Diagnostic system and method for pumps and pump bearings

Abstract

This system detects the condition of the pump bearings without using sensors that are directly attached to the bearings. [Solution] A pump comprising a motor, a shaft connected to the motor, a bearing having a land portion and supporting the shaft, power wiring, and a current sensor for detecting the current value of the power wiring, wherein the current sensor is configured to communicate with an analysis unit that performs analysis of the current value using a fast Fourier transform.

Description

[[TECHNICAL FIELD]]

[0001] The present disclosure relates to a pump, and a diagnosis system and a diagnosis method for a pump bearing. [[BACKGROUND ART]]

[0002] Conventionally, technological development for investigating the degree of pump failures and deterioration of pump components has been progressing.

[0003] Patent Document 1 discloses a vibration measurement device including: a vibration sensor that outputs a signal corresponding to the vibration of the pump; an A / D converter that converts an analog signal corresponding to the signal output by the vibration sensor into a digital signal; a rotation sensor that outputs a signal having a frequency corresponding to the rotation speed of the rotation shaft of the pump; and a Fourier transformer, wherein the A / D converter is configured to convert the analog signal into the digital signal at a sampling frequency corresponding to the frequency of the signal output by the rotation sensor. [[PRIOR ART DOCUMENTS]] [[PATENT DOCUMENTS]]

[0004] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2002-48633 [[SUMMARY OF THE INVENTION]] [[Problem to be Solved by the Invention]]

[0005] Since the bearing, impeller, and other components of a pump are installed inside the pump, they remain immersed in liquid such as water during operation and standby periods. Furthermore, if the liquid is corrosive, the bearing, impeller, and other components are placed in an environment where they are prone to corrosion over a long period of time. As a result, crevice corrosion or the like may occur in the base metal of the bearing, reducing the adhesive strength of the sliding material, which may lead to abnormalities such as peeling of the sliding material. Peeling of the sliding material is a cause of vibration generation in pumps and is one of the factors that induce pump failure.

[0006] The vibration measuring device described in Patent Document 1 requires the installation of vibration sensors and rotation sensors at predetermined locations on the pump body. However, it is difficult to directly attach vibration sensors to bearings, impellers, etc., and it is necessary to attach them indirectly to the nearby pump casing, etc., to measure the vibrations. As a result, it can be difficult to accurately diagnose the degree of abnormality from the detected data. Furthermore, it can be difficult to pinpoint the location of the abnormality, and there is room for improvement. In addition, if bearings, impellers, etc. are submerged in liquid, corrosion and deterioration of the sealing function may occur in the vibration sensors themselves and the signal cables, making it difficult to ensure long-term reliability, and the sensors may need to be replaced.

[0007] The purpose of this disclosure is to detect the condition of a pump bearing without using a sensor that is directly attached to the pump bearing. [Means for solving the problem]

[0008] The pump of this disclosure comprises a motor, a shaft connected to the motor, a bearing having a land portion and supporting the shaft, power wiring, and a current sensor for detecting the current value of the power wiring, wherein the current sensor is configured to communicate with an analysis unit that performs analysis of the current value using a fast Fourier transform.

[0009] The pump bearing diagnostic system of this disclosure is a system for diagnosing the condition of the bearing of a pump comprising a motor, a shaft connected to the motor, a bearing having a land portion and supporting the shaft, power wiring, and a current sensor for detecting the current value of the power wiring, and comprises an analysis unit that performs analysis of the current value by fast Fourier transform, and a determination unit that determines the difference between the feature quantities of the operating data obtained by the analysis and reference data. [Effects of the Invention]

