A method of reinforcing a storage tank wall and a composite liner for reinforcing a storage tank wall

Abstract

The present application belongs to the technical field of gathering and storage tank repair, and particularly relates to a storage tank wall reinforcing method and a composite material liner for reinforcing a storage tank wall, comprising: selecting a composite material liner with optimal performance parameter values from N different structures of composite material liners according to performance parameters, and recording the selected composite material liner as a selected composite material liner; the performance parameters include tensile strength and bending strength; the structure of the composite material liner comprises, from inside to outside, k1 layers of square cloth, k2 layers of four-axis cloth and k3 layers of carbon fiber cloth; if the difference between the wall thickness of the storage tank wall after being reinforced by the selected composite material liner and the minimum thickness of the storage tank wall is greater than or equal to L1, and L1>0, then the selected composite material liner is determined to be suitable for the storage tank wall; and the selected composite material liner is used to reinforce the storage tank wall to which the selected composite material liner is suitable. Thus, the present application solves the problem of high repair cost of the storage tank wall in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of storage tank repair technology, specifically relating to a method for reinforcing tank walls and a composite material liner for reinforcing tank walls. Background Technology

[0002] Currently, some oilfields are facing problems such as corrosion and aging of a large number of steel structures, which seriously affect oilfield production. For example, one oilfield currently has 73 main large gathering and transportation storage tanks in operation, of which 72% have been in service for more than 15 years. Even worse, some of the existing storage tanks have exceeded their service life and are severely corroded.

[0003] For tank repair, current technologies mainly include demolition and reconstruction, wall panel replacement, and leak sealing. Demolition and reconstruction: has a long construction period and high cost; wall panel replacement: suitable for partial repairs, lower cost, requires hot work, and bottom replacement requires tank cleaning; leak sealing: is a temporary measure, lower cost, but leaks may recur after being subjected to media erosion and corrosion.

[0004] Considering the advantages of carbon fiber composites, such as corrosion resistance, high temperature resistance, good mechanical properties, and high elastic modulus, they have been successfully applied to the reinforcement and repair of civil engineering structures in countries such as Europe, America, and Japan. Their application originated in Europe and America in the 1920s and 30s, with early applications in the aerospace field. In large aircraft, the amount of composite materials used has reached 40%-50%, and the main reinforcing materials include glass fiber, carbon fiber, boron fiber, and organic fibers.

[0005] With decreasing material costs and advancements in processing technology, fiberglass reinforced plastic (FRP) pipes have been widely used in oilfield water supply, oil storage, and oil transportation, and have also been promoted and applied in production system pipelines in some oilfields. In the 1950s, the United States first used polyester FRP pipes for oil and gas gathering and transportation pipelines and storage tanks. In the 1970s, research began abroad on using fiber composite materials for repairing pressure vessels and pipelines, and by the late 1990s, carbon fiber composite repair technology was successfully applied to reinforce and repair buried steel pipelines. It is far superior to traditional reinforcement methods in terms of ease of construction and reinforcement effect. Using high-strength carbon fiber composite liners to repair the entire inner wall of metal tanks provides both reinforcement and corrosion protection, significantly extending the service life of metal storage tanks. Summary of the Invention

[0006] The purpose of this invention is to provide a method for reinforcing tank walls and a composite material inner liner for reinforcing tank walls, so as to solve the problem of high cost of tank wall repair in the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution provided by this invention and the corresponding beneficial effects of the technical solution are as follows:

[0008] A method for reinforcing the wall of a storage tank according to the present invention includes the following steps:

[0009] 1) Select a composite material liner with superior performance parameter values ​​from N different composite material liner structures based on performance parameters, and denot it as the selected composite material liner, where N≥2; the performance parameters include tensile strength and flexural strength.

