TILTING JACK OFFSHORE PLATFORM

Abstract: The invention relates to a tilting jack offshore platform (1) comprising a work deck (2) and legs (3) supporting the work deck (2) , wherein each of the legs (3), at one of their respective ends is attached to the work deck (2) by a, in relation to the work deck (2), movable coupling (4, 6). The coupling is arranged such that the legs in their longitudinal direction can be positioned beside or underneath the work deck (2).

Description: Tilting jack offshore platform The invention relates to a tilting jack offshore platform comprising a work deck and legs supporting the work deck, each of the legs, at one of their respective ends being attached to the work deck by a, in relation to the work deck, movable coupling. The tilting jack offshore platform serves to provide a work deck that can be used independently of the water motion. US-A-3 , 592, 013 discloses such a tilting jack offshore platform, where the legs are attached to a, in relation to the work deck, movable coupling. The known tilting jack offshore platform comprises legs standing substantially upright, allowing the work deck to be moved up and down along said legs in order to bring it to the desired working height and in order to ensure that the tilting jack offshore platform can be used at different water depths. The known tilting jack offshore platform has a number of disadvantages. For example, the known tilting jack offshore platform has poor stability when it is used in deep water. On such an occasion the work deck is almost at its highest position. This involves water depths of approximately 30 metres. On the other hand, when using the tilting jack offshore platform in shallow water, the legs may extend far above the water level and above the work deck, which is an impediment when the prior art tilting jack offshore platform has to pass under bridges and the like. Moving the known tilting jack offshore platform in deep water is also difficult; this is rendered more difficult by the resistance offered by the legs which are then almost entirely submerged in the water. A further disadvantage of the known tilting jack offshore platform is that the leg portions that are above the surface of the water reduce the effective load of the tilting jack offshore platform. The known tilting jack offshore platform may, for example, have a maximum load capacity of 3,000 tons; of this the legs of the tilting 2 jack offshore platform possibly account for approximately 1,000 tons, so that only 2,000 tons effective capacity remain. It is the object of the invention to provide a tilting jack offshore platform wherein these disadvantages are removed. The tilting jack offshore platform according to the invention is characterized in that the coupling of the legs to the work deck is arranged such that the legs in their longitudinal direction can be positioned beside or underneath the work deck. This achieves that when the tilting jack offshore platform is not in operation, the legs are for a large part, or entirely, submerged in the water, allowing them to contribute considerably to the floating power of the tilting jack offshore platform. In addition, it is avoided that the legs extend above the work deck, so that passing under bridges will cause no problems. Preferably, the submerged legs may be shaped such as to displace a maximum amount of water, thereby maximally increasing the effect on the floating power of the tilting jack offshore platform. In a first preferred embodiment the tilting jack offshore platform according to the invention is embodied such that the movable coupling can be moved over substantially the whole length of the work deck. By moving the coupling of the legs along the work deck, this measure makes it possible to adjust the desired working height of the work deck without the legs having to extend to a lesser or greater extent above the work deck. On the contrary, with this embodiment the legs do not extend above the work deck at all, which is a decisive advantage over the known tilting jack offshore platform and results in the fact that even when the tilting jack offshore platform is in the operative state, the legs actually increase the effective floating power of the tilting jack offshore platform, instead of reducing it. Thus the tilting jack offshore platform according to the invention can be embodied to have a floating power that is increased by 1,600 tons instead of being reduced by 1,000 tons, while maintaining the same work deck dimensions . As additional stabilizing measure it is desirable to position the legs such as to slope from the work deck outward. For the sake of overall stability of the tilting jack offshore platform according to the invention it is desirable that a shore be provided between each leg and