The invention relates to a system for holding a pile to be installed in the seabed, e.g. a pile adapted to support an offshore wind turbine, e.g. a monopile, and a method therefor. The invention further relates to a vessel comprising such a system, and a pile installation method in which use is made of such a vessel and/or a pile holding system.

Installation of an offshore wind turbine comprises the step of installing the foundation, often in the form of a pile, of the offshore wind turbine. A pile is installed by driving the pile into the seabed after which the upper part of the wind turbine is arranged on top of the pile. In known methods, the pile is initially supported on a jack-up vessel in a horizontal orientation. In a typical operational sequence to install the pile, the pile is firstly upended, i.e. is pivoted in an upright position. Subsequently, the pile is lowered to the seabed at the pile installation location. Finally the pile, more in particular a lower part of the pile, is driven into the seabed.

During the processes of upending, lowering, and pile driving, commonly a gripping tool suspended from a lifting device, for instance a crane, and a pile upending and holding system is used. The pile upending and holding system comprises an upending tool and a holding tool, mounted to or integral with the vessel, for instance mounted to an edge of the vessel. The vessel is typically a jack-up vessel, of which the legs limit motions of the vessel induced by waves and currents.

During upending, a first longitudinal end of the pile is gripped by the gripping tool of the lifting device and lifted by the lifting device while a second longitudinal end of the pile is vertically supported by the upending tool of the system. As a consequence, the first longitudinal end moves upwards relative to the second longitudinal end, so that the pile pivots upwards. The pivoting continues until the pile is in a substantially vertical orientation. To enable the pivoting of the pile, the upending tool, or at least a part thereof that is supporting the second longitudinal end of the pile, is pivotal around a substantially horizontal axis relative to the vessel.

During lowering of the pile towards the seabed, the lifting device is operated to lower the pile while still the gripping tool still retains the pile at the first longitudinal end. The holding tool of the system engages the pile during this process, to horizontally keep the pile in place while at the same time enabling vertical movement thereof relative to the tool to enable the lowering. In a possible method, as soon as the seabed provides sufficient vertical support for the pile, it is decoupled from the gripping tool and a driving hammering tool is installed onto the pile. In another method the pile is not decoupled. In this method, during driving of the pile into the seabed, the pile is vertically supported by the seabed and horizontally held in place by the holding tool.

The pile is driven into the seabed until the desired depth is reached and the pile has been fixed in the seabed. Finally the pile is decoupled from the pile holder.

Publication EP3517479 discloses a pile upending and holding system, comprising an upending tool and holding tool. Both tools are mounted to a side of the vessel. A crane is used to lift the pile into the upending tool and for subsequently lifting the first longitudinal end to upend the pile while supported by the upending tool. Thereafter the pile is engaged by the holding tool, after which the crane is operated for lowering the pile towards the seabed and for the subsequent pile driving, while the pile is held by the holding tool to maintain the vertical position of the pile.

There is a trend towards larger wind turbines, and a desire to install offshore wind turbines at locations with larger water depths than currently encountered. Both result in larger and heavier foundations - including piles, e.g. monopiles. Hence, it is expected that in the near future piles need to be installed that are longer than 100 metres, possibly 120 metres or longer. The weight of such piles may be more than 1000mt, possibly 1300mt or above. The increase in size and weight makes that transporting and manipulating these piles, in particular upending these piles, is increasingly difficult.

After upending and during installation, the pile should be held vertical. That is, its verticality should be maintained within tight limits. Any vertical inclination of the pile outside of these limits, that is, any non-verticality, should be corrected in order to keep the pile under control and, in embodiments, prevent the pile to topple over or slip away. The verticality should be maintained during lowering, during pile driving, but also preferably directly after upending and prior to lowering. A momentum of the pile at the end of the upending stage towards the vertical position, in particular in combination with unfavourable external forces, may cause the pile to overshoot beyond vertical and tip overboard. The pile, in practical situations, should finally be installed with a verticality in the order of 0.25° from vertical.

Prior to lowering of the upended pile, the pile may be subject to external forces such as the wind and/or currents. It moves along with the vessel, which vessel is in turn subject to external forces induced by the motions of the sea, e.g. waves and currents. The movability of the pile relative to the vessel due to the lifting device generally only vertically supporting the pile, the vessel being asymmetrically loaded by the weight of the pile, and the center of gravity of the pile being raised to quite a distance above the pile holder, may cause the pile to move relative to the vessel in reaction to these external forces. In particular, the pile may vertically incline, e.g. forwards or backwards around the tilt axis while being held vertically inside the pile holder. Such tilting is highly unfavourable in particular during this stage of the process, as then the center of gravity of the pile is at its highest above the pile holder. Tilting of an upended pile while being held prior to lowering, entails the risk for the pile to become unstable and tip overboard. The lifting device, generally a crane, is generally unable to pull the first longitudinal end of the pile to counteract tilting of the pile.

When lowering the pile, as soon as the pile is introduced into the sea, waves and/or currents start to exert forces on the pile which could cause it to become slanted relative to the vertical, or to start swinging like a pendulum, tilting it about one or more horizontal axes relative to the vessel. The severity of this swinging depends on sea conditions at that time and natural period of the pile. Furthermore, in the last phase of the lowering, a shift in the landing position of the pile on the seabed may tilt the pile.

In many prior art systems, including EP 3 517479, the pile is held at a single circumference prior and during lowering, e.g. by a single ring, after being transferred from an upending tool to the holding tool. To compensate for motions in the horizontal plane, EP 3 517479 proposes an actuator system configured to translate the pile relative to the vessel in the horizontal plane while being held by the holding tool. A tilting of the pile is counteracted by a movement of the single ring of the pile holder relative to the vessel, for example by an X-Y motion compensation mechanism.

Non-prepublished NL2023880 by the present applicant proposes an integrated upending and holding tool that comprises two axially spaced rings held by a frame. This may, in embodiments, allow for a moment to be exerted by the tool on the pile, applying radially onto the exterior of the pile at two longitudinally spaced circumferences engaged by pile engaging devices of the respective rings, e.g. to counteract a tilting or other undue motion of the pile, e.g. as long as the pile is suspended from the crane and has not contacted or penetrated into the seabed.

Prior art solutions for monitoring the verticality of the pile being handled include the use of a levelling device against the pile - however, such determination is sensitive to local disturbances in the pile exterior, e.g. dumps or skewed welds. WO2014133381 proposes to employ cameras directed, e.g. from a distance between 5 and 30 meters, at the pile itself and intelligent visual object recognition software, based on which any inclination of the pile may be corrected. For example, the system visually detects the left and right vertical edges of the monopile. Another known solution disclosed in EP3382335 is to carry out measurements using a 3D distance measurement device arranged on the vessel and directed at the pile to obtain a real-time three-dimensional image of the pile. This digital 3D object data is fitted on 3D information of the pile, so as to determine the position and/or attitude of the pile. The figures of EP3382335 illustrate that a monopile is installed using a single ring type pile holder. The 3D measurement device(s) are directed at the portion of the monopile that extends above the pile holder.

It is an object of the invention to provide an alternative system and method for holding a pile while measuring its verticality, e.g. to enable a more efficient monitoring thereof and a more effective control of the verticality based on this monitoring, e.g. a system and method for holding and upending a pile.

It is a further object of the invention to provide a system and method for holding a pile that allows for a more controlled and/or efficient handling of the pile during the installation process, e.g. a system and method for holding and upending a pile that allows therefor.

