Deterioration diagnosis method for fiber-reinforced plastic liquid storage tanks

Abstract

To easily and accurately diagnose deterioration of a liquid storage tank. [Solution] A fiber-reinforced plastic liquid storage tank has a liquid storage tank body (10) and a manhole (20) that communicates with the interior of the liquid storage tank body (10). The manhole (20) has a tubular portion (21) that protrudes outward from the liquid storage tank body (10) and a lid (30) that is provided to open and close the tip opening of the tubular portion (21). The lid (30) has a lid body (30A) and a plate portion (40) that protrudes from the inner surface of the lid body (30A). The thickness of the plate portion (40) is greater than the thickness of the wall portion (11) of the liquid storage tank body (10).

Description

[Technical Field]

[0001] The present invention , fiber This invention relates to a method for diagnosing deterioration of a liquid storage tank made of fiber-reinforced plastic. [Background technology]

[0002] BACKGROUND ART Tanks made of fiber-reinforced plastics (hereinafter referred to as FRP), which are composite materials of resin and reinforcing fibers, have been well known (see, for example, Patent Document 1). There are also liquid storage tanks for storing chemical liquids such as strong acids such as hydrochloric acid and strong bases such as caustic soda. These liquid storage tanks are usually made of corrosion-resistant FRP. The corrosion-resistant FRP has a reinforcing layer and a corrosion-resistant layer that is fixed to the inner surface of the reinforcing layer and forms the liquid-contacting surface. The reinforcing layer, also called the outer layer, is a layer that provides the liquid storage tank with appropriate structural strength. The corrosion-resistant layer is a layer that provides the liquid storage tank with appropriate corrosion resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-247468 Summary of the Invention [Problem to be solved by the invention]

[0004] However, corrosion due to chemicals gradually progresses over time in FRP liquid storage tanks, so there is a demand for an easy and accurate method for diagnosing deterioration of liquid storage tanks. [Means for solving the problem]

[0005] Various aspects of a fiber-reinforced plastic liquid storage tank and a method for diagnosing deterioration of a fiber-reinforced plastic liquid storage tank for solving the above problems will be described below. [Aspect 1] A liquid storage tank made of fiber reinforced plastic, the liquid storage tank having a liquid storage tank body and a manhole communicating with the interior of the liquid storage tank body, the manhole has a cylindrical portion protruding outward from the liquid storage tank body and a lid provided to open and close an opening at a tip of the cylindrical portion, The lid has a lid body and a plate portion protruding from an inner surface of the lid body, The thickness of the plate portion is greater than the thickness of the wall portion of the liquid storage tank body. Fiber-reinforced plastic storage tank.

[0006] This configuration enables deterioration diagnosis of the liquid storage tank body as follows. First, the plate portion is separated from the lid body. Next, a test piece is formed by cutting the side surface of the plate portion opposite to the side surface in the thickness direction of the plate portion so that the thickness is the same as the wall thickness of the liquid storage tank body, while leaving one side surface intact. The test piece thus formed can be considered to have substantially the same mechanical properties as the wall surface of the liquid storage tank body after deterioration. Furthermore, the mechanical properties of the wall surface of the liquid storage tank body after deterioration change depending on the degree of deterioration of the wall surface. Therefore, by measuring the mechanical properties of the test piece and determining the deterioration state of the liquid storage tank body based on the mechanical properties, deterioration diagnosis of the liquid storage tank can be performed without cutting out a portion of the liquid storage tank body.

[0007] Furthermore, according to the above configuration, a plate portion that serves as a test piece for deterioration diagnosis is provided on the manhole cover, so there is no need to change the configuration of the liquid storage tank body, unlike when the plate portion that serves as the test piece is separately placed inside the liquid storage tank body.

[0008] Therefore, deterioration of the liquid storage tank can be diagnosed easily and accurately. [Aspect 2] The lid has a plurality of the plate portions. A liquid storage tank made of fiber-reinforced plastic according to embodiment 1.

[0009] According to this configuration, since the lid has multiple plates, when repeatedly diagnosing deterioration of the storage tank at intervals, such as every few years, the multiple plates can be used in turn as test pieces, making it easy to repeatedly diagnosing deterioration of the storage tank at intervals while reusing the lid.

