EP2766528A1

EP2766528A1 - Template

Info

Publication number: EP2766528A1
Application number: EP12784085.8A
Authority: EP
Inventors: Installer As Norwind
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-09-23
Filing date: 2012-09-18
Publication date: 2014-08-20
Anticipated expiration: 2032-09-18
Also published as: NO333643B1; WO2013043055A1; EP2766528B1; NO20111294A1

Abstract

Retrievable pre-piling template (10) for offshore wind turbine foundations, comprising a plurality of pile guide sleeves (12) interconnected by connection elements (14, 16, 18), where said pile guides sleeves (12) are arranged to rest on the ocean floor and to receive a pile (70), wherein said connection elements (14, 16, 18) are assembled to form a continuous circular O-ring structure (20), and a number of the pile guide sleeves (12) are arranged to be releasable mounted to the structure (20).

Description

TEMPLATE

The present invention relates to a retrievable pre-piling template for offshore wind turbine foundations, comprising a plurality of pile guide sleeves interconnected by connection elements, where said pile guides sleeves are arranged to rest on the ocean floor and to receive a pile.

Installation of offshore jacket foundations for wind turbine can either be carried out by pre-piling or by post-piling operation. In both cases, jackets are installed on piles which ensure their stability with the jacket to pile connection operated by grouting.

In pre-piling, the piles are driven into the seabed before the jacket is installed onto the piles. In post-piling, the piles are driven into the seabed after the jacket is lowered down on the seabed.

Pre-piled jackets bring the huge benefit of eliminating most of the jacket leveling challenge. When installed, and even before the grout has cured, jackets are seated on a stable support offered by the piles. If the piles are properly leveled (all piles sticking up at the same height), then no further action has to be taken and the jacket can be installed on top of the piles identified as being sufficiently leveled. If the piles are not sufficiently leveled, some shimming can be added to make up for the height variation. Still, the jacket leveling is straight, safe, and easy.

Driving all piles at a correct height is important to reduce the shimming work, but the only part of the exercise that matters the most -as far as the pile height is

concerned- is to work out a reliable measurement of the actual height obtained after piling. Similarly, piles must be installed at a precise location (deviation in footprint can for instance be:

Δ = ±100mm), so that all jacket legs can be seated at the center of the pile and the grout annulus to have its minimum thickness preserved.

The jacket legs usually penetrate the piles up to 5 or 7 m, and requirements of pile verticality tilt are quite strict in order to maintain an acceptable distance (grout thickness) between the jacket leg and pile wall all along the grouted connection. The offshore wind industry is not yet standardized. From one wind farm to the other and even within the same wind farm sometimes, foundation technologies can vary a lot and require very different pile installations. As far as the template is concerned, one recognizes four main parameters of significance:

-The Foot print shape: square (for 4 leg jackets) / triangle (for 3 leg jackets & tripods)

-The Pitch Circle Diameter (PCD) of the footprint (from for instance 026.9m to 0 34m)

-The Pile diameter (from for instance 01 .8 to 02.5m)

-The Pile Stick-up (from for instance 3.0m to 9.5m)

In addition to that, it should be added that the nature of seabed influences the type (and size) of bed-plates as well.

From patent literature the most relevant document is considered to be EP2309063A, which corresponds to Norwegian patent application NO20093082, applicant Aker Jacket Technology AS. The document discloses a retrievable template for piles, used in connection with offshore windmills.

The template of EP2309063A is a rectangular lattice structure with a pile guide in each corner, said pile guides being welded to the lattice structure. The pile guides are equipped with hydraulic actuators connected to bed plates and are arranged to level the pile guides with respect to the ocean floor, while at the same time the inner part, receiving the pile, is kept in a mainly vertical position. Said hydraulic actuators are used to also horizontally level the template. Thus, the pile guide is at the lower part equipped with a conical tubular element surrounding the tubular pile guide, and in where the conical tubular element is connected to the bed plates, and can move with respect to the lower part of the pile guide. The system can further be equipped with cameras for surveillance of pile installation. Cameras can also be used to measure the penetration of the piles, and hence also the height above the ocean floor, by measuring the distance from an opening in the pile guide and to a specific point on the hydraulic hammer.

