Restraint degree experimental device, experimental system and experimental method for pipeline ring welding joint

Abstract

The invention discloses an experimental device, an experimental system and an experimental method for the restraint degree of a pipeline ring welding joint, relates to the technical field of pipeline welding, and aims to solve the problem of how to determine the restraint degree of a welding seam in the pipeline ring welding joint so as to judge the cracking tendency of the welding seam. The restraint degree experiment device comprises a first clamp and a second clamp, the first clamp comprises a first main body part and a first connecting part, and the first main body part is suitable for being connected with a first pipeline test plate; the second clamp comprises a second main body part and a second connecting part, the second main body part is suitable for being connected with a second pipeline test plate, and a root welding seam is arranged between the second pipeline test plate and the first pipeline test plate; the first connecting part and the second connecting part are suitable for being connected with a stretching device and can move in the direction away from each other under the driving of the stretching device so as to test the restraint degree of a root welding seam between the first pipeline test plate and the second pipeline test plate.

Description

Technical Field

[0001] The present application relates to the technical field of pipeline welding, and in particular to a constraint degree experimental device, an experimental system and an experimental method for pipeline girth weld joints. Background Art

[0002] In pipeline engineering, girth welding is commonly used for pipe joints. During the welding process, changes in the microstructure and properties of the weld and heat-affected zone, coupled with residual stress and diffusible hydrogen, can cause cold cracks in the weld. These cracks can seriously impact the quality and safety of the pipeline system. The weld's restraint is one factor that influences its crack susceptibility. Generally, the higher the weld's restraint, the greater its cracking tendency.

[0003] In the prior art, it has been impossible to accurately determine the degree of weld constraint during girth welding of pipe joints, and thus it has been impossible to judge the tendency of weld cracking. Summary of the Invention

[0004] The purpose of this application is to provide a constraint test device, an experimental system and an experimental method for pipeline girth weld joints, aiming to solve the problem of how to determine the weld constraint in pipeline girth weld joints to judge the weld cracking tendency.

[0005] In a first aspect of the present application, a device for testing the restraint of a pipe girth weld joint is provided, comprising a first fixture and a second fixture.

[0006] The first clamp includes a first main body and a first connecting portion connected to the first main body, the first main body being adapted to connect to a first pipe test plate of the pipe girth weld joint. The second clamp includes a second main body and a second connecting portion connected to the second main body, the second main body being adapted to connect to a second pipe test plate of the pipe girth weld joint, a root weld being provided between the second pipe test plate and the first pipe test plate.

[0007] The first connecting portion and the second connecting portion are suitable for connecting to a stretching device and can move away from each other under the drive of the stretching device to test the restraint of the root weld between the first pipeline test plate and the second pipeline test plate.

[0008] In the above solution, the first pipe test plate and the second pipe test plate are connected by a root weld. The first pipe test plate is connected to the first main body of the first clamp, and the second pipe test plate is connected to the second main body of the second clamp. The first connecting portion of the first clamp and the second connecting portion of the second clamp are simultaneously connected to a stretching device, which drives the first and second connecting portions to move away from each other. In this way, the stretching device simultaneously drives the first and second pipe test plates to move away from each other, thereby stretching the root weld. The degree of constraint of the root weld can be calculated based on the deformation across the width of the root weld after stretching, thereby determining the cracking tendency of the root weld. The structure is simple and easy to operate.

[0009] Optionally, the first main body and the second main body are in the shape of arc plates, the first main body is suitable for matching with a first arc plate-shaped pipeline test plate; the second main body is suitable for matching with a second arc plate-shaped pipeline test plate.

[0010] Optionally, the constraint test device further includes a first connecting structure and a second connecting structure, wherein the first connecting structure is used to detachably connect the first pipeline test plate to the first main body, and the second connecting structure is used to detachably connect the second pipeline test plate to the second main body.

[0011] Optionally, both the first connection structure and the second connection structure are threaded connections.

[0012] Optionally, there are multiple first connection structures, and the multiple first connection structures are arranged at intervals on the first main body;

[0013] There are multiple second connection structures, and the multiple second connection structures are arranged at intervals on the second main body.

