A non-invasive flange sealing contact condition monitoring method and system

Abstract

The application discloses a kind of non-invasive flange sealing contact state monitoring method and system, method includes: obtaining the mechanical property parameter data of flange sealing ring, and establishes flange sealing state monitoring model according to mechanical property parameter data;Real-time strain distribution data of flange surface is monitored in real time using sealing state monitoring model, when monitoring that real-time strain distribution data reaches monitoring early warning threshold, early warning is carried out.The application establishes flange sealing state monitoring model by the change rule of strain distribution and sealing contact state of flange surface, identifies the sealing contact state in the flange, and combines the comprehensive factors of mechanical property parameters to analyze the rule of strain distribution and sealing contact state of flange surface, realizes the abnormal monitoring of flange sealing contact state of multiple factors, and can realize local abnormal positioning potential leakage risk, discovers flange sealing failure risk in advance, improves the monitoring accuracy and early warning timeliness of sealing contact state.

Description

Technical Field

[0001] This invention relates to the field of industrial equipment sealing performance monitoring technology, and in particular to a non-invasive method and system for monitoring the contact status of flange seals. Background Technology

[0002] Flange sealing structures are widely used in industries such as petrochemicals and power due to their advantages of simple structure, good tightness, and convenient replacement. Flange sealing structures primarily achieve a seal by compressing the sealing elements through tightening bolts, filling the gap between the flanges, and ensuring that the contact stress on the sealing surface exceeds the oil pressure passing through the flange. The key indicator for judging the quality of a flange seal is the magnitude and distribution of the contact stress on the sealing ring, i.e., the sealing contact state. Analysis reveals that the key factors causing abnormal contact states in flange sealing structures can be categorized into three types: first, installation factors, including whether the sealing ring has come out of its groove or broken, and whether the bolt tightening sequence is standardized and the preload is adequate; second, material factors, namely the creep relaxation characteristics of the sealing ring itself; and third, environmental and aging factors, encompassing the effects of temperature fluctuations and the aging failure of the sealing ring after long-term use. Flange sealing condition assessment requires a comprehensive consideration of these multiple factors, and the effects of temperature and sealing ring aging are time-sensitive, necessitating dynamic analysis based on actual usage conditions.

[0003] In practical engineering, the root cause of flange sealing structure leakage is abnormal sealing contact. This not only leads to system shutdown and economic losses, but in severe cases, it can trigger major safety accidents, causing casualties. Flange sealing structures cannot be disassembled or have their sealing contact surfaces damaged during operation; the internal sealing contact state cannot be directly measured, and abnormal contact states are unpredictable. Current technologies are insufficient to address the numerous factors causing abnormal flange sealing contact states, the inability to directly measure internal contact, and the difficulty or impermissibility of modifying the flange sealing surface structure. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a non-invasive flange seal contact state monitoring method and system to achieve non-invasive real-time monitoring of various flange seal contact state anomalies.

[0005] Therefore, the technical solution adopted by the present invention is as follows:

[0006] A non-invasive method for monitoring the contact status of flange seals is provided, characterized in that the method includes:

[0007] The mechanical performance parameters of the flange sealing ring are obtained, and a flange sealing condition monitoring model is established based on the mechanical performance parameters. The flange sealing condition monitoring model constructs the hyperelastic curve and viscoelastic curve of the flange sealing ring based on the mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition.

[0008] A sealing condition monitoring model is used to monitor the real-time strain distribution data on the flange surface. When the real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

[0009] According to the above scheme, the mechanical performance parameters of the flange sealing ring are obtained by conducting uniaxial tensile and uniaxial compression mechanical tests, as well as stress relaxation and creep tests at different temperatures, on the sealing ring used for flange sealing based on the actual working conditions and the sealing ring compression rate.

[0010] According to the above scheme, the mechanical performance parameter data specifically include the sealing ring material constant, shear relaxation parameter, delay time constant, and time-temperature offset factor of the sealing ring at different temperatures.

