Crane vessel

Abstract

 A deck-load barge (10) has a sheerleg crane (11) that is translatable over the deck whilst under loading, with winching units (25, 19) for the sheerleg support tackle (22) and load carrying tackle (16) in fixed positions on deck, and synchronised operation of the winching units to enable the vertical position of the load to be controlled whilst the sheerleg is being translated over the deck.

Description

[0001] This invention relates to a crane vessel.

[0002] In the offshore construction industry today, the trend is for building ever larger structural units for offshore installations, e.g. platform deck modules, and this is creating a demand for crane vessels of ever increasing load handling capacity. Conventional crane vessels which can carry a load on deck are limited in the size of load which they can handle by the capacity of their crane in its slewing mode. For handling heavier loads, more than one crane on a conventional vessel must be used, or else more than one crane vessel. In either case, an additional vessel is needed to transport the load and enable it to be picked up by the cranes. Transferring heavy loads between vessels offshore is to be avoided whereever possible. What is desired, therefore, is a crane vessel having the capacity for handling the sort of heavy loads which can be expected nowadays, as well as the ability for transporting the loads itself, and the proposal is to use a vessel with a sheerleg type of crane.

[0003] Various proposals have been made in the past for equipping a vessel with a sheerleg type of crane. However, these proposals were made at a time when the magnitude of the loads which these cranes were intended to handle were but a small fraction of the loads which require to be handled nowadays. These early proposals, therefore, are not able to provide a realistic practical solution to the problems of providing crane vessels for handling loads of today. For example, a cargo barge having a sheerleg type of crane was proposed in 1930 in GB Patent No. 383730. This barge was intended to carry its cargo in holds below deck. Since the cargo consisted of such loads as construction blocks, or possibly, railway rolling stock, i.e. of perhaps 50 tons, this presented no problem. However, with the sort of single loads of the magnitude which can be expected nowadays, perhaps 30,000 tons, it would be almost impossibly difficult to design a vessel capable in practice of carrying such heavy single loads below its deck. The proposal in GB 383730 is for the sheerleg to be supported by cable and winch from a mast which extends up from the deck of the barge. For a barge working in the calm conditions of a harbour and with relatively light loads, as in the case of the barge of GB 383730, this again presented no problems. However, for handling one of today's monolithic constructions, such as a platform deck module, and at the mercy of the wind and the sea in an offshore location, the mast arrangement of GB 383730 would be totally unsuitable because of the difficulties of making it strong enough to withstand the sheerleg and load forces and the problems of instability of the vessel which the mast would create. GB 383730 proposes mounting its sheerleg on a carriage which is movable over the deck on rails. Since this carriage is in the form of a platform which extends right across the deck, this again makes the barge of GB 383730 an unrealistic practical proposal because it denies the use of any area of the deck covered by the travel of the carriage; even the hatches to the cargo holds would present an obstruction, if not battened down.

[0004] The present invention provides a crane vessel comprising a deck for supporting loads, at least one sheerleg, carriage means pivotally connected to the lower end of the sheerleg to mount the sheerleg on the deck for linear movement in a direction longitudinally of the vessel and for pivotal movement about a horizontal axis extending transversely of the vessel, means supporting the sheerleg at a variable angle relative to the deck, the sheerleg supporting means comprising first cable means extending between the sheerleg and first winch means mounted on the deck in a first fixed position, with the sheerleg extending upwardly and away from said first fixed position on the deck, means for carrying a load by the sheerleg, the load carrying means comprising second winch means mounted on the deck in a second fixed position, pulley means mounted at the upper end of the sheerleg and second cable means having at one end means for attachment to a load and passing over the pulley means to a second end engaged by the second winch means, means for translating the sheerleg carriage means over the deck in said longitudinal direction towards or away from said first fixed position whilst the sheerleg is carrying a load, and means for synchronising operation of the first and second winch means with the sheerleg carriage translating means to enable control of the vertical position of the load whilst the sheerleg is being translated along the deck, the sheerleg comprising at its lower end a pair of transversely spaced apart leg members, and there being respective transversely spaced apart carriage means and carriage translating means for each leg member whereby the arrangement leaves clear an area of the deck for carrying loads without obstructing longitudinal movement of the sheerleg over the deck.

