Method for diagnosing deterioration of FRP liquid storage tanks and method for evaluating repair plans for FRP liquid storage tanks

Abstract

It can accurately diagnose the deterioration state of the side panels of the liquid storage tank. [Solution] The method for diagnosing the deterioration of an FRP liquid storage tank is a method for diagnosing the deterioration state of the wall portion 30 of a rectangular liquid storage tank. The wall portion 30 is a flat plate-shaped side plate 12 having a reinforcing layer 31 and a corrosion-resistant layer 32 provided inside the reinforcing layer 31. The deterioration diagnosis method includes a measurement step of measuring the mechanical property values ​​related to the bending characteristics of the side plate 12, and the mechanical property values ​​measured in the measurement step, and the thickness (t) of the reinforcing layer 31. t ), and the thickness of the reinforcing layer 31 (t t The system includes a determination step which calculates the maximum deflection of the side plate 12 based on the design specifications of the liquid storage tank other than the above, and determines that the side plate 12 cannot withstand the maximum stress if the value obtained by dividing the maximum deflection by the actual height of the side plate 12 is equal to or greater than a preset standard value.

Description

[Technical Field]

[0001] The present invention relates to a method for diagnosing deterioration of FRP liquid storage tanks and a method for evaluating repair plans for FRP liquid storage tanks. [Background technology]

[0002] Conventionally, tanks made of fiber-reinforced plastics (FRP), which are composite materials of resin and reinforcing fibers, are well known (see, for example, Patent Document 1). Furthermore, there are storage tanks for storing chemical solutions such as strong acids like hydrochloric acid and strong bases like caustic soda. These storage tanks are usually made of corrosion-resistant FRP. Corrosion-resistant FRP has a reinforcing layer and a corrosion-resistant layer fixed to the inner surface of the reinforcing layer and forming the wetted surface. The reinforcing layer, also called the outer layer, is a layer that provides the storage tank with appropriate structural strength. The corrosion-resistant layer is a layer that provides the storage tank with appropriate corrosion resistance.

[0003] In FRP (fiber-reinforced plastic) storage tanks, corrosion due to chemicals gradually progresses over time. Therefore, deterioration assessments of storage tanks are conducted. These assessments typically involve visual inspection and hardness measurement. In the visual inspection, the inspector evaluates, for example, the degree of cracks and fissures in the walls of the storage tank, the degree of discoloration and fading, and the degree of leaching on a four-point scale. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-247468 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, FRP (fiber-reinforced plastic) storage tanks have the characteristic that liquids such as hydrochloric acid can penetrate the walls. Therefore, walls that appear to have sufficient strength may actually be weakened due to deterioration. Consequently, conventional visual inspection methods for diagnosing deterioration have the problem of varying results depending on the inspector.

[0006] Furthermore, when repairing deteriorated wall sections, the entirety of the corrosion-resistant layer and a portion of the thickness of the reinforcing layer are removed by grinding, and then the reinforcing layer and corrosion-resistant layer are sequentially bonded to the removed wall section. In this process, to ensure effective repair of the wall section, it is necessary to evaluate the appropriateness of the thickness of the reinforcing layer to be added to the removed wall section before carrying out the repair work. [Means for solving the problem]

[0007] This paper describes various methods for diagnosing the deterioration of FRP liquid storage tanks and evaluating repair plans for FRP liquid storage tanks in order to solve the above problems. [Aspect 1] A deterioration diagnosis method for diagnosing the deterioration state of the wall portion of an FRP (fiber-reinforced plastic) liquid storage tank, The aforementioned liquid storage tank is a rectangular tank, The wall portion is a flat side plate having a reinforcing layer and a corrosion-resistant layer provided inside the reinforcing layer. The aforementioned deterioration diagnosis method is: A measurement step for measuring the mechanical property values ​​related to the bending characteristics of the side plate, The system includes a determination step, which determines whether the side plate can withstand the maximum stress acting on the side plate, based on the mechanical property values ​​measured in the measurement step, the thickness of the reinforcing layer, and the design specifications of the liquid storage tank other than the thickness of the reinforcing layer. The aforementioned mechanical properties are bending strength and bending modulus. In the aforementioned determination step, Based on the bending strength, the thickness of the reinforcing layer, the stress concentration coefficient of the side plate, the hydrostatic pressure acting on the side plate, the specific gravity of the liquid stored in the reservoir, and the design pressure, the maximum height, which is the maximum height of the side plate that can withstand the maximum stress, is calculated using equation (1). Based on the maximum height, the deflection coefficient of the side plate, the hydrostatic pressure, the specific gravity of the liquid, the design pressure, the flexural modulus, and the thickness of the reinforcing layer, the maximum deflection amount, which is the amount of deflection of the side plate when the maximum stress acts on the side plate at the maximum height, is calculated using equation (2). If the value obtained by dividing the maximum deflection by the actual height of the side plate is greater than or equal to a predetermined reference value, it is determined that the side plate cannot withstand the maximum stress.

