JP7555738B2 - Liquefied Gas Carrier - Google Patents

Description

The present invention relates to a liquefied gas carrier.

Liquefied gas carriers that transport liquefied gas such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas) as cargo are equipped with liquefied gas tanks in the cargo compartment for storing the liquefied gas.
If the hull of a liquefied gas carrier is damaged and the cargo compartment becomes flooded, not only will the cargo compartment lose buoyancy, but the liquefied gas tanks may also be damaged, causing the liquefied gas to leak out. Therefore, the IMO (International Maritime Organization) has established a standard called the IGC Code to ensure that the hull maintains sufficient stability in the event of damage.
One structure to ensure stability in the event of damage as stipulated in the IGC Code is to widen the ship's width and increase the distance between the ship's sides and the tanks to ensure the metacentric height in the event of flooding, but this makes the ship larger and heavier, and increases the cost of the ship.
There is a structure in which the cargo compartment and the surrounding watertight compartments are divided into smaller compartments to reduce the volume of each compartment, thereby reducing the buoyancy lost in the event of damage, but this increases the number of bulkheads and tanks, increases the weight of the hull, and increases the cost of the ship. In addition, this structure causes water to flood asymmetrically in the event of damage, making it prone to a phenomenon called heeling, in which the hull tilts sideways to sink toward the damaged side (Patent Document 1).
Patent Document 1 describes a water injection structure that, like a cross-flooding device, injects water into the flooded ship's side and watertight compartments on the opposite side of the ship to alleviate heel, but this structure increases the ship's weight by the amount of the water injection structure, resulting in a higher ship price.
There are structures that ensure stability by lowering the center of gravity of the ship by using tanks such as bilobe tanks, which have a lower center of gravity than cylindrical tanks, as liquefied gas tanks, but bilobe tanks are more complex and heavier than cylindrical tanks, which increases the ship's weight and increases the ship's price. In addition, this structure alone cannot reduce heel (Patent Document 2).

JP 2016-055672 A Special table 2019-515209 publication

Thus, in order to ensure stability in the event of damage as stipulated by the IGC Code, conventional liquefied gas carriers had to increase the weight of the hull, and depending on the structure, it was necessary to provide a separate structure to mitigate heeling in the event of damage, which further increased the weight of the hull.
The present invention has been made in consideration of the above problems, and has an object to provide a liquefied gas carrier that can reduce heeling during a collision without increasing the hull weight and ensure stability.

The liquefied gas carrier of the present invention is a liquefied gas carrier equipped with a hull having a cargo compartment in which independent tanks for storing liquefied gas as cargo are installed, and is characterized in that it has watertight compartments arranged on the outboard side of the cargo compartment on the left and right sides when viewed from the longitudinal direction of the ship, and has a plurality of side watertight compartments in contact with the side shell plating and the cargo compartment, and the plurality of side watertight compartments are arranged on the left and right ship sides, and include independent watertight compartments which are watertight compartments independent of the cargo compartment, and communicating compartments which are arranged in at least a pair on the left and right ship sides, and which are connected to the cargo compartment and integrated to form an integrated watertight compartment.

In this configuration, some of the multiple watertight compartments on the ship's sides are connected to the cargo compartment, and if water floods the cargo compartment from one side, the connected compartment on the opposite side is also flooded through the cargo compartment, mitigating the heel, so stability can be ensured even with fewer watertight bulkheads than before. Therefore, the number of transverse bulkheads in the cargo compartment is reduced to reduce the hull weight. Reducing the number of transverse bulkheads makes the watertight compartments in the cargo compartment longer in the longitudinal direction, which allows the tank length to be increased, so the number of tanks can be reduced without reducing the tank volume, and the tank weight can also be reduced.
This makes it possible to reduce heeling during a collision without increasing the hull weight, and ensure stability.

The present invention provides a liquefied gas carrier that can reduce heeling during a collision without increasing the ship's weight and ensure stability.

