Method for non-destructive testing of flange seals in groove condition based on acoustic emission

Abstract

The application discloses a kind of based on acoustic emission's flange sealing piece in groove state nondestructive testing method, comprising the following steps: AE sensor and excitation device are correspondingly arranged on the two sides of flange sealing structure, AE sensor and excitation device are connected on data processing terminal equipment;Excitation device starts, and excitation vibration is generated on flange sealing structure, and AE signal generated from excitation device is collected by AE sensor, and is transferred to data processing terminal;According to AE signal analysis, judges the groove state of flange sealing piece.The application can detect the groove state of sealing piece in the process of flange installation without disassembling cover, can retain the structural integrity of flange sealing system, improve detection precision by intelligent algorithm, avoid the risk of re-injury to sealing piece in disassembling process.

Description

Technical Field

[0001] This invention specifically relates to a non-destructive testing method for flange seals in a grooved state based on acoustic emission. Background Technology

[0002] Flange sealing structures mainly consist of upper and lower flanges, sealing elements, and bolts. As a simple sealing connection method, it has been widely used in industrial fields such as aerospace, petrochemicals, energy, and hydropower stations. The sealing element is a crucial component of the flange sealing system; leakage not only affects the normal function of the sealing system but also severely pollutes the working environment, causing significant economic losses. During the installation of flange sealing connections, it is of great significance and application value to determine the state of the sealing element within the groove (such as whether it is fully seated, whether there is any twisting or damage) in real time, in situ, efficiently, and non-destructively without removing the cover.

[0003] Regarding the issue of detecting the in-groove condition of flange seals, existing detection methods mainly include visual inspection and leak detection. These methods require passing the entire equipment through a pressurized medium and then observing leaks to determine the seal's in-groove condition. This approach is not only costly in terms of manpower and time, and cumbersome, requiring the collaboration of professional maintenance personnel, but also makes it impossible to directly observe whether the seal is not fully seated, twisted, or damaged during seal replacement, necessitating further disassembly and inspection. In large flange sealing structures, there are also issues such as difficulty in disassembly, time-consuming and labor-intensive installation, and the risk of seal damage from repeated disassembly and reassembly, becoming significant pain points in the actual installation process of flange sealing structures.

[0004] To address this issue, existing research has proposed a class of solutions that employ invasive sensing methods to monitor the contact state of flange seals. For example, a "smart gasket" is created by embedding a piezoelectric ceramic patch between two pre-machined flat metal rings and introducing it into the structure as a sensor to monitor changes in bolt preload; or a piezoelectric sensor is embedded between the seal and the flange contact surface to monitor changes in seal contact stress in real time. However, a drawback of these methods is that they require drilling holes or slots in the flange sealing system to encapsulate the sensor, which compromises the structural integrity of the flange sealing system and weakens the flange's structural strength.

[0005] In modern industrial environments, different mechanical structures generate varying sources of acoustic emission (AE). Some are naturally induced within the structure due to material interactions, while others are introduced into the structure under test as needed. Research has found that acoustic emission signals can be introduced into the structure under test by using an impact hammer, and AE wave propagation can be captured using an AE sensor. The resulting acoustic emission signals can then be used to assess and classify damage and defects within the structure. Therefore, this invention focuses on flange seals and proposes a non-invasive, real-time detection method based on acoustic emission sensors for flange seals in a grooved state, ensuring sealing reliability during flange installation. Summary of the Invention

[0006] The purpose of this invention is to provide a non-destructive testing method for flange seals in the groove state based on acoustic emission. This method performs non-invasive real-time non-destructive testing on flange seals in the groove state during flange installation, preserving the structural integrity of the flange sealing system. The method also ensures testing accuracy through intelligent algorithms and avoids the risk of seal damage that may occur from re-opening the cover for testing.

[0007] The technical solution adopted in this invention is:

[0008] A non-destructive testing method for flange seals in a grooved state based on acoustic emission includes the following steps:

[0009] Step 1: During flange installation, the AE sensor and excitation device are respectively arranged on both sides of the flange sealing structure, and the AE sensor and excitation device are connected to the data processing terminal equipment.

[0010] Step 2: The excitation device is activated and acts on the flange sealing structure to generate excitation vibration. The AE sensor collects the excitation vibration generated by the excitation device and transmits it as an AE signal to the data processing terminal equipment.

[0011] Step 3: The data processing terminal equipment analyzes and judges the condition of the flange sealing structure based on the AE signal.

