KR20160009198A - Structure for moonpool - Google Patents

Abstract

According to an embodiment of the present invention, a structure for a moon pool comprises a guide unit provided adjacent to a moon pool and protruded toward a floor surface of a hull so as to prevent sea water from flowing into the inside of the moon pool. According to the invention, the structure for a moon pool can reduce damage of the inside of the moon pool caused by a flow of sea water and can minimize fluid resistance generated at the moon pool, through a simple structure alteration of a drillship or a semi-submersible marine structure without using a complex system.

Description

Structure of moonpool {Structure for moonpool}

The present invention relates to a layout structure.

Due to the recent rapid industrialization, the use of resources such as oil has skyrocketed, and the stable production and supply of oil is becoming a very important issue. However, the oil field in the continental or coastal waters has already been drilled. In recent years, interest has been focused on the development of a deep-sea deep-sea oil field. Drilling is generally used to drill deep-sea oilfields.

Drill ship is an offshore structure that is equipped with advanced drilling equipment and is built in a shape similar to that of a ship so that it can be sailed by its own power. It is capable of collecting raw oil or gas in deep sea area where an offshore platform can not be installed, It is advantageous that the drilling can be terminated and the drilling can be carried out by moving to another point.

Such drillings include Derrick, which has a Moonpool structure in a vertically penetrating form and is located above the drum and has drilling rigs. Hereinafter, the process of drilling the bottom of the drill ship will be described.

First, the drill ship uses its own power to move to the drilling area and drives a Dynamic Positioning System (DPS) using a plurality of thrusters to maintain the position.

Thereafter, the drill bit is connected to a drill pipe by a drill bit, and a plurality of drill pipes are connected by a sufficient length by using a Hoisting System and a Handling System provided in Derrick, And the drilling pipe is rotated through a rotating system to form a borehole.

Once drilling is completed, Derek picks up the drill pipe, installs the casing pipe on the borehole, and performs the cementing process to fill the concrete between the casing pipe and the borehole. The drilling operation used and the casing and cementing work for installing the casing pipe are repeatedly performed to maintain the shape of the borehole having a certain depth.

When the casing pipe is installed enough to prevent the borehole from falling down, BOP (Blow Out Preventer) is connected to the riser to be connected to the borehole. In this case, the inside of the riser becomes the path of movement of the drill pipe and casing pipe.

However, lubrication and cooling of the drill bit in the drilling process, and processing of the crushed material such as rock mass produced in the borehole are required. Therefore, the drill feeds the mud to the inside of the drill pipe so that the mud is discharged at the end of the drill bit, and after the mud performs lubrication and cooling of the drill bit, (Mud Circulation System) is used. The recovered mud is re-used after the pulverized material is filtered.

The drillship repeatedly performs drilling, casing and cementing operations until the drill bit reaches the well, while driving this mud circulation system. In this case, as the diameter of the casing pipe used in the casing work becomes smaller, Drilling can be implemented continuously by replacing small drill bits.

As such, the drill rig has a system for installing and using pipes and risers, a system using a mud, and the like. In order to smoothly perform drilling work using such a system, a drill hole structure, a derrick structure, and a load structure Is required to be disposed within a certain space, so that research and development are being continuously carried out as a result of a high technological power being required.

However, in the drilling operation, it is necessary to open the riser and the like in order to move up and down. However, since an opening is formed at the center of the hull such as drill bit, resistance due to flow inside the drum occurs. Of course, There is a problem that the seawater is introduced and the equipment in the door pool is damaged.

In order to prevent this, Korean Open No. 10-1999-0079571 (Nov. 5, 1999), an opening and closing door is installed in the lower part of the doorpost in a door-dropping resistance reducing device of a ship. In the case where an opening- Even if the door is closed in a floating state, the already inflowed seawater is contained in the inside of the door, the resistance is increased due to the sloshing phenomenon caused by the swirling of the seawater, and it is easy to manage afterward due to corrosion or attachment of marine organisms not. In addition, if a malfunction of the opening / closing device occurs during operation, since the opening and closing device is locked in seawater, it may be difficult to repair it immediately.

SUMMARY OF THE INVENTION The present invention has been made to improve the prior art, and it is an object of the present invention to provide a door frame structure capable of reducing the fluid resistance by sloshing by lowering the momentum of the fluid flowing into the interior of the door of the drill.

