WO2002018711A1

WO2002018711A1 - An apparatus and a device for driving an object by vibration or impact

Info

Publication number: WO2002018711A1
Application number: PCT/NL2000/000600
Authority: WO
Inventors: François Bernard
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-29
Filing date: 2000-08-29
Publication date: 2002-03-07
Anticipated expiration: 2003-02-28
Also published as: AU2000273232A1

Abstract

The invention relates to an apparatus for driving an object by vibration or impact, in particular a pile or sheet to be driven into the ground or to be removed therefrom, at an underwater target position, comprising drive means, such as an eccentrically rotatable weight, and means for activating said drive means, characterized in that, the apparatus comprises a beacon to transmit acoustic rays and plurality of thrusters to control the position of said apparatus with respect to the underwater target position.

Description

Title: An apparatus and a device for driving an object by vibration or impact.

The present invention relates to an apparatus for driving an object by vibration or impact, in particular a pile or sheet to be driven into the ground or to be removed therefrom, at an underwater target position, comprising drive means, such as an eccentrically rotatable weight, and means for activating said drive means.

In the present text reference is made to an object to be driven into the ground or to be moved therefrom, in particular a pile or a sheet. It should be understood that the appa- ratus according to the present invention can be used for installing or extracting elongated piles, anchors or any other designed type of connection between a subsea superstructure and the seabottom.

An apparatus as defined at the outset is known from WO 99/47757.

The prior art apparatus comprises drive means having a first eccentrically rotatable weight and a second eccentrically rotatable weight, which weights are interconnected by a phaseshifter which is capable of adjusting the rotational position of the weights relative to each other. Vibration can be produced by having an eccentrically rotatable weight, that is, a rotatable mass whose center of gravity does not lie on the axis of rotation, rotate about its axis. If said vibration comprises sufficient energy, it is possible to set an object vibrating therewith so as to drive said object into the ground by vibration. The alternating upwards and downwards movements generated by the cyclic movement of the apparatus will cause a reduction in the soil strength and will temporarily liquefy the soil such that the foundation or anchoring device is penetrating the soil by its own weight.

According to the prior art the apparatus for driving an object by vibration is fixed, to for instance a pile, and deployed towards the underwater target position by means of a hoisting wire. In order to position the pile just above the target position, normally the movement of the vessel itself will be used. However, when an object has to be driven into the seabed at an increasing depth it is not longer possible to achieve the required accuracy in positioning the object above the target position, using the movement of the vessel only.

The object of the invention is therefore to enhance the accuracy of the positioning of an apparatus as defined at the outset during deployment thereof.

To obtain this object the apparatus according to the present invention is characterized in that the apparatus comprises a beacon to transmit acoustic rays and plurality of thrust- ers to control the position of said apparatus with respect to the underwater target posi- tion.

During deployment the apparatus is controlled by controlling equipment on board of a vessel floating on the seasurface. The controlling equipment needs to know the exact location of the apparatus as accurate as possible. To that end, the beacon on board of the apparatus transmits acoustic rays through the seawater to the vessel. An appropriate acoustic receiver receives these acoustic rays and converts them into electrical signals used to calculate the position of the apparatus with respect to the vessel. When the exact position of the apparatus with respect to the vessel is known, the thrusters can be used to control the position of said apparatus with respect to the underwater target po- sition.

In the preferred embodiment, the apparatus comprises a first unit provided with the drive means, such as an eccentrically rotatable weight, and, a second unit provided with the beacon and the plurality of thrusters, the first and second unit being provided with coupling means for coupling the first and the second unit.

When the drive means are activated, these drive means will not only induce vibration to the object to be driven into the ground, but also to the apparatus itself. That means that components of the apparatus must be able to withstand the forces, vibrations and other loads induced by the driving means. The apparatus according to the invention however comprises delicate components such as the beacon to transmit acoustic rays and the thrusters. In order not to risk damaging of these delicate components during installation of a pile or a sheet in the seabed, it is advantageous to be able to decouple a first unit provided with the drive means from a second unit provided with the more delicate components. Before the actual installing of the object to be driven into the seabed, both units will be split. After the installation has been finished, both units can be coupled to each other in order to be able to remove the apparatus from the underwater target posi- tion.

It is advantageous that the apparatus is provided with connector means to provide an electrical and/or hydraulical connection between the first and second unit.

Moreover it is possible that the connector means comprise a plug- and socket-assembly, the first unit comprising a first part of said plug- and socket-assembly, and the second unit comprising a corresponding second part of said plug- and socket-assembly.

In order to be able to activate the drive means in the apparatus according to the inven- tion, a multiple amount of electric-hydraulic power conversion stations capable to feed the hydraulic motors of the drive means, will be present in the apparatus. When an electrical and/or hydraulical connection between the first and second unit is present, it is possible to mount the electric/hydraulic power conversion stations on board of the second unit. That means that also these electric/hydraulic power conversion stations will not be exposed to the vibrational, potential damaging, forces produced by the drive means of the first unit.

According to the invention it is possible that the connector means comprise a connector line and a reel for selectively reeling in and out the connector line in order to be able to respectively decrease or increase the distance between the first and second unit.

When the second unit of the apparatus is removed from the first unit, the connection between both units can be maintained by having an electrical/hydraulic connection between the two. For instance the first unit is equipped with an umbilical reel, being a constant tension umbilical reel. When the second unit is moved towards the first unit, the umbilical will be reeled in automatically, and cannot get stuck between both units, or between other items when recoupling both units. Please note that in the present text the wording "coupling means", refers to means for physically fixing a first unit to a second unit. The word "connecting means" refers to for instance an umbilical, for transferring electrical and/or hydraulic energy.

