JPS5920421Y2 - Liftable offshore work platform - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an elevating offshore work platform, and its purpose is to reduce the size and weight of the work platform body (platform) and simplify the structure.

For example, some offshore work platforms such as oil rigs are equipped with multiple (3 to 4) support legs on the work platform body, and the work platform body and support legs can be raised and lowered relative to each other. The structure is as follows.

With such an elevating work platform, when moving to a destination or changing work areas, the support legs are raised relative to the work platform body, and at the destination, the support legs are raised relative to the work platform body. After the support legs have landed, the workbench body is raised relative to the support legs, thereby installing the workbench body above the sea level.

FIG. 1 shows the installation state of a conventional elevating offshore work platform.

That is, 1 is a workbench main body, 2 is a support leg, and 3 is a landing body 4 provided at the lower end of the support leg, which is a relative lifting device.

As mentioned above, the support legs 2 are provided at a plurality of locations on one workbench main body 1, and one support leg 2 is provided at a plurality of locations (usually three).
The cords 2A of the book) are framed parallel to each other by connecting reinforcing members 2B and are integrated.

The landing body 3 is called a spud tank, and is composed of a hollow body having a certain extent in the horizontal direction.

The problem with an elevating offshore work platform that makes contact with the seabed 6 via a landing body 3 made of a spud tank as illustrated in FIG. 1 is that the landing body 13 exerts the effect of supporting downward force. However, it cannot produce the effect of supporting upward force.

Therefore, the overturning moment) M generated on the elevating offshore work platform due to wind waves m is reduced by the downward force F1 caused by the landing body 3. F2
Must be supported only.

That is, the weight of the workbench body must be W, the reaction force of the sea-surface ground 6 acting on the lower surface of the landing body 3 must be fl, f2, and the distance between the two supporting legs 2 must be L.

■If the formula is not satisfied, the offshore work platform cannot be established from the viewpoint of stability.

On the other hand, sea conditions (wave height,
Once the wind speed, ocean current, water depth, etc.) are determined, the magnitude of the above-mentioned overturning moment M is determined.

Therefore, according to formula (2), it is necessary to take the following measures to make the offshore work platform stable.

(1) It is desirable that the weight W of the workbench body be as large as possible, but as the weight W increases, it is necessary to increase the buoyancy capacity during movement, which inevitably results in an increase in size.

(2) It is desirable to make the distance between the support legs as large as possible, but doing so will not only make the workbench larger and require extra steel, but also increase the bending moment generated in the workbench. This is disadvantageous in terms of structural mechanics.

The present invention has been devised in view of the above, and examples thereof will be described below with reference to FIGS. 2 to 4.

In Fig. 2, 11 is the workbench body, 12 is the support leg, 1
3 is a landing body, 14 is a lifting drive device, and is similar to the conventional one explained in FIG. be.

The cord 12A of the support leg 12 is composed of a tubular body, as shown in FIG.
As is clear from FIG. 4, a spiral pile 16 is provided inside.

The spiral pile 16 has spiral blades 16B arranged along almost the entire length of the rotating shaft 16A.
It has a pressure waterway 17 in the center thereof, and a downward high-pressure water injection port 17A is opened at its tip.

Note that the pressure feed channel 17 and the high-pressure water injection port 17A do not necessarily need to be provided depending on the properties of the seabed ground 18.

That is, when the seabed ground 18 is rock, it is advantageous to provide these.

A spiral bearing 19 is fixed to the inner surface of the lower end of the cord 12A.

The spiral bearing 19 has a grooved guide groove 19A set at the same pitch as the spiral blade 16B, and the outer peripheral edge of the spiral blade 16B is fitted and held in the guide groove 19A.

Therefore, the spiral pile 16 is only allowed to move up and down while rotating in the forward or reverse direction.
It's decorated.

On the other hand, a vertical groove 20 is formed on the inner surface of the upper end of the cord 12A.
A pair of guide members 20 having A are fixed at symmetrical positions via the axis of the cord 12A, and a reducer 22 integrated with a motor 21 is held between these guide members 20 so as to be able to move only up and down.