The main technical features of the present invention, which at least can be regarded as a "doughnut" shape of lattice structure, in where at least three or four pile guides can be releasable mounted, a moving guide belt mounted within the sleeve, and a pile measuring system, comprising a camera and depth sensor, and using marking on the pile, are thus not known from EP2309063A, although a camera measuring system is disclosed.

Reference is also made to US4537533A, which is related to installation and levelling of subsea templates for subsea drilling, comprising a rectangular structure with pile guides. This document is merely showing background technique, and is not considered relevant to the patentability of the invention.

The system is based on a subsea piling template, a hammer, a follower and a noise mitigation system as the main system equipment pieces. The template acts as a pile guide when the piles are hammered into the seabed. Except for the pre-piling template according to the invention, the rest of the system and the method for using such a system is regarded as known to a man skilled in the art.

The template according to the invention is designed for subsea operations down to 60 meters, at least, and to withstand the repetitive strain caused by maybe hundreds of installations per year. The template is reused from one location to the other.

The template may guarantee accurate location of the piles, their verticality and the equal level of the piles within the following desired tolerances (as examples):

- Max tilt angle (inclination of piles from vertical axis): ±1 °

- Max pile top elevation difference: Δ = ±200mm, measured with an accuracy of ±50mm

- Max deviation in footprint: Δ = ±100mm

- Heading: Δ = ± 2° One of the advantages brought by the present invention is that no ROV's are needed to carry out the pile installation under normal condition of operation. The cost of the total operation is this way considerably reduced. Experience shows that working with ROVs makes an operation very much

dependant on reliable weather conditions. Taking away the ROVs increases the schedule reliability and effectiveness because it eliminates uncertainties of time due to operation of the ROV -or waiting for weather conditions that allow operation of the ROV-.

Furthermore, the mobilized ROV no longer acts as the onboard "workhorse" but as a powerful backup tool giving a lot more possibilities when it comes to anticipating the unforeseen. To make this possible, the present invention includes several new features over the traditional installation methods. Amongst the principal ones, it is that the template is equipped with measuring devices for online reporting of all main information to the installation vessel and final verification of pile stick up and verticality. Likewise, the template is equipped with high technology observation package providing the top side operators and crane driver with a live and precise image of the subsea operation enabling efficient installation regardless any condition of subsea visibility.

The present pre-piling template can be installed from a fixed rig, a jack-up vessel or most preferably from a floating vessel. Using a floating vessel saves time losses due to jacking up and down, waiting on weather before jacking up and down and transiting at low speed.

The present template is as mentioned preferably designed with a central "doughnut" of lattice structure giving support to dismountable pile guiding sleeves mounted on it, with for instance flanged connections.

Traditionally, the sleeves are integrated to the structure and the template is manufactured and structured as a monoblock. With the present invention, the pile guide sleeves can be arranged as self supporting units connected to a central structure. By doing so, the sleeves can be individually moved, modified, taken off or even damaged without affecting anything of the total global structure. Due to this original O-ring (doughnut) structure design and due to the fact that sleeves can be attached to the structure on different locations, the present template can be arranged to give support to either 3 or 4 sleeves, or more or less sleeves for that matter.

Furthermore, by inserting extension pieces, one can modify the PCD of the sleeve arrangement. Extensions pieces do not, in the simplest form, have to be more than straight tubes inserted in the flanges to link the sleeve to the ring structure.

Thus, it is an object of the present invention to provide an improved pre-piling template for offshore wind turbine and wind mill foundations, and which is easier to install and to retrieve from the ocean floor, thus reducing the cost involved.

It is a further object to provide a pre-piling template which easily can be equipped with a desired number of pile guides, dependent on the jacket foundation of the wind turbine or wind mill. It is also an object of the invention to provide a template which is easier to level on the sea floor, and in where the pile guides easily can be leveled and tilted.

Said objects are achieved with a retrievable pre-piling template for offshore wind turbine foundations, comprises a plurality of pile guide sleeves interconnected by connection elements, where said pile guides sleeves are arranged to rest on the ocean floor and to receive a pile, wherein said connection elements are assembled to form a continuous circular O-ring structure, and a number of the pile guide sleeves are arranged to be releasable mounted to the structure.

Alternative embodiments are disclosed in the dependent claims.

