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 fluid swivel is described, which enable the measurement and the adjustment of separation of seal surfaces. The fluid swivel includes inner and outer walls that are rotatably coupled about an axis and that form an annular chamber and a pair of gaps extending from the chamber. A hollow region is formed along each gap for holding a face seal, and the gap forms an extrusion gap portion extending radially from each hollow region. The inner and outer walls form axially-spaced wall surfaces adjacent to the hollow region, and one of the walls has a gage-passing passage leading from the outside of the wall to the space between the wall surfaces to pass a gage for measuring the separation gap between the wall surfaces. One of the walls includes a plurality of parts and also includes shims between the parts for enabling slight adjustment of the spacing between the seal surfaces, depending on the thickness of the shims.

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: An offshore terminal of the type which includes a dedicated vessel which rigidly supports a transfer structure beyond one end of the vessel, and with the transfer structure held by catenary chains to the sea floor. The transfer structure lies very close to an end of the vessel, but is has an underwater lower end which lies at a level substantially no higher than the adjacent end of the vessel, to avoid the possibility of the catenary chains hitting the vessel. The transfer structure extends from below water to above water, and the hose structure extending up from the sea floor extends through the transfer structure to protect it from surface waves. A product distribution unit (PDU) lies at the top of the transfer structure and has a turning portion connected to the vessel, the PDU being connected to the vessel independently of a massive mooring structure that connects a rotatable portion of the transfer structure to the vessel to transfer large loads.

Abstract: An offshore terminal is described, of the type which includes a dedicated vessel that supports a transfer structure loosely anchored as by several chains, and a fluid conduit structure that extends from the sea floor through the transfer structure to the vessel, wherein the vessel and transfer structure can be quickly disconnected to avoid potentially damaging surface conditions such as ice flows and hurricanes. The nonrotatable portion of the transfer structure, together with upper portions of the chains and underwater fluid conduit, can be detached from the rest of the transfer structure to sink below the surface, but to a predetermined depth which is considerably above the sea floor, so the vessel and a portion of the transfer structure can be sailed away from the region.

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 system which can be set up in emergencies to moor an offloading vessel and transfer oil between it and a seabed pipeline, as to remove oil from a grounded tanker or to deliver fuel to the shore under hostile or emergency conditions. The system includes a barge containing a fluid swivel as well as a mooring buoy and buoy-holding chain. The barge can be towed to a desired location and pipes and hoses connected to the fluid swivel, and the barge then can be sunk to the seabed. Upon sinking, the barge is already connected to the seabed pipeline and to hoses that extend from the barge to the sea surface to connect to an offloading vessel, as well as being connected through a chain to a buoy floating at the sea surface which has a hawser for mooring the vessel. A vessel can be utilized to tow out the seabed pipeline, to facilitate installation of the pipeline as to enable connection of the pipeline to the fluid swivel on the barge prior to sinking the barge.

Abstract: A heavy-duty slowly pivoting shaft and bearing system for an offshore mooring terminal, of a type which includes a heavy-duty shaft with opposite ends that are each rotatably mounted on a radial bearing assembly, wherein bearings at each of the assemblies can be removed while the shaft continues to be rotatably supported to permit its uninterrupted use. Each bearing assembly includes a housing arm with a hole that receives an end of the shaft, a main bearing lying near the outer end of the hole to permit its replacement by sliding it off an extreme end of the shaft, and an auxiliary bearing lying at the inner end of the hole near the middle of the shaft. The auxiliary bearing is formed in a plurality of segments that each extend by less than a half circle around the shaft, to permit the segments to be individually placed about the shaft and forced between the housing arm and shaft.

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 fluid swivel is described, of the type which includes an annular chamber formed at the interface between the stationary and rotatable parts of the swivel, which facilitates the passage of a pig through the chamber. A pig diverter device lies beside the outlet formed in one of the parts through which fluid normally exits the chamber, to divert a pig moving through the chamber into the outlet. The diverter device can include a projection lying on the downstream side of the outlet. The projection can extend radially only up to the interface between the two swivel parts, to facilitate disassembly of the swivel. The diverter device can also include a valving mechanism that can shut off fluid flow immediately downstream of the outlet, to direct the fluid stream and pig into the outlet, and the upstream end of the outlet can extend tangent to the chamber to facilitate pig entry therein.

Abstract: A single leg mooring terminal is described, of the type which includes a riser extending up from the sea floor to moor a vessel, and a separate fluid conduit extending up from the sea floor to carry oil to or from the vessel, and wherein the riser and hose structure must both rotate without limit about the same vertical axis to follow drifting of the vessel. A turntable near the sea floor, rotatably supports the riser about a vertical axis, and has a hole along its vertical axis through which a portion of the fluid conduit extends. A fluid swivel of the fluid conduit, lies under the turntable and is accessible through a hole in the turntable.

Abstract: A system which can be set up in emergencies to moor an offloading vessel and transfer oil between it and a seabed pipeline, as to remove oil from a grounded tanker or to deliver fuel to the shore under hostile or emergency conditions. The system includes a barge containing a fluid swivel as well as a mooring buoy and buoy-holding chain. The barge can be towed to a desired location and pipes and hoses connected to the fluid swivel, and the barge then can be sunk to the seabed. Upon sinking, the barge is already connected to the seabed pipeline and to hoses that extend from the barge to the sea surface to connect to an offloading vessel, as well as being connected through a chain to a buoy floating at the sea surface which has a hawser for mooring the vessel. A vessel can be utilized to tow out the seabed pipeline, to facilitate installation of the pipeline as to enable connection of the pipeline to the fluid swivel on the barge prior to sinking the barge.