System and method for measuring bolt axial force of electrolytic cell in real time based on ultrasonic waves

Abstract

The invention discloses an ultrasonic-based electrolytic bath bolt axial force real-time measurement system and method, and the system comprises an ultrasonic sensing network, a parameter storage unit, a central analysis server, an early warning unit, a cloud platform and a visual terminal. By combining Hooke's law and inherent physical parameters of the bolt, accurate calculation and real-time monitoring of the axial force of the bolt are realized. The method solves the technical problems that a traditional torque indirect measurement method is large in error and cannot dynamically monitor, can reflect the stress state of the electrolytic cell in real time, ensures the stability of the sealing performance and the electrical performance of the electrolytic cell, has the advantages of being high in anti-jamming capability, wide in adaptability and convenient to operate, and is suitable for full-life-cycle monitoring of various large electrolytic cell bolts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolytic cell detection and operation and maintenance, in particular to an electrolytic cell bolt axial force real-time measurement system and method based on ultrasonic waves; and is especially suitable for bolt axial force monitoring of large electrolytic cells in the fields of chlor-alkali industry and non-ferrous metal electrolysis. BACKGROUND

[0002] As the core equipment of electrolysis process, the sealing performance and electrical performance of the electrolytic cell directly determine the production efficiency and operation safety. The cell body is fastened by a large number of high-strength bolts, and the sealing of the electrolytic cell depends on the stability of the bolt pretightening force (i.e. axial force). The bolt axial force is not only the key to maintaining the sealing surface pressure, but also the core index reflecting the overall stress state of the electrolytic cell. Insufficient axial force will lead to electrolyte leakage, causing safety accidents, and will also cause the contact resistance between the electrode plate and the diffusion layer current collector to increase, resulting in an increase in cell voltage, an increase in energy consumption, and a decrease in efficiency. Excessive axial force will cause plastic deformation of the bolt and cracking of the electrolytic cell shell, directly affecting the stability of the electrical performance and causing huge economic losses.

[0003] The existing electrolytic cell bolt axial force measurement mainly adopts two methods: one is the torque wrench measurement method, which indirectly estimates the axial force by controlling the bolt tightening torque. However, the conversion between torque and axial force is affected by factors such as bolt surface roughness, lubrication state, and thread friction coefficient, and the error is generally as high as 15%-20%, which cannot meet the high-precision sealing requirements. The second is the strain gauge measurement method, which directly measures the strain by pasting strain gauges on the surface of the bolt. However, the strain gauge is easily affected by high temperature and corrosive gas in the electrolytic cell working environment, has a short service life, and is complex to install, making it impossible to achieve long-term real-time monitoring.

[0004] In addition, the existing technologies are difficult to adapt to the demand for synchronous monitoring of multiple bolts of the electrolytic cell, and lack a temperature compensation mechanism. Temperature fluctuations during the operation of the electrolytic cell will cause changes in the Young's modulus of the bolt material and a shift in the ultrasonic wave propagation speed, further amplifying the measurement error. Therefore, developing a high-precision, real-time, and anti-interference electrolytic cell bolt axial force measurement technology has become the key to solving the operation and maintenance problems of the electrolytic cell. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide an electrolytic cell bolt axial force real-time measurement system and method based on ultrasonic waves, which realizes accurate and dynamic monitoring of the bolt axial force, reflects the stress state of the electrolytic cell in real time, and ensures the sealing performance and operation safety of the electrolytic cell.

[0006] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows: The utility model relates to an ultrasonic based electrolytic cell bolt axial force real -time measurement system, including the ultrasonic monitoring mechanism that sets up in monitoring bolt, the ultrasonic monitoring mechanism includes high frequency ultrasonic probe, signal conditioning module and acoustic time acquisition submodule, high frequency ultrasonic probe fixed mounting is in the end of the bolt of being monitored, signal conditioning module carries out modulation and filtering to the ultrasonic wave signal of emission; The acoustic time acquisition submodule accurately captures the propagation time data of the ultrasonic wave in the bolt, denoted as real-time acoustic time t1; the acoustic time of the detected bolt in the pre-tightening state is denoted as initial acoustic time t0, t0 as the reference data for subsequent measurement; and the acoustic time variation Δt = |t1-t0| is calculated. According to the acoustic time variation, the real-time elongation ΔL of the bolt is calculated in combination with the acoustic velocity of the ultrasonic wave in the bolt material; and the real-time axial force F of the bolt is calculated according to the real-time elongation and the physical parameters of the monitored bolt, including the bolt stress cross-sectional area A, the material Young's modulus E, and the effective length L. The real-time axial force F = (A × E × ΔL) / L.

[0007] Further, the temperature compensation module is further included for modifying the parameters, according to the correction curve of the Young's modulus E of the bolt material varying with temperature and the temperature correction formula of the ultrasonic wave propagation velocity v, and the actual working temperature T of the monitored bolt is collected through the temperature collection module; the corrected Young's modulus E is calculated as ET and the corrected ultrasonic wave propagation velocity v is calculated as vT through the actual working temperature T, The vT = v0 × (1 + α × T) v0 is the propagation velocity of the ultrasonic wave in the bolt material at the standard ambient temperature; α is the acoustic velocity temperature coefficient of the bolt material.