[0011] According to the above scheme, the variation law of flange surface strain distribution and sealing contact state is obtained through finite element simulation analysis;

[0012] Specifically, the variation law of flange surface strain distribution and sealing contact state includes the variation law of flange surface strain distribution and sealing contact state under different bolt preload, the variation law of flange surface strain distribution and sealing contact state under different oil pressure, the variation law of flange surface strain distribution and sealing contact state under different temperatures, and the variation of flange surface strain distribution under different abnormal working conditions.

[0013] According to the above scheme, different abnormal working conditions specifically include bolt preload less than the reference threshold, uneven distribution of bolt preload, and local damage to the sealing ring.

[0014] According to the above scheme, the hyperelastic curve is calculated based on the material constant of the sealing ring and the Green strain tensor invariant to calculate the strain energy density function; the viscoelastic curve is calculated based on the instantaneous modulus of the sealing ring rubber material, the shear relaxation parameter of the rubber material, and the Prony delay time constant to calculate the real-time modulus of the sealing ring rubber material.

[0015] According to the above scheme, the strain distribution and sealing contact state of the flange surface under different bolt preloads are specifically determined by increasing the bolt preload of the flange sealing ring at a preset frequency and measuring the changes in the contact area and contact pressure between the flange and the sealing ring.

[0016] The variation law of strain distribution and sealing contact state on flange surface under different oil pressures is specifically determined by increasing the oil in the flange at a preset frequency and measuring the strain distribution on flange surface under different oil pressures.

[0017] The variation law of strain distribution and sealing contact state of flange surface under different temperatures is specifically calculated by increasing the temperature of the environment in which the flange is located at a preset frequency, and calculating the displacement change and stress change of flange sealing ring under different temperatures.

[0018] According to the above scheme, the real-time strain distribution data of the flange surface is monitored in real time through a distributed optical fiber sensor and a distributed optical fiber demodulator. The distributed optical fiber sensor is specifically installed at the middle circumference of the annular area formed by the axial projection of the sealing ring onto the flange surface.

[0019] According to the above scheme, the monitoring and early warning threshold for the flange sealing condition is obtained in the following way:

[0020] The response function of flange surface strain to sealing contact stress is obtained by fitting the strain distribution and sealing contact state of the flange surface. The critical contact pressure of the sealing ring is calculated based on the sealing ring material and substituted into the response function to solve for the critical strain value and ultimate strain deviation rate of the flange surface. The monitoring and early warning threshold is set according to the ultimate strain deviation rate.

[0021] A non-invasive flange seal contact condition monitoring system is also provided, the system comprising:

[0022] The model building module is used to acquire the mechanical performance parameter data of the flange sealing ring and build a flange sealing condition monitoring model based on the mechanical performance parameter data. The flange sealing condition monitoring model constructs the hyperelastic curve and viscoelastic curve of the flange sealing ring based on the mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition.

[0023] The data monitoring module is used to monitor the real-time strain distribution data of the flange surface using the sealing condition monitoring model. When the monitored real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

[0024] A computer storage medium is also provided, which stores a computer program executable by a processor, the computer program performing the non-invasive flange seal contact status monitoring method described above.

[0025] The beneficial effects of this invention are as follows: This invention establishes a flange sealing condition monitoring model by observing the variation law of strain distribution and sealing contact state on the flange surface, identifies the sealing contact state inside the flange, and analyzes the law of strain distribution and sealing contact state on the flange surface by combining comprehensive factors of mechanical performance parameters. This enables the monitoring of abnormal flange sealing contact state affected by multiple factors, and can locate potential leakage risks in local anomalies, detect flange sealing failure risks in advance, and take timely measures to avoid leakage, thereby improving the accuracy of sealing contact state monitoring and the timeliness of early warning. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of the non-invasive flange seal contact status monitoring method according to an embodiment of the present invention;

[0027] Figure 2 This is an architecture diagram of a sealing condition monitoring system according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the fiber optic cable laying position on the flange surface according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the flange fracture in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram showing the strain distribution on the flange surface and the contact stress distribution of the sealing ring when the flange is in good sealing condition in an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram showing the strain distribution on the flange surface and the contact stress distribution of the sealing ring when the flange has a fracture in an embodiment of the present invention.