[0010] According to this disclosure, the condition of the pump bearing can be detected without using a sensor that is directly attached to the pump bearing. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the overall configuration of the pump in the embodiment. [Figure 2A] This is a top view showing a damaged bearing in the pump of the embodiment. [Figure 2B] Figure 2A is a longitudinal cross-sectional view showing the bearing. [Figure 3] This flowchart shows a diagnostic method for pump bearings according to an embodiment. [Figure 4] This is a diagram showing the configuration of a diagnostic system for pump bearings according to an embodiment. [Figure 5A] This is a cross-sectional view showing the uppermost bearing when the pump of the embodiment is operating normally. [Figure 5B] This is a cross-sectional view showing the middle bearing of the pump in the embodiment when it is operating normally. [Figure 6A] This is a cross-sectional view showing the uppermost bearing in the pump of the embodiment when a malfunction occurs. [Figure 6B] Figure 6A is a cross-sectional view showing the middle bearing installed in a pump where a malfunction has occurred in the uppermost bearing. [Figure 7] This graph shows the change in output current from the pump in the example over time. [Figure 8] This graph shows the change in output current over time when there is a malfunction in the bearing of the pump in the example. [Figure 9] This graph shows the amplitude spectrum obtained by performing an FFT analysis on the output current waveform in Figure 7. [Figure 10] This graph shows the amplitude spectrum obtained by performing an FFT analysis on the output current waveform in Figure 8. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the pump and the pump bearing abnormality diagnosis system and diagnosis method relating to this disclosure will be described with reference to the drawings. [Examples]

[0013] FIG. 1 is a cross-sectional view showing the overall configuration of a pump according to an embodiment.

[0014] The pump 100 shown in the drawing is a vertical shaft pump of a long type having a long underground portion and including a plurality of bearings in the underground portion. The pump 100 includes a motor 10, a shaft 20, bearings 30a, 30b, 30c, an impeller 40, a stationary vane 50 (guide vane), a casing 60, and a bent barrel 70.

[0015] The shaft 20 is connected downward to the motor 10. The impeller 40 is provided at the lower end of the shaft 20. The shaft 20 is installed inside the casing 60. The stationary vane 50 is provided around the impeller 40.

[0016] The motor 10 is supported on the upper surface of a foundation 80 and installed on an above-ground section together with the bent barrel 70. Meanwhile, the shaft 20, the bearings 30a, 30b, 30c, the impeller 40, the stationary vane 50 and the casing 60 are installed in an underground section. Liquid such as water is stored in the underground section. The impeller 40, the stationary vane 50 and the like are installed below the water surface.

[0017] The bearings 30a, 30b, 30c are respectively arranged at different positions in the vertical direction inside the casing 60. It should be noted that the number of installation positions of the bearings is not limited to three in the vertical direction, and may be two or four or more.

[0018] The pump 100 operates by driving the motor 10 with an external power source to rotate the shaft 20 and the impeller 40. The shaft 20 and the impeller 40 rotate with the central axis of the shaft 20 as the rotation axis. At this time, upward vertical pressure is applied to water or the like existing between the impeller 40 and the stationary vane 50. The water or the like rises through the flow path inside the casing 60, has its flow direction changed to the horizontal direction by the bent barrel 70 in the above-ground section, and is then sent to a predetermined location.

[0019] The shaft 20 is subjected to centrifugal force due to rotation and forces from the flow of water, etc., causing it to wobble relative to its axis of rotation. This wobble may cause the shaft 20 to come into contact with and slide against the bearings 30a, 30b, and 30c.

[0020] Figure 2A is a top view showing the pump bearing in the embodiment in a damaged state.

[0021] In this figure, seven bearing sliding parts 230 (land parts) are installed on the inner wall surface of a bearing base plate 260 having a flange. The bearing sliding parts 230 are convex parts, and when the shaft 20 (Figure 1) rotates and wobbles, the shaft 20 does not come into direct contact with the inner wall surface of the bearing base plate 260. In addition, the installation of the bearing sliding parts 230 can reduce the amount of wobble of the shaft 20. The bearing base plate 260 is made of stainless steel or the like. The bearing sliding parts 230 are made of rubber, PTFE (polytetrafluoroethylene), or the like.

[0022] In this figure, one of the seven bearing sliding parts 230 is damaged and has peeled away from the inner wall surface (peeled part 235).

[0023] Figure 2B is a longitudinal cross-sectional view showing the bearing in Figure 2A.

[0024] As shown in this figure, the bearing sliding portion 230 is fixed to the inner wall surface of the bearing base plate 260 via an adhesive portion 231. In this figure, the lower part of the bearing sliding portion 230 has peeled off and is lifted away from the inner wall surface of the bearing base plate 260.

