System to transfer people and/or cargo during offshore operations

Abstract

A system to transfer people and/or cargo during offshore operations includes a base with a stationary part and a moveable part that is rotatable relative to the stationary part about a substantially vertical first axis; a support arm having a first free end and a second free end opposite the first free end of the support arm; a boom having a first free end and a second free end opposite the first free end of the boom; a load support element; a measurement system; an actuator system; and a control system. The support arm at a location in between the first and second free end of the support arm is mounted to the moveable part of the base such that the support arm is rotatable relative to the moveable part about a substantially horizontal second axis.

Claims

1. A vessel provided with a system to transfer people and/or cargo during offshore operations, the system comprising: a) a base with a stationary part and a moveable part that is rotatable relative to the stationary part about a substantially vertical first axis; b) a support arm having a first free end and a second free end opposite the first free end of the support arm; c) a boom having a first free end and a second free end opposite the first free end of the boom; d) a load support element that is configured to be loaded with people and/or cargo; e) a measurement system; f) an actuator system; and g) a control system, wherein the support arm at a location in between the first and second free end of the support arm is mounted to the moveable part of the base such that the support arm is rotatable relative to the moveable part about a substantially horizontal second axis, wherein the boom at a location in between the first and second free end of the boom is mounted to the first free end of the support arm such that the boom is rotatable relative to the support arm about a substantially horizontal third axis, wherein the load support element is configured to be supported by the first free end of the boom and is configured to support the people and/or cargo during transfer, wherein the measurement system is configured to measure relative movement of the load support element relative to a reference, wherein the actuator system is configured to rotate the moveable part relative to the stationary part using a first actuator assembly, to rotate the support arm relative to the moveable part using a second actuator assembly, and to rotate the boom relative to the support arm using a third actuator assembly, wherein the control system is configured to drive the actuator system in dependency of an output of the measurement system to compensate for the relative movement of the load support element, wherein the support arm comprises a counterweight at the second free end of the support arm, wherein the boom comprises a counterweight at the second free end of the boom, wherein the second and third actuator assemblies comprise secondary and tertiary electric drives, wherein the counterweight at the second free end of the support arm compensates for at least 25% of a moment (M2) that is present around the second axis to the support arm and that is equal to a sum of sub-moments caused by weight forces of the load support element, including people and/or cargo present therein during a transfer operation, of the boom, of the counterweight at the second free end of the boom, and of the support arm, wherein the counterweight at the second free end of the boom compensates for at least 25% of a moment (M1) that is present around the third axis to the boom and that is equal to a sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, and of the boom, wherein the second actuator assembly further comprises a cable extending between the moveable part of the base and the second free end of the support arm to be paid out or hauled in by the corresponding electric drive, and wherein the third actuator assembly further comprises a cable extending between the first free end of the support arm and the second free end of the boom to be paid out or hauled in by the corresponding electric drive.

2. The vessel provided with a system according to claim 1, wherein the counterweight at the second free end of the support arm compensates for at least 50% of the moment (M2) that is present around the second axis to the support arm and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, of the boom, of the counterweight at the second free end of the boom, and of the support arm, and/or wherein the counterweight at the second free end of the boom compensates for at least 50% of the moment (M1) that is present around the third axis to the boom and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, and of the boom.

3. A vessel provided with a system according to claim 1, wherein the support arm has an operative segment with a first length that extends between the second axis and the first free end, and wherein the support arm has a free end segment with a second length that extends between the second axis and the second free end, wherein the second length is at least 20% of the first length, and/or wherein the boom has an operative segment with a first length that extends between the third axis and the first free end, and in which the boom has a free end segment with a second length that extends between the third axis and the second free end, wherein the second length is at least 20% of the first length.

4. A vessel provided with a system according to claim 1, wherein the first actuator assembly comprises a primary electric drive.

5. The vessel provided with a system according to claim 1, wherein the secondary electric drive is arranged on the second free end of the support arm.

6. The vessel provided with a system according claim 1 wherein the tertiary electric drive is arranged on the second free end of the boom.