[0005] When the sheerleg is under loading and being translated over the deck at a relatively slow speed it may be possible for an operator to manually operate the first and second winch means to control the vertical position of the load.

[0006] Preferably the sheerleg supporting includes derrick means mounted on the deck between the sheerleg and said first fixed position, which derrick means may conveniently comprise a jib with carriage means mounting the jib for longitudinal movement over the deck, third cable means extending between the jib and the sheerleg, and translating means operable between the jib carriage means and the deck for translating the jib longitudinally along the deck towards or away from the said first fixed position.

[0007] The sheerleg carriage means and the jib carriage means may be connected so that the sheerleg and the jib are translatable in unison.

[0008] The respective carriage means may be integrally formed.

[0009] Either carriage means may comprise a wheeled vehicle, which wheeled vehicle may have wheels running on cooperating rails of the deck. Additionally or alternatively, either carriage means may comprise sliding blocks engageable with a sliding surface of the deck or skidding beams.

[0010] Either translating means may be integral with the carriage means and comprise drive means mounted on the vehicle, or it may comprise pulling means, such as a cable and winch, connected to the vehicle.

[0011] The crane vessel may comprise a plurality of like sheerlegs which are operable in parallel for lifting and/or translating a load.

[0012] The invention further provides a method of handling a load using a crane vessel as defined herein, which method includes the steps of attaching the load to the second cable means, actuating the second winch means to tension the second cable means so as to lift the load into a position in which it is supported beneath the pulley means of the sheerleg, actuating the sheerleg carriage translating means while the sheerleg is under loading to thereby translate the sheerleg and hence the load relative to the deck in a longitundinal direction towards or away from the said first fixed position, and controlling the vertical position of the load by synchronising operation of the first and second winch means with the sheerleg translating means whilst the sheerleg is being translated along the deck.

[0013] By way of example, several embodiments of the invention will now be described with reference to the accompanying drawings, in which:-

Figures 1A and 1B are side views showing an embodiment with sheerleg and jib connected to a common travelling drive unit,

Figures 2A and 2B are side views showing an alternative embodiment with separate travelling drive units for sheerleg and jib,

Figures 3A and 3B are side views showing another alternative embodiment with a non-travelling jib,

Figures 4A and 4B are side views showing a further alternative embodiment without a jib,

Figures 5A and 5B are end views showing two sheerlegs in combined operation,

Figure 6 is an end view showing a single sheerleg in operation,

Figure 7 is a plan view showing the vessel with a load on deck,

Figure 8 is a sectional detail showing a sheerleg travelling carriage,

Figure 9 is a side view of the carriage ofg Figure 8,

Figure 10 is a side view showing an alternative vessel embodiment,

Figure 11 is a side view showing an alternative travelling drive unit for the embodiment of Figures 4A and 4B, and

Figure 12 illustrates diagrammatically a synchronising control system for the sheerleg.

[0014] As seen in Figs. 1A and 1B, lifting apparatus is provided on a crane vessel 10 according to the invention. Here the lifting apparatus comprises a sheerleg 11 which is supported on the deck 12 of the vessel 10 by means of a travelling carriage 13. The sheerleg 11 is pivotally connected to the travelling carriage 13 by a pivot 14 at the lower end of the sheerleg. At the upper end of the sheerleg 11 there is mounted a pulley unit 15. A hoisting cable (or cables) 16 passes over the pulley unit 15 and at one end the hoisting cable has a block 17 for attachment of a load 18, whilst the other end of the hoisting cable is engaged by a winching unit 19. The sheerleg 11 here is supported by means of a jib 20, which is supported on the deck 12 of the vessel 10 by means of another travelling carriage 21, in this embodiment fixedly connected with the other travelling carriage 13, and first and second derrick tackles 22 and 23. The jib 20 is pivotably connected to its travelling carriage 21 by a pivot 24 at the lower end of the jib. The first derrick tackle 22 is connected via suitable pulleys between the sheerleg 11 and jib 20 and its adjustment is controlled by a winching unit 25. The second derrick tackle 23 is connected via suitable pulleys between the jib 20 and a support structure 26 on the deck 12 and its adjustment is controlled by a winching unit 27. The support structure 26 is fixedly anchored on the deck 12 of the vessel 10 and may conveniently be an A-frame. The winching units are also mounted fixedly relative to the deck. Also seen in Figs. 1A and 1B is a storage and workshop facility 28, with power plants and accommodation 29. Here, the two travelling carriages 13 and 21 are wheeled and are arranged to run on rails 30. Alternative arrangements are of course possible, such as sliding blocks engagable with a sliding surface of the vessel for example. Movement of the two travelling carriages 13 and 21 here is effected by a common travelling drive unit 31. The load 18 is attachable to the block 17 using suitable slings 32 and can be lifted off the deck 12 by using the winching unit 19 to tension the hoisting cable 16 urging the load upwardly towards the pulley unit 15. This is seen in Fig. 1A. To handle the load 18, e.g. for setting the load down on an offshore structure, the sheerleg 11 can be translated along the vessel 10 by using the travelling drive unit 31 to drive the sheerleg carriage 13 along the deck rails 30. Handling of a load, particularly a bulky load, is facilitated because the load is translated by moving the sheerleg relative to the deck while it is under loading, which does not necessitate varying the angle of the sheerleg.

