JPS5922007B2 - How to lift the legs of an elevating offshore work platform - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for lifting legs of an elevating type offshore work platform.

The legs of a jack-up type oil rig usually have a triangular cross section and are very long, for example, 125 m.

Therefore, the upper half of the 65m leg cannot be loaded in the construction dock, so an oil rig with only the lower half of the leg attached was towed offshore and installed, and the upper half of the leg was carried offshore and a large floating crane was used to install it. A connection was being made.

However, according to this method, the suspension rope is attached to the upper end of the upper half leg, so if the seabed where the lower half leg is to be installed is shallow, the upper half leg will need to be placed above the lifting height of the floating crane. It became necessary to lift the oil rig and the legs of the upper half to a deep place, which was very inconvenient.

As a way to deal with this problem, as shown in FIGS. There is a method of attaching suspension ropes 3, 3 to the suspension beams 2, 2 and lifting the legs 1.

In addition, in the figure, 4 is a lower half leg, 5 is an oil rig supported by the lower half leg 4, and 6 is a floating crane.

However, this method has the following problems.

■ The weight of the hanging beam becomes large, which increases the cost and also makes handling difficult.

■ Since the legs have a triangular cross-section, they must be hung at a point that is off the center of gravity, which causes the legs to tilt, making it difficult to connect the upper and lower legs.

■ After the legs are joined, the suspension beam must be removed before the crane ship leaves, and it is very difficult to remove the suspension beam on the workbench.

The present invention proposes a method for lifting legs that can solve the above problems, and one embodiment thereof will be described below with reference to FIGS. 3 to 9.

Reference numeral 11 denotes an elevating offshore work platform (for example, an oil rig), which is supported by three legs 12.

Each of the legs 12 is formed of a pipe, and its cross-sectional shape is triangular with the pipe disposed at each vertex.

Further, each leg 12 is divided into two parts, and the parts are joined by a crane ship 13 on the sea.

12a is the upper leg of its upper half.

A predetermined location of the upper leg 12a, that is, a position within the lifting range of the crane 14 when raised by the crane 14 of the crane ship 13, and above the center of gravity in the longitudinal direction, and opposite to two adjacent sides of the upper leg 12a. hanging truss 15,
15 is installed.

In addition, the tips 15a, 15a of the above-mentioned hanging truss 15°15
The center of gravity of the triangular cross section of the upper leg 12a is located on the line connecting the two.

The suspension trusses 15, 15 are removably attached to the upper leg 12a via the attachment member 16, and therefore, the upper leg 12a is designed to serve as a work platform when the upper leg 12a is removed.

Next, the work will be explained.

The lower leg 12b, which is the lower half of the leg 12, is assembled together with the workbench 11 in a construction dock, and then transported to a predetermined location at sea and fixed therein.

After that, the suspension trusses 15, 15 are attached to the upper legs 12a on the ground.
Attach the upper leg 12a to the vicinity of the lower leg 12b, as shown in Fig. 5, and carry it by purge etc.
Next, as shown in FIGS. 6 and 7, the crane ship 13
The suspension ropes 17, 17 are lowered from the cranes 14, 14 of the 02 set and connected to both suspension trusses 15, 15 of the upper leg 12a, and the lower part of the upper leg 12a is supported by the hem ropes 1B, 1B.

Then, as shown in FIGS. 8 and 9, the upper leg 12a
was raised by cranes 14, 14, and the lower legs 12
b, and the upper and lower legs 12a and 12b are joined and integrated.

In addition, after the legs are joined, the crane ship 13 has a suspension truss of 15°1.
5 can be left on the legs 12, the hanging trusses 15, 15 can be removed after the workbench 11 has been jacked up to make the work easier.

As described above, according to the method for hoisting the legs of an elevating offshore work platform of the present invention, the legs are hoisted via the suspension trusses attached to both sides of the legs within the lift range of the crane when the legs are erected. Because it is raised, it can be lifted even if the upper end of the leg is higher than the lifting height of the crane.

Furthermore, since the center of gravity of the leg cross section is placed on the line connecting both ends of the suspension truss, the leg can be lifted in a stable state.

[Brief explanation of drawings]

Figure 1 is a side view of the conventional example, Figure 2 is a plan view of the same, Figures 3~
Fig. 9 shows an embodiment of the present invention, Fig. 3 is an enlarged front view of the main part, Fig. 4 is a plan view of the same, Fig. 5 is a diagram of the transportation state of the upper leg, and Fig. 6 is a diagram of the upper leg. Figure 7 is a plan view of the same, Figure 8 is a diagram of the state when the upper legs are raised, and Figure 9 is a diagram of the state of the lifting operation.
The figure is an overall plan view when the upper and lower legs are joined. 11... Workbench, 12... Legs, 12a
...... Upper leg, 12b... Lower leg, 13
・・・・・・Crane ship, 14・・・・・・Crane,
15... Hanging truss, 15a... End of hanging truss, 16... Mounting member.

Claims (1)

[Claims] 1. When lifting the legs of an elevating offshore work platform with a triangular cross section using a crane, first, when the legs are in a horizontal state,
Attach suspension trusses at predetermined positions on both sides of the leg within the lift range of the crane when the leg is erected, such that a line connecting the ends of the dual-purpose truss passes through the center of gravity of the triangular cross section of the leg;
A method for lifting a leg of an elevating offshore work platform, characterized in that the tip of the dual-purpose truss is then lifted by each crane of a crane ship having two sets of cranes.