JP6781086B2 - Abnormal diagnosis method of sludge scraper - Google Patents

Description

The present invention relates to a method for diagnosing an abnormality of a sludge scraper that scrapes sludge by moving a scraping plate (flight) by two or more endless chains used in a sewage treatment plant or the like.

As shown in FIG. 9, the sludge scraper 41 is composed of a drive device 43, an endless chain 45, a sprocket 47, a flight 49, etc., and the flight 49 is attached to the endless chain 45 at regular intervals, and the flight 49 is attached to the drive shaft and the driven shaft. It is a device that is driven via a sprocket, moves the flight 49 in contact with the rail surface of the settling basin 51, and continuously attracts the sludge settled in the settling basin 51 into the sludge hopper.
In the sludge scraper 41 shown in FIG. 9, sprocket 47s are provided at five locations, and the outer diameter is one size larger than that of the drive device sprocket 53 and the drive shaft drive sprocket 54 (coordinated with the driven shaft driven sprocket 55, respectively). And drive shaft driven sprockets 55, 57, 59, 61.

Examples of the abnormal phenomenon in the sludge scraper 41 include elongation of the endless chain 45, wear of the sprocket 47 and flight 49, and the like.
The endless chain 45 and the sprocket 47 are in mesh with each other as shown in FIG. 10, and as shown in FIG. 11, corrosion wear (diagonal portion in the figure) may occur at the root of the tooth 63 of the sprocket 47. ..

However, the rotation speed of the drive device 43 is a very low rotation speed of, for example, about 0.4 rpm, and the traveling speed of the flight 49 is, for example, 0.3 m / min, which is a device that travels very slowly to collect sludge. Moreover, since most of the device is in the water, it is difficult to detect the abnormality with all five senses from the outside of the sedimentation basin 51.

Therefore, a general method for checking the presence or absence of abnormalities in the sludge scraper 41 is to drain the water in the settling basin 51, expose the drive system, and wash the inside of the tank and the drive system with high-pressure washing water. After that, the worker goes down to the bottom of the settling basin to inspect each part, and after the inspection, the restoration work is performed.
However, the settling basin 51 may have a depth of 10 m or more, which requires a long time to drain water and involves dangerous work, which requires a great deal of labor and cost for the inspection work itself, and the settling basin 51 to be inspected. Since the inflow of sewage is stopped, the sewage treatment performance deteriorates.

Therefore, it is desired to detect such an abnormality of the sludge scraper 41 more easily. For example, "A method for detecting an abnormality of a sludge scraper chain or the like" in Patent Document 1 or "Chain" in Patent Document 2. A "flight-type sludge scraper" has been proposed.

According to Patent Document 1, "a detection means for emitting ultrasonic waves and receiving a reflected signal thereof is arranged around the endless chain, and the measured value output from the front-rear detection means is compared with a reference value. It is characterized in that it determines the presence or absence of an abnormality in the endless chain or the flight and displays the image information on the screen. ”(See claim 1).

Further, in Patent Document 2, "a detection unit provided at the same position of opposing driven sprockets on which a pair of chains are hung and a detection means for detecting the detection unit and transmitting a signal are provided. The detection means is characterized by being connected to a control unit that acquires the signal and stops the sludge scraper when there is a time lag in the transmission of the signal. " (See claim 1)

Japanese Unexamined Patent Publication No. 9-122404 Japanese Unexamined Patent Publication No. 2005-138023

All of the above-mentioned ones disclosed in Patent Documents 1 and 2 are intended to detect an abnormality by installing a sensor or the like at a place where an abnormality is expected to occur.
Therefore, it is necessary to install a sensor or the like on a sprocket or the like underwater, and there is a problem that it is not possible to detect an abnormality of a sprocket or the like currently in operation.
Further, even if the sensor or the like can be attached to a predetermined place at the time of inspection or the like, the sensor or the like is installed in sewage, so that the sensor itself may fail, and there is a possibility of false detection due to the failure. There is a problem.

