Draining structure of ballast tank

Abstract

The present application provides a drainage structure for a ballast tank which does not significantly lengthen the time for discharging residual ballast water from the ballast tank even if the number of water passages is reduced compared to the prior art. Four small partitioned chambers (2-1) to (2-4) included in a lateral small partitioned chamber row (20W) are in a communication state via three water passages (25) respectively penetrating three longitudinal frame members (17) within the lateral small partitioned chamber row (20W). In addition, a plurality of small partitioned chambers respectively included in four longitudinal small partitioned chamber rows (20L) are each in a communication state by a plurality of water passages (25) respectively penetrating a plurality of floor members (13), the four longitudinal small partitioned chamber rows (20L) being composed of a plurality of small partitioned chambers [(1-1) to (4-1), (1-2) to (4-2), (1-3) to (4-3), (1-4) to (4-4)] including one of the four small partitioned chambers (2-1) to (2-4) constituting the lateral small partitioned chamber row (20W) and arranged in a longitudinal direction (L) of the ship.

Description

TECHNICAL FIELD

[0001] The present application relates to a ballast tank drainage structure for draining residual ballast water from a bottom region of a ballast tank formed between a ship's bottom shell and inner bottom shell in a shorter time. BACKGROUND

[0002] The time required to drain residual ballast water from the bottom region of the ballast tank at the time of loading and unloading of a ship's cargo is an important issue related to the profits of a cargo owner and a shipping company that bears the sea transport.

[0003] Suppose that when the drainage time exceeds a certain time, the cargo loading and unloading time increases, that is, the port occupancy time increases and improvement is required by the port, and there is a risk of becoming a very serious problem for the shipping company. In addition, in the case where the amount of residual water in the ballast tank is large, sometimes the prescribed amount of cargo cannot be loaded, and for the cargo owner, it becomes a factor of loss of profits.

[0004] However, the more the drainage is completed in a short time or the final amount of residual water in the ballast tank is minimized, the more the above-mentioned risk is minimized, and it is also related to the improvement of the value of the ship. In order to eliminate the above-mentioned problems, as an example of working on the structure for draining residual ballast water, in Japanese Patent Application Publication No. 54-66390 (Patent Document 1), there is disclosed an invention in which a notch portion reaching the bottom shell is provided in the center of the lower edge portion of a floor provided on the bottom shell in the ballast tank, and residual ballast water is drained from the notch portion. In addition, in Japanese Patent Application Publication No. 2010-120469 (Patent Document 2), a structure is shown in which a plurality of water passages are formed in the lower portions of a plurality of longitudinal girders provided on the bottom shell, and ballast water is made to flow from the water passages in the direction of the centerline of the ship body from the ship side.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 54-66390

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-120469 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, in the past, in order to shorten the time for discharging the residual ballast water, only the shape and number of the water passage holes through which the residual ballast water passes have been simply studied, and there has been no sufficient study on the case where the number of the water passage holes is reduced and the time for discharging the residual ballast water does not significantly increase. If the number of the water passage holes is reduced, it is possible to greatly reduce the labor and time consumed by the work and also to prevent the decrease in the mechanical strength of the ballast tank.

[0011] An object of the present application is to provide a water discharge structure of a ballast tank which does not significantly increase the time for discharging the residual ballast water from the ballast tank even if the number of the water passage holes is reduced.