[0008]

number

[0009] Method for diagnosing deterioration of FRP (fiber-reinforced plastic) liquid storage tanks. The bending strength and bending modulus, which are mechanical properties related to the bending characteristics of the side plate, change depending on the deterioration state of the side plate.

[0010] Furthermore, assuming the deterioration state of the side panels is the same, the smaller the thickness of the reinforcing layer that makes up the side panel, the smaller the maximum stress that the side panel can withstand. According to the above method, the bending strength and bending modulus of the side plate are measured during the measurement process.

[0011] Furthermore, in the determination process, the maximum height, which is the maximum height of the side plate that can withstand the maximum stress, is calculated using equation (1) based on the bending strength, the thickness of the reinforcement layer, the stress concentration coefficient of the side plate, the hydrostatic pressure acting on the side plate, the specific gravity of the liquid stored in the reservoir, and the design pressure.

[0012] Furthermore, using the maximum height, the deflection coefficient of the side plate, the hydrostatic pressure, the specific gravity of the liquid, the design pressure, the flexural modulus, and the thickness of the reinforcement layer, the maximum deflection amount, which is the amount of deflection of the side plate when the maximum stress acts on the side plate at its maximum height, can be calculated using equation (2).

[0013] Furthermore, if the value obtained by dividing the maximum deflection by the actual height of the side plate is greater than or equal to a predetermined standard value, it is determined that the side plate cannot withstand the maximum stress. Therefore, the deterioration state of the side panels of FRP liquid storage tanks can be diagnosed with high accuracy.

[0014] [Aspect 2] A frame-shaped reinforcing member is fixed to the outer surface of the liquid storage tank, extending horizontally and surrounding the liquid storage tank. The determination step involves determining whether the side plate can withstand the maximum stress for each region of the side plate that is separated vertically by the reinforcing material. A method for diagnosing deterioration of an FRP liquid storage tank as described in Embodiment 1.

[0015] In large liquid storage tanks, reinforcement is provided by installing a frame-shaped reinforcing member that extends horizontally along the outer surface of the tank and surrounds the tank. In this case, the hydrostatic pressure acting on the side plate differs depending on the region separated vertically by the reinforcing member, so the maximum deflection of the side plate also differs depending on the region. For this reason, it is necessary to determine whether the side plate can withstand the above-mentioned maximum stress for each region.

[0016] In this respect, according to the method described above, in the judgment process, a determination is made for each region as to whether or not the side plate can withstand the maximum stress. Therefore, the deterioration state of the side plate can be accurately diagnosed for each region of the side plate.

[0017] In large liquid storage tanks, reinforcement is provided by installing a frame-shaped reinforcing member that extends horizontally along the outer surface of the tank and surrounds the tank. In this case, the hydrostatic pressure (P) acting on the side plate differs depending on the region separated vertically by the reinforcing member, so the maximum deflection (δmax) of the side plate differs depending on the region. For this reason, it is necessary to determine whether the side plate can withstand the above-mentioned maximum stress for each region.

[0018] In this respect, according to the method described above, in the judgment process, a determination is made for each region as to whether or not the side plate can withstand the maximum stress. Therefore, the deterioration state of the side plate can be accurately diagnosed for each region.

[0019] [Aspect 3] The system includes a process for obtaining a portion of the side plate as a test specimen. In the measurement step, the mechanical properties of the test piece are obtained. A method for diagnosing deterioration of an FRP liquid storage tank as described in Embodiment 1 or Embodiment 2.

[0020] This method allows the measurement process to be carried out in a location separate from where the liquid storage tank is installed. Therefore, the measurement process can be easily performed. [Aspect 4] In the determination step of the deterioration diagnosis method for an FRP liquid storage tank described in any one of embodiments 1 to 3, if it is determined that the side plate cannot withstand the maximum stress, a repair plan evaluation method is provided for evaluating the plan to add the reinforcement layer and corrosion-resistant layer to the side plate in order by adhesive, after removing the entire corrosion-resistant layer and a portion of the thickness of the reinforcing layer from the side plate, prior to the repair, When the aforementioned determination step is designated as the first determination step, The aforementioned repair plan evaluation method is: An existing thickness acquisition step to acquire the existing thickness which is the thickness of the reinforced layer after removal, A repair thickness calculation step, which calculates the repair thickness, which is the thickness of the reinforced layer after repair, based on the existing thickness and the additional thickness, which is the thickness of the reinforced layer to be added. A post-repair physical property calculation step, which calculates the mechanical property of the side plate after repair by weighted averaging based on the mechanical property of the side plate in the deteriorated state measured in the measurement step, the mechanical property of the new reinforcement layer to be added, the existing thickness, and the added thickness. The system includes a second determination step, which determines whether the side plate can withstand the maximum stress based on the mechanical properties of the side plate after repair, the thickness after repair, and the design specifications of the liquid storage tank other than the thickness after repair. The determination method in the second determination step is the same as the determination method in the first determination step. A method for evaluating repair plans for FRP (fiber-reinforced plastic) liquid storage tanks.