the work deck which is movably coupled to the work deck and hingingly coupled with the leg. The movable coupling of the tilting jack offshore platform according to the invention may be embodied in various ways. A very robust embodiment is characterized in that the movable coupling connecting each leg and/or each shore with the work deck, is embodied with a mobile carriage with which the respective leg and/or shore is hingingly coupled. For a secured positioning of the movable coupling it would then be useful if the mobile carriage were to run over a switch belt . In a second preferred embodiment the tilting jack offshore platform is provided with couplings which are embodied as guide members for the legs, hingingly coupled with the work deck, wherein the position of the guide members in relation to the legs is adjustable, and the guide members are equipped to be positioned in their longitudi- nal direction beside or underneath the work deck. This has the additional advantage that the weight of the legs can be reduced from approximately 1,000 tons per leg to approximately 300 to 400 tons per leg, which provides a great saving in weight and costs . As a result the underside of the work deck, where the legs are positioned, may be embodied such as to be lighter also. This embodiment also profits optimally from the floating power of the legs which, in the non-operable state of the tilting jack offshore platform, are almost or entirely under the sur- face of the water. It is observed that WO 92/08849 discloses a tilting jack offshore platform which is provided with legs that are hingingly coupled with the work deck. However, in the non-operable state the legs are located on the work deck, 4 so that they do not contribute to the floating power of the tilting jack offshore platform, on the contrary, as a result of the weight load they confer on the work deck, they actually reduce the floating power. It is further desirable that the guide members be embodied as sleeves encasing the legs and provided with slide bearings. This affords a very safe and operation-reliable form of construction, allowing the relative position between the guide members and the legs to be adjusted accurately with the aid of adjustment techniques which are in themselves known to the person skilled in the art . Preferably the tilting jack offshore platform is conveniently embodied such that the guide members are coupled with the work deck by means of an attachment con- struction extending perpendicularly to the plane of the work deck. This affords a simple means for positioning the legs in their longitudinal direction beside or underneath the work deck. In order to render the tilting jack offshore plat- form suitable for application up to very great water depths, it is desirable that the legs can be parted. It is further preferred that at their lower end the legs be provided with removable feet. If the tilting jack offshore platform rests on a somewhat sandy floor, said feet may, for example be designed as plates. If the tilting jack offshore platform has to rest on an uneven, rocky floor, the lower ends of the legs are preferably pointed. The invention will now be explained in more detail with reference to the drawings which in Figs. 1 and 2 show the tilting jack offshore platform in a first embodiment according to the invention in side and front view; and Figs 3 and 4 show the tilting jack offshore platform in a second embodiment according to the invention in a top and side view. Identical parts in the Figures are indicated with the same reference numbers . The tilting jack offshore platform 1 according to the invention comprises a work deck 2 and legs 3 support- 5 ing the work deck, see Figs, l and 2 as well as Figs. 3 and . Such legs 3 are provided at each of the four corner points of the work deck 2, see Fig. 3. At their end nearest the work deck 2, each of the legs 3 is attached to the work deck 2 by means of a movable coupling 4. Preferably the legs 3 are positioned such as to slope from the work deck outward, as shown in Figs. 1 and 2. In the first preferred embodiment according to Figs . 1 and 2 a shore 5 is provided between each leg 3 and the work deck 2, which shore is coupled by a movable coupling 6 with the work deck 2 and at one end 7 by a hinge coupling with the leg 3. The movable coupling 4 or 6 respectively of each leg 3 or each shore 5 respectively, is provided with a mobile carriage 8 or 9 respectively, with which the respective leg 3 or shore 5 respectively is hingingly coupled. Preferably the mobile carriages 8 and 9 run over a switch belt indicated by the dashed lines 10 and 11, and can be moved over the entire length of the work deck 2. In the second preferred embodiment according to Figs . 