Abstract: Thrusters in communication with a feedback control system are provided on a cylindrical offshore marine member, such as a spar, for reducing and/or controlling vortex-induced-vibrations, low-frequency drift oscillations due to random waves, and low-frequency wind induced resonant oscillations. The thrusters are provided thrust instruction from the feedback control system based on marine member displacement and current velocity.

Abstract: A very large diameter turret for mooring a VLCC class FPSO vessel. A large diameter rail and wheel bearing system is disposed between a turret main deck and the hull of the vessel. The turret is designed for a flexibility to allow the turret main deck to conform to the sag or hog of the vessel so that excessive forces on the wheels of the bearing system are avoided. The turret's main deck, in a preferred embodiment, includes a center hub, an outer ring, and spokes between the hub and outer ring. A lower chain deck is preferably connected to the main deck by pillars or columns, or alternatively by riser tubes alone, or other structures that achieve the desired flexibility of the main deck.

Abstract: A single hoisting mechanism is positioned on a turret of either an external or an internal turret mooring system for a FSO or FPSO vessel and is releasably securable to each of a plurality of anchor leg chains. The mechanism is mounted for angular rotation about the center-line of the turret in order that the hoist can be angularly aligned and selectively engaged with each of the anchor leg chains or riser/umbilicals spaced around the turret.

Abstract: The present invention relates to a passive stabilizer (3) which is installed in the lower part of a tanker used in floating production systems which make use of a mechanism which enables the tanker (1) to rotate about a vertical axis (turret). The stabilizer gives the tanker greater directional stability and makes it possible to install the turret in a more central position along the tanker.

Abstract: The invention is a bearing unit and bearing system for supporting a large rotatable element, such as a mooring turret. The bearing unit includes a hydrostatic suspension system which enables the bearing unit to accommodate fabrication tolerances and also enables the bearing unit to conform to relative movements between the ship and the turret, thereby providing a compliant bearing system. The system includes multiple bearing units of the invention which serve as thrust and/or radial bearings for supporting the turret. By manifolding a plurality of bearing units together in a fluidly-isolated group, the pressure applied to the bearing units in that group is self-equalizing so that all the bearing units act in unison to equally support the load, while also allowing some degree of self-alignment and tilting of the load. As a result, the bearing system emulates a self-aligning bearing system and is able to compensate for axial and angular misalignment.

Abstract: A device for installation in a floating vessel which is intended for receiving a buoy or a turret in a submerged receiving space at the bottom of the vessel. The device comprises a tubular body (5) dimensioned for installation in a shaft (2) extending vertically through the hull of the vessel and which, at its lower end, is arranged to receive a module unit (6) provided with a through opening (8) for receiving the buoy/turret. When the module unit (6) is installed in the tubular body (5), the module unit at its lower end forms a seal (37) against the tubular body (5), and at its upper end the module unit (6) is fixed in relation to the tubular body (5) by locking means (40).

Abstract: The invention is a bearing unit and bearing system for supporting a large rotatable element, such as a mooring turret. The bearing unit includes a hydrostatic suspension system which enables the bearing unit to accommodate fabrication tolerances and also enables the bearing unit to conform to relative movements between the ship and the turret, thereby providing a compliant bearing system. The system includes multiple bearing units of the invention which serve as thrust and/or radial bearings for supporting the turret. By manifolding a plurality of bearing units together in a fluidly-isolated group, the pressure applied to the bearing units in that group is self-equalizing so that all the bearing units act in unison to equally support the load, while also allowing some degree of self-alignment and tilting of the load. As a result, the bearing system emulates a self-aligning bearing system and is able to compensate for axial and angular misalignment.

