A test device, test method and threshold stress intensity factor determination method for pipeline steel hydrogen-induced cracking under hydrogen sulfide conditions

Abstract

The present invention discloses a device, test method, and threshold stress intensity factor determination method for hydrogen-induced cracking of pipeline steel under hydrogen sulfide-containing conditions. The device includes a hydrogen-induced cracking test container, a pressure test pump, and a hydrogen sulfide storage tank. The hydrogen-induced cracking test container is made of target pipeline steel and has at least one set of prefabricated cracks prefabricated on its inner wall. Each prefabricated crack group consists of at least two prefabricated cracks of different depths. The pressure test pump and the hydrogen sulfide storage tank are connected to the hydrogen-induced cracking test container. The test method includes: determining experimental parameters for a hydrogen-induced cracking test of pipeline steel under hydrogen sulfide-containing conditions; preparing a hydrogen-induced cracking test container prefabricated with a prefabricated crack group; and conducting a hydrogen-induced cracking test. The determination method includes: conducting a hydrogen-induced cracking test on the target pipeline steel, determining the maximum crack depth at which crack propagation does not occur and the minimum crack depth at which crack propagation occurs; and then determining the threshold stress intensity factor.

Description

Technical Field

[0001] The invention relates to a hydrogen-induced cracking test device for pipeline steel under hydrogen sulfide-containing conditions, a test method, and a threshold stress intensity factor determination method. Background Art

[0002] Oil and gas pipelines are the lifeblood of energy, but they are flammable and explosive, making pipeline transportation safety a public safety issue. The development, extraction, and transportation of sour gas fields both domestically and internationally often contain a certain amount of H2S gas. This process can easily lead to hydrogen-induced cracking damage in pipelines, severely impacting their service life. Therefore, crack prediction and control in hydrogen sulfide-containing conditions are of utmost importance.

[0003] The threshold stress intensity factor (TSIF) is the maximum stress intensity factor at which a cracked body does not experience delayed fracture. Using this factor can effectively assess the safety of pipes in service. However, existing conventional hydrogen-induced cracking testing methods have several problems: first, they cannot fully meet the requirements for theoretical model verification and key parameter correction; second, measuring the TSIF requires a large number of experiments; and finally, conventional hydrogen-induced cracking testing methods can only simulate conditions under simple loading conditions and are difficult to match with actual field conditions.

[0004] Therefore, how to provide a detection method for accurately evaluating the threshold stress intensity factor of pipeline steel is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a hydrogen-induced cracking test device for pipeline steel under hydrogen sulfide conditions, which can be used to accurately evaluate the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions.

[0006] The object of the present invention is to provide a hydrogen induced cracking test method for pipeline steel under hydrogen sulfide conditions, which can be applied to accurately evaluate the hydrogen induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions.

[0007] The object of the present invention is to provide a method for effectively determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a device for testing hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide, wherein the device comprises:

[0010] Hydrogen-induced cracking test vessels, pressure test pumps, hydrogen sulfide storage tanks; among them,

[0011] The hydrogen-induced cracking test container is made of target pipeline steel and has at least one group of prefabricated cracks prefabricated on its inner wall; each prefabricated crack group consists of at least two prefabricated cracks of different depths;

[0012] The pressure test pump is connected to the hydrogen-induced cracking test container to pressurize the interior of the hydrogen-induced cracking test container; the hydrogen sulfide storage tank is connected to the hydrogen-induced cracking test container to provide hydrogen sulfide to the interior of the hydrogen-induced cracking test container.

[0013] According to the test device provided in the first aspect, preferably, the hydrogen-induced cracking test container comprises a tubular side wall and two end surfaces, the two end surfaces are provided at both ends of the tubular side wall, and the tubular side wall and the two end surfaces form a closed cavity;

[0014] More preferably, the prefabricated cracks on the inner wall of the hydrogen-induced cracking test container are provided on the tubular side wall;

[0015] More preferably, the outer diameter of the tubular sidewall is the same as the outer diameter of the pipeline made of the target pipeline steel when it is in service, and the inner diameter of the tubular sidewall is the same as the inner diameter of the pipeline made of the target pipeline steel when it is in service.

[0016] According to the test device provided in the first aspect, preferably, each prefabricated crack group includes at least three prefabricated cracks with different depths and with depths distributed in a step-like manner;

[0017] More preferably, each prefabricated crack group includes a prefabricated crack with a depth of 0.2 mm, a prefabricated crack with a depth of 0.6 mm, a prefabricated crack with a depth of 1.0 mm, a prefabricated crack with a depth of 1.4 mm, and a prefabricated crack with a depth of 1.8 mm.

[0018] According to the test device provided in the first aspect, preferably, the hydrogen-induced cracking test container is further provided with a sewage outlet with a sewage valve.

[0019] According to the test device provided in the first aspect, preferably, a one-way vent valve is provided on the connecting pipeline between the hydrogen sulfide storage tank and the hydrogen-induced cracking test container.

[0020] According to the test device provided in the first aspect, preferably, the pipeline steel hydrogen induced cracking test device under hydrogen sulfide conditions further comprises a barometer, and the barometer is used to detect the pressure inside the hydrogen induced cracking test container.

[0021] In a second aspect, the present invention provides a method for testing hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide, the method being performed using the above-mentioned apparatus for testing hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide; wherein the method comprises:

[0022] 1) Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0023] The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution;

[0024] The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure;

[0025] The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content;

[0026] The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method;

[0027] 2) preparing a hydrogen-induced cracking test vessel with a prefabricated crack group;

[0028] 3) Filling the hydrogen-induced cracking test container with the rated solution, rated hydrogen sulfide content, rated pressure, and rated pressure application method, pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure and maintaining the pressure using the rated pressure application method; while maintaining the rated pressure inside the hydrogen-induced cracking test container, filling the hydrogen sulfide into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the filling of hydrogen sulfide and starting crack growth monitoring of prefabricated cracks inside the hydrogen-induced cracking test container until the crack growth monitoring time meets the preset service time or the presence of a prefabricated crack with a crack growth depth reaching the rated value is detected.

