Abstract: A fluid swivel is described, of the type that carries oil, water or natural gas at high pressure between an undersea well and a weathervaning ship, which has a seal device of increased lifetime. The seal device (56, FIG. 2 ) lies in a cavity of a first swivel part (12) and includes a rigid seal ring (62) that is slidable toward and away from a sealed surface (66). A deformable seal (60) can be backed up by the seal ring, with the seal ring sliding to close the extrusion gap (70) into which the seal could extrude when high pressure fluid enters the swivel. A pressure source (80) coupled to the cavity urges the backup part to deform radially and slide toward the sealed surface with a force that increases as the pressure of fluid in the swivel increases.

Abstract: A vessel with a rotatable turret thereon is moored in a manner that minimizes turret tilt while avoiding the need to maintain precisely concentric upper and lower turret bearings. A mooring structure (152, FIG. 7) is formed by a group of mooring lines (162, 164) such as chains, with the upper ends of the lines coupled to the vessel through a connecting apparatus (154) that comprises a group of arms (166) each connected to a corresponding one of the lines. Each arm is pivotally mounted (at 170) on the turret to hang therefrom, so the arm transmits primarily vertical forces to the turret and the turret bearing (185) has to support primarily vertical forces. Each arm carries a bearing pad (174) that presses horizontally against a vessel lower bearing ring (182) mounted directly on the vessel hull independently of the turret.

Abstract: A fluid swivel is described, of the type which includes a ring-shaped outer structure (12, FIG. 2 ) that rotates about a ring-shaped inner structure (14), and which form an annular chamber (18) between them and a pair of gap passages (24, 26) between them which are sealed by pressure seals (30, 32). The outer structure includes a body (70) forming part of the annular chamber and a seal ring (72) mounted on an end of the body and abutting one side of the pressure seal. The seal ring is axially shiftable on the end of the body, so that when the body expands radially as a result of high pressure fluid being introduced into the annular chamber, the seal ring does not have to expand a similar amount and therefore does not have to cause a large increase in the width of the extrusion gap (62) at the downstream end of the pressure seal.

Abstract: A fluid swivel, of the type that carries oil, natural gas, or other fluid between an undersea well or pipeline and a weathervaning ship, wherein the seal arrangement that prevents leakage of fluid is constructed to increase the seal lifetime and reduce the cost of the fluid swivel. The seal arrangement includes a recess (44, FIG. 2) in a first of the swivel parts and a seal assembly (46) therein which includes a pressure seal (50) and a backup ring (56). The backup ring has a dynamic side (64) lying adjacent to the portion (54) of the second swivel part that is sealed against, and has an opposite distal edge portion (72). The dynamic side of the backup ring has a tapered downstream portion (80) that is tapered at an angle A of no more than 30.degree. to the axis of rotation (16) of the fluid swivel, with the downstream edge (82) of the tapered portion lying on a downstream wall (86) of the first swivel part rather than overhanging it.

Abstract: A multiple fluid swivel arrangement is described, for connecting stationary undersea pipes to rotatable pipes on a weathervaning ship, which provides ready access to each of the fluid swivels and which minimizes the diameters of the fluid swivels and their seals and other parts. Each of the multiple fluid swivels, except for the uppermost one, includes a largely horizontal arm (40A, FIG. 2) with an inner end (38) that can pivot about a largely vertical axis (32) on a fluid swivel body (33) that is connected to a stationary pipe (12A) extending to a deep underwater location. The outer end (42) of the arm is detachably connected to one of a plurality of couplings (44A, 46A) mounted on the ship. As the ship weathervanes and the arm approaches one of the vertical stationary pipes (12B), the outer end of the arm is disconnected from a coupling (44A), the arm is pivoted until its outer end lies adjacent to a second coupling (46A), and the outer end of the arm is attached to the second coupling.

Abstract: A mooring system is provided, which can be rapidly installed and which is of relatively low cost. The system includes a transfer structure attached to a vessel, an anchor line extending from the transfer structure to a chain table near the sea floor, and catenary chains extending from the chain table to the sea floor. A weight hangs from the chain table to help in setting up the system and in mooring a vessel thereafter. The transfer structure includes a platform that can rotate with respect to the vessel, and a direction sensor for controlling a motor that rotates the platform opposite to rotation of the vessel, to avoid twist of the anchor line.

