Bearing arrangement for an electric swivel

Abstract

A electric swivel, LVES, in a swivel stack, includes an annular outer element defining a cylindrical chamber around an axis S and an cylindrical inner element coaxial with the outer element. The cylindrical chamber is sealed at an upper side with an annular cover and is configured for rotation relative to the inner and outer element around the axis S. The inner element includes at an inner radial side first and second bearing parts defining an inner bearing. The outer element includes at an outer radial side first and second bearing parts defining an outer bearing. The inner bearing includes an inner annular interface between the first and second bearing parts, the outer bearing includes an outer annular interface between the first and second bearing parts. Each of the annular interfaces is coaxial with the inner and outer element, and each annular interface is configured as a flame conducting path.

Claims

1. A low voltage electric swivel (LVES) for use in a swivel stack, comprising an annular outer element defining a cylindrical chamber around a longitudinal axis S and an cylindrical inner element coaxial with the outer element, wherein the cylindrical chamber is sealed at an upper side with an annular swivel cover and is configured for rotation relative to the inner and outer element around the longitudinal axis S; the inner element comprising at an inner radial side a first bearing part and a second bearing part defining an inner bearing; the outer element comprising at an outer radial side another first bearing part and another second bearing part defining an outer bearing; wherein the swivel is adapted for use with voltages up to 3 kV; the annular swivel cover being connected at the inner radius thereof with the second bearing part of the inner bearing and at the outer radius thereof with the another second bearing part of the outer bearing, wherein the inner bearing comprises an inner annular interface between the first and second bearing part, the outer bearing comprises an outer annular interface between the another first and second bearing parts, wherein each of the inner and outer annular interfaces is coaxial with the inner and outer element, and wherein each annular interface is configured as a flame path.

2. The low voltage electric swivel according to claim 1, wherein in the inner bearing an inner annular gap is designed between the first and second bearing parts that functions as an inner flame path, and wherein in the outer bearing an outer annular gap is designed between the another first and second bearings parts that functions as an outer flame path.

3. The low voltage electric swivel according to claim 2, wherein the width of the inner gap is 0.3 mm or less.

4. The low voltage electric swivel according to claim 2, wherein the width of the outer gap is 0.3 mm or less.

5. The low voltage electric swivel according to claim 1, wherein each annular interface comprises lubricant to reduce wear of each annular interface during operation.

6. The low voltage electric swivel according to claim 5, wherein each annular interface is sealed at both transversal sides with a respective seal ring.

7. The low voltage electric swivel according to claim 1, wherein each annular interface comprises a ball bearing opening that defines in the direction of the longitudinal axis S, a lower and upper annular interface part below and above the ball bearing, respectively.

8. The low voltage electric swivel according to claim 7, wherein a longitudinal length of each lower annular interface part is at least 25 mm.

9. The low voltage electric swivel according to claim 7, wherein a longitudinal length of each upper annular interface part is at least 25 mm.

10. The low voltage electric swivel according to claim 7, wherein a longitudinal length of each lower annular interface part is at least 27.5 mm.

11. The low voltage electric swivel according to claim 7, wherein a longitudinal length of each upper annular interface part is at least 27.5 mm.

12. The low voltage electric swivel according to claim 1, wherein a height of each first bearing part is equal to a height of the corresponding second bearing part.

13. The low voltage electric swivel according to claim 1, wherein the annular swivel cover consists of two or more concentric rings that are connected at their interfaces.

14. The low voltage electric swivel according to claim 13, wherein an inner ring of said concentric rings is attached to said second bearing part of the inner bearing, and wherein an outer ring of said concentric rings is attached to said another second bearing part of said outer bearing.

15. The low voltage electric swivel according to claim 1 for use in a swivel stack located on a FPSO/FLNG turret and adapted for transmitting electrical information and power from rotating to fixed parts of said swivel stack.

16. A swivel stack, comprising a low voltage electric swivel according to claim 1.

17. A vessel for offshore operations and comprising a turret mooring system, wherein the turret mooring system is equipped with a low voltage electric swivel according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. They are intended exclusively for illustrative purposes and not to restrict the inventive concept, of which the scope is defined by the appended claims.

(2) FIG. 1 shows a schematic view of a swivel seal of a low voltage electric swivel according to an embodiment of the invention;

(3) FIG. 2 shows a schematic view of the inner bearing shown in section II of FIG. 1;

(4) FIG. 3 shows a schematic view of the outer bearing shown in section III of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) FIG. 1 shows a schematic view of a swivel seal of a low voltage electric swivel 1. The low voltage electric swivel 1 comprises a cylindrical inner element 2 around a longitudinal axis S and an annular outer element 3. The outer element 3 defines a cylindrical chamber coaxial with the inner element 2. The low voltage electric swivel 1 further comprises an annular swivel cover 4. The annular swivel cover 4 is connected at an inner radial part with the cylindrical inner element 2 and at an outer radial part with the annular outer element 3. The annular swivel cover 4 thus seals the cylindrical chamber at an upper side. The swivel cover 4 is arranged for rotating movement relative to the inner and outer element 2, 3 around the longitudinal axis S.

