Not Applicable
The present invention relates generally to transferring fluids between an onshore facility and a floating vessel. Specifically, the present invention provides an auto-balancing hose system that accommodates vessel motions as well as relative displacements between a transfer pipeline and a loading platform.
Ships move goods and commodities from shore to shore. In some cases, a vessel is docked near shore and serves as a storage unit or production unit. Fluids need to be transferred between the vessel and a shore-based facility through a transfer pipeline. The pipeline is typically supported above water on a port/jetty/trestle and extended from onshore to a loading platform near a vessel. For cryogenic fluids such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), or any other fluids at a cryogenic temperature, expansion loops or bellows are used at an interval along the transfer pipeline to accommodate thermal expansion and contraction due to temperature changes.
A vessel requires a certain water depth for docking and is subjected to motions caused by waves and currents. A manifold onboard a vessel is typically elevated from several meters to 25 meters depending on a vessel type and size. A flexible connection is required between the end of the pipeline and a manifold onboard the floating vessel. This is typically done by an articulated arm made of hard pipes and swivel joints. This hard arm is anchored at its base on a loading platform, and has a riser and an arm to reach the vessel manifold as disclosed in U.S. Pat. No. 3,434,491 to Bily.
Improvements have been made for hard arms. For example, U.S. Pat. No. 8,176,938 to Queau and Maurel discloses a loading system with a movable supporting frame that allows end displacements of a transfer pipeline. Regardless of these improvements, all the hard arms have the followings in common: rigid pipes and a number of swivel joints, and a heavy supporting structure. In reality, most hard arms are fixed at their base and the transfer pipeline is not allowed to expand and contract at the base of the arms. Some hard arms have suffered damage due to thermal expansion of transfer pipelines and/or ground settlements of loading platforms. In addition, these arms are costly and require maintenance with leakage potential at the swivel joints.
Flexible hoses have been developed and used for fluid transfer. One simple way to handle the hoses is to lay the hoses on a loading platform, and manually make connection with ship manifolds (i.e., vessel manifolds) after a ship is docked. By its flexible nature, the hose adjusts its orientation from a horizontal axis on a loading platform to a vertical axis near a ship hull and back to a horizontal axis on a manifold platform onboard the ship. The hoses on the platform are subjected to wearing or kinks, and are applicable to calm water only. To avoid the above problems, U.S. Pat. No. 6,886,611 to Dupont et al discloses a suspended hose in air with one end tied to the top of a rigid riser and another end tied to a vessel manifold. A rigid riser raises the hang-off point for the hose up on the onshore side so that the entire hose is above the water level. This hose system avoids swivel joints and offers great flexibility. However, similar to the hard arm, the rigid riser is anchored at its base and any pipe expansion/contraction of the transfer pipeline or ground movement at the platform could cause high stress around the riser base.
Other systems use a combination of hose and rigid pipe with swivel joint. One common riser tower design has a rigid riser rotatable at its base with a winch to control its top position. The riser top has a n-shape bend with a downward flange and a hose is hung from the downward flange. By gravity, the other end of the hose rests near the bottom of the tower. To connect with a ship manifold, a crane lifts the low end toward a ship while the riser rotates toward the ship and the entire hose moves close to the ship. Other configurations include an articulated arm that lifts both ends of the hose with a connected end and a mobile end. The connected end is fluidly connected to storage units with rigid pipes and swivel joints. For fluid transfer, the arm delivers the mobile end of the hose to vessel manifolds. U.S. Pat. No. 7,147,021 to Dupont and Paquet discloses a similar system that has a riser attached to a vertical post with a rotatable connection. A boom hangs a hose and delivers the mobile end of the hose to a LNG ship. All the above systems require swivel joints and a tall supporting structure.
U.S. Pat. No. 8,915,271 to Liu discloses a transfer system with a vertical shaft and a hose freely hanging inside the shaft. Since the hose is hung below a transfer pipeline with a downward pipe branch and stored under the water level, there is no need to raise the hang-off point on the onshore side. The system avoids swivel joints and allows the pipeline end to expand and contract freely at the shaft. This system is ideal for a transfer pipeline located underground, for example inside a tunnel. The shaft rises up from the end of the tunnel at the seabed, and provides a dry space under water and protection for hoses and other equipment. However, this vertical shaft involves a different installation method rather than conventional piling and is likely to result in a higher construction cost for the cases where transfer pipelines are supported above the sea level.
Earthquakes, storm surges and soil erosions often trigger permanent ground deformations at a slope ground such as a coastal line or a river delta. The ground movements often overstress pipelines and/or loading systems. Strengthening the slope around a coast or river bank is possible, but results in huge construction costs. None of the systems mentioned above addresses the impact of permanent ground deformations that are likely to cause the movements of loading platforms.
In summary, there is a need to develop a robust and cost-effective loading system for terminals and loading stations where transfer pipelines are located above the sea level and relative displacements between transfer pipelines and loading platforms occur.
The present invention provides an auto-balancing hose system for fluid transfer between an onshore facility and a vessel docked at a loading platform. The system comprises a transfer pipeline extended from the onshore facility to the loading platform and subjected to displacements relative to the loading platform, a hose with a first end fluidly connected to the transfer pipeline and a second end fluidly connected with a ship manifold (i.e., vessel manifold), a hose saddle or sheave that elevates the hose and divides the hose into a riser at the first end and a freely suspended U-tube next to the second end, and a counterweight or a winch with a predetermined pulling force that maintains a top tension to the riser. As a result, the entire hose is in tension. The hose is able to accommodate large ship motions, pipe end displacements and movements of the loading platform. When the loading platform sinks or slides down a slope due to soil consolidation, earthquakes or mudslides, the hose automatically adjusts its position without stressing the hose and the transfer pipeline.