[0015] The result of translating the shearleg 11 away from the derrick support structure 26 is seen in Figure 1B.

[0016] Preferably, means is provided to control operation of the hoisting cable winching unit 19 so as to winch in or pay out the cable 16 during translation of the sheerleg carriage 13. This enables the possibility to maintain the load 18 at a prescribed height. Such control means may be by computer. Similar control, conveniently also by computer, is preferably also provided for the jib and derrick tackle winching units 25 and 27. For slow rates of travel of the sheerleg over the deck, it may be possible for an operator to manually operate the winching units to control the height of the load, although an automatic system would be desirable. A synchronising control system is illustrated diagrammatically in Figure 12.

[0017] The lifting apparatus seen in Figures 2A and 2B differs from that seen in Figures 1A and 1B in that separate travelling drive units, 33 and 34 respectively, are provided for the sheerleg carriage 13 and the jib carriage 21.

[0018] The lifting apparatus seen in Figures 3A and 3B is again different and here, the sheerleg carriage 13 has its own travelling drive unit 35, whereas the jib 20 has its lower pivotal end connection 36 in a fixed position on the deck 12 of the vessel 10.

[0019] In Figures 4A and 4B, the lifting apparatus is without a jib. Instead, support for the sheerleg 11 is provided by means of tackle 37 connected between the shearing and the support structure 26 by suitable pulleys. Adjustment of the tackle 37 here is controlled by winching unit 38.

[0020] In Figures 5A and 5B there can be seen liftingapparatus having a pair of sheerlegs 11A and 11B arranged side by side and working in unison with load 18.

[0021] In Figure 6 there is seen lifting apparatus having only one sheerleg 11. Here, four blocks 17 are being used for handling the load 18, but any number of blocks, even only one, may be used.

[0022] Figure 7 shows the deck layout of the lifting apparatus seen in Figs. 5A and 5B. Some features, such as the sheerlegs and jibs, have been omitted. However, there can be seen the two sets of deck rails 30 on which the sheerleg carriages travel. Also seen are the sheerleg winching units 19, the power plant and accommodation 29 and the storage and workshop facility 28. Anchor lines 39 are shown in dashed lines. The anchor lines 39 are installed prior to handling of the load, e.g. if the load is a platform module, for installing or removing the module on or from its support jacket.

[0023] In Figure 8 there is seen a preferred form of travelling carriage 13 for the sheerleg 11. The sheerleg 11 can be seen pivotally connected to the carriage 13 by its pivot 14. The pivot 14 here is in the form of a pin 40 mounted in a bifurcated bracket 41 on the carriage 13. The lower end of the sheerleg 11 is journalled on the pin 40 by a spherical bearing 42. The carriage 13 has side by side wheelsets 43, which run on the deck rails 30 and which are mounted to the carriage via spherical bearings 44.

[0024] In Figure 9 the sheerleg carriage 13 can be seen together with part of its travelling drive unit 31. The carriage 13 is connected to the drive unit 31 by a strut 45. Both the carriage 13 and the drive unit 31 might be arranged to travel along the same deck rails 30. Here it can be seen that the carriage 13 has front and back wheelsets 43. The drive unit might work with a rack and pinion system or a hydraulic gripping system or a power screw system etc. Alternatively, the driving force may be obtained by the system shown in Figure 11 which uses pulling lines 46 and a winching unit 47 on at least one side of the carriage 13.

