Method for measuring clearance value of ship bearing

Abstract

The invention relates to the technical field of ship bearing detection, in particular to a method for measuring a clearance value of a ship bearing, which comprises the following steps of: setting four measuring points on the outer circumference of the bearing by adopting an ultrasonic thickness gauge, and calculating the clearance value by receiving and analyzing two echo signals; the surface is subjected to graded cleaning treatment before measurement, so that the measurement precision is ensured; the thickness gauge selects a specific model, and an optimized parameter combination including pulse width, threshold level and trigger mode is set; during measurement, environment temperature and probe pressure are controlled, and multiple times of measurement are performed to obtain an average value; multi-position measurement is realized by rotating the probe, and complete bearing clearance data is established; the method solves the problems that a traditional feeler gauge is low in measurement precision and limited in application range, the gap between the arc-shaped bearing and the bearing with the limited installation position can be accurately measured, and the measurement precision reaches + / -0.01 mm; the measuring process is safe and reliable, and the method is suitable for bearing detection in static and low-speed operation states.

Description

Technical Field

[0001] The present invention relates to the technical field of ship bearing detection, in particular to a method for measuring the clearance value of a ship bearing. Background Art

[0002] Measuring bearing clearances on ships is a crucial step in ship maintenance. Currently, feeler gauges are commonly used for this purpose, but this method has significant shortcomings. The feeler gauge must be inserted directly into the bearing clearance, and measurement accuracy is significantly affected by operator experience, with errors typically exceeding 0.1mm. Accurate insertion of the feeler gauge is difficult for arc-shaped bearings or bearings with restricted mounting positions, resulting in an inability to obtain valid measurement data.

[0003] Furthermore, feeler gauge measurements pose a safety hazard when the bearing is in motion. While existing ultrasonic thickness measurement technology allows for non-contact measurement, when applied directly to bearing clearance measurement, the echo signal is susceptible to interference due to the specific bearing structure, resulting in unstable measurement results. This is particularly true in marine environments, where factors such as vibration and humidity can further affect measurement accuracy. Summary of the Invention

[0004] The object of the present invention is to provide a method for measuring the clearance value of a ship bearing to solve the problems raised in the above background technology.

[0005] A method for measuring the clearance value of a ship bearing comprises the following steps: S1: Establish a 2D coordinate system based on the cross section of the bearing to be measured, select the measurement position, select the required echo parameters according to the measurement requirements, and select the required measurement accuracy; S2: Clean the selected measurement location to prevent stains at the selected location from affecting the measurement accuracy; S3: Select an appropriate thickness gauge, calibrate and filter the thickness gauge, and place the calibrated thickness gauge at the measuring position on the outer surface of the bearing assembly to be measured; S4: The thickness gauge emits ultrasonic waves, receives the first transmitted echo at the selected measurement position, and calculates the distance L1 traveled by the first reflected echo; S5: Receive the second transmitted echo at the selected measurement position and calculate the distance L2 traveled by the second transmitted echo; S6: Obtain the distance difference by calculating the formula: ΔL=L2-L1. This distance difference is the bearing clearance value to be measured. S7: Change the measuring position of the thickness gauge, repeat the above operation, and measure the bearing clearance values ​​at different positions.

[0006] Furthermore, in S1, four measurement positions are selected on the outside of the bearing, namely A, B, C and D. The four measurement positions are the intersection points of the horizontal and vertical directions of the bearing, and the difference between two adjacent measurement positions is ninety degrees. The echo parameters are selected as the second and third echo signals.

[0007] Furthermore, in S2, the measurement position cleaning steps are as follows: preliminary mechanical cleaning: use a soft brush or lint-free cloth to remove loose particles on the surface. For stubborn stains, use a plastic scraper to carefully scrape them off; solvent cleaning: use a volatile solvent such as isopropyl alcohol or a special electronic cleaner to avoid using silicone or grease-containing cleaners to ensure complete evaporation and drying after cleaning; special treatment of the ultrasonic probe contact area: use a fine abrasive paste (such as 2000 mesh or above) to lightly polish the contact surface to ensure that the surface roughness Ra is <1.6μm; final inspection: visually check for visible stains and touch with gloves to confirm that there is no graininess.

[0008] Furthermore, in S3, an Olympus 38DL PLUS ultrasonic thickness gauge is selected, and a low-frequency probe (1-5 MHz) is used to test thick materials or high-attenuation materials. The pulse is selected as a wide pulse (200-500 ns), and the threshold level is set to 2-3 times the noise amplitude (usually 5%-10% of the full scale). If it is too low, it is easy to trigger falsely. The trigger mode is selected as rising edge trigger, which is commonly used and has a fast response.