[0029] According to the test method provided in the second aspect, preferably, the solution for determining hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions comprises:

[0030] Determine the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide;

[0031] Determine the solution for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions based on the acidity and alkalinity of the service environment of the target pipeline steel when in service without hydrogen sulfide;

[0032] More preferably, the solution for testing hydrogen-induced cracking of pipeline steel under hydrogen sulfide-containing conditions, determined based on the acidity and alkalinity of the service environment of the target pipeline steel when in service without hydrogen sulfide, comprises:

[0033] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is acidic, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide is 2.5-2.8, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution A; solution A is a mixed solution of CH3COOH and NaCl;

[0034] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is alkaline, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide is 8.1-8.3, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution B; solution B is synthetic seawater without heavy metal ions;

[0035] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is neutral, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide and is 6.8-7.2, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution C; solution C is a mixed solution of CH3COONa and NaCl;

[0036] Further preferably, based on the mass of the A solution being 100%, the mass concentration of CH3COOH in the A solution is 0.48-0.52%, and the mass concentration of NaCl is 4.9-5.1%;

[0037] At this time, the pH value of solution A is usually around 2.5-2.8; after solution A is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 2.7-3.3;

[0038] Further preferably, the B solution can be prepared with reference to the composition ratio of synthetic seawater disclosed in ASTM standard D1141-98;

[0039] For example, based on the volume of the B solution, the composition of the B solution is as shown in Table 1:

[0040] Table 1

[0041]

[0042] At this time, the pH value of solution B is usually around 8.1-8.3; after solution B is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 4.8-5.4;

[0043] Further preferably, based on the mass of the C solution being 100%, the mass concentration of CH3COONa in the C solution is 0.38-0.42%, and the mass concentration of NaCl is 4.9-5.1%;

[0044] At this time, the pH value of solution C is usually around 6.8-7.2; after solution C is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 4.6-5.6;

[0045] Further preferably, when the test solution is solution A, the preset service time is 96 hours;

[0046] Further preferably, when the test solution is solution B, the preset service time is 96 hours;

[0047] Further preferably, when the test solution is solution C, the preset service time is 96-2160h.

[0048] According to the test method provided in the second aspect, preferably, determining the hydrogen sulfide content of the pipeline steel hydrogen-induced cracking test under hydrogen sulfide-containing conditions comprises:

[0049] Determine the hydrogen sulfide content in the service environment of the target pipeline steel;

[0050] Determine the hydrogen sulfide content of the hydrogen sulfide cracking test of the pipeline steel under hydrogen sulfide containing conditions based on the hydrogen sulfide content of the service environment of the target pipeline steel during service;

[0051] Among them, the hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions should be able to better simulate the hydrogen sulfide content of the service environment when the target pipeline steel is in service. For example, the hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions can be directly selected from the hydrogen sulfide content of the service environment when the target pipeline steel is in service.

[0052] According to the test method provided in the second aspect, preferably, the hydrogen sulfide content determined in the hydrogen sulfide-containing conditions for the pipeline steel hydrogen-induced cracking test is the saturated hydrogen sulfide content in the rated solution at the rated pressure.

[0053] According to the test method provided in the second aspect, preferably, determining the test pressure of the pipeline steel hydrogen-induced cracking test under hydrogen sulfide conditions includes:

[0054] Determine the pressure of the service environment of the target pipeline steel when in service;

[0055] Determine the test pressure of the hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions based on the pressure of the service environment of the target pipeline steel during service;

[0056] Among them, the test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions should be able to better simulate the pressure of the service environment of the target pipeline steel when it is in service. For example, the test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions directly selects the pressure of the service environment of the target pipeline steel when it is in service.

[0057] According to the test method provided in the second aspect, preferably, the rated value is 60% of the wall thickness of the wall used for prefabricating the prefabricated crack group in the hydrogen-induced cracking test container.

[0058] According to the test method provided in the second aspect, preferably, the rated pressure application method is performed by constant pressure loading, step-by-step pressurization or fatigue pressurization.

[0059] According to the test method provided in the second aspect, preferably, the method comprises:

[0060] Repeat steps 1) to 3) to complete hydrogen-induced cracking tests with different rated solutions, different rated hydrogen sulfide contents, different rated pressures, and / or different rated pressure application methods;

[0061] Achieve simulation of hydrogen-induced cracking of target pipeline steel under different service environments and different pressure application modes;

[0062] More preferably, the different rated solutions include solution A, solution B, and solution C;

[0063] More preferably, the different rated pressure application modes include constant pressure loading, step-by-step pressurization and fatigue pressurization;

[0064] In a preferred embodiment, steps 1) to 3) are repeated to complete orthogonal hydrogen-induced cracking tests under rated hydrogen sulfide content, rated solution, different rated solutions, and different rated pressure modes.

[0065] According to the test method provided in the second aspect, preferably, in step 3), after crack extension monitoring is completed, the hydrogen sulfide and / or oxygen content is further determined, and if the content is unqualified, steps 2) to 3) are repeated.

[0066] According to the test method provided in the second aspect, preferably, the hydrogen sulfide content is measured by the following method:

[0067] Iodine (I2) is used to oxidize sulfur ions (S - ) method to determine the hydrogen sulfide content.

[0068] In a third aspect, the present invention provides a method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions, the method comprising:

[0069] Conducting a hydrogen-induced cracking test on the target pipeline steel using the aforementioned hydrogen-induced cracking test method for pipeline steel under hydrogen sulfide conditions to determine the maximum depth of cracks that do not propagate and the minimum depth of cracks that propagate in the prefabricated crack group of the target pipeline steel under the same experimental conditions;

[0070] Then, based on the maximum depth of the cracks in the prefabricated crack group that do not propagate and the minimum depth of the cracks that propagate, in combination with the rated pressure and the outer diameter and inner diameter of the wall surface of the hydrogen-induced cracking test container used to prefabricate the prefabricated crack group, a threshold stress intensity factor is determined.

[0071] According to the determination method provided in the third aspect, preferably, determining the threshold stress intensity factor based on the maximum depth of cracks in the prefabricated crack group that do not undergo crack propagation and the minimum depth of cracks that undergo crack propagation, in combination with the rated pressure and the outer diameter and inner diameter of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group, includes:

[0072] Determining a maximum stress intensity factor of a crack that does not propagate based on a maximum depth of a crack that does not propagate in the prefabricated crack group, in combination with a rated pressure and outer and inner diameters of a wall surface of a hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0073] Determining a minimum stress intensity factor for a crack that is subject to crack propagation based on a minimum depth of a crack that is subject to crack propagation in the prefabricated crack group, in combination with a rated pressure, and outer and inner diameters of a wall surface of a hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0074] Determining a threshold stress intensity factor based on the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates;

[0075] More preferably, based on the maximum depth of the crack that does not propagate, combined with the rated pressure, the outer diameter and the inner diameter of the wall surface used to preform the prefabricated crack group in the hydrogen-induced cracking test container, the maximum stress intensity factor of the crack that does not propagate is determined by the following formula:

[0076]

[0077] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a In The maximum depth of a crack without crack extension, in meters;

[0078] More preferably, based on the minimum depth of the crack at which crack propagation occurs in the prefabricated cracks, combined with the rated pressure, the outer diameter and the inner diameter of the wall surface of the hydrogen-induced crack test container used to prefabricate the prefabricated crack group, the minimum stress intensity factor of the crack at which crack propagation occurs is determined by the following formula:

[0079]

[0080] Where K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a Iy The minimum depth of the crack at which crack propagation occurs, in m;

[0081] More preferably, the threshold stress intensity factor is determined based on the maximum stress intensity factor of the crack that does not expand and the minimum stress intensity factor of the crack that expands by the following formula:

[0082] K Ⅰth =(K Ⅰy +K Ⅰn )÷2

[0083] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ;K Ⅰth is the threshold stress intensity factor, unit: MPa·m 1 / 2 ;

[0084] More preferably, the maximum stress intensity factor of the crack that does not extend and the minimum stress intensity factor of the crack that extends satisfy:

[0085] K Iy -K In ≤0.1·(K Iy +K In )

[0086] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 .

