Field detection method for axial displacement sensor

Abstract

The invention provides a field detection method for an axial displacement sensor, belongs to the technical field of rotating machinery monitoring, and can at least partially solve the problems of long offline detection time consumption and poor working condition matching in the prior art. The method comprises the steps that a sensor probe is installed on a detection device, and the original wiring state of an extension line and a front-end device is kept; a displacement reference is established through a laser interferometer; driving the simulation target sheet to move according to the detection point sequence and acquiring a standard value and a measurement value; and performing error calculation and linearity analysis on the acquired data to generate a detection report. According to the invention, near-in-situ field detection of the sensor is realized, the downtime is obviously shortened, and the detection result can be traced to the measurement standard.

Description

Technical Field

[0001] This invention relates to the field of rotating machinery monitoring technology, and specifically to a field detection method for an axial displacement sensor. Background Technology

[0002] The TSI system is a safety monitoring system for large rotating machinery. It monitors parameters such as shaft displacement, shaft vibration, and eccentricity using displacement sensors, and bearing housing vibration using speed sensors. It collects key operating parameters of the unit in real time, triggering alarms or shutdown protection when parameters exceed limits to prevent major accidents such as shaft rubbing and bearing failure. This system is widely used in large rotating machinery such as steam turbines and gas turbines, and is of great significance for ensuring the safe and stable operation of critical infrastructure such as power and petrochemical industries.

[0003] Currently, TSI sensors are generally tested or calibrated offline in laboratories. This method has the following technical defects and engineering problems.

[0004] First, the verification and calibration process is time-consuming. Sending sensors offline to a verification and calibration institution for verification or calibration not only includes the actual verification and calibration time, but also the time required to remove the sensor extension cable and preamplifier, travel time, and waiting time at the verification and calibration institution, which significantly increases the unit's downtime and causes substantial economic losses.

[0005] Second, it lacks flexibility and mobility. During unit operation, the sensor's sensitivity may drift due to factors such as ambient temperature, electromagnetic interference, and mechanical vibration, creating a blind spot. Because the unit cannot be shut down for extended periods, and sensor extension cables cannot be removed, problems at individual measuring points cannot be quantified and verified in a timely manner. These issues may have to wait until maintenance to be addressed, requiring a lengthy process including turbine shutdown and cooling, disassembly of the sensor, extension cables, and preamplifier, testing, reassembly, and restart commissioning.

[0006] Third, poor compatibility with operating conditions. The laboratory calibration environment is typically a static environment at room temperature (23℃ ± 5℃), free from electromagnetic interference, which differs significantly from actual field conditions. During operation, the bearing housing is at a high temperature, and a strong magnetic field exists around the generator, causing laboratory calibration results to fail to accurately reflect the true performance in the field.

[0007] Therefore, how to design an on-site testing method that does not involve complete disassembly and assembly and closely reflects the actual working conditions, and solve the inherent defects of offline external verification and calibration, is a core problem that urgently needs to be solved in the field of rotating machinery monitoring. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method for on-site detection of axial displacement sensors.

[0009] To achieve the above objectives, the present invention provides a field detection method for an axial displacement sensor, comprising: Sensor transfer and installation: Remove the probe of the displacement sensor to be tested from the original measuring point and install it on the sensor mounting bracket of the detection device. The extension cable and preamplifier connected to the displacement sensor shall remain in their original wiring state. Displacement reference establishment: The simulated target is adjusted to the position directly in front of the probe. The distance between the simulated target and the probe is adjusted according to the displacement value of the measuring point displayed by the monitoring system until the displacement value is zero. The current position of the simulated target is recorded by a laser interferometer as the zero point of the displacement reference. Automatic detection execution: After inputting the detection parameters, the detection is started, driving the simulated target to move sequentially according to the preset detection point sequence, and collecting the actual displacement value measured by the laser interferometer at each detection point as the standard value and obtaining the displacement value displayed by the monitoring system as the measured value; Data processing and judgment: Calculate the single-point error and sensor linearity of each detection point based on the standard value and the measured value, and output the judgment result based on the comparison of the calculation result with the preset allowable range, and generate a detection report.

[0010] Furthermore, the process of transferring and installing the sensor also includes on-site preparation: After confirming that the unit is in a shutdown state, place the detection device near the displacement sensor to be measured; Connect the detection device to the unit's grounding terminal via a grounding wire, and ensure that the grounding resistance is not greater than the preset grounding resistance threshold. Check the battery level of the detection device, the emergency stop button function, and the surface condition of the simulated target.

[0011] Furthermore, the sensor transfer installation also includes: After loosening the mounting nut of the displacement sensor, remove the probe from the original measuring point; The probe is mounted on the sensor mounting bracket and secured with a clamp. Ensure that the simulated target is parallel to the end face of the probe.

