An axial reinforcement method for reinforcing a pipe using a fiber composite

Abstract

This invention discloses an axial reinforcement method for pipelines using fiber composite materials. Specifically, the method involves: first, obtaining the characteristic parameters of the pipeline to be reinforced, the adhesive, and the composite material; then, controlling the shear stress of the adhesive to obtain the minimum axial reinforcement extension *l* on both sides of the pipeline defect, ensuring that the adhesive does not debond before the pipeline yields; next, measuring the axial length *d* of the pipeline defect, and performing reinforcement construction based on preset adhesive thickness parameters and a total reinforcement length of 2l+d. The beneficial effects of this invention are: ensuring that the adhesive does not debond before the pipeline yields, and fully utilizing the reinforcement effect of the composite material.

Description

Technical Field

[0001] This invention relates to the field of oilfield pressure vessel reinforcement technology, and in particular to a method for axial reinforcement of oil and gas pipelines using fiber composite materials. Background Technology

[0002] Oilfield steel pipelines are currently the most economical and safest long-distance gas-liquid transportation tool. Statistics show that by 2019, the total length of oil and gas pipelines in my country reached 139,000 kilometers, and it is projected to reach 240,000 kilometers by 2025. Most of my country's gas-liquid transportation steel pipelines were built in the 1880s, have been in service for a long time, and have been subjected to harsh conditions such as pressure, corrosive media, high temperatures, and humid environments, leading to defects such as corrosion, thinning of the pipe wall, and cracks. Traditional pipeline reinforcement techniques (such as pipe replacement and welding) have disadvantages such as high construction difficulty, shutdown and production stoppage for construction, and the introduction of open flames during construction. Resin-based fiber composite materials are lightweight, high-strength, and corrosion-resistant. Fiber composite material pipeline reinforcement technology has advantages such as convenient construction, no need for high temperatures during construction, and the ability to be carried out under pressure, overcoming the shortcomings of traditional repair methods.

[0003] Fiber-reinforced composite materials have been widely used in the reinforcement of pipes with thinned (non-penetrating) walls, but the reinforcement technologies and methods for non-penetrating / penetrating cracks are still immature. Prestressed fiber-reinforced composite materials can effectively repair cracked pipes, but because cracks can propagate, inadequate reinforcement or repair can still lead to pipe leakage or even bursting, causing economic damage or even safety accidents. Therefore, the reinforcement of cracked steel pipes has become a key research focus in the field of pipe reinforcement. Summary of the Invention

[0004] In order to improve the reinforcement quality of non-penetrating / penetrating cracked pipelines, this invention provides an axial reinforcement method for oilfield pipelines using fiber composite materials.

[0005] To achieve the above-mentioned objective, this invention provides a method for axial reinforcement of oilfield pipelines using fiber composite materials, the reinforcement method comprising the following steps:

[0006] Obtain the characteristic parameters of the pipe to be reinforced, the adhesive, and the composite material, and calculate the minimum axial elongation for reinforcement on both sides of the defect in the pipe. l ;

[0007] Measure the axial length of the defect in the pipe to be reinforced d ;

[0008] Based on the preset adhesive thickness parameters and the overall reinforcement length 2 l+d Reinforcement work will be carried out.

[0009] Among them, the axial reinforcement extension on both sides of the defect in the pipeline under testl The calculation method includes the following steps:

[0010] Step S1: Measure or calculate the elastic modulus of the pipe to be reinforced. E s Pipe outer diameter D Yield pressure P and residual wall thickness t s ; Obtain the elastic modulus of the adhesive E a shear modulus G a ,thickness t a and shear strength t f ; Measure the elastic modulus of composite materials E c and composite material thickness t c ;

[0011] Step S2: Substitute the parameters from Step S1 into the following formula to obtain the minimum axial reinforcement elongation on both sides of the defect in the pipe to be tested. l :

[0012]

[0013] in, .

[0014] The formula in step S2 is obtained through the following method:

[0015] Step S201: Based on the stress relationship between the pipe, adhesive, and composite material, establish the equilibrium equation:

[0016] (1)

[0017] (2)

[0018] (3)

[0019] In the formula, , , These are the axial stress of the pipe, the axial stress of the composite material, and the shear stress of the adhesive, respectively.

