Rock installation vessel with a fall pipe

Abstract

The invention relates to a rock installation vessel for installing rocks onto a seabed, wherein the rock installation vessel comprises a hull and a fall pipe that is suspended from the hull, wherein the fall pipe comprises a distal ejection pipe having an ejection pipe outer wall defining an ejection pipe channel having an ejection pipe center line, and that ends in a distal ejection pipe outlet, wherein the ejection pipe is arranged under an inclination angle, wherein the ejection. pipe guides the rocks through the ejection pipe channel towards and through the ejection pipe outlet in an installation direction, wherein the rock installation vessel comprises a water flow generator with a water flow outlet for outputting a water flow, wherein the water flow outlet is arranged. at the ejection pipe to impact rocks passing through the ejection pipe channel.

Description

l P143258NLOO Rock installation vessel with a fall pipe BACKGROUND The invention relates to a rock installation vessel with a fall pipe, and a method for installing rocks onto a seabed. Offshore structures, for example monopiles for offshore wind turbines, are installed in the seabed. The underwater part of the offshore structure that is located above the seabed is affected by scouring from sand, water, and stones due to flow thereof. In order to protect the offshore structures against scouring, rocks are installed onto the seabed at, near or around the offshore structures. The rocks are shipped towards the offshore structure by Ineans of a rock installation. vessel with. a fall pipe. The rocks are installed onto the seabed by means of the fall pipe that extends into the sea towards the seabed. A known fall pipe comprises an inlet above sea level for receiving the rocks, and an outlet that is in operation underwater near the offshore structure for delivering the rocks onto the sea bed. The fall pipe is vertically suspended from the hull of the vessel so that rocks are dumped vertically through the fall pipe. Alternatively, the fall pipe is configured to have an inclined angle so that rocks are delivered in an inclined downwards direction. Rocks fall through the fall pipe under their own weight by gravity against the resistance of the seawater that is present inside the fall pipe. The outlet of the fall pipe is kept spaced apart from the offshore structure at a prescribed safety distance in horizontal direction therefrom. This safety distance is maintained. to prevent allision. of the offshore structure and. the fall pipe, as the vessel may move unexpectedly under the influence of waves, swell or wind. Allision could cause damage to the offshore structure and / or the fall pipe, and, therefore, should be prevented. SUMMARY OF THE INVENTION The rock installation vessel with fall pipe can only operate when. the prescribed. safety distance can. be maintained In. practice, the window of operation. wherein the sea conditions are sufficiently to maintain the safety distance is limited A. disadvantage of the known vessel with fall pipe is, therefore, that there is only a limited window of operation in which the vessel with fall pipe may be put in operation. It is an object of the present invention to provide a vessel with a fall pipe that overcomes at least in part the disadvantage of the conventional vessel with fall pipe. According to a first aspect, the invention relates to a rock installation vessel for installing rocks onto a seabed, wherein the rock installation vessel comprises a hull and a fall pipe that is suspended from the hull, wherein the fall pipe comprises a distal ejection pipe having an ejection pipe outer wall defining an ejection pipe channel having an ejection pipe center line, and that ends in. a distal ejection. pipe outlet, wherein the rock installation vessel has a shipping mode and an installation mode, wherein in the installation mode the ejection pipe is arranged under an inclination angle, wherein. the ejection. pipe guides the rocks through the ejection pipe channel towards and through the ejection pipe outlet in an installation direction, wherein the rock installation vessel comprises a water flow generator for generating a water flow, wherein the water flow generator comprises a water flow outlet for outputting the water flow in a water flow direction and. with a water flow velocity, and wherein the water flow outlet is arranged at the ejection pipe to impact rocks passing through the ejection pipe channel. The rock installation vessel is used to install rocks onto the seabed. Rocks include debris of natural rock material, as well as artificially created rock material such as reef balls. During installing rocks onto the seabed via the fall pipe the water flow generated by the water flow generator impacts the rocks that pass through. the ejection. pipe channel. Impact by the water flow while the rocks are still inside the ejection pipe channel or when the rocks have exit the ejection pipe channel results therein that the rocks are accelerated or diverted in the direction of the water flow. This allows for adjusting the fall direction or the fall velocity of the rocks after they have exit the ejection pipe so that the rocks land further away from the ejection pipe outlet in horizontal direction onto the seabed compared to when the rocks fall passive against the water resistance. The fall direction is for example adjusted in the direction of the offshore structure. As a result, the horizontal direction between the ejection pipe outlet and the offshore structure may be increased during installation. This is advantageous as the window of operation in which the rock installation vessel may be put in operation is increased. In an embodiment the water flow direction has a