Method for analyzing the sealing performance of a cryogenic fluid transfer pipe and joint weld

Abstract

The application discloses a kind of ultra-low temperature fluid conveying pipeline and joint weld seam place sealing performance analysis method, comprising the following steps: establishing the sealing performance analysis finite element model of ultra-low temperature flexible pipeline and joint under the joint action of normal temperature internal pressure load and low temperature load and internal pressure, and the numerical analysis of joint sealing structure is carried out according to the sealing performance analysis finite element model established;Determine failure criterion, the equivalent stress of weld seam obtained by analysis is used as the key index for measuring the sealing performance of ultra-low temperature fluid conveying pipeline and joint weld seam place;For weld seam gap, fillet size, weld reinforcement three factors, the sensitivity analysis of weld seam equivalent stress is carried out, the most sensitive parameter affecting weld seam strength is determined, and the most sensitive parameter value when the sealing performance is best is obtained.The application can provide engineering application reference for the sealing structure design analysis of ultra-low temperature fluid conveying pipeline and joint.

Description

Technical Field

[0001] This invention relates to a method and system for analyzing the sealing performance of weld seams in cryogenic fluid transportation pipelines and joints suitable for transporting liquefied natural gas or liquid hydrogen, belonging to the field of cryogenic fluid transportation technology. Background Technology

[0002] A certain deep-sea area in my country possesses oil and gas resources equivalent to more than 100 billion tons of oil, of which natural gas resources account for 83%. Among the natural gas resources, 70% come from deep water areas more than 500 kilometers away from the Chinese mainland. How to economically and effectively develop the natural gas resources in the deep sea has become one of the focuses of attention.

[0003] A floating production storage and offloading unit (FLNG) is a floating production facility used for offshore gas field development. Positioned at sea via a mooring system, it performs the functions of extracting, processing, liquefying, storing, and loading / unloading natural gas. Used in conjunction with liquefied natural gas (LNG) carriers, it enables the extraction and transportation of natural gas from offshore gas fields. Utilizing FLNG for offshore gas field development breaks the single mode of relying solely on pipeline transportation to shore, saving transportation costs and not occupying onshore space. Furthermore, FLNG can be reused after the gas field is completed, being placed in other gas fields, resulting in high economic efficiency.

[0004] An LNG unloading arm is a rigid, articulated piping system installed on a dock or FLNG terminal for unloading LNG. Its main structure includes a three-dimensional rotary joint, outer arm, inner arm, top rotary joint, foundation riser, and rotary joints connecting the inner arm and foundation riser, along with supporting structures and accessories. The large LNG unloading arm stands at the forefront of the LNG receiving terminal's wharf area, serving as a crucial core piece of equipment connecting LNG carriers to onshore pipelines and storage facilities—the "throat" of the entire terminal. When an LNG carrier arrives at the dedicated wharf, LNG is delivered into the terminal's storage tanks via the liquid phase unloading arm and unloading pipelines, using cryogenic pumps on board. Simultaneously, the boil-off gas (BOG) in the storage tanks returns to the LNG carrier through return gas pipelines and a gaseous return arm. During LNG unloading operations, a traction line guides the end of the unloading arm to the LNG carrier's receiving end for accurate docking under relative motion. The hydraulic system controlling the unloading arm is designed to withstand the speed and acceleration effects caused by the ship's movement.

[0005] Given the harsh sea conditions in my country's deep seas, if existing mooring technologies and traditional rigid unloading arms cannot effectively address the differential motion between FLNG and the transport vessel, a specially designed cryogenic unloading system is needed to meet the stringent requirements of low temperatures and sloshing conditions. Cryogenic hose delivery systems offer significant advantages in terms of weight, flexibility, corrosion resistance, and insulation. For FLNG unloading operations, an effective method is tandem mooring, where the vessel is connected to the LNG carrier via mooring cables, and cryogenic hoses are used for LNG unloading. This requires the cryogenic hoses to withstand extremely low temperatures while also overcoming the effects of relative motion between the FLNG and the LNG carrier.

[0006] Furthermore, the successful implementation of liquid hydrogen shipping trials provides a more economical and safer method for the liquid hydrogen industry chain, which is of positive significance for the global promotion and use of hydrogen energy and has strong future development potential. Liquid hydrogen has extremely low temperatures, is highly volatile, and is flammable and explosive, making its ship-to-shore loading and unloading challenging, with high safety requirements and numerous technical barriers. Liquid hydrogen ship-to-shore loading and unloading systems operate under harsh conditions, require stringent precision, and involve complex electromechanical system coordination. They must possess functions such as rapid docking, emergency disengagement, and automatic shutdown, while also withstanding prolonged exposure to ultra-low temperatures of -253°C and automatically adapting to tidal variations. Only a very few countries in the world have mastered the key technologies for its design and manufacturing.