[0008] Further, the high-frequency ultrasonic probe is used for emitting and receiving ultrasonic wave signals to the target bolt of the electrolytic cell, the working frequency range is 2MHz-15MHz, and the high-frequency ultrasonic probe is a longitudinal wave ultrasonic probe.

[0009] Further, the utility model further includes: A parameter storage unit is used for pre-storing the physical parameters and calibration parameters of the target bolt, including the bolt stress cross-sectional area A, the material Young's modulus E, the effective length L, the propagation velocity v0 of the ultrasonic wave in the bolt material, and the axial force preset threshold range corresponding to the sealing performance of the electrolytic cell; A central analysis server is electrically connected with the ultrasonic wave sensing network and the parameter storage unit, receives the real-time acoustic time data transmitted by the acoustic time acquisition submodule, has a built-in algorithm engine, and is used for executing the real-time axial force calculation, temperature compensation, stress cloud map generation, and diagnostic logic; Early warning unit: electrically connected with the data operation unit, when the calculated axial force F exceeds the threshold range preset by the parameter storage unit, automatically trigger the sound and light early warning or remote signal transmission; Cloud platform and visual terminal: including touch display screen and data interface, for real-time display of bolt axial force, elongation, acoustic time data and electrolytic cell stress state, providing stress cloud chart and early warning information, supporting parameter modification, data export and historical data query.

[0010] Further, the parameter storage unit adopts a partition storage architecture, which is divided into four independent partitions: "basic parameter area", "calibration parameter area", "threshold parameter area" and "historical data area"; Basic parameter area: stores fixed information of bolt physical parameters (A, E, L), probe model and channel number, supports one-time writing or batch import, and the data retention time is unlimited; Calibration parameter area: stores ultrasonic wave propagation speed v0, temperature correction coefficient a, actual working temperature T and corrected ultrasonic wave propagation speed vT, automatically updates after each calibration, retains calibration records for easy tracing of calibration accuracy; Threshold parameter area: stores or inputs independent threshold range for different bolts, which adapts to the sealing requirements of different positions of the electrolytic cell; Historical data area: adopts a circular coverage storage method, supports data export, and is used for trend analysis and fault tracing.

[0011] Further, the central analysis server is built-in temperature compensation module, provided with temperature sensor to monitor the working temperature of the bolt, the temperature compensation module pre-stores the correction curve of Young's modulus E of the bolt material with temperature change and the temperature correction formula of ultrasonic wave propagation speed v, and real-time corrects the values of E and v according to the working temperature of the electrolytic cell.

[0012] Further, the central analysis server is built-in moving average filtering algorithm, which includes filtering processing of the collected acoustic time data, eliminating transient errors caused by vibration and electromagnetic interference, and when the deviation of certain acoustic time data and historical average value exceeds 5%, it is determined as abnormal data and is eliminated, ensuring the stability of the calculation result.

[0013] An electrolytic cell bolt axial force real-time measurement method based on ultrasonic wave, the measurement method is based on Hooke's law, the bolt elongation is calculated by the change of ultrasonic acoustic time, and then the axial force is derived, the specific steps are as follows, including the following steps: 1) Device deployment and parameter initialization: fix the high-frequency ultrasonic probe on the end face of the target bolt of the electrolytic cell, input the physical parameters (A, E, L) of the target bolt through the cloud platform and visual terminal, and calibrate the ultrasonic wave propagation speed v0; The calibration process is: taking a standard sample with the same material and specification as the target bolt as the object, emitting ultrasonic waves to it, recording its ultrasonic wave propagation time as t standard, combining the known length of the standard sample as L standard, and calculating v0=L standard / t standard; 2) Initial reference value acquisition: when the electrolytic cell is not running or the bolt is in the initial pre-tightening state, the ultrasonic wave sensing network emits ultrasonic waves to the target bolt, and records the initial acoustic time t0 as the reference data for subsequent measurement; 3) Real-time acoustic time monitoring: during the operation of the electrolytic cell, the ultrasonic detection unit continuously emits ultrasonic waves to the target bolt, and real-time acoustic time t1 is collected, and the acoustic time change Δt=|t1-t0| is calculated by the data operation unit; 4) Temperature compensation and parameter correction: the temperature compensation module collects the real-time working temperature T of the electrolytic cell, adjusts the Young's modulus E to ET according to the pre-stored correction curve, and calculates the corrected ultrasonic wave propagation velocity vT according to the formula vT=v0×(1+α×T); 5) Elongation and axial force calculation: the central analysis server calculates the real-time elongation ΔL of the bolt according to the corrected vT and acoustic time change Δt through the formula ΔL=(vTΔt) / 2; then ET, A, L, ΔL are substituted into the formula F=(A×ET×ΔL) / L to obtain the real-time axial force F of the bolt; 6) Stress state judgment and early warning: the central analysis server compares the real-time axial force F with the threshold range preset in the parameter storage unit, if F is within the threshold range, it is determined that the stress of the electrolytic cell is normal, and the sealing performance meets the standard; if F is lower than the lower threshold, it is determined that the sealing is at risk of failure; if F is higher than the upper threshold, it is determined that the bolt is overloaded or the structure stress of the electrolytic cell is out of standard, and the warning unit triggers the corresponding warning immediately; 7) Data recording and output: the cloud platform and visual terminal display the axial force F, elongation ΔL, working temperature T and stress state in real time, and automatically store historical data, which supports exporting to terminal equipment for trend analysis through data interface.

