BEARING DEVICE FOR A TURNTABLE OR THE LIKE USED IN ANCHORING VESSELS

Abstract: A device for supporting a turntable (1) on a vessel, especially a vessel for use in connection with drilling for and production of oil, which vessel is anchored to the sea floor, via the turntable (1). The turntable (1) comprises a horizontal circular flange portion (2) and a cylindrical portion (3) extending coaxially relative to the latter and downwards from the flange portion (2) into a vertical through hole (7) in the hull (6). Said device comprises bearing means (21, 22, 23, 24) which are connected with the vessel's hull (6) and comprise one or a plurality of bearing members (31, 34, 41, 46) adapted to bear against the respective bearing faces (11, 12, 13, 14) of the turntable flange portion (2). The bearing means permit relative rotation of the turntable (1) and the hull (6) about a substantially vertical axis. According to the invention first and second bearing means (21 and 22, respectively) are provided beneath the peripheral portion of the turntable flange and are designed to support turntable (1). The bearing member or members of the second bearing means are raisable and lowerable, so that the turntable (1) can be moved in a vertical direction between a first lowered position and a second raised position. In the first position, the turntable (1) is carried only by the first bearing means (21), and in the second position the turntable (1) is carried only by the second bearing means (22).

Description: The invention relates to a device for mounting a turntable or turning body on a vessel, especially a vessel for use in connection with drilling for and production of oil, said vessel being anchored to the sea floor, via said turntable, and the turntable comprising a horizontally extending, circular flange portion, and a cylindrical portion extending coaxially relative to the latter and downwards from said flange portion into a vertically extending through hole in the hull, the device comprising bearing means which are connected with the hull of the vessel and comprise one or a plurality of bearing members adapted for contact with respective bearing faces of the turntable flange portion, and said bearing means and faces permitting mutual rotation of the turntable and the vessel about a substantially vertical axis, first and second bearing means being adapted to support the turn table. Mounting means of a kind similar to the above mentioned are previously known and comprise a bearing means which is provided below the flange portion of a turntable, and a bearing means provided radially outside the latter. Furthermore, turntables are known (EP-A-0 259 072), where a bearing means with bearing members adapted for contact with an associated bearing face of the cylindrical portion of the turntable is mounted in the through hole and on the portion of the hull which is submerged in water. The bearing means below the flange portion of the turntable carries the turntable and prevents vertical movement downwards of turntable, and the bearing means positioned radially outside the flange portion or cylindrical portion, respectively, of the turntable, prevents horizontal motion and tilting of the latter about horizontal axes. In this case the weight of the turntable and the force of anchoring cables exerted against the turntable are to prevent any upwards directed vertical movement of the turntable. For repair or maintenance of the bearing means provided immediately below the flange portion of the turntable, the turntable must be raised and any running drilling or production operations must be interrupted. It may also be necessary to remove the turntable completely from the hole in order to carry out such work in connection with the bearing means or bearing surface in the submerged portion of the through hole in the hull. If the vessel floats on the water divers may be required to carry out desired operations in connection with the bearing faces. It is an object of the invention to provide a bearing means of the kind mentioned above, which is not burdened with the above disadvantages. The characteristics of the invention will appear from the characterizing features stated in the claims. The invention is disclosed in more detail below with reference to the drawing which shows a diagrammatical embodiment of a bearing means according to the invention. Figure 1 is an elevational view, partly in section, of a vessel's hull with a mounting means according to the invention. Figure 2 is a plan view of the hull portion shown in Figure 1, with a portion of the turntable removed, showing only some of the bearing means. Figure 3 is an elevational view of a bearing means. Figure 4 is a view of the bearing means shown in Figure 3, as seen in the direction of arrow A. As shown in Figure 1 a vertically extending through hole 7 with a circular cross section is provided in the hull 6 of a vessel with a deck 8 and a bottom 9. A turntable 1 comprising a cylindrical portion 3 and a circular flange portion 2 which is firmly connected with the upper end portion of said cylindrical portion is provided in hole 7. Furthermore, turntable 1 comprises a through hole 4 extending coaxially with cylindrical portion 3. The diameter of the hole 7 is larger than the external diameter of the cylindrical portion 3 of the turntable, but smaller than the external diameter of flange portion 2, and the length of cylindrical portion 3 is larger than the distance between the deck 8 and the bottom 9 of the vessel. The turntable is provided to be substantially coaxial in the hole 7, its lower portion being level with the bottom 9 of the vessel and, via cables 10, being connected with anchors not shown. The flange portion, thus, extends in parallel with the deck 8 and radially outwards from the edge of the hole 7. Flange portion 2 has a first or inner, and a second or outer annular bearing face or race 11, and 12, resp. on its underside, and a third annular bearing face or race 13 on its upper side, these bearing faces extending in planes normal to the longitudinal axis 5 of the turntable. Along its periphery flange portion 2, furthermore, has a radially outwards facing fourth bearing face or race 14, like the remaining bearing faces extending coaxially with longitudinal axis 5 of the turntable. On the deck, immediately above the bearing faces 11, 12, 13, 14 first, second, third, and fourth bearing means 21, 22, 23, and 24, respectively, are mounted to be in contact with the associated bearing faces with low friction. The first and second bearing means 21, and 22, respectively, which are provided below the flange portion 2 of the turntable, are designed to support the turntable. The third bearing means which is provided above the turntable is designed to prevent any essential vertical movement upwards of the turntable, and the fourth bearing means which is provided radially outside the flange portion of the turntable, is provided to prevent essential horizontal movement of the turntable relative to the vessel's hull. The first bearing means comprises a vertically extending hollow cylindric bracket 30, the lower end portion of which is attached to the deck 