[0012] Means for solving the problem

[0013] A plate girder structure is formed in a ballast tank formed between a ship bottom outer plate and an inner bottom plate of a ship. In the plate girder structure, a plurality of beam members and a plurality of floor members are arranged so as to form a plurality of large partition rooms in a lattice shape between the ship bottom outer plate and the inner bottom plate, the plurality of beam members are arranged so as to extend in a longitudinal direction of the ship on the ship bottom outer plate and are spaced apart in a transverse direction orthogonal to the longitudinal direction, the plurality of floor members are arranged so as to cross the plurality of beam members on the ship bottom outer plate and are spaced apart in the transverse direction within the ballast tank, a plurality of longitudinal frame members are arranged on the ship bottom outer plate within the plurality of large partition rooms, the plurality of longitudinal frame members are arranged so as to extend in the longitudinal direction and are spaced apart in the transverse direction. Further, the plate girder structure has a plurality of small partition rooms which are partitioned by the plurality of longitudinal frame members in the transverse direction by respective ship bottom side regions within the plurality of large partition rooms. Further, at least one suction port is provided for at least one small partition room within one large partition room. Further, a plurality of water passage holes through which the ballast water flows among the plurality of large partition rooms are provided in the plurality of beam members and the plurality of floor members. In addition, a plurality of water passage holes are provided in the plurality of beam members, the plurality of floor members, and the plurality of longitudinal frame members, the plurality of water passage holes guide the residual ballast water remaining in the plurality of small partition rooms within the plurality of large partition rooms to one small partition room in which the suction port is provided.

[0014] In the drainage structure of the ballast tank according to the present application, a plurality of water passages are provided to allow residual ballast water in a plurality of small division rooms in other large division rooms to be sucked into at least one suction port through a plurality of small division rooms included in at least one lateral small division room row composed of a plurality of small division rooms including at least one small division room provided with the suction port and arranged in series in the lateral direction. When this drainage structure is used, the water level difference between the plurality of small division rooms in the lateral small division room row is small, and the ballast water is efficiently collected from the plurality of small division rooms in the lateral small division room row to the small division room provided with the suction port. In other words, an effect is produced in which the suction port extends to the plurality of small division rooms in the lateral small division room row. As a result, even if the number and area of the water passages provided between the plurality of beam members and the plurality of longitudinal frame members sandwiching other small division rooms arranged in the longitudinal direction with respect to the plurality of small division rooms in the lateral small division room row are reduced, the residual ballast water can be introduced to the suction port in the same time as when the number and area of the water passages are not reduced. As a result, according to the present application, the number and area of the water passages can be reduced, the working hours for manufacturing the ballast tank can be reduced, and a decrease in the mechanical strength of the ballast tank can be suppressed.

[0015] Alternatively, two small division rooms among the plurality of small division rooms included in one lateral small division room row can be provided with suction ports, respectively. In this case, the suction function of the lateral small division room row can be improved.

[0016] Preferably, as the provision of the plurality of water passages, the plurality of small division rooms included in the lateral small division room row are in communication via a plurality of lateral water passages each passing through a plurality of longitudinal frame members and a plurality of beam members in the lateral small division room row, and the plurality of small division rooms included in each of a plurality of longitudinal small division room rows are each in communication via a plurality of longitudinal water passages each passing through a plurality of floor members, the plurality of longitudinal small division room rows being composed of a plurality of small division rooms including one small division room constituting the lateral small division room row and arranged in the longitudinal direction of the ship. In this case, the flow resistance between the suction port and each small division room can be made smaller, and thus even if the number of water passages is reduced, the drainage time can be suppressed from becoming longer. In this case, it is not necessary to form the lateral water passages in the longitudinal frame members and the plurality of beam members separating two small division rooms adjacent in the lateral direction other than the small division rooms included in the lateral small division room row. As a result, the number of water passages can be reduced.

[0017] Preferably, the opening area of each of the plurality of lateral water passages and the opening area of the plurality of longitudinal water passages are determined in a manner such that the water level difference between two small division rooms adjacent in the lateral small division room row becomes close to 0. When this state is provided, the suction function of the lateral small division room row can be improved.

[0018] Further, it is preferable that the cross-sectional shape of the transverse water passage hole and the longitudinal water passage hole be such that the length in the longitudinal direction is longer than the length in the height direction, respectively. When such a cross-sectional shape is adopted, even if the amount of residual ballast water decreases, the suction amount does not become extremely small. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 (A) to (E) of FIG. 1 are perspective views for explaining the conventional structure of a ballast tank of a ship.