When the apparatus according to the present invention is used at even increasing depth for instance up to 3,000 meter or more, it is found that the accuracy of the location measurement decreases due to bending of the acoustic rays in the seawater. In order to be able to use the apparatus according to the invention also in deep water, it is preferred that it is provided with a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus. Thus, the velocity of sound at a certain location in the fluid can be continuously measured and used to update a sound velocity profile, i.e., data as to the sound velocity as a function of depth in the fluid. From these data, local bending of the acoustic rays can be determined on-line (real time). This allows corrections of location measurements in real time.

In a preferred embodiment, the thrusters comprise a first set of thrusters arranged to provide a torque control function and a second set of thrusters arranged to provide at least a translation function, each thruster of the second set of thrusters being provided with a rotary actuator.

This is a very advantageous embodiment. Only two thrusters are necessary to prevent any undesired rotation of the apparatus attached to the load during deployment thus avoiding all problems related to twisting and turning of hoist wires carrying the load, as already explained in the earlier patent application WO 99/61307 in the name of the same applicant. Moreover, only two rotatable thrusters are needed to control positioning of the apparatus with its load attached to it to the desired horizontal coordinates. Thus, prior to lowering the load with the apparatus the apparatus can move the load to the desired horizontal coordinates and when these coordinates have been reached the hoist wire(s) can lower the load to its desired location on the seabed while the thrusters keep the load on the desired coordinates and prevent any undesired rotation of the load. Only when the desired target position on the seabed is reached a possible rotation of the load to a desired orientation need be carried out by the thrusters dedicated to the torque control. In order to be able to get even more information about the position of the apparatus and the characteristics of the surrounding fluid, it is advantageous to provide the apparatus according to the present invention with a gyrocompass with motion sensors, to sense heading, acceleration, roll and pitch of the apparatus in use; a Doppler-log unit, to measure current strength of said fluid, load cells to measure weight of a load engaged by the apparatus; a temperature sensor to measure temperature in the surrounding fluid and to transmit temperature data real time; and to provide the apparatus with a salinity meter, to measure salinity of said fluid and to transmit salinity data real time.

Please note that in the present text the wording "real-time" is meant to be the opposite of "post-processing".

The apparatus according to the present invention will be deployed using a lifting wire in combination with one or more umbilicals. It is known to provide such lifting wires with a heave compensation system, in order to compensate movements of the vessel with respect to the seabed due to influences of waves and the wind. Because of the fact that it is essential to be able to position the apparatus according to the present invention with a high accuracy, it is advantageous to be able to fine-tune such a heave compensation system. Therefore according to an embodiment of the apparatus according to the invention the apparatus is provided with a lifting assembly to deploy and recover the apparatus with respect to a vessel, wherein the lifting assembly is provided with a hydraulic cylinder, the cylinder being connected to means for controlling the length of the cylinder for controlling the vertical position of the apparatus with respect to the target position.

The cylinder has the form of a double-working hydraulic cylinder. That means that the cylinder is provided with a plunger, which engages a fluid reservoir on both sides thereof. By controlling the hydraulic pressure in the cylinder, the plunger can be moved. By moving the plunger in the cylinder, the heave compensation can be fine-tuned.

The cylinder provides a secondary heave compensation system, which can either be connected to the same software as the primary heave compensation system or which could perform a lock-on motion, taking reference from the seabed. Therefore the cylinder will work in phase with the primary heave compensation system or alternatively will be set independently.

In order to be able to control the length of the cylinder in the lifting assembly, it is pos- sible the apparatus is provided with a pressure sensor to measure the depth in a fluid surrounding said apparatus and to transmit pressure data in real time.

Alternatively it is possible that the apparatus is provided with a sonar unit to determine the position of said apparatus with respect to at least one object external to said appa- ratus.

The invention also relates to a vibratory hammer comprising one or more excentrally rotatable weights, wherein said weights are accomodated in a housing, the housing being filled with a liquid, such as oil, in order to make the weights run in the liquid.

According to the invention it is advantageous that means are provided for selectively introducing liquid in the housing, or removing liquid from the housing, in order to adjust the liquid pressure inside the housing.

When extra liquid is introduced in the housing the pressure in the housing will increase. The selective introducing or removing of liquid to and from the housing could be performed in a manual mode.

Vibratory hammers according to the prior art normally comprise rotatable weight, the weight being rotatably fixed inside the housing filled with air. When such a hammer would be used at increasing depth, such as 3000 meters or more, the difference in pressure inside and outside the gearbox accomodating the rotatable weight, would be too large. Therefore, it is advantageous to be able to balance the pressure inside the gearbox and outside the gearbox. According to the present invention the housing is filled with a liquid in order to balance those pressures.

According to the present invention it is advantageous that the housing comprises a member, such as a cylinder able to move under influence of pressure exerted on the interior and the exterior of said member, in order to keep the liquid inside the housing at ambient pressure. When deploying the vibratory hammer according to the present invention, the pressure outside the vibratory hammer will increase while the pressure inside the gearbox of the vibratory hammer must increase as well. When, for instance, the wall of the housing comprises a channel equipped with a free-moving cylinder, during deployment the cylinder can move through the channel in order to balance between the pressures inside the gearbox and outside the gearbox. Alternatively, it would be possible to provide the wall of the gearbox with a membrane, such as a flexible membrane.

According to the invention it is possible that the hammer comprises means, such as a valve, to respectively permit or prevent the movement of said member.

This member, such as a cylinder, could be embodied in the form of a free moving member. When the hammer is activated, the weight in the hammer will be rotating. The rotation of the weight in the liquid will introduce rapid increases and decreases in liquid pressure. Therefore if the free moving member, such as a cylinder, would be able to response to the alterations of pressures, the free moving member would be moving at a high speed, and almost constantly. Because of this uncontrolled movement of the free moving member several problems could occur. For instance the seals between the free moving member and the channel where the free moving member is positioned in, could be deteriated because of wear. Also ambient water could be introduced in the housing, when the effectiveness between the cylinder and the housing would suffer from the uncontrolled movement of the member.

