JP7518808B2 - Diagnostic method, diagnostic program, and diagnostic device - Google Patents

Description

The present invention relates to a diagnostic method, a diagnostic program, and a diagnostic device for diagnosing a centrifugal dehydrator.

A commonly used method for diagnosing equipment with a rotary drive unit is to focus on the vibrations that occur during the operation of the equipment and perform diagnosis based on electrically measured vibration waveforms. For example, JP 8-122305 A (Patent Document 1) discloses a bearing abnormality diagnosis device that uses an AE sensor to measure acoustic emissions (AE) generated by bearings and diagnoses bearing abnormalities based on the AE signal output by this AE sensor.

Japanese Unexamined Patent Publication No. 8-122305

However, while the technology in Patent Document 1 takes into account the periodic changes in the presence or absence of an AE signal, it does not take into account the periodic changes in the strength of the detected signal. In a device that produces a humming noise, the effective value of the vibration waveform changes periodically, so the diagnosis results may vary depending on the selection of the vibration waveform data region used for diagnosis. As a result, when diagnosing a device that produces a humming noise, it is necessary to obtain vibration waveform data over a period sufficiently longer than the expected humming period in order to suppress the above-mentioned variation, which causes problems such as longer working hours for workers engaged in the diagnosis and a greater load on the calculation processing required to obtain the diagnosis results.

Therefore, there is a need to realize a diagnostic method, diagnostic program, and diagnostic device that can shorten the time required to acquire vibration waveform data while obtaining appropriate diagnostic results by diagnosing a centrifugal dehydrator that may generate groaning noise.

The diagnostic method according to the present invention is a diagnostic method for diagnosing a centrifugal spin-drying machine having an outer body and an inner body that rotate at different rotation speeds, based on vibration waveform data caused by the vibration of the centrifugal spin-drying machine, and includes an acquisition step for acquiring the vibration waveform data, a beat analysis step for analyzing the vibration waveform data to identify a beat period, which is a beat period caused by the difference between the rotation speed of the outer body and the rotation speed of the inner body, and a diagnosis step for calculating an effective value of the amplitude for an arbitrary region of the vibration waveform data and diagnosing the centrifugal spin-drying machine based on the effective value, characterized in that the time length of the region for which the effective value is calculated is an integer multiple of the beat period.

The diagnostic program according to the present invention is capable of diagnosing a centrifugal dehydrator having an outer body and an inner body that rotate at different rotational speeds based on vibration waveform data caused by the vibration of the centrifugal dehydrator, and when executed by a computer, causes the computer to realize an acquisition function for acquiring the vibration waveform data, a beat analysis function for analyzing the vibration waveform data and identifying a beat period caused by the difference between the rotational speed of the outer body and the rotational speed of the inner body, and a diagnostic function for calculating an effective value of the vibration amplitude for any region of the vibration waveform data and diagnosing the centrifugal dehydrator based on the effective value, and is characterized in that the time length of the region for which the effective value is calculated is an integer multiple of the beat period.

The diagnostic device according to the present invention is capable of diagnosing a centrifugal spin-drying machine having an outer body and an inner body that rotate at different rotational speeds based on vibration waveform data caused by the vibration of the centrifugal spin-drying machine, and includes a vibration measuring device and a computer, and the vibration measuring device is configured to acquire the vibration waveform data and input the vibration waveform data to the computer, and the computer is configured to realize a beat analysis function that analyzes the vibration waveform data input from the vibration measuring device and identifies the beat period caused by the difference between the rotational speed of the outer body and the rotational speed of the inner body, and a diagnostic function that calculates the effective value of the vibration amplitude for any region of the vibration waveform data and diagnoses the centrifugal spin-drying machine based on the effective value, and is characterized in that the time length of the region for which the effective value is calculated is an integer multiple of the beat period.

In these configurations, the beat period is identified in the beat analysis process, and the vibration waveform data of a region whose time length is an integer multiple of the identified beat period is used as the basis for diagnosis, which successfully achieves consistent diagnostic results regardless of the starting point of that region. This makes it possible to obtain appropriate diagnostic results while shortening the time length for acquiring vibration waveform data.

The following describes preferred embodiments of the present invention. However, the scope of the present invention is not limited to the preferred embodiments described below.

In one aspect of the diagnostic method according to the present invention, the beat analysis process preferably includes an envelope processing step for identifying an envelope of the vibration waveform data, and a beat period identification step for identifying the beat period based on the envelope.

