Service life prediction method suitable for natural gas hydrogen-doped pipeline

Abstract

The invention relates to the field of pipeline testing, and particularly provides a service life prediction method suitable for a natural gas hydrogen-doped pipeline. The service life prediction method suitable for the natural gas hydrogen-doped pipeline comprises the following steps: establishing a failure evaluation diagram, and drawing a load ratio cut-off line and a toughness ratio cut-off line in the failure evaluation diagram to form a reference line and a safe area. And respectively calculating a load ratio # imgabs0 # and a toughness ratio # imgabs1 # based on the i crack calculation depths a, and forming corresponding coordinate points (# imgabs2 # and # imgabs3 #) to obtain a critical crack depth # imgabs4 #. When the circumferential stress direction borne by the pipeline is the main stress direction of the crack, the service life of the pipeline is calculated according to # imgabs 5 #, and when the axial stress direction borne by the pipeline is the main stress direction of the crack, the service life of the pipeline is calculated according to # imgabs 6 #. The service life prediction method suitable for the natural gas hydrogen-doped pipeline has high accuracy.

Description

Technical Field

[0001] The invention relates to the field of pipeline testing, and in particular to a service life prediction method suitable for a natural gas hydrogen-blended pipeline. Background Art

[0002] Cracks will occur in pipelines during the manufacturing, construction and operation process, such as weld cracks during the manufacturing process, cracks caused by mechanical damage during the transportation and construction process, and cracks caused by corrosion during operation. When pipelines are used to transport fuel, cracks are an important factor affecting the service life of pipelines. Therefore, related technologies have proposed life prediction methods for pipelines that transport oil and gas. However, after hydrogen is added to the natural gas pipeline, the pipeline will produce hydrogen embrittlement under the influence of hydrogen. The cracks will further expand due to hydrogen embrittlement, causing the pipeline to fail due to brittle cracking. Therefore, natural gas hydrogen-blended pipelines are more prone to safety accidents such as leakage than oil and gas pipelines. However, the life prediction methods for oil and gas pipelines in related technologies are not applicable to natural gas hydrogen-blended pipelines, and it is impossible to accurately predict the service life of natural gas hydrogen-blended pipelines. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, the present invention proposes a service life prediction method applicable to a natural gas hydrogen-blended pipeline.

[0005] The service life prediction method applicable to a natural gas hydrogen-blended pipeline of the present invention comprises: Establish a failure assessment diagram, and draw a load ratio cutoff line and a toughness ratio cutoff line in the failure assessment diagram, wherein the load ratio cutoff line is ,in is the maximum load ratio of the pipe, The tensile strength of the pipe in a natural gas hydrogen-mixed environment. is the tensile strength of the pipe in an inert environment, and the toughness ratio cutoff line is ,in is the fracture toughness of the pipe in a natural gas hydrogen-doped environment, is the fracture toughness of the pipe in an inert environment. In the failure assessment diagram, the load ratio cutoff line, the toughness ratio cutoff line, and the partial failure assessment curve connected between the load ratio cutoff line and the toughness ratio cutoff line are used as the baseline, and the area surrounded by the baseline and the coordinate system of the failure assessment diagram is the safety zone; Calculate the load ratio based on the calculated depth a of the i cracks and toughness ratio , the values ​​of the calculated depth a of i cracks are , +k, +2k...... + (i-1) k, where k is a constant, is the initial crack depth, and the load ratio corresponding to each crack calculation depth a is As the abscissa of the failure evaluation diagram, the corresponding toughness ratio As the ordinate of the failure assessment diagram, so that each crack calculation depth a has a corresponding coordinate point in the failure assessment diagram ( , ), among the i coordinate points, the coordinate point located in the safety zone and with the smallest distance from the reference line is taken as the critical coordinate point, and the crack calculation depth a corresponding to the critical coordinate point is the critical crack depth ; When the hoop stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline. When the axial stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline, where and m are Paris parameters, is the load fluctuation frequency, is the internal pressure load fluctuation of the pipeline, D is the diameter of the pipeline, and t is the thickness of the pipeline.

[0006] Furthermore, the service life prediction method of the natural gas hydrogen blending pipeline also includes: Characterize the defects of the pipeline and regularize the cracks of the pipeline to obtain the characterization depth of the regularized cracks , for Multiply the defect characterization size by the safety factor.

[0007] Furthermore, when defect characterization is performed on the pipeline, exist When , the pipeline is unqualified; exist When , the crack is regularized as and If the semi-elliptical surface crack , the crack is regularized as Semicircular surface cracks; in is the actual depth of the crack, is the actual length of the crack, is the wall thickness of the pipe, is the characterization depth of the regularized crack, It is 1 / 2 of the characterization length of the regularized crack.