[0012] Furthermore, the detection parameters include set displacement values ​​for multiple detection points, the number of which is no less than 5 and is distributed within the range; Before starting the detection, sensor information must be entered, including sensor model, range, and sensitivity.

[0013] Furthermore, during the automatic detection process, a stepper motor drives a ball screw via a reducer to move the simulated target. The simulated target remains at each detection point for a preset time to wait for the display reading of the monitoring system to stabilize.

[0014] Furthermore, the formula for calculating the single-point error is as follows: ; in, This indicates the single-point error. This indicates the measured value. This represents the standard value.

[0015] Furthermore, the linearity is calculated as follows: The least squares method was used to perform linear fitting on the data of all the detection points to obtain a fitted straight line; Calculate the deviation between the measured value at each detection point and the corresponding value of the fitted straight line; The ratio of the maximum absolute value of the deviation to the range is taken as the linearity.

[0016] Furthermore, the automatic detection process also includes dual safety limit protection: When the distance between the simulated target and the probe is less than a preset minimum distance threshold or greater than a preset maximum distance threshold, the photoelectric limit switch triggers a shutdown. When the photoelectric limit switch fails, the mechanical block prevents the simulated target from moving further.

[0017] Furthermore, the test report includes unit identification information, sensor identification information, test time, standard value and measured value of each test point and single-point error, linearity value, error curve and judgment result.

[0018] Furthermore, after generating the detection report, the process also includes sensor reassembly: Control the simulated target to return to its initial position; Remove the probe from the sensor mounting bracket; The probe was reinstalled at the original measurement point location.

[0019] The beneficial effects of this invention are as follows: This invention enables near-in-situ on-site testing of sensors by simply adjusting the installation position of the sensor probe, without removing extension cables, preamplifiers, and secondary cables. This significantly reduces downtime and lowers testing costs.

[0020] This invention introduces a laser interferometer as a displacement reference, which solves the problem of reference traceability in the field environment, ensures the accuracy and traceability of the test data, and the test results can be traced back to the national metrological standard.

[0021] This invention employs a dual safety limit design combining photoelectric limit switches and mechanical stops, effectively preventing the target from overtraveling and impacting the sensor probe, reducing the risk of equipment damage, and improving the safety of the detection operation.

[0022] This invention enables intelligent and automated execution of the testing process, automatically completing operations such as testing point operation, error calculation, and report generation. Operators only need to read and input the values ​​displayed on the monitoring system, and the entire process takes only 15 to 30 minutes, significantly improving testing efficiency. Attached Figure Description

[0023] Figure 1 This is a flowchart of the on-site detection method for the axial displacement sensor of the present invention; Figure 2 This is a schematic diagram of the detection data processing flow of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0025] The on-site testing method for axial displacement sensors of the present invention is applicable to TSI systems of rotating machinery such as steam turbines and gas turbines. It enables on-site testing and performance verification of displacement sensors by simply changing the probe installation position. This method is based on a portable testing device, which consists of a standard displacement unit, a main control and data acquisition processing unit, a human-machine interface unit, a power management unit, and a safety protection unit.

[0026] The standard displacement unit includes a stepper motor, a reducer, a ball screw, a simulated target, a laser interferometer, and a sensor mounting bracket. The stepper motor is connected to the ball screw via the reducer, driving the simulated target to adjust its axial displacement. The laser interferometer measures the actual displacement of the simulated target as a standard value for detection. The sensor mounting bracket fixes the probe of the displacement sensor under test, ensuring it is aligned with the simulated target. The laser interferometer uses a helium-neon laser light source with a wavelength of 632.8 nm, a resolution of 0.001 μm, and a measurement uncertainty of no more than 0.5 μm, meeting the accuracy requirements of the displacement sensor. The simulated target is made of 45# steel or 42CrMn steel, with a surface roughness Ra of no more than 0.8 μm, consistent with the surface material and roughness of the turbine shaft, ensuring the simulated detection closely approximates real-world conditions.

[0027] The main control and data acquisition unit is based on a microprocessor, coupled with a data acquisition module and a storage module. The microprocessor is responsible for executing the detection algorithm, including data processing tasks such as linearity calculation and error analysis. The data acquisition module is responsible for acquiring the measurement data from the laser interferometer and controlling the operation of the stepper motor. The storage module can store no fewer than 3000 detection records and supports data encryption, using the AES-256 encryption algorithm to encrypt the detection data, preventing tampering and ensuring data authenticity.