[0014] Optionally, the first connecting portion includes a first supporting top plate and a first connecting protrusion, wherein the first supporting top plate is connected to an end of the first main body portion facing away from the second main body portion and is perpendicular to the first main body portion, and the first connecting protrusion is provided on a side of the first supporting top plate facing away from the first main body portion;

[0015] The second connecting portion includes a second supporting top plate and a second connecting protrusion. The second supporting top plate is connected to an end of the second main body portion facing away from the first main body portion and is perpendicular to the second main body portion. The second connecting protrusion is provided on a side of the second supporting top plate facing away from the second main body portion.

[0016] Optionally, the constraint test device further includes a measuring device, which is suitable for measuring the root weld width.

[0017] Optionally, the measuring device is an extensometer.

[0018] In a second aspect of the present application, a constraint test system for a pipe girth weld joint is provided, which is applied to a stretching device and a constraint test device, wherein the stretching device is connected to a first connection portion of a first clamp and a second connection portion of a second clamp of the constraint test device.

[0019] A third aspect of the present application provides a method for testing the constraint of a pipe girth weld joint, which is applied to a constraint test device and / or a constraint test system;

[0020] The constraint test method includes:

[0021] Using the first main body of the first clamp and the second main body of the second clamp to respectively connect the first pipe test plate and the second pipe test plate of the pipe girth welding joint;

[0022] Measuring an initial width D1 and a length L of a root weld between the first pipeline test plate and the second pipeline test plate;

[0023] Applying a preset load F to the first clamp and the second clamp to drive the first clamp and the second clamp to move away from each other and maintain the load for a preset time;

[0024] Measure the width D2 of the root weld after stretching;

[0025] The constraint degree of the root weld is obtained according to the initial width D1 of the root weld, the length L of the root weld, the preset load F and the width value D2 of the root weld after stretching.

[0026] It should be noted that the technical effects brought about by the implementation methods of the second and third aspects of this application can be referred to the technical effects brought about by the corresponding implementation methods of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 A schematic structural diagram of a device for testing the restraint of a pipe girth weld joint provided in an embodiment of the present application;

[0029] Figure 2 for Figure 1 A schematic structural diagram of the first clamp;

[0030] Figure 3 for Figure 1 Schematic diagram of the structure of the first pipeline test plate.

[0031] Reference numerals:

[0032] 1. First clamp; 11. First main body; 12. First connecting portion; 121. First supporting top plate; 122. First connecting protrusion;

[0033] 2. Second clamp; 21. Second main body; 22. Second connecting portion; 221. Second supporting top plate; 222. Second connecting protrusion;

[0034] 3. First pipe test plate; 4. Second pipe test plate; 5. Through hole; 6. Bolt; 7. Extensometer; 8. Root weld. DETAILED DESCRIPTION

[0035] In the embodiments of the present application, the terms "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, a feature specified as "first," "second," "third," "fourth," "fifth," and "sixth" may explicitly or implicitly include one or more of the features.

[0036] In the embodiments of the present application, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0037] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0038] In the embodiments of the present application, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is as determined by a person of ordinary skill in the art taking into account the measurement being discussed and the errors associated with the measurement of a specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0039] Pipelines are generally made by connecting multiple sections of pipe body by girth welding. Depending on their usage scenarios, their materials, thickness, and radial dimensions may vary.

[0040] Pipelines usually have a circular cross-section and can be used to transport crude oil, refined oil, natural gas, etc.

[0041] Pipeline welding can be done using gas welding, arc welding, stick arc welding, gas shielded welding and other welding methods. The corresponding welding method can be selected according to the usage.

[0042] However, during the welding process, changes in the microstructure and properties of the weld and heat-affected zone, coupled with residual stress and diffusible hydrogen, can lead to hydrogen-induced cracking. As pipeline strength grades increase, the problem of cold cracking during girth welding becomes increasingly prominent, posing a serious threat to the safe operation of pipelines. This is particularly true due to its delayed nature, making it particularly hazardous. Therefore, determining the cracking propensity of pipeline welds is crucial.

[0043] In actual pipe joint girth welding, root welding is typically performed first (i.e., only the first girth weld is performed around the root of the joint). After the root welding is completed, the relevant positioning equipment is removed. The constraint of the root weld of a pipe joint plays a decisive role in whether the entire weld will crack. Therefore, this application focuses on testing the constraint of the root weld at pipe joints.