[0008] Furthermore, the service life prediction method of the natural gas hydrogen blending pipeline also includes: The pipe is subjected to a slow strain rate tensile test in an inert environment to obtain the tensile strength of the pipe in an inert environment. ; The pipeline is subjected to a slow strain rate tensile test in a natural gas hydrogen-doped environment to obtain the tensile strength of the pipeline in the natural gas hydrogen-doped environment. .

[0009] Furthermore, the service life prediction method of the natural gas hydrogen blending pipeline also includes: The fracture toughness test of the pipe is carried out in an inert environment to obtain the fracture toughness of the pipe in an inert environment. ; The fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the fracture toughness of the pipe in the natural gas hydrogen-doped environment. .

[0010] Furthermore, the fracture toughness test is performed on the pipeline in an inert environment to obtain the J-integrated fracture toughness of the pipeline in an inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the J-integrated fracture toughness of the pipe in a natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment ;or The fracture toughness test of the pipe is carried out in an inert environment to obtain the CTOD fracture toughness of the pipe in an inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the CTOD fracture toughness of the pipe in a natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment ; Where E is the elastic modulus of the pipe, is the yield strength of the pipe, is the Poisson's ratio of the pipe.

[0011] Furthermore, the failure assessment curve is .

[0012] Further, when the crack is an axial crack of the pipeline, according to , , and Load ratio calculated with ; When the crack is a circumferential crack of the pipeline, according to and Load ratio calculated with ; in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the yield strength of the pipe, c is Multiply the defect characterizing size by the safety factor, where R is the radius of the pipe.

[0013] Further, according to Calculate the toughness ratio ,in for Multiply the material fracture toughness by the safety factor, is the plasticity correction factor, is the stress intensity factor caused by the primary stress, is the stress intensity factor caused by secondary stress.

[0014] Further, according to ) Calculate the stress intensity factor caused by the primary stress , according to ) Calculate the stress intensity factor caused by secondary stress , in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the membrane stress component of the secondary stress, is the bending stress component of the secondary stress, , , c is Multiply the defect characterizing size by the safety factor.

[0015] Furthermore, with the plasticity correction factor Toughness ratio The corresponding load ratio <0.8, according to Calculate the plasticity correction factor ; With plasticity correction factor Toughness ratio The corresponding load ratio 0.8< <1.1, according to Calculate the plasticity correction factor ; With plasticity correction factor Toughness ratio The corresponding load ratio >1.1, ; in The value of and The coordinate graph curve is obtained.

[0016] Furthermore, the material fracture toughness safety factor is 1.15 to 1.25, and the defect characterization size safety factor is 1.05 to 1.15.

[0017] Furthermore, the service life prediction method of the natural gas hydrogen blending pipeline also includes: The pipeline is subjected to fatigue crack growth tests in an inert environment and a natural gas hydrogen-doped environment to obtain the Paris parameters in the Paris formula. and Paris parameter m.

[0018] The service life prediction method for natural gas hydrogen-blended pipelines of the present invention calculates the load ratio based on i crack calculation depths a respectively. and toughness ratio To form i coordinate points in the failure assessment map, and obtain the critical crack depth according to the baseline and safety zone in the failure assessment map Then, according to the main stress direction of the crack, the corresponding service life formula is selected and the predicted service life of the pipeline is calculated. The load ratio cutoff line and toughness ratio cutoff line in the failure assessment diagram are both based on the inert environment and the natural gas hydrogen-doped environment, making the baseline and safety zone more accurate, so that the critical crack depth can be obtained. More accurate. At the same time, the service life formula is based on the Paris parameter, which also makes the service life formula more accurate. In addition, based on the calculated depth a of i cracks, i coordinate points are obtained, and the coordinate point located in the safety zone and with the smallest distance from the baseline is selected from the i coordinate points to obtain the critical crack depth , in order to obtain the accurate critical crack depth , so that the accuracy of the service life formula is higher. Therefore, the service life prediction method applicable to the natural gas hydrogen blending pipeline of the present invention has a higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1Schematic diagram of defect characterization in a service life prediction method for a natural gas hydrogen blending pipeline according to an embodiment of the present invention Figure 1 ; Figure 2 Schematic diagram of defect characterization in a service life prediction method for a natural gas hydrogen blending pipeline according to an embodiment of the present invention Figure 2 ; Figure 3 Schematic diagram of defect characterization in a service life prediction method for a natural gas hydrogen blending pipeline according to an embodiment of the present invention Figure 3 ; Figure 4 It is an example diagram of a failure assessment diagram in a service life prediction method applicable to a natural gas hydrogen-blended pipeline according to an embodiment of the present invention; Figure 5 The service life prediction method for a natural gas hydrogen blending pipeline according to an embodiment of the present invention is and Coordinate diagram of . DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0021] Reference below Figure 1-Figure 5 A method for predicting the service life of a natural gas hydrogen-blended pipeline according to an embodiment of the present invention is described.

