JP2004175137A - Rocking suppressing method and mechanism of floating structure, and seawater pumping device using the method and mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rocking suppression method and mechanism for a floating structure capable of preventing a resonance with the period of waving, annex structure, etc. by changing the natural period of the rocking generated by waves and provide a seawater pumping device using the method and mechanism. <P>SOLUTION: The rocking suppression method and mechanism of the floating structure include a marine fertilizing device 1 equipped with the rocking suppression mechanism 50 structured so that a pipe tower part 20 furnished with a balance tank 52 is installed upright on the body part 10 equipped with a ballast tank 51 and water is delivered via a line 53 between the ballast tank 51 and the balance tank 52, and the weight balance about the vertical direction is changed to change the distance between the center of gravity and the center of buoyancy by moving the water between the ballast tank 51 and the balance tank 52, and thereby the natural period is changed to prevent generation of resonance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and a mechanism for suppressing fluctuations caused by waves of a floating structure which is levitated and installed on the water surface such as the sea, and a seawater pumping apparatus using the same.
[0002]
[Prior art]
In the case of floating structures floating on the water surface, such as offshore oil rigs and offshore plants, if the wave period matches the natural period of the vibration of the floating structure, resonance occurs, causing large fluctuations and instability. Therefore, it is designed such that the natural period of the floating structure is shifted in advance with respect to the period of the wave that prevails in the installation sea area. In addition, it is necessary to avoid natural vibration resonance with the incidental structure.
[0003]
However, since the wave cycle is not constant depending on the season and weather, it is necessary to take measures against waves with different cycles. The same applies to a floating structure that can be towed and whose installation sea area is not specified.
[0004]
As a configuration capable of suppressing the fluctuation of the floating structure due to the wave, there is one as disclosed in Patent Document 1.
[0005]
This is a semi-submersible marine structure that supports the workbench with a column that penetrates the water surface standing on a floating body that floats below the water surface. Forming a plurality of space chambers that can be opened and closed with a lid whose top is open, change the shape of the waterline by opening and closing the lid of each space chamber, attenuate the wave forcing generated by the incident wave, It is intended to suppress the motion of marine structures.
[0006]
[Patent Document 1]
JP-A-7-25382
[Problems to be solved by the invention]
However, in the sway suppressing configuration that changes the shape of the waterline as described above, although it is possible to suppress the sway in the vertical direction, the sway or the sway that swings back and forth or right and left around the center of gravity of the structure is performed. There is a problem that it cannot be suppressed.
[0008]
When the natural period of the oscillation matches the period of the wave, resonance occurs, the amplitude gradually increases, and there is a risk of eventually overturning. Further, if there is a connected incidental structure or the like, there is a possibility that the connecting portion may be damaged.
[0009]
The present invention has been made in view of the above problems, and in particular, can change the natural periods of pitching and rolling caused by the influence of waves to prevent resonance with wave periods and incidental structures. An object of the present invention is to provide a method and a mechanism for suppressing fluctuation of a floating structure and a seawater pumping apparatus using the same.
[0010]
[Means for solving the problem]
In order to achieve the above object, the method for suppressing the movement of a floating structure according to the present invention is characterized in that, in a floating structure floatingly installed on the water surface, a distance between a center of gravity and a floating center is changed by changing a vertical weight balance. It is characterized in that generation of resonance is prevented by appropriately changing the period.
[0011]
In this method, by changing the vertical weight balance and changing the distance between the center of gravity and the buoyant center, the natural period of pitching and rolling that is correlated with the distance between the center of gravity and the buoyant center is changed, and resonance is performed. Sway can be suppressed outside the region.
[0012]
In addition, the mechanism for suppressing the movement of the floating structure includes a balance weight member and a weight moving means for vertically moving the balance weight member in the floating structure floatingly installed on the water surface, and a balance weight by the weight moving means. It is configured to change the weight balance in the vertical direction by moving the member in the vertical direction, change the distance between the center of gravity and the buoyant center, change the natural period appropriately, and prevent the occurrence of resonance. I do.