(6) The inner and outer element 2, 3 each comprise first bearing parts 7, 7 and corresponding second bearing parts 8, 8 at opposite radial sides of the swivel cover 4. The combination of a first bearing part 7, 7 with the corresponding second bearing part 8, 8 defines respectively an inner bearing 5 and an outer bearing 6.

(7) FIG. 2 shows a schematic view of an inner bearing 5 of the low voltage electric swivel 1 as described in FIG. 1. The inner bearing is formed by a first bearing part 7 and a second bearing part 8. The first bearing part 7 is connected to the inner element 2 and the second bearing part 8 is connected to the swivel cover 4, wherein the second bearing part 8 is provided at the inner radial side of the swivel cover 4. The first and second bearing parts 7, 8 are arranged for rotating movement relative to each other around the longitudinal axis S.

(8) An inner annular gap is designed in between the first and second bearing parts 7, 8 that is coaxial to the swivel axis and that can function as an inner flame path.

(9) The inner bearing 5 further comprises an annular interface 9 coaxial with the inner and outer element 2, 3 connecting the first and second bearing part 7, 8. This annular interface may substantially coincide with the inner annular gap, at least along the upper and lower circumferential edges of said annular gap.

(10) In an embodiment of the invention, the annular interface 9 comprises a ball bearing opening 12 defining a lower and upper annular interface part 10, 11. The bearing opening 12 may of course have a diameter that is larger than the inner annular gap between the first bearing part 7 and the second bearing part 8, at least along the upper and lower circumferential edges of said annular gap.

(11) In an embodiment of the invention a longitudinal length of the lower annular interface part 10 is at least 25 mm, more preferably 27.5 mm.

(12) In an embodiment of the invention a longitudinal length of the upper annular interface part 11 is at least 25 mm, more preferably 27.5 mm.

(13) In an embodiment of the invention, the width of the inner gap is 0.3 mm or less, at least along the circumferential upper and bottom edges of said gap.

(14) In an embodiment of the invention a height of the first bearing part 7 is equal to a height of the second bearing part 8.

(15) In an embodiment of the invention the annular interface 9 is sealed at both transversal sides with a respective seal 14.

(16) FIG. 3 shows a schematic view of an outer bearing 6 of the low voltage electric swivel 1 as described in FIG. 1. The outer bearing is formed by a first bearing part 7 and a second bearing part 8. The first bearing part 7 is connected to the outer element 3 and the second bearing part 8 is connected to the swivel cover 4, wherein the second bearing part 8 is provided at the outer radial side of the swivel cover 4. The first and second bearing parts 7, 8 are arranged for rotating movement relative to each other around the longitudinal axis S of the swivel.

(17) The outer bearing 6 further comprises an annular interface 9 coaxial with the inner and outer element 2, 3 connecting the first and second bearing part 7, 8.

(18) An outer annular gap is designed in between the first and second bearing parts 7, 8 that is coaxial to the swivel axis and that can function as an outer flame path. The annular interface may substantially coincide with the outer annular gap, at least along the upper and lower circumferential edges of said annular gap.

(19) In an embodiment of the invention the annular interface 9 comprises a ball bearing opening 12 defining a lower and upper annular interface part 10, 11. The bearing opening 12 may of course have a diameter that is larger than the outer annular gap between the first bearing part 7 and the second bearing part 8, at least along the upper and lower circumferential edges of said annular gap.

(20) In an embodiment of the invention a longitudinal length of the lower annular interface part 10 is at least 25 mm, more preferably 27.5 mm.

(21) In an embodiment of the invention a longitudinal length of the upper annular interface part 11 is at least 25 mm, more preferably 27.5 mm.

(22) In an embodiment of the invention, the width of the outer gap is 0.3 mm or less, at least along the circumferential upper and bottom edges of said gap.

(23) In an embodiment of the invention a height of the first bearing part 7 is equal to a height of the second bearing part 8.

(24) In an embodiment of the invention, the annular interface 9 is sealed at both transversal sides with a seal ring 15.

(25) According to an embodiment, the annular swivel cover 4 may consist of two or more concentric rings that are interconnected at their interfaces. As shown in FIG. 1, the annular swivel cover 4 comprises an inner ring 4a, a central ring 4b and an outer ring 4c, that are interconnected at their respective interfaces. Using concentric rings to construct the annular swivel cover 4 allows relatively easy removal of the cover 4 and thus simpler inspection or maintenance.

(26) Other alternatives and equivalent embodiments of the present invention are conceivable within the idea of the invention, as will be clear to the person skilled in the art. The scope of the invention is limited only by the appended claims.

LIST OF REFERENCE SIGNS

(27) 1. Low Voltage Electric Swivel 2. Inner Element 3. Outer Element 4. Swivel Cover 4a, 4b, 4c. Concentric Rings 5. Inner Bearing 6. Outer Bearing 7, 7. First bearing part 8, 8. Second bearing part 9, 9. Annular Interface 10, 10. Lower Annular Interface Part 11, 11. Upper Annular Interface Part 12, 12. Ball Bearing Opening 14 Seal 15 Seal