WO2001015968A1

WO2001015968A1 - A device for rapidly interconnecting and disconnecting a plurality of hull sections

Info

Publication number: WO2001015968A1
Application number: PCT/NO2000/000282
Authority: WO
Inventors: Jan VATSVÅG
Original assignee: Navion Asa; Global Maritime As
Priority date: 1999-08-30
Filing date: 2000-08-29
Publication date: 2001-03-08
Also published as: AU7043000A; EA003292B1; EA200200315A1; NO994194D0; NO994194L

Abstract

A device for rapidly connecting and disconnecting a plurality of hull sections (6, 8, 10) each of which, along at least one of its broadsides, is provided with a connection portion (14) having engagement means (16) cooperating with mating engagement means (16) of a connection portion (14) on a broadside of a juxtaposed other hull section. The hull sections (6, 8, 10) are releasably interlocked in juxtaposed position by means of wires (24) or locking pins (50). The juxtaposed and interconnected hull sections (6, 8, 10) provide a floating structure (4) such as a drilling platform or barge.

Description

A DEVICE FOR RAPIDLY INTERCONNECTING AND DISCONNECTING A

PLURALITY OF HULL SECTIONS

The invention relates to a device and a method for rapidly interconnecting and disconnecting a plurality of hull sections. When interconnected the hull sections provide a vessel or other form of floating structure, for example, offshore platform, ship, barge or the like.

The invention is particularly contemplated for use in the recovery of petroleum deposits under the Caspian Ocean which, in spite of being the oldest oil pro- ducing area of the world, is scarcely exploited. Geological explorations have indicated large reserves and large undiscovered reserves are expected. There is a growing interest among the international oil companies for exploration and recovery in this area. However, the number of drilling and production vessels present in the area is far too small compared to the exploration and recovery rate called for by the oil companies. Also, the technical condition of existing drilling platforms is poor compared to western standards, while the ship yard capacities are limited. Technical equipment has to be imported from western countries.

A main cause of the above situation is probably the geographical localisation of the Caspian Ocean. This ocean is actually a lake, with no other sea route connections to the surrounding world than by the river Volga. This fact limits to a large extent the size of vessels capable of reaching the ocean. Effective offshore oil recovery requires relatively large (long and wide) drilling and production vessels hardly manoeuverable in the partly narrow and shallow waters of the Caspian Ocean. These circumstances also limit the possibility of a rapid retreat of the drill- ing and production units in an emergency situation which might occur, for example, owing to the unstable political situation in the countries bordering the Caspian Ocean.

The present invention offers a solution of the above problems, in a manner as stated in the appending patent claims. Briefly, the solution is a vessel comprising a plurality (two or more) of hull sections capable of being interconnected and disconnected quickly and easily. Admittedly, devices permitting interconnection and disconnection of hull sections are priorily known, see for example US patent publications 1 266 362, 3 486 476, 3 841 254, 3 614 938 and 3 983 830. However, none of these prior devices lend themselves easily to being used in connection with oil recovery in environments as discussed above.

A structural problem that is overcome by the solution according to the in- vention, is to satisfy the relatively large structural tolerances required for the connecting portions of the respective sections to practically permit interconnection of the sections as quickly as desired, while permitting transmission of forces in all directions between the hull sections. The fact that the solution according to the invention permits the entire connecting operation to be carried out from the deck level of the sections, also adds in simplifying the operation and minimizing time expenditure.

When applying the invention, such as for operations in the Caspian Ocean, the respective hull sections will be built and launched separately and towed to their destination or site where they will be interconnected in a manner to provide an operative vessel.

The invention will now be described in detail with reference to the highly schematic drawings which illustrate the invention in three perspective figures, figures 1 , 2 and 3.

Thus, fig. 1 shows a vessel according to the invention, which at first is sepa- rated in a plurality of independently floating hull sections, while fig. 2 shows details of an embodiment according to the invention for releasable interconnection of the sections according to fig. 1 , and fig. 3 shows a variant of the embodiment shown in fig. 2.