[0020] Figure 2 (A) of FIG. 2 is a view showing the structure of an experimental model of a drainage structure of the present embodiment prepared in order to confirm the basic idea of the present application, Figure 2 (B) of FIG. 2 is a view showing the structure of an experimental model of a drainage structure of a comparative example.

[0021] Figure 3 is a view showing the time change of the drainage amount of residual water in the drainage structure of (B) of FIG. 2 due to the difference in the number of small partitioned chambers in which the suction port is provided. Figure 2 is a view showing the time change of the drainage amount of residual water in the drainage structure of (B) of FIG. 2 due to the difference in the number of small partitioned chambers in which the suction port is provided.

[0022] Figure 4 is a view showing the time change of the drainage amount due to the difference in the size of the pump capacity.

[0023] Figure 5 is a view showing the time change of the drainage amount due to the difference in the size of the opening portion of the water passage hole.

[0024] Figure 6 is a view showing the shape and size of the water passage hole used in the experiment.

[0025] Figure 7 is a view showing the time change of the drainage amount due to the difference in the size of the opening portion of the water passage hole.

[0026] Figure 8 is a view showing the time change of the drainage amount due to the difference in the size of the opening portion of the water passage hole in the case where the longitudinal small partitioned chamber row is provided.

[0027] Figure 9 is a view showing the time change of the drainage amount in the case where the width and height of the opening of the water passage hole are set to B.24 mm x H.9 mm and B.18 mm x H.9 mm, for the presence and absence of the longitudinal small partitioned chamber row.

[0028] Figure 10 is a view showing an expanded modified example.

[0029] EXPLANATION OF REFERENCE NUMERALS:

[0030] 1 ballast tank

[0031] 3 Bottom outer plating

[0032] 5 inner floor

[0033] 7 Bottom Side Cabin

[0034] 9-plate rib structure

[0035] 11 Beams

[0036] 13 Flooring components

[0037] 15, 15A-15P large partitioned rooms

[0038] 17. Longitudinal frame components

[0039] 19 Small Division Room

[0040] 20W Horizontal Small Division Room Column

[0041] 20L longitudinal small-division chamber row

[0042] 21 suction port

[0043] 23 Water flow holes

[0044] 25 water hole. Detailed Implementation

[0045] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0046] [General Structure of Ballast Tanks]

[0047] Figure 1 (A) to (E) are perspective views used to illustrate the conventional structure of a ship's ballast tanks. Figure 1 (A) represents a three-dimensional view of the intermediate section of a ship equipped with ballast tanks. Figure 1 (B) is to Figure 1 An enlarged 3D view extracted from the area indicated by the dashed line in (A) as a cross section. Figure 1 (C) indicates from Figure 1 (B) is a perspective view showing the state after removing the inner bottom plate 5 and the bottom side tank ramp 6. A portion of the ballast tank 1 is formed between the outer bottom plate 3 and the inner bottom plate 5 of the hull. Additionally, a bottom side tank 7, constituting part of the ballast tank 1, is also formed between the outer side plate 4 and the bottom side tank ramp 6. A plate rib structure 9 is formed within the ballast tank 1 formed between the outer bottom plate 3 and the inner bottom plate 5. It should be noted that... Figure 1 In the directional markings shown, L represents the length direction of the ship, i.e., longitudinal, and W represents the width direction of the ship, i.e., transverse.