[0010] The composite material liner, from the inside out, comprises: k1 layer of woven fabric, k2 layer of tetraaxial fabric, and k3 layer of carbon fiber fabric, where k1 > 0, k2 > 0, and k3 ≥ 0. The woven fabric is used to bond the composite material liner to the tank wall; the tetraaxial fabric is used to increase the stress of the composite material liner; and the carbon fiber fabric is used to increase the stress, tensile strength, and flexural strength of the composite material liner. The difference between the N different composite material liner structures lies in the different values ​​of k1, k2, and k3 in each structure.

[0011] 2) Determine whether the tank wall meets condition 1. If the tank wall meets condition 1, then it is determined that the selected composite material liner is suitable for the tank wall. Condition 1 is that the difference between the thickness of the tank wall reinforced with the selected composite material liner and the minimum thickness of the tank wall is greater than or equal to L1, where L1 > 0.

[0012] 3) Reinforce the tank wall to which the selected composite material liner is applicable based on the selected composite material liner.

[0013] The beneficial effects of the above technical solution are as follows: This invention determines the inner liner structure of the composite material based on tensile strength and flexural strength, ensuring that both the tensile and flexural strengths of the composite material inner liner meet the requirements. Furthermore, by comparing the minimum allowable thickness of the tank wall with the tank thickness after reinforcing the composite material inner liner, and ensuring that the tank thickness after reinforcing the composite material inner liner is greater than the minimum allowable thickness of the tank wall, the applicable range of the selected composite material inner liner structure is determined. This comprehensive approach ensures the service life of the tank and the cost of tank repair. This method fully considers the allowable stress and safety factor of the material when determining the minimum thickness, resulting in a suitable minimum allowable thickness for pipe wall repair materials. Using this method will significantly improve the service life of metal tanks, especially for "reconstruction" tanks, as the inner liner repair process does not require tank disassembly, effectively reducing replacement costs.

[0014] Furthermore, to ensure a long service life for the storage tank, L1 is the corrosion allowance value for the tank wall.

[0015] Furthermore, to ensure a long service life for the storage tank, L1 is the sum of 0.1 times the minimum thickness of the tank wall and 1.1 times the corrosion allowance of the tank wall.

[0016] Furthermore, to reduce costs while ensuring performance, N=3; in the first structure of the composite material liner, k1=1, k2=2, k3=0; in the second structure of the composite material liner, k1=1, k2=3, k3=1; in the third structure of the composite material liner, k1=1, k2=4, k3=2.

[0017] Furthermore, the minimum thickness of the tank wall is calculated based on the allowable stress of the tank wall steel plate material; the formula for calculating the allowable stress of the tank wall is:

[0018]

[0019] In the formula, n1 is the safety factor of the steel plate material; n2 is the safety factor of the composite material liner; σ1 is the tensile strength of the steel plate material; σ2 is the tensile strength of the composite material liner; δ1 is the thickness of the steel plate material; and δ2 is the thickness of the composite material liner.

[0020] Furthermore, the safety factor n1 for the steel plate material is set to 2; the safety factor n2 for the composite material liner is set to 6.5.

[0021] Furthermore, L1 = 2; L2 = 3, in millimeters.

[0022] This invention provides a composite material inner liner for reinforcing the wall of a storage tank. The structure of the composite material inner liner, from the inside out, includes: a k1 layer of woven fabric, a k2 layer of four-axis fabric, and a k3 layer of carbon fiber fabric, where 3 ≥ k1 ≥ 1, k2 = 3, and k3 ≥ 1. The woven fabric is used to bond the composite material inner liner to the tank wall; the four-axis fabric is used to increase the stress of the composite material inner liner; and the carbon fiber fabric is used to increase the stress, tensile strength, and bending strength of the composite material inner liner.

[0023] The beneficial effects of the above technical solution are as follows: the composite material liner has superior tensile and flexural strength, making it suitable for reinforcing tank walls and ensuring that the tensile and flexural strength of the composite material liner meets the requirements; the composite material liner comprehensively considers multiple aspects to ensure the service life of the tank wall and the cost of tank wall repair. The composite material liner fully considers the allowable stress and safety factor of the material, and using this composite material liner will significantly improve the service life of metal tank walls, especially for tank walls that require "reconstruction and demolition," effectively reducing replacement costs.