[0087] The technical solution provided by the present invention can effectively simulate the actual service environment by adjusting the pressure and H2S content; it can use full-scale crack growth experiments to simulate the hydrogen-induced cracking behavior of pipeline steel in the actual service environment, accurately obtain reasonable and reliable failure modes of pipeline steel in complex environments, and determine the threshold stress intensity factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 This is a schematic structural diagram of a test apparatus for hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions provided by one embodiment of the present invention.

[0089] Figure 2 A schematic flow chart of a method for testing hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions provided in one embodiment of the present invention.

[0090] Figure 3 Schematic diagram of a method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions provided by one embodiment of the present invention.

[0091] Figure 4 Schematic diagram of a prefabricated crack group in one embodiment of the present invention. DETAILED DESCRIPTION

[0092] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0093] See also Figure 1 One embodiment of the present invention provides a hydrogen-induced cracking test device for pipeline steel under hydrogen sulfide conditions, wherein the device comprises:

[0094] Hydrogen induced cracking test vessel 1, pressure test pump 2, hydrogen sulfide storage tank 3; among which,

[0095] The hydrogen-induced cracking test vessel 1 is made of target pipeline steel and has at least one set of prefabricated cracks prefabricated on its inner wall; each prefabricated crack set consists of at least two prefabricated cracks of different depths;

[0096] The pressure test pump 2 is connected to the hydrogen-induced cracking test container 1 to pressurize the interior of the hydrogen-induced cracking test container 1 ; the hydrogen sulfide storage tank 3 is connected to the hydrogen-induced cracking test container 1 to supply hydrogen sulfide to the interior of the hydrogen-induced cracking test container 1 .

[0097] Furthermore, the hydrogen-induced cracking test container 1 includes a tubular side wall and two end surfaces, the two end surfaces are arranged at both ends of the tubular side wall, and the tubular side wall and the two end surfaces form a closed cavity;

[0098] Furthermore, the prefabricated cracks on the inner wall of the hydrogen-induced cracking test container 1 are provided on the tubular side wall;

[0099] Furthermore, the outer diameter of the tubular sidewall is the same as the outer diameter of the pipeline made of the target pipeline steel when it is in service, and the inner diameter of the tubular sidewall is the same as the inner diameter of the pipeline made of the target pipeline steel when it is in service.

[0100] Furthermore, each prefabricated crack group includes at least three prefabricated cracks with different depths and with depths distributed in a step-like manner;

[0101] Furthermore, each prefabricated crack group includes a prefabricated crack with a depth of 0.2 mm, a prefabricated crack with a depth of 0.6 mm, a prefabricated crack with a depth of 1.0 mm, a prefabricated crack with a depth of 1.4 mm, and a prefabricated crack with a depth of 1.8 mm.

[0102] Furthermore, the hydrogen-induced cracking test container 1 is further provided with a sewage outlet with a sewage valve 4 .

[0103] Furthermore, a one-way vent valve 5 is provided on the connecting pipeline between the hydrogen sulfide storage tank 3 and the hydrogen-induced cracking test container 1 .

[0104] Furthermore, the pipeline steel hydrogen-induced cracking test device under hydrogen sulfide conditions further comprises a barometer 6 , which is used to detect the pressure inside the hydrogen-induced cracking test container.

[0105] See also Figure 2 One embodiment of the present invention provides a method for testing hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide. The method is performed using a test apparatus for hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide provided in an embodiment of the present invention (the structure of the test apparatus for hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide is described in detail in the embodiment of the test apparatus for hydrogen-induced cracking of pipeline steel under conditions containing hydrogen sulfide of the present invention, which will not be described in detail here). The method comprises:

[0106] Step S1: Determine the experimental parameters for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0107] The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution;

[0108] The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content;

[0109] The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure;

[0110] The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method;

[0111] Step S2: preparing a hydrogen-induced cracking test container prefabricated with a prefabricated crack group;

[0112] Step S3: Conduct hydrogen-induced cracking test under rated solution, rated hydrogen sulfide content, rated pressure, and rated pressure application mode:

[0113] The rated solution is filled into a hydrogen-induced cracking test container, and the interior of the hydrogen-induced cracking test container is pressurized to the rated pressure using a rated pressure application method and maintained; while the interior of the hydrogen-induced cracking test container is maintained at the rated pressure, hydrogen sulfide is filled into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, after which the filling of hydrogen sulfide is stopped and crack growth monitoring of prefabricated cracks in the hydrogen-induced cracking test container is started until the crack growth monitoring time meets the preset service time or the presence of a prefabricated crack with a crack growth depth reaching the rated value is detected.

[0114] Furthermore, it is determined that the solutions for hydrogen-induced cracking testing of pipeline steel under hydrogen sulfide conditions include:

[0115] Determine the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide;

[0116] Determine the solution for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions based on the acidity and alkalinity of the service environment of the target pipeline steel when in service without hydrogen sulfide;

[0117] Furthermore, based on the acidity and alkalinity of the service environment of the target pipeline steel when in service without hydrogen sulfide, the solution for the hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to include:

[0118] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is acidic, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide is 2.5-2.8, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution A; solution A is a mixed solution of CH3COOH and NaCl;

[0119] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is alkaline, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide is 8.1-8.3, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution B; solution B is synthetic seawater without heavy metal ions;

[0120] When the service environment of the target pipeline steel does not contain hydrogen sulfide and is neutral, that is, when the pH value of the service environment of the target pipeline steel does not contain hydrogen sulfide and is 6.8-7.2, the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution C; solution C is a mixed solution of CH3COONa and NaCl;

[0121] Furthermore, based on the mass of solution A being 100%, the mass concentration of CH3COOH in solution A is 0.48-0.52%, and the mass concentration of NaCl is 4.9-5.1%;

