JP7843222B2 - Diagnostic device, diagnostic method, and diagnostic program - Google Patents

Description

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

As a method for diagnosing devices with a rotary drive unit, a commonly used method focuses on vibrations generated during the operation of the device and performs diagnosis based on electrically measured vibration waveforms. For example, Japanese Patent Publication No. 8-122305 (Patent Document 1) discloses a bearing abnormality diagnostic device that measures acoustic emissions (AE) generated by a bearing using an AE sensor and diagnoses bearing abnormalities based on the AE signal output by this AE sensor.

Japanese Patent Application Publication No. 8-122305

However, while the technology described in Patent Document 1 could determine the presence or absence of bearing abnormalities, it could not estimate the location of those abnormalities. Therefore, even when disassembling and servicing the device after detecting an abnormality, the entire device had to be examined to find the cause of the abnormality, which sometimes resulted in a long time being required to resolve the problem.

Therefore, there is a need for a diagnostic device, diagnostic method, and diagnostic program that can not only identify the presence or absence of an abnormality but also estimate its location.

The diagnostic device according to the present invention is a diagnostic device for diagnosing a centrifugal dewatering machine having an outer shell and an inner shell arranged concentrically and supported by two bearing portions provided at both ends in the extending direction, and rotating at different rotational speeds from each other, and comprising vibration sensors provided at least one at each of the two bearing portions, and a calculation device, wherein the calculation device identifies the waveform of the hum of the centrifugal dewatering machine based on the detected values of the two vibration sensors, and identifies the residual unbalance of the centrifugal dewatering machine based on the waveform of the hum.

The diagnostic method according to the present invention is a diagnostic method for diagnosing a centrifugal dewatering machine comprising an outer and inner drum arranged concentrically, supported by two bearing portions provided at both ends in the extending direction, and rotating at different rotational speeds, and characterized by comprising the steps of: identifying the waveform of the hum of the centrifugal dewatering machine to be diagnosed based on the detection values of vibration sensors provided at least one at each of the two bearing portions; and identifying the residual unbalance of the centrifugal dewatering machine based on the waveform of the hum.

The diagnostic program according to the present invention is a diagnostic program for diagnosing a centrifugal dewatering machine comprising an outer and inner drum arranged concentrically, supported by two bearing sections located at both ends in the extending direction, and rotating at different rotational speeds. The program, when executed by a computer, is characterized by its ability to: identify the waveform of the hum of the centrifugal dewatering machine being diagnosed based on the detection values of vibration sensors provided at least one at each of the two bearing sections; and identify the residual unbalance of the centrifugal dewatering machine based on the hum waveform.

With this configuration, the presence or absence of residual unbalance can be diagnosed and its location estimated based on the detection values of vibration sensors, each of which is provided on at least one bearing section.

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

In one embodiment of the diagnostic device according to the present invention, it is preferable that the calculation device uses the detection values of the two vibration sensors to solve a mechanical model of a centrifugal dehydrator in which residual unbalance is set at a predetermined position, and obtains a solution that represents the actual residual unbalance based on the residual unbalance in the mechanical model, thereby identifying the residual unbalance of the centrifugal dehydrator to be diagnosed.

This configuration allows for a reduction in computational processing load because the detected values are applied to a pre-defined dynamic model to obtain a solution.

In one embodiment of the diagnostic device according to the present invention, it is preferable that the calculation device separates the residual unbalance of the centrifugal dehydrator to be diagnosed into the residual unbalance of the outer drum of the centrifugal dehydrator and the residual unbalance of the inner drum of the centrifugal dehydrator.

This configuration allows for the diagnosis of residual imbalance in both the outer and inner shells, as well as the estimation of the location of its cause.

In one embodiment of the diagnostic device according to the present invention, it is preferable that the calculation device identifies the phase difference between residual unbalance located at one end of the centrifugal dewatering machine to be diagnosed in the extending direction and residual unbalance located at the other end of the extending direction.

This configuration allows for a more detailed identification of the relative positions of residual imbalances in the outer and inner casings.

In one embodiment of the diagnostic device according to the present invention, it is preferable that the calculation device further identifies the envelope of the hum waveform of the centrifugal dehydrator to be diagnosed.

This configuration allows for a reduction in the number of data points to be processed compared to a case without envelope processing, thereby lowering the computational load.

