JP2007314027A - Ballast tank corrosion protection member and suction bell-mouth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent corrosion of the neighborhood of a suction bell-mouth in a ballast tank of a marine vessel and a marine structure. <P>SOLUTION: Ballast tank corrosion preventive members 8, 16 have mounting members 10, 17 to head end parts of plumbing devices 2, 3 and anode members 10, 18, an electric current flows in the sea water which is an electrolyte toward a steel material of an inner wall of the ballast tank which is higher in electric potential than the anode members 10, 18 which are low in electric potential, a vessel's bottom on the high electric potential side comes to be in an anticorrosion state and stabilized and corrosion of a vessel's bottom part near the suction bell-mouth 2 is effectively prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to the prevention of corrosion in ballast tanks of ships and offshore structures.

Ballast tanks for ships and offshore structures are exposed to seawater and are susceptible to corrosion (rust). Therefore, it is necessary to take measures to prevent corrosion. Patent Document 1 describes that nitrogen gas is supplied into a ballast tank to keep the oxygen concentration at 2% or less. Patent Document 2 describes that wet air in a ballast tank space is replaced with dry air to remove moisture and to control temperature.

Non-Patent Document 1 describes that an anticorrosion current is supplied by providing an anode such as zinc in a ballast tank to prevent corrosion of the ballast tank.
JP 2002-234487 A Japanese Patent Application Laid-Open No. 8-2169795 Company Profile

The methods described in Patent Document 1 and Patent Document 2 may theoretically be effective in preventing corrosion, but the ballast tank has a large volume, and drainage and water supply are frequently performed. Implementing is costly and impractical.

The anticorrosion method of Non-Patent Document 1 is effective and is also used in ships. This method is intended to uniformly protect the entire ballast tank. However, the entire steel plate in the ballast tank does not corrode uniformly. In the vicinity where the suction mouth bell is installed, the ribs of the suction mouth bell come into contact with the steel plate on the bottom of the ship, so that the coating for preventing corrosion is easily peeled off, and corrosion is more likely to proceed than in other parts. Furthermore, because of the water supply and drainage by the suction mouthbell, this part is exposed to running water and comes into contact with oxygen and electrolytes in water. The anticorrosion method of Non-Patent Document 1 is insufficient to prevent such local corrosion.

An object of the present invention is to provide a ballast tank corrosion preventing member and a suction mouth bell that can effectively prevent corrosion in the vicinity of the suction mouth bell in a ballast tank of a ship or an offshore structure.

In order to solve the above-described problems, the ballast tank corrosion preventing member of the present invention has a member attached to the tip of the water supply / drainage device and an anode member. As an attachment member to the tip of the water supply / drainage device, for example, a U band attached to the water supply / drainage pipe or a connection member attached to the flange portion of the suction bell mouth can be used. Moreover, you may provide the insulating member attached to the rib front-end | tip of a suction bell mouth. As the anode member, for example, zinc can be used.

Further, the suction bell mouth of the present invention is provided with a zinc anode member at the flange portion and an insulating member at the rib tip.

The ballast tank corrosion preventing member and the suction bell mouth of the present invention have the effect of effectively supplying a corrosion preventing current to the steel plate near the suction mouth bell and preventing the ballast tank from corroding. Installation in the ballast tank is easy and the anode member can be easily replaced.

The best mode for carrying out the present invention will be described with reference to the drawings. 1 is a partial cross-sectional front view showing the tip of a water supply / drainage device including a suction bell mouth, FIG. 2 is a cross-sectional view showing a second ballast tank corrosion preventing member in the AA cross-sectional view, and FIG. 4 is a front view showing the anode member mounting member, FIG. 5 is a front view thereof, FIG. 6 is a partial sectional plan view showing the suction bell mouth main body, and FIG. 7 is a front sectional view of the same portion. 8 is a perspective view showing the insulating member, FIG. 9 is a front view showing the ballast tank, and FIG. 10 is a plan view thereof.

A ship ballast tank 1 is provided with a suction bell mouth 2 and a water supply / drainage pipe 3 as a water supply / drainage device. The suction bell mouth 2 is connected to a water supply / drainage pump 4 by a water supply / drainage pipe 3 so that seawater can be taken in or discharged from a water supply / drainage port 5.

In this example, the suction bell mouth 2 is of a type connected to the pipe joint flange 6 and the bolt 7, but may be of a type fixed to the water supply / drainage pipe 3 by welding.

A first ballast tank corrosion prevention member 8 is attached to the pipe joint flange 6 with bolts 7. The first ballast tank corrosion preventing member 8 includes a connecting member 9 and an anode member 10 attached to the connecting member 9. The connecting member 9 is a plate-like member having a bent portion 11 and is made of, for example, stainless steel. Bolt holes 12 for passing the bolts 7 are provided, and linear protrusions 13 are provided on both sides of the bolt holes 12. The bolt 7 is for connecting the pipe joint flange 6 and is not provided for the present invention. The first ballast tank corrosion prevention member 8 is attached to the suction bell mouth 2 by closing the bolt 7 through the bolt hole 12. Since the protrusions 13 on both sides of the bolt hole 12 abut against the lower surface of the pipe joint flange 6, both are securely connected electrically.

