A method for quantitatively evaluating service risk of a p92 ring-shaped welded joint containing spherical defects

Abstract

The application discloses a kind of P92 ring welding joint containing spherical defect service risk quantitative evaluation method, belong to the technical field of life assessment of power plant pressure-bearing component.This application establishes the service risk evaluation system of spherical defect in P92 ring welding joint by means of three-dimensional modeling and finite element numerical analysis, and the maximum equivalent stress of spherical defect in ring welding joint can be predicted and its service risk can be evaluated.Through the above-mentioned P92 ring welding joint spherical defect service risk evaluation method, the treatment scheme of the welding joint containing spherical defect can be optimized, secondary damage caused by excavation and repair of the pipeline can be avoided, and the service life of the pipeline welding joint is prolonged.

Description

Technical Field

[0001] This invention belongs to the technical field of life assessment of pressure-bearing components in thermal power plants, and in particular, it is a method for quantitatively assessing the service risk of P92 annular welded joints with spherical defects. Background Technology

[0002] Porosity and linear voids are common defects in the welds of the four main pipelines in power plants. Currently, these defects are mainly treated by patching and repair, but this process often causes secondary damage to the welds, leading to a decline in the service performance of the materials. Therefore, risk assessment of these defects is a necessary task in this field.

[0003] This invention proposes a quantitative assessment method for the service risk of P92 annular welded joints containing spherical defects. It performs three-dimensional modeling of defects such as spherical inclusions and porosity in the welded joint, conducts research on the maximum equivalent stress analysis and characterization method of spherical defects at different welded joints, and studies the service risk assessment method for spherical defects at different locations of the welded joint. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned deficiencies in the prior art and provide a method for quantitatively assessing the service risk of P92 annular welded joints containing spherical defects. The method is based on a combination of three-dimensional modeling and finite element numerical analysis to assess the risk of spherical defects in P92 welds.

[0005] The technical solution adopted by this invention to solve the above problems is: a method for quantitatively assessing the service risk of P92 annular welded joints containing spherical defects, characterized by comprising the following steps:

[0006] S1. Establish a three-dimensional model of annular welded joint containing spherical defects. Use three-dimensional modeling software to establish annular welded joints containing spherical defects of different sizes and distributed at different wall thicknesses.

[0007] S2. Maximum equivalent stress analysis of spherical defects: The stress analysis of the annular welded joint containing spherical defects was carried out using finite element analysis software, and the maximum equivalent stress of the defects was recorded and its variation trend was analyzed.

[0008] S3. The maximum equivalent stress of spherical defects can be characterized by establishing a prediction equation for the maximum equivalent stress of spherical defects under different specifications and design pressures based on the straight pipe specification ID318×106mm of the main steam pipeline of this invention.

[0009] S4. Establish a quantitative evaluation system for the service risk of components containing spherical defects. Based on the aforementioned calculations, the maximum equivalent stress σ of the spherical defect at different wall thickness locations of the welded joint can be determined. maxBy reviewing relevant standards, risk quantification assessment criteria were established.

[0010] S5. Establish a spherical defect risk quantification assessment system. Utilize Python language to establish a spherical defect risk quantification assessment system based on P92 annular welded joints, which can conduct risk assessments on spherical defects of the same type of P92 welded joints.

[0011] S6. Conduct service risk assessment on spherical defects. Utilize the Python language from step S5 to establish a spherical defect risk quantification assessment system based on the P92 annular welded joint, and conduct service risk quantification assessment on the spherical defects of the P92 annular welded joint.

[0012] Furthermore, the specific implementation method of step S1 is as follows: the pipe specifications for this simulation are: ID318×106mm, design pressure P=35.33Mpa, design temperature is 610℃, elastic modulus E=1688GPa at the calculation temperature, and linear expansion coefficient at the calculation temperature is 12.3×10 -6 / ℃. Spherical defects with distances to the inner wall of 5mm, 10mm, 20mm, 40mm, 60mm, 80mm, and 100mm are constructed in a P92 pipe. The dimensions of these defects are as follows: 4mm, 5mm, 6mm, 8mm.

[0013] Furthermore, step S2 includes the following sub-steps:

[0014] S21. Analysis of the influence of different sizes of spherical defects on the maximum equivalent stress. According to the maximum equivalent stress of spherical defects of different sizes at the same wall thickness position of the annular welded joint, the size of the spherical defect has little effect on the stress concentration, indicating that the size of the spherical defect has no effect on the maximum equivalent stress.

