Marine vessel

Abstract

To provide a marine vessel that can suppress harmful electrochemical reaction of a hull surface due to a counter current method.SOLUTION: A marine vessel comprises: a metal hull including an underwater part immersed in sea water; an underwater electric field reduction device which includes an underwater electrode provided on the underwater part and flows a counter electric current into sea water via the underwater electrode, thereby reducing an underwater electric field around the hull; and an insulation protective member which is provided on the underwater part so as to surround the underwater electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to marine vessels. [Background technology]

[0002] The following Patent Document 1 discloses a method for reducing the underwater electric potential (UEP) of a ship, which reduces the underwater electric potential (UEP) around the hull by passing an electric current between first and second electrodes arranged in a part of the hull that is immersed in seawater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-88542 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the UEP reduction method described in Patent Document 1 (hereinafter, the "counter current method"), it is assumed that the current flowing between the first and second electrodes (hereinafter, the "counter current") passes through seawater. However, research by the inventors has shown that when the hull is made of metal, part of the counter current flowing between the first and second electrodes becomes a stray current and passes through the hull, which has low electrical resistance. It has also been shown that on the hull surface near the anode where the counter current flows from seawater into the hull, paint peeling and hydrogen embrittlement occur due to a hydrogen generation reaction, and that on the hull surface near the cathode where the counter current flows out from the hull into the seawater, corrosion thinning occurs.

[0005] Therefore, an object of the present disclosure is to provide a ship that can suppress harmful electrochemical reactions (one or both of hydrogen generation reaction and corrosion thinning) on ​​the hull surface caused by the counter current method. [Means for solving the problem]

[0006] A ship according to one embodiment of the present disclosure comprises a metal hull including an underwater portion that is immersed in seawater, an underwater electric field reduction device that includes an underwater electrode provided in the underwater portion and reduces the underwater electric field around the hull by passing a counter current into the seawater via the underwater electrode, and an insulating protective member provided in the underwater portion so as to surround the underwater electrode. Effect of the Invention

[0007] This configuration makes it possible to suppress harmful electrochemical reactions on the hull surface caused by the counter current method. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side view of a ship. [Diagram 2] FIG. 2 is a schematic bottom view of the vessel. [Diagram 3] FIG. 3 is a diagram showing the flow of the counter current when no countermeasures are taken. [Figure 4] FIG. 4 is a diagram showing a modified example of the protective member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described. Fig. 1 is a schematic side view of a ship 100 according to this embodiment, and Fig. 2 is a schematic bottom view of the ship 100 according to this embodiment. The ship 100 may be a surface vehicle that travels on seawater with only the bottom of the ship submerged in seawater, or an underwater vehicle that travels in seawater with the entire hull submerged in seawater.

[0010] As shown in Fig. 1, a ship 100 according to this embodiment includes a hull 10, an underwater electric field reduction device 20, and a protective member 30. Below, these components will be described in order.

[0011] <Hull> The hull 10 includes an underwater section 11 that is immersed in seawater. When the ship 100 is a surface vehicle, only the bottom portion of the hull 10 is the underwater section 11, and when the ship 100 is an underwater vehicle, the entire hull 10 is the underwater section 11. The hull 10 of this embodiment is made of metal. Specifically, the hull 10 is made of carbon steel. However, the hull 10 may be made of a material other than carbon steel. The metal hull 10 is a hull 10 that is substantially made of metal, and also includes a hull 10 that uses FRP or rubber in part.

[0012] In addition, an underwater electric field is generated in the seawater around the hull 10 of this embodiment. There are various causes for the generation of the underwater electric field, but there are underwater electric fields caused by hull magnetism and anticorrosion currents. Those caused by hull magnetism include magnetization of the hull 10 due to welding during manufacturing and magnetism of equipment. On the other hand, those caused by anticorrosion currents include those caused by cathodic protection, which is a measure to prevent corrosion of the hull 10.

[0013] <Underwater electric field reduction device> The underwater electric field reduction device 20 is a device for reducing the underwater electric field around the above-mentioned hull 10 by the counter current method. By reducing the underwater electric field around the hull 10, for example, when the ship 100 passes through a dangerous sea area, it is possible to avoid attacks by mines or the like that react to the underwater electric field. The underwater electric field reduction device 20 of this embodiment has an underwater electrode 21 provided in the underwater part 11 of the hull 10.

