WO2006073316A1

WO2006073316A1 - Safe anchor handling system

Info

Publication number: WO2006073316A1
Application number: PCT/NO2006/000008
Authority: WO
Inventors: Torstein Gjerde; Trond Myklebust; Øyvind Gjerde KAMSVÅG
Original assignee: Odim Asa; Bourbon Offshore Norway As; Ulstein Design As
Priority date: 2005-01-07
Filing date: 2006-01-09
Publication date: 2006-07-13
Also published as: NO20050106D0

Abstract

A method putting out an anchor from a deck of a vessel and for taking onboard an anchor from the sea, wherein a displaceable resting surface for supporting the anchor is provided. The resting surface may be displaced from a substantially horizontal position to a substantially vertical position to simplify and to avoid damage on vessel and equipment during anchor handling operations. A device for realization of the method is also described.

Description

P2490PC00

SAFE ANCHOR HANDLING SYSTEM Technical field

The present invention relates to a method and device for safe handling of a heavy load or cargo that is taken up from below sea level to the deck of a vessel, or put out from the deck to the sea, respectively. More specifically, the present invention relates to a method and a device for anchor handling, where special care is taken for the security and equipment.

Background art

Floating offshore installation for the oil and gas exploration, development of oil and gas fields and exploration of oil and gas, are kept in position by means of anchors. The anchors are placed at the sea bed, moved and taken up by means of supply ships and anchor handling ships.

The anchors are lifted and lowered by means of wires operated by winches at the deck level of the supply or anchor handling ship. The wire used to lift an anchor is normally operated by a winch placed close to the forward end of the cargo deck. The wire runs over the deck and over a redirecting body or roller at the rear end of the cargo deck. The critical operations in anchor handling are bringing the anchor from the sea on board the ship, and bringing the anchor from the ship's deck out in the sea, respectively. During this phase the anchor, the wire and the are exposed for greater forces than during other parts of the operation.

The result of this imbalance is that the wire has to be dimensioned for the force that is necessary during the above mentioned critical operations. Additionally, there is a danger for the wire to break. A wire that breaks during this kind of stress represents a great danger for the ship, equipment and personnel.

This problem has not been adequately addressed. Accordingly there is a need for a method and a device for avoiding the problems described above connected to the operations of taking the anchor onboard a ship and bringing the anchor from the deck of a ship out into the sea. Summary of the invention

According to a first aspect, the present invention relates to a method for putting an anchor out an anchor from a deck of a vessel into the sea, the anchor being connected to a winch by means of a wire, rope or chain, the method comprising the steps of: - placing the anchor on a displaceable resting surface being in an inboard position where the resting surface is in a substantially horizontal position or having an angle of less than 10° from the horizontal position, keeping the anchor at the resting surface by means of the winch during displacement of the resting surface from the inboard position to an outboard position where the resting surface is in a substantially vertical position or having an angle of less than 20 ° from the vertical position, and lowering the anchor by means of the winch.

According to a second aspect, the present invention relates to a method for taking an anchor onboard a vessel from the sea, the anchor being connected to, and pulled in by a winch by means of a wire, rope or chain, the method comprising the steps of: providing a displaceable resting surface in an outboard position, where the resting surface is in a substantially vertical position or having an angle less than 20 ° from the vertical position, pulling in the anchor by means of the winch until the anchor towards said resting surface, keeping the anchor at the resting surface by means often winch during displacement of the resting surface from the outboard position to an inboard position, where the resting surface is in a substantially horizontal position or having an angle of less than 10° from the horizontal position.

The method may additionally comprise the additional step of moving the anchor from the resting surface onto a deck of the vessel. This step may be preferred if the anchor is to be transported to another location or to be exchanged with another anchor.

The resting surface being in its inboard position has preferably an angle of about 0 to 10°, e.g. such as about 5 °, from the horizontal position, declining towards the deck of the vessel. The resting surface may in the inboard position be- at level with the deck of the vessel. It might, however, be preferred to raise the aft part of the ram slightly, e.g. up to 10°, more preferred 10 ° relative to the front part of the ram, to stabilize the anchor onboard the vessel: additionally, the raised aft part of the ram may make it easier to handle the anchor at the ram and from the ram to the deck.

The ream being in its outboard position, has preferably an angle of about 0 to 20°, e.g. such as about 10 °, from the vertical position, the resting surface inclining out from the vessel from the bottom to the top thereof. This angle makes it easier to hoist the anchor up to the level of the ram without the anchor being hindered by the ram or the stern of the ship during the hoisting operation.

According to a thirds aspect the present invention relates to a device for handling of an anchor during the operations of putting out an anchor from a vessel into the sea, or taking the anchor onboard the vessel from the sea, respectively, wherein the device comprises a displaceable ram connected to the vessel, the ram being displaceable between to positions, an inboard position where a resting surface of the ram is in a substantially horizontal position or having an angle of less than 10° from the horizontal position substantially horizontal, and an outboard position where the resting surface is in a substantially vertical position or having an angle less than 20 ° from the vertical position.