[0007] In summary, key technologies for cryogenic fluid transport systems, such as LNG rigid unloading arms, LNG cryogenic hose transfer systems, and liquid hydrogen ship-to-shore loading and unloading systems, involve numerous aspects including cryogenic material selection, molding and manufacturing, sealing, and testing and verification. Material selection and structural design are challenging, processing and manufacturing are difficult, performance testing is challenging, cryogenic sealing, connection, and leak monitoring are difficult, and the entire cryogenic fluid transport system has a complex structure and high safety requirements. Among these, the flexible pipes and sealing joints of the cryogenic transport system are critical components, and their performance directly affects the safe and stable operation of the cryogenic fluid transport system. Currently, the flexible pipes and sealing joints used in existing technologies mainly suffer from the following technical defects: As a key component of cryogenic fluid transportation systems, sealing joints play a crucial role in connection and sealing. Sealing joints are installed at room temperature (typically 20°C), primarily subjected to bolt preload during installation, and may also be subject to some tensile and bending loads. When transporting cryogenic fluids (such as LNG), the joints are mainly affected by the pressure and temperature of the cryogenic medium inside the pipe (typically -163°C), making the safety of the welded area critical to the reliability of the joint seal. Currently, research on the sealing performance of cryogenic flexible pipe joints is limited, with some studies focusing on the welding performance of structural components and the influence of temperature on sealing performance. Overall, existing technologies lack analytical methods specifically for joint sealing performance. Summary of the Invention

[0008] This invention aims to solve the technical problems existing in the prior art. Therefore, this invention provides an analytical method for the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, providing an engineering application reference for the design and analysis of the sealing structure of cryogenic fluid transport pipelines and joints.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, comprising the following steps: A finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure load and low temperature load and internal pressure was established, and numerical analysis of the joint sealing structure was carried out based on the established finite element model for sealing performance analysis. The failure criteria were determined, and the obtained weld equivalent stress was analyzed as a key indicator to measure the sealing performance of welds in cryogenic fluid transport pipelines and joints. Sensitivity analysis was conducted on the equivalent stress of the weld by considering three factors: weld gap, blunt edge size, and weld reinforcement. The most sensitive parameter affecting the weld strength was determined, and the value of the most sensitive parameter when the sealing performance was optimal was obtained.

[0010] The preferred embodiment of the analytical method is as follows: establishing a finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure load and low temperature load combined with internal pressure, and performing numerical analysis of the joint sealing structure based on the established finite element model for sealing performance analysis. A finite element model was established to analyze the sealing performance of ultra-low temperature flexible pipes and joints. The sealing performance of ultra-low temperature flexible pipes and joints under the combined action of low temperature load and internal pressure was calculated by finite element model. The temperature distribution cloud map of the joint as a whole was obtained. The temperature change and the average stress change of the weld were extracted, the average stress of the weld as a function of temperature was obtained, and the law of average stress change of the weld as a function of temperature was analyzed. Finite element models were used to calculate the sealing performance of the joint under pressure at room temperature and under the combined action of low temperature and pressure. The equivalent cloud diagram stress of the weld under pressure at room temperature and low temperature was obtained. By comparing the calculation results of the two models, it was determined that temperature has a significant impact on the sealing performance of the joint, and the effect of low temperature must be considered in actual engineering.

[0011] The aforementioned analysis method, preferably, involves conducting sensitivity analysis on the equivalent stress of the weld due to three factors: weld gap, blunt edge dimension, and weld reinforcement, to determine the most sensitive parameter affecting weld strength and obtain the most sensitive parameter value for optimal sealing performance, including: Single-factor influence analysis of weld gap; Single-factor influence analysis of blunt edge dimensions; Single-factor influence analysis of weld reinforcement height; Analysis of the synergistic effect of weld gap and blunt edge size.

[0012] The analytical method described herein, preferably, includes the following specific single-factor influence analysis of the weld gap: Based on the finite element model of the quarter-sealing performance analysis of the ultra-low temperature flexible pipe and joint, the equivalent stress distribution of the joint weld was calculated. Then, by changing the weld gap value, the variation law of the average stress of the joint weld under different weld gap sizes and different internal pressures was analyzed. The influence of weld gap on the average stress value of weld was obtained, and the optimal weld gap size was determined to be 2mm.