[0022] like Figure 1-Figure 5 As shown, the service life prediction method of the natural gas hydrogen blending pipeline according to the embodiment of the present invention includes: Establish failure assessment diagrams, specifically, Figure 4 As shown, the horizontal axis of the failure assessment diagram is the load ratio , the vertical axis is the toughness ratio . And draw the load ratio cutoff line in the failure assessment diagram (such as Figure 4 The line L1 shown) and the toughness ratio cutoff line (as shown Figure 4 The load ratio cut-off line is ,in is the maximum load ratio of the pipe, The tensile strength of the pipe in a natural gas hydrogen-mixed environment. is the tensile strength of the pipe in an inert environment, and the toughness ratio cutoff line is ,in is the fracture toughness of the pipe in a natural gas hydrogen-doped environment, It is the fracture toughness of the pipe in an inert environment.

[0023] In the failure assessment diagram, the load ratio cutoff line (such as Figure 4The line L1 shown), the toughness ratio cut-off line (such as Figure 4 The line L2 shown in FIG. 1 ), and the partial failure assessment curve connected between the load ratio cutoff line and the toughness ratio cutoff line (the failure assessment curve is shown in FIG. Figure 4 The line L3 shown in the figure is used as the baseline, and the area formed by the baseline and the coordinate system of the failure assessment map is the safe zone. In other words, the area between the baseline and the horizontal axis and the vertical axis of the failure assessment map is the safe zone, and the other areas of the failure assessment map are the non-safe zones.

[0024] Calculate the load ratio based on the calculated depth a of the i cracks and toughness ratio , the values ​​of the calculated depth a of i cracks are , +k, +2k...... + (i-1) k, in other words, the calculated depth a of the first crack is The second crack calculation depth a is +k, the third crack calculation depth a is taken as +2k......The value of the calculated depth a of the i-th crack is + (i-1) k, where k is a constant, is the initial crack depth.

[0025] The load ratio corresponding to the calculated depth a of each crack As the horizontal axis of the failure assessment diagram, the corresponding toughness ratio As the ordinate of the failure assessment diagram, so that each crack calculation depth a has a corresponding coordinate point in the failure assessment diagram ( , Among the i coordinate points, the coordinate point that is located in the safety zone and has the smallest distance from the baseline is taken as the critical coordinate point, and the calculated crack depth a corresponding to the critical coordinate point is the critical crack depth .

[0026] When the hoop stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline.

[0027] When the axial stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline.

[0028] in and m are Paris parameters, is the load fluctuation frequency, is the internal pressure load fluctuation of the pipeline, D is the diameter of the pipeline, and t is the thickness of the pipeline.

[0029] It should be noted that the inert environment includes an air environment and an inert gas environment.

[0030] The service life prediction method for a natural gas hydrogen-blended pipeline according to an embodiment of the present invention is to calculate the load ratio based on i crack calculation depths a respectively. and toughness ratio To form i coordinate points in the failure assessment map, and obtain the critical crack depth according to the baseline and safety zone in the failure assessment map , and then select the corresponding service life formula according to the principal stress direction of the crack and calculate the predicted service life of the pipeline.

[0031] The load ratio cutoff line and toughness ratio cutoff line in the failure assessment diagram are both based on the inert environment and the natural gas hydrogen-doped environment, which makes the accuracy of the baseline and the safety zone higher, so that the critical crack depth can be obtained. More precise.

[0032] At the same time, the service life formula is based on the Paris parameter, which also makes the service life formula more accurate.

[0033] In addition, based on the calculated depth a of i cracks, i coordinate points are obtained, and the coordinate point located in the safety zone and with the smallest distance from the baseline is selected from the i coordinate points to obtain the critical crack depth , in order to obtain the accurate critical crack depth , making the service life formula more accurate.

[0034] Therefore, the service life prediction method applicable to the natural gas hydrogen blending pipeline according to the embodiment of the present invention has high accuracy.

[0035] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes characterizing defects of the pipeline and regularizing cracks of the pipeline, and obtaining the characterization depth of the regularized cracks. , for Multiply the defect characterization size by the safety factor.