It is a further object of the invention to provide a system and method for holding a pile that allows for a stiffer response to a non-verticality of the pile during the installation process, e.g. a system and method for holding and upending a pile that allows therefor.

It is a further object of the invention to provide a system and method for holding a pile that reduces the risk of an instable pile to damage the vessel during the installation process, e.g. a system and method for holding and upending a pile that allows therefor.

Throughout this disclosure, the longitudinal direction of the pile holder is in the direction of the center axis and thus of the held pile. Radial directions extend in a radial plane, perpendicular to the center axis. X-Y locations extend within a horizontal X/Y plane, which coincides with a radial plane of the pile holder when the center axis is vertical. Therein a forward direction along the X-axis extends perpendicular to the tilt axis, from the hull of the vessel to which the system is to be mounted, through the support frame and the center axis of the pile holder towards the sea, and a backward direction extends perpendicular to the tilt axis from the sea through the center axis of the pile holder and the support frame towards the hull of the vessel. Lateral directions extend parallel to the tilt axis.

In a first aspect thereof, the invention provides a system for holding a pile to be installed in the seabed, for example a pile adapted to support an offshore wind turbine, such as a monopile. The system is configured to be mounted on a vessel, and comprises a support assembly, configured to be mounted on the vessel, for example on a deck of the vessel, and a pile holder mounted on the support assembly. The pile holder has a center axis, and is configured to in a vertical orientation of the pile holder, in which the center axis is substantially vertical, hold the pile with a longitudinal axis thereof along the center axis, and guide the pile while it moves along the center axis.

The pile holder comprises a lower ring, an upper ring, and a pile holder frame supporting the lower ring and upper ring mutually spaced along the center axis. Each of the lower ring and the upper ring comprises a ring structure, and multiple pile engaging devices. The pile engaging devices are connected to the ring structure of the respective ring such as to be distributed about the circumference thereof. Each pile engaging device is adapted to engage an exterior of the pile extending through the lower and upper ring for holding and guiding the pile.

The lower ring comprises one or more lower sensors, and the upper ring comprises one or more upper sensors. The lower and upper sensors are arranged such that a comparison between the indications indicates a vertical inclination of the longitudinal axis of the pile held along the center axis of the pile holder.

The first aspect of the invention is based on the insight that the provision that the pile is engaged by the pile engaging devices of the pile holder at two different, longitudinally spaced regions along the pile, enables sensor measurements in both the lower and upper ring, which measurements, for example, indicate positions of the respective regions relative to one another, such as to be indicative for the verticality of the whole pile. The provision of two rings in the pile holder , that are supported by a pile holder frame spaced along the center axis, instead of a pile holder with just one ring, makes a comparison between sensor measurements made by sensors arranged on the two rings possible, and thus, for example, a comparison between the positions of the two pile regions engaged thereby. This comparison is indicative for the verticality of the longitudinal axis of the pile held by the pile holder along the center axis. Such measurements at longitudinally spaced locations of the pile holder, and thus a comparison thereof indicative for verticality, is not possible in a pile holder according to the prior art having a single ring.

The first aspect of the invention may provide more direct and/or accurate feedback on the position and orientation of the pile than the prior art. For example, in EP3382335 and WO2014/133381 the cameras mounted onboard the vessel require an unobstructed view on a major section of the pile above the pile holder in order to be practical. This makes arrangement of such cameras difficult. Also when the pile is sunk, e.g. hammered, deeper into the seabed the cameras of these systems have less and less pile in their field of view. Thereby the present invention may allow for a more accurately and/or efficiently response to any vertical inclination of the pile, and therefore, for a more controlled handling of the pile.

In an embodiment, the lower ring comprises one or more lower position sensors and the upper ring comprises one or more upper positioning sensors. The lower and upper position sensors are each configured for providing an indication of the horizontal position of, respectively, a lower region and of an upper region of the pile, respectively extending inside the lower and upper ring. The position sensors are arranged such that a comparison between the indications indicates a vertical inclination of the center axis of the pile holder, and therewith of the longitudinal axis of the pile.

For example, upon tilting forwardly, e.g. away from the vessel, the upper region of the pile will displace forwardly relative to the lower region of the pile. A backwards tilting of the pile will result in a backwards displacement of the upper pile region relative to the lower pile region. Detecting such relative displacement thus indicates a tilting of the pile - and the direction thereof indicates whether the pile tilts forwards or backwards. Furthermore, measuring the extent of the relative displacement provides an indication of the vertical inclination angle.

The pile being held by the rings, makes that the displacement of the upper and lower regions thereof is transferred to the rings. Measuring displacements of the rings therefore provides an indication of the occurrence, the direction and the extent of the tilting. For example, the relative displacement of the upper and lower region of the pile may be determined by measuring positions of the pile engaging devices of the upper and lower ring, and/or of the ring structure of the upper and lower ring.

The position sensors may be for instance be configured to measure a relative or absolute position, displacement, distance, velocity and/or acceleration of the ring structure and/or or pile engaging devices. Such sensors are as such known in the art. In an example, each respective ring comprises GPS-sensors measuring absolute position, e.g. being provided on the pile engaging devices, or on the ring structure. In an example, each respective ring comprises distance sensors measuring the distance of the ring structure and/or pile engaging devices of the ring relative to the support structure, the other one of the rings, e.g. the pile engaging devices thereof, or the vessel, e.g. the hull of the vessel. In an example each respective ring comprises displacement sensors measuring displacements of the ring structure and/or pile engaging devices of the ring relative to the support structure, the other one of the rings, e.g. the pile engaging devices thereof, or the vessel. In an example each respective ring comprises distance and/or displacement sensors measuring the distances and/or displacements of the pile engaging devices relative to the ring structure.

In an embodiment, e.g. combined with the embodiment with the position sensors, the lower and upper sensors are lower and upper force sensors. Each of these force sensors are configured for providing an indication of a force exerted by, respectively, the lower region and the upper region of the pile on respectively the lower and upper ring.

Tilting of the pile may result in a difference in the forces exerted by the pile onto the pile engaging devices of the lower and upper ring. For example, upon tilting forwardly, the pile will exert a force in the tilting direction on a front region of the upper ring, and simultaneously on a back region of the lower ring. In particular, tilting forwardly may result in the pile exerting a tilting force on backwardly arranged pile engaging devices of the upper ring, and on forwardly arranged pile engaging devices of the lower ring. The reverse is true for a backwards tilting of the pile. Measuring the exerted forces in the rings, for example at the pile engaging devices, for example at the interface thereof with the pile exterior, thus provides an indication of the tilting - and the vertically.

In a second aspect thereof, the invention also relates to a system as described in relation to the first aspect of the invention, with the rings comprising the force sensors, wherein instead of both rings comprising the respective force sensors, only one of the rings comprises the force sensors. Therein, for example, when only the upper ring comprises force sensors, an exertion of a force by the pile in the tilting direction on a front region of the upper ring is indicative of a forward tilting, and an exertion of a force on a back region of the upper ring is indicative of a backwards tilting. The reverse is true for a backwards tilting. When only the lower ring comprises force sensors, the pile exerting a tilting force on a front or back region of the ring is indicative of a backwards or forwards tilting, respectively.

In a third aspect thereof, the invention also relates to a system as described in relation to the first aspect of the invention, wherein instead of the lower and upper ring comprising the lower and upper sensors, respectively, the lower ring comprises one or more lower markers and the upper ring comprises one or more upper markers, e.g. at an exterior surface of the respective ring. The markers are arranged and configured such that their positions are observable externally from and remote from the pile holder, and such that in an external and remote view on the pile holder, their observed positions are indicative of a vertical inclination of the center axis of the pile holder, and therewith of the longitudinal axis of the pile.