In the example according to the drawing the vessel is shown as a drilling platform or barge 4, assembled from three hull sections: a central section 6 and two opposite, substantially similar lateral sections 8, 10. Central section 6 is equipped with i.a. derrick 12 and moon pool (not shown). In the interconnected (not shown) position of hull sections 6, 8, 10 vessel 4 is substantially symmetrical about a longitudinal axis through central section 6. The central section may, as illustrated, be somewhat shorter than lateral sections 8, 10 providing a recess at each end of the barge to receive the bow or stern portions of another vessel, which could be a towboat or pusher. According to the invention each hull section 6, 8, 10, along at least one broadside thereof, has a connection portion 14 provided with engagement means 16 (fig. 2). Thus, in the example shown, central section 6 will be provided with engagement means 16 at either broadside thereof while the two lateral sections 8, 10 will be provided with connection portions 14 having mating engagement means 16 along at least one broadside thereof.

In an advantageous embodiment shown in fig. 2, engagement means 16 are in form of corrugations, i.e. spaced protrusions or ribs 20 and intermediate indentations or grooves 22 extending longitudinally of the hull section. The corru- gations on the broadsides of each hull section are vertically offset with respect to the corrugations on the lateral surface of the adjacent hull section, such that when the hull sections are caused to approach each other the ribs 20 of one section will engage the grooves 22 of the adjacent section. In the example shown the corrugations are trapezoidal ribs 20 and grooves 22. However, they may of course be formed in a different shape, such as sinusoidal. Advantageously, the pitch or "wave length" of the corrugations, i.e. the centre distance between the ribs, could be about 850 mm. The corrugations are contemplated to be formed either directly into the hull lateral surface or into about 50 mm thick steel plates welded to the vessel broadside. Further, along each hull side provided with connection portion 14 there are, preferably at deck level, trapezoidal protrusions 23 adapted to engage mating recesses 25 on the adjacent hull section. The corrugations 16 together with protrusions 23 and recesses 25 will primarily resist translational and rotational movements between the hull sections in a vertical plane and accommodate all resulting shear forces. The corrugations 16, which preferably extend along substantially the entire length of each hull section, will normally transmit loads at selected load- supporting areas only. Beyond these areas the purpose of the ribs is to prevent water from flowing freely through the connection between the sections. Preferably, ribs 20 are coated with a load-supporting and sound-deadening material, e.g. a high pressure and high strength elastomeric material such as neoprene which serves to enhance shear force distribution while also deadening squeak noises from between the sections. Preferably also the horizontal protrusions 22 of the deck and bottom levels of the hull sections are provided with such load-supporting material.

Fig. 2 also illustrates an advantageous technique for interlocking assembled hull section connection portions. The locking operation can be carried out by advancing wire straps 24 (of which only the end are shown) through horizontal guide tubes 26, 28 in upper and lower part of each hull section. The wires are tightened or pre-tensioned sufficiently to avoid slackening due to external loads and prevent the sections from moving apart, whereupon the tightened wire is locked as more fully explained below. Each guide tube 26, 28 has an outer end opening into connection portion

14. The upper guide tube 26 extends horizontally laterally of the connection portion to an inner end opening into the sidewall of a recess 32 in the hull deck. The lower guide tubes 28, in the shown example, also extend horizontally in lateral direction opening at their inner end into the bottom of recess 32 via a tube bend 34 having a relatively large curvature and a vertical tube portion 36. Preferably, the lower guide tube 28 is positioned between bulk heads and framework and anchored thereto by means of ribs (not shown).

The wire straps 24 that are advanced through the guide tubes 26, 28 for interconnecting hull sections, have an anchor means 38 at one end, e.g. in the form of a disk engaging a wall of recess 32, the other end thereof being associated with a wire tightening and locking device 40 which can be of a per se well- known type (often referred to as "jack"), for example those that are used in similar wire technique in other applications, such as interconnecting bridge sections.

The wire guides 26, 28 may be arranged in pairs side by side in recesses 32 as shown in fig. 2. While only one such pair is shown in the figure, it should be understood that such wire connection pairs, with associated guide tubes, anchors and tighteners, will preferably be uniformly spaced along the hull sides.

