KR101616992B1 - A ship for reducing vibromotive force - Google Patents

Abstract

A propeller cavitation organic exciter-powered vessel is disclosed. In accordance with an aspect of the present invention, there is provided a propeller-cavitation-induced propulsion-reduction vessel comprising: a hull having a propeller; And a working gas receiving bag having a working gas pocket in which a working gas for generating a reflected wave for causing a destructive interference phenomenon with an incident wave generated when the propeller rotates is enclosed and accommodated; And a camera module having a camera for monitoring the working gas receiving membrane pads in real time and disposed within the hull adjacent to the working gas receiving membrane pads.

Description

A ship for reducing vibromotive force,

TECHNICAL FIELD The present invention relates to a propeller cavitation organic exciter force reduction type vessel, and more particularly, to a propeller cavitation organic exciter force reduction type vessel capable of real time monitoring of a work gas receiving membrane pad.

When the propeller provided at the rear of the ship rotates in water, the water flows to the propeller blade surface, causing a difference in hydraulic pressure between the front and back surfaces of the propeller blade surface. The propulsion generated in this way allows the ship to be operated at sea.

On the other hand, when the propeller is operated for the operation of the ship, that is, when the propeller is rotated in water, a fluctuating pressure is generated in the water due to the propeller as the rotating body. The fluctuating pressure thus generated increases the excitation force to the hull, (Including noise).

Particularly, when cavitation occurs in the water by the propeller, vibration of the hull is severely generated because the excitation force is further increased.

This is because when the pressure in the water is low, the gas contained in the water escapes from the water and collects at a low pressure. As a result, bubbles are generated in the water, and when the bubbles reach the high pressure part, Thereby generating a fluctuating pressure.

In order to solve the problem of increased excitation force due to such fluctuating pressure, it is necessary to design the shape and size of the propeller blade itself differently, to improve the shape of the rear of the ship, to attach a separate reinforcing material for preventing noise and vibration, Or by applying various methods such as attaching a guide device for guiding the flow of the water flowing in the propeller, reducing the size of the propeller, or the like. However, it is practically effective to reduce the excitation force it's difficult.

The vibration problem including the noise transmitted to the hull by the propeller is increased when the propeller is operated. For example, when the ship is a cruise ship, such as a cruise ship or a warship, .

Accordingly, the present applicant has filed with the Korean Intellectual Property Office (KIPO) a number of technologies for reducing the excitation force by forming an air layer in the form of an air bubble on the surface of the hull adjacent to the propeller.

However, most of the prior art attempts to use the air layer, including the last-filed technology, require air to be continuously injected using a compressor to form an air layer, so that due to the installation and operation of the compressor and its related components Energy consumption and so on.

Accordingly, it is an object of the present invention to prevent vibrations from occurring in the hull by increasing the excitation force at the time of operation of the propeller while fundamentally preventing the burden of energy consumption due to the installation and operation of the compressor and related parts, A method of applying a working gas containing membrane pad accommodated in one side to a hull can be considered.

However, when such a working gas receiving membrane pad is intended to be applied to the hull, the work gas receiving membrane pads may be damaged due to tearing or the like, and if the working gas receiving membrane pads are damaged, A method for real-time monitoring of the situation is required.

Prior Art _1; Japanese Patent Application Laid-Open No. 8-188192 Prior Art _2; Japanese Unexamined Patent Application Publication No. 2009-274705 Prior Art_3; Korea Patent Office Application No. 10-2007-0006095

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is therefore an object of the present invention to provide a propulsion device for a propeller which is capable of preventing a vibration from being generated in a hull by increasing propulsion force during operation of a propeller while fundamentally preventing a burden of energy consumption, And it is possible to monitor the working gas receiving membrane pads in real time so that the maintenance work on the working gas receiving membrane pads can be carried out without delay and the propeller cavitation organic excitation force reducing type vessel can be provided.

According to an aspect of the present invention, there is provided a hull comprising: a hull having a propeller; A working gas accommodating membrane pad having a working gas pocket in which a working gas generating a reflected wave for causing a destructive interference phenomenon with an incident wave generated when the propeller rotates is hermetically sealed; And a camera module having a camera for real time monitoring of the working gas receiving membrane pads, the camera module being disposed in the hull adjacent to the working gas receiving membrane pads.