[0014] Further, the calibration process of the standard sample in step 1 needs to be carried out at 25°C standard environment temperature, and the calibration is not less than 3 times, and the average value of v0 is taken as the reference propagation speed, to ensure that the calibration error is ≤0.1%.

[0015] Further, the warning level of the warning unit in step 6 is divided into three levels, and a "dynamic threshold+delay trigger" design is adopted, the first level warning of the axial force F close to the threshold boundary is yellow prompt; the second level warning of the axial force F exceeding the threshold within 5% is orange audible and light alarm; the third level warning of the axial force F exceeding the threshold by more than 5% is red audible and light alarm and sends a remote alarm signal to the operation and maintenance terminal at the same time.

[0016] The advantages and beneficial effects of the present application are: 1. High measurement accuracy: With microsecond-level timing accuracy of ultrasonic waves, direct correlation of micro-elongation of bolts, and temperature compensation mechanism, the axial force measurement error is ≤2%, far superior to the traditional torque method (15%-20% error), meeting the high-precision sealing requirements of electrolytic cells and industrial-level measurement requirements.

[0017] 2. Real-time dynamic monitoring: Sampling frequency can reach 1Hz-10Hz, not only monitoring individual bolts, but also macroscopically grasping the health status of the entire electrolytic cell through stress distribution cloud map, real-time capturing of bolt axial force changes, timely detection of abnormal axial force decay, mutation, etc., avoiding leakage or structural damage risks. Ensure that the sealing performance of the electrolytic cell is always in a controlled state.

[0018] 3. Strong anti-interference ability: Through signal filtering, high-temperature coupling agent, temperature compensation, etc., it can withstand high temperature, electromagnetic interference, and corrosive environment of electrolytic cells, and adapt to long-term stable operation. Suitable for harsh industrial scenes.

[0019] 4. Data-driven decision-making: Accumulated long-term axial force data provides a solid data foundation for predictive maintenance, optimization of fastening process, and extension of equipment life. Establish a fixed sensing network for uninterrupted or on-demand monitoring throughout the life cycle of the electrolytic cell, realizing the transition from "periodic maintenance" to "condition monitoring".

[0020] 5. Convenient operation and maintenance: Non-contact measurement, no need to stop operation and disassemble bolts, cloud platform and visual terminal interface are intuitive, support data export and remote early warning, reduce operation and maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a logic diagram of an electrolytic cell bolt axial force real-time measurement system based on ultrasonic waves of the present application; Figure 2 is a structural schematic diagram of an electrolytic cell bolt axial force real-time measurement system based on ultrasonic waves in the present application; Figure 3 is a partial enlarged schematic diagram of a magnetic seat in the present application; In the figure: 1, ultrasonic monitoring mechanism; 2, magnetic seat; 3, monitored bolt; 4, magnetic core; 5, mounting seat; 6, magnetic plate; 7, through hole; 8, bolt end face; 9, reinforced shell; 10, gasket assembly; 11, positioning protrusion; 12, positioning groove; 13, coupling agent storage groove; 14, filling cavity; 15, communication pipe; 16, liquid injection hole; 17, exhaust valve; 18, electrolytic cell end pressure plate; 19, high-frequency ultrasonic probe. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application are further described below in conjunction with examples. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0023] An ultrasonic-based electrolytic cell bolt axial force real-time measurement system, as shown in the figure, mainly consists of an ultrasonic sensing network, a parameter storage unit, a central analysis server, a warning unit, a cloud platform and a visualization terminal, and each unit works cooperatively to realize the full-process automation from signal collection to result output. Figure 1 The ultrasonic sensing network: the core is a high-frequency ultrasonic probe 19, which includes a signal conditioning module and a time-of-flight acquisition submodule, and each probe is fixedly installed at the end of a monitored bolt 3. This is the front-end sensing layer of the system, and a longitudinal wave ultrasonic probe with high temperature resistance, magnetic resistance and IP67 or above protection level is selected. A small groove or plane is processed at the center of the end of the detected target bolt, and the probe is fixed in this position by using a high-strength magnetic seat 2 or a special fixture. The coupling surface between the probe and the bolt end surface 8 is kept stable and good acoustic coupling by high-temperature coupling agent. All high-frequency ultrasonic probes 19 are connected to the on-site signal concentrator box located on the electrolytic cell operation platform through shielded twisted pair or coaxial cable. The cable should be laid in a high-temperature resistant cable slot to avoid mechanical damage and high-temperature baking.

[0024] The ultrasonic monitoring mechanism 1 is composed of a high-frequency ultrasonic probe 19, a signal conditioning module and a time-of-flight acquisition submodule. The high-frequency ultrasonic probe 19 adopts a longitudinal wave type, and the working frequency range is 2MHz-15MHz, which can effectively penetrate the bolt and accurately reflect the signal. It is installed at the end of the monitored bolt 3 through a magnetic fixing structure (using neodymium iron boron strong magnetic material, suction force ≥50N), and 1-3mm adjustable shims are provided at the bottom to adapt to the flatness error of the bolt end surface 8 ≤0.5mm. A 3-8mm thick high-temperature silicon coupling agent layer is applied to the end surface to ensure close fitting and wear resistance and corrosion resistance in the electrolytic cell working environment of-20℃-150℃. The signal conditioning module is responsible for power amplification of the transmitted ultrasonic signal, filtering, noise reduction and gain adjustment of the received reflected signal to eliminate signal interference caused by electrolytic cell vibration and electromagnetic interference; the time-of-flight acquisition submodule accurately captures the ultrasonic propagation time data with a time resolution of 0.1μs, providing high-precision raw data for subsequent calculation.