In order to overcome these problems it is advantageous to be able to lock the free moving member, such as a cylinder. For instance the locking of the member could be achieved by means of a solinoid. It would be possible to activate the solinoid when the hammer itself is actuated.

Because of the fact that the rotatable weight according to the present invention rotates in a liquid, it is advantageous that said weights are shaped cylindrically, the body of the weight being provided with one or more cavities. When the outside shape of the weight would not be cylindrical, but instead thereof would be asymmetrical, the weight would encounter too much friction inside the liquid when the weight would be rotated. The weight would work like a "liquid pump". It is necessary to provide the cavities in order to be able to induce a excentrical force when rotating the weight.

According to the present invention it is advantageous that the cavities are in communication with the liquid inside the housing. Because of the fact that the cavities inside the weight are in communication with the liquid inside the housing, it is possible that the cavities are filled with, for instance, oil. Because of the fact that the specific weight of oil is much lower than the specific weight of a suitable material for the weight, such as steel, the weight will induce a vibrational movement when rotating the weight.

The invention also relates to a processing arrangement arranged to drive an apparatus for driving an object by vibration or impact, at an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters to control positioning of said apparatus with respect to said underwater target position, and a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real-time, the processing arrangement being provided with an acoustic receiver to receive said acoustic rays, the processing arrangement is arranged to use data derived from said acoustic rays in a calculation to determine the position of the apparatus characterized in that the processing arrangement is arranged to receive on-line sound velocity meter data from said sound velocity meter to determine a sound velocity profile in said fluid and to calculate from said sound velocity profile bending of said acoustic rays transmitted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus in real-time.

Such a processing arrangement is able to control the driving of said apparatus to a target underwater location in a desired orientation with very high accuracy, even at great depth under water. While the apparatus with the object to be driven into the seabed is lowered, the processing arrangement constantly receives sound velocity data and determines a sound velocity profile comprising sound velocity data from the water surface to the depth of the apparatus. The processing arrangement uses these data to determine acoustic ray bending as a function of the depth in the water and thus corrects any position calculation of the apparatus.

Such a processing arrangement may be on board of a vessel floating on the water surface. However, it is to be understood that part of the functionality of determining the sound velocity profile and calculating the acoustic ray bending may be carried out by one or more processors located elsewhere, even on board of the apparatus itself.

Preferably, a further sound velocity meter is provided just below the water surface to provide actual data regarding any ray bending in the water surface layers and thus to further correct any position calculation of the apparatus.

Reception of the acoustic rays transmitted by the apparatus is preferably performed by an acoustic array attached to the hull of the vessel.

In a very preferred embodiment, the vessel, the acoustic array and the apparatus are all provided with a distinct gyrocompass measuring respective heading, acceleration, heave, roll and pitche. Output data from these gyrocompasses are used to further increase accuracy of the position measurement of the apparatus.

The invention also relates to a system comprising such a vessel and an apparatus together.

Moreover the invention relates to a vessel provided with a processing arrangement, as mentioned above.

The invention also relates to a system comprising a vessel and an apparatus, wherein the apparatus and the processing arrangement on a vessel are arranged to communicate with one another.

In the system according to the present invention the apparatus and the processing arrangement will be connected by means of multiple cables, which cables can be reeled out and reeled in from a vessel. It is advantageous not to have the risk of the cables getting entangled, when the cables are set overboard. This will improve the control, in terms of vortex shading, over the cables when the apparatus is deployed. Therefore the system according to the invention is preferably provided with a bundling apparatus for bundling the cables, when reeled out, in order to provide a single cable assembly between this bundling apparatus and the apparatus according to the invention.

The invention also relates to a method for controlling the apparatus for driving an object by vibration or impact, according to the present invention, which methods comprise the steps of:

- securing the apparatus to the object to be driven into the ground, - deploying the apparatus and the object to be driven into the ground from a vessel by means of a lifting assembly towards the underwater target position,

- de-cqupling the second unit from the first unit after reaching the target position and

- moving the second unit away from the first unit, and

- driving the object into the ground by activating the drive means.

This method can be improved by using the apparatus which is provided with a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus and to transmit velocity data in real time, wherein the method comprises the steps of:

- receiving said acoustic rays - using data derived from said acoustic rays in a calculation to determine the position of the apparatus,

- receiving sound velocity meter data from said sound velocity meter and determining a sound velocity profile in said fluid, and

- calculating from said sound velocity profile bending of said acoustic rays transmit- ted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus.

These methods may be entirely controlled by a suitable computer program after being loaded by a processing arrangement. Therefore, the invention also relates to a computer program product comprising data and instructions that after being loaded by a processing arrangement provides said arrangement with the capacity to carry out a method as defined above. The present invention will be explained in detail with reference being made to the drawings. These drawings are only intended to illustrate the invention and not to limit the scope which is only defined by the dependent claims.

Figure 1 shows schematically the driving of a pile in the seabed according to the prior art.

Figure 2 shows the deployment of a pile to be driven into the seabeds, from a vessel according to the invention.

Figure 3 shows actual driving of a pole in the seabeds using the apparatus according to the invention.

Figure 4 shows an embodiment of the apparatus according to the present invention.

Figure 5 shows an A-frame for deploying the apparatus according to the present invention.

Figure 6 shows a clamp for clamping the inside of a hollow structure such as a pile, to be used with the apparatus according to the present invention.

Figure 7 shows an embodiment of the hammer according to the invention.

Figure 8 shows an embodiment of a eccentric weight to be used in the hammer according to figure 7.

Figure 9 shows a detail of the second unit, showing a rotary platform fixed to the frame of the second unit, and showing a stub received in the second unit.

Figure 10 shows a detail of the coupling between the stub and the second unit.

