JPS631409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of offshore work platforms (rigs) used in oil drilling and other operations, and more specifically, the present invention relates to improvements in offshore work platforms (rigs) used in oil drilling and other operations. By generating force, the reaction force is dispersed and the weight of the legs is reduced.

Offshore work platforms include bottom-mounted offshore work platforms that have legs with footings planted on the seabed to support the platform so that it can be raised and lowered, and others that float above the water surface and hold their position using mooring cables. There is also a moored offshore work platform.

The present invention relates to a bottom-mounted offshore work platform. This bottom-mounted offshore work platform has a footing fixed to the lower end of the legs, the footing is seated on the seabed, and the legs support the platform so that it can be raised and lowered above the sea surface.

General structure of offshore work platform First, the general structure of a commonly used offshore work platform will be explained.

FIG. 1 is an exploded perspective view of the main components of the offshore workbench. The offshore workbench P includes a platform 1 consisting of a floating body, and legs 4 inserted into holes 3 of a jack house 2 arranged around the platform 1. and,
A footing 5 provided at the lower end of this leg 4
It consists of a living area 6, a helipad deck 7, an auxiliary base 8, and a derrick tower 9 that is erected on the auxiliary base 8.

During the work, the footing 5 is fixed to the seabed in the area where oil is to be drilled, and the jacking device in the jacking house 2 is operated to raise and lower the platform 1 to a predetermined height, positioning it while drilling for oil. .

Leg 4 has 4 cords 10 (in some cases 3 cords)
These cords 10 are connected by support members, ie, horizontal members 11 and diagonal members 12, to form a tower-like structure. Note that the distance L between the cords 10 is 8 to 10 m.

Of the cords 10, two diagonally arranged cords 10 are provided with racks 13, and the pinions of the jacking device in the jacking house 2 are engaged with the racks 13.

Structure of the part that bears horizontal force Figure 2 shows the relationship between the legs 4 and the jack house 2 provided on the platform 1. An upper guide 15 is attached to the upper end of the jack house 2, and a hole 3 provided in the platform 1 is attached to the upper guide 15 at the upper end of the jack house 2. Lower guide 1 at the lower end of
6 are provided respectively. 17 is a jacking device, and a pinion 18 provided thereon meshes with a rack 13 provided on the two cords 10.

FIG. 3 is an explanatory diagram showing the state of the horizontal force applied to the upper and lower guide legs, and shows that the footing 5 at the lower end of the legs 4 of the offshore work platform P is seated on the seabed 20, and the platform 1 is positioned above the sea surface 21. When the leg body 4 is exposed to wave force F or an external force such as wind force acts on the platform 1, the leg body 4 tends to fall down.
6 to maintain a stable state.

Now, with the conventional offshore work platform P, there was a problem in sharing the force when the legs tend to fall due to the wind force applied to the platform 1, the wave force applied to the legs 4, and the tidal force.

Size of the offshore platform This bottom-mounted offshore platform is suitable for extremely large structures (for example, the platform length is 70 m and the width is 60 m).
The height of the platform is 7m, the length of the legs is 120m, the weight of the legs is 2000 tons, and the weight of the platform is approximately 6000 tons including the attached equipment. It is difficult to achieve accuracy, and therefore it is often impossible to distribute the horizontal force to all of the legs, so the design inevitably takes safety into consideration, and the size of the legs increases accordingly. There are drawbacks.

To give a specific example, the leg size is 30 to 50.
A cylindrical body with a diameter of 1 to 1.2 m and a length of 5 to 10 m is made by bending a steel plate with a diameter of 1 mm to 1.2 m and a length of 5 to 10 m. Two or three of these cylinders are connected to form a long cylinder. After making a rack and welding a rack etc. to this long cylindrical body, prepare 3 or 4 long cylindrical bodies (cord 10) and connect horizontal material 11 and diagonal material 1 between them.
2 (supporting member) is used to fabricate a tower-shaped unit leg body, and 7 to 10 unit leg bodies are assembled in series to form a leg body 4 having a predetermined length.