directional component parallel to the ejection pipe center line and in the installation direction. In an embodiment the water flow direction has a directional component transverse to and towards the ejection pipe center line. In an embodiment the water flow outlet is arranged. at the ejection. pipe outlet. In an embodiment thereof the water flow outlet is arranged. at a lowest portion of the ejection pipe outlet, wherein the lowest portion is the portion of the ejection pipe outlet closest to the seabed when in the installation mode. This allows for impacting the falling rocks from. below, which is advantageous as the rocks may be accelerated or diverted in an upwards or horizontal direction by the water flow. Thereby the rocks may land onto the seabed far away enough to maintain. the safety distance in horizontal direction from the ejection pipe outlet. In an embodiment the water flow outlet is provided outside the ejection pipe channel. In an embodiment the water flow outlet is provided inside the ejection pipe channel. This allows for accelerating or diverting the rocks while the rocks are still inside the ejection pipe channel. This is advantageous as the water flow is not yet affected. by currents of the surrounding seawater. In an embodiment the water flow generator comprises a water pump for generating the water flow, wherein the water flow outlet is in fluid connection with the water pump. Examples of the water pump are a tunnel thruster or an axial flow pump that each output a different type of water flow. The tunnel thruster provides for example a water flow having a high flow rate with a low pressure, thereby providing a mass flow. Alternatively, the axial flow pump provides for example a water flow having a low flow rate with a high pressure. In an embodiment the water flow generator comprises a water flow adjustment mechanism for adjusting the water flow direction of the water flow that is outputted by the water flow outlet. In an embodiment the water flow generator comprises a water flow adjustment mechanism for adjusting the water flow velocity of the water flow that is outputted by the water flow outlet. In an embodiment the fall pipe comprises a transport pipe having a transport pipe outer wall defining a transport pipe channel having a transport pipe center line, wherein the transport pipe is connected in series with the ejection pipe, wherein the transport pipe is configured for guiding the rocks through the transport pipe channel towards and into the ejection pipe channel. In an embodiment the inclination angle is between 30°80°. This is with respect to a horizontal reference. In. an embodiment the rock installation vessel comprises a vessel connector for connecting the hull and the fall pipe to each other. According to a second aspect, the invention provides a method for installing rocks onto a seabed using the rock installation vessel of the first aspect, wherein the method comprises the steps of: guiding rocks through the ejection pipe channel towards and through the ejection pipe outlet, wherein the rocks fall through the ejection pipe channel with a fall velocity; generating a water flow using the water flow generator; and impacting the rocks passing the ejection. pipe channel with the water flow. In an embodiment thereof the rocks are installed onto the seabed at, near or around a subsea offshore structure. The rocks are for example installed around a monopile that is inserted into the seabed or around and between the legs of a jacket. The various aspects and. features described. and shown. in the specification. can. be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which: Figure IA. is a schematic overview of a rock installation vessel with a fall pipe at an offshore construction site; Figure IB is a detailed section of figure IA; Figure 2 is a side view of the fall pipe as shown in figure IA comprising a transport pipe and an ejection pipe; Figures 3A and 3B are a side view and isometric front view of the ejection pipe as shown in figure 2; and Figure 4 is an isometric front view of the ejection pipe of the fall pipe according to another exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION Figure IA. is a schematic overview of a rock installation vessel I floating at an offshore construction site 50 at a sea 4. The offshore construction site 50 includes an offshore structure 10 that is inserted into a seabed 3 of the sea 4. The offshore structure 10 is in this example a Inonopile 10 having a foot 11 that is inserted into the seabed. 3, and. a top 12 that extends above the waterline 51 of the sea 4. Another example of the offshore structure is a jacket with multiple legs on the seabed 3. The rock installation vessel I is floating in the sea 4 near the monopile 10 and comprises a hull 7 with a nonshown bow, a stern 8, and a nonshown cargo hold for rocks, a main cabin 9, a deck I9 with a loading area and a rock Ihandling' installation. for rocks, and. a fall pipe 2 that is suspended from the hull 7. The rock installation vessel I supplies and installs rocks 5 onto the seabed 3 via the fall pipe 2. The monopile IO is protected against scouring by a rock pile 6, of which a part is shown during its build up in figures IA and IB by means of the installed rocks 5. Once the rocks 5 are installed onto the seabed 3 they become part of the seabed 3. The fall pipe 2 is connected. to the hull. 7 by means of a fall pipe connector I4, which is preferably a ball and socket joint so that the fall pipe 2 may be arranged in different positions relative to the hull 7. The rock installation vessel I further comprises za deployment mechanism I5 for deploying the fall pipe 2 relative to the hull 7. The deployment mechanism. I5 comprises in this example an Arframe I6 that is supported by the