[0025] Figure 3 is a flowchart illustrating a pump bearing diagnostic method according to an embodiment. As a prerequisite for this method, during pump trial operation, the FFT intensity is acquired and recorded as initial data (reference data) using a method similar to that shown in this figure. Here, FFT stands for Fast Fourier Transform.

[0026] In this diagram, the pump is started (step S300), and the motor's output current is measured periodically or over the entire period (step S310). Here, the output current fluctuates depending on the mechanical output when the pump is used to pump water or the like.

[0027] Then, an FFT analysis is performed on the obtained current waveform (step S320). From the results of this FFT analysis, the FFT intensity during actual operation is obtained and recorded as operation data (step S330).

[0028] Next, the operating data is compared with the initial data (step S340). If there are no differences in the feature quantities such as FFT intensity and peak frequency, in other words, if the difference in the feature quantities between the operating data and the initial data is within a predetermined range, it is diagnosed as normal (step S350). On the other hand, if there are differences in the FFT intensity, peak frequency, etc., in other words, if the difference in the feature quantities between the operating data and the initial data is outside a predetermined range, it is diagnosed as abnormal (step S360).

[0029] Figure 4 is a diagram showing the configuration of a pump bearing diagnostic system according to an embodiment.

[0030] In this figure, the diagnostic system for the bearings 30a, 30b, and 30c of the pump 100 includes an ammeter 420 (current sensor) that detects the current value of the three-phase power wiring 410, an analysis unit 430 that performs FFT analysis on the obtained current value, a determination unit 440 that determines the difference in feature quantities, and a recording unit 450 composed of an HDD (Hard Disk Drive) or the like. The recording unit 450 records and stores the data from the analysis unit 430 and the determination unit 440. The ammeter 420 may be a sensor (coil, etc.) that detects the current value from the magnetic field generated by the current flowing through the power wiring 410, or it may be a clamp meter. The ammeter 420 may also be a component of the pump 100.

[0031] It is desirable that at least two of the components of the ammeter 420, analysis unit 430, determination unit 440, and recording unit 450 are connected to each other in a way that allows them to communicate with one another. In this case, the communication may be wired or wireless, and may be connected via the Internet, intranet, etc.

[0032] Figure 5A is a cross-sectional view showing the uppermost bearing when the pump of the embodiment is operating normally.

[0033] In this figure, five bearing sliding parts 530a (land parts) are installed on the inner wall surface of the bearing base plate 560. During pump operation, the shaft 20 vibrates relative to its rotation axis, so the central axis of the bearing base plate 560 and the central axis of the shaft 20 do not coincide.

[0034] Figure 5B is a cross-sectional view showing the middle bearing of the pump in the embodiment when it is operating normally.

[0035] In this figure, seven bearing sliding parts 530b (land parts) are installed on the inner wall surface of the bearing base plate 560.

[0036] The number of lands on the bearings shown in Figures 5A and 5B is 5 and 7, respectively, and they are different. When multiple bearings have different numbers of lands, it is possible to identify which bearing is malfunctioning.

[0037] Furthermore, it is desirable that the number of these land areas differs from the number of impeller blades. By configuring the number of land areas to differ from the number of impeller blades Z, the frequency components generated in accordance with the number of land areas will have different values ​​from the rotational speed frequency component N excited by the impeller rotational force (unbalance) and the N×Z component frequency excited by the interference between the impeller blades and the stationary vanes. Therefore, it becomes possible to diagnose whether the bearing is abnormal by frequency analysis using FFT analysis.

[0038] Figure 6A is a cross-sectional view showing the uppermost bearing in the pump of the embodiment when a malfunction occurs.

[0039] In this figure, one of the five bearing sliding parts 530a in the uppermost row, indicated by a dashed line, is detached and missing (bearing sliding part 535a).

[0040] Figure 6B is a cross-sectional view showing the middle bearing installed in a pump where the uppermost bearing is malfunctioning, as shown in Figure 6A.

