotary interface being perpendicular to the common rotation axis, 
 wherein the fixed annular element comprises an inner wall and an outer wall,
 a first end of the inner wall connected to an inner portion of the fixed annular disk, and one end of the outer wall connected to an outer portion of the fixed annular disk, such that the fixed annular element forms a “U-shape” in cross-section, 
 and the rotary interface between the rotating annular element and the fixed annular element being arranged in between the inner and outer walls of the fixed annular element, 
 
 wherein the rotating annular element has at least one outlet aperture passing through outlet aperture configured to provide a fluid communication between the toroidal chamber and outgoing product piping, 
 wherein the at least one outlet aperture extends perpendicularly from the flat circular end surface of the rotating annular element and parallel to the common rotation axis, and 
 wherein in a top region of the toroidal cavity, crossbars are fixedly arranged in radial direction in the cavity between the inner wall and the outer wall. 
 
     
     
       2. The swivel according to  claim 1 , wherein the annular disk has at least one inlet aperture that couples the incoming fluid line to the toroidal cavity. 
     
     
       3. The swivel according to  claim 2 , wherein the at least one inlet aperture comprises a plurality of externally interconnected inlet apertures distributed over the circle of the toroidal cavity, and the at least one outlet aperture comprises a plurality of externally interconnected outlet apertures distributed over the circle of the toroidal chamber. 
     
     
       4. The swivel according to  claim 1 , further comprising:
 retaining elements that retain the rotating annular element between the inner and outer walls of the fixed annular element, the retaining elements being fixed to the inner and outer walls and configured to hold the rotating annular element in position over the toroidal cavity. 
 
     
     
       5. The swivel according to  claim 1 , wherein the swivel comprises sealing means adjacent to the edges of the toroidal cavity between the annular disk and the rotating annular element. 
     
     
       6. The swivel according to  claim 1 , wherein the crossbars are distributed about the toroidal cavity at a constant intermediate angle. 
     
     
       7. The swivel according to  claim 1 , wherein the toroidal cavity extends over 360° around the common rotation axis. 
     
     
       8. A vessel for offshore operations comprising a turret mooring system, wherein the turret mooring system is equipped with a swivel according to  claim 1 .