[0028] The human-machine interface unit is equipped with a color touchscreen and an emergency stop physical button. The touchscreen is used to input sensor information and detection parameters, input data for the monitoring system, and display data tables and detection curves. The emergency stop button is used for safety control; when triggered, it immediately stops the stepper motor and controls the simulated target to return to a safe position.

[0029] The power management unit uses a lithium battery pack, along with a power management chip and a fast charging module. This unit has a battery life of over 3 hours, supports fast charging, and meets the needs of long-term on-site testing. The output voltage is stable, preventing interference from power grid fluctuations on the device's signal.

[0030] The safety protection unit comprises two parts: mechanical limit and electrical protection. The mechanical limit employs a dual design of photoelectric limit switches and mechanical blocks. The photoelectric limit switch uses a through-beam photoelectric sensor, installed at both ends of the simulated target's movement path. When the simulated target moves close to the probe end face, it blocks the light path of the photoelectric sensor, triggering a limit signal. The mechanical block is a rigid metal block installed at both ends of the ball screw's travel. When the photoelectric limit switch fails, it physically prevents the simulated target from exceeding its travel range. The electrical protection includes overcurrent protection and electrostatic discharge protection, effectively addressing on-site electrical interference and electrostatic risks.

[0031] Example 1 This embodiment uses the field detection of a turbine shaft displacement sensor in a thermal power plant as an application scenario. The turbine shaft displacement sensor is used to monitor changes in the rotor's axial position to prevent shaft rubbing accidents, and its safety requirements are extremely high.

[0032] See Figure 1 The detection method in this embodiment includes the following steps.

[0033] Step S1: On-site preparation.

[0034] Confirm that the turbine unit is in a shutdown state and ensure that the on-site conditions are suitable for the testing work. Stably place the testing device on a platform near the shaft displacement sensor to be tested, with the distance between the device and the sensor not exceeding 1.5 meters, so that the extension cable can be connected to the testing device.

[0035] Check the status of the testing device to ensure the lithium battery charge is not less than 80%. If the charge is below 80%, it needs to be charged until the required level is reached before starting the testing. Check if the emergency stop button is functioning properly; the stepper motor should stop immediately after the emergency stop button is pressed. Check the surface of the simulated target for deformation, scratches, or other damage, ensuring the target surface is flat and smooth.

[0036] Perform grounding by connecting the detection device to the grounding terminal of the turbine body via a grounding wire. Measure the grounding resistance using a grounding resistance tester, ensuring the grounding resistance does not exceed 4Ω. Good grounding reduces the impact of electromagnetic interference on the detection data and improves measurement accuracy.

[0037] Step S2: Sensor transfer and installation.

[0038] Use a special wrench to loosen the mounting nut of the displacement sensor of the shaft under test, and remove the sensor probe from the original measuring point. During disassembly, take care to protect the probe end face from damage and avoid collisions with other metal parts. The extension cable, preamplifier, and secondary cables connected to the sensor should remain in their original wiring state without disassembly. This is a core feature that distinguishes this invention from traditional offline verification.

[0039] The probe is mounted on the sensor mounting bracket of the detection device. The sensor mounting bracket adopts a V-groove structure design to accommodate sensor probes of different diameters. The probe is placed into the V-groove, and the outer cylindrical surface of the probe is fixed with a clamp. The mounting nut is tightened to secure the probe in place. After installation, the axis of the probe should be coaxial with the direction of movement of the simulated target.

[0040] Adjust the position of the simulated target plate so that it faces the probe end face. Use a parallelism measuring tool to check the parallelism between the simulated target plate and the probe end face; the parallelism deviation should not exceed 0.05 mm. Leave an initial gap so that the distance between the simulated target plate and the probe end face is approximately the middle of the sensor's measurement range. In this embodiment, the sensor range is 0 to 2 mm, and the initial gap is set to 1 mm.

[0041] Step S3: Establish displacement reference.

[0042] Observe the displacement value of the measuring point displayed on the TSI system engineering station screen. Since the sensor probe has moved from its original measuring point position to the detection device, the displacement value displayed on the engineering station will change. Using the manual adjustment knob of the detection device, slowly adjust the distance between the simulated target and the probe until the displacement value displayed on the engineering station screen gradually approaches zero.

[0043] When the displacement value displayed on the engineer's workstation reaches 0 μm, adjustment stops. At this point, the distance between the simulated target and the probe end face is the zero point of the sensor. The laser interferometer records the current position coordinates of the simulated target and sets this position as the zero point of the displacement reference. In subsequent testing, all displacement values ​​measured by the laser interferometer are calculated based on this zero point.

[0044] Step S4: Automatic detection and execution.