[0025]

[0026] ​Data storage unit: This unit is installed in the field control cabinet, close to the electrolytic cell. Hardware components: contains multi-channel ultrasonic pulse emission and reception card, high-precision time-to-digital converter, multi-channel switch and temperature acquisition module. It is responsible for transmitting high-voltage pulse excitation signals to each ultrasonic probe in sequence, and receiving and digitizing the returned echo signals with high precision. Its core task is to accurately measure the time of flight of ultrasonic waves from transmission to reception, i.e. sound time, with a measurement accuracy of nanoseconds.

[0027] And this unit adopts the partition storage architecture of "basic parameter area + calibration parameter area + threshold parameter area + historical data area", realizing data classification management and efficient calling. The basic parameter area stores fixed information such as bolt stress cross-sectional area A, material Young's modulus E, effective length L, probe model, channel number, etc., supports one-time writing or batch import, and data retention is unlimited; The calibration parameter area stores calibration data such as ultrasonic standard propagation speed v0, temperature correction coefficient α, real-time working temperature T, corrected sound speed vT, etc. After each calibration, it is automatically updated and records are kept to facilitate tracing the calibration accuracy; The threshold parameter area can set independent axial force threshold range according to the sealing requirements of bolts at different positions of the electrolytic cell; The historical data area adopts a circular coverage storage method, supports data export, and is used for axial force trend analysis and fault tracing, and the storage interval can be flexibly set between 1s-3600s.

[0028] Central analysis server: This is an industrial computer or server. Built-in dedicated analysis software, including sound time extraction module: uses cross-correlation algorithm or threshold detection method to accurately calculate the sound time value t from the collected echo signal. Temperature compensation module: receives signals from the platinum resistance thermometer installed near the bolt. According to the formula, the sound speed is corrected in real time, or the sound time-temperature fitting relationship is established for compensation. Axial force calculation module: executes the core calculation logic. Diagnosis and early warning module: performs axial force range judgment and uniformity analysis.

[0029] As the data processing core of the system, the central analysis server is electrically connected with the ultrasonic monitoring mechanism 1 and the parameter storage unit, and is provided with an algorithm engine and multiple function modules. The core functions thereof include: 1. receiving real-time acoustic time data transmitted by the acoustic time acquisition submodule, performing an axial force calculation logic, converting an acoustic time change into an elongation, and then combining with bolt physical parameters to derive real-time axial force; 2. a temperature compensation module is built-in, real-time bolt temperature is obtained through a temperature sensor (collection accuracy ±0.5℃), Young's modulus E is corrected to ET (correction accuracy ≤0.5%) and sound speed v0 is corrected to vT (correction accuracy ≤0.3%) according to a pre-stored correction curve and formula; 3. a moving average filtering algorithm is carried, acoustic time data is filtered, and an “abnormal data elimination” function is provided, when single acoustic time data deviates from historical average value by more than 5%, it is automatically determined as abnormal data and eliminated, to ensure stability of calculation results; 4. a stress cloud of the electrolytic cell is generated, axial force data and geographic position information of all monitoring bolts are combined, and stress distribution uniformity of the cell body is intuitively displayed.

[0030] The early warning unit is electrically connected with the central analysis server, adopts a three-level early warning mechanism of “dynamic threshold + delay trigger”, and avoids false alarms caused by instantaneous fluctuations: the first level of early warning (yellow prompt) corresponds to axial force F close to the threshold boundary and lasting for ≥30s, and only a display prompt is given on the visual terminal; the second level of early warning (orange audible and visual alarm) corresponds to axial force exceeding the threshold within 5% and lasting for ≥10s, intermittent audible and visual alarm is given; the third level of early warning (red audible and visual alarm) corresponds to axial force exceeding the threshold by more than 5%, continuous audible and visual alarm is given, a remote signal is sent to the operation and maintenance terminal at the same time, and even a “load reduction” signal of the electrolytic cell control system is triggered. The cloud platform and the visual terminal provide a humanized man-machine interface, including a real-time monitoring interface (axial force (accurate to 0.1kN), elongation (accurate to 0.001mm), acoustic time and temperature data are displayed in the form of a dashboard and numbers), a parameter setting interface (bolt parameters can be manually input or scanned and input, and temperature correction coefficient α preset value can be selected according to materials), a data query interface (historical data can be queried according to time and channel number, an axial force / temperature change curve can be generated, and zooming and screenshot are supported), and a system maintenance interface (probe connection, communication and power state are displayed, firmware upgrade, self-checking and fault positioning are supported).

[0031] Specifically, the measurement method matched with the scheme of the present application strictly follows a whole-process logic of “calibration-benchmark acquisition-real-time monitoring-compensation calculation-early warning recording”, and the specific steps are as follows: 1. Device deployment and parameter initialization: Fix the high-frequency ultrasonic probe 19 to the target bolt end face 8 of the electrolytic cell and apply high-temperature coupling agent. Input the physical parameters (A, E, L) of the bolt through the cloud platform. In addition, under the standard environment temperature of 25°C, test the standard sample with the same material and specification as the target bolt, emit ultrasonic waves, and record the propagation time ttag. Calculate the standard sound velocity v0(v0=Ltag / ttag) by combining the length of the standard sample Ltag. The calibration should be performed at least 3 times, and the average value should be taken to ensure that the calibration error is ≤0.1%. At the same time, set the axial force threshold range.

