JP2002002584A - Intake system for ballast water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take in ballast water having few impurities such as dirty mud, by switching a plurality of intake ports according to conditions. SOLUTION: This intake system for ballast water comprises the plural intake ports 6a to 6c disposed at a different height in a hull 1, a pump 10 functioning as an intake means for taking the ballast water through all or arbitrary some of the plural intake ports 6a to 6c, an intake controlling portion 5 functioning as a selecting means for selecting an intake port conducting taking water from the plural intake ports 6a to 6c on the basis of a predetermined standard, and valves 9a to 9c functioning as a switching means for switching the intake ports 6a to 6c conducting taking water on the basis of the selected result of the intake controlling portion 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water intake system for taking out ballast water in various ships.
In particular, the present invention relates to a ballast water intake system that can take in ballast water with little impurities such as sludge.

[0002]

2. Description of the Related Art The hulls of various ships such as cargo ships and passenger ships are provided with ballast tanks and water intake systems. Then, by injecting water such as seawater into the ballast tank through the water intake system, it is possible to adjust the balance of the hull and the draft position.

FIG. 9 shows a vertical sectional view of a ship provided with such a conventional water intake system. In FIG. 9, an intake system includes an intake 100 provided near the bottom of the ship.
And a pump 101 for sucking ballast water through the water intake port 100 and a water intake control unit 102 for controlling the pump 101. When the pump 101 is driven under the control of the water intake control unit 102, ballast water is withdrawn through the water intake port 100, and each ballast tank 103 of the hull (shown by an imaginary line).
It is poured into water. The reason why the water intake port 100 is provided near the bottom of the ship is to enable water intake even when the waterline is positioned below the hull by the ship being unloaded.

[0004] In recent years, discharge of ballast water mixed with impurities such as sludge and microorganisms to the outside of a ship has been gradually restricted. In particular, when a ship enters port, the ballast water that has been withdrawn in another country is discharged, which may cause microorganisms to enter the country.
Draining impure ballast water is more closely monitored. Therefore, it is preferable to take in only ballast water in which impurities are not mixed as much as possible when taking in ballast water.

[0005]

However, in the conventional ballast water intake system, the intake port 100 is simply provided in the vicinity of the bottom of the ship as described above. It was difficult. In other words, when a ship enters a shallow bay,
Bottom 1 by the ship itself or a tugboat towing the ship
Because the sediment 105 of 04 is rolled up or soared by the influence of the water flow due to water intake, when water is taken from the water intake 100 near the water bottom 104, sludge, microorganisms, and the like are mixed. There was a high possibility of getting it. As a result, a lot of sludge or the like enters the ballast tank 103, and it is necessary to replace ballast water before entering the port to discharge sludge or the like, or when impurities are accumulated in the ballast tank 103. And the like, there is a problem that an operator needs to clean the ballast tank.

The present invention has been made in view of the above-mentioned problems in the conventional ballast water intake system. By switching a plurality of intake ports in accordance with the situation, it is possible to reduce the amount of impurities such as sludge. It is an object of the present invention to provide a ballast water intake system capable of taking ballast water.

[0007]

In order to achieve the above object, a ballast water intake system according to claim 1 is provided.
A plurality of intake ports arranged at different heights of the hull, intake means for taking ballast water through all or any part of the plurality of intake ports, and a plurality of intake ports based on a predetermined standard Selecting means for selecting an intake from which water is taken, and
Switching means for switching a water intake port for taking water based on a selection result of the selection means is provided.

In this water intake system, a plurality of water intakes are switched and used based on a predetermined standard. As the predetermined standard, any standard for taking in ballast water containing no impurities as much as possible can be used. According to such a system, ballast water with less impurities can be taken by switching the position of the water intake according to the situation. Therefore, the possibility of impurities being deposited in the ballast tank is reduced,
The trouble of cleaning the inside of the ballast tank can be omitted.

The term “impurities” refers to impurities that can be restricted by various regulations relating to the discharge of ballast water, and all impurities that are not related to regulations but can adversely affect ships by being mixed into ballast water. I do. One example is sludge and microorganisms deposited on the bottom of the water.