And a paddle rotation control unit coupled to the work gas receiving membrane pads and the camera module, the paddles being provided in the hull to rotationally drive the work gas receiving membrane pads so that the work gas pockets of the work gas receiving membrane pads can be moved in and out of the hull, And may further include a driving unit.

The pad rotation driving unit may include a pad and a module supporting body supporting the working gas accommodating membrane pad and the camera module, one side being hemispherical; A waterproof rotary shaft connected to the pad and the module support to form a rotation axis of the pad and the module support; And a shaft rotating part connected to the waterproof rotating shaft to rotate the waterproof rotating shaft.

The shaft rotation unit includes: a rotation motor; A driving gear connected to a motor shaft of the rotary motor; And a driven gear coupled to an end of the waterproof rotary shaft and meshing with the drive gear.

The camera module may further include a module support coupled to the pad and the module support while supporting the camera.

And a seawater inflow preventing cover disposed inside the hull to surround the working gas receiving membrane pad to prevent inflow of seawater.

A drain portion may be coupled to the side portion of the seawater inflow prevention cover, and a detachable lid having a handle may be provided on the upper portion of the seawater inflow prevention cover.

According to the present invention, it is possible to prevent vibrations from occurring in the hull due to increased propulsive force at the time of operation of the propeller while fundamentally preventing the burden of energy consumption due to the installation and operation of the compressor and related parts. The gas-receiving membrane pads can be monitored in real-time, allowing maintenance work on the working gas-receiving membrane pads to be carried out without delay.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural view of a propeller area of a propeller cavitation organic exciter force reduction type ship according to a first embodiment of the present invention; FIG.
FIG. 2 is a schematic view showing an installation structure of a work gas accommodating membrane pad, which is a region A in FIG.
3 is an operation diagram of Fig.
Fig. 4 is a chart for measuring the impedance of water, rubber, and air.
5 is a view for explaining the principle of incident wave and reflected wave.
6 is a view of a working gas receiving membrane pad for illustrating equation (1).
Fig. 7 is a view showing a state where a working gas receiving membrane pad is installed in a region on the upstream side of the propeller, and shows a plurality of variable pressure measuring points.
Figure 8 is a graphical representation of the efficiency of a working gas receiving membrane pad relative to the frequency of the propeller.
Figure 9 is a graph summarizing the results of the 150 Hz band for the working gas receiving membrane pads corresponding to Figure 7;

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

FIG. 1 is a structural view of a propeller area of a propeller cavitation propellant-reducing type propulsion vessel according to a first embodiment of the present invention. FIG. 2 is a view schematically showing an installation structure of a working gas receiving membrane pad, And Fig. 3 is an operation diagram of Fig.

Referring to these drawings, the propeller cavitation propulsion reduction type ship according to the present embodiment can prevent the burden of energy consumption and the like due to the installation and operation of the related parts including the compressor, It is possible to prevent vibrations from occurring in the hull 110 due to an increase in excitation force and to monitor the working gas receiving membrane pads 130 in real time so that the maintenance work for the working gas receiving membrane pads 130 is delayed And includes a hull 110, a working gas receiving membrane pad 130 having a working gas bag 132 and a camera module 180 for monitoring the working gas receiving membrane pad 130 in real time, And a pad rotation driving unit 150 for rotating the working gas receiving membrane pad 130 to rotate.

At the rear of the hull 110, a propeller 120 for propelling the hull 110 is provided. A rudder 125 for adjusting the traveling direction of the ship is provided around the propeller 120. The rudder 125 may be a normal rudder or a bulb rudder.

For reference, the ship to which the present invention is applied may include all of marine vessels, warships, fishing vessels, carriers, drillships, cruise ships, special work ships, and the like, as well as floating marine structures. Therefore, the scope of right of the present embodiment can not be limited to a specific ship.

As described above, when the propeller 120 is operated, that is, when the propeller 120 is rotated in water, a fluctuating pressure is generated in the water due to the propeller 120 as a rotating body. ), Which causes vibration (including noise) in the hull.

The vibration transmitted to the hull 110 may be a serious problem, for example, as a cruise ship or a warship such as a warship, and should be prevented.

