A JACK-UP VESSEL

Abstract

A jack-up vessel has a buoyant hull, a plurality of jack-up legs including leg chords having racks, and jacking assemblies to relatively move the associated leg chord relatively to the buoyant hull vertically. The jacking assemblies include actuators and a pinion group, including a plurality of pinions arranged vertically above each other. Jacking assemblies include a sensor system for sensing the load distribution associated with a pinion group. The jack-up vessel includes a control system configured for receiving information about an intended use and/or future environmental conditions and determining a pre-operation load distribution over the pinions in the pinion group, in which pre-operation load distribution the loads within this pinion group are unequally distributed, such that during the intended use and/or during the future environmental conditions the loads within this pinion group are equally distributed.

Claims

1. A jack-up vessel, the jack-up vessel comprising: a buoyant hull; a plurality of jack-up legs, each jack-up leg comprising one or more leg chords, each leg chord having at least one rack; a plurality of jacking assemblies, each jacking assembly being associated with a leg chord and being configured to vertically move the associated leg chord relatively to the buoyant hull, wherein each jacking assembly comprises: a pinion group comprising a plurality of pinions arranged vertically above each other, each pinion engaging the rack of a leg chord and being configured for transferring load between the hull and the leg chord resulting in a load distribution over the plurality of pinions within the pinion group; actuators for actuating the pinions of the pinion group, each actuator being configured for actuating a corresponding pinion; and a sensor system configured for sensing the load distribution over the plurality of pinions associated with each pinion group, and configured for emitting sensor signals indicative of the sensed load distribution; and a control system configured to perform a routine comprising: receiving information about an intended use and/or about future environmental conditions for the jack-up vessel; determining, based on the received information, a pre-operation load distribution over the plurality of pinions of the pinion group, in which pre-operation load distribution the loads over the pinions within the pinion group are unequally distributed, such that in an operational load distribution during the intended use and/or during the future environmental conditions, the loads over the pinions within the pinion group are equally distributed; receiving the sensor signals indicative of the sensed load distribution, and determining/computing a difference between the pre-operation load distribution and the sensed load distribution; and emitting, in response to the difference, control signals to the actuators, such that the actuators are operated and the sensed load distribution of the pinion group is made to correspond to the pre-operation load distribution.

2. The jack-up vessel according to claim 1, wherein the pre-operation load distribution for the plurality of pinions of the pinion group is such that one or more lower pinions of the pinion group have lower loads thereon than one or more higher pinions of the pinion group.

3. The jack-up vessel according to claim 1, wherein a load increase from the pre-operation load distribution to loads in the intended use and/or during the future environmental conditions for one or more lower pinions of the pinion group is larger than for one or more higher pinions of the pinion group.

4. The jack-up vessel of according to claim 1, wherein the control system is configured to determine the pre-operation load distribution for each pinion group individually.

5. The jack-up vessel according to claim 1, wherein the control system is configured to determine the pre-operation load distribution for each of the pinion groups corresponding to a jack-up leg.

6. The jack-up vessel according to claim 1, wherein the jack-up vessel comprises a crane.

7. The jack-up vessel according to claim 6, wherein the pre-operation load distribution is calculated on the basis of a hoisting load of the crane.

8. The jack-up vessel according to claim 1, wherein the control system further comprises a user interface to receive information about an intended use and/or future environmental conditions from an operator.

9. A method for operating a jack-up vessel the jack-up vessel comprising: a buoyant hull; a plurality of jack-up legs, each jack-up leg comprising one or more leg chords, each leg chord having at least one rack; a plurality of jacking assemblies, each jacking assembly being associated with a leg chord, each jacking assembly being configured to vertically move the associated leg chord relatively to the buoyant hull, wherein each jacking assembly comprises: a pinion group comprising a plurality of pinions arranged vertically above each other, each pinion engaging the rack of a leg chord and being configured for transferring load between the hull and the leg chord resulting in a load distribution over the plurality of pinions within the pinion group; actuators for actuating the pinions of the pinion group, each actuator being configured for actuating a corresponding pinion; and a sensor system configured for sensing the load distribution over the plurality of pinions associated with each pinion group, and configured for emitting sensor signals indicative of the sensed load distribution; and a control system, the method comprising the steps of: operating the jacking assemblies to lower the jack-up legs for engagement with a seabed and raising the buoyant hull to a distance above a water level; receiving information about an intended use and/or about future environmental conditions; determining, based on the received information, a pre-operation load distribution over the plurality of pinions of a pinion group, in which pre-operation load distribution the loads over the pinions within the pinion group are unequally distributed, such that in an operational load distribution during the intended use and/or during the future environmental conditions, the loads within the pinion group are equally distributed; sensing an actual load distribution associated with the pinion group, and emitting sensor signals indicative of the sensed load distribution; the control system receiving the sensor signals indicative of the sensed actual load distribution and determining/computing a difference between the pre-operation load distribution and the sensed actual load distribution; and the control system emitting, in response to the difference, control signals to the actuators such that the actuators are operated and cause the sensed actual load distribution of the pinion group to correspond to the pre-operation load distribution.