The invention according to the third aspect is based on the insight that providing that the pile is engaged by the pile holder at two different, longitudinally spaced regions along the pile while holding the pile by the longitudinally spaced lower and upper ring, enables markers on the lower and upper ring of which the positions are externally and remotely observable, e.g. visible, to be indicative of the positions of the respective regions relative to one another such as to be indicative for the verticality of the whole pile. The provision of two rings instead of one, makes a comparison of positions of visible markers on the two rings possible, and thus, a comparison between the positions of the two pile regions engaged thereby. This comparison is indicative for the verticality of the longitudinal axis of the pile held by the pile holder along the center axis. The provision of such observable markers at longitudinally spaced locations of the pile holder, and thus a comparison of the positions thereof indicative for verticality, is not possible in a pile holder according to the prior art comprising a single ring.

The inclination being indicated based on the engagement by the two rings, makes that the invention may provide more direct and/or accurate feedback on the position and orientation of the pile than the prior art, in which the indication is obtained e.g. by visual inspection of the pile. Thereby the present invention may allow for a more accurately and/or efficiently response to any vertical inclination of the pile, and therefore, for a more controlled handling of the pile.

In an embodiment, the markers are configured such that their positions are visible externally from and remote from the pile holder, e.g. are embodied as beacons, light reflectors, and/or lights, e.g. projected laser beams, so that their positions are visible externally from and remote from the pile holder. For example, the positions are observable directly by vision of an operator, and/or by means of one or more cameras, for example connected to monitors observed by an operator, for example on the vessel. In an embodiment the positions are not visible, but observable otherwise - for example the markers being embodied as heat radiators, the positions thereof being observable by e.g. infrared cameras. In a fourth aspect thereof, the invention also relates to a system as described in relation to the first or third aspect of the invention, wherein instead of the lower and upper ring comprising the respective lower and upper sensors, and/or lower and upper markers, the pile holder frame comprises the lower and upper sensors, and/or lower and upper markers, at longitudinally spaced locations along the center axis of the pile holder, for example the sensors and/or markers being arranged longitudinally at the same location as the respective rings or close to the respective rings.

By enabling more direct and/or accurate feedback on the verticality of the pile, the invention according to the first, second and third aspect of the invention may enable the same system to be operated in a more stiff manner in response to any tilting of the pile - that is, to counteract a non-verticality more directly such as to reduce the extent thereof. Thus it may advantageously make the same system behave stiffer.

In a fourth aspect thereof, the invention relates to a system as described in relation to the first or third aspect of the invention, wherein instead of the lower and upper ring comprising the respective lower and upper sensors, and/or lower and upper markers, the pile holder frame comprises the lower and upper sensors, and/or lower and upper markers, at longitudinally spaced locations along the center axis of the pile holder, for example the sensors and/or markers being arranged longitudinally at the same location as the respective rings or close to the respective rings.

By enabling more direct and/or accurate feedback on the verticality of the pile, the invention according to the first, second and third aspect of the invention may enable the same system to be operated in a more stiff manner in response to any tilting of the pile - that is, to counteract a non-verticality more directly such as to reduce the extent thereof. Thus it may advantageously make the same system behave stiffer.

The invention furthermore relates to a system for holding a pile, which system is configured to be mounted on a vessel and comprises a support assembly configured to be mounted on the vessel, and a pile holder. The pile holder has a center axis, is mounted on the support assembly. It is furthermore configured to in a vertical orientation of the pile holder, in which the center axis is substantially vertical, hold the pile with a longitudinal axis thereof along the center axis, and guide the pile while it moves along the center axis. The pile holder comprises one or more rings, for example a lower ring and an upper ring, and a pile holder frame supporting the one or more rings. In case of multiple rings, e.g. the lower and upper ring, the pile holder frame supports these mutually spaced along the center axis. Each of the one or more rings comprises a ring structure and multiple pile engaging devices connected to the ring structure such as to be distributed about the circumference of the respective ring, each pile engaging device being adapted to engage an exterior of a respective region of the pile extending inside the respective ring for holding and guiding the pile. The pile holder comprises one or more sensors or markers which are spaced from each other along the center axis and arranged such that a comparison between indications by the sensors or between observed positions of the markers indicates a vertical inclination of the longitudinal axis of the pile held along the center axis of the pile holder.

In a fifth aspect thereof, the invention provides a system for holding a pile, which system is configured to be mounted on a vessel and comprises a support assembly configured to be mounted on the vessel, and a pile holder.

The pile holder has a center axis, is mounted on the support assembly. It is furthermore configured to in a vertical orientation of the pile holder, in which the center axis is substantially vertical, hold the pile with a longitudinal axis thereof along the center axis, and guide the pile while it moves along the center axis. The pile holder comprises one or more rings, for example a lower ring and an upper ring, and a pile holder frame supporting the lower ring and upper ring mutually spaced along the center axis. wherein each of the one or more rings comprises a ring structure and multiple pile engaging devices connected to the ring structure such as to be distributed about the circumference of the respective ring, each pile engaging device being adapted to engage an exterior of a respective region of the pile extending inside the respective ring for holding and guiding the pile.

The support assembly comprises one or more actuators configured to move the pile holder at least horizontally away from the vessel, e.g. forwardly, and towards the vessel, e.g. backwardly, e.g. configured to horizontally translate the pile holder away from and towards the vessel.

The one or more rings are movable into an opened position, in which the rings between free ends thereof define an opening of the pile holder for passage of the pile out of the pile holder in a direction perpendicular to the center axis and away from the vessel, for example a forward direction. In an example, each ring comprises a ring base fixed to the pile holder frame and one or more movable jaws, e.g. two semi-circular jaws, each jaw being movable relative to the ring base of the respective ring such as to move the pile holder into the opened position thereof.

This system enables an operation of the system such that the pile may be moved away from the vessel and released into the sea, when an anomalous situation is detected - for example the pile being unstable beyond possible correction, for example slipping away with a lower end region thereof, toppling over or otherwise having become unusable.

The fifth aspect of the invention in particular relates to the situation that a pile held in vertical orientation in a pile holder exhibits undesirable motion, e.g. due to the lower pile end sliding away sideways. In the extreme, due to the vast dimensions and mass of a pile, e.g. in case the pile is a monopile for a wind turbine, this situation may lead to forces that cannot be absorbed by the pile holder and/or the vessel.

The invention according to the fifth aspect reduces the risk of an instable pile to damage the vessel during the installation process, e.g. a system and method for holding and upending a pile that allows therefor. Whilst the release of the pile out of the pile holder and into the sea may result in the pile coming to lie on the seabed, and thus potentially the need for later retrieval of the pile, the approach avoids any undesirable situation from become more problematic.

In a preferred embodiment, the pile holder comprises one or more sensors or markers which are longitudinally spaced from each other and arranged such that a comparison between indications by the sensors or between observed positions of the markers indicates a vertical inclination of the longitudinal axis of the pile held along the center axis of the pile holder. For example, the sensors or markers are provided in or on the rings of the pile holder or the pile holder frame thereof, as discussed in relation to the first, second and third aspects. This embodiment of the system enables operation thereof such that in response to an indicated non-verticality of the longitudinal axis, the pile may be moved away from the vessel and released into the sea when the indicated vertical inclination indicates that the pile is instable beyond possible correction, for example when the pile slides away or topples over.

