JPH04215587A - Installation method for vertical mooring type offshore floating platform - Google Patents

Abstract

PURPOSE:To eliminate the launching work at the installation site, decrease the underwater work, and improve the efficiency of the installation work when installing an offshore floating platform constituted of a hull, a tendon and a template on the site. CONSTITUTION:A template shell 10 is suspended under a hull A with a temporary wire 21, and the lower end of a tendon C is fixed to the template shell 10. The tendon C is wound on a tendon reel 22 and mounted on the hull A. The hull A is floated on the sea, the template shell 10 is suspended under the water, and they are towed to the installation site. The tendon C is delivered at the installation site, the template shell 10 is lowered and installed on the sea bottom, underwater concrete is placed in the template shell 10, then the tendon C is stretched to apply necessary tension.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for installing a vertically moored offshore floating platform (TLP) for use as an offshore facility such as a fishing base or an underground resource mining base.

0002

[Prior Art] Conventionally, this type of vertically moored offshore floating platform has a hull constructed by integrally supporting a deck plate on the upper ends of three or more hollow cylindrical buoyant bodies.
A template is connected under each of the buoyant bodies via vertical tendons, and by making the length of the buoyant bodies sufficiently long, vertical and horizontal rocking due to wave force is minimized. Conventionally, when installing this offshore floating platform, the hull, tendon, and template were each separated and loaded onto a work barge, and each part was hung in sequence using a crane boat at the installation site. Divers performed various tasks such as installing templates and connecting tendons.

0003

[Problems to be Solved by the Invention] The conventional installation method as described above has the following problems. ■Loading, transportation, and on-site launching operations are required for each hull and template. ■A large crane ship is required for on-site launching work. ■After launching on site, underwater work (diver or ROV) is required to connect the tendons to the template, which takes time and construction costs.

[0004] In view of the problems of the conventional method, the present invention has been developed to eliminate the launching work using a crane at the installation site,
The object of the present invention is to provide a method for installing a vertically moored offshore floating platform that reduces underwater work, allows safe and efficient installation work in a short time.

[0005]

[Means for achieving the object] A feature of the present invention for achieving the above-mentioned object is that a plurality of hollow column-shaped buoyant bodies are vertically arranged, and a deck plate is integrally supported at the upper end of the buoyant bodies. When installing a vertically moored offshore floating platform consisting of a vertically moored hull, a heavy mooring template sunk to the bottom of the water directly below the hull, and a tendon that vertically connects the hull and the mooring template, it is necessary to The hollow template outer shell constituting the shell is fixed under the buoyant body of the hull via a hanging wire, and the tendon is mounted on the hull and its lower end is fixed to the template outer shell, and then the hull is fixed. The template is floated on the ocean and towed, and at the installation site, the template outer shell is suspended from the hull while the tendons are being fed out, and is grounded on the water bottom vertically below it. Underwater concrete is poured into the grounded outer shell to form a predetermined position. After reaching the weight of the tendon, the necessary tension is applied to the tendon.

[0006]

[Operation] In the installation method of the present invention, the hull,
The tendon and template shell are assembled on land and lifted by a crane and launched into the water. However, since the template shell is hollow, there is no large increase in weight compared to conventional on-site launching of a hull. Because it can be launched from land,
A permanently installed large cargo handling crane can be used, eliminating the need for a large crane ship.

At the installation site, when the template shell is sunk, it is done by letting out a hanging wire using a winch installed on the hull or a small crane mounted on a work boat, and at the same time, the template shell is sunk by using a tendon that has been connected in advance. is fed out, eliminating the need for underwater tendon connection work. Concreting the template
It is possible to place underwater concrete using tremie tubes as is conventionally done, and this concrete placement provides a pre-designed template of the required weight. The necessary tension on the tendon is provided by adjusting the buoyancy of the hull and tensioning the upper end of the tendon.

[0008]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a vertically moored offshore floating platform installed according to the present invention, and in the figure, A indicates a hull, B indicates a template, and C indicates a tendon. The hull A is composed of four vertically oriented buoyant bodies 1 in the shape of hollow cylinders and a deck plate 2 integrally supported at the upper ends of the buoyant bodies 1.

[0009] The template B is constructed by integrating four blocks 3 located vertically below each buoyant body 1 and connecting them by a linking structure 4 made of steel. The tendon C is stretched between each buoyant body 1 and the block 3, and is moored in a state in which the buoyant body is pulled into the water by a tension necessary to prevent the buoyant body 1 from overturning even at the lowest tide level.

Each buoyant body 1 is provided with a tendon attachment chamber 5 in its upper end, and a tendon upper end fastening device 6 is provided on the floor of the chamber 5.
The upper end of tendon C is fixed by. The tendon C passes through the tendon insertion tube 7 at the center of the buoyant body 1 and extends downward. In addition, the tendon attachment chamber 5 of the buoyant body 1
Below is a buoyancy adjustment chamber 8 into which ballast water is poured and drained by a pump (not shown). In addition, in the figure, 9 is a bell mouth that relaxes the curvature of the tendon C. Each block 3 of template B is constructed by pouring underwater concrete 11 into a template outer shell 10 made of steel. A horizontal hole 13 is formed in this block 3 from the side surface near the bottom toward the center, and the lower end of the tendon C is inserted into a tendon insertion tube 14 that is opened through between the upper surface of the horizontal hole 13 and the upper surface of the block. It is inserted and fixed with a nut 15.

The template outer shell 10 has a downwardly extending skirt portion 10a extending from the outer periphery of the bottom surface thereof, and the underwater concrete 11 is inserted into the surface of the water bottom 12 with this skirt portion 10a extending downward.
The bottom shape is made to match the shape of the bottom surface of the water.

Next, the process of installing the platform described above will be explained.

