Method for treating the inner surface of cargo tanks of tankers and other cargo ships

Abstract

To provide a cargo ship having a tank capable of maintaining a more stable state. [Solution] A cargo ship 1 has a double hull structure and is equipped with a plurality of cargo tanks 2 and a plurality of ballast tanks 3. An FRP layer is formed on the inside of the inner surfaces 2A, 3A of each of the cargo tanks 2 and ballast tanks 3 by inner surface treatment of the inner surfaces 2A, 3A. This FRP layer provides each of the cargo tanks 2 and ballast tanks 3 with high corrosion resistance, high waterproofing, etc., and also achieves high durability.

Description

[Technical field]

[0001] The present invention relates to a method for treating the inner surface of a tank. [Background technology]

[0002] Cargo ships such as tankers are equipped with one or more cargo tanks for carrying cargo. When the ship is empty, the draft becomes shallow and the ship becomes unstable. Therefore, cargo ships equipped with cardan are equipped with ballast tanks to ensure stability even when the ship is empty. In double-hull cargo ships, which have double outer plates, ballast tanks are often allocated in the space between the double outer plates.

[0003] The inner surface of a cargo tank may be painted with paint to prevent corrosion caused by the cargo or to maintain high quality standards of the cargo (see, for example, Patent Document 1). The paint is selected depending on the type of cargo, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-40066 A Summary of the Invention [Problem to be solved by the invention]

[0005] Paint is prone to deterioration due to scratches or peeling. Therefore, regular repainting is necessary. Deterioration may also require frequent repairs. For these reasons, paint tends to require high maintenance costs. For this reason, it is important to be able to maintain the condition of tanks, not only cargo tanks, but also tanks installed on cargo ships in a more stable manner.

[0006] Therefore, the present invention provides a technology that enables tanks installed on cargo ships to be maintained in a more stable state. [Means for solving the problem]

[0007] A tank inner surface treatment method according to one embodiment of the present disclosure includes a cleaning process for cleaning the inner surface of a tank to be installed on a cargo ship, and a forming process for forming an FRP layer on the inside of the inner surface after the cleaning process. Effect of the Invention

[0008] The present invention allows tanks installed on cargo ships to be maintained in a more stable condition. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an example of a cargo ship to which a tank inner surface treatment method according to an embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example, including modified examples, and the technical scope of the present invention is not limited to this. Various modified examples are also included in the technical scope of the present invention.

[0011] FIG. 1 is a cross-sectional view showing an example of a cargo ship to which a tank inner surface treatment method according to an embodiment of the present invention is applied. The cargo ship 1 is, for example, a tanker. As shown in Fig. 1, the ship has a double hull structure and is equipped with a plurality of cargo tanks 2 and a plurality of ballast tanks 3. The inner surfaces 2A, 3A of each of the cargo tanks 2 and ballast tanks 3 are both subjected to a tank inner surface treatment method according to this embodiment (hereinafter referred to as "this method"). Here, for convenience, the following description will focus on the cargo tank 2.

[0012] The cargo tank 2 itself is a storage facility manufactured using a plurality of steel materials. An FRP (Fiber Reinforced Plastics) layer (not shown) is formed on the inside of the inner surface 2A of the cargo tank 2.

[0013] Compared to paint, FRP has excellent properties such as high corrosion resistance and waterproofing, high durability, and long life. In addition, FRP has excellent properties such as the ability to maintain the performance of the internal structure even if the surface is damaged, the ability to be used as part of the structure rather than simply protecting the surface, and resistance to impact and weight. For these reasons, by forming an FRP layer inside, the cargo tank 2 can maintain its state more stably while satisfying the required properties. As a result, the costs required for maintenance, including time, can be reduced. As a result, it is expected that the operating rate of cargo ships can be increased and that cargo ships will have a longer life.

[0014] This method can be applied during both the construction and maintenance of a cargo ship. For convenience, the explanation will be given assuming that the cargo tank 2 is being maintained. The cargo in the cargo tank 2 is assumed to be a flammable liquid such as black oil or liquefied natural gas. Such liquid will be referred to as "flammable liquid" hereafter.

[0015] When carrying out this method, first, the flammable liquid present in the cargo tank 2 is removed, and then the gas is measured using a measuring device (not shown). The gas is measured in order to confirm the concentration of gas that is dangerous to workers, such as flammable gas (hereinafter referred to as "flammable gas"), in the cargo tank 2. If the concentration is at a level that is determined to be dangerous, the flammable gas and even the flammable liquid present in the cargo tank 2 are removed, making the inside of the cargo tank 2 safe.

[0016] Next, the cargo tank 2 is filled with water and an absorbent material for absorbing the flammable liquid is sprayed therein. The water is sprayed to, for example, about half the capacity of the cargo tank 2. After filling the cargo tank 2 with water, the absorbent material is sprayed therein to absorb the flammable liquid. The water from which the flammable liquid has been separated is discharged through a separation tank (not shown) as described below.

[0017] Next, a water pressure test is performed on the cargo tank 2 and various pipes installed in the cargo tank 2. This test is performed after the removal of the flammable liquid is completed, with the cargo tank 2 filled with water. This test is used to check whether or not the flammable liquid leaks.