[0021] According to this method, the existing thickness is obtained, and the thickness after repair is calculated based on the existing thickness and the added thickness. Furthermore, the mechanical properties of the side plate after repair are calculated by weighted averaging based on the mechanical properties of the deteriorated side plate measured in the measurement process, the mechanical properties of the new reinforcing layer added by bonding, the existing thickness, and the added thickness. Then, in the second judgment process, it is determined whether or not the side plate can withstand the maximum stress, in the same manner as in the first judgment process. Therefore, the appropriateness of the added thickness, i.e., the appropriateness of the repair plan, can be evaluated before carrying out the repair work.

[0022] [Aspect 5] A frame-shaped reinforcing member is fixed to the outer surface of the liquid storage tank, extending horizontally and surrounding the liquid storage tank. The first determination step involves determining whether the side plate can withstand the maximum stress for each region of the side plate that is separated vertically by the reinforcing material. The second determination step determines whether the side plate can withstand the maximum stress for each region. A method for evaluating the repair plan of an FRP liquid storage tank as described in Embodiment 4.

[0023] According to this method, in the second determination step, similar to the first determination step, it is determined whether the side plate can withstand the maximum stress in each of the multiple regions. This allows for the evaluation of the appropriateness of the additional thickness, i.e., the appropriateness of the repair plan, for each of the multiple regions of the side plate before performing repair work. Therefore, it contributes to the effective repair of the side plate. [Effects of the Invention]

[0024] The present invention provides a method for diagnosing the deterioration of an FRP liquid storage tank, which allows for accurate diagnosis of the deterioration state of the side plates of the liquid storage tank. Furthermore, the present invention provides a method for evaluating the repair plan of an FRP liquid storage tank, which allows for evaluation of the validity of the repair plan before carrying out the repair work. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a perspective view of a liquid storage tank according to one embodiment. [Figure 2] Figure 2 is a side view of a liquid storage tank according to one embodiment. [Figure 3] Figure 3 is an enlarged cross-sectional view centered on the side plate of the liquid storage tank. [Figure 4] Figure 4 is a cross-sectional view of the side panel before repair. [Figure 5] Figure 5 is a cross-sectional view of the reinforced layer after removal. [Figure 6] Figure 6 is a cross-sectional view of the side panel after repair. [Modes for carrying out the invention]

[0026] The following describes one embodiment of a method for diagnosing deterioration of an FRP liquid storage tank and a method for evaluating a repair plan for an FRP liquid storage tank, with reference to Figures 1 to 6. <Configuration and design specifications of the liquid storage tank> As shown in Figures 1 to 3, the FRP liquid storage tank (hereinafter referred to as the liquid storage tank 10) of this embodiment is a rectangular tank. The liquid storage tank 10 of this embodiment stores hydrochloric acid with a concentration of 35%. The liquid storage tank 10 of this embodiment is installed outdoors.

[0027] The liquid stored in the storage tank 10 is not limited to hydrochloric acid; other liquids may be used. Furthermore, the storage tank 10 may be installed indoors. As shown in Figure 2, the liquid storage tank 10 has a bottom plate 11, side plates 12, and a top plate 13.

[0028] The base plate 11 is a flat plate with a rectangular shape when viewed from above. The side plate 12 is a rectangular tube with a rectangular cross-section, composed of four flat plates that are rectangular in side view. The side plate 12 is fixed to the periphery of the bottom plate 11.

[0029] The top plate 13 is a flat, rectangular plate in plan view and is fixed to the upper edge of the side plate 12. A frame-shaped reinforcing member 40 is fixed to the outer surface of the liquid storage tank 10, extending horizontally and surrounding the liquid storage tank 10. The reinforcing member 40 is made of steel.

[0030] As shown in Figure 3, the reinforcing member 40 is a rectangular tube with a square cross-section. A filler material 50 is filled between the side plate 12 and the reinforcing member 40. In addition, an FRP surface protection layer 60 is provided to cover the side plate 12 and the reinforcing member 40. This fixes the reinforcing member 40 to the side plate 12.

[0031] In this embodiment, four reinforcing members 40 are provided spaced apart from each other in the vertical direction. As shown in Figures 1 and 2, the side plate 12 has five regions 21 to 25 (from bottom to top, the first region 21, the second region 22, the third region 23, the fourth region 24, and the fifth region 25) separated vertically by a reinforcing member 40.

[0032] As shown in Figure 4, the wall portion 30 targeted for deterioration diagnosis is a side plate 12 having a reinforcing layer 31 and a corrosion-resistant layer 32 provided inside the reinforcing layer 31. The reinforcing layer 31 has a well-known configuration and is composed of, for example, a thermosetting resin and glass fibers. The corrosion-resistant layer 32 has a well-known configuration and is composed of, for example, a thermosetting resin and glass fibers.