With this configuration, the number of data points to be processed in the beat period determination step can be reduced compared to when envelope processing is not performed, thereby reducing the load of the calculation process.

In one aspect of the diagnostic method according to the present invention, in at least one of the acquisition step and the beat analysis step, extracted data is obtained by extracting a predetermined frequency range from the vibration waveform data that includes a rotational frequency determined based on the rotation speed of the outer body and the rotation speed of the inner body, and the envelope of the extracted data is determined in the envelope processing step.

With this configuration, diagnosis is performed after narrowing down the frequency range to be analyzed in detail based on known operating conditions, i.e., the rotation speeds of the outer and inner bodies, thereby reducing the load on calculation processing.

In one aspect of the diagnostic method according to the present invention, it is preferable that in the diagnostic process, the centrifugal dehydrator is diagnosed as being abnormal if the effective value exceeds a predetermined threshold value.

This configuration allows for the detection of abnormalities in the centrifugal dehydrator using a relatively simple concept, reducing the load on calculation processing and providing diagnostic results with high data interpretability.

In one aspect of the diagnostic method according to the present invention, the diagnostic process preferably includes a calculation step of calculating the effective value, a storage step of storing the calculated effective value in a storage device, and a diagnosis step of diagnosing the centrifugal dehydrator based on the calculated effective value and the past effective values stored in the storage device.

This configuration makes it possible to perform diagnosis taking past history into account, so diagnostic results that include information about trends can be obtained.

In one aspect of the diagnostic method according to the present invention, the diagnostic step preferably includes predicting the time when the effective value will exceed a predetermined threshold value based on the calculated effective value and past effective values stored in the storage device.

This configuration makes it possible to predict the occurrence of abnormalities, allowing maintenance of the centrifugal dehydrator to be carried out in a planned manner.

Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments, which are given with reference to the drawings.

1 is a diagram showing a configuration of a centrifugal dehydrator according to an embodiment. 1 is a block diagram showing a configuration of a diagnostic device according to an embodiment; FIG. 2 is a flow chart showing the configuration of a diagnostic method according to an embodiment. 13 is an example of an envelope according to an embodiment.

Embodiments of the diagnostic method, diagnostic program, and diagnostic device according to the present invention will be described with reference to the drawings. In the following, an example will be described in which the diagnostic method, diagnostic program, and diagnostic device according to the present invention are applied to a diagnostic method for diagnosing a centrifugal dehydrator 100 using a diagnostic device 1. The diagnostic program according to this embodiment is installed in the diagnostic device 1.

[Configuration of the centrifugal dehydrator]
First, the configuration of a centrifugal dehydrator 100 to be diagnosed by the diagnostic method, diagnostic program, and diagnostic device according to this embodiment will be described. The centrifugal dehydrator 100 includes an outer body 101 and an inner body 102 (FIG. 1). More specifically, the outer body 101 is a cylindrical body that rotates while accommodating a solid-liquid mixture such as a slurry-like sludge to be separated therein, and is a part that performs solid-liquid separation by centrifugal force. The inner body 102 is implemented as a screw, and is a part that plays a role of transporting the solid-liquid mixture and the solid components after solid-liquid separation. A feed pipe is provided inside the shaft 102a of the inner body 102, and the solid-liquid mixture is supplied to the centrifugal dehydrator 100 through the feed pipe.

In the centrifugal dehydrator 100, the outer body 101 and the inner body 102 rotate at different rotation speeds. Specifically, the rotation speed of the inner body 102 is about 3 to 5 rpm higher than the rotation speed of the outer body 101. As a result, the inner body 102 (screw) rotates relatively faster than the outer body 101 (cylindrical body), so inside the outer body 101, the solid-liquid mixture and solid components are transported gradually downstream (to the right in Figure 1) by the inner body 102. The rotation speed of the outer body 101 is set appropriately taking into account the properties of the object to be centrifuged and requirements from downstream processes, and can be, for example, 1500 to 3600 rpm. The rotation speed of the inner body 102 is set to a value about 3 to 5 rpm higher than the rotation speed of the outer body 101 depending on the rotation speed of the outer body 101.