[0020] Step S202: Relationship between stress and displacement in composite materials and pipelines:

[0021] (4)

[0022] (5)

[0023] In the formula, and These are the axial displacement of the composite material and the axial displacement of the pressure vessel, respectively.

[0024] Step S203: Based on the relationship between the adhesive, the composite material, and the axial displacement of the pressure vessel:

[0025] (6)

[0026] (7)

[0027] In the formula, For the shear strain of the adhesive; For adhesive thickness; The shear modulus of the adhesive;

[0028] Step S204: Combining equations (1), (2), (4), (5), (6), and (7), we obtain the following formula:

[0029] (8)

[0030] (9)

[0031] Step S205: Boundary conditions:

[0032] (10)

[0033] Step S206: Substitute the boundary condition (10) into equation (8) to obtain

[0034] (11)

[0035] Step S207: According to equation (3) of the equilibrium equation, we obtain

[0036] (12)

[0037] (13)

[0038] It can be derived from formula (13) l The formula.

[0039] Among them, the yield pressure of the pipeline to be reinforced P It is obtained through the following formula:

[0040] (14)

[0041] (15)

[0042] (16)

[0043] In the formula, The circumferential stress at the yield point of the pipeline. The axial stress at which the pipe yields. The yield strength of the pipeline. r c The initial outer diameter of the pipe. r i This is the initial inner diameter of the pipe. r a This refers to the outer diameter of the defective area in the pipeline.

[0044] The specific boundary conditions in step S205 are as follows: the adhesive-pressure vessel and adhesive-composite material interfaces do not debond before yielding; under the action of yield pressure, the maximum value of the axial shear stress of the adhesive is equal to its shear strength; when x equals 0, the axial strain of the composite material, adhesive and pressure vessel are equal; when x equals 1, the shear stress of the adhesive is equal to its shear strength.

[0045] The beneficial effects of the present invention are: the reinforcement method of the present invention can realize the design of the axial reinforcement length of the composite material reinforced pipeline, ensure that the adhesive does not fail axially before the pipeline bursts, and can give full play to the axial tensile properties of the composite material. Detailed Implementation

[0046] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0047] Example 1

[0048] This invention provides an axial reinforcement method for pipes using fiber composite materials. The reinforcement method includes the following steps:

[0049] Obtain the characteristic parameters of the pipe to be reinforced, the adhesive, and the composite material, and calculate the minimum axial elongation for reinforcement on both sides of the defect in the pipe. l ;

[0050] Measure the axial length of the defect in the pipe to be reinforced d ;

[0051] Based on the preset adhesive thickness parameters and the overall reinforcement length 2 l+d Reinforcement work will be carried out.

[0052] Among them, the axial reinforcement extension on both sides of the defect in the pipeline under test l The calculation method includes the following steps:

[0053] Step S1: Measure or calculate the elastic modulus of the pipe to be reinforced. Es Pipe outer diameter D Yield pressure P and residual wall thickness t s ; Obtain the elastic modulus of the adhesive E a shear modulus G a ,thickness t a and shear strength t f ; Measure the elastic modulus of composite materials E c and composite material thickness t c ;

[0054] Step S2: Substitute the parameters from Step S1 into the following formula to obtain the minimum axial reinforcement elongation on both sides of the defect in the pipe to be tested. l :

[0055]

[0056] in, .

[0057] The formula in step S2 is obtained through the following method:

[0058] Step S201: Based on the stress relationship between the pipe, adhesive, and composite material, establish the equilibrium equation:

[0059] (1)

[0060] (2)

[0061] (3)

[0062] In the formula, , , These are the axial stress of the pipe, the axial stress of the composite material, and the shear stress of the adhesive, respectively.

[0063] Step S202: Relationship between stress and displacement in composite materials and pipelines:

[0064] (4)

[0065] (5)

[0066] In the formula, and These are the axial displacement of the composite material and the axial displacement of the pressure vessel, respectively.