[0122] At this time, the pH value of solution A is usually around 2.5-2.8; after solution A is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 2.7-3.3;

[0123] Furthermore, solution B can be prepared according to the composition ratio of synthetic seawater disclosed in ASTM standard D1141-98;

[0124] For example, based on the volume of solution B, the composition of solution B is shown in Table 1;

[0125] At this time, the pH value of solution B is usually around 8.1-8.3; after solution B is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 4.8-5.4;

[0126] Furthermore, based on the mass of solution C being 100%, the mass concentration of CH3COONa in solution C is 0.38-0.42%, and the mass concentration of NaCl is 4.9-5.1%;

[0127] At this time, the pH value of solution C is usually around 6.8-7.2; after solution C is saturated with hydrogen sulfide under a certain pressure, the pH value can reach 4.6-5.6;

[0128] Furthermore, when the test solution is solution A, the preset service time is 96 h;

[0129] Furthermore, when the test solution is solution B, the preset service time is 96h;

[0130] Furthermore, when the test solution is solution C, the preset service time is 96-2160h.

[0131] Furthermore, determining the hydrogen sulfide content in the hydrogen sulfide-containing pipeline steel hydrogen-induced cracking test includes:

[0132] Determine the hydrogen sulfide content in the service environment of the target pipeline steel;

[0133] Determine the hydrogen sulfide content of the hydrogen sulfide cracking test of the pipeline steel under hydrogen sulfide containing conditions based on the hydrogen sulfide content of the service environment of the target pipeline steel during service;

[0134] Among them, the hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions should be able to better simulate the hydrogen sulfide content of the service environment when the target pipeline steel is in service. For example, the hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions can be directly selected from the hydrogen sulfide content of the service environment when the target pipeline steel is in service.

[0135] Furthermore, the hydrogen sulfide content of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the saturated hydrogen sulfide content in the rated solution at the rated pressure.

[0136] Furthermore, the test pressure for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to include:

[0137] Determine the pressure of the service environment of the target pipeline steel when in service;

[0138] Determine the test pressure of the hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions based on the pressure of the service environment of the target pipeline steel during service;

[0139] Among them, the test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions should be able to better simulate the pressure of the service environment of the target pipeline steel when it is in service. For example, the test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions directly selects the pressure of the service environment of the target pipeline steel when it is in service.

[0140] Furthermore, the rated value is 60% of the wall thickness of the wall used for preforming the preformed crack group in the hydrogen-induced cracking test container.

[0141] Furthermore, the rated pressure application method is performed by constant pressure loading, step-by-step pressurization or fatigue pressurization.

[0142] Furthermore, the method comprises:

[0143] Repeat steps S1-S3 to complete hydrogen-induced cracking tests under different rated solutions, different rated hydrogen sulfide contents, different rated pressures, and / or different rated pressurization methods;

[0144] Achieve simulation of hydrogen-induced cracking of target pipeline steel under different service environments and different pressure application modes;

[0145] Furthermore, the different rated solutions include solution A, solution B, and solution C;

[0146] Furthermore, different rated pressure application modes include constant pressure loading, step-by-step pressurization and fatigue pressurization.

[0147] Furthermore, in step S3, after crack extension monitoring is completed, the hydrogen sulfide and / or oxygen content is further determined, and if the content is unqualified, steps S2-S3 are repeated;

[0148] In one specific embodiment, the rated solution is solution A, and when the hydrogen sulfide content is the saturated hydrogen sulfide content, the hydrogen sulfide content is considered qualified if it is not less than 2300 ppm after the crack growth monitoring is completed;

[0149] In one specific embodiment, the rated solution is solution B, and when the hydrogen sulfide content is the saturated hydrogen sulfide content, the hydrogen sulfide content is considered qualified if it is not less than 2300 ppm after the crack growth monitoring is completed;

[0150] In one specific embodiment, the rated solution is solution C, and when the hydrogen sulfide content is the saturated hydrogen sulfide content, the hydrogen sulfide content is considered qualified if it is not less than 2300 ppm after the crack growth monitoring is completed;

[0151] In one embodiment, the oxygen content is considered qualified if it does not exceed 0.05 ppm after the crack growth monitoring is completed.

[0152] In one embodiment, the method for testing hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions includes:

[0153] 1) Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0154] The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution;

[0155] The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content;

[0156] The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure;

[0157] The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method;

[0158] 2) preparing a hydrogen-induced cracking test vessel with a prefabricated crack group;

[0159] 3) Carry out hydrogen-induced cracking test under rated solution, rated hydrogen sulfide content, rated pressure and rated pressure mode:

[0160] Filling a rated solution into a hydrogen-induced cracking test container, and pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure using a rated pressure application method and maintaining the pressure; while the interior of the hydrogen-induced cracking test container is maintained at the rated pressure, filling the hydrogen sulfide into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the filling of hydrogen sulfide and starting crack growth monitoring of prefabricated cracks in the hydrogen-induced cracking test container until the crack growth monitoring time meets a preset service time or a prefabricated crack with a crack growth depth reaching a rated value is detected;

[0161] Optionally, after crack growth monitoring is completed, the hydrogen sulfide and / or oxygen content is further determined, and if the content is unqualified, steps 1) to 3) are repeated;

[0162] 4) Repeat steps 1)-3) to complete hydrogen-induced cracking tests under different rated solutions, different rated hydrogen sulfide contents, different rated pressures, and / or different rated pressure application methods, and determine the threshold stress intensity factor, thereby simulating hydrogen-induced cracking under different pressure application methods under different service environments.

[0163] Furthermore, the hydrogen sulfide content was determined by the following method:

[0164] Iodine (I2) is used to oxidize sulfur ions (S - ) method to determine the hydrogen sulfide content;

[0165] The reactions that occur during the measurement are:

[0166] S - +I2(excess)→S↓+2I - +I2(remaining)

[0167] I2+2Na2S2O3→Na2S4O6+2NaI

[0168] For specific steps, please refer to standard QJ / ASHL02.08.021; please refer to Zhao Biliang's "Determination of dissolved hydrogen sulfide content in desulfurization liquid (potentiometric titration method)" (Engineering Technology, 2016(11):00261-00261).

[0169] See also Figure 3 One embodiment of the present invention provides a method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions, the method comprising:

[0170] Step T1: Conducting a hydrogen-induced cracking test on a target pipeline steel using the hydrogen-induced cracking test method for pipeline steel under hydrogen sulfide conditions provided in an embodiment of the present invention (for details on the hydrogen-induced cracking test method for pipeline steel under hydrogen sulfide conditions, see the embodiment of the hydrogen-induced cracking test method for pipeline steel under hydrogen sulfide conditions of the present invention), and determining the maximum depth of a crack that does not propagate and the minimum depth of a crack that propagates in a prefabricated crack group of the target pipeline steel under the same experimental conditions;

[0171] Step T2: Determine the threshold stress intensity factor based on the maximum depth of the cracks that do not propagate and the minimum depth of the cracks that propagate in the prefabricated crack group, combined with the rated pressure and the outer and inner diameters of the wall of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group.