7. The vessel provided with a system according to claim 1, wherein the counterweight at the second free end of the support arm does not fully compensate the moment (M2) that is present around the second axis to the support arm and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, of the boom, of the counterweight at the second free end of the boom, and of the support arm.

8. The vessel provided with a system according to claim 7, wherein the counterweight at the second free end of the support arm does not compensate for between 1-10% of the moment (M2) that is present around the second axis to the support arm and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, of the boom, of the counterweight at the second free end of the boom, and of the support arm, and/or does not compensate for between 50-150 kg weight load at the first free end of the support arm.

9. The vessel provided with a system according to claim 1, wherein the counterweight at the second free end of the boom does not fully compensate the moment (M1) that is present around the third axis to the boom and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, and of the boom.

10. The vessel provided with a system according to claim 9, wherein the counterweight at the second free end of the boom does not compensate for between 1-10% of the moment (M1) that is present around the third axis to the boom and that is equal to the sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, and of the boom, and/or does not compensate for between 50-150 kg weight load at the first free end of the boom.

11. The vessel provided with a system according to claim 1, wherein the load support element is a cage with at least one access door.

12. The vessel provided with a system according to claim 1, wherein the support arm and/or the boom are embodied as a frame work.

13. The vessel provided with a system according to claim 1, wherein the load support element is connected to the boom by means of cables or chains.

14. The vessel provided with a system according to claim 1, wherein the load support element is connected swingable to the boom, and/or wherein the load support element is connected rotatable to the boom, in particular with a rotation drive unit and/or a damper acting between them.

15. A method for transferring people or cargo between a first object and a second object using a system comprising: a base with a stationary part and a moveable part that is rotatable relative to the stationary part about a substantially vertical first axis; a support arm having a first free end and a second free end opposite the first free end of the support arm; a boom having a first free end and a second free end opposite the first free end of the boom; a load support element that is configured to be loaded with people and/or cargo; a measurement system; an actuator system; and a control system, wherein the support arm at a location in between the first and second free end of the support arm is mounted to the moveable part of the base such that the support arm is rotatable relative to the moveable part about a substantially horizontal second axis, wherein the boom at a location in between the first and second free end of the boom is mounted to the first free end of the support arm such that the boom is rotatable relative to the support arm about a substantially horizontal third axis, wherein the load support element is configured to be supported by the first free end of the boom and is configured to support the people and/or cargo during transfer, wherein the measurement system is configured to measure relative movement of the load support element relative to a reference, wherein the actuator system is configured to rotate the moveable part relative to the stationary part using a first actuator assembly, to rotate the support arm relative to the moveable part using a second actuator assembly, and to rotate the boom relative to the support arm using a third actuator assembly, wherein the control system is configured to drive the actuator system in dependency of an output of the measurement system to compensate for the relative movement of the load support element, wherein the support arm comprises a counterweight at the second free end of the support arm, wherein the boom comprises a counterweight at the second free end of the boom, wherein the second and third actuator assemblies comprise secondary and tertiary electric drives, wherein the counterweight at the second free end of the support arm compensates for at least 25% of a moment (M2) that is present around the second axis to the support arm and that is equal to a sum of sub-moments caused by weight forces of the load support element, including people and/or cargo present therein during a transfer operation, of the boom, of the counterweight at the second free end of the boom, and of the support arm, wherein the counterweight at the second free end of the boom compensates for at least 25% of a moment (M1) that is present around the third axis to the boom and that is equal to a sum of sub-moments caused by the weight forces of the load support element, including people and/or cargo present therein during a transfer operation, and of the boom, wherein the second actuator assembly further comprises a cable extending between the moveable part of the base and the second free end of the support arm to be paid out or hauled in by the corresponding electric drive, and wherein the third actuator assembly further comprises a cable extending between the first free end of the support arm and the second free end of the boom to be paid out or hauled in by the corresponding electric drive, said method comprising the following steps: a) moving the load support element from the first object to a position in between the first and second object; b) compensating relative movements between load support element and second object; c) moving the load support element to the second object for transfer while compensating the relative movements between load support element and second object; and d) allowing people or cargo to transfer to or from the second object.