[0014] The underwater electrode 21 includes an anode 22 and a cathode 23. Both the anode 22 and the cathode 23 are electrically insulated from the hull 10. The underwater electric field reduction device 20 passes a counter current into the seawater via the underwater electrode 21 so as to generate an underwater electric field in the opposite direction to the direction of the underwater electric field around the hull 10. In other words, a counter current is passed from the anode 22 through the seawater to the cathode 23. This generates a new underwater electric field, making it possible to reduce the underwater electric field around the hull 10.

[0015] However, when the counter current method is implemented, there is a risk of harmful electrochemical reactions occurring on the surface of the hull 10. FIG. 3 is a diagram showing the flow of the counter current when no countermeasures against the counter current method are implemented. As shown by the dashed line in FIG. 3, in the counter current method, most of the counter current flows from the anode 22 through the seawater toward the cathode 23. However, when no countermeasures against the counter current method are implemented, as shown by the dashed line in FIG. 3, a part of the counter current becomes a stray current, flows from the anode 22 into the seawater, and then flows into the hull 10 near the anode 22. Then, the stray current that flows into the hull 10 passes through the hull 10, flows out of the hull 10 into the seawater near the cathode 23, and flows toward the cathode 23.

[0016] In the portion of the hull 10 where the stray current flows in, i.e., near the anode 22, there is a risk of paint peeling and hydrogen embrittlement due to a hydrogen generation reaction. In addition, in the portion of the hull 10 where the stray current flows out, i.e., near the cathode 23, there is a risk of corrosion and thinning. In order to suppress such harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method, the ship 100 according to this embodiment is provided with a protective member 30, which will be described below, on the hull 10.

[0017] <Protective materials> The protective member 30 is a member that suppresses harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method. The protective member 30 is an insulator, and is provided in the underwater section 11 of the hull 10. The protective member 30 may be provided in the underwater section 11 instead of a part of the underwater section 11, or may be affixed to the surface of the underwater section 11. As shown in FIG. 2, the protective member 30 of this embodiment includes an anode vicinity hull protective member 31 and a cathode vicinity hull protective member 32.

[0018] The anode vicinity hull protection member 31 is installed so as to surround the anode 22. By installing the anode vicinity hull protection member 31, which is an insulator, so as to surround the anode 22 in this manner, it is possible to suppress the inflow of stray current into the hull 10. As a result, the hydrogen generation reaction near the anode 22 is suppressed, and in turn, harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method can be suppressed. Note that although the anode vicinity hull protection member 31 in this embodiment is installed around the entire circumference of the anode 22, the anode vicinity hull protection member 31 may be installed, for example, in a range of 180 degrees or more and less than 360 degrees in total around the anode 22.

[0019] The anode-nearby hull protection member region 33, which is the region where the anode-nearby hull protection member 31 is installed, includes the anode-nearby hull protection range 34. Here, the anode-nearby hull protection range 34 is a range in which the electrode potential is equal to or lower than a predetermined lower limit when the underwater electric field reduction device 20 generates a counter current. The above-mentioned "predetermined lower limit" varies depending on the material of the hull 10. For example, when the hull 10 is formed of carbon steel with a yield strength of less than 550 MPa, alloy steel with a yield strength of less than 550 MPa, aluminum alloy, or copper alloy containing aluminum, the "predetermined lower limit" is minus 1.10 V vs. Ag / AgCl seawater (Ag / AgCl seawater is used as the reference electrode in this embodiment). For example, when the hull 10 is formed of carbon steel with a yield strength of 550 MPa or more, or alloy steel with a yield strength of 550 MPa or more, the "predetermined lower limit" is minus 0.95 V vs. Ag / AgCl seawater. For example, if the hull 10 is made of martensitic stainless steel, the "predetermined lower limit" is minus 0.80 V vs. Ag / AgCl seawater. For example, if the hull 10 is made of titanium alloy, the "predetermined lower limit" is minus 0.75 V vs. Ag / AgCl seawater.

[0020] The anode nearby hull protection area 34 defined as above is a portion where stray currents are particularly likely to flow into the hull 10. Therefore, by including the anode nearby hull protection member area 33 in the anode nearby hull protection area 34, it is possible to efficiently prevent stray currents from flowing into the hull 10. The electrode potential at each position on the hull 10 when the underwater electric field reduction device 20 generates a counter current may be actually measured or may be calculated by simulation.