[0009] Furthermore, in said S3, the steps for calibrating the thickness gauge are as follows: using a standard test block: coupling the probe to a calibration test block of known thickness (such as a 4mm steel block). Reading the measured value: the thickness displayed by the instrument should be consistent with the nominal value of the test block. Adjusting the zero point: if the displayed value deviates greatly, enter the instrument calibration mode, input the actual thickness of the test block, and the instrument automatically corrects the zero offset. Some instruments require manual fine-tuning of the "Probe Delay" parameter, and verification is required after calibration: Repeat measuring the test block: confirm that the error between the displayed value and the nominal value is within the allowable range (such as ±0.02mm). Cross-validation: use another calibrated thickness gauge to measure the same position, compare the results, and perform bandpass filtering: the cutoff frequency is set to ±30% of the probe center frequency.

[0010] Furthermore, in S4, the thickness gauge also receives an echo signal at the measurement position. Since this echo signal is not the required one, it is automatically ignored. To ignore the first echo signal on the Olympus 38DL PLUS, enter the "Gate Setup" menu, set the Gate1 Start value to a value greater than the first echo arrival time, adjust the Gate Width to an appropriate range, and enable the "Gate1 Only" mode to receive the first echo signal. After receiving the first echo signal, the formula for calculating L1 is:

[0011] L1: target distance (unit: meters, m).

[0012] v: The propagation speed of ultrasound in the medium (unit: meter / second, m / s).

[0013] t: The time difference from transmission to reception of echo (unit: seconds, s).

[0014] Divide by 2: Since ultrasonic waves travel back and forth, the one-way distance must be taken.

[0015] Furthermore, in S5, the specific process of receiving the echo is: original signal acquisition → 2. Bandpass filtering → 3. TVG compensation → 4. Envelope extraction → 5. Echo identification → 6. Time measurement → 7. Sound velocity compensation → 8. Thickness calculation → 9. Results show that the specific calculation formula of L2 is:

[0016] L2: target distance (unit: meters, m).

[0017] v: The propagation speed of ultrasound in the medium (unit: meter / second, m / s).

[0018] t: The time difference from transmission to reception of echo (unit: seconds, s).

[0019] Divide by 2: Since ultrasonic waves travel back and forth, the one-way distance must be taken.

[0020] Furthermore, in S6, the accuracy indicators of ΔL, L2 and L1 are: static: ±0.01mm; dynamic (10r / min): ±0.03mm. L2 and L1 are measured at least three times, and the average value is taken after the test. This can improve the accuracy of the test. The specific requirements during the test are: constant temperature: 23±1℃ (ISO standard), constant pressure: probe pressure 10±1N, and stabilization time: preheating for 15 minutes.

[0021] Furthermore, in S7, the specific operation of changing the measurement position is to rotate the selected thickness gauge ninety degrees clockwise from position A to position B, repeat the above operation and record the bearing clearance value, and then move the thickness gauge to positions C and D in turn for ultrasonic thickness measurement, and record the clearance values ​​of the bearings at different positions.

[0022] Furthermore, in S7, when operating the thickness gauge to move, it is necessary to wear an anti-static wristband and turn off the power of the instrument, use a wrench to loosen the fixing screws, pre-set a positioning mark at the position to be switched, and use screws to fix the thickness gauge in the position of the positioning mark. The verticality of the probe needs to be checked every time a position is changed.

[0023] By adopting the above technical solution, it is possible to use a high-precision thickness gauge and utilize the principle of multiple echoes to measure various bearing clearance values. The present invention improves accuracy while ensuring precision, is easy to operate, and improves work efficiency. It has a wide range of applications, reduces labor costs, and has practical significance.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the method for measuring the clearance value of ship bearings is By optimizing probe placement and signal processing algorithms, non-contact measurement of arc-surface bearings is possible. Compared to traditional feeler gauge methods, this method achieves over five times higher measurement accuracy and is not limited by measurement space. Practical applications have demonstrated that in ship propulsion shafting bearing inspections, clearance anomalies exceeding 0.02 mm can be accurately identified, providing a reliable basis for bearing condition assessment. Measurement data can be exported via a USB port, facilitating the establishment of bearing wear trend profiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the main cross-sectional structure of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] See also Figure 1 This invention provides a technical solution: a method for measuring the clearance of ship bearings. Before measurement, prepare an Olympus 38DL PLUS ultrasonic thickness gauge equipped with a 1-5 MHz low-frequency probe. Check that the instrument is fully charged and the probe cable is securely connected. Prepare auxiliary items such as a standard test block, coupling agent, and cleaning tools.