10. (canceled)

11. The method according to claim 9, wherein the pre-operation load distribution for the plurality of pinions of the pinion group is such that one or more lower pinions of the pinion group have lower loads thereon than one or more higher pinions of the pinion group.

12. The method according to claim 9, wherein a load increase from the pre-operation load distribution to loads in the intended use and/or during the future environmental conditions for one or more lower pinions of the pinion group is larger than for one or more higher pinions of the pinion group.

13. The method according to claim 9, wherein the control system determines the pre-operation load distribution for each pinion group individually.

14. The method according to claim 9, wherein the control system determines the pre-operation load distribution for each of the pinion groups corresponding to a jack-up leg.

15. The method according to claim 9, wherein the jack-up vessel comprises a crane, and wherein the pre-operation load distribution is calculated on the basis of a hoisting load of the crane.

16. The method according to claim 9, wherein said receiving information about an intended use and/or about future environmental conditions comprises receiving information about a predicted storm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0116] The invention will be further elucidated in relation to the drawings, in which:

[0117] FIG. 1 is a side view of a jack-up vessel;

[0118] FIG. 2a is a side view of a jack-up vessel in an operational position;

[0119] FIG. 2b is a side view of a jack-up vessel in an operational position during a hoisting operation;

[0120] FIG. 3a is a perspective view of a jack-up leg showing jacking assemblies;

[0121] FIG. 3b is a perspective view showing a jacking assembly;

[0122] FIG. 4 is a schematic representation of a sensor system and control system;

[0123] FIG. 5a is an illustration of load distribution with Christmas Tree Behaviour;

[0124] FIG. 5b is an illustration of a pre-operation load distribution;

[0125] FIG. 6a shows a side view of a gearbox for a pinion which is mounted in a resilient way by using resilient parts;

[0126] FIG. 6b shows a cross section of FIG. 6a, taken along the line VIb-VIb in FIG. 6a;

[0127] FIG. 6c shows a side view of the gearbox of FIG. 6a.

[0128] FIG. 7 shows the jacking assembly of FIGS. 3a, b when mounted to the hull,

[0129] FIG. 8 shows an alternative mounting of the jacking assembly to the hull.

DETAILED DESCRIPTION OF EMBODIMENTS

[0130] Although the drawings illustrate a jack-up vessel performing an operation of installing components of a wind turbine at a wind turbine installation site, this does not mean that the invention is limited to this operation. The invention may also be applied to jack-up vessels used for other operations, for example a jack-up vessel drilling for natural resources such as oil. In practice, most jack-up vessels perform a pre-loading step and may be required to withstand environmental conditions such as storms.

[0131] In FIG. 1 a jack-up vessel 1 for installing one or more components of a wind turbine at a wind turbine installation site is shown. The jack-up vessel is not in an operational position, but in a condition where it can travel to or from a wind turbine installation site. The jack-up vessel 1 includes a buoyant hull 5 and a crane 14. In an operational position of crane 14, not shown in FIG. 1, crane 14 is configured for hoisting one or more components 2, 3a, 3b, 4a, 4b of a wind turbine.

[0132] In this embodiment, wind turbine components 2, 3a, 3b, 4a and 4b are positioned on the buoyant hull 5 for transport to a wind turbine installation site. In other embodiments, some or all wind turbine components may be transported to the wind turbine installation site by other vessels.

[0133] The crane 14 is shown in a transport position. In embodiments, the vessel may include more than one crane, such as two, in which case both cranes are e.g. mounted on the same side of the buoyant hull 5.