[0067] Step S203: Based on the relationship between the adhesive, the composite material, and the axial displacement of the pressure vessel:

[0068] (6)

[0069] (7)

[0070] In the formula, For the shear strain of the adhesive; For adhesive thickness; The shear modulus of the adhesive;

[0071] Step S204: Combining equations (1), (2), (4), (5), (6), and (7), we obtain the following formula:

[0072] (8)

[0073] (9)

[0074] Step S205: Boundary conditions:

[0075] (10)

[0076] Step S206: Substitute the boundary condition (10) into equation (8) to obtain

[0077] (11)

[0078] Step S207: According to equation (3) of the equilibrium equation, we obtain

[0079] (12)

[0080] (13)

[0081] It can be derived from formula (13) l The formula.

[0082] Among them, the yield pressure of the pipeline to be reinforced P It is obtained through the following formula:

[0083] (14)

[0084] (15)

[0085] (16)

[0086] In the formula, The circumferential stress at the yield point of the pipeline. The axial stress at which the pipe yields. The yield strength of the pipeline. r c The initial outer diameter of the pipe. r i This is the initial inner diameter of the pipe. r a This refers to the outer diameter of the defective area in the pipeline.

[0087] The specific boundary conditions in step S205 are as follows: the adhesive-pressure vessel and adhesive-composite material interfaces do not debond before yielding; under the action of yield pressure, the maximum value of the axial shear stress of the adhesive is equal to its shear strength; when x equals 0, the axial strain of the composite material, adhesive and pressure vessel are equal; when x equals 1, the shear stress of the adhesive is equal to its shear strength.

[0088] Example 2

[0089] This invention provides a method for calculating the axial reinforcement length of pipes reinforced with fiber composite materials, comprising the following steps:

[0090] Obtain the characteristic parameters of the pipe to be reinforced, the adhesive, and the composite material, and calculate the minimum axial elongation for reinforcement on both sides of the defect in the pipe. l ;

[0091] Measure the axial length of the defect in the pipe to be reinforced d ;

[0092] Based on the preset adhesive thickness parameters and the overall reinforcement length 2 l+d .

[0093] Among them, the axial reinforcement extension on both sides of the defect in the pipeline under test l The calculation method includes the following steps:

[0094] Step S1: Measure or calculate the elastic modulus of the pipe to be reinforced. E s Pipe outer diameter D Yield pressure P and residual wall thickness t s ; Obtain the elastic modulus of the adhesive E a shear modulus G a ,thickness t a and shear strength t f ; Measure the elastic modulus of composite materials E c and composite material thickness tc ;

[0095] Step S2: Substitute the parameters from Step S1 into the following formula to obtain the minimum axial reinforcement elongation on both sides of the defect in the pipe to be tested. l :

[0096]

[0097] in, .

[0098] The formula in step S2 is obtained through the following method:

[0099] Step S201: Based on the stress relationship between the pipe, adhesive, and composite material, establish the equilibrium equation:

[0100] (1)

[0101] (2)

[0102] (3)

[0103] In the formula, , , These are the axial stress of the pipe, the axial stress of the composite material, and the shear stress of the adhesive, respectively.

[0104] Step S202: Relationship between stress and displacement in composite materials and pipelines:

[0105] (4)

[0106] (5)

[0107] In the formula, and These are the axial displacement of the composite material and the axial displacement of the pressure vessel, respectively.

[0108] Step S203: Based on the relationship between the adhesive, the composite material, and the axial displacement of the pressure vessel:

[0109] (6)

[0110] (7)

[0111] In the formula, For the shear strain of the adhesive; For adhesive thickness; The shear modulus of the adhesive;

[0112] Step S204: Combining equations (1), (2), (4), (5), (6), and (7), we obtain the following formula:

[0113] (8)

[0114] (9)

[0115] Step S205: Boundary conditions:

[0116] (10)

[0117] Step S206: Substitute the boundary condition (10) into equation (8) to obtain

[0118] (11)

[0119] Step S207: According to equation (3) of the equilibrium equation, we obtain

[0120] (12)

[0121] (13)

[0122] It can be derived from formula (13) l The formula.

