JP2001330510A - Abnormality diagnostic method of rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality diagnostic method of a rotating machine allowing quantitative and accurate diagnosis of an abnormality caused by abrasion of a bearing. SOLUTION: At least two vibration detectors are disposed in a casing of a machine body with phase shifted circulferentially of a rotating shaft, frequencies of vibration waveforms simultaneously detected by respective vibration detectors are analyzed. Regarding to the vibration waveforms, vibration amplitude in a frequency band region including frequency regions before and after a rotation frequency and a phase at the rotation frequency wave number of the other vibration waveform with reference to the vibration waveform with the largest vibration amplitude are determined. Each vibration vector 32 of the other vibration detector is determined based on the determined vibration amplitude and the phase, each changing vector 33 of a difference between a reference vibration vector 31 predetermined in a normal state and each vibration vector 32 is determined, and the changing vector 33 is compared with a predetermined discrimination reference 34. Thus, certainty of abnormality occurrence of the bearing is discriminated quantitatively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of diagnosing abnormalities of a rotary machine such as a pump, and more particularly to a method of diagnosing abnormalities of a rotary machine which detects vibrations generated by bearings of a rotary shaft and diagnoses whether there is any abnormality.

[0002]

2. Description of the Related Art In general, in rotating machines such as pumps and turbines used in power generation plants, during operation, abrasion of a rotating shaft bearing progresses, and when an abnormality occurs, the vibration often changes. For this reason, in this type of rotating machine, a method of constantly monitoring for the presence or absence of abnormality in the bearing of the rotating shaft has been conventionally employed.

FIG. 7 shows an example of a rotating machine which causes a problem of vibration. In FIG. 7, reference numeral 50 denotes a casing accommodating the impeller, and 51a and 51b denote bearings for rotatably supporting the rotating shaft of the impeller. 52 is a drive motor.

[0004] As the wear progresses in the bearings 51a and 51b, the spring constant and damping constant of the bearings decrease, and the shaft vibration increases. If the impeller is left as it is, the impeller comes into contact with the casing 50, and finally the vibration of the casing 50 itself increases, leading to a fatigue failure in the pipes and the like joined to the casing 50. In order to prevent such abnormal vibration, an allowable wear amount is set in advance for the bearings 51a and 51b. Usually, the wear amount of the bearing is measured by regular overhaul and the wear of the bearing is measured. Monitors life expectancy.

[0005] Accelerometers 53a and 53b for evaluating vibration from acceleration are attached to the bearing housings 51a and 51b. Further, a shaft vibrometer 54 is arranged so that a frequency analysis of the shaft vibration can be performed. Conventionally, when monitoring an abnormality of a bearing due to sampling of vibration, a frequency analysis is performed using a rotation pulse meter 55 to detect a reference circumferential position of the rotation shaft, and an accelerometer 53 is used.
a, 53b, the presence or absence of abnormality is determined from the absolute value of the phase magnitude at the rotation frequency for the vibration detected by the shaft vibrometer 54.

[0006]

However, in some rotating machines, the rotation axis cannot be measured because the rotating shaft is not exposed to the outside. In such a rotating machine, the phase at the rotation frequency is obtained. Because you ca n’t
There are situations in which it is not possible to easily perform a bearing abnormality diagnosis.

On the other hand, in the abnormality diagnosis based on the frequency analysis of the vibration, since the change in the vibration caused by the wear of the bearing is very small, a highly accurate diagnosis as to whether the wear amount of the bearing is compared with an allowable value or not is performed. Until then, it is difficult. Therefore, usually, the rotating machine is periodically disassembled and inspected while monitoring the vibration, and the wear amount of the bearing is measured to determine whether or not the life has been reached.
As a practical matter, the overhaul of rotating machinery is a large-scale operation and cannot be performed frequently.Therefore, it is necessary to replace the bearing early even though there is sufficient room for the bearing's wear life. Often have.