[0013]
With this configuration, by moving the balance weight member in the vertical direction by the weight moving means, the weight balance in the vertical direction is changed to change the distance between the center of gravity and the buoyant center. The natural period of a certain pitching and rolling can be changed, and the oscillation can be suppressed outside the resonance range.
[0014]
Further, the floating structure has a tank at a lower part thereof, and the weight moving means includes a balance tank provided at an upper part of the floating structure, and a liquid moving pipe connected between the tank and the balance tank. And a liquid moving means for moving and driving the liquid between the tank and the balance tank, wherein the liquid in the tank is used as the balance weight member.
[0015]
With this configuration, the water in the tank is transferred to the balance tank disposed at the top via the liquid transfer pipe by the water supply means, thereby changing the vertical weight balance without changing the overall weight, The natural period can be changed while maintaining the draft position of the floating structure.
[0016]
In addition, the floating structure has a ballast tank at its lower portion for adjusting the floating and sinking by pouring and draining water. The weight moving means includes a balance tank provided at an upper portion of the floating structure, the ballast tank and the balance tank. And a water supply means for moving and driving water between the ballast tank and the balance tank, and configured to use water in the balance tank as the balance weight member. It is characterized by having.
[0017]
According to this configuration, the water in the ballast tank for performing the ups and downs adjustment is transferred by the water supply means to the balance tank disposed at the top via the water supply pipe line, so that the vertical weight can be maintained without changing the overall weight. By changing the weight balance, the natural period can be changed while maintaining the draft position of the floating structure.
[0018]
Further, as a seawater pumping device using a mechanism for suppressing the movement of the floating structure, a device body including the ballast tank and a pumping mechanism, a tower portion provided upright at a predetermined height in the device body and including the balance tank. A water intake pipe connected to a predetermined depth, which is connected to a lower part of the apparatus main body, and by adjusting buoyancy by pouring and discharging the ballast tank, during pumping operation, the apparatus main body is positioned at the sea surface during operation, and maintenance and inspection is performed. It is characterized in that the apparatus body is sometimes positioned on the sea surface during maintenance and inspection.
[0019]
According to this, when the apparatus main body having a large volume is pumped, the operating sea surface is submerged at a predetermined depth below the water surface, so that the influence of waves can be reduced and the shaking can be suppressed.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a front view showing an external appearance of a marine fertilizer, which is an example of a configuration of a seawater pumping apparatus to which a method for suppressing the movement of a floating structure according to the present invention is applied, FIG. 2 is a longitudinal sectional view thereof, and FIG. FIG. 3A is a sectional view taken along line AA of FIG. 1, and FIG. 3B is a sectional view taken along line BB of FIG.
[0021]
In the illustrated marine fertilizer apparatus 1, a tube tower section 20 as a tower section having a predetermined height is erected above a main body section 10 as an apparatus main body having a substantially disc shape having a predetermined thickness. The water intake pipe 30 is connected to the lower side, and is provided with a vibration suppression mechanism 50 that suppresses the vibration due to resonance by shifting the natural periods of the pitching and the rolling from the wave period. 1 and 2, the main body 10 is in a submerged state during the operation of pumping and discharging the deep water, and the deep water pumped up through the intake pipe 30 and the pipe tower section are shown. The surface water taken in through 20 is mixed and released and diffused as a density current to the surrounding side to form an artificial upwelling current. At the time of maintenance and inspection, the upper surface of the main body 10 is in a state of floating above the sea surface.
[0022]
Next, each part will be described in detail.
The main body 10 is configured such that a ballast tank 51 is disposed around the central equipment room 11, and the overall buoyancy can be adjusted by the amount of water injected into the ballast tank 51.