Further, in the ballast water intake system according to claim 2, the predetermined reference in the selection means is an intake port located at a highest position among intake ports located below a waterline of the hull. Is set to be selected. This is an example of the selection criteria of the intake port.In this case, since the intake is always performed from the intake port at the highest position, impurities wound up near the water bottom enter the ballast tank. That can be prevented to the utmost. In addition, the position lower than the water line is the position directly below the water line,
This includes a position separated by a predetermined distance from the waterline for safety.

In the ballast water intake system according to the third aspect, the predetermined criterion in the selection means is that all of the intake ports located at a position lower than the waterline of the hull, which are separated from the water bottom by a predetermined distance or more. Is set so as to select the water intake. This shows another example of the selection criteria of the intake, for example, when there are a plurality of intakes that can be taken, and when a plurality of intakes are sufficiently away from the bottom of the water, Water can be taken in through all water intakes remote from the water bottom. When water is taken from a plurality of water intakes in this way, the water intake speed can be improved.

The ballast water intake system according to a fourth aspect of the present invention, wherein the position of the intake port located at the highest position among the plurality of intake ports is set to a position below the waterline of the hull in the maximum loading state. The water intake port located at a lower position is located below the waterline of the hull in the no-load state. This shows an example of the basis of the arrangement position of the plurality of intake ports. In this case, the maximum loading state (the state where the waterline is located at the highest position)
, Water can be taken from at least one water inlet, and water can be taken from at least one water inlet even in a no-load state (a state where the waterline is located at the lowest position).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a ballast water intake system according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited by the embodiment.

(Embodiment 1) FIG. 1 is a side view of a ship provided with a ballast water intake system according to this embodiment, FIG. 2 is a longitudinal sectional view of the ship of FIG. 1, and FIG. It is a part enlarged view. The present embodiment generally relates to a ballast water intake system in which a plurality of intake ports having different heights are provided, and the plurality of intake ports are switched based on a draft position to perform intake.

As shown in FIGS. 1 and 2, a plurality of ballast tanks 2 (shown by imaginary lines) are provided on a hull 1 of a ship at substantially equal positions in the vertical and horizontal directions. Ballast water is injected into each of these ballast tanks 2 through a water intake system 3. The water intake system 3 includes first to fourth water intake systems 4a to 4d, and these water intake systems 4a to 4d.
(A fourth water intake system 4d is not shown).

Of the first to fourth water intake systems 4a to 4d,
As shown in FIGS. 1 and 2, the first and second water intake systems 4a and 4b are arranged substantially symmetrically at the center of the hull 1. In addition, the third and fourth intake systems 4
c and 4d are arranged substantially symmetrically at the rear of the hull 1. As described above, it is preferable that the water intake systems 4a to 4d are arranged so that water can be taken in a well-balanced manner in front, rear, left, and right of the hull 1. However, the intake system 4a
The number, arrangement position, and the like of 4d to 4d are arbitrary, and can be changed according to the desired water intake capacity, the shape of the hull 1, and the like. For example,
More intake systems can be provided in addition to the first to fourth intake systems 4a to 4d.

Since the first to fourth intake systems 4a to 4d have the same configuration, the first intake system 4a will be described below.
This will be described with reference to a. This first water intake system 4a
As shown in FIGS. 1 and 2, a plurality of (three in the present embodiment) water intake ports 6, water intake pipes 7 connected to each water intake port 6, and a common connection to these water intake pipes 7. Main pipeline 8
And a valve 9 disposed in the conduit of each intake conduit 7 and a pump 10 disposed in the conduit of the main conduit 8 (hereinafter, the intake port 6, the intake conduit). 7, and the valve 9 are shown with subscripts a to c from the bottom to the top as shown in FIG. 2).

As shown in FIG. 3, each of the water intake ports 6a to 6c is provided on an outer wall 1a of the hull 1 and includes a water intake wall 11 having a plurality of through holes and a water intake chamber 12 adjacent to the water intake wall 11. It is comprised including. Then, water (in the case of a marine vessel, seawater) flows into the water intake chamber 12 from the outside of the hull through the through hole 11a provided in the water intake wall 11, and water can be taken. Here, when water passes through the through hole 11a of the water intake wall 11, relatively large impurities such as wood chips are removed.

Further, in the water intake chamber 12, the precipitation of impurities in the water is promoted, so that impurities flowing into the water intake pipes 7a to 7c can be reduced. The water intake chamber 12 can be provided with a plurality of partition walls to make it difficult for impurities to flow into the water intake pipes 7a to 7c, or can be provided with a mechanism for removing impurities such as a filter or a cyclone separator. .