[0036] Obtaining the regularized crack characterization depth through defect characterization , to obtain the initial crack depth , which is used to calculate the load ratio based on the calculated depth a of the i cracks and toughness ratio .

[0037] In some embodiments, when performing defect characterization on a pipeline, Specifically, if Figure 1 As shown, in When the crack is regularized, and Since the regularized through-cracks penetrate the wall of the pipe along the thickness direction of the pipe, the pipe is unqualified. In other words, the service life of the pipe is zero. There is no need to continue to predict the service life of the pipe.

[0038] exist When , the crack is regularized into and The semi-elliptical surface cracks, such as Figure 2 If In other words, if , the crack is regularized into Semicircular surface cracks, such as Figure 3 shown.

[0039] in is the actual depth of the crack, is the actual length of the crack, is the wall thickness of the pipe, is the characterization depth of the regularized crack, is 1 / 2 of the regularized crack characterization length. In other words, 2 is the characterization length of the regularized crack.

[0040] So as to obtain the regularized crack characterization depth , to obtain the initial crack depth .

[0041] In some embodiments, the defect characterization size safety factor is 1.05 to 1.15, preferably 1.1, therefore, =1.1 .

[0042] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes obtaining pipe material information and crack defect information of the pipeline. The pipe material information includes the wall thickness of the pipeline. etc. Crack defect information includes the location of the crack, the actual length of the crack , the actual depth of the crack Etc. This enables defect characterization of the pipeline.

[0043] Specifically, the crack defect information can be obtained by internal detection methods such as ultrasonic detection, magnetic flux leakage detection, eddy current detection, etc., and external detection methods such as girth weld nondestructive testing can also be used.

[0044] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes performing a slow strain rate tensile test on the pipeline in an inert environment to obtain the tensile strength of the pipe in the inert environment. The slow strain rate tensile test is carried out on the pipeline in the natural gas hydrogen-doped environment to obtain the tensile strength of the pipe in the natural gas hydrogen-doped environment. .

[0045] Specifically, the slow strain rate tensile test preferably but not limited to uses a smooth tensile specimen, and the smooth tensile specimen preferably but not limited to uses a base material specimen or a weld specimen, and the length direction of the base material specimen of the smooth tensile specimen is the circumferential direction of the pipeline. In other words, the length direction of the base material specimen of the smooth tensile specimen is the circumferential direction of the pipeline. The length direction of the weld specimen of the smooth tensile specimen is perpendicular to the extension direction of the weld of the pipeline, and the center position of the gauge section of the weld specimen is located at the center of the weld. If the wall thickness and diameter of the pipeline cannot meet the sampling size requirements of the base material specimen and the weld specimen, a smooth tensile specimen is obtained along the axial direction of the pipeline, and the length direction of the obtained smooth tensile specimen is the axial direction of the pipeline.

[0046] The smooth tensile specimen is in the shape of a round rod. The surface roughness of the gauge section of the smooth tensile specimen is Ra≤0.8μm. The tensile rate of the smooth tensile specimen is less than or equal to 2x10 -5 s -1 .

[0047] The pipeline is subjected to slow strain rate tensile tests in an inert environment and a natural gas hydrogen-doped environment respectively. For the slow strain rate tensile test in each environment, multiple sampling positions are set along the circumference of the pipeline, and multiple smooth tensile specimens are obtained at each sampling position. Preferably, three sampling positions are set along the circumference of the pipeline, and three smooth tensile specimens are obtained at each sampling position.

[0048] When a slow strain rate tensile test is performed on a pipeline in a natural gas hydrogen-doped environment, it is necessary to pre-fill hydrogen into the slow strain rate tensile test equipment to simulate the natural gas hydrogen-doped environment when the pipeline is in operation. The pre-filling time is greater than 24 hours. After the pre-filling is completed, an in-situ slow tensile test is performed to complete the slow strain rate tensile test on the pipeline in a natural gas hydrogen-doped environment.

[0049] After the slow strain rate tensile test was performed on the pipeline in an inert environment and a natural gas hydrogen-doped environment, the displacement-stress curve of the pipe was obtained, thereby obtaining the tensile strength of the pipe in an inert environment. and tensile strength in natural gas mixed with hydrogen environment .

[0050] The tensile strength of the pipe in an inert environment is obtained by performing slow strain rate tensile tests on the pipe in an inert environment and a natural gas hydrogen-doped environment. and tensile strength in natural gas mixed with hydrogen environment , which is used to obtain the load ratio cutoff line in the failure assessment diagram.