In addition, in the downstream end region of the inner body 102, the thickness of the shaft 102a is gradually increased from the upstream side to the downstream side, so that the space formed between the outer body 101 and the shaft 102a gradually decreases. As a result, in the end region, the solid components are compressed between the shaft 102a and the inner wall of the outer body 101, and a dehydrated cake is formed. The dehydrated cake is discharged from the downstream end of the centrifugal dehydrator 100. Meanwhile, the liquid components after solid-liquid separation are discharged from the upstream end of the centrifugal dehydrator 100.

[Configuration of diagnostic device]
Next, a description will be given of the configuration of the diagnostic device 1 according to this embodiment. The diagnostic device 1 according to this embodiment includes a vibration measuring device 2 and a diagnostic terminal 3 (an example of a computer) (FIG. 2).

The vibration measuring device 2 may be a known sensor capable of converting vibrations into an electrical signal. Examples of sensors that can be used include an acceleration sensor, a speed sensor, and a non-contact displacement sensor. The vibration measuring device 2 is electrically connected to the diagnostic terminal 3, and is configured to be able to acquire vibration waveform data caused by the vibrations of the centrifugal dehydrator 100 and to input the vibration waveform data to the diagnostic terminal 3.

The vibration measuring device 2 can acquire vibration waveform data by using any location on the centrifugal dehydrator 100 as a measurement point. Typically, a user installs the vibration measuring device 2 on the surface of the bearing housing of the centrifugal dehydrator 100 body to acquire vibration waveform data. Note that there may be one or more vibration measuring devices 2, but if multiple vibration measuring devices 2 are provided, vibration waveform data for, for example, two mutually orthogonal axes can be acquired, which can improve diagnostic accuracy.

The vibration measuring device 2 may have a filter circuit. In this case, the vibration waveform data output from the vibration measuring device 2 is extracted data in which a specific frequency range determined according to the characteristics of the filter circuit is extracted from the vibration waveform data itself caused by the vibration of the centrifugal dehydrator 100. It is preferable that the characteristics of the filter circuit are determined taking into account the rotation speed of the outer body 101 and the rotation speed of the inner body 102.

The diagnostic terminal 3 is a terminal equipped with a computing unit 31, a storage unit 32, an input terminal 33, a display 34, and an input device 35. The diagnostic terminal 3 may be a dedicated terminal having a configuration known in the technical field of this type of diagnostic device, measuring device, etc., or may be a general-purpose information terminal such as a personal computer, a tablet terminal, or a smartphone.

The arithmetic unit 31 is configured to be capable of executing various arithmetic processes related to the diagnostic method and diagnostic program according to this embodiment, and is implemented as a known CPU. The storage device 32 is a storage device capable of storing various data handled by the diagnostic terminal 3, and is implemented as a magnetic memory such as a hard disk drive (HDD) or a semiconductor memory such as a solid state drive (SSD). The input terminal 33 is a terminal electrically connected to the vibration measuring device 2, and vibration waveform data is input to the diagnostic terminal 3 through the input terminal 33.

The display 34 and the input device 35 are components that function as a user interface section of the diagnostic terminal 3. The display 34 is provided for the purpose of displaying various data handled by the diagnostic terminal 3 and presenting (outputting) information to the user, and is implemented as a known liquid crystal display or the like. The input device 35 is provided for the purpose of accepting various input operations from the user to the diagnostic terminal 3, and is implemented as a keyboard, mouse, button, touch panel, or the like.

[Configuration of diagnostic method]
Next, the configuration of the diagnostic method according to this embodiment will be described. The diagnostic method according to this embodiment includes an acquisition step S10, a beat analysis step S20, and a diagnosis step S30 (FIG. 3). The diagnostic method according to this embodiment is implemented using a diagnostic device 1, and each function of the diagnostic program according to this embodiment is executed in each step. Therefore, it can be said that the subject that executes the acquisition step S10, the beat analysis step S20, and the diagnosis step S30 is the diagnostic terminal 3 (particularly the computing device 31) of the diagnostic device 1.

In the following, an example will be described in which the rotation speed of the outer body 101 is 3600 rpm and the rotation speed of the inner body 102 is 3603 rpm. In the explanation, a description to the effect that the rotation speed of the centrifugal dehydrator 100 is approximately 3600 rpm will be used.

(1) Acquisition step S10
The acquisition step S10 is a step of acquiring (causing the diagnostic terminal 3 to acquire) vibration waveform data caused by the vibration of the centrifugal dehydrator 100. Specifically, the vibration measurement is performed at an arbitrary position of the centrifugal dehydrator 100. The device 2 is installed to obtain vibration waveform data caused by the vibration of the centrifugal dehydrator 100, and the vibration waveform data is input to the diagnostic terminal 3.