FIG. 1 is a side view showing an overview of a liquefied gas carrier according to an embodiment of the present invention. FIG. 2 is a front view of FIG. 1 . FIG. 2 is a plan view of FIG. 1 . FIG. 2 is a plan view in which the exposed deck and superstructure above the cargo compartment in FIG. 1 are omitted. FIG. 4 is a diagram showing a case where water has flooded the port-side communicating compartment and the independent watertight compartment adjacent to the communicating compartment, and the hatched areas indicate the flooded areas. 5 is damaged and flooded in the structure shown in FIG. 4 without the communicating section, and the hatched area shows the flooded area. FIG. 11 is a cross-sectional view of a hull showing a modified example of a watertight compartment on the side of the ship. FIG. 4 shows a modified example in which a coffer dam is provided between the machinery space and the cargo space. This is a modified example showing a case where a communication section is provided at a position adjacent to the bow section in FIG. 4 .

Hereinafter, the configuration of a liquefied gas carrier 1 according to this embodiment will be described with reference to FIGS. 1 to 9.
As shown in Figures 1 to 4, the liquefied gas carrier 1 comprises a hull 3, a cargo compartment 7, a liquefied gas tank 17, and a watertight compartment 79 on the side of the ship.

The hull 3 is a structural body that forms the hull of the liquefied gas carrier 1, and is configured to surround the interior of the ship with a ship bottom 71, side shell plating 73, and exposed deck 61, as shown in FIG. 1. The specific hull shape and hull structure are designed as appropriate depending on the application of the liquefied gas carrier 1.

The draft of the liquefied gas carrier 1 depends on the water depth of the waterway in which it navigates, but if the liquefied gas carrier 1 is a river vessel, the designed draft FD shown in Fig. 2 is preferably less than 6 m. The designed draft FD is the vertical distance from the deepest point of the ship bottom 71 to the designed waterline LWL.
If the designed draft FD is less than 6 m, the liquefied gas carrier 1 can navigate at least up to the middle reaches of continental rivers such as the Yangtze River.
In addition, shallow draft ships such as river vessels often have narrower waterways than sea vessels, making it difficult to widen the vessel's width to ensure stability, so this embodiment, which can ensure stability without widening the vessel's width, is particularly useful.

As shown in FIG. 1, the hull 3 has a cargo compartment 7 in which liquefied gas is loaded. More specifically, the hull 3 has an engine compartment 5, a cargo compartment 7, and a bow compartment 9 arranged in that order from the stern to the bow as onboard compartments.

The engine compartment 5 is a compartment in which the power sources of the propulsion mechanisms of the liquefied gas carrier 1, such as the main engine, are arranged, and is the sternmost compartment of the hull 3 in the longitudinal direction of the ship.
A watertight transverse bulkhead 15 is provided at the bow-direction tip of the engine compartment 5, and the engine compartment 5 and the cargo compartment 7 are separated in the longitudinal direction by the engine bulkhead 15.
A decorative chimney 13 in which an exhaust pipe for discharging exhaust gas generated by the combustion of the main engine is arranged, and an engine casing 11 in which exhaust gas treatment equipment, etc. are housed are provided as necessary on the exposed deck 61 above the engine compartment 5.

The cargo compartment 7 is a compartment in which cargo to be transported by the liquefied gas carrier 1 is placed, and is provided between the engine compartment 5 and the bow compartment 9 in the longitudinal direction of the ship as shown in FIG.
A cargo hold bulkhead 21, which is a watertight transverse bulkhead, is provided at the bow-direction tip of the cargo compartment 7, and the bow compartment 9 and the cargo compartment 7 are separated in the bow direction by the cargo hold bulkhead 21.

A liquefied gas tank 17 is installed in the cargo compartment 7.
The liquefied gas tank 17 is a tank for storing liquefied gas as cargo. Liquefied gas is a gas that is liquefied by cooling or compressing a gas at normal temperature and pressure, and examples of the liquefied gas include LNG, LPG, ethane, ethylene, ammonia, and hydrogen.