In one embodiment, the diagnostic device according to the present invention preferably generates a virtual waveform in which the angular velocity is the same as the angular velocity of the outer drum or the angular velocity of the inner drum, and the amplitude is greater than 0 and less than or equal to the minimum amplitude of the envelope, generates an added waveform obtained by adding the virtual waveform and the envelope, and based on the added waveform, separates the residual unbalance of the centrifugal dehydrator to be diagnosed into the residual unbalance of the outer drum of the centrifugal dehydrator and the residual unbalance of the inner drum of the centrifugal dehydrator.

This configuration allows for the diagnosis of residual imbalance in both the outer and inner shells, and the estimation of the location of the cause, through relatively simple calculations.

In one embodiment, the diagnostic device according to the present invention further comprises an outer drum tachometer for measuring the rotational speed of the outer drum of a centrifugal dehydrator to be diagnosed, and an inner drum tachometer for measuring the rotational speed of the inner drum of the centrifugal dehydrator, wherein the calculation device identifies the residual unbalance of the centrifugal dehydrator to be diagnosed based on the hum waveform, the rotational speed of the outer drum, and the rotational speed of the inner drum.

This configuration allows for the identification of the cause of residual unbalance by distinguishing between one end and the other in the extending direction of the outer and inner drums, as well as the vibration sensors (at least one of each) located at each of the two bearing sections, based on the detected values of these sensors, the rotational speed of the outer drum, and the rotational speed of the inner drum. It also allows for the identification of the phase difference between the two ends.

Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments, with reference to the drawings.

This is a diagram showing the configuration of a centrifugal dehydrator according to an embodiment. This is a block diagram showing the configuration of the diagnostic device according to the embodiment. This is a flowchart showing the configuration of the diagnostic method according to the embodiment. This is an example of an envelope according to the embodiment. This is a schematic diagram showing the phase difference of acceleration detected in the embodiment. This is a schematic diagram of the mechanical model according to the embodiment.

Embodiments of the diagnostic device, diagnostic method, and diagnostic program according to the present invention will be described with reference to the drawings. Below, 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 the diagnostic device 1. The diagnostic program according to this embodiment is installed on the diagnostic device 1.

[Configuration of a centrifugal dehydrator]
First, the configuration of the centrifugal dewatering machine 100, which is the target of diagnosis by the diagnostic method, diagnostic program, and diagnostic device according to this embodiment, will be described. The centrifugal dewatering machine 100 comprises an outer shell 101 and an inner shell 102 (Figure 1). More specifically, the outer shell 101 is a cylindrical body that rotates while containing a solid-liquid mixture such as slurry-like sludge to be separated, and is the part that performs solid-liquid separation by centrifugal force. The inner shell 102 is mounted as a screw and is the part that plays the 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 shell 102, and the solid-liquid mixture is supplied to the centrifugal dewatering machine 100 through the feed pipe.

The outer casing 101 and inner casing 102 are pivotally supported at two bearing sections 103 (103a, 103b) located at both ends in the extending direction (left-right direction in Figure 1). The outer casing 101 and inner casing 102 are rotated together by the driving force of a drive mechanism (not shown), and a differential speed is applied by a differential speed device 104. As a result, the outer casing 101 and inner casing 102 rotate at different rotational speeds.

The rotational speed of the inner cylinder 102 is approximately 3 to 5 rpm higher than that of the outer cylinder 101. This causes the inner cylinder 102 (screw) to rotate relatively faster than the outer cylinder 101 (cylindrical body), thus gradually conveying the solid-liquid mixture and solid components downstream (to the right in Figure 1) within the outer cylinder 101. The rotational speed of the outer cylinder 101 is set appropriately considering the properties of the material being centrifuged and the requirements from downstream processes, but it can be, for example, 1500 to 3600 rpm. The rotational speed of the inner cylinder 102 is set to a value approximately 3 to 5 rpm higher than that of the outer cylinder 101.

Furthermore, in the downstream end region of the inner cylinder 102, the diameter of the shaft 102a is gradually increased from the upstream side to the downstream side, thereby gradually reducing the space formed between the outer cylinder 101 and the shaft 102a. As a result, in this end region, the solid components are compressed between the shaft 102a and the inner wall of the outer cylinder 101, forming a dewatered cake. This dewatered cake is discharged from the downstream end of the centrifugal dewaterer 100. Conversely, the liquid components after solid-liquid separation are discharged from the upstream end of the centrifugal dewaterer 100. Hereafter, the side to which the solid-liquid mixture is supplied (left side in Figure 1) will be referred to as the "supply side," and the side from which the dewatered cake is discharged (right side in Figure 1) will be referred to as the "discharge side." The supply side and discharge side are at opposite ends in the extending direction of the centrifuge 100.