[0024] Furthermore, k1 = 1, k2 = 3, k3 = 1.

[0025] Furthermore, the thickness of the woven fabric is 0.56 mm, the thickness of the tetraaxial fabric is 0.86 mm, and the thickness of the carbon fiber fabric is 0.175 mm. Attached Figure Description

[0026] Figure 1This is a flowchart of a tank wall reinforcement method according to the present invention;

[0027] Figure 2 This is a comparison diagram of the tensile strength and flexural strength of composite material liners with different structures in an embodiment of a tank wall reinforcement method of the present invention;

[0028] Figure 3 This is a structural diagram of the tank wall after reinforcement using the tank wall reinforcement method of the present invention.

[0029] In the diagram: 1. Tank wall; 2. Woven cloth; 3. Four-axis cloth; 4. Carbon fiber cloth. Detailed Implementation

[0030] This invention employs a composite material liner containing novel carbon fiber composite material to reinforce gathering and transportation storage tanks. By comparing the minimum allowable thickness of the tank wall (minimum thickness) with the thickness of the tank reinforced using this composite material, the applicable range of a specific composite material liner structure is determined. This invention fully considers the allowable stress and safety factor of the material, resulting in a suitable minimum allowable thickness for the pipe wall repair material. Using this invention to reinforce storage tanks will significantly improve the service life of metal storage tanks, especially for tanks undergoing "demolition and reconstruction." The composite material liner repair process of this invention eliminates the need for tank disassembly, effectively reducing replacement costs.

[0031] This invention first identifies three composite material liner materials: woven fabric, tetraaxial fabric, and carbon fiber fabric. These materials are then fabricated into three different liner structures. Performance tests determine the tensile and flexural strengths of the different composite material liners. Considering material strength and cost factors, a specific composite material liner structure is determined. Next, the minimum allowable thickness of the tank wall is compared with the tank thickness after reinforcing the composite material liner. Under the condition that the tank thickness after reinforcing the composite material liner is greater than the minimum allowable thickness of the tank wall, the applicable range of the specific composite material liner structure is determined. This method fully considers the allowable stress and safety factor of the material, resulting in a suitable minimum allowable thickness for the pipe wall repair material. Using this method will significantly improve the service life of metal storage tanks. To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] An embodiment of a tank wall reinforcement method:

[0033] An embodiment of a tank wall reinforcement method provided by the present invention is as follows: Figure 1 As shown, the specific steps are as follows:

[0034] Step 1: Determining the structure of the composite material liner. The tensile and flexural strengths of different composite material liners are determined through performance testing. Then, considering material strength and cost factors, a composite material liner with a specific structure is selected.

[0035] (1) The composite liner material was determined to be woven fabric, tetraaxial fabric, and carbon fiber fabric, and three different composite material structures were prepared: Structure 1 consists of one layer of woven fabric and two layers of tetraaxial fabric; Structure 2 consists of one layer of woven fabric, three layers of tetraaxial fabric, and one layer of carbon fiber fabric; Structure 3 consists of one layer of woven fabric, four layers of tetraaxial fabric, and two layers of carbon fiber fabric. The woven fabric is located in the innermost layer and is used to bond the composite liner to the tank wall; the tetraaxial fabric is placed in the middle layer to increase the stress of the composite liner; and the carbon fiber fabric is placed in the outermost layer for corrosion protection and to increase the stress and tensile and bending strength of the composite liner.

[0036] (2) Through performance tests, the tensile strength and flexural strength of composite materials with different structures were obtained.

[0037] When determining the tensile strength of different composite material inner linings, based on the preparation of resin matrix carbon fiber composite plates by vacuum injection method, tensile test plate specimens are prepared by water saw. The specimens are fixed at the clamp of the tensile testing machine, and the specimens are adjusted so that the force direction coincides with the length direction of the plate. The extensometer is fixed on the specimen with a rubber band to measure the deformation.