8 radially outside the hole 7 in the hull 6, and is concentric with and immediately outside said hole. A slider means or segment 31 showing good sliding properties is attached to upper portion of bracket 30. The second bearing means comprises a number of bearing pedestals 32 which are provided equally spaced along a circle radially outside bracket 30. As shown in Figures 3 and 4, a crank-like shaft 33 is mounted in each bearing pedestal 32. On each side of a central portion, which is mounted in bearing pedestal 32, said shaft has an elongation or shaft journal 36, 37, the longitudinal axis of which extends in parallel with, but is not coaxial with said central portion. On one shaft journal 37 a roller or wheel 34 is rotatably mounted, and the second shaft journal 36 is directly connected with the outer end portion of the piston rod of a hydraulic cylinder 35, the cylinder portion of which is articulated to the deck 8. The longitudinal axis of the portions of shaft 33 extends radially relative to the longitudinal axis of hole 7, so that rollers 34 may be activated to roll along the second bearing face 12. By actuating hydraulic cylinder 35 to retract the plunger means into the cylinder means, roller 34 will, thus, be lowered, and vice versa. When rollers 34 er lowered the distance between deck 8 and the top of rollers will be less than the distance between deck 8 and the top op slider means 31, and when rollers 34 are raised the distance between deck 8 and the top of rollers will be larger than the distance between deck 8 and the top of slider means 31. Movement of the turntable between a first lowered position and a second raised position is, thus, permitted. In the first position of the turntable it is carried by and may rotate only on the first bearing means 21, and in the second position it is carried by and may rotate only on the second bearing means 22. The third bearing means 23, like second bearing means 22, comprises a series of brackets 40 which may, e.g. be firmly connected with deck 8 radially outside bearing pedestals 32. Brackets 40 extend in a yoke shape radially inwards and across flange portion 2 of the turntable, and they terminate in a portion projecting down towards third bearing face 13 of the turntable. A slider 41 is here attached to bracket 40, in such a way that there is a slight clearance between slider and the associated third slide face 31 when the turntable is in its second raised position. Any possible tilting movement of the turntable about a horizontal axis will, thus, be limited corresponding to said slight clearance when the turntable is raised. In order to restrict such a tilting movement to the same degree when the turntable is lowered, a hydraulic cylinder 42 is attached to each bracket and carries a block or spacer 43 to the lower side of which a slider means with good sliding property is secured. By the aid of the hydraulic cylinders the blocks 43 may be moved horizontally between a first position, in which they are present in the space between third bearing face 13 of turntable 1 and slider means 41 of bracket 40, and a second position in which they are radially outside flange portion 2 of the turntable. The height of the blocks 43 corresponds to the vertical distance of displacement of turntable 1 when the latter is moved from its first to its second position by the aid of the second bearing means, and when the blocks are in said first position they preferably contact the respective slider means 41 of the bracket 40. Radially outside the cylindric face of the flange portion 2 of the turntable a hydraulic cylinder 45 is attached to each bracket 40 and carries a slider means 46 which is adapted for contact with the fourth bearing face 14, and has good sliding properties. Before raising or lowering the turntable 1 the slider means 46 are moved radially away from the fourth bearing face 14 by the aid of the hydraulic cylinders 45, so that they do not block the turntable during the raising or lowering movement. After completed raising or lowering of the turntable, the slider means 46 are again moved radially inwards towards the fourth bearing face 14 of the turntable flange by the aid of the hydraulic cylinders 45. The function of the support means is as follows, assuming that the turntable 1 initially is in its first, lowered position. This position of the turntable is selected when the direction of wind is stable or the forces exerted by the turntable on second bearing means 22 are so large that there is a hazard of overloading the latter. If the direction of the wind is expected to turn and there is no hazard of overloading, as mentioned above, the blocks 43 of the third bearing means 23 are removed from the space between the slider means 41 and the third bearing face 13 of the turning means. The rollers 34 of the second bearing means 22 are now raised, causing the turning means to be raised and the third bearing face 13 to be moved into a position where it is close to the underside of slider means 41 of the third bearing means. The ship's hull may in this connection be turned very easily relative to the turntable, so that the longitudinal axis of the ship will always coincide with the direction of the wind. In this position of the turntable maintenance and repair work may also be carried out in connection with the first bearing means or face. If periods without any danger of change of the direction of wind should occur again, the rollers 34 of the second bearing means may be lowered, so that the sliders 31 of the first bearing means 21 may be made to contact the first bearing face 11, whereupon spacers or spacer blocks 43 are moved radially inwards, towards the longitudinal axis 5 of the turntable by the aid of the hydraulic cylinders 42, to cause the clearance between the third bearing face and the cooperating stationary bearing face to remain the same. In this position of the turntable the second bearing means is not subjected to wear, which is advantageous this device comprising the most expensive components. In this position of the turntable it is also possible to carry out maintenance and repair work in connection with the second bearing means. If a change of the direction of wind should occur meanwhile, the ship's hull can still turn due to the fact that first bearing face and cooperating slider 31 show good sliding properties. Even though the first, third, and fourth bearing means have sliders and the second bearing means has rollers, more than said second bearing means may, obviously, be provided with rollers or the second bearing means may also be provided with slider means in stead of rollers, provided that easy relative movability of hull and turning means is ensured. Furthermore, slider means 41 of the third bearing means may be raisable and lowerable by the aid of associated hydraulic cylinders, either by being provided, e.g. on the plunger member of the respective hydraulic cylinders, the stroke length of which corresponds to the displacement of the turntable, or by being provided on a crank means similar to the crank means of second bearing means. In the last mentioned case blocks 43 and hydraulic cylinders 42 are omitted.