[0012] Furthermore, in the flange sealing structure, the excitation signal of the lower end cover of the flange passes through different media, resulting in different signal attenuation. Based on this principle, the state of the flange seal in the groove can be preliminarily judged. The principle of monitoring the state of the flange seal in the groove based on the AE signal in this paper is as follows: (1) The signal sensed by the AE sensor originates from the excitation vibration, which propagates in the medium in the form of waves. (2) When the vibration propagates in different media, its vibration attenuation rate is also different. The attenuation in solids is less than that in gases. (3) The flange sealing groove as a whole can be regarded as the medium for vibration propagation. When there is a sealing ring in the sealing groove, it is regarded as a solid as a whole, and the attenuation rate is small. When the sealing ring is damaged, there is a certain amount of air medium, and the attenuation rate will increase to a certain extent. When there is no sealing ring in the sealing groove, it is regarded as an air medium, and the attenuation rate is the largest at this time.

[0013] Preferably, the flange sealing structure includes an upper flange cover, a sealing layer, and a lower flange cover arranged in sequence; wherein, the sealing layer includes a sealing groove provided between the upper flange cover and the lower flange cover and a sealing element disposed in the sealing groove.

[0014] Preferably, the seal is an elastomeric sealing ring.

[0015] Preferably, a simplified cross-sectional view of the flange sealing structure is shown below. Figure 1 As shown, the flange sealing system mainly consists of three media layers: an upper flange cover, a sealing layer, and a lower flange cover. The blue part represents the sealing element within the sealing groove. When there is no sealing element in the sealing groove, the sealing layer is represented by a white block. Since the flange sealing system is a typical static seal with no relative movement between the sealing surfaces, an excitation signal wave is generated by striking the flange end cover with an excitation hammer. The excitation signal enters the lower flange end cover and then, after passing through the three media layers, the response signal wave is transmitted to the point where the AE signal sensor is located. The response signal is sensed by the AE sensor and transmitted to the data processing terminal equipment, where various signal analysis and processing methods can then be used for relevant processing and analysis. When the sealing element is in an abnormal state within the groove, due to the different attenuation rates of the sealing medium, the response signal collected by the AE sensor after the excitation signal passes through the sealing layer will also show certain differences.

[0016] Preferably, the excitation device is an excitation hammer, used to strike the flange end cover to generate excitation.

[0017] Preferably, in step 3, the data processing terminal device determines whether the seal in the flange sealing structure is intact in the groove state based on the degree of attenuation of the AE signal in different media of the flange sealing structure.

[0018] Preferably, in step 3, the specific process of analyzing and determining the flange sealing structure based on the AE signal is as follows:

[0019] Step 3.1: Perform time-domain and frequency-domain data processing on the acquired AE signal, extract the signal feature values ​​in the time and frequency domains, and then find the key features that can effectively reflect different states.

[0020] Step 3.2: Based on the extracted signal feature values, determine the state of the corresponding flange sealing structure's sealing element in the groove.

[0021] The state of the flange sealing structure's sealing element in the groove includes three different types of flange sealing ring groove states: "normal in groove", "partially bonded", and "partially defective".

[0022] Preferably, the normal state in the groove includes two states: intact sealing and good adhesion.

[0023] In step 3.1, the extracted signal feature values ​​include the signal energy value, ring count, amplitude value, time-domain peak-to-peak value, time-domain waveform factor, time-domain peak factor, and root mean square.

[0024] Furthermore, the extracted signal features also include duration, rise count, rise time, root mean square, and average signal level.

[0025] In step 3.2, the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal are calculated based on the signal characteristic values. Then, based on the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal, the state of the corresponding flange sealing structure's seal in the groove is determined.

[0026] In step 3.2, the specific process of determining the state of the sealing element of the corresponding flange sealing structure in the groove is as follows: when the average energy attenuation rate is less than the set value A, the average amplitude attenuation rate is less than the set value B1, and the average cumulative ringing count is greater than the set value C1 and less than the set value C2, the sealing structure is in normal groove condition.

[0027] When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B2, and the average cumulative ring count is greater than the set value C2, the sealing structure is in a local defect.

[0028] When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B1 but less than the set value B2, and the average cumulative ring count is less than the set value C1, the sealing structure is in a state of partial debonding.

[0029] The beneficial effects of this invention are:

[0030] In this invention, during flange sealing installation, an AE sensor and an excitation device are respectively arranged on both sides of the flange sealing structure. The excitation device acts on the flange sealing structure to generate excitation vibration, and the AE sensor collects the vibration signal generated by the excitation device as the AE signal. The data processing terminal equipment analyzes and judges the condition of the flange sealing structure based on the AE signal. It can perform non-invasive real-time non-destructive testing of the flange seal in the groove state as needed during the installation process. It can preserve the structural integrity of the flange sealing system, improve the detection accuracy through intelligent algorithms, and avoid the risk of damage to the flange seal caused by the re-opening inspection process. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the operation of the non-destructive testing method for flange seals in the groove state based on acoustic emission in an embodiment of the present invention.

[0032] Figures 2a-2b The embodiments of the present invention simulate and construct models of flange seals under different states, wherein,

[0033] Figure 2a This is a simulation model of the flange seal under normal conditions in this embodiment of the invention;

[0034] Figure 2b This is a model of a flange seal under abnormal conditions, constructed for simulation purposes in this embodiment of the invention.

