METHOD FOR GUIDING A CABLE OR CONDUIT THROUGH A HOLE IN A WALL AND UNIVERSAL WALL ENTRY SYSTEM FOR PERFORMING THE METHOD

The invention generally relates to a method for guiding a cable or conduit through a hole in a wall and to a universal wall entry system for performing the method.

The invention has for its object to develop a universal guiding method and system for guiding cables or conduits into a hollow housing. In practice there are many situations on land as well as in the waters, in which such a method and system would be advantageous. Some examples are pipelines, tankers and (offshore) wind turbines. With regard to the latter example of offshore wind turbines it is customary practice to provide the mono pile of a wind turbine with a retaining pipe for guiding a marine cable lying on the sea floor upwards into the mono pile of the wind turbine. Generally retaining pipes are known as J-tubes or l-tubes. One example of such a retaining pipe is a telescopic retaining pipe comprising an outer pipe and an inner pipe which can be displaced within the outer pipe. As a result, the height of the end of the cable or conduit above the sea floor can be varied, so that the end is in contact with the sea floor as much as possible. This known retaining pipe is described in the European Patent EP1616377 of the applicant of this invention. The universal wall entry system according to the invention and the method for guiding a cable by using this system provides a cheaper alternative to the known retaining pipes and use thereof.

The method for guiding a cable or conduit through a hole in a wall, comprising the steps of: (a) positioning a guiding element for the cable or conduit adjacent the hole on one side of the wall;

(b) positioning an insert comprising a sealing element in the hole, said insert and sealing element being hollow for passage of the cable or conduit;

(c) positioning a fixating element adjacent the hole on the other side of the wall, said fixating element being hollow for passage of the cable or conduit;

(d) assembling a cable protection string by mutually connecting the guiding element, the insert and the fixating element;

(e) fixating the cable protection string in the hole; and

(f) guiding the cable or conduit through the cable protection string into its final position.

The universal wall entry system for guiding a cable or conduit through a hole in a wall, comprising: (a) a guiding element, which is to be positioned adjacent the hole on one side of the wall;

(b) an insert to be positioned in the hole, said insert being hollow for passage of the cable or conduit;

(c) a sealing element to be positioned around the insert; and (d) a fixating element for the insert, which fixating element is to be positioned adjacent the hole on the other side of the wall, said fixating element being hollow for passage of the insert, wherein the guiding element, the insert, the fixating element and the sealing element are arranged to be mutually connected to form a cable protection string and wherein the insert element and the sealing element are arranged to co act such as to fixate the cable protection string in the hole.

The method and system according to the invention have a number of advantages over the known prior art. For starters the preinstalled retaining pipe can be dispensed with and is replaced by the cable protection string formed by the guiding element, the insert, the fixating element and the sealing element, which will lead to a costs saving. Furthermore the interior of the hollow housing, in this example the mono pile of the wind turbine, is sealed off with a fluid tight seal. This allows the interior to be treated with a biodegradable corrosion inhibitor to prevent corrosion.

Contrary thereto in the prior art to prevent corrosion an anode must be positioned on the retaining pipe, which can now be dispensed with and leads to a further costs savings.

In a preferred embodiment the positioning of the guiding element, insert including sealing element and the fixating element is achieved by attaching the cable protection string to the cable or conduit and pulling the cable or conduit with cable protection string through the hole until the desired positions of the guiding element, the insert, the fixating element and the sealing element are reached. Advantageously, by manoeuvring the cable protection string all elements can be positioned in one go at the same time.

In a practical preferred embodiment by allowing the insert and the sealing element to co act such as to press the sealing element between the insert and the hole the fixating step is achieved with a fluid tight seal.

In a first preferred embodiment of the method according to the invention thereto the insert is shifted relative to the sealing element. In a second, alternative embodiment the sealing element is inflated.

In an elegant embodiment the universal wall entry system according to the invention, the insert comprises two parts having different diameters, the larger diameter being greater than the inner diameter of the sealing element, and the cable protection string comprises adjusting means for drawing the larger diameter part of the insert into the sealing element.

Further advantageous embodiments of the universal wall entry system according to the invention are described in the remaining sub claims.