[0048] Figure 1 (D) is Figure 1A magnified stereoscopic view of (C). Figure 1 (E) is Figure 1 A magnified stereoscopic view of (D). Such as these... Figure 1 As shown in (D) and (E), in the plate rib structure 9, multiple beam members 11 and multiple floor members 13 are arranged to form multiple large partitioned chambers 15 in a grid pattern between the outer bottom plate 3 and the inner bottom plate 5. The multiple beam members 11 are arranged to extend along the longitudinal direction L of the hull on the outer bottom plate 3 and are spaced apart along a transverse direction W orthogonal to the longitudinal direction L. The multiple floor members 13 are arranged to intersect with the multiple beam members 11 on the outer bottom plate 3 and extend along the transverse direction W and are spaced apart along the longitudinal direction L within the ballast tank 1. Multiple longitudinal frame members 17 are arranged on the outer bottom plate 3 within the multiple large partitioned chambers 15, and these longitudinal frame members 17 are arranged to extend along the longitudinal direction L and are spaced apart along the transverse direction W. Furthermore, the plate rib structure 9 has multiple small partitioned chambers 19, which are obtained by the multiple longitudinal frame members 17 dividing each bottom side area within the multiple large partitioned chambers 15 along the transverse direction W. As will be described later, an intake 21 is provided for a small subdivision chamber 19 within a large subdivision chamber 15 (in... Figure 1 (shown by dashed lines in (E)) The suction inlet 21 has a bell mouth at the front end of the drain pipe extending from the drain pump. Furthermore, multiple drainage holes 23 are provided on the multiple beam members 11 and multiple floor members 13 to allow ballast water to flow between the multiple large partition chambers 15. Additionally, multiple water passage holes 25 are provided on the multiple beam members 11, multiple floor members 13, and multiple longitudinal frame members 17, which guide residual ballast water remaining in the multiple small partition chambers 19 within the multiple large partition chambers 15 to a small partition chamber 19 where the suction inlet 21 is located.

[0049] It should be noted that the ballast water in the bottom side compartment 7 is eventually transferred as residual ballast water to the large partition chamber 15 in the plate rib structure 9, so it does not need to be considered in special terms.

[0050] [Implementation Method]

[0051] Figure 2 (A) is a diagram showing the structure of an experimental model of the drainage structure of this embodiment, prepared to confirm the basic idea of ​​the present invention. Figure 2 (B) is a diagram showing the structure of the experimental model of the drainage structure for the comparative example. Figure 2The model of (A) is a model of a drainage structure in which four large partition rooms 15A to 15D each have four small partition rooms 19. For the sake of distinguishing each small partition room, the 16 small partition rooms 19 are labeled with numbers (1-1) to (4-4). In addition, the symbol "B" indicates the position of a suction bell mouth B of the suction port 21. The suction bell mouth B is opposed to the ship bottom plate 3 with a prescribed gap between the suction bell mouth B and the ship bottom plate 3. Figure 2 (B) indicates the structure of an experimental model of the drainage structure of the comparative experimental example. Note that, Figure 2 The direction labels L and W shown in (A) and (B) indicate the length direction of the ship, i.e., the longitudinal direction, and the width direction of the ship, i.e., the lateral direction, respectively.

[0052] In Figure 2 In the experimental model of (A), a plurality of water passages 25 are provided to suction the residual ballast water in the plurality of small partition rooms in the other large partition rooms 15A, 15C, and 15D to the suction port 21 through the four small partition rooms (2-1) to (2-4) included in the lateral small partition room row 20W, and the lateral small partition room row 20W is composed of the four small partition rooms (2-1) to (2-4) including the one small partition room (2-2) in which the suction port 21 is provided and arranged in series in the lateral direction W in one large partition room 15B. Specifically, as the arrangement of the plurality of water passages 25, the four small partition rooms (2-1) to (2-4) included in the lateral small partition room row 20W are in communication via three water passages (lateral water passages) 25 each of which penetrates three longitudinal frame members 17 located in the lateral small partition room row 20W. In addition, the plurality of small partition rooms included in the four longitudinal small partition room rows 20L are each in communication via a plurality of water passages (longitudinal water passages) 25 each of which penetrates a plurality of floor members 13, and the four longitudinal small partition room rows 20L include one small partition room constituting the lateral small partition room row 20W and are composed of a plurality of small partition rooms [(1-1) to (4-1), (1-2) to (4-2), (1-3) to (4-3), (1-4) to (4-4)] arranged in the longitudinal direction L of the ship. In this way, the flow path resistance between the suction port 21 and each small partition room can be made smaller. Note that, in this structure, no water passage (lateral water passage) 25 is formed at the portion of the longitudinal frame member 17 that separates two small partition rooms adjacent in the lateral direction other than the small partition rooms (2-1) to (2-4) included in the lateral small partition room row 20W.