[0051] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes obtaining the pipe material information and the pipe service information of the pipeline. The pipe material information includes the type of pipe material, the wall thickness of the pipe, , the diameter D of the pipeline, the thickness t of the pipeline, as well as the welding process, chemical composition, mechanical tensile properties, elastic modulus, Poisson's ratio, etc. of the weld. The pipeline service information includes the design pressure, operating pressure, design temperature, operating temperature of the pipeline, as well as the maximum hydrogen mixing ratio, load, and stress generated during the operation of the pipeline. Therefore, the slow strain rate tensile test can be performed on the pipeline in an inert environment and a natural gas hydrogen mixing environment respectively.

[0052] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes performing a fracture toughness test on the pipeline in an inert environment to obtain the fracture toughness of the pipe in the inert environment. The fracture toughness test of the pipeline was carried out in a natural gas hydrogen-doped environment to obtain the fracture toughness of the pipe in a natural gas hydrogen-doped environment. .

[0053] Specifically, the fracture toughness test preferably uses, but is not limited to, a compact tensile specimen. In the fracture toughness test, the compact tensile specimen preferably uses, but is not limited to, a base material specimen or a weld specimen. The crack extension direction on the base material specimen of the compact tensile specimen is the axial direction of the pipeline, and the crack extension direction on the weld specimen of the compact tensile specimen is the extension direction of the weld of the pipeline.

[0054] In the fracture toughness test, the thickness of the compact tensile specimen is greater than 85% of the design thickness of the pipe, preferably but not limited to greater than the wall thickness of the pipe. The tensile rate of the compact tensile specimen is 0.1 MPa·m 1 / 2 / min~1MPa·m 1 / 2 / min.

[0055] The fracture toughness test is carried out on the pipeline in an inert environment and a natural gas hydrogen-doped environment respectively. For the fracture toughness test in each environment, multiple sampling positions are set along the circumference of the pipeline, and multiple compact tensile specimens are obtained at each sampling position. Preferably, three sampling positions are set along the circumference of the pipeline, and three compact tensile specimens are obtained at each sampling position.

[0056] When conducting a fracture toughness test on a pipeline in a natural gas hydrogen-doped environment, it is necessary to pre-fill hydrogen into the fracture toughness testing equipment to simulate the natural gas hydrogen-doped environment when the pipeline is in operation. The pre-filling time is greater than 24 hours. After the pre-filling is completed, an in-situ fracture toughness test is performed to complete the fracture toughness test on the pipeline in a natural gas hydrogen-doped environment.

[0057] The fracture toughness of the pipe in an inert environment and a natural gas hydrogen-doped environment is tested to obtain the fracture toughness of the pipe in an inert environment. and fracture toughness in natural gas mixed with hydrogen , which is used to obtain the toughness ratio cutoff line in the failure assessment diagram.

[0058] In some embodiments, the fracture toughness test is performed on the pipe in an inert environment to obtain the J-integrated fracture toughness of the pipe in the inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in the natural gas hydrogen-doped environment to obtain the J-integral fracture toughness of the pipe in the natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment , where E is the elastic modulus of the pipe, is the yield strength of the pipe, is the Poisson's ratio of the pipe.

[0059] In some embodiments, the fracture toughness test is performed on the pipe in an inert environment to obtain the CTOD fracture toughness of the pipe in an inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in the natural gas hydrogen-doped environment to obtain the CTOD fracture toughness of the pipe in the natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment , where E is the elastic modulus of the pipe, is the yield strength of the pipe, is the Poisson's ratio of the pipe.

[0060] Therefore, the fracture toughness of the pipeline is tested in an inert environment and a natural gas hydrogen-doped environment respectively, and the J-integral fracture toughness of the pipe in an inert environment can be obtained. and J-integrated fracture toughness in natural gas mixed with hydrogen , to calculate the fracture toughness of the pipe in an inert environment and fracture toughness in natural gas mixed with hydrogen , and the CTOD fracture toughness of the pipe in an inert environment can also be obtained and CTOD fracture toughness in natural gas mixed with hydrogen , to calculate the fracture toughness of the pipe in an inert environment and fracture toughness in natural gas mixed with hydrogen Thus, the toughness ratio cutoff line in the failure assessment diagram is obtained.

[0061] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes obtaining the pipe material information, crack defect information and pipeline service information of the pipeline. The pipe material information includes the type of pipe material, the wall thickness of the pipe , pipe diameter D, pipe thickness t, as well as welding process, chemical composition, mechanical tensile properties, elastic modulus, Poisson's ratio, etc. Crack defect information includes the location of the crack, the actual length of the crack , the actual depth of the crack The pipeline service information includes the design pressure, operating pressure, design temperature, operating temperature of the pipeline, as well as the maximum hydrogen blending ratio, load, stress generated during the operation of the pipeline, etc. Therefore, the fracture toughness test of the pipeline can be carried out in an inert environment and a natural gas hydrogen blending environment respectively.