The door frame structure according to an embodiment of the present invention includes a guide portion provided adjacent to the door frame and protruding from the bottom surface of the hull to prevent the seawater from moving into the door frame.

Specifically, the guide portion may include a shielding plate protruding from a bottom surface of the hull, And an elevating member for elevating and lowering the blocking plate.

Specifically, the elevating member includes a roller provided on the hull and guiding the lifting and lowering of the blocking plate.

Specifically, the roller is in contact with both surfaces of the shield plate, thereby guiding the rising and falling of the shield plate.

Specifically, the present invention is characterized by further comprising a winch portion that fixes a wire to the upper portion of the blocking plate and winds up or loosens the wire according to the rising and falling of the blocking plate.

Specifically, the blocking plate is characterized in that holes are formed to suppress vortex flow.

The structure of the door frame according to the present invention can minimize the fluid resistance generated in the door frame by reducing the mobility of the fluid through a simple structure change of the drill rig without using a complicated system and reduce the damage inside the door frame due to the flow of seawater .

1 is a view conceptually showing a structure of a door frame according to a first embodiment of the present invention.
FIG. 2 is a view conceptually showing a structure of a door frame according to a second embodiment of the present invention.
3 is a view conceptually showing a structure of a door frame according to a third embodiment of the present invention.
FIG. 4 is a view conceptually showing a structure of a door frame according to a fourth embodiment of the present invention.
FIG. 5 is a view conceptually showing a structure of a door frame according to a fifth embodiment of the present invention.
FIGS. 6 to 8 are conceptual views of the angular state of the guide portion of the door frame structure according to the fifth embodiment of the present invention.
FIG. 9 is a view conceptually showing a structure of a door frame according to a sixth embodiment of the present invention.
10 is a view conceptually showing a front surface of a hull in which a door frame structure according to a sixth embodiment of the present invention is formed.

BRIEF DESCRIPTION OF THE DRAWINGS The objects, particular advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. It should be noted that, in the present specification, the reference numerals are added to the constituent elements of the drawings, and the same constituent elements are assigned the same number as much as possible even if they are displayed on different drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

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

1 is a view conceptually showing a structure of a door frame according to a first embodiment of the present invention.

As shown in FIG. 1 (the dotted line is a general structure of the door frame), the door frame structure 100 according to the first embodiment of the present invention includes the door frame 110 and the guide portion 120.

The platform 110 forms a space through the center of the hull (not shown), for example, to operate the equipment for drilling, such as drilling.

In the case of a drill, a drum 110 is provided at a central portion of a hull forming a single sub-fluid, in a shape penetrating from an upper deck (not shown) of the hull to a base line (not shown) And may be equipped with a propelling means (not shown) so as to allow the user to navigate by himself.

The door frame 110 may extend substantially vertically and pass through equipment such as a drilling rig and a robot into the door frame 110. That is, the portal 110 can be used as a passage for the equipment. Here, the drilling equipment includes a riser (not shown) for drilling, a drill pipe (not shown), and the drilling equipment can be stored and installed in the hull adjacent to the periphery of the platform 110 .

In addition, a space is formed on the cellar deck 113 with a step difference, and a blow out preventer (BOP, not shown) may be provided in the space of the cellar deck.

The door frame 110 may have a polygonal shape. For example, the door frame 110 may have a rectangular parallelepiped shape so as to form a first side wall 111 provided in the stern direction and a second side wall 112 provided in the aft direction. And a cell deck 113 having a concave stepped portion in the direction of the arrow.

The guide unit 120 guides the flow of seawater flowing into the interior of the door frame 110 to prevent the seawater from moving to the upper portion of the cellard 113.

The guide portion 120 of this embodiment is recessed in the first sidewall 111 which is the inner side wall in the stern direction of the door frame 110. [ For example, the guide portion 120 may be concave upward from the bottom surface of the hull, and may include a first concave member 121 and a second concave member 122.

The first concave member 121 guides the flow of the seawater flowing through the bottom surface of the hull to relieve the flow of the seawater flowing into the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior, The first side wall 111 can be inclined so that the length thereof becomes smaller toward the stern side. Accordingly, the seawater flowing around the hull is guided in the stern direction by the first concave member 121 so as to prevent the seawater flowing along the first side wall 111 from riding on the first side wall 111 while flowing on the bottom surface of the hull, It is possible to reduce the amount of the upward flow in the interior.