Accordingly, an object of the present invention is to provide a method for diagnosing abnormalities in a rotating machine which solves the problems of the prior art described above and is capable of quantitatively and accurately diagnosing abnormalities caused by bearing wear. To provide.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 diagnoses an abnormality from a change in vibration generated during operation of a rotating machine having a rotating shaft supported by a bearing. A method comprising: arranging at least two vibration detectors on a casing of a machine main body with a phase shift in a circumferential direction of a rotating shaft, and performing a frequency analysis on vibration waveforms simultaneously detected by the respective vibration detectors. For each of the vibration waveforms, the vibration amplitude in the frequency band including the frequency band around the rotation frequency and the frequency band around the rotation frequency, and the phase at the rotation frequency for the other vibration waveforms based on the vibration waveform with the largest vibration amplitude are obtained. From the obtained vibration amplitude and phase, the respective vibration vectors for other vibration detectors are obtained, and the reference vibration vector and the vibration vector previously obtained in a normal state are obtained. Determination of the difference between the change vectors, respectively, by comparing the change vector and predetermined criteria, those characterized by quantitatively determining the likelihood of the occurrence of abnormality in the bearing.

According to the present invention, the degree of change of the vibration vector to be compared with the reference vibration vector is determined based on both change vectors, so that vibration measurement or rotation pulse cannot be easily measured. Quantitatively diagnose changes in vibration mode for rotating machinery,
Even a slight change in the vibration mode due to bearing wear can be detected.

According to a second aspect of the present invention, in the first aspect, at least two vibration detectors whose phases are shifted in the circumferential direction of the rotation shaft are regarded as one set, and at least two vibration detectors of another set are used. Are arranged at different positions in the axial direction of the rotating shaft. According to the present invention, a change in the vibration mode can be detected with higher accuracy, and the accuracy of diagnosis can be increased.

The criterion is a circle centered on the end point of the reference vector and having a radius equal to a threshold value which is a basis for determination as an abnormal event. It is possible to quantitatively determine the probability of occurrence of an abnormality from the size and direction of the vector within the circle.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows a canned pump 10 as an example of a rotating machine to which the diagnostic method according to the present invention is applied. This canned pump 10 has a structure in which the rotating shaft is not exposed to the outside, and has a structure in which a rotating pulse cannot be measured from the outside as described in the related art.

The can pump 10 is installed such that the lower half of the main body is buried in the base 11.
The impeller 12, the rotating shaft 13, and the rotor 14 are integrated, and are sealed inside a casing 15. The rotating shaft 13 is
It is rotatably supported by an upper bearing 16 and a lower bearing 17. When the upper bearing 16a and the lower bearing 16b wear, the spring constant and the damping constant of the bearing decrease, and the shaft vibration increases. If the bearing wear is left unattended, the vibration of the casing 15 may increase, and the pipes (not shown) connected to the casing 15 may be damaged by fatigue.

In order to quantitatively detect a change in vibration caused by wear of the upper bearing 16a and the lower bearing 16b as a change in a vibration mode having an amplitude and a phase as well as the magnitude of the vibration, a casing 15 is provided. Has accelerometers at the following locations:

FIG. 2A shows the mounting positions of the accelerometers 17 and 18 mounted on the lower part of the casing 15.
In this case, the accelerometer 17 and the accelerometer 18 have the same axial position, but have a positional relationship deviated by 90 degrees in the circumferential rotation direction. Similarly, FIG.
Shows the mounting positions of the accelerometers 19 and 20 mounted on the upper part of FIG. In this case, the accelerometer 19 and the accelerometer 20
The lower accelerometer 17 and the accelerometer 18 have a positional relationship shifted in the axial direction, but the position in the circumferential rotation direction has a positional relationship deviated by 90 degrees like the lower accelerometers 17 and 18. .

The vibrations are simultaneously measured by the four accelerometers 17 to 20 to perform frequency analysis, and the wear state of the upper bearing 16a and the lower bearing 16b is diagnosed as follows.

FIG. 3 shows a vibration mode at a rotation frequency during operation of the canned pump 10. Vibration modes measured by the accelerometers 17 and 18 at the lower part of the casing can be displayed by waveforms of an ellipse 20a (when normal) and an ellipse 20b (when deteriorated). Similarly, the vibration modes measured by the accelerometers 19 and 20 in the upper part of the casing can be indicated by an ellipse 21a (when normal) and an ellipse 21b (when the bearing is deteriorated). Since the waveforms of the vibration modes are different between normal operation and when the bearing is deteriorated, it can be seen that bearing wear can be diagnosed by comparing the two. For example, a diagnosis can be made to some extent by comparing the deflection directions of the vibration waveforms and the magnitudes of the major axis and the minor axis thereof. In the present invention, diagnosis is specifically performed as follows.