[0032] 2. Initial reference value collection: When the electrolytic cell is not running or the bolt is in the initial pre-tightening state, the ultrasonic monitoring mechanism 1 emits ultrasonic waves to the bolt, records the initial acoustic time t0, and uses it as the reference data for subsequent measurements to eliminate the effects of initial installation errors on the results.

[0033] 3. Real-time acoustic time monitoring: During the operation of the electrolytic cell, the ultrasonic monitoring mechanism 1 continuously emits ultrasonic waves at a set sampling frequency of 1 Hz-10 Hz, and real-time acoustic time monitoring is performed. The central analysis server calculates the acoustic time change At = |t1-t0|.

[0034] 4. Temperature compensation and parameter correction: The temperature compensation module collects the real-time working temperature T of the electrolytic cell, modifies the Young's modulus E to ET according to the pre-stored correction curve, and modifies the sound velocity v0 to vT through the formula vT=v0×(1+α×T) to eliminate the interference of temperature on the calculation accuracy.

[0035] 5. Elongation and axial force calculation: The central analysis server calculates the real-time elongation of the bolt according to the formula ΔL=(vT×Δt) / 2, and then substitutes it into the formula F=(A×ET×ΔL) / L to obtain the real-time axial force F.

[0036] 6. Stress state judgment and early warning: Compare the real-time axial force F with the threshold range in the parameter storage unit. If F is within the threshold, the stress is normal and the seal is qualified. If F is below the lower limit, it indicates a risk of seal failure. If F is above the upper limit, it indicates that the bolt is overloaded or the cell stress is out of standard. The early warning unit triggers the corresponding warning according to a three-level mechanism.

[0037] 7. Data recording and output: The cloud platform displays the axial force, elongation, temperature, and stress state in real time, automatically stores historical data, and supports export, providing trend analysis and fault troubleshooting data support for operation and maintenance personnel.

[0038] Example 1: Bolt monitoring of a 30kA electrolytic cell in a chlor-alkali plant 1. Preliminary preparation and deployment Eight M30 bolts from a 30kA electrolytic cell in a chlor-alkali plant were selected as monitoring targets. A high-frequency ultrasonic probe 19 with a working frequency of 5MHz was installed on the end face 8 of each bolt using a magnetic fixing structure, and a 5mm thick layer of high-temperature silicon-based coupling agent was applied. A multi-channel switching module was connected, and the sampling frequency was set to 5Hz to meet dynamic monitoring requirements. The physical parameters of the M30 bolts were input through a cloud platform: stress cross-sectional area A = 561mm², Young's modulus E = 206GPa, and effective length L = 200mm. The ultrasonic propagation speed was calibrated under a standard environment of 25℃. Using an M30 standard sample of the same material and specifications (length Lstandard = 200mm), the propagation time was measured in three calibrations to be 33.9μs, 33.8μs, and 33.9μs, respectively. The average value tstandard = 33.87μs was taken, and v0 = Lstandard / tstandard = 200mm / 33.87μs ≈ 5900m / s was calculated. Considering the sealing requirements of the electrolytic cell, the axial force threshold range was set to 180kN-220kN.

[0039] 2. Measurement process and results After the electrolytic cell starts up, the system collects data in real time at a sampling frequency of 5Hz: the initial acoustic time recorded under the initial pre-tightening state is t0=67.8μs; during operation, the real-time working temperature of the bolt is monitored to be T=65℃. The temperature compensation module corrects the Young's modulus E to ET=202GPa based on the pre-stored correction curve, using the formula vT=v0×(1+α×T) (the sound velocity temperature coefficient of the bolt material is α=1.2×10). -5 / ℃) The calculated value is vT = 5900 m / s × (1 + 1.2 × 10⁻⁶ ... -5 (65℃ / ℃) = 5940m / s; The real-time acoustic acquisition time t1 = 68.1 μs. The change in acoustic time Δt = |68.1μs - 67.8μs| = 0.3μs; Substitute into the elongation formula ΔL=(vT×Δt) / 2=(5940m / s×0.3×10 -6 s) / 2=0.891mm; Substitute into the axial force formula: F=(A×ET×ΔL) / L =(561mm 2 ×202GPa×0.891mm) / 200mm≈200kN, If the axial force is within the threshold range of 180kN-220kN, the electrolytic cell is considered to have normal stress and satisfactory sealing performance.

[0040] 3. Anomaly Simulation and Early Warning Response To verify the effectiveness of the early warning function, the bolt preload was artificially adjusted to simulate abnormal shaft force: when the bolt shaft force decreased to 175 kN, the system monitored t1=67.98 μs, calculated Δt=0.18 μs, ΔL=0.85 mm, F=178 kN, at this time the shaft force was close to the lower limit of the threshold, the system triggered a first-level yellow early warning, and the visual terminal displayed prompt information; continue to reduce the shaft force to 170 kN, monitor t1=67.95 μs, calculate F=170 kN, the shaft force exceeds the lower limit of the threshold by more than 5%, the system immediately triggers a second-level orange audible and light alarm, after receiving the alarm signal, the operation and maintenance personnel timely tighten the bolt to avoid the risk of electrolyte leakage, and verify the timeliness and effectiveness of the system early warning.

