A method for quantifying the distribution of surface crack density of a pressure vessel induced by welding

Abstract

The present application provides a kind of hardfacing induced pressure vessel surface crack density distribution quantification method, comprising the following steps: step S1. Input the basic size of pressure vessel;Step S2. Key parameters of hardfacing process are defined;Step S3. The number of surface cracks at different depths in unit length hardfacing bead is calculated;Step S4. Evaluate the overall density of hardfacing induced pressure vessel surface cracks;Step S5. Quantify the density distribution of different size surface cracks in pressure vessel.The present application provides a kind of pressure vessel surface crack density distribution quantification technology considering the influence of hardfacing process, which can reasonably represent the distribution rule of different size surface cracks in pressure vessel with hardfacing layer, and effectively support the structural integrity risk assessment of in-service pressure vessel.

Description

Technical Field

[0001] This invention belongs to the field of pressure vessel structural integrity assessment, specifically relating to a method for quantifying the density distribution of surface cracks induced by welding on pressure vessels. Background Technology

[0002] Pressure vessels are widely used in critical sectors such as petroleum, chemical, and nuclear power, and need to operate under harsh conditions such as high temperature, high pressure, and highly corrosive media for extended periods. To meet the requirements for long-term stable and safe service, pressure vessels are typically coated with an anti-corrosion alloy layer using a welding process during manufacturing. However, the material properties of the weld overlay layer differ significantly from those of the pressure vessel's base material. Furthermore, the welding process involves complex thermal cycles and metallurgical reactions, which can easily lead to the initiation of micro-defects in the welded pressure vessel, potentially developing into surface cracks. These surface cracks can initiate and propagate under the combined effects of external loads and corrosive environments, ultimately causing pressure vessel leakage or even rupture. Therefore, accurately quantifying the number and distribution of surface cracks induced by welding is a crucial prerequisite for conducting structural integrity risk assessments of in-service pressure vessels.

[0003] Currently, the determination of surface cracks in pressure vessels induced by welding mainly relies on empirical methods such as ultrasonic testing and penetrant testing. These methods have low efficiency, narrow coverage, and limited accuracy, making it difficult to reasonably assess the overall distribution of surface cracks in pressure vessels and failing to provide effective data support for evaluating the structural integrity of pressure vessels. Summary of the Invention

[0004] The purpose of this invention is to propose a method for quantifying the surface crack density distribution of pressure vessels induced by welding, aiming to provide technical support for the structural integrity risk assessment of in-service pressure vessels.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for quantifying the surface crack density distribution of a pressure vessel induced by welding includes the following steps:

[0007] Step S1: Obtain the basic dimensions of the pressure vessel and the key parameters of the welding process; the basic dimensions include the thickness of the welding layer of the pressure vessel; the process parameters include the number of welding layers and the weld width of the pressure vessel.

[0008] Step S2: Characterize the cross-sectional shape of the surface cracks in the pressure vessel as a semi-ellipse. Based on the obtained thickness of the pressure vessel weld overlay and the surface crack depth set according to the actual engineering analysis requirements, use the pre-built evaluation model of the number of surface cracks in a unit length weld overlay to calculate the number of surface cracks at different depths in a unit length weld overlay.

[0009] Step S3: Calculate the weld length of all weld overlays based on the number of layers and weld width of the pressure vessel weld overlay;

[0010] Step S4: Based on the number of surface cracks at different depths in the weld bead per unit length and the weld bead length of all weld bead layers, evaluate the overall density of surface cracks induced by weld overlay on the pressure vessel according to different crack depths.

[0011] Step S5: Based on the surface crack depth set in Step S2 and the semi-elliptical surface crack depth-to-length ratio set according to actual engineering analysis requirements, the density ratio of surface cracks of different sizes is calculated using the pre-constructed pressure vessel surface crack length distribution model. Based on the overall density of pressure vessel surface cracks at different crack depths and the density ratio of surface cracks of different sizes obtained in Step S4, the density distribution of surface cracks of different sizes in the pressure vessel is quantified.

[0012] Preferably, the construction steps of the evaluation model for the number of surface cracks per unit length of weld bead are as follows:

[0013] Multiple sets of empirical data were obtained, including the thickness of the weld overlay on pressure vessels, the depth of surface cracks, and the number of surface cracks at the corresponding depth within a unit length of weld bead. Using the weld overlay thickness and the depth of surface cracks as variables, and the number of surface cracks at the corresponding depth within a unit length of weld bead as the dependent variable, the least squares method was used for fitting to obtain an evaluation model for the number of surface cracks in a unit length of weld overlay.

[0014] Preferably, the calculation of the weld bead length of all weld overlay layers based on the number of layers and weld width of the pressure vessel weld overlay is as follows:

[0015] Calculate the weld length per unit area of ​​the weld overlay based on the weld width of the pressure vessel weld overlay.

