Method for treating the inner surface of cargo tanks in cargo ships such as tankers.

Abstract

This technology provides capabilities to maintain the condition of tanks installed on cargo ships more stably. [Solution] The cargo ship 1 has a double-hull structure and is equipped with multiple cargo tanks 2 and multiple ballast tanks 3. Each cargo tank 2 and each ballast tank 3 has an internal surface treatment applied to its inner surface 2A and 3A, forming an FRP layer on the inside of the inner surface 2A and 3A. This FRP layer provides each cargo tank 2 and each ballast tank 3 with high corrosion resistance, high waterproofness, and high durability.

Description

Technical Field

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

Background Art

[0002] One or more cargo tanks for loading cargo are installed in a cargo ship such as an oil tanker. When the cargo is empty, the draft becomes shallow and the cargo ship becomes unstable. Therefore, in a cargo ship equipped with a ballast tank, a ballast tank is installed so that it can be stabilized even when the cargo is empty. In a double-hull cargo ship with a double hull, the space between the double hulls is often assigned as a ballast tank.

[0003] The inner surface of the cargo tank may be painted for the purpose of suppressing corrosion by the cargo or maintaining high quality standards of the cargo (see, for example, Patent Document 1). The paint is selected according to the type of cargo and the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In painting, deterioration due to scratches, peeling, etc. is likely to occur. Therefore, periodic repainting is necessary. In some cases, frequent repairs may be required due to deterioration. For these reasons, painting tends to increase the cost required for maintenance. Thus, it is considered important to be able to maintain the state more stably not only for cargo tanks but also for tanks installed in cargo ships.

[0006] Therefore, the present invention provides a technique for more stably maintaining the state of a tank installed in a cargo ship. [Means for solving the problem]

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

[0008] This invention makes it possible to maintain a more stable condition for tanks installed on cargo ships. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an example of a cargo ship to which the tank internal surface treatment method according to an embodiment of the present invention has been applied. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described below with reference to the figures. The embodiments described below, including modifications, are merely examples, and the technical scope of the present invention is not limited thereto. The technical scope of the present invention includes various modifications.

[0011] Figure 1 is a cross-sectional view showing an example of a cargo ship to which the tank internal surface treatment method according to an embodiment of the present invention has been applied. This cargo ship 1 is, for example, a tanker. As shown in Figure 1, it has a double-hull structure and is equipped with multiple cargo tanks 2 and multiple ballast tanks 3. The inner surface treatment method for tanks according to this embodiment (hereinafter referred to as "this method") is applied to the inner surfaces 2A and 3A of each cargo tank 2 and each ballast tank 3. Hereafter, for convenience, we will focus on the cargo tanks 2 in our explanation.

[0012] Cargo tank 2 itself is a storage facility manufactured using multiple steel materials. Inside its inner surface 2A, an FRP (Fiber Reinforced Plastics) layer (not shown) is formed.

[0013] Compared to paint, FRP offers superior corrosion resistance and waterproofing, as well as excellent durability and a long lifespan. Furthermore, it retains its internal structural performance even if the surface is damaged, can be used as part of the structure rather than merely for surface protection, and is resistant to impact and heavy loads. Therefore, by forming an FRP layer inside, cargo tank 2 can maintain its required properties more stably. As a result, maintenance costs, including time, can be reduced. This can lead to higher operational rates for cargo ships and a longer service life for the vessels themselves.

[0014] This method can be applied either during the construction or maintenance of a cargo ship. For convenience, this explanation will assume that the procedure is performed during the maintenance of cargo tank 2. The cargo in cargo tank 2 is assumed to be flammable liquids such as black oil and liquefied natural gas. These liquids will be referred to as "flammable liquids" from now on.

[0015] When implementing this method, first, the flammable liquid present in cargo tank 2 is removed, and then the gas is measured using a measuring instrument not shown. The gas is measured to confirm the concentration of gases that are dangerous to workers, such as flammable gases (hereinafter referred to as "flammable gases"), in cargo tank 2. If the concentration is deemed to be at a dangerous level, the flammable gases and flammable liquids present in cargo tank 2 are removed to make the inside of cargo tank 2 safe.

[0016] Next, the cargo tank 2 is filled with water, and an absorbent material that absorbs flammable liquids is sprayed onto it. The water filling is done to about half the capacity of the cargo tank 2, for example. After filling with water, the absorbent material is sprayed onto it to absorb the flammable liquid. The water from which the flammable liquid has been separated is discharged through a separation tank (not shown), as will be described later.