[0032] Figure 7 This is a simulation diagram comparing the strain distribution of the sealing ring with and without a fracture in an embodiment of the present invention.

[0033] Figure 8 This is a diagram showing the actual strain distribution of the sealing ring in an embodiment of the present invention, with and without a fracture.

[0034] Figure 9 This is a schematic diagram of the system structure of the non-invasive flange seal contact status monitoring system according to an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] To address the problem that existing monitoring methods are insufficient to meet the needs of flange sealing contact state monitoring due to the numerous factors causing abnormalities, the inability to directly measure internal contact, and the difficulty or impermissibility of modifying the flange sealing surface structure, this invention provides a non-invasive flange sealing contact state monitoring method. Figure 1 As shown, the method includes:

[0037] S1. Obtain the mechanical performance parameters of the flange sealing ring and establish a flange sealing condition monitoring model based on the mechanical performance parameters.

[0038] S2. The real-time strain distribution data of the flange surface is monitored in real time using the sealing condition monitoring model. When the real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

[0039] Specifically, the flange sealing condition monitoring model constructs the hyperelastic and viscoelastic curves of the flange sealing ring based on mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition.

[0040] Specifically, based on the compression ratio of the sealing ring under actual working conditions, mechanical tests such as uniaxial tensile and uniaxial compression mechanical tests, stress relaxation tests at different temperatures, and creep tests are conducted on the sealing ring used for flange sealing to obtain mechanical performance parameter data of the sealing ring; the mechanical performance parameter data specifically includes the sealing ring material constant, shear relaxation parameter, delay time constant, and time-temperature offset factor of the sealing ring at different temperatures.

[0041] Specifically, in this embodiment, a flange sealing condition monitoring model is established based on mechanical performance parameter data. Specifically, simulation fitting curves of key parameters in the hyperelastic model and viscoelastic model of the sealing ring are constructed based on the mechanical performance parameter data. The key parameters include the hyperelastic material constant and WLF constant of the sealing ring.

[0042] In this embodiment, the Mooney-Rivlin hyperelastic model is used to describe the nonlinear stress-strain relationship of the sealing ring under large deformation; the viscoelastic model is used to describe the creep relaxation effect of the sealing ring, which is achieved by defining the Prony series; and the William-Landel-Ferry (WLF) theory is used to describe the viscoelasticity of the sealing ring at different temperatures.

[0043] The sealing ring is characterized by the Mooney-Rivlin model for hyperelasticity, and its specific strain energy function is expressed as follows:

[0044]

[0045] In the formula: Let be the strain energy density function; , These are material constants; , These are the two principal invariants of the Green strain tensor.

[0046] The viscoelastic model describing the creep relaxation effect of the sealing ring can be specifically expressed as follows:

[0047]

[0048] In the formula: It is the real-time modulus of the rubber material; It is the instantaneous modulus of the rubber material; It is the shear relaxation of rubber materials; It is the Prony delay time constant.

[0049] Specifically, the viscoelasticity of the sealing ring at different temperatures can be determined using the "time-temperature equivalence" of the WLF theory, thereby establishing the mechanical properties of the sealing ring at different temperatures, which can be expressed as:

[0050]

[0051] In the formula: It is the time-temperature shift factor; and It is the WLF constant. This is a reference temperature. It is the temperature at which the offset occurs, i.e., the actual temperature.