In other words, the vibrating force is increased due to the fluctuating pressure generated in the water during the operation of the propeller 120 to prevent the vibration of the hull 110 from being generated. For this purpose, in this embodiment, the working gas receiving membrane pad 130 ) Is applied.

As will be described in detail below, the working gas receiving membrane pad 130 applied to the vessel of the present embodiment has a completely different form from the structures forming the air layer, which is a conventional air bubble shape.

In other words, since the working gas receiving membrane pad 130 applied in the present embodiment is only a structure in which the air is confined, there is no need to install or operate the relevant parts including the compressor which should be used in the past .

Therefore, it is possible to fundamentally prevent the burden of installing and operating the compressor and related parts, and energy consumption.

The working gas receiving membrane pad 130 in this role is coupled to the hull 110 adjacent to the propeller 120 as shown in Figure 1 and is connected to the hull 110 as it is generated during rotation of the propeller 120, And has a shape in which a reflected wave is generated to cancel an incident wave, and a working gas is accommodated in one side.

In this embodiment, the working gas receiving membrane pad 130 may be coupled to the wall surface of the hull 110 on the upper side of the propeller 120.

And is further augmented with respect to the mounting position of the working gas receiving membrane pad 130. In this embodiment, the working gas receiving membrane pads 130 are positioned between the 0.5 diameter D of the propeller 120 and the 0.5 diameter D of the propeller 120 in the aft direction with respect to the propeller 120, As shown in FIG. In other words, when the diameter of the propeller 120 is 50 cm, the working gas receiving membrane pad 130 may be disposed between the propeller 120 and the point 25 cm in the aft direction.

The working gas receiving membrane pad 130 is disposed between the one diameter D of the propeller 120 in the starboard direction and the one diameter D of the propeller 120 in the port direction relative to the rotational axis of the propeller 120 . In other words, when the diameter of the propeller 120 is 50 cm, the working gas receiving membrane pad 130 can be disposed between the starboard and the 50 cm point in the port direction with respect to the rotational axis of the propeller 120.

The working gas accommodating membrane pad 130 includes a pad body 131 and a working gas pocket 130 formed at one side of the pad body 131 and adapted to be enclosed and accommodated in the working gas accommodating membrane pad 130. Specifically, (132).

(Or anode) is attached to the working gas receiving membrane pad 130 to prevent fouling of foreign matter or the like from adhering to the working gas receiving membrane pad 130 during long-time vessel operation. Can be applied.

In this embodiment, the material of the working gas receiving membrane pad 130 may be rubber, and the working gas may be air. However, the scope of the rights of the present embodiment is not limited thereto. That is, if the material of the working gas receiving membrane pad 130 is a material similar to rubber, it is sufficient, and the working gas may be applied to various gases as long as it is not a liquid.

The pad body 131 forming the working gas receiving membrane pad 130 is a flat structure made of rubber and supports the working gas pocket 132.

In this embodiment, the pad body 131 has a rectangular shape, but the pad body 131 may have a rectangular shape, a circular shape, or a triangular shape. Therefore, the right range of the present embodiment can not be limited to the shape of the pad body 131. [

The working gas bag 132 is formed inside the pad body 131 and has a shape swollen to one side of the pad body 131.

Although the working gas pocket 132 has a circular shape in the present embodiment, the shape of the working gas pocket 132 may also be various polygonal shapes such as a triangle shape and a square shape. Therefore, Can not be.

As described above, the working gas bag 132 is filled with air as a working gas. The working gas filled in the working gas pocket 132 is formed integrally with the working gas receiving membrane pad 130 when the working gas receiving pocket 132 is formed, It does not.

On the other hand, as described above, since the working gas pocket 132 has a rubber material, the working gas pocket 132 of the working gas receiving membrane pad 130 having the rubber material in the marine condition may be damaged, such as tearing.

If the working gas bag 132 is damaged due to tearing or the like, the air inside the working gas bag 132 can escape, so that the effect of the present embodiment can not be provided.

Therefore, if the working gas bag 132 is damaged such as tearing, it is necessary to replace or maintain the working gas receiving membrane pad 130, in order to monitor the working gas receiving membrane pad 130 in real time. To this end, a camera module 180 is provided.