Three to four legs 4 are prepared and passed through the holes 3 of a jack house 2 provided on the platform 1, and a lifting device is provided for raising and lowering the platform 1 with respect to the legs 4.

Therefore, the leg body 4 has manufacturing errors as will be described later during the various manufacturing steps described above.

Manufacturing Errors Specifically, manufacturing errors are: (1) Diameter errors that occur when forming a steel plate into a cylindrical body, (2) Errors due to longitudinal warpage that occur when welding both edges of a steel plate, (3) ) Errors that occur when welding multiple cylindrical bodies to lengthen them in a straight line; (4) Errors in the radius and length of the cylindrical body that occur when welding protrusions such as racks on the surface of the cylindrical body; ( 5) Errors that occur when assembling the cylindrical body into unit legs using horizontal members and diagonal members (supporting members); (6) Errors that occur when the unit legs are connected in series and assembled into a huge leg of the required length. There are various types of errors such as .

Defects Based on Manufacturing Errors If there are various errors when assembling the leg 4, the accumulation of these errors will result in a very large error in the fitting part between the leg 4 and the platform 1. . Therefore, in anticipation of this error, a sufficient gap must be provided at the fitting portion between the leg 4 and the upper guide 15 and lower guide 16 provided on the platform 1.

If such errors are not taken into consideration, it will cause problems in the lifting and lowering of the platform.

If the error is large as described above, the platform 1 will be subjected to wind force from the lateral direction, and when the leg body 4 receives wave force, a large and local reaction force will act on the leg body 4. Taking this into consideration, in order to avoid destruction of the legs 4, it is necessary to design the legs 4 and the jack house 2 that supports them with great safety in mind, which inevitably increases the manufacturing cost of the offshore work platform P. There were flaws.

As mentioned above, many processes are adopted when manufacturing the legs 4, but errors occur in this process, so "inspection" is carried out to eliminate these errors.
− It was necessary to repeat “corrections”.

However, as mentioned above, the legs 4 and the platform 1 are extremely large, so there is a gap between the pressure receiving part of the legs 4 and the upper guide 15 and lower guide 16 provided in the jack house 2, as shown in FIG. As shown in -B, about 15 mm was expected to occur in portion C. In other words, this gap in part C was inevitably created as long as the above-described manufacturing process for the offshore work platform was employed.

Relationship between manufacturing error and reaction force of the supporting part of the leg If there is a dimensional error in the range described above between the leg 4 and its supporting part, the wave force F will be generated in the state shown in Figure 3-A. The reaction force in the horizontal direction that supports the leg 4 so that it does not fall when exposed to wind force F' is R1 at the upper guide 15 position, R2 at the lower guide 16 position, and R3 at the footing 5. However, these reaction forces R1 and R2 are diagonal to each other as shown in FIG. 3-B.

That is, in the conventional structure for supporting the legs 4 of the offshore work platform P, when looking at one cord 10, there are manufacturing errors in the legs 4 and guides 1 supporting it.
Due to manufacturing errors between cords 5 and 16, the structure is such that it cannot bear the stress in the horizontal direction from the entire circumference of the leg body 4, and normally cord 1
Only half of the circumference of 0 is in contact with the guides 15 and 16.

As shown in FIG. 3-B, reaction forces R1 and R2 are generated diagonally with respect to one leg 4. If we focus on the plane, one leg 4 as shown in FIG. A reaction force R1 shown by solid arrows is generated on the upper guides 15 of two cords 10 among the leg bodies 4, but no reaction force is generated on the other two upper guides 15. On the other hand, a reaction force R2 shown by a dotted line is generated in the lower guide 16. Therefore, Figure 3-B
As shown in FIG. 2, a gap C is formed in the lower guide 16 located below the upper guide 15 supporting the cord 10.

That is, as shown in Figure 3-A, the wave force F is applied to the leg 4.
If we focus on one leg 4, the third
As shown in Figure-C, there are a total of 4 upper guides 15 and 2 lower guides 16 installed in the jack house 2.
will generate a reaction force.

In this way, in the conventional offshore work platform P, the reaction force supporting the legs 4 is two upper guides 15 and two lower guides 16, a total of four guides, each of which is located in the same horizontal plane. Cord 1 that does not act simultaneously on 8 guides, that is, a total of 8 guides at the top and bottom, and has the strength to withstand such reaction force.
0 must be used to manufacture the legs 4.