The present invention has been made to solve such a problem, and is applicable to a sludge scraper in operation, and provides a method for diagnosing an abnormality of a sludge scraper with less false detection due to a device failure or the like. It is an object.

The inventor earnestly studied a method capable of detecting an abnormality without attaching a sensor or the like to a sprocket 47 or the like in water as in a conventional example, and focused on the peculiarity of the sludge scraper 41.
That is, as described above, since the sludge scraper 41 is a device that moves slowly at a very low speed as compared with a high-speed rotating machine such as a pump or a blower, almost no vibration or abnormal noise is generated under normal conditions.
However, as shown in FIG. 11, when the sprocket 47 is worn or the endless chain 45 is stretched, the meshing pitch between the endless chain 45 and the sprocket 47 is displaced or slipped, and strong impact vibration is generated at that time. It is thought that. Since such vibrations occur in water, they cannot be captured by the five senses outside the sedimentation basin 51.
However, in the sludge scraper 41, since the endless chain 45 is stretched with a predetermined tension, it is considered that the above vibration is transmitted to the drive device 43 on the ground via the endless chain 45, and this is transmitted by the vibration sensor. We obtained the knowledge that anomalies could be detected by catching them.
The present invention is based on such findings, and specifically has the following configuration.

(1) The method for diagnosing an abnormality of a sludge scraper according to the present invention is to continuously move sludge settled in a settling pond by moving flights attached to an endless chain wound around a sprocket and circulated by a drive device at predetermined intervals. It is a method of diagnosing an abnormality in the sludge scraper that scrapes into the sludge.
A vibration waveform is acquired from a vibration sensor installed near the drive shaft of the drive device installed outside the sedimentation basin, a peak value and an rms value are acquired from the vibration waveform, and the ratio of the peak value to the rms value is obtained. It is characterized in that the wave height ratio is obtained and the presence or absence of an abnormality is determined based on the wave height ratio.

(2) Further, in the case described in (1) above, it is determined whether or not the peak value has periodicity, and if there is periodicity, the meshing cycle of the chain and the sprocket and the cycle of the peak value are used. It is characterized in that a relationship is obtained and it is determined whether or not an abnormality is present in the sprocket based on the relationship.

(3) Further, in the above (1) or (2), the current waveform is acquired from the sensor attached to the power cable of the motor of the drive device, and an abnormality is obtained based on the sideband wave level of the current waveform. It is characterized in that it determines the presence or absence of.

In the present invention, the vibration waveform is acquired from the vibration sensor mounted near the drive shaft of the drive device installed outside the settling pond, the peak value and the rms value are acquired from the vibration waveform, and the peak value and the rms are obtained. Since the wave height rate, which is the ratio of the values, is calculated and the presence or absence of an abnormality is determined based on the wave height rate, it can be applied to a sludge scraper in operation, and an abnormality diagnosis with few false positives due to failures etc. can be performed. It can be carried out.

It is explanatory drawing of the apparatus used for the abnormality diagnosis method of the sludge scraper which concerns on embodiment of this invention. It is a figure which graph-displayed the wave height rate obtained by the abnormality diagnosis method of the sludge scraper which concerns on embodiment. It is an example of the vibration waveform obtained by the abnormality diagnosis method of the sludge scraper according to the embodiment, and shows the frequency analysis waveform in addition to the vibration waveform (No. 1). It is an example of the vibration waveform obtained by the abnormality diagnosis method of the sludge scraper according to the embodiment, and shows the frequency analysis waveform in addition to the vibration waveform (Part 2). This is a waveform obtained by subjecting the vibration waveform of FIG. 4 to envelope processing. This is an example of the current waveform obtained by the abnormality diagnosis method of the sludge scraper according to the embodiment. It is explanatory drawing explaining the reason why the current waveform is used (the 1). It is explanatory drawing explaining the reason why the current waveform is used (the 2). It is explanatory drawing explaining the whole structure of the general sludge scraper. It is explanatory drawing explaining a part of the structure of the sludge scraper shown in FIG. 9 is an explanatory view of one aspect of the abnormal phenomenon of the sludge scraper shown in FIG. 9, and FIG. 11B is a cross-sectional view taken along the line AA of FIG. 11A.