[0035] Figure 3 This is the mesh defined in the groove state model of the flange seal under normal sealing conditions in the simulation of this embodiment of the invention.

[0036] Figure 4 This refers to the model boundary settings for the acoustic emission elastic wave physical field used in the simulation analysis of this invention.

[0037] Figures 5a-5j The simulation results obtained from the simulation calculations in this embodiment of the invention include important instantaneous state diagrams of the AE signal during the entire transmission process in different flange seal states under groove conditions, wherein:

[0038] Figure 5a This is a diagram showing the AE signal excitation stage in the normal sealing state according to an embodiment of the present invention;

[0039] Figure 5b This is a diagram showing the AE signal excitation stage under abnormal sealing conditions in an embodiment of the present invention.

[0040] Figure 5c This is a diagram showing the propagation stages of the AE signal under normal sealed conditions in an embodiment of the present invention.

[0041] Figure 5dThis is a diagram illustrating the propagation stages of the AE signal under abnormal sealing conditions in an embodiment of the present invention.

[0042] Figure 5e This is a diagram of the first-stage propagation of the AE signal under normal sealed conditions in an embodiment of the present invention.

[0043] Figure 5f This is a diagram of the first-stage propagation of the AE signal under abnormal sealing conditions in an embodiment of the present invention.

[0044] Figure 5g This is a diagram showing the second-stage propagation of the AE signal under normal sealed conditions in an embodiment of the present invention.

[0045] Figure 5h This is a diagram illustrating the second-stage propagation of the AE signal under abnormal sealing conditions in an embodiment of the present invention.

[0046] Figure 5i In this embodiment of the invention, the AE signal reaches the bottom surface under normal sealing conditions.

[0047] Figure 5j In this embodiment of the invention, the sealing abnormality state AE signal reaches the bottom surface.

[0048] Figure 6 The results are the transmitted wave signals under different sealing states obtained from the simulation calculations of this invention.

[0049] Figure 7 This is a flowchart of the non-destructive testing method for flange seals in the groove state based on acoustic emission in this invention.

[0050] Figures 8a-8c These are physical images of different flange seals of the present invention in the grooved state, wherein:

[0051] Figure 8a This is a photograph of the flange seal, which is normally sealed in its disassembled state, in its grooved state, according to the present invention.

[0052] Figure 8b This is a photograph of the flange seal in the groove state when the seal is partially detached in the disassembled state according to the present invention.

[0053] Figure 8c This is a photograph of the flange seal in the groove state when it is in a disassembled state and has a local defect.

[0054] Figure 9 This is a diagram illustrating the actual operation of AE sensor arrangement and excitation tapping during the implementation of the non-destructive testing method for flange seals in the groove state based on acoustic emission in this invention.

[0055] Figures 10a-10c The following are time-domain plots of the AE signals acquired under different sealing conditions in the groove, where:

[0056] Figure 10a This is a time-domain diagram of the AE signal under normal sealing conditions in this invention;

[0057] Figure 10b This is a time-domain diagram of the AE signal under the localized bonding state in this invention;

[0058] Figure 10c This is a time-domain diagram of the AE signal under local defect conditions in this invention.

[0059] Figure 11 This is a confusion matrix diagram of the recognition results of the state recognition classification model trained by the non-destructive testing method for flange seals in the groove state based on acoustic emission in this invention.

[0060] In the diagram: a - transmitted wave signal of normal sealing; b - transmitted wave signal of abnormal sealing; 1 - flange; 2 - seal. Detailed Implementation

[0061] 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.

[0062] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0063] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0064] Example 1

[0065] A non-destructive testing method for flange seals in the grooved state based on acoustic emission, such as... Figure 1 and Figure 7 As shown, it includes the following steps:

[0066] Step 1: During the installation of the flange sealing structure, the AE sensor and excitation device are respectively arranged on both sides of the flange sealing structure, and the AE sensor and excitation device are connected to the data processing terminal equipment.

[0067] Step 2: The excitation device is activated and acts on the flange sealing structure to generate excitation vibration. The AE sensor collects the excitation vibration generated by the excitation device and transmits it as an AE signal to the data processing terminal equipment.

[0068] Step 3: The data processing terminal equipment analyzes and determines the groove status of the flange seal based on the AE signal.

[0069] Furthermore, in the flange sealing structure, the excitation signal of the lower end cover of the flange passes through different media, resulting in different signal attenuation. Based on this principle, the state of the flange seal in the groove can be preliminarily judged. The principle of monitoring the state of the flange seal in the groove based on the AE signal in this paper is as follows: (1) The AE signal sensed by the AE sensor originates from the excitation vibration, which propagates in the medium in the form of waves. (2) When the vibration propagates in different media, its vibration attenuation rate is also different. The attenuation in solids is less than that in gases. (3) The flange sealing groove as a whole can be regarded as the medium for vibration propagation. When the sealing groove has a sealing ring, it is regarded as a solid whole with a small attenuation rate. When the sealing ring is damaged, there is a certain amount of air medium, and the attenuation rate increases to a certain extent. When there is no sealing ring in the sealing groove, it is regarded as an air medium, and the attenuation rate is the largest at this time.