[0033] As shown in Figure 4, the thickness (t) of the reinforcing layer 31 that constitutes the side plate 12 of this embodiment t The thickness (c) of the corrosion-resistant layer 32 that makes up the side plate 12 is 8 mm. The thickness (t) of the entire side plate 12 is 2 mm. a ) is 10 mm.

[0034] As shown in Figure 2, the longitudinal length of the liquid storage tank 10 is 2800 mm in internal dimensions. The internal length of the liquid storage tank 10 in the width direction is 1950 mm. The height of the liquid storage tank 10 is 1700 mm.

[0035] The actual capacity of the liquid storage tank 10 is 9.2 m³. 3 That is the case. The specific gravity (I) of the liquid stored in the liquid storage tank 10 is 1.20. The specific gravity of FPR is 1.65.

[0036] The design pressure is 0 Pa. That is, the liquid inside the storage tank 10 is not pressurized. The design temperature is 60°C.

[0037] Table 1 shows the actual height (h) of each region 21-25 of the side plate 12 and the hydrostatic pressure (P) acting on each region 21-25.

[0038] [Table 1]

[0039] <Method for diagnosing deterioration of liquid storage tanks> The deterioration diagnosis method is a method for diagnosing the deterioration state of the wall portion 30 (side plate 12), and comprises an acquisition step, a measurement step, and a determination step.

[0040] (Acquisition process) In the acquisition process, a portion of the side plate 12 is cut out to obtain a test specimen. Alternatively, a projection twice the thickness of the test specimen may be provided on the inner surface of the side plate 12 or a manhole (not shown), and the test specimen may be obtained from this projection. In this case, the test specimen can be obtained by processing the projection in half in the thickness direction.

[0041] (Measurement process) In the measurement process, the mechanical property value (X) related to the bending characteristics of the test specimen is measured. For the mechanical property value (X) of the side plate 12 at the time of new installation, a small sample with the same configuration as the side plate 12 is prepared, and the mechanical property value (X) is measured using this sample.

[0042] Since the liquid storage tank 10 is a rectangular tank, the mechanical property value (X) is the bending strength (σ max ) and the modulus of elasticity (E). Table 2 shows the bending strength of the side plate 12 when newly installed (σ max The values ​​shown in Table 2 are the elastic modulus (E) and the bending modulus (R). Note that the values ​​shown in Table 2 are in the gravitational unit system.

[0043] [Table 2]

[0044] Bending strength of side plate 12 (σ max The elastic modulus (E) and the flexural modulus change with temperature. Tables 3 and 4 show the bending strength (σ max The temperature correction factors (K1, K2) for the flexural modulus (E) and the flexural modulus (E) are shown for each temperature.

[0045] [Table 3]

[0046] [Table 4]

[0047] The design temperature of this embodiment is 60°C as described above. Therefore, the bending strength (σ max ) and bending elastic modulus (E) shown in Table 2 are multiplied by the temperature correction coefficients (K1, K2) at 60°C and the coefficient 0.0980665 which is for converting the weight unit system to the SI unit system, so as to calculate the bending strength (σmax) and bending elastic modulus (E) at the design temperature in the SI unit system.

[0048] Table 5 shows the bending strength (σ max ) and bending elastic modulus (E) at the design temperature at the time of new construction. Note that the values shown in Table 5 are in the SI unit system.

[0049]

Table 5

[0050] Next, Table 6 shows the bending strength (σ max ) and bending elastic modulus (E) of the side plate 12 at the time of deterioration. Note that the values shown in Table 6 are in the gravitational unit system.

[0051]

Table 6

[0052] Similar to the time of new construction, the bending strength (σ max ) and bending elastic modulus (E) at the design temperature in the SI unit system are also calculated for the time of deterioration. Table 7 shows the bending strength (σ max ) and bending elastic modulus (E) at the design temperature at the time of deterioration. Note that the values shown in Table 7 are in the SI unit system.

[0053]

Table 7

[0054] (Judgment step) In the judgment step, the mechanical property value (X) measured in the above measurement step, the thickness (t t ) of the reinforcing layer 31, and the thickness (tt Based on the design specifications of the liquid storage tank 10 other than those specified above, it is determined whether the side plate 12 can withstand the maximum stress acting on it.

[0055] Furthermore, since the corrosion-resistant layer 32 is a decay-resistant layer and does not contribute to the mechanical strength of the wall portion 30, the thickness of the wall portion 30 (side plate 12) should be used in various strength calculations, and the thickness of the reinforcing layer 31 (t t It only contains ).