[0172] Specifically, the method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions includes:

[0173] 1) Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0174] The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution;

[0175] The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content;

[0176] The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure;

[0177] The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method;

[0178] 2) Prepare a hydrogen-induced cracking test vessel with a prefabricated crack group

[0179] 3) Carry out hydrogen-induced cracking test under rated solution, rated hydrogen sulfide content, rated pressure and rated pressure mode:

[0180] Filling a rated solution into a hydrogen-induced cracking test container, and pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure using a rated pressure application method and maintaining the pressure; while the interior of the hydrogen-induced cracking test container is maintained at the rated pressure, filling the hydrogen sulfide into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the filling of hydrogen sulfide and starting crack growth monitoring of prefabricated cracks in the hydrogen-induced cracking test container until the crack growth monitoring time meets a preset service time or a prefabricated crack with a crack growth depth reaching a rated value is detected;

[0181] 4) determining the maximum depth of cracks that do not propagate and the minimum depth of cracks that propagate in the prefabricated crack group in the hydrogen-induced cracking test in step 2);

[0182] 5) Based on the maximum depth of cracks that do not propagate in the prefabricated crack group and the minimum depth of cracks that propagate, the threshold stress intensity factor is determined in combination with the rated pressure and the outer and inner diameters of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group.

[0183] Furthermore, step T2 includes:

[0184] Determining a maximum stress intensity factor of a crack that does not propagate based on a maximum depth of a crack in the prefabricated crack group that does not propagate, in combination with the rated pressure, the outer diameter and the inner diameter of a wall surface in a hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0185] Determining a minimum stress intensity factor for a crack that is subject to crack propagation based on a minimum depth of a crack that is subject to crack propagation in the prefabricated crack group, in combination with the rated pressure, the outer diameter and the inner diameter of a wall surface of a hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0186] determining a threshold stress intensity factor based on a maximum stress intensity factor of a crack that does not propagate and a minimum stress intensity factor of a crack that propagates;

[0187] Furthermore, the maximum stress intensity factor of a crack that does not propagate is determined by the following formula:

[0188]

[0189] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, in dimensionless units; a In The maximum depth of a crack without crack extension, in meters;

[0190] Furthermore, the minimum stress intensity factor for crack growth is determined by the following formula:

[0191]

[0192] Where K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a Iy The minimum depth of the crack at which crack propagation occurs, in m;

[0193] Furthermore, the threshold stress intensity factor is determined based on the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates by the following formula:

[0194] K Ⅰth =(K Ⅰy +K Ⅰn )÷2

[0195] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ;KⅠth is the threshold stress intensity factor, unit: MPa·m 1 / 2 ;

[0196] The value of the shape factor F can be determined in accordance with conventional methods in the art. For example, the corresponding F value can be obtained based on the F-α curve corresponding to different n=R1 / R2 values ​​according to the figure in Section 4.6.4.2 of the Stress Intensity Factor Handbook. a i is the depth of the crack;

[0197] Furthermore, the maximum stress intensity factor of a crack that does not grow and the minimum stress intensity factor of a crack that grows satisfy:

[0198] K Iy -K In ≤0.1·(K Iy +K In )

[0199] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 .

[0200] In a specific embodiment, before determining the threshold stress intensity factor based on the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates, it is determined whether the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates meet K Iy -K In ≤0.1·(K Iy +K In ), where K In K is the maximum stress intensity factor of the crack without crack extension, Iy is the minimum stress intensity factor of the crack for crack growth to occur;

[0201] If the conditions are met, determining a threshold stress intensity factor based on a maximum stress intensity factor of a crack that does not extend and a minimum stress intensity factor of a crack that extends;

[0202] If the conditions are not met, the depths of the prefabricated cracks in the prefabricated crack group are re-determined, and at least one prefabricated crack in the crack group has a depth greater than the maximum depth of the crack that does not propagate and less than the minimum depth of the crack that propagates. A hydrogen-induced cracking test vessel with the prefabricated crack group is then re-prepared and steps T1 to T2 are repeated.

[0203] In one embodiment, a method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions includes:

[0204] 1) Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0205] The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution;

[0206] The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content;

[0207] The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure;

[0208] The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method;

[0209] 2) preparing a hydrogen-induced cracking test vessel with a prefabricated crack group;

[0210] 3) Carry out hydrogen-induced cracking test under rated solution, rated hydrogen sulfide content, rated pressure and rated pressure mode:

[0211] Filling a rated solution into a hydrogen-induced cracking test container, and pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure using a rated pressure application method and maintaining the pressure; while the interior of the hydrogen-induced cracking test container is maintained at the rated pressure, filling the hydrogen sulfide into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the filling of hydrogen sulfide and starting crack growth monitoring of prefabricated cracks in the hydrogen-induced cracking test container until the crack growth monitoring time meets a preset service time or a prefabricated crack with a crack growth depth reaching a rated value is detected;

[0212] Optionally, after crack growth monitoring is completed, the hydrogen sulfide and / or oxygen content is further determined. If the content is unqualified, steps 1) to 3) are repeated; if the content is qualified, step 4) is performed;

[0213] 4) determining the maximum depth of cracks that do not propagate and the minimum depth of cracks that propagate in the prefabricated crack group in the hydrogen-induced cracking test in step 3);

[0214] 5) Determine the maximum stress intensity factor of a crack that does not propagate based on the maximum depth of the crack in the prefabricated crack group that does not propagate, in combination with the rated pressure and the outer and inner diameters of the wall of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0215] 6) Determine the minimum stress intensity factor of a crack that is subject to crack propagation based on the minimum depth of the crack that is subject to crack propagation in the prefabricated crack group, in combination with the rated pressure, the outer diameter and the inner diameter of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group;

[0216] 7) Determine whether the maximum stress intensity factor of the crack without crack extension and the minimum stress intensity factor of the crack with crack extension meet K Iy -K In ≤0.1·(K Iy +K In ), where K In K is the maximum stress intensity factor of the crack without crack extension, Iy is the minimum stress intensity factor of the crack for crack growth to occur;

[0217] If satisfied, proceed to step 8);

[0218] If not, re-determine the depth of the prefabricated cracks in the prefabricated crack group, and there is at least one prefabricated crack in the crack group whose depth is greater than the maximum depth of the crack that does not crack propagate and less than the minimum depth of the crack that crack propagates; then re-prepare a hydrogen-induced cracking test container prefabricated with the prefabricated crack group, and repeat steps 3)-7);

[0219] 8) determining a threshold stress intensity factor based on the maximum stress intensity factor of a crack that does not propagate and the minimum stress intensity factor of a crack that propagates;

[0220] Optionally, step 9) is repeated to complete hydrogen-induced cracking tests and threshold stress intensity factor determination under different rated solutions, different rated hydrogen sulfide contents, different rated pressures, and / or different rated pressurization modes, thereby simulating hydrogen-induced cracking and determining threshold stress intensity factors under different pressure application modes in different service environments.