[0013] In this method, the hull A, template B, and tendon C are moved to the installation site by floating them on the ocean and towing them in a state where they are temporarily connected in advance. First, prior to launching, template B and hull A are temporarily joined together before concrete is poured, as shown in FIG. For temporary connection, temporary connection posts 20 are previously set up on each template outer shell 10, as shown in FIGS. 3 and 4. This temporary connection post 20 consists of two short columns 2 on the center side of the template.
0a, 20a and two long columns 20b outside of them
, 20b and the beam member 20 connecting each column 20a, 20b.
The outer long column bodies 20b, 20b are located outside the buoyant body 1 of the hull A.

[0014] The hull A is lifted by a crane and placed on the temporary connection post 20 installed on each template outer shell 10 in this manner. At this time, the load of the hull A is received by each short column 20a, and the long column 20b is extended along the outer surface of each buoyant body 1 to prevent horizontal displacement between them.

After the hull A is placed, the hull A and the template outer shell 10 are connected with a temporary fixing wire 21.

On the other hand, a tendon reel 22 is rotatably placed on the deck plate 2 of the hull A at a square position as shown in FIG. and the tendon insertion tubes 7 and 14 of the template outer shell 10, and insert the nut 1 in the side hole 13.
5 and fix it to template B. In this way, the hull A and the template outer shell 10 are temporarily joined, and the tip of the tendon C is connected to the template outer shell 10, and as shown in FIG. 6, it is lifted up by the crane 23 and floated on the ocean. At this time, balance water necessary to maintain overall stability is injected into the buoyant body 1. In this way, floating on the ocean,
Towed to the installation site.

After arriving at the installation site, as shown in FIG. 7, the template outer shell 10 in the water is suspended by the crane 24 on the ship using the hanging wire 24a, and the weight of the ballast water is transferred to the buoyant body. 1, and the temporary bonding by the temporary fixing wire 21 is released. After that, the hanging wire 24a of the crane 24 is gradually paid out, and the template outer shell 1 is
0 to the specified position on the bottom of the water. At this time, since the tip of the tendon C is connected to the template outer shell 10 in advance, the tendon C is drawn out as it settles. After the template shell 10 is deposited, underwater concrete 11 is placed. When placing this concrete, as shown in FIG. More underwater concrete is poured into the tremie pipe 25.

After the underwater concrete 11 cast in this manner is solidified, the buoyancy of the hull A is adjusted and the tendons are tensioned. This work is carried out using the tide level, and without draining the ballast water 28 from the state shown in Fig. 9(A) at low tide level, the tendon upper end connection position 6a is raised to the planned height as shown in Fig. 9(B). When the tide level rises and tension is applied to the tendon C as shown in the same figure (C), the ballast water is removed as shown in the same figure (D), and the buoyant body 1 is placed at the planned position. Produces buoyancy. By this, tendon C
The necessary tension is applied to the vessel, and it is moored vertically without moving up or down even with changes in the tide level or waves.

In the present invention, when applying tension to the tendon C, the hull A may be suspended by a crane without using the tide level, and the ballast water may be drained while maintaining stability.

[0020]

As described above, in the offshore floating platform installation method of the present invention, the outer shell of the template is temporarily joined to the hull without filling it with concrete;
The template was floated on the ocean and towed to the installation site, and the template outer shell was submerged to allow the tendons to roll out.Afterwards, underwater concrete was filled into the template outer shell and the template was installed on the bottom of the water as a template of the required weight. This makes transporting the whole thing easier, and since the hull and template are not lifted into the air at the installation site, there is no need for a large crane ship.Furthermore, there is less underwater work, which solves the problem of difficulty in diving work, especially at great depths. This means that the installation work can be done safely and in a short period of time.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the completed state.

FIG. 2 is a vertical cross-sectional view of the main parts of the same.

FIG. 3 is a plan view of the template outer shell with temporary fixing posts attached.

FIG. 4 is a side view of the same.

FIG. 5 is a plan view of the hull with the tendon reel installed.

FIG. 6 is a side view showing the state at the time of launch.

FIG. 7 is a side view showing the step of settling the template shell.

FIG. 8 is a side view showing the underwater concrete placement state.

FIGS. 9A to 9D are side views showing a tendon tensioning process.

[Explanation of symbols]

A Hull B Template C Tendon 1. Buoyant body 2 Deck plate 3 Block 4 Concatenation 5 Tendon installation room 6 Tendon upper end connection device 7 Tendon insertion tube 8 Buoyancy adjustment room 9 Bell mouth 10 Template outer shell 10a Skirt part 11 Underwater concrete 12 Underwater 13 Side hole 14 Tendon insertion tube 15 Nut 20 Temporary connection post 20a Short columnar body 20b long columnar body 20c Girder material 21 Temporary fastening wire 22 Tendon reel 23, 24 Crane 25 tremie tube 26 Concrete pouring opening 27 Work boat 28 Ballast water

Claims (1)

[Claims] Claim 1: A hull in which a plurality of buoyant bodies in the shape of hollow columns are vertically arranged and a deck plate is integrally supported at the upper end thereof, and a gravity mooring template sunk in the bottom of the water directly below the hull. , when installing a vertically moored offshore floating platform consisting of the hull and a tendon vertically connecting the mooring template, a hollow template outer shell constituting the outer shell of the mooring template is suspended below the buoyant body of the hull. At the same time, the tendon is mounted on the hull and its lower end is fixed to the template outer shell, and then the hull is floated on the ocean and towed, and at the installation site, the tendon is rolled out and attached to the template. The outer shell is suspended from the hull and grounded to the bottom of the water vertically below it, and after pouring underwater concrete into the grounded outer shell to achieve a predetermined weight, the necessary tension is applied to the tendon. How to install a vertically moored floating platform.