The second concave member 122 is configured to guide the seawater introduced into the interior of the door frame 110 downward. The second concave member 122 is configured to guide the seawater flowing downward from the first side wall 111 of the door frame 110 to a position lower than the horizontal line of the cellade 113 And the inclination can be made such that the pine length decreases from the upper part to the lower part. For example, the second concave member 122 may be formed on the upper portion of the first concave member 121, and preferably, the concave member 122 may be inclined so that the longer the concave member 121 is, . The seawater flowing into the interior of the door frame 110 flows along the inclined surface of the second concave member 122 and is guided downward by hitting against the upper surface of the second concave member 122, It is possible to mitigate the flow of seawater.

Here, the shape of the first concave member 121 and the shape of the second concave member 122 are in the form of a straight line, but they may be curved.

As described above, in the present embodiment, seawater flowing around the bottom surface of the hull is guided by the guide part 120 (see FIG. 1) so that the hull is prevented from flowing into the interior of the door 110 on the first side wall 111, The seawater flowing into the interior of the door frame 110 moves along the second concave member 122 and is guided along the first concave member 121 of the second concave member 122 in the stern direction, So as to be guided downward. Accordingly, it is possible to reduce the mobility of the seawater flowing into the interior of the door frame 110, and to prevent the seawater from rising to the upper portion of the sea deck 113.

FIG. 2 is a view conceptually showing a structure of a door frame according to a second embodiment of the present invention. The same or corresponding elements as those of the first embodiment described above are denoted by the same reference numerals, and redundant description thereof will be omitted.

As shown in FIG. 2, the door frame structure 200 according to the second embodiment of the present invention includes a door frame 110 and a guide portion 220.

As described above, the door frame 110 is formed as a drill-through, which is substantially perpendicular to the door 110 and through which equipment such as a drilling rig and a robot can pass through the door frame 110.

The embodiment of the present invention is not limited to the structure in which the guide part 120 is formed on the first sidewall 111 of the first embodiment. The guide part 220 may be formed on each of the first sidewall 211 and the second sidewall 212,

The guide unit 220 guides the flow of seawater flowing into the interior of the door frame 110 to prevent the seawater from moving to the upper portion of the cellard 113. The guide portion 220 of the present embodiment may include a first curved surface member 221 and a second curved surface member 222.

The first curved surface 221 is configured to guide the seawater flowing into the interior of the door frame 110 and reduce the flow of the seawater to the upper portion of the shelved deck 113. The first curved surface 221 has a first sidewall (Not shown).

The second curved surface member 222 may be recessed in the second side wall 212 provided on the forward side of the door frame 110 to guide the seawater flowing in the interior of the door frame 110.

Each of the first curved surface member 221 and the second curved surface member 222 is concave in a hemispheric shape. The first curved surface member 221 and the second curved surface member 222 are curved in a semi- (Fore and aft direction) from the center of the base plate 110. Accordingly, the seawater introduced into the door frame 110 from the front of the hull is curved in the first side wall 211, which is the inner side wall of the rear side of the door frame 110, and curved downwardly in the second side wall 212, Can flow.

As described above, in the present embodiment, when the hull is operated, the seawater is guided along the first curved surface member 221 which is a depression formed in the first side wall 211, and when the moving direction is bent to flow forward, And guided along the two curved surface members 222 and bent in the moving direction to guide the seawater introduced into the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the door 110, Can be reduced.

3 is a view conceptually showing a structure of a door frame according to a third embodiment of the present invention. The same or corresponding elements as those of the first and second embodiments described above are denoted by the same reference numerals, and a duplicate description thereof will be omitted.

As shown in FIG. 3 (the dotted line is a general structure of the door frame), the door frame structure 300 according to the third embodiment of the present invention includes the door frame 110 and the guide portion 320.

As described above, the door frame 110 is formed in the drill hole as an opening through which the equipment such as the drilling rig and the robot can pass through the interior of the door frame 110, substantially vertically extending.