The liquefied gas tank 17 is an independent tank. An independent tank means a tank that can maintain liquid-tightness and internal pressure within the tank itself and is independent from the hull 3.
In the case of an independent tank, the tank shape can be appropriately selected from cylindrical tanks, spherical tanks, bilobe tanks, multilobe tanks, and the like.
It is more preferable that the liquefied gas tank 17 is a cylindrical tank, because the tank structure and support structure are simpler than those of other independent tanks, and therefore the number of members constituting the tank and support structure is reduced, making it easier to reduce the weight.
In Fig. 1, two liquefied gas tanks 17 are arranged in series in the longitudinal direction of the ship. A transverse cargo hold bulkhead 31, which is a watertight bulkhead, is arranged between the two liquefied gas tanks 17. The cargo compartment 7 is divided into an aft cargo compartment 7a located toward the stern and a bow cargo compartment 7b located toward the bow by the transverse cargo hold bulkhead 31. Therefore, even if one of the aft cargo compartment 7a and the bow cargo compartment 7b is flooded, the transverse cargo hold bulkhead 31 prevents water from flooding the other compartment.

The side watertight compartments 79 are watertight compartments located on the outboard side of the cargo compartment 7 on the left and right sides, and are compartments that are in contact with the side shell plating 73, which is the outer wall of the ship's side of the hull 3, and the cargo compartment 7.
In FIG. 4, a double side structure is illustrated as an example of the watertight compartment 79 on the side of the ship.
In this structure, the space between the side shell plating 73 and the inner sidewall 75 that is disposed inside the side shell plating 73 and constitutes the side wall of the cargo compartment 7 is the side watertight compartment 79. The side shell plating 73 and the inner sidewall 75 are connected by a plurality of inner side transverse bulkheads 77, which are transverse bulkheads, and a plurality of compartments surrounded by the side shell plating 73, the inner sidewall 75, the inner side transverse bulkheads 77, the ship's bottom 71, and the exposed deck 61 constitute the side watertight compartment 79.

As shown in FIG. 4 , the ship's side watertight compartment 79 includes an independent watertight compartment 80 and a communicating compartment 81 .
The independent watertight compartment 80 is a watertight compartment separated from the cargo compartment 7, and even if the cargo compartment 7 is flooded, water will not enter the compartment unless the water pressure exceeds the withstand pressure of the inner side wall 75. The independent watertight compartment 80 is a watertight compartment for adjusting the buoyancy of the hull 3, and is, for example, a ballast tank. Since the independent watertight compartments 80 are provided on both sides, it is preferable that there is at least one on each side, that is, one pair on both the port and starboard sides.
The communication compartment 81 is a compartment that communicates with the cargo compartment 7. In Fig. 4, the communication compartment 81 does not have an inner side wall 75, and this portion constitutes a communication part 83 that communicates with the cargo compartment 7. However, since the communication part 83 only needs to have a size and shape that allows flooding to progress between the cargo compartment 7 and the communication compartment 81 as one compartment, it may also be a hole provided in the inner side wall 75.
The communicating section 81 is integrated with the cargo section 7 via a communicating portion 83 to form an integral watertight section 85, which is a watertight section shown by hatching in Fig. 4. The communicating section 81 is a void space that is not used as a ballast tank because it does not become a watertight section by itself.
Since the double side sections are provided on both the port and starboard sides, at least a pair of communication sections 81 are provided on both the port and starboard sides in the cargo section 7. That is, one is provided on each side. For example, in FIG. 4, a pair (port communication section 81a and starboard communication section 81b) are provided on both the port and starboard sides of the stern cargo section 7a.
In addition, when there are a plurality of cargo compartments 7 as shown in Fig. 4, a pair of communication compartments 81 is provided in at least one of the cargo compartments 7. In Fig. 4, one communication compartment 81 is provided on each of the port and starboard sides of the aft cargo compartment 7a.