It is preferred that the resting surface at the end adjacent to the deck, is substantially in the same level as a deck of the vessel, when the ram is in its first position. This makes it easier to relocate an anchor, or any other cargo, from the cargo deck to the ram and vice versa.

It is preferred that a first roller having a substantially horizontal axis of rotation, is provided at one end of the ram adjacent to the deck of the vessel. The roller is used for supporting wires, chains, ropes etc. and avoid or reduce the friction between the wires, ropes and chains and the ram. It is also preferred that second roller having an axis of rotation substantially parallel to the first roller, where the second roller is arranged at the end of the ram opposite to the first roller. This second roller has the same function as the first roller. Additionally, this roller is at the stern of the vessel when the ram is in its resting position. Accordingly, it may be used as a traditional stern rollen.

Preferably, the ram is displaced from said first position to said second position by means of hydraulic actuators. Hydraulic actuators are the most reliable and simple means for displacing the ram.

Brief description of the figures

Figure 1 is a perspective drawing of an anchor handling vessel including an anchor handling system according to the present invention, Figure 2 is a bird's view of the after-deck of the anchor handling vessel of figure 1, wherein the anchor handling system is in a parking position,

Figure 3 is a section view along A-A in figure 2,

Figure 4 is a bird's view of the after-deck of the anchor handling vessel of figure 1, wherein the anchor handling system is in an inboard position, Figure 5 is a section view along B-B in figure 4,

Figure 6 is a bird's view of the after-deck of the anchor handling vessel of figure 1, wherein the anchor handling system is in an outboard position,

Figure 7 is a section view along C-C in figure 6, and

Figure 8 is a perspective drawing of the after-deck wherein the anchor handling system is in the outboard position.

Detailed description of the invention

Figure 1 is a perspective drawing of the aft part of an anchor handling vessel 1, being equipped with an anchor handling system according the present invention. The vessel 1 has an open cargo deck 2, being limited at both sides by cargo rails 3. A ram 4 is provided at the stern part of the cargo deck 2. Cranes 5, are provided for different lifting operations. Additionally, a number of not shown winches and drums for wires, cables, ropes etc. are provided, normally in the front part of the cargo deck 2, in connection with a superstructure 6 in the bow part of the vessel. The ram 4 is provided with a stern roller 10 and a forward roller 11, at the aft and front parts of the ram 4, respectively. Both rollers are normally split in two rollers both covering half the width of the ram. The rollers 10, 11 have a rim 18 at both ends, intended to keep wires, ropes etc. from sliding from one of the split rollers to the other during operations. A resting surface 8 bridging the gap between the rollers 10, 11, is provided at the ram. The resting surface is a surface substantially flat surface intended for supporting the anchor at the ram.

The ram is also provided with side supports 12, 12', that are fixed to the ram 6 to make effective opening in the stern wider than the width of the ram. The ram 6 and the side supports 12, 12' are arranged in a recess 13 in the stern part of the cargo deck. The bottom of the recess 13 constitutes a support 14 for the ram 3, and is preferably inclined towards the sea.

A pair of arms 15 are close to a first end thereof, rotary connected to corresponding brackets 16 that are fastened to the support 14. The axis of rotation for the rotary connection between the arms 15 and the brackets 16 are substantially horizontal and perpendicular to the length axis of the vessel.

Close to the opposite or second end, of the arms 15, the arms are rotary connected to the ram 4. Preferably, the axis of rotation for the rotary connection 7 between the arms and the ram is substantially parallel to the axis of rotation between the arms and the brackets 16. Additionally, the axis of rotation between the arms and the ram substantially coincides with the axis of rotation of the stern roller 10.

In the resting position illustrated in figures 2 and 3, the arms 15 are locked to locking brackets 18, 18' by means of posterior locking bolts operated by hydraulic locking actuators 19. The locking bolts interact with corresponding posterior locking grooves 20 in the arms 15. Additionally, the ram is locked to the brackets 16 by means of anterior locking bolts that are operated by means of hydraulic actuators 21, connected to the brackets 16. The anterior locking bolts interact with anterior locking groves 22 in the ram. The stern ram is operated by means of two hydraulic actuators 17 connected to the support 14 and to the ram. Unlocking the posterior locking bolts and actuating the actuators 17 results in a rotation of the ram about the anterior locking bolts to lift the anterior end of the ram including the stern roller into an inboard position, as illustrated in figures 4 and 5. In the inboard the top of the front roller is approximately at the same level as the cargo deck. The aft end of the ram including the stern roller is lifted so high that the flat top surface has an acute angle towards the cargo deck. In figure 5, the angle towards the cargo deck is about 5°. Preferably said angle is between -10 and +10°, i.e. slightly inclined from the stern roller to slightly incline towards the stern roller. More preferably the angle is between 0 and 5°, i.e. the stern roller at the same level or slightly higher than the cargo deck.

In the inboard position an anchor, or any other object, may be placed on the ram, or be removed from the ram, by being moved into the deck or by being moved from the deck, respectively.