[0062] In some embodiments, the failure assessment curve is .

[0063] Specifically, Figure 4 As shown, the load ratio As the horizontal axis and the toughness ratio The coordinate system of the failure assessment diagram is established as the vertical axis, and the failure assessment curve is drawn based on the coordinate system of the failure assessment diagram (such as Figure 4 Line L3 shown) , draw the original load ratio cutoff line based on the coordinate system of the failure assessment diagram (such as Figure 4 Line L4 shown) , to form a failure assessment diagram.

[0064] Then draw the load ratio cutoff line (such as Figure 4 Line L1 shown) and toughness ratio cutoff (e.g. Figure 4 Line L2 shown) , thereby determining the baseline and safety zone.

[0065] It is understood that the failure assessment diagram is not limited to having the original load ratio cutoff line. In other embodiments, the failure assessment diagram may be based on the load ratio cutoff line. As the horizontal axis and the toughness ratio A coordinate system of the failure assessment diagram is established as a vertical axis, and a failure assessment curve is plotted based on the coordinate system of the failure assessment diagram to form a failure assessment diagram.

[0066] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes obtaining pipe material information of the pipeline, and the pipe material information of the pipeline includes the maximum load ratio of the pipe material. Etc. This enables the creation of a failure assessment diagram.

[0067] In some embodiments, cracks are divided into pipeline axial cracks and pipeline circumferential cracks according to the extension direction. Pipe axial cracks extend along the axial direction of the pipeline, and pipeline circumferential cracks extend along the circumferential direction of the pipeline, in other words, along the circumferential direction of the pipeline.

[0068] When the crack is an axial crack in the pipe, according to , , and Load ratio calculated with .

[0069] When the crack is a circumferential crack in the pipeline, according to and Load ratio calculated with .

[0070] in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the yield strength of the pipe, c is Multiply the defect characterization size by the safety factor, where R is the radius of the pipe.

[0071] Thus, the load ratio corresponding to each crack calculation depth a is calculated .

[0072] In some embodiments, according to Calculate the toughness ratio ,in for Multiply the material fracture toughness by the safety factor, is the plasticity correction factor, is the stress intensity factor caused by the primary stress, is the stress intensity factor caused by secondary stress.

[0073] Thus, the toughness ratio corresponding to each crack depth a is calculated .

[0074] In some embodiments, the material fracture toughness safety factor is 1.15 to 1.25, preferably 1.2, and the defect characterization size safety factor is 1.05 to 1.15, preferably 1.1. Therefore, c=1.1 , =1.2 .

[0075] In some embodiments, according to ) Calculate the stress intensity factor caused by the primary stress .according to ) Calculate the stress intensity factor caused by secondary stress .in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the membrane stress component of the secondary stress, is the bending stress component of the secondary stress, , , c is Multiply the defect characterization size by the safety factor.

[0076] Film stress components based on primary stress and the bending stress component of the primary stress The stress intensity factor caused by the primary stress is calculated , membrane stress components based on secondary stress and the bending stress component of the secondary stress The stress intensity factor caused by secondary stress is calculated , and thus the toughness ratio is calculated .

[0077] In some embodiments, the present invention also includes obtaining service information of the pipeline, and the pipeline service information includes stresses generated by the pipeline during operation, including the pressure of the transport medium and the stress generated by it, the gravity load of the transport medium and the structure and the stress generated by it, external mechanical loads and the stress generated by them, loads such as vibration and wind loads and the stress generated by them, welding residual stresses caused by welding, stresses generated by structural geometric discontinuities such as misaligned edges, edges and corners, local thinning of walls, unequal thicknesses, etc. when loads act on them, thermal temperature difference stresses or thermal stresses generated by temperature differences, uncoordinated thermal expansion and contraction, etc.

[0078] The stress generated during the operation of the pipeline is divided into primary stress and secondary stress. The primary stress includes the stress caused at the connecting pipe due to the thermal expansion of the pipeline system. The secondary stress includes the residual stress caused by welding, the local stress caused by misalignment, edges and corners, and local thickness difference, and the thermal stress caused by the wall temperature difference or the different thermal expansion coefficients of the materials.

[0079] The film stress component of the primary stress is obtained according to the primary stress , the bending stress component of the primary stress , according to the secondary stress, the film stress component of the secondary stress is obtained and the bending stress component of the secondary stress , so that the load ratio can be calculated and toughness ratio .

