Deterioration diagnosis method for FRP liquid storage tanks and repair plan evaluation method for FRP liquid storage tanks

Abstract

The deterioration state of the wall of the corrosion-resistant equipment can be diagnosed with high accuracy. [Solution] The deterioration diagnosis method for FRP corrosion-resistant equipment is a method for diagnosing the deterioration state of a wall portion 30 of the FRP corrosion-resistant equipment. The wall portion 30 has 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 mechanical property values ​​of the wall portion 30, and a step of comparing the mechanical property values ​​measured in the measurement step with the thickness (t t ), and the thickness (t t and a determining step of determining whether the wall portion 30 can withstand the force acting on the wall portion 30 in the usage environment based on the design specification values ​​of the corrosion-resistant equipment other than the above.

Description

[Technical Field]

[0001] The present invention is made of FRP liquid storage tank Deterioration diagnosis method and FRP liquid storage tank This relates to a method for evaluating repair plans. [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 like hydrochloric acid and strong bases like 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.

[0003] In FRP liquid storage tanks, corrosion caused by chemicals progresses gradually over time. Therefore, deterioration diagnosis of the liquid storage tank is carried out. Deterioration diagnosis is generally carried out by visual inspection and hardness measurement. In the visual inspection, the inspector evaluates, for example, the degree of cracks and fissures in the wall that makes up the liquid storage tank, the degree of discoloration and decolorization, the degree of elution, etc. on a four-point scale. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-247468 Summary of the Invention [Problem to be solved by the invention]

[0005] However, FRP liquid storage tanks have the characteristic that liquids such as hydrochloric acid penetrate their walls. As a result, walls that appear to be sufficiently strong may actually be weakened due to deterioration. For this reason, the conventional deterioration diagnosis method using visual inspection has the problem that the results of deterioration diagnosis vary depending on the inspector.

[0006] Furthermore, when repairing a deteriorated wall, the entire corrosion-resistant layer and a portion of the thickness of the reinforcing layer are removed by grinding, and then the reinforcing layer and the corrosion-resistant layer are adhered to the removed wall in that order. In this case, in order to effectively repair the wall, it is necessary to evaluate the appropriateness of the thickness of the reinforcing layer to be added to the removed wall before the repair work is carried out. [Means for solving the problem]

[0008] FRP products to solve the above problems liquid storage tank Deterioration diagnosis method and FRP liquid storage tank Each aspect of the repair plan evaluation method is described below. [Aspect 1] Made of FRP liquid storage tank A method for diagnosing the deterioration state of a wall portion of a the liquid storage tank is a cylindrical tank, The wall portion is It has a cylindrical side panel, A reinforcement layer and a corrosion-resistant layer provided inside the reinforcement layer, The aforementioned Side panel a measuring step of measuring mechanical property values ​​of the The mechanical property values ​​measured in the measuring step, the thickness of the reinforcing layer, and the values ​​other than the thickness liquid storage tank Based on the design specifications, under the operating environment Side panel The force acting on Side panel and a determining step of determining whether the 、 The mechanical property value is the axial tensile elastic modulus (Et L ) and In the determination step, The inner diameter (D) of the side plate, the thickness (t t ), design vertical seismic coefficient (K MW Based on the overturning moment (M1') acting on the liquid storage tank when it is full due to the earthquake load of ), the stress (σ CH ) is calculated, The inner diameter (D) of the side plate, the thickness (t t ), the weight of the side plate and the roof of the liquid storage tank (W V ) based on (Equation 12), the weight of the side plate and the roof of the liquid storage tank (W V ) generated in the side plate (σ CO ) is calculated, The design vertical seismic coefficient (K MW ) and the weight of the side plate and the roof of the liquid storage tank (W V ) generated in the side plate (σ CO ) based on (Equation 13), the design vertical seismic coefficient (K MW The stress (σ CV ) is calculated, The thickness (t t ), the design internal pressure of the liquid storage tank (P), and the internal diameter of the side plate (D), the stress (σ P ) is calculated, The stress (σ CH ), the stress (σ CV ), the stress (σ CO ), the stress (σ P ) and (Equation 10) is used to calculate the axial buckling stress (σ c1 ) is calculated, The inner diameter (D) of the side plate, the axial tensile modulus of elasticity (Et L ), and the thickness (t t ) and (Equation 15) is used to calculate the allowable buckling stress (σ K ) is calculated, The axial buckling stress (σ c1 ) is the allowable buckling stress (σ K ) or less, the design vertical seismic coefficient (K MW ) seismic load, while determining that the side plate can withstand the axial buckling stress (σ c1 ) is the allowable buckling stress (σ K ), the design vertical seismic coefficient (K MW ) and it is determined that the side panel cannot withstand the earthquake load. Ru,

number

[0009] Tensile strength and tensile modulus liquid storage tank The mechanical properties of the wall vary depending on the state of deterioration of the wall. Furthermore, if the deterioration state of the wall portion is the same, the thinner the reinforcing layer, the less the wall portion can withstand the force acting on the wall portion under the usage environment.

[0010] According to the above method, in the measuring step Side plate of a cylindrical liquid storage tank Then, in the determination step, the mechanical property values, the thickness of the reinforcing layer, and the thickness other than the thickness are measured. liquid storage tank Based on the design specifications, under the operating environment Side panel The force acting on Side panel It is determined whether or not the liquid storage tank of Side panel The deterioration state of the vehicle can be diagnosed with high accuracy. [Aspect 2] The mechanical property value is the long-term axial tensile stress (ft L ) and In the determination step, The stress (σ CH ), the stress (σ CO ), the stress (σ P ) and (Equation 16) based on the axial tensile stress (σ t1 ) is calculated, The axial tensile stress (σ t1 ) is the long-term axial tensile stress (ft L ) multiplied by 1.5. L ) or less, the side plate is MW ) earthquake load, while the axial tensile stress (σ t1 ) is the short-term axial tensile stress (1.5 ft L ) is greater than the design vertical seismic coefficient (K MW ) earthquake load,

number

number

[0011] [Aspect 4 ] before The side panel is made up of a plurality of step areas each having a predetermined height, the determining step determines, for each of the plurality of stages, whether or not the side plate can withstand a force acting on the side plate under a usage environment. Aspect 1 any one of aspects 3 to 3 FRP material described in liquid storage tank Deterioration diagnosis method.

[0012] The side plate is made up of multiple areas each having a predetermined height. The force acting on the side plate varies for each of the multiple areas. liquid storage tank In some cases, the thickness of the reinforcing layer constituting the side plate varies among a plurality of regions.

[0013] According to the above method, in the assessment step, it is assessed for each of the multiple regions whether the side panel can withstand the force acting on the side panel in the usage environment, thereby enabling accurate assessment of the deterioration state for each of the multiple regions of the side panel.

[0014] [Aspect 5 ] The aforementioned Side panel an obtaining step of obtaining a part of the sample as a test piece; In the measuring step, the mechanical property values ​​of the test piece are acquired. Aspect 1 from Aspects One of 4 FRP material described in liquid storage tank Deterioration diagnosis method.