[0056] In the determination process, the bending strength (σ max ) and the thickness of the reinforcement layer 31 (t t ) and the stress concentration factor (β2) of the side plate 12, the hydrostatic pressure (P) acting on the side plate 12, the specific gravity (I) of the liquid stored in the liquid storage tank 10, and the design pressure (P s Based on ) and , equation (1) gives the maximum height (h) which is the maximum height of the side plate 12 that can withstand the maximum stress. max Calculate ).

[0057] Note that equation (1) is derived from the general equation, equation (3). Furthermore, in the determination process, the maximum height (h max ) and the deflection coefficient of the side plate 12 (α2), the hydrostatic pressure (P), the specific gravity of the liquid (I), and the design pressure (P s ) and maximum height (h max ) and the bending modulus of elasticity (E), and the thickness of the reinforced layer 31 (t t ) and, therefore, by equation (2), the maximum height (h max The maximum deflection amount (δ) is the amount of deflection of the side plate 12 when the maximum stress is applied to the side plate 12. max Calculate ).

[0058] The deflection coefficient (α2) of the side plate 12 in this embodiment is 0.03. The stress concentration factor (β2) of the side plate 12 in this embodiment is 0.5. Maximum deflection (δ max The value obtained by dividing (δ) by the actual height (h) of the side plate 12. max If the value of / h) is greater than or equal to a preset reference value (1 / 200 in this embodiment), it is determined that the side plate 12 cannot withstand the maximum stress.

[0059]

number

[0060] The determination process involves determining whether the side plate 12 can withstand the maximum stress for each region 21 to 25 of the side plate 12. Table 8 shows the thickness (t) of the reinforcing layer 31 in each region 21-25 when newly constructed. t ), hydrostatic pressure (P), maximum height (h max ), maximum deflection (δ max ), actual height (h), and maximum deflection (δ max The value obtained by dividing (δ) by the actual height (h) max The / h) and the judgment result are shown.

[0061] [Table 8]

[0062] As shown in Table 8, when newly constructed, δ applies to all regions 21-25. max Since / h < 1 / 200, the result is "OK". Table 9 shows the thickness of the reinforcing layer 31 in each region 21-25 during degradation (t t ), hydrostatic pressure (P), maximum height (h max ), maximum deflection (δ max ), actual height (h), and maximum deflection (δ max The value obtained by dividing (δ) by the actual height (h) max The / h) and the judgment result are shown.

[0063] [Table 9]

[0064] As shown in Table 9, during degradation, the second region 22, the third region 23, and the fourth region 24 are δ max Since / h < 1 / 200, the result is "OK". On the other hand, for the first region 21 and the fifth region 25, δ max Since / h < 1 / 200 is not met, the result is "NG".

[0065] <Repair of liquid storage tank> If, in the aforementioned determination process, it is determined that the side plate 12 cannot withstand the maximum stress, that is, if it is determined to be "NG" in any of the determination processes of this embodiment, the side plate 12 is repaired as follows.

[0066] In other words, as shown in Figure 5, the entire corrosion-resistant layer 32 and the thickness of the reinforcing layer 31 of the wall portion 30 (side plate 12) (t t A portion of the wall is removed. Then, as shown in Figure 6, a reinforcing layer 131 and a corrosion-resistant layer 132 are sequentially added to the removed wall portion 30 by adhesive.

[0067] Furthermore, as a repair method, it is preferable to adopt the repair method for fiber-reinforced plastic liquid storage tanks developed by the present inventor, Patent No. 6527986. Specifically, first, the surface portion of the corrosion-resistant layer 32 is polished. Next, the resin of the surface portion is dissolved by applying a solvent mainly composed of dichloromethane to the surface portion. Next, the fibers of the surface portion are lifted by scratching the surface portion using a jig. Next, the residue containing dichloromethane and dissolved resin is removed by washing the surface portion. Next, a new reinforcement layer 131 and a corrosion-resistant layer 132 are bonded to the surface portion in order with an adhesive. However, the repair method is not limited to the above method.

[0068] <Method for evaluating repair plans for liquid storage tanks> The repair plan evaluation method is a method for evaluating the repair plan prior to the repair of the wall section 30 (side plate 12) described above. Hereafter, the judgment process described above will be referred to as the first judgment process.

[0069] The repair plan evaluation method comprises a step of obtaining the existing thickness, a step of calculating the thickness after repair, a step of calculating the mechanical property values ​​after repair, and a second determination step. In the process of obtaining the existing thickness, the total thickness (t) of the wall section 30 (side panel) before repair is obtained. a ) and the thickness t of the removed portion rem Based on this, the thickness of the reinforced layer 31 after removal is calculated using the following formula (4): o ) is obtained (see Figures 5 and 6). In the existing thickness acquisition process of this embodiment, the existing thickness (t) is obtained for each region 21 to 25. o ) obtain.

[0070] In the process of calculating the thickness after repair, the existing thickness (t o ) and the additional thickness (t) which is the thickness of the additional reinforcement layer 131. n Based on the above, the thickness of the reinforced layer 131 after repair, which is the thickness after repair (t), is calculated using the following formula (5). comp ) is calculated (see Figure 6). In the repair thickness calculation process of this embodiment, the repair thickness (t) is calculated for each region 21 to 25. comp Calculate ).