hull 7 and that extends therefrom, a stay wire I7 that extends between the Arframe I6 and the fall pipe 2, and a cable tackle I8 between the hull 7 and the Arframe I6. An alternative for the Aeframe is using hydraulic cylinders. In the exemplary embodiment of figure IA, the fall pipe 2 is connected to a longitudinal side, i.e. starboard, of the hull 7. Alternatively, the fall pipe 2 may be connected. at the stern 8, or in any other suitable position for installing the rocks 5 around the monopile 10. The rock installation. vessel 1 has a shipping mode and an installation mode. When the rock installation vessel 1 is in the shipping mode, which is not shown in the figures, the fall pipe 2 is retracted and positioned entirely above the waterline 51 and is suspended parallel along the hull 7 or on the deck I9. This is, for example, when the rock installation vessel I ships to the monopile IO, or ships to a subsequent monopile. When the rock installation vessel I is in the installation mode, which is shown in the figures, the fall pipe 2 is suspended from the hull 7 and extends into the sea 4 towards the seabed 3. The part of the fall pipe 2 that is located underwater, thus below the waterline 5I, is filled with sea water. The fall pipe 2 comprises subsequently from the hull 7 towards the seabed 3 in series a funnel I3, a transport pipe 40 and a distal ejection pipe 20. The funnel 13 defines the inlet for rocks into the transport pipe 40. As shown in figure 4, the transport pipe 40 comprises a transport pipe outer wall 45 with a transport pipe inlet 42 and a transport pipe outlet 43, and defines a transport pipe channel 44 having a transport pipe center line T. In this example, the transport pipe 40 comprises multiple transport pipe sections 41 in series that are connected to each other by means of flanges 47. The ejection pipe 20 comprises an ejection pipe outer wall 25 with an ejection pipe inlet 22 and an ejection pipe outlet 23, and defines an ejection pipe channel 24 having an ejection pipe center line E. In this example, the transport pipe center line T and the ejection pipe center line E extend in line with each other. As best shown in figure 2, the ejection pipe inlet 22 is located at an inlet level and the ejection pipe outlet 23 is located at an outlet level under the inlet level. The ejection pipe 20 extends under an inclination angle 0 with respect to a horizontal reference, such as the sea bed 3. Preferably the inclination angle 0 is non vertical so that the inclination angle @ ensures that the ejection pipe inlet 22 and the ejection pipe outlet 23 are spaced apart from each other in the horizontal direction. When in the installation mode, the inclination angle @ is preferably between 30° and 80°. As best shown in figure 3A, the ejection. pipe outlet 23 extends ill a plane transverse 11) the ejection pipe center line E. The ejection pipe outlet 23 is therefore arranged. under an inclination. angle d that is equal to 900 minus the inclination angle 0 of the ejection pipe 20. Thus d = 90° 8. As best shown in figures 1B, 3A and 3B, the fall pipe 2 comprises a water flow generator 30 for generating a water flow 60. The water flow generator 30 has a water pump 31, a water flow pipe 34, and in this example four water flow outlets 35, 36, 37, 38 that each output a water flow 60. The water flow outlets 35, 36, 37, 38 are in this example nozzles. The water pump 31 has a pump inlet 32 and a. pump outlet 33, and. is provided. at the outer circumference of the ejection pipe outer wall 25 whereto it is connected by means of two pump connectors 39. The water pump 31 is powered by a nonshown power supply, and is in this example an axial flow pump. The water flow pipe 34 is in fluid connection with the pump outlet 33 and with each of the water flow outlets 35, 36, 37, 38, and is provided outside the ejection pipe channel 24. The water flow outlets 35, 36, 37, 38 are arranged at the ejection pipe 20, and in this example at or near the lowest portion 26 of the ejection pipe outlet 23, wherein the lowest portion 26 is the portion of the ejection. pipe outlet 23 that is closest towards the seabed 3 in the vertical direction. The water pump 31 is configured for pumping seawater through the water flow pipe 34, through the water flow adjustment mechanism 70, and towards and through the water flow outlets 35, 36, 37, 38. The water flows 60 mix with the surrounding seawater, and impact the rocks 5 passing the ejection pipe channel 24. Each water flow 60 has a water flow velocity and is directed in a water flow direction W1, W2, W3, W4 towards the rocks 5 passing the ejection pipe channel 24. The water flow directions W1, W2, W3, W4 have a first directional component that is parallel to the ejection pipe center line E and. in the first fall direction, and. they have a second directional component that is perpendicular to and towards the ejection pipe center line E. The water flow generator 30 further comprises a water flow adjustment mechanism 70 in the form of a manifold for adjusting the water flow velocities and water flow directions W1, W2, W3, W4 of each of the water flows 60 generated by the water flow generator 30. The water flow adjustment mechanism 70 is arranged at the ejection pipe 20 between the water flow pipe 34 and the water flow outlets 35, 36, 37, 38, and is in fluid connection therewith. The individual water flow directions W1, W2, W3, W4 and. the water flow velocities of the water flows 60 are adjustable IO in dependence on several variables including the inclination angle 0 of the ejection pipe 20, the distance, in horizontal direction, between the ejection pipe outlet 23 and the monopile 10, and the height of the rock pile 6 created so far. Figure 4 shows a second embodiment of the ejection pipe according