The connecting member 9 is provided with an anode member mounting portion 13 in which a male screw is formed. On the other hand, the anode member 10 is provided with a hole (not shown) through which the anode member mounting portion 13 can pass. The anode member mounting portion 13 is passed through this hole, and a nut ( By attaching (not shown), the connecting member 9 and the anode member 10 are detachably coupled. Here, an insulating rubber 15 is inserted between the connecting member 9 and the anode member 10, and electrical contact on a surface other than the anode member mounting portion 13 is cut off. Therefore, the connection member 9 and the anode member 10 are electrically connected only via the anode member mounting portion 13. The anode member 10 is made of a metal having a lower potential than the steel constituting the inner wall of the ballast tank 1, and for example, aluminum, zinc, magnesium, or an alloy containing these can be used. Here, a material made of zinc is used.

The second ballast tank corrosion prevention member 16 is attached near the tip of the water supply / drainage pipe 3. The second ballast tank corrosion prevention member 16 includes a U band 17 and an anode member 18. A screw portion 21 to which the nut 20 can be attached and detached is formed at the distal end portion of the U band 17. Moreover, the protrusion part 22 for ensuring the electrical contact with the water supply / drainage pipe 3 is formed. The anode member 18 is provided with a through hole 23 for passing the U band 17 and a bag hole 24 in which the nut 20 is accommodated.

The U band 17 is positioned near the tip of the water supply / drainage pipe 3, and the U band 17 and the anode member 18 are connected by the nut 20. Here, an insulating rubber 25 is inserted between the water supply / drainage pipe 3 and the anode member 18, and electrical contact at this portion is interrupted. Therefore, the water supply / drainage pipe 3 and the anode member 18 are electrically connected only via the U band 17 and the protrusion 22 thereof. The material of the anode member 18 is the same as that of the anode member 10 of the first ballast tank corrosion prevention member 8.

The suction bell mouth body 26 is provided with ribs 27 at three locations. The rib 27 protrudes below the mouth of the suction bell mouth main body 26, and a sufficient distance necessary for the flow of seawater is ensured between the suction bell mouth main body 26 and the bottom surface of the ballast tank 1. . An insulating member 28 is attached to the tip of the rib 27.

Next, the operation of the ballast tank corrosion preventing members 6 and 16 and the suction bell mouth 2 will be described. Only one or both of the first ballast tank corrosion preventing member 8 and the second ballast tank corrosion preventing member 16 may be used. An electric current flows in the seawater which is an electrolytic solution toward the steel material on the inner wall of the ballast tank which is higher in potential than the anode members 10 and 18 which are in low potential. At this time, the anode members 10 and 18 which are low potential metals are consumed as ions as sacrificial anodes, but the bottom of the ship on the high potential side is in an anticorrosive state and is stable. In particular, a lot of anticorrosion current flows into the bottom of the ship near the suction bell mouth 2. Thereby, corrosion of the ship bottom near the suction bell mouth 2 is effectively prevented.

Since the insulating member 28 is attached to the rib 27 of the suction bell mouth 2, the rib 27 and the ballast tank bottom are electrically insulated. Although the bottom surface of the ballast tank is made of steel, the surface of the rib 27 is galvanized and easily corroded if different metals come into contact with it, but the insulating member 28 prevents contact between different metals. Moreover, the surface of the insulating member 28 is formed smoothly, and even if it contacts the bottom surface of the ballast tank, the surface coating is hardly damaged.

As described above, corrosion of the bottom surface near the suction bell mouth 2 is prevented by the ballast tank corrosion preventing members 8 and 16 and the suction bell mouth 2 of the present invention. As a result, accidents in operation due to a hole in the bottom of the ballast tank are prevented, and loss of opportunity and repair costs due to operation stoppage due to repairs are prevented. Installation of the ballast tank corrosion prevention members 8 and 16 is extremely easy, and there is no need to change the structure of conventional ships and offshore structures. The anode members 10, 18 that are consumed as sacrificial anodes can be easily replaced.

The example of the ballast tank of the ship has been described above, but the present invention can be applied to a ballast tank of an offshore structure or the like.

It is a partial cross section front view which shows a water supply / drainage device front-end | tip part. It is sectional drawing which shows a 2nd ballast tank corrosion prevention member. It is an expanded sectional view of a U band. It is a front view which shows an anode member attachment member. It is the same front view. It is a partial cross section top view which shows a suction bell mouth main-body part. It is the same section sectional front view. It is a perspective view which shows an insulating member. It is a front view which shows a ballast tank. It is the same top view.

Explanation of symbols

1. 1. Ballast tank 2. Suction bell mouth 5. Water supply / drainage pipe 6. Pipe joint flange Bolt 8. First ballast tank corrosion prevention member9. Connecting members 10, 18. Anode member 16. Second ballast tank corrosion prevention member 17. U band 26. Suction bell mouth main body 27. Insulation material

Claims (6)

A ballast tank corrosion preventing member having a member attached to the tip of the water supply / drainage device and an anode member. The ballast tank corrosion prevention member according to claim 1, wherein the attachment member to the tip of the water supply / drainage device is a U band attached to the water supply / drainage pipe. The ballast tank corrosion prevention member according to claim 1, wherein the attachment member to the tip of the water supply / drainage device is a connection member attached to the flange portion of the suction bell mouth. The ballast tank corrosion preventing member according to claim 2 or 3, further comprising an insulating member attached to a rib tip of the suction bell mouth. The ballast tank corrosion preventing member according to any one of claims 1 to 4, wherein the anode member is zinc. A suction bell mouth in which an anode member made of zinc is provided at the flange portion and an insulating member is provided at the tip of the rib.

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