The pile guide sleeves can be individually arranged to be mounted to, and

dismounted from, a respective selected assembly point on the structure, thereby providing support for a desired number of sleeves. The sleeves can be mounted to the structure in respective assembly points, by a number of connections arms bolted or welded to the structure, and/or a number of connections arms mounted on flanges. The connections arms may be exchangeable, or extendable, wherein pitch circle diameter of the template can be adjusted.

According to a second aspect of the invention, the pile guide sleeves can comprise at least one moving guide belt assembly, said guide belt assembly being arranged to move from an active pile guide position to an inactive position with no pile guiding effect, thereby releasing the template from the piles. The pile guide assembly can comprises a circular belt surrounding the sleeve, said belt being connected to a number of pressure cylinders for said movement, and the belt can be equipped with a number of guide wedges arranged to extend into the sleeve through a corresponding number of slits in the sleeve. The pressure cylinders can be individually controlled, in order to move and tilt the belt, and thus the guide wedges, with respect to the sleeve during said movement of the belt.

The guide wedge can comprise an elongated main body with an abutment edge, said main body being narrower towards a distal end, and the wedge can comprise a connection heel, in where the heel is extending through the slit and is connected to the belt. Said abutment edge, against the pile, can have a rounded surface, and a second abutment edge, against the inside of the sleeve, can have a rounded surface, thus allowing the wedges to roll against respective surfaces of the pile and sleeve.

According to a third aspect of the invention, the pile guide sleeve can comprise a pile height measuring apparatus, said apparatus being mounted on the outside of the sleeve and comprises a camera and a depth sensor movable with respect to an aperture in a sleeve wall of the sleeve, and in where the camera is arranged to register a marking on the pile, and the depth sensor is arranged to register the depth of the camera. The camera and the depth sensor can be mounted to a piston rod of a pressure cylinder, and be movable with respect to the aperture in the sleeve wall. The piston rod can be movable arranged in a guide rail. According to a fourth aspect of the invention, the pile guide sleeve may comprise a depth sensor, said depth sensor can measure the level of the template. The depth sensors of each pile guide sleeve can be arranged at a predetermined distance from the top of the sleeve, wherein the exact depth of all sleeves can be measured. The present invention shall now, as an example, be explained further with the help of the enclosed drawings, in where:

Figure 1 shows a typical installation process of a pile using a template.

Figure 2 shows a planar view of the pre-piling template according to the invention, with a square sleeve configuration.

Figure 3 shows a side view of the template in figure 2.

Figure 4 shows a planar view of the pre-piling template according to the invention, with a triangular sleeve configuration. Figure 5 shows similar to figure 4 a triangular sleeve configuration, but with a larger pitch circle diameter.

Figures 6a shows a cross sectional view and a partial top view of a pile guide sleeve, and figures 6b and 6c show different side views and top views of the pile guide sleeve according to the invention.

Figure 7 shows a planar view of a moving guide belt according to the invention.

Figure 8 shows a side view of the moving guide belt in figure 7.

Figure 9 shows a cross sectional view of the moving guide belt in figure 7. Figure 10 shows a side view of a guide wedge of the moving guide belt in figures 7-9, arranged in the pile guide sleeve.

Figures 1 1 a, 1 b, 1 1c and 1 1 d shows side views of the moving guide belt in different positions on the pile guide sleeve.

Figure 12 shows a partial cross sectional view of a pile height measuring system according to the invention, mounted to a pile guide sleeve.

Figure 13 shows a principle drawing of pile height measuring and template level.

Figure 1 shows a typically installation process of piles for a subsea jacket foundation used with offshore wind turbines, or similar structures. A pre-piling template is lowered from the sea level 82 and down to the sea floor 80, where after the template is leveled. When the template is in correct position, piles 70 are forced into the sea floor by using for instance a hammer 72 connected to a follower 74. A noise mitigation system may also be used. Said process is assumed known for a man skilled in the art, and is thus not further explained.

Figures 2 to 5 shows a pre-piling template 10 according to the invention. The template is configured with a circular "doughnut" shaped O-ring structure 20 comprising a number of connection element 14, 16, 18. The number of connection elements may vary dependent on desired strength and size of the template 10.