[0010] [Aspect 3] A method for diagnosing a deterioration state of a fiber-reinforced plastic liquid storage tank according to aspect 1 or aspect 2, comprising: a separation step of separating the plate portion from the lid main body; a test piece forming step of forming a test piece by cutting a side surface of the plate portion opposite to the side surface in the thickness direction of the plate portion while leaving one side surface of the plate portion in the thickness direction so that the side surface has the same thickness as the wall portion of the liquid storage tank body; a measuring step of measuring mechanical property values ​​of the test piece; and a determination step of determining a deterioration state of the liquid storage tank body based on the mechanical property values. A method for diagnosing deterioration of fiber-reinforced plastic liquid storage tanks.

[0011] According to this method, the same effects as those of the fiber-reinforced plastic liquid storage tank described in the first aspect can be achieved. [Aspect 4] the lid has a plurality of the plate portions, The deterioration diagnosis of the liquid storage tank body is repeatedly performed at time intervals, and a different plate part is used for each deterioration diagnosis. A deterioration diagnosis method for a liquid storage tank made of fiber-reinforced plastic according to aspect 3.

[0012] According to this method, the same effects as those of the fiber-reinforced plastic liquid storage tank described in aspect 2 can be achieved. [Effects of the Invention]

[0013] According to the present invention, deterioration of a liquid storage tank can be easily and accurately diagnosed. [Brief explanation of the drawings]

[0014] [Figure 1] Figure 1 is a cross-sectional view centered on the wall of the liquid storage tank body and the manhole in the fiber-reinforced plastic liquid storage tank of one embodiment. [Figure 2] Figure 2 is a rear view of the lid of the manhole in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the wall of the liquid storage tank body in Figure 1. [Figure 4] Figure 4 is a cross-sectional view of the plate portion. [Figure 5] Figure 5 is a flowchart showing the procedure of the deterioration diagnosis method for the fiber-reinforced plastic liquid storage tank of one embodiment. [Figure 6] Figure 6 is a cross-sectional view of the lid and is a diagram for explaining the separation process. [Figure 7] Figure 7 is a cross-sectional view of the plate portion in a state separated from the lid and is a diagram for explaining the test piece formation process. [Figure 8] Figure 8 is a cross-sectional view of the test piece. [Figure 9] Figure 9 is a cross-sectional view of the wall of the deteriorated liquid storage tank body.

Embodiments for Carrying out the Invention

[0015] Hereinafter, referring to FIGS. 1 to 9, an embodiment of a fiber-reinforced plastic (hereinafter, FRP) liquid storage tank and a method for diagnosing deterioration of the FRP liquid storage tank will be described. <Configuration of FRP Liquid Storage Tank> As shown in FIG. 1, the FRP liquid storage tank stores a chemical solution such as hydrochloric acid, and has a liquid storage tank body 10 and a manhole 20 communicating with the inside of the liquid storage tank body 10.

[0016] The liquid storage tank of this embodiment is, for example, a so-called round tank and has a cylindrical liquid storage tank body 10. Note that the liquid storage tank is not limited to a round tank, and may be a square tank having a rectangular parallelepiped liquid storage tank body 10.

[0017] The manhole 20 has a cylindrical portion 21 that protrudes outward from the liquid storage tank body 10 and a lid 30 that is provided to open and close the tip opening of the cylindrical portion 21. The tubular portion 21 has a cylindrical shape. An annular flange 22 is integrally formed at the tip of the tubular portion 21.

[0018] As shown in FIGS. 1 and 2, the flange 22 is provided with a plurality of bolt holes 23 spaced apart from one another in the circumferential direction of the flange 22. The lid 30 has a lid main body 30A and a plate portion 40 that protrudes from the inner surface of the lid main body 30A.

[0019] 2, the lid body 30A is disk-shaped. A plurality of bolt holes 31 are provided at intervals in the circumferential direction of the lid 30 on the outer periphery of the lid body 30A. As shown in FIG. 1, a bolt 61 is inserted through the bolt hole 31 of the lid 30 and the bolt hole 23 of the flange 22, and a nut 62 is screwed onto the bolt 61, thereby fastening and fixing the lid 30 to the flange 22.