16. The method according to claim 15, wherein the system is arranged on the first object and wherein the first object is a vessel.

17. The method according to claim 15, further comprising the steps of: e) moving the load support element away from the second object to a position in between the first and second object while compensating the relative movements; f) stopping the compensation of the relative movements; and g) moving the load support element to the first object.

18. The method according to claim 15, wherein the system is arranged on a third object, wherein the third object is a vessel, and wherein prior to step a) the following steps are performed: a1) moving the load support element from the third object to a position in between the first and third object; a2) compensating relative movements between load support element and first object; a3) moving the load support element to the first object while compensating the relative movements between load support element and first object; and a4) allowing people or cargo to transfer from the first object.

19. The method according to claim 15, wherein the system is arranged on a third object, wherein the third object is a vessel, and wherein after step d) the following steps are performed: a5) moving the load support element away from the second object to a position in between the first and second object while compensating the relative movements between load support element and second object; a6) stopping the compensation of the relative movements between load support element and second object; a7) compensating relative movements between load support element and first object; a8) moving the load support element to the first object while compensating the relative movements between load support element and first object; and a9) allowing people or cargo to transfer to the first object.

20. The method according to claim 15, wherein the first object is a vessel and wherein the second object is an offshore platform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts a system to transfer people and/or cargo during offshore operations according to an embodiment of the invention; and

(2) FIG. 2 shows front, upper and side views of an alternative embodiment of the system.

DETAILED DESCRIPTION OF THE INVENTION

(3) FIG. 1 depicts a system 1 for transferring people and/or cargo during offshore operations according to an embodiment of the invention. Offshore operations may include the transfer of people and/or cargo from a vessel 2 to a fixed construction 3, e.g. a platform or other fixed offshore installation, and/or vice versa. However, offshore operations may also include transfer of people and/or cargo between two vessels, and rescue or recovery operations to retrieve people and/or cargo from the water. Hence, system 1 is preferably used in cases in which there are undesired relative movements between two objects preventing an easy transfer of people and/or cargo.

(4) In this embodiment, the system is mounted on a deck 4 of the vessel 2, but alternatively, the system 1 could have been mounted on the fixed construction 3.

(5) The system 1 comprises a base 10, a support arm 20, a boom 30, a load support element 40, a measurement system 50, an actuator system, and a control system 70.

(6) The measurement system 50 and the control system 70 have been schematically indicated for simplicity reasons. Dashed lines indicate inputs and outputs to the measurement system 50 and the control system 70, respectively. The skilled person will understand that other locations and/or embodiments of the measurement system and control system are possible, and is well-familiar with practical implementations of the required functions, so that these will not be elucidated here.

(7) The base 10 comprises a stationary part 11 mounted to the deck 4 of the vessel 2, and a moveable part 12 that is rotatable relative to the stationary part 11 about a substantially vertical first axis 13. The stationary part 11 may also be mounted indirectly to the deck, e.g. via a support frame or a pedestal, which support frame or pedestal may also be used for other purposes.

(8) It is explicitly noted here that the stationary part 11 being mounted to the deck of the vessel does not necessarily mean that the stationary part 11 cannot be moved over the deck. It may well be the case that the stationary part 11 is moveable over the deck of the vessel to move the system 1 between an operational position, e.g. at a side of a vessel to get closer to another object, and a rest position, e.g. in a centre of a vessel for improved stability during sailing.

(9) The stationary part 11 may further be integrated with the deck 4 of the vessel 2, but may also be a frame to be placed as a self-supporting unit on the deck 4.

(10) To rotate the moveable part 12 relative to the stationary part 11, the actuator system comprises a first actuator assembly 61, here embodied in the form of a slewing ring 61a with external tooth gear arranged on the stationary part 11 cooperating with an electric drive 61b that drives a gear 61c engaging with the slewing ring 61a, wherein the electric drive 61b and the gear 61c are arranged on the moveable part 12.