However, the connection elements 14, 16, 18 will normally be assembled as a lattice structure, or the like. A circular O-ring lattice structure will further give better tensile strength and stress to the structure, and improve resistance to torsional forces, then a rectangular structure known from the prior art.

The structure 20 is further equipped with a number of pile guide sleeves 12, in the example in figure 2 with four sleeves 12 and in the example in figures 4 and 5 with three sleeves 12. Thus, the structure 20 can be equipped with a desired number of pile guides sleeves 12, dependent on the configuration of the jacket foundation for the wind turbine. Further, it is also possible to change the configuration of the sleeves, in case changes must be made on site due, or in case of using the template with a another jacket foundation having a different footprint, or another multimember foundation.

The sleeves 12 can thus be releasable connected to and dismounted from the O-ring structure by bolting, welding or any other fastening means, and dismounted by unscrewing, torch cutting, sawing, etc. The connection points for the sleeves on the O-ring structure may constitute respective assembly points 20a. In that respect, a number of connections arms 22 can be used, which may be bolted or welded to the structure 20, and/or a number of connections arms 24 may in addition be mounted to for instance flanges 26 in the assembly points 20a. The connection can thus for instance be made stiff by four diagonal arms (connection arms 22) bolted on each side of the assembly point 20a and two straight arms (connection arms 24) mounted on flanges 26, as shown in figures 6a-6c.

To adjust the sleeve extension, in order to adjust pitch circle diameter PCD of the template, as shown for instance in figure 4 and 5, the connection arms 22, 24 can be shortened or lengthened (by re-fabrication or cut and welded) and extension pieces can be added between the sleeve flanges and the main structure flanges. In an alternative embodiment, the connections arms 22, 24 can be extendable, for instance by using telescopic arms or by other means of extendable arms. In case of extreme extension (PCD over 30m), diagonal arms should be reinforced with diagonal beams in order to extend the lattice structure.

The pile guide sleeves 12 may further be quipped with a leveling system 90, comprising several pressure cylinders 92 arranged to level a lower bed plate 94 on the sleeve 12.

In order to release the template 10 from the piles 70 driven into the seabed and to guide the piles 70 into the pile guide sleeve 12 during the installation process, the pile guide sleeves 12 are preferably equipped with one or more moving guide belts assemblies 40, according the present invention. The guide belt assembly 40 is capable to move from an active pile guide position to an inactive position with no pile guiding effect, thereby releasing the template 10 from the piles 70. As shown in figures 7 to 9 the pile guide assembly 40 comprises a circular belt 42, said belt having a larger diameter then the outside diameter of the sleeve 12. The belt 40 can be moved up and down on the outside of the sleeve 12 by a number of pressure cylinders 46, for instance hydraulic cylinders. The guide belt assembly 40 can be used with any kind of pile guide sleeves, not only the ones disclosed in this specification.

The guide belt 42 is further equipped with a number of guide wedges 44. The innovative guide belt assembly 40 aims to loose the guiding wedges 44 when they are blocked between the sleeve 2 and the pile 70 pressing on. The guide wedges 44 extend into the sleeve 12 through a corresponding number of slits or apertures 48 in the sleeve 12. Figure 10 shows a cross sectional view of the sleeve 12 with the aperture 48 and a wedge 44 inserted in the aperture. The left hand side of the drawing shows the inside surface of the sleeve, and the outside surface of the pile 70 is indicated on the right hand side.

As apparent from figure 10, the guide wedge 44 comprises an elongated main body 50 with an first abutment edge 52 for abutment with the outside surface of the pile 70, and a second abutment edge 58 for abutment with the inside surface of the sleeve 12. The main body 50 of the wedge is preferable narrower towards a distal end 56a, and may also be narrower toward the other end 56b, then the middle part of the main body. The wedge 44 further comprises a heel 54, in where the heel 54 is extending through the slit 48 and is connected to the belt 42. The abutment edge 52, against the pile 70, may have a rounded surface, and the second abutment edge 58, against the inside of the sleeve 12, may also have a rounded surface, thus allowing the wedges 44 to roll against respective surfaces of the pile 70 and sleeve 12.

The pressure cylinders 46 can be individually controlled, in order to move and tilt the belt 42, and thus the guide wedges 44, with respect to the sleeve 12 during said movement of the belt 42, thus forcing it in either a low position in which the guiding is active or an up position in which the belt can freely "follow" the pile with no guiding effect. The belt 42 is preferable not deformable.