[Configuration of the diagnostic device]
Next, the configuration of the diagnostic device 1 according to this embodiment will be described. The diagnostic device 1 according to this embodiment includes a vibration sensor 2, an outer casing tachometer 3, an inner casing tachometer 4, and a computer 5 (an example of a computing device) (Figure 2). One vibration sensor 2 is provided in each of the two bearing sections 103a and 103b. When distinguishing between them, the one provided in the supply-side bearing section 103a is referred to as vibration sensor 2a, and the one provided in the discharge-side bearing section 103b is referred to as vibration sensor 2b.

As the vibration sensor 2, a known sensor capable of converting vibration into an electrical signal can be used. Examples of usable sensors include acceleration sensors, velocity sensors, and non-contact displacement sensors. While it is not prohibited for the two vibration sensors 2a and 2b to be of different types, it is preferable for the two vibration sensors 2a and 2b to be of the same type from the viewpoint of simplifying component procurement and calculation processing. For the purpose of explanation below, the case where both vibration sensors 2a and 2b are acceleration sensors will be described as an example, but the diagnostic device 1 according to this embodiment will function similarly even when other types of vibration sensors are used.

The vibration sensor 2 is electrically connected to the computer 5 and is configured to input measured values to the computer 5. The vibration sensor 2 may input the measured physical quantity itself to the computer 5, or it may input a value that has undergone some processing.

As an example of a configuration capable of such processing, the vibration sensor 2 may have a filter circuit. In this case, the measured values output from the vibration sensor 2 become extracted data, which is obtained by extracting a specific frequency range determined according to the characteristics of the filter circuit from the measured values themselves that are caused by the vibration of the centrifugal dewatering machine 100. The characteristics of the filter circuit are preferably determined considering the rotation speed of the outer drum 101 and the rotation speed of the inner drum 102.

The outer drum tachometer 3 is a tachometer that measures the rotational speed of the outer drum 101, and any known tachometer can be used. If the centrifugal dehydrator 100 already has a tachometer for measuring the rotational speed of the outer drum 101, instead of providing the outer drum tachometer 3 in the diagnostic device 1, a signal line may be connected so that the output value of the tachometer already installed in the centrifugal dehydrator 100 is input to the computer 5.

The inner drum tachometer 4 is a tachometer that measures the rotational speed of the inner drum 102, and any known tachometer can be used. The measurement methods of the outer drum tachometer 3 and the inner drum tachometer 4 may be the same or different. If the centrifugal dewatering machine 100 is equipped with a tachometer that measures the rotational speed of the inner drum 102, similar to the outer drum tachometer 3, this may be used instead of the inner drum tachometer 4.

Computer 5 is a terminal comprising an arithmetic unit 51, a storage device 52, an input terminal 53, a display 54, and an input device 55. Computer 5 may be a dedicated terminal with a configuration known in the technical field of diagnostic and measuring devices of this type, or it may be a general-purpose information terminal such as a personal computer, tablet terminal, or smartphone.

The arithmetic unit 51 is configured to execute 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 52 is a storage device capable of storing various data handled by the computer 5, 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 53 is electrically connected to the vibration sensors 2 (2a, 2b), the outer casing tachometer 3, and the inner casing tachometer 4, and vibration waveform data is input to the computer 5 through the input terminal 53. The input signals from the vibration sensors 2, the outer casing tachometer 3, and the inner casing tachometer 4 input to the input terminal 53 are synchronized.

The display 54 and input device 55 are components that function as the user interface of the computer 5. The display 54 is provided for the purpose of displaying various data handled by the computer 5 and presenting (outputting) information to the user, and is implemented as a known liquid crystal display, etc. The input device 55 is provided for the purpose of receiving various input operations from the user to the computer 5, and is implemented as a keyboard, mouse, buttons, touch panel, etc.