Figure 10 shows how the lifting apparatus can be provided on different vessels, in this case, a semi-submersible.

Figure 12 shows a typical synchronising control system which may be incorporated to make the operator task easier. The reference symbols in Figure 12 are as follows:

VT :	Travel speed selection
TDC :	Travel drive control unit
TD :	Travel drive
TS :	Travel speed
a :	Boom angle
x :	Boom position from stern
SC :	Synchronisation control unit
BHW :	Boom hoist winch
BHWC :	Boom hoist winch control unit
HW :	Hoist winch
HWC :	Hoist winch control unit
VR :	Rope speed

Claims

1. A crane vessel comprising a deck for supporting loads, at least one sheerleg, carriage means pivotally connected to the lower end of the sheerleg to mount the sheerleg on the deck for linear movement in a direction longitudinally of the vessel and for pivotal movement about a horizontal axis extending transversely of the vessel, means supporting the sheerleg at a variable angle relative to the deck, the sheerleg supporting means comprising first cable means extending between the sheerleg and first winch means mounted on the deck in a first fixed position, with the sheerleg extending upwardly and away from said first fixed position on the deck, means for carrying a load by the sheerleg, the load carrying means comprising second winch means mounted on the deck in a second fixed position, pulley means mounted at the upper end of the sheerleg and second cable means having at one end means for attachment to a load and passing over the pulley means to a second end engaged by the second winch means, means for translating the sheerleg carriage means over the deck in said longitudinal direction towards or away said first fixed position whilst the sheerleg is carrying a load, and means for synchronising operation of the first and second winch means with the sheerleg carriage translating means to enable control of the vertical position of the load whilst the sheerleg is being translated along the deck, the sheerleg comprising at its lower end a pair of transversely spaced apart leg members, and there being respective transversely spaced apart carriage means and carriage translating means for each leg member whereby the arrangement leaves clear an area of the deck for carrying loads without obstructing longitudinal movement of the sheerleg over the deck.

2. A crane vessel as claimed in claim 1 wherein the sheerleg supporting means includes derrick means mounted on the deck between said first fixed position and the sheerleg.

3. A crane vessel as claimed in claim 2 wherein the derrick means comprises a jib with carriage means mounting the jib for longitudinal movement over the deck, third cable means extending between said jib and the sheerleg, and translating means operable between the jib carriage means and the deck for translating the jib longitudinally along the deck towards or away from the said first fixed position.

4. A crane vessel as claimed in claim 3 wherein the sheerleg carriage means and the jib carriage means are connected so that the sheerleg and the jib are translatable in unison.

5. A crane vessel as claimed in claim 4 wherein the respective carriage means are integrally formed.

6. A crane vessel as claimed in any preceding claim wherein the or at least one of the carriage means comprises a wheeled vehicle.

7. A crane vessel as claimed in claim 6 wherein the or at least one of the wheeled vehicles has wheels running on cooperating rails of the deck.

8. A crane vessel as claimed in any of claims 1 to 5 wherein the or at least one of the carriage means comprises sliding blocks engagable with a sliding surface of the deck.

9. A crane vessel as claimed in either of claims 6 and 7 wherein the or at least one of the translating means is integral with the carriage means and comprises drive means mounted on the vehicle.

10. Lifting apparatus as claimed in either of claims 6 and 7 wherein the or at least one of the translating means comprises pulling means connected to the vehicle.

11. A crane vessel as claimed in any preceding claim comprising a plurality of like sheerlegs which are operable in parallel for lifting and/or translating a load.

12. A method of handling a load using a crane vessel as claimed in any preceding claim and including the steps of attaching the load to the second cable means, actuating the second winch means to tension the second cable means so as to lift the load into a position in which it is supported beneath the pulley means of the sheerleg and actuating the sheerleg carriage translating means while the sheerleg is under loading to thereby translate the sheerleg and hence the load relative to the deck in a longitudinal direction towards or away from the said first fixed position, and controlling the vertical position of the load by synchronising operation of the first and second winch means with the sheerleg carriage translating means while the sheerleg is being translated under load.

Drawing