[0015] S22. Analysis of the influence of spherical defects at different wall thicknesses on the maximum equivalent stress. Based on the simulation results above, the size of the spherical defect has no effect on the maximum equivalent stress in the annular welded joint. Therefore, this invention takes... The spherical defect was analyzed, and its maximum equivalent stress at different wall thicknesses was examined. The results show that the maximum equivalent stress decreases with increasing distance from the inner wall, conforming to the following functional equation:

[0016]

[0017] In the formula: x is the distance from the defect to the inner wall, σ max This represents the maximum equivalent stress of the defect.

[0018] Furthermore, the specific implementation method of step S3 is as follows: Based on the straight pipe specification ID318×106mm of the main steam pipeline of this invention, a prediction equation for the maximum equivalent stress of spherical defects under different specifications and design pressures of the same material (P92) can be established. Assume the inner diameter of the straight pipe of the same material but different specifications is D. ix The outer diameter is D ox The design pressure is P x And the distance from the defect to the inner wall is d. x According to the LM formula, the distance from the inner wall d to the straight pipe of different specifications is... x Circumferential stress σ at the location θ for:

[0019]

[0020] Because the inner diameter of the straight pipe with ID318×106mm is D i1 The outer diameter is D o1 Given a design pressure of P1, the distance d1 from the inner wall of a straight pipe with ID318×106mm under the same circumferential stress state can be calculated using the above formula:

[0021]

[0022] Based on the above function formula (1) of the distance from the defect to the inner wall minus the maximum equivalent stress, the maximum equivalent stress of a spherical defect under the design pressure of straight pipes of different specifications made of the same material (P92) can be characterized:

[0023]

[0024] In the formula, d1 represents the circumferential stress state at any wall thickness position of a straight pipe of different specifications, and the equivalent wall thickness when the straight pipe of specification ID318×106mm is the same.

[0025] Furthermore, the specific implementation method of step S4 is as follows: Based on the aforementioned calculations, the maximum equivalent stress σ of the spherical defect at different wall thickness locations in the welded joint is known. max Since the structure is discontinuous at the defect, its equivalent stress can be considered as secondary stress, with 2 / 3 of the yield strength (σ) s / 1.5) is the criterion for determining allowable stress. Referring to Part 4 of GB / T 16507.4-2022, in the secondary stress zone, the maximum average stress on the inner and outer walls or the average equivalent stress of the cross section should not exceed 1.5 times the allowable stress; in the secondary stress zone, the maximum equivalent stress or the equivalent stress resulting from the sum of the average stress of the cross section and the bending stress should not exceed 3 times the allowable stress. Referring to ASME Code Case 2179-9, the yield strength of P92 material at the operating temperature T℃ is σ. sIn this invention, f is defined as the risk index. For components containing spherical defects, the service risk index is calculated as shown in Equation 5.

[0026]

[0027] The risk index of spherical defects at different locations of the annular welded joint can be obtained from the above characterization method. Different risk index ranges correspond to different risk levels, thus forming a service risk quantitative evaluation system containing spherical defects, as shown in Table 1.

[0028] Table 1. Quantitative Evaluation System for Service Risk of Welded Joints with Spherical Defects

[0029]

[0030]

[0031] Furthermore, step S5 includes the following sub-steps:

[0032] S51. Construction of a stress prediction model for spherical defects: A stress prediction model for spherical defects is constructed using the Python language.

[0033] S52. Construction of a quantitative evaluation system for the service risk of spherical defects: A stress prediction model for spherical defects was constructed using Python.

[0034] Furthermore, the specific implementation method of step S6 is as follows: input the material, size, wall thickness, allowable stress, yield strength, and size of the spherical defect obtained by detection and its position in the P92 annular welded joint into the spherical defect risk quantification assessment system established in step S5, and perform risk quantification assessment of the spherical defect in its annular welded joint.