[0044] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of a device for testing the constraint of a pipe girth weld joint, provided in an embodiment of the present application. The device comprises a first fixture 1 and a second fixture 2. The first fixture 1 includes a first main body 11 and a first connecting portion 12 connected to the first main body 11. The first main body 11 is suitable for connecting to the first pipe test plate 3 of the pipe girth weld joint.

[0045] In some examples, the first fixture 1 may be integrally formed, for example, by machining or casting.

[0046] In other examples, the first clamp 1 may be a split structure. For example, the first main body 11 and the first connecting portion 12 are connected as one body by welding or connecting members such as bolts 6.

[0047] In some examples, the first main body 11 and the first pipe test plate 3 can be connected by a connector such as a bolt 6. For example, threaded holes are provided in both the first main body 11 and the first pipe test plate 3, and the bolts 6 are provided in the threaded holes to connect them.

[0048] In other examples, the first main body 11 and the first pipeline test plate 3 can be connected by hanging or other connection methods. For example, a hanging hole is provided on one of the first main body 11 and the first pipeline test plate 3, and a hook is provided on the other, and the hook is connected to the hanging hole.

[0049] The second fixture 2 includes a second main body 21 and a second connecting portion 22 connected to the second main body 21. The second main body 21 is suitable for connecting to the second pipe test plate 4 of the pipe girth weld joint. A root weld 8 is provided between the second pipe test plate 4 and the first pipe test plate 3.

[0050] In some examples, the second clamp 2 can have the same structure as the first clamp 1 .

[0051] In other examples, the second clamp 2 may have a different structure from the first clamp 1 .

[0052] In some examples, the second fixture 2 may be integrally formed, for example, by machining or casting.

[0053] In other examples, the second clamp 2 may be a split structure. For example, the second main body 21 and the second connecting portion 22 are connected as one body by welding or connecting members such as bolts 6.

[0054] In some examples, the second main body 21 and the second pipe test plate 4 can be connected by a connector such as a bolt 6. For example, threaded holes are provided in both the second main body 21 and the second pipe test plate 4, and the bolts 6 are provided in the threaded holes to connect them.

[0055] In other examples, the second main body 21 and the second pipe test plate 4 can be connected by hanging or other connection methods. For example, a hanging hole is provided on one of the second main body 21 and the second pipe test plate 4, and a hook is provided on the other, and the hook is connected to the hanging hole.

[0056] It should be understood that during the girth welding operation of the pipe joint, specific welding procedures and welding materials will be specified in the operation instructions. Root welding is performed on the first pipe test plate 3 and the second pipe test plate 4 according to the welding procedures and welding materials given in the operation instructions to obtain the root weld between the first pipe test plate 3 and the second pipe test plate 4. The root weld between the first pipe test plate 3 and the second pipe test plate 4 is then stretched to evaluate the constraint of the root weld.

[0057] In order to stretch the root weld 8 between the first pipeline test plate 3 and the second pipeline test plate 4, the first connecting portion 12 and the second connecting portion 22 are suitable for connecting to a stretching device and can move away from each other under the drive of the stretching device to test the restraint of the root weld 8 between the first pipeline test plate 3 and the second pipeline test plate 4.

[0058] It should be noted that the stretching device usually comes with a clamping device when it leaves the factory. The first connecting part 12 and the second connecting part 22 can be set to a shape and size that matches the clamping device and can be clamped and connected by the clamping device.

[0059] The actual sizes of the first pipeline test plate 3 and the second pipeline test plate 4 can be set according to the actual conditions of the simulated pipeline.

[0060] In the above scheme, the first pipe test plate 3 and the second pipe test plate 4 are connected via a root weld 8. The first pipe test plate 3 is connected to the first main body 11 of the first fixture 1, and the second pipe test plate 4 is connected to the second main body 21 of the second fixture 2. The first connecting portion 12 of the first fixture 1 and the second connecting portion 22 of the second fixture 2 are simultaneously connected to a stretching device, which drives the first connecting portion 12 and the second connecting portion 22 to move away from each other. In this way, the stretching device simultaneously drives the first and second pipe test plates 3 and 4 to move away from each other, thereby stretching the root weld 8. The degree of constraint of the root weld 8 can be calculated based on the deformation across the width of the root weld 8 after stretching, thereby determining the cracking tendency of the root weld 8. The structure is simple and easy to operate.