Abstract: A chain table for connecting mooring legs to a turret. The chain table includes downwardly sloping connection flanges with bosses for forming holes for pivoting members of a coupler assembly. The downward slope of the flanges allows forces from connected anchor legs to be better directed to the chain table as compared to connecting flanges which extend perpendicularly from the body of the chain table. As a result, the chain table can be made smaller which allows it to be fabricated by casting techniques. An anchor leg pattern is established by connecting vessel end portions of anchor legs to the chain table while the vessel is in port, installing at a mooring site seabed portions of anchor legs according to an anchor leg pattern, and after the vessel arrives at the mooring site, connecting each vessel end portion to each corresponding seabed anchor leg portion to establish the anchor leg pattern for mooring the vessel.

Abstract: A lower bearing arrangement between a turret of an FPU and a moonpool. The outer housing of the bearing is mounted about the turret instead of the FPU's hull structure. Bearing segments are captured between an outer ring of the turret and an inner ring of the outer housing. The outer housing of the bearing assembly is coupled to a reaction ring of the moonpool so that rotation forces of the vessel are transferred to the outer housing of the bearing. The coupling also includes an arrangement by which the outer housing contacts said reaction ring in the nature of a spherical joint.

Abstract: A lower bearing arrangement between a turret of an FPU and a moonpool. The outer housing of the bearing is mounted about the turret instead of the FPU's hull structure. Bearing segments are captured between an outer ring of the turret and an inner ring of the outer housing. The outer housing of the bearing assembly is coupled to a reaction ring of the moonpool so that rotation forces of the vessel are transferred to the outer housing of the bearing. The coupling also includes an arrangement by which the outer housing contacts said reaction ring in the nature of a spherical joint.

Abstract: Connection arrangements for a male probe and female receiver for selective connection of a spider buoy with a turret for mooring a vessel in offshore waters. A resilient member is provided in the male probe to absorb forces on the probe as it is being pulled into the receiver. A seal is provided between surfaces of the probe and the receiver to seal seawater from the interior of the turret. Contact rings at the bottom opening of the receiver and at the base of the male probe are machined of hardened strengthened steel and test assembled together prior to bolting of the rings to the receiver and the spider buoy respectively.

Abstract: A vessel with a mooring tube assembly with swivel mounted chain supports. The assembly includes a frame arranged and designed for support within a vertical opening of the vessel at its bow and/or its stern. A plurality of chain tubes are carried on the outer side of the frame in an arc such that their top ends extend upwardly generally parallel to the vertical axis of opening of the vessel. The vessel includes a deck mounted above the upper end of the frame. A track on the deck allows a single winch to be moved so that a pull-in line can be registered with any of the top ends of the tubes. A plurality of chain supports are rotationally mounted on the frame where each chain support has an outlet and an inlet. A trunnion chain stopper is provided between the outlet and inlet of the chain support. The outlet of each chain stopper is in registration with the lower end of one of the chain tubes.

Abstract: An improved turret for a turret mooring arrangement characterized by the turret including an upper section and a lower section which are coupled together by a flex joint. The turret mooring arrangement also includes a turret insert tube with a lower section that is rotatably coupled to the vessel by a radial bearing assembly. The radial bearing assembly includes an outer member having an outer profile arranged and designed to cooperate with a complementary profile in the interior of the turret insert tube so that the outer member is turned by the turret insert tube when the vessel rotates about said turret, without fixed attachment of the outer member to the turret insert tube. Methods of installing a turret and lower bearing assembly within a turret insert tube of a vessel are also disclosed.

Abstract: Thrusters in communication with a feedback control system are provided on a cylindrical offshore marine member, such as a spar, for reducing and/or controlling vortex-induced-vibrations, low-frequency drift oscillations due to random waves, and low-frequency wind induced resonant oscillations. The thrusters are provided thrust instruction from the feedback control system based on marine member displacement and current velocity.

Abstract: A method and apparatus for ensuring against explosion of the gaseous atmosphere of a closed chamber, such as the QDCD room of an internal turret of an offshore production and offloading buoy wherein the closed chamber has production risers and conduit connectors that represent a potential source of flammable gas. The method comprises mixing and diluting the oxidant content of the air by introducing within the closed chamber a sufficient quantity of inert gas to render the mixture of the air and any flammable gas non-combustible regardless of the flammable gas content of the mixture. The method includes removal of the non-combustible mixture of air and any flammable gas from the closed chamber by purging thereof to the natural atmosphere, while introducing inert gas, thereby leaving a substantially inert atmosphere within the closed chamber.