The plurality of intake ports 6a to 6a configured as described above.
6c, as shown in FIG. 1, positions at different heights (heights H1, H2, H3 (H1 <H2 <H
3)). Thus, the intake 6
Since a to 6c are arranged at different heights, it is naturally possible to take water at different heights.
However, as long as this function can be performed, the number and arrangement height of the water intake ports 6a to 6c can be appropriately changed other than those illustrated. For example, the plurality of water intake ports 6a to 6c do not necessarily have to be juxtaposed along the vertical direction, but may be juxtaposed in an inclined direction slightly inclined with respect to the vertical.

In the present embodiment, the position H3 of the intake port 6c arranged at the highest position is determined by the maximum allowable number of personnel and the load on the hull 1 (the maximum loading state). This is a position below the waterline. Also,
The position H1 of the intake port 6a disposed at the lowest position is a position below the waterline of the hull 1 in a state where the minimum number of personnel and loads are loaded on the hull 1 (no load state).

Therefore, in the maximum loading state, it is possible to take water from the intake ports 6a to 6c of the height H3, and in the non-load state, the intake port 6a of the height H1.
Can take water from. In addition, the height H2 of the water intake port 6b arranged at the intermediate position is substantially the center position between the heights H1 and H3. In addition, as the water intake port 6a having the height H1, a water intake port that is conventionally provided near the bottom of the hull 1 can be used.

The intake lines 7a to 7c, the main line 8, and the pump 10 connected to the intakes 6a to 6c.
Constitutes a water intake means for taking in ballast water through the water intake ports 6a to 6c. That is, when the pump 10 is driven, each of the water intake pipes 7a to 7a through the water intake ports 6a to 6c.
Water is led to 7 c, and this water is further led to the pump 10 through the main line 8. A branch pipe (not shown) is connected to a stage subsequent to the pump 10, and ballast water is injected into each ballast tank 2 via the branch pipe. This branch pipe can be configured similarly to the conventional one.

The structures of the water intake lines 7a to 7c, the main line 8, and the pump 10 are not limited to those shown in the drawings, and it is possible to perform water intake through at least a plurality of water intakes 6a to 6c. What is necessary is just to be able to switch the water intake ports 6a to 6c in cooperation with the valves 9a to 9c as switching means described in detail later. For example, the pump 10 may be arranged in each of the intake lines 7a to 7c instead of the main line 8, and in this case, the intake lines 7a to 7c are directly connected to the branch lines, and The road 8 can be omitted. Further, specific specifications of the water intake conduits 7a to 7c, the main conduit 8, and the pump 10 can be appropriately determined so as to correspond to a required water intake amount and water intake speed.

The valves 9a to 9c provided in the water intake pipes 7a to 7c are remote valves that are automatically opened and closed under the control of the water intake control unit 5, and when opened, the valves 9a to 9c are open. Intake pipeline 7 where 9c is arranged
water can be withdrawn through a to 7c, and in a closed state, water cannot be withdrawn through the intake pipes 7a to 7c in which the valves 9a to 9c are arranged. . That is, by controlling the opening and closing of the valves 9a to 9c, the water intakes 6a to 6c used for water intake can be switched. In this respect, the valves 9a to 9c
Functions as switching means for switching the water intake ports 6a to 6c.

However, other components besides the valves 9a to 9c can be used as means for switching the intake ports 6a to 6c. For example, as described above, each of the intake pipes 7a
7c is provided with a pump 10,
Can be individually switched by turning on / off the water intake ports 6a to 6c.
Functions as switching means for the water intake ports 6a to 6c.

Next, the water intake control section 5 will be described.
The water intake control unit 5 includes first to fourth water intake systems 4a to 4d.
Are electrically connected to and control the valves 9a to 9c, the pumps 10, and the draft gauge 13 described later. The details of control by the water intake control unit 5 will be described in detail later, but generally, a plurality of water intake ports 6a are determined based on the position of the waterline measured by the water gauge 13.
6c functions as a selecting means for selecting a water intake for water intake, and controls the valves 9a to 9c and the pumps 10 to perform water intake in accordance with the selected content.