[0052] Based on the above formula, and using the obtained hyperelastic test data of the rubber material of the sealing ring under uniaxial tensile and uniaxial compression deformation modes, the least squares method is used to determine the hyperelastic material parameters in the hyperelastic constitutive model. , Fitting and identification were performed; simultaneously, based on the obtained stress relaxation and creep test data of the rubber material of the sealing ring at different temperatures, the Prony parameters in the viscoelastic constitutive model at different temperatures were fitted and identified using the least squares method, and the fitting was obtained through "time-temperature superposition" processing. , and ,in, Select the glass transition temperature of the sealing ring.

[0053] Based on the above formula, a physical model of the flange structure is established in the finite element software ANSYS: the material model is assigned, mesh is generated, boundary conditions and load conditions are applied, contact relationships and solution calculations are set for the flange structure model, so as to realize the finite element modeling and analysis of the flange structure, thereby obtaining the variation law of flange surface strain distribution and sealing contact state.

[0054] Specifically, the bolt preload is set to be gradually increased from an initial zero value to the standard specified load in a uniform manner. Two core analyses are carried out through this loading process: First, the dynamic changes in the contact state between the flange and the seal (or flange mating surface) are tracked, including the evolution of contact area, contact pressure distribution and contact stability; Second, the strain field distribution characteristics and changing trends of the flange surface are quantitatively analyzed, and the areas with the most sensitive surface strain response (i.e., the locations with the largest changes in strain values ​​and the most significant feedback to the preload loading process) are identified.

[0055] Specifically, for standard bolt preload and its uniform distribution, the strain distribution and sealing contact state of the flange surface under different oil pressures are simulated and analyzed. The strain data on the circumference of the sensor installation position are extracted and used as the reference strain distribution under different oil pressures.

[0056] Specifically, the simulation analysis calculates the creep relaxation effect of the sealing ring at different temperatures, analyzes the influence of the creep relaxation effect of the sealing ring on the sealing contact state, and analyzes the response of the strain distribution change of the sensor placement position to the creep relaxation of the sealing ring. The surface strain distribution response is correlated with the change of sealing contact state to obtain the response law of the flange surface strain distribution to the change of sealing contact state under the influence of creep relaxation effect.

[0057] Specifically, simulation analysis is performed on several typical abnormal operating conditions (such as insufficient bolt preload, uneven bolt preload, and localized damage to the sealing ring) to analyze the response of surface stress distribution to abnormal sealing contact conditions. The differences are compared with the baseline strain distribution to summarize the variation law of surface strain distribution with contact state. The flange surface strain distribution and sealing contact state data for each abnormal operating condition are extracted and labeled with the corresponding operating conditions.

[0058] Specifically, assuming uniform bolt preload, the strain distribution on the flange surface is calculated when the bolt preload is reduced to the lowest sealing contact stress, and 80% of the maximum deviation rate from the standard strain distribution is taken as the boundary.

[0059] Based on the obtained variation patterns of strain distribution and sealing contact state on the flange surface under different working conditions, the monitoring and early warning threshold for flange sealing state is determined.

[0060] Specifically, a mapping relationship library of "sealing contact pressure - surface strain" is established based on the variation law of strain distribution on the flange surface and sealing contact state. Based on the aforementioned finite element simulation results, the effective contact pressure peak distribution (ES) of the sealing ring under various working conditions and the equivalent strain distribution (CP) at the sensor monitoring point location are extracted. Using numerical fitting methods (such as polynomial fitting or neural network fitting), the response function of flange surface strain to sealing contact stress, ES=f(CP,P), is constructed, where P is the oil pressure. This function quantitatively characterizes the response characteristics of the strain field on the outer surface of the flange when the sealing contact pressure decreases with creep or load changes.