[0071] In the process of calculating mechanical properties after repair, the mechanical property value (Xo) of the wall portion 30 in the deteriorated state measured in the measurement process, the mechanical property value (Xn) of the new reinforced layer 131 to be added, and the existing thickness (t) are used. o ) and additional thickness (t n Based on this, the mechanical properties (X) of the repaired wall section 130 (side plate 12) are calculated using equation (6), that is, by weighted average. comp ) is calculated. In the repaired mechanical property value calculation step of this embodiment, the mechanical property value (X) of the repaired wall portion 30 (side plate 12) is calculated for each region 21 to 25. comp Calculate ).

[0072]

number

[0073] The second determination step involves determining the mechanical properties (X) of the wall section 130 (side plate 12) after repair. comp ), thickness after repair (t comp ), and thickness after repair (t compBased on the design specifications of the liquid storage tank 10 other than those specified above, it is determined whether the side plate 12 can withstand the maximum stress acting on it.

[0074] In the second determination process, the bending strength (σ max ) and the thickness after repair (t comp ) and the stress concentration factor (β2) of the side plate 12, the hydrostatic pressure (P) acting on the side plate 12, the specific gravity (I) of the liquid stored in the liquid storage tank 10, and the design pressure (P s Based on ) and , equation (1) gives the maximum height (h) which is the maximum height of the side plate 12 that can withstand the maximum stress. max Calculate ).

[0075] Furthermore, in the second determination step, the maximum height (h max ) and the deflection coefficient of the side plate 12 (α2), the hydrostatic pressure (P), the specific gravity of the liquid (I), and the design pressure (P s ) and maximum height (h max ) and the bending modulus of elasticity (E), and the thickness after repair (t comp ) and, therefore, by equation (2), the maximum height (h max The maximum deflection amount (δ) is the amount of deflection of the side plate 12 when the maximum stress is applied to the side plate 12. max Calculate ).

[0076] Maximum deflection (δ max The value obtained by dividing (δ) by the actual height (h) of the side plate 12. max If the value of / h) is greater than or equal to a preset reference value (1 / 200 in this embodiment), it is determined that the side plate 12 cannot withstand the maximum stress. In other words, the determination method in the second determination step is the same as the determination method in the first determination step.

[0077] (Repair plan for liquid storage tank) Table 10 shows the thickness of the reinforcement layer 31 before repair (t t ), thickness of corrosion-resistant layer 32 (c), overall thickness of side plate 12 (t a ), thickness (t) of the wall portion 30 to be removed rem ), existing thickness (t o ), additional thickness due to repair (t n ), thickness after repair (t comp), the thickness of the corrosion-resistant layer 132 (c), and the overall thickness of the side plate 12 after repair (t a An example of this is shown for each region 21-25. In this embodiment, regardless of regions 21-25, the thickness of the reinforcing layer 31 (t t ), thickness of corrosion-resistant layer 32 (c), thickness of wall portion 30 to be removed (t rem ), additional thickness (t n ) and other factors are kept constant.

[0078] [Table 10]

[0079] Table 11 shows the bending strength (σ) of the new reinforced layer 131. max The values ​​shown in Table 11 are the elastic modulus (E) and the bending modulus (E). Note that the values ​​shown in Table 11 are in SI units.

[0080] [Table 11]

[0081] Table 12 shows the bending strength (σ) of the side plate 12 after repair. max The values ​​shown in Table 12 are in SI units. The bending strength (σmax) and bending modulus (E) of the side plate 12 after repair are calculated using the above formula (6).

[0082] [Table 12]

[0083] Table 13 shows the bending strength at the design temperature after repair (σ max The values ​​shown in Table 13 are the elastic modulus (E) and the bending modulus (R). Note that the values ​​shown in Table 13 are in SI units.

[0084] [Table 13]

[0085] Table 14 shows the thickness (t t ) of the reinforcement layer 31 in each of the repaired regions 21 to 25, the head pressure (P), the maximum height (h max ), the maximum deflection amount (δ max ), the actual height (h), and the value (δ max ) obtained by dividing the maximum deflection amount (δ max ) by the actual height (h) (δ

[0086]

Table 14

[0087] As shown in Table 14, after repair, for any of the regions 21 to 25, δ max / h < 1 / 200, so the judgment result is "OK". In the above example, the judgment result is that the repair plan is reasonable. However, depending on the thickness (t rem ) of the wall part 30 (reinforcement layer 31) to be removed, the additional thickness (t n ), or the type of FRP material constituting the reinforcement layer 131 added by repair, etc., the judgment result may be "NG". Therefore, it is preferable to search for the optimum values of various thicknesses by repeating the second judgment step while appropriately changing various thicknesses.