[Structure of the 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 diagnostic step S30 (Figure 3). The diagnostic method according to this embodiment is performed using the diagnostic device 1, and each function of the diagnostic program according to this embodiment is executed in each step. Therefore, the main entity that executes the acquisition step S10, the beat analysis step S20, and the diagnostic step S30 is the computer 5 (particularly the arithmetic unit 51) of the diagnostic device 1.

In the following explanation, we will use the example where the rotation speed of the outer cylinder 101 is 3600 rpm and the rotation speed of the inner cylinder 102 is 3603 rpm. In the explanation, we may sometimes use statements to the effect that the rotation speed of the centrifugal dewatering machine 100 is approximately 3600 rpm.

(1) Acquisition step S10
The acquisition process S10 is a process of acquiring (having the computer 5 acquire) vibration waveform data caused by vibrations of the centrifugal dehydrator 100, the rotation speed of the outer drum 101, and the rotation speed of the inner drum 102. Specifically, the measured values measured by the vibration sensors 2 (2a, 2b), the outer drum tachometer 3, and the inner drum tachometer 4 are input to the computer 5.

(2) Beat analysis process S20
The beat analysis step S20 is a step in which the waveform of the beat of the centrifugal dehydrator 100 is identified based on the detection values of the two vibration sensors 2.

A humming noise occurs during operation of the centrifugal dewatering machine 100 due to the difference in rotational speed between the outer drum 101 and the inner drum 102. The humming period is determined by dividing 60 seconds by the difference in rotational speed between the outer drum 101 and the inner drum 102, and is approximately 12 to 20 seconds. This causes the vibration intensity of the centrifugal dewatering machine 100 to change periodically with a period of approximately 12 to 20 seconds. As an example, if the rotational speed of the outer drum 101 is 3600 rpm and the rotational speed of the inner drum 102 is 3603 rpm, the difference in rotational speed between the outer drum 101 and the inner drum 102 is 3 rpm, and the humming period can be theoretically derived as 20 seconds.

In the beat analysis step S20 of this embodiment, the envelope of the vibration waveform data (a plot with time on the horizontal axis and the measured value of the vibration sensor 2 on the vertical axis) is identified (S21), and feature values are extracted from the envelope (S22). In this embodiment, the identification of the envelope (S21) and the extraction of feature values (S22) are performed for each measured value of the vibration sensor 2a (supply side) and the vibration sensor 2b (discharge side).

Corresponding to the rotational speed of the centrifugal dehydrator 100, which is approximately 3600 rpm, the centrifugal dehydrator 100 vibrates with a period of approximately 17 milliseconds (60 seconds ÷ 3600 ≈ 0.017 seconds). The envelope of the vibration waveform data is identified by performing a Hilbert transform on the vibration waveform data vibrating with a period of approximately 17 milliseconds, or by sequentially connecting the points where the absolute value is maximum in each period (Figure 4).

The vibration waveform data acquired in acquisition step S10 contains components such as noise in addition to components caused by the vibration of the centrifugal dehydrator 100. Therefore, filtering may be performed to extract data within a predetermined frequency range, including the rotational frequency (approximately 60 Hz) determined based on the rotational speed of the outer drum 101 and the inner drum 102 (rotational speed of the centrifugal dehydrator 100: approximately 3600 rpm), from the vibration waveform data. This filtering can be a bandpass filter. In this case, the envelope is identified using the extracted data obtained through filtering.

Furthermore, if the vibration sensor 2 has a filter circuit and filtered extracted data is input from the vibration sensor 2 to the computer 5, envelope processing is performed on that extracted data. In other words, the extraction of the extracted data may be performed either hardware-wise in the vibration sensor 2 or software-wise in the computer 5.

Next, based on the identified envelope, various feature values to be used in the calculation process in diagnostic step S30 are extracted. First, the beat period is extracted. The envelope shows a waveform that oscillates with a constant period, and this period coincides with the beat period. Second, the maximum value _V1 and minimum value _V2 of the amplitude in the identified envelope are extracted.

(3) Diagnostic process The diagnostic process S30 is a process of identifying the residual unbalance of the centrifugal dehydrator 100 based on the envelope and characteristic values of the envelope identified in the beat analysis process S20. The procedure broadly includes identifying the amplitude (S31), identifying the phase difference (S32), and applying a mechanical model (S33).