[0018] Next, the cargo tank 2 is disconnected from various pipes. In other words, all pipes connected to the cargo tank 2 are disconnected. After this disconnection, a cleaning process is performed. In this cleaning work, for example, first, the water in the cargo tank 2 is pumped out and discharged through a separation tank to drain the water. After this drainage, absorbent material is sprayed on the sludge in the cargo tank 2, and a 6% emulsified solution is added to the surface to extremely reduce the generation of flammable gas, and the sludge is disposed of together with the cleaning wastewater inside the cargo tank 2. Furthermore, a blasting process is performed to remove rust, burrs, etc. present in the cargo tank 2 and expose the bare steel surface. At this time, the inside of the cargo tank 2 is also visually inspected.

[0019] This visual inspection checks the location and number of corrosion, scratches, jig marks, etc. Here, the hole contact measurement checks the depth, location, number, etc. of the hole contact parts found by visual inspection, etc. In addition, the plate thickness measurement checks the plate thickness of the steel plate that constitutes the cargo tank 2 with an ultrasonic thickness gauge.

[0020] In the penetrant inspection, a red or fluorescent penetrant is applied to the surface of the object, and the liquid is allowed to penetrate into the flaw. The liquid remaining on the surface is then removed, and the liquid remaining in the flaw is sucked up with fine powder of a developer, forming an image that is enlarged compared to the original flaw and has a high contrast with the surroundings. In the visual inspection, such an inspection may be performed as necessary.

[0021] If a visual inspection reveals any areas that require repair or renovation, the repair or renovation process is carried out on those areas. If relatively large-scale repairs are required, such as when the corrosion is deep or there are many areas that need repair, the repair or renovation process is carried out according to a plan. Repairs are carried out by means of plate welding, overlay welding, anti-corrosion coating, etc.

[0022] Next, an FRP lining is applied to the inner surface 2A of the cargo tank 2. The lining of the inside of the tank 2 is first applied with a primer coating. After the primer coating, a predetermined number of plies are laminated using, for example, FRP prepreg sheets (not shown), and then cured by irradiating with ultraviolet rays. Note that the inner surface 2A of the cargo tank 2 actually includes the structure inside the cargo tank 2. However, to avoid confusion, a description of the structure will be omitted here.

[0023] The type of FRP, that is, the resin, fibers, etc. used in the FRP, must be selected according to the cargo expected to be loaded into the cargo tank 2 and the expected state of the cargo. For example, black oil may be injected into the cargo tank 2 at a relatively high temperature, for example, about 80 degrees. In that case, it is necessary to use not only a resin that is suitable for the black oil, but also a resin and fibers that can withstand that temperature. Therefore, it is necessary to select carbon fiber or ceramic fiber as the fiber.

[0024] A specific method for attaching FRP is as follows, for example. First, after applying a primer coat to the base as described above, a prepreg sheet made of FRP is applied starting from a predetermined position on the inner surface 2A of the tank 2. For example, one side of this prepreg sheet is coated with adhesive in advance, and the coated side is covered with a plastic sheet. When applying, the plastic sheet is peeled off so that no gas phase is generated between the sheet and the inner surface 2A of the tank 2. In this way, the prepreg sheet (FRP) is applied to the inner surface 2A of the tank 2. The prepreg sheet (FRP) may be applied to the entire inner surface 2A, or may be applied only within a specified range.

[0025] In this way, by the adhesion process of adhering the prepreg sheet to the inner surface 2A of the tank 2, an FRP layer is formed on the inside of the entire inner surface 2A of the cargo tank 2. As a result, the adhesion process is a forming process for forming an FRP layer. After this adhesion process, the prepreg sheet is irradiated with ultraviolet rays to harden the FRP. This hardening completes the formation of the FRP layer.

[0026] In the above-mentioned method, the FRP layer is formed by lining with a prepreg sheet, but the FRP layer may be formed by a method other than lining. For example, the FRP layer may be formed by applying or spraying the FRP onto the inner surface 2A of the tank 2 with a brush or the like.

[0027] This method makes it possible to realize a cargo tank 2 with an FRP layer formed on the inside of the inner surface 2A. The formation of the FRP layer not only makes it possible to maintain the state more stably, but also realizes high durability of the cargo tank 2 with high corrosion resistance, high waterproofing, etc. This makes it possible to reduce costs, including the time required for subsequent maintenance, and is expected to extend the life of the cargo tank 2 and the cargo ship on which it is loaded.

[0028] In the above description, it is assumed that this method is applied during maintenance of the cargo tank 2, but this method may also be applied during manufacturing of the cargo tank 2. The applicable tank (storage facility) is not limited to the cargo tank 2. The tank may be a ballast tank 3. It may also be a fuel tank. [Explanation of symbols]

[0029] 1 cargo ship, 2 cargo tank, 2A, 3A interior, 3 ballast tank.

Claims

1. A cleaning process for cleaning the inner surface of a tank to be installed on a cargo ship; a forming process of forming an FRP layer on the inner surface after the cleaning process; A method for treating the inner surface of a tank, comprising:

2. The cleaning process includes a blast process. The method for treating the inner surface of a tank according to claim 1.

3. Steel materials forming tanks to be installed on cargo ships; An FRP layer formed on the inside of the steel material; A tank comprising:

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