Accordingly, it is a principal object of the invention to provide a loading system that accommodates relative displacements between a transfer pipeline and loading platform.
It is another object of the invention to keep the hose above the sea level and away from ocean waves.
It is another object of the invention to provide a hose system that is applicable for large ship motions (e.g., 5.5 m wave height, and 15 m heave motion).
It is another object of the invention to provide a loading system that is applicable for cryogenic fluids or hot fluids with pipe end displacements at a loading platform.
It is another object of the invention to provide a loading system that accommodates the movements of loading platforms resulted from permanent ground deformations.
It is another object of the invention to provide a loading system in which the hose can be easily inspected and replaced.
It is another object of the invention to provide a loading system with a minimum cost and maintenance.
The loading system, method and advantages of the present invention will be better understood by referring to the drawings, in which:
The hose saddle 13 is preferably to have a low-friction surface to reduce wearing to the hose surface. One way to achieve low friction is to have a group of roller bars or rollers arranged at a semi-circular shape. Alternatively, low friction-coefficient materials can be used at the surface. These materials include metal with a smooth surface (such as stainless steel), PTFE (polytetrafluoroethyle, such as Teflon), etc.
In order for the riser 33 to remain in tension, it is required that the lowest point of the U-tube 35 be lower than the first end 32. In another word, the hose segment remained immediately below the hose saddle (i.e., extended from the hose saddle to the lowest point of the U-tube) over-weights the riser 33. When a crane is used to lift the second end 26 of the hose, care must be taken to keep the lowest point of the U-tube lower than the first end 32 in order to keep the entire hose in tension. A fender 36 is for protecting a vessel and keeping a distance between the loading platform 14 and a vessel.
In this figure, the hose saddle 13 (redirecting hose up to 180 degree) is supported by a column 46. It is preferred that the hose saddle 13 is rotatable along the column 46 when the vessel drifts forward or backward under water currents/waves. A half saddle 44 (redirecting hose up to 90 degree) is located at the edge of a manifold platform 25 and supports the U-tube 35 near the second end. This half saddle 44 is preferably to have a smooth surface and guides at the both sides to prevent the hose from falling off. There is a breakaway coupler 45 at the second end of the hose. There is also a quick connecting/disconnecting coupler 47 for quick connection with the vessel manifold 24. In order to keep the hose from falling off the hose saddle 13, two semi-guides 48 are preferably to have a height at twice the hose size. A control valve 49 is located on the transfer pipeline near the free end 16. When a pipe-in-pipe configuration is used for the transfer pipeline, the inner pipe has a short exposed section that ties-in to this control valve 49. Alternatively, another hose saddle is located near the first end and adjusts hose direction there when needed.
As shown in both
Alternatively, the mobile saddle 63 is replaced with a sheave. Alternatively, the elbow 64 is oriented perpendicular to the hose-hanging plane, and has a swivel joint (not shown). When not in use, the dry connector 65 is facing downward. After connecting with a ship manifold, the swivel joint allows the elbow 64 to adjust its orientation automatically during ship motions.
At the loading platform 14, an upward pipe branch 21 is fluidly connected to a transfer pipeline 15 and has an upward flange tied-in to the riser 33. A sheave 68 is supported on a column 46 and elevates the hose. A motor 69 drives the sheave 68 at its axle and applies riser top tension (i.e., a predetermined holding power) through the hose-in-contact segment 34. When the transfer pipeline 15 contracts (for example), the tension in the riser tends to increase. When the riser tension exceeds the holding power, the riser starts to move along the transfer pipeline until the tension is re-balanced with the holding power. Alternatively, a counterweight 42 is hung from the sheave 68 on the U-tube side and adapted to keep the riser 33 in tension.
Similarly, a hose 75 has a first end fluidly connected to the transfer pipeline 15 and a second end fluidly connected to a vessel manifold 24. Around a manifold platform 25, a manifold extension 72 extends from the vessel manifold 24, passes through a vertical support 73 and ends with a downward flange 74. The hose 75 is fluidly connected with the downward flange 74 at the second end. Alternatively, the second end of the hose 75 is directly connected to the vessel manifold 24 with the assistance of a half saddle on the manifold platform 25 (as shown in
This hose configuration shown in
Similarly, a counterweight 82 is attached to a middle flange 81 with two cables 83 and hung below the hose saddle 13. The counterweight 82 is made of a flexible tube filled with sand or other granular materials. The counterweight 82 helps reduce the height of the hose saddle and/or the length of the hose. In order for the second end of the hose 75 to reach the maximum elevation shown in
Alternatively, a vessel 71 is a production vessel. Alternatively, the hose 75 is a hose-in-hose with an inner hose and outer hose. The middle flange 81 is on the outer hose while the inner hose is continuous (not shown). With suitable materials, the hose 75 is used for transferring cryogenic fluids or hot fluids.
The method for establishing an auto-balancing hose loading system between a transfer pipeline having an upward pipe branch and a floating vessel with a vessel manifold essentially includes one step: 1) elevating a hose near the upward pipe branch and dividing the hose into a riser at a first end and a U-tube at a second end. With the first end fluidly connected to the transfer pipeline at the upward pipe branch and the second end fluidly connected to a vessel manifold, the entire hose is kept above the sea level. As a result, the hose is kept in tension and adapted to balance its positions automatically when subjected to ship motions, pipe end displacements and/or platform movements.
This application claims priority of U.S. Provisional Patent Application Ser. No. 62/317,533 filed on Apr. 2, 2016. U.S. Patent Documents 3,434,491March 1969Bily137/3156,886,611May 2005Dupont et al141/2797,147,021December 2006Dupont et al141/3828,176,938May 2012Queau et al137/6158,915,271December 2014Liu141/382
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