to the invention. The ejection pipe 120 comprises, except for the ejection pipe outlet and some components of the water flow generator, the same components as the ejection pipe 20 described earlier. Components that are different compared. to the first exemplary embodiment are reintroduced and renumbered in the description and in figure 4. The ejection pipe 120 comprises an ejection pipe outlet 123 that is cutoff in a plane that is not transverse to the ejection pipe center line E of the ejection. pipe 120. The ejection. pipe 120 of the second embodiment as shown 111 figure 4 further differs from the ejection pipe 20 of the first embodiment as shown in figures 13 in that the water flow generator 130 comprises multiple water pumps 131, and multiple water flow outlets 135, 136, 137, 138, 139. The water flow outlets 135, 136, 137, 138, 139 are in this example nozzles. Each water pump 131 has a pump inlet 132 and a pump outlet, and is provided at the outer circumference of the ejection pipe outer wall 25. The water pumps 131 are powered by a nonshown power supply, and are in this example submersible pumps or thrusters that extend parallel to each other. Each water flow outlet 135, 136, 137, 138, 139 is in fluid connection with. the pump outlet of a different water pump 131. The water flow outlets 135, 136, 137, 138, 139 are arranged at the ejection pipe 120, and in this example at or near the lowest portion 126 of the ejection pipe outlet 123, wherein the lowest portion 126 is the portion of the ejection pipe outlet 123 that is closest towards the seabed. 3 in the vertical direction. Each water pumps 131 is configured for pumping seawater towards and through the water flow outlet II I35, I36, I37, I38, I39 that is in fluid connection therewith. Each water flow outlet I35, I36, I37, I38, I39 outputs a water flow that has a waterflow velocity and that is directed in a water flow direction WI, W2, W3, W4, W5 towards the rocks passing the ejection pipe channel 24. The water flow directions WI, W2, W3, W4, W5 have a first directional component that is parallel to the ejection pipe center line E and in the first fall direction. The water flow directions may be adjusted by the water flow adjustment mechanism 70 to have a second directional component that is perpendicular to and towards the ejection pipe center line E. The working principle of the rock installation vessel 1 is described by reference to the first embodiment. The rocks 5 that are installed onto the seabed 3 via the fall pipe 2 have dimensions so that the rocks 5 fit inside the transport pipe channel 44 and the ejection pipe channel 24 of the fall pipe 2. Preferably, :multiple rocks 5 fit within the diameters of the transport pipe channel 44 and the ejection pipe channel 24 aside each other without getting stuck therein. When. in the installation. mode, the rocks 5 are fed by the rock handling installation on the deck 19 into the funnel 13. The rocks 5 are subsequently guided through the transport pipe channel 44, through the ejection pipe channel 24, and through the ejection pipe outlet 23. The rocks 5 fall through the fall pipe 2 under the influence of gravity. Falling also includes sliding of the rocks 5 through the fall pipe 2 along inclined sections of the fall pipe 2. As the fall pipe 2 is located mainly below the waterline 5I, the rocks 5 experience resistance of the water after crossing the waterline 51. The submerged rocks 5 fall through the ejection pipe channel 24 with a first fall velocity and. in a first fall direction. RI that is parallel to the ejection pipe center line E. In the meantime, the water flow generator 30 I2 generates the water flows 60 that are outputted. by the water flow outlets 35, 36, 37, 38 in the water flow directions W1, W2, W3, W4. The water flow velocity of the water flows 60 is preferably higher than. the first fall velocity. When the rocks 5 have exit the ejection pipe 20 through the ejection pipe outlet 23, the rocks 5 fall in a second fall direction R2 with a second fall velocity towards the seabed 3. The water flows 60 impact the rocks 5 that passed through the ejection pipe channel 24. Impacting occurs in a water flow impact area 80 (shown in figure 1B), wherein impacting means that the water flows 60 accelerate or divert the rocks 5. The rocks 5 are accelerated or diverted by the water flows 60, preferably towards the monopile 10. As the water flows 60 accelerate or divert the falling rocks 5, the water flows 60 determine the second fall direction R2 of the rocks 5. The water flows 60 results therein that the rocks 5 land closer towards the monopile 10 in the horizontal direction, compared to when no water flow is generated by the water flow generator 30. The water flows 60 thus adjusts the position. where the rocks 5 that are installed via the fall pipe 2 land onto the seabed. 3. When. the water pump 31 of the water flow generator 30 is turned off, and therefore no water flow 60 is generated, the rocks 5 land in a different landing area 81 which is closer to or directed below the ejection pipe outlet 23 in horizontal direction. Alternatively, the water flow outlets 35, 36, 37, 38 are provided. inside the ejection. pipe channel 24, so that they output the water flows 60 inside the ejection pipe channel 24 ill a direction towards the ejection pipe outlet 23. In this example, the rocks 5 are accelerated by the water flows while still being inside the ejection pipe channel 24. This acceleration of the rocks 5 as well results therein. that the rocks 5 land. onto the seabed. 3 closer towards the monopile IO, compared to when no water flow is generated by the water flow generator 30. I3 It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will 5 be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention. l4