[0035] Compared with existing technologies, this invention has the following advantages and effects: It utilizes a combination of 3D modeling and finite element numerical analysis to quantitatively assess the service risk of spherical defects within the P92 annular welded joint. Compared to traditional defect handling methods, this method can classify the risk of spherical defects through quantitative analysis. For low-risk spherical defects, it recommends supervised operation; for medium-risk spherical defects, it recommends supervised operation and timely handling; and for high and extremely high-risk spherical defects, it recommends patching and repair. This method effectively avoids secondary damage to the annular welded joint caused by repair, thus extending the service life of the P92 annular welded joint. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method of the present invention;

[0037] Figure 2 This is a schematic diagram of a spherical defect model in a welded joint according to an embodiment of the present invention;

[0038] Figure 3 This is a stress distribution diagram of an annular welded joint containing spherical defects in an embodiment of the present invention;

[0039] Figure 4 This is a stress distribution diagram of spherical defects of different sizes at different wall thicknesses in an embodiment of the present invention;

[0040] Figure 5 As described in the embodiments of the present invention Stress distribution diagrams of spherical defects at different wall thicknesses;

[0041] Figure 6 This is an interface diagram of the spherical defect service risk quantification assessment system for annular welded joints in an embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram of the operation of the spherical defect service risk quantification assessment system for annular welded joints in an embodiment of the present invention. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0044] Example

[0045] like Figure 1 As shown, a method for quantitatively assessing the service risk of a P92 annular welded joint containing spherical defects includes the following steps:

[0046] S1. Establish a 3D model of annular welded joints containing spherical defects. Using 3D modeling software, establish annular welded joints containing spherical defects of different sizes and distributions at different wall thicknesses. Specific steps are as follows: The pipe specifications for this simulation are: ID318×10⁶ mm, design pressure P=35.33MPa, design temperature 610℃, elastic modulus E=1688GPa at the calculation temperature, and linear expansion coefficient 12.3×10⁻⁶ at the calculation temperature. -6 / ℃. Spherical defects with distances to the inner wall of 5mm, 10mm, 20mm, 40mm, 60mm, 80mm, and 100mm are constructed in a P92 pipe. The dimensions of these defects are as follows: 4mm, 5mm, 6mm, 8mm, spherical defect models as follows Figure 2 As shown;

[0047] S2. Maximum equivalent stress analysis of spherical defects: Using finite element analysis software, stress analysis was performed on the annular welded joint containing spherical defects. The maximum equivalent stress of the defects was recorded, and its variation trend was analyzed. Specifically, the following steps were included:

[0048] S21. Analysis of the influence of different sizes of spherical defects on their maximum equivalent stress, such as... Figure 3 As shown. Based on the maximum stress at the same wall thickness location of spherical defects of different sizes in annular welded joints, the size of the spherical defect has little effect on the stress concentration. Figure 4 As shown, this indicates that the size of the spherical defect has no effect on its maximum equivalent stress;

[0049] S22. Analysis of the influence of spherical defects at different wall thicknesses on the maximum equivalent stress. According to the simulation results above, the size of the spherical defect has no effect on the maximum equivalent stress at the annular welded joint. Therefore, in this embodiment, we take... A spherical defect was identified, and its maximum equivalent stress at different wall thicknesses was analyzed. Figure 5 Analysis results show that the maximum equivalent stress of the defect decreases with increasing distance from the inner wall, and conforms to the following functional equation:

[0050]

[0051] In the formula: x is the distance from the defect to the inner wall, σ max This represents the maximum equivalent stress of the defect.

[0052] S3. The maximum equivalent stress characterization of spherical defects can be based on the straight pipe specification ID318×106mm of the main steam pipeline of this invention. A prediction equation for the maximum equivalent stress of spherical defects of the same material (P92) under different specifications and design pressures can be established. The specific steps are as follows:

[0053] Assume that the inner diameter of straight pipes of the same material but different specifications is D. ix The outer diameter is D ox The design pressure is P x And the distance from the defect to the inner wall is d. x According to the LM formula, the distance from the inner wall d to the straight pipe of different specifications is... x Circumferential stress σ at the location θ for:

[0054]

[0055] Because the inner diameter of the straight pipe with ID318×106mm is D i1 The outer diameter is D o1 Given a design pressure of P1, the distance d1 from the inner wall of a straight pipe with ID318×106mm under the same circumferential stress state can be calculated using the above formula:

[0056]

[0057] Based on the above-mentioned function formula (3) of the distance from the defect to the inner wall minus the maximum equivalent stress, the maximum equivalent stress of the spherical defect under the design pressure of straight pipes of different specifications of the same material (P92) can be characterized:

[0058]

[0059] In the formula, d1 is the circumferential stress state at any wall thickness position of straight pipes of different specifications and the equivalent wall thickness when the same as that of a straight pipe with specification ID318×106mm.