[0070] Furthermore, the flange sealing structure includes an upper flange cover, a sealing layer, and a lower flange cover arranged in sequence; wherein, the sealing layer includes a sealing groove provided between the upper flange cover and the lower flange cover and a sealing element disposed in the sealing groove.

[0071] Furthermore, the sealing element is a sealing ring.

[0072] Furthermore, a simplified cross-sectional diagram of the flange sealing structure is shown below. Figure 1 As shown, the flange sealing system mainly consists of three media layers: an upper flange cover, a sealing layer, and a lower flange cover. The blue part represents the sealing element within the sealing groove. When there is no sealing element in the sealing groove, the sealing layer is represented by a white block. Since the flange sealing system is a typical static seal with no relative movement between the sealing surfaces, an excitation signal wave is generated by striking the flange end cover with an excitation hammer. The excitation signal enters the lower flange end cover and then, after passing through the three media layers, the response signal wave is transmitted to the point where the AE signal sensor is located. The response signal is sensed by the AE sensor and transmitted to the data processing terminal equipment, where various signal analysis and processing methods can then be used for relevant processing and analysis. When the sealing element is in an abnormal state within the groove, due to the different attenuation rates of the sealing medium, the response signal collected by the AE sensor after the excitation signal passes through the sealing layer will also show certain differences.

[0073] Furthermore, the excitation device is an excitation hammer, used to strike the flange end cover to generate vibration excitation.

[0074] Example 2

[0075] Based on Example 1, step 3 was further specified.

[0076] Furthermore, in step 3, based on the attenuation degree of the AE signal in different media of the flange sealing structure, the data processing terminal device determines the groove state of the flange seal based on the attenuation degree of the AE signal in different material media of the flange sealing structure.

[0077] Furthermore, the specific process for analyzing and determining the condition of the flange sealing structure based on the AE signal is as follows:

[0078] Step 3.1: Extract signal features from the acquired AE signal, extract signal feature values ​​in the time domain and frequency domain, and find key features that can effectively reflect different states.

[0079] Step 3.2: Based on the extracted signal feature values, determine the state of the corresponding flange sealing structure's sealing element in the groove.

[0080] The state of the sealing element in the groove of the flange sealing structure includes "normal in the groove", "partial adhesion" and "partial defect" for different types of flange sealing rings in the groove.

[0081] Furthermore, the normal state in the groove includes two aspects: a perfectly sealed state and a well-bonded state.

[0082] In step 3.1, the extracted signal feature values ​​include the signal energy value, ring count, amplitude value, time-domain peak-to-peak value, time-domain waveform factor, time-domain peak factor, and root mean square.

[0083] Furthermore, the extracted signal features also include duration, rise count, rise time, root mean square, and average signal level.

[0084] Further, in step 3.2, the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal are calculated based on the signal characteristic values. Then, based on the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal, the state of the corresponding flange sealing structure's seal in the groove is determined.

[0085] Furthermore, in step 3.2, the specific process of determining the state of the sealing element of the corresponding flange sealing structure in the groove is as follows: when the average energy attenuation rate is less than the set value A, the average amplitude attenuation rate is less than the set value B1, and the average cumulative ringing count is greater than the set value C1 and less than the set value C2, the sealing structure is in normal groove condition.

[0086] When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B2, and the average cumulative ring count is greater than the set value C2, the sealing structure is in a local defect.

[0087] When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B1 but less than the set value B2, and the average cumulative ring count is less than the set value C1, the sealing structure is in a state of partial debonding.

[0088] Among them, the set value A is 93%~95%; the set value B1 is 22%~24%; the set value B2 is 26%~27%; the set value C1 is 230~240; and the set value C2 is 270~280. The values ​​of A, B1, B2, C1, and C2 will be different depending on the material of the flange sealing structure.

[0089] In step 3, extracting the feature values ​​of the AE signal includes extracting eight time-domain feature parameters from the AE signal based on previous experimental research results. These parameters are:

[0090] Amplitude

[0091] Ring count (Counts)

[0092] Duration

[0093] Energy

[0094] Rise Counts

[0095] Rise Time

[0096] Root Mean Square (RMS)

[0097] Average Signal Level (ASL)

[0098] Through tests on four different types of flange sealing rings in the groove condition—"perfect seal," "good adhesion," "partial adhesion," and "partial defect"—three characteristic parameters with significant differences were identified: ① Energy attenuation rate, which calculates the attenuation rate of energy from the maximum value to the first attenuation for each data set; ② Cumulative ring count, which is the accumulation of ring counts during the attenuation process; ③ Amplitude attenuation rate, which calculates the attenuation rate of amplitude from the maximum value to the first attenuation for each data set.