Figure 1 schematically shows a vessel 1 to be used for deploying a pile 2 to be driven in the seabed 3. From the vessel 1 the pile 2 is deployed together with an apparatus for driving the pile by vibration or impact. The apparatus 4 is a hammer, provided with for instance eccentric rotatable weight, in order to induce vibration, or a falling weight to induce impact. The pile 2 is fixed to the hammer 4. The hammer 4 and the pile 2 are deployed by means of a hoisting wire 5 which is connected to a crane 6. In order to provide the required electrical or hydraulic energy to the hammer 4, the vessel is also connected to the hammer by means of an umbilical 7.

The pile 2 according to figure 1 is to be driven into the seabed 3 at the target position 8. In order to position the pile 2 just above the target position 8, the movement of the ves- sel 1 and the crane 6 will be used. However, when the pile 2 has to be driven into the seabed 3 at an increasing depth, it is not longer possible to achieve the required accuracy in positioning the pile above the target position 8, using the movement of the vessel and the crane only.

In figure 2 schematically a vessel is shown which could be used in combination with the apparatus for driving an object by vibration, according to the present invention. The vessel 10 comprises an A-frame 11 which can be used to set the apparatus according to the invention overboard. Possible embodiments of the A-frame 11 are shown with reference to figure 5.

The vessel comprises multiple winches for selectively reeling in and out at least one lifting wire and at least one umbilical, for respectively deploying the apparatus according to the present invention and for supplying the required electrical energy to this apparatus. In figure 2 schematically one winch 12 is shown. Possible embodiments of the positioning of the winches with respect to the A-frame 11 is shown in figure 5.

In figure 2 the apparatus according to the invention 15 is shown schematically. A possible embodiment of the apparatus according to the invention is shown in more detail in figures 3 and 4.

A pile 2 to be driven into the seabed initially can lie on the deck of the vessel 10 and brought overboard in an essential horizontal position. This is drawn in dashed lines. Before deployment the pile 2 will be upended outboard using a pile rotating support 16. The pile 2 will be placed outboard and will be lowered by means of a winch. Thereafter the apparatus 15 according to the present invention will be set overboard and will clamp onto the pile 2. Alternatively it is also possible to clamp the pile 2 onto the apparatus 15 and then deploy the apparatus 15 and the pile 2 together.

The assembly of the apparatus 15 and the pile 2 will be lowered by means of a lifting wire while using a multiple heave compensation system. A primary heave compensation system will compensate for the movements of the vessel 10 with respect to the seabed due to influence of wind and waves. The system further comprises a secondary heave compensation system which is linked to the primary heave compensation system. An embodiment of the secondary heave compensation system will be described with reference to figure 4.

During the employment of the assembly of the pile 2 and the apparatus 15 a lifting wire winch be set in a heave compensation or a constant tension mode. Between the vessel 10 and the apparatus 15 will so be visible contact by means of an umbilical. This umbilical will provide electrical power from the vessel towards the apparatus and will provide fibre optic data communication between the vessel and the apparatus. The umbilical winch or winches will be working at a constant tension. It is advantageous to pro- vide the system with a second umbilical, for solely providing electrical power to the drive mechanism, such as an eccentrically rotatable platform, which is present in the apparatus 15. A winch for reeling out and reeling in the second umbilical will also be working at a constant tention. Constant tention of both winches will be determined by load cells positioned in the A-frame 11 and the apparatus lifting attachments which in turn are integrated in a control system operating the winches. At any depth the primary heave compensation, for compensating waves and winds, can be activated. In order to exactly determine the position of this apparatus 15 with respect to the vessel and the apparatus an acceleration meter will be present. Also the apparatus will provided with a depth sensor and both acceleration meter and the depth sensor will send information to a control unit present on the vessel 10, using optic fibre, and integrated software in order to achieve real-time response to the lifting rope winch. The secondary heave compensation, which is built into the lifting connection between the lifting wire and the apparatus 15, can be used for achieving very small vertical displacements. The secon- dary heave compensation will be activated when the pile 2 reaches the target position at the seabed.

When the pile 2 has reached the target position at the seabed the apparatus 15 is split up into a first unit provided with the drive means, such as an eccentrically rotatable weight, and a second unit provided with more delicate parts of the apparatus, such as a beacon and a plurality of thrusters. This situation is shown in figure 3.

In figure 3 the pile 2 is ready to be driven into the seabed by means of the apparatus 15 according to the present invention. According to figure 3 the pile 2 is used to provide an interface between the soil 3 and the superstructure 20 positioned on the seabed 3.

The apparatus 15 according to the present invention comprises a first unit 151 which serves as a hammer, for driving the pile 2 in the seabed 3 by means of vibration or impact. The second unit 152 has been disengaged from the first unit 151. Between both units 151, 152 a connector line 153 is present for providing an electrical and/or a hydraulical connection between the units 151, 152. At the end thereof the connector line 153 is connected the a rotary table 158, which is present at the underside of the second unit 152.

The second unit itself comprises thrusters 154 in order to control the position of the apparatus with respect to the underwater target position, in this case the superstructure 20. Moreover, the second unit 152 comprises a set of clamps 155 in order to couple the second unit 152 to the first unit 151. In order to be able to clamp on the first unit 151, the unit 151 could comprise a stub as is shown in figure 4 and 7.

When a relatively long pile has to be guided towards an underwater target position, it is also possible to deploy the assembly of the apparatus 15 and the pile 2, using the clamps 155 of the second unit 152 to clamp on the pile itself, for instance at the middle thereof.

In order to drive the drive means present in the first unit, a relatively high amount of energy is needed. Therefore on the second unit 152 multiple electric/hydraulic power conversion stations will be present. The stations can be seen in figure 4. It is possible to connect the second unit 152 to the vessel 10 by means of a first umbilical in order to provide energy to the second unit 152 and to provide a fibre-optic connection between the vessel 10 and the second unit 152 in order to transfer information. A secondary um- bilical could be used solely to provide the electric hydraulic conversion stations with the required amount of energy.