[0041] Example 2: Synchronous monitoring of multiple bolts of a 50 kA electrolytic cell in a non-ferrous metal electrolytic plant 1. Deployment and parameter setting Twelve M36 bolts of a 50 kA electrolytic cell in a non-ferrous metal electrolytic plant were selected as monitoring objects, a high-frequency ultrasonic probe 19 with a working frequency of 8 MHz was used, and the probe was fixed to the end face of the bolt 8 by magnetic attraction and coated with high-temperature coupling agent; the sampling frequency was set to 8 Hz to meet the higher operating condition fluctuation requirements of the electrolytic cell; the M36 bolt parameters were input: A=817 mm², E=208 GPa, L=250 mm; v0=5920 m / s was calibrated at 25°C; according to the sealing requirements of the bolts at different positions of the electrolytic cell, the threshold range of the end bolts was set to 220 kN-260 kN, and the threshold range of the middle bolts was set to 200 kN-240 kN (the sealing pressure requirement of the middle part was slightly lower than that of the end part).

[0042] 2. Monitoring and stress analysis During the operation of the electrolytic cell, the system real-time collected the shaft force data of the 12 bolts and generated a stress distribution cloud chart: within 1 hour of operation, the shaft forces of 10 bolts were stable within the threshold range, among which the shaft forces of 2 end bolts were 245 kN and 242 kN respectively, and the shaft forces of 8 middle bolts were between 210 kN and 225 kN; the shaft forces of 2 middle bolts (No. 3# and 7#) continuously decreased from the initial 220 kN to 205 kN (30 minutes after operation), at this time the shaft force was close to the lower limit of the threshold, the system triggered a first-level early warning; after a period of time, the shaft force of 3# bolt decreased to 198 kN, exceeding the lower limit of the threshold by 1%, triggering a second-level early warning, the operation and maintenance personnel quickly located the positions of 3# and 7# bolts through the stress cloud chart, found that there was slight deformation of the electrolytic cell shell in this area, which caused uneven stress on the bolts, timely adjusted the shell and tightened the bolts, finally the shaft force was restored to 215 kN, ensuring the stable operation of the electrolytic cell.

[0043] 3. Data tracing and trend analysis After 30 days of continuous operation, maintenance personnel exported historical data from the cloud platform, generating axial force variation curves for 12 bolts. Analysis revealed that the average fluctuation range of the axial force of the end bolts was ±3kN, and the average fluctuation range of the middle bolts was ±2kN, indicating good overall axial force stability. Simultaneously, a brief abrupt change in axial force was observed in bolt #7 on the 25th day of operation (from 220kN to 235kN). Combined with the temperature data at that time (T=140℃, 15℃ higher than usual), it was determined that the instantaneous axial force change was caused by thermal expansion and contraction of the bolt due to a sudden temperature rise. Since the duration was only 2 seconds, the system did not trigger an alarm, verifying the effectiveness of the "dynamic threshold + delayed trigger" design in avoiding false alarms. Based on the 30 days of historical data, maintenance personnel established a bolt maintenance cycle for this type of electrolytic cell, adjusting the original monthly manual inspection to once every two months, and combining real-time system monitoring data for on-demand maintenance, significantly reducing maintenance costs.

[0044] Example 3: The magnetic base 2 serves as the core fixing component of the high-frequency ultrasonic probe 19, such as Figure 2 , 3 As shown, the magnetic base 2 needs to balance strong adsorption, environmental adaptability, and installation flexibility. It includes a magnetic core 4 made of neodymium iron boron (NdFeB) strong magnetic material. The magnetic core 4 enables the magnetic base 2 to possess the required magnetism. The magnetic core 4 is cylindrical and has a through hole 7 along its axial direction for the ultrasonic probe to pass through. The magnetic base 2 structure also includes an externally encased reinforced shell 9. The reinforced shell 9 can be made of 1.5-2mm thick 304 stainless steel, thus protecting the magnetic core 4 from corrosive gases in the electrolytic cell environment and preventing the magnetic field from interfering with external equipment. One end of the magnetic core 4 is provided with a magnetic guide plate 6, and the other end is provided with a mounting base 5 for a high-frequency ultrasonic probe 19. The high-frequency ultrasonic probe 19 is fixed to the mounting base 5 by a threaded connection. The probe part of the high-frequency ultrasonic probe 19 is located at the end near the magnetic guide plate 6 through the through hole 7. The threaded connection of the high-frequency ultrasonic probe 19 allows for convenient disassembly and replacement during maintenance. The magnetic plate 6 is annular and 3-5mm thick. It is used to ensure that there is no stress concentration when it is in contact with the bolt end face 8, and at the same time enhances the magnetic field concentration effect, so that the overall attraction force is ≥50N, which meets the fixing requirements under the vibration condition of the electrolytic cell.

[0045] Further, in order to adapt the error of flatness, an adjustable gasket assembly 10 is arranged at the bottom of the magnetic seat 2 and below the magnetic conducting plate 6, the gasket assembly 10 is made of polytetrafluoroethylene material, which can withstand -20℃-260℃, adapt to the working temperature of the electrolytic cell; and the thickness specification is 1mm, 2mm, 3mm, which can be combined and stacked according to the flatness error (≤0.5mm) of the bolt end face 8. The gasket and the magnetic conducting plate 6 are connected through a clamping groove type connection, the gasket edge is provided with a positioning protrusion 11, and the bottom of the magnetic conducting plate 6 is provided with a corresponding positioning groove 12, so that the gasket does not deviate after installation; at the same time, the surface of the gasket is treated with frosted treatment (roughness Ra1.6), which enhances the friction force with the bolt end face 8 and further improves the fixing stability.