[0060] S4. Based on the above calculations, the maximum equivalent stress σ of the spherical defect at different wall thickness locations in the welded joint can be determined. max Since the structure is discontinuous at the defect, its equivalent stress can be considered as secondary stress, with 2 / 3 of the yield strength (σ) s / 1.5) is the criterion for determining allowable stress. Referring to Part 4 of GB / T 16507.4-2022, in the secondary stress zone, the maximum average stress on the inner and outer walls or the average equivalent stress of the cross section should not exceed 1.5 times the allowable stress; in the secondary stress zone, the maximum equivalent stress or the equivalent stress resulting from the sum of the average stress of the cross section and the bending stress should not exceed 3 times the allowable stress. Referring to ASME Code Case 2179-9, the yield strength of P92 material at the operating temperature T℃ is σ. s In this embodiment, f is defined as the risk index. For components containing spherical defects, the service risk index is calculated as shown in Equation 5.

[0061]

[0062] The risk index of spherical defects at different locations of different annular welded joints can be obtained from the above characterization method. Different risk index ranges correspond to different risk levels, thus forming a quantitative evaluation system for service risks of different locations containing spherical defects, as shown in Table 1.

[0063] Table 1. Quantitative Evaluation System for Service Risk of Welded Joints with Spherical Defects

[0064]

[0065]

[0066] S5. Establish a quantification assessment system for the risk of spherical defects. Utilize Python to establish a quantification assessment system for the risk of spherical defects in P92 annular welded joints, such as… Figure 6 As shown. A risk assessment of spherical defects in similar P92 welded joints can be performed, specifically including the following steps:

[0067] S51. Construction of a stress prediction model for spherical defects: A stress prediction model for spherical defects is constructed using the Python language.

[0068] S52. Construction of service risk quantification evaluation method: Construction of spherical defect stress prediction model using Python language;

[0069] S6. Conduct a service risk assessment of the spherical defect. Using the spherical defect risk quantification assessment system for P92 annular welded joints established in step S5 using Python, conduct a service risk quantification assessment of the spherical defect in the P92 annular welded joint. Specifically, input the obtained spherical defect size r = 4mm, the P92 annular welded joint position d = 30mm, the pipe wall thickness 106mm, the pipe inner diameter 318mm, the operating pressure 35.33MPa, the operating temperature 630℃, the allowable stress 165MPa, and the yield strength 247MPa into the spherical defect risk quantification assessment system established in step 5 to perform a risk quantification assessment of the spherical defect in the annular welded joint. Figure 7 As shown, the maximum equivalent stress of this defect is 131.69 MPa, and the risk level is high.

[0070] This embodiment combines 3D modeling and finite element numerical analysis to construct a quantitative evaluation system for the service risk of P92 annular welded joints containing spherical defects. It predicts the maximum equivalent stress of spherical defects at different locations within the annular welded joint and assesses their risk. This allows inspection personnel to quickly assess the risk of defects. For defects in low-risk areas, the treatment plan is supervised operation; for defects in medium-risk areas, supervised operation is followed by opportunistic treatment to minimize secondary damage to the P92 annular welded joint; when defects are in high or extremely high-risk areas, the treatment plan is patch repair. These methods effectively improve the service life of the welded joint.

[0071] Any content not described in detail in this specification is prior art known to those skilled in the art.

[0072] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the scope of protection of the present invention. Any modifications and refinements made by those skilled in the art without departing from the concept and scope of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for quantitatively assessing the service risk of P92 annular welded joints containing spherical defects, characterized in that, Includes the following steps: S1. Establish a three-dimensional model of annular welded joint containing spherical defects. Use three-dimensional modeling software to establish annular welded joints containing spherical defects of different sizes and distributed at different wall thicknesses. S2. Maximum equivalent stress analysis of spherical defects: The stress analysis of the annular welded joint containing spherical defects was carried out using finite element analysis software, and the maximum equivalent stress of the defects was recorded and the trend of change was analyzed. S3. Characterization of the maximum equivalent stress of spherical defects: Based on the straight pipe specification of ID318×106 mm of the main steam pipeline, a prediction equation for the maximum equivalent stress of spherical defects of the same material under different specifications and design pressures is established. The specific implementation method of step S3 is as follows: Based on the straight pipe specification of the main steam pipeline ID318×106 mm, establish the prediction equation for the maximum equivalent stress of spherical defects under different specifications and design pressures of the same material. Assuming the inner diameter of straight pipes of the same material but different specifications is... D ix Outer diameter is D ox Design pressure is P x And the distance from the defect to the inner wall is d x According to the LM formula, the inner wall diameter of straight pipes of different specifications is calculated. d x Circumferential stress at the location σ θ for: Because the inner diameter of the straight pipe with ID318×106 mm is D i1 The outer diameter is D o1 Given a design pressure of P1, the distance from the inner wall of a straight pipe with ID318×106 mm to the inner wall under the same circumferential stress state can be calculated using the above formula. d 1 for: Based on the above function formula (1) of the distance from the defect to the inner wall minus the maximum equivalent stress, the maximum equivalent stress of the spherical defect under the design pressure of straight pipes of the same material but different specifications is characterized: In the formula, d 1 The circumferential stress state at any wall thickness location of straight pipes of different specifications is equivalent to the wall thickness of a straight pipe with specifications of ID318×106 mm. S4. Establish a quantitative evaluation system for the service risk of components containing spherical defects, and calculate the maximum equivalent stress of spherical defects at different wall thickness locations of welded joints. σ max By reviewing relevant standards, risk quantification assessment criteria were established. S5. Establish a spherical defect risk quantification assessment system. Use Python language to establish a spherical defect risk quantification assessment system based on P92 annular welded joints, and conduct risk assessment of spherical defects in P92 welded joints of the same type. S6. Conduct service risk assessment on spherical defects. Utilize the Python language from step S5 to establish a spherical defect risk quantification assessment system based on the P92 annular welded joint, and conduct service risk quantification assessment on the spherical defects of the P92 annular welded joint.