As described above, the water intake control unit 5 includes
Since the fourth intake system 4a-4d is provided in common, it is possible to perform the same control for all the intake systems 4a-4d and to perform a well-balanced intake control over the entire hull. It is. However, it is also possible to separately provide the water intake control unit 5 for each of the water intake systems 4a to 4d. In this case, it is possible to perform different detailed water intake control in each part of the hull. The water intake control unit 5 is specifically composed of a CPU (Central Processing Unit) and a program analyzed and executed by the CPU. Can be shared with the department. However, the intake control unit 5
Can be configured by wired logic.

Next, a criterion for selecting the water intake ports 6a to 6c for performing water intake in the water intake control unit 5 will be described. As this criterion, any criterion for removing water containing no impurities as much as possible can be used.
For example, at least the intake ports 6a to 6c capable of taking water (first selection criterion), and when there are a plurality of intake ports 6a to 6c capable of taking water, the mixing ratio of impurities is considered to be relatively low. An intake that satisfies that one or a plurality of intakes 6a to 6c (second selection criterion) is selected.

In order to determine the first selection criterion, in the present embodiment, as shown in FIG.
3 are provided. The draft gauge 13 measures a height from a ship bottom to a draft line (hereinafter, a draft position) and outputs a signal corresponding to the height. As the draft gauge 13, a gauge conventionally provided for ship navigation can also be used. The output from the draft meter 13 is input to the water intake control unit 5, and the water intake control unit 5 analyzes the output to obtain the position of the water line and the preset height H1 of each of the water intakes 6a to 6c. By comparing H3 to H3, it is determined which of the water intake ports 6a to 6c can take water.

Specifically, if the heights H1 to H3 of the water intakes 6a to 6c are slightly lower than the position of the waterline (or in consideration of the safety factor, the height of the water intake 6a relative to the position of the waterline 6a). In the case where the heights H1 to H3 of ６6c are lower than or equal to the predetermined distance, it is determined that water can be taken and there is no possibility of inadvertently taking in air. For example, assuming that the position of the water line is H4, if H4 ≧ H3, water can be taken from the water inlets 6a to 6c, and H3>
When H4 ≧ H2, water can be taken from the water inlets 6a and 6b. When H2> H4 ≧ H1, water can be taken from the water inlet 6a.
It is determined that water can be taken from The measurement of the position of the draft line by the water gauge 13 is preferably performed as close as possible to the intake ports 6a to 6c.

In addition, various means other than the output from the water gauge 13 can be used to determine the first selection criterion. For example, if the presence or level of water flowing into each of the intake ports 6a to 6c is detected, or water is experimentally taken from each of the intake ports 6a to 6c, and air is mixed in the water, It may be determined that water intake is impossible.

As a method for judging the second selection criterion, the water intake control unit 5 in the present embodiment uses one of the plurality of water intake ports 6a to 6c capable of withdrawing water at the highest position. The mouth is set to be selected as a water intake that seems to have a relatively low impurity contamination rate. This setting can be described as one condition of the control program of the water intake control unit 5, for example.

The reason why such a setting is made is that it is considered that sediment and microorganisms rolled up from the bottom of the water are most unlikely to be mixed into the water at the highest position. In addition,
Other methods can be used to determine the second selection criterion. For example, a plurality of water intake ports 6a capable of taking water.
６6c from each of the intake ports 6a
It is also possible to measure the impureness of the water taken from # 6c and select the intake port with the lowest impurity.

The water intake control in the water intake system thus configured will be described. 4 to 6 are diagrams showing the relationship between the draft position and the water intake position, and FIG. 7 is a flowchart showing the control contents of the water intake control unit. In the following, it is assumed that when the ship is moored in a shallow place such as in a bay, the state sequentially changes to a maximum loading state (FIG. 4), a medium loading state (FIG. 5), and a non-loading state (FIG. 6). The following description focuses on water intake control.

First, as shown in FIG. 4, when the ship is in the maximum loading state, the draft line 1b of the hull 1 is located relatively higher due to the load of the cargo. In this state, when the start of the water intake control is instructed by any means, the following water intake control is executed by the water intake control unit 5. First, the output of the draft gauge 13 is fetched (S701), and selection based on the first selection criterion is performed based on this output.
That is, the position of the water line 1b obtained by analyzing the output of the water gauge 13 and the predetermined intake port 6a
6a to 6c based on the heights H1 to H3 of the
Of these, the water intake that can be taken is specified (S702).
In the example of FIG. 4, all the water intakes 6a to 6c are specified as water intakes that can take water.