In a method according to the fifth aspect using such system, after detection of an anomalous situation, e.g. by means of the sensors and/or by the observation of the markers, the support assembly is caused to move, by the actuators thereof, the pile holder and the pile held thereby in a direction away from the vessel, for example forwardly. The pile holder is moved to the opened position thereof, e.g. by opening the one or more jaws, if present, and the pile is allowed to fall out of the pile holder through the defined opening in a direction away from the vessel, e.g. forwardly, into the sea. Optionally, the support assembly is caused to retract the pile holder towards the vessel, e.g. while the pile holder is still in the opened position thereof. For example, the opening of the one or more movable jaws is done at least partly simultaneously with the moving of the pile holder and the pile held thereby in a direction away from the vessel.

The movement of the pile holder and the pile held thereby in a direction away from the vessel in step e. and optionally step f., the support assembly preferably imparts a velocity to the pile high enough for it to keep moving in a direction away from the vessel while during its fall still vertically within the contour of the vessel.

In an embodiment the system comprises a computerized controller which has stored therein an emergency routine. Upon start of the emergency routine, the routine causes the support assembly to move the pile holder in step e. and the opening of the one or more jaws in step f., and optionally the retracting of step g.

The method may further comprise, after the detection of the anomalous situation, starting the emergency routine by operation of an emergency button in connection with the computerized controller, e.g. by an operator.

A control unit of the system, or of the vessel, may comprise the computerized controller, e.g. is embodied as such. The detecting step may comprise an automated evaluation by the computerized controller of one or more parameters related to the pile installation process.

Embodiments according to the first, second, third, fourth and fifth aspect of the invention may be readily combined. The following discussion relates to any of the discussed aspects.

In an embodiment, the system is configured to be mounted on a floating vessel, wherein the support assembly is configured to provide compensation for wave-induced motion of the vessel to maintain a predetermined X-Y location of the pile holder independent of the wave- induced motion of the vessel.

In a preferred embodiment, the pile holder is mounted on the support assembly such as to be tiltable about a substantially horizontal tilt axis relative to the support assembly between a horizontal orientation, in which the center axis is substantially horizontal, and the vertical orientation, while holding the pile longitudinally along the center axis. In this embodiment, the system advantageously enables tilting of the pile around the tilt axis by enabling tilting of the pile holder around the tilt axis while holding the pile longitudinally along the center axis.

In an embodiment, the system is embodied as a system for holding and upending the pile. The pile holder is mounted on the support assembly such as to, while holding the pile longitudinally along the center axis, be tiltable about the tilt axis relative to the support assembly between a horizontal orientation, in which the center axis of the pile holder is substantially horizontal, and a vertical orientation, in which the center axis is substantially vertical.

Preferably, the pile holder is provided, below the lower ring thereof, with a pile foot end support that is secured to the pile holder frame and that is configured to engage with a lower end region of a pile in order to limit longitudinal movement of the pile, at least during an upending of the pile. In this embodiment, the inclination around the tilt axis may also be provided by the sensors and/or markers during upending of the pile. Based on this inclination, the upending movement and the associated mechanical stress on the system and the vessel may be more accurately monitored, predicted and controlled. For example during the last phase of the upending when the pile is near vertical, feedback on the inclination of the pile may be used to prevent overshooting of the pile beyond vertical.

In an embodiment wherein the pile holder comprises the sensors, the pile engaging devices of one or more of the rings comprise the sensors, for example the pile engaging devices of the lower ring comprising the lower sensors, and/or of the upper ring comprising the upper sensors. For example pile guiding rollers of the pile engaging devices comprise the lower and upper sensors. In an embodiment, the respective ring structures of the one or more of the rings comprise the sensors, e.g. distributed around the circumference of the respective ring. In an embodiment, the sensors of one or more of the rings are provided between the pile engaging devices and the ring structure of the respective ring.

In an embodiment at least one of the rings comprises one or more actuators operative between the respective ring structure and the pile engaging devices connected thereto, configured to radially move the pile engaging devices of the respective ring such as to radially move the region of the pile extending inside the respective ring, thereby moving the pile holder, and thereby the pile, to a vertical orientation thereof, e.g. based on a comparison of the indications by the lower and upper sensors, when present, and/or the observed positions of the lower and upper markers, when present, e.g. the comparison being made by the control unit, if present. In case both of the rings comprise the one or more actuators, the actuators of the upper ring are operable to move the pile engaging devices of the upper ring independently of the pile engaging devices of the lower ring, and vice versa.

This embodiment enables to correct a detected non-verticality of the pile by radially moving the regions of the pile horizontally relative to each other. For example, to correct a detected forward tilting of the pile, the pile engaging devices of the upper ring may be moved radially such that the upper region of the pile shifts backwardly, and/or the pile engaging devices of the lower ring may be moved radially such that the lower region of the pile shifts forwardly, so that the center axis of the pile holder is vertical again, thereby moving the pile holder back to the vertical orientation. For example, thereafter the pile engaging devices of both rings may be moved simultaneously such as to shift the vertical center axis back to its initial position, if needed.

In an embodiment the system comprises one or more tilt actuators, operative between the support frame and the pile holder and configured to tilt the pile holder around the tilt axis, e.g. operative in dependence of a comparison of the indications by the sensors and/or markers, e.g. the indication produced by the control unit, if present. This embodiment enables to operate, or adjust the operation of, the tilt actuators to the indicated inclination of the pile such as to counteract a non-verticality of the pile by actively tilting the pile holder around the tilt axis. In case the system is embodied as a pile holding and upending system, the tilt actuators may facilitate upending of the pile by actively tilting the pile holder around the tilt axis.

In an embodiment, e.g. an embodiment according to the fifth aspect of the invention, the support assembly comprises one or more actuators configured to move the pile holder at least horizontally away from the vessel, e.g. forwardly, and towards the vessel, e.g. backwardly, e.g. configured to horizontally translate the pile holder away from and towards the vessel. This embodiment enables to, in some situations, correct a non-verticality of the pile by translating the pile holder as a whole. For example, upon early detected forward tilting of the pile when its center of gravity is still amply higher than the pile holder, e.g. when still above the water level, the pile holder as a whole may be accelerated forwardly relative to the support assembly to correct the non-verticality - in case of backward tilting, a backward acceleration may correct the non-verticality. Correspondingly, forward and backward tilting in case that the center of gravity of the pile is amply lower than the pile holder, may be corrected by respectively forward and backward acceleration of the pile holder relative to the support assembly. For example, after the correction, the pile holder may be translated back slowly with constant speed, while keeping the center axis, and thereby the longitudinal axis of the pile, vertical. In an embodiment, a control unit is provided which is configured to receive the indications by the sensors, when present, and/or markers, when present. The control unit is furthermore configured to produce based on these indications, e.g. based on a comparison of any sensor indications and/or observed marker positions of the lower ring with those of the upper ring, an indication of the vertical inclination of the pile. The measurements of any sensors present in the system and/or the observed positions of the any markers present in the system may be processed by the control unit for determining based on said measurements the occurrence, direction, and/or the extent of a vertical inclination of the pile.

The control unit is furthermore configured to cause the pile holder to move relative to the vessel based on the produced indication of the vertical inclination, and for example a determined occurrence, direction and/or extent of the vertical inclination,. The control unit is configured to in case of an indication of non-verticality of the pile, move the pile holder to the vertical orientation thereof. Thereto the control unit is configured to operate one or more actuators of the system according to the invention, and/or of the vessel, such as to counteract the vertical inclination and move the pile holder, and thereby the pile held thereby, back to the vertical orientation. The control unit may for example operate one or more actuators of the system provided for translating or tilting of the pile holder, for moving one or more of the rings relative to the pile holder frame, and/or for moving the pile engaging devices of one or both of the rings relative to the ring structure thereof, as discussed before. These movements may be established separately or in combination.