[0221] Example 1

[0222] This embodiment provides a hydrogen-induced cracking test device for pipeline steel under hydrogen sulfide conditions, wherein the device comprises:

[0223] Hydrogen-induced cracking test vessel, pressure test pump, hydrogen sulfide storage tank, one-way vent valve, and barometer;

[0224] The hydrogen-induced cracking test vessel is made of target pipeline steel; the hydrogen-induced cracking test vessel comprises a tubular sidewall and two end faces, the two end faces being arranged at both ends of the tubular sidewall, the tubular sidewall and the two end faces forming a closed cavity, the outer diameter of the tubular sidewall being the same as the outer diameter of a pipeline made of the target pipeline steel when in service, and the inner diameter of the tubular sidewall being the same as the inner diameter of a pipeline made of the target pipeline steel when in service; a group of prefabricated cracks is prefabricated on the inner wall of the tubular sidewall of the hydrogen-induced cracking test vessel, the prefabricated crack group comprising five prefabricated cracks of different depths and in a step-wise distribution, and the prefabricated cracks in the prefabricated crack group;

[0225] A pressure test pump is connected to the hydrogen-induced cracking test container to pressurize the interior of the hydrogen-induced cracking test container; a hydrogen sulfide storage tank is connected to the hydrogen-induced cracking test container to supply hydrogen sulfide to the interior of the hydrogen-induced cracking test container 1; the hydrogen-induced cracking test container is provided with a sewage outlet with a sewage valve; a one-way vent valve is provided on the connecting pipeline between the hydrogen sulfide storage tank and the hydrogen-induced cracking test container; a barometer is connected to the hydrogen-induced cracking test container to detect the pressure inside the hydrogen-induced cracking test container.

[0226] This embodiment also provides a method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions, the method comprising:

[0227] 1. Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions:

[0228] 1.1. Determine the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide; determine the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions as the rated solution based on the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide;

[0229] When the service environment of the target pipeline steel during service is acidic without hydrogen sulfide, that is, when the pH value of the service environment of the target pipeline steel during service is 2.5-2.8 without hydrogen sulfide, solution A is selected as the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions; solution A is a mixed solution of CH3COOH and NaCl; based on the mass of solution A being 100%, the mass concentration of CH3COOH in solution A is 0.5%, and the mass concentration of NaCl is 5%;

[0230] When the target pipeline steel is in an alkaline service environment without hydrogen sulfide, that is, when the pH value of the target pipeline steel is 8.1-8.3 without hydrogen sulfide, solution B is selected as the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions. Solution B is synthetic seawater without heavy metal ions. The composition of solution B is shown in Table 1 based on the volume of solution B.

[0231] When the service environment of the target pipeline steel is neutral without hydrogen sulfide, that is, when the pH value of the service environment of the target pipeline steel is 6.8-7.2 without hydrogen sulfide, the solution used for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is solution C; solution C is a mixed solution of CH3COONa and NaCl; based on the mass of solution C being 100%, the mass concentration of CH3COONa in solution C is 0.4%, and the mass concentration of NaCl is 5%;

[0232] 1.2. Determine the pressure of the service environment of the target pipeline steel during service; the pressure of the service environment of the target pipeline steel during service is selected as the test pressure of the hydrogen-induced cracking test of the pipeline steel under hydrogen sulfide conditions, which is the rated pressure;

[0233] In this embodiment, the rated pressure is 4.0 MPa;

[0234] 1.3. Determine the hydrogen sulfide content of the service environment of the target pipeline steel during service; the hydrogen sulfide content of the service environment of the target pipeline steel during service is selected as the hydrogen sulfide content for the hydrogen-induced cracking test of the pipeline steel under hydrogen sulfide-containing conditions, which is the rated hydrogen sulfide content;

[0235] The hydrogen sulfide content in this embodiment is the saturated hydrogen sulfide content in the rated solution at the rated pressure;

[0236] 1.4. The rated pressure application method is constant pressure loading, step-by-step pressurization or fatigue pressurization as the pressure application method for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions;

[0237] In this embodiment, the rated pressure application mode is constant pressure loading.

[0238] 2. Prepare a hydrogen-induced cracking test vessel with a prefabricated crack group;

[0239] like Figure 4 As shown, the prefabricated crack group includes a prefabricated crack with a depth of 0.2 mm, a prefabricated crack with a depth of 0.6 mm, a prefabricated crack with a depth of 1.0 mm, a prefabricated crack with a depth of 1.4 mm, and a prefabricated crack with a depth of 1.8 mm.

[0240] 3. Conduct hydrogen-induced cracking tests under rated solution, rated hydrogen sulfide content, rated pressure, and rated pressure application method:

[0241] Filling a hydrogen-induced cracking test container with a rated solution, and pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure using a rated pressure application method and maintaining the pressure; while maintaining the rated pressure inside the hydrogen-induced cracking test container, filling the hydrogen-induced cracking test container with hydrogen sulfide until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the addition of hydrogen sulfide (testing the pH value of the solution after ventilating for 60 minutes, and closing the one-way vent valve after the pH reaches the pH requirement for reaching the rated hydrogen sulfide content), and commencing crack growth monitoring of prefabricated cracks inside the hydrogen-induced cracking test container until the crack growth monitoring time meets the preset service time or the presence of prefabricated cracks with a crack growth depth reaching a rated value (60% of the wall thickness of the wall surface of the hydrogen-induced cracking test container used to prefabricate the prefabricated crack group) is detected, and the crack growth monitoring time cannot exceed the preset service time, and no prefabricated cracks with a crack growth depth exceeding the rated value exist;

[0242] After crack growth monitoring is completed, further determine the hydrogen sulfide and oxygen content. If the content is unqualified, repeat steps 1 to 3;

[0243] When solution A is selected as the rated solution, the initial pH value is 2.7±0.1; the pH value when saturated with hydrogen sulfide is 2.7-3.3; the preset service time is 96 hours; the pH value at the end is pH<4.0, the hydrogen sulfide content is not less than 2300ppm, and the oxygen content does not exceed 0.05ppm;

[0244] When solution B is selected as the rated solution, the initial pH value is 8.1-8.3; the pH value when saturated with hydrogen sulfide is 4.8-5.4; the preset service time is 96 hours; the pH value at the end is less than the pH value when saturated with hydrogen sulfide, the hydrogen sulfide content is not less than 2300ppm, and the oxygen content does not exceed 0.05ppm;

[0245] When solution C is selected as the rated solution, the initial pH value is 6.8-7.2; the pH value when saturated with hydrogen sulfide is 4.6-5.6; the preset service time is 96 hours; the pH value at the end is less than the pH value when saturated with hydrogen sulfide, the hydrogen sulfide content is not less than 2300ppm, and the oxygen content does not exceed 0.05ppm;

[0246] Among them, the hydrogen sulfide content is oxidized by iodine (I2) to sulfide ions (S - ) method to determine the hydrogen sulfide content.