When water can be taken from the plurality of water intakes 6a to 6c in this way, selection is made according to the second selection criterion. That is, a plurality of water intake ports 6a to 6c capable of water intake.
Of these, the intake port 6c at the highest position is finally selected as an intake port for performing intake (S703, S705).
In order to take water from the water intake 6c, the valve 9 is used.
The valves 9a and 9b are closed, and the valve 9c is opened (S706). The correspondence between the intake ports 6a to 6c and the opening and closing of the valves 9a to 9c is set in advance, for example, as a correspondence table, and is referred to by the intake control unit 5 as needed.

After completion of the opening and closing of the valves 9a to 9c,
The pump 10 is driven (S707), and water intake is started. According to such control, the intake port 6 at the highest position
Since water is taken from c, water can be taken at a position farthest from the water bottom 14, and ballast water with less impurities can be taken. Thereafter, it is determined whether or not the water intake is completed based on an output from any detection means (S
708) If water intake is not completed, step S
Step 701 is performed again. Thereafter, steps S701 to S701 are performed until the completion of water intake is detected by any means.
Step 708 is repeated.

When the cargo 1c starts to be unloaded from the ship, the waterline 1b gradually moves downward with respect to the hull 1. Then, when the state shown in FIG.
In 02, only the two water intakes 6a and 6b are specified as water intakes capable of water intake. Then, in steps S703 to S708 similar to the above, the valves 9a to 9c are switched so that water is taken from the highest position of the two water intakes 6a and 6b. That is, the valve 9b is opened and the valves 9a and 9c are closed. Therefore, in this case, water can be taken at the water intake 6b at a position farthest from the water bottom 14, and ballast water with the least impurities can be taken.

After that, when the cargo 1c is further unloaded from the ship, and becomes a state of no load as shown in FIG. 6, the waterline 1b moves further downward with respect to the hull 1. Then, in step S702, only one water intake 6a is selected as a water intake capable of taking water. As described above, when only one intake port 6a is selected, the intake port 6a is selected without performing the selection based on the second selection criterion.
It is finally selected that “a” is a water intake for performing water intake (S703, S704). Then, the valves 9a to 9c are switched so as to perform water intake at the water intake 6a (S706). Here, the valve 9a is opened and the valves 9b and 9c are closed. Thereafter, when it is determined in step S708 that the water intake is completed, the pump 10 is stopped (S709), and the water intake control is completed.

In the above description, when the load 1c is gradually reduced (when the position of the waterline 1b is gradually lowered).
However, the same intake control can be performed when the load 1c gradually increases (when the position of the waterline 1b gradually increases). In this case, the intake 6a → the intake 6b → the intake. Switching is performed gradually in the order of 6c. Naturally, the water intake control can be performed in the same manner as described above, not only when the load 1c changes, but also when the position of the waterline 1b changes due to any cause.

In the flowchart of FIG. 7,
Since a loop is formed from step S708 to step S701, the output from the draft gauge 13 is periodically taken into the water intake control unit 5, and each time the position of the water intake port for performing water intake is determined. Become. However, when the frequency of determination increases in this way, the load on the water intake control unit 5 increases. In order to avoid this, the water intakes 6a to 6
It may be always determined whether or not it is necessary to change the position of c, and only when it is necessary, the positions of the water intakes 6a to 6c may be determined.

Specifically, only a change in the position of the waterline 1b is constantly monitored, and this change is determined by a predetermined reference distance (for example,
The position of the water intake ports 6a to 6c may be determined only when the distance becomes 2m) or more. In this case, the load on the water intake control unit 5 can be reduced.

(Embodiment 2) FIG. 8 is a longitudinal sectional view of a ship provided with a ballast water intake system according to this embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 8, pumps 10a to 10c are provided in intake lines 7a to 7c of the intake ports 6a to 6c, respectively, and these pumps 10a to 10c can be individually controlled by the intake control unit 5 ( In FIG. 8, the electric lines are not shown).