The door frame 110 of this embodiment has the same functions and functions as those of the above-described embodiments. However, the door frame 110 has the guide portions 120 and 220 formed on the first sidewalls 111 and 211 and the second sidewalls 112 and 212 of the first and second embodiments, Different forms can be made. The guide part 320 may be formed on each of the first sidewall 311 and the second sidewall (not shown) forming the inner wall of the door frame 110.

The guide unit 320 guides the flow of seawater flowing into the interior of the door frame 110 to prevent the seawater from moving to the upper part of the cellard 113. The guide portion 320 of the present embodiment may include a first inclined member 321 and a second inclined member 322. [

The first inclined member 321 separates the flow of seawater and reduces the flow of seawater into the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior But is inclined such that the protruding length becomes smaller as it goes from the lower part to the upper part.

The second inclined member 322 is configured to guide the flow of the seawater flowing into the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the interior of the door 110 The projecting length becomes larger.

For example, when the ship hits the first inclined member 321 protruding from the bottom surface of the hull to the inside of the hull 110 when the sea water flows around the hull 110, The movement of seawater flowing into the interior of the door frame 110 can be reduced. The seawater is guided along the second inclined member 322 and is guided along the first inclined member 321 to the lower portion of the door 110 And moves to the outside.

As described above, in this embodiment, when the hull is operated, the sea water is guided along the first inclined member 321, which is a protrusion formed on the first side wall 311, and when the moving direction is bent to flow forward, 2 directional inclined member 322 and is moved downward to be guided so as to be moved to the outside of the door 110 when the seawater flows into the door 110. As a result, Can be reduced.

FIG. 4 is a view conceptually showing a structure of a door frame according to a fourth embodiment of the present invention. The same or corresponding elements to those of the first, second, and third embodiments described above are denoted by the same reference numerals, and a duplicate description thereof will be omitted.

As shown in FIG. 4, the door frame structure 400 according to the fourth embodiment of the present invention includes a door frame 110 and a guide portion 420.

As described above, the door frame 110 is formed in the drill hole as an opening through which the equipment such as the drilling rig and the robot can pass through the interior of the door frame 110, substantially vertically extending.

The door frame 110 of this embodiment has the same functions and functions as those of the above-described embodiments. However, the guide portions 120, 220, and 320 are formed on the first sidewalls 111, 211, and 311 and the second sidewalls 112 and 212 of the first, It can be done differently from what it is. The first side wall 411 and the second side wall 412 may be formed on the inner wall of the door frame 110 and the guide portion 420 may be formed on the second side wall 412.

The guide part 420 is provided on the door frame 110 to smooth the flow of seawater moving to the upper part of the cellard 113. The guide portion 420 of the present embodiment may be inclined so as to be cut to the side of the selvedock 113 from the forward side of the door 110. [

The guide part 420 is formed by the space on the side of the sella deck 113 being recessed so that the upper space of the door frame 110 is expanded and the second side wall 412 is cut forward, . Here, although the guide part 420 has a sloping plane, the guide part 420 may have a wrinkle on the guide part 420 to alleviate the flow of seawater.

As described above, according to the present embodiment, the end portion of the seladec 113 has a chamfer shape, so that when the seawater hits the selad deck 113, the impact can be mitigated and smoothly flows into the selad deck 113, Can be stabilized.

FIG. 5 is a conceptual illustration of a door frame structure according to a fifth embodiment of the present invention, and FIGS. 6 to 8 conceptually show a modified angle state of the guide part of the door frame structure according to the fifth embodiment of the present invention FIG.

The same or corresponding elements as those of the above-described embodiments are denoted by the same reference numerals, and redundant description thereof will be omitted.

5 to 8, the door frame structure 500 according to the fifth embodiment of the present invention includes a door frame 110 and a guide portion 520. As shown in FIG.

The door frame 110 is formed in the drill hole as an opening, as described above. The door frame 110 of this embodiment has the same functions and functions as those of the above-described embodiments, but the shape of the guide unit 520 may be different. The present embodiment has a first side wall 411 and a second side wall 412 forming the inner wall of the door frame 110 and a guide portion 520 is provided on each of the first side wall 411 and the second side wall 412 .