The invention will now be discussed in more detail with reference to the drawings, in which:

The invention will now be discussed in more detail with reference to the drawings, in which:

Figures 1 , 2, 3, 4 and 6 schematically show a universal wall entry system according to the invention in different positions illustrating the steps of the method according to the invention;

Figure 5 shows a part of the universal wall entry system of figure 4 in more detail partly in cross section;

Figure 7 shows a part of the universal wall entry system of figure 6 in more detail partly in cross section; and

Figure 8 shows the universal wall entry system according to the invention plus cable in its final position.

The same reference numerals designate the same components in the figures.

Figure 1 schematically shows a preferred embodiment of a universal wall entry system 1 according to the invention. In this preferred embodiment the system according to the invention is arranged for guiding a marine cable 100 through a hole in the wall of a mono pile of a wind turbine situated under the sea level. For

illustration purposes only the wall 200 of the mono pile is shown. In the wall 200 a hole 201 is present through which the front part of the universal pile entry system 1 is guided by means of wires 13 and 16.

Figures 2, 3 and 4 show the universal pile entry system 1 in different positions illustrating the steps of the method according to the invention.

The universal pile entry system 1 consists of a cable protection string 2 through which the marine cable 100 is to be guided. The cable protection string 2 is comprised of a guiding element 3, which is to be positioned inside the monopile. An insert 4 is connected to one end of the guiding element 3 by means of a connection element 12. One example of a suitable connection element is a ring of polyurethane. The insert 4 is to be positioned in the hole 201. Around the insert 4 a sealing element 5 is placed. The insert 4 is supported by a fixating element 6, which is to be positioned against the outer side of the wall 200 adjacent the hole 201. The guiding element 3 and the insert 4 are all hollow for passage of the marine cable 100. The fixating element 6 is arranged to accommodate the insert 4.

At the other end of the fixating element 6 a protective device comprising a plurality of pipe elements 11 for the marine cable 100 is attached. Preferably the protective device is the PRO-PIPE designed by the applicant of the present invention and protected by European Patent EP1616377. A cable stopper 14 is used to fixate the pipe elements 11 to the marine cable

100. Applicant provides a suitable cable stopper for this purpose that is arranged to prevent movement of the cable relative to the pipe elements 11 . The known cable stopper consists of a pipe element 1 1 having an inner part of polyurethane that is designed to clamp onto the cable. The known cable stopper is known in the art as the Pro Pipe Cable Stopper and is available in different sizes indicated by numbers, such as Pro_CPS 115500 CS having an inner diameter of 115 mm and a length of 500 mm. It is noted that in the figures only a small amount of pipe elements 11 are shown. In practice the pipe elements 11 form a long pipe.

The universal pile entry system 1 is installed for guiding a marine cable following the steps of the method according to the invention:

Step 1

In the first step the mono pile is prepared. A hole 201 needs to be present in the wall 200. Preferably the hole has an upwards angle of about 45 degrees and is

located above the regular sea floor. A messenger wire 13 is let down from the platform of the wind turbine through the hollow mono pile and extends through the hole 201 in the wall 200 for connection to the marine cable 100.

Step 2

Next the cable protection string 2 is assembled by mutually connecting the guiding element 3, the insert 4 and the fixating element 6. Around the insert 4 the sealing element 5 is present. The cable protection string 2 with all protection equipment has to be assembled on board of a vessel. The marine cable 100 will be pulled through the assembled cable protection string and is preferably connected with a D Chinese fi 23 on the messenger wire 13. Preferably a protective device, such as the above mentioned PRO-PIPE, is attached around the marine cable for connection to the cable protection string 2. A swivel 9 is used to make the connection. Preferably the swivel 9 is rotatable allowing the use of the method and system according to the invention even in situations where in the hole 201 lies close to the sea floor. At the end of the protective device the cable stopper 14 is attached.

