A calculation method for the strength of a pipe segment

Abstract

The present invention provides a method for calculating the strength of a pipe segment, which is used to calculate the remaining strength of a pipe segment with both internal and external indentations, including the steps of: S100, analyzing the parameters of the internal and external indentations of the pipe segment to determine the first parameter and the second parameter of the internal indentation and the third parameter and the fourth parameter of the external indentation that affect the remaining strength of the pipe segment; S200, calculating the failure pressure P of the pipe segment when the internal and external indentations act together i and the failure pressure P0 of the pipe segment when the internal indentation or the external indentation acts alone; S300, calculating the interaction coefficient ω between the internal and external indentations and determining whether there is an interaction between the internal and external indentations; S400, calculating the remaining strength P of the pipe segment according to the first parameter value d1, the second parameter value L1, the third parameter value d2, and the fourth parameter value L2 h . The present invention can accurately calculate the remaining strength of a pipeline with internal and external corrosion, and solves the problem that the ultimate bearing capacity of the remaining strength of the pipeline under the coupling action of internal and external corrosion is unclear.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and particularly relates to a calculation method for the strength of a pipe section. Background Art

[0002] At present, different evaluation standards and evaluation system methods for the remaining strength of corroded pipelines have been introduced at home and abroad, such as: ASME B3IG criterion, modified B31G criterion, ASME B31G-2012 standard, RSTRENG method, DNV-RP-F101 standard (2017), PCORRC method, SY / T6151-2009 standard, etc. These calculation methods are only applicable to the case of external corrosion or internal corrosion acting alone, and cannot distinguish the interaction between internal and external corrosion. Therefore, it is impossible to accurately calculate the remaining strength of pipelines with both internal and external corrosion. Summary of the Invention

[0003] The purpose of the present invention is to provide a simple and easy calculation method for the strength of a pipe section, which can accurately calculate the remaining strength of a pipeline with both internal and external corrosion, and solves the problem of unclear ultimate bearing capacity of the remaining strength of a pipeline under the coupling action of internal and external corrosion.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A calculation method for the strength of a pipe section is used to calculate the remaining strength of a pipe section with both internal indentation and external indentation. The inner diameter of the pipe section is R, the outer diameter is D, and the wall thickness is t, and it includes the steps:

[0006] S100. Analyze the parameters of the internal indentation and the external indentation of the pipe section to determine the first parameter and the second parameter of the internal indentation that affect the remaining strength of the pipe section, and the third parameter and the fourth parameter of the external indentation that affect the remaining strength of the pipe section;

[0007] S200. Calculate the failure pressure P of the pipe section when the internal indentation and the external indentation act together i , and at the same time calculate the failure pressure P0 of the pipe section when the internal indentation or the external indentation acts alone;

[0008] S300. Calculate the interaction coefficient ω between the internal indentation and the external indentation according to P i obtained in step S200 and P0, and judge whether there is an interaction between the internal indentation and the internal indentation. If so, enter S400;

[0009] S400. Calculate the remaining strength P of the pipe section according to the first parameter value d1, the second parameter value L1 of the internal indentation and the third parameter value d2, the fourth parameter value L2 of the external indentation h ;

[0010] In S400

[0011] wherein, R n is the ultimate tensile strength of the pipe segment, K d1 is the action coefficient of the first parameter, K L1 is the action coefficient of the second parameter, K d2 is the action coefficient of the third parameter, K L2 is the action coefficient of the fourth parameter.

[0012] Preferably, step S100 includes the steps of:

[0013] S110. Simulate the parameters of the pipe segment by finite element software and obtain a relationship curve between each parameter and the failure pressure of the pipe segment;

[0014] S120. Determine the first parameter and the second parameter of the internal indentation and the third parameter and the fourth parameter of the external indentation that can affect the remaining strength of the pipe segment by comparing the relationship curves between each parameter and the failure pressure of the pipe segment.