[0053] When this drainage structure is used, the water level difference in the small chambers (2-1) to (2-4) in the lateral small chamber row 20W is small, and the ballast water is efficiently collected from the small chambers (2-1) to (2-4) in the lateral small chamber row 20W to the small chamber (2-2) provided with the suction port. In other words, an effect is produced in which the suction port 21 extends to the small chambers [(2-1) to (2-4)] in the lateral small chamber row 20W. As a result, it is possible to introduce the residual ballast water to the small chambers [(2-1) to (2-4)] in the lateral small chamber row 20W from the small chambers [(1-1) to (1-4), (3-1) to (3-4), (4-1) to (4-4)] in the other lateral small chamber rows than the lateral small chamber row 20W including the small chamber (2-2) provided with the suction port 21 in the same time as in the case where the number and area of the through holes are not reduced.

[0054] On the other hand, in the drainage structure of the comparative experimental example of (B) of the present application, Figure 2 In the drainage structure of the comparative experimental example of (B) of the present application, a through hole (lateral through hole) 25 is formed in a portion of the vertical frame member 17 that separates two small chambers in the lateral direction in the small chambers (1-1) to (1-4), (3-1) to (3-4), and (4-1) to (4-4) included in three lateral small chamber rows other than the lateral small chamber row 20W including the small chamber (2-2) provided with the suction port 21 and composed of four small chambers (2-1) to (2-4) arranged in series in the lateral direction W.

[0055] Hereinafter, experiments using the drainage structures of (A) and (B) of the present application for confirming the effects of the present application are described. Figure 2

[0056] [Outline of the experiments]

[0057] In the experiments, the drainage structures of (A) and (B) of the present application were used. Figure 3 ​A 1 / 10 scale model of the structures shown in (A) and (B) was constructed. Acrylic material was used for ease of observation. Furthermore, to allow for repositioning of the water inlet 25, slots were made in the walls of the longitudinal frame member 17 and floor member 13 facing the small partition chamber 19, and sealing plates were inserted into these slots. Purified water (tap water) was used in the experiment instead of seawater. A process pump (manufactured by TACMINA Co., Ltd., FXD-FXW-8) was used to pump the purified water out of the experiment. This pump links three diaphragm pumps, suppresses pulsation, and allows for linear suction. A digital ultrasonic sensor (manufactured by Keyence Co., Ltd., FW-02) was used to measure the tank water level. The cumulative flow rate was calculated based on the volume change of purified water within the tank according to the tank water level. It should be noted that calibration was achieved by comparing the cumulative flow rate with the pump suction volume during the experiment.

[0058] To address the impact of pump flow rate and flow within the ballast tank on the drainage time of residual water (equivalent to residual ballast water), the experiment was designed to study the following four factors in order to observe the differences in residual water drainage volume: 1) the location of the pump inlet 21 (suction bell B), 2) the pump suction volume, 3) the size of the water passage 25, and 4) the presence or absence of a longitudinally divided sub-chamber row 20L. It should be noted that in the experiment, because the switching of the stripping pump was not considered and the pump flow rate was kept constant, air was entrained while suction was performed in the final stage of residual water drainage, resulting in approximately 5 mm of residual water.

[0059] [Experimental Results]

[0060] The experimental results are shown below.

[0061] (1) Setting the location of the small partitioned chamber of the suction inlet 21