[0021] In this embodiment, the anode near hull protection member area 33 includes the entire anode near hull protection range 34, but it is sufficient that the anode near hull protection member area 33 includes 50% or more of the anode near hull protection range 34. Even if the anode near hull protection member area 33 does not include the entire anode near hull protection range 34 due to the structure of the hull 10, as long as the anode near hull protection member area 33 includes 50% or more of the anode near hull protection range 34, harmful electrochemical reactions on the surface of the hull 10 can be suppressed to a certain extent.

[0022] Also, in this embodiment, the portion of the anode nearby hull protection member area 33 that is not the anode nearby hull protection range 34 is 50% or less. In this way, in this embodiment, by reducing the portion of the anode nearby hull protection member area 33 that is not the anode nearby hull protection range 34, the anode nearby hull protection member 31 can be made smaller. As a result, the manufacturing costs of the hull 10 can be reduced.

[0023] The cathode vicinity hull protection member 32 is installed so as to surround the cathode 23. By installing the cathode vicinity hull protection member 32, which is an insulator, so as to surround the cathode 23 in this manner, it is possible to suppress stray currents from flowing out of the hull 10. As a result, it is possible to suppress corrosion thinning near the cathode 23, that is, harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method. Note that the cathode vicinity hull protection member 32 in this embodiment is installed around the entire circumference of the cathode 23, but the cathode vicinity hull protection member 32 may be installed, for example, in a range of 180 degrees or more and less than 360 degrees in total around the cathode 23.

[0024] The cathode near hull protection member region 35, which is the region where the cathode near hull protection member 32 is installed, includes the cathode near hull protection range 36. Here, the cathode near hull protection range 36 is the range in which the electrode potential becomes greater than the predetermined upper limit when the underwater electric field reduction device 20 generates a counter current. The above-mentioned "predetermined upper limit" varies depending on the material of the hull 10. For example, when the hull 10 is formed of carbon steel, alloy steel, or aluminum alloy, the "predetermined upper limit" is minus 0.80 V vs. Ag / AgCl seawater. For example, when the hull 10 is formed of austenitic stainless steel with a PREN of less than 40, nickel-based alloy, duplex stainless steel, or martensitic stainless steel with a PREN of less than 40, the "predetermined upper limit" is minus 0.50 V vs. Ag / AgCl seawater. Note that PREN (pitting corrosion index) = Cr (chromium content) + 3.3Mo (molybdenum content) + 16N (nitrogen content). For example, if the hull 10 is made of a copper alloy, the "predetermined upper limit" is minus 0.45 V vs. Ag / AgCl seawater. For example, if the hull 10 is made of an austenitic stainless steel with a PREN of 40 or greater, or a nickel-based alloy with a PREN of 40 or greater, the "predetermined upper limit" is minus 0.30 V vs. Ag / AgCl seawater.

[0025] The near-cathode hull protection area 36 defined as above is a portion from which stray currents that have flowed into the hull 10 are particularly likely to flow out of the hull 10. Therefore, by including the near-cathode hull protection member area 35 in the near-cathode hull protection area 36, ​​it is possible to efficiently prevent stray currents from flowing out of the hull 10. The electrode potential at each position on the hull 10 when the underwater electric field reduction device 20 generates a counter current may be actually measured or may be calculated by simulation.

[0026] In this embodiment, the cathode near hull protection member region 35 includes the entire cathode near hull protection range 36, but it is sufficient that the cathode near hull protection member region 35 includes 50% or more of the cathode near hull protection range 36. Even if the cathode near hull protection member region 35 does not include the entire cathode near hull protection range 36 due to the structure of the hull 10, harmful electrochemical reactions on the surface of the hull 10 near the cathode 23 can be suppressed to a certain extent as long as the cathode near hull protection member region 35 includes 50% or more of the cathode near hull protection range 36.

[0027] Also, in this embodiment, the portion of the cathode near hull protection member region 35 that is not the cathode near hull protection range 36 is 50% or less. In this way, in this embodiment, by reducing the portion of the cathode near hull protection member region 35 that is not the cathode near hull protection range 36, the cathode near hull protection member 32 can be made smaller. As a result, the manufacturing costs of the hull 10 can be reduced.

[0028] The protective member 30 of this embodiment may be made of rubber, a composite material, a resin, or ceramic. However, if the protective member 30 is made of rubber, a composite material, or a resin, toughness can be ensured and the protective member 30 can be easily processed into any shape, making it easy to match the shape to the hull 10. Furthermore, if the protective member 30 is made of a composite material, it has both surface smoothness and strength, so the surface smoothness and strength of the hull 10 can be maintained.