As a result, the weight of the leg 4 increases, resulting in an increase in material costs.

OBJECTS OF THE INVENTION AND MEANS FOR ACHIEVING THE OBJECTS The present invention aims to eliminate the drawbacks of the conventional offshore work platforms, namely, manufacturing errors in the legs and the means for supporting the legs, and the problems caused by this. The means for achieving this object has a plurality of legs and a platform that moves up and down along the legs, and the legs have at least three cords extending in parallel. The platform is connected by a support member and assembled in a tower shape, and the platform has at least an upper guide and a lower guide as horizontal reaction force bearing members, and this guide bears the reaction force in the entire circumferential direction of the leg body. It is characterized by having means.

DESCRIPTION OF EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 is a sectional view of the guide portion showing the first embodiment.

The cord 10 constituting the leg 4 has a semi-cylindrical shape, and a plate 25 is provided at the cut end of the cord 10, and racks 26 are provided on both sides of the plate 25. Furthermore, a protruding member 27 is welded to the surface of the plate material 25. This cord 10 has a horizontal member 11 at an angle α, for example, three cords 1
When assembling 0, use 4 cords 10 at 60°.
When assembled, it is welded to the surface of cord 10 at a 90° angle. Further, a contact piece 28 is welded to the back surface of the plate material 25, and the protrusion member 2
A contact piece 28 is also provided on the surface of 7.

Reference numeral 30 denotes a guide section, which means an upper guide 15 provided in the upper part of the jack house 2 or a lower guide 16 provided in a hole in the platform 1.

As described above, the guide portion 30 is provided with an opening 31 having a U-shaped cross section, and the protruding pieces 32 are welded to the inner surfaces of the openings 31, respectively, and the protruding pieces 32 and the contact piece 28 are opposed to each other. .

When actually assembling the legs 4, as in the past, inspections in various processes are easily completed, unit legs are assembled, and then these unit legs are added to form legs of a predetermined length. is the same as before.

In this state, since the inspection is simplified, there are some parts where the dimensional accuracy is lower than that of the conventional leg body. However, it is clear that the process is greatly simplified because the inspection and the correction processing based on the inspection are simplified.

The unit legs are assembled using the process simplified as described above, and once the assembly of the legs is completed, the projecting piece 32 and plate material 25 provided on the guide portion 30 are assembled.
The contact piece 28 provided on the contact piece 28 and the contact piece 28 provided on the protrusion member 27 are machined. When the machining is completed in this way, the contact piece 28 on the leg 4 side and the protrusion piece 32 on the platform 1 side are machined to exactly match dimensions.

The protrusion 32 provided on the guide portion 30 is cut between the upper guide 15 and the lower guide 16 using a special cutting device when the assembly of the jack house 2 on the platform 1 is almost completed. Cut to form a precise plane.

The most suitable structure for implementing the present invention is the fourth
As shown in the figure, a plate member 25 provided on the cord and a member, that is, a protrusion piece 32, which approaches the protrusion member 27 provided on the plate member 25 and generates a reaction force are provided.

By configuring in this way, the protruding piece 32 and the protruding member 27 are attached to the guide portion 30 and the plate material 25, which is the member on the cord side, respectively.
The facing surface facing the plate material 25 and the facing surface facing the guide portion 30 of the projection member 27 are perpendicular to each other, and both facing surfaces form a pair of facing members. The surfaces are contact pieces 28, 28
Since it is constructed so as to be in sliding contact with the facing member via the cord, a portion is formed that prevents the plate member 25, that is, the cord 10, from moving in any direction. In other words, code 10
It is as if a member is provided that generates a reaction force in a 360° range. This is important because even if the legs 4 and the platform 1 try to move relative to each other, they can be prevented from moving in either direction. Therefore, each of the cords 10 constituting the leg 4 is provided with a supporting member or a stress-bearing member, and when wave force and/or wind force acts as shown in FIG. 3-A, Each cord 10 will be supported individually.