Step 3

By pulling the messenger wire 13 the cable plus cable protection string is pulled towards the hole 201 in the wall 200 of the monopile. During pulling the cable protection string is given slack on board of the vessel. During pulling the movements of the cable protection string are monitored, preferably by means of an ROV (Remote Operating Vehicle). Such ROVD s are known in practice and are provide with a ca allowing a diver less operation. The pulling is followed through until the guiding element 3 is positioned inside of the mono pile, the insert 4 is positioned inside the hole 201 and the fixating element 6 is positioned adjacent the hole against the outer side of the wall 200. The fixating element 6 is provided with an abutting face 6A to abut the outside wall. This position is shown in figure 4. Figure 5 shows a part of figure 4 in more detail partly in cross section.

In figure 5 it is shown that the insert 4 has a part 4A and a part 4B having different outer diameters. Part 4A has a larger outer diameter than part 4B.

The outer diameter of part 4A, is larger than the inner diameter of the sealing element 5. The outer diameter of the smaller part 4B is approximately equal to the

inner diameter of the sealing element 5. Adjusting means 7 are provided for adjusting the position of the insert 4 relative to the sealing element 5. The adjusting means 7 comprise two adjusting screws extending in longitudinal direction of part 4B of the insert 4 and the fixating element 6. Around the smaller diameter part 4B a holding element is provided comprising an inner ring 8 that is arranged for surrounding the insert 4 and an outer ring 10 that is arranged for surrounding the inner ring 8. Inner ring 8 comprises two parts. Both inner ring 8 and outer ring 10 comprise screw thread, preferably trapezoid thread, on their cooperating surfaces. The fixating element 6 comprises a recess for accommodating ring 10. The fixating element 6 furthermore comprises screw thread for cooperation with the adjusting screws 7. The adjusting screws 7 are accommodated in the inner ring 8.

Step 4

The next step is directed to fixating the cable protection string 2 in the hole 201. This is achieved by allowing the insert 4 and the sealing element 5 to co act such as to press the sealing element 5 by means of the insert 4 against the hole 201 . By adjusting the screws 7 the larger diameter part 4A is drawn into the sealing element 5 pressing the sealing element 5 against the edges of the hole 201. Suitable energizing tools are available in the art for adjusting screws below sea level. The material of the sealing element 5 is able to flex to a certain extent and will as a consequence be compressed against the edges of the hole 201. Thereby the insert 4 (and thus the cable protection string 2) is secured in position. Furthermore a fluid tight seal of the hole 201 is achieved. This position is shown in figure 6. Figure 7 shows a part of figure 6 in more detail partly in cross section. Different materials can be used for the elements of the cable protection string.

The guiding element 3 preferably is a bend limiter for protecting the marine cable from over bending and thus damaging. Suitable bend limiters are known in the art. Preferably the sealing element 5 is made of a flexible, wear resistant material, such as polyurethane having a relative low hardness value, such as 70 Shore A. The fixating element 6 is made of a wear resistant material, such as polyurethane having a higher hardness value, such as 60 Shore D. The latter is also suitable for the insert 4. Suitable materials for the connection elements, such as the swivel 9 and part of the insert 4, are stainless steel and cast iron.

As an alternative (not shown in the figures) the sealing element may be inflatable. In a preferred embodiment the sealing element comprises one or more bellows that are inflatable by means of fluid.

Step 5

Now the cable protection string 2 is secured in position in the mono pile, the marine cable 100 must be guided through the cable protection string into its final position. This can be achieved by releasing the cable stopper 14 on board of the vessel and pulling the messenger wire 13 upwards until the marine cable 100 has reached its intended position. This final position is shown in figure 8.

Step 6

Finally, when the cable 100 has reached its final in-pile position at the hang- off the cable protective device can be moved into its final position. Thereto the cable stopper must be closed and deployed from the vessel. The cable protective device can now be laid down on the sea floor as close to the mono pile as possible. Thereby it needs to be ensured that the end of the cable protective device is in contact with the sea floor as much as possible. This prevents subsequent damage to the cable protective device or respectively to the cable or the conduit protected within it. This is especially advantageous in situations where in the sea floor around the mono pile has a non flat surface, for instance due to scouring. If necessary the cable protective device can be trenched. The manoeuvring of the cable protective device can be monitored by the ROV as well.

The invention is of course not limited to the described and shown preferred embodiment, but extends to any embodiment which falls within the scope of protection as defined in the claims, as seen in the light of the forgoing description and accompanying drawings.