[0028] Establish a two-dimensional coordinate system with the center of the cross-section of the bearing being measured as the origin. Mark four measurement points, A, B, C, and D, on the outer circumference of the bearing. These four points are located at the tangent points in the horizontal and vertical directions, with 90-degree intervals between adjacent points. Use a soft-bristled brush to remove dust and oil from the surface of the measurement points. For stubborn stains, carefully use a plastic scraper. Next, wipe the surface with a non-woven fabric soaked in isopropyl alcohol. After the solvent has completely evaporated, polish the probe contact area with a 2000-grit abrasive paste to ensure a surface roughness Ra of less than 1.6 μm.

[0029] Turn on the thickness gauge and preheat it for 15 minutes before entering calibration mode. Couple the probe to a 4mm standard steel test block and observe the displayed value. If there is a deviation from the nominal value, enter the calibration menu and enter the actual thickness of 4mm. The instrument will automatically correct the zero point. Set the bandpass filter range to ±30% of the probe center frequency, adjust the pulse width to 300ns, and set the threshold level to 2.5 times the noise amplitude. After calibration, verify using a standard test block. The error between three measurements should not exceed ±0.02mm.

[0030] Apply coupling agent evenly to measurement point A. Press the probe vertically against the surface, maintaining a pressure of 10±1N. Enter the Gate Setup menu and set Gate 1's start time to after the arrival of the first echo and its width to cover the second echo range. After triggering the measurement, the instrument automatically records the first effective echo time t1 and the second echo time t2. Calculate the distance value according to the formulas L1 = v × t1 / 2 and L2 = v × t2 / 2, where v is 5920m / s (the speed of sound in steel). The bearing clearance ΔL is L2-L1, and the instrument directly displays the calculated result. Repeat the measurement three times at 23±1°C and take the average value as the clearance value at point A.

[0031] After measuring point A, turn off the power and loosen the probe's mounting screws. Rotate the probe 90 degrees clockwise to point B, align it with the pre-marked positioning point, and re-tighten the screws. Use a square to check the perpendicularity of the probe to the surface, ensuring the error is less than 0.5 degrees. Follow the same steps to measure the gap value at point B. Rotate the probe 180 degrees and 270 degrees, respectively, to complete the measurement at points C and D, rechecking the probe's perpendicularity after each rotation.

[0032] During the measurement process, ensure the couplant thickness is uniform and avoid bubbles. While the bearing is in operation, perform dynamic measurements at a stable speed of 10 r / min. The system automatically compensates for motion errors, maintaining an accuracy of ±0.03 mm. After measuring four points, compare the gap values ​​at each point. The difference between the maximum and minimum values ​​represents the bearing's ovality error.

[0033] This method achieves non-contact measurement of arc-surface bearings by optimizing probe placement and signal processing algorithms. Compared to traditional feeler gauge methods, it achieves over five times higher measurement accuracy and is not limited by measurement space. Practical applications have demonstrated that it can accurately identify clearance anomalies exceeding 0.02 mm in ship propulsion shafting bearing inspections, providing a reliable basis for bearing condition assessment. Measurement data can be exported via a USB port, facilitating the establishment of bearing wear trend profiles.

[0034] When operating, be careful to ensure the instrument is waterproof when measuring in humid environments, and ensure the probe cable has a bend radius of at least 50mm. When not in use for extended periods, remove the batteries and store in a dry box. Instrument accuracy should be calibrated using a standard test block every six months. If the measurement results deviate by more than 0.05mm, return the instrument to the factory for repair.

Claims

1. A method for measuring the clearance value of a ship bearing, characterized in that: The steps include: S1: Establish a 2D coordinate system based on the cross section of the bearing to be measured, select the measurement position, select the required echo parameters according to the measurement requirements, and select the required measurement accuracy; S2: Clean the selected measurement location to prevent stains at the selected location from affecting the measurement accuracy; S3: Select an appropriate thickness gauge, calibrate and filter the thickness gauge, and place the calibrated thickness gauge at the measuring position on the outer surface of the bearing assembly to be measured; S4: The thickness gauge emits ultrasonic waves, receives the first transmitted echo at the selected measurement position, and calculates the distance L1 traveled by the first reflected echo; S5: Receive the second transmitted echo at the selected measurement position and calculate the distance L2 traveled by the second transmitted echo; S6: Obtain the distance difference by calculating the formula: ΔL=L2-L1. This distance difference is the bearing clearance value to be measured. S7: Change the measuring position of the thickness gauge, repeat the above operation, and measure the bearing clearance values ​​at different positions.

2. A method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S1, four measurement positions are selected on the outside of the bearing, namely A, B, C and D. The four measurement positions are the intersection points of the bearing in the horizontal and vertical directions respectively. The difference between two adjacent measurement positions is ninety degrees. The echo parameters are selected as the second and third echo signals.