In figure 3 between the vessel 10 and the second unit 152 a single cable assembly 21 is drawn. The single cable assembly 21 comprises multiple lifting wires and umbilicals. The cables are connected by means of bundling elements, such as rings or clips during the deployment of the multiple cables. Because of the presence of these bundling elements there is no risk of the cables getting entangled. Moreover, when deploying the apparatus 15 and the pile 2 there will be more control of the cables. A preferred bundling apparatus is disclosed in the co-pending application PCT/NL00/00183, in the name of the same applicant.

When the first unit 151 is activated, a vibration will be generated. The alternating upward and downward movement generated by the first unit 151 will cause that the pile 2 reduces the soil strength or temporarily liquefies the soil such that the pile is penetrat- ing the soil by its own weight. By means of the cyclic wave generated by the first unit 151 it is possible to reduce the soil resistance, causing the pile or the anchor to penetrate into the sea bottom. In order to control the handling of the units 151 and 152 it is possible to add an RON (remote operable vehicle) to the apparatus 15 according to the present invention. The RON 156 is drawn schematically. For instance the RON is provided with a light source and a camera.

In figure 4 a possible embodiment of the apparatus 15 according to the present invention is shown. Figure 4 shows the first unit 151 to be used as a hammer for driving a pile 2. The unit 151 is fixed to the pile 2 by means of a clamping system 30. In order to provide the electric and/or hydraulic connection between the first unit and the second unit 152, a connector line 153 is present. This connector line 153 is for instance an umbilical. The first unit 151 is provided with an umbilical reel 31. Using this umbilical reel it is possible to reel in and reel out collector line 153. At the end of the connector line a plug 32 is present. This plug can be used for a quick coupling of the connector line 153 with the corresponding socket 40 present on the second unit 152. On top of the first unit 151 a stub 157 is shown. The set of clamps 155 present on the second unit 152 can be used in order to fix the second unit 152 on the stub 157.

The second unit 152 resembles an apparatus for deploying a load, which has been disclosed in the co-pending patent application PCT/NL00/00184 in the name of the same applicant. The second unit 152 comprises a main module 41 and a counter module 42. Moreover the second unit 152 comprises an arm 43. The arm 43 is provided with the recess 44. On the opposite sides of this recess 44 two clamps or jacks 155 are provided, at least one of which can be moved relative to the other. In between the end surfaces of the jacks 155 an object, such as a pile 2 (drawn in dashed lines) can be clamped. In order to improve the contact between the jacks 155 and the object (pile 2), the respective ends of the jacks 155 are accommodated with clamping shoes, lined with friction elements. The second unit 152 is coupled to a vessel by means of a lifting wire 50, which can be operated using hoist means, for instance a winch. Furthermore between the vessel and the second unit 152 an umbilical 51 will be present. The electricity wiring for providing power to the unit 152, as well as electric wiring or optical fibres, are accommodated in this umbilical 51. The hydraulic power will be used for controlling i.a. the thrusters 154 and auxiliary tooling amenities present in the unit 152.

Because of the fact that the thrusters 154 of the main module 41 and of the counter module 42, respectively, are positioned at opposite sides of the lifting wire 50, counter- torque can be exerted at the hoist wire 50 in two directions. In this way by means of the system an anti-twist device is formed. In order to improve proof the abilities of this anti-twist device, preferably, the distance between the main module 51 and the counter- module 52 can be altered. The module 152 is provided with electric/hydraulic power conversion stations in order to convert electrical power into hydraulic power. Because of the fact that the first unit 151 in use will require a lot of energy, a number of electric/hydraulic units 47 will be present in the system. The units 47 are positioned on a rotary table 158, which is fixed to the underside of the main module 41. The rotary table 158 could comprise a first and a second part, the parts being connected by means of bolts. The first part is rotatably fixed to the main module 41. Then, depending on specific energy requirements a second part provided with a certain amount of electric/hydraulic units 47 can be bolted to the first part.

In order to position a pile at exactly the right target position at the seabed, it is essential that the controlling equipment onboard of the vessel knows the exact location of the apparatus 15, as accurate as possible. Therefore the position of the apparatus 15 must be communicated to the vessel. In order to communicate relevant data both absolute and relative to other objects, to the control system and/or an operator onboard of the vessel, the second module 152 further comprises sensor means and control means that will be explained in detail below. The unit 152 is equipped with a sensor junction box. Moreover, the module 152 comprises light-sources, a gyrocompass including heave, roll and pitch sensors, a pan and tilt and colour camera, a USBL-transponder including a digiquartz depth sensor, a sound velocity meter, and a sonardyne mini rovnav. At the underside of the unit 152 are mounted on several platforms light-sources, a pan and S.I.T.-camera, an altimeter, a Doppler log unit and dual head scanning sonar. They are installed there to have only clear seawater below them in use. For a further explanation of the communication between the equipment in the apparatus 15 and the processing arrangement will be present on the vessel reference is made to the above-mentioned patent application PCT/NLOO/00184.

During the deployment of the apparatus 15 with respect to the vessel, movements of the vessel with respect to the seabed due to influence such as waves and wind will be compensated for by means of a heave compensation system. Such heave compensation systems are well-known in the prior art. Normally a heave compensation comprises a computer which receives data about roll and pitch of the vessel and which converts those data into control signals in order to control a winch. At an increasing depth the working of such a heave composition system can be too limited in order to provide the required accuracy at great depth.

In order to fine-tune the influence of the first compensation means, according to the present invention between a connection of the lifting wire 50 and the second module 152 a secondary heave composition system can be present. According to figure 4 the secondary heave compensation 60 comprises at least one double acting hydraulic cylinder. In use a pressure sensor 6 will be used to measure the depth in the fluid surrounding the apparatus 15. These pressure data in combination with an accelerometer will be transmitted to the processing arrangement and will be used for controlling the length of the cylinder(s) of the secondary heave compensation system 60. Alternatively a sonar unit can be used in order to determine the relative position of the second unit 152 with respect to at least one object external to the unit 152. This object external to the unit 152 for instance is the superstructure 20 positioned on the seabed.