[0041] In this figure, no abnormalities such as peeling have occurred in the seven bearing sliding parts 530b in the middle section.

[0042] Next, we will explain how the output current changes before and after an abnormality like the one shown in Figure 6A occurs in the bearing.

[0043] The following conditions are assumed in the explanation below.

[0044] The pump (motor) is powered by a 50Hz AC power supply. There are two bearings. The upper bearing has 5 lands, and the lower bearing has 7 lands. The shaft rotation speed is 1500 (min). -1 ) and its frequency is 25Hz.

[0045] Figure 7 is a graph showing the change in output current from the pump in the embodiment over time. The horizontal axis represents time, and the vertical axis represents the amplitude of the current.

[0046] In this diagram, the output current from the pump is detected as the sum of pulsed currents.

[0047] When the pump is running, the shaft oscillates and periodically slides close to the land. This periodically narrows the flow path between the land and the shaft, and each time it experiences mechanical resistance in the form of a reaction force or friction that pushes the fluid away. Consequently, torque fluctuations occur in the pump (motor). As a result, a pulsed current with a period different from the power supply frequency is detected by the ammeter.

[0048] Therefore, the current detected by the ammeter is the sum of the current from the AC power supply and the pulsed current. In this figure, the 50Hz AC current is not shown in order to focus on the changes in the pulsed current.

[0049] In this embodiment of the pump, bearings are installed in two locations, and the output current value is the sum of the pulse currents originating from each of these bearings.

[0050] Assuming the bearing lands are in a normal state, in the case of a bearing with 5 lands, the shaft approaches the lands 5 times during one rotation, so the frequency of the pulse current due to mechanical resistance is 25Hz × 5 = 125Hz.

[0051] On the other hand, in the case of a bearing with seven lands, the shaft approaches the lands seven times during one rotation, so the frequency of the pulse current due to mechanical resistance is 25Hz × 7 = 175Hz.

[0052] If the bearing land is delaminated, an abnormal pulse current will be generated. Conversely, if the bearing land is damaged or missing, the shaft will not experience mechanical resistance even when approaching that land, and therefore no pulse current will be generated attributable to that land.

[0053] In this figure, since the bearing land is in a normal state, the amplitude of the reference output current (i.e., the data included in the reference data, which is the same output current as the initial data) is obtained.

[0054] Figure 8 is a graph showing the change in output current over time when there is a malfunction in the bearing of the pump in the embodiment.

[0055] In this figure, the amplitude of the output current is lower than the value of the curve shown in Figure 7, within the range indicated by the dashed circle. This is thought to indicate that an abnormality has occurred, such as a defect in the bearing's land area. Specifically, this would occur if a defect occurs in one of the five land areas of a bearing.

[0056] Figure 9 is a graph showing the amplitude spectrum obtained by performing an FFT analysis on the output current waveform in Figure 7. The horizontal axis represents frequency, and the vertical axis represents amplitude.

[0057] Figure 9 shows that amplitude peaks exist at frequencies of 125 Hz and 175 Hz. Here, for the sake of simple comparison, the maximum amplitude of each peak has been normalized to 1, but in actual operation, normalization is not always necessary.

[0058] Figure 10 is a graph showing the amplitude spectrum obtained by performing an FFT analysis on the output current waveform in Figure 8.

[0059] In Figure 10, the amplitude peak at a frequency of 125 Hz is reduced. This is thought to correspond to an abnormality in the bearing, which has five lands. Since the peak reduction rate is approximately 20%, it is thought that one of the five lands is missing.

[0060] Furthermore, in the amplitude spectrum shown in this figure, amplitude peaks occur when the frequency is a multiple of 25. Consequently, the amplitude peak at 175 Hz, which corresponds to the bearing with 7 lands, increases slightly and becomes greater than 1.

[0061] The effects of the pump, diagnostic system, and diagnostic method related to this disclosure are explained below.