[0088] <The effects of this embodiment> (1) The bending strength (σ max ) and the bending elastic modulus (E), which are mechanical property values related to the bending characteristics of the side plate 12, change according to the deterioration state of the side plate 12.

[0089] Also, if the deterioration state of the side plate 12 is the same, the smaller the thickness (t t ) of the reinforcement layer 31 constituting the side plate 12, the smaller the maximum stress that the side plate 12 can withstand. According to the above method, the bending strength (σ max ) and the bending elastic modulus (E) of the side plate 12 are measured in the measurement step.

[0090] Also, in the judgment step, the bending strength (σmax ) and the thickness (t t ) of the reinforcing layer 31, the stress concentration coefficient (β2) of the side plate 12, the water head pressure (P) acting on the side plate 12, the liquid specific gravity (I) of the liquid stored in the liquid storage tank 10, and the design pressure (P s ), based on which, according to Equation (1), the maximum height (h max ), which is the maximum value of the height of the side plate 12 that can withstand the maximum stress, is calculated.

[0091] Also, based on the maximum height (h max ), the deflection coefficient (α2) of the side plate 12, the water head pressure (P), the liquid specific gravity (I), the design pressure (P s ), the maximum height (h max ), the bending elastic modulus (E), and the thickness (t t ) of the reinforcing layer 31, according to Equation (2), the maximum deflection amount (δ max ), which is the deflection amount of the side plate 12 when the maximum stress acts on the side plate 12 with the maximum height (h max ), is calculated.

[0092] And when the value (δ max / h) obtained by dividing the maximum deflection amount (δ max ) by the actual height (h) of the side plate 12 is greater than or equal to a preset reference value, it is determined that the side plate 12 cannot withstand the maximum stress.

[0093] Therefore, the deterioration state of the side plate 12 of the FRP liquid storage tank 10 can be accurately diagnosed. (2) In the liquid storage tank 10 with a large height dimension, the liquid storage tank 10 is reinforced by providing a frame-shaped reinforcing member 40 that extends along the horizontal direction and surrounds the liquid storage tank 10 on the outer peripheral surface of the liquid storage tank 10. In this case, since the water head pressure (P) acting on the regions 21 to 25 of the side plate 12 separated vertically by the reinforcing member 40 is different, the maximum deflection amount (δ max ) of the side plate 12 is different for the regions 21 to 25. For this reason, it is necessary to determine whether the side plate 12 can withstand the above maximum stress for each of the regions 21 to 25.

[0094] In this regard, according to the method described above, in the determination process, a determination is made for each region 21 to 25 as to whether or not the side plate 12 can withstand the maximum stress. Therefore, the deterioration state of the side plate 12 can be accurately diagnosed for each region 21 to 25.

[0095] (3) In the acquisition process, a portion of the wall 30 is acquired as a test piece, and in the measurement process, the mechanical properties of the test piece are acquired. This makes it possible to perform the measurement process in a location other than where the liquid storage tank 10 is installed. Thus, the measurement process can be easily carried out.

[0096] (4) The repair plan evaluation method includes a process for obtaining the existing thickness, a process for calculating the thickness after repair, a process for calculating the physical properties after repair, and a process for determining the mechanical properties (X) of the wall portion 130 after repair. n ), thickness after repair (t comp ), thickness after repair (t comp The system includes a second determination step, which determines whether the side plate 12 can withstand the maximum stress based on the design specifications of the liquid storage tank 10 other than those specified above.

[0097] According to this method, the existing thickness (t o ) is obtained, along with the existing thickness (t o ) and additional thickness (t n Based on this, the thickness after repair (t comp The bending strength (σ) of the side plate 12 in the deteriorated state measured during the measurement process is calculated. max ) and the bending modulus of elasticity (E), and the bending strength (σ) of the side plate 12 of the new reinforcing layer 131 added by bonding. max ) and the bending modulus of elasticity (E), and the existing thickness (t o ) and additional thickness (t n Based on this, the bending strength (σ) of the repaired side plate 12 is calculated by weighted average. max The bending modulus (E) and the bending modulus (F) are calculated. Then, in the second determination step, the maximum deflection amount (δ) with respect to the height (h) of the side plate 12 is calculated in the same manner as in the first determination step. max Based on the ratio of ), it is determined whether the side plate 12 can withstand the maximum stress. Therefore, before carrying out the repair work, the additional thickness (tn The appropriateness of the repair plan can be evaluated.

[0098] (5) The second determination step determines whether the side plate 12 can withstand the maximum stress for each region 21 to 25. According to this method, in the second determination step, in the same manner as in the first determination step, it is determined whether the side plate 12 can withstand the above maximum stress for each of the multiple regions 21 to 25. As a result, before performing repair work, an additional thickness (t) is added to each of the regions 21 to 25 of the side plate 12. n The validity of the repair plan can be evaluated. Therefore, it contributes to the effective repair of the side panel 12.