[0134] Jack-up vessel 1 includes a plurality of jack-up legs 6, 8. In this embodiment, jack-up vessel 1 includes four jack-up legs and four jacking assemblies. Jack-up legs 6 and 8 are shown; not shown are two other legs which are positioned, in this side view, behind legs 6 and 8. In other embodiments, the number of legs may be different, e.g. six. The legs may also be positioned at other locations than shown in FIG. 1. For example, one or more legs may be positioned in the middle of buoyant hull 5. Two legs may be positioned at one end of buoyant hull 5 and the other legs at the opposite end.

[0135] Each jack-up leg comprises one or more leg chords. In FIG. 1, each jack-up leg comprises three leg chords. Jack-up leg 6 includes leg chords 20, 21 and a third leg chord which is not shown in this side view. Jack-up leg 6 is shown in detail in FIG. 3a.

[0136] Jack-up vessel 1 comprises a plurality of jacking assemblies 10, 11, 12, 13, each jacking assembly being associated with a leg chord. In the embodiment shown in FIG. 1, jacking assembly 10 is associated with leg chord 20, and jacking assembly 11 is associated with leg chord 21. Jacking assemblies 12 and 13 are associated with two chords of jack-up leg 8. Jacking assemblies associated with the third chords of jack-up legs 6 and 8 is not shown in this side view.

[0137] In this embodiment, jacking assemblies 10 and 11 are positioned at the same vertical position relative to buoyant hull 5. In other embodiments, jacking assemblies may be positioned at different vertical positions.

[0138] Jacking assemblies 10, 11 are configured to move the corresponding jack-up leg 6 vertically relative to the buoyant hull. Jacking assemblies 12, 13 are configured to move the corresponding jack-up leg 8 vertically relative to the buoyant hull.

[0139] In FIG. 2a, jack-up vessel 1 is in an operational configuration of the jack-up vessel. This operational configuration is achieved by lowering jack-up legs 6, 8 for engagement with the seabed 16 and raising buoyant hull 5 to a distance above water level 15.

[0140] In this figure, legs 6 and 8 extend relative above and below buoyant hull 5. Crane 14 is in an operational configuration, such that a hoisting operation can be performed. Crane 14 may hoist one or more components to and from a wind turbine installation site. In this figure, no wind turbine component is being hoisted. This may be the case when jack-up vessel 1 has not yet started operation at the current site; alternatively, this may be the case when jack-up vessel 1 has finished hoisting of a wind turbine component, such as wind turbine component 4a. In this embodiment, wind turbine components 2 and 3b are positioned on buoyant hull 5. In other embodiments some or all wind turbine components may be positioned on other vessels. Wind turbine component 4a may also have been installed by a separate vessel, which may be a jack-up vessel or a different type of vessel, which is suitable for hoisting wind turbine component 4a.

[0141] In FIG. 2b, jack-up vessel 1 is in the operational configuration and hoists wind turbine component 3b using crane 14, for example to an intended position 3b on wind turbine component 4a. This may be at the same wind turbine installation site as in FIG. 2. Alternatively, this may be at a different wind turbine installation site. Wind turbine component 3b may have been hoisted from a position on buoyant hull 5, or from a different position, for example a position on a separate vessel.

[0142] Alternatively, the intended position of wind turbine component 3b may be a position on buoyant hull 5, or on a separate vessel. A wind turbine component 3b may have already been positioned on wind turbine component 4a, such as when wind turbine component 3b was incorrectly placed on wind turbine component 4a or when jack-up vessel 1 is used in a situation where for instance maintenance or decommissioning of a wind turbine requires hoisting wind a wind turbine component such as wind turbine component 3b.

[0143] In FIG. 3a, leg 6 is shown in more detail. In this embodiment, leg 6 consists of three chords 20, 21 and 22, each chord having two racks. Rack 23 of chord 20 is visible, and rack 26 of chord 22 is visible. Both racks 24 and 25 arranged on chord 21 are visible. In this embodiment, chords 20, 21 and 22 are interconnected via a truss structure.

[0144] Also shown in FIG. 3a are: [0145] jacking assembly 27, corresponding to leg chord 20, shown engaging with rack 23 and an opposed rack of corresponding leg chord 20; [0146] jacking assembly 28, corresponding to leg chord 21, shown engaging with racks 24 and 25 of corresponding leg chord 21; and [0147] jacking assembly 29, corresponding to leg chord 22, shown engaging with rack 26 and an opposed rack of corresponding leg chord 22.