[0123] Among them, the yield pressure of the pipeline to be reinforced P It is obtained through the following formula:

[0124] (14)

[0125] (15)

[0126] (16)

[0127] In the formula, The circumferential stress at the yield point of the pipeline. The axial stress at which the pipe yields. The yield strength of the pipeline. r c The initial outer diameter of the pipe. r i This is the initial inner diameter of the pipe. r a This refers to the outer diameter of the defective area in the pipeline.

[0128] The specific boundary conditions in step S205 are as follows: the adhesive-pressure vessel and adhesive-composite material interfaces do not debond before yielding; under the action of yield pressure, the maximum value of the axial shear stress of the adhesive is equal to its shear strength; when x equals 0, the axial strain of the composite material, adhesive and pressure vessel are equal; when x equals 1, the shear stress of the adhesive is equal to its shear strength.

[0129] Example 3

[0130] Based on the reinforcement method in Example 1, the fiber composite material can be carbon fiber cloth.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An axial reinforcement method for reinforcing a pipe with a fiber composite material, characterized by, The reinforcement method includes the following steps: Obtain the characteristic parameters of the pipe to be reinforced, the adhesive, and the composite material, and calculate the minimum axial elongation for reinforcement on both sides of the defect in the pipe. l This ensures that the adhesive does not suffer axial damage before the pipeline bursts. Measuring the axial length of defects of a pipe to be reinforced d ; According to the preset adhesive thickness parameter, the total reinforcement length 2 l+d , reinforcement construction is carried out, The axial reinforcement elongation on both sides of the pipeline defect to be tested l The calculation method comprises the following steps: Step S1: Measure or calculate the elastic modulus of the pipe to be reinforced. E s Pipe outer diameter D Yield pressure P and residual wall thickness t s ; Obtain the elastic modulus of the adhesive E a shear modulus G a ,thickness t a and shear strength τ f ; Measure the elastic modulus of composite materials E c and composite material thickness t c ; Step S2: Substitute the parameters from Step S1 into the following formula to obtain the minimum axial reinforcement elongation on both sides of the defect in the pipe to be tested. l : wherein , the yield pressure of the pipe to be reinforced P is obtained by the following equation: （14） （15） （16） in, The circumferential stress at the yield point of the pipeline. The axial stress at which the pipe yields. The yield strength of the pipeline. r c The initial outer diameter of the pipe. r i This is the initial inner diameter of the pipe. r a This refers to the outer diameter of the defective area in the pipeline.

2. The method of reinforcement of claim 1, wherein, The formula for step S2 is obtained through the following method: Step S201: Based on the stress relationship between the pipe, adhesive, and composite material, establish the equilibrium equation: (1) (2) (3) wherein , , are the pipe axial stress, the composite axial stress, and the adhesive shear stress, respectively. Step S202: Relationship between stress and displacement in composite materials and pipelines: (4) (5) wherein and respectively the composite axial displacement and the pressure vessel axial displacement; Step S203: Based on the relationship between the adhesive, the composite material, and the axial displacement of the pressure vessel: (6) (7) wherein is the adhesive shear strain; is the adhesive thickness; is the shear modulus of the adhesive; Step S204: Combining equations (1), (2), (4), (5), (6), and (7), we obtain the following formula: (8) (9) Step S205: Boundary conditions: (10) Step S206: Substitute the boundary condition (10) into equation (8) to obtain (11) Step S207: According to equation (3) of the equilibrium equation, we obtain (12) (13) The formula of (13) can be derived from the formula of (12) as follows. l The formula of (13) can be derived from the formula of (12) 3. The method of reinforcement of claim 2, wherein, The specific boundary condition for step S205 is that the adhesive-pressure vessel and adhesive-composite material interfaces do not debond before yielding occurs.

4. The reinforcement method according to claim 3, characterized in that, The specific boundary condition in step S205 is: under the action of yield pressure, the maximum value of the axial shear stress of the adhesive is equal to its shear strength.

5. The method of reinforcement of claim 4, wherein, The specific boundary condition for step S205 is: when x equals 0, the axial strain of the composite material, adhesive, and pressure vessel are equal.

6. The method of reinforcement of claim 4, wherein, The specific boundary condition for step S205 is: when x equals l, the shear stress of the adhesive is equal to its shear strength.

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