[0061] In some embodiments, see Figure 1 、 Figure 2 、 Figure 3The first and second main bodies 11, 21 are curved plates. The first main body 11 is adapted to fit within the curved first pipe test plate 3, while the second main body 21 is adapted to fit within the curved second pipe test plate 4. The curved surfaces of the first and second main bodies 11, 21 better align with the curved surfaces of the first and second pipe test plates 3, 4, enabling more accurate simulation of the root weld 8 in a circular girth weld, resulting in more accurate test results.

[0062] In some examples, the curvature of the first pipe test plate 3 is the same as the curvature of the second pipe test plate 4 , which is equivalent to a welded connection between two pipes of the same diameter.

[0063] In other examples, the curvature of the first pipe test plate 3 is different from the curvature of the second pipe test plate 4 , which is equivalent to a welding connection between two pipes of different diameters.

[0064] In some specific examples, the curvature of the first body portion 11, the second body portion 21, the first pipe test plate 3, and the second pipe test plate 4 can be 35°, 36°, 37°, 38°, 39°, 40°, etc. The curvature refers to the ratio of the arc length of the plate to the radius of the circle.

[0065] In some embodiments, see Figure 1 The constraint test device also includes a first connecting structure and a second connecting structure. The first connecting structure is used to detachably connect the first pipeline test plate 3 to the first main body 11, and the second connecting structure is used to detachably connect the second pipeline test plate 4 to the second main body 21. The first and second connecting structures enable detachable connections between the first pipeline test plate 3 and the first main body 11, and between the second pipeline test plate 4 and the second main body 21. This detachable connection facilitates installation and replacement of the first and second pipeline test plates 3 and 4.

[0066] In some examples, the first connection structure and the second connection structure are the same.

[0067] In other examples, the first connection structure is different from the second connection structure.

[0068] In some examples, the first connection structure can be a hook. For example, a hook can be provided on either the first pipe test plate 3 or the first main body 11, and the hook can be connected to the hook. The connection method of the second connection structure can be similar to that of the first connection structure.

[0069] In some specific examples, the first connection structure and the second connection structure are both threaded connectors, which are connected by the threaded connectors for easy assembly and disassembly.

[0070] In some examples, the first and second connection structures include through-holes 5, bolts 6, and nuts. The through-holes 5 are provided in the first pipe test plate 3, the second pipe test plate 4, the first body 11, and the second body 21. Bolts 6 are provided in the through-holes 5 of the first body 11 and the first pipe test plate 3 and tightened with nuts. Bolts 6 are provided in the through-holes 5 of the second body 21 and the second pipe test plate 4 and tightened with nuts.

[0071] In another example, the first and second connecting structures include through-holes 5, screw holes, and bolts 6 or screws. One of the first pipe test plate 3 and the first main body 11 is provided with through-holes 5, and the other with screw holes. One of the second pipe test plate 4 and the second main body 21 is provided with through-holes, and the other with screw holes. Bolts 6 or screws are threadedly connected to the screw holes through the through-holes 5 and locked securely.

[0072] In some embodiments, there are multiple first connection structures, each of which is spaced apart on the first body portion 11. There are multiple second connection structures, each of which is spaced apart on the second body portion 21. The first pipe test plate 3 is connected to the first body portion 11, and the second pipe test plate 4 is connected to the second body portion 21 via multiple first connection structures and second connection structures, thereby improving connection stability.

[0073] In some examples, the first body portion 11 is adapted to be provided with a plurality of through holes 5 in correspondence with the first pipe test plate 3, and each corresponding through hole 5 is connected by a bolt 6. The second body portion 21 is adapted to be provided with a plurality of through holes 5 in correspondence with the second pipe test plate 4, and each corresponding through hole 5 is connected by a bolt 6.