[0023]
The equipment room 11 is a flat octagonal sealable space in which a control device and the like are installed, and a water intake pipe 14 is vertically disposed at the center. On the upper side of the machine room 11, a disc-shaped discharge passage 16 having a predetermined thickness and being opened in the entire circumferential direction is formed by a flow path plate 15 disposed at a predetermined interval. A pump 40 is provided at the center of the plane.
[0024]
The pump 40 has upper and lower water inlets, the lower end of the tower 20 (tubular body 21) is connected to the upper inlet, and the intake line 14 penetrating the equipment room 11 is connected to the lower inlet. Are connected to each other, so that seawater is sucked from the upper and lower suction ports, respectively, mixed, and discharged to the surrounding discharge passage 16.
[0025]
The ballast tank 51 has the same height (thickness) as the equipment room 11 and is formed with a uniform width over the entire outer periphery of the equipment room 11, and the inside thereof corresponds to each side outside the equipment room 11 by a partition wall. It is divided into trapezoidal compartments 51A-51H. The compartments 51A to 51H of the ballast tank 51 are supplied with water and drained by a water injection / drain circuit described later in detail. In addition, a fixed ballast 17 is provided at the bottom of the ballast tank 51 for stably maintaining the posture of the marine fertilizer 1 even if the intake pipe 30 is to be lost. .
[0026]
The tube tower section 20 is configured such that an upper deck 22 having a larger diameter than the tubular body 21 is provided at an upper end of a tubular body 21 having a predetermined diameter and a predetermined length connected to a pump 40 at a lower end thereof. A surface water intake 21A is formed at a predetermined height of the tubular body 21.
[0027]
The upper deck 22 is formed integrally with an upper machine room 22A that houses a power generation device and the like and a balance tank 52 having a predetermined capacity below the upper machine room 22A. The balance tank 52 is connected to each of the compartments 51A to 51H of the ballast tank 51 via a pipe 53 provided inside the tubular main body 21.
[0028]
The water intake pipe 30 is a tubular member having a predetermined diameter and a predetermined length, and an upper end thereof is connected to a lower part of the main body 10 and communicates with the water intake pipe 14. The lower end is set so as to reach a deep water area (for example, a water depth of 200 m or less) at which water is to be taken.
[0029]
The sway suppressing mechanism 50 includes a ballast tank 51, a balance tank 52 provided on the upper deck 22 of the pipe tower section 20, a pipe 53 as a water supply pipe for injecting or draining water therefrom, and a control device (not shown). It consists of.
[0030]
A pipe 53 for injecting / draining water into / from the ballast tank 51 and the balance tank 50 is configured as shown in a circuit diagram in FIG.
[0031]
That is, the pipe 53 is connected to a main pipe 53A which is connected to a suction port opened to the water intake pipe 14 and an external discharge port, a balance adjusting pipe 53B reaching the balance tank 52, and each compartment of the ballast tank 51. The branch pipes 53C to 53F reaching 51A to 51H are respectively connected, a water supply pump 54 is interposed in the balance adjustment pipe 53B, and the downstream side of the water supply pump 54 of the balance adjustment pipe 53B and the main pipe 53A. Are connected by a bypass pipe 53C. Further, the control valve 55 is interposed before and after the balance adjustment pipe 53B of the main pipe 53A branches, before and after the bypass pipe 53C of the balance adjustment pipe 53B branches, and before and after the bypass pipe 53C of the main pipe 53A merges. A control valve 55 is provided in each of the branch pipes 53C to 53F that reach the compartments 51A to 51H. The water pump 54 and each control valve 55 are driven and controlled by a control device provided in the equipment room 11. In this configuration example, each of the compartments 51A to 51H of the ballast tank 51 is a set of two adjacent rooms.
