WO2008148464A1

WO2008148464A1 - Pipelaying and crane vessel

Info

Publication number: WO2008148464A1
Application number: PCT/EP2008/004059
Authority: WO
Inventors: Edoardo Rolla; Roberto Faldini
Original assignee: Saipem S.P.A.
Priority date: 2007-06-05
Filing date: 2008-05-21
Publication date: 2008-12-11
Also published as: GB0710735D0; BRPI0812591A2

Abstract

A pipelaying and crane vessel comprises a revolving crane 3 and a J-lay tower 5 for J-laying a pipeline. The J-lay tower 5 is associated with the crane 3 and revolves with the crane 3 when, during use of the crane, the crane revolves.

Description

Pipelaying and Crane Vessel

Technical Field

This invention relates to a pipelaying and crane vessel. Such a vessel is of particular use in the offshore industry relating to oil and gas production.

Background of the Invention

Amongst the equipment required in the off-shore industry are large cranes that can carry out lifting operations. As a result, it is known to provide heavy lifting crane vessels, which in some cases are semi- submersible vessels.

Another of the tasks that is carried out by certain vessels in the off-shore industry is that of laying pipelines, either by S-laying or by J-laying. J-laying, in which the pipeline is lowered down an upright tower on a vessel and curves round in a single direction to become approximately horizontal along the seabed, is used primarily for laying pipeline in deep water (that is typically deeper than 1000m) . It has been known to provide a vessel that is a heavy lifting crane vessel but which also carries a permanent or detachable J-lay tower for J- laying of pipeline. The vessel is then able to carry out both lifting and pipelaying activies. Examples of such vessels are shown in WO 0005525 and US 6425709. In both these cases, however, the presence of the J-laying facility limits the extent to which the heavy lifting crane is able to rotate.

EP 1265017 describes a vessel which has a non- rotatable lifting frame 3 for carrying out lifting operations over the stern of the vessel. In this case a

J-lay tower is able to be stowed on a deck or lifted by the lifting frame to an operative position adjacent to the lifting frame.

Svπmnary of the Invention

It is an object of the invention to provide an improved pipelaying and crane vessel.

According to the invention there is provided a pipelaying and crane vessel comprising: a revolving crane; and a J-lay tower for J-laying a pipeline, wherein the J-lay tower is associated with the crane and revolves with the crane when, during use of the crane, the crane revolves. By associating the J-lay tower with the crane and arranging for the J-lay tower to revolve when the crane revolves, it becomes possible to avoid the presence of the J-lay tower impeding the operation of the crane. The crane is preferably free to revolve or rotate (in this specification the words "revolve" and "rotate" have the same meaning) through 360 degrees. Because the J-lay tower rotates with the crane, the movement of the crane need not be obstructed by the J-lay tower. Preferably the J-lay tower is an integral part of the structure of the crane. The crane is preferably of a generally conventional design including an A-frame as part of its structure. Preferably the J-lay tower provides another part of the structure of the crane and an upper part of the A-frame is connected to an upper part of the J- lay tower. Preferably the centre of gravity of the J-lay tower is on the opposite side of the axis about which the crane revolves to the free end of a jib of the crane. In that case, the J-lay tower can act as a counterweight and it is possible to reduce, or entirely eliminate, the usual counterweight required for such a crane. In order to simplify the design, the J-lay tower is preferably of fixed inclination, and is preferably substantially vertical.

The J-lay tower preferably includes a loading arm for loading a length of pipe, the loading arm being movable from a substantially horizontal position extending away from the tower to an upright position alongside the tower. The movement of the loading arm may be a pivotal movement about an axis in the region of the base of the J-lay tower. Preferably, when the loading arm is in a substantially horizontal position extending away from the tower, it extends in a direction transverse to a longitudinal axis of the vessel and/or transverse to the direction in which a jib of the crane extends. Preferably, the crane is mounted towards one end of the vessel, and preferably also to one side of a longitudinal centreline of the vessel. In this case, the crane preferably has a position in which a jib of the crane extends along the length of the vessel and the loading arm, when in a substantially horizontal position, extends across the vessel. Such an arrangement facilitates the effective operation of both the crane and the J-lay tower.

The invention may be applied to a wide variety of vessels, including mono hull vessels, but it is preferred that the vessel is a semi-submersible vessel. Preferably the semi-submersible vessel has a pair of longitudinally extending hulls and the crane is positioned over one of the hulls.

The crane preferably has a lifting capacity greater than 2000 metric tonnes and more preferably greater than 4000 metric tonnes.

A recess open on one or more sides, or an opening closed on all sides, may be provided in the vessel for allowing the passage of a pipeline laid during operation of the J-lay tower. - A -

Brief Description of the Drawings

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, of which:

Fig. 1 is a side view of a pipelaying and crane vessel, Fig. 2 is a front end view of the vessel of Fig. 1, and Fig. 3 is a plan view of the vessel of Fig. 1.