The reason for communicating a part of the ship's side watertight compartment 79 with the cargo compartment 7 in this manner will now be explained.
As shown in Fig. 5, assume that one side of the hull 3, in this case the port side, is hit by another ship, causing damage to the ship's side shell plating 73 near the port communicating compartment 81a, which is the independent watertight compartment 80 on the port side and the communicating compartment 81 on the port side. In the IGC Code, when a watertight compartment is damaged, design is performed assuming that two adjacent compartments in the longitudinal direction are damaged depending on the range of damage specified in the rules, so here it is assumed that both the independent watertight compartment 80 and the port communicating compartment 81a are flooded. In addition, in a general arrangement, it is assumed that the inner sidewall 75 is also damaged in consideration of the depth of the damage, and design is performed assuming that the independent watertight compartment 80 is also flooded.
In this case, flooding reaches the starboard communicating compartment 81b, which is the communicating compartment 81 between the damaged area and the opposite side, from the independent watertight compartment 80 and the port communicating compartment 81a via the aft cargo compartment 7a. On the other hand, the independent watertight compartment 80 between the damaged area and the opposite side is not flooded because it is separated from the aft cargo compartment 7a. Therefore, although the buoyancy of the volume equivalent to the integrated watertight compartment 85 and one independent watertight compartment 80 is lost due to flooding, the difference in flooded volume between the port and starboard sides with respect to the hull centerline C is only the volume of one independent watertight compartment 80. The hull centerline C means a straight line parallel to the ship's length that passes through the center position in the width direction of the hull 3 in a plan view.
On the other hand, if there is no communicating compartment 81 as shown in Figure 6 and all the ship's side watertight compartments 79 are independent watertight compartments 80, when the same location as in Figure 5 is damaged and flooded, the flooded water will flow into the aft cargo compartment 7a. However, since all the ship's side watertight compartments 79 on the starboard side are independent watertight compartments 80, they will not be flooded, and the flooded areas will be the aft cargo compartment 7a and the two independent watertight compartments 80 on the port side.
Therefore, compared to when a communicating section 81 is provided, the flooded volume is smaller by the volume of one communicating section 81, but the heel is larger because the flooded area is biased toward the port side.

In this way, by communicating a part of the ship's side watertight compartment 79 with the cargo compartment 7, when flooding occurs on one side, the flooded water flows through the cargo compartment 7 to the communicating compartment 81 on the opposite side, making the flooded compartments symmetrical, mitigating heel and ensuring stability. As a result, the heel can be mitigated compared to when all the ship's side watertight compartments 79 are independent watertight compartments 80, and stability can be ensured even if the number of watertight bulkheads is reduced, so that the number of cargo hold transverse bulkheads 31, which are transverse bulkheads of the cargo compartment 7, can be reduced to reduce the hull weight. Reducing the number of cargo hold transverse bulkheads 31 makes the watertight compartments in the cargo compartment 7 longer in the ship's length direction, and the tank length of the liquefied gas tanks 17 can be increased, so that the number of tanks can be reduced without reducing the tank volume, and the tank weight can be reduced. In addition, with this structure, if water floods one side, the water pressure at the time of flooding will cause the water to flow through the cargo compartment 7 into the connecting compartment 81 on the opposite side, so there is no need to install a separate structure such as a cross-flooding device to inject water into the opposite side, and there is no risk of the weight increasing due to the water injection structure.
Therefore, the liquefied gas carrier 1 can reduce heeling during a collision without increasing the ship's weight, and can ensure stability.
The above is an explanation of the reason why a part of the ship side watertight compartment 79 is in communication with the cargo compartment 7.

It is preferable that the liquefied gas carrier 1 satisfies the condition shown in the following formula (1).
(1/3) Lpp ^(2/3) <L _F < (1/2) D...Formula (1)
In formula (1), "Lpp" is the perpendicular length of the hull 3 shown in FIG. 1. "L _F " is the ship-length length of one communication section 81, and it is preferable that all communication sections 81 satisfy formula (1). In FIG. 4, both the length L _fa1 of the port communication section 81a and the length L _fb1 of the starboard communication section 81b are L _F , and it is preferable that they satisfy formula (1). "D" is the ship-length length of the cargo section 7 in which the communication section 81 is provided. When the cargo section 7 is divided in the ship-length direction as shown in FIG. 4, D is the length of only the section in which the communication section 81 is provided. In FIG. 4, the communication section 81 is provided only in the aft cargo section 7a, so D is the ship-length length of only the aft cargo section 7a.