[0080] In some embodiments, the plasticity correction factor Toughness ratio The corresponding load ratio <0.8, according to Calculate the plasticity correction factor . With the plasticity correction factor Toughness ratio The corresponding load ratio 0.8< <1.1, according to Calculate the plasticity correction factor . With the plasticity correction factor Toughness ratio The corresponding load ratio >1.1, .in The value of and The coordinate diagram (such as Figure 5 The curve shown is obtained.

[0081] According to the plasticity correction factor The toughness ratio can be calculated .

[0082] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes performing fatigue crack growth tests on the pipeline in an inert environment and a natural gas hydrogen-blended environment to obtain the Paris parameter in the Paris formula. and Paris parameter m.

[0083] Specifically, the fatigue crack growth test preferably uses, but is not limited to, a compact tensile specimen. In the fatigue crack growth test, the compact tensile specimen preferably uses, but is not limited to, a base material specimen or a weld specimen. The crack extension direction on the base material specimen of the compact tensile specimen is the axial direction of the pipeline, the crack extension direction on the weld specimen of the compact tensile specimen is the extension direction of the weld of the pipeline, and the weld specimen is taken from the center of the weld.

[0084] In the fatigue crack growth test, the thickness of the compact tensile specimen is greater than 85% of the design thickness of the pipe, preferably but not limited to greater than the wall thickness of the pipe. 85% of the total.

[0085] Fatigue crack growth tests are performed on the pipeline in an inert environment and a natural gas hydrogen-doped environment respectively. For the fatigue crack growth test in each environment, multiple sampling positions are set along the circumference of the pipeline, and multiple compact tensile specimens are obtained at each sampling position. Preferably, three sampling positions are set along the circumference of the pipeline, and three compact tensile specimens are obtained at each sampling position.

[0086] When performing fatigue crack growth test on pipeline in natural gas hydrogen-doped environment, it is necessary to pre-fill hydrogen into fatigue crack growth test equipment to simulate the natural gas hydrogen-doped environment when pipeline is in operation, and the pre-filling time is more than 24 hours.

[0087] The test frequencies of fatigue crack growth tests on pipelines in an inert environment and a natural gas hydrogen-doped environment are both 0.1 Hz to 1 Hz.

[0088] By performing fatigue crack growth tests on pipelines in an inert environment and a natural gas hydrogen-doped environment, the Paris parameters in the Paris formula can be obtained based on the Paris formula. and Paris parameter m, so that the service life of the pipeline can be calculated.

[0089] In some embodiments, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention further includes obtaining the pipe material information and the pipe service information of the pipeline. The pipe material information includes the type of pipe material, the wall thickness of the pipe, , the diameter D of the pipeline, the thickness t of the pipeline, as well as the welding process, chemical composition, mechanical tensile properties, elastic modulus, Poisson's ratio, etc. of the weld. The pipeline service information includes the design pressure, operating pressure, design temperature, operating temperature of the pipeline, as well as the maximum hydrogen mixing ratio, load, and stress generated during the operation of the pipeline. Therefore, fatigue crack growth tests can be performed on the pipeline in an inert environment and a natural gas hydrogen mixing environment respectively.

[0090] Preferably, the service life prediction method of the natural gas hydrogen-blended pipeline of the embodiment of the present invention first obtains the pipe material information, crack defect information and pipeline service information of the pipeline, and then performs slow strain rate tensile test, fracture toughness test and fatigue crack growth test respectively.

[0091] In the description of the present invention, it should be understood that “plurality” means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0092] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0093] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A service life prediction method applicable to natural gas hydrogen blending pipeline, characterized in that: include: Establish a failure assessment diagram, and draw a load ratio cutoff line and a toughness ratio cutoff line in the failure assessment diagram, wherein the load ratio cutoff line is ,in is the maximum load ratio of the pipe, is the tensile strength of the pipe in a natural gas hydrogen-mixed environment. is the tensile strength of the pipe in an inert environment, and the toughness ratio cutoff line is ,in is the fracture toughness of the pipe in a natural gas hydrogen-doped environment, is the fracture toughness of the pipe in an inert environment. In the failure assessment diagram, the load ratio cutoff line, the toughness ratio cutoff line, and the partial failure assessment curve connected between the load ratio cutoff line and the toughness ratio cutoff line are used as the baseline, and the area surrounded by the baseline and the coordinate system of the failure assessment diagram is the safety zone; Calculate the load ratio based on the calculated depth a of the i cracks and toughness ratio , the values ​​of the calculated depth a of i cracks are , +k, +2k...... + (i-1) k, where k is a constant, is the initial crack depth, and the load ratio corresponding to each crack calculation depth a is As the abscissa of the failure evaluation diagram, the corresponding toughness ratio As the ordinate of the failure assessment diagram, so that each crack calculation depth a has a corresponding coordinate point in the failure assessment diagram ( , ), among the i coordinate points, the coordinate point located in the safety zone and with the smallest distance from the reference line is taken as the critical coordinate point, and the crack calculation depth a corresponding to the critical coordinate point is the critical crack depth ; When the hoop stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline. When the axial stress direction of the pipeline is the main stress direction of the crack, according to Calculate the service life of the pipeline, where and m are Paris parameters, is the load fluctuation frequency, is the internal pressure load fluctuation of the pipeline, D is the diameter of the pipeline, and t is the thickness of the pipeline.

2. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 1, characterized in that: Also includes: Characterize the defects of the pipeline and regularize the cracks of the pipeline to obtain the characterization depth of the regularized cracks , for Multiply the defect characterization size by the safety factor.

3. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 2, characterized in that: When defect characterization is performed on the pipeline, exist When , the pipeline is unqualified; exist When , the crack is regularized into and The semi-elliptical surface crack , the crack is regularized into Semicircular surface cracks; in is the actual depth of the crack, is the actual length of the crack, is the wall thickness of the pipe, is the characterization depth of the regularized crack, It is 1 / 2 of the characterization length of the regularized crack.

4. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 1, characterized in that: Also includes: The pipe is subjected to a slow strain rate tensile test in an inert environment to obtain the tensile strength of the pipe in an inert environment. ; The pipeline is subjected to a slow strain rate tensile test in a natural gas hydrogen-doped environment to obtain the tensile strength of the pipeline in the natural gas hydrogen-doped environment. .

5. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 1, characterized in that: Also includes: The fracture toughness test of the pipe is carried out in an inert environment to obtain the fracture toughness of the pipe in an inert environment. ; The fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the fracture toughness of the pipe in the natural gas hydrogen-doped environment. .

6. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 5, characterized in that: The fracture toughness test of the pipe is performed in an inert environment to obtain the J-integrated fracture toughness of the pipe in an inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the J-integrated fracture toughness of the pipe in a natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment ; or The fracture toughness test of the pipe is carried out in an inert environment to obtain the CTOD fracture toughness of the pipe in an inert environment. ,according to Calculate the fracture toughness of pipes in an inert environment , the fracture toughness test of the pipeline is carried out in a natural gas hydrogen-doped environment to obtain the CTOD fracture toughness of the pipe in a natural gas hydrogen-doped environment ,according to Calculation of the fracture toughness of pipes in a natural gas hydrogen-doped environment ; Where E is the elastic modulus of the pipe, is the yield strength of the pipe, is the Poisson's ratio of the pipe.

7. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 1, characterized in that: The failure assessment curve is .

8. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 3, characterized in that: When the crack is an axial crack of the pipeline, according to , , and Load ratio calculated with ; When the crack is a circumferential crack of the pipeline, according to and Load ratio calculated with ; in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the yield strength of the pipe, c is Multiply the defect characterizing size by the safety factor, where R is the radius of the pipe.

9. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 3, characterized in that: according to Calculate the toughness ratio ,in for Multiply the material fracture toughness by the safety factor, is the plasticity correction factor, is the stress intensity factor caused by the primary stress, is the stress intensity factor caused by secondary stress.

10. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 9, characterized in that: according to ) Calculate the stress intensity factor caused by the primary stress , according to ) Calculate the stress intensity factor caused by secondary stress , in is the membrane stress component of the primary stress, is the bending stress component of the primary stress, is the membrane stress component of the secondary stress, is the bending stress component of the secondary stress, ， , c is Multiply the defect characterizing size by the safety factor.

11. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 9, characterized in that: With plasticity correction factor Toughness ratio The corresponding load ratio <0.8, according to Calculate the plasticity correction factor ; With plasticity correction factor Toughness ratio The corresponding load ratio 0.8< <1.1, according to Calculate the plasticity correction factor ; With plasticity correction factor Toughness ratio The corresponding load ratio >1.1, ; in The value of and The coordinate graph curve is obtained.

12. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 9, characterized in that: The material fracture toughness safety factor is 1.15 to 1.25, and the defect characterization size safety factor is 1.05 to 1.

15.

13. The method for predicting the service life of a natural gas hydrogen-blended pipeline according to claim 1, characterized in that: Also includes: The pipeline is subjected to fatigue crack growth tests in an inert environment and a natural gas hydrogen-doped environment to obtain the Paris parameter in the Paris formula. and Paris parameter m.

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