[0062] exist Figure 2 The middle indicates in Figure 3 The variation of residual water discharge over time in the drainage structure of (B) due to the different small partitions with suction inlets 21 is shown. It should be noted that in the experiment, a 1 / 10 geometric scale to the actual ship was maintained, with the pump capacity equivalent to 1000 ton / h (27.8 L / sec in the experiment), the height of the longitudinal frame member 17 set to 300 mm (30 mm in the experiment), the initial water level equivalent to 500 mm (50 mm in the experiment), and the opening size of the slit forming the water passage 25 set to a width of B.240 mm × a height of H.90 mm (B.24 mm × H.9 mm in the experiment). Regarding the pump capacity and the presence or absence of the balance angle, the pump capacity, which affects the cumulative flow, was set to a fixed value, and the balance angle was set to none. Based on this...Figure 4 As for the small division chamber in which the suction port 21 is provided, it is determined that the drainage efficiency is good when the small division chamber (2-2) or the small division chamber (1-2) is selected from the small division chambers which are offset from the center line in the lateral direction by one division, and it is determined that it is particularly good to provide the suction port 21 to the small division chamber (2-2). The efficiency is poor when the suction port 21 is provided to the small division chamber (1-1).

[0063] (2) Pump flow rate

[0064] In Figure 4 , the time variation of the drainage amount resulting from the difference in the size of the pump capacity is shown. In Figure 4 , the pump capacity is set to the pump equivalent capacity of the actual ship. In the experiment, the suction port 21 was provided to the small division chamber (2-2), the height of the longitudinal frame member 17 was set to 30 mm, the initial water level was set to 50 mm, and the opening size of the slit in which the through-hole 25 was provided was set to width B. 18 mm x height H. 9 mm. According to Figure 4 , it is known that a large drainage amount cannot be obtained in the case where the pump capacity is relatively small, but a convergence value appears in the case where the pump capacity is increased, and in this case, 800 ton / h. and 1000 ton / h. are substantially the same. Therefore, Figure 5 is shown to indicate that it is sometimes difficult to show the effect even if the pump capacity is increased.

[0065] (3) Size of the through-hole 25

[0066] In Figure 5 , the time variation of the drainage amount resulting from the difference in the size of the opening of the through-hole 25 is shown. In the experiment, the pump capacity was made to correspond to 1000 ton / h., the position at which the suction port 21 was provided was set to the small division chamber (2-2), the height of the longitudinal frame member 17 was set to 30 mm, and the initial water level was set to 50 mm.

[0067] In Figure 6 , the time variation of the drainage amount resulting from the difference in the height when the width of the opening of the through-hole 25 is set to a constant value of 9 mm is shown. When the height of the opening is increased, a convergence value appears, and in this case, B. 9 mm x H. 18 mm and B. 9 mm x H. 24 mm are substantially the same. Therefore, is shown to indicate that it is sometimes difficult to show the effect even if the height of the opening is increased. In Figure 7 , the shape and size of the through-hole 25 used in the experiment are shown.

[0068] In Figure 2The figure shows the change in drainage volume over time due to different widths when the height of the opening of the water passage 25 is set to a constant value of 9 mm. When the width of the opening is increased, the drainage volume increases, especially when the width is B.24 mm × H.9 mm.

[0069] (4) The setting of longitudinal small-division chambers 20L

[0070] like Figure 2 As shown in (A), an investigation was conducted on whether reducing the number of discharge openings in each compartment by setting up longitudinal small-division chamber rows 20L could improve drainage efficiency. Here, as... Figure 8 As shown in (A), consider the following situation: each of the four longitudinal subdivision chamber rows 20L contains multiple subdivision chambers that are connected through multiple water passages (longitudinal water passages) 25 that pass through multiple floor pieces 13. The four longitudinal subdivision chamber rows 20L contain one of the four subdivision chambers (2-1) to (2-4) that constitute the transverse subdivision chamber row 20W and are composed of multiple subdivision chambers arranged along the longitudinal direction L of the ship [(1-1) to (4-1), (1-2) to (4-2), (1-3) to (4-3), (1-4) to (4-4)].

[0071] exist Figure 9 The figure shows the change in drainage volume over time due to the different sizes of the openings of the water passages 25 when the longitudinally divided small-division chambers 20L are set. In this figure, the figure shows the change in drainage volume over time due to the different widths of the openings of the water passages 25 when the height of the openings is set to a constant value of 9 mm. When the width of the opening is increased, the drainage volume increases as observed in (3), and in particular, the effect is evident when the width is B.24 mm × H.9 mm.