In figure 5 a possible embodiment is shown of the A-frame 11 to be used for setting the apparatus 15 according to the present invention overboard. The A-frame 11 is connected to the deck 70 of the vessel by means of hydraulic cylinders 71. In figure 5 only unit two 152 of the apparatus 15 according to the present invention is shown. The unit 152 of the apparatus according to the present invention is connected to the vessel by means of at least a primary winch lifting wire to be reeled out and reeled in from a primary winch 73, and a primary umbilical to be reeled in and reeled out from a primary umbilical winch 72. Because of the fact that a relatively high amount of energy is needed, moreover a secondary umbilical can be connected to the apparatus to be reeled out and reeled in on a secondary umbilical winch 74. When deploying the apparatus the multiple cables will be bundled to a single cable assembly by means of a bundling apparatus 80 to be connected to the A-frame 11.

The apparatus according to the present invention which has been described above can be used for piles or sheets, or other objects to be used as a connection between a seabed superstructure and the sea bottom. When the apparatus according to the present invention would be clamped on the outside of such an object the object could not be driven into the sea bottom completely. On the upper side of the objects to be driven into the seabed always a ridge must be left free in order to clamp the apparatus on the outside thereof. In order to be able to drive an object completely into the seabed, it is ad- vantageous to use a clamp which is able to grab the object to be driven into the seabed from inside. In figure 6 a tool is shown which could be used as an interface between the apparatus according to the invention and the object to be driven into the seabed. The tool according to figure 6 has an upper part 80 which can be clamped by means of the clamps of the second unit of the apparatus according to the present invention. Moreover the tool according to figure 6 has a bottom part 81 provided with clamps 82 which can move with respect to the center of the tool. The upper part 80 and the bottom part 81 can be separated. The upper part 80 could be fixed on top of the first unit, or hammer, 151 as shown in figure 4, the bottom part 81 being fixed to the underside of the first unit 151, in order to grap and hold an object, such as a pile 2.

In figure 7 a possible embodiment of the first unit 151 is shown. The first unit 151 according to figure 7 is designed as a vibratory hammer. The hammer comprises an outerframe 160, at the top thereof provided with a stub 157. The stub 157 can be used in order to provide coupling means to couple the hammer to a second unit 152, as described above.

The outerframe 160, by means of shock absorbing elements 161, is connected to the mounting plates 172 of the gearbox 162. The gearbox 162 forms a housing to accomodate multiple eccentrically rotating weights 163-170. The weights 163-169 are all connected the the adjacent weights 164-170. Contrary to the prior art hammers, the gearbox is filled with a liquid in stead of air.

In order to keep the oilpressure in the gearbox 162 at ambient pressure, at least one free moving cylinder 171 is present. The cilinder 171 will experience the pressure of the ambient fluid (seawater) at one side and the pressure of the oil inside the gearbox at the other side. A slight imbalance of pressure on one side of the cilinder will make it move to a position to balanced position, as the cilinder is not restrained by any means other than the friction of its own seals.

When the hammer is activated, the weights 163-170 will be rotating. The rotation of those weights 163-170 will introduce pressure fluctuations inside the housing. When the cylinder 171 is not locked in any way, the cylinder 171 during the use of the hammer would be moving up and down at a high speed. Therefore it is advantageous just before activating the hammer, to lock the cylinder 171 in its position, in order to have a constant liquid pressure inside the housing. Therefore a lock 200 is present in order to restrict the flow of liquid from the housing towards the cylinder 171 and backwards. Alternatively (not shown) also the cylinder itself could be provided with a lock, in order to lock the cylinder 171 in its respective position.

In order not to induce too much friction between the rotating weights 163-170 and the surrounding liquid, such as oil in the gearbox 162 it is advantageous that the weights 163-170 are shaped cylindrical.

In figure 8 a possible embodiment of a excentrically rotatable weight 133-170 is shown. The rotatable weight 163 is shaped cylindrically. The weight 163 is provided with teeth 100 in order to operate with teeth of the adjacent weight. The weight 163 can be made of any suitable material, such as stainless steel or ordinary steel. The body of the weight 163 is provided with several chambers or cavities 101. The cavities 101 by means of small apertures 103 are in communication with the surrounded liquid in the housing 162 (see figure 7). Because of the presence of the apertures 103 liquid can enter the cavities 101. The specific weight of liquid will be much lower than the specific weight of the keel body of the weight. Therefore, when rotating the weight 163, a vibration motion will be caused due to the unbalance of the weight 163. In order to enhance the vibrating motion of the weight 163 when rotating the weight 163, it is also possible to provide the body of the weight 163 with further chambers or cavities 102. These cavities 102 can be filled with a material having a higher specific weight than steel. The cavities for instance could be filled with lead. Also, the cavities 102 by means of apertures 104 are in communication with the surrounding liquid. Because of the apertures 104 possible differences in pressure in the cavities 102 and the surrounding liquid can be compensated.

In figure 9 a further detail is shown of the second unit of the apparatus according to the invention. Figure 9 shows the rotary platform 158 which is rotatably connected to the frame 110 of the mean module, which is described with reference to figure 4. The frame 110 is provided with members 111, which are positioned in the frame 110. The rotary table 158 can rotate with respect to the members 111. The outside of the rotary table for instance is covered with a coating such as Teflon in order to lower the friction between the rotary table and the members 111. The rotary table itself could be used to carry tools, such as the electric/hydraulic conversion rotations which were described with reference to figure 4. Different types of platforms 158a can be bolted to the rotary platform 158. The rotation of the platform 158 with respect to the frame 110 will be achieved by hydraulic means, such as a hydraulic motor or cylinder.