(2) Beat Analysis Step S20
The beat analysis step S20 is a step of analyzing the vibration waveform data to identify the beat period, which is the period of the beat caused by the difference between the rotation speed of the outer case 101 and the rotation speed of the inner case 102.

Due to the difference in the rotation speed between the outer body 101 and the inner body 102, a humming noise occurs during operation of the centrifugal dehydrator 100. The humming period, which is the period of the humming noise, is specified as the number of seconds obtained by dividing 60 seconds by the difference in the rotation speed between the outer body 101 and the inner body 102, and is about 12 to 20 seconds. As a result, the intensity of the vibration of the centrifugal dehydrator 100 changes periodically with a period of about 12 to 20 seconds. As described above, if the rotation speed of the outer body 101 is 3600 rpm and the rotation speed of the inner body 102 is 3603 rpm, the difference in the rotation speed between the outer body 101 and the inner body 102 is 3 rpm, and the humming period can theoretically be derived as 20 seconds. However, it is difficult to accurately measure the rotation speed of each of the outer body 101 and the inner body 102, and the difference in the rotation speed between the two.

The beat analysis process S20 according to this embodiment includes an envelope processing step S21 for identifying the envelope of the vibration waveform data, and a beat period identification step S22 for identifying the beat period based on the envelope.

The centrifugal dehydrator 100 vibrates at a period of approximately 17 milliseconds (60 seconds ÷ 3600 ≒ 0.017 seconds), which corresponds to a rotation speed of approximately 3600 rpm. In the envelope processing step S21, the envelope of the vibration waveform data is identified by sequentially connecting the points at which the absolute value is maximum in each period of the vibration waveform data that vibrates at a period of approximately 17 milliseconds (Figure 4).

The vibration waveform data acquired in the acquisition step S10 itself includes components such as noise in addition to components caused by the vibration of the centrifugal dehydrator 100. Therefore, in the envelope processing step S21, a filter process may be performed from the vibration waveform data to extract extracted data of a predetermined frequency range including a rotation frequency (60 Hz) determined based on the rotation speed of the outer body 101 and the rotation speed of the inner body 102 (rotation speed of the centrifugal dehydrator 100: approximately 3600 rpm). The filter process may be a band-pass filter process. In this case, the envelope is determined for the extracted data obtained by the filter process.

When the vibration measuring device 2 has a filter circuit and filtered extracted data is input from the vibration measuring device 2 to the diagnostic terminal 3, envelope processing is performed on the extracted data. In other words, extraction of the extracted data may be performed by hardware in the vibration measuring device 2, or may be performed by software in the diagnostic terminal 3.

The envelope identified in the envelope processing step S21 represents a waveform that oscillates at a constant period. This period coincides with the beat period. Therefore, in the beat period identification step S22, the vibration period of the envelope identified in the envelope processing step S21 is identified, and this vibration period is identified as the beat period of the centrifugal dehydrator 100.

(3) Diagnosis process S30
The diagnosis process S30 is a process of calculating an effective value of the amplitude for any region of the vibration waveform data and diagnosing the centrifugal dehydrator 100 based on the effective value. The diagnosis process S30 includes a calculation step S31, a storage step S32, and a diagnosis step S33.

Calculation step S31 is a step for calculating the effective value of the amplitude for any region of the vibration waveform data. Here, the time length of the region for which the effective value of the amplitude is to be calculated is set to an integer multiple of the beat period.

As mentioned above, the envelope of the vibration waveform data oscillates at a period that coincides with the beat period (Figure 4). This means that the amplitude of the vibration waveform data oscillates at a period that coincides with the beat period. Therefore, when the effective value of the amplitude is calculated for a region whose time length is not an integer multiple of the beat period, the effective value obtained differs depending on the start point of the region. For example, when the effective value of the amplitude is calculated for regions R1 and R2 whose time length is 10 seconds (which is 0.5 times the beat period), the effective value in region R1, which includes a section in the beat period where the amplitude is small, will be smaller than the effective value in region R2, which includes a section in the beat period where the amplitude is large.