Abstract: A bearing arrangement is described for mounting a turret on the outer ends of beams whose inner ends are supported by a vessel that can weathervane about the turret. A lower bearing arrangement that mounts a lower portion of the turret in rotation about a vertical axis to a lower beam, permits the lower turret portion to pivot about a pair of lower horizontal axes. An upper bearing arrangement that mounts an upper portion of the turret to an upper beam in rotation about the vertical axis, permits the upper turret portion to pivot about a pair of upper horizontal axes.

Abstract: A fluid swivel is described, of a type which forms an annular chamber and a pair of gap passages extending in opposite directions from the chamber to the environment, with face seals along each gap passage. The fluid swivel uses a minimum number of parts and minimizes entrapment of sediment in the isolation seal lying between the chamber and the closest pressure seal. The high pressure ends of the primary and secondary seals in each gap passage, face in opposite radial directions, and the low pressure end of each secondary seal lies about as far from the axis of rotation of the swivel as the low pressure end of the corresponding primary seal. The gap passage includes a tapered portion leading from the annular chamber to the isolation seal, to enable circulation of fluid up to the isolation seal to minimize the buildup of sediment.

Abstract: An offshore fluid transfer system is described for transferring fluid between an underwater pipe and a dynamically positioned vessel at the sea surface, which is relatively lightweight and economical. The system includes a riser having an upper end attached to the vessel and a lower end having a chain table held by chains extending in catenary curves to the sea floor and weighted by a weight hanging by the chain table. The riser supplied substantially the only mooring force most of the time, while thruster equipment on the vessel supplies sufficient additional force a small amount of the time to limit vessel drift in violent storms. The upper several meters of the riser is a rigid pipe, and an instrument that measures tilt of the pipe indicates the amount and direction of drift of the vessel.

Abstract: An offshore system of the articulated tower type is provided, which utilizes chain devices extending in different directions from the upper portion of the tower to the seabed to help maintain the tower in a largely vertical orientation. In one system wherein the tower must be held close to the vertical orientation, as where the system is used for drilling underwater hydrocarbon wells, an inclinometer is utilized to measure small angles of tilting of the tower, to operate one or more winches that pull on the chain devices. The chain devices can be in the form of heavy chains extending in loose curves. In another system, the chain devices are lines of highly stretchable material such as nylon, and which may be nearly neutrally buoyant, and with the lines extending in almost straight lines between the tower and seabed.

Abstract: A mooring system is provided, which can be rapidly installed and which is of relatively low cost. The system includes a transfer structure attached to a vessel, an anchor line extending from the transfer structure to a chain table near the sea floor, and catenary chains extending from the chain table to the sea floor. A weight hangs from the chain table to help in setting up the system and in mooring a vessel thereafter. The transfer structure includes a platform that can rotate with respect to the vessel, and a direction sensor for controlling a motor that rotates the platform opposite to rotation of the vessel, to avoid twist of the anchor line.

Abstract: An improved hose structure is provided for passing fluid across a pivot joint, that permits a transfer structure to pivot about two horizontal axes with respect to a vessel or the like at the sea surface. A middle conduit has a lower end connected to a pipe on the transfer structure and an upper end connected to a pipe on the vessel. The middle conduit can pivot, either by being flexible to bend along its length, or by being rigid but with flexible joints at its opposite ends. The pipe on the vessel can move up and down and is biased upwardly. When the transfer structure tilts, to raise or lower the lower end of the hose, the upper end can also rise or fall.

Abstract: An improved hose structure is provided for passing fluid across a universal joint, that permits a transfer structure to pivot about two horizontal axes with respect to a vessel or the like at the sea surface. A hose or other flexible conduit has a lower end connected to a pipe on the transfer structure and an upper end connected to a pipe on the vessel which can move up and down and which is biased upwardly. When the transfer structure tilts, to raise or lower the lower end of the hose, the upper end can also rise or fall to minimize bending of the hose, so that a substantially straight hose can be used.