A longer L _F is preferable from the viewpoint of the effect of mitigating heeling, because the length of the communicating section 81 in the ship's longitudinal direction is longer, and the flooded volume of the communicating section 81 on the opposite side becomes larger when one side of the ship is damaged. However, if the length of the communicating section 81 in the ship's longitudinal direction is too long, the volume of the section that loses buoyancy due to flooding when the side of the ship is damaged becomes larger, and there is a risk that the draft of the hull 3 will be too low and the ship will sink. In addition, the volume of the independent watertight section 80 that is not communicating with the cargo section 7 will be reduced, so there is a possibility that the tank capacity will be insufficient when the independent watertight section 80 is used as a ballast tank. Therefore, L _F is preferably less than (1/2)D.

A shorter L _F is preferable from the viewpoint of ensuring buoyancy in the event of damage, because the length of the communicating section 81 in the ship's longitudinal direction is shorter, and the volume of the section that will be flooded and lose buoyancy when the ship's side is damaged is smaller. However, if the length of the communicating section 81 in the ship's longitudinal direction is too short, the volume of the communicating section 81 may be too small to fully mitigate heeling. In addition, if the length falls short of the minimum dimension permitted as a section in the IGC Code, the communicating section 81 is treated as not existing as a section in design. Therefore, it is preferable that L _F is greater than (1/3)Lpp ^(2/3) .

It is more preferable that the liquefied gas carrier 1 satisfies the condition shown in the following formula (2).
(1/3) Lpp ^(2/3) <L _F < (1/3) D...Formula (2)
Formula (2) is obtained by changing the upper limit of formula (1) to a smaller value, (1/3) D. By satisfying the upper limit of formula (2), the length of the communication section 81 in the ship longitudinal direction becomes shorter than that of formula (1), and the buoyancy lost by the hull 3 when the integrated watertight section 85 is flooded can be further reduced.

In FIG. 4, the ship's side watertight compartment 79 has a double ship's side structure, and the communicating compartment 81 is a part of a divided watertight compartment that constitutes the double ship's side structure.
In this structure in which the ship's side watertight compartment 79 has a double ship side structure and part of the watertight compartment in the double ship side is a communicating compartment 81, the communicating compartment 81 can be formed simply by connecting part of the existing double ship side with the cargo compartment 7, thereby reducing the design and manufacturing costs of the communicating compartment 81.

However, the side watertight compartment 79 is located on the outboard side of the cargo compartment 7 on the left and right sides when viewed from the longitudinal direction of the ship, and as long as it is a compartment that is in contact with the side shell 73 and the cargo compartment 7, it does not have to have a double side structure.
7, a double bottom compartment 91 arranged below the bottom 93 of the cargo compartment 7 may be used as the ship's side watertight compartment 79. The double bottom compartment 91 is separated into multiple compartments in the longitudinal direction of the ship by multiple transverse bulkheads (not shown), so one of the separated compartments may be provided with a communication section 83 to communicate with the cargo compartment 7 to form a communicating compartment 81, and the other compartments may be used as independent watertight compartments 80.

By making the double bottom compartment 91 a watertight compartment 79 on the ship's side, even in a liquefied gas carrier that does not have a double ship side, a communicating compartment 81 can be formed simply by connecting one of the existing double bottom compartments 91 to the cargo compartment 7, thereby reducing the design and manufacturing costs of the communicating compartment 81.