[0061] Secondly, determine the critical contact pressure value for seal failure. Based on the theory of porous media leakage in gasket seals, determine the minimum residual contact stress σ required for the sealing ring to ensure no leakage. min The formula for calculating this value is:

[0062] σ min =m×P medium +b

[0063] In the formula, P medium The internal medium pressure (oil pressure) that causes the leakage driving force; m is the gasket coefficient, which depends on the sealing ring material (i.e., the rubber material properties measured in this embodiment); b is the preload specific pressure constant related to the flange surface roughness and sealing level. σ min Defined as the contact pressure under the "critical failure state", that is, the greater the internal pressure, the higher the required residual contact stress.

[0064] Then, the critical strain distribution and maximum allowable deviation are solved in reverse. The critical contact pressure σ obtained above is then used as the basis for further calculation. min Substitute the response function and solve in reverse for the corresponding critical strain value of the flange surface. Simulation yields the reference strain value. This refers to the initial healthy strain reading of the equipment under standard preload, without aging or leakage. The limiting strain deviation rate is defined. The calculation formula can be expressed as:

[0065]

[0066] η max This represents the maximum strain change that the sensor can detect from a healthy state to the point of leakage failure.

[0067] Finally, tiered monitoring and early warning thresholds are set. To allow maintenance time before a leak actually occurs, a two-tiered early warning threshold is set, taking into account the engineering safety factor:

[0068] Level 1 warning threshold K1: Primarily targets stress relaxation caused by viscoelasticity. Taking 50%~60% of the ultimate strain deviation rate as the boundary, it can be expressed as:

[0069] K1= ±( η max ×0.6)

[0070] When the strain reaches this value in real-time monitoring, it indicates that the contact pressure of the sealing ring has dropped significantly due to viscoelastic relaxation. Although there is no leakage, planned maintenance is required.

[0071] Level 2 alarm threshold (leakage warning value) K2: which is "80% of the maximum deviation rate" mentioned in this embodiment, can be expressed as:

[0072] K2= ±( η max ×0.8)

[0073] That is, when factors such as creep relaxation, uneven preload, and local damage to the sealing ring are applied, and the strain exceeds this threshold in real time, it is determined that the sealing contact state has approached σ. min The risk of leakage is extremely high, triggering an immediate system alarm.

[0074] In addition, after obtaining the monitoring and early warning threshold for the flange sealing status, a system is established as follows: Figure 2 The sealing condition monitoring system based on flange surface strain distribution shown includes: specifically, using polyimide-coated optical fiber and an OFDR distributed optical fiber demodulator for condition monitoring; and establishing a data analysis and early warning system to display the flange surface strain distribution monitoring signal and reference signal in real time, allowing staff to intuitively perceive the strain distribution and deviation. A built-in strain distribution deviation rate calculation algorithm calculates the deviation rate in real time, and simultaneously reads judgment thresholds stored in the database for early warning. Samples of abnormal surface strain distribution are imported into the database as historical records for system training of an intelligent algorithm to accurately determine the causes of abnormal flange contact conditions. An SQL database is also constructed, containing various data types to store basic information about the monitored flange, its corresponding reference stress distribution, thresholds for accurately judging abnormal sealing contact condition distribution, flange surface strain distributions from several typical failure cases obtained through simulation, and historical monitoring data, all connected to the data analysis and early warning system.

[0075] Preferably, considering the sealing performance of the sealing ring and the monitoring accuracy requirements of the sensor, the middle circumference of the annular area formed by the axial projection of the sealing ring onto the flange surface is selected as the optimal installation position for the flange surface monitoring sensor, thereby enabling the monitoring of strain distribution data on the flange surface.

[0076] Specifically, data monitoring is performed using sensors arranged on the flange surface. In this embodiment, 353ND adhesive is used to attach and lay the distributed optical fiber sensors. Localized light pressing and localized cooling with coolant are used to change the local strain of the optical fiber, displaying information about the strain and distance. The specific locations of the optical fiber sensing signals on the flange surface are mapped to determine the optimal placement of the optical fiber sensors. Preferably, a stress-free section of the distributed optical fiber is selected as a temperature compensation section to monitor the flange sealing status during flange installation and actual operation.