(11) It will be apparent for the skilled person that the first actuator assembly 61 can also be embodied in other forms, e.g. the slewing ring 61a, electric drive 61b and gear 61c can also be arranged internally of the moveable and stationary parts 11, 12. Further, more than one electric drive and corresponding gear can be provided. Also, the slewing ring can be provided on the moveable part 12 and the electric drive and gear can be provided on the stationary part. Other actuator principles are also envisaged.

(12) The support arm 20 has a first free end 21 and a second free end 22 opposite the first free end 21 of the support arm 20.

(13) The moveable part 12 of the base 10 comprises a first support beam 14 to which the support arm 20 can be connected at a location in between the first 21 and second 22 free end of the support arm. The support beam 14 defines a substantially horizontal second axis 15 allowing the support arm 20 to rotate relative to the moveable part 12 of the base 10 about said second axis 15.

(14) In order to rotate the support arm 20 relative to the moveable part 12 of the base 10, the actuator system is provided with a second actuator assembly 62 comprising in this embodiment, two electrically driven winches 62a arranged on the second free end 22 of the support arm 20 and two corresponding cables 62b that extend between the winches 62a on the support arm 20 and the moveable part 12. Moveable part 12 is therefore provided with a beam 16 so that the connection of the cable 62b can be aligned with its corresponding winch 62a.

(15) An advantage of using two winches 62a and corresponding cables 62b may be that there is redundancy in case one of the winches 62a or cables 62b fails, is replaced or maintenance is carried out on one of the winches 62a or cables 62b.

(16) Rotation of the support arm 20 is thus possible by paying out or hauling in the cables 62b using the respective winches 62a.

(17) The first axis 13 of the base 10 does not intersect the support arm 20 due to the fact that the support arm 20 is connected to the moveable part 12 via the support beam 14 extending sideways from a main body of the moveable part 12. This has the advantage that the rotational movement of the support arm 20 about the second axis 15 is not limited by the main body of the moveable part 12, so that the support arm 20 for instance can also be positioned in a substantially vertical orientation parallel to the first axis 13.

(18) The boom 30 has a first free end 31 and a second free end 32 opposite the first free end 31 of the boom 30.

(19) The boom 30 is connected to the first free end 21 of the support arm 20 at a location in between the first free end 31 and the second free end 32 of the boom. The support arm 20 at this location defines a substantially horizontal third axis 23 allowing the boom 30 to rotate relative to the support arm 20 about said third axis 23.

(20) In order to rotate the boom 30 relative to the support arm 20, the actuator system is provided with a third actuator assembly 63 comprising in this embodiment, two electrically driven winches 63a arranged on the second free end 32 of the boom 30 and two corresponding cables 63b that extend between the winches 63a on the boom 30 and the first free end 21 of the support arm 20.

(21) Rotation of the boom 30 is thus possible by paying out or hauling in the cables 63b using the respective winches 63a.

(22) Again, an advantage of using two winches 63a and corresponding cables 63b may be that there is redundancy in case one of the winches 63a or cables 63b fails, is replaced or maintenance is carried out on one of the winches 63a or cables 63b.

(23) The load support element 40 is configured to be supported by the first free end 31 of the boom 30 and is configured to support the people and/or cargo during transfer. In this embodiment, the load support element is embodied as a cage 40 with at least one access door 41.

(24) The load support element 40 may be permanently connected to the boom 30, but may also be temporarily connected allowing to use the system with different types of load support elements depending on the type of transfer. Further, it allows to leave the load support element behind after transfer. This allows for instance to limit the use of the entire system and/or for the vessel carrying the system to perform other tasks, possibly at another location, in between subsequent transfers.

(25) In an embodiment, the load support element 40 comprises tubing and/or hoses at least connected to the first free end of the boom allowing to transfer fluid material, e.g. grout or cement. However, applications may also be limited to transferring solid goods and/or people, where solid goods also comprise liquids or powder held in solid containers or bags.

(26) As mentioned before, system 1 is preferably used in cases in which there are undesired relative movements between two objects preventing an easy transfer of people and/or cargo between those two objects. In the embodiment of FIG. 1 this relative movement is caused by sea- and/or wind-induced movement of the vessel 2 while the fixed construction is not movable.