Movement of the moving guide belt 42 is shown in figures 1 1 a to 1 1d. In figure 1 1 a the belt 42 is in a lower position, in where the guide wedges 44 acts like passive wedges between the pile and the inside surface of the sleeve 12. The guide belt cylinders 46 can be fitted with rod position feedback so that an operator knows at anytime if the belt is secured in a low position or left free to move in a high position.

When in use (during for instance the first meters of pile drive), the moving guide belt 42 is wedged in a fixed position between the pile 70 and the sleeve wall 12a, where the fitting is tight so that no move is allowed. When not in use (the rest of the time), the moving guide belt 42 is moved up until it reaches a position in which it suddenly gains some freedom of move. The freedom of move may be relatively small, but being sufficient to release the pressure and thus to disengage the template.

An example of moving the guide belt 42 may be as follows. When pulling the belt 42 up, the belt starts rotating around the one guide wedge 44 wedged between the pile and the sleeve. Thanks to the particular design of guide wedges 44, as disclose above, the rotation goes with no friction as the guide wedges rolls on the sleeve wall in the same time as it rolls on the pile wall. In the same time the wedged guide is being rolled out, the pressure cylinders 46 continuously act on the belt 42 to lift it up. At a certain stage, the friction forces can be overcome by the lifting forces and the belt 42 can slide up. Figure 1 1 a shows the belt 42 in a lower position, and figure 1 b shows the belt in an intermediate and tilted position. Figures 1 1 c and 1 1d show the belt 42 in an upper position, free to move with respect the slits 48 and the pile 70.

Guides are amongst the most heavily loaded pieces of the structure. The

compression effort they are prone to withstand can be tremendous. It is thus not desirable to have any mechanical actuator to support this force unless it should be disproportionately powerful. One aim is thus to keep the number of moving parts to a minimum and to preserve the fundamental nature of guides, that is to be

mechanically passive wedges.

According to the invention, the pile guide sleeve 12 can further be equipped with a pile height measuring apparatus 60, as shown in figure 12. The pile height measuring apparatus can be used with any kind of pile guide sleeves, not only the ones disclosed in this specification.

The apparatus 60 is mounted on the outside of the sleeve 12 and comprises a camera 64 and a depth sensor 66 movable with respect to an aperture 12b in a sleeve wall 12a of the sleeve, and in where the camera 64 is arranged to register a marking 70a on the pile 70, and the depth sensor is arranged to register the depth of the camera 64. The camera 64 and the depth sensor 66 are preferably mounted to a piston rod 62a of a pressure cylinder 62, and are thus movable with respect to the aperture 12b in the sleeve wall 12a. The piston rod 62a is movable arranged in a guide rail 68, in order to secure the movement of the rod 62a.

Piles should be individually marked with a visible band 70a to serve as a visible marker easily seen by the operator. By moving the camera 64 up and down, one can visually scan the pile surface over a length of for instance about 1 m, seeking for the marking painted on the piles at a known height. Once the mark is found and the camera is horizontally aligned with this mark, the depth sensors indicates at which depth the camera is, which at the same tells at which depth the pile mark is. It should be noted that the scan for the band 70a, and the alignment of the camera, may be automatically performed by scanning means.

The pile height measuring apparatus may also allow measure of the template level. The template leveling can be checked at any time by retracting all four depth sensors (and cameras) to the zero stroke position of the cylinders supporting them. Then, depth sensors are not used to measure any pile height, but just to measure the exact depth of all four sleeves. When the depths are found equal, the template is leveled. The pressure signals given by the sensors are then recorder and processed to filter out the "noise" of the local pressures variations due to wave. Filtering is mainly done by averaging the signal over the time.

When measuring the relative heights: for either qualifying a correct pile leveling or template leveling, it is necessary that all measurements are done at all locations in the same time. The precaution is required to eliminate all time related deviations among which the sway effect comes first.