[0077] Specifically, the flange sealing condition monitoring model was established and applied using the method of this embodiment, wherein the fiber optic cable laying positions on the flange surface are as follows: Figure 2 The flange fracture diagram is shown in the red circle. Figure 4 As shown in the diagram; when the flange is in good sealing condition, the strain distribution on the flange surface and the contact stress distribution of the sealing ring are shown in the diagram. Figure 5 As shown in the diagram; when the flange has a fracture, the strain distribution on the flange surface and the contact stress distribution of the sealing ring are shown in the diagram. Figure 6 As shown; in addition, the simulation diagram comparing the strain distribution of the intact sealing ring and the ring with a fracture is shown in the figure. Figure 7 As shown in the figure, the actual result is as follows. Figure 8 As shown.

[0078] Depend on Figure 5 , Figure 6 and Figure 7 As shown, when the sealing ring is damaged, and the preload of the six bolts is exactly the same, the contact stress in the damaged area of ​​the sealing ring is significantly lower than that in other normal areas, and the stress on the flange surface at the corresponding location shows a significant local attenuation phenomenon. Under the condition of the damaged sealing ring, the strain distribution on the flange surface no longer shows a periodicity. At the location of the damaged sealing ring, the trough of the strain curve drops significantly, and the strain peaks on both sides of the corresponding location also decrease significantly. Therefore, the location of the damaged sealing ring or the local decrease in contact stress can be intuitively identified by comparing the strain distribution curves on the flange surface.

[0079] In addition, this embodiment of the invention also provides a non-invasive flange seal contact state monitoring system for implementing the non-invasive flange seal contact state monitoring method described in this embodiment, such as... Figure 9 As shown, the system includes:

[0080] The model building module is used to acquire the mechanical performance parameter data of the flange sealing ring and build a flange sealing condition monitoring model based on the mechanical performance parameter data. The flange sealing condition monitoring model constructs the hyperelastic curve and viscoelastic curve of the flange sealing ring based on the mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition.

[0081] The data monitoring module is used to monitor the real-time strain distribution data of the flange surface using the sealing condition monitoring model. When the monitored real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

[0082] The various modules or mechanisms of the system are mainly used to implement the various steps of the above method embodiments, and will not be described in detail here.

[0083] In addition, embodiments of the present invention also provide a computer storage medium storing a computer program executable by a processor, the computer program performing the non-invasive flange seal contact state monitoring method described above.

[0084] This invention provides a non-invasive flange sealing contact state monitoring method and system. It establishes a flange sealing state monitoring model by analyzing the strain distribution on the flange surface and the changing patterns of the sealing contact state. This model identifies the sealing contact state inside the flange and, by combining comprehensive factors of mechanical performance parameters, analyzes the strain distribution on the flange surface and the patterns of the sealing contact state. This enables abnormal monitoring of the flange sealing contact state under the influence of multiple factors, and allows for the localization of potential leakage risks through local anomaly detection. It also enables early detection of flange seal failure risks and timely implementation of measures to prevent leakage, thus improving the accuracy and timeliness of sealing contact state monitoring and early warning.

[0085] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0086] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0087] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A non-invasive method for monitoring the contact status of flange seals, characterized in that, The method includes: The mechanical performance parameters of the flange sealing ring are obtained, and a flange sealing condition monitoring model is established based on the mechanical performance parameters. The flange sealing condition monitoring model constructs the hyperelastic curve and viscoelastic curve of the flange sealing ring based on the mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition. A sealing condition monitoring model is used to monitor the real-time strain distribution data on the flange surface. When the real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

2. The non-invasive flange seal contact state monitoring method according to claim 1, characterized in that, The mechanical performance parameters of the flange sealing ring are obtained by conducting uniaxial tensile and uniaxial compression mechanical tests, as well as stress relaxation and creep tests at different temperatures, on the sealing ring used for flange sealing based on the compression ratio of the sealing ring under actual working conditions.