Inside the axis of rotation of the rotary table a cylindric housing is present, suited to accomodate a docking stub 112, on which a load can be hung. The docking stub 112 for instance could be connected to the bottom part 81 which has been described with reference to figure 6. The docking strip 112 is provided with guiding members 113 and the cylindrical housing with a guiding member 114 so as to secure the positioning of the docking strip 112 within the cylindric housing inside the rotary platform 158. The docking stub is provided with several latches 115, which will be described with reference to figure 10. The members 111, which form a spider frame, are connected by means of a cover 118. At the underside of this cover 118 a protruding multi-angular shape is fixed. The cap of the strip is provided with a void having a corresponding multi-angular shape. The protruding element at the underside of the cover 118 and the void inside the strip 112 will avoid rotation of the strip with respect to the frame 110. Therefore it is possible to exert a torque at the load connected to the strip 112.

The docking stub 112 can be removed from the cylindric housing inside the rotary table 158 by moving the latches 115. Removing of the latches 115 is controlled by means of a cylinder 116. The function thereof will be clarified hereinbelow.

In figure 10 a detail of the connection between the cover 118 and the docking stub 112 is shown. The cover 118 is provided with the cylinder 116. Inside the cylinder 116 a plunger 117 is present, by means thereof a bolt 120 can be moved up and down with respect to the cover 118. The bolt 120 moves inside the protruding elements 119 at the underside of the cover 118. For moving the bolt 120 upwardly the latches 115 will be moving inside the docking stub 112, because of the presence of spring elements 121. When the bolt 120 is moved downwardly, the latches 115 will be moved outwardly in order to fix the docking stub inside the cylindric housing of the rotary table 158.

Claims

1. Apparatus for driving an object by vibration or impact, in particular a pile or sheet to be driven into the ground or to be removed therefrom, at an underwater target position, comprising drive means, such as an eccentrically rotatable weight, and means for activating said drive means, characterized in that, the apparatus comprises a beacon to transmit acoustic rays and plurality of thrusters to control the position of said apparatus with respect to the underwater target position.

2. Apparatus according to claim 1, wherein the apparatus comprises a first unit provided with the drive means, such as an eccentrically rotatable weight, and, a second unit provided with the beacon and the plurality of thrusters, the first and second unit being provided with coupling means for coupling the first and the second unit.

3. Apparatus according to claim 2, wherein the apparatus is provided with connector means to provide an electrical and/or hydraulical connection between the first and second unit.

4. Apparatus according to claim 3, wherein the connector means comprises a plug- and socket-assembly, the first unit comprising a first part of said plug- and socket-assembly, and the second unit comprising a corresponding second part of said plug- and socket-assembly.

5. Apparatus according to claim 3 or 4, wherein the connector means comprise a con- nector line and a reel for selectively reeling in and out the connector line in order to be able to respectively decrease or increase the distance between the first and second unit.

6. Apparatus according to one of the preceding claims, wherein the apparatus comprises a multiple amount of electric hydraulic power conversion stations.

7. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real time.

8. Apparatus according to one of the preceding claims, wherein said thrusters comprise a first set of thrusters arranged to provide a torque control function and a second set of thrusters arranged to provide at least a translation function, each thruster of said second set of thrusters being provided with a rotary actuator.

9. Apparatus according to one of the preceding claims, wherein said apparatus provided with a gyrocompass with motion sensors to sense heading, acceleration, roll and pitch of the apparatus in use.

10. Apparatus according to claim 9, wherein the apparatus is provided with a Doppler- log unit to measure current strength of said fluid.

11. Apparatus according to one of the preceding claims, comprising load cells to meas- ure weight of a load engaged by the apparatus.

12. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a temperature sensor to measure temperature in said fluid and to transmit temperature data in real time.

13. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a salinity meter to measure salinity of said fluid and to transmit salinity data in real time.

14. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a lifting assembly to deploy and recover the apparatus with respect to a vessel, wherein the lifting assembly is provided with a hydraulic cylinder, the cylinder being connected to means for controlling the length of the cylinder for controlling the vertical position of the apparatus with respect to the target position.

15. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a pressure sensor to measure the depth in a fluid surrounding said apparatus and to transmit pressure data in real time.

16. Apparatus according to one of the preceding claims, wherein the apparatus is provided with a sonar unit to determine the position of said apparatus with respect to at least one object external to said apparatus.

17. Vibratory hammer comprising one or more eccentrically rotatable weights, wherein said weights are accommodated in a housing, the, housing being filled with a liquid, such as oil, in order to make the weights run in the liquid.

18. Vibratory hammer according to claim 17, wherein means are provided for selectively introducing liquid in the housing, or removing liquid from the housing, in order to adjust the liquid pressure inside the housing.

19. Vibratory hammer according to claim 17, wherein the housing comprises a member, such as a cilinder, able to move under influence of pressure excelled on the interior and the exterior of said member, in order to keep the liquid inside the housing at ambient pressure.

20. Vibratory hammer according to claim 19, wherein the hammer comprises means, such as a valve, to respectively permit or prevent the movement of said member.

21. Vibratory hammer according to claim 17-20, wherein said weights are shaped cilindrically, the body of the weights being provided with one or more cavities.

22. Vibratory hammer according to claim 17-21, wherein the cavities are in communication with the liquid inside the housing.

23. A processing arrangement arranged to drive an apparatus for driving an object by vibration or impact, at an underwater target position, according to claims 1-16, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters to control positioning of said apparatus with respect to said underwater target position, and a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real-time, the processing arrangement being provided with an acoustic receiver to receive said acoustic rays, the processing arrangement is arranged to use data derived from said acoustic rays in a calculation to determine the position of the apparatus characterized in that the processing arrangement is arranged to receive on-line sound velocity meter data from said sound velocity meter to determine a sound velocity profile in said fluid and to calculate from said sound velocity profile bending of said acoustic rays transmitted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus in real-time.