(27) As a result of these undesired relative movements, the load support element 40 will move relative to fixed construction 3 in an uncontrollable manner, which will make it very difficult to move and position the load support element 40 with respect to the fixed construction 3. There will be a high risk of collision with damage as a result.

(28) In order to compensate for the undesired relative movements, the system 1 is provided with the measurement system 50 configured to measure directly or indirectly the undesired relative movement of the load support element 40 relative to a reference. This can be done in various ways, including direct and indirect ways, for instance: 1) by measuring the relative motions of the vessel 2 or stationary part 11 using e.g. gyroscopes. The earth itself then acts as reference, but as the fixed construction 3 is directly arranged on the ground, the fixed construction 3 can also be considered to be the reference; and/or 2) by measuring relative movements of the vessel 2 directly with respect to the fixed construction, e.g. by using laser measurements systems, for instance based on laser interferometry in which a laser beam is reflected of between the fixed construction 3 and the vessel 2.

(29) Relative movements may be measured by measuring acceleration, velocity and/or position relative to the reference as long as these measurements can be used to compensate for the relative movements.

(30) An output of the measurement system 50, here indicated by dashed arrow 51, which is representative for the relative movements, is fed to the control system 70. Another input may be user input indicated by dashed arrow 52, which may represent desired movements or relative positions of the load support element 40.

(31) The control system 70 is configured to drive the actuator system in dependency of the output 51 of the measurement system to compensate for the undesired relative movement of the load support element 40. As a result, if there is no desired movement of the load support element 40, the load support element 40 will be stationary relative to the fixed construction 3 although the vessel 2 carrying the load support element will move due to wave and wind action.

(32) In addition to the compensation, the control system 70 may be configured to control the position of the load support element 40 relative to the fixed construction 3, i.e. the reference, based on a desired position or movement of the load support element, which desired position can be based on user input.

(33) In the embodiment of FIG. 1, the control system 70 provides drive signals to the electric drives of the first, second and third actuator assemblies as indicated by the dashed arrows 71, 72a, 72b, 73a and 73b.

(34) Due to the offshore situation, it is expected that there will be undesired movements continuously. This means that the actuator assemblies are continuously driven to move the moveable part 12 of the base 10 (and everything supported thereby), the support arm 20 and the boom 30.

(35) To keep the driving forces within limits, the support arm 20 comprises a counterweight 24 at the second free end 22 of the support arm, and the boom comprises a corresponding counterweight 33 at the second free end 32 of the boom 30.

(36) As described above, the winches 62a of the second actuator assembly and the winches 63a of the third actuator assembly are arranged on the respective second free ends of the support arm 20 and the boom 30, thereby also functioning as counterweights.

(37) The support arm 20 and the boom 30 are configured such that the counterweights do not fully compensate the moment applied to the respective first ends of the support arm 20 and the boom 30 so that the cables 62b and 63b of respectively the second and third actuator assemblies are kept taut at all times of the operation.

(38) An advantage of the system 1 according to the invention is that the total weight of the system can be kept low. In combination with the presence of the counterweights, the necessary forces to drive the system can also be kept low, so that energy efficient electric drives can be utilized instead of energy inefficient hydraulic drives.

(39) Although the support arm and the boom have been embodied as frame works, it will be apparent for the skilled person that they at least partially can easily be embodied as box elements or as beam type elements, etc.

(40) In FIG. 2 same components have been given the same reference numerals. Here an embodiment is shown in which the arm 20 and the boom 30 are embodied as beam types. Here it is also clearly indicated that the arm 20 has an operative segment 20a with a first length L1 that extends between the second axis 15 and its first free end 21, and a free end segment 20b with a second length L2 that extends between the second axis 15 and its second free end 22. The length L2 here is chosen to be larger than 20%, and in particular about 33%, of the length L1.

(41) Likewise it is clearly indicated here that the boom 30 has an operative segment 30a with a first length L1 that extends between the third axis 23 and its first free end 31, and a free end segment 30b with a second length L2 that extends between the third axis 23 and its second free end 32. The length L2 here is chosen to be larger than 20%, and in particular about 33%, of the length L1.