The camera module 180 is disposed within the hull 110 adjacent to the work gas receiving membrane pads 130 and includes a camera 181 for monitoring the work gas receiving membrane pads 130 in real time, (Not shown).

The camera 181 may be a CCD camera capable of autofocusing. By allowing the camera 181 to monitor the working gas receiving membrane pads 130 in real time, as in the present embodiment, the working gas receiving membrane pads 130 can be immediately checked if they are torn or damaged, There is an advantage that the pad 130 can be maintained.

The module support 182 is connected to a pad and module support 160, which will be described later, and serves to support the camera 181.

The module support 182 may support the camera 181 in a rotatable manner within a certain angle range in addition to the function of simply supporting the camera 181. [

This may be a function for preventing the camera 181 from being damaged by the movement of the ship. Therefore, it is preferable that the module support 182 is provided with a separate damper (not shown) in order to rotatably support the camera 181 within a certain angle range.

If the working gas receiving membrane pads 130 are damaged, such as by tearing the working gas pockets 132, the working gas receiving membrane pads 130 are moved into the inside of the hull 110 to be replaced or maintained in the hull 110 Maintenance work should be carried out. In order to do so, a means for rotating the working gas receiving membrane pad 130 is required, which is performed by the pad rotation driving unit 150.

The pad rotation driving unit 150 is provided in the hull 110 and is coupled to the work gas receiving membrane pads 130 and the camera module 180 and is connected to the working gas pockets 132 of the work gas receiving membrane pads 130. [ Receiving membrane pads 130 so as to move the working gas receiving membrane pads 130 inside and outside the hull 110.

The pad rotation driving unit 150 includes a pad and module support 160, a waterproof rotation shaft 162 connected to the pad and the module support 160 to form the rotation axis of the pad and module support 160, And a shaft rotating part 164 connected to the rotating shaft 162 to rotate the waterproof rotating shaft 162.

The pad and module support 160 supports the work gas receiving membrane pad 130 and the camera module 180, one side of which is hemispherical. The hemispherical diameter of the pad and module support 160 may be the same as the diameter of the working gas pocket 132.

As the pad and module support 160 thus support the working gas receiving membrane pads 130 and the camera module 180, they can be a single body. 3, when the working gas bag 132 of the working gas receiving membrane pad 130 is disposed outside the hull 110 and the pad and the module supporting body 160 are rotated, the working gas receiving membrane pad 130 The working gas pocket 132 may be disposed within the hull 110 and this time the hemispherical portion of the pad and module support 160 may be disposed outside the hull 110. [

The waterproof rotary shaft 162 is connected to the pad and module support 160 and is rotated by the shaft rotation part 164 to rotate the pad and the module support 160.

At this time, the waterproof rotary shaft 162 is partially covered with the shaft case 162a so that the pad and the module support 160 can be rotated while preventing the inflow of seawater.

The shaft rotation portion 164 is connected to the end of the waterproof rotary shaft 162 and is connected to the drive gear 164b and the gear 164b, And a driven gear 164c to be engaged therewith.

When the rotary motor 164a is operated, its power is transmitted to the driving gear 164b, the driven gear 164c and the waterproof rotary shaft 162 to rotate the pad and the module support 160, The working gas bladder 132 of the working gas receiving membrane pads 130 connected to the working electrode 160 may be rotated together with the pad and the module support 160 as shown by the arrow A in Fig.

On the other hand, when the work gas accommodating membrane pad 130 is being replaced as shown by the arrow A in FIG. 3, it is difficult to enter seawater into the hull 110. Thus, in this embodiment, the cover 170 for preventing inflow of seawater is provided.

The cover 170 for preventing the inflow of seawater is arranged to surround the work gas receiving membrane pad 130 inside the hull 110 to prevent inflow of seawater.

A drain portion 172 is coupled to a side portion of the cover 170 for preventing seawater inflow. A pump (not shown) may be connected to the drain portion 172.