[0013] The aforementioned analysis method, preferably, specifically involves the single-factor influence analysis of the blunt edge size as follows: Based on the finite element model of the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the value of the blunt edge size, the variation law of the average stress of the joint weld under different blunt edge sizes and different internal pressures was analyzed. The influence of the blunt edge size on the average stress value of the weld was obtained, and the optimal blunt edge size was determined to be 2mm.

[0014] The aforementioned analysis method, preferably, specifically includes the single-factor influence analysis of weld reinforcement height as follows: Based on the finite element model of the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the value of the weld reinforcement, the variation law of the average stress of the joint weld under different weld reinforcement sizes and different internal pressures was analyzed. The influence of weld reinforcement on the average stress value of the weld was obtained, and the optimal weld reinforcement size was determined to be 0.5 mm.

[0015] The analytical method described herein, preferably, specifically involves the analysis of the synergistic effect of the joint gap and the blunt edge dimension as follows: Based on the finite element model for the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the values ​​of the weld gap and blunt edge size, the variation law of the average stress of the joint weld under different weld gap and blunt edge size was analyzed. It was found that the change of the joint weld gap and blunt edge size leads to the change of the joint weld volume. Under the action of temperature load, the average stress of the weld changes significantly. At the same time, when the blunt edge size is kept constant, it can be seen from the change of the average stress of the weld that the change of the weld gap value leads to a large change in the average stress of the weld, and the sealing performance changes significantly. It is determined that the weld gap is the most sensitive parameter affecting the sealing performance of the joint weld.

[0016] Secondly, the present invention provides an analysis system for the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, comprising: The first processing unit is used to establish a finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure load and low temperature load and internal pressure, and to perform numerical analysis of the joint sealing structure based on the established finite element model for sealing performance analysis. The second processing unit is used to determine the failure criteria and analyze the obtained weld equivalent stress as a key indicator to measure the sealing performance of the weld joint of the cryogenic fluid transportation pipeline. The third processing unit is used to conduct sensitivity analysis on the equivalent stress of the weld by three factors: weld gap, blunt edge size, and weld reinforcement, to determine the most sensitive parameter affecting the weld strength and to obtain the value of the most sensitive parameter when the sealing performance is best.

[0017] Thirdly, the present invention provides a computer storage medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, implements the steps of the analysis method described in the first aspect of the present invention.

[0018] Fourthly, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the steps of the analysis method described in the first aspect of the present invention.

[0019] The present invention has the following advantages due to the adoption of the above technical solutions: To study the sealing performance of joints under cryogenic fluid transportation conditions, this invention conducts a mechanical-thermal coupling analysis and establishes a finite element model for the sealing performance of non-bonded internal corrugated cryogenic flexible pipe and joint welds under normal temperature internal pressure load and cryogenic load combined with internal pressure. The equivalent stress of the welded area obtained from the analysis is used as a key indicator to measure the pressure-bearing capacity of the sealing structure. Furthermore, sensitivity analysis is conducted on the equivalent stress of the welded area based on three factors: weld gap, blunt edge size, and weld reinforcement height. This can provide an engineering application reference for the design and analysis of sealing structures of cryogenic fluid transportation pipes and joints. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. As shown in the figures: Figure 1 This is a schematic diagram of the connection between the cryogenic fluid transport pipeline and the joint; Figure 2 This is a schematic diagram showing the stress conditions at the weld joint of a cryogenic fluid transport pipeline. Figure 3This is a schematic diagram of the finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints; Figure 4 This is a cloud map showing the overall temperature distribution of the joint under conditions of -163℃. Figure 5 This is a schematic diagram showing how the average stress of the weld changes with temperature. Figure 6 a and Figure 6 b shows the equivalent stress cloud diagrams at the weld at room temperature and at -163℃, respectively; Figure 7 This is the equivalent stress distribution cloud diagram of the finite element model for the quarter-sealing performance analysis of the joint; Figure 8 It is a graph of the average stress of welds with different weld gap sizes under internal pressure of 2MPa and 5MPa; Figure 9 It is a graph showing the average stress curves of welds with different blunt edge sizes under internal pressures of 2MPa and 5MPa; Figure 10 It is a graph of the average stress of welds with different weld reinforcement heights under internal pressure of 2MPa and 5MPa. Figure 11 It is a cloud diagram of the average stress of welds with different weld gaps and blunt edge sizes under an internal pressure of 2MPa. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the system or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the use of terms such as "first" and "second" to define components is merely for the convenience of distinguishing the aforementioned components. Unless otherwise stated, these terms have no special meaning and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The following is a detailed description, with reference to the accompanying drawings, of the method and system for analyzing the sealing performance of the weld seam of the cryogenic fluid transport pipeline and joint provided in the embodiments of the present invention.