[0099] Table 3-1 Comparison of Characteristic Parameters of Acoustic Emission Signals

[0100]

[0101] The comparison results are shown in Table 3-1. The characteristic parameters of a perfectly sealed and well-bonded system are almost identical, and they can be classified together as a perfectly sealed state. Furthermore, they differ significantly from the other two states. The energy attenuation rate and amplitude attenuation rate are both higher in the state with local defects than in the state with local debonding, and also higher in the states with perfectly sealed and well-bonded systems. This indicates that a greater degree of defect leads to more significant energy and amplitude attenuation. The cumulative ringing count is higher in the state with local defects than in the state with perfectly sealed and well-bonded systems, and also higher in the state with local debonding.

[0102] In step 2, before acquiring the AE signal, the sensor needs to be configured and set according to the environment, such as noise threshold and filtering settings.

[0103] In step 3, there are various signal processing and analysis methods, including but not limited to: time-domain waveform analysis, frequency-domain spectrogram analysis, wavelet packet decomposition, Hilberg-Huang transform, etc., and multiple analysis and processing methods can be selected according to the characteristics of the signal.

[0104] In step 3, the data processing terminal device is equipped with an intelligent classification model. The AE signal generated by the hammer impact in the unknown groove state is collected and input into the intelligent classification model. The intelligent classification model analyzes and judges the condition of the flange sealing structure based on the AE signal. The intelligent classification model includes, but is not limited to, decision trees, support vector machines, random forests, nearest neighbor algorithms, etc. Multiple models can be selected for training according to actual needs, and the optimal model can be selected as the final application model. The intelligent classification model can be trained using a dataset, and new data can be input into the classification model to obtain the state results and record the detection results to form sample data rules. A full life cycle prediction model can be constructed using large sample data.

[0105] Furthermore, in step 1, the AE sensor is arranged on one side surface of the flange end cover along the sealing groove or sealing element in the flange sealing structure, and the excitation point of the excitation device is arranged on the other side flange end cover surface of the flange sealing structure.

[0106] Furthermore, the AE sensor placement point set on one side of the flange end cover should be as close as possible to the sealing groove. The optimal position is the flange end cover surface directly opposite the sealing groove. The hammer impact point should be placed on the flange end cover surface on the other side, and the side or end face can be selected according to the actual structure.

[0107] In step 2, the communication connection between the sensor and the host computer, which serves as the data processing terminal, needs to be determined based on the actual settings of the sensor, and it is necessary to ensure that the host computer can control the AE sensor.

[0108] The states in step 8 include: the seal is in the groove normally, there are local defects, and there is local detachment.

[0109] The working principle of this invention: In the flange sealing structure, the excitation signal of the lower end cover of the flange passes through different media, resulting in different signal attenuation. Based on this principle, the state of the flange seal in the groove can be preliminarily judged. The principle of monitoring the state of the flange seal in the groove based on the AE signal in this paper is as follows: (1) The AE signal sensed by the AE sensor originates from the excitation vibration, which propagates in the medium in the form of a wave. (2) When the vibration propagates in different media, its vibration attenuation rate is also different. The attenuation in solids is less than that in gases. (3) The flange sealing groove as a whole can be regarded as the medium for vibration propagation. When the sealing groove has a sealing ring, it is regarded as a solid whole with a small attenuation rate. When the sealing ring is damaged, there is a certain amount of air medium, and the attenuation rate increases to a certain extent. When there is no sealing ring in the sealing groove, it is regarded as an air medium, and the attenuation rate is the largest at this time.

[0110] Simulation verification process of non-destructive testing method for flange seals in grooved state based on acoustic emission: Construct geometric models of flange seals in different grooved states, such as... Figure 2a and Figure 2b As shown, simulation analysis was performed.

[0111] The different flange seals constructed are meshed in the groove state model. Since the model is a two-dimensional structure, free triangles are used for meshing. The mesh size should be less than 1 / 2 of the AE signal wavelength. Here, the maximum mesh size is set to 1 / 6 of the AE signal wavelength.

[0112] Figure 3The mesh is based on a normal sealing state. Since the model is two-dimensional, free triangles are used for mesh generation. Regarding mesh size, if the mesh is too large, multiple AE waves will exist within a single mesh. Therefore, to ensure the integrity of the AE waveform, the mesh size should be less than half the wavelength; here, the maximum mesh size is set to 1 / 6 of the wavelength. AE signal waves have different propagation speeds in different media, and thus different wavelengths in different media. The sound speed in 1045 steel flange material is greater than that in NBR material. Therefore, with a fixed AE signal frequency, its wavelength in 1045 steel is shorter than its wavelength in NBR material.