[0045] Select the displacement sensor detection mode on the touchscreen of the detection device. Enter the relevant parameters of the sensor in the parameter setting interface, including: sensor model is eddy current shaft displacement sensor, sensor number is the device number of the measuring point, range is 2 mm, and sensitivity is 7.87 mV / μm.

[0046] The detection point parameters are set. This embodiment sets seven detection points: 50μm, 100μm, 125μm, 150μm, 200μm, 250μm, and 300μm. The number and location of these detection points can be adjusted according to the sensor's range and detection accuracy requirements, but the number should be no less than five. These detection points should be distributed within the sensor's range to comprehensively evaluate the sensor's linearity characteristics.

[0047] After clicking the start detection button on the touchscreen, the detection device automatically performs the following operations. The stepper motor drives the ball screw to rotate through the reducer, causing the simulated target to move sequentially according to a preset detection point sequence. First, it moves to the first detection point position of 50μm, then the stepper motor stops running, and the simulated target remains stationary for 3 seconds, waiting for the reading displayed on the engineer's workstation screen to stabilize.

[0048] During the dwell time of the simulated target, the operator observes the displacement value displayed on the engineering workstation screen. Once the reading stabilizes, the value is input into the touchscreen of the detection device. Simultaneously, the laser interferometer automatically measures and records the actual displacement value of the simulated target. After both data acquisitions are completed, the stepper motor continues to operate, driving the simulated target to the next detection point.

[0049] Data acquisition for all detection points is completed sequentially according to the above process. In this embodiment, the detection process for the 7 detection points takes approximately 5 minutes. During the detection process, the safety protection unit continuously monitors the position of the simulated target. When the distance between the simulated target and the probe is less than 0.1 mm, the photoelectric limit switch is triggered, and the stepper motor immediately stops to prevent the simulated target from impacting the probe. When the distance between the simulated target and the probe is greater than 5 mm, the limit switch is also triggered to prevent exceeding the measurement range. If the photoelectric limit switch fails, the mechanical stop will physically prevent the simulated target from continuing to move. The distance between the mechanical stop and the probe end face is set to 0.05 mm to ensure that even in extreme situations, the probe will not be damaged by impact.

[0050] See Figure 2 Step S5: Data processing and judgment.

[0051] The main control unit processes the acquired data. The standard value is the actual displacement value of the simulated target sheet measured by the laser interferometer, denoted as... The measured value is the displacement value read and input by the operator from the engineering station screen, denoted as... .

[0052] Calculate the single-point error at each detection point. The formula for calculating the single-point error is: ; in, This indicates the single-point error. This indicates the measured value. This represents the standard value.

[0053] Calculate the linearity of the sensor. Use the least squares method to perform linear fitting on the data from all detection points. Let the number of detection points be... The standard value sequence is , ... The sequence of measured values ​​is , ... The slope of the least squares fitted line. and intercept The calculation formula is: ; ; in, This represents the slope of the fitted line. This represents the intercept of the fitted line. Indicates the number of testing points. The value range is 1 to .

[0054] Calculate the fitted values of each detection point according to the fitted straight line. The calculation formula for the fitted value is as follows: ; Calculate the deviation between the measured value and the fitted value of each detection point : ; Take the ratio of the maximum absolute value of the deviation to the sensor range L as the linearity : ; Among them, represents the linearity percentage, represents the maximum absolute value of the deviation, represents the sensor range. In this embodiment, takes a value of 2000μm.

[0055] Make a judgment based on the calculation results. Compare the single-point error of each detection point with the preset allowable error limit. In this embodiment, the allowable error limit is set to 1% of the range, that is, 20μm. When the single-point error of all detection points is not greater than 20μm, it is determined that the accuracy of the sensor is qualified. Compare the linearity with the preset allowable linearity limit. In this embodiment, the allowable linearity limit is set to 1%. When the linearity is not greater than 1%, it is determined that the linearity of the sensor is qualified.

[0056] The touch screen automatically displays a detection data table, and the table content includes the serial number of each detection point, the standard value, the measured value, and the single-point error. At the same time, an error curve and a linearity curve graph are displayed to visually display the performance characteristics of the sensor. According to the judgment result, the touch screen displays a prompt message of good channel linearity or deviation of channel linearity, and gives a conclusion on whether the error is within the allowable range.

[0057] Step S6: Report generation and sensor reinstallation.

[0058] After the data processing is completed, the detection device automatically generates a detection report. The detection report adopts a standardized format, and the content includes: unit identification information including power plant name and unit number; sensor identification information including model, number, and installation position; detection time including detection date and specific time; detection environment information including environmental temperature and humidity; a data table of the standard value, the measured value, and the single-point error of each detection point; the linearity value; an error curve and a linearity curve graph; a judgment result including qualified or unqualified and specific description; the name of the operator and the signature column.