(3-1) Amplitude Identification As described above, the humming of the centrifugal dehydrator 100 is caused by the difference in rotational speed between the outer drum 101 and the inner drum 102. This phenomenon can be explained by the fact that when the phases of the residual unbalance of the outer drum 101 and the residual unbalance of the inner drum 102 are close, the vibrations caused by both act additively and become larger, and when the phases are far apart, the vibrations caused by both act in a way that cancels each other out and becomes smaller. Therefore, in the envelope identified in the humming analysis step S20, the point where the amplitude takes its maximum value _V1 is the point where the phases of the residual unbalance of the outer drum 101 and the residual unbalance of the inner drum 102 coincide, and the point where the amplitude takes its minimum value _V2 is the point where the phase difference is 180°.

Here, if we denote the component due to residual unbalance in the outer shell 101 as having amplitude a _B and angular velocity ω _B , and the component due to residual unbalance in the inner shell 102 as having amplitude a _S and angular velocity ω _S , then the acceleration A detected by the vibration sensor 2 is expressed as a function of time t by the following equation (1).

The envelope identified in beat analysis step S20 is obtained by sequentially connecting the points where the absolute value is maximum in each period of the waveform represented by equation (1). Therefore, the maximum value _V1 and minimum value _V2 of the envelope amplitude are expressed by the following equations (2) and (3).

Equation (3) can be divided into the following cases depending on the relative magnitudes of a _B and a _S.

Therefore, when a _B > a _S , a _B and a _S can be determined from the system of equations (2) and (3-1) as follows.

Similarly, when a _B < a _S , a _B and a _S can be determined from the system of equations (2) and (3-1) as follows.

In other words, if the relative magnitudes of _aB and _aS can be determined, then aB and _aS can _{be determined based on the maximum amplitude values V1 and V2 extracted from the envelope. However, the relative magnitudes of aB and aS cannot be} determined from the envelope itself, so a process is needed to determine this.

Therefore, in this embodiment, a virtual waveform A _i is created with the amplitude set to the minimum value _V2 of the envelope and the angular velocity to _ωB . The minimum value _V2 of the envelope can be extracted from the envelope, and the angular velocity _ωB can be determined from the rotational speed of the outer shell 101, so both can be determined. The rotational speed of the outer shell 101 used at this time may be an actual value measured by the outer shell tachometer 3, or a rough value based on the operating conditions (3600 rpm in this embodiment) may be used. In any case, the virtual waveform A _i can be created from the information available at this point. The following describes the case where an actual value of the rotational speed of the outer shell 101 is used. The virtual waveform A _i is expressed by the following equation (6).

Next, the waveform obtained by adding the acceleration A detected by the vibration sensor 2 and the virtual waveform A _i is calculated. This added waveform is represented by the following equation (7).

Now, substitute equation (3) into equation (7).

When a _B > a _S , V ₂ = a _B - _{a S} (Equation (3-1)), so Equation (8) can be transformed as follows.

Considering the case where the amplitude of the envelope takes its minimum value _V2 , at this time the component due to the residual unbalance of the outer shell 101 and the component due to the residual unbalance of the inner shell 102 are in opposite phase, so sin( _ωBt ) = -sin( _ωSt ). Therefore, equation (8-1) can be further transformed as follows.

The right-hand side of equation (8-2) is nothing more than twice the acceleration A (equation (1)) detected by the vibration sensor 2. Therefore, when a _B > a _S , the minimum value V ₂ of the envelope is doubled by adding the virtual waveform A _i to the acceleration A. Note that if a rough value is used for the rotation speed of the outer casing 101, the minimum value V ₂ of the envelope is approximately doubled.

On the other hand, when a _B < a _S , V ₂ = a _S - _{a B} (equation (3-2)), so equation (8) can be transformed as follows.

Similar to the case where a _B > a _S , if we consider the case where the amplitude of the envelope takes its minimum value V ₂ , then equation (8-3) can be further transformed as follows using sin(ω _B t) = -sin(ω _S t).

From equation (8-4), when a _B < a _S , the minimum value of the envelope V ₂ becomes 0 by adding the virtual waveform A _i to the acceleration A. Furthermore, when a rough value is used for the rotational speed of the outer casing 101, the minimum value of the envelope V ₂ becomes approximately 0.