[0032]
Thereby, by the drive control of the water pump 54 and each control valve 55 by the control device, water is injected into each of the compartments 51A to 51H of the ballast tank 51, drainage from each of the compartments 51A to 51H, and seawater in the ballast tank 51. The movement to the balance tank 52 and the drainage from the balance tank 52 can be performed. The individual buoyancy and inclination of the entire marine fertilizer 1 can be adjusted by the individual water injection and drainage of the compartments 51A to 51H of the ballast tank 51, and the seawater in the ballast tank 51 can be adjusted by the balance tank. By moving to 52, the vertical weight balance of the marine fertilizer 1 can be changed.
[0033]
The sway suppressing mechanism 50 having the above-described configuration moves the seawater in the ballast tank 51 to the balance tank 52 to resonate the natural cycle of pitching and swaying with the wave cycle and the intake pipe 30 as an incidental structure. The fluctuation is controlled so as not to cause the fluctuation.
[0034]
That is, as shown in FIG. 5, which is a graph showing the relationship between the pitching cycle and the amplitude in a plurality of examples in which the distance between the center of gravity and the center of gravity (metacenter height: GoM) is changed, for example, the natural period of the pitching is the center of gravity and the center of the floating. Since the correlation is inversely proportional to the distance between the hearts (the shorter the distance between the center of gravity and the center of buoyancy, the longer the natural period of pitching becomes), the seawater is moved between the ballast tank 51 and the balance tank 52, and the marine fertilizer is used. By moving the position of the center of gravity up and down to change the distance between the center of gravity and the buoyant center, the natural period of pitching is set so as not to cause resonance with the wave period and the natural vibration of the intake pipe 30, and the vertical The vibration can be suppressed by preventing the resonance of the sway and the roll.
[0035]
For example, in FIG. 5, when GoM = 1 m, resonance occurs for a wave having a period of 14 seconds, but by changing this to GoM = 0.5 m, resonance can be avoided.
[0036]
Since the weight balance is changed by the movement of seawater between the ballast tank 51 and the balance tank 52, there is no weight change as a whole, and the marine fertilizer 1 maintains a predetermined draft position without floating and sinking. be able to.
[0037]
Here, if the installation sea area is specified and the period of the wave that prevails in the sea area is known, the natural period of the marine fertilizer 1 can be set in advance so as not to resonate. However, as in the present configuration example, the main body portion 10 moves vertically between a position where the main body portion 10 is submerged at a predetermined depth below the water surface and a position where it floats on the water surface, and at this time, the draft passes through the discharge passage 16. If the water line area changes greatly due to the passage, it is desirable to set the distance between the center of gravity and the center of gravity as large as possible in order to maintain stability during the floating movement. However, on the other hand, even when the main body 10 is located at a predetermined depth, the natural period may coincide with the wave period if the distance between the center of gravity and the center of gravity remains unchanged. In such a case, resonance can be prevented by changing the natural period. In other words, sedimentation and levitation can be performed in a highly stable state by injecting water only into the ballast tank 51, and can be set to an arbitrary natural period in which water is injected from the ballast tank 51 to the balance tank 52 to prevent resonance during work. is there. For example, in FIG. 2, the center of gravity: GC1 at the time of settling and ascent is changed to the center of gravity: GC1, and the center of gravity: GC2 is changed at the time of work to prevent resonance.
[0038]
The marine fertilizer 1 configured as described above floats on the sea surface with its central axis being vertical by the weight of the fixed ballast 17 and the water intake pipe 30, is moored to the sea floor by the mooring line 2 such as a chain, and Installed in sea area.
[0039]
At the time of pumping and discharging the deep water, the buoyancy is adjusted by pouring into and out of the ballast tank 51 so that the discharge passage 16 is placed in a floating state so as to be located at a predetermined discharge depth (for example, a water depth of 30 m) in the luminous layer. The surface water taken in from the tube tower section 20 and the deep water pumped up through the water intake pipe 30 are mixed by the driving of 40 and discharged from the discharge passage 16 to the surroundings. The released deep water is diffused horizontally as a density stream in the euphotic layer, and promotes the growth of phytoplankton by its nutrition. As a result, a fishing ground can be created in a natural environment.