Abstract: A vessel (1) includes a relatively small sized turret (2) located near keel level. The upper part (3) of the turret wall is located below a level halfway between deck level (12) and keel level (7). Via a relatively small diameter product shaft (9), the product pipe (18) which connects to a riser (17) extends up to deck level (12). The lower part (6) of the turret wall extends along the height of the chain table (8), which is connected thereto via an axial and a radial bearing (23, 24). In this way the chain table (8) can adequately take up the bending moments exerted by the mooring chains (13) or cables. After use of the vessel (1) as a floating production storage and offloading vessel, the lower part (6) of the turret wall can be easily removed and the vessel (1) can be converted back to a transport tanker. Preferably the lower part (6) of the turret wall is releasably connected to the upper part (3) by means of releasable bolts (27) through the upper slide bearings (23) of the chain table (8).

Abstract: When mooring a production ship (10) above a submarine production well, minimum three (usually e.g. eight) anchor lines are used in the form of mooring chains (16b, 16a′, 16b′, 16c′) each extending from a stationary point at the seabed to a separate attachment point on the ship (10). At least one anchor line (16b, 16c) (of a minimum line number of three) has a fixed length and leads to an attachment hook (20) on-board the ship, while the or each of the remaining anchor lines (16a′, 16c′, 16d′), as known per se, has a changeable, shortenable length between the stationary seabed point and a point (34) on the ship (10), e.g. by means of a winch (30) for each of said longitudinally changeable anchor lines (16a′, 16c′, 16d′), simplifying the mooring arrangement constructively and the mooring operations functionally.

Abstract: A vessel with a mooring tube assembly with swivel mounted chain supports. The assembly includes a frame arranged and designed for support within a vertical opening of the vessel at its bow and/or its stem. A plurality of chain tubes are carried on the outer side of the frame in an arc such that their top ends extend upwardly generally parallel to the vertical axis of opening of the vessel. The vessel includes a deck mounted above the upper end of the frame. A track on the deck allows a single winch to be moved so that a pull-in line can be registered with any of the top ends of the tubes. A plurality of chain supports are rotationally mounted on the frame where each chain support has an outlet and an inlet. A trunnion chain stopper is provided between the outlet and inlet of the chain support. The outlet of each chain stopper is in registration with the lower end of one of the chain tubes.

Abstract: A swivel device for a ship (10) equipped so as to serve as i.a. a production and/or a drilling ship by exploitation of submarine wells or reservoirs, respectively, containing oil and/or gas, where the ship (10) is formed with a vertically through-going shaft (12). Within the shaft (12), a turret (16) having a substantially vertical axis is rotatably mounted in relation to the hull and is included in said swivel device. Thus, when the turret (16) is moored to the seabed, the ship (10) may turn about said vertical axis, dependent on wind and/or sea currents. The swivel device comprises a first pipe (32) substantially concentrical with the turret (16) and with a smaller external diameter than the internal diameter of the turret (16), so that, between the outside of said first pipe (32) and the inner side of the turret (16), a vertically through-going annulus is formed for accommodating of several production risers (34).

Abstract: A vessel-turret assembly with an opening (3) in the hull of the vessel wherein a turret (4) is rotatably received. The axial bearings (8) between the hull structure and the turret have a number of circumferentially spaced bogies (12) running on raceways. Each of the bogies (12) is mounted on a displacement element such as an elastically deformable element. The bogie body may comprise a side plate with flange or shaft which in a hingepoint is hingedly attached to the hull structure. This point is located near or on the plane defined by the load bearing surfaces of the wheels. In this way a radial movement of the load bearing surfaces of the wheels. In this way a radial movement of the load bearing surfaces of the wheels due to the elastical deformable elements is prevented. Alternatively, each bogie may comprise one or more axial wheels for engaging the hull structure and/or the turret to prevent radial movement of the bogie structure at the position of the load bearing surface of the wheels.