[0059] The test report can be stored locally on the SD card of the storage module, or exported to a USB flash drive via USB interface, or transmitted to a host computer system via wireless network. The testing device also supports generating sensor sensitivity drift trend curves, comparing and analyzing parameter changes from multiple consecutive tests by the same sensor, providing data support for sensor lifespan prediction.

[0060] After the report is generated, the stepper motor automatically reverses direction, driving the simulated target back to its initial position, providing sufficient operating space for sensor disassembly. Loosen the clamps and mounting nuts on the sensor mounting bracket and remove the probe from the bracket. Reinstall the probe at its original measuring point position on the turbine body and tighten the mounting nuts to securely position the probe. Check if the displacement value displayed on the engineer's workstation screen is normal, confirming that the sensor has returned to normal working status.

[0061] The entire testing process in this embodiment takes approximately 22 minutes, including about 5 minutes for on-site preparation, about 3 minutes for sensor transfer and installation, about 2 minutes for establishing the displacement reference, about 7 minutes for automatic testing, about 2 minutes for data processing and judgment, and about 3 minutes for sensor reinstallation. Compared with the traditional offline testing method, the testing time is reduced from several days to less than half an hour, significantly improving testing efficiency.

[0062] Example 2 This embodiment uses the field testing of a gas turbine shaft vibration sensor as an application scenario. Gas turbines are widely used in combined cycle power plants, distributed energy systems, and industrial drives. Their shaft vibration sensors are used to monitor the radial vibration amplitude of the rotor, which is an important parameter for judging the unit's operating status and bearing health. Compared with the shaft displacement sensor in Embodiment 1, the shaft vibration sensor has a larger measurement range and different detection accuracy requirements, but the overall detection process follows the same methodological framework. This method is also applicable to the static displacement detection of the shaft vibration sensor.

[0063] See Figure 1 The detection method in this embodiment includes the following steps.

[0064] Step S1: On-site preparation.

[0065] Confirm that the gas turbine unit is shut down. Gas turbines operate at high temperatures, with exhaust temperatures reaching over 500°C. After shutdown, wait for the unit to cool to a safe temperature before commencing any testing. This typically takes 4 to 8 hours for the unit to cool to near ambient temperature. Before testing, ensure the bearing housing temperature has dropped below 60°C to guarantee operator safety.

[0066] The detection device is placed near the shaft vibration sensor to be tested. Sensor installation space in gas turbines is typically limited, and the portable design of the detection device allows it to fit into such confined spaces. The overall dimensions of the detection device are controlled within 400mm × 300mm × 200mm, and its weight does not exceed 8 kg, facilitating transport and placement within the confined engine room. The detection device is placed on a level and stable platform, with the distance between the device and the sensor not exceeding 1.5 meters.

[0067] Check the status of the testing device to ensure the lithium battery charge is not less than 80%. Since it is typically inconvenient to connect an external power source inside the gas turbine nacelle, the entire testing process must be powered by the lithium battery. Check that the emergency stop button functions correctly; the stepper motor should stop immediately after the emergency stop button is pressed. Check the surface of the simulated target for deformation, scratches, or other damage, ensuring the target surface is flat and smooth with a surface roughness Ra not exceeding 0.8 μm.

[0068] Grounding is performed by connecting the detection device to the grounding terminal of the gas turbine body via a grounding wire. Strong electromagnetic interference exists around the gas turbine during operation. Although the electromagnetic interference weakens when the turbine is shut down, proper grounding is still necessary to reduce the impact of residual interference on the detection data. The grounding resistance is measured using a grounding resistance tester to ensure that the grounding resistance does not exceed 4Ω.

[0069] Step S2: Sensor transfer and installation.

[0070] Shaft vibration sensors also utilize the eddy current principle, but their installation method differs slightly from that of shaft displacement sensors. Shaft vibration sensors are typically mounted on a bearing housing, with the probe end face directly opposite the rotor journal surface, measuring the radial vibration of the rotor relative to the bearing housing. In this embodiment, the shaft vibration sensor is mounted at the top of the compressor-end bearing housing of the gas turbine, with the sensor probe pointing vertically downwards towards the rotor journal.

[0071] Use a special wrench to loosen the mounting nut of the vibration sensor on the shaft under test, and remove the sensor probe from the bearing housing. During disassembly, take care to protect the probe end face from damage and avoid collision with the metal surface of the bearing housing. Do not disconnect the extension cable, preamplifier, and secondary cables connected to the sensor, keeping them in their original wiring state. The allowable length of the extension cable should be sufficient to transfer the probe from the bearing housing to the sensor mounting bracket of the detection device. If the extension cable is fixed through the cylinder and the allowable length is short, the detection device should be placed as close as possible to the sensor mounting position.