[0074] In some embodiments, the first connecting portion 12 includes a first supporting top plate 121 and a first connecting protrusion 122. The first supporting top plate 121 is connected to the end of the first main body portion 11 facing away from the second main body portion 21 and is perpendicular to the first main body portion 11. The first connecting protrusion 122 is provided on the side of the first supporting top plate 121 facing away from the first main body portion 11. The second connecting portion 22 includes a second supporting top plate 221 and a second connecting protrusion 222. The second supporting top plate 221 is connected to the end of the second main body portion 21 facing away from the first main body portion 11 and is perpendicular to the second main body portion 21. The second connecting protrusion 222 is provided on the side of the second supporting top plate 221 facing away from the second main body portion 21. The first connecting protrusion 122 of the first connecting portion 12 is connected to the stretching device and is also connected to the first supporting top plate 121. The tensile force of the stretching device is transmitted to the first supporting top plate 121 through the first supporting top plate 121 and then to the first main body 11. Compared with the tensile force of the stretching device being directly transmitted from the first connecting protrusion 122 to the first main body 11, the force transmission is more uniform, preventing the root weld 8 from being stretched due to excessive local tensile force and causing different deformation amounts at different locations. The second connecting protrusion 222 of the second connecting portion 22 is connected to the stretching device and is also connected to the second supporting top plate 221. The tensile force of the stretching device is transmitted to the second supporting top plate 221 through the second supporting top plate 221 and then to the second main body 21. Compared with the tensile force of the stretching device being directly transmitted from the second connecting protrusion 222 to the second main body 21, the force transmission is more uniform, preventing the root weld 8 from being stretched due to excessive local tensile force and causing different deformation amounts at different locations.

[0075] In some examples, the first supporting top plate 121 and the first connecting protrusion 122 may be connected by screw threads or by welding.

[0076] In some examples, the first support top plate 121 and the first main body 11 are detachably connected, such as by bolts 6 and nuts.

[0077] In other examples, the first supporting top plate 121 and the first main body portion 11 are connected by welding.

[0078] In some other examples, the first supporting top plate 121 and the first main body portion 11 are connected by riveting.

[0079] It should be noted that the connection method between the second support top plate 221 and the second connection protrusion 222 in the second connection portion 22 can refer to the connection method between the first support top plate 121 and the first connection protrusion 122 in any of the above-mentioned first connection structures, and will not be repeated here.

[0080] In some embodiments, the constraint test device further includes a measuring device adapted to measure the width of the root weld 8. The constraint of the root weld 8 is calculated by measuring the width of the root weld 8 by the measuring device, which is simple and easy to operate.

[0081] In some examples, the measuring device may be a vernier caliper.

[0082] In other examples, the measuring device may be a root weld 8 detector.

[0083] In some specific examples, the measuring device is an extensometer 7. Measuring the width of the root weld 8 by using the extensometer 7 has the advantages of high measurement accuracy and convenient operation.

[0084] In some embodiments, a stretching device is connected to the first clamp 1 and the second clamp 2 of the constraint test apparatus. The stretching device drives the first clamp 1 and the second clamp 2 to move away from each other, thereby stretching the root weld 8 between the first pipe specimen and the second pipe specimen. This has a simple structure and is easy to operate.

[0085] The connection between the stretching device and the first clamp 1 and the second clamp 2 can be any existing connection method suitable for the stretching device.

[0086] In some embodiments, the constraint test method comprises:

[0087] The first main body 11 of the first clamp 1 and the second main body 21 of the second clamp 2 are used to respectively connect the first pipe test plate 3 and the second pipe test plate 4 of the pipe girth welding joint;

[0088] Measure the initial width D1 and the length L of the root weld 8 between the first pipeline test plate 3 and the second pipeline test plate 4;

[0089] Applying a preset load F to the first clamp 1 and the second clamp 2 to drive the first clamp 1 and the second clamp 2 to move away from each other and maintain the preset load for a predetermined time;

[0090] Measure the width D2 of the root weld 8 after stretching;

[0091] The restraint degree of the root weld 8 is obtained according to the initial width D1 of the root weld 8, the length L of the root weld 8, the preset load F and the width value D2 of the root weld 8 after stretching.

[0092] It should be understood that the width of the root weld 8 refers to the weld size of the root weld 8 along the line connecting the first pipeline test plate 3 and the second pipeline test plate 4. The length L of the root weld 8 refers to the weld size of the root weld 8 along the length of the butt joint of the first pipeline test plate 3 and the second pipeline test plate 4.