[0015] According to this method, liquid storage tank Therefore, the measurement process can be easily performed at a location other than the site where the device is installed. [Aspect 6 ] Aspect 1 to Aspect 5 FRP material described in any one of liquid storage tank In the determination step of the deterioration diagnosis method Side panel However, under the operating environment, Side panel If it is determined that the product cannot withstand the force acting on it, Side panel After removing the entire corrosion-resistant layer and a part of the thickness of the reinforcing layer, Side panel 1. A method for evaluating a plan for adding a reinforcing layer and a corrosion-resistant layer to a concrete structure by adhesive bonding in sequence prior to the repair, comprising: When the determination step is a first determination step, An existing thickness acquisition step of acquiring an existing thickness, which is the thickness of the reinforced layer after the removal; and a post-repair thickness calculation step of calculating a post-repair thickness, which is the thickness of the reinforced layer after the repair, based on the existing thickness and the added thickness, which is the thickness of the reinforced layer to be added. The deterioration state measured in the measuring step Side panel The mechanical property values ​​of the newly added reinforcing layer, the existing thickness, and the added thickness are used to calculate the weighted average of the mechanical property values ​​of the newly added reinforcing layer, the existing thickness, and the added thickness. Side panel a post-repair mechanical property value calculation step of calculating the mechanical property value; The after-repair Side panel The mechanical property values, the thickness after repair, and the other values ​​than the thickness after repair liquid storage tank Based on the design specifications of Side panel However, under the operating environment, Side panel and a second determination step of determining whether the device can withstand the force acting on the device. 、 The determination method in the second determination step is the same as the determination method in the first determination step. Ru, FRP liquid storage tank Repair plan evaluation method.

[0016] According to this method, the existing thickness is acquired, and the thickness after repair is calculated based on the existing thickness and the additional thickness. Side panel The mechanical properties of the new reinforced layer added by bonding, the existing thickness, and the added thickness are used to calculate the weighted average of the mechanical properties of the new reinforced layer added by bonding, the existing thickness, and the added thickness. Side panel The mechanical properties of the concrete are calculated. In addition, the mechanical properties, thickness after repair, and other properties other than the thickness after repair are calculated. liquid storage tank Based on the design specifications, Side panel However, under the operating environment Side panel Therefore, before carrying out repair work, it is possible to evaluate the appropriateness of the additional thickness, i.e., the appropriateness of the repair plan.

[0017] [Aspect 7 ] before The side panel is made up of a plurality of step areas each having a predetermined height, the first determination step determines, for each of the plurality of step regions, whether the side plate can withstand a force acting on the side plate in a usage environment; The aforementioned The existing thickness acquisition step acquires the existing thickness for each of the plurality of step regions, The aforementioned The post-repair thickness calculation step calculates the post-repair thickness for each of the plurality of step regions, The aforementioned The post-repair mechanical property value calculation step calculates the post-repair mechanical property value for each of the plurality of stages. side wall Calculating the mechanical property values ​​of The second determination step is to determine the condition of the repaired portion of each of the plurality of step regions. side wall The mechanical property values, the thickness after repair, and the other values ​​than the thickness after repair liquid storage tank Based on the design specifications, under the operating environment side wall Determine whether the device can withstand the force acting on it. Aspects 6 FRP material described in liquid storage tank Repair plan evaluation method.

[0018] According to this method, in the second determination step, it is determined for each of the multiple regions whether the side panel can withstand the force acting on the side panel in the usage environment. This makes it possible to evaluate the appropriateness of the additional thickness, i.e., the appropriateness of the repair plan, for each of the multiple regions of the side panel before carrying out repair work. Therefore, Side panel This contributes to the effective repair of [Effects of the Invention]

[0019] The FRP material of this invention liquid storage tank According to the deterioration diagnosis method, liquid storage tank of Side panel Furthermore, the deterioration state of the FRP material of the present invention can be accurately diagnosed. liquid storage tank According to the repair plan evaluation method, the validity of the repair plan can be evaluated before the repair work is carried out. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a side view of a liquid storage tank according to one embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the reservoir of FIG. [Figure 3] FIG. 3 is a cross-sectional view of the liquid storage tank of FIG. 1, focusing on the upper part thereof. [Figure 4] FIG. 4 is a cross-sectional view showing the layer structure of the wall portion before repair. [Figure 5] FIG. 5 is a cross-sectional view of the reinforcing layer after removal. [Figure 6] FIG. 6 is a cross-sectional view showing the layer structure of the wall portion after repair. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of a method for diagnosing deterioration of corrosion-resistant FRP equipment and a method for evaluating a repair plan for corrosion-resistant FRP equipment will be described below with reference to Figures 1 to 6. In this embodiment, an FRP liquid storage tank will be described as an example of the corrosion-resistant FRP equipment.

[0022] <Configuration and design specifications of the liquid storage tank> As shown in FIGS. 1 to 3, the FRP liquid storage tank of this embodiment (hereinafter referred to as liquid storage tank 10) is a cylindrical tank. Liquid storage tank 10 of this embodiment stores hydrochloric acid with a concentration of 35%, but the liquid stored is not limited to hydrochloric acid and may be other liquids. Furthermore, although liquid storage tank 10 of this embodiment is installed outdoors, liquid storage tank 10 may also be installed indoors.

[0023] The side plate 12 is cylindrical and has a central axis extending in the vertical direction. The liquid storage tank 10 has a bottom plate 11 that closes the lower opening of the side plate 12, a top plate 14 that closes the upper opening of the side plate 12, and accessories 15 such as handrails.

[0024] The bottom plate 11 of this embodiment has a flat plate shape. The shape of the top plate 14 in this embodiment is a 10% dished end plate. Hereinafter, the bottom plate 11, the side plates 12, and the top plate 14 may be collectively referred to as a wall portion 30. The top plate 14 and the accessories 15 may be collectively referred to as a roof portion 13.

[0025] As shown in FIG. 2, the side plate 12 is made up of a plurality of stages (five stages in this embodiment) of regions 21 to 25, each having a predetermined height. 4, the wall portion 30 has a reinforcing layer 31 and a corrosion-resistant layer 32 provided inside the reinforcing layer 31. The reinforcing layer 31 has a well-known structure, for example, made of a thermosetting resin and glass fiber. The corrosion-resistant layer 32 has a well-known structure, for example, made of a thermosetting resin and glass fiber.

[0026] As shown in FIG. 2, the height (dt) of the side plate 12 of the liquid storage tank 10 is 6450 (mm). The spatial height (de), which is the height from the highest liquid level in the liquid storage tank 10 to the upper end of the side plate 12, is 200 (mm).

[0027] As shown in FIG. 3, the inner diameter (D) of the side plate 12 of the liquid storage tank 10 is 3200 (mm). The actual capacity of the liquid storage tank 10 is 51.84 (m 3 ) Liquid specific gravity (ρ w ) is 1.2.

[0028] FPR specific gravity (ρ m ) is 1.65. The design pressure (P) is 0 (kPa) for both positive and negative pressures. The design temperature (T) is room temperature.

[0029] The fixed load of the bottom plate 11 is 1,716 (N). The fixed load of the side plate 12 is 11,376 (N). The fixed load of the top plate 14 is 1,765 (N).

[0030] The fixed load of the tabletop attachment is 3,923 (N). The fixed load of the side panel attachment is 2,452 (N). The total fixed load of the bottom plate 11, side plates 12, top plate 14, top plate attachments, and side plate attachments, that is, the fixed load of the entire liquid storage tank 10, is 21,231 (N).

[0031] The snow load (ws) is 4,732 (N). The snow load (ws) is calculated using (Formula 1). In (Formula 1), "sp" is the standard snow load, which is 588 (Pa). Also, "r" is 1 / 2 of the inner diameter (D), which is 1600 (mm).

[0032]

number

[0033] Table 1 shows the height (y) from the lower end of each of the regions 21-25 of the side plate 12 to the upper end of the side plate, the total pressure (P+p) acting on each of the regions 21-25 of the side plate 12, the hydrostatic pressure (p), and the liquid weight (wo) in each of the regions 21-25 of the side plate 12. The total pressure (P+p) is the sum of the design pressure (P) and the hydrostatic pressure (p). In this embodiment, since the design pressure (P) is 0 (kPa) as described above, the total pressure (P+p) is equal to the hydrostatic pressure (p).