[0025] Example 1 like Figure 1 As shown, the bellows lining and joint of the cryogenic fluid transport pipeline achieve sealing through welding. The joint is installed at room temperature (generally 20℃), primarily subjected to bolt pre-tightening force, and may also be subject to some tensile and bending loads during installation. However, the load conditions on the joint under operating conditions are complex. For example, during LNG transport at sea, the cryogenic fluid transport pipeline itself is at room temperature, while the LNG is at -163℃. The entire transport process lasts 2-3 hours. As transport continues, the temperature of the cryogenic fluid transport pipeline drops rapidly, eventually reaching a steady-state temperature. At this point, the internal temperature of the cryogenic fluid transport pipeline and joint is at its lowest value, while the external environment is at room temperature. This temperature difference leads to the following stress conditions at the weld of the cryogenic fluid transport pipeline and joint under operating conditions: Figure 2 As shown. By Figure 2 It is known that the joint is subjected to LNG pressure, and due to the temperature difference between the inner and outer walls, there will be thermal stress at the weld. Under the combined effect of the above two loads, the sealing performance of cryogenic fluid transport pipelines and joints is affected. Therefore, the safety of the welded area is crucial to the sealing reliability of the joint.

[0026] Based on the above analysis, this invention provides a method for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, comprising the following steps: S100. Establish finite element models for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure loads and the combined action of low temperature loads and internal pressures. Based on the established finite element model for sealing performance analysis, perform numerical analysis of the joint sealing structure, specifically including: S101: Establishing a finite element model for the sealing performance analysis of cryogenic flexible pipes and joints: The joint, from the outermost layer to the innermost layer, consists of a fastening retaining ring, two reverse spiral-wound armor layers, an inner retaining ring, and the innermost layer formed by welding the joint flange and the bellows liner together. For ease of loading, the ends of the armor layers are fixed to the fastening retaining rings. The finite element model for analyzing the sealing performance of the joint is as follows: Figure 3 As shown.

[0027] S102. A finite element model was used to calculate the sealing performance of ultra-low temperature flexible pipes and joints under the combined action of low temperature load and internal pressure, and the overall temperature distribution cloud map of the joint was obtained (e.g., Figure 4 As shown), by Figure 4 It can be seen that the surface temperature of the fastening clasp of the joint is as low as -102℃, while the temperature of the bellows lining layer, which is in direct contact with the LNG medium, is -163℃, the same as the medium temperature. The overall temperature of the joint gradually increases from the inside to the outside. Under actual working conditions, the joint temperature changes from ambient temperature (20℃) to contact with -163℃ liquefied natural gas; this temperature change is a process. Therefore, the changes in temperature at the joint weld and the changes in the average stress of the weld are extracted to obtain the curve of the average stress of the weld versus temperature (e.g., ...). Figure 5 As shown in the figure, the variation of the average stress in the weld with temperature is analyzed. Figure 5 It can be seen that as the temperature at the weld decreases, the average stress at the weld gradually increases. When the temperature at the weld reaches -163℃, the average stress at the weld reaches its maximum of 16MPa. For the sealing structure of the joint, under working conditions, the average stress at the weld is greater than the critical failure pressure of the joint. According to the theory of critical failure of sealing, the joint meets the minimum requirements for achieving a seal. At the same time, since the average stress at the weld is much less than the allowable strength of the weld material, there is no strength failure in the sealing structure of the joint. Therefore, the joint achieves a seal under working conditions.

[0028] S103. A finite element model was used to calculate the sealing performance of the joint under the combined effects of 2MPa pressure at room temperature and 2MPa pressure at -163℃. The equivalent stress cloud diagram of the weld under 2MPa pressure at room temperature was obtained (e.g., Figure 6 (as shown in a) and the equivalent stress cloud diagram of the weld under 2MPa pressure at -163℃ (as shown in a). Figure 6 (as shown in b), by Figure 6 As can be seen from a, the stress is greatest on the inner side of the weld where it comes into contact with the pressure; at room temperature, the equivalent stress on the inner side of the weld is 5.11 MPa under a pressure of 2 MPa. Figure 6 As shown in b, under the combined conditions of -163℃ low temperature and internal pressure, the inner side of the weld where it contacts the pressure is the most stressed. When subjected to 2MPa pressure at -163℃, the equivalent stress on the inner side of the weld is 16MPa, which is 10.89MPa higher than the result calculated at room temperature. This proves that temperature affects the equivalent stress of the weld. Low temperature leads to increased stress, which affects the sealing performance.