As shown in FIG. 7 , a part of the top side tank 63 may be used as a watertight compartment 79 on the ship side.
The top side tank 63 is a watertight compartment provided above the ship's side near the ship's side, and is mainly used as a ballast tank. As shown in FIG. 7, the top side tank 63 is a watertight compartment surrounded by a ship's side shell 73, an exposed deck 61, and a connecting wall 62. The connecting wall 62 is a side wall that connects the ship's side shell 73 and the exposed deck 61, which is the ceiling wall of the cargo compartment 7, and extends in the ship's length direction of the cargo compartment 7, and has an L-shaped curved shape as seen from the ship's length direction. The top side tank 63 is also separated into a plurality of compartments in the ship's length direction by a plurality of transverse bulkheads (not shown). Therefore, a communication part 83 may be provided in one of the separated compartments to communicate with the cargo compartment 7 to form a communicating compartment 81, and the other compartments may be independent watertight compartments 80.
By making the top side tank 63 the ship's side watertight compartment 79, even if a part of the ship's side is not double-walled, a communication compartment 81 can be formed simply by connecting one of the existing top side tanks 63 to the cargo compartment 7. This reduces the design and manufacturing costs of the communication compartment 81. This structure is also advantageous when it is difficult to secure space in the hull 3 to make the entire ship's side double-walled, for example, because the liquefied gas tank 17 is a wide tank that is located close to the ship's side shell 73, such as the bilobe tank 17a shown in Figure 7.

As shown in FIG. 4, the pair of communication sections 81 on both the port and starboard sides are preferably disposed symmetrically with respect to the hull centerline C in a plan view.
When a pair of communicating sections 81 are arranged symmetrically on both the left and right sides, the hull 3 heels around the hull centerline C as its central axis when water enters the cargo section 7, and therefore does not heel around an axis inclined relative to the hull centerline C, making it difficult for a torsional moment to be applied to the hull 3 when heeling.
However, if the torsional moment can be tolerated, the pair of communicating sections 81 on both the port and starboard sides may be arranged asymmetrically with respect to the hull centerline C in a plan view.

The installation position of the communication compartment 81 in the longitudinal direction can be set as appropriate within the cargo compartment 7 in which the liquefied gas tanks 17 are installed. However, it is preferable to place the communication compartment 81 adjacent to the aft transverse bulkhead of the cargo compartment 7. In Figure 4, the aft transverse bulkhead of the cargo compartment 7 is the machinery bulkhead 15 which separates the machinery compartment 5 from the cargo compartment 7, so it is preferable to place the communication compartment 81 in contact with the machinery bulkhead 15. In this configuration, the machinery bulkhead 15 becomes the transverse bulkhead on the stern side of the communication compartment 81. The reason why it is preferable to place the communication compartment 81 adjacent to the machinery compartment 5 is as follows.
In the IGC Code, when one watertight compartment is flooded, the design is made assuming that two adjacent compartments in the longitudinal direction are flooded depending on the extent of damage stipulated in the rules. Therefore, if the communicating compartment 81 is arranged adjacent to the machinery compartment 5, when the machinery compartment 5 is damaged and flooded, the adjacent communicating compartment 81 in the longitudinal direction will also be flooded depending on the extent of damage. In this case, flooding reaches the left and right communicating compartments 81, which has the effect of mitigating heel. In particular, the machinery compartment 5 is the compartment in which the main engine that generates the power required for propulsion of the hull 3 is arranged, and therefore has a large volume among the compartments in the ship, and is likely to experience a large heel when flooded. Therefore, arranging the communicating compartment 81 adjacent to the machinery compartment 5 is even more advantageous in mitigating heel.
Incidentally, the rearmost transverse bulkhead of the cargo compartment 7 may not be the engine bulkhead 15. For example, as shown in Figure 8, when a coffer dam 6 such as a fuel tank is provided between the engine compartment 5 and the cargo compartment 7 in the longitudinal direction, the rearmost transverse bulkhead of the cargo compartment 7 becomes the coffer dam bulkhead 16, which is a transverse bulkhead separating the coffer dam 6 and the cargo compartment 7. In this case, it is preferable that the communication compartment 81 is disposed adjacent to the coffer dam bulkhead 16.