[0072] In addition, it was learned that, when the width of the opening of the water passage 25 is set to a constant value of 9 mm, the change in drainage volume over time due to different heights shows the same convergence value as that examined in (3), and even if the opening height is increased, it is difficult to show any effect.

[0073] exist Figure 10In order to clarify the characteristics of the longitudinal small-division-chamber row 20L, the time variation of the discharge amount in the case where the opening width and height of the through-water hole 25 are set to B.24 mm x H.9 mm and B.18 mm x H.9 mm is compared and shown for the presence or absence of the longitudinal small-division-chamber row 20L. According to the graph, in the case where the longitudinal small-division-chamber row 20L is not provided and the number of openings of the through-water hole 25 is large, the discharge amount becomes large. However, the time variation of the discharge amount of the through-water hole (B.18 mm x H.9 mm) in the case where the longitudinal small-division-chamber row 20L is not provided is approximately the same as the time variation of the discharge amount of the through-water hole (B.24 mm x H.9 mm) in the case where the longitudinal small-division-chamber row 20L is provided, and thus it is known that the provision of the longitudinal small-division-chamber row 20L is effective for reducing the number of openings of the through-water hole 25.

[0074] From this experiment, the following findings were obtained.

[0075] 1) With respect to the position of the small-division chamber of the suction port 21 of the pump, the position of the suction port 21 is separated from the center line of the tank or separated from the tank wall, and then the improvement of the discharge efficiency is achieved.

[0076] 2) Even if the pump capacity is increased, the lowering of the water level of the small-division chamber provided with the suction port 21 becomes remarkable, and the effect is small. It is desirable to select an appropriate pump capacity to improve the discharge efficiency.

[0077] 3) With respect to the size of the through-water hole 25, the opening width of the through-water hole 25 plays a role in improving the discharge efficiency compared to the opening height of the through-water hole 25.

[0078] 4) It is expected that the provision of the longitudinal small-division-chamber row 20L effectively plays a role in improving the discharge efficiency, and is effective for reducing the number of openings of the through-water hole 25.

[0079] The present application is completed on the basis of the above findings, and the purpose is achieved by providing the transverse small-division-chamber row 20W and appropriately determining the position, number, and opening area of the through-water hole 25 of the longitudinal small-division-chamber row 20L. Thus, even in the case where the through-water hole 25 is formed in a part of the small-division chamber included in the longitudinal small-division-chamber row 20L in the longitudinal frame member 17, this scheme is not excluded from the scope of the technology of the present application at all.

[0080] [Others]

[0081] It is preferable that the opening area of each of the plurality of transverse through-water holes and the opening area of the plurality of longitudinal through-water holes be determined in a manner such that the water level difference in the two small-division chambers adjacent to each other within the transverse small-division-chamber row becomes a state close to 0. When set to this state, the suction function of the transverse small-division-chamber row can be improved.

[0082] Furthermore, when applying this invention to actual ballast tanks, such as Figure 10 As shown, it becomes a structure with multiple large compartments and smaller sub-compartments. Figure 10 In this case, there are 16 large partition chambers 15A to 15P and 64 small partition chambers. In this example, the two large partition chambers 15B and 15J, each containing eight small partition chambers 19, are directly connected to form a horizontal small partition chamber column 20W. In addition, eight vertical small partition chamber columns 20L are formed by connecting eight small partition chambers 19 in series.

[0083] Only ​ In such multiple sub-chambers, if the discharge time of residual ballast water becomes longer, additional suction bells may be provided for sub-chambers (2-4), as shown by the dashed lines. Alternatively, the eight sub-chambers 19 contained in the two large sub-chambers 15C and 15K may be directly connected to form an additional transverse sub-chamber row. In this case, it is preferable to also equip at least one sub-chamber contained in this additional transverse sub-chamber row with a suction bell. It should be noted that, without significantly affecting the effects obtained by the present invention, the arrangement of providing water passage holes 25 in a portion of the beam member 11 or longitudinal frame member 17 located at a certain distance from the suction bell is also included within the scope of the present invention.