3. The non-invasive flange seal contact state monitoring method according to claim 2, characterized in that, The mechanical performance parameters specifically include the sealing ring material constant, shear relaxation parameter, delay time constant, and time-temperature offset factor of the sealing ring at different temperatures.

4. The non-invasive flange seal contact state monitoring method according to claim 1, characterized in that, The variation law of strain distribution on flange surface and sealing contact state was obtained through finite element simulation analysis; Specifically, the variation law of flange surface strain distribution and sealing contact state includes the variation law of flange surface strain distribution and sealing contact state under different bolt preload, the variation law of flange surface strain distribution and sealing contact state under different oil pressure, the variation law of flange surface strain distribution and sealing contact state under different temperatures, and the variation of flange surface strain distribution under different abnormal working conditions.

5. The non-invasive flange seal contact status monitoring method according to claim 4, characterized in that, Different abnormal operating conditions include bolt preload less than the reference threshold, uneven distribution of bolt preload, and local damage to the sealing ring.

6. The non-invasive flange seal contact state monitoring method according to claim 3, characterized in that, The hyperelastic curve is calculated based on the material constants of the sealing ring and the Green strain tensor invariant to determine the strain energy density function; the viscoelastic curve is calculated based on the instantaneous modulus of the sealing ring rubber material, the shear relaxation parameter of the rubber material, and the Prony delay time constant to determine the real-time modulus of the sealing ring rubber material.

7. The non-invasive flange seal contact state monitoring method according to claim 4, characterized in that, The variation law of strain distribution and sealing contact state on flange surface under different bolt preload is specifically studied by increasing the bolt preload of flange sealing ring at a preset frequency and measuring the change of contact area and contact pressure between flange and sealing ring. The variation law of strain distribution and sealing contact state on flange surface under different oil pressures is specifically determined by increasing the oil in the flange at a preset frequency and measuring the strain distribution on flange surface under different oil pressures. The variation law of strain distribution and sealing contact state of flange surface under different temperatures is specifically calculated by increasing the temperature of the environment in which the flange is located at a preset frequency, and calculating the displacement change and stress change of flange sealing ring under different temperatures.

8. The non-invasive flange seal contact state monitoring method according to claim 1, characterized in that, Real-time monitoring of strain distribution data on the flange surface is achieved through signal monitoring and demodulation using a distributed fiber optic sensor and a distributed fiber optic demodulator. Specifically, the distributed fiber optic sensor is installed at the center circumference of the annular area formed by the axial projection of the sealing ring onto the flange surface.

9. The non-invasive flange seal contact state monitoring method according to claim 1, characterized in that, The monitoring and early warning threshold for flange sealing status is obtained in the following way: The response function of flange surface strain to sealing contact stress is obtained by fitting the strain distribution and sealing contact state of the flange surface. The critical contact pressure of the sealing ring is calculated based on the sealing ring material and substituted into the response function to solve for the critical strain value and ultimate strain deviation rate of the flange surface. The monitoring and early warning threshold is set according to the ultimate strain deviation rate.

10. A non-invasive flange seal contact condition monitoring system, characterized in that, The system includes: The model building module is used to acquire the mechanical performance parameter data of the flange sealing ring and build a flange sealing condition monitoring model based on the mechanical performance parameter data. The flange sealing condition monitoring model constructs the hyperelastic curve and viscoelastic curve of the flange sealing ring based on the mechanical performance parameters, obtains the variation law of flange surface strain distribution and sealing contact state, and determines the monitoring and early warning threshold of flange sealing condition. The data monitoring module is used to monitor the real-time strain distribution data of the flange surface using the sealing condition monitoring model. When the monitored real-time strain distribution data reaches the monitoring and warning threshold, an early warning is issued.

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