The control unit may be provided on the system, or on the vessel, e.g. connected to or integrated with a general control unit on the vessel, e.g. at least including the dynamic positioning (DP) system of the vessel.

In an embodiment, the control unit is furthermore connected to the dynamic positioning (DP) system of the vessel. For example, the control unit is configured to provide the DP-system of the vessel with the indications of the sensors, if present, and/or with the observed locations of the markers, if present, with indications of a non-verticality as determined by the control unit, with indications of a movement of the pile holder towards the vertical position thereof in reaction to the non-verticality, and/or with indications of a movement of the pile holder to release an instable pile into the sea according to the fifth aspect of the invention. The control unit may be configured to cause an adjustment of the operation of the DP-system, e.g. such as to facilitate such movements. For example, to prevent the DP-system from adjusting the position of the vessel in response to a reaction force on the vessel encountered as a consequence of the movement of the pile holder, e.g. releasing the pile into the sea. Such vessel movement may undesirably counteract the movement of the pile holder if not prevented.

The invention furthermore relates to a method for installing a pile into the seabed from a vessel, wherein use is made of a system according to the invention.

In an embodiment the method comprises: a1. holding the pile by the pile engaging devices of the pile holder in a substantially vertical orientation, a2. optionally, lowering the pile into the water while being held and guided by the pile engaging devices of the pile holder, a3. optionally, driving the pile into the seabed while being held and guided by the pile engaging devices of the pile holder, b. during steps a1 , step a2 and/or step a3, preferably during all of steps a1-a3, measuring a verticality of the central axis of the pile holder, and therewith of the pile, by means of the sensors, when present, and/or by observing the location of the markers, when present, e.g. by means of one or more cameras, and c. when the sensors indicate that the central axis is vertically inclined, moving the pile holder, and thereby the pile, towards the vertical orientation thereof.

In an embodiment wherein use is made of the system according to at least the first aspect of the invention, the measuring of step b. includes a comparison of the indication by the lower sensors with the indication by the upper sensors.

In an embodiment wherein use is made of the system according to at least the third aspect of the invention, the measuring includes a comparison of the observed locations of the lower markers with the observed location of the upper markers, and possibly also of the observed locations of the lower and upper markers with previously observed locations of the markers when the pile holder is in the vertical position.

In an embodiment wherein use is made of a system wherein the pile holder is tiltable around the tilt axis, the movement of the pile holder to the vertical orientation includes tilting the pile holder relative to the support frame around the tilt axis, e.g. by operating one or more tilt actuators operative between the pile holder and the support assembly, if present. In an embodiment wherein use is made of a system wherein the pile engaging devices are radially movable, the movement of the pile holder to the vertical orientation includes radially moving the pile engaging devices of at least one of the rings, for example by operating one or more actuators operative between the pile engaging devices and the respective ring structure to which these devices are connected, for example radially moving the pile engaging devices of the lower ring independently from the pile engaging devices of the upper ring.

In an embodiment the method further comprises: h. providing a dynamic positioning system of the vessel with the indications of the sensors, if present, and/or with the observed locations of the markers, if present, and/or with indications of the movement of the pile holder towards the vertical position thereof, and i. adjusting a dynamic positioning of the vessel by the dynamic positioning system to the movement of the pile holder towards the vertical position thereof, such that the dynamic positioning system facilitates the movement of the pile holder towards the vertical position thereof.

In an embodiment use is made of the system according to at least the fifth aspect. The method comprises the steps of: d1. detecting, by means of the sensors and/or by the observation of the markers, an anomalous situation, e.g. a lower end region of the pile sliding away, e. thereafter, causing the support assembly to move the pile holder and the pile held thereby in a direction away from the vessel, e.g. forwardly, and f. moving the pile holder to the opened position thereof, e.g. by opening the one or more movable jaws, if present, and letting the pile fall out of the pile holder through the defined opening in a direction away from the vessel, e.g. forwardly, into the sea, g. optionally, causing the support assembly to retract the pile holder towards the vessel, e.g. the pile holder still in the opened position thereof.

The moving of the pile holder to the opened position in step f. is preferably done at least partly simultaneously with the moving of the pile holder and the pile held thereby in a direction away from the vessel in step e.

In the movement of the pile holder and the pile held thereby in a direction away from the vessel in step e. and optionally step f., the support assembly preferably imparts a velocity to the pile high enough for it to keep moving in a direction away from the vessel while during its fall still vertically within the contour of the vessel. In an embodiment the system comprises a computerized controller, having stored therein an emergency routine. Upon start of the emergency routine, the routine causes the support assembly to move the pile holder in step e. and the opening of the one or more jaws in step f., and optionally the retracting of step g.

The method may further comprise: d2. after the detection of the anomalous situation in step a1 , starting the emergency routine by operation of an emergency button in connection with the computerized controller, e.g. by an operator.

In an embodiment wherein the system has the control unit as described, the control unit comprises the computerized controller, e.g. is embodied as such. The detecting of step d1. may comprise an automated evaluation by the computerized controller of one or more parameters related to the pile installation process, as described herein.

In an embodiment the method further comprises: j. providing a dynamic positioning system of the vessel with the indications of the sensors, if present, and/or with the observed locations of the markers, if present, and/or with indications of the movement of the pile holder in step e., and k. adjusting a dynamic positioning of the vessel by the dynamic positioning system to the movement of the pile holder towards the vertical position thereof, such that the dynamic positioning facilitates the pile falling out of the pile holder through the defined opening in a direction away from the vessel, e.g. forwardly, into the sea.

The invention furthermore relates to a vessel provided with a system as described herein in relation to any of the aspects of the invention. In an embodiment, the vessel is furthermore provided with a control unit as described herein.

The invention furthermore relates to a method for installation of a pile in the seabed from a vessel, wherein use is made of the system according to any of the aspects of the invention, or a vessel provided with such system, the method for example being embodied as described herein before.

The invention will now be described with reference to the appended figures. In the figures: Fig. 1 shows an example of a system according to the invention on board a vessel in a perspective view with the pile holder in vertical orientation, Fig. 2 shows the system of figure 1 in side view,

Fig. 3 shows the system of figure 1 in front view,

Fig. 4 shows the system of figure 1 in top view,

Fig. 5 shows the system of figure 1 with the pile holder in horizontal orientation, seen in side view,

Fig. 6 shows the system of figure 5 in top view,

Fig. 7 shows a monopile for a wind turbine placed horizontally in the system of figure 1 , in a perspective view,

Fig. 8 shows the system of figure 7 in side view,

Fig. 9 shows the situation wherein the pile has been upended using the system of figure 1 ,

Fig. 10 illustrates placing the monopile with a crane in the system of figure 1,

Fig. 11 illustrates connecting a crane to the upper end of the horizontal oriented pile,

Fig. 12 illustrates the upending of the pile using the system of figure 1 and a crane,

Fig. 13 illustrates the pile in upended, vertical orientation, retained by the system of figure 1 and the crane,

Fig. 14 illustrates the change of angular orientation of the pile using the system of figure 1,

Fig. 15 illustrates clearing the pile foot end support from the upended pile,

Fig. 16 illustrates lowering of the pile through the system of figure 1 using the crane,

Fig. 17 illustrates placing a pile driving device on top of the pile for driving the pile deeper into the seabed, and driving said pile into the seabed until a desired penetrating depth is achieved guided by the system of figure 1,

Fig. 18 illustrates the system after an emergency ejection of the monopile from the pile holder,

Figs. 19,20 schematically illustrate pile engaging devices of the system engaging piles of different diameters,

Fig. 21 illustrates the system in a detailed side view,

Figs. 22a-b illustrate in a top view the upper ring of the system,

Fig. 22c illustrates in a top view the lower ring of the system, and

Fig. 22d illustrates in a front view the system with the pile holder in a horizontal orientation.