[0148] In embodiments, these jacking assemblies are arranged on buoyant hull 5, but for illustrative purposes, hull 5 is omitted in FIG. 4.

[0149] In this embodiment, jacking assemblies 27, 28 and 29 are configured in the same way, but in other embodiments, different jacking assemblies may be used for different chords, for different legs, or for both.

[0150] In FIG. 3b, jacking assembly 28 is shown in more detail. Each jacking assembly comprises at least one pinion group. The number of pinion groups is generally equal to the number of racks. In this embodiment, jacking assembly 28 comprises two pinion groups, 34 and 35. Each pinion group comprises a plurality of, in this figure five, pinions 40 arranged vertically above each other.

[0151] Each pinion 40 engages a rack 24, 25 of its associated leg chord 21 and is configured for transferring a part of the load of the buoyant hull 5 to the leg chord 21, resulting in each pinion 40 having a transferred load associated with the pinion.

[0152] In the shown embodiment, each pinion 40 is formed identical, but in other embodiments, different pinions may be comprised by jacking assemblies. In embodiments, pinions within a pinion group may be the same; alternatively, different pinions may be used within a pinion group, or for different pinion groups, or for different jacking assemblies, or for a combination thereof.

[0153] Jacking assembly 28 further comprises a plurality of actuators 30, each actuator configured for actuating a respective pinion 40. An actuator may actuate just one pinion, but it is also possible that an actuator actuates a plurality of pinions, e.g. 2 pinions at the same vertical position, or all pinions in one pinion group. In the shown embodiment, jacking assemblies also comprise a plurality of gearboxes 31, brakes 32 and parallel parts 33.

[0154] Actuator 30 may be a hydraulic motor or an electric motor. In the embodiment shown, actuator 30 is an electric motor. In the case of an electric motor, actuation of a pinion 40 may be done directly coupled to actuator 30, or there may be a gearbox to provide the transmission from actuator 30 to pinion 40, such as a planetary gearbox 31. A parallel part 33 may also be included in the transmission.

[0155] Braking may be achieved by actuating actuator 30, or by actuating brake 32. Alternatively, brake 32 may be a failsafe brake, to be used in cases wherein using actuator 30 for braking does not give a sufficient result, such as when actuator 30 fails. Brake 32 may be embodied as a brake which brakes in a neutral position and is kept in a non-braking configuration by means of electric power, such that in case of a power failure, rendering actuator 30 inoperable, brake 32 is activated. In embodiments, brake 32 acts on the same shaft as the shaft on which actuator 30 acts.

[0156] In embodiments, gearboxes 31 are of the same type to keep the number of spares minimal. In embodiments, this also applies for actuators 30.

[0157] In FIG. 4, a sensor system 150 and a control system 152 are schematically represented. Pinions 140a and 140b engage with rack 125 of associated leg chord 121.

[0158] Sensor system 150 is configured for sensing the load distribution associated with a pinion group, and emitting sensor signals indicative of the sensed load distribution.

[0159] In this figure, one sensor system is associated with a pinion group. It is conceivable that a jack-up vessel comprises one sensor system for the entire jack-up vessel. It is also conceivable that each pinion, each pinion group, each rack, each chord, each jacking assembly, or each leg may have a sensor.

[0160] Sensor signals may be emitted to the control system 152 by a wire from a sensor to the control system, or there may be an intermediate component which combines one or more sensor signals and emits a signal to the control system. Such an intermediate component may also perform calculations.

[0161] Here, sensor system 150 comprises sensor 151a and 151b, sensing parameters representative of transferred loads associated with pinion 140a and pinion 140b, respectively. Pinion loads associated with pinions may be measured in many different ways, e.g. by load cells on the pinions or the pinion shaft. In a preferable embodiment they may be measured by integrated sensors at the pre-stages of the gearboxes 131a and 131b. This is a more practical location than the actual pinion or pinion shaft, because the actual pinion is in a harsher environment and more difficult to reach.

[0162] The jack-up vessel comprises a control system 152. Control system 152 receives the sensor signals indicative of the sensed load distribution from sensor system 150.

[0163] Control system 152 is configured for receiving information about an intended use and/or future environmental conditions. In embodiments, an operator may use user interface 154 to provide the control system with characteristics of the pre-load operation, the load to be hoisted, weather conditions, etc. Alternatively, this information may be received before the vessel is deployed and stored in the control system. Based on the received information, the control system determines a pre-operation load distribution, e.g. automatically. For example, in a hoisting operation, a characteristic of the load to be hoisted may be measured by a hoisting system in communication with the control system.