Therefore, reaction forces R1 and R2 are not generated on the diagonally diagonal upper and lower guides as shown in FIG. 3-B, but reaction forces are generated on all the upper guides 15 and the lower guides. 4 cords 1 as in the example
If there are a total of eight guides on the top and bottom, such as the leg body 4 made of zero, reaction forces will be generated at eight locations, and the horizontal reaction force on each cord 10 can be reduced.

In addition, as a means for further enhancing the action and effect, the contact piece 2 is removed when the assembly of the leg 4 and the platform 1 fitted to the leg 4 is completed, or when most of the assembly is completed.
8. By cutting the projecting piece 32 to match the dimensions, the accuracy of the contact area can be greatly improved compared to that of conventional offshore work platforms, and in this way, the reaction force can be reduced. By improving the fitting accuracy of the parts that occur, "all upper and lower guides"
A reaction force can be generated, and the leg body 4 can be supported more reliably.

In this embodiment, in order to reduce the amount of cutting as much as possible, the guide part 30 and the rack 2 are
Contact pieces 28, 32 are attached to the plate material 25 provided with 6 on both sides.
Although the contact piece 28 and the protruding piece 32 are cut by cutting the contact piece 28 and the protruding piece 32, it is also possible to cut a part of the plate material 25 itself or the guide part 30 itself.

FIG. 5 is a sectional view of a portion of the jacking device 17 in which the pinion 33 is provided in the first embodiment.

The jacking device 17 has a contact piece 35 and a protruding piece 32a near both ends of the plate material 25, and maintains the pinion 18 in the correct position.

FIG. 6 shows a second embodiment, in which the plate material 25
A semi-cylindrical cord 10 is welded to both sides of the plate material 25, and racks 26, 26 are welded to both ends of this plate material 25 to form a cylindrical cord 10 as a whole.

In the embodiment shown in FIG. 6, the plate material 25
A contact piece 28 is welded to both sides of the contact piece 28. Further, a projection 32 is welded to the recess of the guide portion 30 in which the rack 26 is accommodated.

FIG. 7 is a perspective view showing the case point portion (the gathering point of the horizontal member and the diagonal member) of the legs of the four cords, and FIG. 8 is a plan view of the same portion.

The four cords 10 are connected to each other by horizontal members 11 to form a tower shape, and a rack 26 is eccentrically welded to the surface of the cylindrical cord 10, and contact pieces 28 are welded to both sides of the rack 26. ing.

If the contact piece 28 is welded to the rack 26 in this way and the upper guide 15 and lower guide 16 are set at this point, the horizontal reaction force will act on this point. The strength of the body 4 can be increased. That is, it is more preferable because the weight of the cord can be reduced.

In addition, there is a part that is locally supported on the platform 1 side, and by machining only this part, a part that bears external force can be formed, so the accuracy of the support part of the leg 4 can be improved. It can be made high.

FIG. 9 shows a third embodiment, and is a cross-sectional view showing the main part of a leg 4 having a cord 10 with a trapezoidal cross section, in which a plate material 25 is welded to the opening of the cord 10 with a trapezoidal cross section. Rack 26 is welded to both ends of 25. The guide portion 30 has the rack 26
A recess 34 is formed in which the recess 34 is accommodated.
A contact piece 35 is welded to the top of the rack 26 so as to come into contact with the front end surface and both sides of the rack 26.

FIG. 10 is a modification of the third embodiment shown in FIG. 9, in which a plate 25 is welded to the opening of the cord 10 having a trapezoidal cross section, and a U-shaped support member 37 is arranged to wrap around the end of the plate 25. A contact piece 35 is welded to the inner surface of the supporting member 37. This embodiment differs from the embodiment shown in FIG. 9 in that there are no lugs at either end of the plate 25.

FIG. 11-A is a plan sectional view showing the entire guide section of FIG. 9, and FIG. 11-B is a plan view showing the main part of the leg body 4 using the guide section.

In FIG. 12-A, a rack 26 is provided at both ends of the bottom piece of the cord 10 having a triangular cross section, and a U-shaped support member 37 is provided on the platform 1 side surrounding this rack 26, and a contact piece 35 is provided on the inner surface of this support member 37. is installed on three sides.