[0015] Preferably, step S110 includes: drawing a relationship curve between the parameter and the failure pressure of the pipe segment by changing the parameters of the internal indentation and calculating the corresponding failure pressure of the pipe segment. At the same time, draw a relationship curve between the parameter and the failure pressure of the pipe segment by changing the parameters of the external indentation and calculating the corresponding failure pressure of the pipe segment.

[0016] Preferably, in step S200, calculate the failure pressure P i of the pipe segment when the internal indentation and the external indentation act together and the failure pressure P0 of the pipe segment when the internal indentation or the external indentation acts alone by finite element software.

[0017] Preferably, in step S300, ω = (P0 / P i ) × 100%.

[0018] Preferably, in step S300, when ω < 95%, it is determined that there is an interaction between the internal indentation and the internal indentation.

[0019] Preferably, in step S400, according to the distance S L along the axial direction of the pipe segment between the internal indentation and the external indentation, determine K d1 , K d2 , K L1 , K L2 .

[0020] Preferably, when When d1 K = 1.092(r1 + r2) / (S L + r1 + r2), where K d2 = 0.918, r1 is the major semi - axis dimension of the internal indentation, and r2 is the major semi - axis dimension of the external indentation;

[0021] When K d1 = K d2 = 1.

[0022] Preferably, when K L1 = 0.5925, K L2 = 1.4223,

[0023] When K L1 = K L2 = 1.

[0024] The technical solution of the present invention, which calculates the remaining strength P of the pipe section according to the first parameter value d1, the second parameter value L1 of the internal indentation, the third parameter value d2, and the fourth parameter value L2 of the external indentation in step S400, h can accurately calculate the remaining strength of the pipeline with internal and external corrosion, and solve the problem that the ultimate bearing capacity of the remaining strength of the pipeline under the coupling action of internal and external corrosion is unclear. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the flow chart of the strength calculation method of the pipe section in Embodiment 1;

[0026] Figure 2 is the curve graph of the failure pressure of the pipe section corresponding to the length of the external indentation;

[0027] Figure 3 is the curve graph of the failure pressure of the pipe section corresponding to the width of the external indentation;

[0028] Figure 4 is the curve graph of the failure pressure of the pipe section corresponding to the depth of the external indentation;

[0029] Figure 5 is the curve graph of the failure pressure of the pipe section corresponding to the major - axis included angle of the external indentation. DETAILED DESCRIPTION OF THE INVENTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes in detail the calculation method of the pipe - section strength of the present invention with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Embodiment 1

[0032] A calculation method for the strength of a pipe section, used to calculate the remaining strength of a pipe section with both internal and external indentations. The inner diameter of the pipe section is R, the outer diameter is D, and the wall thickness is t. As Figure 1 shown, it includes the steps:

[0033] S100. Analyze the parameters of the internal and external indentations of the pipe section to determine the first parameter and the second parameter of the internal indentation that affect the remaining strength of the pipe section, and the third parameter and the fourth parameter of the external indentation that affect the remaining strength of the pipe section;

[0034] S200. Calculate the failure pressure P of the pipe section when the internal and external indentations act together, i and at the same time calculate the failure pressure P0 of the pipe section when the internal or external indentation acts alone;

[0035] S300. Calculate the interaction coefficient ω between the internal and external indentations according to P i and P0 obtained in step S200, and determine whether there is an interaction between the internal and external indentations. If so, enter S400;

[0036] S400. Calculate the remaining strength P of the pipe section according to the first parameter value d1, the second parameter value L1 of the internal indentation, the third parameter value d2, and the fourth parameter value L2 of the external indentation h ;

[0037] In S400

[0038] wherein, R n is the ultimate tensile strength of the pipe section, K d1 is the action coefficient of the first parameter, K L1 is the action coefficient of the second parameter, K d2 is the action coefficient of the third parameter, K L2 is the action coefficient of the fourth parameter.