[0164] If during a pre-loading step the actual transferred loads are measured and a difference between one or more of these loads is determined to be higher than a desired amount, the pre-operation load distribution may be reactively determined such that the load distribution is more even across the pinions in a pinion group. In other words, after receiving information about the intended use and determining a pre-operation load distribution, feedback during the operation may be received after which the control system may determine a second pre-operation load distribution. This may be determined at any point before or during operation and subsequently stored in the control system. At any point after storing this pre-operation load distribution it may be replaced by a different pre-operation load distribution. It is also possible that the control system is configured for storing a plurality of pre-operation load distributions, e.g. each time that a new pre-operation load distribution is determined, the previous pre-operation load distribution is added to a memory of possible load distributions, such that a previous pre-operation load distribution may be selected at any later point, for instance by the operator or automatically based on a characteristic that the control system detects.

[0165] In embodiments, control system 152 receives information about future environmental conditions using telecommunication means 153.

[0166] User interface 154 may provide the operator with information on the load distribution, for example the current load distribution, or information about integrity of the sensor system, i.e. whether the system detects that sensors in sensor system 150 are working properly or malfunctioning.

[0167] Control system 152 determines a difference between the pre-operation load distribution and the actual transferred load. It emits, in response to the difference, control signals to one or more actuators 130a, 130b, such that the pre-operation load distribution corresponds to the actual transferred loads. In embodiments, the one or more actuators 130a, 130b actuate their associated pinion 140a, 140b by using the respective gearbox 131a, 131b. It may suffice for one pinion to be actuated: for example, if the load on pinion 140a is higher than desired, and the load on pinion 140b is higher than desired, after actuating either actuator 130a or actuator 30b, the actual transferred loads may correspond to the pre-operation load distribution. Alternatively, it may be required or desired to actuate more than one actuator, for example all actuators in a pinion group. It is also possible to actuate a plurality of pinions at a certain vertical location, i.e. first actuating upper pinions, then middle pinions, etc.

[0168] FIGS. 5a and 5b illustrate the effect of a load distribution for a leg chord 21 with two racks and for a jacking assembly 28 with two pinion groups 34,35, each pinion group comprising three pinions. Both figures show next to the pinions loads associated with the pinions as two horizontal bars. Each highest bar represents the load associated with the pinion before load is increased, each lowest bar represents the load associated with the pinion after load is increased. The behaviour illustrated in FIG. 5a may be called Christmas Tree Behaviour. If the load on the jack-up leg increases while brakes are applied (e.g. during a pre-loading step, during storm conditions or during a hoisting operation of crane 14), the lower pinions might take more load than the upper pinion.

[0169] This can be counteracted by adjusting the load distribution before increasing the load on a leg to a pattern that gives an even distribution when the high leg load is applied. This can be achieved by adjusting the settings of a (re-) torque system. The resulting load distribution is shown in FIG. 5b. The pre-operation load distribution before increasing load may be called a Reverse Christmas Tree. When load is applied, the loads associated with the pinions are equal, illustrated by the lower bars in FIG. 5b.

[0170] The lower pinions in a pinion group will generally have the largest increases in load from the pre-operation load distribution to the loads in the intended use and/or during the future environmental conditions, in particular in embodiments wherein the hull is suspended from the jacking frame. In certain pre-operation load distributions, these pinions transfer a low load or approximately no load and have a large increase in load in the intended use and/or during the future environmental conditions.

[0171] It may however be desirable to achieve an even larger increase in load. In this case, in the pre-operation load distribution the loads of these pinions can be thought of as having a desired load corresponding to a value below zero, a negative pre-operation load so to say. In other words, the slanted dashed line in FIG. 5b, when extrapolated to lower pinions, would cross the vertical axis. This can be achieved by positioning these pinions with respect to the rack so that they do not engage the rack in the pre-operation load distribution. In other words, a certain backlash or play is introduced, i.e. a clearance that the rack and/or the pinion can move before they engage each other. In this way, below a certain load on the rack these pinions transfer essentially no load, and above a certain load on the rack, these pinions will engage the rack and transfer part of the load on this rack.