The abnormality diagnosis method of the sludge scraper according to the embodiment of the present invention (hereinafter, simply referred to as “abnormality diagnosis method”) is in the vicinity of the drive shaft of the drive device 43 installed outside the sedimentation pond 51, specifically, The vibration waveform is acquired from the vibration sensor 1 (see FIG. 1) mounted near the output shaft of the motor (the position indicated by P in FIG. 1), and the peak value and the rms value are obtained from the vibration waveform in the vibration diagnostic device 3. The feature is that the wave height rate, which is the ratio of the peak value and the rms value, is obtained, and the presence or absence of an abnormality is determined based on the wave height rate.
Further, in the present embodiment, when a current waveform is acquired from a sensor attached to a power cable (not shown) of the motor of the drive device 43 and the sideband wave level of the current waveform exceeds a predetermined predetermined value. In addition, it is used for diagnosis according to the result of the above wave height rate.

In the present embodiment, as an example of the device used for abnormality diagnosis, a vibration sensor unit 5 having a vibration sensor 1 installed near the drive shaft of the drive device 43, and a clamp sensor as a sensor attached to the power cable (not shown). , And the vibration diagnostic device 3 that inputs the vibration waveform acquired by the vibration sensor unit 5 and the current waveform acquired by the clamp sensor to perform an abnormality diagnosis.
First, the equipment to be used will be outlined based on FIG. 1, and then the abnormality diagnosis method will be described. In FIG. 1, the reference numerals indicating the respective parts of the sludge scraper 41 are the same as those in FIG.

<Vibration sensor unit>
As shown in FIG. 1, the vibration sensor unit 5 includes a vibration sensor 1 including a piezoelectric element 9 and a magnet 7 for installing the piezoelectric element 9 at a measurement location, and an amplifier that amplifies a signal output from the sensor unit 9. 11 and an A / D converter 13 that converts the vibration amplified by the amplifier 11 into a digital signal.
The vibration waveform acquired by the vibration sensor unit 5 is transmitted to the vibration diagnostic device 3 via the cable 15.

In the present embodiment, an example in which one vibration sensor unit 5 is used is shown, but in the present invention, the number of vibration sensor units 5 is not limited to one, and a plurality of vibration sensor units 5 are used. Is not excluded.

<Clamp sensor>
The clamp sensor is attached to a three-phase power cable (any of the U, V, and W phases) of the motor of the drive device 43 to be diagnosed in the electric chamber, and collects current waveform data.

<Vibration diagnostic device>
The vibration diagnostic device 3 is composed of devices and programs mounted on a portable PC.
As shown in FIG. 1, the vibration diagnostic apparatus 3 includes a vibration waveform data storage means 17, a current waveform data storage means 19, a vibration level calculation means 21, a wave height rate calculation means 23, a periodicity analysis means 25, and the like. It includes a frequency analysis means 27, a current waveform analysis means 29, an input means 31, and a display means 33.
Hereinafter, each means will be described in detail.

<< Vibration waveform data storage means >>
The vibration waveform data storage means 17 inputs a signal transmitted from the vibration sensor unit 5 and appropriately filters and stores the vibration waveform data.
The acquisition time of the vibration waveform data is a predetermined time determined in advance.

<< Current waveform data storage means >>
The current waveform data storage means 19 stores the current waveform data transmitted from the clamp sensor.

<< Vibration level calculation means >>
The vibration level calculating means 21 calculates a vibration level, for example, a peak value or an rms value, based on the vibration waveform data.