[0093] The constraint of the root weld 8 is calculated by measuring the width of the root weld 8 before and after stretching. The greater the constraint value of the root weld 8 calculated, the greater the sensitivity of the root weld 8 and the greater the possibility of cracking of the root weld 8.

[0094] In some examples, the stretching device can be a tensile testing machine.

[0095] It should be noted that in order to ensure the effectiveness of stretching, the stretching time should generally not be less than 2 hours.

[0096] In some specific examples, the calculation method of the constraint of the root weld 8 is: R = F / ((D 2-D1) * L);

[0097] Among them, R is the constraint degree of the root weld 8; F is the applied load, unit is N; D2 is the width of the root weld 8 after stretching, unit is mm; D1 is the initial width of the root weld 8, unit is mm; L is the length of the root weld 8, unit is mm.

[0098] In the description of the embodiments of the present application, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0099] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A device for testing the restraint of pipe girth weld joints, characterized in that: include: a first clamp, comprising a first main body and a first connecting portion connected to the first main body, wherein the first main body is suitable for connecting to the first pipe test plate of the pipe girth weld joint; a second clamp, the second clamp comprising a second main body and a second connecting portion connected to the second main body, the second main body being adapted to be connected to a second pipe test plate of the pipe girth weld joint, a root weld being provided between the second pipe test plate and the first pipe test plate; The first connecting portion and the second connecting portion are suitable for connecting to a stretching device and can move away from each other under the drive of the stretching device to test the restraint of the root weld between the first pipeline test plate and the second pipeline test plate.

2. The restraint test device according to claim 1, characterized in that: The first main body and the second main body are in the shape of arc plates. The first main body is suitable for matching with the first arc plate-shaped pipeline test plate; the second main body is suitable for matching with the second arc plate-shaped pipeline test plate.

3. The restraint test device according to claim 1, characterized in that: It also includes a first connection structure and a second connection structure, wherein the first connection structure is used to detachably connect the first pipeline test plate to the first main body, and the second connection structure is used to detachably connect the second pipeline test plate to the second main body.

4. The restraint test device according to claim 3, characterized in that: The first connection structure and the second connection structure are both threaded connections.

5. The restraint test device according to claim 4, characterized in that: There are multiple first connection structures, and the multiple first connection structures are spaced apart and arranged on the first main body; There are multiple second connection structures, and the multiple second connection structures are arranged at intervals on the second main body.

6. The restraint test device according to claim 2, characterized in that: The first connecting portion includes a first supporting top plate and a first connecting protrusion, wherein the first supporting top plate is connected to an end of the first main body portion facing away from the second main body portion and is perpendicular to the first main body portion, and the first connecting protrusion is provided on a side of the first supporting top plate facing away from the first main body portion; The second connecting portion includes a second supporting top plate and a second connecting protrusion. The second supporting top plate is connected to an end of the second main body portion facing away from the first main body portion and is perpendicular to the second main body portion. The second connecting protrusion is provided on a side of the second supporting top plate facing away from the second main body portion.

7. The restraint test device according to claim 1, characterized in that: Also included is a measuring device adapted to measure the root weld width.

8. The restraint test device according to claim 7, characterized in that: The measuring device is an extensometer.

9. A constraint test system for pipe girth weld joints, characterized in that: include: A stretching device and the constraint test device according to any one of claims 1 to 8, wherein the stretching device is connected to the first connecting portion of the first clamp and the second connecting portion of the second clamp in the constraint test device.

10. A method for testing the restraint of a pipe girth weld joint, characterized in that: Applicable to the restraint test device according to any one of claims 1 to 8, and / or the restraint test system according to claim 9; The constraint test method includes: Using the first main body of the first clamp and the second main body of the second clamp to respectively connect the first pipe test plate and the second pipe test plate of the pipe girth welding joint; Measuring an initial width D1 and a length L of a root weld between the first pipeline test plate and the second pipeline test plate; Applying a preset load F to the first clamp and the second clamp to drive the first clamp and the second clamp to move away from each other and maintain the load for a preset time; Measure the width D2 of the root weld after stretching; The constraint degree of the root weld is obtained according to the initial width D1 of the root weld, the length L of the root weld, the preset load F and the width value D2 of the root weld after stretching.

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