[0062] A current sensor installed in the pump's power wiring detects the current value of the power wiring and determines the output current value. This current sensor is configured to communicate with an analysis unit that performs Fast Fourier Transform analysis on the current value. This current sensor measures the motor's output current periodically or over the entire duration of pump operation. In this case, the output current does not necessarily need to be measured at fixed intervals, and the measurement period does not need to be constant. This makes it possible to provide a pump that can analyze changes in output current caused by the condition of the bearings. Furthermore, it eliminates the need to install the sensor in liquid.

[0063] By performing an FFT analysis on the output current of the pump motor and monitoring the change in FFT intensity (amplitude), it is possible to detect a bearing malfunction. In this case, if the number of lands on the bearing is different from the number of blades on the impeller, the bearing malfunction can be distinguished from the impeller blade malfunction and detected accordingly.

[0064] Furthermore, even if the number of lands on the bearing is equal to the number of impeller blades, the mechanical resistance caused by the bearing lands and the mechanical resistance experienced by the impeller are thought to have different changes over time. Therefore, it is considered possible to distinguish bearing abnormalities from impeller blade abnormalities and detect the current value accordingly.

[0065] Furthermore, by configuring multiple bearings so that the number of lands differs from one another, it becomes possible to identify which bearing is malfunctioning.

[0066] By installing a current sensor that detects the current value of the pump's power wiring at the pump's installation location (indoors) and configuring it to be able to communicate with the outside, the pump can be remotely diagnosed even if the analysis unit that performs analysis using Fast Fourier Transform on the current value detected by the current sensor, and the determination unit that determines the difference in feature quantities between the operating data obtained from the analysis and the reference data are installed in a location other than the pump's installation location. [Explanation of Symbols]

[0067] 10: Motor, 20: Shaft, 30a, 30b, 30c: Bearings, 40: Impeller, 50: Stationary vanes, 60: Casing, 70: Curved shell, 80: Base, 100: Pump, 230, 530a, 530b, 535a: Bearing sliding parts, 231: Adhesive parts, 235: Detachable parts, 260, 560: Bearing base metal, 410: Power wiring, 420: Ammeter, 430: Analysis unit, 440: Judgment unit, 450: Recording unit.

Claims

1. Motor and, A shaft connected to the motor, A bearing having a land portion and supporting the shaft, Power wiring and The system includes a current sensor that detects the current value of the power supply wiring, The current sensor is configured to communicate with an analysis unit that performs analysis of the current value using a fast Fourier transform, and is located in a pump.

2. The bearing is installed at multiple locations, The pump according to claim 1, wherein the number of lands on each of the bearings is different from one another.

3. It is further equipped with an impeller having blades, The pump according to claim 1, wherein the number of land portions is different from the number of blades of the impeller.

4. The pump according to claim 1, wherein the current sensor is a clamp meter.

5. Motor and, A shaft connected to the motor, A bearing having a land portion and supporting the shaft, Power wiring and A system for diagnosing the condition of the bearings of a pump, comprising a current sensor for detecting the current value of the power supply wiring, An analysis unit that performs analysis of the aforementioned current value using Fast Fourier Transform, A diagnostic system for pump bearings, comprising: a determination unit that determines the difference in feature quantities between the operating data obtained by the above analysis and the reference data.

6. The pump bearing diagnostic system according to claim 5, wherein the determination unit determines that an abnormality has occurred in the bearing when the difference between the characteristic quantity of the operating data and the reference data is not within a predetermined range.

7. The pump bearing diagnostic system according to claim 6, wherein the aforementioned feature quantity is the frequency or amplitude.

8. Motor and, A shaft connected to the motor, A bearing having a land portion and supporting the shaft, Power wiring and A method for diagnosing the condition of the bearing of a pump, which includes a current sensor for detecting the current value of the power supply wiring, The analysis unit performs an analysis of the current value using the Fast Fourier Transform, A method for diagnosing pump bearings, wherein a determination unit determines the difference in feature quantities between the operating data obtained by the analysis and the reference data.

9. The method for diagnosing a pump bearing according to claim 8, wherein the determination unit determines that an abnormality has occurred in the bearing when the difference between the characteristic quantity of the operating data and the reference data is not within a predetermined range.

10. The method for diagnosing a pump bearing according to claim 9, wherein the aforementioned feature quantity is the frequency or amplitude.

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