The installation position of the communication compartment 81 in the longitudinal direction may be a position adjacent to the bow compartment 9. Specifically, as shown in Fig. 9, it may be a position adjacent to the cargo hold bulkhead 21, which is a watertight transverse bulkhead separating the cargo compartment 7 and the bow compartment 9. In this configuration, the cargo hold bulkhead 21 becomes the transverse bulkhead on the bow side of the communication compartment 81. The reason why it is preferable to dispose the communication compartment 81 adjacent to the bow compartment 9 is as follows.
The bow section 9 is located at the very front end of the hull 3 in the longitudinal direction, and is therefore generally at the very front end in the direction of travel when maneuvering, and is the section most likely to collide with other ships and become flooded among the sections within the ship. Therefore, by arranging the communication section 81 adjacent to the bow section 9, which is prone to flooding, it becomes even more advantageous in mitigating heeling when flooding occurs.

The width of the ship's side watertight compartment 79 in the ship's beam direction is set appropriately within a range in which the liquefied gas tank 17 and its supporting structure do not interfere with the ship's side watertight compartment 79. If the ship's side watertight compartment 79 is used as a ballast tank, it should be set within a range that can secure the necessary amount of ballast water.

At least one pair of communicating compartments 81 should be provided on each of the port and starboard sides, but two or more pairs may be provided on each of the port and starboard sides. However, the more communicating compartments 81 there are, the smaller the volume of the independent watertight compartments 80 becomes, and the volume of the compartments that will be flooded and lose buoyancy when the ship's side is damaged will increase, and there is a risk that the draft of the hull 3 will be too low and the ship will sink. Furthermore, since the volume of the independent watertight compartments 80 that are not communicating with the cargo compartments 7 is reduced, there is a possibility that the tank capacity will be insufficient when the independent watertight compartments 80 are used as ballast tanks. Therefore, the number of communicating compartments 81 is appropriately set in consideration of the range in which the necessary buoyancy and tank capacity can be secured in the event of flooding, etc.
It is preferable that the pair of communicating compartments 81 have the same volume, since this makes it difficult for a heel to occur when water enters the compartments.
In addition, it is preferable that the difference in the ship-length direction between a pair of communication sections 81 in the same cargo section 7 is small, and it is most preferable that they are the same length. For example, in Fig. 4, it is preferable that the ship-length direction length _Lfa1 of the port communication section 81a provided in the stern cargo section 7a and the ship-length direction length _Lfb1 of the starboard communication section 81b are the same length.

From the viewpoint of reducing the weight of the liquefied gas tank 17, it is preferable to have a smaller number of liquefied gas tanks 17, and one tank is the most preferable. However, as the number of liquefied gas tanks 17 decreases, the number of watertight compartments in the cargo compartment 7 decreases, and the amount of buoyancy lost in the event of flooding increases. In addition, the size of the equipment at the manufacturing factory restricts the size of the tanks that can be manufactured for the liquefied gas tanks 17. Therefore, the number of liquefied gas tanks 17 is determined by the number of cargo hold transverse bulkheads 31 and their installation intervals in the longitudinal direction, which are determined from the viewpoint of the buoyancy that can be lost in the event of flooding, and the tank size of the liquefied gas tanks 17 that can be manufactured by the factory that manufactures the liquefied gas tanks 17. Although FIG. 1 illustrates a case in which the number of tanks is two, the number of tanks may be one or three depending on the conditions of buoyancy and tank size. Or, four or more tanks may be used.
The above is a description of the configuration of the liquefied gas carrier 1 according to this embodiment.