[0016] Based on the number of layers of the pressure vessel weld overlay and the weld length per unit area of ​​the weld overlay, the weld length of all weld overlay layers is calculated.

[0017] Preferably, the steps for constructing the surface crack length distribution model of the pressure vessel are as follows:

[0018] Multiple sets of empirical data including surface crack depth, surface crack depth-to-length ratio, and surface crack density ratio of corresponding dimensions were obtained. With surface crack depth and surface crack depth-to-length ratio as variables and surface crack density ratio of corresponding dimensions as dependent variables, the least squares method was used for fitting to obtain the surface crack length distribution model of the pressure vessel.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention constructs an evaluation model for the number of surface cracks on pressure vessels induced by welding. This model can take into account the influence of pressure vessel geometry and welding process.

[0021] 2. This invention can be widely applied to various pressure vessels with weld overlay in industries such as petroleum, chemical, and nuclear power, and can achieve reasonable quantification of the surface crack density distribution of different sizes in pressure vessels with weld overlay. Attached Figure Description

[0022] Figure 1 A flowchart of a method for quantifying the surface crack density distribution of a pressure vessel induced by welding.

[0023] Figure 2 A schematic diagram of a pressure vessel and its weld overlay.

[0024] Figure 3 This is a schematic diagram of surface cracks;

[0025] Figure 4 This is a schematic diagram of the pressure vessel surface crack quantity assessment model constructed in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the surface crack length distribution model of the pressure vessel constructed in an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the density distribution of surface cracks of different sizes in a pressure vessel obtained in an embodiment of the present invention. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1-6 The technical solution of the present invention will be described in detail below.

[0029] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0031] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0033] like Figure 1 As shown, the present invention proposes a method for quantifying the surface crack density distribution of pressure vessels induced by welding, comprising the following steps:

[0034] Step S1: Input the basic dimensions of the pressure vessel (e.g., ...) Figure 2 As shown), it specifically includes the following:

[0035] Step S11: Input the thickness t of the pressure vessel weld overlay. c ;

[0036] Step S2: Determine the key parameters of the welding process (such as...) Figure 2 As shown), it specifically includes the following:

[0037] Step S21: Determine the number of weld overlay layers N of the pressure vessel;

[0038] Step S22: Determine the weld width w of the pressure vessel weld overlay. c ;

[0039] Step S3: Calculate the number of surface cracks at different depths per unit length of weld bead, specifically including the following:

[0040] Step S31: Referring to the national standard "Safety Assessment of Defective Pressure Vessels in Use (GB / T 19624-2019)", the surface crack shape of the pressure vessel is characterized as a semi-ellipse (e.g., Figure 3 (as shown)

[0041] Step S32: Set the surface crack depth 'a' of the pressure vessel according to the actual engineering analysis requirements;

[0042] Step S33: Based on empirical data of pressure vessels, construct an evaluation model for the number of surface cracks per unit length of weld overlay using the least squares method;

[0043]

[0044] In the formula: n is the number of surface cracks of different depths in a unit length of weld bead; a is the surface crack depth; t c The thickness of the weld overlay on the pressure vessel; f represents the relationship between n, a, and t. c The functional relationship between them;

[0045] Step S34: Based on the surface crack depth a set in step S32 and the evaluation model of the number of surface cracks constructed in step S33, calculate the number of surface cracks n at different depths in a unit length of weld bead.

[0046] Step S4: Evaluate the overall density of surface cracks induced by weld overlay on the pressure vessel, specifically including the following:

[0047] Step S41: Based on the weld overlay width w input in step S22 c Calculate the weld bead length l under the weld overlay per unit area. u ;

[0048]

[0049] In the formula: l u The length of the weld bead under the weld overlay per unit area; w c To increase the weld width;

[0050] Step S42: Based on the number of weld overlay layers N input in step S21, and the weld bead length l under the weld overlay layer per unit area obtained in step S41. u Calculate the weld bead length l of all weld overlay layers. c ;

[0051]

[0052] In the formula: l c For the weld bead length of all weld overlay layers; l u N represents the weld bead length per unit area of ​​the weld overlay; N is the number of weld overlay layers.