<< Means for calculating wave height rate >>
The crest rate calculation means 23 obtains the crest rate, which is the ratio of the peak value and the rms value, based on the peak value and the rms value calculated by the vibration level calculation means 21.
Since the sludge scraper 41 has an output shaft rotation speed of about 0.4 rpm, which is an ultra-low speed rotation, the generated vibration itself is a small value, so it is difficult to evaluate the absolute value using a judgment reference value such as that of a blower pump. is there.
However, as a general characteristic in the case of a low-speed rotating machine, there is a characteristic that a peak vibration relatively large with respect to the rms value is generated when an abnormality occurs. The crest factor is a numerical value of this characteristic. The crest rate is a value of the ratio with the peak value and is obtained by the following equation (1).
Crest rate = peak value / rms value ... (1)
The crest factor is a parameter indicating the strength of the impact of the waveform, and the larger the peak vibration is included in the waveform, the larger the crest factor becomes.

FIG. 2 shows a summary of the wave height rates obtained for the 29 sludge scrapers 41 currently in operation at a sewage treatment plant. In FIG. 2, the vertical axis is the wave height ratio, and the horizontal axis is the number of the sludge scraper 41 to be diagnosed.
In this example, the crest rates of No. 17 and No. 18 are higher than the others. Therefore, it can be seen that peak vibrations were generated in the sludge scrapers No. 17 and No. 18.

<< Periodic analysis means >>
The periodicity analysis means 25 analyzes the periodicity of the vibration waveform based on the vibration waveform data.
FIG. 3 shows an example of the analysis result, FIG. 3 (a) is the vibration waveform of No. 18 and FIG. 3 (b) is the vibration waveform of No. 19. As can be seen by comparing the two, periodic peak oscillation can be seen in No. 18 of FIG. 3 (a).

FIG. 4 shows another analysis example of the periodic analysis means 25. FIG. 4 (a) is the vibration waveform of No. 9, and FIG. 4 (b) is the vibration waveform of No. 11. As can be seen by comparing the two, periodic peak oscillation can be seen in No. 11 of FIG. 4 (b). FIG. 5 shows a waveform obtained by subjecting the vibration waveform of FIG. 4 (b) to envelope processing. As shown in FIG. 5, it can be seen that the impact vibration is generated in a cycle of about 26 seconds (s). Since such periodic shock vibration can be detected, it can be effectively used for abnormality diagnosis as described later.

<< Frequency analysis means >>
The frequency analysis means 27 analyzes the frequency of the vibration waveform based on the vibration waveform data. This makes it possible to know the frequency band when peak vibration occurs.

<< Current waveform analysis means >>
The current waveform analysis means 29 analyzes the current waveform based on the current waveform data to analyze the presence or absence of an abnormality.
As a result of measuring the current of 29 sludge scrapers 41, the sideband wave level of the motor rotation frequency component (fL ± fr) of No. 18 tended to be large. (FL = 50Hz (power frequency), fr = 24.7Hz (motor rotation frequency)
FIG. 6A shows the current waveform which is the analysis result. For comparison, the No. 19 wave whose sideband wave level is not so large is also shown in FIG. 6 (b).

When the endless chain 45 and the sprocket 47 are worn, it is considered that the load affects the drive device 34 (motor) that drives the endless chain 45, and the increase in the wave component on the drive device side as described above is considered to occur. There is a tendency. Therefore, detecting the presence or absence of an increase in the wave component on the drive device side is effective for diagnosing an abnormality in the sludge scraper.

To outline the wave component on the drive device side, FIG. 7 schematically shows a current waveform, FIG. 7 (a) shows a normal current waveform, and FIG. 7 (b) shows an abnormal current waveform. It shows. At the time of abnormality, the current waveform is modulated, and the modulation of this waveform appears as a sideband wave component as shown by being surrounded by the broken line ellipse in FIG. Therefore, by detecting the presence / absence of the sideband wave component, the presence / absence of modulation of the current waveform can be detected.

《Input means》
The input means 31 is for the operator to input information for work instructions and the like, and is generally composed of a keyboard.

<< Display means >>
The display means 33 displays an analysis result or the like, and is generally configured by a PC monitor, and displays the above-mentioned graph of wave height ratio, vibration waveform, current waveform, etc., and an operator performs an abnormality diagnosis. Contribute to.