A detachable lid 174 having a handle 173 is provided on the upper portion of the seawater inflow prevention cover 170. The normal detachable lid 174 can be coupled to the seawater inflow preventing cover 170 by the bolt B. [

As a result, if the pad rotation driving part 150 is operated as shown in FIG. 3 A, when the work gas receiving membrane pad 130 exposed to the outside of the hull 110, i.e., the seawater is to be replaced or maintained, The working gas pocket 132 of the membrane pad 130 may be disposed within the hull 110 and the hemispherical portion of the pad and module support 160 may be disposed outside the hull 110, To remove the seawater introduced into the seawater inflow preventing cover 170 through the opening 170 and to open the removable lid 174 as shown in FIG. 3B to maintain the damaged working gas receiving membrane pad 130 in the hull 110, .

Hereinafter, the principle of reducing the exciting force due to the working gas receiving membrane pad 130 in which the working gas is hermetically sealed will be described in detail with reference to FIG. 4 to FIG.

Fig. 4 is a graph showing impedance of water, rubber and air, Fig. 5 is a view for explaining the principle of an incident wave and a reflected wave, Fig. 6 is a drawing of a working gas receiving membrane pad for explaining [Equation 1] 7 is a view showing a state in which a working gas receiving membrane pad is installed in a region immediately upstream of the propeller, and FIG. 8 is a graph showing the efficiency of the working gas receiving membrane pad based on the frequency of the propeller And FIG. 9 is a graph summarizing the results of the 150 Hz band for the working gas receiving membrane pads corresponding to FIG.

Referring to these drawings, referring first to FIG. 4, an acoustic impedance (which means an acoustical resistance) of rubber, which is a material of the working gas receiving membrane pad 130 of the present embodiment, , While it is almost infinitely greater than air.

Typically, when sound waves propagate in a specific medium and a medium having a different impedance is encountered, a transmission phenomenon and a reflection phenomenon occur. Since the impedance of seawater and rubber is similar, only the reflection phenomenon occurs without reflection at the boundary between sea water and rubber.

For example, as shown in FIG. 5, the incident wave generated in the operation of the propeller 120 passes through the rubber layer, which is the wall surface of the working gas pocket 132, and then flows into the work gas filled in the working gas pocket 132, And is reflected by the phase opposite to the incident wave, that is, it is formed as a reflected wave. This reflected wave causes a destructive interference phenomenon with the incident wave, so that the incident wave generated in the operation of the propeller 120 is canceled. By such a phenomenon, the exciting force is reduced and the occurrence of vibration of the ship 110 can be reduced.

I will explain this again. The spherical pressure wave generated by the cavitation during the operation of the propeller 120, that is, the incident wave, can be propagated omnidirectionally.

In this case, when the working gas receiving membrane pads 130 filled with air are installed on the surface of the hull 110 around the propeller 120, the working gas pockets 132 of the working gas receiving membrane pads 130 The incident incident wave passes through the rubber layer, which is the wall surface of the working gas pocket 132, but is reflected by the working gas filled in the working gas pocket 132, i.e., air, in a phase opposite to that of the incident wave.

When the incident wave is formed as a reflected wave that is reflected by the opposite phase and strikes against the air, the reflected wave meets an incident wave incident on the workpiece receiving membrane pad 130, causing a destructive interference phenomenon with the incident wave.

As a result, the fluctuating pressure transmitted from the outside of the working gas receiving membrane pad 130 to the hull 110 is reduced, and when the fluctuating pressure is reduced, the exciting force is reduced. Therefore, 110 are reduced.

On the other hand, such a reduction performance is limited to a specific frequency band of the propeller as shown in the following equation (1).

[Equation 1]

In this case, f is the reduced frequency band of the propeller, ca (= 340m / s) and cw (= 1500m / s) A " and " b " denote the inner diameter and outer diameter of the working gas receiving membrane pads 130a to 130c, respectively, when they are regarded as equivalents.

A model test was carried out to verify these items. That is, as shown in FIG. 7, one working gas receiving membrane pad 130 having a reducing effect in the frequency band of 150 Hz is designed (or attached) to the wall surface of the hull 110 on the STBD region side, P2, P3, and P4, as well as vibrations were measured in the transom region, which is a steel plate supporting above the stern of the hull 110. In addition,

8, the horizontal axis (x axis) indicates the frequency, and the vertical axis (y axis) indicates the amount of increase / decrease after attachment of the work gas accommodating membrane pad 130 to the workpiece accommodating pad 130. In the vicinity of 135 Hz Work gas accommodating Membrane pads (130) Increase in pressure and vibration after installation Although the increase in pressure and vibration is noticeable, a remarkable reduction effect appears in the vicinity of the design frequency of 150 Hz.