In the figures a vessel is partly indicated with reference numeral 1.

In this example, the vessel is equipped with a crane 2 configured to lift a monopile 10 for an offshore wind turbine.

For example, the vessel 1 has a deck 3 on which one or more monopiles 10 are stored in horizontal orientation, e.g. transverse to the longitudinal axis of the vessel. The vessel 1 is equipped with an pile upending and holding system 20 according to the invention, that is configured to be mounted on the vessel 1 , e.g. on a deck 3 thereof, e.g. on a deck thereof and in close proximity to the crane 2.

The system 20 is used in conjunction with the crane 2, and a pile driving device 100, for installation of the monopile 10 into the seabed. A wind turbine, e.g. with a transition piece in between, is then placed on the monopile.

Generally the system 20 comprises a support assembly 30 that is configured to be mounted on the vessel 1 , e.g. on a deck 3 of the vessel, and a pile holder 50. The support assembly 30 is configured to provide compensation for wave-induced motion of the vessel 1 to maintain a predetermined X-Y location of the pile holder 50 independent of the wave-induced motion of the vessel 1.

The pile holder 50 is tiltable mounted on the support assembly 30. The pile holder 50 has a center axis 51 and is mounted such as to be tiltable about a substantially horizontal tilt axis 40 relative to the support assembly 30 between a horizontal orientation and a vertical orientation while holding the monopile 10 longitudinally, with its longitudinal axis 11, along the center axis 51. In the horizontal orientation, the center axis 51 of the pile holder is substantially horizontal, see figures 1-4, 9, 11. In the vertical orientation the center axis 51 is substantially vertical, see figures 5-8, 10, 13, 15, 17, 18. In figure 12, the pile holder 50 and the held pile 10 is in between the horizontal and vertical orientation.

The pile holder comprises a lower ring 55, an upper ring 60, and a pile holder frame 53 which supports the lower ring 55 and upper ring 60, mutually spaced along the center axis 51. Thus, the upper ring 60 is vertically above the lower ring 55 when the pile holder 50 is in substantially vertical orientation.

The lower ring 55 comprises multiple lower pile engaging devices 56, and the upper ring 60 comprises multiple upper pile engaging devices 61. The pile engaging devices are distributed about the circumference of the respective ring, see e.g. figure 4, each pile engaging device being adapted to be engage an exterior of respectively a lower region 101 and an upper region 10u of the pile, respectively extending inside the lower and upper ring 55, 60, for holding and guiding the pile. The pile engaging devices each comprise one or more pile guiding rollers 61 r, most clearly visible in figures 19-21. The lower ring 55 comprises one or more lower sensors and the upper ring 60 comprises one or more upper sensors, which sensors (not shown) are arranged such that a comparison between the indications indicates a vertical inclination of the longitudinal axis 11 of the pile held along the center axis of the pile holder.

The lower and upper sensors comprise lower and upper force sensors, each being configured for providing an indication of a force exerted by, respectively, the lower region 101 and the upper region 10u of the pile 10 on respectively the lower and upper ring 55, 60. The lower and upper force sensors are provided in the rollers of the pile engaging devices 56, 61.

The lower and upper sensors comprise lower and upper position sensors, each being configured for providing an indication of the horizontal position of, respectively, the lower region 101 and the upper region 10u of the pile 10, the position sensors being arranged such that a comparison between the indications provided thereby indicates a vertical inclination of the center axis 51 of the pile holder 50, and therewith of the longitudinal axis of the pile. The lower and upper position sensors are provided in the ring structure of respectively the lower and upper ring 55, 60. As shown, the markers are distributed around the circumference of the respective ring 55, 60.

The lower ring 55 comprises one or more lower markers 55m and the upper ring 60 comprises one or more upper markers 60m at an exterior surface of the rings 55, 60, arranged and configured such that their positions are observable externally from and remote from the pile holder 50, and such that in an external and remote view on the pile holder 50, their positions are indicative of a vertical inclination of the center axis 51 of the pile holder 50, and therewith of the longitudinal axis 11 of the pile 10. The markers are embodied as beacons, so as to be configured such that their positions are visible externally from and remote from the pile holder 50. Their positions are observable externally from and remote from the pile holder 50 by means of cameras and/or by an operator on the vessel. The markers are distributed around the circumference of the respective ring.

The support assembly 30 comprises one or more actuators configured to translate the pile holder 50 at least horizontally forwardly away from the vessel and backwardly towards the vessel. The rings 55, 60 are movable into an opened position, in which the rings between free ends thereof define an opening 52 of the pile holder 50 for passage of the pile 10 out of the pile holder 50 in a direction perpendicular to the center axis 51 and away from the vessel, for example a forward direction. The opening 52 is indicated in figures 18 and 22b. Each of the lower ring and upper ring 55, 60 comprises a ring base 55b, 60b fixed to the pile holder frame 53, indicated in the top views of figure 4 and figures 22a, b. Each ring 55, 60 further comprises two semi-circular movable jaws 58, 59, 62, 63, each jaw being movable such as to move the rings between a closed position, wherein the rings form a closed annulus, and the opened position. In this embodiment the jaws 58, 59, 62, 63, are for this purpose each pivotal around respective longitudinal pivot axes. In figure 22a, the upper ring 60 is shown with the jaw 63 opened and jaw 62 closed, and in figure 22b with both jaws 62, 62 opened. With the jaws of the lower ring 55 opened as well, free ends 55e of the lower ring 55 define together with free ends of the upper ring 60 an opening 52 of the pile holder 50 for passage of the pile 10.

In figure 22c the lower ring 55 is shown with both of its jaws 58, 59 closed. The lower ring 55 has the same functionality for the opening and closing of its jaws 58, 59 as shown for the upper ring 60 in figures 22a and 22b. In figure 18, the jaws of both rings 55,60 are in the opened position. In the opened position, the rings 55, 60 between free ends thereof define an opening 52 of the pile holder 50 for passage of the pile 10 through the opening 52 into and out of the pile holder.

The system enables a method comprising detecting, by means of the sensors and/or by the observation of the markers, an anomalous situation, e.g. a lower end region of the pile 10 sliding away, subsequently causing the support assembly 30 to move the pile holder 50 and the pile held thereby in a direction away from the vessel 1, and moving the pile holder to the opened position thereof, e.g. by opening the one or more movable jaws 58, 59, 62, 63, if present, and letting the pile fall out of the pile holder through the defined opening 52 in a direction away from the vessel. In this case, the pile holder 50 is translatable, and the pile 10 releasable through the opening 52, in a forward direction. The method comprises causing the support assembly 30 to retract the pile holder 50 towards the vessel 1 with the pile holder 50 still in the opened position thereof.

Figure 18 illustrates the situation after release of the pile 10 while retracting the pile holder 50.