<Abnormal diagnosis method>
An abnormality diagnosis method for a sludge scraper using the above device will be described below.
First, in order to install the vibration sensor 1 near the bearing portion of the drive device 43 on the ground, collect the vibration acceleration waveform for a certain period of time, and transfer the collected acceleration waveform to the vibration diagnostic device 3, the inside of the vibration sensor unit 5. A / D conversion is performed at the above, the acceleration waveform data is transferred to the vibration diagnostic apparatus 3, and stored by the vibration waveform data storage means 17.
Further, the current waveform is input from the clamp sensor and stored by the current waveform data storage means 19.

The basic diagnostic method of the present embodiment is to analyze by each means based on the above-mentioned stored vibration waveform data and current waveform data, and the operator diagnoses the presence or absence of abnormality based on the analysis result. ..
In the present embodiment, considering that the above-mentioned wave height rate is effective, the peak value and the rms value are acquired from the acquired vibration waveform, the wave height rate which is the ratio of the peak value and the rms value is obtained, and the wave height rate is obtained. It is to judge the presence or absence of abnormality based on.
Specifically, a preset threshold value for the crest rate for the presence or absence of abnormality is determined, and when the threshold value is exceeded, it is determined that there is an abnormality. Alternatively, as shown in FIG. 2, the wave height ratio may be obtained for a plurality of sludge scrapers 41, and those having a relatively high wave height ratio may be determined to have an abnormality.

Further, as another diagnostic method, it is determined from the vibration waveform acquired by the periodicity analysis means 25 of the vibration diagnostic apparatus 3 whether or not the peak value has periodicity, and if there is periodicity, the endless chain 45 The relationship between the meshing period of the sprocket 47 and the period of the peak value may be obtained, and it may be determined whether or not there is an abnormality in the sprocket 47 based on the relationship.
The endless chain 45 and the sprocket 47 are engaged as shown in FIG. 9, and as shown in FIG. 10, corrosion wear may occur at the roots of the teeth 63 of the sprocket 47, which causes periodic shock vibration. Since it is thought that it will occur, we focused on this.
This method will be described more specifically.

In the above description, as shown in FIG. 5, it can be seen that the No. 11 sludge scraper generates impact vibration at a cycle of about 26 seconds (s).
Since this impact vibration may cause a malfunction in the meshing of the endless chain 45 and the sprocket 47, the meshing cycle of the sprocket 47 at the five points of the sludge scraper 41 shown in FIG. 1 is investigated in Table 1 below. Is.

As can be seen from Table 1, the meshing period of the drive shaft driven sprockets 55, 57, 59, 61 is 26.0, which is consistent with the period shown in FIG. From this, it can be inferred that the drive shaft driven sprockets 55, 57, 59, 61 in the water may be worn and the meshing may be abnormal.
By using such a diagnosis result, it is useful to know where to concentrate the inspection at the time of inspection.

The above is an abnormality diagnosis based on the information from the vibration sensor 1. In addition to this, a current waveform is acquired from a sensor attached to the power cable of the motor of the drive device 43, and the sideband wave level of the current waveform is determined in advance. If it exceeds the specified specified value, it may be determined that there is an abnormality.
That is, by referring to the current waveform, it is possible to understand how much the degree of abnormality found in the vibration waveform affects the addition of the motor, which is an index for the timing of starting the inspection. That is, when the abnormality in the current waveform is large, it is considered that the load is large and the degree of wear is advanced, so an early inspection is required.

As described above, according to the abnormality diagnosis method of the present embodiment, it is possible to accurately diagnose the sludge scraper 41 currently in operation without installing a sensor or the like in water.

In the above diagnostic method, the operator makes an individual or comprehensive judgment based on the data obtained by the vibration diagnostic device 3, but as shown below, the vibration diagnostic device 3 is provided with an automatic diagnostic means. It is also possible to make an automatic diagnosis by providing it.
That is, the assumed cause of abnormality of the sludge scraper 41 is defined in advance, and for each cause of abnormality, the vibration level / wave height rate when the abnormality occurs, the dominant frequency component / waveform periodicity / current frequency, etc. Detailed information is registered as an abnormality cause analysis matrix as shown in Table 2, for example.