[0072] The probe is mounted on the sensor mounting bracket of the detection device. The sensor mounting bracket adopts a V-groove structure design, which can accommodate various sensor probes with diameters ranging from 8mm to 25mm. In this embodiment, the shaft vibration sensor probe has a diameter of 11mm. The probe is placed in the V-groove, and the outer cylindrical surface of the probe is fixed using a clamp. The mounting nut is tightened to securely position the probe. After installation, the axis of the probe should be coaxial with the direction of movement of the simulated target, with a coaxiality deviation of no more than 0.1mm.

[0073] Adjust the position of the simulated target plate so that it faces the probe end face. Use a parallelism measuring tool to check the parallelism between the simulated target plate and the probe end face; the parallelism deviation should not exceed 0.05 mm. Leave an initial gap so that the distance between the simulated target plate and the probe end face is approximately the middle of the sensor's measurement range. In this embodiment, the range of the shaft vibration sensor is 0 to 5 mm, and the initial gap is set to 2.5 mm. Due to the large measurement range, the effective stroke of the ball screw is designed to be 6 mm, which can cover all the detection requirements of the 0 to 5 mm range sensor.

[0074] Step S3: Establish displacement reference.

[0075] Observe the vibration value of the measuring point displayed on the TSI system engineering station screen. Since the sensor probe has been moved from the bearing housing to the detection device, the vibration value displayed on the engineering station will change. It should be noted that in static detection mode, the engineering station displays the change in the gap distance between the probe and the simulated target, not the dynamic vibration amplitude.

[0076] Using the manual adjustment knob of the detection device, slowly adjust the distance between the simulated target and the probe until the value displayed on the engineer's station screen gradually approaches zero. The adjustment should be performed smoothly and slowly to avoid collision between the simulated target and the probe. Stop adjusting when the value displayed on the engineer's station screen reaches 0 μm.

[0077] At this point, the distance between the simulated target and the probe end face is the zero point of the sensor. The laser interferometer records the current position coordinates of the simulated target and sets this position as the zero point of the displacement reference. The laser interferometer uses a helium-neon laser light source with a wavelength of 632.8 nm, a resolution of 0.001 μm, and a measurement uncertainty of no more than 0.5 μm. In subsequent detection processes, all displacement values ​​measured by the laser interferometer are calculated based on this zero point position.

[0078] Step S4: Automatic detection and execution.

[0079] Select the displacement sensor detection mode on the touchscreen of the detection device. Enter the relevant parameters of the sensor in the parameter setting interface, including: sensor model is eddy current shaft vibration sensor, sensor number is the device number for this measurement point, measuring range is 5 mm, and sensitivity is 7.87 mV / μm. The sensitivity of different shaft vibration sensor models may vary; the actual input should refer to the sensor nameplate or factory calibration certificate.

[0080] The detection point parameters are set. Because the shaft vibration sensor in this embodiment has a large measurement range, to comprehensively evaluate the sensor's linearity characteristics across the entire range, this embodiment sets nine detection points: 100μm, 250μm, 500μm, 750μm, 1000μm, 1500μm, 2000μm, 3000μm, and 4000μm. The distribution of these detection points covers the main range of the sensor, with a denser distribution of detection points in the lower range to more accurately evaluate the sensor's performance in its commonly used operating range.

[0081] After clicking the start detection button on the touchscreen, the detection device automatically performs the following operations. The stepper motor drives the ball screw to rotate through the reducer, causing the simulated target to move sequentially according to a preset detection point sequence. First, it moves to the first detection point position of 100μm, then the stepper motor stops, and the simulated target remains stationary for 3 seconds, waiting for the reading displayed on the engineer's workstation screen to stabilize.

[0082] During the dwell time of the simulated target, the operator observes the values ​​displayed on the engineering workstation screen. Once the readings stabilize, the values ​​are input into the touchscreen of the detection device. Simultaneously, the laser interferometer automatically measures and records the actual displacement value of the simulated target. After both data acquisitions are completed, the stepper motor continues to operate, driving the simulated target to move to the next detection point position of 250μm.

[0083] Data acquisition for all nine detection points was completed sequentially following the above procedure. Due to the large measurement range and numerous detection points, the detection process for all nine points in this embodiment took approximately 7 minutes. During the detection process, the safety protection unit continuously monitored the position of the simulated target. When the distance between the simulated target and the probe was less than 0.1 mm, the photoelectric limit switch was triggered, and the stepper motor immediately stopped to prevent the simulated target from impacting the probe. When the distance between the simulated target and the probe was greater than 6 mm, the limit switch was also triggered to prevent exceeding the effective stroke of the ball screw. If the photoelectric limit switch failed, the mechanical stop would physically prevent the simulated target from continuing to move. The distance between the mechanical stop and the probe end face was set to 0.05 mm to ensure that even in extreme circumstances, the probe would not be damaged by impact.