[0038] The formula for calculating tensile strength is:

[0039]

[0040] In the formula, F is the maximum load reached by the tensile specimen during the process of being stretched to failure; b is the width of the tensile specimen cross section; and h is the thickness of the tensile specimen cross section.

[0041] To determine the bending strength of different composite material liners, a specimen with a load-applying indenter parallel to the fiber direction was used. The three-point bending test method was employed to test the bending resistance of the fiber composite plate. The cut specimen was placed on the bending test apparatus, and the span was adjusted to 20 mm. The loading rate was set to 1 mm / min, and the stress on the specimen was recorded using a computer to obtain the strain curve.

[0042] The formula for calculating flexural strength is:

[0043]

[0044] In the formula, P is the maximum load on the specimen at failure; L is the test span of the specimen; b is the width of the specimen cross-section; and h is the thickness of the specimen cross-section.

[0045] Here, the thickness of the woven fabric is 0.56 mm, the thickness of the tetraaxial fabric is 0.86 mm, and the thickness of the carbon fiber fabric is 0.175 mm. The tensile strength and flexural strength test results of the three different composite material liner structures in this embodiment are shown in Table 1-1.

[0046] Table 1-1 Tensile and flexural strength test results of three composite material liners with different structures

[0047] structure Tensile strength (MPa) Bending strength (MPa) Structure 1 (1 layer of woven fabric, 2 layers of four-axis fabric) 403 585 Structure 2 (1 layer of woven fabric, 3 layers of tetraaxial fabric, 1 layer of carbon fiber fabric) 543 470 Structure 3 (1 layer of woven fabric, 4 layers of tetraaxial fabric, 2 layers of carbon fiber fabric) 477 529

[0048] (3) Determine the structure of the composite material liner

[0049] The wall thickness of the oilfield storage tanks referred to here is generally around 5cm, while the wall thickness of the tanks to be repaired is around 3-4cm. In accordance with the standards, the lower limit of the material strength standard should be greater than 390MPa. Based on the tensile strength and flexural strength, the focus is on the higher tensile strength. At the same time, considering that carbon fiber cloth is the most expensive of the three materials, the appropriate composite material structure is selected with the tensile strength and flexural strength within an optimal range and the cost of carbon fiber cloth being relatively low.

[0050] Based on the above conditions Figure 2 If a combination of woven fabric and tetraaxial fabric is used, the tensile strength of 1 layer of woven fabric + 3 layers of tetraaxial fabric and 1 layer of woven fabric + 4 layers of tetraaxial fabric are below the lower limit of the strength standard (390 MPa), which does not meet the requirements. The tensile strength of 1 layer of woven fabric + 2 layers of tetraaxial fabric meets the lower limit of the strength standard, but it just reaches the lower limit, and the performance is not strong, requiring further optimization. If a combination of woven fabric, tetraaxial fabric, and 1 layer of carbon fiber fabric is used, all three combinations meet the lower limit of the strength standard, but the tensile strength of the 1 layer of woven fabric + 3 layers of tetraaxial fabric + 1 layer of carbon fiber fabric structure is the strongest. If a combination of woven fabric, tetraaxial fabric, and 2 layers of carbon fiber fabric is used, all three combinations meet the lower limit of the strength standard, but the cost of 2 layers of carbon fiber fabric is higher, and cost can be optimized. Figure 2 The table shows a comparison of the tensile and flexural strength test results of various composite material liner structures. As shown in Table 1-2, the tensile and flexural strengths increase with the increase of the number of carbon fiber cloth layers in the composite material; however, the flexural strength of the tetraaxial cloth decreases significantly with the increase of the number of layers, and the tensile strength also decreases. Considering material strength, quality, and cost, this embodiment adopts structure 2, which includes: 1 layer of woven fabric, 3 layers of tetraaxial cloth, and 1 layer of carbon fiber cloth.