[0046] Further, a coupling agent storage and sealing structure is also provided, specifically, an annular coupling agent storage groove 13 is arranged around the magnetic conducting plate 6 at the bottom of the magnetic seat 2, which has a width of 5-8mm and a depth of 3-5mm, and surrounds the reinforcing shell 9 for storing high-temperature silicon-based coupling agent, the inside of the coupling agent storage groove 13 is provided with a cavity structure, and the coupling agent is injected into the cavity during installation, and the coupling agent is made of a material with elasticity, specifically, fluororubber, which has a certain elasticity and is oil and corrosion resistant; the inside of the coupling agent storage groove 13 is provided with a plurality of communication pipes 15, which pass through the magnetic conducting plate 6 radially and communicate to the through hole 7 inside the probe, so that the coupling agent is injected between the probe and the end face of the bolt, and because the coupling agent storage groove 13 has elasticity, the elastic pressure can keep the internal coupling agent at a certain pressure, so that it can completely fill the space between the probe and the bolt end face 8, and ensure that the probe and the bolt end face 8 always maintain good acoustic coupling. When the magnetic seat 2 is adsorbed to the bolt end face 8, it can effectively prevent the coupling agent from leaking, and avoid the influence of external dust and electrolyte on the coupling effect. The coupling agent storage groove 13 is provided with a liquid injection hole 16, and the top is provided with an exhaust hole, the coupling agent can be supplemented regularly through a syringe, the exhaust hole can be opened for exhaust when the coupling agent is filled for the first time, and the coupling agent can be directly injected into the coupling agent storage groove 13 when supplemented subsequently, without disassembling the magnetic seat 2, reducing the operation complexity.

[0047] The above is only the preferred embodiment of the present application, it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A real-time measurement system for the axial force of bolts in an electrolytic cell based on ultrasound, characterized in that, The bolt monitoring device comprises an ultrasonic monitoring mechanism arranged on a monitored bolt, the ultrasonic monitoring mechanism comprising a high-frequency ultrasonic probe, a signal conditioning module and a sound time acquisition submodule, the high-frequency ultrasonic probe being fixedly installed at an end of the monitored bolt, the signal conditioning module being configured to modulate and filter the transmitted ultrasonic wave signals; The sound time acquisition submodule is configured to accurately capture the propagation time data of the ultrasonic wave in the bolt, denoted as real-time sound time t1; the sound time of the detected bolt in a pre-tightening state is denoted as initial sound time t0, t0 serving as the reference data for subsequent measurement; and the sound time variation Δt = |t1-t0| is calculated; According to the sound time variation, the real-time elongation ΔL of the bolt is calculated in combination with the sound velocity of the ultrasonic wave in the bolt material; and according to the real-time elongation and the physical parameters of the monitored bolt, the real-time axial force F of the bolt is calculated, the physical parameters of the monitored bolt including the bolt stress cross-sectional area A, the material Young's modulus E and the effective length L. The real-time axial force F = (A x E x ΔL) / L.

2. The ultrasonic-based real-time measurement system for bolt axial force in an electrolytic cell of claim 1, wherein, The temperature compensation module is further configured to modify the parameters according to a correction curve of the Young's modulus E of the bolt material varying with temperature and a temperature correction formula of the ultrasonic wave propagation velocity v, and to acquire the actual working temperature T of the monitored bolt through a temperature acquisition module; the modified Young's modulus E is calculated as ET and the modified ultrasonic wave propagation velocity v is calculated as vT through the actual working temperature T, The vT = v0 x (1 + α x T) v0 is the propagation velocity of the ultrasonic wave in the bolt material at a standard ambient temperature; α is the sound velocity temperature coefficient of the bolt material.

3. The ultrasonic based real-time measurement system for bolt axial force in electrolytic cells according to claim 1, wherein, The high-frequency ultrasonic probe is configured to transmit and receive ultrasonic wave signals to the target bolt of the electrolytic cell, the working frequency range being 2 MHz-15 MHz, and the high-frequency ultrasonic probe being a longitudinal wave ultrasonic probe.

4. The ultrasonic-based real-time measurement system for bolt axial force in an electrolytic cell of claim 1, wherein, Further comprising: a parameter storage unit configured to pre-store the physical parameters and calibration parameters of the target bolt, including the bolt stress cross-sectional area A, the material Young's modulus E, the effective length L, the propagation velocity v0 of the ultrasonic wave in the bolt material and the axial force preset threshold range corresponding to the sealing performance of the electrolytic cell; a central analysis server electrically connected with the ultrasonic wave sensing network and the parameter storage unit, configured to receive the real-time sound time data transmitted by the sound time acquisition submodule, and comprising an algorithm engine configured to perform the real-time axial force calculation, temperature compensation, stress cloud map generation and diagnosis logic; a warning unit electrically connected with the data operation unit, configured to automatically trigger an audible and light warning or a remote signal transmission when the calculated axial force F exceeds the preset threshold range of the parameter storage unit; a cloud platform and a visual terminal comprising a touch display screen and a data interface, configured to display the bolt axial force, elongation, sound time data and electrolytic cell stress state in real time, provide stress cloud map and warning information, and support parameter modification, data export and historical data query.