To summarize the above process, when a virtual waveform A i created from the minimum amplitude V ₂ extracted from the envelope and the angular velocity ω _B determined from the rotational speed of the outer shell 101 is added to the identified _envelope , the minimum amplitude of the added waveform will be either twice the minimum value V ₂ of the original envelope or zero. Based on this difference in behavior, the relationship between a _B and a _S can be determined. That is, when the minimum amplitude of the added waveform is twice the minimum value V ₂ of the original envelope, a _B > a _S , and when the minimum amplitude of the added waveform is zero, a _B < a _S.

Thus, by using the virtual waveform A _i , the relative magnitudes of a _B and a _S can be determined, and a _B and a _S can be identified using equations (4-1) and (5-1), or equations (4-2) and (5-2).

In the above, the angular velocity of the virtual waveform A _i was denoted as ω _B , but instead, the angular velocity of the virtual waveform A _i may be denoted as ω _S. In this case as well, the measured value of the angular velocity ω _S may be used, or an approximate value may be used. In this case, conversely to the above case, equation (8-4) holds when a _B > a _S , and equation (8-2) holds when a _B < a _S.

The above processing is performed on each envelope identified from the measured values of vibration sensor 2a (supply side) and vibration sensor 2b (discharge side). This identifies the amplitude a _Bk of the component of the acceleration on the supply side due to residual unbalance of the outer shell 101, the amplitude a Bh of the component of the acceleration on the discharge side due to residual unbalance of the outer shell 101, the amplitude a _Sk of the component of the acceleration on the supply side due to residual unbalance of the inner _shell 102, and the amplitude a _Sh of the component of the acceleration on the discharge side due to residual unbalance of the inner shell 102.

(3-2) Identification of Phase Difference When the sensor-direction component of acceleration is expressed using the four amplitudes identified above, the acceleration _A1 on the supply side and acceleration _A2 on the discharge side due to residual unbalance in the outer casing 101, and the acceleration _A3 on the supply side and acceleration _A4 on the discharge side due to residual unbalance in the inner casing 102 are expressed as follows. Note that Δφ is the phase difference between the supply side and the discharge side of acceleration due to residual unbalance in the outer casing 101, and Δξ is the phase difference between the supply side and the discharge side of acceleration due to residual unbalance in the inner casing 102.

Furthermore, the acceleration _Ak detected by the supply-side vibration sensor 2a and the acceleration _Ah detected by the discharge-side vibration sensor 2b are expressed as follows. The accelerations _Ak and _Ah are measured by the vibration sensors 2a and 2b. Note that acceleration _Ak is the acceleration measured by the vibration sensor 2a for a wave with amplitude _ak , and acceleration _Ah is the acceleration measured by the vibration sensor 2b for a wave with amplitude _ah .

Considering the moment when acceleration A _k is at its maximum, this corresponds to the moment when the component due to residual unbalance in the outer casing 101 and the component due to residual unbalance in the inner casing 102 are in phase on the supply side and reach the sensor mounting position. That is, at this time, sin(ω _B t) = sin(ω _S t) = 1. Figure 5 schematically illustrates the relationship between the acceleration and phase of the outer and inner casings on the supply and discharge sides at this time. Note that Δθ in the figure is the phase difference between the acceleration of the outer and inner casings on the discharge side, and is determined as the phase difference of the envelopes identified from the measured values of vibration sensors 2a and 2b, respectively.

If _ΔθB is the phase difference between the acceleration _ah on the discharge side and the acceleration _aBh which is the component of the acceleration _ah caused by the residual unbalance of the inner cylinder 101, then the following equation holds.

From equations (10-1) and (10-2), the following equation (11) is derived.

Furthermore, the phase difference Δθ _D between acceleration A _k and acceleration A _h is determined. Let t _B be the period of the waveform of acceleration A _k , and let Δt be the difference between the time when the acceleration at the sensor position is maximum in the waveform of acceleration A k and the time when the acceleration at the sensor position is maximum in _the waveform of acceleration A _h . Then Δθ _D is given by the following equation (12).

The phase difference Δφ between the supply side and discharge side of acceleration due to residual unbalance in the outer shell 101, and the phase difference Δξ between the supply side and discharge side of acceleration due to residual unbalance in the inner shell 102, are given by the following equations, respectively.

(3-3) Application of a Mechanical Model In diagnostic step S30, a mechanical model (Figure 6) is assumed in which one load exists on the supply side and one on the discharge side of the outer shell 101 and inner shell 102, respectively, and the masses of the four loads placed in this mechanical model are identified. In other words, rather than identifying the location and size of the actual factors causing residual unbalance (such as adhesion or damage), the residual unbalance of the centrifugal dewatering machine 100 is identified by a model in which these are represented by four loads.