[0034] [Table 1]

[0035] Table 2 shows the height (y) from the lower end of each region 21 to 25 of the side panel 12 to the upper end of the side panel, and the thickness (t t ), the thickness (c) of the corrosion-resistant layer 32, the total thickness (ta ), and weight w1 (N).

[0036] [Table 2]

[0037] As shown in Figure 4, the total thickness (t a ) is the thickness (t t ) and the thickness (c) of the corrosion-resistant layer 32. In this embodiment, the total pressure (P+p) increases in the lower regions 21 to 25, so the thickness (t t ) is set large.

[0038] <Deterioration diagnosis method for liquid storage tanks> The deterioration diagnosis method is a method for diagnosing the deterioration state of the wall portion 30, and includes an acquisition step, a measurement step, and a determination step.

[0039] (Test piece acquisition process) In the test piece obtaining step, a part of the wall portion 30 is cut out to obtain a test piece. (Measurement process) In the measurement step, the mechanical property value (X) of the test piece is measured. Note that, for the mechanical property value of the wall portion 30 at the time of new construction, a small sample having the same configuration as the wall portion 30 is prepared, and the mechanical property value (X) is measured using the sample.

[0040] Since the liquid storage tank 10 of this embodiment is a cylindrical tank, the allowable tensile stress (ft) and the tensile modulus of elasticity (Et) are used as the mechanical property values ​​(X). Table 3 shows the allowable tensile stress (ft) and tensile modulus of elasticity (Et) for each of the bottom plate 11, top plate 14, side plate 12 (axial direction), and side plate 12 (circumferential direction) at the time of new construction.

[0041] [Table 3]

[0042] Table 4 shows the allowable tensile stress (ft) and the tensile modulus of elasticity (Et) of each of the bottom plate 11, the top plate 14, the side plate 12 (axial direction), and the side plate 12 (circumferential direction) when deteriorated.

[0043] [Table 4]

[0044] Hereinafter, the allowable tensile stress (ft) may be referred to as the long-term allowable tensile stress (ft). The liquid storage tank 10 has a structure in which strip-shaped mats (not shown) containing reinforcing fibers are attached via an adhesive so as to extend in the circumferential direction and are layered in the radial direction. As described above, the thickness of the reinforcing layer 31 is made different by varying the number of mats layered in each of the regions 21 to 25 of the side plate 12. Therefore, the allowable tensile stress (ft) of the side plate 12 differs between the axial direction and the circumferential direction. Hereinafter, the allowable tensile stress in the axial direction will be referred to as the axial tensile allowable stress (ft L ) and the allowable tensile stress in the circumferential direction is set to the allowable tensile stress in the circumferential direction (ft C )

[0045] Similarly, the tensile elastic modulus (Et) of the side plate 12 differs between the axial direction and the circumferential direction. Therefore, the axial tensile elastic modulus is defined as the axial tensile elastic modulus (Et L ) and the circumferential tensile modulus of elasticity is the circumferential tensile modulus of elasticity (Et C )

[0046] (Judgment process) The determination step is performed based on the mechanical property value (X) measured in the measurement step, the thickness (t t ), and the thickness of the reinforcing layer 31 (t t ) is used to determine whether the wall 30 can withstand the force acting on the wall 30 in the usage environment. The determination step also determines, for each of the multiple stages of regions 21 to 25, whether the side plate 12 can withstand the force acting on the side plate 12 in the usage environment.

[0047] The corrosion-resistant layer 32 is a corrosion barrier and does not contribute to the mechanical strength of the wall 30. Therefore, the thickness of the wall 30 is calculated by subtracting the thickness of the reinforcing layer 31 (t t ) only. (1. Diagnosis of deterioration of the tabletop) (1-1. Diagnosis of whether the tabletop can withstand internal pressure) The minimum thickness (t min ) is calculated using (Equation 2) based on the long-term tensile allowable stress (ft) of the top plate 14, the design pressure (P), the inner radius (R) of the center of the top plate 14, the head plate coefficient (M), and the thickness (c) of the corrosion-resistant layer 32.

[0048] The head coefficient (M) is calculated based on the inner radius (ro) of the corners of the top plate 14 and the inner radius (R) of the center of the top plate 14 using (Equation 3).

[0049]

number

[0050] In the determination step, the total thickness (t a ) is the minimum thickness (t min ), it is determined that the top plate 14 can withstand the internal pressure. The total thickness of the top plate 14 at the time of installation (t a ) is 9 (mm) (see Table 2).

[0051] In this embodiment, the design pressure (P) is "0" as described above. Therefore, whether it is a new installation or a deteriorated installation, the minimum thickness (t min ) is "2 (mm)". Therefore, the thickness of the top plate 14 (t a ) is the minimum thickness (t min ), it is determined that the top plate 14 can withstand the internal pressure.

[0052] (1-2. Check whether the tabletop can withstand external pressure such as snow accumulation) The external pressure buckling strength (Pcr) of the top plate 14 is determined by the outer radius (Ro) of the top plate 14, the tensile modulus of elasticity (Et), and the thickness (t t ), and the safety factor (S), it is calculated using (Equation 4).

[0053]

number

[0054] Here, in the determination step, if the external pressure buckling strength (Pcr) of the top plate 14 is greater than the design external pressure (Po), it is determined that the top plate 14 can withstand the external pressure. The thickness (t t ) is 7 (mm) (see Table 2).

[0055] The outer radius (Ro) of the top plate 14 is 3,209 (mm), and the tensile modulus of elasticity (Et) at the time of installation is 12,480 (N / mm 2 ), and the safety factor (S) is 2.5. In addition, the design extraneous pressure (Po) is 0.0012 (Mpa). Therefore, the external pressure buckling strength (Pcr) of the top plate 14 at the time of new construction is 0.00855 (MPa), which is greater than the design extraneous pressure (Po), and it is therefore determined that the top plate 14 can withstand the external pressure.

[0056] On the other hand, the tensile modulus of elasticity (Et) after deterioration is 6,500 (N / mm 2 ) Therefore, the external pressure buckling strength (Pcr) of the top plate 14 in the deteriorated state is 0.00445 (MPa), which is greater than the external design pressure (Po), and therefore it is determined that the top plate 14 can withstand the external pressure.

[0057] (2. Diagnosis of deterioration of side panels) (2-1. Minimum thickness required for side panels) (2-1-1. Diagnosis of whether the side panels can withstand internal pressure) The minimum axial thickness (t L) is the allowable axial tensile stress (ft L ), the maximum operating pressure (Pi) in each of the regions 21 to 25, the inner diameter (D) of the liquid storage tank 10, and the thickness (c) of the corrosion-resistant layer 32 in each of the regions 21 to 25, are calculated using (Equation 5).

[0058] In addition, the minimum thickness in the circumferential direction (t C ) is the circumferential tensile allowable stress (ft C ), the maximum operating pressure (Pi) in each of the regions 21 to 25, the inner diameter (D) of the liquid storage tank 10, and the thickness (c) of the corrosion-resistant layer 32 in each of the regions 21 to 25, are calculated using (Equation 6).

[0059]

number

[0060] The maximum operating pressure (Pi) in each of the regions 21 to 25 is the design pressure (P), the liquid level (h j ), specific gravity of the liquid ρ w Based on this, it is calculated using (Equation 7).

[0061]

number

[0062] In the determination step, the total thickness (t a ) is the minimum axial thickness (t L ) and the allowable tensile stress in the circumferential direction (ft C ), it is determined that the side panel 12 can withstand the internal pressure.

