JPS6268914A - Controlling method for upsetting moment of jack-up rig - Google Patents

Abstract

PURPOSE:To prevent legs from being upset without enlarging a jack-up rig, by arranging preload tanks around the leg well of a platform, and by loading ballast in the preload tanks on the wave and windward side. CONSTITUTION:Around the leg well of a platform 11 with penetrating legs 12f, 12p, 12s, preload tanks Tf, Tp, Ts are arranged, and the tanks are provided with pumps Pf, Pp, Ps for injection and drainage. When wave 16 or wind 17 strikes the foreleg 12f, then through a computer 15, on the basis of load cells Ls, Lp, Lf detecting loads applied to the legs 12f, 12p, 12s, a necessary quantity of ballast is injected into the preload tank Tf around the foreleg 12f. As a result, the applied loads are worked on the wave and windward side of the platform 11, and a jack-up rig can be prevented from being upset.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling the overturning moment of a jack up rig.

2. Description of the Related Art As shown in FIG. 2, a conventional jack-up rig has a structure in which a platform 3 is supported by a plurality of legs 2a and 2b that touch the bottom of the water 1.

By the way, in the jacked-up state where the platform 3 is lifted to the water surface 4J:, an overturning moment (M) due to waves 5 and wind 6 acts on the entire rig. In order to balance this overturning moment (M), each leg 2a, 2t+
A balancing moment (V9.) occurs. Here, (see) is the distance between legs 2a, 2b.

On the other hand, due to the weight of platform 3 and legs 2 and 2,
A vertical force (W) is acting on the legs 2a and 2b. Therefore, the vertical reaction forces Ra and Rb acting on the legs 2a and 2b are determined by the following equations.

Ra=W+V- wave, leeward leg (2a) Rb=W-V-
...Wave, windward leg (2b) Problem to be solved by the invention In the above, the force (V) on the wave and windward side becomes larger than the vertical force (W), and the vertical reaction force (Rb) A negative value means the rig will tip over.

To avoid this fall, increase the vertical force (W),
The force (V) must be reduced.

However, in order to increase the vertical force (W), the weight of the platform 3 must be increased, which requires increasing the strength of the legs 2a, 2b and the platform 3. As a result.

This is a problem because the initial cost of the rig increases.

On the other hand, in order to reduce the force (V), the distance (9J) must be increased. For this purpose, it is necessary to increase the size of the plant form 3, and as a result, the weight of the platform 3 also increases, resulting in the same problem as the above-mentioned increase in initial cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to effectively prevent the legs from falling over without increasing the initial cost due to an increase in the size of the platform.

Means for Solving the Problems In order to solve the above problems, the present invention provides for loading ballast into a preload tank arranged around the leg well of the platform through which the leg located on the windward side of the wave passes, and This applies an additional load to the

In other words, when a jack-up rig is installed in a predetermined position, the platform is lifted above the water surface after the legs have landed on the bottom, and the load is applied to the legs by injecting water into a preload tank provided within the platform. This ensures that the legs are installed on the bottom of the water tank.After the legs are installed, the inside of the preload tank is drained. Ballast is loaded into the preload tank part around the leg located on the windward side to give additional load to the leg.If you do this, the load acting on the leg will increase, so
It is possible to prevent the vertical reaction force from becoming a negative value and prevent the leg from falling. In addition, the preload tank, the pump for filling and draining into the tank, etc. that are already built into conventional ones can be used, and it is possible to effectively prevent the legs from falling over without increasing the size of the platform or legs.

Embodiment FIG. 4 shows a plan view of a jack up rig, in which 11 is a platform, 12f is a foreleg, 12P is a port leg, and 12s is a starboard leg. 13 is Legwell. Further, (T1) to (T8) are preload tanks, which are divided into sections within the platform 11. Preload tank (T5) is plant form 1
The other preload tanks (T□) to (T, ) and (T6) to (T8) are formed at full depth. 14 is a bomb plume for injecting seawater as ballast into the tanks (T1) to (T8).

FIG. 3 shows a control device for injecting and discharging ballast into tanks (T□) to (T6). Here, preload tanks (T1) to (T,) are 1 for convenience.
Tank (Tf) around 2f (Tank (T,) (T2)
etc.), the tank around boat leg 12P (Tp
)(Tank around this leg 12ρ (T,)(T,)(T
, ), etc.), and the tank (TS) around the starboard leg 12s (tank around the main leg 12s (TS)
S) (Te) (T7), etc.) will be explained separately.

Each preload tank (Tf) (Tp) (Ts) has a ballast pump (Pf) (Pp
) (Ps) are connected, and these pumps (pf) (
The operation of Pp) and Ps is controlled by a computer 15. Also, computer 15 has leg 1
Signals from load cells (Lf) (Lp) (Ls) for detecting the load applied to 2f, 12p, and 12s are input.

Now, as shown in Figure 1, there is a wave 16 on the foreleg L2f.
When wind 17 hits, the necessary amount of ballast weight (
Load additional load) (ΔW) and satisfy the following formula.

Rb=W+AW-V>0+(7-jin) The appropriate margin is about 200 to 500 tf.

The specific amount of ballast to be loaded is determined based on information from each load cell (Lf) (Lp) (Ls).

The computer 15 controls the ballast pump (P f) (P
p) (P s) is automatically controlled. Alternatively, the computer 15 is not installed and the operator manually operates the pump (P f) (Pp) (PS).
Preload tank (T f) with appropriate amount of ballast (T
p) (T s).

As described above, according to the present invention, by applying the ballast heavy electric current (ΔW) as an additional load, it is possible to reliably prevent the jack-up rig from overturning, and it is particularly preferable to apply it to a jack-up rig for deep water. In addition, the only new equipment required is a simple combi coater, and the rest can be used as is, making it simple and inexpensive, making it easy to convert existing rigs to deep water applications. be able to. In addition, in the case of manual operation as described in L, a computer described in "2" is also not required.

Effects of the Invention According to the present invention, it is possible to prevent overturning without increasing the size of the jackup rig, and there is no need to increase the weight of the platform or legs, so the initial cost is reduced to 1. can be kept low. Moreover, since there is no need to increase the size of the platform 11, the wind pressure receiving area does not increase, and from this point of view as well, there is an advantage that the overturning moment 1- can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic LE view of an embodiment of the present invention, FIG. 2 is a schematic front view of a conventional example, FIG. 3 is a schematic diagram of a control device in an IJ of the present invention, and FIG. It is a top view of a luck up rig. 12f...Foreleg, 12p...Bow 1-leg,
12s...Starboard leg, 13...Legwell, (Tf) (Tp) (Ts)...Preload tank,
(ΔW)...Balance 1 ~ East load (additional load) Agent Yoshihiro Morimoto Figure 2 Ra Rb Figure 3

Claims (1)

[Claims] 1. Overturning moment control for a jack-up rig characterized by loading ballast into a preload tank placed around the leg well of a platform penetrated by a leg located on the windward side of the waves, and applying additional load to the leg. Method.