[0040]
As described above, when the main body 10 having a large volume is submerged at a predetermined depth below the water surface during operation, the area of the water line can be made extremely small, so that the influence of waves can be reduced and the shaking can be suppressed. Further, when there is a possibility that the wave cycle resonates with the natural cycle of the marine fertilizer 1, the natural cycle is changed by moving the seawater between the ballast tank 51 and the balance tank 52 by the fluctuation suppressing mechanism 50. Resonance can be prevented, stable installation is possible, and a load acting on a structure such as a joint between the main body 10 and the water intake pipe 30 can be reduced. It can be built.
[0041]
On the other hand, at the time of maintenance and inspection, it is possible to increase the buoyancy by draining the water from the ballast tank 51 so that the upper surface of the main body 10 is floated so as to be above the water surface.
[0042]
The above configuration example is an application of the present application to a seawater pumping apparatus, but is not limited to this and can be applied to other floating structures. Further, the configuration example of the above-mentioned fluctuation suppressing mechanism is to change the weight balance in the vertical direction by moving water between the ballast tank 51 and the balance tank 52, but the configuration for changing the weight balance is not limited to this. Instead, for example, it is possible to appropriately change the configuration such that the balance tank 52 is independently and externally supplied with water and drained from the ballast tank 51 in synchronism.
[0043]
【The invention's effect】
As described above, the method for suppressing the movement of a floating structure according to the present invention includes changing the distance between the center of gravity and the floating center by changing the vertical weight balance of the floating structure that is installed floating on the water surface. In addition, the occurrence of resonance is prevented by changing the natural period.
[0044]
Thus, by changing the vertical weight balance and changing the distance between the center of gravity and the buoyant center, the natural periods of pitch and roll, which are correlated with the distance between the center of gravity and the buoyant center, are changed outside the resonance range. , Can be suppressed.
[0045]
In addition, the mechanism for suppressing the movement of the floating structure includes a balance weight member and a weight moving means for vertically moving the balance weight member in the floating structure floatingly installed on the water surface, and a balance weight by the weight moving means. It is characterized in that the weight balance in the vertical direction is changed by moving the member in the vertical direction to change the distance between the center of gravity and the floating center, and the natural period is changed to prevent the occurrence of resonance.
[0046]
According to this configuration, by moving the balance weight member in the vertical direction by the weight moving means, the weight balance in the vertical direction is changed, thereby changing the distance between the center of gravity and the buoyant center, and correlating with the distance between the center of gravity and the buoyant center. The natural period of the pitching and the rolling related to each other is changed out of the resonance range, and the vibration can be suppressed.
[0047]
Further, the floating structure has a tank at a lower part thereof, and the weight moving means includes a balance tank provided at an upper part of the floating structure, and a liquid moving pipe connected between the tank and the balance tank. And a liquid moving means for moving and driving the liquid between the tank and the balance tank, wherein the liquid in the tank is used as the balance weight member.
[0048]
According to this configuration, the water in the tank provided at the lower part of the floating structure is transferred to the balance tank provided at the upper part via the liquid transfer pipe by the water supply means, thereby changing the overall weight. The weight balance in the vertical direction can be changed without any change, the natural period can be changed while maintaining the draft position of the floating structure, resonance can be prevented, and sway can be suppressed.
[0049]
In addition, the floating structure has a ballast tank at its lower portion for adjusting the floating and sinking by pouring and draining water. The weight moving means includes a balance tank provided at an upper portion of the floating structure, the ballast tank and the balance tank. And a water supply means for moving and driving water between the ballast tank and the balance tank, and configured to use water in the balance tank as the balance weight member. It is characterized by having.
[0050]
According to this configuration, the water in the ballast tank for performing the ups and downs adjustment is transferred by the water supply means to the balance tank disposed at the top via the water supply pipe line, so that the vertical weight can be maintained without changing the overall weight. By changing the natural balance while changing the weight balance and maintaining the predetermined draft position adjusted for floating, the resonance can be prevented and the sway can be suppressed.
