SE422670B - Cableway between offshore platform and supply vessel - Google Patents

Abstract

In order to facilitate transports between a supply vessel 15 and an offshore platform 10 and eliminate the risks associated with handling by means of a hoisting crane 12, a cableway 14 is used in which a section 21 of supporting cable is held stretched essentially parallel with the deck 16 of the vessel between transverse trestle constructions 18, 19 placed on the front edge and back edge respectively of the deck at some height above the uppermost cargo level. The crew of the vessel can then under tolerable working conditions moor the freight parcel 20 to the hoisting gear 22 of the cableway. The cable can be constituted by a single, crude wire or hawser, supporting a travelling carriage 22a which is displaced along the cable in any preferred known manner. Alternatively, the cable can be constituted by a multiple- shear tackle 14a, in which a hoisting gear 22b is borne by first wire parts 34 running out towards the platform, whilst a return part 38 from the platform is fixed to the vessel. The hoisting gear 22a is hauled up by the vessel being moved away from the platform, as wire is simultaneously fed out from a winch 31. <IMAGE>

Description

8006303-5 2 is provided with guide wheels for the cable, and the bending constructions are otherwise arranged so that a portion of the cable, between them, is kept substantially parallel to the load deck and at a distance above this exceeding the maximum calculated load height. The crew can then always work with the hoist hook in the correct position over the current package, and need-; vez * is not bothered by the hook moving over large areas of the deck which is the case when the platform crane is used.

The operation of the hoist hook takes place via the crew and not via the crane operator, who is located far from the supply vessel.

The steering in both buoy structures is preferably displaceable in the transverse direction of the vessel.

The cable can consist of a single strong wire or rope, one of the trolleys supported by the same being provided with wheel arrangements which allow passage past the aft steering wheels. Alternatively, the cable may consist of a multi-cut hoist, where the cargo lifter is fixedly mounted on the outgoing part of the supply vessel, while a return part of the wire end is attached to the vessel.

The invention will be described below with reference to the accompanying drawings, in which Fig. 1 schematically illustrates a cableway according to the invention, Fig. 2 shows a supply vessel equipped according to the invention, Fig. 3 is a plan view of the ship's deck (somewhat schematic) Fig. 4 shows a trolley design, Fig. 5 shows a modification, where the cable consists of a multi-cut hoist and Fig. 6 shows a plan view of the hoist. In Fig. 1, an offshore platform of any kind is denoted by 10. It can be a drilling rig or a production or housing platform, which rests on legs 11, which either reach down to the seabed, or rest on pontoons, which are submerged so deep that the platform is not affected by wave movements. In the latter case, the platform is anchored.

Of interest for the invention is that the platform 8006303-5 is equipped with a jib crane 12 and a boom post 13 or corresponding support structure, where one end of a cable ïü can be attached at a height suitable for receiving goods.

A supply boat, which can be of any known type, is denoted by 15, and is provided with a stern out available cargo deck 16. The vessel may also be equipped for transport of liquid cargo, water, fuel oil, so-called mud o.d. - which is transmitted in the usual way via hose line.

The cable 14 is conveniently stored during voyages on board the vessel 15, and is discharged at transport times.

The crane's 12 load hook - 17, stretched position - is lowered to a suitable height above the ship's deck and the end of the cable is fastened. This is the only time when the crew on the ship needs to catch a cargo hook from the platform and attach it to any object on the ship.

The cable 14 is attached to the boom pile IB and the vessel moves away from the platform so that the cable is kept stretched at a suitable slope. The vessel is - see also Fig. 2 - provided with a transverse trestle structure 18, 19 at the leading edge resp. aft edge of the cargo deck 16.

The load to be handled can be of varying nature, but is illustrated here by unit containers 20, which are stacked on top of each other in two layers. It can, of course, alternatively be a matter of bundles of pipes or other goods, but the handling will in principle be the same.

The boom structures 18, 19 are so high that there is a space of about 2 meters between the uppermost cargo layer and the portion 21 of the cable 1a which extends between the boom structures, substantially parallel to the ship's deck.

A lifting device 22a works on the cable, which can be designed in different ways. Since the cable is always kept in a certain position above the deck, there will be no large movements at the hoist hook, and it will be easy for the crew to attach it to the selected package 20. The buck constructions 18, 19 are provided with guide means 23, 24 for the cable, and these are, see Fig. 3, mounted on the bow structures so that they can be displaced in the transverse direction of the ship. The lifting device 22a can easily be moved along the cable to the desired position, and by lateral displacement of the guide means 23, 24, the lifting device can be moved exactly over the desired package.