The guide part 520 is provided on the door frame 110 to reduce the flow of seawater flowing into the door frame 110. The guide part 520 of the present embodiment is provided so as to be able to descend downward from the base line of the hull to lower the flow of seawater flowing into the interior of the door frame 110. The guide portion 520 may be provided on each of the front and rear (front and rear) sides of the door frame 110 so as to face the direction of travel of the hull, or may be provided on the front (bottom side of the bow).

For example, the guide portion 520 may include a blocking plate 521 and an elevating member 522.

The blocking plate 521 may be provided so as to be inserted into the bottom surface adjacent to the door frame 110. If necessary, the protrusion length from the bottom surface may be adjusted to reduce the flow of seawater flowing into the door platform 110 .

The elevating member 522 moves the blocking plate 521 up and down. The blocking plate 521 is in the form of a plate, and the elevating member 522 can be installed on the deck (not shown) of the hull. Here, the deck on which the elevating member 522 is installed may vary depending on the entire length and design of the upper deck or the second third deck of the lower deck, such as the blocking plate 521.

Further, the elevating member 522 can secure a space for raising and lowering the blocking plate 521. This means a space corresponding to the thickness of the blocking plate 521 when the blocking plate 521 descends.

The elevating member 522 may include a roller 5221 for guiding the lifting and lowering of the blocking plate 521. At this time, the roller 5221 may be provided to have sufficient frictional force with the blocking plate 521 to prevent the blocking plate 521 from descending due to its own weight. Alternatively, the lifting member 522 may include a driving belt, which is the same as or similar to the operation of the roller 5221. [

The rollers 5221 are brought into close contact with both sides of the blocking plate 521 and the blocking plate 521 is brought into contact with both sides of the blocking plate 521, Can be guided downward. This is to prevent the blocking plate 521 from tilting. In addition, a plurality of rollers 5221 may be provided in the upper and lower portions so that the blocking plate 521 can smoothly move up and down.

When the blocking plate 521 is moved up and down using the roller 5221, the frictional force between the roller 5221 and the blocking plate 521 is secured sufficiently to prevent the blocking plate 521 from falling due to its own weight I can not. Therefore, in this embodiment, the roller 5221 may be replaced with a rack gear (not shown). In this case, a rack (not shown) may be provided on the blocking plate 521 to engage with the rack gear. Therefore, the lifting member 522 can prevent unnecessary descent of the blocking plate 521 through engagement of the gear teeth.

The present embodiment may further include a winch portion 5222. [ The winch portion 5222 has a structure in which a wire 5223 is fixed to an upper portion of the blocking plate 521 and the wire 5223 is wound or unwound as the blocking plate 521 ascends and descends. The protruding length of the blocking plate 521 can be adjusted by the roller 5221. However, since the winch portion 5222 winds or loosens the wire 5223, It can also be adjusted.

As described above, the blocking plate 521 protruding from the bottom surface of the hull can be moved up and down. The blocking plate 521 protrudes from the bottom of the hull during drilling operation, Can be stabilized. The flow of seawater may be blocked by the guide part 520 provided on the bottom surface of the hull so that the flow of seawater around the hull 110 may be mitigated.

A hole (not shown) or a porous medium may be formed in the shield plate 521 of the guide unit 520 to reduce eddy currents and reduce resistance.

In the present embodiment, as shown in FIG. 5, the blocking plate 521 is vertically raised and lowered to protrude from the bottom surface of the hull. However, the blocking plate 521 is provided to reduce the inflow of seawater into the interior of the door frame 110. In addition to the vertical up and down, the blocking plates 5201, 5202 and 5203 are inclined Up and down may be performed. At this time, as shown in FIG. 6, a pair of blocking plates 5201 provided at fore and aft ends may be inclined so as to be centered on the lower side. Alternatively, as shown in FIG. 7, The blocking plate 5202 may be inclined so as to extend from the center of the lower side, or it may be inclined in parallel as shown in Fig.

The support of the blocking plates 5201, 5202 and 5203 and the mechanism of the ascending and descending steel can be replaced with the mechanism in which the blocking plate 521 of the guide unit 520 described above is moved up and down. The state in which the rollers 5221 of the lifting members 522 supporting the blocking plates 5201, 5202 and 5203 are disposed is provided on both sides of the movement path of the blocking plates 5201, 5202 and 5203, As shown in Fig.

