AU734658B2

AU734658B2 - Device for the implementation of an anchor into the sea bottom

Info

Publication number: AU734658B2
Application number: AU74578/98A
Authority: AU
Inventors: Sigmund Askestad
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 1997-05-21
Filing date: 1998-05-15
Publication date: 2001-06-21
Anticipated expiration: 2018-05-15
Also published as: NO311624B1; CN1203166A; EP0983187B1; EP0983187A1; NO972330D0; DK0983187T3; NO972330L; WO1998052819A1; CA2290564A1; ID24342A; BR9809847A; AU7457898A

Description

Device for the implementation of an anchor into the sea bottom The present invention concerns an invention for lowering an anchor or similar into the sea bed. In particular, the present invention concerns a device for lowering the type of anchor described in the applicant's own Norwegian patent application no.

964139.

The stated Norwegian patent application describes an anchor which comprises a polygon with concave side surfaces and which, in the lowered, "anchored" position, has very great anchoring capacity in relation to its weight.

Anchors of this type can, as described in the application, be lowered into the sea bed as a pile anchor or as a suction anchor. As a suction anchor, the top of the anchor is closed with a lid or similar so that negative pressure relative to the :':"Furroundings can be applied in the cavity space of the anchor in order to pull the e anchor down into the sea bed. One disadvantage of self-sucking anchors is that they iannot be pulled further down into the sea bed than to the top of the anchor (the lid).

.i'Another disadvantage concerning anchors with concave side surfaces is that they *'must be reinforced in order to withstand the internal negative pressure, which also increases the weight.

present invention represents a device for anchors, in particular anchors :consisting of a polygon with concave side surfaces, which makes it possible to pull the anchor below the surface of the sea bed and in connection with which the need I for reinforcement is eliminated, thus avoiding any increase in weight..

*:for reinforcement is eliminated, thus avoiding any increase in weight.

la According to one aspect of this invention there is provided a device including an implementation tool and an anchor for lowering into the sea bed, where the implementation tool can be removed from the anchor, which includes one or more hollow bodies being closed at the top and being preferably cylindrical and which are designed to have negative pressure applied to them and to lower the anchor into the sea bed, wherein the anchor is a polygon and that the implementation tool includes one or more hollow cylindrical bodies each body being designed to be removably fastened inside the anchor or outside the anchor.

*.go The present invention will be described in further detail in the following using examples and with reference to the drawings where: Fig. 1 shows an implementation tool in accordance with the present invention seen from the side and above, Fig. 2 shows an alternative embodiment of an implementation tool in accordance with the present invention, also seen from the side and from above, and Fig. 3 shows, in a sequence of drawings from A to E, how an anchor is installed the sea bed using the implementation tool in accordance with the present invention.

Sg.

*i i*Fig. 4 shows a further developed embodiment of the solution shown in Fig. 2.

Fig. 1 shows, seen from the side and from above respectively, an implementation 1 in the form of a mainly cylindrical body 1 arranged inside a three-sided anchor *...body 2 with an anchor line 18. The cylindrical body is closed at the top but open at bottom and extends expediently from the lower end of the anchor 2 to some ::".distance above this. The body 1 is supported by three brackets 4 which are permanently connected to the anchor at each of its sides and which are arranged to absorb fully or partially the forces which arise in connection with lowering the anchor into the sea bed 28. In addition to or as a replacement for the brackets 4 at the bottom of the anchor 2, brackets 4' may be arranged on the side of the body 1 which are designed to rest on the top of the sides of the anchor and which fully or partially transfer the forces in connection with lowering the anchor into the sea bed.

WO 98/52819 PCT/N098/00148 3 A locking mechanism with a locking hook 5 is designed to fasten the cylinder body 1 to the anchor until the anchor has been lowered into the sea bed or to pull the anchor up again. The locking hook 5 is designed to be twisted out of the locked position (dotted line) to the free position (unbroken line) using, for example, an electrically or hydraulically driven motor 3 via a shaft 6 so that the implementation tool is freed from the anchor and can be pulled up. A pump 7, electrically or hydraulically driven, is arranged on the top of the body 1 in order to pump water out of the body during the lowering operation. The pump 7 and the motor 3 are supplied with power via lines 8, 9.

Fig. 2 shows, seen from the side and from above, an alternative embodiment in which the implementation tool 11 comprises three preferably cylindrical bodies which are interconnected via a three-sided frame structure 12. As in the previous example, the bodies 10 are closed at the top but open at the bottom and are strong enough to withstand the negative pressure and forces which arise while an anchor is lowered into the sea bed.

In the example shown here, the anchor 13 is fastened in, and can be removed from, the frame structure between the bodies 10 by means of a locking mechanism in the form of rotary hooks 14, one at each corner of the frame, which are designed to engage with a locking bracket 15 on the anchor and are released from this when the anchor is in place and the implementation tool is to be pulled up. The rotary hooks 14 may be driven by an electrical or a hydraulic motor (not shown).