Detailed Description of Embodiments

The vessel shown in the drawings is a semi-submersible vessel generally comprising a pair of longitudinal hulls IA, IB, supporting, via four columns 4, a¹ main deck 2 on which are provided a revolving crane 3 and a J-lay tower 5 incorporated in the structure of the crane 3. In Figs. 1 and 2 the line S marks the sea level.

The revolving crane 3 is mounted at one end of the vessel above one of the hulls. In the particular example shown the crane 3 is mounted at the bow of the^" vessel above the hull IA. The crane 3 is a heavy lift crane having a high lifting capability, for example greater than 4000 metric tonnes and is mounted so that it can revolve through an entire revolution about a vertical axis V (Fig. 1). Thus the crane 3 may be referred to as a full slewing crane . In many respects the structure of the revolving crane 3 is conventional: for example, it includes an arm or jib 6, and an A-frame 7 which is inclined upwardly away from the arm 6 to meet, at the top of the A-frame, a vertical structure which in accordance with the invention is the J-lay tower 5. Thus the J-lay tower 5 replaces the vertical structure that would conventionally be provided extending downwardly from the top of the A-frame 7. As shown, for example in Fig. 1, the crane arm or jib 6 extends outwardly from the crane 3 on the opposite side of the axis V to the J-lay tower 5 and thus the J-lay tower 5 is also able to serve as a counterweight for the crane 3. Apart from the fact that the J-lay tower 5 provides the required counterweight for the crane 3, it will be understood that the basic operation of the crane 3 is the same as for a conventional heavy lift revolving crane and the crane arm 6 can be pivoted about its connection to the base of the A-frame to allow the free end of the arm 6 to be raised and lowered, whilst the crane can also be rotated through 360 degrees from the position shown in the drawings during its operation. While the crane 3 is operating the J-lay tower 5 is not used.

The J-lay tower 5 is generally of a construction known per se, and in the example shown, the arrangement is similar to that shown in WO 0005525, the description of which is incorporated herein by reference. As in the case of the arrangement shown in WO 0005525, the J-lay tower 5 includes a pipe loading arm 8 which is pivotally mounted at a pivot 9 to the J-lay tower 5 at its base and is movable, by winding in a cable 13, between a horizontal position shown in Figs. 1 and 2 and a vertical position (not shown) in which the arm 8 lies alongside the J-lay tower 5. When the crane 3 is being used the loading arm 8 is stowed in its vertical position.

As shown in Fig. 3, individual lengths of pipe 10 may be stowed on the deck 2 and may be joined into jointed pipe sections, each including a plurality of lengths of pipe. In the particular example of the invention described herein, the individual pipe lengths are each of 12 m length and three lengths are welded together to form a jointed pipe section (pipe string) of 36 m length at a prefabricating station (not shown) . The jointed pipe sections shown by reference numeral 11 in Fig. 3 are arranged across the vessel in the vicinity of the pipe loading arm 8 on a platform 12 (Fig. 2) . As shown in Fig. 3, a crawler crane 14 may be provided for handling the individual pipe lengths and the jointed pipe sections and a pipe loader with loading arms 15 may be provided for loading one jointed pipe section 11 at a time onto the loading arm 8. As can be seen from Fig. 2, the loading arm 8 is above the main deck 2 at the level of the platform 12 when in its horizontal position and therefore jointed pipe sections must be raised to that level for loading onto the arm 8.

The J-lay tower 5 includes the usual devices employed when J-laying a pipeline from jointed sections of pipe. For example, there is a welding station 16 at the base of the tower for welding a jointed pipe section that has. been lifted to lie alongside the tower onto the end of the pipeline, there is a travelling clamp 17 which is movable vertically along the tower 5 and which is able to grip the pipe section and lower the pipeline with the new pipe section welded thereto, and there is a fixed clamp 18 below the welding station for holding the pipeline while a new jointed pipe section is welded to the top of the pipeline.

In the example of the invention illustrated in the drawings, a portion of the base of the vessel is absent to provide an open region 20 (Fig. 3) immediately below the tower 5 through which the pipeline can pass as it is lowered into the sea. An alternative arrangement would be to move the crane 3 with the tower 5 clear of the end of the vessel so that. the tower 5 projects over the end of the vessel. In this case the platform 12 would also project over the end of the vessel and may be pivotally or detachably connected to the vessel so that, when J-laying is not in progress, the platform can be stowed inboard of the vessel. As will now be understood, when the vessel is used for J-laying, the crane 3 is rotated to the position shown in the drawings and remains in that position. The pipe loading arm 8 is then free to be pivoted between a vertical position alongside the tower and a horizontal position shown in Figs. 2 and 3. A jointed pipe section 11 can be raised from its horizontal position on the platform 12 above the main deck 2 to a vertical position alongside the tower 5, transferred into the tower by appropriate pipe handling systems on the tower and the bottom of the pipe section 11 can be welded at the welding station 16 to the top end of a pipeline being laid. During that welding operation the fixed clamp 18 can hold the pipeline stationary relative to the vessel. After welding, the fixed clamp 18 can be released and the travelling clamp 17 lowered through a distance corresponding to one jointed pipe section 11. The fixed clamp 18 can then be fastened around the pipeline, the travelling clamp 17 raised back to its upper position and a new jointed pipe section 11 brought into the tower by the loading arm 8. Thus, in this mode of operation, the vessel is able to perform J-laying of pipeline. In Figs. 1 and 2 the pipeline is shown by reference numeral 21, extending downwardly from the fixed clamp 18.