[0099] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0100] In the above embodiment, regardless of the region 21-25 of the side plate 12, the thickness of the reinforcing layer 31 (t t ) is kept constant, but the thickness of the reinforced layer 31 (t) varies depending on the region 21-25. t ) can also be made different.

[0101] For example, in a liquid storage tank 10 with a small height dimension, the reinforcing material 40 can be omitted. In this case, the side plate 12 can be made from a single region. [Explanation of Symbols]

[0102] 10...Liquid storage tank 11...Bottom plate 12... Side panel 13... Tabletop 21…First area 22…Second area 23…Third area 24...Fourth area 25…5th area 30...Wall part 31…Reinforcement layer 32...Corrosion-resistant layer 40…Reinforcement material 50...Filling material 60…Surface protective layer

Claims

1. A deterioration diagnosis method for diagnosing the deterioration state of the wall portion of an FRP (fiber-reinforced plastic) liquid storage tank, The aforementioned liquid storage tank is a rectangular tank, The wall portion is a flat side plate having a reinforcing layer and a corrosion-resistant layer provided inside the reinforcing layer. The aforementioned deterioration diagnosis method is: A measurement step for measuring the mechanical property values ​​related to the bending characteristics of the side plate, The system includes a determination step, which determines whether the side plate can withstand the maximum stress acting on the side plate, based on the mechanical property values ​​measured in the measurement step, the thickness of the reinforcing layer, and the design specifications of the liquid storage tank other than the thickness of the reinforcing layer. The aforementioned mechanical properties are bending strength and bending modulus. In the aforementioned determination step, Based on the bending strength, the thickness of the reinforcing layer, the stress concentration coefficient of the side plate, the hydrostatic pressure acting on the side plate, the specific gravity of the liquid stored in the reservoir, and the design pressure, the maximum height, which is the maximum height of the side plate that can withstand the maximum stress, is calculated using equation (1). Based on the maximum height, the deflection coefficient of the side plate, the hydrostatic pressure, the specific gravity of the liquid, the design pressure, the flexural modulus, and the thickness of the reinforcing layer, the maximum deflection amount, which is the amount of deflection of the side plate when the maximum stress acts on the side plate at the maximum height, is calculated using equation (2). If the value obtained by dividing the maximum deflection by the actual height of the side plate is greater than or equal to a predetermined reference value, it is determined that the side plate cannot withstand the maximum stress. [Math 1] Method for diagnosing deterioration of FRP (fiber-reinforced plastic) liquid storage tanks.

2. A frame-shaped reinforcing member is fixed to the outer surface of the liquid storage tank, extending horizontally and surrounding the liquid storage tank. The determination step involves determining whether the side plate can withstand the maximum stress for each region of the side plate that is separated vertically by the reinforcing material. A method for diagnosing deterioration of an FRP liquid storage tank according to claim 1.

3. The system includes a process for obtaining a portion of the side plate as a test specimen. In the measurement step, the mechanical properties of the test piece are obtained. A method for diagnosing deterioration of an FRP liquid storage tank according to claim 1.

4. A repair plan evaluation method for evaluating a repair plan in the determination step of a deterioration diagnosis method for an FRP liquid storage tank according to any one of claims 1 to 3, wherein, in the determination step, it is determined that the side plate cannot withstand the maximum stress, the plan to add the reinforcement layer and corrosion-resistant layer sequentially to the side plate after removing the entire corrosion-resistant layer and a portion of the thickness of the reinforcing layer is evaluated, When the aforementioned determination step is designated as the first determination step, The aforementioned repair plan evaluation method is: An existing thickness acquisition step to acquire the existing thickness which is the thickness of the reinforced layer after removal, A repair thickness calculation step, which calculates the repair thickness, which is the thickness of the reinforced layer after repair, based on the existing thickness and the additional thickness, which is the thickness of the reinforced layer to be added. A post-repair physical property calculation step, which calculates the mechanical property of the side plate after repair by weighted averaging based on the mechanical property of the side plate in the deteriorated state measured in the measurement step, the mechanical property of the new reinforcement layer to be added, the existing thickness, and the added thickness. The system includes a second determination step, which determines whether the side plate can withstand the maximum stress based on the mechanical properties of the side plate after repair, the thickness after repair, and the design specifications of the liquid storage tank other than the thickness after repair. The determination method in the second determination step is the same as the determination method in the first determination step. A method for evaluating repair plans for FRP (fiber-reinforced plastic) liquid storage tanks.

5. A frame-shaped reinforcing member is fixed to the outer surface of the liquid storage tank, extending horizontally and surrounding the liquid storage tank. The first determination step involves determining whether the side plate can withstand the maximum stress for each region of the side plate that is separated vertically by the reinforcing material. The second determination step determines whether the side plate can withstand the maximum stress for each region. A method for evaluating a repair plan for an FRP liquid storage tank according to claim 4.

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