In the mechanical model (Figure 6), loads 61 and 62 are set on the supply side and discharge side of the outer shell 101, respectively, as well as loads 63 and 64 are set on the supply side and discharge side of the inner shell 102. Each parameter of loads 61 to 64 is represented by the symbols shown in the table below. However, parameters other than the masses m _B1 , m _B2 , m _S1 , and m _S2 of loads 61 to 64 are constants predetermined when the mechanical model is set up. Also, the mass on the supply side of the centrifugal dewatering machine 100 is M _k , the mass on the discharge side is M _h , and the total length is L ₀ .

Table 1: Symbols representing each parameter of load in the mechanical model

Solving this dynamic model, assuming equilibrium of excitation forces, yields the following solution.

Specifically, using the accelerations A _k and A _h detected by the vibration sensors 2 (2a, 2b), the angular velocity ω _B calculated from the rotational speed detected by the outer casing tachometer 3, and the angular velocity ω _S calculated from the rotational speed detected by the inner casing tachometer 4, the amplitude a _Bk of the component of the acceleration on the supply side due to residual unbalance of the outer casing 101, the amplitude a Bh of the component of the acceleration on the discharge side due to residual unbalance of the outer casing 101, the amplitude a _Sk of the component of the acceleration on the supply side due to residual unbalance of the inner casing 102, and the amplitude a _Sh of the component of the acceleration on the discharge side due to residual unbalance of the inner casing ₁₀₂ Furthermore, by identifying the phase difference Δφ between the supply side and discharge side of acceleration due to residual unbalance in the outer shell 101 and the phase difference Δξ between the supply side and discharge side of acceleration due to residual unbalance in the inner shell 102, and substituting these into equations (15-1) to (15-4), the masses m _B1 , m _B2 , m _S1 , and m _S2 of the loads 61 to 64 can be determined. The masses m _B1 , m _B2 , m _S1 , and m _S2 of the loads 61 to 64 determined at this time can be said to represent the residual unbalance that actually exists in the centrifugal dewatering machine 100.

From the determined masses m _B1 , m _B2 , m _S1 , and m _S2 , the relative magnitudes of residual unbalance in the four regions divided into the supply and discharge sides of the outer shell 101 and inner shell 102, as well as the overall degree of residual unbalance in the centrifugal dewatering machine 100, can be estimated. For example, if mass m _B1 is larger than the others, it can be estimated that there is a significant cause of residual unbalance in the supply side region of the outer shell 101 compared to the other regions. Furthermore, by periodically identifying masses m _B1 , m _B2 , m _S1 , and m _S2 and monitoring their trends, changes in the residual unbalance of the centrifugal dewatering machine 100 can be identified. This allows for the estimation of residual unbalance without disassembling the centrifugal dewatering machine 100, enabling timely maintenance.

[Other Embodiments]
Finally, other embodiments of the diagnostic device, diagnostic method, and diagnostic program according to the present invention will be described. Note that the configurations disclosed in each of the following embodiments can be applied in combination with configurations disclosed in other embodiments, provided that this does not create a conflict.

In the above embodiment, a configuration in which four loads 61 to 64 are set in the mechanical model (Figure 6) was described as an example. However, when using a mechanical model in the present invention, the number of loads set is not limited.

In the above embodiment, a configuration in which the diagnostic device 1 includes an outer drum tachometer 3 and an inner drum tachometer 4 was described as an example. However, as mentioned above, in the diagnostic device, diagnostic method, and diagnostic program according to the present invention, it is also possible to use approximate values instead of actual measured rotational speeds, so one or both of the outer drum tachometer and the inner drum tachometer may be omitted.

In the above embodiment, a configuration in which the envelope is identified at the beginning of a series of analyses was described as an example. However, it is also possible to analyze the vibration sensor's detector directly without identifying the envelope. However, from the viewpoint of reducing the amount of computational processing required for the analysis, it is preferable to identify the envelope.

In the above embodiment, a configuration was described as one in which the phase difference Δφ between the supply side and discharge side of acceleration due to residual unbalance in the outer cylinder 101, and the phase difference Δξ between the supply side and discharge side of acceleration due to residual unbalance in the inner cylinder 102, are identified. However, even if the identification of the phase difference is omitted, the residual unbalance of the centrifugal dewatering machine can be identified at a practical level, although the accuracy may be lower compared to the above embodiment.