[0051] Among them, the square woven fabric is the innermost layer of fabric, which mainly serves to bond with the tank wall; the four-axis fabric is the middle layer of fabric, which has the function of increasing stress. The larger the number of fabric layers, the less the resin thickness is while maintaining the same total thickness, and the lower the bonding strength between the fabrics. The thicker the fabric, the less effective it is in terms of reinforcement; the carbon fiber fabric is the outermost layer of fabric, which has the functions of corrosion protection, increasing stress, tensile strength and bending strength.

[0052] Table 1-2 Test results of tensile strength and flexural strength of various different strengths

[0053]

[0054]

[0055] Step 2: Scope of Application for Composite Material Liner Structures. The steps for determining the scope of application for a specific composite material liner structure include: comparing the minimum allowable thickness of the tank wall with the thickness of the tank after reinforcing it with a composite material liner to determine the scope of application for the specific composite material liner structure.

[0056] Taking a water injection tank in an oilfield water injection station as an example, the diameter of the bottom ring wall plate of the water injection tank is D = 8.92m, the height of the tank wall is H = 8.95m, and there are a total of 6 rings of wall plates. The tank walls are connected by an overlapping structure.

[0057] (1) Determine the allowable stress of composite steel plates.

[0058] The allowable stress of the composite steel plate for the tank wall is:

[0059]

[0060] In the formula, n1 is the safety factor of the steel plate material; n2 is the safety factor of the composite material; σ1 is the tensile strength of the steel plate material; σ2 is the tensile strength of the composite material; δ1 is the thickness of the steel plate material; and δ2 is the thickness of the composite material.

[0061] The safety factor n1 for steel plate materials is 2; the safety factor n2 for composite materials is 6.5.

[0062] The thickness of the composite material here is 3.315 mm. The allowable stress of the composite material under different metal steel plate wall thicknesses of 1 mm, 2 mm, 3 mm, and 4 mm is determined. Substituting into the allowable stress model of the composite steel plate in the tank wall, the allowable stresses under different metal steel plate wall thicknesses are 91.3 MPa, 96.2 MPa, 99.6 MPa, and 102 MPa, respectively.

[0063] (2) Determine the minimum allowable thickness of the tank wall.

[0064] The minimum allowable thickness of the storage tank is:

[0065]

[0066] In the formula, t is the calculated thickness of the tank wall plate under the storage medium conditions (also known as the minimum allowable thickness or minimum thickness); D is the inner diameter of the storage tank; H is the height from the calculation point of the tank wall to the highest liquid level (also known as the calculation height); [σ] is the allowable stress of the tank wall material (abbreviated as allowable stress); ρ is the relative density of the stored liquid; This refers to the joint coefficient. The set joint coefficient... The value is 0.9, where n1 is the safety factor for steel plate material; n2 is the safety factor for composite material; σ1 is the tensile strength of steel plate material; σ2 is the tensile strength of composite material; δ1 is the thickness of steel plate material; and δ2 is the thickness of composite material.

[0067] Preferably, the safety factor n1 for steel plate material is 2; and the safety factor n2 for composite material is 6.5. Substituting into the minimum allowable thickness model for tank wall thickness, the minimum allowable thickness varies for different metal steel plate wall thicknesses at different calculation heights, as detailed in Tables 2 to 5.

[0068] Table 2. Calculation results for composite materials with a wall thickness of 4 mm and an allowable stress of 102 MPa.

[0069]

[0070] Table 3 shows the calculation results for a composite wall thickness of 3 mm and an allowable stress of 99.6 MPa.

[0071]

[0072] Table 4 shows the calculation results for a composite wall thickness of 2 mm and an allowable stress of 96.2 MPa.

[0073]

[0074]

[0075] Table 5. Calculation results for a composite wall thickness of 1 mm and an allowable stress of 91.3 MPa.

[0076]

[0077] (3) Determine the applicable range of the composite material inner liner structure.

[0078] The thickness after construction is the sum of the carbon fiber composite material thickness and the tank wall thickness. Taking a wall thickness of 4mm as an example, the composite material thickness is 3.315mm. Therefore, the thickness after construction = 4 + 3.315 = 7.315mm, meaning the tank thickness after reinforcing the composite material liner is 7.315mm, which is 7.32mm after rounding to two decimal places. This thickness after reinforcing the composite material liner is also referred to as the tank wall thickness after reinforcement with the selected composite material liner.