X= H2 - H1 Ax±50 mm,

SU=WD - H2 + a A_su ±200 mm The inaccuracy induced on the measure of pile relative height, the only really relevant measurement, is kept to a minimum because of the very few intermediaries involved in the calculation. The only sources of deviation are: - The painted mark position (a)

- Alignment of the camera lens on painted mark

- The absolute pressure calibration of the sensor

- The measure of water pressure

- The averaging of the water pressure

The template 10 may further be equipped with any known means for the installation and retrieval procedure, such as lifting ears, support for HPU, support for surveillance cameras, etc.

Claims

1. Retrievable pre-piling template (10) for offshore wind turbine foundations, comprising a plurality of pile guide sleeves (12) interconnected by connection elements (14, 16, 18), where said pile guides sleeves (12) are arranged to rest on the ocean floor (80) and to receive a pile (70), cha racterised in that

- said connection elements (14, 16, 18) are assembled to form a continuous circular O-ring structure (20), and

- a number of the pile guide sleeves (12) are arranged to be releasable mounted to the structure (20).

2. Pre-piling template (10) of claim 1, cha racterised in that the pile guide sleeves (12) individually are arranged to be mounted to, and dismounted from, a respective selected assembly point (20a) on the structure (20), thereby providing support for a desired number of sleeves (12).

3. Pre-piling template (10) of claim 1, cha racterised in that the sleeves (12) are mounted to the structure (20) in respective assembly point (20a), by a number of connections arms (22) bolted to the structure (20), and/or a number of connections arms (24) mounted on flanges (26).

4. Pre-piling template (10) of claim 3, cha racterised in that the connections arms (22, 24) are exchangeable, or extendable, wherein pitch circle diameter of the template is arranged to be adjusted.

5. Pre-piling template (10) of claim 1, cha racterised in that the pile guide sleeves (12) comprise at least one moving guide belt assembly (40), said guide belt assembly (40) being arranged to move from an active pile guide position to an inactive position with no pile guiding effect, thereby releasing the template (10) from the piles (70).

6. Pre-piling template (10) of claim 5, cha racterised in that the pile guide assembly (40) comprises a circular belt (42) surrounding the sleeve (12), said belt (42) being connected to a number of pressure cylinders (46) for said movement, and the belt (42) is equipped with a number of guide wedges (44) arranged to extend into the sleeve (12) through a corresponding number of slits (48) in the sleeve (12).

7. Pre-piling template (10) of claim 6, cha racterised in that the pressure cylinders (46) are arranged to be individually controlled, in order to move and tilt the belt (42), and thus the guide wedges (44), with respect to the sleeve (12) during said movement of the belt (42).

8. Pre-piling template (10) of claim 6 or 7, characterised in that the guide wedge (44) comprises a elongated main body (50) with an abutment edge (52), said main body (50) being narrower towards a distal end (56a), and the wedge (44) comprises a heel (54), in where the heel (54) is extending through the slit (48) and is connected to the belt (42).

9. Pre-piling template (10) of claim 8, characterised in that the abutment edge (52), against the pile (70), has a rounded surface, and a second abutment edge (58), against the inside of the sleeve (12), has a rounded surface, thus allowing the wedges (44) to roll against respective surfaces of the pile (70) and sleeve (12).

10. Pre-piling template (10) of claim 1, cha racterised in that pile guide sleeve (12) comprises a pile height measuring apparatus (60), said apparatus (60) being mounted on the outside of the sleeve (12) and comprises a camera (64) and a depth sensor (66) movable with respect to an aperture (12b) in a sleeve wall (12a) of the sleeve, and in where the camera (64) is arranged to register a marking (70a) on the pile (70), and the depth sensor is arranged to register the depth of the camera (64).

11. Pre-piling template (10) of claim 10, cha racterised in that the camera (64) and the depth sensor (66) are mounted to a piston rod (62a) of a pressure cylinder (62), and are thus movable with respect to the aperture (12b) in the sleeve wall (12a).

12. Pre-piling template (10) of claim 11, cha racterised in that piston rod (62a) is movable arranged in a guide rail (68).

13. Pre-piling template (10) of claim 1, characterised in that the pile guide sleeve (12) comprises a depth sensor (66), said depth sensor (66) being arranged to measure the level of the template (10).

14. Pre-piling template (10) of claim 13, characterised in that the depth sensors (66) of each pile guide sleeve (12) are being arranged at a predetermined distance from the top of the sleeve (12), wherein the exact depth of all sleeves (12) can be measured.