FIG. 9 summarizes the results of the 150 Hz band. Referring to FIG. 9, the fluctuating pressures at the positions P2, P3 and P4 located outside the working gas receiving membrane pad 130 are reduced by an average of about 70% As a result, the vibration level is also remarkably reduced by 70% or more.

According to the present embodiment having the structure and function as described above, it is possible to prevent vibrations from being generated in the hull 110 by increasing the excitation force at the time of operating the propeller 120, and more particularly, It is possible to fundamentally prevent obstacles such as installation of components and burden of energy consumption due to operation.

As a result, it is possible to effectively prevent vibration from being generated in the hull 110. Thus, for example, in the case of a ship for which a quiet operation is to be premised, such as a cruise ship or a warship, The noise-containing vibration problem can be appropriately solved.

In particular, the structure according to the present embodiment is different from the structure of the present embodiment in that the shape and size of the blade 120 itself of the propeller 120 are designed differently, the shape of the tail of the ship is improved, a separate reinforcing material for blocking noise and vibration is padded, A method of improving noise and vibration by reducing various loss such as attaching a guide device for guiding the flow of water flowing from the propeller 120 or reducing the size of the propeller 120 Technically differentiated. In addition, since the present technology provides a margin for eliminating the restraint condition of vibration in the propeller design by shielding the excitation force, it is possible to greatly increase the size of the propeller 120, It is expected.

As described above, according to the present embodiment, it is possible to prevent vibrations from occurring in the hull by increasing the excitation force at the time of operation of the propeller while fundamentally preventing the burden of energy consumption due to installation and operation of the compressor and other related components And can easily replace the working gas receiving membrane pads 130 without complicated or laborious work even if the working gas receiving membrane pads 130 are damaged.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

110: Hull 120: Propeller
125: rudder 130: working gas receiving membrane pad
131: Pad body 132: Working gas pocket
150: pad rotation driving part 160: pad and module support
162: waterproof rotary shaft 162a: shaft case
164: shaft rotation part 164a: rotation motor
164b: drive gear 164c: driven gear
170: Seal inflow preventing cover 172: Drain part
173: handle 174: detachable cover
180: camera module 181: camera
182: Module support

Claims (7)

A hull with a propeller;
A working gas accommodating membrane pad including a working gas pocket in which a working gas generating a reflected wave for causing a destructive interference phenomenon with an incident wave generated when the propeller rotates is hermetically sealed;
A camera module having a camera for monitoring the working gas receiving membrane pads in real time and disposed in the hull adjacent to the working gas receiving membrane pads; And
And a paddle rotation control unit coupled to the work gas receiving membrane pads and the camera module, the paddles being provided in the hull to rotationally drive the work gas receiving membrane pads so that the work gas pockets of the work gas receiving membrane pads can be moved in and out of the hull, And a driving unit,
The pad rotation driving unit includes:
A pad and a module support supporting the work gas accommodating membrane pad and the camera module, one side being hemispherical;
A waterproof rotary shaft connected to the pad and the module support to form a rotation axis of the pad and the module support; And
And a shaft rotating part connected to the waterproof rotary shaft to rotate the waterproof rotary shaft. delete delete The method according to claim 1,
The shaft-
A rotary motor;
A driving gear connected to a motor shaft of the rotary motor; And
And a driven gear coupled to an end of the waterproof rotary shaft and meshing with the drive gear. The method according to claim 1,
Wherein the camera module further comprises a module support coupled to the pad and the module support while supporting the camera. The method according to claim 1,
Further comprising a seawater inflow preventing cover disposed inside the hull so as to surround the working gas receiving membrane pad to prevent inflow of seawater. The method according to claim 6,
A drain portion is coupled to a side portion of the seawater inflow prevention cover,
And a detachable lid having a handle is provided on an upper portion of the cover for preventing seawater inflow.

Images