From the inboard position, the ram may again be rotated into the resting position, before the anterior locking bolt again is brought into interaction with the anterior locking groves in the ram.

When the ram is in the resting position, the posterior locking bolts may be deactivated to go out of interaction with the anterior locking groves. Actuating the actuators when the posterior locking bolts are not activated, results in the ram rotating about the rotary connection 7, thus lifting the posterior end of the ram and the front roller to an outboard position, hi the outboard position the top surface of the ram is substantially vertical or is slightly outboard angled, e.g 0 to 20° from the vertical position.

To put out an anchor from the cargo deck into the sea, the ram is firstly in the inboard position. If the anchor is not at the resting surface 8 of the ram, the anchor is moved onto the ram. The wire holding the anchor is then tightened by means of a winch before the ram is tilted from its inboard position to the outboard position as described above. The tension in the wire is adjusted during this operation to keep the anchor at the ram. When the ram is in the outboard position, the anchor may be lowered into the sea and towards the sea bed in a traditional manner. After the anchor has left and is clear of the ram, the ram may again be tilted from the outboard position to the resting position for the rest of the procedure.

To take an anchor onboard the vessel, the anchor is hoisted up from the sea bed by means of the winch in a traditional manner, until it is a few meters below sea level. The ram is then tilted to the outboard position. When the ram is in the outboard position, the anchor is hoisted up towards the resting surface 8, until the anchor is at the same level as the ram. The anchor is then held at the ram by means of the winch keeping the tension in the wire, while the ram is tilted firstly to the resting position and then to the inboard position. If necessary, the anchor may then be moved onto the deck of the vessel.

During the mentioned operations, the anchor is also connected to a chain in addition to one or more ropes. The handling of the ropes and chain is not described as it is not important for the understanding of the present invention. Additionally, the skilled man in the art will understand which adjustments that may be necessary for the handling of the chain and ropes in using the present device.

The skilled man in the art will understand the illustrated embodiment is only an example of a possible embodiment of the present invention and that several other embodiments are possible without leaving the scope of the protection as defined in the attached claims. The present embodiment is, however, the preferred embodiment as the use of the arms 15 having two connection points each to the support in the hull, allows the realization of a strong, compact and reliable solution having a relatively low centre of gravity.

Claims

1.

A method for putting an anchor out an anchor from a deck of a vessel into the sea, the anchor being connected to a winch by means of a wire, rope or chain, the method comprising the steps of: placing the anchor on a displaceable resting surface being in an inboard position where the resting surface is in a substantially horizontal position or having an angle of less than 10° from the horizontal position, keeping the anchor at the resting surface by means of the winch during displacement of the resting surface from the inboard position to an outboard position where the resting surface is in a substantially vertical position or having an angle of less than 20 ° from the vertical position, and lowering the anchor by means of the winch.

2.

A method for taking an anchor onboard a vessel from the sea, the anchor being connected to, and pulled in by a winch by means of a wire, rope or chain, the method comprising the steps of: - providing a displaceable resting surface in an outboard position, where the resting surface is in a substantially vertical position or having an angle less than 20 ° from the vertical position, pulling in the anchor by means of the which until the anchor towards said resting surface, - keeping the anchor at the resting surface by means often winch during displacement of the resting surface from the outboard position to an inboard position, where the resting surface is in a substantially horizontal position or having an angle of less than 10° from the horizontal position.

3.

The method according to claim 2, the method comprising the additional step of moving the anchor from the resting surface onto a deck of the vessel.

4.

The method of claim 1 or 2, wherein resting surface being in its inboard position has an angle of about 0 to 10°, e.g. such as about 5 °, from the horizontal position, declining towards the deck of the vessel.

5.

The method of claim 1 or 2, wherein resting surface being in its outboard position has an angle of about 0 to 20°, e.g. such as about 10 °, from the vertical position, the resting surface inclining out from the vessel from the bottom to the top thereof.

6.

A device for handling of an anchor during the operations of putting out an anchor from a vessel into the sea, or taking the anchor onboard the vessel from the sea, respectively, wherein the device comprises a displaceable ram connected to the vessel, the ram being displaceable between to positions, an inboard position where a resting surface of the ram is in a substantially horizontal position or having an angle of less than 10° from the horizontal position substantially horizontal, and an outboard position where the resting surface is in a substantially vertical position or having an angle less than 20 ° from the vertical position.

7.

The device according to claim 6, wherein the resting surface at the end adjacent to the deck, is substantially in the same level as a deck of the vessel, when the ram is in its first position.

8.

The device according to claim 6 or 7, wherein a first roller having a substantially horizontal axis of rotation, is provided at one end of the ram adjacent to the deck of the vessel.

9.

The device according to claim 8, wherein a second roller having an axis of rotation substantially parallel to the first roller, where the second roller is arranged at the end of the ram opposite to the first roller.

10.

The device according to any of the claims 6 to 9, wherein the ram is displaced from said first position to said second position by means of hydraulic actuators.