[0029] Analysis of the sealing performance using the finite element model reveals that under the combined effects of temperature and internal pressure, the overall temperature of the joint exhibits a gradient change from the inside to the outside. This is due to the contact between the medium and the bellows lining, the significant temperature difference between the low temperature of the internal medium (-163℃) and the ambient temperature (20℃) of the joint's exterior, causing heat flow and a substantial drop in the temperature of the outermost wall, ultimately reaching -102℃. This temperature difference generates thermal stress, increasing the stress at the weld and affecting the joint's sealing performance. The stress is highest on the inner side of the weld. Under a pressure of only 2MPa at room temperature, the average stress in the inner layer of the weld is 5.11MPa. When the internal pressure and low-temperature load are combined, the average stress on the inner side of the weld reaches 16MPa. Comparing the calculation results of the two models, the 10.89MPa increase in average stress at the bellows weld is due to thermal stress generated by temperature. The analysis demonstrates that temperature has a significant impact on the joint's sealing performance, and the effects of low temperatures must be considered in practical engineering.

[0030] S200. Determine the failure criteria and analyze the obtained weld equivalent stress as a key indicator to measure the sealing performance of welds in cryogenic fluid transport pipelines and joints; S300. A sensitivity analysis is conducted on the equivalent stress of the weld based on three factors: weld gap, blunt edge dimension, and weld reinforcement. The most sensitive parameter affecting the weld strength is determined, and the value of the most sensitive parameter that achieves the best sealing performance is obtained. The specific process is as follows: S301. Single-factor influence analysis of weld gap: During welding, the size of the weld gap affects the weld strength. To study the influence of the weld gap on the sealing performance of the joint, a finite element model was first used to analyze the quarter-sealing performance of the cryogenic flexible pipe and the joint. The equivalent stress distribution of the joint weld was then calculated (e.g., Figure 7 (As shown), then change the weld gap value and analyze the variation law of the average stress of the joint weld under different weld gap sizes and different internal pressures (e.g.) Figure 8 (As shown). In this embodiment, the internal pressure is set to 2MPa and 5MPa. According to the recommendation of standard GB / T 985.1-2008, the weld gap is set to 1mm, 2mm, 3mm and 4mm respectively. To ensure that the influence of other key factors is excluded, the blunt edge size is set to 2mm and the weld reinforcement is set to 1mm, which remains unchanged. At the same time, in order to simplify the calculation, since the joint weld is an axisymmetric structure and the load is also axisymmetrically distributed, the calculation can be performed based on the quarter-sealing performance analysis finite element model.

[0031] Depend on Figure 7 It can be seen that the equivalent stress distribution results of the finite element model for quarter-sealing performance analysis are consistent with the stress distribution results of the finite element model for overall sealing performance analysis, indicating that the results are accurate. Figure 8 Analysis of the variation patterns of weld gap and average weld stress reveals that the weld gap has a significant impact on the average weld stress. When the joint is subjected to pressures of 2 MPa and 5 MPa, the average stress at the weld initially increases and then decreases as the weld gap increases. Under the same pressure, the average stress is highest with a 2 mm weld gap: 21.78 MPa at 2 MPa and 53.68 MPa at 5 MPa. However, with a 1 mm weld gap, the minimum stress is 18.85 MPa at 2 MPa, a difference of 3.93 MPa (20.85%) compared to the calculated result for a 2 mm gap. At 5 MPa, the minimum stress is 47.36 MPa with a 1 mm weld gap, a difference of 6.32 MPa (13%). Higher weld stress results in better sealing performance. Based on the calculations, the optimal weld gap size is 2 mm.

[0032] S302. Single-factor influence analysis of blunt edge dimensions: Similarly, during the welding process, the size of the blunt edge is also a key parameter affecting the weld strength. To study the influence of the blunt edge size on the joint seal, a finite element model of the quarter-sealing performance of the ultra-low temperature flexible pipe and the joint was used to calculate the equivalent stress distribution of the joint weld (e.g., Figure 7 (As shown), then change the value of the blunt edge dimension, and analyze the variation law of the average stress of the weld joint under different blunt edge dimensions and different internal pressures (e.g.) Figure 9 (As shown). In this embodiment, the internal pressure is set to 2MPa and 5MPa, and the blunt edge dimensions are set to 2mm, 3mm and 4mm respectively to ensure that the influence of other key factors is excluded. The weld gap is set to 1mm and the weld reinforcement is set to 1mm, which remain unchanged.