[0063] Table 5 shows the height (y) from the bottom end of each of the regions 21 to 25 of the side plate 12 to the top end of the side plate 12, the height (h j ), maximum operating pressure in each area 21 to 25 (P i), allowable axial tensile stress at new construction (ftL), minimum axial thickness (t L ), circumferential tensile allowable stress (ft C ), minimum thickness in the circumferential direction (t C ), total thickness (t a ), and the judgment results are shown.

[0064] [Table 5]

[0065] Table 6 shows the height (y) from the bottom end of each of the regions 21 to 25 of the side plate 12 to the top end of the side plate 12, the height (h j ), maximum operating pressure in each area 21 to 25 (P i ), allowable axial tensile stress at degradation (ftL), minimum axial thickness (t L ), circumferential tensile allowable stress (ft C ), minimum thickness in the circumferential direction (t C ), total thickness (t a ), and the judgment results are shown.

[0066] [Table 6]

[0067] At the time of new construction, for all areas 21 to 25, a >ft L , and t a >ft C Therefore, the result is "OK". Even during deterioration, t a >ft L , and t a >ft C Therefore, the result is "OK".

[0068] (2-1-2. Diagnosis of whether the side panels can withstand external pressure such as wind) The external pressure buckling strength (Pcr) of the side plate 12 is determined by the Poisson's ratio (v) of the FRP material constituting the liquid storage tank 10, the circumferential tensile elastic modulus (Et C ), the height of the side panel 12 (dt), the thickness of the reinforcing layer 31 constituting the side panel 12 (t t ) and the radius of curvature (r) of the side plate 12, it is calculated by (Equation 8).

[0069] The coefficient (Z) is determined by the thickness (t t ), the radius of curvature (r) of the side plate 12, the height (dt) of the side plate 12, and the Poisson's ratio (v) of the FRP, and is calculated using (Equation 9).

[0070]

number

[0071] Here, in the determination step, if the external pressure buckling strength (Pcr) of the side plate 12 is greater than the design external pressure (P), it is determined that the side plate 12 can withstand the external pressure. The Poisson's ratio (v) of the FRP material of this embodiment is 0.3.

[0072] The axial tensile elastic modulus of the side panel 12 at the time of installation (Et L ) is 13,040(N / mm 2 ) The height (dt) of the side plate 12 is 6,450 (mm). The thickness (t t The average value of ) is 5 (mm).

[0073] The radius of curvature (r) of the side plate 12 is 1,602 (mm). In addition, the non-design pressure (P) is 0.00094 (Mpa). The external pressure buckling strength (Pcr) of the side plate 12 at the time of new construction is 0.00162 (MPa), which is greater than the design external pressure (P), and therefore it is determined that the side plate 12 can withstand the external pressure.

[0074] On the other hand, the axial tensile modulus of elasticity (Et L ) is 8,900(N / mm 2 ) Therefore, the external pressure buckling strength (Pcr) of the side plate 12 in the deteriorated state is 0.00110 (MPa), which is greater than the design external pressure (P), and therefore it is determined that the side plate 12 can withstand the external pressure.

[0075] (2-2. Stresses in the side panels due to wind loads or earthquakes) (2-2-1. Axial buckling stress occurring in the side plate) In order to calculate the stress generated in the side plate 12, it is necessary to determine the overturning moment (M1) as will be described later.

[0076] The overturning moment (M1) used here is the larger of the overturning moment due to an earthquake (M1) and the overturning moment due to wind load such as a typhoon. In the case of the liquid storage tank 10, the overturning moment due to an earthquake (M1) is used because it is several times larger than the overturning moment due to wind load. Therefore, the procedure for calculating the overturning moment due to wind load will not be described here.

[0077] Table 7 shows the height of the center of gravity (H), weight of snow and work floor (wp), weight of the main body (wd), weight scale (w), floor load (Wv), horizontal force due to earthquake (F H ), and the earthquake-induced overturning moment (M1).

[0078] [Table 7]

[0079] As shown in FIG. 2, the height of the center of gravity (H) is the height from the bottom surface of the liquid storage tank 10 to the center position of each of the regions 21 to 25 in the height direction. The weight scale (w) is the sum of the weight of snow, work platform, etc. (wp) and the weight of the main body, etc. (wd).

[0080] Horizontal force due to earthquake (F H ) is the weight scale (w) and the seismic coefficient (kH ) is the product of In this embodiment, the seismic coefficient (k H ) is said to be 0.4 (equivalent to a seismic intensity of 6+ to 7-).

[0081] The earthquake-induced overturning moment (M1) is calculated by the weight scale (w) and the seismic coefficient (k H ) and the height of the center of gravity (H). The axial buckling stress (σ c1 ) is the stress (σ CH ), design vertical seismic coefficient (K MW ) vertical earthquake force on the side panel 12 (σ CV ), the stress (σ CO ), and the stress (σ P ) and is calculated using (Equation 10).

[0082] Here, the stress (σ CH ) is the inner diameter (D) of the side plate 12, the thickness (t t ), and design vertical seismic coefficient (K MW ) is calculated by (Equation 11) based on the overturning moment (M1') acting on the liquid storage tank 10 when full due to the earthquake load.

[0083] The stress (σ CO ) is the inner diameter (D) of the side plate 12, the thickness (t t ), and the weight (Wv) of the side panels 12 and roof portion 13, is calculated using (Equation 12).

[0084] Design vertical seismic coefficient (K MW ) vertical earthquake force on the side panel 12 (σ CV ) is the design vertical seismic coefficient (K MW ) and the stress due to the weight of the roof part 13 (σ CO ) and is calculated using (Equation 13).

[0085] The stress (σ P ) is the thickness (t t ), the design internal pressure (P), and the inner diameter (D) of the side plate 12, and is calculated using (Equation 14).

[0086] In addition, the allowable buckling stress (σ K ) is the inner diameter (D) of the side plate 12, the axial tensile modulus of elasticity (Et L ), and the thickness (t t ) and is calculated using (Equation 15).

[0087]

number

[0088] Here, in the judgment process, the axial buckling stress (σ c1 ) is the allowable buckling stress of the side plate 12 (σ K ) or more When the side plate 12 is in the lower position, the side plate 12 is subjected to the design vertical seismic coefficient (K MW ) earthquake load.

[0089] Table 8 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1), stress (σ CH ), stress (σ CO ), stress (σ CV ), stress (σ P ), axial buckling stress (σ c1 ), axial tensile modulus of elasticity at new construction (Et L ), allowable buckling stress (σ K ), and the judgment results are shown.

[0090] [Table 8]

[0091] Table 9 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1), stress (σ CH ), stress (σ CO ), stress (σ CV ), stress (σ P ), axial buckling stress (σ c1 ), axial tensile modulus of elasticity at degradation (Et L ), allowable buckling stress (σ K ), and the judgment results are shown.

[0092] [Table 9]

[0093] As shown in Table 8, at the time of new construction, σ c1 ≦σ K Therefore, the result is "OK". As shown in Table 9, in the deteriorated state, σ c1 ≦σ K Therefore, the judgment result is "OK." On the other hand, for the first region 21 and the second region 22, σ c1 >σ K Therefore, the result is "NG".

[0094] (2-2-2. Axial tensile stress occurring in the side plate) The axial tensile stress (σ t1 ) is the stress (σ CH ), the stress (σ CO ), and the stress (σ P ) and is calculated using (Equation 16).

[0095]

number

[0096] Here, in the determination step, the axial tensile stress (σ t1 ) is the long-term axial tensile stress (ft L ) multiplied by 1.5. L ) or less, the side panel 12 is MW ) earthquake load R It is determined that:

[0097] Table 10 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1), stress (σ CH ), stress (σ CO ), stress (σ P ), axial tensile stress (σ t1 ), axial tensile stress at new installation (ft L ), short-term axial tensile stress at new construction (1.5ft L ), and the judgment results are shown.