(42) As an example the cabin 40 may have a weight of about 500 kg, while the operative segment 30a of the boom 30 may have a weight of 700 kg. The free end segment 30b of the boom 30 then may have a weight of at least 250 kg, in particular about 500 kg, whereas the counterweight 33 mounted thereto may have weight of at least 500 kg, in particular about 750 kg. Thus the counterweight 33 at the second free end 32 of the boom 30 compensates for at least 75%, in particular between 95-99%, of a moment M1 applied around the third axis 23 to the boom 30. At the same time the counterweight 33 does not compensate for the entire moment M1 applied around the third axis 23 to the boom 30. In particular it does not compensate for between 1-5% of this moment M1 and leaves a remaining weight load F1 of between 50-150 kg at the first free end 31 of the boom 30, also depending on the weight of the people and/or cargo that is present inside the cabin 40.

(43) With this it is noted that the moment M1 around the third axis 23 to the boom 30 comprises the sum of sub-moments caused by: a weight force of the cabin 40 including people and/or cargo present therein times a horizontal distance between its centre of gravity and to the third axis 23; and a weight force of the operative segment 30a times a horizontal distance between its centre of gravity and to the third axis 23.

(44) This moment M1 is partly compensated by: a weight force of the free end segment 30b times a horizontal distance between its centre of gravity and the third axis 23; and a weight force of the counterweight 33 times a horizontal distance between its centre of gravity and the third axis 23.

(45) Furthermore as an example the operative segment 20a of the arm 20 may have a weight of 2100 kg. The free end segment 20b of the arm 20 then may have a weight of at least 250 kg, in particular about 1500 kg, whereas the counterweight 24 mounted thereto may have weight of at least 500 kg, in particular about 2500 kg. Thus the counterweight 24 at the second free end 22 of the arm 20 compensates for at least 75%, in particular between 95-99%, of a moment M2 around the second axis 15 to the arm 20. At the same time the counterweight 24 does not compensate for the entire moment M2 around the second axis 15 to the arm 20. In particular it does not compensate for between 1-5% of this moment and leaves a remaining weight load F2 of between 50-150 kg at the first free end 21 of the arm 20, again also depending on the weight of the people and/or cargo that is present inside the cabin 40.

(46) With this it is noted that the moment M2 around the second axis 15 to the arm 20 comprises the sum of sub-moments caused by: the weight force of the cabin 40 including people and/or cargo present therein times a horizontal distance between its centre of gravity and the second axis 15; the weight force of the operative segment 30a times a horizontal distance between its centre of gravity and the second axis 15; the weight force of the free end segment 30b times a horizontal distance between its centre of gravity and the second axis 15; the weight force of the counterweight 33 times a horizontal distance between its centre of gravity and the second axis 15; and a weight force of the operative segment 20a times a horizontal distance between its centre of gravity and the second axis 15.

(47) This moment M2 is partly compensated by: a weight force of the free end segment 20b times a horizontal distance between its centre of gravity and the second axis 15; and a weight force of the counterweight 24 times a horizontal distance between its centre of gravity and the second axis 15.

(48) Since the arm 20 also carries the boom 30 with the cabin 40 and the counterweight 33, and thus also needs to be compensated for their weight forces, the weight of the free end segment 20b of the arm 20 and/or the weight of the counterweight 24 preferably are chosen larger than the weight of the free end segment 30b of the boom 30 and/or the weight of the counterweight 33, in particular at least two times larger, more in particular at least three times larger.

(49) Although the first rotation axis is defined as being substantially vertical and the second and third axis are defined as being substantially horizontal, an alternative definition may be that the second and third axis are parallel to each other, but perpendicular to the first axis, or that the first, second and third axis are oriented such that a 3DOF, where each DOF is a translation, positioning system is obtained.

(50) Reference is made in this description to the term counterweight. Although any mass being present at an opposite side of a pivot axis may be considered a counterweight, counterweights according to the invention compensate for at least 25% of the moment, preferably for at least 50% of the moment and more preferably for at least 75% of the moment.