[0033] Depend on Figure 9 Analysis of the relationship between the blunt edge size and the average stress of the weld shows that when the joint weld is subjected to pressures of 2 MPa and 5 MPa, the average stress at the weld decreases as the blunt edge size increases. Under the same pressure, the average stress is highest for a blunt edge size of 2 mm. At 2 MPa pressure, the average stress at the weld is 18.85 MPa, and at 5 MPa pressure, it is 47.36 MPa. Therefore, based on the calculation results, the optimal blunt edge size is 2 mm.

[0034] S303. Single-factor influence analysis of weld reinforcement height: During welding, the weld reinforcement height also affects the weld strength. To study the impact of weld reinforcement height on joint sealing, a finite element model of the quarter-sealing performance of a cryogenic flexible pipe and joint was used to calculate the equivalent stress distribution of the joint weld (e.g., Figure 7(As shown), then change the weld reinforcement value and analyze the variation law of the average stress of the joint weld under different weld reinforcement values ​​and different internal pressures (e.g. Figure 10 (As shown). In this embodiment, the internal pressure is set to 2MPa and 5MPa, and the weld reinforcement is set to 0.5mm, 1mm, 1.5mm and 2mm respectively. To ensure that the influence of other key factors is eliminated, the weld gap is set to 1mm and the blunt edge size is set to 1mm, which remains unchanged.

[0035] Depend on Figure 10 Analysis of the relationship between weld reinforcement height and average weld stress reveals that when the joint weld is subjected to pressures of 2 MPa and 5 MPa, the average stress at the weld decreases as the weld reinforcement height increases. Under the same pressure, the average stress is highest at a weld reinforcement height of 0.5 mm. At 2 MPa pressure, the average stress at the weld is 19.09 MPa, and at 5 MPa pressure, it is 47.90 MPa. Therefore, based on the calculation results, the optimal weld reinforcement height is 0.5 mm.

[0036] The above analysis shows that, comparing the sensitivity analysis of the three key parameters affecting the sealing performance of the welded area of ​​the joint, under pressures of 2MPa and 5MPa, the [results are not specified in the original text]. Figure 8 It can be seen that as the weld gap increases, the average stress at the weld first increases and then decreases. Figure 9 and Figure 10 It can be seen that as the blunt edge size and weld reinforcement increase, the average stress at the weld decreases. According to the change in average stress, the stress change in the joint weld is greatest when the weld gap changes. At a pressure of 2 MPa, the difference between the maximum and minimum average stress is 20.85%, which has the greatest impact on the joint sealing performance. By analyzing the sensitivity of key parameters, it can be seen that the weld volume changes due to the change in the joint weld gap, and the change in weld gap directly leads to the change in the contact area between the weld and the medium. Under the action of internal pressure and temperature, the stress change at the weld is even greater. Therefore, the weld gap is determined to be the most sensitive parameter affecting the sealing performance.

[0037] S304. Analysis of the synergistic effect of weld gap and blunt edge size: Sensitivity analysis was conducted by comparing and analyzing three key parameters affecting weld stress. The weld gap and blunt edge size had a significant impact on the average weld stress. However, changes in the weld gap and blunt edge size affected the weld structure volume. Temperature loads applied to different weld volumes resulted in significant variations in weld temperature stress. To investigate the synergistic effect of weld gap and blunt edge size on joint sealing, a finite element model of the quarter-sealing performance of a cryogenic flexible pipe and joint was used to calculate the equivalent stress distribution of the joint weld (e.g.,...). Figure 7(As shown), then change the weld gap and blunt edge size, and analyze the variation law of the average stress of the joint weld when the weld gap and blunt edge size are different (e.g. Figure 11 (As shown). In this embodiment, within the reference range, the weld gap is set to 1mm, 2mm, 3mm, and 4mm, and the blunt edge size is set to 2mm, 3mm, and 4mm, with 12 values ​​set to eliminate the influence of weld reinforcement height. The weld reinforcement height is always 1mm. Single-factor sensitivity analysis shows that setting the load to 2MPa yields a more obvious variation pattern. Specific parameters are shown in Table 1.

[0038] Table 1. Values ​​of weld gap and blunt edge dimensions

[0039] Depend on Figure 11 It can be seen that the stress is highest when the joint weld gap is 2mm and the blunt edge dimension is 2mm, with an average stress of 21.78MPa; the stress is lowest when the joint weld gap is 3mm and the blunt edge dimension is 4mm, with an average stress of 17.42MPa, a change of 25%. The results indicate that changes in the joint weld gap and blunt edge dimension lead to changes in the joint weld volume. Under temperature load, the average stress at the joint weld changes significantly. Furthermore, when the blunt edge dimension remains constant, the stress variation shows that changes in the weld gap value result in a larger stress variation at the weld, and a significant change in sealing performance. This proves that the weld gap is the most sensitive parameter affecting the sealing performance of the joint weld.

