WO1999035031A1

WO1999035031A1 - Device for transfer of very cold fluids from a platform to a vessel

Info

Publication number: WO1999035031A1
Application number: PCT/NO1999/000002
Authority: WO
Inventors: Ragnar Molvik; Kåre Rygg JOHNSEN; Ole Martin Moe; Per Erik Christiansen
Original assignee: Kvaerner Maritime AS
Current assignee: Moss Maritime AS
Priority date: 1998-01-06
Filing date: 1999-01-05
Publication date: 1999-07-15
Anticipated expiration: 2000-07-06
Also published as: NO980060D0; NO980060L; AU1789699A; NO308105B1

Abstract

A device for transferring e.g. LNG from a platform (1) to a vessel (48), wherein the device comprises an arm arrangement which supports at least one pipeline. The device comprises two arms (22, 33) which are interconnected via a universal joint (31), and a slewing device (3, 4, 5, 24, 25) for pivoting the arms. The pipeline comprises two rigid pipes (22, 33) which extend along and are supported by the respective arms, and at least one flexible pipe (41) is arranged at the linkage (31) between the arms (20, 30), connecting the rigid pipes (22, 33) with each other. A swivel device (6, 55) is provided between the rigid pipes (22, 33) and adjacent rigid, stationary pipes of the platform (1) and the vessel (48) respectively.

Description

Device for transfer of very cold fluids from a platform to a vessel

The invention concerns a device for transferring very cold fluids such as natural gas in liquid form or vapour form via at least one pipeline, from a first structure to a second structure and vice versa, at sea, hereinafter called a platform and a vessel respectively, wherein the device comprises an arm arrangement which extends between the platform and the vessel and supports the pipeline.

From the prior art a device is known for transferring oil at a temperature which corresponds to the temperature of the environment, between structures at sea. The hoses which are employed in this device would have been unable to withstand the stresses to which they are hereby subjected if the fluid flowing through the hoses had had a temperature of, e.g. -163°C corresponding to the temperature of liquid natural gas, and a pressure of approximately 8 bar corresponding to the transfer pressure, since the hoses would thereby have become very brittle.

Moreover it is known that LNG can be discharged from a ship at a quay. With this kind of discharge there is normally only very slight relative movement of the ship and the quay, and for this process a rigid boom or arm and swivels are employed between the pipeline and adjacent pipe arrangements in the ship or on the quay. A boom of this kind, however, is not suitable for use at sea where the distance between the platform and the vessel may be, e.g. 80 m and where the relative movements thereof are great.

There are flexible hoses on the market which can withstand the above- mentioned low temperature, but they have a relatively small diameter and there is uncertainty associated with whether they can withstand the severe and sustained movements which can occur during a transfer of LNG as mentioned above.

The object of the invention is to provide a device of the type mentioned in the introduction which is not encumbered with the above-mentioned disadvantages.

The characteristics of the device according to the invention are presented in the characteristic features indicated in the claims. The invention will now be described in more detail with reference to the drawing which schematically illustrates embodiments of a device according to the invention.

Fig. 1 is a side view of a first embodiment of a device according to the invention.

Fig. 2 is a plan view of the device which is illustrated in fig. 1.

Fig. 3 is a side view of a section at the interconnection of two arms, where the arms are located in a position wherein they extend parallel and close to each other. Fig. 4 is a side view corresponding to that illustrated in fig. 3, but where the arms extend at an angle relative to each other.

Fig. 5 is a view in the direction of the arrow V in fig. 4.

Fig. 6 shows a portion of a section along the line VI - VI in fig. 4.

As illustrated in figs. 1 and 2 there is provided on a platform 1 a slew ring 2 which forms a first slewing device, and whereupon there is attached a crane pedestal 3. The crane pedestal 3 can be rotated via the slew ring 2 about a vertical axis relative to the platform by means of a drive device such as at least one hydraulic torque motor or the like (not shown). In the crane pedestal there is mounted at least one first hydraulic cylinder or winch 4 for pulling in or paying out at least one first rope 5.

On the platform there are provided two pipe systems 6,7 comprising two groups of swivels 8,9,10 and 11,12,13 respectively, where first swivels 8 and 11 respectively connect pipes (not shown) which are stationary relative to the platform, with first, movable pipe pieces 14 and 15 respectively. Two second swivels 9,12 connect the first pipe pieces 14, 15 with the first ends of second pipe pieces 16 and 17 respectively, and two third swivels 10,13 are provided on the second ends of the second pipe pieces 16 and 17 respectively.