The analysis data obtained by the vibration diagnostic apparatus 3 is collated with the abnormality cause analysis matrix defined in Table 2, and the similarity calculation is performed to automatically diagnose the abnormality cause. Then, as a result, the name of the cause of the abnormality with a high possibility is displayed on the screen.

An example of a specific automatic diagnosis method is as follows.
As the judgment criteria, it is defined as (i) and (ii) below.
(i) Threshold values are set in advance for each of the judgment indexes a to o shown in Table 2, and if the measured data exceeds the threshold value, the condition is satisfied (1.0) and the threshold value is set. If it is less than, the condition is not satisfied (0.0).
(ii) If the result of multiplying multiple judgment indexes is 1.0, it is judged that there is a possibility of the cause of the abnormality. If even one condition is not met, it is judged that there is no possibility of the cause of the abnormality.

The threshold values of the determination indexes a to o are set as follows, for example.
a to c: Threshold value for determining vibration level If the vibration level at a preset measurement point is equal to or higher than the set value, a to c = 1.0,
If it is a normal value, a to c = 0.0
d to f: Threshold value for determining crest rate d to f = 1.0 if the crest rate at a preset measurement point is equal to or greater than the set value.
If it is less than the set value, d ~ f = 0.0
g to i: Threshold value for periodicity analysis g to i = 1.0 if the preset period range and the period of the measurement point match.
If they do not match, g ~ i = 0.0
j to l: Threshold value for frequency analysis If a frequency component that matches a preset frequency range is included above the set value
j ~ l = 1.0,
If it is less than the set value, j ~ l = 0.0
m to o: Threshold value for frequency analysis of current If a frequency component that matches a preset frequency range is included above the set value
m ~ o = 1.0,
If it is less than the set value, m ~ o = 0.0

On the premise of the above conditions, for example, when a × d × g × j × m = 1.0 × 1.0 × 1.0 × 1.0 × 1.0 = 1.0, it is determined that there is chain wear.

1 Vibration sensor 3 Vibration diagnostic device 5 Vibration sensor unit 7 Magnet 9 Sensor unit 11 Amplifier 13 A / D converter 15 Cable 17 Vibration waveform data storage means 19 Current waveform data storage means 21 Vibration level calculation means 23 Wave height rate calculation means 25 Cycle Sex analysis means 27 Frequency analysis means 29 Current waveform analysis means 31 Input means 33 Display means 41 Sludge scraper 43 Drive device 45 Endless chain 47 Sprocket 49 Flight 51 Sedimentation pond 53 Drive device sprocket 54 Drive shaft drive sprocket 55, 57, 59, 61 Drive shaft driven sprocket 63 teeth

Claims (3)

Wear and / or wear of the sprockets in a sludge scraper that moves flights attached to endless chains that are wound around a plurality of sprockets and orbited by a drive device at predetermined intervals to continuously scrape the sludge that has settled in the sedimentation pond. A method for diagnosing the elongation of the endless chain .
A vibration waveform is acquired from a vibration sensor installed near the drive shaft of the drive device installed outside the sedimentation pond, a peak value and an rms value are acquired from the vibration waveform, and the ratio of the peak value to the rms value is obtained. A method for diagnosing an abnormality of a sludge scraper, which comprises obtaining a wave height ratio, and determining whether or not the sprocket is worn and / or the endless chain is stretched based on the wave height ratio. It is determined whether or not the peak value has periodicity, and if there is periodicity, the relationship between the meshing period of the chain and the sprocket and the period of the peak value is obtained, and whether there is an abnormality in the sprocket based on the relationship. The method for diagnosing an abnormality of a sludge scraper according to claim 1, wherein it is determined whether or not. The sludge according to claim 1 or 2, wherein a current waveform is acquired from a sensor attached to a power cable of a motor of the drive device, and the presence or absence of an abnormality is determined based on the sideband wave level of the current waveform. Abnormality diagnosis method for the scraper.

Images