[0040] Example 2 The above-described embodiment 1 provides a method for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints. Correspondingly, this embodiment provides a system for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints. The analysis system provided in this embodiment can implement the analysis method of embodiment 1. This analysis system can be implemented through software, hardware, or a combination of both. For example, the analysis system may include integrated or separate functional modules or units to execute the corresponding steps in the analysis methods of embodiment 1. Since the analysis system in this embodiment is basically similar to the analysis method embodiment, the description process in this embodiment is relatively simple. Relevant details can be found in the description of embodiment 1. The analysis system in this embodiment is merely illustrative.

[0041] The system for analyzing the sealing performance of cryogenic fluid transport pipelines and joint welds provided in this embodiment includes: The first processing unit is used to establish a finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure load and low temperature load and internal pressure, and to perform numerical analysis of the joint sealing structure based on the established finite element model for sealing performance analysis. The second processing unit is used to determine the failure criteria and analyze the obtained weld equivalent stress as a key indicator to measure the sealing performance of the weld joint of the cryogenic fluid transportation pipeline. The third processing unit is used to conduct sensitivity analysis on the equivalent stress of the weld by three factors: weld gap, blunt edge size, and weld reinforcement, to determine the most sensitive parameter affecting the weld strength and to obtain the value of the most sensitive parameter when the sealing performance is best.

[0042] Example 3 This embodiment provides a processing device for implementing the analysis method provided in Embodiment 1. The processing device can be a client-side processing device, such as a mobile phone, laptop, tablet computer, desktop computer, etc., to execute the analysis method of Embodiment 1.

[0043] The processing device includes a processor, a memory, a communication interface, and a bus. The processor, memory, and communication interface are connected via the bus to enable communication between them. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the analysis method provided in Embodiment 1.

[0044] Preferably, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0045] Preferably, the processor can be any type of general-purpose processor such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation herein.

[0046] Example 4 The analysis method of this embodiment 1 can be specifically implemented as a computer program product. The computer program product may include a computer-readable storage medium on which computer-readable program instructions for executing the analysis method described in this embodiment 1 are loaded.

[0047] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, characterized in that, Includes the following steps: A finite element model was established for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure load and under the combined action of low temperature load and internal pressure. Based on the established finite element model, a numerical analysis of the joint sealing structure was performed, specifically: A finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints was established: the joint consists of a fastening ring, two reverse spiral wound armor layers, an inner ring, and the innermost layer formed by the joint flange and the bellows liner connected together by a weld, which fixes the end of the armor layer to the fastening ring. A finite element model was used to calculate the sealing performance of ultra-low temperature flexible pipes and joints under the combined action of low temperature load and internal pressure. The temperature distribution cloud map of the entire joint was obtained. The temperature change and the average stress change at the weld were extracted to obtain the average stress curve of the weld with temperature. The law of average stress change with temperature was analyzed. For the sealing structure of the joint, under the working state, the average stress of the weld is greater than the critical failure pressure of the joint. According to the critical failure theory of sealing, the joint meets the minimum requirements for achieving a seal. At the same time, since the average stress of the weld is much less than the allowable strength of the weld material, there is no strength failure in the sealing structure of the joint. Therefore, the joint achieves a seal under the working state. Finite element models were used to calculate the sealing performance of the joint under pressure at room temperature and under the combined action of low temperature and pressure. Equivalent stress cloud diagrams of the weld were obtained when the weld was under pressure at room temperature and low temperature. By comparing the calculation results of the two models, it was determined that temperature has a significant impact on the sealing performance of the joint, and the effect of low temperature must be considered in actual engineering. The failure criteria were determined, and the obtained weld equivalent stress was analyzed as a key indicator to measure the sealing performance of welds in cryogenic fluid transport pipelines and joints. Sensitivity analysis was conducted on the equivalent stress of the weld by considering three factors: weld gap, blunt edge size, and weld reinforcement. The most sensitive parameter affecting the weld strength was determined, and the value of the most sensitive parameter when the sealing performance was optimal was obtained.

2. The analytical method according to claim 1, characterized in that, The aforementioned sensitivity analysis of the equivalent stress of the weld, considering three factors—weld gap, blunt edge dimension, and weld reinforcement—determines the most sensitive parameter affecting weld strength and obtains the most sensitive parameter value for optimal sealing performance. Single-factor influence analysis of weld gap; Single-factor influence analysis of blunt edge dimensions; Single-factor influence analysis of weld reinforcement height; Analysis of the synergistic effect of weld gap and blunt edge size.