[0084] See Figure 2 Step S5: Data processing and judgment.

[0085] The main control unit processes the acquired data. The standard value is the actual displacement value of the simulated target sheet measured by the laser interferometer, denoted as... The measured value is the value read and input by the operator from the engineering station screen, and is denoted as... .

[0086] Calculate the single-point error at each detection point. The formula for calculating the single-point error is: ; in, This indicates the single-point error. This indicates the measured value. This represents the standard value.

[0087] Calculate the linearity of the sensor. Use the least squares method to perform linear fitting on the data from all 9 detection points. Let the number of detection points be... In this embodiment The standard value sequence is equal to 9. , ... The sequence of measured values ​​is , ... The slope of the least squares fitted line. and intercept The calculation formula is: ; ; Calculate the fitted value for each detection point based on the fitted straight line. : ; Calculate the deviation between the measured value and the fitted value at each detection point. : ; Take the maximum absolute value of the deviation and the sensor range. The ratio of the linearity is used as the linearity. : ; in, Indicates the percentage of linearity. This represents the maximum absolute value of the deviation. This indicates the sensor's measurement range. In this embodiment, The value of is 5000μm.

[0088] Judgment is made according to the calculation results. The single-point error at each detection point is compared with a preset allowable error limit value. In this embodiment, the allowable error limit value is set to 1% of the range, that is, 50μm. When the single-point error at all detection points is not greater than 50μm, it is determined that the accuracy of the sensor is qualified. The linearity is compared with a preset allowable linearity limit value. In this embodiment, the allowable linearity limit value is set to 1%. When the linearity is not greater than 1%, it is determined that the linearity of the sensor is qualified.

[0089] The touch screen automatically displays a detection data table, and the table content includes the serial number of each detection point, the standard value, the measured value, and the single-point error. At the same time, an error curve and a linearity curve graph are displayed to intuitively show the performance characteristics of the sensor. According to the judgment result, the touch screen displays a prompt message of good channel linearity or deviation of channel linearity, and gives a conclusion on whether the error is within the allowable range.

[0090] Step S6: Report generation and sensor reinstallation.

[0091] After the data processing is completed, the detection device automatically generates a detection report. The detection report adopts a standardized format, and the content includes: unit identification information including power station name and gas turbine unit number; sensor identification information including model, number, installation position, i.e., the compressor end bearing seat; detection time including detection date and specific time; detection environment information including environmental temperature and humidity; a data table of the standard value, the measured value, and the single-point error at each detection point; the linearity value; an error curve and a linearity curve graph; judgment result including qualified or unqualified and specific description; operator's name and signature column.

[0092] The detection report supports local storage to the SD card of the storage module, can also be exported to a USB flash drive through a USB interface, or transmitted to the upper computer system through a wireless network. The detection device also supports generating a sensor sensitivity drift trend curve, comparing and analyzing the parameter changes of the same sensor detected continuously for multiple times, and providing data support for sensor life prediction.

[0093] After the report is generated, the stepping motor automatically runs in reverse, driving the simulation target to return to the initial position, providing enough operating space for sensor disassembly. Loosen the clamp and mounting nut on the sensor mounting bracket, and remove the probe from the bracket. Reinstall the probe to the original measurement point position of the gas turbine bearing seat, and tighten the mounting nut to firmly position the probe. Check whether the value displayed on the engineer station screen is normal, and confirm that the sensor has resumed normal working status.

[0094] The entire testing process in this embodiment takes approximately 27 minutes, including about 5 minutes for on-site preparation, about 4 minutes for sensor transfer and installation, about 2 minutes for establishing the displacement reference, about 9 minutes for automatic detection execution, about 3 minutes for data processing and judgment, and about 4 minutes for sensor reinstallation. Compared to traditional offline testing methods that take several days, the method of this invention significantly improves testing efficiency.

[0095] Comparative Experiment: To verify the effectiveness of the method of this invention, six shaft displacement sensor measuring points of a steam turbine unit in a thermal power plant were selected for comparative testing. The testing scheme included: the on-site detection method of this invention and the traditional offline laboratory calibration method.

[0096] Testing time comparison: The average testing time for a single sensor using the method of this invention is 22 minutes; the traditional method requires removing the extension cable and preamplifier, sending for testing, and reassembling, taking an average of 5 days. The testing efficiency of the method of this invention is improved by approximately 327 times.