[0098] [Table 10]

[0099] Table 11 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1'), stress (σ CH ), stress (σ CO ), stress (σ P ), axial tensile stress (σ t1 ), axial tensile stress during degradation (ft L ), short-term axial tensile stress during degradation (1.5ft L ), and the judgment results are shown.

[0100] [Table 11]

[0101] As shown in Table 10, at the time of new construction, σ t1 ≦1.5ft L Therefore, the result is "OK". As shown in Table 11, during deterioration, σ t1 ≦1.5ft L Therefore, the result is "OK".

[0102] (2-2-3. Circumferential stress occurring in the side plate) The stress (σ Φ0 ) is the thickness (t t ), the inner diameter (D) of the side plate 12, and the sum of the hydrostatic pressure and the internal pressure (Pi), calculated by (Equation 17).

[0103] Horizontal seismic intensity for design (K H ) The stress σ generated in the side panel 12 by the horizontal force of the earthquake ΦH is the maximum liquid level (H L ), the thickness (t t ), horizontal force (F e ) and is calculated using (Equation 18).

[0104] Design vertical seismic coefficient (K MW ) The stress σ generated in the side panel 12 by the vertical force of the earthquake ΦV is the design vertical seismic coefficient (K MW ) and the stress (σ Φ0 ) and is calculated using (Equation 19).

[0105] Circumferential tensile stress σ generated in the side plate 12 Φ1 is the stress σ ΦH , stress σ ΦV , and stress σ Φ0 Based on this, it is calculated using (Equation 20).

[0106]

number

[0107] In the determination process, when all of the following three conditions are met, the side panel 12 is determined to have a design vertical seismic coefficient (K MW ) earthquake load. The stress (σ Φ0 ) is the allowable tensile stress in the circumferential direction (ft C ) or less, that is, (Equation 21) holds.

[0108] Circumferential tensile stress σ generated in the side plate 12 Φ1 However, the short-term circumferential tensile allowable stress (1.5ft C ) or less, that is, (Equation 22) holds. The axial buckling stress (σ c1 ) and the absolute value of the circumferential tensile stress σ generated in the side plate 12 Φ1 The sum of the short-term circumferential tensile allowable stress (1.5ft C ) or less, that is, (Equation 23) holds.

[0109]

number

[0110] Table 12 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), stress (σ Φ0 ), stress (σ ΦH ), stress (σ ΦV ), the sum of stresses (|σ C1 |+σ Φ1 ), circumferential tensile stress at new installation (ft C ), short-term circumferential tensile stress at new construction (1.5ft C ), division value (σ Φ0 / ft C ), division value (σ Φ1 / 1.5ft C ), division value ((|σ C1 |+σΦ1 ) / 1.5ft C ), and the judgment results are shown.

[0111] [Table 12]

[0112] Table 13 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), stress (σ Φ0 ), stress (σ ΦH ), stress (σ ΦV ), the sum of stresses (|σ C1 |+σ Φ1 ), circumferential tensile stress during deterioration (ft C ) Short-term circumferential tensile stress during deterioration (1.5ft C ), division value (σ Φ0 / ft C ), division value (σ Φ1 / 1.5ft C ), division value ((|σ C1 |+σ Φ1 ) / 1.5ft C ), and the judgment results are shown.

[0113] [Table 13]

[0114] As shown in Table 12, at the time of new installation, all of the regions 21 to 25 satisfy (Formula 21), (Formula 22), and (Formula 23), and therefore the judgment result is "OK." As shown in Table 13, in the deteriorated state, the second region 22 to the fifth region 25 satisfy (Formula 21), (Formula 22), and (Formula 23), and therefore the judgment result is "OK." On the other hand, the first region 21 does not satisfy (Formula 23), and therefore the judgment result is "NG."

[0115] <Repair of storage tank> If, in the aforementioned judgment process, it is judged that the wall portion 30 cannot withstand the forces acting on the wall portion 30 in the usage environment, i.e., if it is judged as "NG" in any of the judgment processes of this embodiment, the wall portion 30 is repaired as follows.

[0116] That is, as shown in FIG. 5, the entire corrosion-resistant layer 32 of the wall portion 30 and the thickness (t t 6, a reinforcing layer 131 and a corrosion-resistant layer 132 are sequentially added to the wall portion 30 after removal by bonding.

[0117] The preferred repair method is the fiber-reinforced plastic liquid storage tank repair method described in Japanese Patent No. 6527986, developed by the inventors of the present application. Specifically, the surface of the corrosion-resistant layer 32 is first polished. A dichloromethane-based solvent is then applied to the surface to dissolve the resin. The surface is then scratched with a jig to lift the fibers. The surface is then cleaned to remove residues, including dichloromethane and the dissolved resin. A new reinforcement layer 131 and a corrosion-resistant layer 132 are then sequentially bonded to the surface with an adhesive. The repair method is not limited to the above method.

[0118] <Repair plan evaluation method for liquid storage tanks> The repair plan evaluation method is a method for evaluating a repair plan prior to repairing the wall portion 30 described above.

[0119] In the following, the above-described determination step will be referred to as the first determination step. The repair plan evaluation method includes an existing thickness acquisition step, a post-repair thickness calculation step, a post-repair mechanical property value calculation step, and a second determination step.

[0120] In the existing thickness acquisition process, the thickness (t a ) and the thickness of the removed part t remBased on this, the thickness of the reinforcement layer 31 after removal, which is the existing thickness (t o ) is acquired (see FIGS. 5 and 6). In the existing thickness acquisition step of this embodiment, the existing thickness (t o ) to get the

[0121] In the post-repair thickness calculation process, the existing thickness (t o ) and the additional thickness (t n ) and the thickness of the reinforced layer 131 after repair (t comp ) is calculated (see FIG. 6). In the post-repair thickness calculation step of this embodiment, the post-repair thickness (t comp ) is calculated.

[0122] In the post-repair mechanical property value calculation step, the mechanical property value (X o ) and the mechanical properties of the new reinforcement layer 131 to be added (X n ) and the existing thickness (t o ), additional thickness (t n ) and (Equation 26), i.e., by weighted averaging, the mechanical property value (X comp In the post-repair mechanical property value calculation step of this embodiment, the mechanical property values ​​(X comp ) is calculated.

[0123]

number

[0124] The second judgment step is to determine the mechanical property value (X comp ), thickness after repair (t comp ), and the thickness after repair (t comp ) for each of the plurality of stages of regions 21 to 25, it is determined whether or not the wall portion 130 can withstand the force acting on the wall portion 130 in the usage environment.comp ), thickness after repair (t comp ), and the thickness after repair (t comp ) is used to determine whether the wall portion 130 can withstand the force acting on it in the usage environment.

[0125] (Repair plan for storage tank) Table 14 shows the thickness (t t ), the thickness of the corrosion-resistant layer 32 (c), the total thickness of the wall 30 (t a ), the thickness (t rem ), existing thickness (t o ), additional thickness due to repair (t n ), the thickness (c) of the corrosion-resistant layer 132, and the thickness after repair (t comp ) are shown for the bottom plate 11, the regions 21 to 25 of the side plate 12, and the top plate 14.

[0126] [Table 14]

[0127] Table 15 shows an example of the allowable tensile stress (ft) and tensile modulus of elasticity (Et) of the reinforcing layer 131 added by repair.

[0128] [Table 15]

[0129] Table 16 shows the existing thickness of the top plate 14 (t o ), additional thickness (t n ), tensile strength after repair (ft), and tensile modulus of elasticity after repair (Et) are shown below.