[0039] Example two

[0040] It may include the steps in step S100:

[0041] S110. Simulate the parameters of the pipe section through finite element software and obtain the relationship curve graph between each parameter and the failure pressure of the pipe section;

[0042] S120. Determine the first parameter and the second parameter of the internal indentation that can affect the remaining strength of the pipe section, and the third parameter and the fourth parameter of the external indentation by comparing the relationship curve graph between each parameter and the failure pressure of the pipe section.

[0043] Among them, step S110 includes: drawing a relationship curve between the parameter and the failure pressure of the pipe section by changing the parameters of the internal indentation and calculating the corresponding failure pressure of the pipe section. At the same time, drawing a relationship curve between the parameter and the failure pressure of the pipe section by changing the parameters of the external indentation and calculating the corresponding failure pressure of the pipe section. Specifically, it is possible to simulate the formation of ellipsoids on the inner and outer walls of the pipe section according to the internal indentation and the external indentation respectively, and change the parameter values of the internal indentation and the external indentation on the pipe section by changing the size of the ellipsoids, and calculate the failure pressure of the pipe section corresponding to different parameter values through finite element software.

[0044] In this embodiment, the length (along the axial direction of the pipe section), width (along the circumferential direction of the pipe section), depth (along the radial direction of the pipe section) and major axis angle of the external indentation are processed respectively to obtain the Figure 2 shown curve of the external indentation length corresponding to the pipe section failure pressure, as Figure 3 shown curve of the external indentation width corresponding to the pipe section failure pressure, as Figure 4 shown curve of the external indentation depth corresponding to the pipe section failure pressure, as Figure 5 shown curve of the external indentation major axis angle corresponding to the pipe section failure pressure. In step S120, by comparing Figure 1 、 Figure 2 、 Figure 3 and Figure 4 , it can be seen that the influence of the width change and the major axis angle change on the failure pressure is very small and can be ignored, while the influence of the depth change and the length change on the failure pressure is very large. Therefore, it is determined that the first parameter d1 is the depth of the internal indentation, the second parameter L1 is the length of the internal indentation, the third parameter d2 is the depth of the external indentation, and the fourth parameter L2 is the depth of the external indentation.

[0045] Next, in step S200, the failure pressure P of the pipe section when the internal indentation and the external indentation act together is calculated through finite element software i and the failure pressure P0 of the pipe section when the internal indentation or the external indentation acts alone. It should be noted that calculating P i and P0 through finite element software is not the inventive point of the present invention, but an existing technology. The present invention only utilizes this existing technology and does not intend to improve it. Therefore, the specific calculation process will not be elaborated here one by one.

[0046] Embodiment III

[0047] In step S300, ω = (P0 / P i ) × 100%. When ω < 95%, it is determined that there is an interaction between the internal indentation and the internal indentation, and then step S400 is entered. It should be noted that if ω ≥ 95%, it can be considered that there is no mutual influence between the internal indentation and the external indentation. At this time, the existing standards in the country can be used to evaluate the remaining strength of the pipe section.

[0048] Specifically, in step S400, according to the distance S between the inner indentation and the outer indentation along the axial direction of the pipe section L , K d1 , K d2 , K L1 , K L2 are determined. Since the first parameter d1 is the depth of the inner indentation, the second parameter L1 is the length of the inner indentation, the third parameter d2 is the depth of the outer indentation, and the fourth parameter L2 is the depth of the outer indentation, so K d1 is the depth action coefficient of the inner indentation, K L1 is the length action coefficient of the inner indentation, K d2 is the depth action coefficient of the outer indentation, and K L2 is the length action coefficient of the outer indentation

[0049] Among them, when , K d1 = 1.092(r1 + r2) / (S L + r1 + r2), K d2 = 0.918, where r1 is the major semi-axis dimension of the inner indentation and r2 is the major semi-axis dimension of the outer indentation. When , K d1 = K d2 = 1. When , K L1 = 0.5925, K L2 = 1.4223. When , K L1 = K L2 = 1.