[0172] It is also conceivable that a part, e.g. a respective pinion, its respective gearbox, a connection between the pinion and the gearbox, and/or a mounting part in the respective jacking assembly is provided as a resilient part. This resilience refers to the ability of this part to absorb energy when it is deformed elastically, and release this energy upon unloading. With a resilient part, when the load on the respective pinion is increased, a part of this load is absorbed by elastic deformation of the resilient part. This allows the total load that can be transferred by this pinion to be higher. Within a pinion group, one more pinions, such as the lowest pinion, may be provided as a resilient part. When more than one pinion are provided as a resilient part, it is conceivable that a lower pinion has a resilient part which can take more load than a higher pinion.

[0173] When a resilient part is provided for a pinion in a pinion group, the pre-operation load distribution is determined such that the combined effect of the pre-operation load distribution and the resilient part leads to the loads within this pinion group being equally distributed in the intended use and/or during the future environmental conditions. For example, the lowest pinion in a pinion group could be provided with a resilient part, such as a flexible mounting of the gearbox. The resilient part can absorb part of an increase in load. The pre-operation load for the lowest pinion would then be the load in the intended use and/or during the future environmental conditions, minus the part of the increase in load which is not absorbed by the resilient part.

[0174] In FIG. 6a, an actuator (not shown) actuates a pinion (not shown) through a gearbox 31, brake 32 and parallel part 33. Gearbox 31 is mounted to a housing 60. Also shown are axial mounting plates 61. In FIG. 6b a cross section of FIG. 6a is shown. Between the gearbox 31 and housing 60 a bearing 62 is provided, here comprising a bronze bushing. The bearing allows rotation of the gearbox 31 with respect to the housing 60. In FIG. 6c, axial mounting plates 61 have been omitted for clarity. Now multiple (8) flexible parts 63 of a flexible or resilient material are visible, e.g. rubber or a polymer, e.g. a fibre-reinforced polymer. These flexible parts are provided between the gearbox 31 and the housing 60. The presence of these flexible parts 63 provides resilience to and limits any rotation of the gearbox 31 with respect to the housing 60.

[0175] As already visible in FIGS. 3a, 3b, and further shown in FIG. 7, the jacking assembly 28 has a frame 28a. This frame 28a supports two pinion groups, each with pinions at levels above one another. Each pinion is driven by an associated actuator, e.g. an electric motor with a reduction gearbox. Here the two pinion groups 34, 35, each have a plurality of pinions arranged vertically above each other in order to engage the two racks 24, 25 on the leg chord 21.

[0176] A hull connector structure 28b is provided at a lower end of the frame 28a of the jacking assembly 28. This hull connector structure 28b connects the jacking assembly 28 to the hull 5. In this arrangement, the load of the hull 5 is effectively suspended from the lower end of the frame 28a of the jacking assembly 28.

[0177] In another embodiment, as shown in FIG. 8, the hull connector structure 28b is provided at an upper end of the frame 28a of the jacking assembly 28, which hull connector structure 28b connects the jacking assembly to the hull 5. In this arrangement, the load of the hull 5 effectively rests on the upper end of the frame 28a of the jacking assembly 28.

[0178] It will be appreciated, that the load distribution over the pinions in a pinion group is influenced by whether the hull connector structure 28b, 28b is present at the lower end of the frame as in FIG. 7 or at the upper end of the frame as in FIG. 8. Yet, the inventive concept for load distribution over the pinions of a group is applicable to each of these variants.

[0179] It is illustrated, that the hull connector structure is configured for a pin connection to the hull. For example, the structure comprises a pair of spaced part eye members 28b1, 28b2, 28b1, 28b2, each receiving a connector pin 28d, 28d therein to connect the hull connector structure to the hull 5, here through one or more associated eye members on the hull. For example, an elastic bushing is provided in eye members 28b1, 28b2, 28b1, 28b2 of the hull connector structure, for example made of a synthetic composite incorporating solid lubricant(s), e.g. made of Orkot.

[0180] It is shown that the pin connection of the frame 28a, 28a of the jacking assembly to the hull may result in a pivotal connection of the jacking assembly to the hull. In such embodiment, and others, a stabilizing connector structure 45, e.g. shown in FIG. 7 at the upper end, may be provided at the other end of the frame of the jacking assembly, generally to avoid undue pivoting of the assembly 28, 28. This stabilizing connector structure may comprise one or more elastic members, e.g. when the hull connector structure also comprises one or more elastic members, e.g. the elastic bushing as described above.