In a particular example of the invention, the J-lay tower is especially suitable for laying jointed pipe sections of 36 m length and the top of the J-lay tower is at a height of about 65 to 70 m above the main deck 2. Typically the tower will have a height in the range of 45 to 85 m.

The vessel described above is. able to switch from carrying out heavy lifting operations to J-laying, and vice versa, very guickly and easily. The same ancillary equipment, such as power systems, may be used in both operations. Furthermore the layout of the vessel is well adapted for both sets of operations. It is envisaged that during typical operation of the vessel it would spend the majority^βO to 75 per cent) of its operational time conducting heavy lift operations.

Whilst a particular embodiment of the invention has been described above with reference to the drawings, it will be understood that many modifications may be made to that embodiment and some of those modifications are mentioned below.

The J-lay tower may take any of a wide variety of forms. For example, as described in WO 0005525, a second welding station may be provided partway up the tower. The pipeline may be held in the tower and/or lowered using crawler track tensioners instead of, or as well as, the travelling and fixed clamps. A guide assembly, which may comprise arcs or rings of rollers, may be provided at the bottom of and/or below, the J-lay tower for guiding the pipeline and limiting its curvature as it leaves the tower. Such a guide assembly may be fixed to the tower or fixed to the vessel itself in the open region 20. In the illustrated embodiment, the J-lay tower has a "C" shaped cross-section and is of a lattice design, but it will be understood that the tower may also be of other designs, for example a box-like design. The invention may be employed to J-lay pipeline in which the jointed sections of pipe are of different lengths and/or include a different number of pipe lengths. The jointed sections of pipe may be prefabricated at one or more prefabrication stations on the platform 12, elsewhere on the vessel or on shore. Also, the J-lay tower may be employed to lay pipeline stored on a reel . Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

1. A pipelaying and crane vessel comprising: a revolving crane; and a J-lay tower for J-laying a pipeline, wherein the J-lay tower is associated with the crane and revolves with the crane when, during use of the crane, the crane revolves.

2. A vessel according to claim 1, in which the revolving crane is free to rotate through 360 degrees.

3. A vessel according to claim 1 or 2, in which the J-lay tower is an integral part of the structure of the crane.

4. A vessel according any preceding claim, in which the crane includes an A-frame as part of its structure, the J-lay tower provides another part of the structure of the crane and an upper part of the A-frame is connected to an upper part of the J-lay tower.

5. A vessel according to any preceding claim, in which the centre of gravity of the J-lay tower is on the opposite side of the axis about which the crane revolves to the free end of a jib of the crane.

6. A vessel according to any preceding claim, in which the J-lay tower is vertical.

7. A vessel according to any preceding claim, in which the J-lay tower includes a loading arm for loading a length of pipe, the loading arm being movable from a substantially horizontal position extending away from the tower to an upright position alongside the tower.

8. A vessel according to claim 7, in which the movement of the loading arm is a pivotal movement about an axis in the region of the base of the J-lay tower.

9. A vessel according to claim 7 or 8, in which, when the loading arm is in a substantially horizontal position extending away from the J-lay tower, it extends in a direction transverse to a longitudinal axis of the vessel.

10. A vessel according to any of claims 7 to 9, in which, when the loading arm is in a substantially horizontal position extending away from the tower, it extends in a direction transverse to the direction in which a jib of the crane extends.

11. A vessel according to any preceding claim, in which the crane is mounted towards one end of the vessel.

12. A vessel according to any preceding claim, in which the crane is mounted to one side of a longitudinal centreline of the vessel.

13. A vessel according to claim 12 when dependent upon claim 7, in which the crane has a position in which a jib of the crane extends along the length of the vessel and the loading arm, when in a substantially horizontal position, extends across the vessel.

14. A vessel according to any preceding claim, in which the vessel is a semi-submersible vessel.

15. A vessel according to claim 14, in which the semi- submersible vessel has a pair of longitudinally extending hulls and the crane is positioned over one of the hulls.

16. A vessel according to any preceding claim, in which the crane has a lifting capacity greater than 2000 metric tonnes .

17. A pipelaying and crane vessel substantially as herein described with reference to the accompanying drawings.