Therefore, in this embodiment, the time length of the region for which the effective value of the amplitude is calculated is set to an integer multiple of the beat period, so that a constant effective value can be obtained regardless of the start point of the region. For example, when the effective value is calculated for regions R3 and R4, which have a time length of 20 seconds (one time the beat period), the entire one cycle of increase and decrease in amplitude is included in both regions R3 and R4. Therefore, the effective value in region R3 and the effective value in region R4 are equal. Note that as long as the region has a time length of 20 seconds, the effective value will be constant regardless of the start point of the region, not limited to regions R3 and R4.

The storage step S32 is a step in which the effective value calculated in the calculation step S31 is stored in the storage device 32. At this time, the calculated effective value is stored in the storage device 32 in association with information such as the vibration waveform data itself, the date and time when the vibration waveform data was acquired, and the cumulative operating time of the centrifugal dehydrator 100 at that date and time.

The diagnostic step S33 is a step for diagnosing the centrifugal dehydrator 100 based on the effective value. The diagnosis performed in the diagnostic step S33 according to this embodiment includes the following:

(a) Diagnosis Based on the Effective Value Itself The first diagnosis is a diagnosis based on the effective value itself calculated in the calculation step S31. For example, a predetermined threshold value related to the effective value is stored in the storage device 32 in advance, and if the calculated effective value exceeds the threshold value, the centrifugal dehydrator 100 is diagnosed as being abnormal.

(b) Diagnosis based on the trend of the effective value The second diagnosis is a diagnosis based on the trend of the effective value. The trend used for the diagnosis is identified based on the effective value calculated in the calculation step S31 and the past effective values stored in the storage device 32. For example, the trend of the effective value is identified by arranging a plurality of effective values, including the past effective values, in a chronological order based on the date and time when the vibration waveform data associated with each effective value was acquired. In addition, the trend of the effective value can also be identified by creating a plot in which the accumulated operating time of the centrifugal dehydrator 100 associated with each effective value is on the horizontal axis and the effective value is on the vertical axis. If parameters such as the average value and the rate of change are identified based on the identified trend of the effective value, the centrifugal dehydrator 100 can be diagnosed based on the parameters.

The time when the effective value will exceed a predetermined threshold value may be predicted based on the trend of the identified effective value. In this case, it is possible to predict the time when the centrifugal dehydrator 100 will need to be replaced or dismantled for maintenance, and to carry out planned maintenance. Methods for predicting when the effective value will exceed a predetermined threshold value may include a method of identifying by extrapolation, a method of predicting by machine learning, and the like.

Other embodiments
Finally, other embodiments of the diagnostic method, diagnostic program, and diagnostic device according to the present invention will be described. Note that the configurations disclosed in the following embodiments can be combined with the configurations disclosed in other embodiments as long as no contradiction occurs.

In the above embodiment, an example has been described in which the acquisition step S10 involves installing a vibration measuring device 2 at an arbitrary location on the centrifugal dehydrator 100 to acquire vibration waveform data resulting from the vibration of the centrifugal dehydrator 100, and inputting the vibration waveform data to the diagnostic terminal 3. However, the acquisition step according to the present invention does not necessarily involve installing a vibration measuring device. For example, if a vibration measuring device is permanently installed on the centrifugal dehydrator, the acquisition step can be performed in such a manner that the vibration waveform data acquired by the vibration measuring device is output from a control panel or the like and input to the diagnostic terminal. In other words, the specific method of performing the acquisition step can be appropriately selected depending on the centrifugal dehydrator to be diagnosed and the configuration of the diagnostic terminal to be used.

In the above embodiment, an example has been described in which the beat analysis process S20 includes an envelope processing step S21. However, the beat analysis process according to the present invention does not necessarily include an envelope processing step. An example of a beat analysis process that does not include an envelope processing step is, for example, a mode in which a beat period is determined using a fast Fourier transform.

In the above embodiment, a configuration has been described in which diagnosis based on the effective value itself and diagnosis based on the trend of the effective value are performed in the diagnosis process S30. However, these are merely examples, and the method of diagnosing the centrifugal dehydrator in the diagnosis process according to the present invention is not limited.

In the above embodiment, the diagnosis process S30 is described as an example of a configuration in which the effective value is calculated for regions R3 and R4 having a time length of 20 seconds, which is one time the beat period. However, in the diagnosis process according to the present invention, the time length of the region for which the effective value is calculated is not limited as long as it is an integer multiple of the beat period, and may be two, three, four or more times the beat period.