The cable car, i.e. The transport arrangement between ship and platform can be designed in different ways. According to Fig. 3, the cable is a coarse wire or cable. The guide members 23, 2ü are then suitably block discs, which are moved laterally by means of some suitable mechanism.

The lifting device 22a (Fig. H) then comprises a trolley 36, which carries a hoist 25 driven by an electric motor. There is some difficulty in getting the trolley past the outer guide member 2Ä, but the upper edge 26 of the trolley can be shaped so that it momentarily presses down the cable from the block disc, while it itself is guided by it. There are, for example at mountain railways, suspension devices in pendulum arms for the supporting wheels 27, so that the passing moment can be solved in different ways.

Transport of the trolley can be arranged in different ways, e.g. by pulling wires 28, 29, which are operated in a known manner. There are also known arrangements, where gripping means on the trolley close the cable and step by step pull the trolley forward along the cable. This presupposes a continuous power supply throughout the transport route, which can be done in a known manner by means of a power cable running along the load-bearing cable.

The width shown in Fig. Ä, where the trolley 22a is pulled by means of wires 28,29, only power is needed to the motor for the pulley 25. This can be achieved by power cable which is temporarily connected at connection 30 during loading and unloading.

In the embodiment according to Figs. 5 and 6, the cable 14a consists of a multi-cut hoist. The winch 31 is mounted next to the load deck, the front guide member 23a consists of a block with three discs, and the aft guide member 2ha consists of a block with six discs. At boom post 13 on the platform, a block 32 with three boards is supported. This is what must be anchored to the hook crane 17 of the platform crane, and hoisted up to the platform. Blocks 23a and 2ha are mounted in the previously described manner in the boom structures 18, 19 so that they can be displaced in the transverse direction of the ship, e.g. by means of a guide screw 37 indicated on the right in Fig. 6.

The wire runs with a part 33 from the winch 31 to a first disc in the front guide means 23a. The part 34 of the wire continues to the aft guide means 24a, further to block 32 via the boom pile 13. The main part 35 of the wire then cuts back and forth several times between the guide means 23a and the block 32, past discs at the guide means aha. Lift-done: 22b is mounted on the first part BÄ starting from block 23a. The return part 38 from the boom pile 13 is returned according to the hoisting principle and fastened to any point in the ship, near the boom structure 19 in deck 16, suitably by means of shock absorbers 39.

When the hoist 14a is rigged up, the vessel assumes a position some distance from the platform. After the desired package has been attached to the hoist and lifted so much that it is free from the ground, the ship drives away from the platform, at the same time as wire is discharged from the winch 31. The part 35 then pulls up the hoist along the part 34, so that it is quickly moved up to the platform. The lifting device is returned to the ship by backing it towards the platform, while taking the wire home at the same time.

With this arrangement, there is no need to take any additional measures for moving the hoist, and another advantage is that the fairly considerable tensile stress to which the cable is subjected when the vessel is put into the lake, will be distributed over several wire sections. The number of parties in the pulley 14a is determined by the expected load and the desired wire dimension. 8006303-5 Embodiments described above and shown in the drawings are only examples, where the components included can be varied in many ways within the scope of the appended claims. What is essential for the invention is the arrangement at the part of the cable which extends over the ship's deck, but for other parts known technology is largely useful.

Claims (5)

8006303-5 P a t e n t k r a v Cableway between an offshore platform (10) unaffected by wave motions and a movable supply vessel (15) with a stern-accessible cargo deck (16), characterized in that the vessel (15) at each end of the cargo deck (16) is provided with a relatively load-bearing transverse bending structure (18, 19), at least the stern (19) of which is provided with guide wheels (24) for the cable (lä), which support a load-lifting device (22a; 22b) which allows passage past the guide wheels and the bending structures (18, 19) are otherwise arranged so that a portion (21) of the coil, between them, is kept substantially parallel to the load deck (lo) and at a distance above this exceeding maximum calculated load height. 2. A cableway according to claim 1, characterized in that cable guides (23, 2Å) at both bending structures (18, 19) are displaceable in the transverse direction of the vessel. Cableway according to one of Claims 1 or 2, characterized in that the cable consists of a single strong wire or cable (1Å) and in that the load-lifting device supported by it comprises a trolley (22a) provided with wheel arrangements (26, 27). ) which allows passage past the aft steering wheels (ZQ). Cableway according to one of Claims 1 or 2, characterized in that the cable consists of a multi-cut tulle (ßßu, 32), the load lifting device (22h) being fixedly mounted on the first part of the supply vessel (Bh), while a return portion (38) of the wire end is attached to the vessel. Cableway according to Claim H, characterized in that the cable is fixed in the ship's deck by means of a shock absorber (39).