[0113] Figure 4 These are the boundaries set for the simulation of elastic wave propagation. To simulate the hammer impact within a certain range on the upper cover, three gray hammer impact points are set on the upper cover as trigger boundaries to generate excitation signal waves. Then, the boundaries for the elastic wave are set, with other boundaries on the left, right, and upper surfaces of the geometric model set as low-reflection boundaries to simulate the propagation and dissipation of the AE wave into the distance. The remaining boundaries are set as free boundaries, allowing the AE wave to be transmitted and reflected freely. Specifically, a calculation boundary is set on the surface of the lower flange cover to simulate and calculate the sound pressure level of the transmitted AE signal.

[0114] The principle of the non-destructive testing method for flange seals in the groove state based on acoustic emission is as follows: The AE wave, in a structure consisting of two flanges sandwiching a sealing ring, needs to pass through two transmission layers—one "flange end cover" and one "sealing ring"—from the upper end cover to the lower end cover. The entire process involves five stages: "excitation triggering → normal propagation → primary transmission → secondary transmission → reaching the bottom surface." A detailed analysis of each stage is as follows:

[0115] (1) Incentive triggering stage; such as Figure 5a and 5b As shown, during the excitation triggering phase, after the simulation calculation begins, three excitation signals, which are not triggered simultaneously but have very short intervals, are emitted from the hammer excitation point set on the upper end cover. After the excitation signals are generated, they propagate outwards in the form of waves. During the excitation triggering phase, since the AE signals do not pass through different structural positions, the AE signals of different flange seals in the groove state are similar.

[0116] (2) Normal transmission stage; such as Figure 5c and 5dAs shown, during the normal propagation phase, the AE signal generated by the excitation propagates downwards in the form of a wave while continuously spreading outwards. During vertical propagation, since the leading edge of the AE signal is still within the medium on the upper end cover of the flange and has not yet reached the first transmission surface, it still exhibits a complete arc-shaped waveform. In the horizontal direction, the AE signal wave reaches the left side of the simulation model. Because the left boundary is set as an absorbing boundary in the simulation settings, after the AE signal wave spreads to the left boundary, the portion that contacts the left boundary is absorbed and no longer reflects, thus eliminating the interference of reflected waves and simulating the actual AE signal weakening to nothing after reaching the far end. In this stage, the simulated states of the AE signal in both states remain similar.

[0117] (3) Primary transmission stage. For example... Figure 5e and 5f As shown, when the AE signal wave reaches the point where the lower end face of the upper flange cover contacts the upper surface of the sealing ring, the AE signal wave will simultaneously be reflected and transmitted. The reflected wave will reverse direction and propagate upwards, while the transmitted wave will continue to propagate downwards. Only the transmitted wave will be analyzed here. After one transmission, the AE signal wave in a normal sealing state will continue to diffuse and transmit downwards in a complete arc within the NBR material medium. However, the AE signal wave in a defective sealing state will pass through the air medium in the middle and the NBR material medium on both sides. Because the acoustic emission signal attenuation of the air medium is much greater than that of the NBR material medium, the AE signal wave passing through the middle air medium experiences significant attenuation upon entering the air medium, while the AE signal waves passing through the NBR material medium on both sides experience less attenuation. Therefore, in the... Figure 5f In the simulation, the AE wave signal exhibits a situation where the arc in the middle air medium disappears. In this stage, because the media traversed by the AE waves in the two states are not exactly the same, the propagation shape of the AE waves shown in the simulation calculations changes.

[0118] (4) Secondary transmission stage. For example... Figure 5g and 5h As shown, when the AE signal wave reaches the point where the lower surface of the sealing ring contacts the upper surface of the lower flange cover, similar to the first transmission stage, the AE signal wave will undergo a second reflection and transmission. Under normal sealing conditions, the AE wave continues to transmit downwards in a complete arc shape; under defective sealing conditions, because the AE wave in the middle part is severely attenuated in the air medium, only the AE waves on both sides that pass through the NBR material medium continue to transmit downwards.

[0119] (5) Reaching the bottom surface stage. For example... Figure 5i and 5jAs shown in the lower left of both figures, a relatively weak acoustic emission (AE) wave propagates to the lower flange surface after secondary transmission. The reason for the weak AE wave energy is that the excited acoustic emission signal wave undergoes multiple medium propagation, two transmissions, and reflections, all of which lead to attenuation of the AE signal, resulting in a very weak AE signal reaching the lower flange surface. Comparing the two different states of normal sealing and defects, the AE signal wave in the normal sealing state is more pronounced than in the defective state.