The moving of the pile holder to the opened position in step is preferably done at least partly simultaneously with the moving of the pile holder and the pile held thereby in a direction away from the vessel. In the movement of the pile holder 50 and the pile held thereby in a direction away from the vessel 1 , the support assembly 30 imparts a velocity to the pile 10 high enough for it to keep moving in a direction away from the vessel while during its fall still vertically within the contour of the vessel. With the pile holder 50 in the horizontal position prior to upending, such as in figures 5, 6, 7, 8, 10, and 11 the opening 52 may be used for entry of the pile 10 to extend through the lower and upper ring 55, 60 with the longitudinal axis 11 of the pile 10 extending along the center axis 51. In the closed position, the respective ring 55, 60 forms a closed annulus enclosing the pile 10 extending through the rings 55, 60 as shown for the lower ring in figure 22c, and for both rings in figures 1-13,15,17.

The provision of the openable jaws 58, 59, 62, 63 enables the pile 10 to be introduced into and released from the pile holder 50 in a radial direction. This may be envisaged from figures 10 and 18, respectively. In the shown horizontal orientation of the pile holder 50 of figure 10, the pile 10 can advantageously be introduced in a horizontal orientation into the pile holder 50.

In the shown embodiment the opening 52 extends substantially horizontally in the horizontal orientation of the pile holder, so that the pile can be introduced from above into the pile holder by a crane. In figure 10, the crane supports the pile 10 in the vertical orientation using a yoke, prior to opening of the jaws 58, 59, 62, 63 of both rings and lowering the pile 10 by the crane into the pile holder 50 via the entry opening 52 created.

The pile holder 50 is embodied so that, when the pile holder 50 is in the horizontal orientation, the ring base 55b, 60b of each ring forms a bottom section of the annulus, for supporting the pile 10 when received in the pile holder 50. This may be envisaged from figure 10 combined with figure 22b.

The pile holder 50 is provided, below the lower ring 55 thereof, with a pile foot end support 70 that is secured to the pile holder frame 53 and that is configured to engage with the lower end region of the pile in order to limit longitudinal movement of the pile 10, at least during upending of the pile 10. Such upending process is illustrated by the consecutive progression of figures 11, 12 and 13.

The tilt axis 40 of the system is located longitudinally between the lower ring 55 and the upper ring 60, namely substantially in the middle there between. Thus in the vertical position, the tilt axis 40 extends vertically in the middle between the rings.

The system 20 comprises two tilt actuators 41 , operative between the support frame 30 and the pile holder 50, see e.g. figure 21. The tilt actuators 41 are configured to move the pile holder 50 between the horizontal orientation and the vertical orientation thereof. During upending, the tilt actuators 41 are operable to apply a force to the pile holder 50 such as to tilt it forwardly, about the tilt axis, from the horizontal to the vertical orientation, see the advancement of figures 11-13. Therewith, the tilt actuators 41 at least assist the crane 2 in upending the pile 10. The tilt actuators 41 may also be operated to decelerate the upending movement, for example in the last part of the upending movement, e.g. to dampen a forward momentum of the pile 10, such as to reduce the risk of the pile 10 to overshoot and topple forward.

Furthermore, the tilt actuators 41 are operable to apply a force to the pile holder 50 such as to tilt it backwardly, about the tilt axis 40 from the vertical to the horizontal orientation, for example after an installation procedure of a pile, e.g. back to the position shown in figures 5 and 10 in order to receive another pile to be subsequently installed. Furthermore, the tilt actuators 41 provide controllability of the upending movement additional to the control of the operation of the crane 2. The tilt actuators 41 may furthermore be applied to correct tilting of an upended pile prior to and during lowering, e.g. over small vertical angles.

In the shown embodiment, the tilt actuators 41 are hydraulic tilt cylinders, of which the piston is connected to the pile holder 50, and the cylinder to the support assembly 30. As is preferred the hydraulic tilt cylinders 41 are connected to the pile holder 40 at a location above the tilt axis 40 and forward thereof when the pile holder 50 is in the vertical orientation. As visible in e.g. figure 5, in the horizontal orientation of the pile holder 10, the tilt cylinder 41 is retracted and extends substantially horizontally.

The support assembly 30 is provided, longitudinally at a distance below the tilt axis 40 with a catching mechanism 42, see e.g. figure 21. This catching mechanism 42 is configured to, in a range of angles of the center axis 51 from a predetermined backward tilting angle to a vertical orientation, engage the pile holder 50 and apply a forward force to the pile holder 50 such as to decelerate a forward tilting movement of the pile holder 50 and the pile 10 held thereby. The effect is that in a last part of the upending movement, as soon as the pile holder reaches the predetermined backward tilting angle, the pile holder 50 is engaged by the catching mechanism 42, and the tilting around the tilt axis 40 is damped by the applied forward force until the pile holder is in its vertical orientation. Thereby, the catching mechanism 42 decelerates the upending movement such as to dampen a forward momentum of the pile 10, reducing the entailed risk of the pile 10 to overshoot and topple forward.

The catching mechanism 42 comprises hydraulic cylinders, which are fully extended when engaging the pile holder at the predetermined backward tilting angle and shorten as the backward tilting angle decreases. The catching mechanism is automatically releasably connectable to the pile holder 50 directly after engagement of the pile holder 50 with a forward end thereof which is a free end prior to the connection.

The catching mechanism is furthermore configured to in a range of angles of the center axis from a vertical orientation to a predetermined forward tilting angle, remain engaged with the pile holder 50 and apply a forward force to the pile holder 50 below the tilt axis 40 such as to decelerate a forward tilting movement of the pile holder 50 and the pile held thereby. Thereby, the catching mechanism 42 counteracts a forward tilting movement of the pile 10, reducing the entailed risk of an upended pile to overshoot and topple forward. The tilt actuators 41 may be used to counteract a backward tilting movement of the pile holder and the pile held thereby.

The support assembly 30 comprises one or more first rails 31 extending in a longitudinal direction, a positioning frame 32 movably supported on said one or more first rails in said longitudinal direction, where the positioning frame is provided with one or more second rails 33 extending in a transverse direction, and a support frame 34 movably supported on said one or more second rails in said transverse direction, wherein the pile holder is tiltable supported by the support frame about the tilt axis 40.

The pile engaging devices 56, 61 of both rings 55, 60 are movable relative to the respective ring structure of the lower and upper ring, respectively. In figure 19 and 20, different possible pile engaging devices 56, 61 are shown in a schematic in which piles 10 with differently sized circumferences are shown in one figure. The pile engaging devices are shown while engaging the pile exteriors at the different circumferences.

Firstly, both the lower and upper pile engaging devices 56, 61 are movable a radial direction relative to the respective ring structure by one or more respective actuators 56a, 61a of the respective ring 55, 60. The lower pile engaging devices 56 are movable independently from the upper pile engaging devices 61, so that as illustrated in figures 19 and 20, they are able to engage differently sized circumferences of the pile 10. The independent radial movability of the devices 56, 61 enables these to continuously hold and guide a pile with a longitudinally varying outer circumference during lowering. Thereby, the devices 56, 61 are able to remain in engagement with the exterior of the pile 10 extending through the rings 55, 60 while a tapered section of the pile 10 passes through the rings along the center axis 51. The pile 10 shown while being lowered in figure 17, has such tapered section. The tapered section tapers upwardly, and is in figure 17 above the upper ring 60, about to extend through the rings 55, 60 when the pile 10 is lowered further. The upper pile engaging devices 61 will move radially inwards further than the lower pile engaging devices 56 as the tapered section extends through the rings.