[0020] 1 and 2, the plate portion 40 is, for example, a rectangular plate. A plurality of plate portions 40 are preferably provided protruding from the inner surface of the lid 30. In this embodiment, three plate portions 40 are arranged in a row at intervals in the thickness direction of the plate portions 40.

[0021] The wall portion 11 of the liquid storage tank body 10, the cylindrical portion 21 of the manhole 20, and the lid 30 (including the plate portion 40) are all made of corrosion-resistant FRP. As shown in FIG. 3, the FRP constituting the wall 11 of the liquid storage tank body 10 has a reinforcing layer 12 and a corrosion-resistant layer 13 fixed to the inner surface of the reinforcing layer 12 to form the liquid-contacting surface.

[0022] The reinforcing layer 12 has a known structure and is made of, for example, a thermosetting resin and glass fiber. The corrosion-resistant layer 13 has a known structure and is made of, for example, a thermosetting resin and glass fiber.

[0023] The thickness Tw of the wall portion 11 is, for example, 7 mm. In this case, the thickness Tw1 of the reinforcing layer 12 is, for example, 5 mm. Also, the thickness Tw2 of the corrosion-resistant layer 13 is, for example, 2 mm. As shown in FIG. 4, the FRP constituting the plate portion 40 has a reinforcing layer 43 and a corrosion-resistant layer 44 that is fixed to the entire surface of the reinforcing layer 43 and forms a liquid contact surface.

[0024] The reinforcing layer 43 is made of the same material as the reinforcing layer 12 that constitutes the wall portion 11. The corrosion-resistant layer 44 is made of the same material as the corrosion-resistant layer 13 that constitutes the wall portion 11. The thickness Tp of the plate portion 40 is greater than the thickness Tw of the wall portion 11 (Tp > Tw). The thickness Tp of the plate portion 40 is preferably at least twice the thickness Tw of the wall portion 11 of the liquid storage tank body 10. In this embodiment, the thickness Tp of the plate portion 40 is twice the thickness Tw of the wall portion 11 of the liquid storage tank body 10.

[0025] The thickness Tp of the plate portion 40 is, for example, 14 mm. In this case, the thickness Tp1 of the reinforcing layer 43 is, for example, 10 mm. Also, the thickness Tp2 of the corrosion-resistant layer 44 is, for example, 2 mm.

[0026] <Method for diagnosing deterioration of FRP liquid storage tank> As shown in FIG. 5, the method for diagnosing deterioration of an FRP liquid storage tank includes a separation step, a test piece formation step, a measurement step, and a determination step.

[0027] As shown by the two-dot chain line in FIG. 6, in the separation step, after being removed from the cylindrical portion 21 of the manhole 20 and washed, the plate portion 40 is separated from the lid body 30A of the lid 30. Here, the plate portion 40 is separated from the lid body 30A by cutting the plate portion 40 at the base end portion 45 with a tool.

[0028] As shown in Figures 7 and 8, in the test piece formation process, the test piece 50 is formed by cutting the side surface 42 of the plate portion 40 opposite the side surface 41 in the thickness direction of the plate portion 40 so that the thickness is the same as the thickness Tw of the wall portion 11 while leaving one side surface 41 in the thickness direction of the plate portion 40.

[0029] The measurement step measures the mechanical property values ​​of the test piece 50. Examples of the mechanical property values ​​of the test piece 50 include the tensile strength and bending strength of the test piece 50. In the determination step, the deterioration state of the liquid storage tank body 10 is determined based on the mechanical property values.

[0030] In this embodiment, the deterioration diagnosis of the liquid storage tank described above is repeatedly performed at time intervals, and a different plate unit 40 is used for each deterioration diagnosis. Here, the time interval is not particularly limited, but may be, for example, 5 years, 10 years, or 15 years.

[0031] <Effects of this embodiment> (1) The cover 30 of the manhole 20 has a cover body 30A and a plate portion 40 that protrudes from the inner surface of the cover body 30A. The thickness of the plate portion 40 is greater than the thickness of the wall portion 11 of the liquid storage tank body 10.