[0079] By comparing the minimum allowable thickness of the tank wall with the thickness of the tank after reinforcing with the composite material liner, firstly, the thickness of the tank after reinforcing with the composite material liner must be greater than the minimum allowable thickness of the tank wall. If so, the selected composite material liner is suitable for the tank wall. Preferably, the corrosion allowance of the steel plate should also be considered based on the minimum allowable thickness. Here, the corrosion allowance is taken as 1 mm, meaning the thickness of the reinforced tank wall must be greater than or equal to the minimum allowable thickness plus the corrosion allowance. If so, the selected composite material liner is suitable for the tank wall. Preferably, to ensure a long service life of the tank, a 10% safety margin is taken based on field experience. That is, the thickness of the reinforced tank wall must be greater than or equal to 1.1 times the sum of the minimum allowable thickness and the corrosion allowance. If so, the selected composite material liner is suitable for the tank wall. Through the above calculations, the optimal implementation method is to ensure that the thickness of the tank after reinforcing with the composite material liner is greater than or equal to 1.1 times the sum of the minimum allowable thickness and the corrosion allowance, using a structural material of 1 layer of woven fabric, 3 layers of four-axis fabric, and 1 layer of carbon fiber fabric for reinforcement and repair. Other materials are not suitable for this type of reinforcement.

[0080] This invention employs a novel carbon fiber composite material liner to reinforce the inner wall of a gathering and transportation storage tank. By comparing the minimum allowable thickness of the tank wall with the thickness of the tank after reinforcement with the composite material liner, the applicable range of a specific composite material liner structure is determined. This method fully considers the allowable stress and safety factor of the material, resulting in a suitable minimum allowable thickness for the pipe wall repair material. Using this method will significantly improve the service life of metal storage tanks, especially for tanks undergoing "reconstruction and demolition," as the liner repair process allows for tank repair without disassembly, effectively reducing replacement costs.

[0081] An embodiment of a composite material inner liner for reinforcing the wall of a storage tank:

[0082] An embodiment of the present invention for a composite material inner liner for reinforcing the wall of a storage tank, such as... Figure 3 The composite material liner shown comprises: a woven fabric 2, a four-axis fabric 3, and a carbon fiber fabric 4; wherein the woven fabric 2 is n1 layers, where 3 ≥ n1 ≥ 1; the four-axis fabric 3 is 3 layers; and the carbon fiber fabric 4 is n2 layers, where n2 ≥ 1. The layers of the composite material liner are bonded together by an adhesive. The woven fabric is located in the innermost layer and is used to bond the composite material liner to the tank wall 1. The four-axis fabric is placed in the middle layer and is used to increase or decrease the allowable stress of the composite material liner. The carbon fiber fabric is placed in the outermost layer and is used for corrosion protection and to increase stress, tensile strength, and flexural strength. The layers of the composite material liner are bonded together by resin. Preferably, the composite material liner comprises 1 layer of woven fabric, 3 layers of four-axis fabric, and 1 layer of carbon fiber fabric. Preferably, the thickness of the woven fabric is 0.56 mm, the thickness of the four-axis fabric is 0.86 mm, and the thickness of the carbon fiber fabric is 0.175 mm.