Thus, the outer ends of guide tubes 26, 28, in the example as shown, extend to the outer face of a rib 20 of one hull section, while the tube outer ends of the adjacent hull section protrude a short distance into a complementary rib groove 22 to form a preferably somewhat tapered or pointed stub 41 which, upon hull section assemblage extend into the end portion 43 of the facing guide tube of the adjacent section. Since the sections are floating, water will always be present in guide tubes 28 up to the water surface. Preferably therefore, a wear resistant plastic coating is crimped onto the wires to prevent them from contact with sea- water.

Preferably, wires 25 will also be provided with a load sensor (not shown) measuring at any time stresses/tensional loads of the connections. Means are provided to tighten and inspect the wires in operation, if necessary.

The dimensioning of the wire system will be adapted to the expected loads. For a drilling platform as in the example illustrated, wire 24 would suitably be comprised of a plurality (e.g. 55) strands or parts of about 15 mm diameter, and the guide tube inner diameter about 320 mm, with a material thickness of about 40 mm.

Since also the lower wire guides 28 extend to deck level, near the upper wire guides 26, the connecting operation can be performed without requiring subsurface operations in order to perform the interconnection. From the above description it should be appreciated that the hull sections are locked in all directions and distortions are prevented. Thus, engagement means 16 primarily prevent vertical movement, means 23 and 25 primarily keep the hull parts together against fore and aft movements, while the wire straps primarily prevent abeam movements and rotations. Fig. 3 illustrates an other possible technique for interlocking juxtaposed hull sections. This technique uses capped locking bolts or pins 50 to be inserted down through bores 52 in ribs 20 in the two hull sections in their juxtaposed or engaged position. Bores 52 will preferably be provided with casings (not shown) made from a wear resistant material. Preferably bolts 50 will be made of high strength steel of a diameter adapted to the above mentioned loads, such as a diameter of about 300 mm, while casings then will have an inner diameter of about 320 mm and outer diameter about 400 mm.

All horizontal loads will be taken up by locking pins 50. Hydraulic cylinders (not shown) secured to hull section top and bottom plates to perform the hull sec- tions approaching and juxtapositioning operation. The cylinders will be released when locking bolts 50 have been positioned in place. Again, ribs 20 will be dressed with a load-supporting material transferring the connection shear stresses to the locking bolts 50 upon release of the cylinders. When implementing the invention the individual hull sections to be interconnected are towed to the selected site of interconnection and brought to approach each other until the corrugations 20, 22 and protrusions/recesses 23, 25 are fully engaged, whereupon locking is carried out by means of the above de- scribed wire technique according to fig. 2 or locking pins according to fig. 3. To assist in aligning the hull sections 6, 8, 10, one of the outer sections, such as 8, could be provided with a guide arm 60 extending perpendicularly outward from the connecting side of the hull section and mating with guide grooves 62, 64 formed in the remaining hull sections 6, 10 as shown in fig. 1. Normally, the hull section will be constructed particularly with a view to being interconnected with other hull sections, to form a functional or operative vessel unit when interconnected. However, it is also contemplated that the individual hull sections alone may provide an independently operativel vessel which, by means of the device according to the invention, also is capable of being interconnected with other independently operative hull sections as components of a composite vessel adapted to carry out operations that the individual hull components alone cannot perform.

Claims

PATENT CLAIMS:

1. A device for rapidly interconnecting and disconnecting a plurality of floating hull sections, each hull section (6, 8, 10), along at least one of its broadsides, pro- vided with a connection portion (14) having engagement means (16) adapted to cooperate with mating engagement means (16) of a connection portion (14) on a broadside of an other hull section to prevent translational and rotational movements between juxtaposed hull sections (6, 8, 10), and means (14; 50) for interlocking the juxtaposed hull sections, characterized in that the engage- ment means (16) are in form of corrugations comprised of ribs (20) and intermediate grooves (22).

2. A device according to claim 1, characterized in that the ribs (20) are trapezoidal.

3. A device according to any one preceding claim, characterized in that the interconnecting means comprise a plurality of wire straps (24) extending laterally across the juxtaposed hull sections and locked in a tightened condition.

4. A device according to claim 3, characterized in that it comprises guide tubes (26, 28) for the wire straps.

5. A device according to claim 1, characterized in that the locking means are locking pins (50) adapted to be inserted through rows of vertically aligned bores (52) in the corrugations.