An output shaft 23A of a spiral pile drive device 23 composed of a motor 21 and a speed reducer 22 is connected to the upper end of the rotating shaft 16A of the spiral pile 16 via a connecting road 24.

According to this, the spiral pile drive device 2
3 is rotated forward and backward, the spiral pile 16 is rotated by the action of the spiral bearing 19, and the code 1
2A, its interior is surrounded by the drive device 23.

FIG. 5 schematically shows how the elevating offshore work platform is installed at the destination.

When traveling on the sea, the support legs 12 are pulled up onto the workbench main body 11 as shown in FIG.

At the destination, the support legs 12 are lowered relative to the workbench main body 11, and the landing body 13 is seated on the seabed ground 18.

In that case, even after the landing body 13 contacts the seabed ground 18, the lifting drive device 14 (see FIG. 1) raises and lowers the workbench main body 11 slightly relative to the support legs 12, so that the landing body 13 is not too large. Load the supporting force If.

At this time, the workbench main body 11 has not yet left the sea surface.

Next, the relative elevation between the workbench main body 11 and the supporting legs 12 is stopped, and the spiral pile 16 is driven into the seabed ground 18.

That is, the spiral pile drive device 23 lowers the spiral pile 16 while rotating it, and causes it to bite into the seabed ground 18 like a screw.

In this case, the guide member 20 indirectly guides the downward movement of the spiral 16 and at the same time supports the rotational reaction force of the spiral drive device 23.

If necessary, the bedrock is destroyed with water jetted from the high-pressure water jet port 17A prior to driving the spiral pile 16.

With the spiral pile 16 driven into the seabed ground 18 in this manner, downward forces F Al and F A2 are supported by the landing body 13 and the spiral pile 16, and upward forces are supported by the spiral pile 16.

That is, as shown in Fig. 2, the overturning moment of the offshore work platform is MA, the weight of the work platform body 11 is WA, and the reaction force of the submarine ground 18 acting on the lower surface of the landing body 13 is f Al, f A
2.If the mutual distance between the two support legs 12 is LA, then the stability of the offshore workbench is guaranteed if the following is satisfied.

■The formula shows that there is no limit to the overturning moment MA, which means that not only the work script and weight WA can be small, but also the distance between the supports and A can be small. means.

Therefore, it is possible to make the workbench main body 11 smaller and lighter, or to omit extra buoyancy capacity, and the bending moment generated in the workbench main body 11 can be significantly reduced, which is advantageous in terms of structural mechanics.

Furthermore, since most of the downward load is supported by the spiral pile 16, it is thought that it will occur around the landing body 13.

Regarding scouring, there is no danger associated with it, and since the landing body 13 is only used for temporary vertical load transmission when driving the spiral pile 16, it can be replaced with a conventional spud. There is no need to construct it with something as large as a tank, and it is better to construct it with a light structure such as a simple mud mat as shown in the figure.

In addition, the spiral pile 16 is rotated in the opposite direction to the seabed ground 18.
The spiral pile 16 is extracted from the cord 12A and housed in the cord 12A, but if this is difficult, it is also possible to bury only the spiral pile 16.

As is clear from the above description, according to the present invention, it is possible to easily reduce the size and weight of an elevating offshore work platform and simplify the structure, which is preferable in terms of resource saving and handling.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the conventional example, Fig. 2 is a schematic side view of the embodiment of the present invention, Fig. 3 is an enlarged cutaway view of the main part in Fig. 2, and Fig. 4 is the XX section in Fig. 3. The arrow view and FIG. 5 are explanatory views of the installation state of the elevating type offshore work platform according to the present invention. 11... Workbench body, 12... Support legs, 12A... Cord, 13... Landing body, 14... Lifting drive device , 16...Spiral pile, 18...Undersea ground, 19...
...Spiral bearing, 23...Spiral pile drive device.

Claims (1)

[Scope of utility model registration request] An elevating offshore workbench having a workbench body, support legs that move up and down relative to the workbench body, and a landing body provided at the lower end of the support legs, which includes a spiral pile that penetrates into seabed ground and its drive. An elevating type offshore work platform, characterized in that a device is installed in the support leg, and a bearing is interposed between the spiral pile and the support leg to allow the spiral pile to move up and down while rotating.