Claims

1. A method for reinforcing the wall of a storage tank, characterized in that: include: 1) Select one composite material liner with superior performance parameter values ​​from N different composite material liner structures based on performance parameters, and denot it as the selected composite material liner, where N≥2; performance parameters include tensile strength and flexural strength. The composite material liner consists of, from the inside out, three layers: k1 (grid fabric), k2 (quadriaxial fabric), and k3 (carbon fiber fabric), where k1 > 0, k2 > 0, and k3 ≥ 0. The grid fabric is used to bond the composite material liner to the tank wall; the quadriaxial fabric is used to increase the stress of the composite material liner; and the carbon fiber fabric is used to increase the stress, tensile strength, and flexural strength of the composite material liner. The difference between N different composite material liner structures lies in the different values ​​of k1, k2, and k3 in each structure. 2) Determine whether the tank wall meets condition 1. If it does, then the selected composite material liner is suitable for the tank wall. Condition 1 is that the difference between the wall thickness of the tank wall reinforced with the selected composite material liner and the minimum allowable thickness t of the tank wall is not less than L1. L1 is the corrosion allowance of the tank wall or: t × safety margin + corrosion allowance value × (1 + safety margin), L1 > 0. D is the inner diameter of the storage tank, H is the height from the calculation point on the tank wall to the highest liquid level, and ρ is the relative density of the stored liquid. For the allowable stress of the tank wall material, This refers to the joint coefficient; 3) Reinforce the applicable tank wall according to the selected composite material liner.

2. The tank wall reinforcement method according to claim 1, characterized in that: The safety margin is 0.

1.

3. The tank wall reinforcement method according to claim 1, characterized in that: Flexural strength is P is the maximum load on the specimen at failure, L is the test span of the specimen, b is the width of the specimen cross-section, and h is the thickness of the specimen cross-section.

4. The tank wall reinforcement method according to claim 1, characterized in that: N=3; In the first structure of the composite material liner, k1=1, k2=2, k3=0; In the second structure of the composite material liner, k1=1, k2=3, k3=1; In the third structure of the composite material liner, k1=1, k2=4, k3=2.

5. The tank wall reinforcement method according to claim 1, characterized in that: Allowable stress of tank wall The calculation formula is: In the formula, n1 is the safety factor of the steel plate material; n2 is the safety factor of the composite material liner; σ1 is the tensile strength of the steel plate material; σ2 is the tensile strength of the composite material liner; δ1 is the thickness of the steel plate material; and δ2 is the thickness of the composite material liner.

6. The tank wall reinforcement method according to claim 5, characterized in that: The safety factor n1 for steel plate material is 2; the safety factor n2 for composite material liner is 6.

5.

7. The tank wall reinforcement method according to any one of claims 1 to 6, characterized in that: L1 = 2, in millimeters.

8. A composite material inner liner for reinforcing the wall of a storage tank, characterized in that: The composite material inner liner structure comprises, from the inside out: a k1 layer of woven fabric, a k2 layer of four-axis fabric, and a k3 layer of carbon fiber fabric, where 3 ≥ k1 ≥ 1, k2 = 3, and k3 ≥ 1. The woven fabric is used to bond the composite material inner liner to the tank wall; the four-axis fabric is used to increase the stress of the composite material inner liner; and the carbon fiber fabric is used to increase the stress, tensile strength, and flexural strength of the composite material inner liner. This composite material inner liner was selected and applied to reinforce suitable tank walls using the following method: 1) Select one composite material liner with superior performance parameter values ​​from N different composite material liner structures based on performance parameters, and denot it as the selected composite material liner, where N≥2; performance parameters include tensile strength and flexural strength. The difference between N different composite material liners lies in the different values ​​of k1, k2, and k3 in each structure; 2) Determine whether the tank wall meets condition 1. If it does, then the selected composite material liner is suitable for the tank wall. Condition 1 is that the difference between the wall thickness of the tank wall reinforced with the selected composite material liner and the minimum allowable thickness t of the tank wall is not less than L1. L1 is the corrosion allowance of the tank wall or: t × safety margin + corrosion allowance value × (1 + safety margin), L1 > 0. D is the inner diameter of the storage tank, H is the height from the calculation point on the tank wall to the highest liquid level, and ρ is the relative density of the stored liquid. For the allowable stress of the tank wall material, This is the joint coefficient.

9. The composite material inner liner for reinforcing the tank wall according to claim 8, characterized in that: The thickness of the woven fabric is 0.56mm, the thickness of the four-axis fabric is 0.86mm, and the thickness of the carbon fiber fabric is 0.175mm.

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