Abstract: A boom is described for use on a single point mooring system to connect a tower thereof to tankers or other vessels, wherein the boom is constructed to enable rapid attachment to a vessel and to protect boom components when not connected to a vessel. The boom has an inner end pivotally connected about a horizontal axis to a transfer structure, and has an outer end forming a compressible structure which can withstand compression and tension loads during coupling to a vessel. The boom end can be pulled up along the bow of a vessel until a secure connection can be made to the vessel, at a level at which a pipe connection at the end of the boom can connect to a pipe connector on the vessel. A buoyancy tank connected by a strut to an outer end portion of the boom holds the outer end of the boom at a considerable height above the water. Tanks lie on either side of the pivot axis of the boom, and a pump can be utilized to transfer water from one tank to the other to raise or lower the boom.

Abstract: An offshore mooring system is provided which is especially useful for mooring ships in moderately shallow seas such as on the order of 300 feet. The system is of the type which includes a tower having a lower end pivotally mounted to the sea floor and an upper end lying above the sea surface and connected through a hawser to a ship. A group of long chains have lower ends anchored at locations spaced about the tower, and upper ends connected to an upper portion of the tower. The chains extend in loose catenary curves, with most of the chain lengths lying on the sea floor in the vertical tower condition, to permit the tower to tilt in any direction by at least 20.degree. from an initial vertical orientation before one of the chains is pulled taut.

Abstract: A fluid swivel is described, which is especially useful for carrying hydrocarbons at high pressures between stationary and rotating walls of a swivel. The swivel forms a fluid-carrying annular chamber and a pair of gap-like passages lying between the walls and extending from opposite sides of the chamber to the environment, with primary and secondary face seals located along each passage. Each passage includes a portion extending between the seals, the passage portion forming a pair of largely radially-extending wall surfaces, one on the outer wall and one on the inner wall. The radially-extending wall surface on the outer wall faces in a first axial direction, and the outer wall at the secondary seal faces in an opposite axial direction. As a result, if the primary seal should fail, this will not change the axial force on the outer wall. The extrusion gaps at the seals extend in radial directions from the seal, so these gaps do not widen when high pressure is applied to the fluid swivel.

Abstract: An improved offshore terminal is described, of the type that includes a riser loosely anchored at the sea floor so its upper end can extend from a deep underwater level up to the surface to moor a tanker and transfer hydrocarbons to it. A weight hangs from the lower end of the column to improved dynamic mooring and, where the riser is disconnected to limit the sink depth of the riser. For movement to the deployed position, the riser is lifted by extending a line downwardly from a winch on the vessel, through a central hole in the connector frame down to the top of the riser, the line being pulled to raise the riser until its upper end lies within the central hole of the connector frame. A perforated upper portion of the riser then is in fluid communication with the inner portion of a fluid swivel, so that hydrocarbons can pass out of a conduit within the riser and into the swivel.

Abstract: An offshore hydrocarbon production system is provided, which is of relatively low cost. The system includes a vessel (12) having a platform (24) that allows the vessel to rotate about a vertical axis with respect to the platform, and a column (14) having an upper end pivotally connected to the platform about horizontal axes (32, 34) and a lower end anchored solely by a group of loose chains (38) that permit the lower column end to tilt and move in every direction. The lower end of the column is weighted by a counterweight and by the chains, so the column acts like a pendulum that tends to return to the vertical when tilted, to urge a drifting vessel back towards its quiescent position. The bottom of the column also moves laterally during such vessel drifting, increasing tension in one chain (38a) and reducing tension in an opposite chain (38b) to also urge the vessel back towards its quiescent position.

Abstract: A tying arrangement is described for use with an offshore terminal wherein a transfer structure near the sea surface is anchored by a group of anchor lines extending at downward inclines to the sea floor. A bumper line extends between a pair of anchor lines, so a ship heading for the transfer structure first encounters a bumper line that gradually stops it. The bumper line also enables the coupling of anchor lines to transfer energy from one to the other, to increase the energy absorption capacity and stiffness of the system.

Abstract: A mooring line handling apparatus comprising a small diameter sheave, a large diameter sheave, the small sheave and the large sheave being axially mounted on a shaft secured to a base, a first line wrapped for at least part of its length on the large sheave, and an elastic line extending from an anchor to the small sheave for resisting rotation, by the elasticity of the elastic line, of the large sheave when a load is applied to unwrap the first line. A plurality of elastic lines of equal length can be used. Another version of mooring line handling apparatus has a lever pivotably secured to a base, a mooring line attached to a first end of the lever, and an elastic line extending from the anchor to the second end of the lever. A load applied to the mooring line pivots the lever which stretches the elastic line thereby effectively increasing the mooring line length as a load is applied.