First, four accelerometers 18 to 20 are used.
By performing frequency analysis of the vibrations collected by the above, the vibration amplitude of each vibration in the frequency band including the frequency band before and after the rotation frequency is determined. Next, among the obtained vibration amplitudes, the one with the larger amplitude is used as a reference vibrometer (here, for example, the amplitude of the vibration measured by the accelerometer 17 is the largest), and the other accelerometers 18 and 19 are used. , 20 is calculated based on the vibration waveform of the accelerometer 17.

In this way, for example, the vibration waveform obtained by the accelerometer 18 is shown in FIG. 4 by its own amplitude and a vibration having a predetermined phase with respect to the reference vibration waveform of the accelerometer 17. Vector display can be performed as the vector 32. Vibration vectors are displayed for vibrations measured by the other accelerometers 19 and 20 in the same manner.

In FIG. 4, reference numeral 31 denotes, for example, a reference vibration vector, which is measured in advance in a normal operation state shown in FIG. 3A, frequency-analyzed, and obtained in correspondence with each accelerometer. This is the reference vibration vector set.

Therefore, in order to see how much the vibration vector 32 to be compared has changed with respect to the reference vibration vector 31, a change vector 33 between the two is calculated. Here, FIG. 8 shows a change in the Lissajous waveform of the vibration obtained by the two accelerometers 17 and 18 separated in the circumferential direction as shown in FIG. 61 is a Lissajous waveform by the accelerometer 18 and 62 is a Lissajous waveform by the accelerometer 17. In the case of a change in vibration caused by the progress of bearing wear, the difference in amplitude between the two Lissajous waveforms 61 and 62 is small, and bearing wear cannot be detected. However, as shown in FIG. 9, the acceleration amplitude a17 of the Lissajous waveform 61
When a vibration vector based on the accelerometer 17 of the accelerometer 18 is obtained from the vibration vector 63 and the acceleration amplitude a17 of the Lissajous waveform 62, a change in which a thin ellipse becomes a wide ellipse is obtained as a change vector 65 of the acceleration amplitude a18. Can be detected.

Next, in FIG. 4, reference numeral 34 is a reference for judging the degree of progress of wear of the bearing between the normal state and the abnormal state for the change vector 33. . This circle 34 is centered on the end point of the reference vector 31 and is either the upper bearing 16 a or the lower bearing 16.
b is a circle having a radius of a threshold value on which the judgment is made that the wear has progressed to the extent that the wear is recognized as an abnormal event requiring replacement, and the magnitude of the change vector 33 is abnormal. A circle having a radius equal to the threshold value determined as
Within, the distance from the center is evaluated from both the size and the direction, and thereby the probability of occurrence of an abnormality is quantitatively determined. For example, as the end point of the change vector 33 approaches the circle 34, it can be evaluated that the wear has progressed more reliably. FIG.
In the above, upper and lower limits may be provided for the magnitude and phase of the amplitude instead of the circle 34 having the radius as the threshold.

In order to more quantitatively determine the likelihood of a judgment on such an abnormal event, the magnitude of the change vector 33 with respect to the threshold value s is determined using a membership function 41 as shown in FIG. Is replaced with the certainty factor for the abnormal event. The membership function 41 can quantitatively evaluate the magnitude of a change vector in association with an abnormal event caused by bearing wear based on empirical data obtained by examining a bearing wear amount or the like in an actual case. It is set in advance as follows. Since the change vector 33 is detected even in a normal operation state, the membership function 41 has a dead area with a predetermined width.

As for the amplitude of the vibration in the accelerometer 18, which is the reference, the confidence of the abnormal event is quantitatively evaluated in the same manner using the membership function 42 as shown in FIG. You may do so. In the membership function 42 shown in FIG. 6, in the case of amplitude, since the amplitude may increase even if the bearing wear amount is small, the lower limit threshold value S1 and the upper limit threshold value S2 are set. The area has been set.

By comparing the confidence data obtained quantitatively as described above with the data collected and accumulated for each abnormal case of actual bearing wear, bearing wear is considerably increased. By estimating the amount and comparing with the allowable amount of wear, it is possible to determine whether or not replacement is necessary. In addition to the bearing wear, the certainty data can be used as data for diagnosing the presence or absence of an abnormality in the operation state of the pump based on the process amount (current, flow rate) conventionally performed.