2. The method for quantitatively assessing the service risk of P92 annular welded joints containing spherical defects according to claim 1, characterized in that: The specific implementation method of step S1 is as follows: The pipe specifications for this simulation are: ID318×106 mm, design pressure P=35.33 MPa, design temperature is 610℃, elastic modulus E=1688 GPa at the calculation temperature, and linear expansion coefficient at the calculation temperature is 12.3×10 -6 / ℃; Spherical defects with distances to the inner wall of 5 mm, 10 mm, 20 mm, 40 mm, 60 mm, 80 mm and 100 mm are constructed in P92 pipes, with defect sizes of φ=3 mm, 4 mm, 5 mm, 6 mm and 8 mm respectively. Step S2 includes the following sub-steps: S21. Analysis of the influence of different sizes of spherical defects on the maximum equivalent stress. Based on the maximum equivalent stress of spherical defects of different sizes at the same wall thickness position of the annular welded joint, the size of the spherical defect has little effect on the degree of stress concentration, indicating that the size of the spherical defect has no effect on the maximum equivalent stress. S22. Analysis of the influence of spherical defects at different wall thicknesses on the maximum equivalent stress. Simulation results show that the size of the spherical defect has no effect on the maximum equivalent stress of the annular welded joint. Therefore, a spherical defect with φ=8 mm is selected, and its maximum equivalent stress at different wall thicknesses is analyzed. The analysis results show that the maximum equivalent stress decreases with increasing distance from the inner wall, conforming to the following functional equation: In the formula: x This is the distance from the defect to the inner wall. σ max The maximum equivalent stress of the defect; The specific implementation method of step S4 is as follows: calculate the maximum equivalent stress of the spherical defect at different wall thickness locations of the welded joint. σ max Because the structure is discontinuous at the defect, its equivalent stress is considered as secondary stress, with 2 / 3 of the yield strength (σ) s / 1.5) is the criterion for determining allowable stress. Referring to Part 4 of GB / T 16507.4-2022, in the secondary stress zone, the maximum average stress on the inner and outer walls or the average equivalent stress of the cross section should not exceed 1.5 times the allowable stress; in the secondary stress zone, the maximum equivalent stress or the sum of the average stress of the cross section and the bending stress should not exceed 3 times the allowable stress. Referring to ASME Code Case 2179-9, the yield strength of P92 material at the operating temperature T℃ is σ. s ,definition f The service risk index is calculated as shown in Equation 5 for components containing spherical defects. The risk index of spherical defects at different locations of the annular welded joint is obtained by the above characterization method. Different risk index ranges correspond to different risk levels, thus forming a service risk quantitative evaluation system containing spherical defects. Step S5 includes the following sub-steps: S51. Construction of a stress prediction model for spherical defects: A stress prediction model for spherical defects is constructed using the Python language. S52. Construction of a quantitative evaluation system for the service risk of spherical defects, using Python to construct a stress prediction model for spherical defects; The specific implementation method of step S6 is as follows: input the material, size, wall thickness, allowable stress, yield strength, and size of the spherical defect obtained by detection and its position in the P92 annular welded joint into the spherical defect risk quantification assessment system established in step S5, and perform risk quantification assessment of the spherical defect in the annular welded joint.

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