[0032] With this configuration, the test piece 50 formed as described above can be considered to have substantially the same mechanical properties as the wall 11 of the liquid-storage-tank body 10 after deterioration. Furthermore, the mechanical properties of the wall 11 after deterioration change depending on the degree of deterioration of the wall 11. For example, the tensile strength and bending strength of the wall 11 decrease as the degree of deterioration of the wall 11 increases. For these reasons, by measuring the mechanical properties of the test piece 50 and determining the deterioration state of the liquid-storage-tank body 10 based on the measured mechanical properties, it is possible to diagnose deterioration of the liquid-storage tank without cutting out a portion of the liquid-storage-tank body 10.

[0033] Furthermore, since the plate portion 40 serving as the test piece 50 for deterioration diagnosis is provided on the cover 30 of the manhole 20, there is no need to change the configuration of the liquid storage tank main body 10, unlike when the plate portion serving as the test piece is separately placed inside the liquid storage tank main body 10.

[0034] Therefore, deterioration of the liquid storage tank can be diagnosed easily and accurately. (2) Since the lid 30 has multiple plate portions 40, when repeatedly diagnosing deterioration of the liquid storage tank at time intervals, for example, every few years, the multiple plate portions 40 can be used in turn as test pieces 50. Therefore, while reusing the lid 30, it is easy to repeatedly diagnosing deterioration of the liquid storage tank at time intervals.

[0035] (3) The deterioration diagnosis method for an FRP liquid storage tank includes a separation step, a test piece formation step, a measurement step, and an evaluation step. This method can achieve the same effect as (1).

[0036] (4) In the method for diagnosing deterioration of an FRP liquid storage tank, the deterioration diagnosis of the liquid storage tank is repeatedly performed at time intervals, and a different plate portion 40 is used for each deterioration diagnosis. This method can achieve the same effect as (2).

[0037] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility. The tubular portion 21 of the manhole 20 is not limited to a cylindrical shape, but may be a square tubular shape with a rectangular cross section. In this case, the lid portion 30 may be a rectangular plate.

[0038] The number of plate portions 40 provided on the lid 30 is not limited to three, but may be two or less, or may be four or more. In the above embodiment, the three plate portions 40 are arranged in a row at intervals in the thickness direction of the plate portions 40, but the arrangement of the plate portions 40 can be changed as appropriate.

[0039] The thickness Tp of the plate portion 40 may be less than twice the thickness Tw of the wall portion 11 of the liquid-storage-tank body 10. Even in this case, if the degree of deterioration of the liquid-storage tank is relatively small, it is possible to form a test piece 50 having substantially the same mechanical properties as the wall portion 11 of the liquid-storage-tank body 10 by cutting the side surface 42 of the plate portion 40. [Explanation of symbols]

[0040] 10...Liquid storage tank body 11...Wall part 12...Reinforcement layer 13...Corrosion-resistant layer 20...Manhole 21...Cylinder part 22...Flange 23...Bolt hole 30…Lid 30A... Lid body 31...Bolt hole 40...Plate section 41, 42...Side 43...Reinforcement layer 44...Corrosion-resistant layer 45...Proximal end 50...Test piece 61...Bolt 62...Nut

Claims

1. A deterioration diagnosis method for a liquid storage tank made of fiber-reinforced plastic, the liquid storage tank having a liquid storage tank body and a manhole communicating with the interior of the liquid storage tank body, comprising: the manhole has a cylindrical portion protruding outward from the liquid storage tank body and a lid provided to open and close an opening at a tip of the cylindrical portion, The lid has a lid body and a plate portion protruding from an inner surface of the lid body, the thickness of the plate portion is greater than the thickness of the wall portion of the liquid storage tank body; a separation step of separating the plate portion from the lid main body; a test piece forming step of forming a test piece by cutting a side surface of the plate portion opposite to the side surface in the thickness direction of the plate portion while leaving one side surface of the plate portion in the thickness direction so that the side surface has the same thickness as the wall portion of the liquid storage tank body; a measuring step of measuring mechanical property values ​​of the test piece; and a determination step of determining a deterioration state of the liquid storage tank body based on the mechanical property values. A method for diagnosing deterioration of fiber-reinforced plastic liquid storage tanks.

2. The lid has a plurality of the plate portions, The deterioration diagnosis of the liquid storage tank is repeatedly performed at time intervals, and a different plate part is used for each deterioration diagnosis. A deterioration diagnosis method for a liquid storage tank made of fiber reinforced plastic according to claim 1.

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