[0017] Next, a hydrostatic pressure test will be conducted on cargo tank 2 and the various piping installed within it. This test will be performed after the removal of the flammable liquid is complete and cargo tank 2 is filled with water. This test will confirm whether or not the flammable liquid leaks out.

[0018] Next, the cargo tank 2 is disconnected from the various piping. That is, all piping connected to cargo tank 2 is disconnected. After this disconnection, a cleaning process is carried out. This cleaning process, for example, first pumps out the water from cargo tank 2 and discharges it through a separation tank to drain the water. After this draining, an absorbent material is sprayed on the sludge inside cargo tank 2, and then a 6% emulsifying solution is added to the surface to suppress the generation of flammable gases to an extremely low level, and the sludge is disposed of together with the cleaning wastewater inside cargo tank 2. Furthermore, blasting is performed to remove rust, burrs, etc. present inside cargo tank 2 and expose the bare steel surface. At this time, the inside of cargo tank 2 is also visually inspected.

[0019] This visual inspection confirms the location and quantity of corrosion, scratches, jig marks, etc. Here, porosity measurement checks the depth, location, and quantity of porosity found through visual inspection, etc. In addition, plate thickness measurement checks the plate thickness of the steel plates constituting cargo tank 2 using an ultrasonic thickness gauge.

[0020] Penetrant testing involves applying a red or fluorescent penetrant to the surface of an object, allowing it to penetrate into the defect, removing the remaining penetrant from the surface, and then using a developer powder to draw out the remaining penetrant from within the defect. This creates a magnified image of the defect with high contrast against the surrounding area. Visual inspection may also be performed as needed.

[0021] If a location that requires repair or modification is found through visual inspection, repair and modification processing for that location is performed. When relatively large-scale repairs such as a deep corrosion depth or many locations requiring repair are necessary, the repair and modification processing is carried out according to a plan. Repairs, etc. are performed by butt welding, build-up welding, anti-corrosion coating, etc.

[0022] Next, FRP lining construction is carried out on the inner surface 2A of the cargo tank 2. For the lining construction inside this tank 2, first, primer coating is applied. After the primer coating, for example, using an FRP prepreg sheet (not shown), a predetermined number of plies are laminated and irradiated with ultraviolet light for curing. In fact, the inner surface 2A of the cargo tank 2 also includes the structures inside the cargo tank 2. However, here, for the sake of avoiding confusion, the description of those structures is omitted.

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

[0024] A specific method of attaching FRP is, for example, as follows. First, as described above, a primer coat is applied to the base coat, and then the FRP prepreg sheet is applied starting from a predetermined position on the inner surface 2A of the tank 2. This prepreg sheet has adhesive applied to one side in advance, and the applied surface is covered with a plastic sheet. When applying, the plastic sheet is peeled off to prevent a gas phase from forming 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. Note that the prepreg sheet (FRP) may be applied to the entire inner surface 2A, or it may be applied only to a defined area.

[0025] In this way, the adhesive process of attaching the prepreg sheet to the inner surface 2A of the tank 2 forms an FRP layer on the entire inner surface 2A of the cargo tank 2. Thus, the adhesive process is a forming process that creates an FRP layer. After this adhesive process, the prepreg sheet is irradiated with ultraviolet light to cure the FRP. This curing completes the formation of the FRP layer.

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

[0027] This method makes it possible to realize a cargo tank 2 in which an FRP layer is formed on the inside of the inner surface 2A. The formation of the FRP layer not only allows for more stable maintenance, but also enhances the durability of the cargo tank 2 by providing high corrosion resistance and high waterproofness. As a result, costs, including the time required for subsequent maintenance, can be reduced, and the lifespan of the cargo tank 2, and even the cargo ship that carries it, can be expected to be extended.

[0028] Although the above explanation assumes that this method will be applied during maintenance of cargo tank 2, it may also be applied during the manufacture of cargo tank 2. The applicable tank (storage facility) is not limited to cargo tank 2. The tank may also be a ballast tank 3 or a fuel tank. [Explanation of Symbols]

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

Claims

1. A cleaning process that cleans the inside of tanks installed on cargo ships, A forming process is performed to form an FRP layer on the inside of the inner surface after the cleaning process, A method for treating the inner surface of a tank, including [a specific substance].

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

3. Steel materials that form tanks installed on cargo ships, The FRP layer formed on the inside of the steel material, A tank equipped with a tank.

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