Although the present invention has been described with reference to the embodiment in which four accelerometers are used, two or more accelerometers which are more sensitive to abnormalities in one of the upper and lower casings are selected. It may be.

[0028]

As is apparent from the above description, according to the present invention, for a rotating machine in which vibration measurement and rotation pulse measurement cannot be easily performed from the outside with respect to a rotating shaft, an abnormality due to bearing wear and the like can be quantitatively and accurately determined. Therefore, the reliability of the rotating machine can be improved.

In addition, since the amount of wear of the bearing can be quantitatively estimated, the life of the bearing can be estimated, and replacement can be performed at an appropriate time, so that appropriate maintenance can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a rotating machine to which a diagnostic method according to the present invention is applied.

FIG. 2 is an explanatory diagram showing an arrangement of an accelerometer according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a change in a vibration mode measured by the accelerometer of FIG. 2;

FIG. 4 is a vibration vector diagram according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an example of a membership function for calculating a certainty factor from diagnostic data in the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of another membership function.

FIG. 7 is an explanatory view of a conventional rotating machine diagnosis method.

FIG. 8 is a diagram showing a change in a Lissajous waveform of vibration measured by two accelerometers separated in a circumferential direction.

FIG. 9 is a diagram showing a change in a vibration vector of the Lissajous waveform in FIG. 8;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 canned pump 11 base stand 12 impeller 13 rotating shaft 14 rotor 15 casing 16 upper bearing 17 lower bearing 17-20 accelerometer 31 reference vector 32 vibration vector 33 change vector 41 membership function 42 membership function

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 11/00 R (72) Inventor Shuichi Omori 4-1 Egasakicho, Tsurumi-ku, Yokohama-shi, Kanagawa No. Tokyo Electric Power Company, Inc. (72) Inventor Yukio Watanabe 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd. 8 Shinsugita-cho, Toshiba Yokohama Office (72) Inventor Hidekazu Usui 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa, Japan Toshiba Yokohama Office (72) Inventor Yoshihiko Uhara, Yokohama, Kanagawa 8 Shinshinsugita-cho, Isogo-ku F-term in Toshiba Yokohama Office (reference) 2G024 AD03 BA21 BA27 CA13 FA04 2G064 AA17 AB01 AB02 AB22 BA02 CC13 CC17 CC41 CC61 2G 075 BA03 CA14 DA09 FA17 FB07 FB09 FB15 FC14 GA21 3J011 EA05 EA10 5H611 AA01 BB01 PP03 PP05 QQ09 RR00 UA04 UA05

Claims (4)

[Claims] 1. A method for diagnosing an abnormality from a change in vibration generated during operation of a rotating machine having a rotating shaft supported by a bearing, wherein at least two vibrations are detected by shifting a phase in a circumferential direction of the rotating shaft. The device is placed in the casing of the machine body, and a frequency analysis is performed on the vibration waveforms simultaneously detected by the respective vibration detectors. The phase at the rotation frequency is obtained for the other vibration waveforms with reference to the vibration amplitude of the vibration and the vibration waveform having the largest vibration amplitude, and the respective vibration vectors for the other vibration detectors are obtained from the obtained vibration amplitude and phase. In each state, a change vector of a difference between a reference vibration vector and a vibration vector obtained in advance is obtained, and the change vector is determined by a predetermined determination base. And by comparing, rotary machine abnormality diagnosis method characterized by quantitatively determining the likelihood of the occurrence of abnormality in the bearing. 2. The method according to claim 1, wherein at least two vibration detectors whose phases are shifted in the circumferential direction of the rotation shaft are regarded as one set, and at least two vibration detectors of another set are positioned at different positions in the axial direction of the rotation shaft. The method for diagnosing abnormality of a rotary machine according to claim 1, wherein the abnormality is disposed in a rotating machine. 3. The criterion is a circle centered on an end point of a reference vector and having a radius as a threshold value on which an abnormal event is determined, and the magnitude and direction of the change vector in the circle. The method for diagnosing abnormality of a rotary machine according to claim 1, wherein the probability of occurrence of an abnormality is quantitatively determined from the data. 4. The method according to claim 3, wherein the criterion comprises a membership function set in advance for an abnormal event that may occur empirically.