5. The ultrasonic based real-time measurement system for bolt axial force in an electrolytic cell of claim 4, wherein, The parameter storage unit adopts a partition storage architecture, and is divided into four independent partitions, i.e. a "basic parameter area", a "calibration parameter area", a "threshold parameter area" and a "historical data area"; the basic parameter area is configured to store the fixed information of the bolt physical parameters (A, E, L), probe model and channel number, support one-time writing or batch import, and has no limit on data retention time; Calibration parameter area: Stores ultrasonic propagation speed v0, temperature correction factor α, actual working temperature T, and corrected ultrasonic propagation speed vT. It is automatically overwritten and updated after each calibration, and the calibration record is retained for easy tracking of calibration accuracy. Threshold parameter area: Store or input independent threshold ranges for different bolts to adapt to the sealing requirements of different positions in the electrolytic cell; Historical data area: Uses a circular overwrite storage method, supports data export, and is used for trend analysis and fault tracing.

6. The ultrasonic based real-time measurement system for bolt axial force in electrolytic cells as claimed in claim 4, wherein, The central analysis server has a built-in temperature compensation module and a temperature sensor to monitor the working temperature of the bolts. The temperature compensation module pre-stores the correction curve of the Young's modulus E of the bolt material as a function of temperature and the temperature correction formula of the ultrasonic propagation speed v. It corrects the values ​​of E and v in real time according to the working temperature of the electrolytic cell.

7. The ultrasonic based real-time measurement system for bolt axial force in electrolytic cells of claim 4, wherein, The central analysis server has a built-in moving average filtering algorithm, which includes filtering the collected acoustic time data to eliminate instantaneous errors caused by vibration and electromagnetic interference. Furthermore, when the deviation of a certain acoustic time data from the historical average exceeds 5%, it is judged as abnormal data and removed to ensure the stability of the calculation results.

8. A real-time measurement method of bolt axial force of an electrolytic cell based on ultrasonic waves, applied to the system of any one of claims 1-7, characterized in that, Includes the following steps: 1) Device deployment and parameter initialization: Fix the high-frequency ultrasonic probe to the end face of the target bolt in the electrolytic cell, input the physical parameters (A, E, L) of the target bolt through the cloud platform and visualization terminal, and calibrate the ultrasonic wave propagation speed v0; The calibration process is as follows: take a standard sample of the same material and specification as the target bolt as the object, emit ultrasonic waves to it, record the ultrasonic wave propagation time as t_standard, and combine it with the known length of the standard sample as L_standard, calculate v0 = L_standard / t_standard; 2) Initial reference value acquisition: When the electrolytic cell is not running or the bolt is in the initial pre-tightening state, ultrasonic waves are emitted to the target bolt through the ultrasonic sensor network, and the initial acoustic time t0 is recorded as the reference data for subsequent measurements. 3) Real-time acoustic time monitoring: During the operation of the electrolytic cell, the ultrasonic detection unit continuously emits ultrasonic waves towards the target bolt, and collects the ultrasonic wave propagation time t1 in real time. The data processing unit calculates the change in acoustic time Δt=|t1-t0|. 4) Temperature compensation and parameter correction: The temperature compensation module collects the real-time working temperature T of the electrolytic cell, adjusts the Young's modulus E to ET according to the pre-stored correction curve, and calculates the corrected ultrasonic propagation speed vT according to the formula vT=v0×(1+α×T). 5) Calculation of elongation and axial force: The central analysis server calculates the real-time elongation ΔL of the bolt based on the corrected vT and the change in acoustic time Δt using the formula ΔL=(vTΔt) / 2; then, ET, A, L, and ΔL are substituted into the formula F=(A×ET×ΔL) / L to obtain the real-time axial force F of the bolt. 6) Stress state judgment and early warning: The central analysis server compares the real-time axial force F with the preset threshold range of the parameter storage unit. If F is within the threshold range, it is determined that the stress of the electrolytic cell is normal and the sealing performance meets the standard. If F is lower than the lower threshold, it is determined that there is a risk of sealing failure. If F is higher than the upper threshold, it is determined that the bolt is overloaded or the stress of the electrolytic cell structure exceeds the standard, and the early warning unit immediately triggers the corresponding early warning. 7) Data recording and output: the cloud platform and the visualization terminal display the axial force F, elongation AL, working temperature T and stress state in real time, and automatically store historical data, supporting export to terminal equipment for trend analysis through a data interface.

9. The method according to claim 8, wherein, The calibration process of the standard sample in step 1 needs to be carried out at a standard ambient temperature of 25°C, and the calibration is not less than 3 times, and the average value of v0 is taken as the reference propagation speed, to ensure that the calibration error is ≤0.1%.

10. The method of claim 8, wherein the method is characterized by: The pre-warning level of the pre-warning unit in step 6 is divided into three levels, the first level of pre-warning when the axial force F approaches the threshold boundary is a yellow prompt; the second level of pre-warning when the axial force F exceeds the threshold within 5% is an orange sound and light alarm; the third level of pre-warning when the axial force F exceeds the threshold by more than 5% is a red sound and light alarm and sends a remote alarm signal to the operation and maintenance terminal at the same time.

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