A first end of a first crane arm or arm 20 is attached to the crane pedestal 3 via a joint axle 21 which extends horizontally and coaxially relative to the third swivels' axis of rotation. Along the arm 20 there extend two rigid pipes 22,23, one end of which is connected to the respective third swivels 10,13. The first rope 5 is attached to an ear 28 of the arm 20 at a distance from the axle 21, with the result that pulling in or paying out the rope 5 causes the arm 20 to pivot in a vertical plane about the axle 21.

On the arm 20 there is attached at least one second hydraulic cylinder or winch 24 which is arranged to pull in or pay out at least one second rope 25 which extends over a disc 26 which is rotatably attached to the arm 20 at its second end.

A second arm 30 is connected via a universal joint 31 to the first arm 20 at a point between the ends of the latter. The second rope 25 is connected to an ear 32 of the second arm at a point between the ends of the latter, with the result that pulling in or paying out the second rope 25 causes the second arm 30 to pivot about the universal joint 31. Along the second arm there extend two rigid pipes 33,34. The pairs of rigid pipes 22,23 and 33,34 are mounted on the respective arms 20,30 via bearing devices 35,36, which permit a heat expansion and contraction of the pipes relative to the arms, substantially without any forces or moments thereby being exerted between the pipes and the arms.

At the universal joint 31 there are provided two flexible pipes 41,42, each of which extends in the form of a loop, since they are wound up in a substantially circular manner slightly more than one turn round a substantially horizontal axis.

The end sections 60,61 and 62,63 of the rigid pipes 22,33 and 23,34 respectively which are located near the universal joint 31 extend across the longitudinal direction to the central sections of the associated rigid pipes. The pipe end sections 60,62 of the pipes on the first arm 20 are connected via releasable couplings with one end of the respective flexible pipes 41 ,42, and the pipe end sections 61,63 of the rigid pipes 33,34 are connected with the second end of the respective flexible pipes 41,42 via similar couplings. When the arms 20,30 pivot relative to each other in a vertical plane during operation of the second hydraulic cylinder 24, the flexible pipes are influenced by bending about the longitudinal axis of the turns, thus causing the diameter of the turn to be increased or reduced.

The flexible pipes 41,42 are each arranged in its cassette 43,44 which is attached to one arm. These cassettes support the flexible pipe turns laterally, permitting simple and safe removal thereof by disconnecting the flexible pipes from the rigid pipes and releasing the cassettes from the arm.

The second ends of the second rigid pipes 33,34 are provided with first connecting members 51,52 which can be connected to respective second connecting members 53,54 which are provided on a vessel 48, and which in turn are connected to associated pipe systems 55,56 with swivels similar to the swivels 8 - 13 and pipe pieces similar to the pipe pieces 14 - 17.

By means of a universal joint 45 a guide pin or male component 46 is connected to the second end of the second arm 30, and near this pin there is secured a guide or draw-in line 49 which hangs freely when the arms are not in use. The guide pin 46 is arranged for insertion in a pipe socket or female component 47 and to be secured therein, thus enabling the first connecting members 51,52 to be coupled to the second connecting members 53,54 of the vessel 48. Figs. 3 - 6 illustrate a second embodiment of turns of flexible pipes in the area of the universal joint connection between two arms, where parts and sections of the second embodiment whose function corresponds to the function of parts and sections of the first embodiment have the same reference numerals. As illustrated in these figures each of the transverse sections 60,61,62,63 of the rigid pipes 22,23,33,34 comprises four connections. Co-operating, i.e. communicating rigid pipes 22,23 and 33,34 respectively are interconnected via four single turns or loops of flexible pipes 71,72,73,74. In fig. 5 only those flexible pipes which are arranged between the rigid pipes 22,33 are illustrated with solid lines, while only the centre lines of corresponding flexible pipes are included between the transverse sections 62,63 of the rigid pipes 23,34. Since four flexible, parallel-connected pipes are provided, the diameter thereof can be small with the same fluid flow quantity per time unit for the associated rigid pipes, and the bending moment for relative movement of the arms can be small. Furthermore, the bending stresses which are exerted in the flexible pipes can be small. The flexible pipes may be advantageously made of corrugated pipes, with the result that they are bellow-shaped and can be easily bent while retaining great resistance to radial deformation. Hollows and ridges in the pipes may hereby extend along the pipes' circumference. Fig. 3 illustrates the form of the assembly of flexible pipes when the arms 20,30 are folded in towards each other and fig. 4 illustrates the form of this assembly when the arms are pivoted away from each other. Fig. 5 is a view of the pipe assembly viewed in the direction of the arrow V in fig. 4. Fig. 6 is an enlarged section along line VI-VI in fig. 4 through the four flexible pipes between the rigid pipes 22,33.