In addition, the shutoff plates 521, 5201, 5202 and 5203 of this embodiment protrude from the bottom surface of the hull to reduce the flow amount of seawater flowing into the inside of the platform 110, 5203 are located on the same line as the bottom surface of the hull so that the seawater can be prevented from flowing into the hull through the holes through the blocking plates 521, 5201, 5202, 5203.

In addition, although not shown in the drawing, the shut-off plates 521, 5201, 5202 and 5203 are structured such that the shut-off plates 521, 5201, 5202 and 5203 are inserted into the cylinder in addition to the roller 5221 of the lifting member 522 And the protruding lengths of the blocking plates 521, 5201, 5202 and 5203 are adjusted according to the amount of hydraulic pressure so that the up and down movement can be performed. At this time, the winch portions 5222 are provided at the lower ends of the blocking plates 521, 5201, 5202, 5203 to prevent the blocking plates 521, 5201, 5202, 5203 from coming off.

As described above, in this embodiment, the guide part 520 protruding from the bottom surface of the hull is provided to stabilize the flow of the seawater flowing into the interior of the door frame 110, and holes or porous materials are formed in the guide part 520 It is possible to reduce the resistance by suppressing the vortex so that the operation and drilling work of the hull can be smoothly performed.

FIG. 9 is a conceptual illustration of a door frame structure according to a sixth embodiment of the present invention, and FIG. 10 is a view conceptually showing a front surface of a hull structure in which a door frame structure according to a sixth embodiment of the present invention is formed. The same or corresponding elements as those of the above-described embodiments are denoted by the same reference numerals, and redundant description thereof will be omitted.

As shown in Figs. 9 and 10, the door frame structure 600 according to the sixth embodiment of the present invention includes a door frame 110 and a guide portion 620. Fig.

As described above, the door frame 110 is formed in the drill hole as an opening through which the equipment such as the drilling rig and the robot can pass through the interior of the door frame 110, substantially vertically extending.

The door frame 110 of this embodiment has the same functions and functions as those of the above-described embodiment, and has a first side wall 111, which is a sidewall in the aft direction, and a second sidewall 111, The space 110 may be formed in the space between the first and second openings 112a and 112b.

However, the guide portion 620 of the present embodiment may be formed in a duct shape. For example, the guide portion 620 may have a semicylindrical shape and may have a shape that covers the lower side of the hull or a cylindrical shape as shown in FIG. 8 .

The seawater passing through the guide portion 620 of the present embodiment is seawater flowing on the bottom surface 12 of the hull 1 and seawater flowing in front of the portal 110 on the bottom surface 12 of the hull, The flow rate of the seawater flowing into the interior of the door 110 can be reduced by rapidly passing under the doorway 110 on the same side of the bottom surface 12 of the hull 1 as the inflow / Identification code 11, which is not described here, refers to the deck of the hull.

Thus, in this embodiment, the seawater flowing on the bottom surface 12 of the hull 1 quickly passes over the lower portion of the door 110, thereby reducing the fluid resistance due to a reduction in the amount of movement of the door 110 into the door 110 .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the present invention. It is obvious that the modification and the modification are possible.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100, 200, 300, 400, 500, 600: Frame structure 110:
111, 211, 311, 411: first side walls 112, 212, 412:
113: Seladec 121: First concave member
122: second concave member 221: first curved member
222: second curved member 321: first inclined member
322: second inclined member 521, 5201, 5202, 5203:
522: lifting member 5221: roller
5222: winch portion 5223: wire
120, 220, 220, 420, 520,

Claims (6)

And a guide portion provided adjacent to the doorpath and protruding from the bottom surface of the hull to prevent the seawater from moving into the interior of the doorpath. The apparatus according to claim 1,
A shield plate protruding from a bottom surface of the hull so as to be raised and lowered; And
And an elevating member for elevating and lowering the blocking plate. 3. The apparatus according to claim 2,
And a roller installed on the hull to guide the lifting and lowering of the blocking plate. 4. The image forming apparatus according to claim 3,
And the guide plate contacts both surfaces of the blocking plate to guide the rising and falling of the blocking plate. 3. The method of claim 2,
Further comprising a winch portion for fixing a wire to the upper portion of the blocking plate and winding or unwinding the wire according to the rising and falling of the blocking plate. The apparatus according to claim 2, wherein the blocking plate
And holes are formed to suppress eddy currents.

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