Claims

l. Stone installation vessel for installing of stones on a seabed, whereby the stone installation vessel comprises a hull and a downpipe that is suspended from the torso, whereby the fall tube has a distal includes a discharge tube with a discharge tube outer wall that a defines efferent duct canal with an efferent duct centerline, and which ends in a distal discharge duct outlet, whereby the stone installation ship a sailing mode and an installation mode has, where in installation mode the discharge pipe is arranged at an angle of inclination, whereby the discharge pipe the guides stones through the discharge tube channel to and through the discharge pipe outlet in an installation direction, where the stone installation vessel includes a water flow generator for the generation of a water flow, whereby the water flow generator includes a water flow outlet for the releasing the water flow in a direction of water flow and with a water flow velocity, and where the water flow outlet is attached to the discharge pipe to remove stones that pass through the to influence or touch the passing of the efferent duct.

2. Stone installation vessel according to one of the previous conclusions, where the water flow direction a direction component has parallel to the discharge pipe centerline and in the installation direction.

3. Stone installation vessel according to one of the previous conclusions, where the water flow direction a directional component has perpendicular to and towards the excretory duct centerline.

4. Stone installation vessel according to one of the previous conclusions, where the water flow outlet is attached to the discharge pipe outlet.

5. Stone installation vessel according to claim 4, where the water flow outlet is mounted on a lower part of the discharge pipe outlet, where the lower part part the part is of the discharge pipe outlet that the is closest to the seabed when in installation mode.

6. stone installation vessel according to one of the previous conclusions, where the water flow outlet is provided outside the discharge tube channel.

7. stone installation ship according to one of the previous conclusions, where the water flow outlet is provided within the discharge tube channel.

8. stone installation ship according to one of the previous conclusions, where the water flow generator a water pump includes for generating the water flow, where the water flow outlet is in fluid connection with the water pump.

9. stone installation ship according to one of the previous conclusions, where the water flow generator a water flow adjustment mechanism includes for adjusting the water flow direction of the water flow that has been released through the water flow outlet.

10. Stone installation vessel according to one of the previous conclusions, where the water flow generator a water flow adjustment mechanism includes for adjusting the water flow velocity of the delivered water stream through the water flow outlet. ll. stone installation ship according to one of the previous conclusions, where the drop tube is a transport tube comprises with a transport tube outer wall that a transport tube channel defines with a transport tube centerline, where the transport tube is in series connected to the discharge pipe, where the transport pipe is configured for guiding the stones by the transport tube channel to and into the discharge tube channel. l2. stone installation ship according to one of the previous conclusions, where the angle of inclination between 30° 800 is. l3. stone installation ship according to one of the previous conclusions, whereby the stone installation vessel a ship connector includes for connecting the fuselage and the downtube.

14. Procedure for installing stones on a seabed using the stone installation vessel according to one of the preceding conclusions, whereby the method includes the following steps: guiding stones through the discharge tube channel to and through the discharge pipe outlet, whereby the stones by fall into the ejection tube at a falling speed; generating a water flow using of the water flow generator; and influencing or touching the with the water flow stones passing through the discharge tube channel.

15. Method according to conclusion l4, whereby the stones are installed on the seabed at, near, or around an underwater, offshore structure. oooooooo

Images