[0120] Subsequently, the lower bottom surface boundary of the flange cover was selected as the calculation boundary. Based on the Comsol simulation analysis results, the transmitted wave signals under different sealing conditions were obtained, such as... Figure 6 As shown, the blue curve corresponds to the sealing defect state, and the green curve corresponds to the sealing integrity state. The AE signal wave reaches the lower end face at 14µs. The two curves are roughly similar in shape because the given excitation signal and the AE signal reaching the bottom of the flange are the same. The main difference between the two curves lies in the signal amplitude. The maximum amplitude of the curve corresponding to the normal sealing state is higher than that of the curve corresponding to the sealing defect state. This can be explained as follows: for a defective seal, the AE wave will experience greater attenuation in the air medium corresponding to the sealing defect location, while for a normal seal, the AE wave will penetrate into the seal material where attenuation is less. When the seal is normal, the AE signal can penetrate more into the lower end cover of the flange, so the AE signal amplitude will be higher than that of the abnormal seal.

[0121] To achieve non-invasive, non-destructive testing of the in-groove state of flange seals under normal operating conditions, this invention proposes a method for detecting the in-groove state of flange seals based on acoustic emission. This method primarily involves selecting points on the flange end cap surface of the flange sealing system to install AE sensors, then tapping the other end cap surface to generate AE signals, and using the AE sensors to collect the response AE signals. Subsequently, the collected AE signals are analyzed and processed to extract signal features and construct a dataset. This dataset is then used to build an intelligent classification model. This intelligent classification model enables high-accuracy detection of the in-groove sealing state of flange seals, including normal in-groove, detached from the groove, and damaged seals. Based on the state, different adjustment measures can be taken to ensure the normal operating condition of the flange sealing system and avoid major safety accidents caused by seal failure.

[0122] The technical roadmap of this invention is as follows: Figure 7 As shown in the figure, the specific implementation method will be described below with reference to the actual object.

[0123] Step 1: Confirm the location of the flange sealing groove, determine the test point, and connect to the PC host computer.

[0124] like Figures 8a-8cAs shown in the figure, this diagram illustrates three states of the flange seal in the groove: normal in groove, partial detachment, and partial defect. Next, locate the position corresponding to the sealing groove on the flange end cap, place the AE sensor at that location, and connect the sensor to the PC host computer, as shown below. Figure 9 As shown. After the sensors are installed, the host computer first initializes and configures each sensor, mainly setting the sampling frequency, signal resolution, and data storage. Then, the host computer controls the sensor signal acquisition function to begin the data trial acquisition phase. During this phase, the main checks are whether the signal exceeds the measurement range, whether the time-domain signal matches the real-time status, and whether the signal can be stored as required. Once it is confirmed that the real-time signal can be completely acquired, the formal acquisition phase begins. In the formal acquisition phase, the signal is formally acquired and stored according to the initialized storage path.

[0125] Step 2: Stimulate the tap and acquire the signal

[0126] like Figure 9 As shown, the AE sensor is placed on the upper end cover of the flange. When the hammer is used to strike the striking point on the lower end cover of the flange, an AE signal is generated and sensed and collected by the sensor, and finally transmitted to the PC host computer.

[0127] Step 3: Signal Preprocessing

[0128] like Figures 10a-10c As shown, the raw signal can be imported into relevant signal analysis software to display the AE signal generated by the impact. Before formal signal analysis and processing, signal preprocessing is necessary, mainly including environmental noise removal and signal time-frequency analysis. Environmental noise removal involves acquiring the signal in the unimpacted state of the flange, then performing time-frequency analysis to obtain the characteristic frequencies of environmental noise. A band-stop filter will then be used to filter out the environmental noise in subsequent signals. Signal time-frequency analysis involves performing a brief time-frequency analysis of the signal to check its quality, identifying issues such as continuous excitation or insufficient excitation, ensuring that its quality meets the expected analysis results.

[0129] Step 4: Signal Feature Extraction

[0130] Based on the principle that the time-frequency characteristics of acoustic emission signals differ under different sealing conditions, feature extraction can be performed on the signals to extract discriminative signal features. After multiple signal acquisitions, equal amounts of signals from normal sealing, partial debonding, and local defects were selected to extract their time-domain feature values ​​of acoustic emission signals. Here, features such as time-domain peak-to-peak value, time-domain waveform factor, time-domain peak factor, ring count, energy value, root mean square (RMS), and amplitude of the AE signal were extracted. Based on the principle of clustering features from the same state and dispersing features from different states, and to improve the discriminative power of the state features and avoid overfitting during classifier training, acoustic emission feature parameters such as amplitude, energy, and RMS were ultimately selected as the sample dataset. The signal characteristics corresponding to the three features are shown in Table 1.

[0131] Table 1. Characteristic values ​​of AE time-domain signals and their application features

[0132]

[0133] Subsequently, 180 signal samples from 6 groups of 10 taps each of the 3 signal types were extracted, and their feature values ​​were extracted. A significance analysis was performed on the feature value dataset. The ANOVA significance analysis is shown in Table 2. It can be seen that the significance of each feature value is generally less than 0.05, indicating that the features used have good significance in classifying different states.