When the arms are folded together and extend vertically, the cassettes with the flexible pipes can be lowered to the deck of the platform by means of suitable crane equipment, and when the arms extend outwardly pivoted in relation to each other, the cassettes can be lowered to the deck of a supply ship.

On the first arm 20, e.g., there may be provided a control house (not shown) from which the arms 20, 30 can be controlled by means of the torque motor and the hydraulic cylinders 4,24 when the device is connected to or disconnected from a vessel. When the arms are not connected, the hydraulic cylinders 4, 24 can be controlled automatically, with the result that the arms are located in a lifted position, wherein the pin 46 is located on a slightly higher level than the female component or the pipe 47. The vessel can then be manoeuvred into a position wherein the pipe 47 is located immediately below the connecting pin 46, thus enabling the hauling line 49 to be gripped by a device or personnel on the vessel and connected to a winch thereon (not shown). When the winch is operated the pin 46 can be retracted into the pipe 47 and locked thereto. The pipe connecting members 51 and 52 on the second arm 30 can then be connected to the pipe connecting members 53 and 54 respectively on the vessel, whereupon a fluid loading operation can be performed. After this loading operation the pin 46 can be disconnected from the pipe 47 and the pipe connecting members 51,52 on the arm 30 disconnected from the pipe connecting members 53,54 on the vessel, whereupon the arms 20,30 can once again, possibly automatically, be raised to the lifted position. An automatic raising of the arms of this kind may advantageously also take place if the pin 46 has to be released from the female component 47 in an emergency.

It has been stated above that two pipelines extend on the arms from the platfαi^tto the vessel. If LNG has to be loaded from the platform to the teasel, LNG is advantageously transported in one pipeline 22,71,72,73,74,33 from the platform 1 to the vessel 48, while in the second pipeline 23,34 vaporised LNG is transported back to the platform from the vessel. In the illustrated embodiment with long, rigid pipes, the pipelines can easily be heat-insulated. Moreover, the arrangement of flexible pipes extending in cassettes can also be effectively heat-insulated. If a leakage should occur, it will most probably occur over the water, with the result that LNG does not touch the platform or the vessel, thereby damaging them.

Claims

PATENT CLAIMS

1. A device for transferring very cold fluids, such as natural gas in liquid form or vapour form, via at least one pipeline (22,23, 33,34), from a first structure, such as a platform (1), to a second structure, such as a vessel (48), and vice versa, at sea, wherein the device comprises an arm arrangement which extends between the platform (1) and the vessel (48) and supports the pipeline (22,23,33,34), and which has a first arm (20) with a first end, which is linked with the platform (1), and a second arm (30) with a first end, which is linked with a second end of the first arm (1), and with a second end, which is arranged to be linked with the vessel (48), where the linkages are provided in such a manner that no forces or moments are transferred from the platform to the vessel or vice versa, the pipeline comprising at least two rigid pipes (22,23,33,34) which extend along and are supported by the respective arms, characterized in that the device comprises at least one flexible pipe (41,42;71,72,73,74) which connects the rigid pipes (22,23,33,34) with one another and extend wound in at least one turn in addition to being contained in a heat-insulated cassette (43,44), which is supported by one of the arms at the linkage between them, and that the rigid pipes (22,23 ;33, 34) are connected to the associated arms (20,30) via connecting devices which permit a substantially unhindered heat expansion and contraction of the pipes (22,23;33,34).

2. A device according to claim 1, characterized in that the arms (20,30) are linked to each other via a universal joint (31).

3. A device according to claim 1 or 2, characterized in that the second arm (30) has a connecting member (46) with a universal joint (45) via which connecting member the arm (30) can be connected to the vessel.

4. A device according to one of the preceding claims, characterized in that the flexible pipes (41 ,42;71,72,73,74) are a corrugated metal pipe.