[0084] The preferred location of the suction bell varies depending on various factors such as the ballast pump capacity, the diameter of the suction pipe, and the spacing of the longitudinal frame members of the small partition chamber. The suction bell location in this embodiment is an example of a drainage method in which the hull is tilted longitudinally aft while residual ballast water is discharged.

[0085] Industrial availability

[0086] According to the present invention, even if the number and area of ​​water passages are reduced, the drainage time of residual ballast water will not be significantly increased, and the manufacturing time of ballast tanks can be reduced, thus suppressing the reduction of the mechanical strength of ballast tanks.

Claims

1. A drainage structure of a ballast tank characterized by, in a ballast tank formed between a ship bottom outer plate and an inner bottom plate of a ship, a plate girder structure is constituted in which a plurality of beam members and a plurality of floor members are arranged in a manner to form a plurality of large divided chambers in a lattice shape between the ship bottom outer plate and the inner bottom plate, the plurality of beam members are arranged in a manner to extend in a longitudinal direction of the ship on the ship bottom outer plate and to be spaced apart in a transverse direction orthogonal to the longitudinal direction, the plurality of floor members are arranged in a manner to cross the plurality of beam members on the ship bottom outer plate and to extend in the transverse direction and to be spaced apart in the longitudinal direction within the ballast tank, a plurality of longitudinal frame members are arranged on the ship bottom outer plate within the plurality of large divided chambers in a manner to extend in the longitudinal direction and to be spaced apart in the transverse direction, a plurality of small divided chambers are formed in respective ship bottom side regions within the plurality of large divided chambers by the plurality of longitudinal frame members being partitioned in the transverse direction, the drainage structure of the ballast tank is provided with: at least one suction port provided for at least one of the small divided chambers within one of the large divided chambers; a plurality of water flow holes provided in the plurality of beam members and the plurality of floor members and allowing the ballast water to flow between the plurality of large divided chambers; and a plurality of water passage holes provided in the plurality of beam members, the plurality of floor members, and the plurality of longitudinal frame members and guiding the residual ballast water remaining in the plurality of small divided chambers within the plurality of large divided chambers to the one of the small divided chambers provided with the suction port, the drainage structure of the ballast tank drains the ballast water within the ballast tank, the drainage structure of the ballast tank is provided with the plurality of water passage holes to cause the residual ballast water in the plurality of small divided chambers within the other of the plurality of large divided chambers to be sucked by the at least one suction port through at least one of the plurality of small divided chambers included in at least one transverse small divided chamber row constituted by the plurality of small divided chambers arranged in series in the transverse direction including the at least one small divided chamber provided with the suction port, the plurality of small divided chambers included in the at least one transverse small divided chamber row are in a communication state via a plurality of transverse water passage holes respectively passing through the plurality of longitudinal frame members and the plurality of beam members within the transverse small divided chamber row, the plurality of small divided chambers respectively included in a plurality of longitudinal small divided chamber rows constituted by a plurality of small divided chambers arranged in the longitudinal direction of the ship including one of the plurality of small divided chambers constituting the transverse small divided chamber row are in a communication state by a plurality of longitudinal water passage holes respectively passing through the plurality of floor members, the transverse water passage holes are not formed in the longitudinal frame members and the plurality of beam members partitioning two small divided chambers adjacent in the transverse direction other than the small divided chambers included in the transverse small divided chamber row.

2. The drainage structure of a ballast tank according to claim 1, characterized by, ​ Two or more of the plurality of small division chambers included in the one lateral small division chamber row are respectively provided with the suction port.

3. The drainage structure of the ballast tank according to claim 1, wherein The opening area of each of the plurality of lateral water passages and the opening area of the plurality of longitudinal water passages are determined in a manner such that the water level difference between adjacent two of the small division chambers in the lateral small division chamber row becomes a state close to 0.

4. The drainage structure of the ballast tank according to claim 1, wherein The cross-sectional shape of each of the lateral water passages and the longitudinal water passages is longer in the width direction than in the height direction.

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