In the water intake system configured as described above, in addition to the same control as in the first embodiment, it is also possible to perform water intake control such that water is simultaneously taken from a plurality of water intakes 6a to 6c. . Specifically, when it is determined that there are a plurality of water intake ports 6a to 6c that can take water, the water intake ports 6a to 6c that are separated from the water bottom 14 by a predetermined distance (a distance at which the mixing ratio of impurities is considered to be small) are determined. In the case where there are a plurality of water intake ports 6a to 6c, the valves 9a to 9c and the pumps 10a to 10c may be controlled so as to simultaneously take water from all of the plurality of water intake ports 6a to 6c.

In FIG. 8, two intake ports 6b, 6c
Is located at a height sufficiently distant from the water bottom 14, water can be taken from both the water intake ports 6b and 6c. When water is taken from the plurality of water inlets 6b and 6c in this manner, the water intake speed can be improved.

[0047]

As described above, according to the ballast water intake system according to the present invention (claim 1), a plurality of intake ports arranged at different heights of the hull, and all of the plurality of intake ports are provided. Or, a water intake means for performing ballast water intake through an arbitrary part, a selection means for selecting an intake port for water intake from a plurality of water intake ports based on a predetermined standard, and a selection result of the selection means. By providing a switching means for switching the water intake for performing water intake, the ballast water with less impurities can be taken by switching the position of the water intake according to the situation.

According to the ballast water intake system according to the present invention (claim 2), the predetermined criterion in the selection means is the highest position among the intake ports located below the waterline of the hull. Is set so as to select the intake port located at the bottom, so that water is always taken from the intake port at the highest position, so that impurities wound up near the water bottom enter the ballast tank 2. It can be prevented to the maximum.

In the ballast water intake system according to the present invention (claim 3), the predetermined criterion in the selection means is a predetermined one from among the water intake ports arranged at a position lower than the waterline of the hull from the water bottom. By setting so as to select all water intake ports separated by a distance or more, water can be taken from a plurality of water intake ports depending on the situation, and the water intake speed can be improved.

According to the ballast water intake system according to the present invention (claim 4), the position of the intake port located at the highest position is the position below the waterline of the hull in the maximum loading state, and the lowest Since the position of the water intake port arranged at the position is set below the waterline of the hull in the no-load state, the maximum loading state (the state where the waterline is located at the highest position) and the no-load state (the waterline is located at the lowest position). State), water can be taken from at least one water inlet.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a ship provided with a ballast water intake system according to Embodiment 1 of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of the ship shown in FIG.

FIG. 3 is an enlarged view of a main part of the configuration of the ship shown in FIG. 2;

FIG. 4 is a diagram showing a relationship between a draft position and a water intake position in a maximum loading state.

FIG. 5 is a diagram showing a relationship between a draft position and a water intake position in a medium loading state.

FIG. 6 is a diagram showing a relationship between a draft position and a water intake position in a non-load state.

FIG. 7 is a flowchart showing control contents of a water intake control unit.

FIG. 8 is a longitudinal sectional view showing a configuration of a ship provided with a ballast water intake system according to a second embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a configuration of a boat provided with a conventional water intake system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hull 1a Outer wall 1b Waterline 1c Cargo 2 Ballast tank 3 Water intake system 4a-4d 1st-4th water intake system 5 Water intake control part 6 Water intake 7 Water intake line 8 Main pipeline 9 Valve 10 Pump 11 Water intake wall 12 Water intake room 13 Draft gauge 14 Water bottom

Claims (4)

[Claims] 1. A plurality of water intake ports arranged at different heights of a hull, water intake means for taking ballast water through all or any part of the plurality of water intake ports, based on a predetermined standard Ballast water, comprising: selecting means for selecting an intake port for taking water from a plurality of water intake ports; and switching means for switching the intake port for taking water based on a selection result of the selecting means. Water intake system. 2. The method according to claim 1, wherein the predetermined criterion in the selection means is set so as to select an intake port located at a highest position among intake ports located at a position lower than a waterline of the hull. The ballast water intake system according to claim 1. 3. The method according to claim 1, wherein the predetermined criterion in the selection means is set so as to select, from among water intake ports arranged at a position lower than the waterline of the hull, all water intake ports separated from the water bottom by a predetermined distance or more. The ballast water intake system according to claim 1, wherein: 4. The position of the intake port located at the highest position among the plurality of intake ports is defined as the position below the waterline of the hull in the maximum loading state, and the position of the intake port located at the lowest position is The ballast water intake system according to any one of claims 1 to 3, wherein the ballast water intake system is located below a waterline of the hull in a no-load state.