[0097] Comparison of test results: The same sensor was tested using two different methods. The measurement errors at six detection points (50μm, 100μm, 150μm, 200μm, 250μm, and 300μm) were compared. The results showed that the deviation between the measurement results of the method of the present invention and the traditional laboratory test results was within ±3μm, which verified the accuracy of the method of the present invention.

[0098] Cost comparison: The cost of a single on-site test using the method of this invention is about 15% of that of the traditional method, which mainly saves on transportation costs, laboratory testing costs and power generation losses caused by extended unit downtime.

[0099] In summary, the embodiments disclosed herein have at least the following technical effects: This invention enables near-in-situ on-site detection of sensors by simply adjusting the installation position of the sensor probe, without removing extension cables, preamplifiers, and secondary cables, thus reducing the detection time from several days to less than 30 minutes.

[0100] This invention introduces a laser interferometer as a displacement reference, with a measurement uncertainty of no more than 0.5 μm, and the detection results are traceable to national metrological standards.

[0101] This invention employs a dual safety limit design combining photoelectric limit switches and mechanical stops to effectively prevent the target chip from overtraveling and impacting the sensor probe, thus protecting the sensor probe, which costs over ten thousand yuan, from damage.

[0102] This invention enables intelligent and automated execution of the testing process, requiring only simple training for operators, thus significantly reducing the difficulty of operation and maintenance.

[0103] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for on-site detection of axial displacement sensor, characterized in that, include: Sensor transfer and installation: Remove the probe of the displacement sensor to be tested from the original measuring point and install it on the sensor mounting bracket of the detection device. The extension cable and preamplifier connected to the displacement sensor shall remain in their original wiring state. Displacement reference establishment: Adjust the simulated target to the position directly in front of the probe, adjust the distance between the simulated target and the probe according to the displacement value of the measuring point displayed by the monitoring system until the displacement value is zero, and record the current position of the simulated target as the zero point of the displacement reference; Automatic detection execution: After inputting the detection parameters, the detection is started, driving the simulated target to move sequentially according to the preset detection point sequence, and collecting the actual displacement value of the simulated target at each detection point as the standard value and obtaining the displacement value displayed by the monitoring system as the measurement value; Data processing and judgment: Calculate the single-point error and sensor linearity of each detection point based on the standard value and the measured value, and output the judgment result based on the comparison of the calculation result with the preset allowable range, and generate a detection report.

2. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The process of transferring and installing the sensor also includes on-site preparation: After confirming that the unit is in a shutdown state, place the detection device near the displacement sensor to be measured; Connect the detection device to the unit's grounding terminal via a grounding wire, and ensure that the grounding resistance is not greater than the preset grounding resistance threshold. Check the battery level of the detection device, the emergency stop button function, and the surface condition of the simulated target.

3. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The sensor transfer and installation also includes: After loosening the mounting nut of the displacement sensor, remove the probe from the original measuring point; The probe is mounted on the sensor mounting bracket and secured with a clamp. Ensure that the simulated target is parallel to the end face of the probe.

4. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The detection parameters include set displacement values ​​for multiple detection points, and the number of detection points is not less than 5 and they are distributed within the range. Before starting the detection, sensor information must be entered, including sensor model, range, and sensitivity.

5. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, During the automatic detection process, a stepper motor drives a ball screw via a reducer to move the simulated target. The simulated target stays at each detection point for a preset time to wait for the display reading of the monitoring system to stabilize.

6. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The formula for calculating the single-point error is as follows: ； in, This indicates the single-point error. This indicates the measured value. This represents the standard value.

7. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The linearity is calculated as follows: The least squares method was used to perform linear fitting on the data of all the detection points to obtain a fitted straight line; Calculate the deviation between the measured value at each detection point and the corresponding value of the fitted straight line; The ratio of the maximum absolute value of the deviation to the range is taken as the linearity.

8. The on-site detection method for axial displacement sensor according to claim 1, characterized in that, The automatic detection process also includes dual safety limit protection: When the distance between the simulated target and the probe is less than a preset minimum distance threshold or greater than a preset maximum distance threshold, the photoelectric limit switch triggers a shutdown. When the photoelectric limit switch fails, the mechanical block prevents the simulated target from moving further.

9. The on-site detection method for an axial displacement sensor according to claim 1, characterized in that, The test report includes unit identification information, sensor identification information, test time, standard value of each test point, measured value and single-point error, linearity value, error curve and judgment result.

10. The on-site detection method for an axial displacement sensor according to claim 1, characterized in that, The process of generating the detection report also includes sensor reinstallation: Control the simulated target to return to its initial position; Remove the probe from the sensor mounting bracket; The probe was reinstalled at the original measurement point location.

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