[0051]
Further, as a seawater pumping device using a mechanism for suppressing the fluctuation of the floating structure, an apparatus body including the ballast tank and the pumping mechanism, a tower section provided with a balance tank erected at a predetermined height in the apparatus body, At the lower part of the device body, there is a water intake pipe connected to a predetermined depth, which is connected to the ballast tank.By adjusting the buoyancy by pouring and draining the ballast tank, the device body is positioned at the sea surface during operation during pumping operation, and the device body is maintained during maintenance and inspection. It is configured to be located on the sea surface during maintenance and inspection.
[0052]
According to this configuration, during pumping operation, the apparatus main body having a large volume is placed below the surface of the water at the time of operation, thereby reducing the influence of waves and suppressing shaking. It is possible to perform maintenance and inspection easily by positioning it on the sea surface during maintenance and inspection. Further, sedimentation and levitation can be performed in the most stable state by injecting only the ballast tank, and in the installed state, water can be injected from the ballast tank to the balance tank to set an arbitrary natural cycle to prevent resonance.
[Brief description of the drawings]
FIG. 1 is a front view showing the appearance of a marine fertilizer, which is an example of the configuration of a seawater pumping apparatus to which a method for suppressing the movement of a floating structure according to the present invention is applied.
FIG. 2 is a longitudinal sectional view of FIG.
3A is a sectional view taken along line AA of FIG. 1, and FIG. 3B is a sectional view taken along line BB of FIG.
FIG. 4 is a pipe circuit diagram of water injection / drainage to a ballast tank and a balance tank.
FIG. 5 is a graph showing a relationship between a pitching cycle and an amplitude.
[Explanation of symbols]
1 Marine fertilizer (floating structure)
10. Main unit (main unit)
20 Tube tower (tower)
30 intake pipe 40 pumping discharge pump (pumping mechanism)
50 Movement Suppression Mechanism 51 Ballast Tank 52 Balance Tank 53 Pipe (Water Pipe)
54 Water supply pump (water supply means)

Claims (5)

In a floating structure floatingly installed on the water surface,
A method for suppressing fluctuation of a floating structure, characterized in that a distance between a center of gravity and a floating center is changed by changing a vertical weight balance, and a natural period is changed to prevent occurrence of resonance. In a floating structure floatingly installed on the water surface,
A balance weight member, and weight moving means for moving the balance weight member in the up-down direction. A fluctuation suppressing mechanism for a floating structure, characterized in that a distance is changed and a natural period is changed to prevent occurrence of resonance. The floating structure has a tank at its lower part,
The weight moving means moves a liquid between the tank and the balance tank, a liquid tank connected to the tank and the liquid tank, and a balance tank disposed above the floating structure. 3. A mechanism for suppressing the movement of a floating structure according to claim 2, wherein the mechanism comprises a liquid moving means to be driven, and the liquid in the tank is used as the balance weight member. The floating structure is provided with a ballast tank at its lower part for adjusting up and down by pouring and draining,
The weight moving means includes a balance tank disposed above the floating structure, a water supply pipe connected between the ballast tank and the balance tank, and water between the ballast tank and the balance tank. The movement suppressing mechanism for a floating structure according to claim 2, wherein the water supply means is configured to move and drive, and the water in the balance tank is used as the balance weight member. An apparatus main body including the ballast tank and the pumping mechanism, a tower section provided with the balance tank erected at a predetermined height in the apparatus main body, and an intake pipe reaching a predetermined depth that is vertically connected to a lower part of the apparatus main body. With
By adjusting the buoyancy by pouring and draining the ballast tank, the apparatus body is positioned on the sea surface during operation during pumping operation, and the device body is positioned on the sea surface during maintenance and inspection during maintenance and inspection. A seawater pumping apparatus using the mechanism for suppressing the movement of a floating structure according to claim 4.

Images