Claims: A device for supporting a turntable or a turning body (1) on a vessel, especially a vessel for use in connection with drilling for and production of oil, which vessel is anchored to the sea floor, via the turntable (1), and the turntable (1) comprising a horizontally extending circular flange portion and a cylindrical portion (3) extending coaxially relative to the flange portion and projecting downwards from flange portion (2) into a vertically extending through hole (7) in hull (6), the device comprising bearing means (21, 22, 23, 24) connected with the hull of said vessel, and one or a plurality of bearing members (31, 34, 41, 46) adapted to bear against the respective bearing faces (11, 12, 13, 14) of the flange portion (2) of the turntable, and the bearing means and faces permitting mutual rotation of turntable (1) and hull (6) about a vertical axis (5), first and second bearing means (21 and 22, resp.) being adapted to support the turntable (1), characterized in that the bearing member(s) (34) of the second bearing means are raisable and lowerable, so that the turntable (1) thereby may be moved in a vertical direction between a first lowered position and a second raised position, the turntable (1) being rotatably carried only by the first bearing means (21) in said first position and being rotatably carried only by the second bearing means (22) in said second position. A device according to claim 1, characterized in that the bearing members of at least one of bearing means (22) are rollers (34) which are rotatably mounted in bearing pedestals (32) which are provided equally spaced along the periphery of flange portion (2) of the turntable. A device according to claim 1 or 2, characterized in that bearing members of at least one of the bearing means (23) are blocks (41) which are covered by a material with good sliding properties, and which are equally spaced along the periphery of flange portion (2) of the turntable. A device according to one of the preceding claims, characterized in that at least one of bearing means (21) comprises a race (31) continuously extending along the periphery of the flange portion (2) of the turntable and manufactured from a material with good sliding properties. A device according to one of the preceding claims, characterized in that the bearing member or each bearing member (34) of second bearing means (22) is mounted on a horizontally extending shaft (33) which is rotatably mounted in said bearing means with an eccentric portion relative to its axis of rotation, on which portion bearing member (34) is mounted so as to be movable towards, and away from, respectively, the flange portion (2) of the turntable (1) by rotation of the shaft (33). A device according to one of the preceding claims, characterized in that a third bearing means (23) is provided above the peripheral portion of flange portion (2) of the turntable and adapted to substantially prevent vertical movement upwards of the turntable, the bearing member or members (41) of the third bearing means (23) also being movable, so that the clearance between the operative bearing members (43, 41) of this bearing means (23) and the bearing members (31, 34) of the first, and second bearing means (21, 22), respectively, will remain the same when the bearing member(s) (34) of the second bearing means is/are lowered or raised, respectively. A device according to claim 6, characterized in that the bearing element or elements of the third bearing means are mounted on a horizontally extending shaft which is rotatably mounted in the bearing means and has a portion extending excentrically relative to its axis of rotation, on which the bearing member is mounted, so that it may be moved towards, and away from, respectively, the flange portion (2) of turntable (1) by rotation of the shaft. A device according to claim 6, characterized in that the third bearing means comprises sliders (41) which are firmly attached to the hull (6) and blocks or spacers (43) which may be moved between a first position, in which they are in the space between the associated bearing face (13) of the turning table and the sliders (41), and a second position, in which they are not present in the space and will, thus, not prevent the turntable (1) from being raised by the aid of the second bearing means (22). A device according to one of the preceding claims, characterized in that fourth bearing means (24) are provided radially outside the flange portion (2) of the turntable and adapted to substantially prevent horizontal movement of the turntable (1) relative to the hull (6). A device according to claim 9, characterized in that said fourth bearing means (24) comprises a series of bearing members (46) which are provided along the periphery of the turntable flange (2) and are movable radially relative to the longitudinal axis (5) of the turntable between a first position, in which the members (46) contact the associated bearing face (14) and a second position, in which they are at a distance from this bearing face.

Inventors: GLORSTAD, TORBJORN
Applicants: GOLAR-NOR OFFSHORE A.S.
Application year: 1990
Main classification: B63B21
IPC codes: B63B21