[0029] Although the protective member 30 in this embodiment includes both the anode vicinity hull protective member 31 and the cathode vicinity hull protective member 32, it may include only one of the anode vicinity hull protective member 31 and the cathode vicinity hull protective member 32. In other words, only one of the anode vicinity hull protective member 31 and the cathode vicinity hull protective member 32 may be provided on the hull 10.

[0030] <Modification> As shown in FIG. 4(a), the protective member 30 (i.e., the anode-proximal hull protective member 31 and the cathode-proximal hull protective member 32) in the above-described embodiment is circular, but the shape of the protective member 30 is not limited. For example, in consideration of ease of processing, the protective member 30 may be rectangular as shown in FIG. 4(b). The protective member 30 may also be divided into multiple parts as shown in FIGS. 4(c) and (d). Furthermore, as shown in FIGS. 4(e) to (g), when a difficult-to-install area 12 such as a hull opening where it is difficult to install the protective member 30 is located near the underwater electrode 21 (i.e., the anode 22 and the cathode 23), the protective member 30 may have a shape that avoids the difficult-to-install area 12.

[0031] (summary) The first item disclosed in this specification is a ship comprising a metallic hull including an underwater section that is immersed in seawater, an underwater electric field reduction device that includes an underwater electrode provided in the underwater section and reduces the underwater electric field around the hull by passing a counter current into the seawater via the underwater electrode, and an insulating protective member provided in the underwater section so as to surround the underwater electrode.

[0032] This configuration makes it possible to suppress harmful electrochemical reactions on the hull surface caused by the counter current method.

[0033] The second item disclosed in this specification is that the protective member includes an anode near-hull protective member surrounding an anode among the underwater electrodes, the anode near-hull protective member being located in an anode near-hull protective member region including an anode near-hull protective range, the anode near-hull protective range being a range in which an electrode potential is equal to or lower than a predetermined lower limit value when the underwater electric field reduction device generates a counter current, the predetermined lower limit value being minus 1.10 V vs. Ag / AgCl seawater when the hull is formed of carbon steel having a proof strength of less than 550 MPa, alloy steel having a proof strength of less than 550 MPa, aluminum alloy, or copper alloy containing aluminum, the predetermined lower limit value being minus 0.95 V vs. Ag / AgCl seawater when the hull is formed of carbon steel having a proof strength of 550 MPa or more, or alloy steel having a proof strength of 550 MPa or more, and the predetermined lower limit value being minus 0.80 V vs. Ag / AgCl seawater when the hull is formed of martensitic stainless steel. In the case where the vessel is seawater and the hull is formed of a titanium alloy, the predetermined lower limit is minus 0.75 V vs. Ag / AgCl seawater.

[0034] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be effectively suppressed.

[0035] A third item disclosed in the present specification is the vessel described in the second item, wherein the anode adjacent hull protection member area includes 50% or more of the anode adjacent hull protection range.

[0036] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be suppressed to a certain extent.

[0037] A fourth item disclosed in this specification is a ship as described in the second or third item, in which a portion of the anode nearby hull protection member area that is not the anode nearby hull protection range is 50% or less.

[0038] This configuration makes it possible to reduce the manufacturing costs of the hull.

[0039] The fifth item disclosed in this specification is that the protective member includes a cathode near-hull protective member surrounding the cathode of the underwater electrodes, the cathode near-hull protective member being located in a cathode near-hull protective member region including a cathode near-hull protective range, and the cathode near-hull protective range is a range in which an electrode potential is equal to or greater than a predetermined upper limit value when the underwater electric field reduction device generates a counter current, and when the hull is formed of carbon steel, alloy steel, or aluminum alloy, the predetermined upper limit value is minus 0.80 V vs. Ag / AgCl seawater, when the hull is formed of an austenitic stainless steel having a PREN of less than 40, a nickel-based alloy, a duplex stainless steel, or a martensitic stainless steel having a PREN of less than 40, the predetermined upper limit value is minus 0.50 V vs. Ag / AgCl seawater, and when the hull is formed of a copper alloy, the predetermined upper limit value is minus 0.45 V vs. Ag / AgCl In the case where the vessel is seawater and the hull is formed of an austenitic stainless steel having a PREN of 40 or greater, or a nickel-based alloy having a PREN of 40 or greater, the predetermined upper limit is minus 0.30 V vs. Ag / AgCl seawater.