In the above embodiment, the centrifugal dehydrator 100 is described as an example in which the thickness of the shaft 102a gradually increases from the upstream side to the downstream side in the downstream end region. However, the structure of the centrifugal dehydrator to be diagnosed in the present invention is not limited to this example. For example, if a structure is adopted in which the thickness of the shaft is constant and the inner diameter of the outer body gradually decreases from the upstream side to the downstream side, a structure in which the space formed between the outer body and the shaft gradually decreases can be realized, similar to the above embodiment.

As for other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects and that the scope of the present invention is not limited thereto. Those skilled in the art will easily understand that appropriate modifications are possible without departing from the spirit of the present invention. Therefore, other embodiments that are modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

The present invention can be used, for example, to diagnose centrifugal dehydrators operating in sewage treatment plants.

REFERENCE SIGNS LIST 1: Diagnosis device 2: Vibration measuring device 3: Diagnosis terminal 31: Arithmetic device 32: Storage device 33: Input terminal 34: Display 35: Input device 100: Centrifugal dehydrator 101: Outer body 102: Inner body 102a: Shaft of inner body

Claims (8)

A diagnostic method for diagnosing a centrifugal dehydrator having an outer body and an inner body that rotate at different rotation speeds based on vibration waveform data caused by vibration of the centrifugal dehydrator, comprising:
An acquisition step of acquiring the vibration waveform data;
a beat analysis step of analyzing the vibration waveform data to identify a beat period, which is a period of a beat caused by a difference between the rotation speed of the outer body and the rotation speed of the inner body;
a diagnosis step of calculating an effective value of an amplitude for an arbitrary region of the vibration waveform data and diagnosing the centrifugal dehydrator based on the effective value,
A diagnostic method in which the time length of the region for calculating the effective value is an integer multiple of the beat period. The beat analysis step includes:
an envelope processing step of identifying an envelope of the vibration waveform data;
The method of claim 1 , further comprising: determining the beat period based on the envelope. In at least one of the acquiring step and the beat analysis step, extracted data is obtained by extracting a predetermined frequency range from the vibration waveform data, the frequency range including a rotation frequency determined based on the rotation speed of the outer body and the rotation speed of the inner body;
3. The diagnostic method of claim 2, wherein said envelope processing step identifies an envelope of said extracted data. The diagnostic method according to any one of claims 1 to 3, wherein in the diagnostic process, if the effective value exceeds a predetermined threshold value, the centrifugal dehydrator is diagnosed as being abnormal. The diagnostic step comprises:
A calculation step of calculating the effective value;
a storage step of storing the calculated effective value in a storage device;
The diagnostic method according to any one of claims 1 to 4, further comprising a diagnostic step of diagnosing the centrifugal dehydrator based on the calculated effective value and past effective values stored in the storage device. The diagnostic method according to claim 5, wherein the diagnostic step includes predicting when the effective value will exceed a predetermined threshold value based on the calculated effective value and past effective values stored in the storage device. A diagnostic program capable of diagnosing a centrifugal dehydrator having an outer body and an inner body that rotate at different rotation speeds based on vibration waveform data caused by vibration of the centrifugal dehydrator, comprising:
When executed by a computer,
An acquisition function for acquiring the vibration waveform data;
a beat analysis function that analyzes the vibration waveform data and identifies a beat period caused by a difference between the rotation speed of the outer body and the rotation speed of the inner body;
a diagnostic function of calculating an effective value of a vibration amplitude for an arbitrary region of the vibration waveform data and diagnosing the centrifugal dehydrator based on the effective value;
A diagnostic program in which the time length of the region for calculating the effective value is an integer multiple of the beat period. A diagnostic device capable of diagnosing a centrifugal dehydrator having an outer body and an inner body that rotate at different rotation speeds based on vibration waveform data caused by vibration of the centrifugal dehydrator, comprising:
a vibration measuring device; and a computer;
the vibration measuring device is configured to be capable of acquiring the vibration waveform data and inputting the vibration waveform data into the computer,
The computer,
a beat analysis function for analyzing the vibration waveform data input from the vibration measuring device and identifying a beat period caused by a difference between the rotation speed of the outer body and the rotation speed of the inner body;
a diagnostic function of calculating an effective value of the amplitude of vibration for an arbitrary region of the vibration waveform data and diagnosing the centrifugal dehydrator based on the effective value,
A diagnostic device in which the time length of the region for calculating the effective value is an integer multiple of the beat period.

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