In the above embodiment, a configuration in which the residual unbalance of the outer drum 101 and the residual unbalance of the inner drum 102 are separated was described as an example. However, this separation may be omitted, and the residual unbalance may be identified as the overall residual unbalance of the centrifugal dewatering machine 100.

Regarding other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention.

This invention can be used, for example, in the diagnosis of centrifugal dehydrators.

1: Diagnostic device 2: Vibration sensor 3: Outer drum tachometer 4: Inner drum tachometer 5: Computer 51: Calculation unit 52: Memory device 53: Input terminal 54: Display 55: Input device 100: Centrifugal dehydrator 101: Outer drum 102: Inner drum 102a: Shaft 103: Bearing section 104: Differential velocity device A: Acceleration

Claims (9)

A diagnostic device for diagnosing a centrifugal dewatering machine comprising an outer and inner drum arranged concentrically, supported by two bearings located at both ends in the extending direction, and rotating at different rotational speeds,
The system comprises vibration sensors provided at least one on each of the two bearing sections, and a computing device.
The aforementioned computing device
Based on the detection values of the two vibration sensors, the waveform of the humming of the centrifugal dehydrator to be diagnosed is identified , and,
A diagnostic device that identifies residual imbalance in the centrifugal dehydrator based on the aforementioned humming waveform. The diagnostic device according to claim 1, wherein the computing device uses the detected values of the two vibration sensors to solve a mechanical model of a centrifugal dehydrator in which residual unbalance is set at a predetermined position, and obtains a solution in which the residual unbalance in the mechanical model represents the actual residual unbalance, thereby identifying the residual unbalance of the centrifugal dehydrator to be diagnosed. The diagnostic device according to claim 1, wherein the calculation device separates the residual unbalance of the centrifugal dehydrator to be diagnosed into residual unbalance of the outer drum of the centrifugal dehydrator and residual unbalance of the inner drum of the centrifugal dehydrator. The diagnostic device according to claim 1, wherein the calculation device identifies the phase difference between residual unbalance located at one end of the centrifugal dehydrator in the extending direction and residual unbalance located at the other end in the extending direction. The diagnostic device according to claim 1, wherein the calculation device further identifies the envelope of the hum waveform of the centrifugal dehydrator to be diagnosed. The calculation device generates a virtual waveform in which the angular velocity is the same as the angular velocity of the outer shell or the inner shell, and the amplitude is greater than 0 and less than or equal to the minimum amplitude of the envelope.
The virtual waveform and the envelope are added together to generate an added waveform, and,
The diagnostic device according to claim 5, which, based on the summation waveform, separates the residual unbalance of the centrifugal dehydrator to be diagnosed into residual unbalance of the outer drum of the centrifugal dehydrator and residual unbalance of the inner drum of the centrifugal dehydrator. The system further comprises an outer drum tachometer for measuring the rotational speed of the outer drum of the centrifugal dehydrator to be diagnosed, and an inner drum tachometer for measuring the rotational speed of the inner drum of the centrifugal dehydrator,
The diagnostic device according to any one of claims 1 to 6, wherein the calculation device identifies the residual unbalance of the centrifugal dehydrator to be diagnosed based on the waveform of the hum, the rotation speed of the outer drum, and the rotation speed of the inner drum. A diagnostic method for diagnosing a centrifugal dewatering machine comprising an outer and inner drum arranged concentrically, supported by two bearings located at both ends in the extending direction, and rotating at different rotational speeds,
A step of identifying the humming waveform of the centrifugal dehydrator to be diagnosed based on the detection value of vibration sensors provided at least one on each of the two bearing parts,
A diagnostic method comprising the step of identifying residual unbalance in the centrifugal dehydrator based on the waveform of the aforementioned hum. A diagnostic program for diagnosing a centrifugal dewatering machine comprising an outer and inner drum arranged concentrically, supported by two bearings located at both ends in the extending direction, and rotating at different rotational speeds,
When executed by a computer,
A function to identify the humming waveform of the centrifugal dehydrator to be diagnosed based on the detection value of vibration sensors provided on each of the two bearing sections,
A diagnostic program that enables a function to identify residual imbalance in the centrifugal dehydrator based on the aforementioned humming waveform.