[0130] [Table 16]

[0131] Table 17 shows the existing thickness (t o ), additional thickness (tn ), axial tensile strength after repair (ft L ), axial tensile modulus after repair (Et L ) is shown below.

[0132] [Table 17]

[0133] Table 18 shows the existing thickness (t o ), additional thickness (t n ), circumferential tensile strength after repair (ft C ), circumferential tensile modulus after repair (Et C ) is shown below.

[0134] [Table 18]

[0135] Table 19 shows the height (y) from the bottom end of each of the regions 21 to 25 of the side panel 12 to the top end of the side panel, and the thickness (t t= t comp ), the thickness (c) of the corrosion-resistant layer 32, the total thickness (t a ), and weight w1(N).

[0136] [Table 19]

[0137] In each of the subsequent repair plan evaluations, it is determined whether the repaired wall portion 130 can withstand the forces acting on the wall portion 30 in the usage environment when repairs are carried out according to the plans exemplified in Tables 14 to 19.

[0138] (3. Evaluation of the tabletop repair plan) (3-1. Evaluation of whether the repaired top plate can withstand internal pressure) The minimum thickness (t min ) is calculated by (Equation 2) as described in (1-1).

[0139] Here, in the second determination step, similarly to the first determination step described in (1-1), the total thickness (t a ) is the minimum thickness (t min ), it is determined that the top plate 14 can withstand the internal pressure.

[0140] The total thickness of the top plate 14 after repair (t a ) is 10 (mm) (see Table 2). In this embodiment, the design pressure (P) is "0" as described above. Therefore, the minimum thickness (t min ) is "2 (mm)". Therefore, the thickness of the top plate 14 (t a ) is the minimum thickness (t min ), it is determined that the repaired top plate 14 can withstand the internal pressure.

[0141] (3-2. Evaluation of whether the tabletop can withstand external pressure such as snow accumulation) The external pressure buckling strength (Pcr) of the top plate 14 is calculated by (Equation 4), as described in (1-2).

[0142] Here, in the second judgment process, as in the first judgment process described in (1-2.), if the external pressure buckling strength (Pcr) of the top plate 14 is greater than the design external pressure (Po), it is judged that the top plate 14 can withstand the external pressure.

[0143] The thickness (t comp =to+tn) is 8 (mm) (see Table 14). In addition, the tensile modulus of elasticity after repair (Et comp ) is 6,649 (N / mm 2) (see Table 16). Therefore, the external pressure buckling strength (Pcr) of the top plate 14 after repair is 0.00595 (MPa), which is greater than the design external pressure (Po), and it is therefore determined that the top plate 14 can withstand external pressure.

[0144] (4. Side Panel Repair Plan Evaluation) (4-1. Minimum thickness required for side panels) (4-1-1. Evaluation of whether the side panels can withstand internal pressure) The minimum axial thickness (t L ) is calculated using Equation 5, as described in (2-1-1).

[0145] In addition, the minimum thickness in the circumferential direction (t C ) is calculated using Equation 6, as described in (2-1-1). Here, in the second determination step, similarly to the first determination step described in (2-1-1), the total thickness (t a ) is the minimum axial thickness (t L ) and the allowable tensile stress in the circumferential direction (ft C ), it is determined that the side panel 12 can withstand the internal pressure.

[0146] Table 20 shows the height (y) from the bottom end of each of the regions 21 to 25 of the side plate 12 to the top end of the side plate 12, the height (h j ), maximum operating pressure in each area 21 to 25 (P i ), allowable axial tensile stress after repair (ftL), minimum axial thickness (t L ), circumferential tensile allowable stress (ft C ), minimum thickness in the circumferential direction (t C ), total thickness (t a ), and the judgment results are shown.

[0147] [Table 20]

[0148] After repair, for all areas 21 to 25, t a >ft L , and t a >ft C Therefore, the result is "OK". (4-1-2. Evaluation of whether the side panels can withstand external pressure such as wind) The external pressure buckling strength (Pcr) of the side plate 12 is calculated by (Equation 8), as described in (2-1-2).

[0149] Furthermore, the coefficient (Z) is calculated using equation (9), as described in (2-1-2). Here, in the second judgment process, as in the first judgment process described in (2-1-2.), if the external pressure buckling strength (Pcr) of the side panel 12 is greater than the design external pressure (P), it is judged that the side panel 12 can withstand the external pressure.

[0150] Here, the axial tensile elastic modulus (Et L ) and the lowest value of each of the regions 21 to 25, 7,998 (N / mm 2 ) will be adopted. In addition, the thickness (t t ) is set to 6 (mm), which is the smallest value among the regions 21 to 25.

[0151] This means that if the condition that the external pressure buckling strength (Pcr) calculated using the minimum values ​​of the axial tensile elastic modulus (EtL) and the thickness of the reinforcing layer 31, 131 is greater than the design external pressure (P) is satisfied, then the axial tensile elastic modulus (Et L ) and the thickness (t t ) can also be considered to satisfy the condition.

[0152] The external pressure buckling strength (Pcr) of the side plate 12 after repair is 0.00157 (MPa), which is greater than the external design pressure (P), and therefore it is determined that the side plate 12 can withstand the external pressure.

[0153] (4-2. Stresses in the side panels due to wind loads or earthquakes) (4-2-1. Axial buckling stress occurring in the side plate) To calculate the stress generated in the side panel 12, it is necessary to determine the overturning moment (M1) as described in (2-2-1).

[0154] Table 21 shows the height of the center of gravity (H), the weight of snow and work floor (wp), the weight of the main body after repair (wd), the weight scale (w), the floor load (Wv), and the horizontal force due to the earthquake (F H ), and the earthquake-induced overturning moment (M1).

[0155] [Table 21]

[0156] The axial buckling stress (σ c1 ) is calculated using Equation 10 as described in (2-2-1). Here, the stress (σ CH ) is calculated using (Equation 11) as described in (2-2-1.).

[0157] The stress (σ CO ) is calculated using Equation 12 as described in (2-2-1). Design vertical seismic coefficient (K MW ) vertical earthquake force on the side panel 12 (σ CV ) is calculated using Equation 13 as described in (2-2-1).

[0158] The stress (σ P) is calculated using Equation 14 as described in (2-2-1). In addition, the allowable buckling stress (σ K ) is calculated using Equation 15 as described in (2-2-1).

[0159] Here, in the second judgment step, as in the first judgment step described in (2-2-1.), the axial buckling stress (σ c1 ) is the allowable buckling stress of the side plate 12 (σ K ) is below, the side panel 12 is MW ) earthquake load.

[0160] Table 22 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1), stress (σ CH ), stress (σ CO ), stress (σ CV ), stress (σ P ), axial buckling stress (σ c1 ), axial tensile modulus of elasticity after repair (Et L ), allowable buckling stress (σ K ), and the judgment results are shown.

[0161] [Table 22]

[0162] As shown in Table 22, after repair, σ c1 ≦σ K Therefore, the result is "OK". (4-2-2. Axial tensile stress occurring in the side plate) The axial tensile stress (σ t1 ) is calculated using Equation 16 as described in (2-2-2.).

[0163] Here, in the second judgment step, similarly to the first judgment step described in (2-2-2.), the axial tensile stress (σ t1 ) is the short-term axial tensile stress (1.5ft L ) or less, the side panel 12 is MW ) earthquake load.

[0164] Table 23 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, the thickness (t t ), weight of the side panels and roof (Wv), overturning moment (M1), stress (σ CH ), stress (σ CO ), stress (σ P ), axial tensile stress (σ t1 ), axial tensile stress after repair (ft L ), short-term axial tensile stress after repair (1.5ft L ), and the judgment results are shown.