[0050] The inventor has proved through a finite number of experiments that the error between the remaining strength of the pipe section calculated by using the calculation method of the pipe section strength of the present invention and the measured value does not exceed 4%.

[0051] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A calculation method for the strength of a pipe section, used to calculate the remaining strength of a pipe section with both internal and external indentations. The inner diameter of the pipe section is R, the outer diameter is D, and the wall thickness is t. It is characterized in that: It includes the steps: S100. Analyze the parameters of the internal and external indentations of the pipe section to determine the first parameter and the second parameter of the internal indentation that affect the remaining strength of the pipe section, and the third parameter and the fourth parameter of the external indentation that affect the remaining strength of the pipe section; S200. Calculate the failure pressure P of the pipe section when the inner indentation and the outer indentation act together i , and at the same time calculate the failure pressure P0 of the pipe section when the inner indentation or the outer indentation acts alone; S300. Calculate the interaction coefficient ω between the inner indentation and the outer indentation according to P obtained in step S200, and determine whether there is an interaction between the inner indentation and the outer indentation. If so, proceed to S400; i and P0, and determine whether there is an interaction between the inner indentation and the outer indentation. If so, proceed to S400; S400. Calculate the remaining strength P of the pipe section based on the first parameter value d1 and the second parameter value L1 of the internal indentation, and the third parameter value d2 and the fourth parameter value L2 of the external indentation h ; In S400, wherein, R n is the ultimate tensile strength of the pipe segment, K d1 is the first parameter action coefficient, K L1 is the second parameter action coefficient, K d2 is the third parameter action coefficient, K L2 is the fourth parameter action coefficient.

2. The calculation method for the strength of a pipe section according to claim 1, characterized in that: In step S100, it includes the steps: S110. Simulate the parameters of the pipe section through finite element software and obtain a relationship curve graph between each parameter and the failure pressure of the pipe section; S120. Determine the first parameter and the second parameter of the internal indentation and the third parameter and the fourth parameter of the external indentation that can affect the remaining strength of the pipe section by comparing the relationship curve graph between each parameter and the failure pressure of the pipe section.

3. The calculation method for the strength of a pipe section according to claim 2, characterized in that: In step S110, it includes: drawing a relationship curve graph between the parameter and the failure pressure of the pipe section by changing the parameters of the internal indentation and calculating the corresponding failure pressure of the pipe section. At the same time, draw a relationship curve graph between the parameter and the failure pressure of the pipe section by changing the parameters of the external indentation and calculating the corresponding failure pressure of the pipe section.

4. The evaluation method for the bending failure of a pipe section according to claim 1, characterized in that: In step S200, the failure pressure P of the pipe section when the inner indentation and the outer indentation act together is calculated by finite element software i and the failure pressure P0 of the pipe section when the inner indentation or the outer indentation acts alone.

5. The calculation method for the strength of a pipe section according to claim 1, characterized in that: In step S300, ω = (P0 / P i ) × 100%.

6. The calculation method for the strength of a pipe section according to claim 5, characterized in that: In step S300, when ω < 95%, it is determined that there is an interaction between the internal indentation and the internal indentation.

7. The calculation method for the strength of a pipe section according to any one of claims 1 to 6, characterized in that: In step S400, determine K L based on the distance S along the axial direction of the pipe segment between the inner indentation and the outer indentation L L , determine K d1 d1 , K d2 d2 , K L1 L1 , K L2 L2 .

8. The calculation method for the strength of a pipe section according to claim 7, characterized in that: When K d1 = 1.092(r1 + r2) / (S L + r1 + r2), K d2 = 0.918, where r1 is the major semi-axis dimension of the inner indentation and r2 is the major semi-axis dimension of the outer indentation; When K d1 = K d2 = 1 9. The calculation method for the strength of a pipe section according to claim 7, characterized in that: When is the case, K L1 = 0.5925, K L2 = 1.4223, When K L1 = K L2 = 1

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