24. A processing arrangement according to claim 23, wherein said thrusters of the apparatus comprise a first set of thrusters arranged to provide a torque control function and a second set of thrusters arranged to provide at least a translation function, each thruster of said second set of thrusters being provided with a rotary actuator, and said processing arrangement is arranged to perform the following functions in use: • to control application of driving power to said thrusters of said first set of thrusters to keep said apparatus in a desired orientation in a first plane defined by driving forces generated by said thrusters of said first set; • to control application of driving power to said thrusters of said second set of thrusters and to said rotary actuators to move said apparatus in a mean direction and a direction perpendicular to said mean direction to a desired location, said mean direction and said direction parallel to said mean direction being in a second plane defined by driving forces generated by said thrusters of said second set.

25. A processing arrangement according to claim 23, in said apparatus said first and second plane not being coincident, the processing arrangement being arranged to receive first sense signals from a gyrocompass with motion sensors on the apparatus regarding heading, acceleration, roll and pitch of the apparatus in use.

26. A processing arrangement according to claim 25, wherein the first sense signals from the gyrocompass with motion sensors are used in the calculation to determine the attitude/heading of the apparatus.

27. A processing arrangement according to any of the claims 23-26, the apparatus including a temperature sensor, wherein the processing arrangement is arranged to receive temperature data from said temperature sensor, to update a temperature profile in said fluid and to assist a correction of determining the position of said apparatus in real-time.

28. A processing arrangement according to any of the claims 23-27, the apparatus including a salinity meter, wherein the processing arrangement is arranged to receive salinity data from said salinity meter, to update a salinity profile in said fluid and to correct determining the position of said apparatus in real-time.

29. A processing arrangement according to any of the claims 23-28, wherein the signals of the pressure sensor are used in order to control the length of the cylinder.

30. A processing arrangement according to any of the claims 23-29, wherein the signals of the sonar unit are used in order to control the length of the cylinder.

31. Vessel provided with a processing arrangement according to any of the claims 23- 30.

32. Vessel according to claim 31, wherein the vessel is provided with an acoustic array attached to a hull of the vessel and an ultra-short base line service unit on board of the vessel arranged to communicate with said acoustic array, the acoustic array being arranged to receive acoustic signals from at least said apparatus and to provide acoustic array output data to said processing arrangement, which is arranged to perform in real time, the calculation of the position of at least said apparatus relative to said acoustic array based on said acoustic array output data.

33. A vessel according to claim 32, wherein the acoustic array comprises a sound velocity meter to measure velocity of sound in fluid just below the vessel and to pro- vide sound velocity meter output data to said processing arrangement, said processing arrangement being arranged to correct said calculation of said position of said apparatus based on said sound velocity meter output data in real time.

34. A vessel according to claim 32 or 33, wherein the acoustic array comprises an acoustic array gyrocompass to measure heading, heave, roll and pitch of the acoustic array and to provide acoustic array gyrocompass output data to said processing arrangement, the processing arrangement being arranged to correct said calculation of said position of said apparatus based on said acoustic array guide gyrocompass output data in real time.

35. A vessel according to any of the claims 31-34, wherein the vessel comprises a vessel gyrocompass to measure, heading, heave, roll and pitch of the vessel and to provide vessel gyrocompass output data to said processing arrangement, the processing arrangement being arranged to correct said calculation of said position of said apparatus based on said vessel gyrocompass output data in real time.

36. System comprising a vessel according to any of the claims 31-35 and an apparatus according to any of the claims 1-16 the apparatus and the processing arrangement being arranged to communicate with one another.

37. System according to claim 36, wherein the apparatus and processing arrangement are coupled via fiber optic (DE) muliplexers interconnected by an optical fiber.

38. System according to claim 36 or 37, wherein the apparatus and the processing arrangement are connected by means of multiple cables, wherein the system is provided with a bundling apparatus for bundling the cables, when reeled out, in order to provide a single cable assembly between the bundling apparatus and the apparatus for driving an object, during deployment thereof.

39. Method for controlling an apparatus for driving an object by vibration or impact, in particular a pile or sheet, to be driven into the ground or to be removed therefrom at an underwater target position, the apparatus comprising a beacon to transmit acoustic rays and a plurality of thrusters to control the position of said apparatus with respect to said underwater target position, wherein the apparatus comprises a first unit provided with the drive means, such as an eccentrically rotatable weight, and a second unit provided with the beacon and the plurality of thrusters, the first and second unit being provided with coupling means, the method comprising the steps of:

- securing the apparatus to the object to be driven into the ground,

- deploying the apparatus and the object to be driven into the ground from a vessel by means of a lifting assembly towards the underwater target position,

- de-coupling the second unit from the first unit after reaching the target position and

- moving the second unit away from the first unit, and

- driving the object into the ground by activating the drive means.

40. Method according to claim 39, wherein the second unit is de-coupled from the first unit, while maintaining an electrical and/or hydraulical connection between both units.

41. Method according to claim 39 or 40, wherein:

- after driving the object into the ground, the second unit is coupled to the first unit, and

- the first and second unit are hauled in towards the vessel.

42. Method according to claim 39-41, wherein the apparatus is provided with a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus and to transmit velocity data in real time, the method comprising the steps of:

- receiving said acoustic rays,

- using data derived from said acoustic rays in a calculation to determine the position of the apparatus,

- receiving sound velocity meter data from said sound velocity meter and determin- ing a sound velocity profile in said fluid, and

- calculating from said sound velocity profile bending of said acoustic rays transmitted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus.

43. A computer program product comprising data and instructions that after being loaded by a processing arrangement provides said arrangement with the capacity to carry out a method according to claim 42.

4. A data carrier provided with a computer program product according to claim 43.