Further, the pile engaging devices 56, 61 of each ring are movable individually, independently from each other, such that local obstructions on the exterior of the pile 10 can pass the pile holder 50 during lowering.

The pile engaging devices 56, 61 are actively radially movable by respective actuators 56a, 61a, so that the engagement and disengagement by the devices 56, 61 of the exterior of the pile 10 held by the pile holder 50 is controllable by operation of these actuators 56a, 61a, e.g. during a lowering stage. Each pile engaging device 56, 61 has a separate associated actuator 56, 61, so that the radial movements of the pile engaging devices 56, 61 are individually controllable, independently from each other. The actuators 56a, 61a are embodied as hydraulic cylinders. In figures 19, each device 56, 61 is shown with the rollers in two positions, engaging a smaller diameter pile and a larger diameter pile, as associated with two positions of the respective actuators 56a, 61a. In figure 20 the leftmost devices are shown engaging a smaller diameter pile and the rightmost devices are shown engaging a larger diameter pile.

The active radial movability of the pile engaging devices 56, 61 allows for radial (re)positioning of the pile 10 being held. For example the lower pile engaging devices 56 are radially moved to correct a tilting of the pile 10, or both the lower and upper pile engaging devices 56, 61 are used to adjust a horizontal position of the pile 10 when in vertical orientation. Moreover, the active radial movability for example enables the pile holder 50 to be adjustable to a range of pile circumferences, so that it is configured to hold piles with different diameters. The pile engaging devices 56, 61 may prior to receipt of a pile be moved to a radially inwards position in case of a small diameter pile, and moved to a radially outwards position for holding a large diameter pile.

The radial movability of the pile engaging devices 56, 61 enables that radial motions of the pile relative to the vessel 1 may be absorbed, and/or at least partly compensated, e.g. completely compensated, e.g. passively. In the vertical position of the pile holder 50, thereby the pile may be held in a stationary radial position relative to the vessel 1 for example when the X-Y compensation of the support assembly 30 is not being applied. The radial movability also enables to incorporate a ring damping mechanism between the pile engaging devices 56, 61 and the ring structures.

The system 20 comprises such ring damping mechanism in the upper ring 60 of the pile holder 50, the damping mechanism being embodied by radially extending cylinders and configured to suppress oscillation during upending and lowering, and/or supress undesired tilting of the upended pile 10. The ring damping system passively damps out movements of the pile in the radial plane of the ring 60, while draining energy from the radial movements of the pile engaging devices 61 involved in such oscillation or tilting. The cylinders passively shorten and extend upon radial movements of the pile engaging devices 61 relative to the ring structure of the upper ring 60.

The pile engaging devices 56 of the lower ring 55 are movable relative to the ring structure of the lower ring 55 along a corresponding arc segment of the closed annulus formed by the lower ring 55 while remaining engaged with the pile exterior, so as to allow for adaptation of the angular position of the pile engaging devices 56, 61 relative to the ring structure and therewith for moving the held pile over an angle around its vertically oriented longitudinal axis 11 into a desired angular position.

The pile engaging devices 61 of the upper ring have a fixed angular position relative to the ring structure of the upper ring 60.

The upper pile engaging devices 61 allow movement of the held pile 10 over an angle around its longitudinal axis 11 into a desired angular position of the pile 11 relative to the pile engaging devices 61 while remaining engaged with the pile exterior. The devices 61 allow slipping of the pile exterior over the associated pile engaging devices 61 in the angular movement direction over a small angle.

The devices 56, 61 are as discussed also actively radially movable, so that the actuators 56a, 61a may be operated to move a part, preferably half, of the devices 56, 61 outwardly such that these disengage the pile exterior and hold these cleared from the pile 10 while the remaining part of the pile engaging devices 56 remains engaged with the pile exterior and moves along respective arc segments to move the pile 10 angularly. After the angular movement the upper pile engaging devices 56, 61 may be moved and radially inwardly to again engage the pile exterior. Subsequently, the moved pile engaging devices 56, 61 may be moved radially outwardly by operation of their respective actuators 56a such as to clear the pile exterior, and while held clear from the pile exterior, be moved back along their arc segments to their initial positions, after which they may be moved back radially inwardly to engage the pile exterior. The moving part of the devices may e.g. be all of the lower pile engaging devices, while the upper pile engaging devices remain in the same angular position, but may also be e.g. half of the lower and half of the upper devices, while the other half of the lower and upper devices remain in the same angular position. The pile foot end support 70 comprises one or more pivotal arms 71 , 72 that are movable into an operative position wherein the one or more pivotal arms 71 , 72 extend underneath the longitudinal end region of the pile and an opened position wherein the one or more pivotal arms 71 , 72 are cleared from the longitudinal end region of the pile.

As illustrated in figures 10 - 17 the system 20 can be used in a method for upending and installation of a pile 10 in the seabed, wherein the method comprises, e.g. with the vessel 1 in floating condition: a. transporting a pile 10 in a horizontal orientation to an offshore installation site, e.g. using the vessel 1 or a barge or the like; b1 . positioning the pile holder 50 in a horizontal orientation; b2. opening the jaws 58, 59, 62, 63 of the lower and upper rings 55, 60, c. with the pile holder in the horizontal orientation, placing the pile 10 in horizontal orientation with a first longitudinal end region thereof on the bases of the lower and upper rings 55, 60, d. closing the jaws 58, 59, 62, 63, e. upending the pile 10, using crane 2, into vertical orientation by means of lifting a second longitudinal end region of the pile 10, so that the pile 10 held at the first longitudinal end region thereof by the pile holder 50 tilts about the horizontal tilt axis 40, wherein the pile foot end support 70 limits longitudinal movement of the pile 10, during the upending of the pile 10, f. disengaging the pile foot end support 70 from the first longitudinal end region of the pile 10, e.g. involving relieving the weight of the pile temporarily from the support 70; and g. lowering the pile 10 into the water while being held and guided by pile engaging devices of the pile holder 50, e.g. lowering onto the seabed, e.g. followed by driving the pile into the seabed using a pile driving device.

Figure 10 illustrates the system 20 on a vessel 1 after step b1 and figure 11 after step d. In figure 12 the system 20 is illustrated halfway step e, and in figure 13 after step e. In figure 14, top views of the rings 55, 60 illustrate an angular adjustment process. Progressing from start to step #1 , half of the pile engaging devices are moved radially outwardly to disengage the pile 10. At step #2, the other half of the upper pile engaging devices 56 have been moved along their respective arc segments to angularly move the pile 10, until abutting the adjacent disengaged pile engaging devices. At the end, all pile engaging devices have moved further angularly to the desired angular position of the pile 10. During the angular adjustment process, the pile 10 continuously remains engaged by half of the pile engaging devices 56, 61.

Figure 15 illustrates the foot end support 70 being disengaged according to step f in three stages, and in the lowermost part during step g. Figure 16 illustrates the system during step g and figure 17 after step g, while a pile driving hammer is placed onto the second longitudinal end region of the pile 10 for subsequent pile driving.

The support assembly 30 provides compensation for wave-induced motion of the vessel to maintain a predetermined X-Y location of the pile holder independent of the wave-induced motion of the vessel at least in step g.

In figure 22d, another use of the angular movability of the pile engaging devices 56, 61 is shown. In the horizontal orientation, a part of the devices may be moved towards the bottom part of the ring bases, so that the pile 10 is supported vertically by multiple pile engaging devices in this orientation. The devices 56, 61 may later be moved to be more evenly distributed over the circumference in the vertical orientation.