3. The analytical method according to claim 2, characterized in that, The single-factor influence analysis of the weld gap is as follows: Based on the finite element model of the quarter-sealing performance analysis of the ultra-low temperature flexible pipe and joint, the equivalent stress distribution of the joint weld was calculated. Then, by changing the weld gap value, the variation law of the average stress of the joint weld under different weld gap sizes and different internal pressures was analyzed. The influence of weld gap on the average stress value of weld was obtained, and the optimal weld gap size was determined to be 2mm.

4. The analytical method according to claim 2, characterized in that, The single-factor influence analysis of the blunt edge size is as follows: Based on the finite element model of the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the value of the blunt edge size, the variation law of the average stress of the joint weld under different blunt edge sizes and different internal pressures was analyzed. The influence of the blunt edge size on the average stress value of the weld was obtained, and the optimal blunt edge size was determined to be 2mm.

5. The analytical method according to claim 2, characterized in that, The single-factor influence analysis of the weld reinforcement height is as follows: Based on the finite element model of the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the value of the weld reinforcement, the variation law of the average stress of the joint weld under different weld reinforcement sizes and different internal pressures was analyzed. The influence of weld reinforcement on the average stress value of the weld was obtained, and the optimal weld reinforcement size was determined to be 0.5 mm.

6. The analytical method according to claim 2, characterized in that, The analysis of the synergistic effect of weld gap and blunt edge size is as follows: Based on the finite element model for the quarter-sealing performance analysis of ultra-low temperature flexible pipes and joints, the equivalent stress distribution of the joint weld was calculated. Then, by changing the values ​​of the weld gap and blunt edge size, the variation law of the average stress of the joint weld under different weld gap and blunt edge size was analyzed. It was found that the change of the joint weld gap and blunt edge size leads to the change of the joint weld volume. Under the action of temperature load, the average stress of the weld changes significantly. At the same time, when the blunt edge size is kept constant, it can be seen from the change of the average stress of the weld that the change of the weld gap value leads to a large change in the average stress of the weld, and the sealing performance changes significantly. It is determined that the weld gap is the most sensitive parameter affecting the sealing performance of the joint weld.

7. A system for analyzing the sealing performance of weld seams in cryogenic fluid transport pipelines and joints, characterized in that, include: The first processing unit is used to establish finite element models for the sealing performance analysis of ultra-low temperature flexible pipes and joints under normal temperature internal pressure loads and the combined action of low temperature loads and internal pressures, and to perform numerical analysis of the joint sealing structure based on the established finite element model for sealing performance analysis, specifically: A finite element model for the sealing performance analysis of ultra-low temperature flexible pipes and joints was established: the joint consists of a fastening ring, two reverse spiral wound armor layers, an inner ring, and the innermost layer formed by the joint flange and the bellows liner connected together by a weld, which fixes the end of the armor layer to the fastening ring. A finite element model was used to calculate the sealing performance of ultra-low temperature flexible pipes and joints under the combined action of low temperature load and internal pressure. The temperature distribution cloud map of the entire joint was obtained. The temperature change and the average stress change at the weld were extracted to obtain the average stress curve of the weld with temperature. The law of average stress change with temperature was analyzed. For the sealing structure of the joint, under the working state, the average stress of the weld is greater than the critical failure pressure of the joint. According to the critical failure theory of sealing, the joint meets the minimum requirements for achieving a seal. At the same time, since the average stress of the weld is much less than the allowable strength of the weld material, there is no strength failure in the sealing structure of the joint. Therefore, the joint achieves a seal under the working state. Finite element models were used to calculate the sealing performance of the joint under pressure at room temperature and under the combined action of low temperature and pressure. Equivalent stress cloud diagrams of the weld were obtained when the weld was under pressure at room temperature and low temperature. By comparing the calculation results of the two models, it was determined that temperature has a significant impact on the sealing performance of the joint, and the effect of low temperature must be considered in actual engineering. The second processing unit is used to determine the failure criteria and analyze the obtained weld equivalent stress as a key indicator to measure the sealing performance of the weld joint of the cryogenic fluid transportation pipeline. The third processing unit is used to conduct sensitivity analysis on the equivalent stress of the weld by three factors: weld gap, blunt edge size, and weld reinforcement, to determine the most sensitive parameter affecting the weld strength and to obtain the value of the most sensitive parameter when the sealing performance is best.

8. A computer storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the analysis method according to any one of claims 1-6.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the analysis method according to any one of claims 1-6.

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