[0165] [Table 23]

[0166] As shown in Table 23, after repair, σ t1 ≦1.5ft L Therefore, the result is "OK". (4-2-3. Circumferential stress occurring in the side plate) The stress (σ Φ0 ) is calculated using Equation 17 as described in (2-2-3).

[0167] Horizontal seismic intensity for design (K H ) The stress σ generated in the side panel 12 by the horizontal force of the earthquake ΦH is calculated by (Equation 18). Design vertical seismic coefficient (K MW ) The stress σ generated in the side panel 12 by the vertical force of the earthquake ΦV is calculated by (Equation 19).

[0168] Circumferential tensile stress σ generated in the side plate 12 Φ1 is calculated by (Equation 20). Here, in the second judgment step, similarly to the first judgment step described in (2-2-3), when all of (Equation 21), (Equation 22), and (Equation 23) are satisfied, the side panel 12 is judged to have a design vertical seismic coefficient (K MW ) earthquake load.

[0169] Table 24 shows the height (h') from the bottom surface of the side panel 12 to the lower end of each of the regions 21 to 25, and the thickness (t t ), stress (σ Φ0 ), stress (σ ΦH ), stress (σ ΦV ), the sum of stresses (|σ C1 |+σ Φ1 ), circumferential tensile stress after repair (ft C ), short-term circumferential tensile stress after repair (1.5ft C ), division value (σ Φ0 / ft C ), division value (σ Φ1 / 1.5ft C ), division value ((|σ C1 |+σ Φ1 ) / 1.5ft C ), and the judgment results are shown.

[0170] [Table 24]

[0171] As shown in Table 24, after repair, all of the regions 21 to 25 satisfy (Formula 21), (Formula 22), and (Formula 23), and therefore the judgment result is "OK." In the above example, the repair plan was judged to be appropriate, but the thickness (t rem ) and additional thickness (t n), or depending on the type of FRP material that constitutes the reinforcement layer 131 added by repair, the judgment result may be "NG".

[0172] <Effects of this embodiment> (1) The deterioration diagnosis method for an FRP liquid storage tank includes a measurement step of measuring the mechanical property value (X) of the wall portion 30, and a measurement step of comparing the mechanical property value (X) measured in the measurement step with the thickness (t t ), and thickness (t t and a determining step of determining whether the wall portion 30 can withstand the force acting on the wall portion 30 in the usage environment based on the design specification values ​​of the liquid storage tank 10 other than the above.

[0173] The mechanical property values ​​(X) of the wall 30 of the liquid storage tank 10, such as the tensile strength and the tensile modulus of elasticity, vary depending on the state of deterioration of the wall 30. In addition, if the deterioration state of the wall portion 30 is the same, the thickness (t t ) is smaller, the wall portion 30 is less able to withstand the force acting on the wall portion 30 in the usage environment.

[0174] According to the above method, the mechanical property value (X) of the wall portion 30 is measured in the measuring step. Then, in the determining step, the mechanical property value (X) and the thickness (t t ), and the thickness (t t Whether the wall 30 can withstand the force acting on the wall 30 in the usage environment is determined based on the design specification values ​​of the liquid storage tank 10 other than the above. Therefore, the deterioration state of the wall 30 of the liquid storage tank 10 can be diagnosed with high accuracy.

[0175] (2) The liquid storage tank 10 is a cylindrical tank having a cylindrical side plate 12 that is a wall portion 30. The side plate 12 is composed of multiple regions 21 to 25, each having a predetermined height. The determination step determines for each of the multiple regions 21 to 25 whether the side plate 12 can withstand the force acting on the side plate 12 in the usage environment.

[0176] The side plate 12 of the cylindrical tank is composed of a plurality of regions 21 to 25 each having a predetermined height. The force acting on the side plate 12 differs for each of the plurality of regions 21 to 25. In addition, in the cylindrical tank, the thickness (t t ) are different.

[0177] According to the above method, in the determination step, it is determined whether or not side plate 12 can withstand the force acting on side plate 12 in the usage environment for each of multiple regions 21 to 25. Therefore, the deterioration state can be accurately diagnosed for each of multiple regions 21 to 25 of side plate 12.

[0178] (3) The deterioration diagnosis method for an FRP liquid storage tank includes an acquisition step of acquiring a part of the wall portion 30 as a test piece. In the measurement step, a mechanical property value (X) of the test piece is acquired. According to this method, the measurement process can be carried out at a location other than the site where the liquid storage tank 10 is installed, such as a testing site, etc. Therefore, the measurement process can be carried out easily.

[0179] (4) The repair plan evaluation method for an FRP liquid storage tank includes an existing thickness acquisition step, a post-repair thickness calculation step, a post-repair mechanical property value calculation step, and a second determination step. According to this method, the existing thickness (t o ) is obtained, and the existing thickness (t o ) and additional thickness (t n ) and the thickness after repair (t comp ) is calculated. Then, the mechanical property value (X o ) and the mechanical properties (X n ) and the existing thickness (t o ) and additional thickness (t n ) and the mechanical property value (X comp ) is calculated. Also, the mechanical property value (X comp ), thickness after repair (t comp ), and the thickness after repair (t comp) is used to determine whether the wall 130 can withstand the force acting on the wall 130 in the usage environment. Therefore, before carrying out the repair work, the additional thickness (t n ) can be evaluated for validity.

[0180] (5) The existing thickness acquisition step acquires the existing thickness (t o The post-repair thickness calculation step calculates the post-repair thickness (t comp The post-repair mechanical property value calculation step calculates the post-repair mechanical property value (X comp In the second determination step, the mechanical property value (X comp ), thickness after repair (t comp ), and the thickness after repair (t comp ) is used to determine whether the wall portion 130 can withstand the force acting on it in the usage environment.

[0181] According to this method, in the second determination step, it is determined whether the side panel 12 can withstand the force acting on the side panel 12 in the use environment for each of the regions 21 to 25 of the plurality of stages. As a result, before carrying out the repair work, it is possible to determine the additional thickness (t n ) can be evaluated, thereby contributing to effective repair of the wall portion 130.

[0182] <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.

[0183] For example, when the height of the side plate 12 is low, the side plate 12 is a It can also consist of a single region where is constant. The liquid storage tank 10 is not limited to a cylindrical tank, i.e., a round tank, but may also be a rectangular tank. In the case of a rectangular tank, the allowable bending stress and the bending elastic modulus may be used as the mechanical property value (X).

[0184] The liquid storage tank 10 is not limited to a vertical tank, but may be a horizontal tank. The corrosion-resistant FRP equipment covered by the present invention is not limited to the liquid storage tank 10, but may also be a scrubber for removing harmful gases, or piping such as a duct. [Explanation of symbols]

[0185] 10...Liquid storage tank 11...Bottom plate 12...Side panel 13...Roof 14...Tabletop 15...Accessories 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