[0053] Step S43: Based on the number n of surface cracks at different depths in the unit length weld bead obtained in step S34, and the weld bead length l of all weld overlay layers obtained in step S42. c To assess the overall density ρ of surface cracks induced by welding on pressure vessels;

[0054]

[0055] Where: ρ is the total surface crack density of the pressure vessel; n is the number of surface cracks at different depths per unit length of weld bead; l c The weld length for all weld overlay layers;

[0056] Step S5: Quantify the density distribution of surface cracks of different sizes in the pressure vessel, specifically including the following:

[0057] Step S51: Set the depth-to-length ratio R of the semi-elliptical surface crack according to the actual engineering analysis requirements;

[0058] Step S52: Based on empirical data of pressure vessels, construct a distribution model of surface crack length of pressure vessels using the least squares method;

[0059]

[0060] In the formula: f R denoted as density ratio of surface cracks of different sizes; a is surface crack depth; R is surface crack depth-to-length ratio; h is f R The functional relationship between a and R;

[0061] Step S53: Based on the surface crack depth a set in step S32, the surface crack depth-to-length ratio R set in step S51, and the surface crack length distribution model constructed in step S52, calculate the density ratio f of surface cracks of different sizes in the pressure vessel. R ;

[0062] Step S54: Based on the total surface crack density ρ of the pressure vessel obtained in step S43, and the density ratio f of surface cracks of different sizes obtained in step S53. R Quantitative analysis of the density distribution of surface cracks of different sizes in pressure vessels .

[0063]

[0064] In the formula: The density distribution of surface cracks of different sizes; ρ is the total density of surface cracks in the pressure vessel; f R This represents the density ratio of surface cracks of different sizes.

[0065] The following example, a pressure vessel with a wall thickness of 0.187 m and weld overlay, illustrates a specific embodiment of the present invention. The weld overlay thickness t of the pressure vessel is... c = 0.007 m, number of weld overlay layers N = 1, weld overlay width w c = 0.02 m.

[0066] Step S1: Input the basic dimensions of the pressure vessel, specifically including the following:

[0067] Step S11: Input the thickness t of the pressure vessel weld overlay. c , here t c = 0.007 m;

[0068] Step S2: Identify the key parameters of the welding process, specifically including the following:

[0069] Step S21: Determine the number of weld overlay layers N of the pressure vessel, where N = 1;

[0070] Step S22: Determine the weld width w of the pressure vessel weld overlay. c , here w c = 0.02 m;

[0071] Step S3: Calculate the number of surface cracks at different depths per unit length of weld bead, specifically including the following:

[0072] Step S31: Referring to the national standard "Safety Assessment of Defective Pressure Vessels in Use (GB / T 19624-2019)", the surface crack shape of the pressure vessel is characterized as a semi-ellipse;

[0073] Step S32: Set the surface crack depth 'a' of the pressure vessel according to the actual engineering analysis requirements, as shown in Table 1;

[0074] Table 1. Crack depth a on the surface of the pressure vessel

[0075]

[0076] Step S33: Based on empirical data from pressure vessels, construct an evaluation model for the number of surface cracks per unit length of weld overlay using the least squares method (e.g., ...). Figure 4 (as shown)

[0077]

[0078] In the formula: n is the number of surface cracks of different depths in a unit length of weld bead; a is the surface crack depth; t c The thickness of the weld overlay on the pressure vessel;

[0079] Step S34: Based on the surface crack depth a set in step S32 and the evaluation model of the number of surface cracks constructed in step S33, calculate the number of surface cracks n at different depths in a unit length of weld bead, as shown in Table 2.

[0080] Table 2. Calculation results of the number of surface cracks n at different depths in a unit length of weld bead.

[0081]

[0082] Step S4: Evaluate the overall density of surface cracks induced by weld overlay on the pressure vessel, specifically including the following:

[0083] Step S41: Based on the weld overlay width w input in step S22 c Calculate the weld bead length l under the weld overlay per unit area. u The weld length l under the weld overlay per unit area can be calculated here. u = 50 m;

[0084]

[0085] In the formula: l u The length of the weld bead under the weld overlay per unit area; w c To increase the weld width;

[0086] Step S42: Based on the number of weld overlay layers N input in step S21, and the weld bead length l under the weld overlay layer per unit area obtained in step S41. u Calculate the weld bead length l of all weld overlay layers. c The weld bead length l of all weld overlay layers can be calculated here.c =50 m;

[0087]

[0088] In the formula: l c For the weld bead length of all weld overlay layers; l u N represents the weld bead length per unit area of ​​the weld overlay; N is the number of weld overlay layers.

[0089] Step S43: Based on the number n of surface cracks at different depths in the unit length weld bead obtained in step S34, and the weld bead length l of all weld overlay layers obtained in step S42. c The overall density ρ of surface cracks induced by welding on pressure vessels was evaluated, as shown in Table 3.