3. The method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S2, the measurement position cleaning steps are as follows: preliminary mechanical cleaning: use a soft brush or lint-free cloth to remove loose particles on the surface. For stubborn stains, use a plastic scraper to carefully scrape them off; solvent cleaning: use a volatile solvent such as isopropyl alcohol or a dedicated electronic cleaner to avoid using silicone or grease-containing cleaners to ensure complete evaporation and drying after cleaning; special treatment of the ultrasonic probe contact area: use a fine abrasive paste (such as 2000 mesh or above) to lightly polish the contact surface to ensure that the surface roughness Ra is less than 1.6μm; final inspection: visually check for visible stains and touch with gloves to confirm that there is no graininess.

4. The method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S3, an Olympus 38DL PLUS ultrasonic thickness gauge is selected. A low-frequency probe (1-5 MHz) is used to test thick or high-attenuation materials. A wide pulse (200-500 ns) is selected for the pulse. The threshold level is set to 2-3 times the noise amplitude (usually 5%-10% of the full scale). If it is too low, false triggering is easy. The rising edge trigger is selected as the trigger mode. It is commonly used and has a fast response.

5. The method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S3, the steps for calibrating the thickness gauge are as follows: using a standard test block: coupling the probe to a calibration test block of known thickness (e.g., a 4mm steel block); reading the measured value: the thickness displayed on the instrument should be consistent with the nominal value of the test block; adjusting the zero point: if the displayed value deviates significantly, enter the instrument calibration mode, enter the actual thickness of the test block, and the instrument will automatically correct the zero offset; some instruments require manual fine-tuning of the "Probe Delay" parameter, and verification is required after calibration: repeatedly measuring the test block: confirming that the error between the displayed value and the nominal value is within the allowable range (e.g., ±0.02mm); cross-validation: measuring the same location with another calibrated thickness gauge and comparing the results; bandpass filtering: setting the cutoff frequency to ±30% of the probe center frequency.

6. The method for measuring the clearance value of a ship bearing according to claim 3, characterized in that: In S4, the thickness gauge also receives an echo signal at the measurement location. Since this echo signal is not the required signal, it is automatically ignored. To ignore the first echo signal on the Olympus 38DL PLUS, enter the "Gate Setup" menu, set the Gate1 Start value to a value greater than the first echo arrival time, adjust the Gate Width to an appropriate range, and enable the "Gate1 Only" mode to receive the first echo signal. After receiving the first echo signal, the formula for calculating L1 is: L1: target distance (unit: meter, m); v: the propagation speed of ultrasonic waves in the medium (unit: meter / second, m / s); t: the time difference from transmission to reception of echo (unit: seconds, s); Divide by 2: Since ultrasonic waves travel back and forth, the one-way distance must be taken.

7. The method for measuring the clearance value of a ship bearing according to claim 6, characterized in that: In S5, the specific process of receiving the echo is: original signal acquisition → 2. Bandpass filtering → 3. TVG compensation → 4. Envelope extraction → 5. Echo identification → 6. Time measurement → 7. Sound velocity compensation → 8. Thickness calculation → 9. Results show that the specific calculation formula for L2 is: L2: target distance (unit: meter, m); v: the propagation speed of ultrasonic waves in the medium (unit: meter / second, m / s); t: the time difference from transmission to reception of echo (unit: seconds, s); Divide by 2: Since ultrasonic waves travel back and forth, the one-way distance must be taken.

8. The method for measuring the clearance value of a ship bearing according to claim 7, characterized in that: In the S6, the accuracy indicators of ΔL, L2 and L1 are: static: ±0.01mm; dynamic (10r / min): ±0.03mm. L2 and L1 are measured at least three times, and the average value is taken after the test to improve the test accuracy. The specific requirements during the test are: constant temperature: 23±1℃ (ISO standard), constant pressure: probe pressure 10±1N, and stabilization time: preheat for 15 minutes.

9. The method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S7, the specific operation of changing the measurement position is to rotate the selected thickness gauge 90 degrees clockwise from position A to position B, repeat the above operation and record the bearing clearance value, then move the thickness gauge to positions C and D in turn for ultrasonic thickness measurement, and record the clearance values ​​of the bearings at different positions.

10. The method for measuring the clearance value of a ship bearing according to claim 1, characterized in that: In S7, when operating the thickness gauge to move, it is necessary to wear an anti-static wristband and turn off the power of the instrument, use a wrench to loosen the fixing screws, pre-set a positioning mark at the position to be switched, and use screws to fix the thickness gauge in the position of the positioning mark. The verticality of the probe needs to be checked every time a position is changed.

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