While the anchor 13 is lowered, forces are transferred from the implementation tool to the anchor via contact pads 16 on the frame structure 12.

In the example shown here, water is also pumped out of the bodies 10 using a pump 21 via a pipe system 27 with remote-controlled valves 26. The negative pressure in the bodies 10 can be controlled individually using valves 26 so that the direction of the anchor/implementation tool can be controlled during the lowering operation. This WO 98/52819 PCT/N098/00148 4 may be necessary, for example, in cases in which the sea bed conditions are uneven.

Fig. 3 shows a sequence of drawings of how an anchor 2 is installed from a vessel 17 using the implementation tool 1, in accordance with the present invention, which is of the same type as that shown in Fig. 1 in the case shown.

Drawing A in Fig. 3 shows how the implementation tool 1 is lifted into place using a winch device 19, 20 on the vessel 17. The locking device is turned so that the locking hook 5 hooks in under the anchor 2, after which the anchor is lifted and lowered towards the sea bed as shown in drawing B.

As soon as the anchor is in place on the sea bed, negative pressure is applied to the implementation tool using the pump 7 and the anchor is pressed down into the bed as shown in drawing C. After the anchor has been lowered, the locking hook 5 is twisted into the free position so that the implementation tool can be pulled up as shown in drawings D and E.

The present invention, as it is shown in the figures and described in the above, is not limited to the use of one or three cylindrical suction bodies. Both two or more than three such bodies may be used, depending on the design of the anchor. The present invention is not necessarily limited to the lowering of anchors but may also be used to lower piles of various designs.

Fig. 4 shows a further developed embodiment of the invention shown in Fig. 2 in a sequence of three drawings in positions F, G and H.

The frame 12, the suction elements 10, the locking mechanism 14, 15 and the pump and pipe system 26, 27 are the same as shown in Fig. 2. However, in order to be able to lower the anchor 13 further down into the sea bed, a passive jacking mechanism 22, 24 is added.

WO 98/52819 PCT/N098/00148 In the case shown here, the jacking mechanism comprises three jack bars 22 arranged in guides 24. The jack bars may expediently be of rack or sawtooth type and may be locked in the positions required using a locking mechanism 23 in the form of mobile tongues and/or remote-controlled locking wedges The jack bars are expediently in contact with each of the corners of the anchor and will, when the anchor is lowered, absorb and transfer the forces to the frame structure via the locking mechanism 23 with the locking wedges 25. The implementation tool with the jacking mechanism functions as follows: the anchor 13, with the bars 22 in the upper position, is first lowered some distance into the sea bed by water being pumped out of the bodies 10, see drawing F. The locking mechanism 23 is then released and water is pumped into the bodies 10 to lift the frame and the bodies 10 to a level in relation to the bars 22 as shown in drawing G. The locking mechanism is reactivated and water is pumped out of the bodies 10, whereby the anchor is lowered further into the sea bed as shown in drawing H. This operation may be repeated until the anchor has been lowered into the sea bed by a distance equivalent to the length of the bars. The advantage of this solution is that small anchors may be used as the holding force increases with the penetration (depth) of the anchor in the sea bed.

Claims

1. A device including an implementation tool and an anchor for lowering into the sea bed, where the implementation tool can be removed from the anchor, which includes one or more hollow bodies being closed at the top and being preferably cylindrical and which are designed to have negative pressure applied to them and to lower the anchor into the sea bed, wherein the anchor is a polygon and that the implementation tool includes one or more hollow cylindrical bodies each body being designed to be removably fastened inside the anchor or outside the anchor.

2. A device in accordance with claim 1, wherein the body is supported by brackets arranged at the lower end of each of the sides of the anchor and/or that the body is provided with brackets which are designed to rest on the top of the sides of the anchor.

3. A device in accordance with claim 1 or 2, wherein the body is designed to be fastened to, and be removable from, the anchor using a locking device 0 0% with one or more locking hooks which are designed to be moved from a released position to a locked position at which the locking hook extends under the anchor..o

4. A device in accordance with claim 3, wherein the locking hook is driven using a remote-controlled pneumatically or electrically driven motor.

A device in accordance with claim 3, wherein the locking device includes rotary hooks arranged on the frame structure, which rotary hooks are designed to be turned from a released position to a locked position at which they are in contact with a locking bracket on the anchor. 7

6. A device for lowering onto the sea bed substantially as herein before described with reference to any one of the embodiments illustrated in the accompanying drawings. DATED: 18 April 2001 PHILLIPS ORMONDE FITZPATRICK Attorneys for: NORSK HYDRO ASA