[0247] 4. Determine the maximum depth of the crack that does not propagate and the minimum depth of the crack that propagates in the prefabricated crack group in the hydrogen-induced cracking test in step 3.

[0248] 5. Based on the maximum depth of the cracks in the prefabricated crack group that do not propagate, combined with the rated pressure, the outer diameter and the inner diameter of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group, determine the maximum stress intensity factor of the cracks that do not propagate using the following formula;

[0249]

[0250] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, in dimensionless units; a In The maximum depth of a crack without crack extension, in meters.

[0251] 6. Based on the minimum depth of a crack in the prefabricated crack group that is subject to crack propagation, combined with the rated pressure, the outer diameter and inner diameter of the wall surface of the hydrogen-induced crack test vessel used to prefabricate the prefabricated crack group, the minimum stress intensity factor of a crack in which crack propagation occurs is determined by the following formula;

[0252]

[0253] Where K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a Iy The minimum depth of a crack at which crack propagation occurs, in meters.

[0254] 7. Determine whether the maximum stress intensity factor of the crack without crack extension and the minimum stress intensity factor of the crack with crack extension meet K Iy -K In ≤0.1·(K Iy +K In ), where K In K is the maximum stress intensity factor of the crack without crack extension, Iyis the minimum stress intensity factor of the crack for crack growth to occur;

[0255] If satisfied, proceed to step 8;

[0256] If not, re-determine the depths of the prefabricated cracks in the prefabricated crack group, and at least one prefabricated crack in the crack group has a depth greater than the maximum depth of the crack that does not propagate and less than the minimum depth of the crack that propagates; then re-prepare a hydrogen-induced cracking test vessel prefabricated with the prefabricated crack group, and repeat steps 3-7;

[0257] 8. The threshold stress intensity factor is determined by the following formula based on the maximum stress intensity factor of the crack that does not grow and the minimum stress intensity factor of the crack that grows;

[0258] K Ⅰth =(K Ⅰy +K Ⅰn )÷2

[0259] Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ;K Ⅰth is the threshold stress intensity factor, unit: MPa·m 1 / 2 .

[0260] In this embodiment, the rated solution is solution A. The inner diameter of the wall surface of the hydrogen-induced cracking test container used to prefabricate the prefabricated crack group is 98 mm, the outer diameter of the wall surface of the hydrogen-induced cracking test container used to prefabricate the prefabricated crack group is 108 mm, the maximum depth of the crack that does not propagate in the prefabricated crack group in the hydrogen-induced cracking test is 1.0 mm, and the minimum depth of the crack that propagates is 1.4 mm; the maximum stress intensity factor (K) of the crack that does not propagate is 1.0 mm. In ) is 43.7 MPa·m 1 / 2 , the minimum stress intensity factor (K Iy ) is 52.3 MPa·m 1 / 2 , the threshold stress intensity factor determined is 48.0 MPa·m 1 / 2 .

[0261] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for determining the hydrogen-induced cracking threshold stress intensity factor of pipeline steel under hydrogen sulfide conditions, the method comprising: Conducting a hydrogen-induced cracking test on the target pipeline steel to determine the maximum depth of a crack that does not propagate and the minimum depth of a crack that propagates in a prefabricated crack group of the target pipeline steel under the same experimental conditions; Then, based on the maximum depth of cracks that do not propagate in the prefabricated crack group and the minimum depth of cracks that propagate, combined with the rated pressure and the outer and inner diameters of the wall surface of the hydrogen-induced cracking test container used to prefabricate the prefabricated crack group, a threshold stress intensity factor is determined; including: Based on the maximum depth of the cracks in the prefabricated crack group that do not propagate, combined with the rated pressure, the outer diameter and the inner diameter of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group, the maximum stress intensity factor of the cracks in which no crack propagation occurs is determined by the following formula: Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a In The maximum depth of a crack without crack extension, in meters; Based on the minimum depth of the cracks in the prefabricated crack group that are subject to crack propagation, combined with the rated pressure, the outer diameter and the inner diameter of the wall surface of the hydrogen-induced cracking test vessel used to prefabricate the prefabricated crack group, the minimum stress intensity factor of the cracks in which crack propagation occurs is determined by the following formula: Where K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ; σ is the stress on the inner wall of the hydrogen-induced cracking test container, in MPa; p is the rated pressure, i.e., the internal pressure of the hydrogen-induced cracking test container, in MPa; R1 is half of the inner diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; R2 is half of the outer diameter of the wall surface of the hydrogen-induced cracking test container used for prefabricating the prefabricated crack group, in m; F is the shape factor, dimensionless; a Iy The minimum depth of the crack at which crack propagation occurs, in m; Determining a threshold stress intensity factor based on the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates; The hydrogen-induced cracking test of the target pipeline steel is performed using the following hydrogen-induced cracking test apparatus for pipeline steel under hydrogen sulfide conditions and the following hydrogen-induced cracking test method for pipeline steel under hydrogen sulfide conditions; The test method for hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions includes: 1) Determine the experimental parameters for hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions: The solution used in the hydrogen induced cracking test of pipeline steel under the condition of hydrogen sulfide is determined to be the rated solution; The test pressure of the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure; The hydrogen sulfide content of the pipeline steel hydrogen induced cracking test under hydrogen sulfide conditions is determined to be the rated hydrogen sulfide content; The pressure application method for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined to be the rated pressure application method; 2) preparing a hydrogen-induced cracking test vessel with a prefabricated crack group; 3) Conduct hydrogen-induced cracking tests under rated solution, rated hydrogen sulfide content, rated pressure, and rated pressure application mode: Filling a rated solution into a hydrogen-induced cracking test container, and pressurizing the interior of the hydrogen-induced cracking test container to the rated pressure using a rated pressure application method and maintaining the pressure; while the interior of the hydrogen-induced cracking test container is maintained at the rated pressure, filling the hydrogen sulfide into the hydrogen-induced cracking test container until the hydrogen sulfide content reaches the rated hydrogen sulfide content, then stopping the filling of hydrogen sulfide and starting crack growth monitoring of prefabricated cracks in the hydrogen-induced cracking test container until the crack growth monitoring time meets a preset service time or a prefabricated crack with a crack growth depth reaching a rated value is detected; The apparatus for testing hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions comprises a hydrogen-induced cracking test vessel, a pressure test pump, and a hydrogen sulfide storage tank. The hydrogen-induced cracking test vessel is made of target pipeline steel and has at least one group of prefabricated cracks prefabricated on its inner wall; each prefabricated crack group consists of at least two prefabricated cracks of different depths. The pressure test pump is connected to the hydrogen-induced cracking test vessel to pressurize the interior of the hydrogen-induced cracking test vessel. The hydrogen sulfide storage tank is connected to the hydrogen-induced cracking test vessel to supply hydrogen sulfide to the interior of the hydrogen-induced cracking test vessel.