In this way, the liquefied gas carrier 1 of this embodiment has a pair of communicating compartments 81 on both the starboard and starboard sides, in which some of the multiple shipside watertight compartments 79 arranged on the outboard side of the cargo compartment 7 are connected to the cargo compartment 7.
In this configuration, if water floods into the cargo compartment 7 from one side, the flooding water flows through the cargo compartment 7 to the other side, mitigating heel and ensuring stability, so the number of transverse cargo hold bulkheads 31 in the cargo compartment 7 is reduced to reduce the hull weight. Reducing the number of transverse cargo hold bulkheads 31 increases the length of the watertight compartments in the cargo compartment 7 in the ship's length direction, so the tank length of the liquefied gas tanks 17 can be increased, reducing the number of tanks without reducing the tank volume, and reducing the tank weight.
Therefore, the liquefied gas carrier 1 can reduce heeling during a collision without increasing the hull weight, and can ensure stability.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the embodiments. It is natural that a person skilled in the art would come up with various modifications and improvements within the scope of the technical concept of the present invention, and these are also included in the present invention.

1 : Liquefied gas carrier 3 : Hull 5 : Engine compartment 6 : Cofferdam 7 : Cargo compartment 7a : Aft cargo compartment 7b : Forward cargo compartment 9 : Forward compartment 11 : Engine casing 13 : Cosmetic funnel 15 : Engine bulkhead 16 : Cofferdam bulkhead 17 : Liquefied gas tank 17a : Bilobe tank 19 : Cargo tank cover 21 : Cargo hold bulkhead 23 : Bridge 31 : Cargo hold transverse bulkhead 61 : Exposed deck 62 : Connecting wall 63 : Topside tank 71 : Ship bottom 73 : Side shell 75 : Inner side wall 77 : Inner side transverse bulkhead 79 : Side watertight compartment 80 : Independent watertight compartment 81 : Communication compartment 81a : Port communication compartment 81b : Starboard communication compartment 83 : Communication section 85 : Integrated watertight compartment 91 : Double bottom compartment 93 : Bottom

Claims (8)

A liquefied gas carrier having a hull with a cargo compartment in which an independent tank for storing liquefied gas as cargo is installed,
a watertight compartment disposed on the outer side of the cargo space on the left and right sides as viewed from the longitudinal direction of the ship, the watertight compartment comprising a plurality of side watertight compartments in contact with the side shell and the cargo space;
The plurality of watertight compartments of the ship side include
An independent watertight compartment arranged on each of the port and starboard sides and being a watertight compartment independent of the cargo compartment;
At least one pair of communication compartments are arranged on the left and right sides of the ship, and communicate with the cargo compartment to form an integral watertight compartment;
A liquefied gas carrier comprising: 2. The liquefied gas carrier according to claim 1, characterized in that, when the perpendicular length of the hull is Lpp, the longitudinal length of one of the communicating sections is L _F , and the longitudinal length of the cargo section in which the communicating section is provided is D, the condition shown in the following formula (1) is satisfied.
(1/3) Lpp ^(2/3) <L _F < (1/2) D...Formula (1) The liquefied gas carrier according to claim 1 or 2, wherein the communication compartment is composed of a void space that is not used as a ballast tank. The watertight compartment of the ship's side is:
a double ship side surrounded by the side shell plating and an inner sidewall arranged inside the side shell plating and constituting a sidewall of the cargo compartment, the double ship side being divided into a plurality of parts in the longitudinal direction by inner side transverse bulkheads connecting the side shell plating and the inner sidewall,
4. A liquefied gas carrier according to claim 1, wherein the independent watertight compartments and the communicating compartments are part of divided compartments constituting the double hull side. A liquefied gas carrier according to any one of claims 1 to 3, wherein the watertight compartment on the side of the ship is a double bottom compartment arranged on the bottom of the cargo compartment. A liquefied gas carrier according to any one of claims 1 to 3, wherein the watertight compartment on the ship's side is a topside tank. A liquefied gas carrier according to any one of claims 1 to 6, wherein the communication compartment is disposed adjacent to the rearmost transverse bulkhead of the cargo compartment. The hull has an engine room, a cargo room, and a bow room arranged in this order from the stern side to the bow side,
The bow compartment and the cargo compartment are separated by a watertight transverse bulkhead, which is a cargo hold bulkhead;
The liquefied gas carrier according to any one of claims 1 to 7, wherein the communication compartment is adjacent to the cargo hold bulkhead.

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