3 and 4 , guide members 4 which are hingingly coupled with the work deck 2 are provided for coupling the legs 3 to the work deck 2, and the position of the guide members 4 in relation to the legs 3 is adjustable. The guide mem- bers 4 are equipped to be positioned in their longitudinal direction beside or underneath the work deck 2, so that the legs 3 in their longitudinal direction are also positioned beside or underneath the work deck 2. This is represented by the dashed lines in Fig. 3. When starting from the situation represented in Fig. 3 in which the tilting jack offshore platform 1 is in the floating state because by means of the guide members 4 the legs 3 are pivoted up beside the work deck 2, the tilting jack offshore platform 1 can be brought into the state shown in Fig. 4 in the manner described hereafter. First it should be noted, however, that in another embodiment which is not shown in the Figures, the legs 3 may be pivoted up underneath, instead of beside the work deck 2, 6 and positioning to reach the state shown in Fig. 4 is carried out in the same manner which is described below. First the legs 3 are positioned in relation to the sleeves 4 such that said legs 3 extend maximally past the edges of the work deck 2. Subsequently the sleeves 4 are moved from their horizontal position into a vertical position, and finally the legs 3 are adjusted in the opposite direction in relation to the sleeves 4, such that when the legs 3 reach bedrock, the tilting jack offshore platform 1 rises out of the water to the desired working height. Performing the above-mentioned operations in reverse order, allows the tilting jack offshore platform 1 to be returned to the floating state. It is preferred that the legs 3 be embodied such that they can be parted below the hinge point 7. This may be achieved in a manner known to the expert, so that there is no need of further elucidation in the Figures. Furthermore, at their lower end the legs are provided with removable feet 12. In the Figures these feet are embodied as plates, however, other embodiments are conceivable such as the legs having a pointed end.

Claims: CLAIMS 1. A tilting jack offshore platform (1) comprising a work deck (2) and legs (3) supporting the work deck, each of the legs (3) , at one of their respective ends being attached to the work deck (2) by a, in relation to the work deck, movable coupling (4, 6), characterized in that the coupling (4, 6) of the legs (3) to the work deck is arranged such that the legs (3) in their longitudinal direction can be positioned beside or underneath the work deck (2) . 2. A tilting jack offshore platform according to claim 1, characterized in that the movable coupling (4, 6) can be moved substantially over the entire length of the work deck (2) . 3. A tilting jack offshore platform according to claim 1 or 2 , characterized in that a shore (5) is provided between each leg (3) and the work deck (2) , which is movably coupled to the work deck (2) , and hingingly coupled with the leg (3) . 4. A tilting jack offshore platform according to one of the claims 1-3, characterized in that the movable coupling (4, 6) connecting each leg (3) and/or each shore (5) with the work deck (2), is embodied with a mobile carriage (8, 9) with which the respective leg (3) and/or shore (5) is hingingly coupled. 5. A tilting jack offshore platform according to claim 4, characterized in that the mobile carriage (8, 9) runs over a switch belt . 6. A tilting jack offshore platform according to claim 1, characterized in that the couplings (4) are embodied as guide members (4) for the legs (3) , hingingly coupled with the work deck (2) , wherein the position of the guide members (4) and the legs (3) in relation to one another is adjustable, and the guide members are equipped to be positioned in their longitudinal direction beside or underneath the work deck (2) . 8 7. A tilting jack offshore platform according to claim 6, characterized in that the guide members (4) are embodied as sleeves (4) encasing the legs (3) and provided with slide bearings (7) . 8. A tilting jack offshore platform according to one of the claims 6-7, characterized in that the guide members (4) are coupled with the work deck by means of an attachment construction extending perpendicularly to the plane of the work deck (2) . 9. A tilting jack offshore platform according to one of the preceding claims, characterized in that the legs (3) are embodied such that they can be parted. 10. A tilting jack offshore platform according to one of the preceding claims, characterized in that at their lower end the legs are provided with removable feet (12) .

Inventors: ZWAGERMAN JAN, ZWAGERMAN, JAN
Applicants: SPACELIFT OFFSHORE B V, ZWAGERMAN JAN, SPACELIFT OFFSHORE B.V., ZWAGERMAN, JAN
Application year: 1999
Main classification: E02B17
IPC codes: E02B17