2. The method according to claim 1, wherein The hydrogen-induced cracking test container comprises a tubular side wall and two end surfaces, wherein the two end surfaces are arranged at both ends of the tubular side wall, and the tubular side wall and the two end surfaces form a closed cavity.

3. The method according to claim 2, wherein: The prefabricated cracks on the inner wall of the hydrogen-induced cracking test container are arranged on the tubular side wall.

4. The method according to claim 2, wherein: The outer diameter of the tubular sidewall is the same as the outer diameter of a pipeline made of the target pipeline steel when it is in service, and the inner diameter of the tubular sidewall is the same as the inner diameter of a pipeline made of the target pipeline steel when it is in service.

5. The method according to claim 1, wherein Each prefabricated crack group includes at least three prefabricated cracks with different depths and a step-by-step distribution of depths.

6. The method according to claim 5, wherein: Each prefabricated crack group includes a prefabricated crack with a depth of 0.2 mm, a prefabricated crack with a depth of 0.6 mm, a prefabricated crack with a depth of 1.0 mm, a prefabricated crack with a depth of 1.4 mm, and a prefabricated crack with a depth of 1.8 mm.

7. The method according to claim 1, wherein The solution for determining the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions includes: Determine the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide; The solution for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions is determined based on the acidity and alkalinity of the service environment of the target pipeline steel when it is in service without hydrogen sulfide.

8. The method according to claim 7, wherein: The solution for the pipeline steel hydrogen-induced cracking test under hydrogen sulfide conditions is determined based on the acidity and alkalinity of the service environment of the target pipeline steel when in service without hydrogen sulfide, and includes: When the pH value of the target pipeline steel service environment is 2.5-2.8 without hydrogen sulfide, solution A is selected as the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions; solution A is a mixed solution of CH3COOH and NaCl; When the pH value of the target pipeline steel service environment is 8.1-8.3 without hydrogen sulfide, solution B is selected as the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions; solution B is synthetic seawater without heavy metal ions; When the pH value of the service environment of the target pipeline steel is 6.8-7.2 without hydrogen sulfide, solution C is selected as the solution for the hydrogen-induced cracking test of pipeline steel under hydrogen sulfide conditions; solution C is a mixed solution of CH3COONa and NaCl.

9. The method according to claim 8, wherein Taking the mass of the A solution as 100%, the mass concentration of CH3COOH in the A solution is 0.48%-0.52%, and the mass concentration of NaCl is 4.9%-5.1%.

10. The method according to claim 8, wherein Taking the mass of the C solution as 100%, the mass concentration of CH3COONa in the C solution is 0.38%-0.42%, and the mass concentration of NaCl is 4.9%-5.1%.

11. The method according to claim 8, wherein When the test solution is solution A, the preset service time is 96 hours.

12. The method according to claim 8, wherein When the test solution is solution B, the preset service time is 96 hours.

13. The method according to claim 8, wherein When the test solution is solution C, the preset service time is 96-2160h.

14. The method according to claim 1, wherein The determination of the hydrogen sulfide content in the hydrogen sulfide-containing pipeline steel hydrogen-induced cracking test includes: Determine the hydrogen sulfide content of the service environment of the target pipeline steel when it is in service; determine the hydrogen sulfide content of the pipeline steel hydrogen-induced cracking test under hydrogen sulfide-containing conditions based on the hydrogen sulfide content of the service environment of the target pipeline steel when it is in service; The test pressure for hydrogen induced cracking test of pipeline steel under hydrogen sulfide conditions includes: Determine the pressure of the service environment of the target pipeline steel when it is in service; determine the test pressure of the hydrogen-induced cracking test of the pipeline steel under hydrogen sulfide conditions based on the pressure of the service environment of the target pipeline steel when it is in service; The rated value is 60% of the wall thickness of the wall used to prepare the prefabricated crack group in the hydrogen-induced cracking test container; The rated pressure application method is constant pressure loading, step-by-step pressurization or fatigue pressurization.

15. The method according to claim 1, wherein The method for testing hydrogen-induced cracking of pipeline steel under hydrogen sulfide conditions comprises repeating steps 1) to 3) to complete hydrogen-induced cracking tests under different rated solutions, different rated hydrogen sulfide contents, different rated pressures, and / or different rated pressurization modes.

16. The method according to claim 15, wherein The different rated solutions include solution A, solution B, and solution C.

17. The method according to claim 15, wherein: The different rated pressure application modes include constant pressure loading, step-by-step pressurization and fatigue pressurization.

18. The method according to claim 1, wherein In step 3), after crack extension monitoring is completed, the hydrogen sulfide and / or oxygen content is further determined. If the content is unqualified, steps 2) to 3) are repeated.

19. The method according to claim 1, wherein The threshold stress intensity factor is determined based on the maximum stress intensity factor of the crack that does not propagate and the minimum stress intensity factor of the crack that propagates by the following formula: K Ⅰth =(K Ⅰy +K Ⅰn )÷2 Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 ; K Ⅰth is the threshold stress intensity factor, unit: MPa·m 1 / 2 .

20. The method according to claim 1, wherein The maximum stress intensity factor of the crack that does not expand and the minimum stress intensity factor of the crack that expands satisfy: K Ⅰy -K Ⅰn ≤0.1·(K Ⅰy +K Ⅰn ) Where K In The maximum stress intensity factor of a crack without crack extension, in MPa·m 1 / 2 ;K Iy The minimum stress intensity factor of the crack for crack propagation to occur, unit: MPa·m 1 / 2 .

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