FIG. 12-B is a plan view of the leg 4 using the cord of the above structure.

FIGS. 13A to 13G are diagrams showing cross-sectional shapes of cords with which the present invention can be implemented.

As is clear from the embodiments shown in FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 27 or rack 26 are provided, and these members are used to surround three sides and provide a member that bears the reaction force, so if you take the members that bear the reaction force on the left and right sides together, the direction is 360°. This means that each cord 10 is provided with a member that supports the cord 10.

This is important because when an external force is applied to the leg 4, each cord 10 is supported. For example, when the leg 4 is made up of four cords 10, , the reaction force will be borne at a total of eight locations, top and bottom.

As mentioned above, the offshore work platform according to the present invention is provided with a portion around the entire circumference that bears the reaction force acting on the cord 10 that constitutes the leg 4, so that it bears all the horizontal reaction force. As a result, the support structure for the legs 4 can be simplified.

The fact that the support structure of the leg body 4 is simplified means that the support structure of the leg body 4 is simplified.
It is possible to make the material thinner, and the material cost is lower.

In a preferred embodiment of the present invention, the accuracy of the fitting portion between the guide and the cord can be improved by mechanical cutting, so that the number of manufacturing steps can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is an exploded perspective view of the components of the offshore work platform, Figure 2 is a simplified view of the fitting part between the legs and the platform, and Figure 3-A is the reaction force acting on the legs. FIG. 3-B is an explanatory diagram showing the reaction force of the part supporting the leg body and the generation of the gap. Fourth
The figure is a sectional view showing the main parts of the cord constituting the offshore work platform of the present invention and the members supporting this cord. A supporting member is shown.
FIG. 5 is a cross-sectional view of a portion of the cord provided with a pinion associated with the structure of FIG. 4; FIG. 6 is a sectional view showing a cord having a plate provided in the center of a semi-cylindrical body and a member supporting the cord. FIG. 7 is a perspective view showing a cord in which a rack is welded to the eccentric surface of a cylindrical body, and FIG. 8 is a plan sectional view of the cord. FIG. 9 is a cross-sectional view showing the relationship between a cord in which a metal plate having a trapezoidal cross section is provided with a plate in its opening, and racks are provided at both ends of the plate, and a member that supports this cord. FIG. 10 is a sectional view showing the relationship between a cord used in pair with the cord shown in FIG. 9 and a member that supports this cord. Figure 11-A
9 is a sectional view showing a support portion of a leg using the cord of FIG. 9, and FIG. 11-B is a plan view of the same leg.
Figure 12-A is a sectional view of a cord with racks provided at both ends of the board and the part that supports this cord;
Figure-B is a plan view of the isopod body. Figure 13 A-F
1 is a diagram showing cross-sectional shapes of various cords to which the present invention is applicable. P...Marine work platform, 1...Platform, 2
...Jayatsuki house, 3...Jayatsuki house hole, 4...Legs, 5...Footing, 6...Living part, 10...Cord, 11...Horizontal material, 12...
... Diagonal material, 13 ... Rack, 15 ... Upper guide, 16 ... Lower guide, 17 ... Jacking device, 18 ... Pinion, 25 ... Plate material, 26 ...
Rack, 27... Projection member, 28... Contact piece, 3
0... Guide portion, 31... Opening, 32... Protrusion, 34... Recess, 35... Contact piece, 36... Plate material, 37... Support member.

Claims (1)

[Claims] 1. A bottom-mounted offshore work platform in which a platform is provided on a plurality of legs having footings at their lower ends so that the platform can be raised and lowered, the legs having at least three cords connected in parallel by a support member, The platform has an upper guide and a lower guide that bear horizontal reaction force when a horizontal external force is applied, and each guide and cord has a portion that faces each other,
The opposing surfaces of the opposing portions are provided in a pair of protrusions so that their directions are orthogonal to each other, and each opposing surface is brought into sliding contact with the opposing member via a contact piece, so that transmission from all the cords is achieved. A marine work platform characterized by having means capable of bearing horizontal forces in all directions.