[0040] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be effectively suppressed.

[0041] A sixth item disclosed in the present specification is the vessel described in the fifth item, wherein the near-cathode hull protection member area includes 50% or more of the near-cathode hull protection range.

[0042] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be suppressed to a certain extent.

[0043] A seventh item disclosed in this specification is the ship according to claim 5 or 6, wherein a portion of the cathode near hull protection member area that is not the cathode near hull protection range is 50% or less.

[0044] This configuration makes it possible to reduce the manufacturing costs of the hull.

[0045] An eighth item disclosed in this specification is the vessel according to any one of the first to eighth items, in which the protective member is made of rubber, a composite material, or a resin.

[0046] According to this configuration, toughness can be ensured and the shape can be easily adjusted to fit the hull since the material can be easily processed into any shape. [Explanation of symbols]

[0047] 10. Hull 11 Underwater part 20 Underwater electric field reduction device 21 Underwater electrode 22 Anode 23 Cathode 30 Protective materials 31 Hull protection member near anode 32 Cathode-near hull protection member 33 Hull protection material area near anode 34 Anode Near Hull Protection Area 35 Cathode-near hull protection area 36 Cathode Near Hull Protection Range 100 ships

Claims

1. A metal hull including a submersible portion that is immersed in seawater; an underwater electric field reduction device including an underwater electrode provided in the underwater portion, the underwater electric field reduction device reducing the underwater electric field around the hull by passing a counter current through the seawater via the underwater electrode; a protective member made of an insulator provided in the underwater portion so as to surround the underwater electrode; A vessel equipped with:

2. The protective member includes an anode vicinity hull protective member surrounding the anode of the underwater electrode, The anode vicinity hull protection member is located in an anode vicinity hull protection member region including an anode vicinity hull protection range, The anode vicinity hull protection range is: The range in which the electrode potential is equal to or lower than a predetermined lower limit when the underwater electric field reduction device generates a counter current, When the hull is made of carbon steel having a yield strength of less than 550 MPa, alloy steel having a yield strength of less than 550 MPa, aluminum alloy, or copper alloy containing aluminum, the predetermined lower limit is minus 1.10 V vs. Ag / AgCl seawater; When the hull is made of carbon steel having a yield strength of 550 MPa or more, or alloy steel having a yield strength of 550 MPa or more, the predetermined lower limit is minus 0.95 V vs. Ag / AgCl seawater; When the hull is made of martensitic stainless steel, the predetermined lower limit is minus 0.80 V vs. Ag / AgCl seawater; 2. The vessel of claim 1, wherein the predetermined lower limit is minus 0.75 V vs. Ag / AgCl seawater when the vessel hull is made of a titanium alloy.

3. 3. The vessel of claim 2, wherein the near-anode hull protection member area comprises 50% or more of the near-anode hull protection range.

4. 3. The ship according to claim 2, wherein a portion of the anode vicinity hull protection member area that is not the anode vicinity hull protection range is 50% or less.

5. The protective member includes a cathode adjacent vessel protective member surrounding the cathode of the underwater electrodes, The cathode near hull protection member is located in a cathode near hull protection member region including a cathode near hull protection range, the cathode vicinity hull protection range is a range in which an electrode potential is equal to or greater than a predetermined upper limit when the underwater electric field reduction device generates a counter current, When the hull is made of carbon steel, alloy steel, or aluminum alloy, the predetermined upper limit is minus 0.80 V vs. Ag / AgCl seawater; If the hull is made of an austenitic stainless steel having a PREN of less than 40, a nickel-based alloy having a PREN of less than 40, a duplex stainless steel, or a martensitic stainless steel, the predetermined upper limit is minus 0.50 V vs. Ag / AgCl seawater; When the hull is made of a copper alloy, the predetermined upper limit is minus 0.45 V vs. Ag / AgCl seawater; 2. The ship of claim 1, wherein the predetermined upper limit is minus 0.30 V vs. Ag / AgCl seawater when the hull is formed of an austenitic stainless steel having a PREN of 40 or more, or a nickel-based alloy having a PREN of 40 or more.

6. 6. The marine vessel of claim 5, wherein said near cathode hull protection member area comprises 50% or more of said near cathode hull protection range.

7. 6. The ship according to claim 5, wherein a portion of the cathode near hull protection member area that is not the cathode near hull protection range is 50% or less.

8. The watercraft according to claim 1 , wherein the protective member is made of rubber, a composite material, or a resin.

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