Claims

1. A method for diagnosing the deterioration state of a wall portion of an FRP liquid storage tank, comprising: the liquid storage tank is a cylindrical tank, the wall portion is a cylindrical side plate and includes a reinforcing layer and a corrosion-resistant layer provided inside the reinforcing layer; a measuring step of measuring mechanical properties of the side plate; a determining step of determining whether the side plate can withstand a force acting on the side plate in a usage environment based on the mechanical property values ​​measured in the measuring step, the thickness of the reinforcing layer, and design specification values ​​of the liquid storage tank other than the thickness, the mechanical property value is the axial tensile elastic modulus (Et L ) of the side plate; In the determination step, Based on the inner diameter (D) of the side plate, the thickness (tt) of the reinforcing layer that constitutes the side plate, and the overturning moment (M1') that acts on the liquid storage tank when it is full due to an earthquake load of design vertical seismic intensity (K MW), calculate the stress (σ CH ) that occurs on the side plate due to the horizontal force acting on the side plate using (Equation 11), Calculate the stress (σ CO ) generated in the side plate due to the weight (WV ) of the side plate and the roof portion of the liquid storage tank using (Equation 12) based on the inner diameter (D) of the side plate, the thickness (tt) of the reinforcing layer constituting the side plate, and the weight (WV ) of the side plate and the roof portion of the liquid storage tank; Based on the design vertical seismic intensity (K MW ) and the stress (σ CO ) generated in the side plate due to the weight (WV ) of the side plate and the roof of the liquid storage tank, calculate the stress (σ CV ) generated in the side plate due to the vertical force of an earthquake with the design vertical seismic intensity (K MW ) using (Equation 13); Calculating the stress (σ P ) generated in the side plate due to the internal pressure of the liquid storage tank using Equation 14 based on the thickness (tt) of the reinforcing layer constituting the side plate, the design internal pressure (P) of the liquid storage tank, and the internal diameter (D) of the side plate; The axial buckling stress (σ c1 ) generated in the side plate is calculated based on the stress (σ CH ), the stress (σ CV ), the stress (σ CO ), and the stress (σ P ) using (Equation 10). Calculating the allowable buckling stress (σ K ) of the side plate using (Equation 15) based on the inner diameter (D) of the side plate, the axial tensile elastic modulus (Et L ) measured in the measuring step, and the thickness (tt ) of the reinforcing layer constituting the side plate, When the axial buckling stress (σ c1 ) is equal to or less than the allowable buckling stress (σ K ), it is determined that the side plate can withstand the seismic load of the design vertical seismic intensity (K MW ) acting on the side plate, whereas when the axial buckling stress (σ c1 ) is greater than the allowable buckling stress (σ K ), it is determined that the side plate cannot withstand the seismic load of the design vertical seismic intensity (K MW ) acting on the side plate. [Equation 7] A method for diagnosing deterioration of FRP liquid storage tanks.

2. The mechanical property value is the long-term axial tensile stress (ft L) of the side plate, In the determination step, The axial tensile stress (σ t1 ) generated in the side plate is calculated based on the stress (σ CH ), the stress (σ CO ), and the stress (σ P ) using (Equation 16). When the axial tensile stress (σ t1 ) is equal to or less than the short-term axial tensile stress (1.5 ft L ), which is 1.5 times the long-term axial tensile stress (ft L ), it is determined that the side plate can withstand the seismic load of the design vertical seismic intensity (K MW ). On the other hand, when the axial tensile stress (σ t1 ) is greater than the short-term axial tensile stress (1.5 ft L ), it is determined that the side plate cannot withstand the seismic load of the design vertical seismic intensity (K MW ). [Equation 8] The deterioration diagnosis method for an FRP liquid storage tank according to claim 1.

3. The mechanical property value is the circumferential tensile allowable stress (ft C) of the side plate, In the determination step, Calculate the stress (σ Φ0 ) generated in the side plate due to the hydrostatic pressure and internal pressure of the liquid storage tank using (Equation 17) based on the thickness (tt) of the reinforcing layer constituting the side plate, the inner diameter (D) of the side plate, and the sum (P i ) of the hydrostatic pressure and internal pressure of the liquid storage tank; Based on the maximum liquid level (HL) of the liquid storage tank, the thickness (tt) of the reinforcing layer constituting the side plate, and the horizontal force (F e ), the stress (σ ΦH ) generated in the side plate due to the horizontal force of an earthquake with a design horizontal seismic intensity (KH ) is calculated using (Equation 18). Based on the design vertical seismic intensity (K MW ) and the stress (σ Φ0 ) generated in the side plate due to the hydrostatic pressure and internal pressure of the liquid storage tank, calculate the stress (σ ΦV ) generated in the side plate due to the vertical force of the earthquake with the design vertical seismic intensity (K MW ) using (Equation 19), Based on the stress (σ ΦH ), the stress (σ ΦV ), and the stress (σ Φ0 ), the circumferential tensile stress (σ Φ1 ) generated in the side plate is calculated using (Equation 20). The stress (σ Φ0 ) is equal to or less than the allowable circumferential tensile stress (ft C ); The stress (σ Φ1 ) is equal to or less than a short-term hoop tensile allowable stress (1.5 ft C ) which is 1.5 times the hoop tensile allowable stress (ft C ); and the sum of the absolute value of the stress (σ c1 ) and the circumferential tensile stress (σ Φ1 ) is equal to or less than the short-term circumferential tensile allowable stress (1.5 ft C ); When all three conditions are met, it is determined that the side panel can withstand the seismic load of the design vertical seismic intensity (K MW), whereas when at least one of the three conditions is not met, it is determined that the side panel cannot withstand the seismic load of the design vertical seismic intensity (K MW). [Equation 9] The deterioration diagnosis method for an FRP liquid storage tank according to claim 2.

4. The side panel is composed of multiple step areas each having a predetermined height, the determining step determines, for each of the plurality of stages, whether or not the side plate can withstand a force acting on the side plate under a usage environment. The deterioration diagnosis method for an FRP liquid storage tank according to claim 1.

5. An acquisition step of acquiring a part of the side plate as a test piece, In the measuring step, the mechanical property values ​​of the test piece are acquired. The deterioration diagnosis method for an FRP liquid storage tank according to claim 1.

6. A method for evaluating a plan for adding a reinforced layer and a corrosion-resistant layer to the side plate in order by gluing them together, in the judgment step of the deterioration diagnosis method for an FRP liquid storage tank described in any one of claims 1 to 5, when it is judged that the side plate cannot withstand the force acting on the side plate in the usage environment, after removing the entire corrosion-resistant layer and a part of the thickness of the reinforced layer of the side plate, prior to repair, wherein the reinforced layer and the corrosion-resistant layer are added to the side plate after removal in that order by gluing them together, When the determination step is a first determination step, an existing thickness acquisition step of acquiring an existing thickness, which is the thickness of the reinforcement layer after the removal; A post-repair thickness calculation process for calculating a post-repair thickness, which is the thickness of the reinforced layer after the repair, based on the existing thickness and the additional thickness, which is the thickness of the reinforced layer to be added; a post-repair mechanical property value calculation process for calculating the mechanical property values ​​of the side panel after repair by weighted averaging based on the mechanical property values ​​of the side panel in a deteriorated state measured in the measurement process, the mechanical property values ​​of the new reinforcing layer to be added, the existing thickness, and the added thickness; a second determination step of determining whether the side plate can withstand a force acting on the side plate in a usage environment based on the mechanical property values ​​of the side plate after the repair, the thickness after the repair, and design specification values ​​of the liquid storage tank other than the thickness after the repair, The determination method in the second determination step is the same as the determination method in the first determination step. Repair plan evaluation method for FRP liquid storage tank.

7. The side panel is composed of multiple step areas each having a predetermined height, the first determination step determines, for each of the plurality of step regions, whether the side plate can withstand a force acting on the side plate in a usage environment; The existing thickness acquisition step acquires the existing thickness for each of the plurality of step regions, The post-repair thickness calculation step calculates the post-repair thickness for each of the plurality of step regions, The post-repair mechanical property value calculation step calculates the mechanical property values ​​of the side plate after the repair for each of the plurality of step regions, the second determination step determines, for each of the plurality of stages, whether the side plate can withstand a force acting on the side plate in a usage environment based on the mechanical property values ​​of the side plate after the repair, the thickness after the repair, and design specification values ​​of the liquid storage tank other than the thickness after the repair. The method for evaluating a repair plan for an FRP liquid storage tank according to claim 6.

Images