[0090]

[0091] Where: ρ is the total surface crack density of the pressure vessel; n is the number of surface cracks at different depths per unit length of weld bead; l c The weld length for all weld overlay layers;

[0092] Table 3 Overall crack density ρ on the surface of pressure vessels

[0093]

[0094] Step S5: Quantify the density distribution of surface cracks of different sizes in the pressure vessel, specifically including the following:

[0095] Step S51: Set the depth-to-length ratio R of the semi-elliptical surface crack according to the actual engineering analysis requirements. Here, we take 1 / 4, 1 / 8, 1 / 12, and 1 / 16, a total of 4 different depth-to-length ratios.

[0096] Step S52: Based on empirical data of pressure vessels, construct a distribution model of crack length on the pressure vessel surface using the least squares method (e.g., Figure 5 (as shown)

[0097]

[0098] In the formula: f R denoted as the density ratio of surface cracks of different sizes; a represents the surface crack depth; R represents the surface crack depth-to-length ratio.

[0099] Step S53: Based on the surface crack depth a set in step S32, the surface crack depth-to-length ratio R set in step S51, and the surface crack length distribution model constructed in step S52, calculate the density ratio f of surface cracks of different sizes in the pressure vessel. R As shown in Table 4;

[0100] Table 4. Density ratio f of surface cracks of different sizes R

[0101]

[0102] Step S54: Based on the total surface crack density ρ of the pressure vessel obtained in step S43, and the density ratio f of surface cracks of different sizes obtained in step S53. R Quantitative analysis of the density distribution of surface cracks of different sizes in pressure vessels The result is as follows Figure 6 As shown;

[0103]

[0104] In the formula: The density distribution of surface cracks of different sizes; ρ is the total density of surface cracks in the pressure vessel; f R This represents the density ratio of surface cracks of different sizes.

[0105] The above are preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for quantifying the surface crack density distribution of a pressure vessel induced by welding, characterized in that, Includes the following steps: Step S1: Obtain the basic dimensions of the pressure vessel and the key parameters of the welding process; the basic dimensions include the thickness of the welding layer of the pressure vessel; the process parameters include the number of welding layers and the weld width of the pressure vessel. Step S2: Characterize the cross-sectional shape of the surface cracks in the pressure vessel as a semi-ellipse. Based on the obtained thickness of the pressure vessel weld overlay and the surface crack depth set according to the actual engineering analysis requirements, use the pre-built evaluation model of the number of surface cracks in a unit length weld overlay to calculate the number of surface cracks at different depths in a unit length weld overlay. Step S3: Calculate the weld length of all weld overlays based on the number of layers and weld width of the pressure vessel weld overlay; Step S4: Based on the number of surface cracks at different depths in the weld bead per unit length and the weld bead length of all weld bead layers, evaluate the overall density of surface cracks induced by weld overlay on the pressure vessel according to different crack depths. Step S5: Based on the surface crack depth set in Step S2 and the semi-elliptical surface crack depth-to-length ratio set according to actual engineering analysis requirements, the density ratio of surface cracks of different sizes is calculated using the pre-constructed pressure vessel surface crack length distribution model. Based on the overall density of pressure vessel surface cracks at different crack depths and the density ratio of surface cracks of different sizes obtained in Step S4, the density distribution of surface cracks of different sizes in the pressure vessel is quantified.

2. The method for quantifying the surface crack density distribution of a pressure vessel induced by welding according to claim 1, characterized in that, The specific steps for constructing the evaluation model for the number of surface cracks per unit length of weld bead are as follows: Multiple sets of empirical data were obtained, including the thickness of the weld overlay on pressure vessels, the depth of surface cracks, and the number of surface cracks at the corresponding depth within a unit length of weld bead. Using the weld overlay thickness and the depth of surface cracks as variables, and the number of surface cracks at the corresponding depth within a unit length of weld bead as the dependent variable, the least squares method was used for fitting to obtain an evaluation model for the number of surface cracks in a unit length of weld overlay.

3. The method for quantifying the surface crack density distribution of a pressure vessel induced by welding according to claim 1, characterized in that, The length of each weld bead in the pressure vessel weld overlay is calculated based on the number of layers and the weld width, as follows: Calculate the weld length per unit area of ​​the weld overlay based on the weld width of the pressure vessel weld overlay. Based on the number of layers of the pressure vessel weld overlay and the weld length per unit area of ​​the weld overlay, the weld length of all weld overlay layers is calculated.

4. The method for quantifying the surface crack density distribution of a pressure vessel induced by welding according to claim 1, characterized in that, The specific steps for constructing the surface crack length distribution model of the pressure vessel are as follows: Multiple sets of empirical data including surface crack depth, surface crack depth-to-length ratio, and surface crack density ratio of corresponding dimensions were obtained. With surface crack depth and surface crack depth-to-length ratio as variables and surface crack density ratio of corresponding dimensions as dependent variables, the least squares method was used for fitting to obtain the surface crack length distribution model of the pressure vessel.

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