[0134] Table 2. ANOVA significance analysis

[0135]

[0136] Step 5: Training the intelligent classification model for state recognition

[0137] The SVM intelligent classification model was trained using the sample dataset, and the classification model with the best recognition performance and its results are shown below. Figure 11 As shown in the confusion matrix, the model's recognition accuracy is 88.3%. Here, 1, 2, and 3 represent normal in the groove, localized debonding, and localized defects, respectively.

[0138] In summary, the present invention has the following three characteristics: (1) Non-destructive: It adopts non-invasive acoustic emission detection technology, which overcomes the shortcomings of traditional detection that requires repeated disassembly and assembly of the sealing structure, preserves the structural integrity of the flange sealing system, and avoids the risk of damage to the sealing components caused by repeated opening of the cover for detection. (2) Real-time: The detection of the flange sealing component in the groove state based on acoustic emission signal can be performed in real time as needed, and there is no need to disassemble and assemble the flange sealing system. It can ensure that the flange sealing system can be detected in normal working condition, without stopping the relevant equipment for detection, which effectively reduces the cost of sealing detection. (3) Accuracy: The result detected by this method is the current groove state of the sealing component, which avoids the human error introduced by the need to disassemble and assemble the flange end cover in "uncovering detection", as well as the multiple compression-relaxation cycles experienced by the sealing gasket, and ensures the original contact stress distribution.

[0139] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "upper" and "lower" are used only to distinguish the relative position of one entity or operation from another entity, and do not necessarily require or imply any such actual relative positional relationship between these entities. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0140] 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-destructive testing method for flange seals in a grooved state based on acoustic emission, characterized in that: Includes the following steps: Step 1: Arrange the AE sensor and excitation device on both sides of the flange sealing structure respectively, and connect the AE sensor and excitation device to the data processing terminal equipment. Step 2: The excitation device is activated and acts on the flange sealing structure to generate excitation vibration. The AE sensor collects the AE signal generated by the excitation device and transmits it to the data processing terminal equipment. Step 3: The data processing terminal equipment analyzes and determines the groove status of the flange seal based on the AE signal. In step 3, the specific process of determining the groove state of the flange seal based on AE signal analysis is as follows: Step 3.1: Process the acquired AE signal, extract the signal feature values, and identify the key features that can effectively reflect different states. Step 3.2: Based on the extracted signal feature values, determine the state of the corresponding flange sealing structure's sealing element in the groove. The state of the sealing element in the groove of the flange sealing structure includes "normal in the groove", "partial adhesion" and "partial defect" for different types of flange sealing rings in the groove; In step 3.2, the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal are calculated based on the signal characteristic values. Then, based on the average energy attenuation, average cumulative ring count, and average amplitude attenuation of the signal, the state of the corresponding flange sealing structure's seal in the groove is determined. In step 3.2, the specific process of determining the state of the sealing element of the corresponding flange sealing structure in the groove is as follows: when the average energy attenuation rate is less than the set value A, the average amplitude attenuation rate is less than the set value B1, and the average cumulative ringing count is greater than the set value C1 and less than the set value C2, the sealing structure is in normal groove condition. When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B2, and the average cumulative ring count is greater than the set value C2, the sealing structure is in a local defect. When the average energy attenuation rate is greater than the set value A, the average amplitude attenuation rate is greater than the set value B1 and less than the set value B2, and the average cumulative ring count is less than the set value C1, the sealing structure is in a state of partial debonding. The flange sealing structure includes an upper flange cover, a sealing layer, and a lower flange cover arranged in sequence; wherein, the sealing layer includes a sealing groove provided between the upper flange cover and the lower flange cover and a sealing element provided in the sealing groove.

2. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: The sealing element is a sealing ring.

3. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: The excitation device is an excitation hammer, which is used to strike the flange end cover to generate excitation.

4. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: The AE sensor is arranged on one side of the flange end cover along the sealing groove or sealing element in the flange sealing structure, and the excitation point of the excitation device is arranged on the other side of the flange end cover surface of the flange sealing structure.

5. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: In step 3, the data processing terminal device determines whether the seal in the flange sealing structure is intact in the groove state based on the attenuation degree of the AE signal in different material media of the flange sealing structure.

6. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: In step 3.1, the extracted signal feature values ​​include the signal energy value, ring count, amplitude value, time-domain peak-to-peak value, time-domain waveform factor, time-domain peak factor, and root mean square.

7. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: The setting value A is 93%~95%; the setting value B1 is 22%~24%; the setting value B2 is 26%~27%; the setting value C1 is 230~240; and the setting value C2 is 270~280.

8. The non-destructive testing method for flange seals in the grooved state based on acoustic emission as described in claim 1, characterized in that: In step 1, the AE sensor is arranged on one side surface of the flange end cover along the sealing groove or sealing element in the flange sealing structure, and the excitation point of the excitation device is arranged on the other side flange end cover surface of the flange sealing structure. The AE sensor placement point on one side of the flange end cover is located on the flange end cover surface directly opposite the sealing groove, while the hammer impact point needs to be placed on the flange end cover surface on the other side.

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