Abstract: Elastomeric pads are arranged radially around the main bearing which rotatably supports a mooring turret with respect to a vessel. The elastomeric pads act as radial springs to react the radial turret loads in the vessel and to compensate for ovaling of the vessel in response to sea environmental forces on the vessel. A radial spring assembly is provided which applies compressive load to the elastomeric pads when the vessel and turret move radially toward each other, but prevent tension from being applied to the pads when the vessel and turret move radially away from each other.

Abstract: An arrangement for turning a turret on a ship comprises two slides that can glide along a flange arrangement being arranged on a rim of a turret. The slides are moveable by respective hydraulic cylinders and provide support for a rotatable pawl arrangement which can be rotated into and out of engagement with apertures in the rim. The two hydraulic cylinders are arranged as mirror images of each other in order for the cylinders to push the rim in opposite directions. When the turret is turned, one of the hydraulic cylinders, with the associated slide and pawl arrangement, is used to push the rim in the desired direction, while the other hydraulic cylinder with associated slide and pawl arrangement is utilized to hold the rim in a fixed position while the first slide is pulled back in order for the pawl arrangement to engage with a new aperture in the rim.

Abstract: A ship type floating oil production system for access to subsea wells through installation of surface wellheads on a ship type surface vessel on the sea comprises a cylindrical turret moored to a seabed is located within a moon pool formed in the ship type surface vessel such that the ship type surface vessel is freely rotatable about the cylindrical turret. A plurality of riser pipes have a rigid structure and extend downward to subsea wells through the cylindrical turret, and each riser pipe is provided at its top portion with a surface wellhead including valves of the riser pipe. Accordingly, workover operations can be facilitated as needed by running workover tools through the surface wellhead of the corresponding riser pipe through use of a work-over-rig installed on the ship type surface vessel.

Abstract: To permit use of a ship as production ship, among other things in conjunction with a so-called STL-buoy (30) and in test production without a buoy (30), and in which the ship (10) is formed with a bottom recess (12) for the reception of the buoy (30) in a mutually pivotal manner, there has been formed, immediately above said bottom recess (12), a vertically oriented cavity (14) in the ship's hull. In this cavity (14) is pivotally supported a sleeve-shaped turret (16) which is configured with at least one through bore, channel or other passage for passing pipelines (24, 24′), pipeline portions (38, 38′), or the like, which may be connected at the one end via a swivel device (22) to one or more pipes or the like (26) fixed in the vessel. The sleeve-shaped turret (16) works alone during test production, but is connected to the buoy (30) so that together they form a turret (16, 30) in regular production.

Abstract: The vessel including a hull and a cylindrical turret well, with a weathervane around a geostationary turret located in the turret well, and at least one swivel supported on the turret. The inner wall of the swivel is connected to rotation drive which allows the fall swivel weight to be transferred directly to the turret. The inner wall of at least one swivel is rotatably connected to a swivel support structure on the turret via a bearing. The rotation drive is adapted for rotating the inner walls in conjunction with the vessel so that relative displacements between the swivel and the turret are reduced such that the layout of the pipe lines connected to the swivel can be simplified by the omission of expansion loops. As the weight of the swivel is carried by the turret, the rotation and pipe support structure can be relatively small. The outer walls of the swivel stack may be fixedly connected to the turret so that a separate rotational drive for the outer walls can be avoided.

Abstract: A turret system is installed on an existing vessel such as an oil tanker. A portion of the existing structure, such as the center splice, is removed to leave an opening. A support structure is attached within the opening. The support structure includes a turret support structure. The turret structure is assembled within the turret support structure. Fluid piping is installed between the turret structure and the pipework of the vessel, including a manifold structure and a fluid swivel. The turret assembly is cladded for environmental protection. In one arrangement, the turret system is within the profile of the original vessel. In another arrangement, the turret system is external to the profile of the original vessel.